Stereospecific synthesis, structural characterisation and resolution of 2-phospha[3]ferrocenophane derivatives - A new chiral scaffold

Article abstract of DOI:10.1002/ejic.200700282

The first 2-phospha[3]ferrocenophanes containing stereogenic carbon atoms in the three-atom bridge have been synthesised from phenylphosphane by stereospecific ring-closing phosphanation reactions. Either α-substituted 1,1′-bis-(hydroxymethyl)ferrocenes or the corresponding 2-oxa-[3]ferrocenophanes have been used as diastereomerically pure starting materials. The resolution of 1,2,3-triphenyl-[2]phosphaferrocenophane has been achieved by chromatographic separation of the diastereomeric adducts of a chiral cyclopalladate complex. The X-ray crystal structures of two 2-phospha[3]ferrocenophane-borane complexes are also reported. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700282

FULL PAPER
DOI: 10.1002/ejic.200700282
Stereospecific Synthesis, Structural Characterisation and Resolution of
2-Phospha[3]ferrocenophane Derivatives – a New Chiral Scaffold
Nicolas Fleury-Brégeot,[a] Armen Panossian,[a] Angèle Chiaroni,[a] and Angela Marinetti*[a]
Keywords: Phosphane ligands / Ferrocenophane / Chiral resolution / Palladium
The first 2-phospha[3]ferrocenophanes containing stereo-
genic carbon atoms in the three-atom bridge have been syn-
thesised from phenylphosphane by stereospecific ring-clos-
ing phosphanation reactions. Either α-substituted 1,1Ј-bis-
(hydroxymethyl)ferrocenes or the corresponding 2-oxa-
[3]ferrocenophanes have been used as diastereomerically
pure starting materials. The resolution of 1,2,3-triphenyl-
[2]phosphaferrocenophane has been achieved by chromato-
graphic separation of the diastereomeric adducts of a chiral
cyclopalladate complex. The X-ray crystal structures of two
2-phospha[3]ferrocenophane-borane complexes are also re-
ported.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
The emergence of monodentate, bulky, electron-rich glected scaffolds. In most known ferrocenyl phosphanes, a
phosphanes is a recent, noteworthy issue in the field of or- phosphorus function and the cyclopentadienyl ring are
ganometallic catalysis. Tris(tert-butyl)phosphane, biphenyl- either directly bonded or separated by a one-carbon spacer
(di-tert-butyl)- and dicyclohexylphosphane are prototypical (representative examples of monodentate derivatives are
compounds of this class. By showing their great potential shown in Figure 1). In only a few cases have two[3d,5,6] or
in palladium-promoted coupling reactions,[1] the pioneering three[3c] ferrocene moieties been connected to the same
work of Nishiyama, Fu and Buchwald stimulated the active phosphorus atom, and ferrocenophane frameworks bearing
search for new catalytic applications[2] as well as for new phosphorus functions in a carbon-tethering chain are espe-
ligand structures. Among others, the synthesis and use of cially uncommon. Thus, ferrocenophane moieties of this
ferrocenyl-based phosphanes have been considered, which series have been selected in this work as target compounds.
combine the steric bulk of the organometallic moiety with
It may be interesting to recall here that, among phospho-
the electron-donating properties of alkyl and/or ferrocenyl rus-containing ferrocenophanes, 1-phospha[1]ferroceno-
phosphorus substituents.[3] Representative examples are phanes are moderately stable compounds that have been ex-
given in Figure 1.
tensively studied mainly as precursors for high-molecular-
weight poly(ferrocenes) by thermal or photochemical ring-
opening polymerisation.[7] Similarly, incorporation of phos-
phorus in the two-atom chain of [2]ferrocenophanes has
been used to generate strained starting materials for the
synthesis of polymeric materials.[8] On the other hand,
three- to five-atom tethers are known to afford stable phos-
phorus derivatives. Thus, for instance, the synthesis and co-
ordinating properties of a 3-phospha[5]ferrocenophane
have been reported.[9] Concerning phosphorus-containing
[3]ferrocenophanes, most known compounds have three
heteroatom bridges. These include 1,3-distanna-,[10] 1,3-di-
thia-[11] and 1,3-diaza-2-phospha[3]ferrocenophanes.[12] The
first [3]ferrocenophanes where phosphorus is included in a
Figure 1. Ferrocenylphosphanes.
An especially attractive and favourable feature of ferro-
cenylphosphanes for routine bench use is their higher resis-
tance to air oxidation with respect to other ligands with
similar bulk and electron-donating ability. This is the basis
of, for instance, the impressive development of ferrocenyl-
based phosphanes in enantioselective catalysis,[4] and it mo-
tivates new studies in these series.
In this context, our purpose is to expand the field of
monodentate, electron-rich ferrocenylphosphanes, and espe-
cially that of chiral species, to include unprecedented or ne-
[a] Institut de Chimie des Substances Naturelles, CNRS UPR
2301,
1, av. de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
E-mail: angela.marinetti@icsn.cnrs-gif.fr
Scheme 1.
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carbon tether have only recently been isolated from the re- found that suitable reactants and conditions for the stereo-
action of 6,6Ј-dimethylfulvene with, successively, the di- specific synthesis of 1 must be selected for each of the tar-
lithiated phosphanes PhPLi2 or CyPLi2, and FeCl2 geted phosphanes. Especially, the availability of dia-
(Scheme 1).[13]
stereomerically pure starting materials is a key prerequisite
for these reactions.
For R = Ph, high-yield, stereospecific synthesis of 1a and
1aЈ has been performed from the meso and dl diols 2aЈ and
2a respectively, by their reactions with PhPH2 in acetic acid
(Scheme 2).
Results and Discussion
Synthesis and Characterisation of 2-
Phospha[3]ferrocenophanes
As far as we know, no chiral, enantiomerically pure
phosphaferrocenophanes where either phosphorus or phos-
phorus-containing chains link the two cyclopentadienyl
rings are known to date.[14] Thus, in this work, 2-phospha-
[3]ferrocenophane derivatives of the general formula 1 (Fig-
ure 2), including optically pure compounds, have been tar-
geted as new bulky, rigid and electron-rich phosphanes for
use in organometallic catalysis.
Figure 2. 2-Phospha[3]ferrocenophane derivatives 1.
Scheme 2.
A key prerequisite for the synthesis of chiral derivatives
is establishing reliable, stereospecific synthetic approaches
Diol 2a can be obtained easily, albeit in an expensive and
to the [3]ferrocenophane scaffold; then convenient resolu- redundant way, by CBS reduction[17] of the corresponding
tion procedures must be defined. The synthetic approach to diketone, 1,1Ј-dibenzoylferrocene. Alternatively,[18–20] diol
2-phospha[3]ferrocenophane shown in Scheme 1 is unlikely 2a can be obtained from the 1:1 mixture of the meso and
to be applied to the stereoselective synthesis of the targeted dl diols produced by NaBH4 reduction of 1,1Ј-dibenzoylfer-
phospha[3]ferrocenophanes 1, given that mixtures of all rocene, by repeated crystallisations from ethyl acetate/hex-
possible stereoisomers of 1 are expected to form as a result ane. The meso diol 2aЈ was obtained by fractional crystalli-
of such a procedure. Thus, alternative approaches that start sation of the meso/dl (2:1) diastereomeric mixture, which is
from preformed, suitably substituted ferrocenes have been produced when the same diketone is reduced with LiAlH4
considered in this work. Known methods for the formation in ether.
