Stabilization of the labile metal configuration in halfsandwich complexes [CpRh(PN)Hal]X

Journal of Organometallic Chemistry 689 (2004) 4244–4262

www.elsevier.com/locate/jorganchem

Stabilization of the labile metal conﬁguration in halfsandwich

complexes [CpRh(PN)Hal]X ^q

a,

Henri Brunner ^*, Andreas Ko¨llnberger, Arshad Mehmood,

1

Takashi Tsuno, Manfred Zabel

a

Institut fu¨r Anorganische Chemie, Universita¨t Regensburg, 93040 Regensburg, Germany

Received 18 June 2004; accepted 21 July 2004

Available online 16 September 2004

Abstract

PN ligands 3 and 4, derived from 2-diphenylphosphanylmethylpyridine 2a, were synthesized, to which in the backbone a tether to

a cyclopentadiene system and for comparison an ⁱPr substituent were attached. The chiral compounds were resolved by introduction

of a menthoxy substituent into the 2-position of the pyridine system and/or palladium complexes with enantiomerically pure co-lig-

ands. The tripod ligand 3b contains three diﬀerent binding sites (Cp, P, N) connected by a resolved chiral carbon atom. (S_C)-con-

ﬁguration of this tripod ligand enforces (R_Rh)-conﬁguration at the metal atom in the halfsandwich rhodium complex

(L_Ment,S_C,R_Rh)-7b. The opposite metal conﬁguration is inaccessible. Substitution of the chloro ligand in (L_Ment,S_C,R_Rh)-7b by halide

(Br, I) or pseudohalide (N₃, CN, SCN) ligands occurs with retention of conﬁguration to give complexes 8b–11b. However, in the

reaction of (L_Ment,S_C,R_Rh)-7b with PPh₃the pyridine arm of the tripod ligand in compound 13b becomes detached from the metal

atom. In the Cp*Rh and CpRh compounds of the bidentate PN ligands 4a and 4b both metal conﬁgurations are accessible and in

complexes 14a–17a and 14b–17b they equilibrate fast. The stereochemical assignments are corroborated by 9 X-ray analyses.

Keywords: Rhodium; Chirality; Metal conﬁguration; Retention

1. Introduction

of the type [(g⁵-C₅H₅)Rh(PN)Cl]PF₆(Scheme 1, top),

which only diﬀer in the metal conﬁguration [1–3]. In

solution these compounds epimerize by a change of

the labile metal conﬁguration initiated by dissociation

of the monodentate ligand or by chelate ring opening

[4,5]. Compounds of this type are catalysts in organic

transformations, such as transfer hydrogenation, isome-

rization, Diels–Alder reactions, etc. [6–8].

In three-legged pianostool complexes of the type [(gⁿ-

Ar)M(LL⁰)X], L–L⁰= unsymmetrical chelate ligand and

X = monodentate ligand, the metal atom is a chiral cen-

ter. With an enantiomerically pure chelate ligand, e.g. an

ⁱPr-substituted (S_C)-conﬁgurated PN ligand, two dia-

stereomers (S_C,R_Rh) and (S_C,S_Rh) arise in compounds

As usually the epimerization at the metal atom is

much faster than the catalytic reaction, two diastereo-

meric catalysts are present [6,7]. It is known that the

stereochemistry of reactions occurring at a metal center

strongly depend on the metal conﬁguration [9]. Thus,

reaction channels with diastereomeric catalysts diﬀering

in the metal conﬁguration tend to produce products

q

Optically Active Transition Metal Complexes, 134. Part 133:

H. Brunner, A. Ko¨llnberger, M. Zabel, Polyhedron 2003, 22, 2639.

*

Corresponding author. Tel./fax: +49 941 943 4439.

E-mail address: henri.brunner@chemie.uni-regensburg.de (H.

Brunner).

1

X-ray structure analyses.

doi:10.1016/j.jorganchem.2004.07.057

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4245

H

CH₃

Rh

H

PF₆

fast

PF₆

Rh

C

H

P

Cl

CH₃

P

Cl

N

C

H₃

N

C

H₃

H

,R_Rh

)

(S_C

,S_Rh

)

(S_C

CH₃

PF₆

Rh

C

H

inaccessible

P

CH₃

Cl

N

,S_Rh

)

(S_C

,R_Rh

)

(S_C

Scheme 1. Stabilization of the metal conﬁguration with a tripod ligand.

with opposite conﬁguration. Diastereomer equilibria in

chiral-at-metal halfsandwich complexes may lie between

50:50 and 99:1 [10–13]. However, although in a 99:1

equilibrium one of the two diastereomers is dominating

by two powers of ten, this is no general solution of the

problem, because the more stable isomer may be the less

reactive catalyst and vice versa as shown for diastereo-

meric complexes of prochiral oleﬁns bonded to Rh(LL*)

fragments in asymmetric hydrogenations [14]. There-

fore, it would be desirable to control the metal conﬁgu-

ration such that only a catalyst with a single metal

conﬁguration is present during catalysis. In this paper,

we describe a new tripod ligand CpH(PN_Ment) which

ﬁx the metal chirality inhibiting any conﬁgurational

change. This ligand has three diﬀerent binding sites, a

cyclopentadiene system (CpH), a diphenylphosphanyl

group (P) and a pyridine ring (N_Ment) connected by an

asymmetric carbon atom. We also report on the biden-

stituent and, thus, the source of diastereomerism, and

their complexes is included in the present study.

2. The Ligands 2–4

Starting materials for the ligands 2–4 were the ortho-

methylpyridines 1a,b (Scheme 2). 2-Methylpyridine (1a)

is commercially available. 2-Menthoxy-6-methylpyri-

dine (1b) was prepared by substitution of the bromo

substituent in 2-bromo-6-methylpyridine [16] for the an-

ion of L-(ꢀ)-menthol. 2-Diphenylphosphanylmethylpy-

ridine (2a) is a known compound [17–19]. For the

synthesis of 6-diphenylphosphanylmethyl-2-menthoxy-

pyridine (2b) the methyl group in a-position of the pyri-

dine ring was deprotonated with BuLi and reacted with

PPh₂Cl to introduce the diphenylphosphanyl group. The

yields of 2a and 2b could be improved provided the syn-

theses were carried out at low temperatures in dilute

solutions. In addition, the lithiated 2-methylpyridine

(1a) and 2-menthoxy-6-methylpyridine (1b) should be

slowly added to the PPh₂Cl solution to avoid transmet-

allation and addition of a second PPh₂group [20].

In the synthesis of the cyclopentadiene derivatives 3a

and 3b the intermediates 2a and 2b were not isolated.

After deprotonation of 2a and 2b with BuLi 6,6⁰-

dimethylfulvene was added. Hydrolysis aﬀorded the

tripod ligands 3a and 3b, containing a new asymmetric

carbon atom at the branching point of the three diﬀerent

binding sites CpH, P and N. We have reported on the

synthesis of 3a in a previous study [21].

tate ligand PN_Ment. The tripod ligand CpH(PN_Ment

)

aﬀorded cationic half-sandwich complexes with

RhCl₃Æ 3H₂O in which only one additional chloro lig-

and is bonded to the Rh atom. For comparison the cor-

responding complexes with a combination of the

bidentate ligand PN_Mentwith a separated Cp or Cp* lig-

and were synthesized. Due to the L-menthyl substituent

diastereomers arise with respect to the conﬁguration of

the branching position (R_C)/(S_C) and the metal conﬁgu-

ration (R_Rh)/(S_Rh). Fortunately, these diastereomers dif-

fer in their ¹H and ³¹P NMR spectra allowing to

monitor separation procedures and to determine diaster-

eomer ratios. Part of this work has been published in a

communication [15]. In addition, the synthesis of the lig-

ands CpH(PN) and PN, devoid of the L-menthyl sub-

In the case of 3a two of the three possible double

bond isomers with respect to the cyclopentadiene system

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H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

PPh₂

R

N

R

N

R

N

R

N

2a,b

1a,b

4a-c

3a,b

1-4

R

H

a

b

c

O

OH

Scheme 2. Ligands 2–4 (only 2-cyclopentadiene isomers shown for 3a and 3b).

1

were observed in the H NMR spectrum in a ratio of

75:25. Only the main isomer is shown in Scheme 2. Slow

diﬀusion of petroleum ether into an acetone solution of

3a aﬀorded single crystals which X-ray analysis proved

to be the racemate with an inversion center between

the (R)- and (S)-enantiomer (Fig. 1). The bond lengths

indicated that the double bonds were between C1/C5

and C2/C3. The saturated carbon atom was C4. After

dissolution of the crystals in CDCl₃both double bond

Ph₂

P

H

Ph₂

P

H

Pd

N

H

Me

N

PF₆

Me₂

O

Pd

N

Me

N

Me₂

1

(L_Ment,R_C)(S)-5b

(S,S)-5a

isomers were observed in the H NMR spectrum.

Resolution of 3a was attempted with the palla-

dium(II) complex of the ortho-metallated ligand (S)-

Ph₂

P

Cl

Pd

Cl

Ph₂

Cl

P

H

N

Pd

H

Cl

HO

O

N

(L_Ment,R_C)-6b

(R_C)-6c

Scheme 3. Complexes (S,S)-5a, (L_Ment,R_C)(S)-5b, (L_Ment,R_C)-6b and

(R_C)-6c.

(ꢀ)-N,N-dimethyl-1-phenylethylamine (NMe₂pea).

A

suspension of [(NMe₂pea–H⁺)PdCl]₂[22] dissolved in

methanol on addition of the racemic mixture of 3a.

After adding NH₄PF₆two diastereomeric Pd complexes

(S,S)- and (R,S)-5a formed in a 1:1 ratio (Scheme 3).

Similar to the free ligand for each diastereomer there

were two double bond isomers with respect to the unco-

ordinated cyclopentadiene system in a ratio of 75:25.

Advantageously, the air-sensitive phosphorus atom of

the ligand was protected in the palladium complex such

that all manipulations could be carried out on air

including chromatography. However, all the experi-

ments to separate the diastereomers by fractional

crystallization failed. The reason was obvious from an

X-ray analysis of crystals obtained by crystallization

from THF solution at ꢀ27 ꢁC. The single crystals con-

Fig. 1. Molecular structure of racemate 3a (only (R)-enantiomer

shown). Hydrogen atoms omitted except of a-carbon atom. Selected

˚

bond lengths [A] and angles [ꢁ]: C1–C2 1.468(3), C2–C3 1.351(3), C3–

C4 1.483(4), C4–C5 1.494(3), C5–C1 1.350(3), C1–C6 1.518(3), P1–C9

1.8894(19), P1–C15 1.8503(19), P1–C21 1.853(2); C10–C9–C6

112.40(15), C6–C9–P1 112.16(12), C10–C9–H9a 107.71, H9a–C9–P1

107.71, C9–P1–C15 101.35(8), C15–P1–C21 100.08(9), C21–P1–C9

102.65(9).

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4247

C1

P1

C7

C22

O1

C26

C13

(S)

N1

C18

C27

C17

C19

C21

C20

Fig. 3. Molecular structure of (L_Ment,S_C)-3b. Hydrogen atoms omitted

˚

except of a-carbon atom. Selected bond lengths [A] and angles [ꢁ]: P1–

C1 1.8504(8), P1–C7 1.8470(15), P1–C13 1.8953(17), O1–C26 1.366(2),

O1–C27 1.455(2), C17–C18 1.464(3), C18–C19 1.340(3), C19–C20

1.474(3), C20–C21 1.480(3), C21–C17 1.348(3); C1–P1–C7 101.06(8),

C7–P1–C13 104.35(9), C13–P1–C1 100.84(8), C27–O1–C26

118.12(13).

Fig. 2. Molecular structure of the 1:1 diastereomer mixture of 5a (only

(S,S)-diastereomer shown). Hydrogen atoms omitted except of a-

carbon atom. Selected bond lengths [A] and angles [ꢁ]: Pd1–N1

2.159(3), Pd1–N2 2.159(3), Pd1–C27 1.994(4), Pd1–P1 2.2342(9), P1–

C13 1.880(3), P1–C1 1.827(3), P1–C7 1.833(3), C17–C18 1.356(5),

C18–C19 1.484(5), C19–C20 1.437(6), C20–C21 1.388(5), C21–C17

1.456(5); N1–Pd1–N2 102.46(12), N2–Pd1–C27 80.57(14), C27–Pd1–

P1 98.92(11), P1–Pd1–N1 79.61(9), Pd1–P1–C7 119.36(11), C7–P1–C1

106.01(15), C1–P1–C13 101.27(10), C13–P1–Pd1 101.27(10).

˚

The cyclopentadiene isomers of 3b interchange in solu-

tion. Therefore, the ³¹P{¹H} NMR spectra of both dia-

stereomers are broad at room temperature. Whereas the

³¹P{¹H} NMR spectrum of (L_Ment,R_C)-3b showed only

an extremely broad peak, for (L_Ment,S_C)-3b the signals

of two cyclopentadiene isomers at ꢀ9.10 and ꢀ8.45

ppm appeared relatively sharp integrating 76:24. On low-

ering the temperature the two ³¹P{¹H} NMR signals of

the 76:24 cyclopentadiene isomers of (L_Ment,S_C)-3b split-

ted into 6 signals due to slowly interconverting conform-

tained the two diastereomers in a 1:1 ratio (Fig. 2) [20].

In the crystal only the 2-cyclopentadiene isomers were

found. On dissolution the 75:25 isomer ratio for both

diastereomers was re-established. Attempts to separate

the diastereomers by chromatography proved diﬃcult.

Successive chromatographies with Merck–Lobar col-

umns using CH₂Cl₂/MeOH 50:1 only gave an enrich-

ment of 65:35 of the two diastereomers. Substitution

of the resolving agent NMe₂pea in the Pd complex by

the unsubstituted ligand NH₂pea (oily products) and

the corresponding naphthyl compound NH₂nea (expen-

sive resolving agent) was also unsuccessful [20].

Whereas 3a was a racemate, due to the L-menthyl

substituent 3b was a pair of diastereomers. The two

diastereomers formed in the ratio (L_Ment,R_C)-

3b:(L_Ment,S_C)-3b = 60:40. From a concentrated pentane

solution of the 60:40-mixture only the (L_Ment,S_C)-3b dia-

stereomer (the ‘‘40%-isomer’’) crystallized at ꢀ27 ꢁC.

