Divinyldisiloxane and divinylsilane complexes of rhodium(I)

Article abstract of DOI:10.1016/S0022-328X(99)00180-1

Reaction of the tetrakis(cyclooctene)rhodium(I) complex [{Rh(C₈H₁₄-c)₂(μ-Cl)}₂] with the appropriate divinyldisiloxane molecules (ViSiR₂)₂O (R=Me or Ph) yields, by displacement of the cycloctene ligands, the complexes [{Rh(ViSiR₂)₂O(μ-Cl)}₂] (R=Me (1) or Ph (2)). These react further with a tertiary phosphine PR₃ to give cis-[Rh{(ViSiR₂)₂O}(PR′₃)Cl] (R′=Ph or C₆H₄Me-p). The complex cis-[{Rh(Vi₂SiMe₂)(μ-Cl)}₂] (7) was similarly prepared by the displacement of ethylene from [{Rh(C₂H₄)₂(μ-Cl)}₂] by the divinyldimethylsilane Vi₂SiMe₂. X-ray molecular structures of the crystalline complexes 1, 2 and 7 show a distorted square planar Rh(I) environment, the CH₂=CH groups being orthogonal to this plane; 1 and 2 have the Rh-(ViSiR₂)₂O metallacycle in the chair conformation, but differ in the nature of the central Rh(Cl)RhCl core, which is planar for 1 and puckered for 2, but each of 1 and 2 is the rac-diastereoisomer, whereas 7 has the meso-configuration. In solution 1 and 2 exist as a mixture of isomers, probably the rac- and meso-pairs as established by multinuclear NMR spectral studies. A series of saturation transfer NMR spectroscopic experiments showed that the divinyldisiloxane ligands in [{Rh(ViSiPh₂)₂O(μ-Cl)}₂] underwent a dynamic process involving the dissociation, rotation and then reassociation of the vinyl groups.

Full text of DOI:10.1016/S0022-328X(99)00180-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 366–375
Divinyldisiloxane and divinylsilane complexes of rhodium(I)ꢀ
Christine J. Cardin a, Peter B. Hitchcock b, Michael F. Lappert b,*, Calum MacBeath b,
Nicholas J.W. Warhurst b
a Reading Uni6ersity, Department of Chemistry, Reading RG6 6AD, UK
b Uni6ersity of Sussex, School of Chemistry, Physics & En6ironmental Science, The Chemistry Laboratory, Brighton, East Sussex BN1 9QJ, UK
Received 22 January 1999; received in revised form 8 March 1999
Abstract
Reaction of the tetrakis(cyclooctene)rhodium(I) complex [{Rh(C8H14-c)2(m-Cl)}2] with the appropriate divinyldisiloxane
molecules (ViSiR2)2O (R=Me or Ph) yields, by displacement of the cycloctene ligands, the complexes [{Rh(ViSiR2)2O(m-Cl)}2]
(R=Me (1) or Ph (2)). These react further with a tertiary phosphine PR3 to give cis-[Rh{(ViSiR2)2O}(PR%3)Cl] (R%=Ph or
C6H4Me-p). The complex cis-[{Rh(Vi2SiMe2)(m-Cl)}2] (7) was similarly prepared by the displacement of ethylene from
[{Rh(C2H4)2(m-Cl)}2] by the divinyldimethylsilane Vi2SiMe2. X-ray molecular structures of the crystalline complexes 1, 2 and 7
show a distorted square planar Rh(I) environment, the CH2ꢀCH groups being orthogonal to this plane; 1 and 2 have the
Rh–(ViSiR2)2O metallacycle in the chair conformation, but differ in the nature of the central Rh(Cl)RhCl core, which is planar
for 1 and puckered for 2, but each of 1 and 2 is the rac-diastereoisomer, whereas 7 has the meso-configuration. In solution 1 and
2 exist as a mixture of isomers, probably the rac- and meso-pairs as established by multinuclear NMR spectral studies. A series
of saturation transfer NMR spectroscopic experiments showed that the divinyldisiloxane ligands in [{Rh(ViSiPh2)2O(m-Cl)}2]
underwent a dynamic process involving the dissociation, rotation and then reassociation of the vinyl groups. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Tetramethyldivinyldisiloxane; Divinyldimethylsilane; Rhodium(I); Dynamic processes; Hydrosilylation
1. Introduction
(Chalk–Harrod) of hydrosilylation postulated that the
initiator was a Pt(0) species, probably formed by reduc-
tion of the chloroplatinic acid by the silane HSiX3.
