Reaction of tris[(diphenylphosphino)dimethylsilyl]methane with molybdenum hexacarbonyl and deprotonation to give a salt with a planar carbanion. Crystal structures of (Ph2PMe2Si)3CH and [Li(tmen)2][C(SiMe2<

Article abstract of DOI:10.1039/a808971j

The compound (Ph₂PMe₂Si)₃CH I reacted (i) with [Mo(CO)₆] to give cis-[Mo(CO)₄{(Ph₂PMe₂Si)₃CH}] 1 in which two phosphine groups are co-ordinated to molybdenum and one i

Full text of DOI:10.1039/a808971j

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Reaction of tris[(diphenylphosphino)dimethylsilyl]methane with
molybdenum hexacarbonyl and deprotonation to give a salt with a
planar carbanion. Crystal structures of (Ph2PMe2Si)3CH and
[Li(tmen)2][C(SiMe2PPh2)3], tmen ؍ N,N,NЈ,NЈ-tetramethyl-
ethane-1,2-diamine
Anthony G. Avent, Dominique Bonafoux, Colin Eaborn,* Sushil K. Gupta, Peter B. Hitchcock
and J. David Smith*
School of Chemistry, Physics and Environmental Science, University of Sussex, Brighton,
UK BN1 9QJ. E-mail: C.Eaborn@sussex.ac.uk; J.D.Smith@sussex.ac.uk
Received 17th November 1998, Accepted 21st January 1999
The compound (Ph2PMe2Si)3CH I reacted (i) with [Mo(CO)6] to give cis-[Mo(CO)4{(Ph2PMe2Si)3CH}] 1 in
which two phosphine groups are co-ordinated to molybdenum and one is free, and (ii) with LiBu in the presence
of N,N,NЈ,NЈ-tetramethylethane-1,2-diamine (tmen) to give [Li(tmen)2][C(SiMe2PPh2)3] 2, which contains discrete
planar carbanions and no Li–P co-ordination. The crystal structures of compounds I and 2 have been determined
and 1 has been characterised spectroscopically.
We have been able to isolate a wide range of novel types of
organometallic compounds by attaching the bulky ligands
C(SiMe3)3 or C(SiMe2Ph)3 to metal centres.1 Recently the
emphasis in our research has moved towards use of ligands of
the type C(SiMe3)2(SiMe2X) and C(SiMe2X)3 that have similar
bulk around the metal centre to which they are attached but
also contain groups X bearing lone pairs capable of co-
ordinating intra- or inter-molecularly to the metal. Those used
previously include C(SiMe3)2(SiMe2X) with X = OMe2 or SMe3
and C(SiMe2X)3 with X = OMe4 or NMe2.5,6 In particular, the
lithium derivative LiC(SiMe2NMe2)3, made by metallation of
the ligand precursor (Me2NMe2Si)3CH, adopts a linear poly-
meric structure in which the planar lithium ion, co-ordinated
by three NMe2 groups, is well separated from the planar carb-
anionic centre. Moreover, the highly unusual Grignard reagent
(Me2NMe2Si)3CMgI has a planar carbanionic centre without
specific interaction with the magnesium atom. We now describe
the synthesis of the analogous phosphorus-containing ligand
precursor I, the molybdenum complex 1, and the lithium deriv-
ative 2 obtained from the reaction between I and LiBu/tmen
(tmen = N,N,NЈ,NЈ-tetramethylethane-1,2-diamine).
the A part of an AXY2 system, with the 12C/13C isotope shift at
phosphorus |δX Ϫ δY| = 0.028. The signal from the ortho carbon
was also analysed as the A part of an AXY2 spin system but
with |δX Ϫ δY| = 0.009; that from the meta-carbon was analysed
as the A part of an AXXЈ2 spin system, as the isotope shift
is attenuated over three bonds. The presence of a 13C nucleus in
a methyl site makes the two remote 31P nuclei magnetically
inequivalent so that the CH3 signal appears as the A part of
an AXYYЈ system with |δX Ϫ δY| = 0.006. The 29Si signal was
analysed as the A part of an AXY2 system with |δX Ϫ δY|
(arising from the 29Si/28Si isotope shift at P) = 0.011. The 29Si
satellites from the quartet assigned to the tertiary carbon
1
showed that the coupling constant JSiC is 33.2 Hz [cf. 38.7 Hz
for (Me3Si)3CH8 and 42 Hz for (Me2NSiMe2)3CH5]. The
phosphorus chemical shift, δ Ϫ51, is close to that, δ Ϫ56.8,
for diphenyl(trimethylsilyl)phosphine.9 Crystals of compound I
suitable for an X-ray study were obtained from heptane–thf.