The (L_Ment,R_C)-3b diastereomer (the ‘‘60%-isomer’’) re-

mained in solution. Thus, it was possible to prepare the

tripod ligand (L_Ment,S_C)-3b with a resolved branching

position in an operationally simple way in multigram

quantities.

ers. The mixture of diastereomers (L_Ment,S_C)-3b/(L_Ment

,

R_C)-3b gave a total of 12 separate signals on cooling [20].

The synthesis of the ⁱPr-substituted ligands 4a and 4b

was similar to that of 3a and 3b. Without isolation the

intermediates 2a and 2b were metallated with BuLi

and subsequently reacted with 2-iodopropane. The race-

mic mixture 4a was not resolved. After chromatographic

puriﬁcation the two diastereomers of 4b were present in

a ratio of 55:45. It was not possible to separate the two

diastereomers by column chromatography. Attempts to

isolate one or both of the diastereomers by crystalliza-

tion failed due to the good solubility in all organic sol-

vents. To convert the oily diastereomer mixture of 4b

into a crystallizing solid, simultaneously protecting the

air-sensitive phosphorus atom, we introduced 4b as a

ligand into palladium complexes. As a separation of

the diastereomers of 4b with the help of the Pd(II) com-

plex containing the ortho-metallated ligand NH₂pea was

unsuccessful, we concentrated on the corresponding

complex with the N,N-dimethylated ligand NMe₂pea.

The diastereomer mixture (L_Ment,R_C)(S)- and (L_Ment,S_C)

(S)-5b was prepared by treatment of [(NMe₂pea–H⁺)

PdCl]₂[22] with the diastereomers of 4b in methanol

in the presence of NH₄PF₆. Recrystallization of the

An X-ray analysis of single crystals of (L_Ment,S_C)-3b

proved the absolute conﬁguration of the newly gener-

ated asymmetric carbon atom at the branching position

to be (S_C) (Fig. 3). Only the 2-cyclopentadiene isomer

was found in the crystal. The double bonds are between

C17/C21 and C18/C19. The CH₂group is located in

3-position of the cyclopentadiene ring at C20.

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H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

white crystalline solid from acetone aﬀorded the pure

diastereomer (L_Ment,R_C)(S)-5b (see below) as colorless

prisms (Scheme 3). No evidence for the presence of the

other diastereomer (L_Ment,S_C)(S)-5b was observed in

1

the H NMR spectrum of recrystallized samples.

Transformation of the pure diastereomer (L_Ment,R_C)

(S)-5b into the dichloro complex (L_Ment,R_C)-6b was

achieved in sulfuric acid (70%), which removed the opti-

cally active amine. Addition of lithium chloride aﬀorded

the dichloro complex (L_Ment,R_C)-6b, which was ex-

tracted into dichloromethane. Recrystallization from

CH₂Cl₂/petroleum ether resulted in ﬁne yellow needles

suitable for X-ray analysis. The coordination around

palladium was square planar with a tetrahedral distor-

tion indicated by the dihedral angles given in Fig. 4.

˚

The Pd–Cl2 bond (2.41 A) was slightly longer than the

Fig. 5. Molecular structure of (R_C)-6c. Hydrogen atoms omitted

˚

Pd–Cl1 bond (2.30 A) consistent with the trans inﬂuence

except of a-carbon atom. Selected bond lengths [A], angles and torsion

angles [ꢁ]: Pd1–Cl1 2.2861(8), Pd1–Cl2 2.4082(8), Pd1–P1 2.1939(7),

Pd1–N1 2.1237(19), P1–C1 1.845(3), P1–C10 1.800(3), P1–C16

1.811(2), C1–C2 1.512(3), C1–C7 1.561(4); Cl1–Pd1–Cl2 88.70(3),

Cl1–Pd1–P1 87.01(3), Cl1–Pd1–N1 169.91(7), Cl2–Pd1–P1 174.98(3),

Cl2–Pd1–N1 100.48(6), P1–Pd1–N1 84.00(6), Pd1–P1–C1 101.98(8),

Pd1–P1–C10 110.06(9), Pd1–P1–C16 122.29(10); Cl2–Pd1–N1–C2

167.4(2), P1–Pd1–N1–C2 ꢀ10.3(2), Pd1–P1–C1–C7 92.14(16), Pd1–

N1–C2–C1 ꢀ9.7(3).

of the phosphorus atom. The ﬁve-membered chelate ring

was not planar but had an envelope structure. The bite

angle of the chelate ring P–Pd–N was 80ꢁ. The isopropyl

group adopted an axial position with respect to the ﬁve-

membered chelate ring. (R_C)-conﬁguration was assigned

to the chiral carbon atom in the ligand backbone indi-

cating (L_Ment,R_C)-conﬁguration for the diastereomer

(L_Ment,R_C)(S)-5b obtained on crystallization and for

the ligand liberated from (L_Ment,R_C)-6b. Ligand

(L_Ment,R_C)-4b was liberated by treating (L_Ment,R_C)-6b

with KCN in water/CH₂Cl₂under nitrogen protection.

Following the protocol to remove the ortho-metal-

lated ligand NMe₂pea from the crystallized complex

(L_Ment,R_C)(S)-5b with H₂SO₄/LiCl a crystalline product

was obtained the X-ray analysis of which showed that it

was not complex (L_Ment,R_C)-6b containing the menthyl-

ated PN ligand but the product of an ether cleavage. It

was complex (L_Ment,R_C)-6c with the PN ligand having a

free phenolic OH group which formed a hydrogen bond

to one of the chlorine ligands. Fig. 5 shows the results of

the X-ray analysis.

3. The conﬁgurationally stable tripod complex

(L_Ment,S_C,R_Rh)-7b and the substitution of its chloro ligand

with retention of conﬁguration

Complexation of (L_Ment,S_C)-3b with RhCl₃Æ 3H₂O in

ethanol at room temperature aﬀorded the complex

(L_Ment,S_C,R_Rh)-7b (Scheme 4, top). After a few minutes

an orange precipitate was formed, which dissolved

within some hours indicating that ligand (L_Ment,S_C)-3b

coordinated slowly and stepwise to the metal center.

After 24 h the red–orange compound (L_Ment,S_C,R_Rh)-

7b was precipitated with pentane. It is soluble in polar

solvents, such as alcohols or chlorinated solvents, and

it is air-stable not only in the solid state but also in

solution.

Interestingly, the cyclopentadiene isomerism present

in ligand (L_Ment,S_C)-3b disappeared on complexation

to (L_Ment,S_C,R_Rh)-7b, because a cyclopentadienyl system

without stereogenicity was formed. Consequently, the

³¹P{¹H} NMR spectrum of (L_Ment,S_C,R_Rh)-7b showed

only one doublet at 72.6 ppm with a P–Rh coupling of

145 Hz. The conﬁguration at the rhodium atom was as-

signed on the basis of the ligand priority sequence

Cp > Cl > P > N [23,24].

Fig. 4. Molecular structure of (L_Ment,R_C)-6b. Hydrogen atoms omit-

˚

ted except of a-carbon atom. Selected bond lengths [A], angles and

torsion angles [ꢁ]: Pd1–Cl1 2.300(5), Pd1–Cl2 2.410(2), Pd1–N1

2.087(6), Pd1–P1 2.210(2), P1–C1 1.846(10); Cl1–Pd1–Cl2 93.35(9),

Cl2–Pd1–N1 95.39(14); Cl1–Pd1–P1 93.82(9), N1–Pd1–P1 80.01(14),

Pd1–P1–C1 98.96(17); C2–N1–Pd1–P1 ꢀ26.04(45), Cl1–Pd1–N1–C2

ꢀ58.7(8), Pd1–P1–C1–C7 80.54(45), Pd1–N1–C2–C1 0.79(75), N1–

C2–C1–C7 ꢀ92.99(70).

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4249

H

Rh

PPh₂

Ph₂

P

RhCl₃·3H₂O

H

Cl

N

O

(L_Ment,S_C)-3b

(L_Ment,S_C,R_Rh)-7b

PPh₃,

NH₄PF₆

NaX or KCN, X = Br, I, N₃

or SCN

NH₄PF₆

Rh

H

Ph₂

P

Ph₂

P

H

PF₆

Cl

X

PF₆

PPh₃

N

O

X

Br

I

13b

(L_Ment,S_C,R_Rh)-8b

(L_Ment,S_C,R_Rh)-9b

(L_Ment,S_C,R_Rh)-10b

(L_Ment,S_C,R_Rh)-11b

(L_Ment,S_C,R_Rh)-12b

N₃

CN

SCN

Scheme 4. Synthesis of (L_Ment,S_C,R_Rh)-7b, 8b, 9b, 10b, 11b, 12b and 13b.

Remarkably, the (L_Ment,S_C)-diastereomer of ligand

3b can only form the complex (L_Ment,S_C,R_Rh)-7b. The

(S_Rh)-conﬁguration is inaccessible for the metal atom

(Scheme 1, bottom). Thus, the (S_C)-conﬁguration of

the a-carbon of the ligand predetermines the (R_Rh)-con-

ﬁguration of the metal center [25]. Even if ligand arms

dissociate from the metal center, the chirality at the me-

tal center does not get lost, because on coming back the

original (R_Rh)-conﬁguration inevitably is restored. Heat-

ing a sample of (L_Ment,S_C,R_Rh)-7b at 60 ꢁC for 3 d did

not show any epimerization, whereas similar com-

pounds lacking the ligand tether typical for

(L_Ment,S_C,R_Rh)-7b (see below) epimerized already under

mild conditions by change of the metal conﬁguration.

Clearly, the opposite metal conﬁguration (S_Rh) is only

accessible with the other diastereomer (L_Ment,R_C)-3b.

Recently there has been a diﬀerent approach to ﬁx the

metal conﬁguration in (g⁶-arene)ruthenium complexes

using planar chirality [26,27]. The synthesis of chiral

CpH(PP⁰) and IndH(PP⁰) ligands has been described

[28]. However, they have been used in complexation

studies unresolved with respect to the branching

position.

In the reaction with RhCl₃Æ 3H₂O the 40:60 mixture

of (L_Ment,S_C)-3b/(L_Ment,R_C)-3b gave a (L_Ment,S_C,R_Rh)-

7b/(L_Ment,R_C,S_Rh)-7b = 40:60 product mixture. The

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H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

³¹P{¹H} NMR spectrum showed two doublets at 72.6

ppm for (L_Ment,S_C,R_Rh)-7b and at 71.3 ppm for

(L_Ment,R_C,S_Rh)-7b, both with a P–Rh coupling of 145

Hz [20]. We also synthesized the parent complex

[(CpPN)RhCl]Cl of tripod ligand (CpH)PN 3a without

the L-menthoxy substituent in 2-position. However,

the racemic mixture was not resolved and the Rh

complex turned out to be nearly insoluble in common

organic solvents [20].

50

25

0

-25

-50

-75

Complex (L_Ment,S_C,R_Rh)-7b is an air-stable, unreac-

tive compound. Activation for catalysis should be possi-

ble by chloride abstraction to give a Lewis acidic

fragment. Furthermore, the easily accessible ligand

(L_Ment,R_C)-3b should form compounds similar to

(L_Ment,S_C,R_Rh)-7b with a variety of transition metal pre-

cursors. Here, a comparison of complexes of CpPN_Ment

systems with complexes containing a combination of a

Cp and a PN_Mentligand will demonstrate the value of

a ﬁxed metal conﬁguration.

-100

-125

-150

250

300

350

400

450

500

550

Wavelength / nm

Fig. 6. CD spectra of (L_Ment,S_C,R_Rh)-7b (c = 2.4 · 10^ꢀ4mol l^ꢀ1: ––),

of its Br analog (L_Ment,S_C,R_Rh)-8b (c = 2.3 · 10^ꢀ4mol l^ꢀ1: -----) and

of its I analog (L_Ment,S_C,R_Rh)-9b (c = 2.2 · 10^ꢀ4mol l^ꢀ1: –––) in

CH₂Cl₂.

The predetermination of the metal conﬁguration by

the tripod ligand (L_Ment,S_C)-3b implies that substitution

reactions of the chloro ligand in (L_Ment,S_C,R_Rh)-7b must

occur with retention of the metal conﬁguration. Stirring

(L_Ment,S_C,R_Rh)-7b with an excess of NaBr or NaI in

methanol at room temperature and subsequent addition

of NH₄PF₆aﬀorded the bromo and iodo derivatives

(L_Ment,S_C,R_Rh)-8b and (L_Ment,S_C,R_Rh)-9b (Scheme 4,

bottom right). The UV–Vis spectra of the starting mate-

rial and products showed a strong absorption maximum

at 275–280 nm. Characteristic for the CD spectra is a

strong negative Cotton eﬀect around 280–290 nm. The

similarity of the CD spectra of the chloro, bromo and

iodo complexes in Fig. 6 is in accordance with the same

conﬁguration at the metal center.

PPh₃ligand in the cation. Therefore, on the basis of

the mass spectral data as well as the elemental analysis

which also showed the presence of Cl, it had to be

assumed that during the substitution the pyridine–rho-

dium bond broke resulting in the formation of 13b hav-

ing the central rhodium atom coordinated to Cp and P

only of the tripod together with the two monodentate

ligands Cl and PPh₃(Scheme 4, bottom left). The chloro

ligand remained a constituent of the cation. Thus, in this

case it was not the chloro ligand which was replaced but

the pyridine system of the tripod ligand.

Interestingly, a ruthenium complex of the non-

menthylated ligand 3a had been synthesized and formu-

lated as a chloride salt [(CpPN)Ru(PPh₃)]Cl [21]. The

cation was thought to be fully coordinated by Cp, P

and N of the tripod with PPh₃occupying the last

Reaction of (L_Ment,S_C,R_Rh)-7b with NaN₃, KCN and

NaSCN, respectively, aﬀorded the corresponding azido,

cyano and thiocyanato substitution products

(L_Ment,S_C,R_Rh)-10b,

(L_Ment,S_C,R_Rh)-11b

and

(L_Ment,S_C,R_Rh)-12b (Scheme 4, bottom right). The UV–

Vis and CD spectra were similar to the chloro complex

except the thiocyanato compound, the 290 nm CD band

of which had the same position but double intensity. This

is interpreted as an indication that the ambidentate

SCN^ꢀligand binds via the soft sulfur atom and not the

hard nitrogen atom as, e.g. in the azido complex. In-

crease of the band intensity is also observed in Fig. 6 in

going from the hard chloro ligand to the soft iodo ligand.