It was shown in 1987 that H2[PtCl6]·xH2O with LL
affords a solution A containing Pt(0) [3]. The evidence
included (i) treatment of solution A with a tertiary
phosphine led to recognisable Pt(0) species, e.g.
[Pt(PPh3)3] when PPh3 was employed; (ii) reaction with
PBut3 gave the X-ray characterised platinum(0) complex
[Pt(LL)(PBut3)] [3], and (iii) the 195Pt{1H}-NMR spec-
trum of solution A showed a signal indicative of a
platinum(0) complex.
Probably the most important catalyst for hydrosilyl-
ation is H2[PtCl6]·xH2O, Speier’s catalyst, discovered in
the mid-1950s [1]. It soon became apparent that for this
to operate efficiently a ‘solvent’ was required in order
to overcome the long and variable induction periods
and the exothermic reactions. Such a solvent-modified
system is the Karstedt catalyst [2], which incorporates
the simplest divinyldisiloxane molecule (CH2ꢀCHSi-
Me2)2O (ꢁLL). The generally accepted mechanism
Subsequently, a crystalline material was isolated from
solution A, the X-ray structure of which established it
to be the binuclear Pt(0) complex of formula
[{Pt(LL)}2(m-LL)] [4]. This demonstrated inter alia that
(i) the new ligand LL was capable of functioning not
ꢀ Dedicated to Professor Helmut Werner, as a mark of esteem and
(by M.F. Lappert) of friendship.
* Corresponding author. Fax: +44-1273-677196.
E-mail address: m.f.lappert@sussex.ac.uk (M.F. Lappert)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00180-1

C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
367
Two other types of Rh(I)–LL complexes have been
reported: [Rh(h5-C5H5)(LL)] (R=H or Me) [9] and
[Rh(acac)(LL)] [10].
An interesting feature of the divinyldisiloxane (LL)
complexes is their stereochemical non-rigidity. Bassin-
1
dale et al. reported that the variable temperature H-
NMR spectra of [Pt(LL)(PBut3)] could be interpreted in
terms of an intramolecular exchange process involving
the dissociation, rotation, then reassociation of the
vinyl groups of the LL ligand [11]. A similar process,
but in this case also involving rotation of an internal
CꢀC group, was proposed for the dynamic behaviour
observed in [Ni(LL%L)] [12].
Scheme 1.
only in a chelating mode (i.e. as a terminal ligand), but
it could also operate in a bridging fashion, and (ii) it
was a reducing agent, converting a Pt(IV) chloride into
a Pt(0) product.
2. Results and discussion
2.1. Synthesis and reactions of chloro(di6inyldisil-
oxane)rhodium(I) complexes
We have shown that the bridging ligand in
[{Pt(LL)}2(m-LL)] was displaced by a mono-, bis- or
tris(tertiary) phosphine to give, respectively, mono-, di-
or trinuclear complexes featuring the di- and tridentate
phosphines in unusual bridging modes [5,6]. The com-
plex [Pt(LL)PPh3] has been prepared from
[Pt(C2H4)(PPh3)2] [7]. The ligand (ViSiPh2)2O (L%L%) was
introduced in the context of Ni(0) chemistry [6]. Thus,
reduction of [NiCl2(PPh3)2] by zinc in the presence of
LL or L%L% afforded the X-ray-characterised [{Ni(m-
L%L%)(PPh3)}2] or its LL analogue.
Each of the binuclear Rh(I) complexes [{Rh-
(ViSiR2)2O(m-Cl)}2] (R=Me (1) or Ph (2)) was synthe-
sised by displacement of the four cyclooctene ligands
from [{Rh(C8H14)2(m-Cl)}2] by the appropriate divinyl-
disiloxane (Scheme 1). Compound 1 was not cleanly
accessible by treatment of RhCl3·xH2O with
(ViMe2Si)2O in ethanol.
2.2. The X-ray molecular structures of [{Rh(ViSiR2)2-
O(v-Cl)}2] (R=Me (1) or Ph (2))
The reaction between nickel atoms and LL under
metal vapour synthesis conditions yielded the tris-
(alkene)nickel(0) complex [Ni(CH2ꢀCHSiMe2OSiMe2-
CHꢀCHSiMe2)SiMe2CHꢀCH2)], [Ni(LL%L)] [8].