The reaction between compound I and molybdenum hexa-
carbonyl gave a white solid which was judged to be the complex
cis-[Mo(CO)4{(Ph2PMe2Si)3CH}] 1 from (i) the mass spec-
trum, which showed the successive loss of four carbonyl groups
from the molecular ion, (ii) the presence of four bands in the
carbonyl stretching region of the infrared spectrum as required
for C2v symmetry, and (iii) the presence in the 29Si and 31P NMR
spectra of two signals with intensities in the ratio 2:1. These are
attributed respectively to complexed SiA,BMe2PPh2 fragments
(with δP Ϫ21, about 30 ppm to higher frequency than the signal
for I), and uncomplexed SiCMe2PPh2 fragments (with δP close
to that for I). The bidentate co-ordination of the ligand in 1
gives a six-membered MoPSiCSiP metallacycle and leaves one
free SiMe2PPh2 fragment. The presence of three signals in each
region of the H and 13C spectra, corresponding to the methyl
1
Results and discussion
and phenyl substituents in uncomplexed SiCMe2PPh2 groups
and SiA,BMe2PPh2 groups on either side of the ring, shows that
the chelate structure is preserved in solution and is not fluxional
on the NMR timescale. In several other complexes MoL(CO)4
The precursor I was obtained in good yield from the reaction
between (BrMe2Si)3CH7 and KPPh2 in tetrahydrofuran (thf)
and characterised by multinuclear NMR spectroscopy. The 1H
NMR spectrum showed the expected signals assigned to SiMe2,
CH and Ph protons. The 13C and 29Si spectra showed complex
multiplets which were simulated by the PANIC program. The
signal from the ipso-carbon of the phenyl group was analysed as
the ligand
L containing three phosphorus centres, e.g.
(Ph2P)3CH10 or (Ph2PCH2)3CCH3,11,12 is bidentate.
Compound I was readily metallated by LiBu in the pres-
ence of tmen. The product 2 was obtained as pale yellow
J. Chem. Soc., Dalton Trans., 1999, 831–834
831

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Table 1 Bond lengths (Å) and angles (Њ) in (Ph2PSiMe2)3CH I and [(Ph2PSiMe2)3C]Ϫ
(Ph2PSiMe2)3CH I
[(Ph2PSiMe2)3C]Ϫ
Si–C
Si–Me
P–Si
1.898(5)a
1.871(6)a
2.275(2)a
1.837(5)a
1.809(7)a
1.879(8)a
2.323(3)a
1.837(8)a
P–Ph
Si1
Si2
Si3
Si1
Si2
Si3
Si–C–Si
Ph–P–Ph
Si–P–Ph
114.7(3)
101.9(2)
101.1(2)
106.5(3)
107.1(3)
116.1(2)
111.5(3)
107.9(2)
103.4(2)
110.1(2)
112.1(3)
101.9(2)
107.9(2)
98.7(2)
106.3(3)
116.1(2)
110.8(3)
108.0(2)
111.5(2)
103.4(2)
114.5(3)
103.0(2)
97.7(2)
106.8(2)
104.6(3)
118.1(2)
110.6(3)
107.3(2)
109.4(2)
106.3(2)
120.7(4)
102.4(3)
106.0(3)
101.4(3)
104.0(4)
114.9(4)
116.6(3)
112.7(2)
105.3(3)
101.8(3)
120.2(4)
105.2(4)
106.3(3)
102.2(3)
105.9(4)
114.6(3)
117.2(3)
114.1(3)
103.3(2)
99.8(3)
118.6(4)
102.2(4)
104.2(3)
106.8(3)
103.4(4)
116.6(3)
114.7(3)
110.8(3)
102.3(3)
107.8(3)
Me–Si–Me
C–Si–Me
C–Si–P
Me–Si–P
a Mean value. Numbers in parentheses indicate the precision of individual measurements, none of which differed significantly from the mean.
