Silicon containing ferrocenyl phosphane ligands

Article abstract of DOI:10.1016/j.jorganchem.2003.12.003

New ferrocenyl phosphane ligands incorporating Si-P linkages, [(η-C₅H₄SiMe₂PR₂) ₂Fe], where R=Ph and Me, and the corresponding metal complexes [Mo(CO)₄(L)] have been prepared and characteri

Full text of DOI:10.1016/j.jorganchem.2003.12.003

Journal of Organometallic Chemistry 689 (2004) 770–774
www.elsevier.com/locate/jorganchem
Silicon containing ferrocenyl phosphane ligands
*
Karl S. Coleman , Simon Turberville, Sofia I. Pascu, Malcolm L.H. Green
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
Received 21 November 2003; accepted 9 December 2003
Abstract
New ferrocenyl phosphane ligands incorporating Si–P linkages, [(g-C5H4SiMe2PR2)2Fe], where R ¼ Ph and Me, and the
corresponding metal complexes [Mo(CO)4(L)] have been prepared and characterised. The molecular structures of
[(g-C5H4SiMe2PR2)2Fe], where R ¼ Ph and Me have been determined by single crystal X-ray diffraction.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; phosphane silyl ligands; Molybdenum
1. Introduction
us and others [9–11]. Herein, we report the synthesis and
properties of ferrocenyl phosphane ligands with a silyl
spacer.
Transition metals containing a bidentate diphosphane
ligand have played an important role in homogeneous
catalysis [1]. A backbone that has attracted considerable
attention in bidentate diphosphane ligands is ferrocene.
The most common ligand in this class is 1,10-bis(diph-
enylphosphino)ferrocene (dppf). The dppf ligand has
been coordinated to most late transition metals [2] and
complexes of this ligand have been used in a range of
catalytic reactions including carbon–carbon coupling
[3,4] and hydroformylation reactions [5]. Transition
metals containing ferrocene-based ligands, such as dppf,
often show superior catalytic activity when compared to
complexes containing other types of bidentate diphos-
phane ligands [6]. The origin of this effect is thought to be
due to the conformational flexibility of the ferrocene
backbone in the coordinated ligand.
Ferrocene diphosphane ligands have been prepared
with additional substituents at the ferrocene cyclopen-
tadienyl ring and with a variety of groups at the phos-
phorus atom [7,8]. However, less attention has focused
on synthesising ligands containing a group between the
ferrocene cyclopentadienyl ring and the phosphorus at-
oms. Bidentate ferrocene diphosphane ligands contain-
ing a carbon spacer have been prepared and studied by
2. Results and discussion
2.1. Synthesis and characterisation of the ligands [(g-
C5H4SiMe2PR2)2Fe] where R ¼ Ph (1) and Me (2)
The ferrocenyl silyl-phosphane ligands [(g-
C5H4SiMe2PR2)2Fe], where R ¼ Ph (1) and Me (2) were
prepared from the reaction of [(g-C5H4SiMe2Cl)2Fe], in
a diethyl ether solution with the corresponding lithium
phosphide at )78 °C to afford, after work-up, the li-
gands as air-sensitive orange solids in high yield, Scheme
1
1. Ligands 1 and 2 were characterised by H, 13C{1H},
31P{1H} and 29Si NMR spectroscopy, elemental analysis
and mass spectrometry. The 31P{1H} NMR spectrum
(C6D6) exhibits a singlet at d )54.5 for ligand 1 and d
)129.0 for ligand 2. Unfortunately, silicon satellites
were not completely resolved in either spectrum. How-
ever, the 29Si NMR shows the expected doublet at d
1
)2.44 and d 0.27 for 1 and 2, respectively, with a JPSi
coupling constant of 22.2 Hz for 1 and 18.5 Hz for 2.
The value of the 31P and 29Si chemical shifts and the
1
magnitude of the JPSi coupling constants are compa-
rable to those of similar compounds and are typical of a
phosphorus(III) centre bound directly to silicon [12–14].
