1,1′,2,2′-Tetrakis(diphenylphosphino)-4,4′-di-tert-butylferrocene, a new cisoid arrangement of phosphino groups

Article abstract of DOI:10.1016/S0022-328X(01)00883-X

The action of two equivalents of 1,2-bis(diphenylphosphino)-4-tert-butylcyclopentadienyllithium on FeCl₂ led to the corresponding 1,1′,2,2′-tetraphosphinoferrocene. The X-ray structure of this bulky ferrocene is described. The spectroscopic results reveal a conformational chirality with a cisoid disposition of the phosphino groups. The first results about the complexation with representative elements of Group IX and X (Rh, Pd, Ir) are reported.

Full text of DOI:10.1016/S0022-328X(01)00883-X

Journal of Organometallic Chemistry 637–639 (2001) 126–133
www.elsevier.com/locate/jorganchem
1,1%,2,2%-Tetrakis(diphenylphosphino)-4,4%-di-tert-butylferrocene, a
new cisoid arrangement of phosphino groups
Roland Broussier a, Emmanuelle Bentabet a, Re´gine Amardeil a, Philippe Richard a,
Philippe Meunier a,*, Philippe Kalck b, Bernard Gautheron a
a Laboratoire de Synthe`se et d’Electrosynthe`se Organome´talliques (UMR 5632), Uni6ersite´ de Bourgogne, 6, boule6ard Gabriel,
21000 Dijon, France
b Laboratoire de Catalyse, Chimie fine et Polyme`res, Ecole Nationale Supe´rieure de Chimie de Toulouse, 118, route de Narbonne,
31077 Toulouse Cedex, France
Received 12 January 2001; received in revised form 15 March 2001; accepted 26 March 2001
Abstract
The action of two equivalents of 1,2-bis(diphenylphosphino)-4-tert-butylcyclopentadienyllithium on FeCl2 led to the corre-
sponding 1,1%,2,2%-tetraphosphinoferrocene. The X-ray structure of this bulky ferrocene is described. The spectroscopic results
reveal a conformational chirality with a cisoid disposition of the phosphino groups. The first results about the complexation with
representative elements of Group IX and X (Rh, Pd, Ir) are reported. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Phosphinoferrocene; Group IX and X complexes; Cisoid; Arrangement
availability of phosphorus atoms and their coordina-
tion capacities are in part directed by the backbone
1. Introduction
rigidity of the ligand as shown in the following
In the field of the ferrocene derivatives and their
polyphosphines. Structurally characterized examples of
coordination chemistry, di or polyphosphines, as the
two biligate coordination modes are reported for
dppf, are powerful auxiliaries [1]. Several types of di or
branched tetradentate phosphines as 2,3-bis[(di-
polyphosphines can be imagined [2] with different sub-
phenylphosphino)methyl] - 1,4 - bis(diphenylphosphino)-
stitution patterns on Cp rings and various steric and
butane [5], 1,2,4,5-tetrakis[(diphenylphosphino)methyl]
electronic properties. We have been interested in the
1,2-disubstitution and original representative examples
of this class have been synthesized and studied: 1,2-bis(-
diphenylphosphino)-3,4,5-trimethylferrocene [3] and
1,2-bis(diphenylphosphino)-4-tert-butylferrocene [4].
These ferrocenes were obtained from a mixture of the
corresponding substituted and unsubstituted cyclopen-
tadienyl lithium salts and FeCl2. Using this approach
or [diphenyl-phosphino]benzene [6] and cis,trans,cis-
1,2,3,4-tetrakis(diphenylphosphino)cyclobutane [7]. The
linear
tetradentate
Ph2PCH2CH2P(Ph)CH2CH2P-
(Ph)CH2CH2PPh2 [8] or MeHP(CH2)3P(Me)(CH2)2P-
(Me)(CH2)3PMeH [9] and the tripodal tetradentate
P(CH2CH2PPh2)3 [10], P(o-C6H4PPh2)3 [11] or
P(CH2CH2CH2PMe2)3 [12] are tetracoordinated to the
metal center. The specific geometry of ferrocene and the
independance of the two Cp rings can make a te-
traphosphine equivalent to two diphosphines or allow a
higher coordination number due to the rings rotation.