Fig. 1 Molecular structure of (Ph2PMe2Si)3CH I.
Fig. 2 Structure of the anion of [Li(tmen)2][C(SiMe2PPh2)3] 2.
crystals from warm toluene and shown by an X-ray study to
be ionic, with a lattice consisting of discrete [Li(tmen)2]ϩ
cations and [C(SiMe2PPh2)3]Ϫ anions. The CSi3 core of
the carbanion is planar, like those in [Li(thf)4][C(SiMe2-
C6H4Me-o)3]13 and [Li(12-crown-4)2][C(SiMe3)(SiMeBut2)-
(SiMe2F)].14 The ionic structure of 2 contrasts with the poly-
meric structure of the amino derivative LiC(SiMe2NMe2)3,5
and the molecular structure of the recently described com-
pound [LiP{C(SiMe3)2}(C6H4CH2NMe2)2] 3,15 which has a
planar carbanionic centre and lithium co-ordinated both by
the lone pair on phosphorus and by those on the two nitrogen
atoms.
anion in 2 nor the corresponding protonated species I has
any crystallographic symmetry. The anion has one SiMe2PPh2
group on one side of the CSi3 plane and two on the other.
{There is a similar configuration of SiMe2C6H4Me-o groups in
the anion [C(SiMe2C6H4Me-o)3]Ϫ.13} In contrast, the molecule I
is propeller-shaped, with approximate C3 symmetry and all the
SiMe2PPh2 groups lying on the side opposite the C–H bond.
The Si–C1 distances are much shorter in the anion (mean 1.809
Å) than in the protonated species I (mean 1.898 Å) showing
that the anionic charge is delocalised into C1–Si bonds, prob-
ably by negative hyperconjugation.16 Data for a number of
related species are given in Table 2. The Si–C1 distances in the
silyl-stabilised carbanions are all short compared with those in
the corresponding silyl-substituted methanes. The bond lengths
show little systematic variation with the nature of the substitu-
ent X. The Si–P bonds are longer in the anion than in I, and
in other organosilylphosphines or organosilylphosphine com-
plexes.20 The P–C bond lengths are in the normal range, 2.20–
2.29 Å, and all the Si–Me bond lengths are, within experimental
error, the same as those in SiMe4 [1.875(2) Å].21 The Si–C–Si
angles are larger in the anion than in the protonated species, as
expected if the ionic charge is delocalised over the CSi3 system
The 31P NMR spectrum of a thf solution of compound 2
consisted of a singlet at δ Ϫ39.4. The absence of Li–P coupling
and the small difference between the chemical shifts of 2 and of
the precursor I indicate that in solution, as in the solid, the
phosphorus atoms in 2 are not co-ordinated to lithium.
The structures of the anion of compound 2 and the corre-
sponding protonated species I are shown in Figs. 1 and 2. (The
cation in 2 is similar to that described in several other com-
pounds and is not discussed further here.) Bond lengths and
angles are given in Table 1. For each species the individual Si–C,
Si–Me, P–Si and P–C bond lengths differ insignificantly from
the corresponding mean values, but there is considerably more
variation in the bond angles, which means that neither the
17
1b
[cf. C(SiMe3)3 and C(SiMe2Ph)3 derivatives]. The other
mean bond angles in I are similar (within 4Њ) to those in the
anion of 2 but there is more scatter in the protonated than
832
J. Chem. Soc., Dalton Trans., 1999, 831–834

View Article Online
Table 2 Si–C1 Distances (Å) in compounds HC(SiMe2X)3 and anions
[C(SiMeX)3]Ϫ
g, 89%), mp 192 ЊC (Found: C, 68.1; H, 6.4; P, 13.8. C43H49P3Si3
requires C, 69.5; H, 6.4; P, 12.5%). No carbon- or phosphorus-
containing impurity was detected by NMR spectroscopy.
δH (C6D6) 0.51 (18 H, s, SiMe2), 1.20 (1 H, q, 3JPH 3.5 Hz, CH),
6.98 (18 H, m, m- and p-H) and 7.52 (12 H, m, o-H). δC 1.9
X
HC(SiMe2X)3 Ref.