of P–C bonds from ferrocenylmethyl derivatives have been
tested and adapted to the synthesis of the ferrocenophane phenylphosphane (Scheme 2) follows the expected pattern:
derivatives 1. retention of the carbon configuration takes place in the
The stereochemical course of the reactions of diols 2 with
Since the pioneering work of Kumada and Hayashi, first, intermolecular nucleophilic substitution step, while
ferrocenylmethyl acetates or the corresponding ammonium the intramolecular ring-closing reaction necessarily induces
salts have been routinely used for the synthesis of (ferrocen- inversion of the carbon configuration. In both steps an
ylmethyl)phosphanes through reactions with secondary iron-stabilised carbocation is formed after departure of the
phosphanes.[15] Starting from α-substituted derivatives, leaving group;[21] however, the entering nucleophiles ap-
these highly stereospecific reactions take place with reten- proach the carbocation once from the face opposite the iron
tion of the carbon configuration, because of the high con- atom and once from the “iron face”. Consequently, the dl
figurational stability of the intermediate carbocation.
diol 2a affords the meso derivative, anti,anti-1,3-diphenyl-2-
Although the use of primary phosphanes in such reac- phospha[3]ferrocenophane 1aЈ, while the meso diol 2aЈ se-
tions has scarcely been reported,[6,16] the method might pro- lectively affords the dl isomer 1a.
vide stereospecific access to 2-phospha[3]ferrocenophanes
The cyclisation reaction is best performed by adding
starting from 1,1Ј-bis(α-acetoxymethyl)ferrocenes. In pre- phenylphosphane to an ice-cooled suspension of diols 2 in
liminary experiments, however, the reaction of 1,1Ј-bis(α- acetic acid and then warming the mixture to room tempera-
acetoxybenzyl)ferrocene with phenylphosphane in usual ex- ture. Prolonged stirring of the diol in acetic acid should be
perimental conditions (room temp. in acetic acid) afforded avoided, in order to prevent epimerisation.
only trace amounts of the expected compounds, together
The [3]ferrocenophanes 1 are air-stable in the solid state
with supposedly polymeric, insoluble material. We thus and oxidise slowly in solution. These compounds, as well
turned our attention to alternative starting materials and as the corresponding borane complexes 3, have been fully
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2-Phospha[3]ferrocenophane Derivatives – a New Chiral Scaffold
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characterised. The crystal structure of the dl isomer 3a has substituted species depends on the nature of the entering
been determined by X-ray diffraction studies (see below). nucleophile and/or on the precise experimental procedure,
Phosphane 1aЈ and corresponding borane 3aЈ have been as- racemisation of the starting alcohol possibly being a com-
2
signed as the anti,anti isomers, based on the small JH–P petitive side reaction. Experimental conditions can be
coupling (6.0 Hz) observed for the CHPh protons in the 1H found where the substitution reaction overcomes the racem-
NMR spectrum of 1aЈ.[22] This isomer is expected to be the isation process induced by the acidic medium and the chiral
thermodynamically favoured one.
alcohols 4 can be conveniently converted into the corre-
The use of ferrocenylmethyl alcohols as precursors for sponding phosphanes by using nucleophilic phosphorus
phosphanes has been rather infrequently reported,[3d,16,23] reagents.
the alcohols usually being converted into acetates before
Returning to our main aim, that is, the stereospecific syn-
their reaction with phosphorus nucleophiles. Thus, having thesis of 2-phospha[3]ferrocenophanes, we next considered
ascertained the high stereoselectivity of the reaction be- synthetic approaches to phosphanes 1b (R = Me). In this
tween diols 2a and phenylphosphane in acetic acid, we won- case, the question arises of the availability of suitable, dia-
dered if the method could also be applied to the stereoselec- stereomerically pure starting materials.[27] It is well known
tive synthesis of simpler phosphanes, directly from enantio- that the diastereomeric mixture of the 1,1Ј-bis(α-hydroxy-
merically enriched alcohols. As a representative example, ethyl)ferrocenes 2b/2bЈ obtained by reduction of 1,1Ј-diace-
the commercially available diisobutylphosphane has been tylferrocene cannot be separated either by chromatography
reacted with (S)-α-ferrocenylpentan-1-ol 4a[24] and (S)-α- or by crystallisation. On the other hand, according to
(ferrocenyl)benzyl alcohol 4b.[25] In both cases the targeted Yamakawa and Hisatome,[18] the corresponding dia-
phosphane could be obtained stereoselectively when suit- stereomeric 2-oxa[3]ferrocenophanes 6b/6bЈ are easily sepa-
able experimental conditions were applied.
rable by column chromatography. The cyclic ethers 6[28]
The (α-ferrocenyl-1-pentyl)diisobutylphosphane 5a is have thus been selected as starting materials for the synthe-
formed with total retention of the carbon configuration sis of phosphanes 1b, which have been isolated as their bo-
when diisobutylphosphane is added to a solution of (S)-4a rane complexes 3b, according to the method shown in
in acetic acid at room temperature. However, in the same Scheme 4.
conditions, the substitution reaction on the α-(ferrocenyl)-
benzyl alcohol (S)-4b induces partial racemisation of the
carbon centre. Racemisation can be avoided by immediately
adding the phosphane to an ice-cooled suspension of the
chiral alcohol 4b in acetic acid. This procedure avoids pro-
longed contact of alcohol 4b with the acidic medium and
thus allows a stereospecific substitution reaction to take
place with the phosphane.
These results corroborate previous data showing lack of
stereochemical control in the substitution reaction between
4b and imidazoles in acidic medium and almost total reten-
tion of the carbon configuration in the analogous substitu-
tion on α-ferrocenylethanol at room temperature.[26] On the
other hand, however, a stereospecific reaction has been re-
ported by Hu to take place between 4b and phenylphos-
Scheme 4.
phane in acetic acid at room temperature.[3d]
Taken together, the results shown in Scheme 3 and litera-
Treatment of diol 2b (1:1 isomeric mixture) with aqueous
ture data afford additional evidence that the stereochemical HCl induces the ring-closure reaction and quantitatively af-
course of the substitution reactions on the α-substitut- fords the diastereomeric ethers 6, which are easily separated
ed(ferrocenyl) alcohols 4 and most particularly on α-aryl- by column chromatography on silica gel with hexane/ethyl
acetate (9:1) as the eluent. The meso-6bЈ isomer was eluted
first (Rf = 0.47), followed by the dl isomer 6b (Rf = 0.35).[29]
For the direct conversion of the cyclic ethers 6 into phos-
phanes, we envisioned a reaction with phenylphosphane in
the presence of acid catalysts. Addition of the acid catalyst
to the bridging oxygen atom is expected to generate a ferro-
cene-stabilised carbocation,[30] which should then react with
the nucleophilic phosphane to afford a phosphonium salt
intermediate. A second, intramolecular, acid-catalysed, nu-
cleophilic substitution between the corresponding phos-
phane and the residual hydroxy function should then lead
to the expected phospha[3]ferrocenophane 1b. The use of
Scheme 3.
both Brønsted and Lewis acid catalysts (HBF4, CF3CO2H,
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N. Fleury-Brégeot, A. Panossian, A. Chiaroni, A. Marinetti
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BF3·Et2O, SnCl4) has been considered. Boron trifluoride
proved to be the best catalyst, affording the desired 2-phos-
pha[3]ferrocenophanes 1b in about 30% yield. The final
phosphane–borane complexes are easily purified by column
chromatography, given that the only side-products formed
in the reaction are insoluble and probably polymeric.
The substitution reaction takes place with total stereose-
lectivity with respect to the carbon configuration, through
a conceivably double inversion process. A single dia-
stereoisomer is obtained from the dl ether 6b, while a mix-
ture of the anti,anti and syn,syn isomers 3bЈ and 3bЈЈ respec-
tively are formed from meso-6bЈ.