* Corresponding author. Tel.: +01865-272681; fax: +01865-272690.
E-mail address: karl.coleman@chem.ox.ac.uk (K.S. Coleman).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.003

K.S. Coleman et al. / Journal of Organometallic Chemistry 689 (2004) 770–774
771
Scheme 1.
Fig. 2. ORTEP diagram of the molecular structure of ligand 2.
Thermal ellipsoids are set at 40%. Hydrogen atoms are omitted for
clarity.
Fig. 1. ORTEP diagram of the molecular structure of ligand 1. Ther-
mal ellipsoids are set at 40%. Hydrogen atoms are omitted for clarity.
The 1H and 13C{1H} NMR spectra of the products
obtained from each reaction were consistent with the
formation of the desired ligand 1 and 2 and their data
are listed in Section 3.
Exposure of ligands 1 and 2 to water results in the
formation of the known siloxane bridged ferroceno-
phane [Fe(g-C5H4)2(SiMe2)2O] due to the reactivity of
the Si–P linkage [15,16].
In ligand 1, the lengths of the Si–P bonds, Si(1)–P(1)
ꢀ
and Si(2)–P(2), are 2.2770(9) and 2.2837(9) A, respec-
tively, whereas in ligand 2, the Si–P bond distance is
ꢀ
2.2578(7) A. These are typical for a Si–P bond [17]
ꢀ
(2.264 A) and compare favourably to the average value
ꢀ
of 2.275 A found in the structurally characterised com-
pound HC(SiMe2PPh2)3 [18]. Similarly, the lengths of
the P–C bonds are comparable. All the Si–C bonds in
ligands 1 and 2 have a similar length and are comparable
to the Si–C bonds found in the compound Fe(g5-
C5H4SiMe3)2 where the average Si–C bond length was
2.2. Molecular structure of ligands 1 and 2
Crystals of the ferrocenyl ligands 1 and 2, suitable for
single crystal X-ray diffraction, were obtained by slow
cooling of a toluene solution and by slow evaporation of a
pentane solution, respectively. An ORTEP view of the
molecular structure of 1 and 2 are shown in Figs. 1 and 2,
respectively, and crystallographic data given in Table 1.
Selected bond lengths and angles are listed in Table 2. The
asymmetric unit of ligand 1 contains two unique mole-
cules that have similar geometry and confirmation,
however, only data for one of the unique molecules
is given in Table 2. The asymmetric unit of ligand 2 con-
tains half a molecule with the rest generated by symmetry.
ꢀ
ꢀ
found to be 1.862A [19]. The average Fe–C (2.050 A (1)
ꢀ
and 2.055 A (2)) and Fe–Cp centroid distance (1.6505 A
ꢀ
ꢀ
(1) and 1.657 A (2)) are also similar to values found in
Fe(g5-C5H4SiMe3)2 [19] and other ferrocenyl-based
compounds [20]. The Cp rings of the ligands are very
close to being eclipsed in 1 and are perfectly eclipsed in
2, however, the substituents at the Cp rings in both
compounds avoid an eclipsing interaction by pointing
away from one another at an angle close to 180°. The
remaining bond lengths and angles are unexceptional
and are within expected limits.

