Expanding the range of "Daniphos"-type P∩P- and P∩N-ligands: Synthesis and structural characterisation of new [(η6-arene)Cr(CO)3] complexes

FULL PAPER

DOI: 10.1002/ejic.200700568

Expanding the Range of “Daniphos”-Type PʝP- and PʝN-Ligands: Synthesis

and Structural Characterisation of New [(η⁶-arene)Cr(CO)₃] Complexes

Elisabetta Alberico,*^[a]Wolfgang Braun,^[b]Beatrice Calmuschi-Cula,^[b]Ulli Englert,^[b]

Albrecht Salzer,*^[b]and Daniel Totev^[b]

Keywords: N,P ligands / Phosphane ligands / Asymmetric catalysis / Arene complexes / Chromium

New PʝP- and PʝN-ligands have been synthesised whose

core structure is an [(η⁶-arene)Cr(CO)₃] unit. These new li-

gands, which extend the range of “Daniphos” ligands, are

endowed with central and planar chirality and have been

prepared through a stereoselective synthetic strategy from

optically pure benzylamines bearing a second substituent on

the arene other than the benzyldimethylamino group. Be-

cause the two faces of unsymmetrically 1,2- and 1,3-disubsti-

tuted benzylamine are diastereotopic, which means that dia-

stereomeric complexes arise upon coordination of the

Cr(CO)₃fragment to either of these two faces, the synthetic

plan has been adjusted by exploiting the trimethylsilyl group

as a temporary steric modulator in order to access both com-

plexes with high diastereoselectivity.

Germany, 2007)

catalytic processes such as hydrogenation,^[3]hydroamina-

tion,^[3a]allylic sulfonation,^[3a]hydrovinylation,^[1b]transfer

hydrogenation^[4]and, more recently, nucleophilic asymmet-

ric ring opening (ARO) of oxabenzonorbornadienes.^[5]

Introduction

“Daniphos” ligands are a class of ligands suitable for

application in catalysis whose core structure is an [(η⁶-

arene)Cr(CO)₃] unit. A stereoselective synthetic strategy de-

veloped recently in our laboratories has provided these li-

gands with a modular and tunable character (Scheme 1).^[1]

Daniphos ligands are usually prepared from commercially

available optically pure benzylamines and are characterised

by the presence of a stereogenic plane and a stereocentre.

Planar chirality is introduced by means of a diastereoselec-

tive directed orthometallation (DOM) assisted by the ben-

zylic amino group and subsequent electrophilic substitution

on the arene ring. Central chirality is preserved by the ster-

eoselective replacement of the dimethylamino group for a

chloride by treatment with chloroethyl chloroformate

(ACE-Cl) and subsequent stereoselective nucleophilic sub-

stitution of the chloro substituent for a different nucleo-

phile. A library of ligands, which comprises mono- and bi-

dentate PʝN and PʝP ligands, has been prepared follow-

ing this approach.^[1–3]The steric and/or electronic proper-

ties of these ligands can be easily tuned by varying the R¹/

R²substituents on the donor atoms D or by reducing their

conformational flexibility by tethering the donor atoms to

an annelated framework^[3e](Scheme 2). These ligands have

been tested in a number of enantioselective homogeneous

Scheme 1. General synthetic strategy for the preparation of “Dani-

phos”-like diphosphanes. ACE-Cl = 1-chloroethyl chloroformate.

Scheme 2. Accessibility of a modular ligand architecture based on

[(η⁶-arene)Cr(CO)₃] complexes.

As shown in Scheme 2, a further possibility for altering

the basic structure of Daniphos ligands is to introduce a

substituent R onto the arene ring. Such substituents might

be important in modulating the electronic properties of the

donor atoms D and, depending on their location on the

arene, also their steric properties. Such substituents can be

introduced at the stage of complexation of the arene to the

[a] Istituto di Chimica Biomolecolare,

CNR, trav. La Crucca 3, Li Punti, 07040 Sassari, Italy,

Fax: +39-079-3961036

E-mail: elisabetta.alberico@icb.cnr.it

[b] Institut für Anorganische Chemie der RWTH,

Landoltweg 1, 52074 Aachen, Germany,

Fax: +49-241-8092288

E-mail: albrecht.salzer@ac.rwth-aachen.de

Eur. J. Inorg. Chem. 2007, 4923–4945

4923

E. Alberico, A. Salzer et al.

FULL PAPER

Cr(CO)₃moiety as a range of chiral amines related to 1-

phenylethylamine that already bear the R substituent are

commercially available. In this paper we detail the synthesis

of these complexes and explore the influence of the R group

on the outcome of some steps of our established synthetic

strategy. The X-ray structures of some intermediates and

some of the target ligands are also provided, which, in cases

of uncertainty, serve to define the stereochemical outcome

of a reaction.

Scheme 3. Yields obtained in the complexation of protected para-

substituted benzylamines with Cr(CO)₆.

Results and Discussion

The amines used to prepare the “Daniphos” ligands re-

ported in this paper are shown in Figure 1. The correspond-

ing primary benzylamines were reductively methylated with

formaldehyde and formic acid following the Eschweiler–

Clarke procedure.^[6]Protection of the amino group prior to

complexation to the Cr(CO)₃moiety is necessary in order

to reduce its coordinating ability towards chromium as this

might lead to incomplete complex formation. The diphos-

phanes PʝP were prepared from the para-substituted ben-

zylamines (S)-1, (S)-2, (R)-3 and (R)-6 while the bidentate

PʝN ligands were prepared from ortho- and meta-methoxy-

substituted benzylamines (S)-4 and (S)-5.

DOM of complexes (S)-7, (S)-8, (R)-9 and (R)-10 was

carried out according to a general procedure consisting of

treatment with tBuLi in diethyl ether at –78 °C for 1.5 h,

subsequent quenching with ClPPh₂, and warming to room

temperature overnight. The relative amounts of products

formed were calculated based on integration of the corre-

sponding ³¹P NMR signals in the spectra of crude reaction

mixtures in all cases. The diastereomeric excesses reported

in the schemes were calculated in a similar manner. Prod-

ucts of very high purity were obtained by flash chromatog-

raphy.

Coordination of the Cr(CO)₃group to the arene en-

hances the kinetic acidity of the ring C–H bonds due to

the strong electron-withdrawing character of the Cr(CO)₃

moiety,^[8c]therefore direct lithiation of the arene ring occurs

more easily than that of the parent chromium-free arene.

Because of the presence of a heteroatom-containing func-

tionality, lithiation can be extremely selective towards the

ortho position due to specific coordination of the base

through its lithium counterion.^[10]

Figure 1. Phenylethylamines which have been complexed to the

Cr(CO)₃moiety to synthesise the “Daniphos” ligands reported in

this paper.

The two hydrogen atoms ortho to the ethylamino group

in complexes (S)-7, (S)-8, (R)-9 and (R)-10 are dia-

stereotopic because of the α-stereogenic centre, which

means that preferential replacement of either of them gives

rise to unequal amounts of two molecules endowed with

the same central chirality but opposite planar chirality.^[11]

Preparation of Daniphos Diphosphanes PʝP

The coordination of amines (S)-1, (S)-2, (R)-3 and (R)-6 When the related complex [{(R)-N,N-dimethyl-1-phenyl-

was accomplished by thermolysis with Cr(CO)₆(Scheme 3). ethylamine}Cr(CO)₃] is treated with tert-butyllithium in di-

The reactions weren carried out under the conditions re- ethyl ether at –78 °C, the ortholithiated species derived from

ported by Mahaffy and Pauson.^[7]The protected benzyl- preferential abstraction of the H_Sproton is formed with

amine and Cr(CO)₆were heated (temperature of the oil 96% diastereoselectivity (Figure 2).^[12]The origin of this

bath: 140 °C) in an 8:1 mixture of di-n-butyl ether and high diastereoselectivity stems from a preferential average

tetrahydrofuran until the evolution of CO ceased or onset solution-state conformation in which both the α-methyl and

of decomposition was observed. The best yield was ob- α-dimethylamino groups lie above the plane of the arene

tained with the para-tert-butyl-substituted benzylamine (S)- ring, opposite the bulky Cr(CO)₃unit (Figure 2, a). This

2. It is known that π-electron-withdrawing groups (e.g. “sensible” spatial arrangement has been inferred by deute-

1

CHO or COOH) slow down complexation and are best pro- rium-labelling and difference NOE H NMR experiments.

tected before complexation, while electron-donating arene According to these data, it can be expected that the ortho-

substituents accelerate complexation.^[8a,8b]Complexation of directing dimethylamino group preferentially directs a pre-

(R)-3 to the Cr(CO)₃moiety gave a modest 43% yield of coordinated lithium base towards the closest H_Sproton

the expected complex. In this case, decomposition during (Figure 2, b). Removal of the H_Rproton would force the

the reaction, as indicated by formation of a grey-green pre- benzylic methyl group below the plane of the arene, thereby

cipitate, was difficult to avoid. This appears to be progress- causing an unfavourable steric interaction with the tricar-

ive and the reaction had to be stopped. The poor yield bonylchromium unit. The absolute configuration of the α-

might also be due to reductive dehalogenation.^[9]

stereogenic centre dictates the relative planar chirality, thus

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Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

indicating that the sense of asymmetric induction is deter- the para-substituted methyl group Ϫ α-proton abstraction

mined in the deprotonation step. The greater discrimination from [(η⁶-arene)Cr(CO)₃] complexes is in fact the thermo-

between the two diastereotopic hydrogens achieved with a dynamically favoured process and the high yield of ring-

sterically more demanding base such as tBuLi is consistent substituted products clearly demonstrates that proton ab-

with this assumption. In fact, although high ortho dia- straction by tert-butyllithium is kinetically controlled.^[14]

stereoselectivity has been demonstrated with both nBuLi

ortho-Functionalisation of [{η⁶-(R)-1-(4-methoxyphen-

and tBuLi, only the latter allows for complete transfer of yl)-N,N-dimethylethylamine}Cr(CO)₃] [(R)-10] according to

side-chain chirality on to the arene ring.

the procedure described above affords a mixture of products

due to the presence of two coordinating substituents

(Scheme 5).

A very useful study has demonstrated that the substitu-

ent effects on regioselectivity in the deprotonation of free

arenes are distinctly different from those found for

[Cr(CO)₃]-complexed arenes.^[15]A series of para-disubsti-

tuted arenes were complexed and deprotonated, and the ra-

tio of the two possible products in each case allowed a reac-

tivity series to be generated. The following ratio of ortho-

directing abilities of functional groups was deduced:

Figure 2. (a) Average solution-state conformation of the benzylic

side chain of [{(R)-N,N-dimethyl-1-phenylethylamine}Cr(CO)₃] as

inferred from NOEDS. (b) Newman projection of the possible di-

rected orthometallation intermediate along the C_α–C_ipsobond.

F Ͼ CONHR Ͼ NHCOR Ͼ CH₂NR₂≈ OMe ϾϾ CH₂OMe

Uemura and Hayashi prepared the first ever reported

P,N ligand of the “Daniphos” type by diastereoselective li-

thiation of [{(R)-N,N-dimethyl-1-phenylethylamine}Cr-

(CO)₃] and subsequent reaction with chlorodiphenylphos-

phane.^[13]

DOM of (S)-7 and (S)-8 proceeds with high diastereo-

selectivity to give the expected products (S,Rp)-11 and

(S,Rp)-12, respectively (Scheme 4). No competitive α-pro-

ton abstraction was observed in the ortho functionalisation

of (S)-7 either from the dimethylaminoethyl group or from

According to this study, when lithiation is performed at

–78 °C with sBuLi for 1.5 h and is followed by electrophilic

quenching with Me₃SiCl, the relative kinetic acidity of a

ring proton takes precedence over simple base coordination

by a heteroatom in the substituent group as the principal

factor in determining the site of metallation in disubstituted

arene complexes. The chromium complex of p-methoxy-

N,N-dimethylbenzylamine provides a comparison of the di-

recting effect of the OMe and CH₂NMe₂groups. In this

case, the two effects, namely OMe-induced labilisation of

the ortho proton by electron withdrawal and CH₂NMe₂co-

ordination of the incoming base, are almost exactly bal-

anced. In line with this result, DOM of (R)-10 produces

similar amounts of products in which lithiation has oc-

curred ortho to the benzylic amino group and ortho to the

methoxy group.

The products reported in Scheme 5 were separated by

means of flash chromatography, although (R)-14M (the

more abundant isomer) and (R)-14m (the less abundant iso-

Scheme 4. Products obtained in the ortho-functionalisation of (S)-

7 and (S)-8.

Scheme 5. Products obtained in the ortho-functionalisation of (R)-10. Yields of isolated products are reported in parentheses. * This

notation indicates the two regioisomeric products bearing a diphenylphosphanyl group ortho to the OMe substituent; the absolute configu-

rations, however, could not be assigned.

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4925

E. Alberico, A. Salzer et al.

FULL PAPER

Table 1. Products obtained in the ortho-functionalisation of (R)-10 along with diagnostic chemical shifts.

Relative amounts^[a]

[%]

Yield^[b]

[%]

δ _H[ppm] (mult)

δ

[ppm] PPh₂ortho to

P

1

31

Complex

CH(Me)NMe₂

OMe

(R)-10

(R,Rp)-13

(R)-14M

–

32

26

–

30

2.96 (q)

4.41 (m)

2.69 (q)

–

–14.22

–

–18.57

30^[c]

(R)-14m

(R,Sp)-15

10

32

2.86 (q)

4.22 (m)

–

–17.92

–17.69

30

–14.23

[a] Ratio of products based on peak integration in the ³¹P NMR spectrum of the crude reaction mixture. [b] Yield of product isolated

after flash chromatography. [c] The two regioisomeric products could not be separated by flash chromatography and were isolated as a

single fraction.

mer), which are the two regioisomeric products bearing a lithium diisopropylamide (LDA) as the base and deute-

diphenylphosphanyl group ortho to the -OMe substituent, roacetic acid as the electrophile led to the observation of a

could not be separated and were collected as a single frac- trideuterated species presumably derived from a trianionic

tion.

species formed during the reaction. Alternatively, complex

The identity of the products was assigned based on the (R,Sp)-15 might arise from successive deprotonation/trap-

1

mass, H and ³¹P NMR, and 2D NMR spectra (Table 1). ping/deprotonation processes enabled by the unreacted

The location of the diphenylphosphanyl group ortho to the tBuLi. This would imply that electrophilic trapping of the

1

dimethylethylamino group was easily inferred from the H base itself is rather slower than deprotonation of the arene

NMR spectrum due to the phosphorus-hydrogen coupling, complex, although the isolation of tBuPPh₂as a by-product

which further splits the signal of the α-hydrogen compared in some cases suggests that this might not be the case.

to the corresponding signal in complex (R)-10. Further-

The stereochemistry of complex (R,Sp)-15 was tenta-

more, this resonance is shifted nearly 2 ppm to lower field tively assigned based on the most stable charge arrange-

due to the proximity of the phenyl groups and their “ring ment of the intermediate dianion considering that both the

current” effect. This is observed both in the spectrum of dimethylethylamino group and the methoxy group favour

the desired (R,Rp)-13 [its diastereomeric product (R,Sp)-13 the formation of the corresponding ortho anion and that

could not be detected in the ¹H NMR spectrum of the the dimethylethylamino group stereoselectively promotes

crude reaction mixture] and in the spectrum of disubsti- abstraction of the pro-S_Portho H atom.

tuted (R,Sp)-15. The chemical shift of the α-hydrogen signal

Lithiation of [{η⁶-(R)-1-(4-chlorophenyl)-N,N-dimethyl-

is nearly unchanged and no H-P coupling is detected in the ethylamine}Cr(CO)₃] [(R)-9] with tBuLi followed by treat-

spectrum of (R)-14M or (R)-14m, which were identified as ment of the lithiated species with ClPPh₂afforded the ex-

the species in which lithiation has occurred ortho to the pected ortho-functionalised diastereomeric complexes

OMe group. The two regioisomers are formed in a 72:28 (R,Sp)-16 and (R,Rp)-16 and the product of metal/halogen

ratio, thereby suggesting a possible influence of the remote exchange [(R)-17; Scheme 6]. According to the ³¹P NMR

stereogenic centre; the absolute planar chirality was not as- spectrum of the crude reaction mixture, the relative ratio of

signed.

(R,Sp)-16 and (R,Rp)-16 is 94:6, which corresponds to an

Formation of complex (R,Sp)-15 might proceed via a di- 88% diastereoselectivity of the ortholithiation reaction

anion stabilized by the strongly electron-withdrawing (Table 2). Pure (R,Sp)-16 was obtained by flash chromatog-

Cr(CO)₃moiety, which could mean that the mono-lithiated raphy. A second fraction contained (R,Rp)-16 as the main

arene ring is sufficiently acidic to allow a second deproton- product. Attempts to further purify this complex failed,

ation or the second deprotonation is faster than the first however, and its structure was assigned based on its ¹H

one.^[16]Unfortunately, to the best of our knowledge, there NMR spectrum, where the diagnostic H-P coupling and

is no reliable structural and spectroscopic information on shift of the -CH(Me)NMe₂signal to lower field are ob-

lithiated [(η⁶-arene)Cr(CO)₃] complexes which would make served. Although directed orthometallation is predominant,

it possible to determine whether the electronic effect of Li competitive chloride/lithium exchange leads to the forma-

as a substituent does or does not deactivate the aromatic tion of complex (R)-17. Interestingly, no lithiation ortho to

ring towards further H-abstraction. The existence of an in- the chloro substituent was detected.

termediate polycarbanion has been postulated recently in a

Because lithium amides enable metallation to be achieved

detailed investigation of multiple substitution of [(η⁶- in preference to metal/halogen exchange,^[18a]lithiation of

arene)Cr(CO)₃] complexes.^[17]The treatment of repre- (R)-9 was repeated with LDA under otherwise identical

sentative complexes such as [{η⁶-1-(tert-butyl-sulfonyl)- conditions. However, only the two diastereoisomers corre-

benzene}Cr(CO)₃], [(η⁶-anisole)Cr(CO)₃] and [(η⁶-N,N-di- sponding to lithiation ortho to the chloro substituent were

methylbenzylamine)Cr(CO)₃] with three equivalents of detected in a nearly 1:1 ratio (Scheme 6). The steric bulk of

2,2,6,6-tetramethylpiperidyllithium (LiTMP), followed by the base most likely prevents coordination by the ethyldi-

electrophilic quenching with Me₃SiCl, provided a series of methylamino group and the electron-withdrawing effect of

di- and trisilylated complexes. Deuteration studies using the chloro substituent prevails in dictating the regiochemis-

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Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

Scheme 6. Products obtained in the ortho-functionalisation of (R)-9. Yields of isolated products are reported in parentheses. * See Table 2.

** This notation indicates the two regioisomeric products bearing a diphenylphosphanyl group ortho to the Cl substituent whose absolute

configuration could not be assigned.

chelation. This was achieved in two steps, both of which are

Table 2. Products obtained in the ortho-functionalisation of (R)-9

along with diagnostic chemical shifts.

highly stereoconservative (Scheme 7). The first step involves

transformation of the phosphanylamino complex into a

chlorobenzyl derivative by treatment of the former with an

excess of 1-chloroethyl chloroformate (ACE-Cl). This pro-

cedure, which has been developed in our laboratory,^[1a]re-

lies on the ability of chloroformates to promote the mild

debenzylation of tertiary amines.^[19]Replacement of the di-

methylamino group by chloride takes place with retention

of configuration and no evidence of epimerisation was ob-

served. All the desired α-chloro derivatives were obtained

in good yields after purification by flash chromatography

except the para-chloro one [(R,Sp)-22], which readily de-

composes while adsorbed on silica gel. The reported yield

of (R,Sp)-22 therefore refers to the crude product after the

removal of excess ACE-Cl and carbamate by-product.

The new C₁-symmetric diphosphane ligands were finally

prepared by treatment of the corresponding benzyl chloride

complexes with a slight excess of a secondary phosphane

(HPRЈ₂) in acetone at room temperature in the presence of

TlPF₆, which acts as a chloride scavenger by precipitation

Complex Rel. amounts^[a]Yield^[b]δ _H[ppm] (mult.)

δ

[ppm]

1

31

P

[%]

CH(Me)NMe₂

(R)-9

(R,Sp)-

16

(R,Rp)-

16

–

77

–

67

2.88 (q)

4.39 (m)

–14.41

–17.53

–7.83

[c]

5

3.57 (m)

3.25 (q)

2.64 (q)

2.75 (q)

(R)-17

18

54

46

18

(R)-18M

–12.06

92^[d]

(R)-18m

–11.83

[a] Relative amounts of products based on peak integration in the

³¹P NMR spectrum of the crude reaction mixture. [b] Yield of

product isolated after flash chromatography. [c] The collected frac-

tion was not clean and contained some (R,Sp)-16 and (R)-17. [d]

The two diastereomeric products (R)-18M and (R)-18m could not

be separated by flash chromatography and were isolated as a single

fraction (see text).

try of deprotonation.^[18b]These complexes could not be sep- of highly insoluble TlCl. The ³¹P NMR spectra of all li-

arated by flash chromatography and the regiochemistry of gands display two doublets Ϫ one for each non-equivalent

1

lithiation was assigned based on the H NMR spectrum of phosphorus atom Ϫ whose splitting is due to coupling to

the mixture of the two diastereoisomers. The two com- the other phosphorus atom in the molecule (Table 3). Large

pounds, the absolute planar chirality of which could not be low-field shifts are observed upon changing the substituent

defined, are labelled as the major [(R)-18M] and minor [(R)- on the α-phosphorus atom from phenyl to cyclohexyl and,

18m] diastereoisomers in Table 2.

to a larger extent, to tert-butyl. This downfield shift with

After the first phosphorus donor has been introduced increasing steric bulk at phosphorus can be explained by a

into the ortho position, a second one has to be appropri- concomitant change in the hybridisation at phosphorus.^[20]

ately placed in the benzylic position for subsequent metal However, within the same set of diphosphanes having the

Eur. J. Inorg. Chem. 2007, 4923–4945

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4927

E. Alberico, A. Salzer et al.

FULL PAPER

Scheme 7. Yields of isolated products (* yield of crude product) obtained from the nucleophilic replacement of the dimethylamino group

by chloride and of diphosphanes prepared by replacement of benzyl chloride with a secondary phosphane HPRЈ₂. Both reactions take

place with retention of configuration.

same substituents on the phosphorus donors, replacing a ⁴J_P,Pcoupling might stem from “through-space” nuclear

hydrogen on the arene directly complexed to chromium spin-spin coupling made possible by partial overlap of the

with either a methoxy, methyl, tert-butyl or chloro substitu- two phosphorus lone pairs.^[23a]The steric crowding pro-

ent does not bring about any meaningful change in the vided by the substituents on phosphorus locks the molecule

properties of the phosphorus donors, as measured by the in a preferred time-average conformation in solution which,

corresponding chemical shifts. This means that the influ- by keeping the substituents on the ortho- and α-donors far

ence of the Cr(CO)₃moiety on the electron richness of the apart, brings the lone pairs into close proximity. The X-

arene, either as an aryl substituent on the phosphorus di- ray structure of ligand (S,Rp)-23b supports this hypothesis

rectly attached to the arene or a benzyl substituent on the (Figure 3).^[24a]The larger values observed for the derivatives

α-phosphorus, is too strong and levels out any electronic bearing bulky cyclohexyl and tert-butyl groups compared

contribution due to substituents on the arene.

to those which only possess phenyl substituents might re-

flect the further restricted conformational freedom caused

by the former substituents, although formal hybridisation

of the coupled nuclei and the electronegativity of their sub-

stituents also play a role.^[22,23b]

Table 3. ³¹P NMR spectroscopic data for the diphosphanes re-

ported in this paper.