At this time, the highlighted behavior are of type
1,2-diphosphine for 1,1%,2,2% tetraphosphine [3] and of
type 1,2 or 1,1% for the 1,2,1% triphosphine [13]. In this
paper, we report a new example of ferrocenic tetraphos-
phine as well as its behavior towards Pd, Rh and Ir
salts leading to various coordination modes.
and
exclusively
1,2-bis(diphenylphosphino)cyclo-
pentadienyl salts, a tetraphosphine of 1,2 and 1%,2%
substitution pattern was expected. Only two ferro-
cenyltetraphosphines are available: the 1,1%,2,2%-tetrak-
is(diphenylphosphino)ferrocene recently reported by
Butler et al. [2] and its hexamethyl analogue [3]. The
* Corresponding author. Fax: +33-3-8039-6100.
E-mail address: philippe.meunier@u-bourgogne.fr (P. Meunier).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00883-X

R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
127
scale should give AA%BB% spectrum. The energy barrier
to ring rotation in bulky substituted ferrocenes is gener-
ally quite low (B13 kcal mol−1 [16]) and the resonance
of nonequivalent ring or substituents protons are re-
solved only in the conformationally ‘frozen’ molecule
when the solution was cooled. In our case, for 1, the
AA%BB% spectrum remained constant when the tempera-
ture was increased up to 90 °C. X-ray structural analy-
sis confirms the NMR observations. The solid-state
structure corresponds to a racemic mixture.
The molecular structure of 1 is shown in Fig. 2. This
structural study shows an example of conformational
chirality or atropoisomery. The two enantiomers are
present in the unit cell. The complex is located on a C2
axis which is bisecting the P(1)ꢀFeꢀP(1)* angle. In the
ferrocenyl part the two symmetrically related Cp planes
are nearly parallel and exhibit a small deviation from
an eclipsed conformation (8°) and the observed Fe-cen-
Scheme 1.
2. Results and discussion
2.1. Synthesis and structure
The reaction of two equivalents of 1,2-bis(di-
phenylphosphino)-4-tert-butylcyclopentadienyllithium
[4] with FeCl2 in toluene at reflux produces 1,1%,2,2%-te-
trakis(diphenylphosphino)-4,4%-di-tert-butylferrocene 1
in excellent yield (70% of orange crystals in toluene)
(Scheme 1).
1 leads to a well-resolved but complicated 31P-NMR
spectrum which cannot be compared with the spectra
observed for the others di, tri or tetraferrocenylphos-
phines [2–4,14], exhibiting only singlets. Fig. 1 shows a
diastereotopy for the phosphorus atoms which form an
AA%BB% spin system [14]. The complete spectrum is
centrosymetric about 1/2 (wA+wB) and shows an over-
lap of twice 12 expected lines. On the basis of calcu-
lated spectrum [15], we propose the following coupling
constants: JAB=75 Hz, JAA%=40 Hz, JAB%=3 Hz and
JBB%=2 Hz. The magnetic nonequivalence between the
two groups of phosphorus atoms exists if the molecular
symmetry is reduced by the presence of a conforma-
tional chirality. A mixture of two enantiomeric con-
formers not interconnecting rapidly on the NMR time
,
troid (CNT) distance is 1.670 A.
Several relative orientations can be considered for
1,2,4 substituted cyclopentadienyl rings in the molecule
[16]. The minimum energy configuration judging from
the X-ray diffraction structure shows four staggered
and two eclipsed substituents. This is quite similar to
the situation encountered in the 1,1%,2,2%,4,4%-hexak-
is(trimethylsilyl)ferrocene [17] with two eclipsed Me3Si
groups. In our case, two conformations corresponding
to a minimum energy with either two PPh2 or two
tert-Bu eclipsed groups are expected. The source of the
conformational preferences for in the actually eclipsed
PPh2 groups, P(1) and P(1)*, becomes clear from the
view of the molecular structure. The phenyl substituents
Fig. 1. 31P-NMR signals (AA%BB% spin system) of 1 in CDCl3.