[C(SiMeX)3]Ϫ
Ref.
Me
Ph
PPh2
NMe2
OMe
Br
1.887(6)
1.895(1)
1.898(5)
17
19(a)
1.818(10)–1.822(10) 17
1.800(3)–1.812(3)
13a
1
2
2
4
(DEPT q, JSiC 33.2, JCP 11.1, CH), 2.0 (m, JCP 8.1, JCP 9.4,
4
3
4
0.4, JPP 9.4, SiMe2), 127.7 (p-C), 128.8 (m, JCP 6.5, JPP 9.4,
This work 1.809(7)
1.793(6)
This work
2
4
m-C), 134.6 (m, JCP 18.4, JPP 9.4, o-C) and 136.5 (m, ipso-C,
5
4
5
4
3
1JCP 18.6, JCP Ϫ0.5, JPP 9.4 Hz). δSi 2.8 (1JSiP 27.2, JSiP Ϫ3.9
Hz). δP Ϫ50.6. m/z 557 (5, M Ϫ PPh2), 370 (75, P2Ph4), 185 (80,
PPh2) and 183 (100%, PPh2 Ϫ H2).
1.805(4)
1.884(5)
19(b)
a For C(SiMe2C6H4Me-o)3.
Compound I reacted slowly (during 1 week) with thf at room
temperature with formation of some P2Ph4, the presence of
which was deduced from the 31P NMR spectrum.
in the unprotonated species. The geometry at phosphorus is
pyramidal with C–P–C and C–P–Si angles less than the tetra-
hedral value, as found in other silylphosphine complexes.20
The chemistry of the compounds described here shows sev-
eral novel features. (a) Although the organolithium compound
2 reacted in the normal way with a stoichiometric amount of
MeOH-d4 to give the expected (Ph2PMe2Si)3CD in high yield,
reactions with other electrophiles e.g. MeI or I2 resulted in
cleavage of Si–P bonds. Similar cleavages have been observed
cis-[Mo(CO)4{(Ph2PMe2Si)3CH}] 1. A suspension of [Mo-
(CO)6] (0.712 g, 2.69 mmol) and I (2.00 g, 2.69 mmol) in toluene
(150 cm3) was slowly heated to reflux, then maintained at reflux
for 3 h to give a red solution. The solution was allowed to cool
to room temperature and the solvent removed to leave a yellow
solid which was judged to be complex 1 (2.34 g, 90%), mp
101 ЊC (Found: C, 52.9; H, 5.4; Mo, 9.9; P, 9.4. C47H49-
MoO4P3Si3 requires C, 59.3; H, 5.2; Mo, 10.1; P, 9.7%). The low
value for the carbon analysis is puzzling since the NMR data
were fully consistent with the proposed structure. νmax/cmϪ1
2018s, 1950 (sh), 1925s and 1880s. δH (C6D6) 0.15 (6 H, d, 3JPH
3.5, SiMe), 0.31 (6 H, d, 3JPH 6.6, SiMe), 0.36 (6 H, d, 3JPH 2.3,
SiMe), 0.93 (1 H, d, 3JPH 5.3 Hz, CH), 6.8–7.2 (18 H, m, m- and
p-H), 7.26 (4 H, m, o-H), 7.50 (4 H, m, o-H) and 7.76 (4 H, m,
20
for Ph2PSiMe3 but it is remarkable that attack at the Si–P
bond in 2 appears to occur more readily rather than that at the
carbanionic centre.
(b) There is a considerable difference in reactivity between
Si–N or Si–S bonds on the one hand and Si–P bonds on the
4,5
other. Whereas the compounds LiC(SiMe2NMe2)3 and LiC-
(SiMe3)2(SiMe2SMe)3 could each be used as a reagent for the
transfer of the C-centred ligands to other metals, reactions of
compound 2 with HgBr2 and PtCl2 did not proceed cleanly.
Tetraphenyldiphosphine P2Ph2 was always obtained as the
principal product but the additional presence of PPh2H in some
cases may indicate that PPh2Li and PPh2Br are intermediates in
the ligand degradation. It has not been possible to isolate the
silicon-containing products in a pure state.