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K.S. Coleman et al. / Journal of Organometallic Chemistry 689 (2004) 770–774
Table 1
Summary of crystallographic data for compounds 1 and 2
Table 2
ꢀ
Selected bond lengths (A) and angles (°) for compounds 1 and 2
Compound 1
1
2
Fe(1)–Cmean
Fe(1)–Cpcentroid
P(1)–Si(1)
Si(2)–P(2)
Si(1)–C(5)
Si(2)–C(13)
Si(1)–C(1)
Si(1)–C(2)
Si(2)–C(3)
Si(2)–C(4)
P(1)–C(15)
2.050
1.6505
P(1)–C(21)
P(2)–C(33)
P(2)–C(27)
1.840(3)
1.845(3)
1.839(3)
Empirical formula
Mr
T (K)
C38H40FeP2Si2
670.67
150
C18H32FeP2Si2
422.41
150
2.2770(9)
2.2837(9)
1.857(3)
1.848(3)
1.874(3)
1.859(3)
1.869(3)
1.872(3)
1.841(3)
Fe(1)–C(5)–Si(1)
Fe(1)–C(13)–Si(2)
P(1)–Si(1)–C(5)
P(2)–Si(2)–C(13)
Si(1)–P(1)–C(15)
Si(1)–P(1)–C(21)
Si(2)–P(2)–C(33)
Si(2)–P(2)–C(27)
125.09(14)
127.17(13)
107.40(9)
108.07(8)
100.27(9)
104.73(9)
98.43(9)
ꢀ
k (A)
Crystal system
0.71073
Monoclinic
P1211
8.7060(10)
15.6610(10)
24.9020(10)
90
0.71073
Orthorhombic
Pbcn
7.3292(1)
12.3212(3)
24.5144(6)
90
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
105.88(9)
92.43(1)
90
90
90
Compound 2
Fe(1)–Cmean
Fe(1)–Cpcentroid
P(1)–Si(1)
ꢀ
V (A)
3392.2(5)
4
1.31
2213.76(8)
4
1.27
2.055
1.657
P(1)–C(2)
1.844(2)
125.7(1)
Z
Fe(1)–C(5)–Si(1)
P(1)–Si(1)–C(5)
Si(1)–P(1)–C(1)
Si(1)–P(1)–C(2)
Dc (Mg mꢀ3
)
2.2578(7)
1.868(2)
1.862(2)
1.844(2)
109.93(6)
100.41(8)
99.72(7)
l (mmꢀ1
)
0.64
1411
0.93
899
Si(1)–C(3)
Si(1)–C(5)
P(1)–C(1)
F0 0 0
Crystal size (mm)
0:30 ꢁ 0:40 ꢁ 0:50
Orange prism
Multi-scan
0:10 ꢁ 0:20 ꢁ 0:30
Orange plate
Multi-scan
0.83, 0.91
Description of crystal
Absorption correction
Transmission coefficients 0.743, 0.825
(min., max.)
a SiMe2PMe2 unit [Mo(CO)4(PMe2SiMe2CH2PMe2)]
(d )88.1) [21]. The 1H and 13C{1H} NMR spectra
showed the expected peaks for the ferrocene ligand
framework and, in each case, two further high frequency
peaks in the 13C{1H} spectra which are assigned to the
carbonyl groups, d 210.3 (triplet, 2JPC ¼ 9.5 Hz), d 216.5
(doublet,2JPC ¼ 11.8 Hz) and d 210.3 (triplet, 2JPC ¼ 9.2
Hz), d 216.5 (doublet, 2JPC ¼ 14.0 Hz) for complex 3 and
4, respectively, with the lower frequency signal corre-
sponding to carbon-trans-carbon and the higher fre-
quency signal to carbon-trans-phosphorus. The coupling
pattern observed for the carbonyl resonances are
consistent with the formation of the cis-coordinated
products, with the apparent doublet pattern for carbon-
trans-phosphorus observed presumably due to unre-
h range for data
collection (°)
Index ranges, hkl
1 6 h 6 27
1 6 h 6 27
0–11, 0-20, )32–32 )9–9, )15–15,
)31–31
7782
7773
0.027
7038
Reflections measured
Unique reflections
Rint
4903
4522
0.046
2953
Observed reflections
ðI > 3rðIÞÞ
Refinement method
Full-matrix least-
squares on F
776
Full-matrix least
squares on F
106
Parameters refined
Weighting scheme
Chebychev 3-term
polynomial
0.9607
Chebychev 3-term
polynomial
1.0468
Goodness of fit
R
0.0266
0.0309
0.0356
0.0365
wR
2
Residual electron dꢀen3 sity )0.47, 0.36
)0.62, 1.32
solved JCP cis coupling which should have afforded a
ꢀ
(min., max.) (e A
)
doublet of doublets. The cis coordination of the phos-
phane ligands to the metal centres were further
confirmed by IR measurements which showed the pres-
ence of four bands in the carbonyl stretching region as
required for C2v local symmetry at the metal centre. The
EI mass spectra of complexes 3 and 4 showed the parent
ions of the desired complexes.