The X-ray molecular structure of crystalline 1 is
illustrated in Fig. 1. Table 1 provides a list of bond
lengths and angles. The molecule is dinuclear, having
,
Fig. 1. The molecular structure of [{Rh(ViSiMe2)2O(m-Cl)}2] (1). Selected bond lengths (A) and angles (°): Rh(1)–C(1)=2.141(5), Rh(1)–C(2)=
2.149(5), Rh(1)–C(5)=2.113(6), Rh(1)–C(6)=2.166(6); Rh(1)–Cl–Rh(2)=96.78(5), Si(1)–O(1)–Si(2)=133.0(3).

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C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
Table 1
the chelating LL ligand. It is noteworthy that crys-
talline 1 is diastereospecifically the rac- (rather than
meso-, or a mixture of the two) isomer.
a
,
Bond lengths (A) and angles (°) for [{Rh(ViSiMe2)2O(m-Cl)}2] (1)
,
Bond lengths (A)
Rh–Cl
The X-ray molecular structure of the dinuclear crys-
talline 2, having a similarly distorted square planar
arrangement about each four-coordinate rhodium, is
shown in Fig. 2, bond lengths and angles being pre-
sented in Table 2. Like 1, crystalline 2 is the rac-
diastereoisomer, but unlike in 1 the Rh(Cl)(Rh)Cl core
in 2 is puckered rather than (as in 1) planar, the angles
at Rh and Cl being similar, an average of 82.1(2) and
81.4(2)°, respectively.
The metallacyclic RhMSiOSi‘M’ fragment in each of
1 and 2 is in the chair conformation, as was previously
found for the chelated PtMSiOSi‘M’ fragments in the
various Pt(0)–LL complexes [3–6]. Some of the average
key bond distances and Si–O–Si% angles in 1 and 2 are
identical and unexceptional: Rh–M 2.02(1)°, CꢀC
2.392(2)
2.141(5)
2.113(6)
1.627(5)
1.850(6)
1.629(4)
1.848(7)
1.382(8)
Rh–Cl%
2.403(1)
2.149(5)
2.166(6)
1.846(6)
1.846(7)
1.880(6)
1.843(7)
1.387(8)
Rh–C(1)
Rh–C(5)
Si(1)–O
Si(1)–C(3)
Si(2)–O
Rh–C(2)
Rh–C(6)
Si(1)–C(2)
Si(1)–C(4)
Si(2)–C(6)
Si(2)–C(8)
C(5)–C(6)
Si(2)–C(7)
C(1)–C(2)
Bond angles (°)
Cl–Rh–Cl%
Cl–Rh–C(2)
83.22(5) Cl–Rh–C(1)
95.4(2)
149.4(2)
165.2(1)
86.9(2)
37.6(2)
93.8(2)
97.2(2)
96.78(5)
108.2(3)
108.8(3)
110.6(3)
109.1(3)
109.7(3)
109.6(3)
71.5(3)
70.9(3)
73.2(3)
69.0(4)
86.2(2)
168.6(1)
155.9(2)
89.5(1)
87.0(2)
112.4(2)
37.8(2)
108.6(2)
111.1(3)
109.5(3)
111.4(2)
108.4(3)
108.6(3)
133.0(3)
115.0(2)
129.5(5)
124.7(2)
121.9(4)
Cl–Rh–C(5)
Cl%–Rh–C(1)
Cl%–Rh–C(5)
C(1)–Rh–C(2)
C(1)–Rh–C(6)
C(2)–Rh–C(6)
Rh–Cl–Rh
O–Si(1)–C(3)
C(2)–Si(1)–C(3)
C(3)–Si(1)–C(4)
O–Si(2)–C(7)
C(6)–Si(2)–C(7)
C(7)–Si(2)–C(8)
Rh–C(1)–C(2)
Rh–C(2)–C(1)
Rh–C(5)–C(6)
Rh–C(6)–C(5)
Cl–Rh–C(6)
Cl%–Rh–C(2)
Cl%–Rh–C(6)
C(1)–Rh–C(5)
C(2)–Rh–C(5)
C(5)–Rh–C(6)
O–Si(1)–C(2)
O–Si(1)–C(4)
C(2)–Si(1)–C(4)
O–Si(2)–C(6)
O–Si(2)–C(8)
C(6)–Si(2)–C(8)
Si(1)–0–Si(2)
Rh–C(2)–Si(1)
Si(1)–C(2)–C(1)
Rh–C(6)–Si(2)
Si(2)–C(6)–C(5)
,
,
1.38(1) A, Rh–Cl 2.39(2) A and Si–O–Si 133.0(3)°; cf.
,
Rh–Cl 2.38(1) A in [{Rh(m-Cl)(COD)}2] [13] and for
,
,
[{Pt(LL)}2(m-LL)]: Pt–M 2.07(2) A, CꢀC 1.39(3) A and
Si–O–Si 134.7(8)° for the chelating Pt(LL) [4a].