[ppm]^[a]

[ppm]

J_P,P[Hz]

31

δ

31

δ

Ligand

R

RЈ

P

o-PPh₂

α-PRЈ

(R,Sp)-27a^[b]

(S,Rp)-23a

(R,Rp)-25a

(R,Sp)-26a

H

Ph

–18.74

–17.56

–17.99

–18.93

10.12

8.47

5.02

7.33

26.5

18.3

11.0

18.3

Me

OMe

Cl

(R,Sp)-27b^[b]

(S,Rp)-23b

(S,Rp)-24

(R,Rp)-25b

(R,Sp)-26b

H

Cy

–19.95

–18.71

–20.83

–17.48

–20.17

16.66

15.85

15.73

15.49

15.20

46.7

38.3

46.7

26.0

39.3

Me

tBu

OMe

Cl

(R,Sp)-27c^[b]

(S,Rp)-23c

(R,Rp)-25c

(R,Sp)-26c

H

tBu

–20.19

–19.79

–18.58

–21.06

50.49

49.33

48.07

48.78

68.0

61.7

54.3

63.2

Me

OMe

Cl

[a] NMR spectra recorded in C₆D₆. [b] These data, which are pro-

vided for comparison, have been taken from ref.^[3a]

.

The diphosphanes are characterised by large four-bond

phosphorus-phosphorus coupling constants whose values

increase from 11–26 Hz in PPh₂/PPh₂diphosphanes to 54–

68 Hz in PPh₂/PtBu₂ones. A similar trend has been re-

ported for the analogous ferrocene-based ligands.^[21]The

two phosphorus donors are bound to an allylic fragment

(P–C_o=C_ipso–C_α–P) and π-systems usually lead to unexpec-

Figure 3. Displacement ellipsoids plot (PLATON) of (S,Rp)-23b.

Ellipsoids are shown at the 30% probability level. The H-atom at-

tached to the stereogenic centre is shown with arbitrary radius;

tedly large long-range couplings.^[22]The large value of the other H-atoms have been omitted for clarity.

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“Daniphos”-Type PʝP- and PʝN-Ligands

The diphosphanes were tested in a variety of hydrogena-

tions in comparison with the complexes without R substitu-

ents. Some of the results of these studies have already been

published elsewhere.^[3c]In most reactions there was a gene-

ral trend in that the more electron-rich para-substituted li-

gands gave better ee values in enantioselective hydrogena-

tions.

Synthesis of Daniphos NʝP Ligands

The two faces of unsymmetrically 1,2- and 1,3-disubsti-

tuted benzylamine (S)-4 and (S)-5, respectively, are dia-

stereotopic, which means that diastereomeric complexes

arise upon coordination of the Cr(CO)₃fragment to either

of these two faces.^[25]

When complexation of (S)-4 is carried out under harsh

conditions [Cr(CO)₆, nBu₂O/thf, 150 °C] the isomer (S,Rp)-

28 is preferentially formed with a diastereoselectivity of

50% (Scheme 8). An excellent diastereoselectivity in favour

of the other diastereoisomer (S,Sp)-28 is achieved when

complexation is carried out using Kündig’s reagent [(naph-

thalene)Cr(CO)₃]. The latter is a good starting material for

the mild synthesis of other [(arene)Cr(CO)₃] compounds by

Cr(CO)₃fragment transfer.^[26]The absolute configuration

of complex (S,Sp)-28 was confirmed by X-ray crystallo-

graphic analysis (Figure 4).

Figure 4. Displacement ellipsoids plot (PLATON) of (S,Sp)-28. El-

lipsoids are shown at the 30% probability level. The H-atom at-

tached to the stereogenic centre is shown with arbitrary radius;

other H-atoms have been omitted for clarity.

Figure 5. (a) Preferred average conformation adopted by (S)-4 in

solution at room temperature as inferred by difference NOE/¹H

NMR experiments. (b) Preferred conformation in the presence of

a bulky –SiMe₃group in the ortho position.

Because flash chromatography and fractional crystallisa-

tion failed to provide the (S,Rp)-28 isomer in acceptable

yield and purity, an alternative synthetic strategy was de-

vised in order to obtain it as a single diastereoisomer. This

Scheme 8. Relative amounts of diastereomeric complexes obtained

in the complexation of (S)-4 under thermodynamic (A) and kinetic

(B) conditions.

These results can be explained on the basis of the pre- strategy is based on the direct complexation of a benzyl-

ferred average conformation adopted by (S)-4 in solution at amine derivative in which a sterically bulky and easily re-

room temperature (Figure 5a), which was inferred by differ- movable trimethylsilyl group has been temporarily intro-

ence NOE/¹H NMR experiments. Thus, a much greater duced at the ortho position of the 1-N,N-dimethylaminoe-

NOE enhancement of the α-CH₃signal is observed com- thyl group in (S)-4.^[27]The presence of this group should

pared to the α-H signal upon irradiation of the ortho-hydro- restrict rotation of the benzylic group at high temperature

gen, thus suggesting that, in order to minimize non-bond- and favour a conformation which, while limiting interaction

ing interactions between the α-substituents and the ortho of the α-Me with the SiMe₃group, preferentially confines

OMe group, the dimethylamino group is preferentially lo- the dimethylamino group to the “upper” face, thus enhanc-

cated below the pro-Rp face of the arene. Under thermo- ing the diastereoselectivity of the complexation (Figure 5b).

dynamic conditions, the Cr(CO)₃fragment coordinates to However, treatment of (S)-4 with tBuLi at –50 °C followed

the less crowded pro-S_Pface of the arene; under milder con- by quenching with ClSiMe₃afforded benzylamine (S)-29 in

ditions, it is delivered to the pro-Rp face due to temporary which lithiation has taken place at the most acidic site of

coordination by the amino group.

the molecule ortho to the methoxy group, instead.^[10b,28]

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4929

E. Alberico, A. Salzer et al.

FULL PAPER

As shown in Scheme 9, the presence of an SiMe₃group

improves the diastereoselectivity of the complexation

which, however, is still not satisfactory in the (S,Rp)-30 iso-

mer, the absolute configuration of which was unambigu-

ously assigned based on an X-ray crystallographic analysis

(Figure 6).

Scheme 10. Stereoselective route to (S,Rp)-28.

Complexation of the meta-substituted benzylamine (S)-5

to the Cr(CO)₃moiety gives rise to equal amounts of the

two possible diastereomers whatever the method of com-

plexation. The same approach used for (S)-4 was therefore

applied to (S)-5 by introduction of an SiMe₃group as steric

modulator. According to a previous report, metallation of

the related compound m-methoxy-N,N-dimethylbenzyla-

mine occurs exclusively at the position mutually ortho to

both the methoxy and the amine side chain.^[27]This was

explained by assuming that the combined ortho-directing

effects of both coordinating substituents and inductive elec-

tron withdrawal by the methoxy group serve to stabilize me-

tallation at the position mutually ortho to these two substit-

uents. In the case of (S)-5, optimisation of the metallation

conditions was carried out using ClPPh₂as electrophile

since this compound allows an easy monitoring of the reac-

tion course by ³¹P NMR spectroscopy (Scheme 11). Table 4

summarises the relative amounts of products formed when

lithiation was carried out using different RLi reagents un-

der different reaction conditions.

Scheme 9. Relative amounts of diastereomeric complexes obtained

in the complexation of (S)-29 under thermodynamic (A) and ki-

netic (B) conditions.

Figure 6. Displacement ellipsoids plot (PLATON) of one indepen-

dent molecule of (S,Rp)-30. Ellipsoids are shown at the 30% prob-

ability level. The H-atom attached to the stereogenic centre is

shown with arbitrary radius; other H-atoms have been omitted for

clarity.

Scheme 11. Lithiation and subsequent electrophilic quenching of

(S)-5.

Treatment of (S)-5 with tBuLi at –78 °C for 4 h in Et₂O

and subsequent quenching of the Li salt formed with

Complexation of (S)-31, in which a second SiMe₃group ClPPh₂did not provide the expected product (S)-33

has been introduced ortho to the benzylamino group by li- (Table 4, entry 5) Ϫ tBuPPh₂and unreacted (S)-5 were iso-

thiation and subsequent electrophilic quenching of (S)-29 lated instead. The bulkiness of the tBu^–anion might ham-

with ClSiMe₃, turned out to be highly selective for the de- per its access to the ortho position between the two coordi-

sired isomer (S,Rp)-32 (Scheme 10).^[24b]Notably, the (S,Rp) nating groups in (S)-5. However, the use of nBuLi both at

isomer is formed preferentially even under the rigorous con- –78 °C and –50 °C (Table 4, entries 1 and 2, respectively)

ditions of the thermal complexation due to hampered rota- was also unsuccessful. Formation of (S)-33 was observed

tion of the amino group around the benzylic bond. The when either sBuLi or tBuLi were used at –50 °C (Table 4,

SiMe₃groups are easily removed by treatment with Bu₄NF, entries 3 and 6, respectively). A further temperature in-

thereby opening a stereoselective route to (S,Rp)-28.

crease up to room temperature favoured formation of a side

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“Daniphos”-Type PʝP- and PʝN-Ligands

Table 4. Relative amounts of products formed in the lithiation of (S)-5 and subsequent quenching with ClPPh₂.

Entry

RLi

T [°C]

Deprotonation time [h]

Products^[a](relative amounts)

RPPh₂

(S)-33

other product

1

2

nBuLi

–78

–50

4

1

10

n.d.^[b]

n.d.

1

3

4

sBuLi

tBuLi

–50

room temp.

4

5

n.d.

1

0.5

3.5

5

–78

–50

4

24

4

1

3

n.d.

3

1

n.d.

1

n.d.

1

6

7^[c]

8

room temp.

1

[a] The ratio of the three products was calculated based on integration of the areas of the corresponding ³¹P NMR signals of the crude

31

reaction mixture: (S)-33: δ = –24 ppm; nBuPPh₂: δ = –17.8 ppm; sBuPPh₂: δ = –0.8 ppm; tBuPPh₂: δ _P= 16.8 ppm; other unidenti-

P

fied product: δ = 115 ppm. [b] n.d. = non detected. [c] The best reaction condi^Ptions are printed in bold.

³¹P

product (δ₃₁_P= 115 ppm) which, unfortunately, could not be

The optimised conditions were applied to the prepara-

identified (Table 4, entries 4 and 8, respectively). The best tion of (S)-34 (Scheme 12), although a large excess of

selectivity and yield for the desired ortho-substituted prod- ClSiMe₃had to be used and the electrophilic trapping fol-

uct (S)-33 were achieved by carrying out the metallation lowing metallation required ten days at room temperature.

with tBuLi at –50 °C for 24 h (Table 4, entry 7). The ident-

ity of this product was unambiguously assigned by X-ray

crystallographic analysis (Figure 7).

Scheme 12. Synthesis of (S)-34.

Complexation of (S)-34 to Cr(CO)₃was carried out

using Kündig’s reagent under mild conditions (Scheme 13).

The diastereoselectivity was 86% in favour of the (S,Rp)-35

isomer, as established from the NMR spectra of the crude

reaction mixture. This complex could be obtained as a sin-

gle diastereoisomer after flash chromatography [the other

diastereoisomer (S,Sp)-35 was not isolated]. Desilylation of

(S,Rp)-35 afforded complex (S,Sp)-36, the absolute config-

uration of which was confirmed by X-ray crystallographic

analysis (Figure 8).

(S,Sp)-37 was obtained by treatment of complex (S,Sp)-

28 with tBuLi at –78 °C for four hours and then with

ClPPh₂(Scheme 14). The site of ortholithiation was con-

firmed by an X-ray crystallographic analysis (Figure 9). The

NMR spectrum of the crude reaction mixture did not show

the formation of other regioisomers. This result is surpris-

ing because the OMe group and the CH₂NMe₂group have

a similar ortho-directing ability in [(η⁶-arene)Cr(CO)₃] com-

plexes.^[15c]Lithiation of the diastereomeric complex (S,Rp)-

28 with opposite planar chirality under analogous condi-

tions failed and was also unsuccessful at higher tempera-

tures or when using the less bulky base nBuLi. Directed

orthometallation adjacent to the OMe group might be ex-

Figure 7. Displacement ellipsoids plot (PLATON) of one indepen-

pected in (S,Rp)-28, as is the case for (S,Sp)-28, whereas

dent molecule of (S)-33. Ellipsoids are shown at the 30% prob-

lithiation adjacent to the CH(Me)NMe₂group is hampered

ability level. The H-atom attached to the stereogenic centre is

due to steric reasons. Removal of the ortho proton by a

shown with arbitrary radius; other H-atoms have been omitted for

clarity.

lithium base pre-coordinated by the amino group would

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4931

E. Alberico, A. Salzer et al.

FULL PAPER

Scheme 13. Stereoselective route to (S,Sp)-36.

Figure 8. Displacement ellipsoids plot (PLATON) of (S,Sp)-36. El-

lipsoids are shown at the 30% probability level. The H-atom at-

tached to the stereogenic centre is shown with arbitrary radius;

other H-atoms have been omitted for clarity.

Figure 9. Displacement ellipsoids plot (PLATON) of (S,Sp)-37. El-

lipsoids are shown at the 30% probability level. The H-atom at-

tached to the stereogenic centre is shown with arbitrary radius;

other H-atoms have been omitted for clarity.

force the benzylic methyl group below the plane of the ar-

ene, thereby causing unfavourable steric interaction with the

Cr(CO)₃unit (Figure 10).

Figure 10. Conformation of (S,Rp)-28 required for ortholithiation

assisted by the benzylic dimethylamino group.

the thermal complexation of (S)-4 with Cr(CO)₆. Thus, af-

ter treatment of this mixture with tBuLi and ClPPh₂,

(S,Sp)-37 and unreacted (S,Rp)-28 were easily separated

and purified by flash chromatography.

When complex (S,Sp)-36 was treated with tBuLi and

then with ClPPh₂, the ³¹P NMR spectrum of the crude re-

action mixture indicated the formation of two products in

a 10:1 ratio, as established from the areas of the corre-

Scheme 14. Lithiation of diastereomeric complexes (S,Sp)-28 and

(S,Rp)-28 and subsequent electrophilic quenching with ClPPh₂.

The latter complex fails to react (see text for experimental condi-

tions).

The inertness of (S,Rp)-28 towards ortho-functionali- sponding NMR signals [81 MHz, CDCl₃; (S,Sp)-38: δ =

sation was advantageously exploited to separate the dia- –16.74 ppm; 39: δ = –12.67 ppm; Scheme 15]. An X-ray

stereomeric mixture of (S,Sp)-28 and (S,Rp)-28 obtained in crystallographic analysis of the major product (S,Sp)-38

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“Daniphos”-Type PʝP- and PʝN-Ligands

indicated that lithiation had occurred ortho to the benzylic perature at which lithiation is carried out. Thus, at 0 °C and

amino group and para to the methoxy group (Figure 11). at room temperature (S,Sp)-38 is not detected and 39 and

The minor product 39 could not be isolated in a pure form. (S,Sp)-40 are formed in equal amounts. This might suggest

that 39 is the product derived from (S,Sp)-36 when the di-

methylamino group can overcome restricted rotation

Scheme 15. Lithiation of (S,Sp)-36 and subsequent electrophilic

quenching with ClPPh₂. * Yield of isolated products. ** The struc-

ture of complex 39 is only a proposal.

Scheme 16. Products arising from ortho-functionalisation of a 1:1

diastereomeric mixture of (S,Sp)-36 and (S,Rp)-36. * The structure

[a]

of complex 39 is only a proposal. Relative amounts of products

as inferred from the ³¹P NMR spectrum of the crude reaction mix-

[b]

ture.

Yield after flash chromatography; only this product was

isolated.

Figure 11. Displacement ellipsoids plot (PLATON) of one indepen-

dent molecule of (S,Sp)-38. Ellipsoids are shown at the 30% prob-

ability level. The H-atom attached to the stereogenic centre is

shown with arbitrary radius; other H-atoms have been omitted for

clarity.

Because (S,Rp)-36 was not available in a pure form, the

1:1 diastereomeric mixture of (S,Sp)-36 and (S,Rp)-36 was

lithiated instead (Scheme 16). A third product [(S,Sp)-40]

was detected along with (S,Sp)-38 and 39 in the ³¹P NMR

spectrum of the crude product [(S,Sp)-40: δ = –10.70 ppm].

This complex was isolated and its structure confirmed by

an X-ray crystallographic analysis (Figure 12). (S,Sp)-40 is

formed from (S,Rp)-36 by selective abstraction of the pro-

ton ortho to both substituents on the arene. The relative

Figure 12. Displacement ellipsoids plot (PLATON) of (S,Sp)-40.

Ellipsoids are shown at the 30% probability level. The H-atom at-

tached to the stereogenic centre is shown with arbitrary radius;

amounts of (S,Sp)-38, 39 and (S,Sp)-40 depend on the tem- other H-atoms have been omitted for clarity.

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4933

E. Alberico, A. Salzer et al.

FULL PAPER

General Methods

around the benzylic bond at higher temperature and the

base is delivered to the other ortho proton through chela-

tion by both substituents on the arene.

A. Methylation of Amines: Benzylamines were methylated accord-

ing to the Eschweiler–Clarke procedure with formic acid and form-

aldehyde.^[6]Formaldehyde (37% aqueous solution, d = 1.090,

3 equiv.) and formic acid (98% aqueous solution, d = 1.220,

5 equiv.) were added dropwise to the amine (1 equiv.) at 0 °C. The

solution was heated at 80 °C for the reported time, then cooled and

acidified with 10  HCl. The solution was extracted with diethyl

ether and then basified with 50% aqueous NaOH. The basic aque-

ous phase was extracted three times with diethyl ether and the com-

bined ether extracts were washed with water and dried with

MgSO₄. Diethyl ether was evaporated and the crude product finally

distilled under reduced pressure.

Some of the complexes containing PʝN ligands coordi-

nated to the Cr(CO)₃moiety have been successfully tested

by us in asymmetric transfer hydrogenation. The results of

these studies have been reported elsewhere.^[4]

Conclusions

The range of “Daniphos” ligands has been expanded to

include NʝP and PʝP ligands bearing a substituent R on

the arene of the [(η⁶-arene)Cr(CO)₃] unit, which might

serve to modulate the steric and electronic properties of the

donor atoms. The stereoselective synthetic strategy origi-

nally devised for the preparation of this class of ligands has

been successfully applied to their preparation. In the case

of NʝP ligands derived from 1,2- and 1,3-disubstituted

benzylamines, because the two faces of such amines are dia-

stereotopic and diastereomeric complexes arise from the co-

ordination of the Cr(CO)₃fragment to either of the two

faces, the synthetic plan has been adjusted by exploiting the

trimethylsilyl group as a temporary steric modulator in or-

der to access both complexes with high diastereoselectivity.

B. Synthesis of [(η⁶-Arene)Cr(CO)₃] Complexes by Thermolysis with

Cr(CO)₆: [(η⁶-arene)Cr(CO)₃] complexes were prepared according

to the Pauson–Mahaffy procedure.^[7]Cr(CO)₆(1.2 equiv.) and the

protected benzylamine (1 equiv.) were refluxed (bath temperature:

140 °C) in an 8:1 di-n-butyl ether/thf mixture ([Cr] = 0.36 ) for

the reported time. The solution was cooled and filtered through a

short pad of Celite on a sintered glass filter, which was then washed

with some additional solvent. The solvents were distilled off on a

rotary evaporator from a water bath held at 60 °C (an oil pump

was required to remove the solvents completely). The crude product

was purified by column chromatography and crystallised from suit-

able solvents.

C. Directed Orthometallation and Functionalisation of [(η⁶-arene)-

Cr(CO)₃] Complexes: The appropriate [(η⁶-arene)Cr(CO)₃] com-

plex (1 equiv.) was dissolved in dry diethyl ether ([Cr] = 0.05 ).

The solution was cooled to –78 °C and tert-butyllithium (1.7  in

pentane, 1.14 equiv.) was added dropwise with a syringe. After

1.5 h, chlorodiphenylphosphane (1.14 equiv.) was added dropwise.

The reaction mixture was warmed slowly to room temperature

overnight and then filtered through a short pad of Celite on a sin-

tered glass filter. The solvent was distilled off on a rotary evapora-

tor and the crude product purified by column chromatography.

Experimental Section

Materials and Methods: All reactions involving air- and moisture-

sensitive compounds, and their subsequent workup, were carried

out under nitrogen using Schlenk and syringe techniques. Reac-

tions were monitored by analytical TLC using either Merck silica

gel 60 F 254 or Merck aluminium oxide F 254 aluminium cards.