The chloro complex (L_Ment,S_C,R_Rh)-7b underwent

clean substitution with PPh₃in the presence of NH₄PF₆

to produce complex 13b in quantitative yield. The UV–

Vis and CD spectra of the orange substitution product

were similar to the chloro complex (Fig. 7). However,

the mass spectrum (ESI in CH₂Cl₂) of substitution prod-

uct 13b showed the peak for the cation at m/z 936 and

not as expected for a Cl^ꢀsubstitution at m/z 901 which

indicated the presence of a chlorine atom along with a

20

0

-20

-40

-60

-80

250

300

350

400

450

500

550

Wavelength/ nm

Fig. 7. CD spectra of (L_Ment,S_C,R_Rh)-7b (c = 2.4 · 10^ꢀ4mol l^ꢀ1: ––)

and its PPh₃substitution product 13b (c = 1.9 · 10^ꢀ4mol l^ꢀ1: ----) in

CH₂Cl₂.

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4251

coordination site. However, in its mass spectrum the

molecular ion included chlorine and the loss-of-chlorine

fragmentation step was observed. Thus, the compound

has to be re-interpreted as [(CpPN)Ru(PPh₃)Cl] with

the tripod coordinated only by Cp and P containing a

dangling pyridine.

ble) should be prepared and contrasted with tripod

complexes (L_Ment,S_C,R_Rh)-[(CpPN_Ment)RhCl]X (ﬁxed

metal conﬁguration) such as (L_Ment,S_C,R_Rh)-7b. As the

pentamethylcyclopentadienyl (g⁵-C₅Me₅= Cp*) com-

pounds of rhodium are more stable than the cyclopenta-

dienyl (g⁵-C₅H₅= Cp) compounds, the Cp*-derivatives

are included in the present study. In a previous study

unsymmetrical tridentate ligands had not been superior

compared to a similar combination of bidentate and

monodentate ligands [29].

4. Half-sandwich Rh complexes with bidentate PN ligands

Formal cleavage of the C–C bond between the cyclo-

pentadienyl ring and the CMe₂group of the tether to the

branching position in (L_Ment,S_C,R_Rh)-7b results in a

combination of a Cp ligand and the bidentate PN_Ment

(L_Ment,S_C)-4b. As shown in Scheme 1 (top), for such a

ligand combination two diﬀerent metal conﬁgurations

(R_Rh) and (S_Rh) are accessible. Therefore, compounds

of type (L_Ment,S_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)-

[Cp(PN_Ment)RhCl]X (both metal conﬁgurations possi-

Reaction of [(Cp*RhCl)₂(l-Cl)₂] with a 1:1 mixture

of the diastereomers (L_Ment,R_C)- and (L_Ment,S_C)-4b af-

forded the diastereomers (L_Ment,R_C)- and (L_Ment,S_C)-

14b in which ligand 4b is only mono-coordinated via

the phosphorus atom (Scheme 5, top). Thus, the prod-

ucts of the ﬁrst complexation step could be isolated here,

whereas in the synthesis of (L_Ment,S_C,R_Rh)-7b in the iso-

lated product the P, N and Cp ligand parts coordinated

simultaneously. Diastereomer (L_Ment,R_C)-14b was

Me

Ph₂

Rh

P

Cl

N

R

Cl

H

(R_C)-14a,b

Me

Rh

Me

Rh

Me

Ph₂

H

Ph₂

P

Cl

P

Cl

H

N

R

(R_C)(S_Rh)-15a,b

(R_C)(R_Rh)-15a,b

14, 15

R

a

H

O

b

Temp./K

193

(R_C)(R_Rh)/(S_C)(S_Rh)-15a

(R_C)/(S_C)-14a

(R_C)(S_Rh)/(S_C)(R_Rh)-15a

75

66

71

69

72

:

13

11

3

:

12

23

26

31

28

213

233

253

0

273

0

Scheme 5. Only (R_C)-enantiomers of 14a and (R_C)-diastereomers of 14b, 15a and 15b shown, respectively (top). Temperature dependence of isomer

composition in system 14a/15a (bottom).

4252

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

isolated in pure form as a sparingly soluble material by

washing the mixture of diastereomers with ether. The

other diastereomer (L_Ment,S_C)-14b was obtained purely

by silica gel chromatography of the concentrated

mother liquor. Although the complexes (L_Ment,R_C)-14b

and (L_Ment,S_C)-14b are diastereomers, their CD spectra

are similar but opposite to each other. Thus, they are

dominated by the asymmetric center in the ligand back-

bone. The stereochemistries of both diastereomers were

determined by X-ray analyses (Figs. 8 and 9).

14a could be observed in the NMR spectra at low tem-

peratures. In addition, however, there were the salt-like

chelate complexes (R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/

(S_C)(R_Rh)-15a in which the metal atom is a chiral center

(Scheme 5). In these ionic species chloride is the counter-

ion. The ³¹P{¹H} NMR spectrum of 14a/15a in CD₂Cl₂

at 193 K showed three phosphorus signals at 75.0 (br d,

1

J_Rh–P= 125.1 Hz), 59.9 (d, J_Rh–P= 141.9 Hz) and 31.0

1

(d, J_Rh–P= 141.9 Hz) ppm, respectively. It is assumed

that the 31.0 ppm signal is the dichloride complex 14a,

the other two signals are due to the two diastereomers

(R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)(R_Rh)-15a.

The ratios (R_C)(R_Rh)/(S_C)(S_Rh)-15a:(R_C)/(S_C)-14a:(R_C)

(S_Rh)/(S_C)(R_Rh)-15a were temperature dependent (see

bottom of Scheme 5). With increasing temperature, the

signal at 31.0 ppm disappeared and the ratios

Surprisingly, the reaction of [(Cp*RhCl)₂(l-Cl)₂] with

the racemic ligand 4a was diﬀerent from that with the

menthylated ligand 4b, in which no ionic species of the

type 15b were detected. The molecular dichloro complex

(R_C)(R_Rh)/(S_C)(S_Rh)-15a:(R_C)(S_Rh)/(S_C)(R_Rh)-15a

in-

creased. This suggested that equilibration between 14a

and the diastereomers of 15a was fast. Assignment of

conﬁgurations to the signals in the ³¹P{¹H} NMR spec-

tra of the chloride diastereomers of 15a was made by

comparison with the hexaﬂuorophosphate diastereo-

mers of 16b for which the stereochemistry was estab-

lished by X-ray analyses (see below).

Reaction of 15a with NH₄PF₆in THF aﬀorded the chi-

ral-at-metal PF₆salts 16a (Scheme 6, top and bottom).

The ratio was (R_C)(R_Rh)/(S_C)(S_Rh)-16a:(R_C)(S_Rh)/

(S_C)(R_Rh)-16a = 74:26. Similarly, treatment of the pure

isomer (L_Ment,S_C)-14b with NH₄PF₆in THF gave the

diastereomers (L_Ment,S_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)-

16b (Scheme 6, bottom). Thus, in the presence of NH₄PF₆

both in the a- and in the b-series the PN ligands 4a and 4b

coordinated in a bidentate way. The ³¹P{¹H} NMR spec-

trum of (L_Ment,S_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)-16b at 193

K showed the signals of two diastereomers at 52.7 (main;

Fig. 8. Molecular structure of (L_Ment,R_C)-14b. Hydrogen atoms

˚

omitted except of a-carbon atom. Selected bond lengths [A] and

angles [ꢁ]: Rh1–Cl1 2.4124(10), Rh1–Cl2 2.4057(9), Rh1–P1 2.3476(7),

Rh1–C1 2.1922(2), Rh1–C2 2.178(3), Rh1–C3 2.207(3), Rh1–C4

2.213(3), Rh1–C5 2.173(3); Cl1–Rh1–Cl2 91.77(3), Cl1–Rh1–P1

91.84(3), Cl2–Rh1–P1 84.90(3), Rh1–P1–C11 117.17(10).

1

¹J_Rh–P= 143.6 Hz) and 61.3 (minor; J_Rh–P= 130.3 Hz)

ppm in the ratio 96:4. The ³¹P{¹H} NMR spectrum was

temperature dependent. In the range between 213 and

273 K the minor phosphorus signal disappeared, whilst

the major broadened appreciably. At 300 K there was

one phosphorus signal at 53.2 ppm as a sharp doublet

1

having J_Rh–P= 142.3 Hz. Similar tendencies were also

1

observed in the H NMR spectra. Processes underlying

this temperature dependency were the sterically hindered

rotation of the menthyl substituent and the inversion

within the puckered chelate ring. Single crystals of the

major isomer were obtained by recrystallization using

acetone/petroleum ether. X-ray analysis established

(L_Ment,S_C)(S_Rh)-conﬁguration (Fig. 10). On dissolution

of the crystals in CD₂Cl₂at 193 K the ³¹P{¹H} NMR

spectrum showed the equilibrium (L_Ment,S_C)(R_Rh)-

16b:(L_Ment,S_C)(R_Rh)-16b = 4:96. Thus equilibration be-

tween (L_Ment,S_C)(R_Rh)-16b and (L_Ment,S_C)(S_Rh)-16b

took place rapidly.

Fig. 9. Molecular structure of (L_Ment,S_C)-14b. Hydrogen atoms

˚

omitted except of a-carbon atom. Selected bond lengths [A] and

angles [ꢁ]: Rh1–Cl1 2.404(2), Rh1–Cl2 2.404(2), Rh1–P1 2.354(2),

Rh1–C1 2.189(9), Rh1–C2 2.193(5), Rh1–C3 2.151(8), Rh1–C4

2.232(9), Rh1–C5 2.227(8); Cl1–Rh1–Cl2 92.97(7), Cl1–Rh1–P1

87.77(7), Cl2–Rh1–P1 87.03(8), Rh1–P1–C11 110.4(3).

Similar to (L_Ment,S_C)-14b (Scheme 6, bottom), reac-

tion of (L_Ment,R_C)-14b with NH₄PF₆aﬀorded the dia-

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4253

Ph₂

Ph

₂H

P

Rh

P

Cl

PF₆

Cl

PF₆

H

N

R

(R_C)(S_Rh)-16a,b

(R_C)(S_Rh)-17b

(R_C)(R_Rh)-16a,b

(R_C)(R_Rh)-17b

NH₄PF₆

Ph₂

P

Ph₂

P

Rh

+

Cl

N

R

N

R

H

Cl

(S_C)-14b

NH₄PF₆

H

Cl

H

(R_C)-14b

Ph₂

P

Ph₂

P

Rh

PF₆

Cl

H

N

R

(S_C)(R_Rh)-16a,b

(S_C)(R_Rh)-17b

(S_C)(S_Rh)-16a,b

(S_C)(S_Rh)-17b

R

16a

⁵-C₅Me₅

⁵-C₅H₅

H

O

16b

17b

O

Scheme 6. Synthesis of half-sandwich Rh complexes with the bidentate PN ligands 4a and 4b.

stereomers (L_Ment,R_C)(R_Rh)- and (L_Ment,R_C)(S_Rh)-16b

(Scheme 6, top). The ³¹P{¹H} NMR spectrum showed

the presence of two diastereomers [major: 55.8 ppm

(¹J_Rh–P= 139.0 Hz), minor: 61.6 ppm (¹J_Rh–P= 142.1

Hz) at 300 K in CD₂Cl₂] in temperature dependent ra-

tios. At 193 K the major:minor ratio of the diastereo-

mers was 76:24, whereas at 300 K it was 92:8.

Reaction of the diastereomer mixture (L_Ment,R_C)- and

(L_Ment,S_C)-14b with NH₄PF₆led to a single crystal con-

spectrum of 16a in CD₂Cl₂at 193 K and at 300 K

showed two phosphorus signals for the two diastereo-

meric pairs of enantiomers.

To switch to the unsubstituted Cp compounds

[(CpRhCl)₂(l-Cl₂)] was reacted with the 1:1 diastereomer

mixture of 4b in THF in the presence of NH₄PF₆. As ex-

pected there were four diastereomers of 17b at 300 K the

³¹P{¹H} NMR spectra, in addition to the PF₆signal

(Scheme 6, top and bottom). By comparison with the

diastereomers of 16b the two low ﬁeld signals were as-

signed to (L_Ment,S_C)(R_Rh)- and (L_Ment,R_C)(S_Rh)-17b (iso-

propyl group towards Cp), while the two high ﬁeld

taining

a

1:1 mixture of the diastereomers

(L_Ment,R_C)(R_Rh)-16b and (L_Ment,S_C)(S_Rh)-16b (Fig. 11).

Analogous to the menthylated molecular chlorides

14b, in the reaction with NH₄PF₆in THF the chloride

mixture 14a/15a was converted into the PF₆salts 16a

(Scheme 6, top and bottom). The ³¹P{¹H} NMR

signals

were

due

to

(L_Ment,R_C)(R_Rh)-

and

(L_Ment,S_C)(S_Rh)-17b. The main product was the

(L_Ment,S_C)(S_Rh)-isomer. Thus, surprisingly, compared

4254

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

5. Experimental

5.1. General

All manipulations and reactions were carried out un-

der an inert atmosphere of dry nitrogen using standard

Schlenk techniques. Solvents were dried by standard

methods and distilled prior to use. Melting points: Buchi

¨

SMP 20 (uncorrected). Mass spectra: Finnigan MAT 95,

Finnigan MAT 311 A and Thermoquest TSQ 7000

spectrometers (only the most intense peak of a cluster

is given). Optical rotations: Perkin–Elmer 241 polarime-

1

ter. CD spectra: JASCO J-710 spectrophotometer. H

Fig. 10. Molecular structure of (L_Ment,S_C)(S_Rh)-16b. Hydrogen atoms,

PF₆anion and two acetone molecules omitted except of a-carbon

atom. Selected bond lengths [A], angles and torsion angles [ꢁ]: Rh1–Cl1

NMR spectra: Bruker AC 250 and ARX 400 and Bruker

Avance 300 and 400 spectrometers. ³¹P NMR spectra:

Bruker ARX 400 and Avance 400 spectrometers

(H₃PO₄ext.). IR spectra: Beckman IR 4240 spectropho-

tometer. Elemental analyses: Elementar Vario EL III. X-

ray structure analyses: STOE-IPDS diﬀractometer (Mo

Ka radiation, 173 K, Oxford cryosystems cooler [30],

graphite monochromator), SIR-97 [31] and SHELXS-

97 [32]. For crystallographic data see Tables 1 and 2. 2-

Methylpyridine (a-picoline) 1a and RhCl₃Æ 3H₂O are

commercially available. 2-Diphenylphosphanylmethyl-

pyridine [17–19] 2a and 2-(2-cyclopentadienyl-1-diphe-

nylphosphanyl-2-methylprop-1-yl)pyridine [21] 3a are

known compounds. [(CpRhCl)₂(l-Cl)₂[33] and

[(Cp*RhCl)₂(l-Cl)₂] [34] were prepared as published.