2.3. NMR spectroscopic studies on the chloro(di6inyl-
disiloxane)rhodium(I) complexes 1 and 6
1
The H-NMR spectrum of [{Rh(LL)(m-Cl)}2] (1) in
[2H8]-toluene at 297 K showed broad signals due to the
vinylic (l 2.8–4.5) and methyl (l −0.5 to +0.5)
protons, which sharpened upon cooling to 253 K (for
data see Section 3.1). At 253 K, two pairs of methyl
signals (equatorial Mee and axial Mea) in a ratio of 2:1
were observed, indicating the presence of two isomers.
The vinylic protons at l 2.8–4.5 were shifted by ca. 2
ppm to a lower frequency relative to the values in the
free ligand LL (l 5.8–6.8). Following Cramer’s descrip-
tion for ‘inner’ (H3 in I) and ‘outer’ (H1 and H2 in I)
hydrogens [14], H1 and H2 are assigned to the signals at
the higher frequency, at l 3.95 and 4.54, respectively; in
the light of the former showing the greater coupling
a Symmetry element (%) x, y, z.
1
constant to H3. Neither the geminal (2H/3H) nor H–
103Rh coupling was observed.
The 13C{1H}-NMR spectrum of 1 in [2H8]-toluene at
303 K (see Section 3.1) also provided evidence for the
existence of two isomers in solution. The CH2H3 signal
for each isomer is believed to be at the higher frequency
than that of CH1, a result confirmed by recording the
proton-coupled spectrum. The 29Si{1H}-NMR spec-
trum of 1 in [2H8]-toluene at 253 K showed two sharp
signals in a ratio of ca. 2:1 (see Section 3.1).
We conclude that the isomers of 1 in solution are
probably the rac- (the major, as in the crystal) and
meso-diastereoisomers, also by analogy with the con-
clusion drawn from a more detailed study on the
[{Rh(LL)(m-Cl)}2] system (vide infra).
Fig. 2. The molecular structure of [{Rh(ViSiPh2)2O(m-Cl)}2] (2).
,
Selected bond lengths (A) and angles (°): Rh(1)–C(1)=2.183(11),
Rh–C(2)=2.124(12), Rh–C(3)=2.149(10), Rh–C(4)=2.128(11);
Rh(1)–Cl(1)–Rh(2)=81.25(9), Si(1)–O(1)–Si(2)=134.7(6).
an inversion centre at the mid-point of the central
Rh(Cl)(Rh)Cl rhombus, the angle at Rh being narrower
at Rh, average 83.2(1)°, than that at Cl, average
96.8(1)°. The local geometry at each four-coordinate
rhodium is thus distorted square planar: RhCl2M2, M
being the mid-point of each orthogonal vinyl group of

C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
369
Table 2 (Continued)
Table 2
Selected bond lengths (A) and angles (°) for 2
,
C(7)–Rh(2)–Cl(1)
C(8)–Rh(2)–Cl(1)
C(5)–Rh(2)–Cl(1)
Cl(2)–Rh(2)–Cl(1)
C(6)–Rh(2)–Rh(1)
C(7)–Rh(2)–Rh(1)
C(8)–Rh(2)–Rh(1)
C(5)–Rh(2)–Rh(1)
Cl(2)–Rh(2)–Rh(1)
Cl(1)–Rh(2)–Rh(1)
Rh(1)–Cl(1)–Rh(2)
155.4(3)
164.3(4)
89.5(4)
,
Bond lengths (A)
Rh(1)–C(2)
Rh(1)–C(4)
Rh(1)–C(3)
Rh(1)–C(1)
Rh(1)–Cl(1)
Rh(1)–Cl(2)
Rh(1)–Rh(2)
Rh(2)–C(6)
Rh(2)–C(7)
Rh(2)–C(8)
Rh(2)–C(5)
Rh(2)–Cl(2)
Rh(2)–Cl(1)
Si(2)–O(1)
Si(2)–C(1)
Si(2)–C(35)
Si(2)–C(21)
Si(3)–O(2)
Si(3)–C(26)
Si(3)–C(7)
Si(3)–C(50)
Si(1)–O(1)
Si(1)–C(15)
Si(1)–C(3)
Si(1)–C(25)
Si(4)–O(2)
Si(4)–C(5)
Si(4)–C(23)
Si(4)–C(41)
2.125(12)
2.128(11)
2.149(10)
2.183(11)
2.381(3)
83.17(12)
135.6(4)
108.4(3)
137.4(4)
120.7(3)
49.45(8)
49.25(8)
81.25(9)
2.387(3)
3.1063(14)
2.090(12)
2.150(11)
2.172(11)
2.188(12)
2.379(3)
2.390(3)
1.622(8)
1.818(14)
1.831(12)
1.873(12)
1.637(9)
1.823(13)
1.846(12)
1.862(13)
1.634(8)
1.824(12)
1.842(10)
1.870(12)
1.627(8)
1.850(15)
1.851(12)
1.881(13)
1
A series of variable temperature H-NMR spectra of
2 in [2H8]-toluene is illustrated in Fig. 3 for the vinyl
region, and indicates that this is a dynamic system
containing two isomers; the low temperature (241 K)
limiting spectral data are recorded in Section 3.2 to-
gether with the assignments. Coupling to 103Rh, as for
1, was not observed. The vinyl groups gave rise, as for
1, to two doublets and a doublet of doublets. At 241 K,
in addition to the three major signals for the vinyl
protons, there were also smaller signals of similar multi-
plicity, attributed to the minor diastereoisomers. At 378
K, only one set of peaks was present, indicating that
the two isomers were undergoing fast exchange; the
coalescence temperature was in the range of 304–308
K. Unlike in 1, the 29Si{1H} spectrum revealed only a
single signal, albeit broad, at l 5.3.