The chromatograms were visualized with UV light. Solutions of

crude reaction mixtures were filtered through a short bed of the

filter aid Fluka Celite 535. The solvent was then evaporated. Flash

chromatography of the crude products was performed either on

silica gel 60 [Merck; particle size: 0.063–0.200; pH 7.0 (0.5)] or alu-

minium oxide 90 II–III [Merck; particle size: 0.063–0.200; pH 9.0

(0.5)]. Solvents were dried and deoxygenated by standard pro-

cedures. NMR spectra were recorded with a Varian Mercury 200

spectrometer operating at 200 (for ¹H), 50 (for ¹³C) or 81 MHz (for

³¹P), a Varian Unity 300 spectrometer operating at 300 (for ¹H),

75.5 (for ¹³C) or 121.5 MHz (for ³¹P), a Varian Mercury Plus spec-

trometer operating at 400 (for ¹H), 100.5 (for ¹³C) or 162 MHz (for

³¹P), or a Varian Unity 500 spectrometer operating at 500 (for ¹H),

125 (for ¹³C) or 202 MHz (for ³¹P) at ambient temperature. Chemi-

cal shifts (δ) are given in ppm relative to TMS (¹H, ¹³C) or 85%

H₃PO₄as external standards (³¹P). IR spectra were recorded with

a Perkin–Elmer FT-IR Model 1720-X spectrometer. Optical rota-

tions were measured in 1-dm cells with a Perkin–Elmer Model 341

polarimeter at ambient temperature. Mass spectra were obtained

by electron impact (EI) or chemical ionisation (CI) with isobutane

with a Finnigan MAT 95 spectrometer. Elemental analyses were

performed with a Carlo Erba Strumentazione Element Analyzer

(Model 1106). Generous loans of chiral amines were kindly pro-

vided by BASF GmbH. [(η⁶-naphthalene)Cr(CO)₃]. was prepared

according to published procedure.^[9,26]All other chemicals were

purchased and used without further purification.

D. Replacement of NMe₂with Cl: The appropriate [(η⁶-arene)-

Cr(CO)₃] complex (1 equiv.) was dissolved in dry thf ([Cr] =

0.05 ). The solution was cooled to –40 °C and 1-chloroethyl chlo-

roformate (d = 1.312, 4 equiv.) was added dropwise. The reaction

mixture was warmed up to room temperature overnight. The

course of the reaction was monitored by ³¹P NMR spectroscopy

on a small sample of the crude reaction mixture dissolved in C₆D₆.

The solvent and unreacted 1-chloroethyl chloroformate were dis-

tilled off. The residue was redissolved in diethyl ether and the solu-

tion filtered through a short pad of Celite on a sintered glass filter

to eliminate the insoluble by-product [(CH₃)₂NC(O)CHClCH₃].

The crude product was purified by column chromatography after

removal of the solvent.

E. Replacement of Cl with PR₂: The appropriate [(η⁶-arene)Cr-

(CO)₃] complex (1 equiv.) was dissolved in dry acetone and HPR₂

(1.1 equiv.) was added. A suspension of TlPF₆(1.1 equiv.) in dry

acetone (final concentration of Cr in acetone = 0.05 ) was added

dropwise to this solution very slowly. A fine white precipitate con-

sisting of TlCl formed immediately. The solution was stirred at

room temperature overnight. NEt₃(1.5 mL per millimol of Cr) was

added, the solution stirred for a further 15 min and then filtered

through a short pad of Celite on a sintered glass filter to remove

TlCl. The solvent and excess NEt₃were distilled off and the crude

product purified by column chromatography.

(S)-N,N-Dimethyl-1-(p-tolyl)ethylamine [(S)-1]: This compound

was prepared according to general procedure A from formaldehyde

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“Daniphos”-Type PʝP- and PʝN-Ligands

(66.1 mL, 0.89 mol), formic acid (55.8 mL, 1.45 mol) and (S)-1-(p- (200 MHz, CDCl₃): δ = 1.30 (d, J = 6.6 Hz, 3 H, α-Me), 2.16 (s, 6

tolyl)ethylamine (40.0 g, 0.30 mol). The reaction mixture was

heated at 80 °C for 18 h. Distillation of the crude product under

reduced pressure gave the protected amine as a colourless oil. Yield

37.1 g (77%). ¹H NMR (500 MHz, C₆D₆): δ = 1.27 (d, J = 6.7 Hz,

3 H, α-Me), 2.12 (s, 6 H, NMe₂), 2.15 (s, 3 H, p-Me), 3.10 (q, J =

6.7 Hz, 1 H, α-CH), 7.04 (d, J = 7.6 Hz, 2 H, H_Ar), 7.25 (d, J =

7.9 Hz, 2 H, H_Ar) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 20.77 (α-

Me), 21.06 (p-Me), 43.34 (NMe₂), 65.92 (α-CH), 127.64 (C_Ar),

129.15 (C_Ar), 136.17 (C_Ar,ipso), 142.50 (C_Ar,ipso) ppm. MS (EI): m/z

(%) 163 (13) [M⁺], 148 (100) [M – Me], 132 (54) [M – NMe₂]. B.p.

H, NMe₂), 3.11 (q, J = 6.6 Hz, 1 H, α-CH), 3.78 (s, 3 H, OMe),

6.75–6.88 (m, 3 H, H_Ar), 7.20 (t, J = 8.1 Hz, 1 H, H_Ar) ppm. ¹³C

NMR (50 MHz, CDCl₃): δ = 20.35 (α-Me), 43.17 (NMe₂), 54.84

(OMe), 65.91 (α-CH), 111.97 (C_Ar), 112.63 (C_Ar) 119.60 (C_Ar),

128.84 (C_Ar), 145.76 (C_Ar,ipso), 159.30 (C_Ar,ipso) ppm.

(R)-N,N-Dimethyl-1-(p-anisyl)ethylamine [(R)-6]: This compound

was prepared according to general procedure A from formaldehyde

(54.0 mL, 0.72 mol), formic acid (45.0 mL, 1.17 mol) and (R)-1-(p-

methoxyphenyl)ethylamine (36.0 g, 0.24 mol). The reaction mixture

was heated at 80 °C for 13 h. Distillation of the crude product un-

der reduced pressure gave the protected amine as a colourless oil.

r.t.

(30 Torr): 115 °C. [α]_D= –61.4 (neat). C₁₁H₁₇N (163.26): calcd.

C 80.93, H 10.49, N 8.58; found C 80.40, H 10.27, N 9.03.

1

Yield 20.7 g (48%). H NMR (500 MHz, C₆D₆): δ = 1.27 (d, J =

(S)-N,N-Dimethyl-1-(p-tert-butylphenyl)ethylamine [(S)-2]: This 6.7 Hz, 3 H, α-Me), 2.12 (s, 6 H, NMe₂), 3.10 (q, J = 6.7 Hz, 1 H,

compound was prepared according to general procedure A by

methylation of (S)-1-(4-tert-butylphenyl)ethylamine (10.00 g,

56.5 mmol) with formaldehyde (12.8 mL, 169.5 mmol) and formic

acid (10.6 mL, 282.5 mmol). The crude product was purified by

column chromatography (aluminium oxide; diethyl ether/hexane =

1:2) and the protected amine was isolated as a colourless oil. Yield

9.70 g (84%). ¹H NMR (200 MHz, CDCl₃): δ = 1.30 (s, 9 H, p-

tBu), 1.35 (d, J = 6.8 Hz, 3 H, α-Me), 2.17 (s, 6 H, NMe₂), 3.22

(q, J = 6.8 Hz, 1 H, α-CH), 7.19 (d, J = 8.3 Hz, 2 H, H_Ar), 7.31

(d, J = 8.3 Hz, 2 H, H_Ar) ppm. ¹³C NMR (125 MHz, CDCl₃): δ =

25.05 (α-Me), 31.38 (p-CMe₃), 34.46 (p-CMe₃), 43.40 (NMe₂),

50.98 (α-CH), 125.43 (C_Ar), 125.48 (C_Ar), 143.78 (C_Ar,ipso), 149.90

(C_Ar,ipso) ppm.

α-CH), 3.34 (s, 3 H, OMe), 6.82 (d, J = 8.9 Hz, 2 H, H_Ar), 7.25 (d,

J = 8.2 Hz, 2 H, H_Ar) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 20.65

(α-Me), 43.26 (NMe₂), 54.73 (α-CH), 65.45 (OMe), 113.90 (C_Ar),

128.63 (C_Ar), 137.34 (C_Ar,ipso), 159.05 (C_Ar,ipso) ppm. MS (EI): m/z

(%) 179 (13) [M⁺], 164 (100) [M – Me], 135 (35) [M – NMe₂], 105

(21) [M – NMe₂– OMe]. B.p. (0.5 Torr): 68 °C. [α]_D= +55.8

(neat). C₁₁H₁₇NO (179.26): calcd. C 73.70, H 9.56, N 7.81; found

C 73.65, H 9.00, N 8.40.

r.t.

[{η⁶-(S)-N,N-Dimethyl-1-(p-tolyl)ethylamine}Cr(CO)₃] [(S)-7]: This

complex was prepared from Cr(CO)₆(24.3 g, 110.0 mmol) and (S)-

1 (15.0 g, 92.0 mmol) in an 8:1 di-n-butyl ether/thf mixture

(327 mL) according to general procedure B. The reaction mixture

was refluxed for 60 h. The crude product was purified by column

chromatography over aluminium oxide using diethyl ether as the

sole eluent (R_f= 0.74). The yellow solid was crystallised from

dichloromethane/hexane at –30 °C. Yield 19.1 g (69%). ¹H NMR

(500 MHz, C₆D₆): δ = 1.08 (d, J = 6.7 Hz, 3 H, α-Me), 1.59 (s, 3

H, p-Me), 1.88 (s, 6 H, NMe₂), 3.07 (q, J = 6.7 Hz, 1 H, α-CH),

4.33 (d, J = 6.6 Hz, 1 H, H_Ar), 4.39 (d, J = 6.4 Hz, 1 H, H_Ar), 4.87

(d, J = 6.4 Hz, 1 H, H_Ar), 5.02 (d, J = 6.6 Hz, 1 H, H_Ar) ppm. ¹³C

(R)-N,N-Dimethyl-1-(p-chlorophenyl)ethylamine [(R)-3]: This com-

pound was prepared according to general procedure A from form-

aldehyde (44.0 mL, 0.59 mol), formic acid (37.0 mL, 0.96 mol) and

(R)-1-(p-chlorophenyl)ethylamine (30.5 g, 0.20 mol). The reaction

mixture was heated at 80 °C for 38 h. Distillation of the crude prod-

uct under reduced pressure gave the protected amine as a colourless

1

oil. Yield 28.8 g (80%) H NMR (500 MHz, C₆D₆): δ = 1.09 (d, J

= 6.7 Hz, 3 H, α-Me), 2.00 (s, 6 H, NMe₂), 2.92 (q, J = 6.7 Hz, 1 NMR (125 MHz, C₆D₆): δ = 13.26 (α-Me), 19.91 (p-Me), 40.72

H, α-CH), 7.02 (m, J = 8.5 Hz, 2 H, H_Ar), 7.13 (m, J = 7.9 Hz, 2

H, H_Ar) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 20.34 (α-Me), 43.09

(NMe₂), 65.28 (α-CH), 128.58 (C_Ar), 128.97 (C_Ar), 132.56 (C_Ar,ipso),

(NMe₂), 61.33 (α-CH), 91.28 (C_Ar), 92.09 (C_Ar), 93.08 (C_Ar), 97.27

(C_Ar), 109.29 (C_Ar,ipso), 109.63 (C_Ar,ipso), 233.92 (CO) ppm. MS

(EI): m/z (%) 299 (16) [M⁺], 255 (100) [M – NMe₂], 243 (31) [M –

143.98 (C_Ar,ipso) ppm. MS (EI): m/z (%) 183 (12) [M⁺], 168 (100) 2 CO], 215 (5) [M – 3 CO]. [α]_D= –18.7 (c = 2.01, CHCl₃). IR

r.t.

[M – Me], 132 (54) [M – NMe₂]. B.p. (0.1 Torr): 54 °C. [α]_D

=

(CHCl₃): ν_CO= 1959, 1876 cm^–1. C₁₄H₁₇CrNO₃(299.29): calcd. C

+60.1 (neat).

56.18, H 5.72, N 4.68; found C 56.02, H 5.68, N 4.73.

(S)-N,N-Dimethyl-1-(o-anisyl)ethylamine [(S)-4]: This compound

was prepared according to general procedure A by methylation of

(S)-1-(2-methoxyphenyl)ethylamine (50.00 g, 0.33 mol) with form-

aldehyde (75 mL, 0.99 mol) and formic acid (62.5 mL, 1.66 mol).

The crude product was purified by column chromatography (alu-

minium oxide; diethyl ether/hexane = 1:2) and the protected amine

was isolated as a light yellow oil. Yield 51.60 g (87%) ¹H NMR

(500 MHz, CDCl₃): δ = 1.31 (d, J = 6.7 Hz, 3 H, α-Me), 2.21 (s, 6

H, NMe₂), 3.80 (s, 3 H, OMe), 3.84 (q, J = 6.7 Hz, 1 H, α-CH),

[{η⁶-(S)-N,N-Dimethyl-1-(p-tert-butylphenyl)ethylamine}Cr(CO)₃]

[(S)-8]: This complex was prepared from Cr(CO)₆(12.50 g,

56.78 mmol) and (S)-2 (9.70 g, 47.32 mmol) in an 8:1 mixture of

di-n-butyl ether and thf (169 mL) according to general procedure

B. The reaction mixture was refluxed for 55 h. The crude product

was purified by column chromatography over aluminium oxide

using diethyl ether as eluent. A yellow microcrystalline product was

obtained after recrystallisation from diethyl ether/hexane at –30 °C.

1

Yield 14.31 g (89%). H NMR (500 MHz, CDCl₃): δ = 1.27 (br. s,

6.86 (d, J = 7.6 Hz, 1 H, H_Ar), 6.94 (t, J = 7.6 Hz, 1 H, H_Ar), 7.19 12 H, p-tBu, α-Me), 2.21 (s, 6 H, NMe₂), 3.49 (q, J = 6.7 Hz, 1 H,

(t, J = 7.6 Hz, 1 H, H_Ar), 7.39 (d, J = 7.6 Hz, 1 H, H_Ar) ppm. ¹³C

NMR (50 MHz, C₆D₆): δ = 21.16 (α-Me), 43.81 (NMe₂), 54.94

(OMe), 57.89 (α-CH), 110.63 (C_Ar), 121.01 (C_Ar) 127.49 (C_Ar),

128.00 (C_Ar), 133.84 (C_Ar,ipso), 157.09 (C_Ar,ipso) ppm.

α-CH), 5.14–5.70 (br. m, 4 H, H_Ar) ppm. ¹³C NMR (125 MHz,

CDCl₃): δ = 11.68 (α-Me), 31.42 (p-CMe₃), 34.22 (p-CMe₃), 41.12

(NMe₂), 61.39 (α-CH), 90.21 (C_Ar), 91.65 (C_Ar), 92.31 (C_Ar), 94.33

(C_Ar), 112.84 (C_Ar,ipso), 123.12 (C_Ar,ipso), 233.74 (CO) ppm. IR (hex-

ane): ν_CO= 1969, 1899 cm^–1.

(S)-N,N-Dimethyl-1-(m-anisyl)ethylamine [(S)-5]: This compound

was prepared according to general procedure A by methylation of

(S)-1-(3-methoxyphenyl)ethylamine (10.00 g, 66.20 mmol) with

formaldehyde (15 mL, 0.20 mol) and formic acid (12.5 mL,

0.33 mol). The crude product was purified by column chromatog-

raphy (Al₂O₃; diethyl ether/hexane = 1:2) and the protected amine

was isolated as a light yellow oil. Yield 9.36 g (79%). ¹H NMR

[{η⁶-(R)-N,N-Dimethyl-1-(p-chlorophenyl)ethylamine}Cr(CO)₃]

[(R)-9]: This complex was prepared from Cr(CO)₆(21.6 g,

98.0 mmol) and (R)-3 (15.0 g, 82.0 mmol) in an 8:1 di-n-butyl ether/

thf mixture (281 mL) according to general procedure B. The reac-

tion mixture was refluxed for 62 h. The product was purified by

flash chromatography (aluminium oxide; diethyl ether, R_f= 0.73)

Eur. J. Inorg. Chem. 2007, 4923–4945

www.eurjic.org

4935

E. Alberico, A. Salzer et al.

FULL PAPER

and recrystallisation from a layered mixture of di-n-butyl ether and

chlorodiphenylphosphane (7.38 g, 33.43 mmol) in dry diethyl ether

hexane at –30 °C. Yield yellow crystals (43%). ¹H NMR (500 MHz, (400 mL). The crude product was purified by column chromatog-

C₆D₆): δ = 0.85 (d, J = 6.8 Hz, 3 H, α-Me), 1.78 (s, 6 H, NMe₂),

2.88 (q, J = 6.8 Hz, 1 H, α-CH), 4.61 (br. d, J = 6.7 Hz, 1 H, H_Ar),

4.64 (br. d, J = 6.4 Hz, 1 H, H_Ar), 4.68 (br. d, J = 6.4 Hz, 1 H,

raphy (aluminium oxide; diethyl ether). Yield yellow crystals 4.59 g

(78%). H NMR (200 MHz, CDCl₃): δ = 1.26 (br. s, 12 H, p-tBu,

1

α-Me), 1.89 (s, 6 H, NMe₂), 4.61 (m, J = 6.1 Hz, 1 H, α-CH), 5.21

H_Ar), 4.81 (br. d, J = 6.1 Hz, 1 H, H_Ar) ppm. ¹³C NMR (125 MHz, (dd, J = 6.6, J = 3.4 Hz, 1 H, H_Ar), 5.34 (s, 1 H, H_Ar), 5.78 (dd, J

C₆D₆): δ = 13.32 (α-Me), 40.62 (NMe₂), 60.92 (α-CH), 89.80 (C_Ar),

90.34 (C_Ar), 91.93 (C_Ar), 95.92 (C_Ar), 108.34 (C_Ar,ipso), 112.89

= 6.6, J = 1.2 Hz, 1 H, H_Ar), 7.39–7.52 (m, 10 H, H_PAr) ppm. ¹³C

NMR (125 MHz, CDCl₃): δ = 5.78 (α-Me), 31.06 (p-CMe₃), 33.81

(p-CMe₃), 37.96 (NMe₂), 58.29 (d, J = 13.7 Hz, α-CH),88.60 (C_Ar),

92.76 (C_Ar), 99.45 (C_Ar), 104.11 (d, J = 24.5 Hz, C_Ar,ipso), 119.89

(C_Ar,ipso), 120.14 (C_Ar,ipso), 127.79–138.20 (C_PAr), 233.07 (CO) ppm.

³¹P NMR (121.5 MHz, CDCl₃): δ = –16.79 ppm. IR (CH₂Cl₂): ν_CO

= 1970, 1904 cm^–1.

(C_Ar,ipso), 232.28 (CO) ppm. MS (CI, isobutane): m/z (%) 320 (1)

r.t.

[M + H], 275 (100) [M – NMe₂], 263 (18) [M – 2 CO]. [α]_D

=

.

+9.7 (c = 1.18, CHCl₃). IR (CHCl₃): ν_CO= 1981, 1888 cm^–1

C₁₃H₁₄ClCrNO₃(319.71): calcd. C 48.84, H 4.41, N 4.38; found C

50.06, H 4.58, N 4.30.

[{η⁶-(R)-N,N-Dimethyl-1-(p-anisyl)ethylamine}Cr(CO)₃] [(R)-10]:

This complex was prepared from Cr(CO)₆(22.1 g, 0.10 mol) and

(R)-6 (15.0 g, 0.84 mol) in an 8:1 di-n-butyl ether/thf mixture

(281 mL) according to general procedure B. The crude product was

purified by column chromatography (aluminium oxide; diethyl

ether). R_f= 0.73 Crystallisation from dichloromethane/hexane at

–30 °C afforded the product as yellow crystals. Yield 22.3 g (85%).

¹H NMR (500 MHz, C₆D₆): δ = 1.04 (d, J = 6.7 Hz, 3 H, α-Me),

1.90 (s, 6 H, NMe₂), 2.96 (q, J = 6.7 Hz, 1 H, α-CH), 2.99 (s, 3 H,

OMe), 4.42 (d, J = 6.4 Hz, 1 H, H_Ar), 4.45 (d, J = 6.4 Hz, 1H H_Ar),

5.03 (d, J = 6.4 Hz, 1 H, H_Ar), 5.12 (d, J = 6.4 Hz, 1 H, H_Ar) ppm.

¹³C NMR (125 MHz, C₆D₆): δ = 14.43 (α-Me), 40.87 (NMe₂),

55.09 (OMe), 61.22 (α-CH), 76.25 (C_Ar), 77.71 (C_Ar), 93.60 (C_Ar),

97.70 (C_Ar), 105. 70 (C_Ar,ipso), 143.34 (C_Ar,ipso), 233.86 (CO) ppm.

MS: m/z (%) 315 (12) [M⁺], 271 (100) [M – NMe₂], 259 (22) [M –

Lithiation of [{η⁶-(R)-N,N-Dimethyl-1-(p-anisyl)ethylamine}Cr-

(CO)₃]: Following general procedure C, lithiation of (R)-10 (4.26 g,

13.5 mmol) with tert-butyllithium (1.7  in pentane; 9.5 mL,

16.2 mmol), followed by addition of chlorodiphenylphosphane

(3.58 g, 16.2 mmol), produced a mixture of products. Column

chromatography (aluminium oxide; hexane/diethyl ether 4:1Ǟ1:4)

gave (R,Sp)-15, (R,Rp)-13 and (R)-14M/(S)-14m in that order.

[{η⁶-(R,Sp)-N,N-Dimethyl-1-[2,5-bis(diphenylphosphanyl)-4-

methoxyphenyl]ethylamine}Cr(CO)₃] [(R,Sp)-15]: Yield orange crys-

tals (1.92 g, 21%). R_f= 0.73 (aluminium oxide; diethyl ether/hex-

1

ane, 1:1). H NMR (500 MHz, C₆D₆): δ = 0.66 (d, J = 6.7 Hz, 3

H, α-Me), 1.55 (s, 6 H, NMe₂), 2.80 (s, 3 H, OMe), 4.22 (m, J =

6.7 Hz, 1 H, α-CH), 4.91 (d, J = 2.44 Hz, 1 H, H_Ar), 5.16 (t, J =

2.44 Hz, 1 H, H_Ar), 7.01–7.16 (m, 12 H, m/p-H_P1Ar, m/p-H_P2Ar),

7.36 (m, J = 7.33 Hz, 2 H, o-H_PAr), 7.49 (m, J = 7.33 Hz, 2 H, o-

H_PAr), 7.69 (m, J = 7.33 Hz, 2 H, o-H_PAr), 7.74 (m, J = 7.33 Hz, 2

H, o-H_PAr) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 6.93 (α-Me),

37.98 (NMe₂), 55.44 (OMe), 58.61 (d, J_C,P= 13.7 Hz, α-CH), 80.27

r.t.