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R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
number, stoichiometry and stereochemistry of the re-
sulting metal complexes: 1,2 mononuclear biligate, 1,1%
mononuclear biligate, 1,2 and 1%,2% bis(mononuclear
biligate) and 1,1%,2 mononuclear triligate. We have ex-
plored the coordination behavior of the tetraphosphine
with Rh(I), Pd(II) and Ir(I) for which planar structure
and tetracoordination have been reported associated
with either 1,1% or 1,2 ferrocenyldiphosphines.
are tightly interlocked so as to give a conformationally
stable arrangement with both parallel and orthogonal
phenyl rings. At the same time, the tert-Bu groups are
sufficiently distant from each other to minimize the
steric effects. The tert-butyl substituents are staggered
(twist angle: 66°). All the phosphorus atoms exhibit an
exo (outside) deviation: the displacement from the aver-
age plan of the ring is different for each atom: P(1)
,
,
0.186(2) A, P(2) 0.254(2) A. For the two eclipsed phos-
phorus atoms, the variation from the perfect eclipse is
of 6°. One originality of the structure lies in this relative
arrangement of the phosphorus atoms. Indeed in the
tetraphosphine [C5Me3(PPh2)2]2Fe [3] a very different
arrangement of the phosphorus atoms is observed: the
two PPh2 substituents of a Cp ring are as distant as
possible from the two PPh2 groups carried by the other
ring.
2.2. Palladium coordination
Studies from NMR experiments on the coordination
chemistry of 1,2,1%-tris(diphenylphosphino)ferrocene
with Pd(COD)Cl2 were described by Butler et al. [13].
Both 1,2 and 1,1% coordination occurs, the high inten-
sity signals being associated to 1,2 coordination. A
similar reaction conducted with our tetraphosphine 1
and PdCl2(PhCN)2 leads exclusively to 1,2 coordination
mode. Addition of two equivalents of palladium salt to
a dichloromethane solution of tetraphosphine 1 gives
the dipalladate complex 2 in quantitative yield (Scheme
2). Spectroscopic data, as the low-field shift of the
phosphorus resonances at l 39.1 and 41.0 ppm, support
the proposed coordination. Reaction of the tetraphos-
phine with an equimolar amount of palladium dichlo-
ride gives more complicated mixture as indicated by
31P-NMR analysis: both 1 and 2 were identified and, in
addition, four signals were observed due to the
monopalladate complex 3 (Fig. 3). The appearance of
the signals suggests an overlap, which occurs for the
eight resonances relative to the four anisochronous
phosphorus atoms in two diastereoisomeric conformers.
From the mixture, it has not been possible to isolate the
dissymmetric complex 3. 3 reacts readily with Pd(-
COD)Cl2 yielding 2. Therefore, only the 1,2 and 1%,2%
bis(mononuclear biligate) coordination is observed and
fully characterized.
Considering the molecular structure, the tetraphos-
phine 1 allows several different chelating geometry at
the metal center, as a consequence of the appropriate
orientation of the coordinating phosphorus lone pairs.
The conformation of PPh2 groups and the degree of
distortion of Cp rings can control the coordination
2.3. Rhodium coordination
Contrary to palladium, a remarkable feature of the
coordination of 1 with [RhCl(CO)2]2 is the number of
isomers obtained. The tetraphosphine ligand 1 coordi-
nates Rh(I) to give complexes with all coordination
modes which can be deduced from the molecular struc-
ture of the ligand. The different possibilities, as 4, 5 and
6, are depicted in Scheme 3. These complexes were
synthesized independently under particular conditions
to reach a single coordination mode. Characterizations
were conducted by elemental analysis, NMR, IR and
mass spectroscopies as well as reaction chemistry inves-
tigations of the complexes.
Fig. 2. ORTEP view of 1. Thermal ellipsoids are drawn at the 50%
probability level. For clarity hydrogen atoms and solvate molecules
are omitted. The starred labels are symmetrically related (C2) to the
non-starred one.