˚

2.3993(12), Rh1–P1 2.3028(10), Rh1–N1 2.1781(3), Rh1–C1 2.240(4),

Rh1–C2 2.252(5), Rh1–C3 2.202(4), Rh1–C4 2.168(4), Rh1–C5

2.170(4); Cl1–Rh1–P1 93.02(4), Cl1–Rh1–N1 86.88(9), P1–Rh1–N1

81.58(8), Rh1–P1–C11 102.10(13), Rh1–N1–C12 118.62(2), Rh1–N1–

C16 124.0(3), P1–C11–C12 107.4(3), N1–C12–C11 117.7(3), P1–C11–

H11 108.04, C12–C11–H11 107.95; Rh–N1–C12–C11 26.4(4), N1–

C12–C11–P1 ꢀ39.5(4), C12–C11–P1–Rh1 32.5(3), C11–P1–Rh1–N1

ꢀ16.13(15), P1–Rh1–N1–C12 ꢀ2.1(2).

5.2. 2-(1R,2S,5R)-Menthoxy-6-methylpyridine 1b

L-(ꢀ)-Menthol (120 g, 768 mmol) was added to NaH

(8.23 g, 343 mmol) under N₂protection without a solvent

and heated to 60 ꢁC. After the formation of H₂had

ceased, the temperature was raised to 90 ꢁC for 2 h. 2-

Bromo-6-methylpyridine [16] (40 g, 232 mmol) was

added and the mixture was kept at 90 ꢁC for 20 h. The ex-

cess of L-(ꢀ)-menthol was removed at 100 ꢁC/2 Torr. In a

bulb-to-bulb distillation at 100 ꢁC/10^ꢀ3Torr 1b was iso-

lated and puriﬁed by chromatography (SiO₂, petroleum

ether (40/60):ethyl acetate (10:1), R_fof 1b = 0.77, R_fof

2-bromo-6-methylpyridine = 0.29). Yield 46.3 g (81%).

¹H NMR (250 MHz, CDCl₃): d = 7.40 (dd, ³J = 8.2 Hz,

Fig. 11. Molecular structure of the 1:1 diastereomer mixture of

(L_Ment,R_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)-16b (only (L_Ment,R_C)(R_Rh)-dia-

stereomer shown). Hydrogen atoms (except of a-carbon atom) and

3

4

³J = 7.2 Hz, 1H, Py–H⁴), 6.56 (dd, J = 7.2 Hz, J = 0.7

˚

PF₆anion omitted. Selected bond lengths [A], angles and torsion

3

4

Hz, 1H, Py–H^3/5), 6.45 (dd, J = 8.2 Hz, J = 0.7 Hz,

angles [ꢁ]: Rh1–Cl1 2.3810(10), Rh1–P1 2.2697(10), Rh1–N1 2.214(2),

Rh1–C1 2.165(4), Rh1–C2 2.225(3), Rh1–C3 2.162(3), Rh1–C4

2.223(4), Rh1–C5 2.196(3); Cl1–Rh1–P1 91.51(4), Cl1–Rh1–N1

100.09(7), P1–Rh1–N1 76.90(6), Rh1–P1–C11 100.22(11), Rh1–N1–

C12 115.02(18), Rh1–N1–C31 122.23(18), P1–C11–C12 107.9(2), N1–

C12–C11 118.3(3), P1–C11–H11 104.84, C12–C11–H11 104.88; Rh1–

N1–C12–C11 ꢀ22.3(3), N1–C12–C11–P1 ꢀ13.3(3), C12–C11–P1–Rh1

39.2(2), C11–P1–Rh1–N1 ꢀ37.26(2), P1–Rh1–N1–C12 38.2(2).

1H, Py–H^3/5), 4.99 (dt, J = 10.7 Hz, J = 4.4 Hz, 1H,

OCH), 2.41 (s, 1H, Py–CH₃), 2.23–2.13 (m, 1H, Ment),

3

2.05 (dsept, J = 2.7 Hz, J = 6.8 Hz, 1H, CH(CH₃)₂),

3

1.78–1.43 (m, 4H, Ment), 1.27–0.94 (m, 3H, Ment),

3

0.92 (d, J = 6.8 Hz, 3H, Ment–CH₃), 0.89 (d, J = 6.8

3

Hz, 3H, Ment–CH₃), 0.77 (d, J = 7.1 Hz, 3H, Ment–

CH₃) ppm. MS (PI–EI, 70 eV): m/z (%) = 247 (M, 9),

110 (100). Optical rotation (c = 2.0, CHCl₃):

RT

578

RT

546

RT

436

to the tripod complex (L_Ment,S_C,R_Rh)-7b the ‘‘less sta-

ble’’ Rh conﬁguration was stabilized in the Cp and

Cp* series with the bidentate PN_Mentligand 4b.

½aꢁ_D¼ ꢀ94, ½aꢁ ¼ ꢀ99, ½aꢁ ¼ ꢀ122, ½aꢁ ¼ ꢀ170,

RT

½aꢁ ¼ ꢀ316. C₁₆H₂₅NO (247.4): Calc. C 77.68, H

365

10.19, N 5.66. Found C 77.52, H 11.09, N 6.06%.

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4255

Table 1

Crystallographic data for 3a, 3b, (S S )-5a, (L_Ment,R_C)-6b and (R_C)-6c

Compound

3a

3b

(S,S)-5a

(L_Ment,R_C)-6b

(R_C)-6c

Empirical formula

C

₂₆H₂₆NP

C₃₆H₄₄NOP

2(C₃₆H₄₀N₂PPd),

2(C₄H₈O), 2(F₆P)

1708.27

C₃₁H₄₀Cl₂NOPPd

C

₂₁H₂₂Cl₂NOPPd

Formula weight

Crystal system

Space group

238.44

Monoclinic

P2₁/c

537.69

Monoclinic

I2

650.93

Monoclinic

P2₁

512.69

Triclinic

P1

Orthorhombic

P2₁2₁2₁

9.5881(11)

12.2895(10)

17.7887(13)

90

˚

a (A)

15.9797(15)

20.9306(17)

90

11.1441(6)

8.1570(4)

35.251(2)

90

10.7999(9)

11.1133(9)

16.4442(13)

88.448(10)

89.082(10)

85.726(10)

1967.3(3)

1

10.4972(7)

15.5449(8)

10.4891(9)

90

˚

b (A)

˚

c (A)

a (ꢁ)

b (ꢁ)

c (ꢁ)

98.511(10)

90

94.988(7)

90

117.861(9)

90

3

˚

V (A )

2093.9(3)

4

1.213

3192.3(3)

4

1.119

1513.2(2)

2

1.429

2096.1(3)

4

1.625

Z

q_calcd(Mg/m³)

1.442

0.615

None

Abs coeﬀ (mm^ꢀ1

Abs correct

)

0.142

None

0.113

None

0.867

1.228

Empirical

0.795/0.399

672

Numerical

0.9381/0.6192

1032

Transmiss min/max

F (0 0 0)

Crystal size (mm)

812

1160

878

0.60 · 0.24 · 0.14

1.97–25.70

16127/3973

0.0805

0.36 · 0.34 · 0.08

1.97–25.80

18814/6079

0.0492

0.30 · 0.20 · 0.08

2.19–26.76

30524/15478

0.0452

0.12 · 0.06 · 0.04

2.27–25.90

12473/5588

0.0630

0.540 · 0.260 · 0.040

2.41–25.78

14991/3975

0.0485

h range (ꢁ)

No. of rﬂns/unique

R_int

No. of data/params

Goodness of ﬁt on F²

R₁/wR₂(I > 2r(I))

R₁/wR₂(all data)

3973/253

0.924

6079/352

0.949

15478/892

0.978

5588/319

0.799

3975/248

1.035

0.0449/0.1131

0.0666/0.1218

0.473/ꢀ0.314

0.0363/ 0.0826

0.0448/0.0855

0.338/ ꢀ0.155

0.0326/0.0755

0.0371 /0.0768

0.942/ꢀ0.343

0.0416/0.0774

0.0691/0.0833

0.554/ꢀ0.730

0.0230/0.0551

0.0242/0.0554

0.604/ꢀ0.344

Largest diﬀ. pea_ꢀk₃

˚

and hole (e A

CCDC No.

)

233216

203094

233215

233217

233219

Table 2

Crystallographic data for Complexes (L_Ment,R_C)-14b, (L_Ment,S_C)-14b, (L_Ment,R_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)16b and (L_Ment,S_C)(S_Rh)16b

Compound

(L_Ment,R_C)-14b

₄₁H₅₅Cl₂NOPRh

(L_Ment,S_C)-14b

₄₁H₅₅Cl₂NOPRh

(L_Ment,R_C)(R_Rh)-and (L_Ment,S_C)(S_Rh)-16b

(L_Ment,S_C)(S_Rh)-16b

Empirical formula

C

2(C₄₁H₅₅ClNOPRh), 2(F₆P)

C₄₁H₅₅ClNOPRh,

2(C₃H₆O), F₆P

1008.32

Formula weight

Crystal system

Space group

782.64

Orthorhombic

P2₁2₁2₁

782.64

Orthorhombic

P2₁2₁2₁

1784.32

Triclinic

P1

Monoclinic

P2₁

˚

a (A)

14.5510(10)

15.6678(9)

16.8954(12)

90

10.4475(8)

17.7055(16)

21.0407(15)

90

8.8682(8)

15.1841(13)

16.5209(13)

91.367(10)

105.515(10)

100.659(10)

2100.3(3)

1

9.9515(7)

17.9193(12)

14.2159(11)

90

˚

b (A)

˚

c (A)

a (ꢁ)

b (ꢁ)

c (ꢁ)

90

106.791(9)

90

3

˚

V (A )

3851.8(4)

4

1.350

3892.1(5)

4

1.336

2427.0(3)

2

1.380

Z

q_calcd(Mg/m³)

1.411

0.605

Abs coeﬀ (mm^ꢀ1

Abs correct

)

0.656

0.649

0.535

Numerical

0.9495/0.8926

1640

Numerical

0.9620/0.9385

1640

Numerical

0.9765/0.9335

924

Empirical

0.879/0.596

1052

Transmiss min/max

F (0 0 0)

Crystal size (mm)

0.260 · 0.180 · 0.140

1.85–25.78

33156/7349

0.0576

0.13 · 0.08 · 0.08

1.94–25.21

31162/6982

0.1720

0.16 · 0.08 · 0.04

1.95–25.82

10131/9496

0.0739

0.580 · 0.100 · 0.040

1.88–25.79

17232/9250

0.0346

h range (ꢁ)

No. of rﬂns/unique

R_int

No. of data/params

Goodness of ﬁt on F²

R₁/wR₂(I > 2r(I))

R₁/wR₂(all data)

7349/424

0.938

6982/424

0.699

9496/875

0.735

9250/508

0.968

0.0277/0.0617

0.0362/0.0635

0.567/ꢀ0.275

0.0489/0.0766

0.1126/0.0910

0.524/ꢀ0.359

0.0454/0.0735

0.1078/0.0878

0.645/ꢀ0.354

0.0391/0.0875

0.0487/0.0904

0.788/ꢀ0.586

Largest diﬀ. pea_ꢀk₃

˚

and hole (e A

CCDC No.

)

233220

233222

233221

233214

4256

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

5.3. 2-(2-Cyclopentadienyl-1-diphenylphosphanyl-2-methyl-

prop-1-yl)-6-[(1R,2S,5R)-menthoxy]pyridine 3b

5.5.

dine 4a

2-(1-Diphenylphosphanyl-2-methylprop-1-yl)pyri-

1b (3.01 g, 12.2 mmol) in 30 ml of Et₂O was added at

ꢀ10 ꢁC to a solution of BuLi (12.3 mmol, 7.7 ml of a 1.6

M solution in hexane) in 30 ml of abs. Et₂O. The red–or-

ange solution was warmed up to 20 ꢁC, stirred for 1 h

and slowly added to a solution of PPh₂Cl (2.23 ml,

12.2 mmol) in 40 ml of Et₂O at ꢀ80 ꢁC. The solution

was allowed to warm up and stirred for 10 h at 20 ꢁC.

BuLi (12.3 mmol, 7.7 ml of a 1.6 M solution in hexane)

was added at 0 ꢁC and the solution was stirred for 1 h at

20 ꢁC. Then, 6,6⁰-dimethylfulvene (1.63 ml, 12.2 mmol)

was added and the reaction mixture was stirred for 20

h at 20 ꢁC. NH₄Cl (651 mg, 12.2 mmol) was added in

20 ml of H₂O and the layers were separated under nitro-

gen. The organic layer was dried over Na₂SO₄and the

solvent was removed to give the two diastereomers

(L_Ment,S_C)-3b and (L_Ment,R_C)-3b, ratio 40:60 as a hon-

ey-like oil in 81% yield (5.31 g).

BuLi (0.03 mol, 20 ml of a 1.6 M solution in hexane)

was mixed with absolute ether (30 ml). At ꢀ5 ꢁC an ether

solution of 3.2 ml (3.0 g, 0.03 mol) of 2-methylpyridine

1a was added dropwise. The color of the solution chan-

ged to yellow–orange after a few min. The reaction mix-

ture was stirred for 1 h at 20 ꢁC. The solution was added

dropwise to a cooled solution (ꢀ78 ꢁC) of PPh₂Cl (5.5

ml, 0.03 mol) in ether. The mixture was warmed to 20

ꢁC and stirred for 10 h. To the reaction mixture was

added another 20 ml of BuLi at 0 ꢁC and stirred for 1

h at 20 ꢁC. To the orange–red reaction mixture was

added dropwise 2-iodopropane (3.0 ml, 0.03 mol) and

stirred for 20 h. Hydrolysis was performed with NH₄Cl

(1.6 g, 0.03 mol) in 20 ml of water. The organic layer

was dried over Na₂SO₄. The solvent was removed to give

1

an oily product. Yield 7.7 g (75%). H{³¹P} NMR (400

MHz, CDCl₃): d = 8.35–8.33 (m, 1H, Py–H⁶), 7.95–

7.90 (m, 1H, Ph), 7.67–7.61 (m, 4H, Ph, Py), 7.46–7.39

(m, 6H, Ph), 7.23–7.18 (m, 1H, Py), 6.99–6.98 (m, 1H,

Py–H⁵), 3.83–3.79 (m, 1H, PCHPy), 2.58–2.51 (m, 1H,

CH(CH₃)₂), 1.14 (d, ³J = 6.8 Hz, 3H, CH₃), 0.96 (d,

J = 6.7 Hz, 3H, CH₃) ppm. ³¹P{¹H} NMR (162 MHz,

CDCl₃): d = ꢀ6.33 (br s, 1P) ppm. C₂₁H₂₂NP (319.4).