3 CO]. [α]_D= –9.5 (c = 1.00, CHCl₃). IR (CHCl₃): ν_CO= 1970,

1873 cm^–1. C₁₄H₁₇CrNO₄(315.29): calcd. C 53.33, H 5.43, N 4.44;

found C 53.21, H 5.41, N 4.47.

[{η⁶-(S,Rp)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-4-tolyl]ethyl- (d, J_C,P= 3.3 Hz, C_Ar), 93.87 (d, J_C,P= 25.7 Hz, C_Ar,ipso), 95.19 (d,

amine}Cr(CO)₃] [(S,Rp)-11]: This complex was prepared according

to general procedure C by lithiation of (S)-7 (6.0 g, 20.0 mmol)

with tert-butyllithium (1.7  in pentane; 13 mL, 22.8 mmol) and

J_C,P= 3.3 Hz, C_Ar), 108.73 (d, J_C,P= 27.9 Hz, C_Ar,ipso), 112.43 (d,

J_C,P= 18.1 Hz, C_Ar,ipso), 128.28 (C_PAr), 128.72 (d, J_C,P= 6.0 Hz,

C_PAr), 128.84 (d, J_C,P= 6.6 Hz, C_PAr), 128.98 (d, J_C,P= 7.1 Hz,

treatment of the lithiated species with chlorodiphenylphosphane C_PAr), 129.65 (C_PAr), 129.90 (C_PAr), 132.45 (d, J_C,P= 20.2 Hz,

(5.0 g, 22.8 mmol) in dry diethyl ether (400 mL). The crude product

was purified by column chromatography (silica gel; diethyl ether/

C_PAr), 133.26 (d, J_C,P= 20.8 Hz, C_PAr), 134.81 (d, J_C,P= 15.4 Hz,

_PAr), 135.55 (d, J_C,P= 21.9 Hz, C_PAr), 135.72 (d, J_C,P= 20.9 Hz,

C

hexane, 1:4, R_f= 0.44). Yield yellow crystals 8.7 g (90%). ¹H NMR C_PAr), 136.42 (d, J_C,P= 16.5 Hz, C_PAr), 137.52 (d, J_C,P= 14.3 Hz,

(500 MHz, C₆D₆): δ = 0.79 (d, J = 6.7 Hz, 3 H, α-Me), 1.46 (s, 3

H, p-Me), 1.55 (s, 6 H, NMe₂), 4.52 (m, J = 6.4 Hz, 1 H, α-CH), C_PAr), 233.18 (CO) ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –14.23

4.66 (dd, J = 6.1, J = 3.2 Hz, 1 H, H_Ar), 4.74 (d, J = 6.1 Hz, 1 H, (P_o-CHMeNMe), –17.69 (P_o-OMe) ppm. MS (CI, isobutane): m/z (%)

C_PAr), 139.00 (d, J_C,P= 6 Hz, C_Ar,ipso), 143.39 (d, J_C,P= 9.9 Hz,

2

H_Ar), 4.91 (s, 1 H, H_Ar), 7.03–7.13 (m, 6 H, m/p-H_PAr), 7.27 (m, J 684 (4) [M + 1], 599 (6) [M – 3 CO], 548 (38) [M – 3 CO – Cr],

= 7.94 Hz, 2 H, o-H_PAr), 7.61 (m, J = 7.02 Hz, 2 H, o-H_PAr) ppm. 455 (29) [M + H – NMe₂– PPh₂], 364 (100) [M + H – 3 CO – Cr –

r.t.

¹³C NMR (125 MHz, C₆D₆): δ = 6.02 (α-Me), 19.75 (p-Me), 37.81 PPh₂], 319 (41) [M + H – 3 CO – Cr – PPh₂– H NMe₂]. [α]_D

(NMe₂), 58.56 (d, J_C,P= 14.3 Hz, α-CH), 88.75 (d, J_C,P= 3.8 Hz,

=

–358.3 (c = 0.24, CHCl₃). IR (CHCl₃): ν_CO= 1962, 1893 cm^–1.

3

α-CH), 94.13 (C_Ar), 101.72 (d, J_C,P= 3.9 Hz, C_Ar), 105 80 (d, J_C,PC₃₈H₃₅CrNO₄P₂(683.64): calcd. C 66.76, H 5.16, N 2.05; found C

= 1.7 Hz, C_Ar,ipso), 107.00 (d, J_C,P= 25.7 Hz, C_Ar,ipso), 118.23 (d,

J_C,P= 19.2 Hz, C_Ar,ipso), 128.07 (d, J_C,P= 1.6 Hz, C_PAr), 128.67 (d,

J_C,P= 6.0 Hz, C_PAr), 129.26 (C_PAr), 132.43 (d, J_C,P= 20.3 Hz,

C_PAr), 135.05 (d, J_C,P= 19.7 Hz, C_PAr), 137.29 (d, J_C,P= 15.9 Hz,

C_PAr), 138.58 (d, J_C,P= 6.0 Hz, C_PAr), 233.28 (CO) ppm. ³¹P NMR

(81 MHz, C₆D₆): δ = –14.32 ppm. MS (CI, isobutane): m/z (%) 484

(15) [M + 1], 439 (100) [M – NMe₂], 399 (34) [M – 3 CO], 348 (18)

66.63, H 5.24, N 2.53.

[{η⁶-(R,Rp)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-4-

methoxyphenyl]ethylamine}Cr(CO)₃] [(R,Rp)-13]: Yield yellow crys-

tals (2.02 g, 30%). R_f= 0.64 (aluminium oxide; diethyl ether/hex-

1

ane, 1:1). H NMR (500 MHz, C₆D₆): δ = 0.82 (d, J = 6.7 Hz, 3

H, α-Me), 1.54 (s, 6 H, NMe₂), 2.87 (s, 3 H, OMe), 4.41 (m, J =

6.4 Hz, 1 H, α-CH), 4.58 (dd, J = 6.7, J = 2.4 Hz, 1 H, H_Ar) 4.80

(dd, J = 7.0, J = 3.0 Hz, 1H H_Ar), 5.10 (d, J = 2.1 Hz, 1 H, H_Ar),

6.68–7.11 (m, 6 H, m/p-H_PAr), 7.29 (m, J = 7.9 Hz, 2 H, o-H_PAr),

7.66 (m, J = 7.0 Hz, 2 H, o-H_PAr) ppm. ¹³C NMR (125 MHz,

C₆D₆): δ = 6.93 (α-Me), 37.89 (NMe₂), 55.27 (OMe), 58.40 (d, J_C,P

= 14.3 Hz, α-CH), 76.78 (C_Ar), 88.97 (d, J_C,P= 3.3 Hz, C_Ar), 89.51

(d, J_C,P= 3.8 Hz, C_Ar), 108.3 (d, J_C,P= 27.4 Hz, C_Ar,ipso), 114.39

r.t.

[M – 3 CO – Cr]. [α]_D= +452.3 (c = 1.09, CHCl₃). IR (CHCl₃):

ν_CO= 1965, 1894 cm^–1. C₂₆H₂₆CrNO₃P (483.47): calcd. C 64.59, H

5.42, N 2.90; found C 64.58, H 5.31, N 2.77.

[{η⁶-(S,Rp)-N,N-Dimethyl-1-[4-tert-butyl-2-(diphenylphosphanyl)-

phenyl]ethylamine}Cr(CO)₃] [(S,Rp)-12]: This complex was pre-

pared according to general procedure C by lithiation of (S)-8

(10.00 g, 29.33 mmol) with tert-butyllithium (1.7  in pentane;

19.70 mL, 33.43 mmol) and treatment of the lithiated species with

(d, J_C,P= 18.6 Hz, C C_Ar,ipso), 127.91 (C_PAr), 128.07 (d, J_C,P

7.7 Hz, C_PAr), 128.71 (d, J_C,P= 6.0 Hz, C_PAr), 129.47 (C_PAr), 132.53

=

4936

www.eurjic.org

Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

(d, J_C,P= 20.9 Hz, C_PAr), 135.17 (d, J_C,P= 19.7 Hz, C_PAr), 136.67

(d, J_C,P= 15.9 Hz, C_PAr), 138.45 (d, J_C,P= 6.0 Hz, C_PAr), 140.25

(d, J_C,P= 2.7 Hz, C_Ar,ipso), 233.45 (d, J_C,P= 1.7 Hz, CO) ppm. ³¹P

NMR (81 MHz, C₆D₆): δ = –14.22 ppm. MS (CI, isobutane): m/z

(%) 500 (4) [M + 1], 455 (100) [M – NMe₂], 415 (43) [M – 3 CO],

C_Ar,ipso), 127.91 (C_PAr), 128.19 (C_PAr), 128.30 (C_PAr), 128.90 (d, J_C,P

= 6.1 Hz, C_PAr), 129.73 (C_PAr), 132.30 (d, J_C,P= 20.8 Hz, C_PAr),

135.01 (d, J_C,P= 20.3 Hz, C_PAr), 136.50 (d, J_C,P= 14.8 Hz, C_PAr),

137.95 (d, J_C,P= 6.0 Hz, C_PAr), 231.61 (CO) ppm. ³¹P NMR

(81 MHz, C₆D₆): δ = –14.41 ppm. MS (CI, isobutane): m/z (%) 504

364 (45) [M – 3 CO – Cr], 319 (45) [M – 3 CO – Cr – HNMe₂]. (21) [M + H], 459 (100) [M – NMe₂], 419 (46) [M – 3 CO], 368

r.t.

[α]_D= –480.9 (c = 0.22, CHCl₃). IR (CHCl₃): ν_CO= 1965, (15) [M – 3 CO – Cr]. [α]_D= –401.9 (c = 0.21, CHCl₃). IR

1882 cm^–1. C₂₆H₂₆CrNO₄P (499.46): calcd. C 62.52, H 5.25, N

2.80; found C 62.08, H 5.01, N 2.97.

(CHCl₃): ν_CO= 1976, 1912 cm^–1. C₂₅H₂₃ClCrNO₃P (503.87): calcd.

C 59.59, H 4.60, N 2.78; found C 60.56, H 4.81, N 2.74.

[{η⁶-(R,Rp)-N,N-Dimethyl-1-[4-chloro-2-(diphenylphosphanyl)phen-

yl]ethylamine}Cr(CO)₃] [(R,Rp)-16]: Yield yellow crystals (0.53 g).

The yield is only indicative as this fraction also contained the other

diastereoisomer and traces of the product derived from metal–halo-

gen exchange. Attempts to further purify the product by means of

crystallisation failed. Only the ¹H and ³¹P NMR spectra are re-

[{η⁶-(R,Rp)-N,N-Dimethyl-1-(3-(diphenylphosphanyl)-4-methoxy-

phenyl)ethylamine}Cr(CO)₃] [(R)-14M] and [{η⁶-(R,Sp)-N,N-Di-

methyl-1-(3-(diphenylphosphanyl)-4-methoxyphenyl)ethyl-

amine}Cr(CO)₃] [(S)-14m]: Yield yellow crystals (1.98 g, 30%). R_f

= 0.15 (aluminium oxide; diethyl ether/hexane, 1:1) The two com-

pounds eluted as a single fraction. Further attempts to separate the

two diastereoisomers by column chromatography failed.

1

ported. R_f= 0.42 (aluminium oxide; hexane/diethyl ether, 2:1). H

1

NMR (500 MHz, C₆D₆): δ = 0.87 (d, J = 6.8 Hz, 3 H, α-Me), 2.00

(s, 3 H, NMe₂), 3.57 (m, 1 H, α-CH), 4.86 (dd, J = 4.9, J = 1.2 Hz,

1 H, H_Ar), 5.06 (dd, J = 1.7, J = 1.0 Hz, 1 H, H_Ar), 5.21 (dd, J =

6.8, J = 2.4 Hz, 1 H, H_Ar), 6.69 (m, 4 H, H_PAr), 7.02–7.05 (m, 6

H, H_PAr), 7.20–7.35 (m, 2 H, H_PAr), 7.51–7.65 (m, 2 H, H_PAr) ppm.

³¹P NMR (81 MHz, C₆D₆): δ = –17.53 ppm.

[{η⁶-(R)-N,N-Dimethyl-1-[4-(diphenylphosphanyl)phenyl]ethyl-

amine}Cr(CO)₃] [(R)-17]: Yield yellow crystals (1.30 g, 18%). R_f=

0.30 (aluminium oxide; hexane/diethyl ether, 3:2). ¹H NMR

(500 MHz, C₆D₆): δ = 0.92 (d, J = 7.0 Hz, 3 H, α-Me), 1.89 (s, 6

H, NMe₂), 3.25 (q, J = 7.0 Hz, 1 H, α-CH), 4.40 (dd, J = 6.4, J =

1.5 Hz, 1 H, H_Ar), 4.75 (m, J = 6.8 Hz, 1 H, H_Ar), 4.84 (ddd, J =

6.4, J = 4.2, J = 1.2 Hz, 1 H, H_Ar), 5.00 (ddd, J = 6.6, J = 5.4, J

= 1.5 Hz, 1 H, H_Ar), 7.04–7.13 (m, 6 H, m/p-H_PAr), 7.39 (m, J =

(R)-14M: H NMR (500 MHz, C₆D₆): δ = 0.97 (d, J = 6.71 Hz, 3

H, α-Me), 1.88 (s, 6 H, NMe₂), 2.69 (q, J = 6.71 Hz, 1 H, α-CH),

2.91 (s, 3 H, OMe), 4.15 (dd, J = 6.71, J = 3.35 Hz, 1 H, H_Ar),

5.02 (t, J = 1.67 Hz, 1 H, H_Ar), 5.13 (dd, J = 6.71, J = 1.67 Hz, 1

H, H_Ar), 7.01–7.10 (m, 6 H, m/p-H_PAr), 7.43 (m, J = 7.33 Hz, 2 H,

o-H_PAr), 7.59 (m, J = 7.33 Hz, 2 H, o- H_PAr) ppm. ¹³C NMR

(125 MHz, C₆D₆): δ = 15.60 (α-Me), 41.04 (NMe₂), 55.63 (OMe),

61.33 (α-CH), 71.61 (C_Ar), 92.66 (d, J_C,P= 24.6 Hz, C_Ar,ipso), 92.84

(C_Ar), 101.73 (C_Ar), 104.753 (C_Ar,ipso), 128.29 (C_PAr), 128.79 (C_PAr),

128.98 (C_PAr), 133.22 (d, J_C,P= 20.3 Hz, C_PAr), 134.92 (d, J_C,P

14.8 Hz,, C_PAr), 135.26 (d, J_C,P= 20.9 Hz, C_PAr), 137.44 (d, J_C,P

=

14.8 Hz, C_PAr), 146.14 (d, J_C,P= 13.7 Hz, C_Ar,ipso), 233.11 (CO)

ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –18.57 ppm.

(R)-14m: ¹H NMR (500 MHz, C₆D₆): δ = 0.87 (d, J = 6.8 Hz, 3

H, α-Me), 1.92 (s, 6 H, NMe₂), 2.86 (q, J = 6.7 Hz, 1 H, α-CH),

2.91 (s, 3 H, OMe), 4.12 (dd, J = 6.7, J = 3.4 Hz, 1 H, H_Ar), 5.10

(t, J = 1.7 Hz, 1 H, H_Ar), 5.25 (dd, J = 6.7, J = 1.7 Hz, 1 H, H_Ar),

7.01–7.10 (m, 6 H, m/p-H_PAr), 7.43 (m, 2 H, o-H_PAr), 7.59 (m, J =

7.3 Hz, 2 H, o-H_PAr) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 14.50

(α-Me), 40.87 (NMe₂), 55.58 (OMe), 61.23 (α-CH), 71.84 (C_Ar),

91.83 (d, J_C,P= 24.1 Hz, C_Ar,ipso), 96.72 (C_Ar), 97. 34 (C_Ar), 128.77

(d, J_C,P= 6.6 Hz, C_PAr), 128.98 (d, J_C,P= 9.9 Hz, C_PAr), 129.81

(C_PAr), 133.09 (d, J_C,P= 20.3 Hz, C_PAr), 135.06 (d, J_C,P= 14.8 Hz,

C_PAr), 135.33 (d, J_C,P= 21.4 Hz, C_PAr), 137.54 (d, J_C,P= 14.8 Hz,

C_PAr), 146.26 (d, J_C,P= 15.3 Hz, C_Ar), 233.26 (CO) ppm. ³¹P NMR

(81 MHz, C₆D₆): δ = –17.92 ppm. The absolute configuration of

the two diastereomers has not been assigned.

7.3, J = 1.5 Hz, 2 H, o-H_PAr), 7.45 (m, J = 7.3 Hz, 2 H, o-H_PAr

)

ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 10.89 (α-Me), 40.55

(NMe₂), 61.04 (α-CH), 89.55 (d, J_C,P= 3.3 Hz, C_Ar), 93.91 (d, J_C,P

= 6.0 Hz, C_Ar), 97.24 (d, J_C,P= 11.5 Hz, C_Ar), 98.42 (d, J_C,P

=

19.2 Hz, C_Ar), 102.36 (d, J_C,P= 19.2 Hz, C_Ar,ipso), 113.71 (C_Ar,ipso),

128.94 (d, J_C,P= 1.1 Hz, C_PAr), 129.00 (d, J_C,P= 1.1 Hz, C_PAr),

129.58 (d, J_C,P= 12.1 Hz, C_PAr), 134.13 (d, J_C,P= 10.9 Hz, C_PAr),

134.29 (d, J_C,P= 11.0 Hz, C_PAr), 135.76 (d, J_C,P= 12.6 Hz, C_PAr),

136.11 (d, J_C,P= 12.6 Hz, C_PAr), 232.93 (CO) ppm. ³¹P NMR

(81 MHz, C₆D₆): δ = –7.83 ppm. MS (EI): m/z (%) 469 (8) [M⁺],

r.t.

385 (100) [M – 3 CO]. [α]_D= –27.4 (c = 1.08, CHCl₃). IR

(CHCl₃): ν_CO= 1970, 1893 cm^–1. C₂₅H₂₄CrNO₃P (469.44): calcd.

C 63.96, H 5.15, N 3.00; found C 63.56, H 4.82, N 3.10.

[{η⁶-(R,Sp)-1-[4-Chloro-3-(diphenylphosphanyl)phenyl]ethyl-

amine}Cr(CO)₃] [(R)-18M] and [{η⁶-(R,Rp)-1-[4-chloro-3-(diphenyl-

phosphanyl)phenyl]ethylamine}Cr(CO)₃] [(S)-18m]: Following gene-

ral procedure C, lithiation of (R)-9 (056 g, 1.75 mmol) with LDA

(2  in pentane, 1.0 mL, 2.0 mmol), followed by addition of chloro-

diphenylphosphane (0.44 g, 2.0 mmol), produced a nearly 1:1 ratio

of two compounds. The two were collected as a single fraction after

column chromatography (R_f= 0.47; aluminium oxide, diethyl

ether). Further attempts to separate them failed. Analytical data

Lithiation of [{η⁶-(R)-N,N-Dimethyl-1-(p-chlorophenyl)ethylamine}-

Cr(CO)₃] [(R)-9]: Following general procedure C, lithiation of (R)-

9 (4.77 g, 14.9 mmol) with tert-butyllithium (1.7  in pentane;

8.8 mL, 14.9 mmol), followed by addition of chlorodiphenylphos-

phane (3.29 g, 14.9 mmol), produced a mixture of three products.

Column chromatography (aluminium oxide; hexaneǞhexane/di-

ethyl ether, 3:2) gave (R,Sp)-16, (R,Rp)-16 and (R)-17 in that order.

[{η⁶-(R,Sp)-N,N-Dimethyl-1-[4-chloro-2-(diphenylphosphanyl)phen-

yl]ethylamine}Cr(CO)₃] [(R,Sp)-16]: Yield yellow crystals 5.0 g refer to the clean fraction collected after flash chromatography.

1

(67%). R_f= 0.54 (aluminium oxide; hexane/diethyl ether, 2:1). H

Yield yellow crystals 0.81 g (92%). M = major diastereoisomer; m

NMR (500 MHz, C₆D₆): δ = 0.66 (d, J = 6.7 Hz, 3 H, α-Me), 1.47 = minor diastereoisomer. ¹H NMR (500 MHz, C₆D₆): δ = 0.74 (d,

(s, 3 H, NMe₂), 4.39 (m, J = 6.7 Hz, 1 H, α-CH), 4.45 (dd, J = 6.4,

J = 2.8 Hz, 1 H, H_Ar), 5.04 (d, J = 5.8 Hz, 1 H, H_Ar), 5.26 (br. s,

J = 6.8 Hz, 3 H, α-Me_m), 0.80 (d, J = 6.8 Hz, 3 H, α-Me_M), 1.78

(s, 6 H, NMe_2M), 1.83 (s, 6 H, NMe_2m), 2.64 (q, J = 6.8 Hz, 1 H,

1 H, H_Ar), 6.69 (m, 4 H, m/p-H_PAr), 7.09 (m, J = 7.3 Hz, 2 H, m/ α-CH_M), 2.75 (q, J = 7.1 Hz, 1 H, α-CH_m), 4.66–4.94 (overlapping

p-H_PAr), 7.20 (m, 2 H, o-H_PAr), 7.56 (m, J = 7.0 Hz, 2 H, o-H_PAr

)

peaks, 3 H_ArM+ 3 H_Arm), 7.04–7.10 (m, overlapping peaks, 6 H,

ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 6.02 (α-Me), 37.78 (NMe₂), H_PArM+ 6 H, H_PArm), 7.27–7.40 (m, overlapping peaks, 2 H, H_PArM

58.40 (d, J_C,P= 14.2 Hz, α-CH), 87.76 (d, J_C,P= 3.3 Hz, C_Ar), + 2 H, H_PArm), 7.50–7.60 (m, overlapping peaks, 2 H, H_PArM+ 2

93.01 (C_Ar), 99.69 (d, J_C,P= 3.8 Hz, C_Ar), 106.58 (d, J_C,P= 29.7 Hz,

C_Ar,ipso), 108.3 (d, J_C,P= 4.4 Hz, C_Ar,ipso), 117.40 (d, J_C,P= 19.2 Hz,

H, H_PArm) ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –12.06 (P_M),

–11.83 (P_m) ppm.