The reaction of an equimolar amount of tetraphos-
phine 1 with [RhCl(CO)2]2 in toluene at room tempera-
ture gave
a mixture of products of the type
Scheme 2.
tetraphosphine bis(chlorocarbonylrhodium) as indi-

R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
129
Fig. 3. 31P-NMR spectrum (CDCl3) corresponding to the reaction of 1 with one equimolar amount of PdCl2(PhCN)2.
cated by mass spectroscopy and elemental analysis. In
such a situation, with two different substituents on the
Rh atom, the complexes can exist theoretically in three
diastereoisomeric forms 6a–c (Schemes 3 and 4). The
evidence for the 1,2 and 1%,2% bis(coordination) shown
in Scheme 4 is clearly demonstrated by 31P-NMR spec-
trum (Fig. 4). Four ABX pattern (A=B=31P; X=
Rh) are observed: one for each racemic form for which
the phosphorus atoms belonging to each of Cp rings
are magnetically equivalent, and two others for the
meso form resulting from the chlorocarbonyl dissym-
metry at the rhodium atom. Although clearly observ-
able by NMR (rac–rac–meso 8:2:6), all attempts to
separate the different diastereoisomers failed.
With the aim to isolate the 1,2 coordinated complex,
the stoichiometry 1: [RhCl(CO)2]2 was varied from 1:1
to 2:1. The reaction running under the same conditions
Scheme 3.
leads to five products: 6a–c and two other compounds,
4 and 5. Both are formed from 1 with only one
rhodium atom, but spectroscopic evidence for the for-
mation of the 1,2 coordinate species could not be
provided. The separation of the various species from
the mixture has not been successful. In addition, 31P-
NMR spectrum of the reaction mixture reveals that
after a few hours, the 1,2,1% species 5 associated with
[RhCl2(CO)2]− afford 6a–c.
The synthesis of 1,1%-coordinate tetraphosphine-
rhodium complex 4 has been successfully achieved inde-
pendently, performing the reaction under a carbon
monoxide atmosphere. The 31P-NMR of 4 at room
temperature exhibits a singlet at −28.0 ppm and a
broad signal centred at −4 ppm, suggesting that an
exchange process occurs between species with different
coordination. The existence of a fast equilibrium in
solution for a triphosphine such as [(triphos)RhCl(CO)]
has been already discussed [18] and attributed to inter-
Scheme 4.

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R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
In conclusion, we have shown a new example for
chirality phenomena in ferrocenic complexes, which are
specifically attributable to the bulky substituted Cp
ligands. Thus, the new ferrocenyltetraphosphine 1 gen-
erate different isomeric complexes with planar tetraco-
ordination. In order to extend these studies the
coordination chemistry concerning tetrahedral and oc-
tahedral surrounded metals is currently in progress and
will be reported in due course.
3. Experimental
3.1. General considerations
Reactions were carried out under an atmosphere of
argon by means of conventional Schlenck techniques.
Solvents were dried and deoxygenated before distilla-
tion from sodium benzophenone ketyl or Na–K alloy.
Elemental analyses were performed by the analytical
service of LSEO of the Universite´ de Bourgogne (Eager
200). Mass spectra were recorded on a Kratos concept
IS machine. For Rh, Pd and Ir complexes the fragmen-
Fig. 4. 31P-NMR (CDCl3) spectrum of 6a–c showing the resonance
attributed to the 31P trans to the carbonyl group.
1
conversion between a geometry in which the rhodium is
pentacoordinated and another in which it is tetracoor-
dinated. This assumption is based on the observation of
very different wCO vibrational bands in solution for each
species (1920 and 2005 cm−1). In the present case, for
4, with regard to the infrared spectrum in the CO
region only one vibration band is detected. Thus, the
equilibrium observed in NMR exhibits species which
for the infrared absorption is almost unaffected. We
propose that a 1,1%U1,2% reversible process occurs, con-
cerning the RhꢀP bond in trans position of the RhꢀCl
bond.