Figure 4. ORTEP view of the 2-phenyl-2-phospha[3]ferroceno-
phane borane complex 3c. Displacement ellipsoids are shown at
the 30% probability level.
Table 1. Selected bond lengths [Å] and angles [°] for 3a, 3c and I
(see Scheme 1).
X-ray Crystal Structures of the Borane Complexes of 2-
Phospha[3]ferrocenophane
dl-3a
3c
I[13]
P–C6
1.855(2)
1.878(2)
1.813(3)
1.910(3)
1.510(3)
1.515(3)
2.025(2)
2.016(2)
108.28(9)
110.20(14)
110.72(14)
113.37(14)
1.826(3)
1.826(3)
1.813(3)
1.929(4)
1.512(3)
1.508(3)
2.024(3)
2.023(2)
105.28(13)
110.57(16)
1.899(2)
1.900(2)
1.844(2)
P–C6Ј
P–C13 or P–C7
P–B
C1–C6
C1Ј–C6Ј
Fe–C1
As compounds 1 and 3 are the first known, stereochemi-
cally defined, phosphorus-bridged ferrocenophanes, the
molecular structure of one of them, the dl-triphenyl-substi-
tuted derivative 3a, has been investigated by X-ray diffrac-
tion studies. Suitable single crystals of 3a were obtained by
slow crystallisation from ethyl acetate/hexane. The ORTEP
drawing is presented in Figure 3.
1.516(3)
1.516(3)
2.034(2)
2.045(2)
109.16(9)
Fe–C1Ј
C6–P–C6Ј
B–P–C13 or C7
C7–C6–P
C7Ј–C6Ј–P
118.5(2)
104.8(2)
The crystal structures of 3a and 3c display roughly the
same preferred arrangement and geometrical features as
other 2-phospha[3]ferrocenophane derivatives.[13,32]
The Cp rings of 3 and, consequently, the C1–C6 and
C1Ј–C6Ј bonds are almost perfectly eclipsed in a synperi-
planar conformation. The ferrocenophane scaffold there-
fore shows a symmetry plane including the iron and phos-
phorus atoms. This symmetry plane will be lost in 3a be-
cause of the presence of the stereogenic α-carbon atoms.
The mean values for the Fe–C distances are identical in the
two complexes at 2.035 Å.
In 3a, the plane of the phenyl ring bonded to C6 forms
a dihedral angle of 74.8° with the Cp ring (pseudoaxial po-
sition), while the phenyl bonded to C6Ј has a dihedral angle
of 40.6° with the Cp plane (pseudoequatorial position). The
phenyl substituent on phosphorus occupies an anti position
with respect to the ferrocenyl moiety, which should mini-
mise steric repulsions.
In both phosphane–borane complexes 3, the cyclopen-
tadienyl rings are slightly tilted toward each other, with di-
hedral angles of 4.8° and 5.6° for 3a and 3c respectively.
Moreover, the angles around the phosphorus atom are very
close to the expected tetrahedral value (109.5°). This sug-
gests a very low degree of ring strain induced by the three-
atom tether.
Figure 3. ORTEP drawing of dl-3a. Displacement ellipsoids are
shown at the 30% probability level.
For comparison purposes, the carbon-unsubstituted P-
phenylferrocenophane 3c has been prepared from the corre-
sponding oxa[3]ferrocenophane[31] and phenylphosphane
(see Experimental Section) and structurally characterised
(Figure 4). Comparative bond lengths and angles for com-
pounds 3a and 3c are given in Table 1, together with rel-
evant values for compound I from ref.[13]
Resolution of dl-1,2,3-Triphenyl-2-phospha[3]ferrocenophane
The final aim of our work is to set up the 2-phospha-
[3]ferrocenophane unit as a new structural motif for the de-
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sign of chiral ligands. Thus, within these first and prelimi-
nary studies, the last step has been the search for a suitable
resolution procedure for the representative phosphane 1a.
For this resolution process we envisioned the use of ortho-
palladate derivatives of optically active amines whose versa-
tility as resolving agents for Lewis bases has been largely
demonstrated.[33] The choice of the chiral amine auxiliary
proved crucial. Attempts to separate diastereomeric palla-
dium complexes derived from either α-methylbenzylamine,
N,N-dimethyl-α-methylbenzylamine or 1-(α-naphthyl)ethyl-
amine were unsuccessful, however better results were ob-
tained with the (R)-configured cyclopalladate complex 7.[34]
The (R)-configured cyclopalladate complex 7 was treated
with the racemic 1,2,3-triphenyl-2-phospha[3]ferroceno-
phane dl-1a to afford a 1:1 mixture of the mononuclear dia-
stereomeric complexes 8a and 8b by displacement of the
chloride bridge (Scheme 5). Separation of the mixture
proved to be straightforward: column chromatography on
silica gel with a heptane/ethyl acetate (8:2) mixture as the
eluent afforded 8a and 8b separately (Rf = 0.5 and 0.3
respectively in heptane/ethyl acetate, 6:4). An X-ray crystal
structure of 8a allowed assignment of the relative configura-
Figure 5. ORTEP view of the cyclopalladate complex 8a. Displace-
ment ellipsoids are shown at the 30% probability level.
Conclusions
This work demonstrates an unprecedented synthetic ap-
tion of the phospha[3]ferrocene ligand with respect to the proach to the 2-phospha[3]ferrocenophane scaffold, which
known (R) configuration of the amine fragment. In com- allows the stereospecific synthesis of α,αЈ-disubstituted de-
plex 8a the 1,2,3-triphenyl-2-phospha[3]ferrocenophane has rivatives. Moreover, optical resolution of the 2-phospha[3]-
an (S,S) configuration (Figure 5).
ferrocenophane 1a, which contains stereogenic carbon
atoms in the three-atom bridge, has been performed. These
preliminary studies open the way to the development of a
new family of phosphorus ligands based on the 2-phos-
pha[3]ferrocenophane unit as a new chiral cyclic scaffold.
Experimental Section
NMR spectra were recorded with Bruker Avance 300 or Avance
500 spectrometers in CDCl3 solutions. Chemical shifts are reported
in ppm with reference to the residual solvent peak (CHCl3) for
1H and 13C. Mass spectra were run on LCT Waters-Micromass
(Electrospray) or on a MALDI-TOF Perseptive Biosystem Voyager
DE-STR (HRMS). [α]D values were recorded with a Jasco P-1010
polarimeter at 20 °C. All reactions were carried out under argon.
General Procedure for the Synthesis of the 1,2,3-Triphenyl-2-phos-
pha[3]ferrocenophanes 1a,1aЈ and Their Borane Complexes 3a,3aЈ:
The known 1,1Ј-bis(hydroxybenzyl)ferrocenes 2a and 2aЈ were ob-
tained according to literature methods.[18,19] NMR spectra are in
good agreement with those reported previously.[17c,19] 1H NMR
(CDCl3), dl-2a: δ = 4.17 (s, 2 H), 4.23 (s, 2 H), 4.28 (s, 2 H), 4.29
(2 H, OH), 4.46 (s, 2 H), 5.55 (s, 2 H, CHPh), 7.2–7.3 (10 H, Ph);
meso 2aЈ: δ = 4.12 (s, 2 H), 4.21 (s, 2 H), 4.25 (s, 2 H), 4.29 (2 H,
OH), 4.33 (s, 2 H), 5.54 (s, 2 H, CHPh), 7.2–7.4 (10 H, Ph) ppm.
Scheme 5.