Eur. J. Inorg. Chem. 2007, 4923–4945

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4937

E. Alberico, A. Salzer et al.

FULL PAPER

[{η⁶-(S,Rp)-1-[2-(Diphenylphosphanyl)-4-tolyl]chloroethyl}Cr(CO)₃]

[(S,Rp)-19]: This complex was prepared from (S,Rp)-11 (6.45 g,

13.0 mmol) and 1-chloroethyl chloroformate (5.8 mL, 53.4 mmol)

in thf (260 mL) according to general procedure D. The crude prod-

uct was purified by column chromatography (R_f= 0.54; silica gel,

ethyl acetate/hexane, 1:1). Yield yellow crystals (5.5 g, 86%). ¹H

NMR (500 MHz, C₆D₆): δ = 1.39 (s, 3 H, p-Me), 1.47 (d, J =

6.7 Hz, 3 H, α-Me), 4.52 (d, J = 6.1 Hz, 1 H, H_Ar), 4.65 (s, 1 H,

H_Ar), 4.87 (dd, J = 6.1, J = 2.5 Hz, 1 H, H_Ar), 5.89 (m, J = 8.8, J

= 6.7 Hz, 1 H, α-CH), 7.01–7.12 (m, 6 H, m/p-H_PAr), 7.39 (m, J =

7.3 Hz, 2 H, o-H_PAr), 7.56 (t, J = 7.3 Hz, 2 H, o-H_PAr) ppm. ¹³C

NMR (125 MHz, C₆D₆): δ = 19.71 (p-Me), 23.84 (α-Me), 54.18 (d,

J_C,P= 29.6 Hz, α-CH), 89.63 (d, J_C,P= 2.8 Hz, C_Ar), 93.50 (C_Ar),

98.30 (d, J_C,P= 2.8 Hz, C_Ar), 104.88 (d, J_C,P= 24.7 Hz, C_Ar,ipso),

107.60 (C_Ar,ipso), 115.28 (d, J_C,P= 20.8 Hz, C_Ar,ipso), 128.71 (d, J_C,P

= 7.2 Hz, C_PAr), 129.98 (d, J_C,P= 6.6 Hz, C_PAr), 129.42 (C_PAr),

C₂₄H₂₀ClCrO₄P (490.84): calcd. C 58.73, H 4.11; found C 58.99,

H 4.01.

[{η⁶-(R,Sp)-1-[4-chloro-2-(diphenylphosphanyl)phenyl]chloroethyl}-

Cr(CO)₃] [(R,Sp)-22]: This complex was prepared as follows.

(R,Sp)-16 (1.80 g, 3.6 mmol) was dissolved in dry diethyl ether

(70 mL), the solution was cooled to –40 °C and 1-chloroethyl chlo-

roformate (1.56 mL, 14.3 mmol) added dropwise. This solution was

warmed slowly overnight. As a ³¹P NMR check revealed only 50%

conversion, the solution was again cooled to –40 °C and two more

equivalents of 1-chloroethyl chloroformate (0.78 mL, 7.1 mmol)

were added. The mixture was stirred at room temperature until

complete conversion. Solvent and volatiles were distilled off, dry

diethyl ether was added and the mixture filtered through a short

pad of Celite on a sintered glass filter. The solvent was evaporated

and the crude product was used for the next step. Yield (of crude

product): yellow crystals (1.42 g, 90 %). ¹H NMR (200 MHz,

C₆D₆): δ = 1.32 (d, J = 6.8 Hz, 3 H, α-Me), 4.66 (dd, J = 6.6, J =

2.9 Hz, 1 H, H_Ar), 4.82 (dd, J = 6.6, J = 1.7 Hz, 1 H, H_Ar), 4.99

(dd, J = 1.7, J = 0.7 Hz, 1 H, H_Ar), 5.72 (dq, J = 9.3, J = 6.8 Hz,

1 H, α-CH), 7.10–6.99 (m, 6 H, m/p-H_PAr), 7.33 (m, 2 H, o-H_PAr),

7.49 (m, 2 H, o-H_PAr) ppm. ³¹P NMR (81 MHz, C₆D₆): δ =

–17.53 ppm.

130.02 (C_PAr), 134.12 (d, J_C,P= 20.3 Hz, C_PAr), 134.54 (d, J_C,P

13.1 Hz, C_PAr), 134.94 (d, J_C,P= 19.8 Hz, C_PAr), 135.76 (d, J_C,P

=

8.8 Hz, C_PAr), 232.49 (d, J_C,P= 2.2 Hz, CO) ppm. ³¹P NMR

(81 MHz, C₆D₆): δ = –17.74 ppm. MS (CI, isobutane): m/z (%) 475

(66) [M + 1], 439 (33) [M – Cl], 390 (61) [M – 3 CO], 354 (22) [M –

r.t.

3 CO – HCl], 305 (100). [α]_D= +291.0 (c = 1.10, CHCl₃). IR

(CHCl₃): ν_CO= 1971, 1888 cm^–1. C₂₄H₂₀ClCrO₃P (474.84): calcd.

[{η⁶-(S,Rp)-1-[2-(Diphenylphosphanyl)-4-tolyl]ethyldiphenyl-

phosphane}Cr(CO)₃] [(S,Rp)-23a]: This complex was prepared from

(S,Rp)-19 (1.07 g, 2.5 mmol), diphenylphosphane (0.51 g,

2.7 mmol) and TlPF₆(0.95 g, 2.7 mmol) in dry acetone (50 mL)

according to general procedure E. The crude product was purified

by column chromatography (R_f= 0.42; aluminium oxide; dichloro-

methane/hexane, 1:4). Yield yellow crystals (1.0 g, 64%). ¹H NMR

(500 MHz, C₆D₆): δ = 1.34 (dd, J = 7.0, J = 5.0 Hz, 3 H, α-Me),

1.44 (s, 3 H, pMe), 4.39 (ddd, J = 6.7, J = 3.4, J = 1.5 Hz, 1 H,

H_Ar), 4.47 (dd, J = 6.7, J = 1.0 Hz, 1 H, H_Ar), 4.91 (dq, J = 9.5, J

= 7.0 Hz, 1 H, α-CH), 5.00 (t, J = 1.5 Hz, H_Ar), 6.95–7.16 (m, 12

H, H_PAr), 7.21 (m, 2 H, H_PAr), 7.25 (m, J = 7.0 Hz, 2 H, H_PAr),

C 60.71, H 4.24; found C 60.87, H 4.38.

[{η⁶-(S,Rp)-1-[4-tert-Butyl-2-(diphenylphosphanyl)phenyl]chloro-

ethyl}Cr(CO)₃] [(S,Rp)-20]: This complex was prepared according

to general procedure D from (S,Rp)-12 (6.00 g, 11.43 mmol) and

1-chloroethyl chloroformate (6.54 g, 45.70 mmol) in dry thf

(250 mL). The crude product was purified by column chromatog-

raphy (aluminium oxide; ethyl acetate/hexane, 4:1). Yield yellow

1

crystals 4.59 g (78%). H NMR (300 MHz, CDCl₃): δ = 1.12 (s, 9

H, p-tBu), 1.56 (d, J = 6.7 Hz, 3 H, α-Me), 5.12 (s, 1 H, H_Ar), 5.32

(br. s, 1 H, H_Ar), 5.65 (d, J = 5.5 Hz, 1 H, H_Ar), 5.93 (m, 1 H, α-

CH), 7.35–7.39 (m, 10 H, H_PAr) ppm. ¹³C NMR (75 MHz, CDCl₃):

δ = 22.85 (α-Me), 30.93 (pCMe₃), 33.96 (pCMe₃), 54.15 (d, J =

28.2 Hz, α-CH), 86.12 (C_Ar), 92.87 (C_Ar), 97.10 (C_Ar), 101.55 (d, J

= 24.5 Hz, C_Ar,ipso), 116.82 (d, J = 22.1 Hz, C_Ar,ipso), 121.48

(C_Ar,ipso), 128.34–135.95 (C_PAr), 232.19 (CO) ppm. ³¹P NMR

(121.5 MHz, CDCl₃): δ = –16.79 ppm. IR (CHCl₃): ν_CO= 1974,

1912 cm^–1.

7.52 (m, J = 7.0 Hz, 2 H, H_PAr), 7.74 (m, J = 7.6 Hz, 2 H, H_PAr

)

ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 16.25 (α-Me), 19.71 (pMe),

33.14 (dd, J = 24.4 Hz, α-CH), 90.10 (dd, J_C,P= 4.8 Hz, C_Ar), 94.00

(C_Ar), 100.04 (d, J_C,P= 2.2 Hz, C_Ar), 104.86 (d, J_C,P= 18.7 Hz,

C_Ar,ipso), 106.23 (C_Ar,ipso), 121.44 (dd, J_C,P= 22.5 Hz, C_Ar,ipso),

128.57 (d, J_C,P= 7.6 Hz, C_PAr), 128.62 (d, J_C,P= 4.4 Hz, C_PAr),

128.93 (d, J_C,P= 6.6 Hz, C_PAr), 129.24 (C_PAr), 129.83 (d, J_C,P

3.9 Hz, C_PAr), 131.60 (d, J_C,P= 15.3 Hz, C_PAr), 134.15 (d, J_C,P

23.6 Hz, C_PAr), 134.54 (dd, J_C,P= 20.3, J_C,P= 2.2 Hz, C_PAr), 135.05

(d, J_C,P= 19.7 Hz, C_PAr), 135.77 (d, J_C,P= 13.7 Hz, C_PAr), 136.28

(d, J_C,P= 9.8 Hz, C_PAr) 136.44 (d, J_C,P= 22.5 Hz, C_PAr), 137.04

(d, J_C,P= 19.2 Hz, C_PAr), 233.34 (CO) ppm. ³¹P NMR (202 MHz,

=

[{η⁶-(R,Rp)-1-[2-(Diphenylphosphanyl)-4-methoxyphenyl]chloro-

ethyl}Cr(CO)₃] [(R,Rp)-21]: This complex was prepared from

(R,Rp)-13 and 1-chloroethyl chloroformate (2.07 mL, 19.0 mmol)

according to general procedure D. The crude product was purified

by column chromatography (R_f= 0.40 (silica gel; ethyl acetate/hex-

1

ane, 3:7). Yield yellow crystals 2.02 g (85%). H NMR (500 MHz,

C₆D₆): δ = –17.56 (d, J_{P, P}= 18.3 Hz, oPPh₂), 8.47 (d, J_{P, P}

=

C₆D₆): δ = 1.52 (d, J = 6.7 Hz, 3 H, α-Me), 2.78 (s, 3 H, OMe),

4.29 (dd, J = 6.7, J = 2.1 Hz, 1 H, H_Ar), 4.77 (dd, J = 2.1, J =

1.2 Hz, 1 H, H_Ar), 5.08 (dd, J = 6.7, J = 2.7 Hz, 1 H, H_Ar), 5.72

(dq, J = 9.2, J = 6.7 Hz, 1 H, α-CH), 6.95–7.10 (m, 6 H, m/p-H_PAr),

7.41 (m, J = 7.6 Hz, 2 H, o-H_PAr), 7.58 (tm, J = 7.6 Hz, 2 H, o-

H_PAr) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 25.12 (α-Me), 53.89

(d, J_C,P= 27.4 Hz, α-CH), 55.09 (OMe), 75.95 (C_Ar), 84.85 (d, J_C,P

18.3 Hz, α-PPh₂) ppm. MS (CI, isobutane): m/z (%) 625 (20) [M +

1], 540 (22) [M – 3 CO], 489 (54) [M – 3 CO – Cr], 439 (100) [M –

PPh₂]. [α]_D^r.t.= +293.6 (c = 1.00, CHCl₃). IR (CHCl₃): ν_CO= 1965,

1894 cm^–1. C₃₆H₃₀CrO₃P₂(624.57): calcd. C 69.23, H 4.84; found

C 69.14, H 5.26.

[{η⁶-(S,Rp)-1-[2-(Diphenylphosphanyl)-4-tolyl]ethyldicyclohexyl-

= 1.7 Hz, C_Ar), 91.22 (d, J_C,P= 3.3 Hz, C_Ar), 102.00 (C_PAr), 106.62 phosphane}Cr(CO)₃] [(S,Rp)-23b]: This complex was prepared from

(d, J_C,P= 24.6 Hz, C_Ar,ipso), 110.10 (C_PAr), 111.16 (d, J_C,P

=

(S,Rp)-19 (1.45 g, 3.0 mmol), dicyclohexylphosphane (0.59 g,

3.0 mmol) and TlPF₆(1.04 g, 3.0 mmol) in dry acetone (60 mL)

according to general procedure E. The crude product was purified

by column chromatography (R_f= 0.54; aluminium oxide; diethyl

19.7 Hz, C_Ar,ipso), 133.79 (d, J_C,P= 13.7 Hz, C_PAr), 134.32 (d, J_C,P

= 20.8 Hz, C_PAr), 135.03 (d, J_C,P= 29.8 Hz, C_PAr), 135.37 (d, J_C,P

= 8.8 Hz, C_PAr), 141.67 (d, J_C,P= 1.6 Hz, C_Ar,ipso), 232.52 (d, J_C,P

= 2.7 Hz, CO) ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –16.69 ppm. ether/hexane, 1:4). Yield yellow crystals (1.2 g, 63%). Crystals suit-

MS (CI, isobutane): m/z (%) 491 (35) [M + 1], 455 (100) [M – Cl],

able for X-ray structure determination were grown from a layered

r.t.

427 (33) [M – Cl – CO], 319 (91) [M – Cl – 3 CO – Cr]. [α]_D

=

mixture of dichloromethane and hexane at –30 °C. ¹H NMR

–311.9 (c = 0.21, CHCl₃). IR (CHCl₃): ν_CO= 1970, 1894 cm^–1. (500 MHz, C₆D₆): δ = 1.00–1.23 (m, 10 H, H_PCy), 1.34 (m, 1 H,

2

4938

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Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

1

H_PCy), 1.39 (dd, J = 7.0, J = 3.4 Hz, 3 H, α-Me), 1.45 (s, 3 H,

61%). H NMR (500 MHz, C₆D₆): δ = 0.95 (s, 9 H, CMe₃), 1.00–

2

pMe), 1.48–1.80 (m, 11 H, H_PCy), 4.24 (dq, J = 7.0 Hz, 1 H, α-

1.23 (m, 11 H, H_PCy), 1.44 (dd, J = 7.0, J = 3.7 Hz, 3 H, α-Me),

2

CH), 4.78 (br. d, J = 6.4 Hz, 1 H, H_Ar), 4.84 (m, J = 6.4, J = 3.35, 1.47–1.91 (m, 11 H, H_PCy), 4.35 (dq, J = 7.0 Hz, 1 H, α-CH), 4.69

J = 0.6 Hz, 1 H, H_Ar), 5.10 (t, J = 1.2 Hz, 1 H, H_Ar), 7.14 (m, J =

(dd, J = 6.7, J = 4 Hz, 1 ²H, H_Ar), 5.40 (dd, J = 6.7, J = 1.5 Hz, 1

7.3 Hz, 4 H, H_PPh), 7.47 (m, J = 7.6 Hz, 2 H, H_PPh), 7.65 (m, J H, H_Ar), 5.62 (t, J = 1.5 Hz, 1 H, H_Ar), 7.02–7.48 (m, 10 H, H

)

PPh₂

2

= 7.6 Hz, 2 H, H_PPh), 7.70 (m, J = 7.6 Hz, 2 H, H_PPh) ppm. ¹³C

ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 14.48 (α-Me), 26.64–30.35

NMR (125 MHz, C₆²D₆): δ = 15.32 αMe), 19.63 (pMe), 26.64 (d,

(10 C, C_PCy), 30.93 (CMe₃), 31.14 (CMe₃), 31.82 (dd, J_C,P

=

2

J_C,P= 3.9 Hz, C_PCy), 27.03 (d, J_C,P= 12.1 Hz, C_PCy), 27.45 (d, 21.3 Hz, α-C²H), 33.63 (d, J_C,P= 22.1 Hz, C_PCy), 33.83 (d, J_C,P

2

J_C,P= 8.2 Hz, C

), 27.82 (d, J_C,P= 5.4 Hz, C

), 28.05 (d, J_C,P

16.3 Hz, C_PCy), 86.54 (t, J_C,P= 3.8 Hz, C_Ar), ²88.17 (C_Ar), 99.77

PCy₂

2

= 13.7 Hz, C_PCy), 30.02 (d, J_C,P= 9.3 Hz, C

), 30.38 (d, J_C,P

=

(d, J_C,P= 3.8 Hz, C_Ar), 101.48 (d, J_C,P= 24.0 Hz, C_Ar,ipso), 119.58

(C_Ar,ipso), 126.47 (C_Ar,ipso), 126.66–139.11 (m, 12 C, C_PPh), 233.50

PCy₂

2

5.5 Hz, C_PCy), 31.58 (dd, J_C,P= 21.4 Hz, α-CH), 31.70 (d, J_C,P

2

12.6 Hz, C_PCy), 33.48 (d, J_C,P= 21.4 Hz, C_PCy), 33.89 (d, J_C,P

(CO) ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –20.83 (²d, J_{P, P}

=

2

r.t.

23.5 Hz, C_PCy), 88.93 (dd, J_C,P= 4.1, J_C,P= 3.8 Hz, C_Ar), 94.92

46.7 Hz, PPh₂), 15.73 (d, J_P,P= 46.7 Hz, PCy₂) ppm. [α]_D

2

(C_Ar), 101.98 (d, J_C,P= 2.8 Hz, C_Ar), 104.70 (dd, J_C,P= 24.1, J_C,P

+306.27 (c = 0.07, CHCl₃). IR (CHCl₃): ν_CO= 1968, 1903 cm^–1.

= 3.3 Hz, C_Ar,ipso), 105 41 (C_Ar,ipso), 124.78 (dd, J_C,P= 22.5, J_C,P

19.2 Hz, C_Ar,ipso), 128.47 (C

=

C₃₉H₄₈CrO₃P₂(678.75): calcd. C 69.01, H 7.13; found C 69.01, H

), 128.78 (d, J_C,P= 7.1 Hz, C_PPh), 7.13.

PPh₂

2

133.90 (dd, J_C,P= 18.6, J_C,P= 2.7 Hz, C_PPh), 135.39 (d, J_C,P

=

[{η⁶-(R,Rp)-1-[2-(Diphenylphosphanyl)-4-methoxyphenyl]ethyl-

diphenylphosphane}Cr(CO)₃] [(R,Rp)-25a]: This complex was pre-

pared from (R,Rp)-21 (0.78 g, 1.59 mmol), diphenylphosphane

(0.32 g, 1.70 mmol) and TlPF₆(0.60 g, 1.70 mmol) in acetone

(32 mL) according to general procedure E. The crude product was

purified by column chromatography (R_f= 0.42; aluminium oxide;

hexane/dichloromethane, 4:1). Yield yellow crystals (0.90 g, 88%

yield). ¹H NMR (500 MHz, C₆D₆): δ = 1.41 (dd, J = 6.9, J =

5.6 Hz, 3 H, α-Me), 2.81 (s, 3 H, OMe), 4.20 (dd, J = 7.0, J =

2.4 Hz, 1 H, H_Ar), 4.65 (dq, J = 9.1, J = 7.0 Hz, 1 H, α-CH), 4.68

(ddd, J = 7.0, J = 3.0, J = 1.8 Hz, 1 H, H_Ar), 5.09 (dd, J = 2.4, J

20.9 Hz, C_{P P h}), 137.35 (dd, J_{C , P}= 14².3, J_{C, P}= 3.9 Hz,

2

C_PPh),138.42 (dd, J_C,P= 7.1, J_C,P= 2.7 Hz, C_PPh), 233.41 (CO)

2

ppm. ³¹P NMR (202 MHz, C₆D₆): δ = –18.71 (d, ²J_P,P= 38.3 Hz,

PPh₂), 15.85 (d, J_P,P= 38.3 Hz, PCy₂) ppm. MS (CI, isobutane):

m/z (%) 637 (82) [M + 1], 580 (16) [M – 2 CO], 552 (100) [M – 3

CO], 501 (16) [M – 3 CO – Cr]. [α]_D^r.t.= +549.7 (c = 0.62, CHCl₃).

IR (CHCl₃): ν_CO= 1963, 1887 cm^–1. C₃₆H₄₂CrO₃P₂(636.67): calcd.

C 67.91, H 6.65; found C 69.12, H 7.75.