2
2
4
o-H). δC 0.64 (d, JCP 14.4, SiMe2), 2.16 (dd, JCP 9.6, JCP 1.2,
SiMe2), 3.25 (d, 2JCP 9.3, SiMe2), 3.45 (q, 2JCP 7.2, CH), 128.06
(A of AXXЈ, 3JCP 9.6, 2JPP ca. 2, m-CA,B), 128.42 (s, p-C), 128.46
(A of AXXЈ, 3JCP 9.4, 2JPP ca. 2, m-CA,B), 128.57 (s, p-C), 129.05
3
2
(s, p-C), 129.14 (d, JCP 7.0, m-CC), 133.61 (A of AXXЈ, JCP
10.3, JPP ca. 2, o-CA,B), 134.69 (d, JCP 18.5, o-CC), 134.84 (d,
2
2
1JCP 17.5, ipso-C), 135.24 (d, JCP 24.0, ipso-C), 135.36 (A of
1
(c) The isolation of complex 1 suggests that in the absence of
electrophiles the compound I has some potential as a mono-,
di- or tri-dentate ligand towards transition metals. This area of
chemistry is however likely to be restricted by ligand degrad-
ation and by slow attack of I on the thf commonly used as a
solvent.
(d) The stability of compound I in the absence of electro-
philes is also shown by the fact that it reacts in the normal
way with metal methyl derivatives, e.g. with LiBu to give the
compound 2.
AXXЈ, JCP 12.3, JPP ca. 2, o-CA,B), 137.56 (d, JCP 25.6, ipso-
2
2
1
2
2
2
C), 206.4 (t, JCP 7.6, cis-CO), 215.9 (dd, JCP-trans 22.2, JCP-cis
9.4, trans-CO) and 216.3 (t, 2JCP 7.6 Hz, cis-CO). δSi Ϫ2.2 (2 Si,
d, 1JSiP 18.7, SiA,B) and 0.1 (1 Si, dt, 1JSiP 30.9, 3JSiP 7.2 Hz, SiC).
δP Ϫ48.7 (1 P, t, 4JPP 2.0, PC) and Ϫ17.7 (2 P, d, 4JPP 2.0 Hz, PC).
₁
δMo Ϫ1290 (∆ν 500 Hz). m/z 924 (8, M Ϫ CO), 896 (30
₂
M Ϫ 2CO), 868 (100, M Ϫ 3CO), 840 (55, M Ϫ 4CO) and 682
(50, M Ϫ 3CO Ϫ PHPh2) and 654 (80%, M Ϫ 4CO Ϫ PHPh2).
[Li(tmen)2][C(SiMe2PPh2)3] 2. A solution of LiBu (3.23
mmol) in hexane (1.3 cm3) was added to a mixture of I (2.0 g, 2.7
mmol) and tmen (4.5 cm3, 30 mmol) in toluene (30 cm3) at room
temperature. After about 30 min an orange solid separated.
This was filtered off, washed first with light petroleum (bp
40–60 ЊC, 2 × 10 cm3) then with benzene (3 × 10 cm3), and
recrystallised from warm toluene to give pale yellow air- and
moisture-sensitive plates of compound 2 (1.73 g, 65%), mp
187 ЊC (decomp.) (Found: C, 66.1; H, 8.2; N, 5.7. C55H80-
LiN4P3Si3 requires C, 67.3; H, 8.2; N, 5.7%). δH (thf-d8) 0.16 (18
H, s, SiMe2), 2.15 (24 H, s, NMe2), 2.31 (8 H, s, CH2), 6.91–7.37
(20 H, m, Ph) and 7.66–7.73 (10 H, m, Ph). δC 4.75 (m, SiMe2),
4.8 (DEPT, q, 1JSiC 59.7, 2JCP 20.3 Hz, CSi3), 46.1 and 58.8 (free
tmen, displaced by solvent), 125.3 (s), 127.8 (m) and 134.8 (m).
δSi Ϫ0.9. δP Ϫ39.4.