2.3. Coordination of ligands 1 and 2 to transition metal
centres
The Mo(0) complexes [{(g-C5H4SiMe2PR2)2Fe}Mo
(CO)4], where R ¼ Ph (3) and Me (4) were prepared,
almost quantitatively, by reaction of the corresponding
ligands 1 and 2 with [(nbd)MoCO4], where nbd ¼ 2,5-
norbornadiene. The 31P{1H} NMR spectra each con-
tained a single resonance that had shifted to higher
frequency when compared to that of the starting li-
gands indicative of coordination of tertiary phosphane
ligands to the metal centre. The 31P{1H} chemical shift
of 3 (d )25.3) and 4 (d )95.7) are similar to the
chemical shifts reported for a a molybdenum tetracar-
bonyl compound containing a coordinated Ph2PSiMe2
group [Mo(CO4){Ph2PMe2Si)3CH}] (d )17.7) [18] and
In summary, new ferrocene-based bidentate phos-
phine ligands have been prepared containing an unusual
Si–P linkage and coordinated, in a cis fashion, to
Mo(CO)4 units.
3. Experimental
3.1. General procedures
All manipulations were carried out under an inert
atmosphere of dinitrogen using standard Schlenk line

K.S. Coleman et al. / Journal of Organometallic Chemistry 689 (2004) 770–774
773
techniques, or in an inert atmosphere dry box con-
taining dinitrogen. All solvents were dried over the
appropriate drying agents and distilled under nitrogen.
NMR spectra were recorded using either a Varian
Mercury 300 (1H, 300 MHz; 13C, 75.5 MHz; 31P, 121.6
MHz) or a Varian UNITYplus (1H, 500 MHz; 13C,
125.7 MHz; 31P, 202.4 MHz; 29Si, 99.3 MHz) spec-
trometer, and at room temperature unless otherwise
stated. The spectra were referenced internally relative to
the residual protio-solvent (1H) and solvent (13C) res-
onances and chemical shifts reported relative to tetra-
methylsilane (1H, 13C, 29Si, d ¼ 0) or externally to
H3PO4 (31P, d ¼ 0). Infrared spectra were recorded on a
Elemental analysis (%): Found (Calc.): C, 67.61 (68.05);
H, 6.27 (6.01); P, 9.28 (9.24)%.
4.2. Preparation of 1,10-bis[dimethyl(dimethylphosph-
ino)silyl]ferrocene (2)
1,10-Bis(chlorodimethylsilyl)ferrocene (3.71 g, 10.0
mmol) was dissolved in Et2O (40 ml) and cooled to
)78 °C. A suspension of LiPMe2 ꢂ 0.5Et2O (2.31 g, 22.0
mmol) in Et2O (20 ml) was then added dropwise to the
cooled solution. The reaction mixture was allowed to
warm to room temperature and stirred for 6 h. The
solvent was then removed under vacuum leaving an
orange solid. The solid was extracted with pentane
(2 ꢁ 30 ml) and upon removal of the volatiles a waxy
orange solid was obtained. Yield ¼ 4.01 g, 95%.
6020 Galaxy Series FT-IR in the range 4000–400 cmꢀ1
.
Samples were prepared in the glovebox as a Nujol-mull
between KBr plates. Electron impact mass spectra were
obtained using a Micromass GCT Probe EI/FI MS.