[{η⁶-(S,Rp)-1-[2-(Diphenylphosphanyl)-4-tolyl]ethyldi-tert-

butylphosphane}Cr(CO)₃] [(S,Rp)-23c]: This complex was prepared

from (S,Rp)-19 (1.02 g, 2.4 mmol), di-tert-butylphosphane (0.34 g, = 1.2 Hz, 1 H, H_Ar), 6.94–7.15 (m, 14 H, H_PPh), 7.29 (m, J =

2

2.6 mmol) and TlPF₆(0.91 g, 2.6 mmol) in dry acetone (48 mL)

according to general procedure E. The crude product was purified

by column chromatography (aluminium oxide; dichloromethane/

hexane, 1:4). R_f= 0.71. Yield yellow crystals (0.88 g, 62%). ¹H

7.0 Hz, 2 H, H_PPh), 7.51 (m, J = 7.9 Hz, 2 H, H_PPh), 7.74 (m, J

2

= 7.0 Hz, 2 H, H_PPh) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 18.12

2

(α-Me), 32.48 (t, J_C,P= 23.1 Hz, α-CH), 56.18 (OMe), 76.05 (C_Ar),

86.82 (C_Ar), 91.24 (dd, J_C,P= 7.0, J_C,P= 3.0 Hz, C_Ar), 106.48 (d,

NMR (500 MHz, C₆D₆): δ = 0.92 [d, J = 9.0 Hz, 9 H, P(CMe₃)₂], J_C,P= 22.5 Hz, C_Ar,ipso), 117.20 (t, J_C,P= 21.2 Hz, C_Ar,ipso), 128.71

1.21, [d, J = 10.7 Hz, 9 H, P(CMe₃)₂], 1.48 (s, 3 H, pMe), 1.55 (dd,

J = 7.0, J = 2.7 Hz, 3 H, α-Me), 4.44 (m, J = 7.0 Hz, 1 H, α-CH),

4.75 (dd, J = 6.7, J = 3.4 Hz, 1 H, H_Ar), 4.80 (br. d, J = 6.7 Hz, 1

(d, J_C,P= 7.7 Hz, C_PPh), 128.97 (d, J_C,P= 6.5 Hz, C_PPh), 129.53

2

(C_PPh), 131.73 (d, J_C,P= 15.9 Hz, C

), 134.57 (d, J_C,P= 22.5 Hz,

PPh₂

2

C_PPh), 134.85 (d, J_C,P= 20.9 Hz, C

), 135.06 (d, J_C,P= 20.3 Hz,

), 136.28 (d, J_C,P= 22.5 Hz,

PPh₂

2

H, H_Ar), 5.23 (br. s, 1 H, H_Ar), 7.06 (m, J = 7.3 Hz, 2 H, H_PPh), C_PPh), 135.59 (d, J_C,P= 7.7 Hz, C

PPh₂

2

7.10–7.16 (m, 4 H, H_PPh), 7.45 (m, J = 7.0 Hz, 2 H, H_PPh), 7.71 C_PPh), 137.25 (d, J_C,P= 18.6 Hz, C_PPh), 140.80 (C_Ar,ipso), 233.51

2

(m, J = 7.0 Hz, 2 H, H_PPh) ppm. ¹³C NMR (125 MHz, C²₆D₆): δ

(CO) ppm. ³¹P NMR (202 MHz, C₆D₆):²δ = 5.02 (d, J_P,P= 11.0 Hz,

2

= 15.54 (α-Me), 19.58 (pMe), 31.59 [dd, J_C,P= 13.2, J_C,P= 3.3 Hz,

P(CMe₃)₂], 32.20 [dd, J_C,P= 13.2, J_C,P= 3.3 Hz, P(CMe₃)₂], 34.67

(d, J_C,P= 31.8 Hz, α-CH), 34.85 [d, J_C,P= 22 Hz, P(CMe₃)₂], 35.15

[d, J_C,P= 23 Hz, P(CMe₃)₂], 89.44 (d, J_C,P= 3.8 Hz, C_Ar), 95.05

α-PPh₂), –17.99 (d, J_P,P= 11.0 Hz, oPPh₂) ppm. MS (CI, isobut-

ane): m/z (%) 505 (22) [M + H – 3 CO – Cr], 319 (100) [M – 3

CO – Cr –HPPh₂]. [α]_D^r.t.= –286.4 (c = 0.22, CHCl₃). IR (CHCl₃):

ν_CO= 1964, 1892 cm^–1. C₃₆H₃₀CrO₄P₂(640.57): calcd. C 67.50, H

(C_Ar), 103.26 (d, J_C,P= 2.8 Hz, C_Ar), 104.15 (d, J_C,P= 28.5 Hz, 4.72; found C 67.57, H 5.27.

C_Ar,ipso), 105.09 (C_Ar,ipso), 125.28 (dd, J_C,P= 20.9 Hz, C_Ar,ipso),

[{η⁶-(R,Rp)-1-[2-(Diphenylphosphanyl)-4-methoxyphenyl]ethyl-

dicyclohexylphosphane}Cr(CO)₃] [(R,Rp)-25b]: This complex was

prepared from (R,Rp)-21, dicyclohexylphosphane (0.47 g,

2.36 mmol) and TlPF₆(0.82 g, 2.36 mmol) in acetone (47 mL) ac-

cording to general procedure E. The crude product was purified by

column chromatography (R_f= 0.51; aluminium oxide; hexane/di-

ethyl ether, 2:1). Yield yellow crystals (1.18 g, 77% yield). ¹H NMR

128.08 (d, J_C,P= 4.9 Hz, C_PPh), 128.9 (C_PPh), 128.72 (d, J_C,P

=

2

6.6 Hz, C_PPh), 129.55 (C_PPh), 133.66 (dd, ²J_C,P= 18.7, J_C,P

2

2.8 Hz, C_PPh), 135.56 (d, J_C²_,P= 20.9 Hz, C_PPh), 138.11 (dd,

J_C,P= 15.4, ²J_C,P= 7.7 Hz, C_PPh), 139 67 (dd², J_C,P= 5 Hz,

C_{P P h}), 233.42 (CO) ppm. ^{3 1}P²NMR (202 MHz, C₆D₆):

2

δ = –19.79 (d, J_P,P= 61.7 Hz, PPh₂), 49.33 [d, J_P,P= 61.7 Hz,

P(CMe₃)₂] ppm. MS (CI, isobutane): m/z (%) 585 (87) [M + 1], 527

(100) [M – CMe₃], 500 (22) [M – 3 CO], 439 (74) [M – P(CMe₃]₂.

(500 MHz, C₆D₆): δ = 1.08–1.36 (m, 8 H, H_PCy), 1.45–1.70 (m, 14

2

H, H_PCy), 1.47 (dd, J = 7.0, J = 4.5 Hz, 3 H, α-Me), 2.84 (s, 3 H,

2

r.t.

[α]_D= +435.2 (c = 1.01, CHCl₃). IR (CHCl₃): ν_CO= 1962,

OMe), 4.00 (m, J = 7.0 Hz, 1 H, α-CH), 4.47 (dd, J = 7.0, J =

2.4 Hz, 1 H, H_Ar), 5.13 (ddd, J = 7.0, J = 3.0, J = 1.5 Hz, 1 H,

H_Ar), 5.19 (dd, J = 2.4, J = 0.9 Hz, 1 H, H_Ar), 7.00–7.11 (m, 6 H,

1891 cm^–1. C₃₂H₃₈CrO₃P₂(584.59): calcd. C 65.75, H 6.55; found

C 65.56, H 6.39.

[{η⁶-(S,Rp)-1-[4-tert-Butyl-2-(diphenylphosphanyl)phenyl]dicyclo- H_PPh), 7.47 (m, J = 7.0 Hz, 2 H, H_PPh), 7.70 (m, J = 7.3 Hz, 2 H,

2

hexylphosphanylethane}Cr(CO)₃] [(S,Rp)-24]: This complex was

prepared according to general procedure E from (S,Rp)-20 (4.59 g,

8.88 mmol), dicyclohexylphosphane (2.00 g, 10.13 mmol) and

H_PPh) ppm. ¹³C NMR (125 MHz, C₆D₆): δ = 17.60 (α-Me), 26.65

(d, J_C²_,P= 10.4 Hz, C_PCy), 27.12 (d, J_C,P= 11.5 Hz, C_PCy), 27.41

2

(d, J_C,P= 8.2 Hz, C

), 27.89 (d, J_C,P= 6.0 Hz, C_PCy), 28.01 (d,

2

PCy₂

TlPF₆(3.10 g, 8.88 mmol) in dry acetone (170 mL). The crude J_C,P= 13.2 Hz, C_PCy), 30.13 (d, J_C,P= 10.4 Hz, C_PCy), 30.44 (d,

2

product was purified by column chromatography (aluminium ox-

ide; diethyl ether). Yield yellow microcrystalline powder (3.70 g,

J_C,P= 6.6 Hz, C_PCy), 30.68 (dd, J_C,P= 26.3, J_C,P= ²19.7 Hz, α-

2

CH), 31.43 (d, J_C,P= 17.0 Hz, C_PCy), 31.79 (C_PCy), 31.95 (d, J_C,P

2

Eur. J. Inorg. Chem. 2007, 4923–4945

www.eurjic.org

4939

E. Alberico, A. Salzer et al.

FULL PAPER

= 7.7 Hz, C_PCy), 33.43 (d, J_C,P= 20.9 Hz, C

), 33.65 (d, J_C,P

=

15.9 Hz, C_PPh), 133.76 (d, J_C,P= 23.1 Hz, C_PPh), 134.43 (d, J_C,P

PCy₂

2

21.9 Hz, C_PCy), 55.25 (OMe), 77.13 (C_Ar), 88.36 (d, J_C,P= 2.2 Hz, = 20.8 Hz, C_PPh), 134.98 (d, J_C,P= 20.9 Hz, C ²), 135.53 (d, J_C,P

PPh₂

C_Ar), 90.58 (d²d, J_C,P= 7.1, J_C,P= 3.3 Hz, C_Ar), 105.37 (dd, J_C,P

24.7, J_C,P= 3.3 Hz, C_Ar,ipso), 120.89 (dd, J_C,P= 21.4, J_C,P

=

= 7.1 Hz, C_PPh), 126.20 (d, J_C,P= 22.5 Hz, C

), 136.68 (d, J_C,P

2

PPh₂

2

= 19.2 Hz, C_PPh), 231.71 (CO) ppm. ³¹P NMR (202 MHz, C₆D₆):

2

19.8 Hz, C_Ar,ipso), 128.41 (d, J_C,P= 7.1 Hz, C_PPh), 128.84 (d, J_C,P

δ = 7.33 (d, J_P,P= 18.3 Hz, aPPh₂), –18.93 (d, J_P,P= 18.3 Hz,

oPPh₂) ppm. MS (CI, isobutane): m/z (%) 645 (22) [M + H], 560

(14) [M – 3 CO], 509 (48) [M + H – 3 CO – Cr], 459 (100) [M –

PPh₂], 432 (28) [M – 3 CO – Cr – Ph], 323 (42) [M – 3 CO – Cr –

2

= 7.1 Hz, C_PPh), 129.89 (C_PPh), 134.22 (dd, J_C,P= 19.2, J_C,P

=

2

2.2 Hz, C_PPh), ²135.46 (d, J_C,P= 20.3 Hz, C_PPh), 136.09 (dd, J_C,P

2

= 14.8, J_C,P= 2.7 Hz, C_PPh), 137.74 (d, J_C,P= 7.7 Hz, C_PPh),

2

140.00 (d, J_C,P= 1.7 Hz, C_Ar,ipso), 233.68 (d, J_C,P= 1.7 Hz, CO) PPh₂]. [α]_D^r.t.= –248.1 (c = 0.10, CHCl₃). IR (CHCl₃): ν_CO= 1976,

ppm. ³¹P NMR (202 MHz, C₆D₆): δ = 15.49 (d, J_P,P= 26.0 Hz, 1912 cm^–1. C₃₅H₂₇ClCrO₃P₂(644.99): calcd. C 65.18, H 4.22; found

PCy₂), –17.48 (d, J_P,P= 26.0 Hz, PPh₂) ppm. MS (CI, isobutane):

m/z (%) 653 (72) [M + H], 568 (100) [M – 3 CO], 517 (85) [M – 3

C 65.84, H 4.74.

[{η⁶-(R,Sp)-1-[4-Chloro-2-(diphenylphosphanyl)phenyl]ethyldi-

cyclohexylphosphane}Cr(CO)₃] [(R,Sp)-26b]: This complex was pre-

pared from (R,Sp)-22 (0.62 g, 1.25 mmol), dicyclohexylphosphane

(0.25 g, 1.25 mmol) and TlPF₆(0.44 g, 1.25 mmol) in dry acetone

(25 mL) according to general procedure E. The crude product was

purified by column chromatography (R_f= 0.69, aluminium oxide;

diethyl ether/hexane, 1:4). Yield yellow crystals (0.30 g, 36%). ¹H

NMR (500 MHz, C₆D₆): δ = 1.00–1.19 (m, 7 H, H_PCy), 1.27 (dd,

J = 7.3, J = 3.7 Hz, 3 H, α-Me), 1.30–1.46 (m, 4 H, H_PCy), 1.48–

1.76 (m, 11 H, H_PCy), 4.13 (m, J = 7.3 Hz, 1 H, α-CH), 4.66 (ddd,

J = 6.7, J = 3.4, J ²= 0.9 Hz, 1 H, H_Ar), 5.08 (dd, J = 6.7, J =

1.8 Hz, 1 H, H_Ar), 5.49 (m, J = 1.8 Hz, 1 H, H_Ar), 7.01–7.10 (m, 6

r.t.

CO – Cr], 433 (44) [M – 3 CO – Cr – C₆H₁₂]. [α]_D= –309.5 (c =

0.21, CHCl₃). IR (CHCl₃): ν_CO= 1963, 1886 cm^–1. C₃₆H₄₂CrO₄P₂

(652.67): calcd. C 66.25, H 6.49; found C 66.00, H 6.74.

[{η⁶-(R,Rp)-1-[2-(Diphenylphosphanyl)-4-methoxyphenyl]ethyldi-

tert-butylphosphane}Cr(CO)₃] [(R,Rp)-25c]: This complex was pre-

pared from (R,Rp)-21 (0.91 g, 1.82 mmol), di-tert-butylphosphane

(0.29 g, 2.00 mmol) and TlPF₆(0.70 g, 2.00 mmol) in acetone

(36 mL) according to general procedure E. The crude product was

purified by column chromatography (R_f= 0.34; aluminium oxide;

hexane/dichloromethane, 4:1Ǟneat dichloromethane). Yield yel-

low crystals (0.84 g, 78%). ¹H NMR (500 MHz, C₆D₆): δ = 0.94

[d, J = 11.0 Hz, 9 H, P(CMe₃)₂], 1.18 [d, J = 10.7 Hz, 9 H,

P(CMe₃)₂], 1.58 (dd, J = 7.4, J = 2.5 Hz, 3 H, α-Me), 2.86 (s, 3 H,

OMe), 4.32 (m, J = 7.0 Hz, 1 H, α-CH), 4.86 (dd, J = 6.7, J =

3.0 Hz, 1 H, H_Ar), 4.55 (dd, J = 6.7, J = 1.6 Hz, 1 H, H_Ar), 5.40

2

H, H_PPh), 7.40 (m, J = 7.6 Hz, 2 H, H_PPh), 7.74 (m, J = 7.6 Hz,

2

2 H, H_PPh) ppm. ¹³C NMR (125 MHz, C₆²D₆): δ = 15.17 (α-Me),

2

26.59 (d, J_C,P= 4.9 Hz, C_PCy), 27.01 (d, J_C,P= 11.5 Hz, C_PCy),

27.44 (d, J_C,P= 7.7 Hz, C_PCy), 27.80 (d, J_C,P= 15.9 Hz, C_PCy),

27.88 (d, J_C,P= 23.5 Hz, C_PCy), 30.40 (d, J_C,P= 9.3 Hz, C_PCy),

2

(d, J = 1.5 Hz, 1 H, H_Ar), 7.00–7.10 (m, 6 H, H_PPh), 7.44 (dd, J =

30.18 (C_PCy), 30.33 (d, J_C,P= 6.6 Hz, C_PCy), 31.57 (dd, J_C,P

=

2

26.8, J_C,P= ²20.3 Hz, α-CH), 31.59 (d, J_C,P= 12.0 Hz, C_PCy), 31.74

7.4 Hz, 2 H, H_PPh), 7.70 (dd, J = 7.0 Hz, 2 H, H_PPh) ppm. ¹³C

2

NMR (125 MHz, C₆D₆): δ = 16.32 (α-Me), 31.51 [dd, ²J_C,P= 13.2,

2

(d, J_C,P= 20.8 Hz, C_PCy), 33.55 (d, J_C,P= 14.8 Hz, C_PCy), 33.72

2

J_C,P= 3.3 Hz, P(CMe₃)₂], 32.22 [d, J_C,P= 14.3 Hz, P(CMe₃)₂],

(d, J_C,P= 15.9 Hz, C_PCy), 87.89 (dd, J_C,P= 3.8 Hz, C_Ar), 93.89

2

34.29 [d, J_C,P= 15.4 Hz, P(CMe₃)₂], 34.51 (dd, J_C,P= 22.5, J_C,P

=

(C_Ar), 100.10 (d, J_C,P= 2.8 Hz, C_Ar), 103.57 (dd, J_C,P= 27.9, J_C,P

= 2.7 Hz, C_Ar,ipso), 107.52 (d, J_C,P= 3.8 Hz, C_Ar,ipso), 124.13 (dd,

J_C,P= 21.9, J_C,P= 19.2 Hz, C_Ar,ipso), 128.29 (C_PPh), 128.35 (C_PPh),

15.3 Hz, α-CH), 34.98 [d, J_C,P= 35.6 Hz, P(CMe₃)₂], 55.38 (OMe),

77.96 (C_Ar), 89.69 (d, J_C,P= 3.9 Hz, C_Ar), 90.76 (C_Ar), 104.83 (d,

J_C,P= 30.2 Hz, C_Ar,ipso), 121.53 (m, J_C,P= 20.8 Hz, C_Ar), 128.72

(d, J_C,P= 6.5 Hz, C_PPh), 129.68 (C_PPh), 133.81 (dd, J_C,P= 19.2,

2

128.59 (C_PPh), 129. 01 (d, J_C,P= 7.7 Hz, C_PPh), 130.42 (C_PPh),

2

133.76 (dd, J_C,P= 18.6, J_C,P= 2.7 Hz, C_PPh), ²135.33 (d, J_C,P

=

2

J_C,P= 2.9 Hz, C_PPh), 135.63 (d, J_C,P= 20.3 Hz, C_PPh), 137.20

21.4 Hz, C_PPh), 136.80 (dd, J_C,P= 14.3, J_C,P= 4.4 Hz, C_PPh),

2

137.83 (dd, J_C,P= 7.1, J_C,P= 2.7 Hz, C_PPh), 231.75 (CO) ppm. ³¹²P

(C_PPh), 139.10 (C_Ar,ipso), 139.34 (d, J_C,P= 5.0 Hz, C_PPh), 233.63

(CO)²ppm. ³¹P NMR (202 MHz, C₆D₆): δ = –18.58 (d, J_{P, P}

=

2

NMR (81 MHz, C₆D₆): δ = 15.20 (d, J_P,P= 39.3 Hz, PCy₂), –20.17

(d, J_P,P= 39.3 Hz, PPh₂) ppm. MS (CI, isobutane): m/z (%) 657

(68) [M + H], 572 (44) [M – 3 CO], 521 (100) [M – 3 CO – Cr],

54.3 Hz, PPh₂), 48.07 [d, J_P,P= 54.3 Hz, P(CMe₃)₂] ppm. MS (CI,

isobutane): m/z (%) 601 (39) [M + H], 543 (32) [M – CMe₃], 516

(54) [M – 3 CO], 465 (100) [M – 3 CO – Cr], 407 (83) [M – 3 CO –

Cr – HCMe₃]. [α]_D^r.t.= –436.4 (c = 0.22, CHCl₃). IR (CHCl₃): ν_CO

= 1963, 1889 cm^–1. C₃₂H₃₈CrO₄P₂(600.599): calcd. C 63.99, H

6.38; found C 63.83, H 6.32.

r.t.

433 (32) [M – 3 CO – Cr – C₆H₁₂]. [α]_D= –346.0 (c = 0.20,

CHCl₃). IR (CHCl₃): ν_CO= 1973, 1906 cm^–1.

[{η⁶-(R,Sp)-1-[4-Chloro-2-(diphenylphosphanyl)phenyl]ethyldi-tert-

butylphosphane}Cr(CO)₃] [(R,Sp)-26c]: This complex was prepared

from (R,Sp)-22 (0.48 g, 0.97 mmol), di-tert-butylphosphane (0.16 g,

1.07 mmol) and TlPF₆(0.37 g, 1.07 mmol) in dry acetone (20 mL)

according to general procedure E. The crude product was purified

by column chromatography (R_f= 0.54; aluminium oxide; dichloro-

methane/hexane, 4:1). Yield yellow crystals (0.18 g, 31%). ¹H NMR

(500 MHz, C₆D₆): δ = 0.86 [d, J = 10.7 Hz, 9 H, P(CMe₃)₂], 1.17

[d, J = 10.5 Hz, 9 H, P(CMe₃)₂], 1.41 (dd, J = 7.3, J = 2.7 Hz, 3

H, α-Me), 4.32 (m, J = 4.6 Hz, 1 H, α-CH), 4.56 (dd, J = 6.8, J =

3.7 Hz, 1 H, H_Ar), 5.12 (dd, J = 6.8, J = 1.7 Hz, 1 H, H_Ar), 5.61

[{η⁶-(R,Sp)-1-[4-Chloro-2-(diphenylphosphanyl)phenyl]ethyldi-

phenylphosphane}Cr(CO)₃] [(R,Sp)-26a]: This complex was pre-

pared from (R,Sp)-22 (0.54 g, 1.1 mmol), diphenylphosphane

(0.23 g, 1.2 mmol) and TlPF₆(0.44 g, 1.2 mmol) in dry acetone

(22 mL) according to general procedure E. The crude product was

purified by column chromatography (R_f= 0.53; aluminium oxide;

diethyl ether/hexane, 1:4). Yield yellow crystals (0.20 g, 28%). ¹H

NMR (500 MHz, C₆D₆): δ = 1.22 (dd, J = 6.9, J = 4.9 Hz, 3 H, α-

Me), 4.24 (d, J = 6.6 Hz, 1 H, H_Ar), 4.76 (d, J = 6.8 Hz, 1 H, H_Ar),

4.80 (dd, J = 9.1, J = 6.9 Hz, 1 H, α-CH), 5.36 (d, J = 1.4 Hz, 1 (d, J = 1.7 Hz, 1 H, H_Ar), 7.02–7.11 (m, 6 H, H_PPh), 7.36 (m, J =

2

H, H_Ar), 6.93–7.12 (m, 16 H, H_PPh), 7.45 (m, J = 7.7 Hz, 2 H,

7.6 Hz, 2 H, H_PPh), 7.62 (m, J = 7.6, J = 1.9 Hz, H_PPh) ppm. ¹³C

2

H_PPh), 7.66 (m, J = 7.7 Hz, 2 H, H_PPh) ppm. ¹³C NMR (125 MHz,

NMR (125 MHz, ²C₆D₆): δ = 15.35 (α-Me), 31.55 [dd, J_C,P= 13.2,

2

C₆D₆²): δ = 16.07 (α-Me), 33.01 (m, J_C,P= 24.2 Hz, α-CH), 89.06 J_C,P= 3.8 Hz, P(CMe₃)₂], 32.15 [d, J_C,P= 13.7 Hz, P(CMe₃)₂],

(C_Ar), 92.97 (C_Ar), 98.10 (C_Ar), 104.43 (d, J_C,P= 25.7 Hz, C_Ar,ipso),

34.54 [d, J_C,P= 32.0 Hz, P(CMe₃)₂], 34.74 (d, J_C,P= 37.0 Hz, α-

108.84 (C_Ar,ipso), 120.68 (m, J_C,P= 21.4 Hz, C_Ar,ipso), 128.54 (C_PPh), CH), 35.08 [d, J_C,P= 32.0 Hz, P(CMe₃)₂], 88.37 (C_Ar), 94.09 (C_Ar),

2

128.66 (C_PPh), 128.72 (C_PPh), 129.14 (d, J_C,P= 7.1 Hz, C_PPh), 101.36 (C_Ar), 103.62 (d, J_C,P= 29.6 Hz, C_Ar,ipso), 107.02 (d, J_C,P

=

2

129.40 (C_PPh), 129.95 (C_PPh), 130.25 (C_PPh), 131.55 (d, J_C,P

=

3.9 Hz, C_Ar,ipso), 124.65 (dd, J_C,P= 21.1 Hz, C_Ar,ipso), 127.91

2

4940

www.eurjic.org

Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

(C_PPh), 128.13 (C_PPh), 128.29 (C_PPh), 128.94 (d, J_C,P= 6.6 Hz, pentane; 19.00 mL, 32.30 mmol, 1.15 equiv.) was added dropwise

2

C_PPh), 129.94 (C_PPh), 133.45 (dd, ²J_C,P= 18.6, J_C,P= 3.3 Hz, and the reaction mixture stirred at –50 °C for 24 h. After addition

2

C_PPh), 135.49 (d, J_C,P= 21.4 Hz, C_PPh), 137.56 (dd, J_C,P= 15.3, of chlorotrimethylsilane (15.17 g, 139.65 mmol, 5 equiv.), the re-

2

J_C,P= 7.7 Hz, C

), 139.03 (m, J_C,P= 4.4 Hz, C_PPh), 231.75 (CO)

sulting mixture was warmed to room temperature, stirred at that

PPh₂

2

ppm. ³¹P NMR (81 MHz, C₆D₆): δ = –21.06 (d, J_P,P= 63.2 Hz, temperature for 80 h and then filtered through a short pad of Celite

PPh₂), 48.78 [d, J_P,P= 63.2 Hz, P(CMe₃)₂] ppm. MS (CI, isobut-

ane): m/z (%) 605 (88) [M + H], 547 (45) [M – CMe₃], 520 (15)

in order to remove LiCl. The solvent and excess ClSiMe₃were dis-

tilled off on a rotary evaporator and the crude product was purified

[M – 3 CO], 459 (14) [M – P(CMe₃]₂, 391 (100) [M – 3 CO – Cr – by column chromatography (aluminium oxide; diethyl ether/hex-

Ph], 407 (83) [M – 3 CO – Cr – HCMe₃]. [α]_D^r.t.= –445.4 (c = 0.22,

CHCl₃). IR (CHCl₃): ν_CO= 1974, 1910 cm^–1.

ane, 1:1) to afford (S)-29 as a light yellow oil. Yield 6.89 g (98%).