Bond angles (°)
C(2)–Rh(1)–C(4)
C(2)–Rh(1)–C(3)
C(4)–Rh(1)–C(3)
C(2)–Rh(1)–C(1)
C(4)–Rh(1)–C(1)
C(3)–Rh(1)–C(1)
C(2)–Rh(1)–Cl(1)
C(4)–Rh(1)–Cl(1)
C(3)–Rh(1)–Cl(1)
C(1)–Rh(1)–Cl(1)
C(2)–Rh(1)–Cl(2)
C(4)–Rh(1)–Cl(2)
C(3)–Rh(1)–Cl(2)
C(1)–Rh(1)–Cl(2)
Cl(1)–Rh(1)–Cl(2)
C(2)–Rh(1)–Rh(2)
C(4)–Rh(1)–Rh(2)
C(3)–Rh(1)–Rh(2)
C(1)–Rh(1)–Rh(2)
Cl(1)–Rh(1)–Rh(2)
Cl(2)–Rh(1)–Rh(2)
C(6)–Rh(2)–C(7)
C(6)–Rh(2)–C(8)
C(7)–Rh(2)–C(8)
C(6)–Rh(2)–C(5)
C(7)–Rh(2)–C(5)
C(8)–Rh(2)–C(5)
C(6)–Rh(2)–Cl(2)
C(7)–Rh(2)–Cl(2)
C(8)–Rh(2)–Cl(2)
C(5)–Rh(2)–Cl(2)
C(6)–Rh(2)–Cl(1)
86.3(5)
113.8(5)
38.0(4)
38.3(5)
93.1(5)
98.7(4)
146.7(4)
95.7(4)
85.7(3)
170.2(3)
86.8(4)
165.4(4)
155.3(3)
89.4(3)
83.18(11)
101.2(4)
120.0(4)
132.3(3)
128.3(3)
49.50(8)
49.20(8)
112.0(5)
86.9(5)
38.9(5)
37.4(4)
96.7(5)
94.7(5)
147.8(3)
87.4(3)
94.2(4)
170.1(3)
87.2(4)
The result of a saturation transfer experiment, car-
ried out on the phenyl region of the 1H-NMR spectrum
2
of 2 in H8-toluene at 353 K, is shown in Fig. 4. Upon
irradiation at the frequency of the signal at l 8.25, there
was a reduction in the intensity of the peak at l 7.89;
this indicates that at this temperature the gem-phenyl
groups of the two isomers 2a and 2b (i.e. the same
proton occurs at l 8.25 in one isomer and l 7.89 in the
other) were exchanging.
The proposed mechanism for this dynamic process is
shown in Scheme 2. The rac- and meso-diastereoiso-
mers are represented by 2a and 2b, respectively. The
scheme shows how dissociation, then rotation of the
vinyl group of one of the divinyldisiloxane ligands can
cause the interconversion of the isomers. The intermedi-
ate 8 has the L%L% ligand in a staggered (or ‘twisted
chair’) conformation similar to the intermediates ob-
served in the dynamic processes involving [Ni(LL%L)]
[12] and [Rh(h5-C5H5)(LL)] [9].