Microanalyses were performed by the microanalytical
department of the Inorganic Chemistry Laboratory,
University of Oxford.
1H NMR (C6D6, 300 MHz): d 0.07 (s,12H, SiCH3),
2
0.64 (d, JPH ¼ 2.35 Hz, 12H, PCH3), 3.93 (m, 4H, Cp-
H), 4.22 (m, 4H, Cp-H). 13C{1H} NMR (C6D6, 75.5
2
MHz): d )3.31 (d, JPC ¼ 13.16 Hz, SiCH3), 7.16 (d,
All reagents were purchased from Aldrich and used
as received unless otherwise stated. LiPMe2 ꢂ 0.5Et2O
was prepared by deprotonating HPMe2 using a modi-
2JPC ¼ 17.95 Hz, PCH3) 72.02 (s, Cp-C), 73.64 (s, Cp-C).
31P{1H} NMR (C6D6, 121.5 MHz): d )128.99 (s,
SiPMe2). 29Si NMR (C6D6, 99.3 MHz): d 0.27 (d,
1JSiP ¼ 18.5 Hz, SiPMe2). MS (EI) m=z 422 [Mþ] (26%).
Elemental analysis (%): Found (Calc.) C, 50.46 (51.18);
H, 7.04 (7.64)%.
t
fication of IssleibÕs method [22] with BuLi was used as
the base instead of PhLi. The reagents LiPPh2 [23],
[Fe(g5-C5H4SiMe2Cl)2] [24], and (nbd)Mo(CO)4 [25]
were prepared using published procedures.
4.3. Preparation of tetracarbonyl[P,P0-bis[dimethyl
(diphenylphosphino)silyl]ferrocene]-molybdenum (3)
4. Syntheses
1,10-Bis[dimethyl(diphenylphosphino)silyl]ferrocene
(1) (1.06 g, 1.6 mmol) was dissolved in THF (20 ml)
to produce an orange solution. This solution was
added dropwise to a stirred solution of (norbornadi-
ene)tetracarbonylmolybdenum (0.47 g, 1.6 mmol) dis-
solved in THF (30 ml). On addition the green-yellow
solution changed to a dark orange colour. Once ad-
dition was complete, the reaction was heated to 65 °C
under nitrogen for 3 h. After cooling to room tem-
perature, volatiles were removed under vacuum and
the resulting orange solid was washed with pentane
(2 ꢁ 10 ml). The solid was then dried under vacuum.
Yield ¼ 0.91 g, 66%.
4.1. Preparation of 1,10-bis[dimethyl(diphenylphosph-
ino)silyl]ferrocene (1)
1,10-Bis(chlorodimethylsilyl)ferrocene (1.86 g, 5.0
mmol) was dissolved in Et2O (40 ml). The clear orange
solution was cooled to )78 °C and a suspension of
lithium diphenylphosphide (2.02 g, 10.5 mmol) in Et2O
(20 ml) was then added dropwise. After addition was
complete, the reaction mixture was allowed to warm to
room temperature and the resulting orange solution
stirred for 12 h. The solvent was then removed under
vacuum and the resulting orange solid extracted with
benzene (3 ꢁ 20 ml). The benzene extracts were com-
bined and pumped down to dryness to yield a crystalline
orange solid. Yield ¼ 2.83 g, 84%.