Compared to the X-ray structures of compounds 3a and
3c, the special feature of the ferrocenophane moiety in 8a
is the synclinal staggered conformation of the cyclopen-
tadienyl rings. The dihedral angle between the Cp rings is
11.7°, that is, slightly larger than in the corresponding bo-
rane complex 3c. This distorted conformation may result
from steric constraints in the hindered palladium complex.
Decomplexation of phosphane 1a from 8 was performed
according to the standard method, by reaction with the che-
lating diphosphane dppe, in dichloromethane, followed by
separation on a short silica column. The optically active
(S,S)-1,2,3-triphenyl-2-phospha[3]ferrocenophane 1a ob-
tained from 8a gave [α]D = +392 (c = 0.2, CHCl3).
A Schlenk tube was charged with acetic acid (6 mL) and ice-cooled
under argon for about 10 min. The 1,1Ј-bis(hydroxybenzyl)ferro-
cene 2 (0.2 g, 0.5 mmol) was added at once, followed by addition
of phenylphosphane (60 µL, 0.6 mmol). The mixture was warmed
slowly to room temperature while stirring for about 1 h. The sol-
vent was removed under vacuum. In order to remove the residual
solvents, degassed CH2Cl2 was added and removed again under
vacuum to afford an orange solid. Starting from the meso isomer
2aЈ, 1H NMR of the crude mixture shows formation of dl-1a as
the single diastereomer of the final product. Starting from dl-2a,
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the thermodynamically favoured anti,anti isomer 1aЈ has been ob-
tained as the major product. Phosphanes 1a and 1aЈ have been
purified by column chromatography under argon.
(CHCp), 71.1 (CHCp), 71.2 (CHCp), 83.1 (CCp), 126.8, 126.9, 127.6,
128.1, 128.2, 129.7, 129.8, 131.1, 132.4, 132.5 (CHPh), 136.5 (CPh
)
ppm. 31P NMR (CDCl3): δ = 51 ppm. MS (MALDI): m/z (%) =
472.1 (100) [M – BH3].
To obtain the borane complexes 3a or 3aЈ, the crude product iso-
lated from the reaction above after removal of acetic acid was dis-
solved in THF. An excess of BH3·THF adduct (1.6 mL, 1  solu-
tion in THF) was added at room temperature. After evaporation
of the solvent, the final product was purified by column chromatog-
raphy.
(S)-1-Ferrocenylpentan-1-ol (4a):[24] A solution of borane–dimethyl
sulfide complex (1.0 mL, 10 mmol) in anhydrous THF (about
10 mL) was prepared under argon. A fifth of this solution (2.2 mL)
was added to a solution of (R)-2-methyl-CBS-oxazaborolidine in
toluene (1 , 3.0 mL, 3.0 mmol) under argon. The remaining BH3–
Me2S solution and a solution of pentanoylferrocene (2.70 g,
10.0 mmol) in THF (10 mL) under argon were added simulta-
neously to this mixture at 0 °C. The addition was carried out over
about 60 min. The mixture was stirred for another 60 min at 0 °C,
then quenched by dropwise addition of methanol (2 mL) and satd.
aqueous NH4Cl (8 mL). The aqueous layer was extracted with di-
ethyl ether. The organic phases were combined, washed with water
and brine, and dried with magnesium sulfate. Purification by col-
umn chromatography (eluent: heptane/ethyl acetate, 5:1) gave (S)-
1-ferrocenylpentan-1-ol as an amber-orange oil. Yield: 2.51 g
anti,syn-1,2,3-Triphenyl-2-phospha[3]ferrocenophane (1a): Complex
1a was purified by column chromatography on silica gel with hex-
ane/ethyl acetate (90:10) as the eluent (Rf = 0.5). It was obtained
1
as an orange solid in 68% yield (160 mg). H NMR (CDCl3): δ =
4.00 (d, JH,P = 12.5 Hz, 1 H, CHPh), 4.09 (d, JH,P = 5.0 Hz, 1 H,
CHPh), 4.13 (m, 1 H, Cp), 4.14 (m, 1 H, Cp), 4.15 (m, 1 H, Cp),
4.18 (m, 1 H, Cp), 4.22 (m, 1 H, Cp), 4.29 (m, 1 H, Cp), 4.34 (m,
1 H, Cp), 4.41 (m, 1 H, Cp), 6.80 (t, 2 H), 6.95 (4 H), 7.06 (4 H),
7.21 (3 H), 7.39 (d, J = 7.5 Hz, 2 H) ppm. 13C NMR (CDCl3): δ
1
1
= 35.9 (d, JP,C = 18.6 Hz, PCH), 44.8 (d, JP,C = 24.0 Hz, PCH),
68.1 (CHCp), 68.3 (CHCp), 68.5 (d, JP,C = 6.3 Hz, CHCp), 68.8
(CHCp), 69.1 (CHCp), 69.5 (d, JP,C = 9.2 Hz, CHCp), 69.7 (CHCp),
1
(92%). H NMR (CDCl3): δ = 0.92 (t, JH,H = 7.0 Hz, 3 H, Me),
3
1.3–1.5 (m, 4 H, CH2), 1.6–1.7 (m, 2 H, CH2), 1.94 (d, JH,H
=
3.5 Hz, 1 H, OH), 4.2 (m, 3 H, CHCp), 4.23 (s, 5 H, Cp), 4.27 (1
H, CHCp), 4.33 (m, 1 H, CHOH) ppm. HPLC [Chiralpak AD; n-
hexane/isopropyl alcohol, 98:2, 1 mL/min; tR/min = 17.2 (R), 23.7
(S)]: ee = 98%. [α]D = +45 (c = 1, CHCl3).
1
70.4 (d, JP,C = 4.2 Hz, CHCp), 85.5 (d, JP,C = 7.4 Hz, CCp), 87.3
(d, JP,C = 15.5 Hz, CCp), 126.0, 126.1, 127.2, 127.3, 127.6, 128.3,
1
1
128.6, 128.7, 128.8, 133.2, 133.3, 134.5 (d, JP,C = 20.5 Hz, CPh),
137.5 (d, 2JP,C = 6.6 Hz, CPh), 141.4 (d, JP,C = 14.4 Hz, CPh) ppm.
2
31P NMR (CDCl3): δ = 26 ppm. MS (MALDI): m/z (%) = 472.1
(100) [M]. HRMS: calcd. for C30H26FeP [M + H] 473.1099; found
473.1122.
(S)-(α-Ferrocenylpentyl)diisobutylphosphane (5a): Diisobutylphos-
phane (4 mL) in hexane (10 wt.-% solution, about 1.8 mmol) was
added to
a degassed solution of (S)-1-ferrocenylpentan-1-ol
(275 mg, 1.0 mmol) in degassed acetic acid (10 mL) under argon.
The mixture was stirred overnight under argon at room tempera-
ture. The solvent and the remaining diisobutylphosphane were
evaporated under vacuum. The residue was purified by chromatog-
raphy on a short silica gel column, under argon. Elution with hep-
tane/ethyl acetate (5:1) gave (S)-(1-ferrocenylpentyl)diisobutylphos-
phane as an amber-coloured oil. Yield: 360 mg (90%). 31P NMR
(CDCl3): δ = –28 ppm. HRMS: calcd. for C23H38FeP [M + H]
401.2041; found 401.2061. [α]D = –39 (c = 0.1, CHCl3); ee = 98%.