¹H NMR (500 MHz, CDCl₃): δ = 0.41 (s, 9 H, SiMe₃), 1.47 (d, J

= 6.7 Hz, 3 H, α-Me), 2.30 (s, 6 H, NMe₂), 3.75 (q, J = 6.7 Hz, 1

H, α-CH), 3.85 (s, 3 H, OMe), 6.23 (t, J = 7.3 Hz, 1 H, H_Ar), 7.42

(d, J = 7.3 Hz, 1 H, H_Ar), 7.59 (d, J = 7.6 Hz, 1 H, H_Ar) ppm. ¹³C

NMR (125 MHz, CDCl₃): δ = –0.03 (SiMe₃), 20.91 (α-Me), 43.43

(NMe₂), 57.95 (OMe), 62.79 (α-CH), 124.16 (C_Ar), 129.58 (C_Ar),

Preparation of [{η⁶-(S)-N,N-Dimethyl-1-(2-methoxyphenyl)ethyl-

amine}Cr(CO)₃] [(S,Sp)-28] and [(S,Rp)-28]. Thermolysis with

Cr(CO)₆: Reaction of (S)-4 (4.00 g, 22.00 mmol) and Cr(CO)₆

(6.00 g, 27.00 mmol) in a 8:1 mixture of di-n-butyl ether and thf

(81 mL) for 50 h according to general procedure B afforded (S,Sp)-

28 and (S,Rp)-28 in a 25:75 ratio (Scheme 8). The two dia-

stereomers were collected as a single fraction after flash chromatog-

raphy (aluminium oxide; diethyl ether). Yield 4.65 g (66%).

Arene Exchange with [(η⁶-Naphthalene)Cr(CO)₃]: (S,Sp)-28 was

prepared in a high-pressure Schlenk tube from (S)-4 (0.86 g,

4.78 mmol) and [(η⁶-naphthalene)Cr(CO)₃] (1.50 g, 5.68 mmol) in

di-n-butyl ether (25 mL). After all reagents and the solvent had

been mixed, a catalytic amount of thf (0.53 g, 7.35 mmol) was

added, the reaction mixture was degassed by means of ultrasound

and three freeze-pump-thaw cycles and then heated in the dark at

75 °C for 95 h. The reaction mixture was then filtered through a

short pad of Celite, the solvent was distilled off on a rotary evapo-

rator and the residue was taken up in diethyl ether and purified

by flash chromatography (aluminium oxide; diethyl ether/hexane =

1:10Ǟ1:2). A yellow crystalline product was isolated after evapora-

tion of the solvents. Crystals suitable for X-ray analysis were grown

by slow diffusion of hexane into a solution of the compound in

diethyl ether at –30 °C. Yield 0.91 g (60%).

132.52 (C_Ar,ipso), 133.84 (C_Ar), 136.90 (C_Ar,ipso), 163.14 (C_Ar,ipso

ppm.

)

Preparation of [{η⁶-(S)-N,N-Dimethyl-1-[2-methoxy-3-(trimethyl-

silyl)phenyl]ethylamine}Cr(CO)₃] [(S,Sp)-30 and (S,Rp)-30]. Ther-

molysis with Cr(CO)₆: Reaction of (S)-29 (2.80 g, 11.00 mmol) and

Cr(CO)₆(3.00 g, 14.00 mmol) in an 8:1 mixture of di-n-butyl ether

and thf (40.5 mL) for 48 h according to general procedure B af-

forded (S,Rp)-30 and (S,Sp)-30 in an 87.5:12.5 ratio (Scheme 9).

The two diastereomers were collected as a single fraction after flash

chromatography (aluminium oxide; diethyl ether). Yield 3.03 g

(79%). Crystals of (S,Rp)-30 suitable for X-ray analysis were grown

by slow diffusion of hexane into a solution of this fraction in di-

ethyl ether.

Arene Exchange with [(η⁶-Naphthalene)Cr(CO)₃]: (S,Sp)-30 was

prepared in a high-pressure Schlenk tube from (S)-29 (1.20 g,

4.78 mmol) and [(η⁶-naphthalene)Cr(CO)₃] (1.50 g, 5.68 mmol) in

di-n-butyl ether (25 mL). After all reagents and the solvent had

been mixed, a catalytic amount of thf (0.53 g, 7.35 mmol) was

added, the reaction mixture was degassed by means of ultrasound

and three freeze-pump-thaw cycles and then heated in the dark at

75 °C for 78 h. The reaction mixture was filtered through a short

pad of Celite, the solvent was distilled off on a rotary evaporator

and the residue was taken up in diethyl ether and purified by flash

chromatography (aluminium oxide; diethyl ether/hexane, 3:1). After

evaporation of the solvents, the product was obtained as a yellow-

orange powder in a mixture with unreacted [(η⁶-naphthalene)-

Cr(CO)₃]. The desired product was isolated in high purity after a

second chromatographic purification (silica gel; diethyl ether/hex-

ane, 1:7). Yield yellow crystals (1.30 g, 70%).

[{η⁶-(S,Sp)-N,N-Dimethyl-1-(2-methoxyphenyl)ethylamine}Cr-

1

(CO)₃] [(S,Sp)-28]: H NMR (500 MHz, CDCl₃): δ = 1.38 (d, J =

6.8 Hz, 3 H, α-Me), 2.37 (s, 6 H, NMe₂), 3.35 (q, J = 6.8 Hz, 1 H,

α-CH), 3.74 (s, 3 H, OMe), 4.89 (t, J = 6.3 Hz, 1 H, H_Ar), 5.00 (d,

J = 6.6 Hz, 1 H, H_Ar), 5.50 (t, J = 6.6 Hz, 1 H, H_Ar), 5.84 (d, J =

6.6 Hz, 1 H, H_Ar) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 19.84

(α-Me), 43.46 (NMe₂), 55.61 (OMe), 60.60 (α-CH), 73.88 (C_Ar),

84.83 (C_Ar), 94.17 (C_Ar), 96.56 (C_Ar), 105.39 (C_Ar,ipso), 141.39

(C_Ar,ipso), 233.41 (CO) ppm. IR (hexane): ν_CO= 1972, 1903. ¹H

NMR (200 MHz, C₆D₆): δ = 1.12 (d, J = 6.6 Hz, 3 H, α-Me), 2.23

(s, 6 H, NMe₂), 2.93 (s, 3 H, OMe), 3.37 (q, J = 6.8 Hz, 1 H, α-

CH), 4.01 (d, J = 6.3 Hz, 1 H, H_Ar), 4.15 (t, J = 6.1 Hz, 1 H, H_Ar),

4.64 (t, J = 6.3 Hz, 1 H, H_Ar), 5.62 (d, J = 6.3 Hz, 1 H, H_Ar) ppm.

[{η⁶-(S,Sp)-N,N-Dimethyl-1-[2-methoxy-3-(trimethylsilyl)phenyl]-

ethylamine}Cr(CO)₃] [(S,Sp)-30]: ¹H NMR (200 MHz, CDCl₃): δ =

0.35 (s, 9 H, SiMe₃), 1.43 (d, J = 6.3 Hz, 3 H, α-Me), 2.34 (s, 6 H,

NMe₂), 3.06 (q, J = 6.3 Hz, 1 H, α-CH), 3.89 (s, 3 H, OMe), 4.83

(t, J = 7.1 Hz, 1 H, H_Ar), 5.44 (d, J = 5.9 Hz, 1 H, H_Ar), 5.79 (d,

J = 6.6 Hz, 1 H, H_Ar) ppm. ¹³C NMR (50 MHz, CDCl₃): δ = 0.31

(SiMe₃), 21.31 (α-Me), 44.06 (NMe₂), 62.07 (OMe), 64.11 (α-CH),

86.39 (C_Ar), 94.13 (C_Ar,ipso), 97.96 (C_Ar), 100.57 (C_Ar), 109.75

[{η⁶-(S,Rp)-N,N-Dimethyl-1-(2-methoxyphenyl)ethylamine}Cr-

1

(CO)₃] [(S,Rp)-28]: H NMR (500 MHz, CDCl₃): δ = 1.32 (d, J =

7.1 Hz, 3 H, α-Me), 2.24 (s, 6 H, NMe₂), 3.74 (s, 3 H, OMe), 4.00

(q, J = 7.1 Hz, 1 H, α-CH), 4.90 (t, J = 6.1 Hz, H_Ar), 5.66 (d, J =

6.1 Hz, 1 H, H_Ar), 5.52 (t, J = 6.3 Hz, 1 H, H_Ar), 4.98 (d, J =

6.6 Hz, 1 H, H_Ar) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 14.10

(α-Me), 41.16 (NMe₂), 54.35 (OMe), 55.93 (α-CH), 73.12 (C_Ar),

84.36 (C_Ar), 94.46 (C_Ar), 94.61 (C_Ar), 102.65 (C_Ar,ipso), 142.29

(C_Ar,ipso), 233.12 (CO) ppm. IR (hexane): ν_CO= 1973, 1903 cm^–1.

¹H NMR (200 MHz, C₆D₆): δ = 1.22 (d, J = 6.8 Hz, 3 H, α-Me),

1.95 (s, 6 H, NMe₂), 2.93 (s, 3 H, OMe), 3.86 (q, J = 7.1 Hz, 1 H,

α-CH), 3.99 (d, J = 6.6 Hz, 1 H, H_Ar), 4.08 (t, J = 6.3 Hz, H_Ar),

4.68 (t, J = 6.1 Hz, 1 H, H_Ar), 5.19 (d, J = 6.1 Hz, 1 H, H_Ar) ppm.

(C_Ar,ipso), 146.36 (C_Ar,ipso), 233.42 (CO) ppm. IR (hexane): ν_CO

=

1975, 1906 cm^–1.

[{η⁶-(S,Rp)-N,N-Dimethyl-1-[2-methoxy-3-(trimethylsilyl)phenyl]-

ethylamine}Cr(CO)₃] [(S,Rp)-30]: ¹H NMR (400 MHz, CDCl₃): δ

= 0.48 (s, 9 H, SiMe₃), 1.40 (d, J = 6.0 Hz, 3 H, α-Me), 2.36 (s, 6

H, NMe₂), 3.93 (q, J = 6.8 Hz, 1 H, α-CH), 4.00 (s, 3 H, OMe),

(S)-N,N-Dimethyl-1-[2-methoxy-3-(trimethylsilyl)phenyl]ethylamine 4.97 (t, J = 6.0 Hz, 1 H, H_Ar), 5.58 (d, J = 5.8 Hz, 1 H, H_Ar), 5.88

[(S)-29]: (S)-4 (5 g, 27.93 mmol, 1 equiv.) was dissolved in diethyl

ether (200 mL) and the solution cooled to –50 °C. tBuLi (1.7  in

(d, J = 6.0 Hz, 1 H, H_Ar) ppm. The X-ray structure is shown in

Figure 6.

Eur. J. Inorg. Chem. 2007, 4923–4945

www.eurjic.org

4941

E. Alberico, A. Salzer et al.

(S)-N,N-Dimethyl-1-[2-methoxy-3,6-bis(trimethylsilyl)phenyl]ethyl- 3.75 mL, 6.37 mmol, 1.14 equiv.) for 24 h at –50 °C in diethyl ether

FULL PAPER

amine [(S)-31]: This complex was prepared by deprotonation of (S)-

29 (4.00 g, 15.94 mmol, 1 equiv.) with tBuLi (1.7  in pentane;

(100 mL) and then treating the lithiated species with chlorodiphen-

ylphosphane (1.4 g, 6.37 mmol, 1.14 equiv.). The reaction mixture

10.70 mL, 18.17 mmol, 1.14 equiv.) for 24 h at –50 °C in diethyl was warmed to room temperature overnight and then filtered

ether (150 mL) and then treatment of the lithiated species with

chlorotrimethylsilane (8.65 g, 79.70 mmol, 5 equiv.). The reaction

mixture was warmed up to room temperature overnight and then

filtered through short pad of Celite in order to remove LiCl. The

solvent and the excess of ClSiMe₃were distilled off on a rotary

evaporator and the crude product was purified by column

chromatography (aluminium oxide; diethyl ether/hexane, 1:1). Yield

light yellow oil (4.62 g, 90%). ¹H NMR (500 MHz, CDCl₃): δ =

0.34 (s, 9 H, SiMe₃), 0.35 (s, 9 H, SiMe₃), 1.47 (d, J = 7.0 Hz, 3 H,

α-Me), 2.20 (s, 6 H, NMe₂), 3.61 (q, J = 7.0 Hz, 1 H, α-CH), 3.80

through a short pad of Celite in order to remove LiCl. The solvent

was distilled off on a rotary evaporator and the crude product puri-

fied by column chromatography (silica gel; diethyl ether/hexane,

1:1). Yield white crystals (1.25 g, 89%). Crystals suitable for X-ray

analysis were grown by slow diffusion of hexane into a solution of

the compound in diethyl ether at –30 °C (diethyl ether/hexane, 1:3).

¹H NMR (500 MHz, CDCl₃): δ = 1.25 (d, J = 6.4 Hz, 3 H, α-Me),

2.10 (s, 6 H, NMe₂), 3.11 (s, 3 H, OMe), 4.62 (m, J = 6.4, J =

2.4 Hz, 1 H, α-CH), 6.59 (dd, J = 8.2, J = 1.2 Hz, 1 H, H_Ar), 7.10–

7.34 (m, 12 H, 10H_PPh+ 2H_Ar) ppm. ¹³C NMR (125 MHz,

2

(s, 3 H, OMe), 7.35 (d, J = 7.3 Hz, 1 H, H_Ar), 7.42 (d, J = 7.3 Hz, CDCl₃): δ = 19.72 (α-Me), 42.98 (NMe₂), 54.64 (OMe), 62.48 (d,

1 H, H_Ar) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 0.24 (SiMe₃),

2.72 (SiMe₃), 21.23 (α-Me), 45.03 (NMe₂), 62.81 (OMe), 62.97 (α-

J_C,P= 31.8 Hz, α-CH), 110.25 (C_Ar), 119.35 (d, J_C,P= 7.1 Hz, C_Ar),

122.54 (d, J_C,P= 20.3 Hz, C_Ar,ipso), 127.01 (C_PPh), 127.15 (C_PPh),

2

CH), 131.83 (C_Ar), 133.60 (C_Ar), 134.37 (C_Ar,ipso), 141.44 (C_Ar,ipso), 127.54 (C_PPh), 127.60 (C_PPh), 127.62 (C_PPh)², 127.65 (C_PPh),

2

144.72 (C_Ar,ipso), 163.60 (C_Ar,ipso) ppm.

131.62 (C_Ar), ²131.64 (C_PPh), 131.90 (C_PPh), 132.06 (C_PPh), 132.22

2

(C_PPh), 137.44 (d, J_C,P= 9.3 Hz, C

), 1²38.35 (d, J_C,P= 11.0 Hz,

PPh₂

2

Preparation of [{η⁶-(S,Rp)-N,N-Dimethyl-1-[2-methoxy-3,6-bis(tri-

methylsilyl)phenyl]ethylamine}Cr(CO)₃] [(S,Rp)-32]. Thermolysis

with Cr(CO)₆: Treatment of (S)-31 (2.50 g, 7.74 mmol) with

Cr(CO)₆(2.21 g, 10.00 mmol) in an 8:1 mixture of di-n-butyl ether

and thf (40.5 mL) for 45 h according to general procedure B af-

forded (S,Rp)-32 in 94% diastereomeric purity (NMR; Scheme 10).

The crude product was purified by column chromatography (alu-

minium oxide; diethyl ether/hexane, 1:1). Yield 2.90 g (82%).

C_PPh), 154.45 (d, J_C,P= 24.7 Hz, C_Ar,ipso), 161.80 (d, J_C,P= 3.3 Hz,

2

C_Ar,ipso) ppm. ³¹P NMR (81 MHz, CDCl₃): δ = –23.98 ppm.

(S)-N,N-Dimethyl-1-[3-methoxy-2-(trimethylsilyl)phenyl]ethylamine

[(S)-34]: This complex was prepared by deprotonation of (S)-5

(5.00 g, 27.93 mmol, 1 equiv.) with tBuLi (1.7  in pentane;

19.00 mL, 32.30 mmol, 1.14 equiv.) for 24 h at –50 °C in diethyl

ether (200 mL) and then treatment of the lithiated species with

chlorotrimethylsilane (15.17 g, 139.65 mmol, 5 equiv.). The reac-

tion mixture was warmed to room temperature, stirred at that tem-

perature for 10 d and then filtered through a short pad of Celite in

order to remove LiCl. The solvent and excess ClSiMe₃were dis-

tilled off on a rotary evaporator and the crude product was purified

by column chromatography (aluminium oxide; diethyl ether/hex-

ane, 1:1). Yield light yellow oil (6.16 g, 88%). ¹H NMR (200 MHz,

CDCl₃): δ = 0.35 (s, 9 H, SiMe₃), 1.29 (d, J = 6.4 Hz, 3 H, α-Me),

2.19 (s, 6 H, NMe₂), 3.49 (q, J = 6.4 Hz, 1 H, α-CH), 3.75 (s, 3 H,

Arene Exchange with [(η⁶-Naphthalene)Cr(CO)₃]: (S,Rp)-32 was

prepared in a high-pressure Schlenk tube from (S)-31 (1.51 g,

4.68 mmol) and [(η⁶-naphthalene)Cr(CO)₃] (1.50 g, 5.68 mmol) in

di-n-butyl ether (25 mL). After all reagents and the solvent had

been mixed, a catalytic amount of thf (0.53 g, 7.35 mmol) was

added, the reaction mixture was degassed by means of ultrasound

and three freeze-pump-thaw cycles and then heated in the dark at

75 °C for 140 h. The reaction mixture was filtered through a short

pad of Celite and the solvent distilled off on a rotary evaporator

to afford (S,Rp)-31 in Ͼ99% de (NMR). The crude product was

purified by flash chromatography (aluminium oxide; diethyl ether/

hexane, 1:7) to yield 1.14 g of yellow crystals (53 %). ¹H NMR

(500 MHz, CDCl₃): δ = 0.37 (s, 9 H, SiMe₃), 0.42 (s, 9 H, SiMe₃),

1.44 (d, J = 7.0 Hz, 3 H, α-Me), 2.16 (s, 6 H, NMe₂), 3.13 (q, J =

7.0 Hz, 1 H, α-CH), 3.74 (s, 3 H, OMe), 4.84 (d, J = 6.4 Hz, 1 H,

H_Ar), 5.51 (d, J = 6.1 Hz, 1 H, H_Ar) ppm. ¹³C NMR (125 MHz,

CDCl₃): δ = 0.40 (SiMe₃), 2.38 (SiMe₃), 25.07 (α-Me), 45.35

(NMe₂), 59.66 (OMe), 62.67 (α-CH), 91.28 (C_Ar,ipso), 93.32 (C_Ar),

103.03 (C_Ar), 105.12 (C_Ar,ipso), 118.63 (C_Ar,ipso), 146.41 (C_Ar,ipso),

233.60 (C_Ar,ipso) ppm. IR (hexane): ν_CO= 1970, 1900 cm^–1.

OMe), 6.69 (d, J = 7.3 Hz, 1 H, H_Ar), 7.17–7.35 (m, 2 H, H_Ar

)

ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 3.12 (SiMe₃), 22.91 (α-

Me), 44.16 (NMe₂), 54.87 (OMe), 63.85 (α-CH), 107.95 (C_Ar),

119.24 (C_Ar), 125.56 (C_Ar,ipso), 130.50 (C_Ar), 153.91 (C_Ar,ipso), 164.46

r.t.