370
C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
Fig. 3. Variable temperature 1H-NMR spectral studies on [{Rh{ViSiPh2)2O(m-Cl)] (2) recorded in [2H8] toluene, 500 MHz.
To establish whether the process was proceeding
2.4. Synthesis, NMR spectra and X-ray molecular
structure of [{Rh(Vi2SiMe2)(v-Cl)}2] (7)
via the dissociation of the vinyl groups, a small
amount of the free L%L% ligand (CH2ꢀCHSiPh2)2O was
added to the sample and the frequency of a signal
due to bound vinyl protons (in this case the doublet
at l 4.40 due to the methylene proton H2 (see I) cis
to the methine proton H1) was irradiated. At 353 K,
there was no reduction in the intensity of any signal.
However, at 400 K, there was a reduction in the
intensity of the peaks at l 6.40 due to the equivalent
protons of the free ligand (Fig. 5). These results show
that the process involves dissociation of the vinyl
groups, which at elevated temperatures can be inter-
molecular.
We have previously reported the synthesis of the
binuclear
divinyldimethylsilane(triphenylphosphine)-
nickel(0) complex [{Ni(m-Vi2SiMe2)(PPh3)}2] (8) [6],
which featured the divinylsilane in a bridging mode II.
We now describe the orange–red crystalline divinylsilane
complex [{Rh(Vi2SiMe2)(m-Cl)}2] (7), prepared by the
displacement of ethylene ligands from [{Rh-
(CH2ꢀCH2)2)(m-Cl)}2], Eq. (1). Complex 7 was air-sensi-
tive, both in the solid state and in solution; it was readily
soluble in both aliphatic and aromatic hydrocarbons.
The 1H and 13C{1H}-NMR spectral data for the
complexes [Rh(LL)(PR%)] R=Ph (3), C6H11-c (4) or
3
C6H4Me-p (5) and [Rh(L%L%)P(C6H4Me-p)3] (6) are
shown in Sections 3.3, 3.4, 3.5 and 3.6, and 29Si{1H}
also for 5 (Section 3.5) and 6.
The 31P{1H}-NMR spectra for each of the com-
plexes 3–6 showed a doublet, with coupling between
the rhodium and phosphorus atoms in the range of
176–186 Hz. These values are closer to those for a
trans-alkene(tertiary phosphine)rhodium(I) complex
than its cis analogue.
The 1H and 13C{1H}-NMR spectra for each of
these complexes displayed only one vinyl environ-
1
ment; no H–103Rh coupling was observed. These re-
sults suggest that the chelating vinylsiloxane ligand in
complexes 3–6 is fluxional, exhibiting dynamic be-
haviour similar to that of the COD ligand in
[Rh(COD)(PPh3)Cl] [15].
(1)

C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
371
Multinuclear NMR spectra of 7 in [2H8]-toluene are
recorded in Section 3.7. In the 1H-NMR spectrum
separate signals were shown for the methyl protons,
consistent with those arising from axial (Mea) and
equatorial (Mee) substituents at silicon in the chelating
ligand. The assignments, shown in III, were made on
the basis of a pair of nOe experiments, which showed
that Mea gave rise to a stronger nOe for H3 than H1,
whereas Mee produced a strong nOe upon H1. Unlike
the ambient temperature spectrum of 2, no minor sig-
nals were observed for 7, which only appeared upon
cooling; as for 2, these are attributed to the two
diastereoisomers. The coalescence temperature was in
the range of 239–243 K; similar features were observed
in the 13C{1H}-NMR spectra, showing twice the num-
ber of peaks at 200 K than at 313 K. Only C-2 showed
coupling to 103Rh. The 29Si{1H}-NMR spectral chemi-
cal shift at l −4.4 is 7.5 ppm to a higher frequency
compared with that in the free silane Vi2SiMe2.
The X-ray molecular structure of crystalline 7 is
shown in Fig. 6; structural parameters are listed in
Table 3. As for 1 and 2, there is a distorted square
planar geometry about each rhodium atom, with the
vinyl groups orthogonal to the plane. The square pla-
nar geometry is likely to place less strain on the
molecule than the trigonal planar geometry for Ni(0) in
[{Ni(m-Vi2SiMe2)(PPh3)}2] (8), enabling the divinylsi-
lane molecule in 7 to act as a chelating ligand. The
average bond angle of 93.8°, formed by the centroid M
of each of the two vinyl groups and the silicon atom, is
significantly smaller than the 117.0° observed in [{Ni(m-
Vi2SiMe2)(PPh3)}2] [6]. Crystalline 7 is the meso-
diastereoisomer, a result which contrasts with those for
1 and 2. As for 2, the Rh(Cl)(Rh)Cl core in 7 is
puckered, the angle at rhodium being slightly wider
(average 85.7(1)°) than that at Cl, average 82.1(3)°.