NMR characterisation has been performed on the corresponding
borane complex, 5a·BH3: 1H NMR (CDCl3): δ = 0.92 (d, 3J =
6.6 Hz, 3 H, Me), 0.95 (d, 3J = 6.6 Hz, 3 H, Me), 1.03 (t, 3 H, Me),
1.04 (d, 3J = 6.9 Hz, 6 H, Me), 1.2–1.7 (7 H, CH2, CH), 1.8–2.1 (5
H, CH2, CH), 2.50 (ddd, J = 8.1, J = 6.6, J = 4.5 Hz, 1 H, CHP),
3.97 (1 H, CHCp), 4.08 (1 H, CHCp), 4.19 (s, 5 H, Cp), 4.2 (2 H,
CHCp) ppm. 13C NMR (CDCl3): δ = 14.0 (Me), 23.0 (CH2), 24.0,
Borane Complex of anti,syn-1,2,3-Triphenyl-2-phospha[3]ferroceno-
phane (3a): Column chromatography was performed with hexane/
ethyl acetate, 80:20 (Rf = 0.4) to afford 3a as a yellow-orange solid.
1H NMR (CDCl3): δ = 4.19 (m, 1 H, Cp), 4.21 (d, JH,P = 4.7 Hz,
1 H, CHPh), 4.24 (m, 1 H, Cp), 4.28 (m, 1 H, Cp), 4.34 (m, 1 H,
Cp), 4.37 (m, 2 H, Cp), 4.46 (d, JH,P = 18.3 Hz, 1 H, CHPh), 5.19
(m, 2 H, Cp), 6.9–7.2 (13 H, Ph), 7.50 (2 H, Ph) ppm. 13C NMR
1
1
(CDCl3): δ = 34.0 (d, JP,C = 27.3 Hz, PCH), 46.7 (d, JP,C
=
26.3 Hz, PCH), 68.3 (CHCp), 68.4 (CHCp), 70.4 (CHCp), 70.5
(CHCp), 70.7 (CHCp), 71.0 (CHCp), 71.1 (CHCp), 81.7 (CCp), 83.8
(CCp), 127.1, 127.4, 127.5, 128.1, 129.6, 130.0, 130.1, 130.4, 132.3,
132.4 (CHPh), 136.6 (CPh) ppm. 31P NMR (CDCl3): δ = 55 ppm.
HRMS (MALDI): calcd. for C30H25FeP [M – BH3] 472.1043;
found 472.1031.
anti,anti-1,2,3-Triphenyl-2-phospha[3]ferrocenophane (1aЈ): Com-
plex 1a was purified by column chromatography on silica gel with
hexane/ethyl acetate (90:10) as the eluent (Rf = 0.5). It was obtained
in 60% yield (70 mg, starting from 0.25 mmol of 2a) as an orange
24.3, 24.6 (d, JP,C = 2.0 Hz), 24.7 (d, JP,C = 1.0 Hz), 25.1 (d, JP,C
=
1
7.5 Hz), 25.3 (d, JP,C = 7.8 Hz), 31.1 (d, JP,C = 30.1 Hz, PCH2),
1
31.4 (d, JP,C = 3.5 Hz, CH2), 32.7 (d, JP,C = 30.3 Hz, PCH2), 33.1
1
solid. H NMR (CDCl3): δ = 4.05 (d, JH,P = 6.0 Hz, 2 H, CHPh),
1
(d, JP,C = 3.5 Hz, CH2), 36.0 (d, JP,C = 26.9 Hz, PCH), 66.9
4.08 (m, 2 H, Cp), 4.26 (m, 2 H, Cp), 4.33 (m, 2 H, Cp), 4.88 (m,
(CHCp), 67.2 (CHCp), 67.9 (CHCp), 68.7 (CHCp), 69.0 (Cp), 88.7
(d, JP,C = 4.1 Hz, CCp) ppm. 31P NMR (CDCl3): δ = 23 ppm. [α]D
= –35 (c = 0.1, CHCl3). The enantiomeric excess of 5a was deter-
mined by HPLC analysis of the corresponding oxide, which was
prepared as follows: (S)-(1-ferrocenylpentyl)diisobutylphosphane
(100 mg, 0.25 mmol) was dissolved in acetone (about 2 mL), and
hydrogen peroxide (35 wt.-% solution in water) was added. The
mixture was stirred overnight at room temp. After addition of
water, the aqueous phase was extracted with dichloromethane. The
organic layer was washed with brine, dried with magnesium sulfate
and concentrated to give (S)-(1-ferrocenylpentyl)diisobutylphos-
2 H, Cp), 6.9 (t, 2 H), 7.0–7.1 (6 H), 7.2 (4 H), 7.2–7.3 (4 H) ppm.
1
13C NMR (CDCl3): δ = 48.7 (d, JP,C = 15.8 Hz, PCH), 67.8, 68.7
(d, JP,C = 7.2 Hz, Cp), 69.8, 70.2 (d, JP,C = 3.9 Hz, Cp), 86.8 (d,
1JP,C = 12.8 Hz, CCp), 125.9, 127.6, 127.7, 128.1, 128.2, 129.0,
1
133.0, 133.3 (CHPh), 135.9 (d, JC,P = 16.0 Hz, PCPh), 141.5 (d,
2JC,P = 11.4 Hz, CPh) ppm. 31P NMR (CDCl3): δ = 21 ppm.
Borane Complex of anti,anti-1,2,3-Triphenyl-2-phospha[3]ferroceno-
phane (3aЈ): Column chromatography was performed with hexane/
ethyl acetate (80:20) (Rf = 0.4) to afford 150 mg of 3aЈ (63% yield)
as a yellow-orange solid. 1H NMR (CDCl3): δ = 4.08 (m, 2 H, Cp),
4.19 (d, JH,P = 17.7 Hz, 2 H, CHPh), 4.20 (m, 2 H, Cp), 4.29 (m,
1
phane oxide as a red-brown oil. H NMR (CDCl3): δ = 0.98–1.07
2 H, Cp), 5.17 (m, 2 H, Cp), 6.9–7.0 (6 H, Ph), 7.1 (4 H, Ph), 7.1– (15 H, Me), 1.3–2.1 (12 H, CH2, CH), 2.71 (ddd, J = 16.2, J = 6.6,
7.33 (3 H, Ph), 7.55 (t, 2 H, Ph) ppm. 13C NMR (selected data,
CDCl3): δ = 45.8 (d, JP,C = 29.1 Hz, PCH), 68.6 (CHCp), 70.9
J = 4.5 Hz, 1 H, CHP), 4.01 (1 H, CHCp), 4.16 (2 H, CHCp), 4.17
1
(s, 5 H, Cp), 4.22 (1 H, CHCp) ppm. 13C NMR (CDCl3): δ = 14.0
3858
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3853–3862

2-Phospha[3]ferrocenophane Derivatives – a New Chiral Scaffold
(Me), 23.3 (CH2), 23.5 (d, JP,C = 3.5 Hz), 23.6 (d, JP,C = 3.6 Hz),
FULL PAPER
ppm. HRMS: calcd. for C14H16FeO 256.0551; found 256.0531. dl-
24.5–25.0 (5 C), 30.1 (CH2), 32.7 (d, J = 3.2 Hz, CH2), 34.5 (d, J 6b: 1H NMR (CDCl3): δ = 1.48 (d, JH,H = 7.0 Hz, 6 H, Me), 4.12
3
3
= 61.7 Hz, PCH2), 36.1 (d, J = 61.8 Hz, PCH2), 40.4 (d, J =
(m, 4 H), 4.22 (m, 2 H), 4.24 (m, 2 H), 4.34 (q, JH,H = 7.0 Hz, 2
H, CHMe) ppm. HRMS: calcd. for C14H16FeO 256.0551; found
58.1 Hz, PCH), 66.9 (CHCp), 67.3 (CHCp), 67.7 (CHCp), 68.2
(CHCp), 68.8 (Cp), 88.3 (CCp) ppm. 31P NMR (CDCl3): δ = 256.0523.