(C_Ar,ipso) ppm. [α]_D= –80.36 (c = 0.21, CHCl₃).

[{η⁶-(S,Rp)-N,N-Dimethyl-1-[3-methoxy-2-(trimethylsilyl)phenyl]-

ethylamine}Cr(CO)₃] [(S,Rp)-35]: This complex was prepared in a

high-pressure Schlenk tube from (S)-34 (2.03 g, 8.10 mmol) and

[(η⁶-naphthalene)Cr(CO)₃] (2.56 g, 9.70 mmol) in di-n-butyl ether

(40 mL). After all reagents and the solvent had been mixed, a cata-

lytic amount of thf (0.9 g, 10.88 mmol) was added, the reaction

mixture was degassed by means of ultrasound and three freeze-

pump-thaw cycles and then heated in the dark at 75 °C for 72 h.

The reaction mixture was then filtered through a short pad of Ce-

lite and the solvent was distilled off on a rotary evaporator to give

the desired product in 86% de (NMR). The crude product was

taken up in diethyl ether and purified by flash chromatography

(aluminium oxide; diethyl ether/hexane, 3:1). A yellow-orange pow-

der contaminated with unreacted [(η⁶-naphthalene)Cr(CO)₃] was

obtained after evaporation of the solvents. The product was iso-

lated in high purity (de Ͼ 98%) after a second chromatographic

purification (silica gel; diethyl ether/hexane, 1:7). Yield 2.24 g

(71%). ¹H NMR (200 MHz, CDCl₃): δ = 0.45 (s, 9 H, SiMe₃),

11.01 (d, J = 6.8 Hz, 3 H, α-Me), 2.22 (s, 6 H, NMe₂), 3.00 (s, 3

H, OMe), 3.53 (q, J = 7.2 Hz, 1 H, α-CH), 4.15 (d, J = 6.8 Hz, 1

H, H_Ar), 5.07 (t, J = 6.8 Hz, 1 H, H_Ar), 5.33 (d, J = 6.4 Hz, 1 H,

H_Ar) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 2.98 (SiMe₃), 23.21

Preparation of [{η⁶-(S,Rp)-N,N-Dimethyl-1-(2-methoxyphenyl)ethyl-

amine}Cr(CO)₃] [(S,Rp)-28]: (S,Rp)-31 (1.61 g, 3.51 mmol) was dis-

solved in thf (30 mL) and the solution cooled to 0 °C. Tetra-n-bu-

tylammonium fluoride (1  in thf; 9.00 mL, 9.00 mmol) was added

dropwise and the solution stirred at 0 °C for 4 h (Scheme 10). After

addition of distilled water the reaction mixture was extracted sev-

eral times with diethyl ether. The combined organic phases were

concentrated on a rotary evaporator and the residue was purified

by column chromatography (aluminium oxide; diethyl ether) to af-

ford (S,Rp)-28 in diastereomerically pure form as yellow crystals.

Yield 0.62 g (56%).

(S)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-3-methoxyphenyl]-

ethylamine [(S)-33]: This complex was prepared by deprotonating

(S)-5 (1.00 g, 5.58 mmol, 1 equiv.) with tBuLi (1.7  in pentane;

4942

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Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

(α-Me), 44.02 (NMe₂), 54.93 (OMe), 60.54 (α-CH), 75.05 (C_Ar),

crystals (0.38 g, 54 %). Crystals suitable for X-ray analysis were

85.51 (C_Ar), 93.94 (C_Ar), 100.00 (C_Ar,ipso), 115.40 (C_Ar,ipso), 147.25 grown by means of slow diffusion of hexane into a solution of the

(C_Ar,ipso), 234.74 (CO) ppm. IR (hexane): ν_CO= 1965, 1895 cm^–1.

compound in diethyl ether at –30 °C. ¹H NMR (500 MHz, CDCl₃):

δ = 1.29 (d, J = 6.7 Hz, 3 H, α-Me), 1.76 (s, 6 H, NMe₂), 3.72 (s,

3 H, OMe), 4.47 (d, J = 5.2 Hz, 1 H, H_Ar), 4.55 (dq, J = 6.7, J =

2.4 Hz, 1 H, α-CH), 5.25–5.29 (m, 2 H, H_Ar), 7.20–7.33 (m, 10 H,

H_PPh) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 10.74 (α-Me), 38.90

(NM²e₂), 56.01 (OMe), 60.17 (d, J_C,P= 19.2 Hz, α-CH), 77.54 (C_Ar),

90.74 (C_Ar), 94.18 (d, J_C,P= 1.9 Hz, C_Ar), 107.83 (d, J_C,P= 18.2 Hz,

C_Ar,ipso), 110.54 (d, J_C,P= 24.0 Hz, C_Ar,ipso), 127.74–134.83 (10 C,

[{η⁶-(S,Sp)-N,N-Dimethyl-1-(3-methoxyphenyl)ethylamine}Cr-

(CO)₃] [(S,Sp)-36]: (S,Rp)-35 (2.03 g, 5.23 mmol) was dissolved in

thf (18 mL) and the solution cooled to 0 °C. Tetra-n-butylammo-

nium fluoride (1  in thf, 6.38 mL, 6.38 mmol) was added dropwise

and the solution was stirred at 0 °C for 4 h. After addition of dis-

tilled water the reaction mixture was extracted several times with

diethyl ether. The combined organic phases were concentrated on

a rotary evaporator and the residue was purified by column

chromatography (silica gel; diethyl ether/acetone) to afford (S,Sp)-

36 as yellow crystals. Yield 1.41 g (85 %). ¹H NMR (200 MHz,

CDCl₃): δ = 0.99 (d, J = 6.8 Hz, 3 H, α-Me), 1.89 (s, 6 H, NMe₂),

3.02 (s, 3 H, OMe), 3.39 (q, J = 6.8 Hz, 1 H, α-CH), 4.25 (d, J =

6.6 Hz, H_Ar), 4.52 (d, J = 6.3 Hz, 1 H, H_Ar), 4.80 (t, J = 6.6 Hz, 1

H, H_Ar), 4.95 (s, 1 H, H_Ar) ppm. ¹³C NMR (50 MHz, CDCl₃): δ =

10.49 (α-Me), 40.58 (NMe₂), 55.65 (OMe), 61.20 (α-CH), 75.78

(C_Ar), 79.26 (C_Ar), 88.48 (C_Ar), 93.98 (C_Ar), 114.42 (C_Ar,ipso), 142.53

(C_Ar,ipso), 233.06 (CO) ppm. IR (hexane): ν_CO= 1970, 1900 cm^–1.

C_PPh), 136.56 (d, J_C,P= 17.3 Hz, C

), 137.58 (d, J_C,P= 5.6 Hz,

PPh₂

2

C_PPh), 140.52 (d, J_C,P= 3.8 Hz C_Ar,ipso), 233.36 (CO) ppm. ³¹P

2

NMR (81 MHz, CDCl₃): δ = –11.22 ppm. IR (hexane): ν_CO= 1970,

1896 cm^–1. C₂₆H₂₆CrNO₄P: calcd. C 62.52, H 5.21, N 2.80; found

62.61, H 6.05, N 2.39.

[{η⁶-(S,Sp)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-5-methoxy-

phenyl]ethylamine}Cr(CO)₃] [(S,Sp)-38]: This complex was pre-

pared according to general procedure C by lithiation of (S,Sp)-36

(1.36 g, 4.30 mmol) with tert-butyllithium (1.7  in pentane;

2.90 mL, 4.90 mmol) and treatment of the lithiated species with

[{η⁶-(S,Sp)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-6-methoxy- chlorodiphenylphosphane (1.80 g, 4.90 mmol) in dry diethyl ether

phenyl]ethylamine}Cr(CO)₃] [(S,Sp)-37]: This complex was pre-

pared according to general procedure C by lithiation of (S,Sp)-28

(0.45 g, 1.43 mmol) with tert-butyllithium (1.7  in pentane;

0.96 mL, 1.63 mmol) and treatment of the lithiated species with

chlorodiphenylphosphane (0.36 g, 1.63 mmol) in dry diethyl ether

(25 mL). The crude product was purified by column chromatog-

raphy (aluminium oxide; diethyl ether/hexane, 2:1). Yield yellow

(250 mL; see Scheme 15). The crude product was purified by col-

umn chromatography (silica gel; diethyl ether/hexane, 1:6). Yield

1.22 g (57%); yellow crystals. ¹H NMR (500 MHz, CDCl₃): δ =

0.82 (d, J = 6.7 Hz, 3 H, α-Me), 1.45 (s, 6 H, NMe₂), 3.01 (s, 3 H,

OMe), 3.97 (d, J = 6.4 Hz, 1 H, H_Ar), 4.65 (m, 1 H, α-CH), 4.92

(d, J = 6.7 Hz, 1 H, H_Ar), 5.05 (s, 1 H, H_Ar), 7.06–7.56 (m, 10 H,

H

_PPh) ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 5.48 (α-Me), 37.85

2

Table 5. Crystallographic data, data collection and structure refinement parameters for (S,Rp)-23b, (S,Sp)-28, (S,Rp)-30 and (S)-33.

(S,Rp)-23b

(S,Sp)-28

(S,Rp)-30

(S)-33

Empirical formula

Formula mass

Crystal habit, colour

C₃₆H₄₂Cr₁O₃P₂

636.68

hexagonal prism, yellow

C₁₄H₁₇CrNO₄

315.29

rod, yellow

0.90ϫ0.16ϫ0.14

orthorhombic

P2₁2₁2₁

6.612(6)

9.932(10)

22.04(2)

C₁₇H₂₅CrNO₄Si

387.47

rod, yellow

0.22ϫ0.05ϫ0.05

monoclinic

C₂

41.416(7)

6.7122(12)

22.578(4)

112.069(4)

5816.6(18)

12

1.327

2448

0.671

Bruker Smart CCD

110(2)

1.7–25.2

24383

9823

0.0941

6761

655

0.0611

0.1337

0.00(3)

C₂₃H₂₆NOP

363.44

rod, colourless

0.53ϫ0.26ϫ0.16

monoclinic

P2₁

9.099(12)

12.294(16)

18.36(2)

92.79(3)

2051(4)

4

1.177

776

0.145

Bruker Smart CCD

293(2)

2.0–28.3

50905

8929

0.0365

7561

477

0.0407

0.1093

–0.06(6)

1.026

Crystal dimensions [mm] 0.74ϫ0.39ϫ0.37

Crystal system

Space group

a [Å]

b [Å]

c [Å]

orthorhombic

P2₁2₁2₁

12.7113(14)

34.4771(17)

7.8497(4)

β [°]

V [Å³]

3440.1(5)

4

1.229

1344

0.458

Enraf Nonius CAD4

293(2)

3.1–26.0

9867

6725

0.083

3278

381

0.0740

0.1507

–0.01(4)

0.999

1447(2)

4

1.447

656

0.802

Bruker Smart CCD

153(2)

1.9–28.3

19784

3582

0.0283

3464

Z

D [gcm^–3]

F(000)

µ(Mo-K_α) [cm^–1]

Diffractometer

T [K]

θ range [°]

Reflections collected

Unique refl.

R_int

Reflections observed

Parameters refined

R₁

185

0.0412

0.1001

0.03(3)

1.313

wR₂

Flack parameter

GooF

1.002

0.40/–0.51

Diff. peak/hole [eÅ^–3]

0.34/–0.24

0.55/–0.29

0.30/–0.141

Eur. J. Inorg. Chem. 2007, 4923–4945

www.eurjic.org

4943

E. Alberico, A. Salzer et al.

FULL PAPER

(NMe₂), 55.08 (OMe), 58.98 (d, J_C,P= 14.4 Hz, α-CH), 73.95 (C_Ar),

79.62 (C_Ar), 99.61 (C_Ar), 100.33 (d, J_C,P= 24.0 Hz, C_Ar,ipso), 120.88

1 H, H_Ar), 4.20 (d, J = 7.3 Hz, 1 H, H_Ar), 4.83 (m, 1 H, α-CH),

4.97 (t, J = 7.3 Hz, 1 H, H_Ar), 7.07–7.31 (m, 8 H, H_PPh), 7.79 (t,

2

(d, J_C,P= 21.1 Hz, C_Ar,ipso), 128.75 (d, J_C,P= 5.8 Hz C_PPh), 129.18 J = 8.3 Hz, 2 H, H_PPh) ppm. ¹³C NMR (125 MHz, CDCl₃): δ =

2

(C_PPh), 132.31 (d, J_C,P= 20.1 Hz, C

), 135.24 (d, J_C,P= 21.1 Hz,

5.80 (α-Me), 38.03 (NMe₂), 54.51 (OMe), 58.88 (d, J_C,P= 22.1 Hz,

PPh₂

2

C_PPh), 137.62 (d, J_C,P= 14.4 Hz, C

), 139.00 (d, J_C,P= 6.7 Hz,

α-CH), 71.48 (C_Ar), 82.47 (C_Ar), 94.03 (C_Ar), 121.98 (d, J_C,P=

PPh₂

2

C_PPh), 142.94 (C_Ar,ipso), 233.01 (CO) ppm. ³¹P NMR (81 MHz, 8.6 Hz, C_Ar,ipso), 123.60 (d, J_C,P= 25.9 Hz, C_Ar,ipso), 127.41–135.83

2

CDCl₃): δ = –16.74 ppm. IR (hexane): ν_CO= 1972, 1908 cm^–1

.

(10 C, C_PPh), 137.60 (d, J_C,P= 14.2 Hz, 1 C, C

), 139.90 (d, J_C,P

PPh₂

C₂₆H₂₆NO₄PCr (499.46): calcd. C 62.52, H 5.21, N 2.80; found C = 6.5 Hz, 1²C, C_PPh), 146.80 (C_Ar,ipso), 233.24 (CO) ppm. ³¹P NMR

62.78, H 5.54, N 2.89.

(81 MHz, C₆D₆):²δ = –10.70 ppm. IR (hexane): ν_CO= 1971,

1903 cm^–1.

[{η⁶-(S,Sp)-N,N-Dimethyl-1-[2-(diphenylphosphanyl)-3-methoxy-

phenyl]ethylamine}Cr(CO)₃] [(S,Sp)-40]: A 1:1 mixture of (S,Sp)-36

X-ray Structure Determination: Crystal data and details of the

and (S,Rp)-36 (4.20 g, 13.33 mmol, 1 equiv.) was dissolved in di- structure determinations are listed in Tables 5 and 6. Data collec-

ethyl ether (250 mL). The solution was cooled to –80 °C and tert-

butyllithium (1.7  in pentane; 8.94 mL, 15.20 mmol, 1.14 equiv.)

was added dropwise (Scheme 16). After stirring for 4 h at –80 °C,

chlorodiphenylphosphane (3.35 g, 15.20 mmol, 1.14 equiv.) was

added dropwise. The reaction mixture was warmed to room tem-

perature overnight, filtered through a short pad of celite to remove

LiCl and the solvent removed in vacuo. Three compounds were

detected in the NMR spectrum of the crude product: (S,Sp)-38, 39

and (S,Sp)-40 in a 31:20:49 ratio. The crude product was purified

by column chromatography (aluminium oxide; diethyl ether/hex-

ane, 1:7). Only (S,Sp)-40 was isolated and further purified by col-

umn chromatography on silica gel. Yield yellow crystals (0.64 g,

22%). Crystals suitable for X-ray analysis were grown by slow dif-

fusion of hexane into a solution of the complex in diethyl ether at

tion was performed with a Bruker Smart CCD (Mo-K_αradiation,

λ = 0.71073 Å, graphite monochromator) fitted with an area detec-

tor for (S,Sp)-28, (S,Rp)-30, (S)-33, and (S,Sp)-40 and an Enraf

Nonius CAD4 diffractometer (Mo-K_αradiation, λ = 0.71073 Å,

graphite monochromator) for (S,Rp)-23b, (S,Sp)-36, (S,Sp)-37 and

(S,Sp)-38. The unit-cell parameters were obtained by least-squares

refinement of up to 8096 reflections for the area detector and 25

reflections for the CAD4 point detector. The structures were solved

by direct methods (SHELXS-97)^[29]and refined by full-matrix

least-squares procedures based on F²with all measured reflections

(SHELXL-97).^[29]The SADABS^[30]program was used for absorp-

tion correction of the structures. All non-hydrogen atoms were re-

fined anisotropically. All H-atoms were introduced at their ideal-

ised positions and were refined using a riding model. The absolute

configuration was confirmed by evaluation of the Flack^[31]param-

eter. Displacement ellipsoid plots were obtained with PLATON.^[32]

1

–30 °C. H NMR (200 MHz, C₆D₆): δ = 0.85 (d, J = 6.3 Hz, 3 H,

α-Me), 1.69 (s, 6 H, NMe₂), 2.59 (s, 3 H, OMe), 3.87 (d, J = 7.3 Hz,

Table 6. Crystallographic data, data collection and structure refinement parameters for (S,Sp)-36, (S,Sp)-37, (S,Sp)-38 and (S,Sp)-40.

(S,Sp)-36

(S,Sp)-37^[a]

(S,Sp)-38

(S,Sp)-40

Empirical formula

Formula mass

Crystal habit, colour

C₁₄H₁₇CrNO₄

315.29

plate, pale yellow

C₂₆H₂₆CrNO₄P

499.45

rod, yellow

0.83ϫ0.20ϫ0.15

orthorhombic

P2₁2₁2₁

12.0203(10)

13.3439(10)

15.6855(10)

2515.9(3)

4

1.319

1040

0.549

Enraf Nonius CAD4

293(2)

C₂₆H₂₆CrNO₄P

499.45

irregular, yellow

0.70ϫ0.60ϫ0.20

orthorhombic

P2₁2₁2₁

7.8948(5)

14.8611(17)

42.615(5)

4999.8(9)

8

1.327

2080

0.053

Enraf Nonius CAD4

223(2)

C₂₆H₂₆CrNO₄P

499.45

platelet, yellow

0.85ϫ0.28ϫ0.06

orthorhombic

P2₁2₁2₁

8.2725(10)

10.8788(13)

29.045(3)

2613.9(5)

4

1.269

1040

0.0529

Bruker Smart CCD

200(2)

Crystal dimensions [mm] 0.52ϫ0.35ϫ0.12

Crystal system

Space group

a [Å]

orthorhombic

P2₁2₁2₁

7.012(3)

8.509(4)

24.36(1)

1453.4(11)

4

b [Å]

c [Å]

V [Å³]

Z

D [gcm^–3]

F(000)

1.44

656

µ(Mo-K_α) [cm^–1]

Diffractometer

T [K]

0.798

Enraf Nonius CAD4

223(2)

θ range [°]

Reflections collected

Unique refl.

R_int

Reflections observed

Parameters refined

R₁

2.4–26.0

12629

2851

0.145

1940

185

0.0656

2.0–25.0

6688

3419

0.0426

2492

302

0.0416

2.4–26.0

14852

9801

0.0536

7770

655

0.0436

2.0–28.3

36050

6499

0.0614

5482

477

0.0547

wR₂

0.1459

0.02(5)

0.954

0.0895

–0.02(3)

1.034

0.0915

–0.008(17)

1.065

0.1325

0.01(3)

1.066

0.60/–0.36

Flack parameter

GooF

Diff. peak/hole [eÅ^–3]

0.73/–1.46

0.19/–0.24

0.35/–0.28

[a] Due to a technical problem with the diffractometer the intensity data collection for the crystal of (S,Sp)-37 had to be stopped at

about 73% completion; the data are, however, sufficient to ensure a reliable assignment of the absolute configuration.

4944

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Eur. J. Inorg. Chem. 2007, 4923–4945

“Daniphos”-Type PʝP- and PʝN-Ligands

[11]

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the Cahn–Ingold–Prelog (CIP) rules. If the shortest path from

the substituent displaying highest priority to the following one

is clockwise, the absolute configuration is denoted as Rp, while

the opposite case is referred to as S_P.

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213–224.

Due to a technical problem with the diffractometer the intensity

data collection for the sample of (S,Sp)-37 had to be stopped at

about 73% completion; the data are, however, sufficient to ensure

a reliable assignment of the absolute configuration.

CCDC-648702 to -648709 contain the supplementary crystallo-

graphic data for this paper. These data can be obtained free of

charge from The Cambridge Crystallographic Data Centre via

www.ccdc.cam.ac.uk/data_request/cif.

[12]

[13]

[14]

[15]

Acknowledgments

The authors are grateful for financial support from the Deutsche

Forschungsgemeinschaft DFG within the Collaborative Research

Center (SFB, 380) “Asymmetric Synthesis with Chemical and Bio-

logical Means” and the Graduiertenkolleg 440 “Methods in Asym-

metric Synthesis” for three scholarships for E. A., B. C.-C. and

D. T. We also thank Dr. K. Ditrich from BASF Corporation for a

generous gift of various chiral phenylethylamines.

[16]

[17]

[18]

[1] a) U. Englert, A. Salzer, D. Vasen, Tetrahedron: Asymmetry

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[2] a) A. Salzer, Coord. Chem. Rev. 2003, 242, 59–72; b) K. Muñiz,

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Dalton Trans. 2003, 1606–1612; c) W. Braun, A. Salzer, F. Spin- [23] a) J.-C. Hierso, A. Fihri, V. V. Ivanov, B. Hanquet, N. Pirio, B.

dler, E. Alberico, Appl. Catal., A 2004, 274, 191–203; d) W.

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Donnadieu, B. Rebière, R. Amardeil, P. Meunier, J. Am. Chem.

Soc. 2004, 126, 11077–11087. b) In the series of Daniphos di-

phosphanes supported on the more rigid scaffold provided by

the indane framework the ⁴J phosphorus-phosphorus coupling

constants are even larger at 58 Hz for the PPh₂/PPh₂diphos-

phane, 64.1 Hz for the PPh₂/PCy₂one and 89.7 Hz for the

PPh₂/PtBu₂one (see ref.^[3e]).

[4] D. Totev, A. Salzer, D. Carmona, L. A. Oro, F. J. Lahoz, I. T.

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Published Online: September 12, 2007

Eur. J. Inorg. Chem. 2007, 4923–4945

www.eurjic.org

4945

Article Doi

Expanding the range of "Daniphos"-type P∩P- and P∩N-ligands: Synthesis and structural characterisation of new [(η6-arene)Cr(CO)3] complexes

DOI: 10.1002/ejic.200700568

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