Experimental
Air and moisture were excluded as far as possible from all reac-
tions by the use of standard Schlenk techniques and Ar as
blanket gas. Solvents were dried by normal procedures and dis-
tilled immediately before use. The NMR spectra were recorded
at 300.13 (1H), 125.8 (13C), 99.4 (29Si), 121.4 (31P) and 32.53
MHz (95Mo) and chemical shifts are relative to SiMe4 for H, C
and Si, H3PO4 for P, and Ξ 6.515 for Mo. The 29Si spectra were
obtained by inverse gated decoupling and signals from ternary
carbon were detected by the DEPT procedure. Coupling con-
stants derived from PANIC simulation are accurate to 0.2 Hz.
The EI mass spectra were recorded at 70 eV: m/z values are
given for 1H, 12C, 28Si and 98Mo.
Syntheses
Reactions of complex 2
(Ph2PMe2Si)3CH I. A solution of KPPh2 (130 cm3, 0.5 M in
thf) was added dropwise to (BrMe2Si)3CH (9.08 g, 21.3 mmol)
in thf (100 cm3) at room temperature and the mixture stirred
for 4 h. The solvent was removed under vacuum, the residue
extracted with benzene (3 × 20 cm3), the extract filtered, the
solvent removed, and the residue recrystallised from thf–
heptane (10:1) to give colourless needles of compound I (14.2
With CD3OD. The compound CD3OD (0.4 cm3) in benzene
(5 cm3) was added to a suspension of 2 (0.94 g, 0.95 mmol) in
benzene (10 cm3) to give a clear solution immediately. The sol-
vent was removed to leave the deuteriated species (Ph2PMe2-
Si)3CD as a white solid (0.54 g, 76%). m/z 558.188 (M Ϫ PPh2);
C31H38DP2Si3 requires m/z 558.190. The 13C and 31P NMR
spectra were identical with those for I; the proportion of I
J. Chem. Soc., Dalton Trans., 1999, 831–834
833

View Article Online
Table 3 Crystallographic data and details of structure refinement for
compounds I and 2
CCDC reference number 186/1330.
See http://www.rsc.org/suppdata/dt/1999/831/ for crystallo-
graphic files in .cif format.
I
2
Acknowledgements
Empirical formula
Formula weight
C43H49P3Si3
743.0
C55H80LiN4P3Si3
981.4
The authors thank the EPSRC for financial support, the EU for
the award of a Marie-Curie Fellowship to D. B. and the Royal
Society for a Commonwealth Visiting Fellowship for S. K. G.
T/K
λ/Å
Crystal system
Space group
a/Å
b/Å
c/Å
173(2)
173(2)
0.71073
0.71073
Monoclinic
P21/n (no. 14)
18.314(4)
10.398(3)
21.859(7)
100.61(2)
4091(2)
4
0.26
2–22
5170
4993
(Rint = 0.0357)
3229
0.053, 0.107
0.105, 0.136
4992/0/446
Monoclinic
P21/n (no. 14)
15.023(4)
16.592(4)
23.174(11)
90.78(3)
5776(3)
4
0.20
2–23
8371
8027
(Rint = 0.0698)
4106
0.090, 0.145
0.189, 0.179
8026/0/595
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With MeI. A solution of MeI (0.36 mmol) in thf (0.72
cm3) was added to compound 2 (0.32 mmol) in thf (10 cm3) at
Ϫ70 ЊC. The mixture was allowed to warm to room temperature
and stirred for 2 h. After removal of the solvent the residue was
extracted with light petroleum to give, according to the 31P
NMR spectrum and integration of the 1H spectrum, a mixture
of PPh2Me (51%), and PPh2H/P2Ph4 (49%), identified by com-
parison of the 31P chemical shifts with those of commercially
available samples and with values in the literature.23 With an
eight-fold excess of MeI, 2 gave a white solid which was shown
by its 1H, 13C and 31P NMR spectra18 to be [PMe2Ph2]I, isolated
in 87% yield. Positive FAB MS: m/z 557 (2, [PPh2Me2]2I) and
215 (90, PPh2Me2).
7 C. Eaborn, P. B. Hitchcock and P. D. Lickiss, J. Organomet. Chem.,
1983, 252, 281.
8 B. Wrackmeyer and W. Biffar, Z. Naturforsch., Teil B, 1979, 34,
1270.