49 ppm. HPLC (Chiralcel OD; n-hexane/2-propanol, 98:2, 1 mL/
(b) 3b: A solution of BF3·Et2O (0.28 mL, 2 mmol) in CH2Cl2
min) tR/min = 10.0 (R), 11.3 (S).
(5 mL) was added to a solution containing 1,3-dimethyl-2-oxa[3]-
ferrocenophane (250 mg, 0.98 mmol) and phenylphosphane
(0.12 mL, 1.1 mmol) in dichloromethane (20 mL) at room tempera-
ture. After two hours of stirring, an excess of BH3·THF was added
(2 mL, 1  solution). The mixture was hydrolysed with water. The
organic layer was dried with MgSO4. After evaporation of the sol-
vents, the crude product was purified by chromatography on silica
gel with hexane/ethyl acetate (8:2) as the eluent. The borane com-
plex 3b was purified by column chromatography.
(S)-(α-Ferrocenylbenzyl)diisobutylphosphane (5b): (a) Phosphane 5b
was first prepared by following the same procedure used for the
synthesis of 5a. Starting from (S)-ferrocenylbenzyl alcohol 4b[17a,30]
(290 mg, 1.0 mmol, 94% ee), phosphane 5b was obtained as a pale
orange solid after chromatography (silica gel, heptane/ethyl acetate,
9:1). Yield 270 mg (65%); ee = 49%. (b) The same phosphane 5b
was then prepared as follows: (S)-ferrocenylbenzyl alcohol 4b
(1 mmol, 96% ee) was added to ice-cooled acetic acid (10 mL) un-
der argon, and diisobutylphosphane was added immediately to the
yellow suspension without waiting for the alcohol to be dissolved.
The mixture was warmed slowly to room temperature. After over-
night stirring, workup was performed as described above for 5a.
Borane Complex of anti,syn-1,3-Dimethyl-2-phenyl-2-phospha[3]fer-
rocenophane (3b): Complex 3b was obtained in 31% yield (105 mg)
as a yellow solid after column chromatography with hexane/ethyl
1
1
acetate (9:1) as the eluent (Rf = 0.5). H NMR (CDCl3): δ = 1.15
Phosphane 5b was obtained in 86% yield (360 mg); ee = 96%. H
(dd, 3J = 12.5, 3J = 7.5 Hz, 3 H, Me), 1.45 (dd, 3J = 15.5, 3J =
3
3
NMR (CDCl3): δ = 0.77 (d, J = 6.5 Hz, 3 H, Me), 0.83 (d, J =
6.5 Hz, 3 H, Me), 0.85 (d, 3J = 6.5 Hz, 3 H, Me), 0.92 (d, 3J =
6.5 Hz, 3 H, Me), 1.1 (m, 3 H), 1.3 (m, 2 H), 1.38 (m, J = 6.5 Hz,
2
7.0 Hz, 3 H, Me), 2.83 (qd, 3J = 7.5, JH-P = 3.0 Hz, 1 H, CHMe),
2
3.16 (dq, JH-P = 16.5, 3J = 7.0 Hz, 1 H, CHMe), 4.04 (m, 1 H,
1
CHCp), 4.11 (m, 1 H, CHCp), 4.14 (m, 1 H, CHCp), 4.16 (m, 1 H,
CHCp), 4.23 (m, 1 H, CHCp), 4.25 (m, 1 H, CHCp), 4.72 (m, 1 H,
CHCp), 4.87 (m, 1 H, CHCp), 7.54 (3 H, Ph), 7.87 (2 H, Ph) ppm.
1 H, CHMe), 3.39 (d, JH–P = 5.0 Hz, CHP), 3.78 (s, 5 H, Cp),
4.08 (1 H, CHCp), 4.12 (1 H, CHCp), 4.14 (1 H, CHCp), 4.18 (1 H,
CHCp), 7.2–7.4 (5 H, Ph) ppm. 13C NMR (CDCl3): δ = 23.8 (d,
2
2
13C NMR (CDCl3): δ = 14.1 (d, JP,C = 6.9 Hz, Me), 16.8 (d, JP,C
3
3JP,C = 9.0 Hz, Me), 24.0 (d, JP,C = 9.2 Hz, Me), 24.2 (Me), 24.3
1
1
1
= 7.0 Hz, Me), 19.2 (d, JP,C = 32.4 Hz, CHMe), 29.4 (d, JP,C
=
(Me), 26.18, 26.28, 26.38, 26.48 (CHMe), 38.7 (d, JP,C = 17.5 Hz,
1
1
32.0 Hz, CHMe), 67.2 (CHCp), 67.6 (CHCp), 67.8 (d, JP,C = 4.1 Hz,
CHCp), 69.8 (d, JP,C = 6.1 Hz, CHCp), 70.1 (CHCp), 70.2 (CHCp),
70.5 (CHCp), 71.6 (CHCp), 84.1 (CCp), 84.4 (CCp), 128.6, 127.8
PCH2), 38.8 (d, JP,C = 17.5 Hz, PCH2), 48.3 (d, JP,C = 15.6 Hz,
PCH), 66.2 (CHCp), 67.3 (d, JC,P = 5.2 Hz, CHCp), 68.1 (CHCp),
68.4 (Cp), 69.4 (CHCp), 91.2 (d, 2JC,P = 14.9 Hz, CCp), 126.1, 127.9,
129.0, 129.1 (CHPh) ppm. 31P NMR (CDCl3): δ = –14 ppm.
HRMS: calcd. for C25H34FeP [M + H] 421.1748; found 421.1738.
The enantiomeric excess of the phosphane was determined by
HPLC analysis of the corresponding oxide, which was prepared as
1
(CHPh), 129.6 (d, JC,P = 43.3 Hz, CPh), 130.9 (d, JC,P = 2.2 Hz,
CHPh), 132.1 (CHPh), 132.2 (CHPh) ppm. 31P NMR (CDCl3): δ =
57 ppm. HRMS: calcd. for C20H21FeP [M – BH3] 348.0730; found
348.0741.
3
described above. 1H NMR (CDCl3): δ = 0.88 (d, J = 6.5 Hz, 3 H,
Borane Complexes of syn,syn- and anti,anti-1,3-Dimethyl-2-phenyl-
2-phospha[3]ferrocenophane (3bЈ and 3bЈЈ): The diastereomeric mix-
ture of anti,anti and syn,syn isomers of the 1,3-dimethyl-2-phenyl-
2-phospha[3]ferrocenophane borane complexes 3bЈ and 3bЈЈ was
characterised by mass spectrometry and 1H NMR spectroscopy.