Compound 5 was prepared by modification of the
experimental conditions: using 1:3 toluene–hexane mix-
ture instead of toluene, precipitation of 5 associated
with [RhCl2(CO)2]− was observed. The 31P-NMR spec-
trum of the cationic rhodium complex 5 indicates a
(1,1%, 2) coordination. One resonance at −30.4 ppm
characteristic of free phosphino group and an ABCX
system (A=B=C=31P; X=103Rh) in the area of the
coordinated phosphorus atom are detected.
tation of non-polymetallic species are omitted. H- and
31P{1H} -NMR spectra were recorded on a Bruker
AC200 spectrometer. The 1,2-bis(diphenylphosphino)-
4-tert-butylcyclopentadienyllithium was prepared ac-
cording a previous report [4].
3.2. Preparation of 1
A yellow solution of 1,2-bis(diphenylphosphino)-4-
tert-butylcyclopentadienyllithium (1.5 g, 3 mM) in 20
ml toluene was added to iron dichloride (250 mg, 1.9
mM) in 10 ml of toluene at room temperature (r.t.).
The mixture was refluxed for 16 h and filtered. The
brown–red solution was concentrated and kept in the
refrigerator for two days. Orange crystals of 1 (1.1 g,
1.06 mM, yield=71%) were obtained, m.p.=228 °C.
Anal. Found: C, 76.33; H, 6.03. Calc. for C66H62FeP4:
1
C, 76.59; H, 6.04%. H-NMR (CDCl3): l 0.70 (s, 18H,
t-Bu), 4.04 (m, 2H, Cp), 4.14 (m, 2H, Cp), 6.4–7.6 (m,
40H, Ph). 31P{1H}-NMR (CDCl3): l −31.5 (m),
−35.5 (m, JPP=75, 40, 3 and 2 Hz). EIMS (200 °C);
m/z (%): 1034 (100) [M+], 1019 (5) [M+−CH3], 849
(30) [M+−PPh2], 665 (5) [M+−2PPh2].
The complete spectroscopic characterization of all
these complexes is reported in Section 3.
2.4. Iridium coordination
3.3. Preparation of 2
The behavior of the tetraphosphine 1 toward the
iridium salt [IrI2(CO)2][N(PPh3)2] has also been exam-
ined. The reaction leads to the complexes 7 and 8
iridium analogous of the rhodium complexes 4 and 5.
They were characterized by 1H- and 31P-NMR spec-
troscopy, mass spectroscopy, IR and elemental analysis
(see Section 3).
A
mixture of
1
(32 mg, 0.031 mM) and
(PhCN)2PdCl2 (24 mg, 0.062 mM) in 15 ml of CH2Cl2
was stirred three days at r.t. The solvent was removed
under reduced pressure and 2 was obtained as a red
powder. The yield was essentially quantitative, m.p.\
260 °C. Anal. Found: C, 56.81; H, 4.55. Calc. for
C66H62 Cl4FeP4Pd2: C, 57.05; H, 4.50%. 1H-NMR

R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
131
(CDCl3): l 0.86 (s, 18H, t-Bu), 4.29 (m, 4H, Cp),
6.5–8.2 (m, 40H, Ph). 31P{1H}-NMR (CDCl3): l 39.1
(s), 41.0 (s). EIMS (200 °C); m/z (%): 1386 (5) [M+],
1298 (5) [M+−2HCl−CH4], 1262 (100) [M+
−3HCl−CH3], 1247 (50) [M+−3HCl−2CH3].
precipitate was immediately formed. After 14 h stirring
at r.t., the solvent was evaporated to dryness and 6 was
obtained as an orange powder. The yield was essentially
quantitative. Anal. Found C, 60.09; H, 4.96. Calc. for
C68H62Cl2FeO2P4Rh2: C, 59.72; H, 4.57%. 1H-NMR
(CDCl3): l 0.74, 0.79, 0.85, 0.94 (four s, t-Bu), 4.55–
3.96 (m, Cp), 8.75–6.65 (m, Ph). 31P{1H}-NMR
(CDCl3): l 24.5, 28.1, 29.4, 31.8 (four dd, JRhP=126
3.4. Preparation of 4
A yellow solution of [RhCl(CO)2]2 (31 mg, 0.159
mM) in 5 ml of toluene was added under CO, at r.t., to
a solution of 1 (166 mg, 0.16 mM) in 15 ml toluene.