MS (CI, NH₃): m/z (%) = 320 (MH, 27), 247 (100).

5.4. (L_Ment,S_C)-3b

The mixture of diastereomers was dissolved in 90 ml

of pentane. At ꢀ27 ꢁC only the (L_Ment,S_C)-diastereomer

of 3b crystallized. Its crystals were washed 3· with 10 ml

of cold pentane (ꢀ27 ꢁC). Yield 1.91 g (29%), m.p. 100–

104 ꢁC. ¹H{³¹P} NMR (400 MHz, 233 K, CDCl₃, major

diastereomer (76%) with respect to the double bonds in

the Cp ring, minor diastereomer (24%) in brackets):

d = 7.66–7.57 (m, 2H, Ph), 7.28–7.13 (m, 5H, Ph), 7.08

5.6. 2-(1-Diphenylphosphanyl-2-methylprop-1-yl)-6-(1R,

2S,5R)-menthoxypyridine 4b

3

[7.07] (dd, J = 8.1 Hz, J = 7.4 Hz, 1H, Py–H⁴), 7.01–

6.89 (m, 3H, Ph), 6.52 [6.17] (ddt, ³J = 5.3 Hz,

^3/4J = 1.5 Hz, ^3/4J = 1.4 Hz, 1H, Cp–H), 6.40 [6.34] (d,

The synthesis of 4b was similar to that of 4a with 2-

menthoxy-6-methylpyridine 1b instead of 2-methylpyri-

dine 1a. After work-up the reaction mixture was passed

through a SiO₂column using petroleum ether/dichloro-

methane (70:30) to remove the impurities. The two dia-

stereomers were present in a ratio of 55:45 in the

mixture. Colorless oil. Yield 73%. ¹H NMR (400

MHz, CDCl₃, signals of the 45%-diastereomer in paren-

theses if distinguishable from the 55%-diastereomer):

d = 7.78–7.68 (m, 1H, Ph), 7.66–7.56 (m, 1H, Ph),

7.54–7.22 (m, 8H, Ph, Py–H⁴), 7.13–7.03 (m, 1H, Ph),

3

³J = 7.4 Hz, 1H, Py–H^3/5), 6.21 [6.20] (d, J = 8.1 Hz,

1H, Py–H^3/5), 6.14 [6.03] (ddt, ³J = 5.3 Hz, ^3/4J = 2.0

Hz, ^3/4J = 1.5 Hz, 1H, Cp–H), [6.08] 5.82 (ddt,

^3/4J = 1.6 Hz, ^3/4J = 2.0 Hz, ^3/4J = 1.5 Hz, 1H, Cp–H),

3

4.90 [4.84] (dt, J = 4.1 Hz, J = 10.8 Hz, 1H, OCH),

4.05 [4.04] (d, ³J = 6.5 Hz, 1H, PCHPy), [2.87] 2.63

(md, ²J = 23.8 Hz, 1H, Cp–CH₂), [2.67] 2.49 (md,

²J = 23.8 Hz, 1H, Cp–CH₂), 2.24–2.14 (m, 1H, Ment),

3

[6.70 (m, 1H, Py–H^3/5)], 6.63 (d, J = 7.2 Hz, 1H, Py–

3

2.02 (dsept, J = 2.6 Hz, J = 6.9 Hz, 1H, CH(CH₃)₂),

1.79–1.55 (m, 3H, Ment), 1.52–1.42 (m, 1H, Ment),

1.48 [1.40] (s, 3H, CH₃CCH₃), [1.38] 1.28 (s, 3H,

CH₃CCH₃), 1.31–1.10 (m, 2H, Ment), 1.0–0.86 (m, 1H,

3

4

H^3/5), [6.37 (ddd, J = 8.2 Hz, J = 1.3 Hz, J = 0.7 Hz,

1H, Py–H^3/5)], 6.35 (ddd, ³J = 8.2 Hz, J = 1.3 Hz,

⁴J = 0.7 Hz, 1H, Py–H^3/5), 5.12–5.05 (m, 1H, OCH),

3.60–3.57 (m, 1H, PCHPy), 2.09–1.98 (m, 2H, Ment,

CH(CH₃)₂), 1.74–1.63 (m, 2H, Ment), 1.61–0.72 (m,

3

Ment), 0.96 (d, J = 6.9 Hz, 3H, Ment–CH₃), 0.89 (d,

³J = 6.9 Hz, 3H, Ment–CH₃), [0.88] 0.76 (d, ³J = 7.0

Hz, 3H, Ment–CH₃) ppm.³¹P{¹H} NMR (162 MHz,

233 K, CDCl₃): d = [ꢀ8.45] ꢀ9.10 (s, 1P) ppm. MS

(PI–EI, 70 eV): m/z (%) = 537 (M, 100). Optical rotation

3

5H, Ment), 0.93 (d, J = 6.3 Hz, 3H, CH₃), [0.90 (d,

³J = 6.9 Hz, 3H, CH₃)], 0.86 (d, ³J = 6.9 Hz, 6H,

CH₃), [0.91 (d, ³J = 6.6 Hz, 6H, 2· CH₃)], 0.78 (d,

³J = 7.4 Hz, 3H, CH₃), [0.77 (d, ³J = 6.6 Hz, 3H,

CH₃)] ppm. ³¹P NMR (162 MHz, CDCl₃): d = ꢀ6.83

(s, 1P), [ꢀ7.50 (s, 1P)] ppm. C₃₁H₄₀NOP (473.6). MS

(PI–DCI, NH₃): m/z (%) = 474 (MH, 100).

RT

(c = 2.0,

CH₂Cl₂):

½aꢁ_D¼ ꢀ210,

½aꢁ ¼ ꢀ221,

578

RT

546

RT

436

RT

365

½aꢁ ¼ ꢀ258, ½aꢁ ¼ ꢀ520, ½aꢁ ¼ ꢀ1117. C₃₆H₄₄

NOP (537.7): Calc. C 80.41, H 8.25, N 2.60. Found C

80.10, H 8.81, N 2.55%.

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4257

3

4

5.7. {2-[(S)-1-N,N-Dimethylaminoethylphenylene-C,N]-

2-[(R/S)-(2-cyclopentadienyl-1-diphenylphosphanyl-2-met-

hylprop-1-yl)-6-(1R,2S,5R)]-menthoxypyridinepalladium

(II)}-hexaﬂuorophosphate 5a

³J = 8.1 Hz, 1H, Py–H⁴), 7.81 (dd, J = 7.7 Hz, J = 1.4

Hz, 1H, Py–H^3/5), 7.78 (dd, J = 7.7 Hz, J = 1.4 Hz,

1H, Py–H^3/5), 7.54–7.39 (m, 4H, Ph), 7.28–7.20 (m, 5H,

Ph), 7.04 (t, J = 7.4 Hz, 1H, Ph), 6.97 (d, J = 7.0 Hz,

3

4

3

1H, Ph), 6.96 (d, J = 8.8 Hz, 1H, Ph), 6.82 (t, J = 7.0

3

Hz, 1H, Ph), 6.68 (d, J = 7.3 Hz, 1H, Ph), 4.80 (br q,

To 200 mg (0.523 mmol) of the air-sensitive ligand 3a,

dissolved in 15 ml of abs. methanol, the suspension of

151 mg (0.260 mmol) of (+)-bis{(l-chloro)[2-(S)-1-

dimethylaminoethylphenylene-C,N]palladium(II)} in 15

ml of methanol was added. After 2 h a twofold excess

of NH₄PF₆(170 mg, 1.04 mmol) in 2 ml of water was

added. The solution was stirred for 10 h. Then, it was

concentrated to 8–10 ml. On addition of water (80 ml)

the palladium complex precipitated as the PF₆salt. It

was ﬁltered and washed with water. For crystallization

it was dissolved in acetone and layered with petroleum

J = 6.6 Hz, 1H, CHCH₃), 4.14 (dt, ³J = 10.9 Hz,

³J = 3.8 Hz, 1H, OCH), 4.01 (dd, J_P–H= 16.1 Hz,

2

4

³J = 2.9 Hz, 1H, PCHPy), 2.92 (d, J_P–H= 3.3 Hz, 3H,

4

NCH₃), 2.60 (d, J_P–H= 2.2 Hz, 3H, NCH₃), 2.29 (br

3

d, J = 12.1 Hz, 1H, Ment), 2.15–1.96 (m, 2H, Ment),

1.78–1.52 (m, 3H, Ment), 1.49 (d, ³J = 7.0 Hz, 3H,

CH₃), 1.46 (d, ³J = 7.0 Hz, 3H, CH₃), 1.31–0.82 (m,

3H, Ment), 1.05 (d, ³J = 7.0 Hz, 3H, CH₃), 0.99 (d,

³J = 6.6 Hz, 3H, CH₃), 0.72 (d, J = 7.3 Hz, 3H, CH₃),

3

0.30 (d, ³J = 7.0 Hz, 3H, CH₃) ppm. ³¹P{¹H} NMR

(162 MHz, CDCl₃): d = 49.2 (s, 1P), ꢀ143.6 (sept,

¹J_F–P= 712.6 Hz, 1P, PF₆) ppm. MS (ESI): m/z (%) =

727 (cation, 100). C₄₁H₅₄F₆N₂OP₂Pd (873.3): Calc. C

56.39, H 6.23, N 3.21. Found C 56.36, H 6.00, N 3.16%.

1

ether 40/60. Yield: 340 mg (83%). H{³¹P} NMR (400

MHz, CD₂Cl₂, signals of the two diastereomers sepa-

rated by a slash; signals of the double bond isomers given

in brackets if distinguishable): d = 8.57 (m, 1H, Py–H⁶),

8.11–7.98 (m, 2H, Ph), 7.65–7.24 (m, 8H, Ph), 7.20–6.95

(m, 4H, Ph, Py), 6.67–6.54 (m, 2H, Ph, Py), 6.25/6.22 (m,

1H, Py), 6.00 (m, 1H, Cp–H), 5.57/5.53 [5.85/5.82] (m,

5.9. Æ[Chloro{2-(2-cyclopentadienyl-1-diphenylphosphan-

yl-2-methylprop-1-yl)-6-[(1R,2S,5R)-menthoxy]pyridine}

rhodium(III)æ-chloride (L_Ment,S_C,R_Rh)-7b

3

1H, Cp–H), 4.90 (m, 1H, Cp–H), 4.57/4.53 (d, J = 5.4

Hz, 1H, PCHPy), [4.58/5.54 (d, ³J = 4.3 Hz), 1H,

3

PCHPy], 3.79/3.78 (q, J = 6.6 Hz, 1H, CHCH₃), 3.17/

3.00 (m, 3H, NMe), 2.64/2.93 (m, 3H, NMe), 2.53 (md,

²J = 24.3 Hz, 1H, Cp–CH₂), 2.42 (md, ²J = 24.3 Hz,

(L_Ment,S_C)-3b (1.00 g, 1.86 mmol) was dissolved in 25

ml of ethanol. RhCl₃Æ 3H₂O (489 mg, 1.84 mmol), dis-

solved in 20 ml of ethanol, and NaHCO₃(156 mg, 1.86

mmol) were added. After stirring at 20 ꢁC for 24 h the

solvent was removed. For puriﬁcation a column chroma-

tography with SiO₂and petroleum ether (40/60):ethyl

acetate (10:1) was carried out. Yield 1.06 g (81%), m.p.

3

1H, Cp–CH₂); 2.02/2.01 (d, J = 6.6 Hz, 3H, CHCH₃),

1.60–1.40 (m, 6H, CH₃CCH₃) ppm. ³¹P{¹H} NMR

(162 MHz, CDCl₃): d = 51.3/52.0 [51.4/52.1] (s, 1P),

1

ꢀ141.6 (sept, J_F–P= 709.7 Hz, 1P, PF₆) ppm. MS

(ESI) m/z (%): 637 (cation, 100). C₃₆H₄₀F₆N₂P₂Pd

(783.1): Calc. C 60.94, H 5.97, N 1.97. Found C 60.33,

H 6.65, N 1.72%.

1

>200 ꢁC. H{³¹P} NMR (400 MHz, CDCl₃): d = 7.57–

7.51 (m, 1H, Ph), 7.41–7.13 (m, 6H, Ph, Py), 6.62 (dd,

4

³J = 8.2 Hz, J = 0.7 Hz, 1H, Py–H^3/5), 6.23 (m, 1H,

5.8. {2-[(S)-1-N,N-Dimethylaminoethylphenylene-C,N]-

2-[(R)-(1-diphenylphosphanyl-2-methylprop-1-yl)]-6-(1R,

2S,5R)-menthoxypyridinepalladium(II)}-hexaﬂuorophos-

phate 5b

Cp–H), 6.10 (m, 1H, Cp–H), 5.79 (dd, ³J = 7.4 Hz,

⁴J = 0.7 Hz, 1H, Py–H^3/5), 5.64 (m, 1H, Cp–H), 5.43

3

(m, 1H, Cp–H), 5.23 (dt, J = 10.7 Hz, J = 4.5 Hz, 1H,

3

OCH), 5.14 (s, 1H, PCHPy), 2.35 (m, 1H, Ment), 2.23–

3

2.15 (m, 1H, Ment), 2.01 (dsept, J = 6.8 Hz, J = 3.0

Hz, 1H, CH(CH₃)₂), 1.86–1.47 (m, 3H, Ment), 1.28 (s,

3H, CH₃CCH₃), 1.21 (s, 3H, CH₃CCH₃), 1.30–1.10 (m,

A suspension of the 1:1 mixture of the diastereomers

of 4b (3.0 g, 6.3 mmol) and (+)-bis{(l-chloro)[2-(S)-1-

dimethylaminoethylphenylene-C,N]palladium(II)} (2.1

g, 3.6 mmol) was stirred in methanol (50 ml). The solid

dissolved giving a clear solution. The reaction mixture

was stirred for 2 h at 20 ꢁC. The mixture was ﬁltered

and the solvent was reduced to half. Addition of NH₄PF₆

(1.03 g, 6.3 mmol) in 10 ml of water followed slowly by

another 20 ml of water precipitated the diastereomers

of [(NMe₂pea-H⁺)Pd(4b)]PF₆. After washing with water,

aqueous methanol and diethylether, the residue was

recrystallized from acetone/hexane to give the pure dia-

stereomer with (R)-conﬁguration at the asymmetric car-

bon atom in the PN backbone. Yield 3.0 g (54%), m.p.