Other geometric parameters are unexceptional.
3. Experimental
3.1. Synthesis of [{Rh(ViSiMe2)2O(v-Cl)}2] (1)
Tetramethyldivinyldisiloxane (5 ml) was added to a
rapidly stirring yellow suspension of [{Rh(C8H14)2(m-
Cl)}2] (1230 mg, 1.7 mmol) in toluene (15 ml) at 25°C
to give a deep red solution. The reaction mixture was
stirred for 1 h at 25°C. The volatiles were removed
under reduced pressure. The residual red solid was
dissolved in toluene (10 ml) and filtered through Celite
(2×2.5 ml), then washed with toluene (2×5 ml). The
combined filtrate and washings were concentrated un-
der reduced pressure to ca. 2 ml, yielding the red
precipitate of 1 (900 mg, 1.39 mmol, 82%), which was
filtered, washed with pentane (2×3 ml) and dried in
vacuo. Red crystals (m.p. 130–131°C) suitable for X-
ray diffraction were obtained by dissolving the red solid
in the minimum amount of toluene and cooling the
solution to 0°C.
Anal. Found: C, 29.3; H, 5.0. C54H48Cl2O2Rh2Si4.
1
Calc. C, 29.6; H, 5.3%. H-NMR (C7D8, 253 K, 360
Fig. 4. Saturation transfer studies on [{Rh(ViSiPh2)2O(m-Cl)}2] (2)
(phenyl region) recorded in [2H8]-toluene at 353 K, 500 MHz. The
upper spectrum results from subtracting the effect of irradiating the
frequency of the peak at l 8.25 from the normal spectrum at this
temperature (shown in the lower spectrum).
MHz) major isomer [minor isomer]: l 0.03 [−0.01] (s,
Mee, 12H), 0.54 [0.43] (s, Mea, 12H), 2.98 [2.94] (d, H3,
4H), 3.59 [3.63] (dd, H1, 4H), 4.54 [4.44] (d, H2, 4H),
3J(1H1–1H2)=11.9 Hz, 3J(1H1–1H3)=14.5 Hz.

372
C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
Scheme 2.
13C{1H}-NMR (C7D8, 303 K, 90 MHz): l −0.9–1.9
(s, Mee), 1.5 [0.5] (s, Mea), 60.0 [62.4] (d, C1), 66.7 (d,
C2), 1J(13C1–103Rh)=13.7 Hz, 1J(13C2–103Rh)=12.5
Hz. 29Si{1H}-NMR (C7D8, 253 K, 72 MHz): l 5.3
(s).
3.3. Synthesis of [Rh{(ViSiMe2)2O}(PPh3)Cl] (3)
Triphenylphosphine (170 mg, 0.64 mmol) was
added to a rapidly stirring solution of 1 (190 mg,
0.29 mmol) in toluene (8 ml) at 25°C. The resultant
solution was concentrated to ca. 2 ml under reduced
pressure. The addition of pentane (4 ml) caused pre-
cipitation of the yellow solid 3 (250 mg, 0.41 mmol,
74%), which was filtered, washed with pentane (2×3
3.2. Synthesis of [{Rh(ViSiPh2)2O(v-Cl)}] (2)
Tetraphenyldivinyldisiloxane (0.20 g, 0.47 mmol)
was added to
a
rapidly stirred suspension of
[{Rh(C8H14-c)2(m-Cl)}2] (0.14 g, 0.21 mmol) in toluene
(5 ml). The reaction mixture was stirred for 1 h, the
colour changing from yellow–orange to deep red. The
mixture was filtered through Celite and then washed
with toluene; the solvent and cyclooctene were re-
moved from the filtrate under reduced pressure to
yield a deep red oil which upon addition of diethyl
ether (2 ml) precipitated deep red crystals of 2 (0. 18
g, 0.16 mmol), m.p. 117–119°C. Crystals suitable for
X-ray diffraction were obtained by dissolving the
solid in the minimum amount of toluene followed by
adding an equal amount of diethyl ether; these sol-
vents were allowed to diffuse during 72 h at 25°C.
Anal. Found: C, 56.7; H, 4.3. C54H48Cl2O2Rh2Si4.