9 H. Schumann and H.-J. Kroth, Z. Naturforsch., Teil B, 1977, 32,
513.
10 J. T. Mague and S. E. Dessens, J. Organomet. Chem., 1984, 262, 347.
11 J. Chatt, G. J. Leigh and N. Thankarajan, J. Organomet. Chem.,
1971, 29, 105.
12 E. J. Fernández, M. C. Gimeno, P. G. Jones, A. Laguna, M. Laguna
and E. Olmos, J. Chem. Soc., Dalton Trans., 1996, 3603.
13 A. I. Almansour, C. Eaborn, S. A. Hawkes, P. B. Hitchcock and
J. D. Smith, Organometallics, 1997, 16, 6035.
14 N. Wiberg, G. Wagner, G. Reber, J. Riede and G. Müller, Organo-
metallics, 1987, 6, 35.
15 W. Clegg, S. Doherty, K. Izod and P. O’Shaughnessy, Chem.
Commun., 1998, 1129.
16 P. v. R. Schleyer, T. Clark, A. J. Kos, G. W. Spitznagel, C. Rohde,
D. Arad, K. N. Houk and N. G. Rondan, J. Am. Chem. Soc., 1984,
106, 6467; E. A. Brinkman, S. Berger and J. I. Brauman, J. Am.
Chem. Soc., 1994, 116, 8304.
17 P. T. Brain, M. Mehta, D. W. H. Rankin, H. E. Robertson,
C. Eaborn, J. D. Smith and A. D. Webb, J. Chem. Soc., Dalton
Trans., 1995, 349.
18 C. Eaborn, N. Retta and J. D. Smith, J. Chem. Soc., Dalton Trans.,
1983, 905; H.-J. Cristau and Y. Ribeill, Synthesis, 1988, 911.
19 (a) C. Eaborn, P. B. Hitchcock and P. D. Lickiss, J. Organomet.
Chem., 1984, 269, 235; (b) A. Farook, D.Phil. Thesis, University of
Sussex, 1998.
20 E. Lukevics, O. Pudova and R. Sturkovich, Molecular Structure of
Organosilicon Compounds, Ellis Horwood, Chichester, 1989, p. 93;
W. S. Sheldrick and A. Borkenstein, Acta Crystallogr., Sect. B, 1977,
33, 2916; J. C. Calabrese, R. T. Oakley and R. West, Can. J. Chem.,
1979, 57, 1909.
With I2. A solution of I2 (0.7 mmol) in thf (0.8 cm3) was
added to compound 2 (0.7 mmol) in thf (10 cm3) at Ϫ78 ЊC,
and the mixture allowed to warm to room temperature. A white
solid was filtered off and the 31P NMR spectrum of the fil-
trate showed the presence of P2Ph4 as the only detectable
phosphorus-containing thf-soluble product. The solid was not
investigated further.
With metal halides. The reaction of compound 2 with PtCl2
gave P2Ph4 and that with HgBr2 gave Hg, P2Ph4 (75% of thf-
soluble products) and PPh2H (25%). Unidentified white solids
were obtained in both reactions and their NMR spectra showed
that they contained neither phosphorus nor aromatic protons.
Crystallography
21 B. Beagley, J. J. Monaghan and T. G. Hewitt, J. Mol. Struct., 1971, 8,
401.
Details are given in Table 3. All non-hydrogen atoms were
refined anisotropically. The H atoms were included in riding
mode with Uiso(H) = 1.2Ueq(C) except for Me groups which
were fixed at idealised geometry but with the torsion angles
defining the H atom position refined and Uiso(H) = 1.5Ueq(C).
The high value of R for complex 2 is a consequence of the weak
diffraction from a thin plate.
22 E. W. Abel, R. A. N. McLean and I. H. Sabherwal, J. Chem. Soc. A,
1968, 2371; P. J. Manning, L. K. Peterson, F. Wada and R. S.
Dhami, Inorg. Chim. Acta, 1986, 114, 15.
23 G. Mavel, Annu. Rep. N.M.R. Spectrosc., 1973, 5B, 1.
Paper 8/08971J
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J. Chem. Soc., Dalton Trans., 1999, 831–834