3

2H, Ment), 1.02–0.82 (m, 1H, Ment), 1.04 (d, J = 6.5

3

Hz, 3H, Ment–CH₃), 0.92 (d, J = 7.1 Hz, 3H, Ment–

CH₃), 0.77 (d, ³J = 7.1 Hz, 3H, Ment–CH₃) ppm.

³¹P{¹H} NMR (162 MHz, CDCl₃): diastereomer

1

(L_Ment,S_C,R_Rh)-7b: d = 72.6 (d, J_Rh–P= 145 Hz, 1P),

diastereomer

(L_Ment,R_C,S_Rh)-7b:

d = 71.3

(d,

¹J_Rh–P= 145 Hz, 1P) ppm. MS (ESI, CH₂Cl₂): m/z

(%) = 674 (cation, 100). Optical rotation of diastereomer

RT

(L_Ment,S_C,R_Rh)-7b (c = 1.1, CHCl₃): ½aꢁ_D¼ ꢀ19,

RT

½aꢁ ¼ ꢀ23, ½aꢁ ¼ ꢀ37, ½aꢁ ¼ ꢀ43. UV–Vis

578

546

436

(c = 2.1 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max(nm) = 271

(e = 1.4 · 10³). CD (c = 2.8 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂):

k_max(nm) = 289 (De = ꢀ47.2), 382 (De = ꢀ5.3), 431

1

160–163 ꢁC. H NMR (400 MHz, CDCl₃): d = 7.97 (t,

4258

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

(De = 8.7). C₃₆H₄₃Cl₂NOPRh (710.5): Calc. C 60.86, H

6.10, N 1.97. Found C 60.88, H 6.18, N 1.72%.

Hz, 1H, Py–H^3/5), 5.63 (m, 1H, Cp–H), 5.43 (m, 1H,

3

Cp–H), 5.24 (dt, J = 10.3 Hz, J = 4.5 Hz, 1H, OCH),

3

2

5.16 (d, J_P–H= 11.2 Hz, 1H, PCHPy), 2.21 (m, 1H,

3

5.10. Substitution of the Cl ligand in (L_Ment,S_C,R_Rh)-7b by

halides (Br, I) and pseudohalides (N₃, CN, SCN) 8b–12b

Ment), 2.20–2.15 (m, 1H, Ment), 2.01 (dsept, J = 6.8

Hz, ³J = 3.0 Hz, 1H, CH(CH₃)₂), 1.84–1.68 (m, 3H,

Ment), 1.28 (s, 3H, CH₃CCH₃), 1.21 (s, 3H, CH₃CCH₃),

1.30–1.10 (m, 2H, Ment), 1.04 (d, ³J = 6.5 Hz, 3H,

The substitution of Cl in (L_Ment,S_C,R_Rh)-7b by ha-

lides and pseudohalides involved metathesis of

(L_Ment,S_C,R_Rh)-7b with the appropriate salts NaBr,

NaI, NaN₃, KCN and NaSCN in methanol. The prepa-

ration of the bromo derivative (L_Ment,S_C,R_Rh)-8b is

representative.

3

Ment–CH₃), 1.02–0.82 (m, 1H, Ment), 0.92 (d, J = 7.1

3

Hz, 3H, Ment–CH₃), 0.77 (d, J = 7.1 Hz, 3H, Ment–

CH₃) ppm. ³¹P{¹H} NMR (162 MHz, CDCl₃):

1

d = 70.9 (d, J_P–Rh= 145 Hz, 1P), ꢀ144.0 (sept, 1P,

PF₆) ppm. MS (ESI, CH₂Cl₂): m/z (%) = 766 (cation,

100). UV–Vis (c = 1.65 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂): k_max

5.11. (L_Ment,S_C,R_Rh)-8b

(nm) = 275 (e = 2.0 · 10³). CD (c = 2.2 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max(nm) = 293 (De = ꢀ127.3), 397

(De = ꢀ10.3), 453 (De = 19.3). C₃₆H₄₃F₆INOP₂Rh

(911.5): Calc. C 47.44, H 4.76, N 1.54. Found C 46.96,

H 4.69, N 1.30%.

(L_Ment,S_C,R_Rh)-7b (0.20 g, 0.28 mmol) was dissolved

in 10 ml of absolute methanol. To this solution NaBr

(0.55 g, 0.53 mmol), dissolved in 20 ml of methanol,

was added. The orange–red solution was stirred for 4

h. Then, NH₄PF₆(48.5 mg, 0.28 mmol), dissolved in

water, was added and the reaction mixture was stirred

for 2 h. The solvent was removed and the product was

extracted with CH₂Cl₂. The solution was passed over a

short silica gel column with CH₂Cl₂(red band). Re-

moval of the solvent aﬀorded an orange–red powder

which was washed with hexane/ether. Yield: 185 mg

5.13. (L_Ment,S_C,R_Rh)-10b

1

Yield 72%, m.p. 187–190 ꢁC. H NMR (400 MHz,

CDCl₃): d = 7.74–7.62 (m, 6H, Ph), 7.60 (m, 1H, Py–

H⁴), 7.49–7.45 (m, 2H, Ph), 7.39–7.33 (m, 2H, Ph),

3

4

6.62 (dd, J = 8.2 Hz, J = 0.7 Hz, 1H, Py–H^3/5), 6.23

3

(m, 1H, Cp–H), 6.00 (m, 1H, Cp–H), 5.78 (d, J = 7.4

1

(87%), m.p. 195–198 ꢁC. H NMR (400 MHz, CDCl₃):

Hz, 1H, Py–H^3/5), 5.64 (m, 1H, Cp–H), 5.43 (br s, 1H,

3

Cp–H), 5.20 (dt, J = 10.3 Hz, J = 4.5 Hz, 1H, OCH),

3

d = 7.73–7.63 (m, 4H, Ph), 7.56–7.53 (m, 2H, Ph),

7.41–7.36 (m, 3H, Ph, Py), 7.29–7.25 (m, 2H, Ph), 6.63

(d, ³J = 8.2 Hz, 1H, Py–H^3/5), 6.23 (m, 1H, Cp–H),

6.01 (m, 1H, Cp–H), 5.79 (d, ³J = 7.6 Hz, 1H, Py–

H^3/5), 5.71 (m, 1H, Cp–H), 5.55 (m, 1H, Cp–H), 5.25

(dt, ³J = 10.3 Hz, ³J = 4.5 Hz, 1H, OCH), 5.19 (d,

²J_P–H= 11.3 Hz, 1H, PCHPy), 2.35 (m, 1H, Ment),

2.21–2.09 (m, 1H, Ment), 2.00 (dsept, ³J = 6.8 Hz,

³J = 3.0 Hz, 1H, CH(CH₃)₂), 1.89–1.61 (m, 3H, Ment),

1.25 (s, 3H, CH₃CCH₃), 1.21 (s, 3H, CH₃CCH₃), 1.30–

1.10 (m, 2H, Ment), 1.02–0.82 (m, 1H, Ment), 1.04 (d,

2

5.16 (d, J_P–H= 11.2 Hz, 1H, PCHPy), 2.22 (m, 1H,

Ment), 2.20–2.15 (br m, 1H, Ment), 2.00 (dsept,

³J = 6.8 Hz, ³J = 2.9 Hz, 1H, CH(CH₃)₂), 1.83–1.70

(m, 4H, Ment), 1.35 (s, 3H, CH₃CCH₃), 1.21 (s, 3H,

3

CH₃CCH₃), 1.20–1.13 (m, 1H, Ment), 1.02 (d, J = 6.5

Hz, 3H, Ment–CH₃), 1.00–0.89 (m, 1H, Ment), 0.87

3

(d, J = 7.1 Hz, 3H, Ment–CH₃), 0.75 (d, J = 7.1 Hz,

3

3H, Ment–CH₃) ppm. ³¹P{¹H} NMR (162 MHz,

1

CDCl₃): d = 73.5 (d, J_P–Rh= 145.0 Hz, 1P), ꢀ143.0

(sept, 1P, PF₆) ppm. MS (ESI, CH₂Cl₂): m/z (%) = 681

(cation, 100). C₃₆H₄₃F₆N₄OP₂Rh (826.6). IR (ﬁlm):

m = 2180 s, 2060 s (N₃) cm^ꢀ1. UV–Vis (c = 1.8 · 10^ꢀ4

mol l^ꢀ1, CH₂Cl₂): k_max(nm) = 272 (e = 1.7 · 10³). CD

3

³J = 6.5 Hz, 3H, Ment–CH₃), 0.90 (d, J = 7.1 Hz, 3H,

Ment–CH₃), 0.77 (d, ³J = 7.0 Hz, 3H, Ment–CH₃)

ppm. ³¹P{¹H} NMR (162 MHz, CDCl₃): d = 66.6 (d,

¹J_Rh–P= 143 Hz, 1P, PPh₂), ꢀ142.0 (sept, 1P, PF₆)

ppm. MS (ESI, CH₂Cl₂): m/z (%) = 718 (cation, 100).

C₃₆H₄₃BrF₆NOP₂Rh (864.5). UV–Vis (c = 1.7 · 10^ꢀ4

mol l^ꢀ1, CH₂Cl₂): k_max(nm) = 274 (e = 1.96 · 10³), 410

(e = 0.4 · 10³). CD (c = 2.3 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂):

k_max(nm) = 291 (De = ꢀ90.4), 381 (D e = ꢀ11.3), 432

(De = 19.7).

(c = 2.8 · 10^ꢀ4mol l^ꢀ1

, CH₂Cl₂): k_max(nm) = 311

(De = ꢀ68.7), 414 (De = ꢀ4.7).

5.14. (L_Ment,S_C,R_Rh)-11b

1

Yield 75%, m.p. 197–200 ꢁC. H NMR (400 MHz,

CDCl₃): d = 7.76–7.65 (m, 6H, Ph), 7.60 (m, 1H, Py–

H⁴), 7.55–7.47 (m, 2H, Ph), 7.39–7.33 (m, 2H, Ph),

3

4

5.12. (L_Ment,S_C,R_Rh)-9b

6.61 (dd, J = 8.2 Hz, J = 0.7 Hz, 1H, Py–H^3/5), 6.23

3

(m, 1H, Cp–H), 6.11 (m, 1H, Cp–H), 5.83 (d, J = 7.4

1

Yield 88%, m.p. 192–195 ꢁC. H NMR (400 MHz,

Hz, 1H, Py–H^3/5), 5.65 (m, 1H, Cp–H), 5.44 (br s, 1H,

3

Cp–H), 5.23 (dt, J = 10.3 Hz, J = 4.5 Hz, 1H, OCH),

3

CDCl₃): d = 7.71–7.60 (m, 4H, Ph), 7.55–7.51 (m, 1H,

Ph), 7.41–7.34 (m, 4H, Ph, Py), 7.29–7.25 (m, 2H, Ph),

2

5.14 (d, J_P–H= 11.2 Hz, 1H, PCHPy), 2.22 (m, 1H,

3

4

3

Ment), 2.20–2.15 (m, 1H, Ment), 2.00 (dsept, J = 6.8

6.63 (dd, J = 8.2 Hz, J = 0.7 Hz, 1H, Py–H^3/5), 6.23

Hz, ³J = 2.9 Hz, 1H, CH(CH₃)₂), 1.83–1.70 (m, 4H,

3

(m, 1H, Cp–H), 6.11 (m, 1H, Cp–H), 5.80 (d, J = 7.4

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4259

Ment), 1.35 (s, 3H, CH₃CCH₃), 1.21 (s, 3H, CH₃CCH₃),

1.20–1.13 (m, 1H, Ment), 1.02 (d, ³J = 6.5 Hz, 3H,

1.50–1.44 (m, 1H, Ment), 1.43 (s, 3H, CH₃), 1.17–1.05

(m, 1H, Ment), 0.96–0.80 (m, 2H, Ment), 0.89 (d, ³J = 7.0

3

Ment–CH₃), 1.00–0.89 (m, 1H, Ment), 0.87 (d, J = 7.1

3

Hz, 3H, CH₃), 0.88 (d, J = 6.6 Hz, 3H, CH₃), 0.69 (d,

3

Hz, 3H, Ment–CH₃), 0.75 (d, J = 7.1 Hz, 3H, Ment–

3

3H, J = 6.9 Hz, CH₃) ppm. ³¹P{¹H} NMR (162 MHz,

CH₃) ppm. ³¹P{¹H} NMR (162 MHz, CDCl₃):

CDCl₃): d = 60.2 (dd, J_Rh–P= 145.0 Hz, J_P–P= 39.7

1 2

Hz, 1P, PPh₂), 34.5 (dd, J_Rh–P= 129.7 Hz, J_P–P= 39.7

1

2

1

d = 72.1 (d, J_P–Rh= 143.0 Hz, 1P), ꢀ143.0 (sept, 1P,

1

PF₆) ppm. MS (ESI, CH₂Cl₂): m/z (%) = 665 (cation,

100). C₃₇H₄₃F₆N₂OP₂Rh (810.6). IR (ﬁlm): m = 2195 s

(CN) cm^ꢀ1. UV–Vis (c = 1.9 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂):

k_max(nm) = 285 (e = 1.5 · 10³). CD (c = 2.9 · 10^ꢀ4

mol l^ꢀ1, CH₂Cl₂): k_max(nm) = 292 (De = ꢀ76.3).

Hz, 1P, PPh₃), ꢀ143.4 (sept, J_F–P= 712.6 Hz, 1P, PF₆)

ppm. MS (ESI, CH₂Cl₂): m/z (%) = 936 (cation, 100).