After 45 min of stirring under CO, the solvent was
evaporated to dryness and 4 was obtained as a red
powder. The yield was essentially quantitative,
m.p.149 °C (dec.). Anal. Found: C, 66.65; H, 5.06.
Hz, JPP=40 Hz), 51.4, 53.4, 54.0, 54.6 (four dd, JRhP=
162 Hz, JPP=40 Hz). FABMS; m/z (%): 1310 (50)
[M+−2CO], 1275 (100) [M+−2CO−Cl]. IR
(CH2Cl2, cm−1): w(CO) 2013.
3.7. Preparation of 7
1
Calc. for C67H62ClFeOP4Rh: C, 66.99; H, 5.20%. H-
A yellow solution of [(PPh3)2N][IrI2(CO)2] (124 mg,
0.12 mM) in 5 ml of CH2Cl2 was added at r.t. to a
solution of 1 (124 mg, 0.12 mM) in 10 ml of CH2Cl2.
The solvent was removed under reduced pressure and
replaced by 10 ml of hexane. We then obtained 7 as a
red precipitate, which is isolated by filtration (14 mg,
0.011 mM, yield=9%). The solution contained 8. Anal.
Found: C, 58.50; H, 4.75. Calc. for C67H62FeIIrOP4: C,
58, 22; H, 4.52%. 1H-NMR (CDCl3): l 0.75 (s, 9H,
t-Bu), 0.81 (s, 9H, t-Bu), 3.73 (m, 1H, Cp), 4.42 (m,
1H, Cp), 4.64 (m, 1H, Cp), 4.90 (m, 1H, Cp), 6.2–8.3
(m, 40H, Ph). 31P{1H}-NMR (CDCl3): l −28.6 (s), 5,0
(m). FABMS; m/z (%): 1353 (98) [M+−CO−H], 1338
(65) [M+−CO−CH4], 1172 (80), 1157 (100). IR
(CH2Cl2, cm−1): w(CO) 1929.
NMR (CDCl3): l 0.81 (s, 18H, t-Bu), 3.95 (m, 1H, Cp),
4.43 (m, 2H, Cp), 4.60 (m, 1H, Cp), 6.5–8.3 (m, 40H,
Ph). 31P{1H}-NMR (CDCl3): l −28 (s), −2 to −5
(m). FABMS; m/z (%): 1165 (90) [M+−Cl], 1137 (100)
[M+−CO−Cl], 1059 (40) [M+−CO−Cl−C6H6].
IR (CH2Cl2, cm−1): w(CO) 1956.
3.5. Preparation of 5 and 5%
(a) A yellow solution of [RhCl(CO)2]2 (41 mg, 0.106
mM) in 5 ml of hexane was added at r.t. to a red
solution of 1 (110 mg, 0.106 mM) in a mixture of
toluene–hexane 5:14. An orange precipitate of 5 was
immediately formed and isolated by filtration. The
counter-ion was [RhCl(CO)2]−. The yield was essen-
tially quantitative. Anal. Found: C, 58.87; H, 4.39.
Calc. for C70H62Cl2Fe O4P4Rh2: C, 59.04; H, 4.39%.
1H-NMR (CDCl3): l 0.81 (s, 9H, t-Bu), 0.86 (s, 9H,
t-Bu), 3.97 (m, 1H, Cp), 4.57 (m, 1H, Cp), 4.71 (m, 1H,
Cp), 5.06 (m, 1H, Cp), 6.4–8.3 (m, 40H, Ph). 31P{1H}-
NMR (C6D6): l −29.7 (s), 17.8 (ddd, JRhꢀP=110 Hz,
3.8. Preparation of 8
A solution of [(PPh3)2N][IrI2(CO)2] (170 mg, 0.165
mM) in 5 ml of CH2Cl2 was added at r.t. under CO to
a solution of 1 (170 mg, 0.165 mM) in 20 ml of toluene.