1H NMR (CD2Cl2, 500 MHz): d 0.38 (br s, 12H,
SiCH3), 3.55 (m, 4H, Cp-H), 4.04 (m, 4H, Cp-H), 6.78–
7.39 (20H, Ar-H). 13C{1H} NMR (CD2Cl2, 125.7
1H NMR (C6D6, 300 MHz): d 0.47 (d, JPH ¼ 4.70
MHz): d )1.76 (t, JPH ¼ 5.91 Hz, SiCH3), 67.40 (d,
3
3
Hz, 12H, SiCH3), 3.93 (m, 4H, Cp-H), 4.21 (m, 4H, Cp-
H), 7.10–7.70 (20H, Ar-H). 13C{1H} NMR (C6D6, 75.5
1JPC ¼ 9.67 Hz, Cpipso-C), 72.04 (s, Cp-C), 74.64 (s, Cp-
C), 127.81 (s, Ar-C), 128.27 (s, Ar-C), 133.49 (s, Ar-C),
2
1
2
MHz): d )1.33 (d, JPC ¼ 14.36 Hz, SiCH3), 69.92 (d,
133.96 (d, JPC ¼ 9.67 Hz, Ar-C), 210.25 (t, JPC ¼ 9.47
2JPC ¼ 15.56 Hz, Cpipso-C), 72.20 (s, Cp-C), 73.94 (s, Cp-
C), 128.51 (s, Ar-C), 128.78 (s, Ar-C), 134.43 (s, Ar-C),
136.31 (d, 1JPC ¼ 16.76 Hz, Ar-C). 31P{1H}
NMR(C6D6, 121.5 MHz): d )54.51 (s, SiP Ph2). 29Si
Hz, cis-CO), 216.49 (d, JPC ¼ 11.82 Hz, trans-CO).
2
31P{1H} NMR (CD2Cl2, 202.4 MHz): d )25.33 (s,
SiPPh2Mo). MS (EI) m=z 880 [Mþ] (100%). Selected IR
data (m(CO) cmꢀ1, nujol mull, KBr plates) 2012 (m),
1912 (s), 1904 (s), 1888 (vs). Elemental analysis (%):
Found (Calc.) C, 57.15 (57.41); H, 5.16 (4.59)%.
1
NMR (C6D6, 99.3 MHz): d )2.44 (d, JSiP ¼ 22.2 Hz,
SiPPh2). MS (EI) m=z 592 [MHþ ) Ph] (100%).

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K.S. Coleman et al. / Journal of Organometallic Chemistry 689 (2004) 770–774
4.4. Preparation of tetracarbonyl[P,P0-bis[dimethyl(dim-
ethylphosphino)silyl]ferrocene]-molybdenum (4)
Acknowledgements
We thank the Royal Society for a University Re-
search Fellowship (K.S.C.), the EPSRC for a student-
ship (S.T.) and Balliol College for a Dervorguilla
Scholarship (S.I.P.).
1,10-Bis[dimethyl(dimethylphosphino)silyl]ferrocene
(2) (0.58 g, 1.4 mmol) was dissolved in THF (20 ml) and
added dropwise to a stirred solution of (norbornadi-
ene)tetracarbonylmolybdenum (0.41 g, 1.4 mmol) dis-
solved in THF (30 ml). On addition the green-yellow
solution changed to an orange colour. Once addition
was complete, the reaction was heated to 65 °C under
nitrogen for 3 h. After cooling to room temperature,
volatiles were removed under vacuum and the resulting
light orange solid was washed with 5 ml of pentane. The
solid was then dried under vacuum. Yield ¼ 0.69 g, 80%.
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ꢀ
monochromated Mo Ka radiation (k ¼ 0:71073 A), as
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summarised in Table 1. The images were processed with
the DENZO and SCALEPACK programs [26]. All solu-
tion, refinement, and graphical calculations were per-
formed using the CRYSTALS program suite [27]. The
crystal structures were solved by direct methods using
the SIR92 program [28] and were refined by full-matrix
least squares on F. All non-hydrogen atoms were refined
with anisotropic displacement parameters. All carbon-
bound hydrogen atoms were generated and allowed to
ride on their corresponding carbon atoms with fixed
thermal parameters.
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Processing of X-ray Diffraction Data Collected in Oscillation
Mode, Methods Enzymology, 276, Academic Press, 1997.
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Cooper, CRYSTALS issue 11, Chemical Crystallography Labora-
tory, Oxford, UK, 2001.
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 224907 for compound 1 and
224908 for compound 2.
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