UV–Vis (c = 1.8 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max

(nm) = 282 (e = 0.96 · 10³), 350 (e = 0.58 · 10³). CD

(c = 1.9 · 10^ꢀ4mol l^ꢀ1

CH₂Cl₂): k_max(nm) = 303

,

(De = ꢀ65.1), 415 (De = ꢀ27.6), 487 (De = 5.3).

C₅₄H₅₈ClF₆NOP₃Rh (1082.3): Calc. C 59.93, H 5.40, N

1.29, Cl 3.28. Found C 58.73, H 5.19, N 1.31, Cl 2.99%.

5.15. (L_Ment,S_C,R_Rh)-12b

1

Yield 80%, m.p. 191–193 ꢁC. H NMR (400 MHz,

CDCl₃): d = 7.79–7.59 (m, 2H, Ph), 7.52–7.42 (m, 4H,

5.17. (L_Ment,R_C)-14b and (L_Ment,S_C)-14b

Ph), 7.41–7.34 (m, 1H, Py–H⁴), 7.32–7.27 (m, 2H, Ph),

3

7.25–6.99 (m, 2H, Ph), 6.61 (d, J = 8.3 Hz, 1H, Py–

To a solution of a 1:1 mixture of (L_Ment,R_C)- and

(L_Ment,S_C)-4b (374 mg, 0.788 mmol) in 2-propanol (40

ml) was added [(Cp*RhCl)₂(l-Cl)₂] (242 mg, 0.392

mmol) under nitrogen at 20 ꢁC. The mixture was stirred

for 4 h and then evaporated. Ether (40 ml) was added to

the residue. The mixture was vigorously stirred and ﬁl-

tered. From the insoluble part (L_Ment,R_C)-14b was ob-

tained in 53% (164 mg) yield based on (L_Ment,R_C)-4b.

The ﬁltrate was evaporated. The residue was chromato-

graphed on silica gel using CH₂Cl₂/EtOAc (1:3) to give

(L_Ment,S_C)-14b in 42% (129 mg) yield based on

(L_Ment,S_C)-4b.

H^3/5), 6.21 (m, 1H, Cp–H), 6.06 (m, 1H, Cp–H), 5.71

3

4

(dd, J = 7.4 Hz, J = 0.7 Hz, 1H, Py–H^3/5), 5.50 (br s,

1H, Cp–H), 5.43 (m, 1H, Cp–H), 5.20 (dt, ³J = 10.7

3

2

Hz, J = 4.2 Hz, 1H, OCH), 5.16 (d, J_P–H= 11.3 Hz,

1H, PCHPy), 2.22 (m, 1H, Ment), 2.20–2.15 (m, 1H,

Ment), 2.00 (dsept, ³J = 6.8 Hz, ³J = 2.9 Hz, 1H,

CH(CH₃)₂), 1.83–1.70 (m, 4H, Ment), 1.35 (s, 3H,

CH₃CCH₃), 1.21 (s, 3H, CH₃CCH₃), 1.20–1.13 (m,

1H, Ment), 1.02 (d, ³J = 6.5 Hz, 3H, Ment–CH₃),

1.00–0.85 (m, 1H, Ment), 0.92 (d, ³J = 7.0 Hz, 3H,

Ment–CH₃), 0.78 (d, ³J = 6.9 Hz, 3H, Ment–CH₃)

ppm. ³¹P{¹H} NMR (162 MHz, CDCl₃): d = 70.2 (d,

¹J_P–Rh= 144.5 Hz, 1P), ꢀ145.0 (sept, 1P, PF₆) ppm.

MS (ESI, CH₂Cl₂): m/z (%) = 697 (cation, 100).

C₃₇H₄₃F₆N₂OP₂SRh (842.7). IR (ﬁlm): m = 2115 s

(SCN) cm^ꢀ1. UV–Vis (c = 1.8 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂):

k_max(nm) = 273 (e = 1.9 · 10³). CD (c = 2.7 ·

10^ꢀ4mol l^ꢀ1, CH₂Cl₂): k_max(nm) = 291 (De = ꢀ125.3),

397 (De = ꢀ12.3), 452 (De = 18.1).

5.18. (L_Ment,R_C)-14b

Mp. 197.5–201 ꢁC. ¹H NMR (400 MHz, 253 K,

CDCl₃): d = 8.45 (dd, ³J = 7.2 Hz, ³J = 9.6 Hz, 2H, Ph),

7.66–7.55 (m, 6H, Ph), 7.40 (t, ³J = 7.8 Hz, 1H, Py–H⁴),

7.18 (br t, J = 6.6 Hz, 1H, Ph), 7.10 (br s, 1H, Ph), 7.00

3

(d, J = 7.2 Hz, 1H, Py–H^3/5), 6.30 (d, J = 8.2 Hz, 1H,

Py–H^3/5), 5.08 (d, J_P–H= 12.3 Hz, 1H, PCHPy), 4.82

2

3

5.16. 13b

(dt, J = 4.3 Hz, J = 10.7 Hz, 1H, OCH), 2.55 (sept,

³J = 6.6 Hz, 1H, CH(CH₃)₂), 1.92–0.65 (m, 8H, Ment),

4

1.24 (d, J_P–H= 3.3 Hz, 15H, Cp–CH₃), 0.99 (d,

(L_Ment,S_C,R_Rh)-7b (80.0 mg, 0.113 mmol) and PPh₃

(154mg, 0.588mmol)weredissolved inabsolute methanol

and stirred for 1.5 h at 20 ꢁC. The solvent was evaporated.

TheresiduewasdissolvedinCH₂Cl₂andﬁlteredtoremove

insoluble salts and excess PPh₃. The yellow solution was

passed through a short silica gel column with CH₂Cl₂.

Yield quant, m.p. 185–188 ꢁC. ¹H NMR (400 MHz,

CDCl₃): d = 7.57ꢀ7.51 (m, 4H, Ph), 7.46–7.26 (m, 6H,

Ph), 7.21–7.14 (m, 6H, Ph, Py–H⁴), 7.10–6.99 (m, 8H,

Ph), 6.87 (m, 2H, Ph), 6.47 (d, ³J = 8.7 Hz, 1H, Py–H^3/5),

6.46 (br s, 1H, Cp–H), 6.32 (m, 1H, Cp–H), 6.10 (d,

³J = 7.1 Hz, 1H, Py–H^3/5), 5.88 (br s, 1H, Cp–H), 5.55

³J = 6.4 Hz, 3H, CH₃), 0.91 (d, J = 6.4 Hz, 3H, CH₃),

3

0.81 (d, J = 7.0 Hz, 3H, CH₃), 0.50 (d, J = 6.9 Hz,

3H, CH₃), ꢀ0.01 (d, ³J = 6.8 Hz, 3H, CH₃) ppm.

³¹P{¹H} NMR (162 MHz, 253 K, CDCl₃): d = 29.8 (d,

¹J_Rh–P= 140.3 Hz, 1P) ppm. MS (ESI, CH₂Cl₂): m/z

(%) = 746 (M–Cl, 100). CD (c = 2.3 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max(nm) = 272 (De = ꢀ5.7), 296 (De = 4.9),

337 (De = ꢀ0.2), 406 (De = 5.6), 492 (De = ꢀ1.7).

C₄₁H₅₅Cl₂NOPRh (782.7): Calc. C 62.92, H 7.08, N

1.79. Found C 62.38, H 6.59, N 1.67%.

2

(m, 1H, Cp–H), 5.22 (d, J_P–H= 10.8 Hz, 1H, PCHPy),

5.19. (L_Ment,S_C)-14b

3

4.50 (br t, J = 9.7 Hz, 1H, OCH), 2.02 (br d, J = 11.5

Hz, 1H, Ment), 1.97 (dsept, ³J = 2.9 Hz, ³J = 6.8 Hz, 1H,

CH(CH₃)₂), 1.88 (s, 3H, CH₃), 1.75–1.65 (m, 3H, Ment),

Mp. 229–231 ꢁC. ¹H NMR (400 MHz, 253 K,

CDCl₃): d = 8.52 (dd, ³J = 8.4 Hz, ³J = 9.8 Hz, 2H,

4260

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

Ph), 7.66–7.54 (m, 5H, Ph), 7.36 (t, ³J = 7.6 Hz, 1H, Py–

and the residue was washed with ether to give

(R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)(R_Rh)-16a in

80% (163 mg) yield. Isomer composition: (R_C)(R_Rh)/

(S_C)(S_Rh):(R_C)(S_Rh)/(S_C)(R_Rh) = 74:26 by ³¹P{¹H}

NMR integration at 300 K. Orange powder, m.p. 145–

3

H⁴), 7.18–7.05 (m, 3H, Ph), 6.98 (br d, J = 7.2 Hz, 1H,

3

Py–H^3/5), 6.29 (d, J = 8.2 Hz, 1H, Py–H^3/5), 5.12 (d,

²J_P–H= 13.3 Hz, 1H, PCHPy), 4.53 (dt, ³J = 3.5 Hz,

3

³J = 10.6 Hz, 1H, OCH), 2.68 (sept, J = 6.6 Hz, 1H,

1

CH(CH₃)₂), 1.97–1.87 (m, 2H, Ment), 1.81–1.70 (m,

2H, Ment), 1.44–0.65 (m, 8H, Ment), 1.22 (d,

⁴J_P–H= 3.3 Hz, 15H, Cp–CH₃), 0.94 (d, ³J = 6.5 Hz,

3H, CH₃), 0.86 (d, ³J = 6.4 Hz, 3H, CH₃), 0.74 (d,

155 ꢁC. H NMR (400 MHz, CD₂Cl₂, major isomers

(R_C)(R_Rh)/(S_C)(S_Rh),

minor

isomers

3

(R_C)(S_Rh)/

(S_C)(R_Rh) in brackets): d = 8.59 (br d, J = 5.8 Hz, 1H,

Py–H⁶), [8.80 (br d, ³J = 5.4 Hz, 1H, Py–H⁶)], 8.06–

3

2

³J = 7.0 Hz, 3H, CH₃), 0.62 (d, J = 7.0 Hz, 3H, CH₃),

7.17 (m, 13H, Ph, Py–H^3–5), 3.91 (dd, J_P–H= 15.1 Hz,

0.10 (d, ³J = 6.8 Hz, 3H, CH₃) ppm. ³¹P{¹H} NMR

³J = 5.3 Hz, 1H, PCHPy), [4.99 (br d, J_P–H= 15.0 Hz,

2

1

(162 MHz, 253 K, CDCl₃): d = 29.5 (d, J_Rh–P= 140.8

1H, PCHPy)], 2.37–2.21 (m, 1H, CH(CH₃)₂), [2.54–

4

2.40 (m, 1H, CH(CH₃)₂)], 1.40 (d, J_P–H= 3.7 Hz,

Hz, 1P) ppm. MS (ESI, CH₂Cl₂): m/z (%) = 746 (M–

Cl, 100). CD (c = 2.4 · 10^ꢀ4mol l^ꢀ1, CH₂Cl₂): k_max

(nm) = 263 (De = ꢀ2.3), 301 (De = ꢀ5.6), 340 (De =

0.63), 406 (De = ꢀ11.4), 493 (De = 4.0). C₄₁H₅₅Cl₂-

NOPRh (782.7): Calc. C 62.92, H 7.08, N 1.79. Found

C 62.84; H 6.70, N 1.74%.

4

15H, Cp–CH₃), [1.51 (d, J_P–H= 3.7 Hz, 15H, Cp–

CH₃)], 0.74 (d, ³J = 6.7 Hz, 3H, CH₃), [1.11 (d,

³J = 7.2 Hz, 3H, CH₃)], 0.32 (d, ³J = 6.9 Hz, 3H,

3

CH₃), [0.38 (d, J = 7.0 Hz, 3H, CH₃) ppm. ³¹P{¹H}

1

NMR (162 MHz, CD₂Cl₂): d = 73.6 (d, J_Rh–P= 135.8

Hz, 1P, R_C,S_Rh/S_C,R_Rh-P), 59.3 (d, J_Rh–P= 143.5 Hz,

1

5.20. (R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)-

(R_Rh)-15a

1P, R_C,R_Rh/S_C,S_Rh-P), ꢀ143.8 (sept, J_F–P= 712.6 Hz,

1P, PF₆) ppm. MS (ESI, CH₂Cl₂): m/z (%) = 592 (cation,

100). C₃₁H₃₇ClF₆NP₂Rh (737.9): Calc. C 50.46, H 5.05,

N 1.90. Found C 50.59, H 5.65, N 1.86%.

To a solution of racemic 4a (284 mg, 0.893 mmol) in

ethanol (30 ml) was added [(Cp*RhCl)₂(l-Cl)₂] (256

mg, 0.414 mmol) under nitrogen at 20 ꢁC. The mixture

was stirred for 5 h and then evaporated. The residue

was washed with 10% dichloromethane/ether to give

(R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)(R_Rh)-15a in

94% (487 mg) yield. Orange powder, m.p. 168–174 ꢁC.

¹H NMR (400 MHz, CD₂Cl₂, major isomers

5.22. (L_Ment,R_C)(R_Rh)- and (L_Ment,R_C)(S_Rh)-16b

(L_Ment,R_C)-14b (116 mg, 0.148 mmol) and NH₄PF₆

(1.26 g, 7.7 mmol) were dissolved in THF (30 ml) under

nitrogen at 20 ꢁC. The mixture was stirred for 16 h and

then evaporated. Chloroform was added to the residue.