ESI-MS: m/z (%) = 348 (100) [M]. A sample of pure syn,syn-3bЈЈ
was obtained by chromatography. syn,syn-3bЈЈ: 1H NMR (CDCl3):
Me), 0.90 (d, 3J = 7.0 Hz, 3 H, Me), 0.93 (d, 3J = 6.5 Hz, 3 H,
3
Me), 0.99 (d, J = 6.5 Hz, 3 H, Me), 1.3–1.5 (4 H), 1.8–1.9 (2 H,
1
CHMe2), 3.75 (d, JH-P = 12.5 Hz, CHP), 3.79 (s, 5 H, Cp), 4.15
(1 H, CHCp), 4.18 (1 H, CHCp), 4.31 (1 H, CHCp), 4.35 (1 H,
CHCp), 7.34 (1 H, Ph), 7.43 (2 H, Ph), 7.54 (2 H, Ph) ppm. 13C
NMR (CDCl3): δ = 23.7 (dd, 2ϫCHMe), 24.4 (Me), 24.5 (Me),
1
1
24.9 (dd, 2ϫMe), 36.5 (d, JP,C = 62.0 Hz, PCH2), 36.6 (d, JP,C
=
3
3
2
δ = 1.37 (dd, J = 15.9, J = 7.5 Hz, 6 H, Me), 2.92 (dq, JH-P
≈
1
61.2 Hz, PCH2), 49.9 (d, JP,C = 56.1 Hz, PCH), 66.9 (CHCp), 68.3
(d, JC,P = 2.2 Hz, CHCp), 68.5 (Cp), 68.6 (CHCp), 70.0 (d, JC,P
3JH,H = 7.5 Hz, 2 H, CHMe), 4.12 (m, 2 H, CHCp), 4.17 (m, 4 H,
=
CHCp), 4.23 (m, 2 H, CHCp), 7.5 (3 H, Ph), 8.2 (2 H, Ph) ppm. 13
C
2.1 Hz, CHCp), 85.6 (CCp), 127.2 (d, JC,P = 1.6 Hz, CHPh), 128.3,
128.4, 129.7, 129.8 (CHPh), 138.5 (d, JC,P = 3.3 Hz, CPh) ppm. 31P
NMR (CDCl3): δ = 45 ppm. HPLC (Chiralpak AD column, n-
hexane/2-propanol, 93:7, 1 mL/min) tR/min = 8.3 (S), 13.9 (R).
1
NMR (CDCl3): δ = 17.7 (Me), 30.0 (d, JP,C = 32.9 Hz, CHMe),
67.6 (CHCp), 68.5 (CHCp), 69.9 (CHCp), 71.5 (d, J = 5.2 Hz, CHCp),
88.7 (CCp), 128.5, 131.4, 134.7 (CHPh) ppm. anti,anti-3bЈ was char-
1
acterised from the mixture of isomers: H NMR (CDCl3): δ = 1.19
(dd, JH-P = 15.5, 3J = 7.0 Hz, 6 H, Me), 2.85 (dq, JH-P = 16.5,
3JH,H = 7.0 Hz, 2 H, CHMe), 4.07 (m, 2 H, CHCp), 4.12 (m, 2 H,
CHCp), 4.21 (m, 2 H, CHCp), 4.72 (m, 2 H, CHCp), 7.5 (3 H, Ph),
7.9 (2 H, Ph) ppm.
3
2
Syntheses of the Borane Complexes of 1,3-Dimethyl-2-phenyl-2-
phospha[3]ferrocenophane (6b, 6bЈ and 3b)
(a) 1,3-Dimethyl-2-oxa[3]ferrocenophanes, 6b,bЈ:[28] 1,1Ј-Bis(acetyl)-
ferrocene (3.0 g, 11 mmol) was reduced with NaBH4 in methanol.
After hydrolysis and extraction in ether, the ether solution of crude
1,1Ј-bis(α-hydroxyethyl)ferrocene was acidified with aqueous HCl
(1 ). After 1 h of stirring at room temperature, the organic layer
was separated, dried with MgSO4 and the final product was sub-
mitted to column chromatography. Elution with hexane/ethyl ace-
tate (9:1) afforded 1.2 g (41% yield) of meso-6bЈ (Rf = 0.47), fol-
lowed by 1.1 g (38% yield) of dl-6b (Rf = 0.35). meso-6bЈ: 1H NMR
Synthesis of the Borane Complex of 2-Phenyl-2-phospha[3]ferroceno-
phane (3c): (a) 2-Oxa[3]ferrocenophane.[35] A solution of 1,1Ј-bis-
(hydroxymethyl)ferrocene (107 mg, 0.43 mmol) in HCl (1 )/ether
(1:1, 12 mL) was stirred vigorously for 6 h. The layers were sepa-
rated and the organic layer dried with MgSO4, filtered and concen-
trated in vacuo. The crude product was purified by flash
chromatography (hexane/ethyl acetate, 8:2) to yield 81 mg (82%) of
3
3
1
(CDCl3): δ = 1.54 (d, JH,H = 6.5 Hz, 6 H, Me), 3.84 (q, JH,H
=
the desired compound as an orange solid. H NMR (CDCl3): δ =
6.5 Hz, 2 H, CHMe), 4.05 (m, 2 H), 4.17 (m, 2 H), 4.27 (m, 4 H)
3.92 (s, 4 H, CH2), 4.17–4.19 (CHCp, 8 H, A2B2) ppm. 13C NMR
Eur. J. Inorg. Chem. 2007, 3853–3862
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3859

N. Fleury-Brégeot, A. Panossian, A. Chiaroni, A. Marinetti
FULL PAPER
(CDCl3): δ = 64.6 (OCH2), 69.9 (CHCp), 70.1 (CHCp), 83.2 (CCp
ppm.
)
and ω-scans, up to θ = 27.5° for compounds 3a and 3c, and only
to 22° for 8c. The structures were solved by direct methods with the
program SHELXS86[38] and refined by full-matrix least-squares, on
the basis of unique F2, with the program SHELXL97.[39] The hy-
drogen atoms were located on difference Fourier maps and fitted
at theoretical positions [d(C–H) = 0.93 or 0.98 Å], except those
fixed to the B atom, which were refined. They were assigned an
isotropic displacement parameter equivalent to 1.12 times that of
the bonded atom.
(b) The same experimental procedure as for the synthesis of 3b was
applied, starting from 2-oxa[3]ferrocenophane. Compound 3c was
obtained in 17% yield as a yellow-orange solid. 1H NMR (CDCl3):
δ = 2.55 (t, JH,P = JH,H = 15.0 Hz, 2 H, CH2), 2.65 (d, JH,H
=
14.0 Hz, 2 H, CH2), 4.02 (s, 2 H, CHCp), 4.11 (s, 2 H, CHCp), 4.22
(s, 2 H, CHCp), 4.61 (s, 2 H, CHCp), 7.56 (3 H, Ph), 7.91 (2 H, Ph)
ppm. 13C NMR (CDCl3): δ = 22.5 (d, 1JP,C = 34.6 Hz, PCH2), 68.0
(CHCp), 69.8 (CHCp), 70.8 (d, JP,C = 5.1 Hz, CHCp), 71.6 (CHCp),
Crystallographic Data for Compound 3a: A small brown-yellow
2
1
78.5 (d, JP,C = 4.6 Hz, CCp), 128.9, 129.0 (CHPh), 130.3 (d, JC,P prismatic crystal of 0.55ϫ0.45ϫ0.45 mm, cut from a larger one,
= 48.8 Hz, CPh), 131.3, 131.4 (CHPh) ppm. 31P NMR (CDCl3):
δ = 46 ppm. HRMS (MALDI): calcd. for C18H17PFe [M – BH3]
320.0417; found 320.0412.
was used. Empirical formula C30H28BFeP, M = 486.15, T = 293 K.
Monoclinic system, centrosymmetric space group P21/n. The unit
cell of parameters a = 7.401(4), b = 29.868(15), c = 11.186(6) Å, β
= 93.75(2)°, V = 2467 Å3 contains four molecules (Z = 4); dcalcd
=
=
Resolution of dl-1,2,3-Triphenyl-2-phospha[3]ferrocenophane (1a):
Complex 7 was obtained from the corresponding amine[36] and pal-
ladium(II) chloride, as described in the literature.[37] anti,syn-1,2,3-
Triphenyl-2-phospha[3]ferrocenophane 1a (100 mg, 0.21 mmol)
and complex 7 (72 mg, 0.11 mmol) were dissolved in acetone
(10 mL) under argon and the mixture was stirred at room tempera-
ture for 2 h. After evaporation of the solvent, the crude product
was obtained as a diastereomeric mixture, which was separated by
column chromatography on silica gel with a heptane/ethyl acetate
(8:2) mixture as the eluent.