After 45 min of stirring under CO, the mixture was
filtered and the solvent was evaporated to dryness. 8
was obtained as an orange powder. Anal. Found: C,
58.02; H, 4.50. Calc. for C68H62FeI2IrO2P4: C, 57.91; H,
JPP=12, 8 Hz), 40.7 (ddd, JRhꢀP=94 Hz, JPP=23, 8
Hz), 43.8 (ddd, JRhꢀP=92 Hz, JPP=23, 12 Hz).
FABMS; m/z (%): 1193 (40) [M+], 1165 (80) [M+
−CO], 1137 (100) [M+−2CO]. IR (CH2Cl2, cm−1):
w(CO) 2005, 2054 ([RhCl2(CO)2]−: 1990, 2068).
(b) 1 (109 mg, 0.105 mM) is dissolved in 15 ml of
toluene. To this red solution were added, at r.t, AgBF4
(20.5 mg, 0.105 mM) in 5 ml of methanol followed by
a solution of [RhCl(CO)2]2 (41 mg, 0.105 mM) in 5 ml
of toluene. After stirring for 30 min, the mixture was
filtered and the solvent was evaporated to dryness. 5%
was obtained as a red powder. The counter-ion was
BF−4 . The yield was essentially quantitative.
1
4.44%. H-NMR (CDCl3): l 0.83 (s, 9H, t-Bu), 0.90 (s,
9H, t-Bu), 3.96 (m, 1H, Cp), 4.62 (m, 1H, Cp), 4.78 (m,
1H, Cp), 5.14 (m, 1H, Cp), 6.3–8.2 (m, 40H, Ph).
31P{1H}-NMR (CDCl3): l −30.7 (s), 1.8 (dd, JPP=8,
6 Hz), 10.4 (dd, JPP=22, 6 Hz), 12.9 (dd, JPP=22, 8
Hz). FABMS; m/z (%): 1283 (30) [M+], 1255 (100)
[M+−CO], 1225 (95) [M+−C4H10]. IR (CH2Cl2,
cm−1): w(CO) 2031, 1981.
3.9. X-ray structure determination of 1
3.6. Preparation of 6
An orange crystal of 1 suitable for X-ray crystallo-
graphic study was obtained from a saturated toluene
solution of 1. The data were collected on a Nonius
Kappa-CCD diffractometer at 110 K using an Oxford
Cryostream low temperature attachment. The structure
A yellow solution of [RhCl(CO)2]2 (58.6 mg, 0.15
mM) in 10 ml of toluene was added at r.t. to a solution
of 1 (156 mg, 0.15 mM) in 15 ml of toluene. A

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R. Broussier et al. / Journal of Organometallic Chemistry 637–639 (2001) 126–133
was solved by direct methods using SHELXS-97 [19] and
refined by full least-squares methods using SHELXL-97
[19] with the aid of the WINGX program [20]. Except for
one disordered toluene solvate molecule, non-hydrogen
atoms were anisotropically refined. Two toluene solvate
molecules were found: one is located around an inver-
sion centre and then refined with an occupancy factor
fixed to m=0.5; the other one is disordered over two
positions with occupancies refined to m1=0.77 and
m2=1−m1=0.23. The carbon atoms of the smaller
contribution to this disorder were isotropically refined.
Hydrogen atoms of the toluene methyl groups were not
included in the model, the other hydrogen atoms were
included in their calculated positions and refined with a
riding model. Crystallographic data are reported in
Table 1.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 150996 for compound 1,
1,1%,2,2%-tetrakis(diphenylphosphino)-4,4%-di-tert-butyl-
ferrocene. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk or www: http:/
/www.ccdc.cam.ac.uk).
Acknowledgements
We thank S. Gourier for technical assistance, and
Prof. R. Pol and Dr J.C. Hierso for helpful discussion.
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(e A
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a R1=ꢀ (ꢁꢁFoꢁ−ꢁFcꢁꢁ)/ꢀ ꢁFoꢁ.
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