The suspension was vigorously stirred and ﬁltered. The

ﬁltrate was evaporated. The red residue was chromato-

graphed on a short silica gel column using acetone as

an eluent. The red fraction was evaporated and the resi-

due was washed with ether to give the orange powder

of (L_Ment,R_C)(R_Rh)-16b:(L_Ment,R_C)(S_Rh)-16b = 91:9 (by

³¹P{¹H} NMR integration at 300 K). Yield: 68.4 mg

(R_C)(R_Rh)/(S_C)(S_Rh),

minor

isomers

3

(S_C)(R_Rh)/

(R_C)(S_Rh) in brackets): d = 8.66 (br d, J = 5.8 Hz, 1H,

Py–H⁶), [8.87 (br d, ³J = 6.4 Hz, 1H, Py–H⁶)], 8.13–

7.17 (m, 13H, Ph, Py–H^3–5), 3.99 (dd, J_P–H= 15.2 Hz,

3

³J = 5.3 Hz, 1H, PCHPy), [5.01 (br d, J_P–H= 16.0 Hz,

1H, PCHPy)], 2.36–2.20 (m, 1H, CH(CH₃)₂), [2.56–

4

2.42 (m, 1H, CH(CH₃)₂)], 1.41 (d, J_P–H= 3.5 Hz, 15H,

3

Cp–CH₃), [1.53 (d, J = 3.7 Hz, 15H, Cp–CH₃)], 0.75

1

(51%), m.p. 164–166 ꢁC. H NMR (400 MHz, CD₂Cl₂,

major diastereomer (L_Ment,R_C)(R_Rh)-16b, minor diaster-

3

(d, J = 6.8 Hz, 3H, CH₃), [1.11 (d, J = 7.2 Hz, 3H,

3

4

CH₃)], 0.32 (d, J_P–H= 6.8 Hz, 3H, CH₃), [0.38 (d,

eomer (L_Ment,R_C)(S_Rh)-16b in brackets): d = 7.96 (t,

³J = 7.0 Hz, 3H, CH₃) ppm. ³¹P{¹H} NMR (162 MHz,

³J = 7.4 Hz, 1H, Py–H⁴), [8.17 (br t, J = 8.5 Hz, 1H,

3

1

CD₂Cl₂): d = [73.9 (d, J_Rh–P= 135.8 Hz, 1P, R_C,

S_Rh/S_C,R_Rh-P)], 59.3 (d, J_Rh–P= 141.9 Hz, 1P,

Py–H⁴)], 7.75–7.56 (m, 6H, Ph), 7.48–7.41 (m, 4H, Ph),

1

3

7.26 (d, J = 7.4 Hz, 1H, Py–H^3/5), [7.04 (br d, J = 8.5

3

R_C,R_Rh/S_C,S_Rh-P) ppm. MS (ESI, CH₂Cl₂): m/z (%) =

592 (cation, 100). C₃₁H₃₇Cl₂NPRh (628.4): Calc. C

59.25, H 5.93, N 2.23. Found C 59.36, H 6.08, N 2.27%.

Hz, 1H, Py–H^3/5)], 7.16 (d, J = 8.4 Hz, 1H, Py–H^3/5),

[7.02 (br d, ³J = 8.5 Hz, 1H, Py–H^3/5)], 4.41 (br q,

³J = 9.6 Hz, 1H, OCH), 4.01 (dd, J_P–H= 13.5 Hz,

2

³J = 3.1 Hz, 1H, PCHPy), 2.42–2.32 (m, 2H, CH(CH₃)₂),

4

1.97–0.95 (m, 8H, Ment), 1.30 (d, J_P–H= 3.7 Hz, 15H,

5.21. (R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)-

(R_Rh)-16a

4

Cp–CH₃), [1.35 (d, J_P–H= 3.9 Hz, 15H, Cp–CH₃)],

1.06 (d, ³J = 7.0 Hz, 3H, CH₃), 1.03 (d, ³J = 6.8 Hz, 6H,

3

CH₃), 0.94 (d, J = 6.4 Hz, 3H, CH₃), 0.36 (d, J = 6.8

3

(R_C)(R_Rh)/(S_C)(S_Rh)- and (R_C)(S_Rh)/(S_C)(R_Rh)-15a

(174 mg, 0.277 mmol) were dissolved in THF (30 ml) un-

der nitrogen at 20 ꢁC. NH₄PF₆(1.08 g, 6.63 mmol) was

added. After stirring for 15 h the solvent was evapo-

rated. Dichloromethane was added to the residue and

the suspension was ﬁltered. The ﬁltrate was evaporated

3

Hz, 3H, CH₃), [0.73 (d, J = 7.0 Hz, 3H, CH₃)], 0.05 (d,

³J = 6.8 Hz, 3H, CH₃), [0.43 (d, J = 7.0 Hz, 3H, CH₃)]

3

ppm. ³¹P{¹H} NMR (162 MHz, CD₂Cl₂): d = 55.8 (d,

¹J_Rh–P= 139.0 Hz, 1P), [61.6 (d, J_Rh–P= 142.1 Hz,

1

1P)], ꢀ143.9 (sept, ¹J_F–P= 710.6 Hz, 1P, PF₆) ppm. CD

H. Brunner et al. / Journal of Organometallic Chemistry 689 (2004) 4244–4262

4261

(c = 2.3 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max(nm) = 289

The mixture was stirred for 2 h and then NH₄PF₆(383

mg, 2.35 mmol) was added. The orange solution was

stirred for 17 h and evaporated. Dichloromethane was

added to the residue and the suspension was ﬁltered to

remove inorganic salts. The ﬁltrate was evaporated

and the residue was subjected to silica gel chromatogra-

phy using 25% EtOH/benzene as an eluent to give a mix-

ture of (L_Ment,R_C)(R_Rh)-, (L_Ment,R_C)(S_Rh)-, (L_Ment,S_C)

(R_Rh)- and (L_Ment,S_C)(S_Rh)-17b. Yield 68.0 mg (75%).

(De = ꢀ2.9), 314 (De = 14.5), 373 (De = ꢀ8.3), 477

(De = 3.3). MS (ESI, CH₂Cl₂): m/z (%) = 746 (cation,

100). HRMS (LSI, MeOH–glycerol): C₄₁H₅₅ClOPRh

(cation) Calc. 746.2758. Found 746.2744.

5.23. (L_Ment, S_C)(S_Rh)-16b

In the above manner the reaction of (L_Ment,S_C)-14b

(38.9 mg, 0.0497 mmol) with NH₄PF₆(228 mg, 1.34

mmol) in THF (15 ml) gave (L_Ment,S_C)(S_Rh)- and

(L_Ment,S_C)(R_Rh)-16b in 41% (18.6 mg) yield. Recrystalli-

zation of the mixture using acetone/petroleum ether 40/

60 aﬀorded pure (L_Ment,S_C)(S_Rh)-16b isolated as orange

needles, m.p. 167–171 ꢁC. ¹H NMR (400 MHz,

CD₂Cl₂): d = 7.96–7.90 (m, 3H, Ph, Py–H⁴), 7.71–7.50

Isomer

composition:

L_Ment,R_C,R_Rh:L_Ment,R_C,S_Rh:

L_Ment,S_C,R_Rh:L_Ment,S_C,S_Rh= 20:25:5:50 by ³¹P{¹H}

NMR integration, m.p. 138–145 ꢁC. ¹H NMR (400

MHz, CDCl₃): d = 8.14ꢀ7.20 (m, 13H, Ph, Py–H^3–5),

3

5.36 (d, J_P–H= 1.2 Hz, 5H, L_Ment,S_C,S_Rh-Cp–H), 5.67

3

(d, J_P–H= 1.6 Hz, 5H, L_Ment,S_C,R_Rh-Cp–H), 5.63 (d,

³J_P–H= 1.6 Hz, 5H, L_Ment,R_C,S_Rh-Cp–H), 5.38 (d,

³J_P–H= 1.2 Hz, 5H, L_Ment,R_C,R_Rh-Cp–H), 4.35 (dt,

³J = 3.9 Hz, ³J = 11.0 Hz, 1H, L_Ment,S_C,S_Rh-OCH),

4.67–4.59 (m, 1H, L_Ment,S_C,R_Rh-OCH), 4.57–4.50 (m,

3

(m, 6H, Ph), 7.35–7.30 (m, 2H, Ph), 7.18 (d, J = 7.2

3

Hz, 1H, Py–H^3/5), 7.03 (d, J = 8.4 Hz, 1H, Py–H^3/5),

4.28 (dt, ³J = 4.1 Hz, ³J = 10.4 Hz, 1H, OCH), 3.93

2

(dd, J_P–H= 13.3 Hz, J = 4.3 Hz, 1H, PCHPy), 2.70

3

1H, L_Ment,R_C,S_Rh-OCH), 4.42 (dt, ³J = 3.9 Hz, ³J =

3

2

10.9 Hz, 1H, L_Ment,R_C,R_Rh-OCH), 4.10 (dd, J_P–H

(dsept, J = 2.4 Hz, J = 6.8 Hz, 1H, Ment–CH(CH₃)₂),

2.42–2.24 (m, 2H, Ment, PCHCH(CH₃)₂), 1.81 (d,

³J = 6.1 Hz, 3H, CH₃), 1.85–1.59 (m, 5H, Ment), 1.43–

=

16.8 Hz, J = 5.3 Hz, 1H, L_Ment,S_C,S_Rh-PCHPy), 4.87

3

2

(br d, J_P–H= 16.2 Hz, L_Ment,S_C,R_Rh-PCHPy), 4.79 (br

4

2

d, J_P–H= 16.2 Hz, L_Ment,R_C,S_Rh-PCHPy), 4.21 (dd,

1.38 (m, 1H, Ment), 1.32 (d, J_P–H= 3.9 Hz, 15H, Cp–

3

CH₃), 1.11–1.01 (1H, m, Ment), 0.90 (d, J = 6.8 Hz,

²J_P–H= 16.6 Hz, ³J = 5.3 Hz, 1H, L_Ment,R_C,R_Rh

-

PCHPy), 2.65–0.80 (m, 10H, Ment, CHCH(CH₃)₂),

3H, CH₃), 0.80 (d, ³J = 6.8 Hz, 3H, CH₃), 0.36 (d,

³J = 6.8 Hz, 3H, CH₃), 0.11 (d, J = 6.8 Hz, 3H, CH₃)

3

1.04 (d, J = 6.4 Hz, 3H, L_Ment,S_C, S_Rh-CH₃), 1.08 (d,

ppm. ³¹P{¹H} NMR (162 MHz, CD₂Cl₂): d = 53.2 (d,

³J = 6.4 Hz, 3H, L_Ment,R_C,R_Rh-CH₃), 1.17 (d, J = 7.2

3

¹J_Rh–P= 142.3 Hz, 1P, PH), ꢀ143.9 (sept, J_F–P

=

710.6 Hz, 1P, PF₆) ppm. MS (ESI, CH₂Cl₂): m/z

Hz, 3H, L_Ment,R_C,S_Rh-CH₃), 0.99 (d, ³J = 7.0 Hz,

3H, L_Ment,S_C,S_Rh-CH₃), 0.98 (d, ³J = 7.0 Hz, 3H,

L_Ment,R_C,R_Rh-CH₃), 1.05 (d, ³J = 7.0 Hz, 3H,

1

(%) = 746 (cation, 100). CD (c = 2.4 · 10^ꢀ4mol l^ꢀ1

,

CH₂Cl₂): k_max(nm) = 280 (De = 4.8), 316 (De = ꢀ29.7),

373 (D e = 14.6), 465 (De = ꢀ3.91). HRMS (LSI,

MeOH–glycerol) C₄₁H₅₅ClNOPRh (cation) Calc.

746.2758. Found 746.2747.

L_Ment,R_C,S_Rh-CH₃),

0.74

(d,

³J = 6.8

Hz,

,

3H, L_Ment,S_C,S_Rh-CH₃), 0.93 (d, ³J = 6.4 Hz, 3H, L_Ment

3

R_C,R_Rh-CH₃), 0.91 (d, J = 7.4 Hz, 3H, L_Ment,R_C,S_Rh

-

CH₃), 0.59 (d, ³J = 6.8 Hz, 3H, L_Ment,S_C,S_Rh-CH₃),

3

0.92 (d, J = 6.4 Hz, 3H, L_Ment,S_C,R_Rh-CH₃), 0.76 (d,

3

5.24. (L_Ment,R_C)(R_Rh)-16b and (L_Ment,S_C)(S_Rh)-16b as

well as (L_Ment,S_C)(S_Rh)-16b

³J = 7.4 Hz, 3H, L_Ment,R_C,R_Rh-CH₃), 0.91 (d, J = 6.6

3

Hz, 3H, L_Ment,R_C,S_Rh-CH₃), 0.33 (d, J = 6.8 Hz, 3H,

L_Ment,S_C,S_Rh-CH₃), 0.39 (d, ³J = 7.2 Hz, 3H, L_Ment

,

-

3

As before a 1:1 mixture of (L_Ment,R_C)- and (L_Ment,S_C)-

14b (87.4 mg, 0.111 mmol) was reacted with NH₄PF₆

(85.7 mg, 0.526 mmol). The residue was dissolved in eth-

anol. The ethanolic solution was diluted with ether and

allowed to stand at room temperature to deposit a 1:1

mixture of the diastereomer (L_Ment,R_C)(R_Rh)- and

(L_Ment,S_C)(S_Rh)-16b (26.5 mg, 27%) as red–orange

prisms. After ﬁltration, further standing at room temper-

ature aﬀorded (L_Ment,S_C)(S_Rh)-16b as orange needles in

40% (19.8 mg) yield.

S_C,R_Rh-CH₃), 0.36 (d, J = 6.8 Hz, 3H, L_Ment,R_C,R_Rh

CH₃), 0.48 (d, ³J = 7.0 Hz, 3H, L_Ment,R_C,S_Rh-CH₃)

ppm. ³¹P{¹H} NMR (162 MHz, CDCl₃): d = 73.0

(d,¹J_Rh–P= 125.1 Hz, 1P, L_Ment,R_C,S_Rh-P), 72.3

(d,¹J_Rh–P= 123.6 Hz, 1P, L_Ment,S_C,R_Rh-P), 59.6 (d,

¹J_Rh–P= 131.24 Hz, 1P, L_Ment,S_C,S_Rh-P), 58.7 (d,

¹J_Rh–P= 129.7 Hz, 1P, L_Ment,R_C,R_Rh-P), ꢀ143.9 (sept,

¹J_F–P= 710.6 Hz, PF₆) ppm. MS (ESI, CH₂Cl₂):

m/z (%) = 676 (cation, 100). C₃₆H₄₅F₆ClNOP₂Rh Æ

(C₆H₆)_1/2(861.1): Calc. C 54.40, H 5.62, N 1.63. Found

C 53.92, H 5.79, N 1.55%.

5.25. (L_Ment,R_C)(R_Rh)-, (L_Ment,R_C)(S_Rh)-, (L_Ment

S_C)(R_Rh)- and (L_Ment,S_C)(S_Rh)-17b

,

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Article Doi

Stabilization of the labile metal configuration in halfsandwich complexes [CpRh(PN)Hal]X

DOI: 10.1016/j.jorganchem.2004.07.057

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