1.309 gcm–3, F(000)
= 1016, µ =
0.692 mm–1, λ(Mo-Kα)
0.71073 Å. A total of 9485 data were collected, giving 6901 mono-
clinic reflections, of which 4806 were unique.[40] Refinement of 307
parameters on F2 led to R1(F) = 0.0382 calculated with the 3942
observed reflections having I Ն 2σ(I) and to wR2(F2) = 0.0946 con-
sidering all 4806 unique reflections. Goodness of fit = 1.050. The
residual density was found to be between –0.36 and 0.29 eÅ–3.
Crystallographic Data for Compound 3c: A yellow prismatic crystal
of 0.25ϫ0.10ϫ0.10 mm was used. Empirical formula
C18H20BFeP, M = 333.97, T = 293 K. Monoclinic system, centro-
symmetric space group P21/a. The unit cell of parameters a =
10.891(4), b = 7.472(4), c = 19.160(6) Å, β = 94.47(2)°, V = 1554 Å3
contains four molecules (Z = 4); dcalcd = 1.427 gcm–3, F(000) =
696, µ = 1.062 mm–1, λ(Mo-Kα) = 0.71073 Å. A total of 14535 data
were collected, giving 6478 monoclinic reflections, of which 3530
were unique. Refinement of 199 parameters on F2 led to R1(F) =
0.0401 calculated with the 2292 observed reflections having I Ն
2σ(I) and to wR2(F2) = 0.0956 considering all 3530 unique reflec-
tions. Goodness of fit = 1.044. The residual density was found to
be between –0.47 and 0.42 eÅ–3.
Complex 8a was eluted first (Rf = 0.5 in heptane/ethyl acetate, 6:4,
35 mg, 40% yield): 1H NMR (CDCl3): δ = 1.96 (d, 3JH,H = 6.5 Hz,
3 H, CHMe), 2.44 (s, 3 H, NMe), 3.08 (d, J = 3.5 Hz, 3 H, NMe),
4.1–4.2 (4 H, Cp, NCHMe), 4.35 (1 H, Cp), 4.44 (2 H, Cp), 4.48
1
(1 H, Cp), 5.42 (d, JH-P = 15.0 Hz, 1 H, CHPh), 5.62 (dd, 1 H,
3
Naph), 5.92 (1 H, Cp), 6.48 (d, J = 7.0 Hz, 1 H, Naph), 6.91 (t, J
= 8.5 Hz, 1 H), 7.0–7.5 (Ar), 7.54 (d, J = 8.5 Hz, 1 H), 8.16 (d, J
= 7.0 Hz, 2 H) ppm. 13C NMR (selected data, CDCl3): δ = 21.8
1
1
(CHMe), 43.4 (d, JP,C = 10.9 Hz, PCH), 46.2 (d, JP,C = 12.1 Hz,
PCH), 48.0 (NMe), 50.3 (NMe), 67.3, 68.1, 68.3, 69.5, 70.5, 70.6,
1
70.7, 71.8, 72.1 (Cp, NCHMe), 84.0 (d, JP,C = 9.2 Hz, CCp), 86.2
(CCp), 121–129 (Ar), 137.4 [C-3Ј (Naph)], 141.2, 145.9, 150.0 (C)
ppm. 31P NMR (CDCl3): δ = 80.4 ppm. MS (MALDI): m/z (%) =
776 (100) [M – Cl]. HRMS (MALDI): calcd. for C44H41FeNPPd
776.1361; found 776.1359. [α]D = +281 (c = 0.2, CHCl3).
Crystallographic Data for Compound 8a: From very small crystals,
a small orange needle of 0.20ϫ0.05ϫ0.012 mm was chosen. Em-
pirical formula C44H41ClFeNPPd·C7H8, M = 904.58, T = 293 K.
Tetragonal system, chiral space group I41. The unit cell of param-
eters a = b = 27.112(7), c = 11.592(5) Å, V = 8521 Å3 contains
eight molecules (Z = 8); dcalcd = 1.410 gcm–3, F(000) = 3891, µ =
0.90 mm–1, λ(Mo-Kα) = 0.71073 Å. A total of 26093 reflections
were collected, giving 5070 unique tetragonal reflections. In ad-
dition, a toluene molecule of crystallisation solvent was found per
molecule. The absolute configuration was calculated from the
anomalous dispersion effects in diffraction measurements. Refine-
ment of 510 parameters on F2 led to R1(F) = 0.0440 calculated with
the 3891 observed reflections having I Ն 2σ(I) and to wR2(F2) =
0.0768 considering all 5070 unique reflections. Goodness of fit =
1.032. The residual density was found to be between –0.28 and
0.25 eÅ–3.
Complex 8b was then eluted with Rf = 0.3 in heptane/ethyl acetate
(6:4). 1H NMR (CDCl3): δ = 2.19 (d, 3JH,H = 6.5 Hz, 3 H, CHMe),
2.73 (s, 3 H, NMe), 3.13 (d, J = 3.5 Hz, 3 H, NMe), 4.18, 4.21,
4.23, 4.28, (Cp), 4.31 (m, NCHMe), 4.35, 4.39 (Cp), 4.77 (d,
3
1JH–P = 17.0 Hz, 1 H, CHPh), 5.47 (1 H, Cp), 5.65 (dd, JH,H
=
4
3
8.5 Hz, JH,P = 5.0 Hz, 1 H, Naph), 6.02 (1 H, Cp), 6.12 (d, J =
8.5 Hz, 1 H, Naph), 6.33 (d, JH–P = 6.5 Hz, 1 H, CHPh), 6.65
1
(2H), 6.88 (t, J = 7.5 Hz, 1 H), 7.0–7.5 (Ar), 7.67 (d, J = 8.5 Hz, 1
H), 7.84 (2H). 13C NMR (selected data, CDCl3): δ = 22.4 (CHMe),
1
1
37.7 (d, JP,C = 15.1 Hz, PCH), 46.6 (d, JP,C = 17.3 Hz, PCH),
48.7 (NMe), 50.9 (NMe), 69.0, 69.2, 69.3, 69.6, 70.1, 70.3, 70.7,
71.5, 73.5 (Cp, NCHMe), 82.1 (CCp), 83.9 (CCp), 123–131 (Ar),
136.2 (CH), 136.3 (CH), 137.2, 138.1, 147.0, 148.0 (C) ppm. 31P
NMR (CDCl3): δ = 75.8 ppm. [α]D = –160 (c = 0.2, CHCl3).
CCDC-636890 (for 3a), -636891 (for 3c) and -636892 (for 8a) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.cccd.cam.ac.uk/data_request/cif.
Complex 8a (32 mg, 0.04 mmol) was treated with 1,2-bis(diphenyl-
phosphanyl)ethane (15 mg) in CH2Cl2 (2 mL) at room temperature
for 3 h. After evaporation, phosphane 1a was isolated by filtration
through a short silica gel column with heptane/ethyl acetate (8:2)
as the eluent (Rf = 0.6). [α]D = +392 (c = 0.2, CHCl3).
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fractometer using graphite-monochromated Mo-Kα radiation, in φ-
3860
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3853–3862

2-Phospha[3]ferrocenophane Derivatives – a New Chiral Scaffold
FULL PAPER
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Eur. J. Inorg. Chem. 2007, 3853–3862
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3861

N. Fleury-Brégeot, A. Panossian, A. Chiaroni, A. Marinetti
FULL PAPER
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Received: March 12, 2007
Published Online: June 29, 2007
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3862
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Eur. J. Inorg. Chem. 2007, 3853–3862