1
Calc. C, 58.7; H, 4.6%. H-NMR (C7D8, 241 K, 500
MHz) major isomer [minor isomer]: l 2.98 [3.30] (d,
H3, 4H), 4.03 [4.26] (dd, H1, 4H), 4.40 (d, H2, 4H),
7.04–7.98 (m, Ph, 40H), 3J(1H1–1H2)=12.2 Hz,
3J(1H1–1H3)=15.6 Hz. 13C{1H}-NMR (C7D8, 298 K,
125.8 MHz): l 58.9 (s, C1), 71.0 (d, C2), 127.6–136.6
(m, Ph), 1J(13C2–103Rh)=10.4 Hz. 29Si{1H}-NMR
(C7D8, 298 K, 99.4 MHz): l −12.1 [−12.15] (s).
Fig. 5. Saturation transfer studies on [{Rh(ViSiPh2)2O(m-Cl)}2] (2)
(phenyl region) recorded in [2H8]-toluene at 413 K, 500 MHz. The
upper spectrum results from subtracting the effect of irradiating the
frequency of the peak at l 4.40 from the normal spectrum at this
temperature (shown in the lower spectrum).

C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
373
,
Fig. 6. The molecular structure of [{Rh(Vi2SiMe2)(m-Cl)}2] (7). Selected bond lengths (A) and angles (°): Rh(1)–C(1)=2.146(8), Rh–C(2)=
2.134(10), Rh–C(3)=2.141(8), Rh–C(4)=2.135(9); Rh(1)–Cl(1)–Rh(2)=82.03(7).
ml) and dried in vacuo. Yellow crystals, m.p. 174–
176°C, were obtained by dissolving the yellow solid in
the minimum amount of toluene and cooling the solu-
tion to −30°C.
Anal. Found: C, 54.9; H, 6.1. C29H39ClOPRhSi2.
Calc. C, 55.4; H, 6.3%. H-NMR (C7D8, 298 K, 500
MHz): l 0.29 (s, Mee, 6H), 0.58 (s, Mea, 6H), 1.95 (s,
MeC6H4, 9H), 2.24 (m, H1, 2H), 2.68 (d, H2, 2H),
4.01 (d, H3, 2H), 6.80–7.85 (m, MeC6H4, 12H),
1
Anal. Found: C, 52.0; H, 8.1. C26H33ClOPRhSi2.
1
3J(1H1–1H2)=12.0
Hz,
3J(1H1-1H3)=14.1
Hz.
Calc. C, 51.6; H, 8.9%. H-NMR (C7D8, 241 K, 500
13C{1H}-NMR (C7D8, 298 K, 125.8 MHz): l 3.0 (s,
Mee), 3.7 (s, Mea), 21.1 (s, MeC6H4), 53.0 (d, C1),
54.2 (d, C2), 128.9–139.9 (m, MeC6H4), 1J(13C1–
MHz): l 0.26 (s, Mee, 6H), 0.50 (s, Mea, 6H), 2.27 (m,
H1, 2H), 2.56 (d, H2, 2H), 3.95 (d, H3, 2H), 6.8–7.8 (m,
3
3
Ph, 15H), J(1H1–1H2)=10.4 Hz, J(1H1–1H3)=14.2
Hz. 13C{1H}-NMR (C7D8, 298 K, 125.8 MHz): l 3.3 (s,
Mee), 3.6 (s, Mea), 53.5 (d, C1), 54.0 (d, C2), 125–136
(m, Ph), 1J(13C1–103Rh)=16.7 Hz, 1J(13C2-103Rh)=
14.7 Hz. 31P{1H}-NMR (C7D8, 303 K, 32 MHz): l 51.2
1
103Rh)=17.0 Hz, J(13C2–103Rh)=13.2 Hz. 29Si{1H}-
NMR (C7D8, 298 K, 99.4 MHz)
l
5.7 (dd),
3J(29Si–31P)=1.7
Hz,
2J(29Si–103Rh)=1.9
Hz.
31P{1H}-NMR (C7D8, 298 K, 101 MHz): l 52.4 (d),
1J(31P–103Rh)=182 Hz.
(d), J(31P–103Rh)=186 Hz.
1
3.4. Synthesis of [Rh{(ViSiMe2)2O}(PCy3)Cl] (4)
3.6. Synthesis of [Rh(ViSiPh2)2O}P(C6H4Me-p)3Cl] (6)
The yellow complex 4 (200 mg, 0.40 mmol, 70%),
m.p. 126–128°C, was prepared in a similar manner to
3, except that dichloromethane was used as the reaction
solvent instead of toluene.
The yellow crystalline complex 6 (0.12 g, 0.14
mmol, 78%), m.p. 194–196°C, was prepared in a sim-
ilar manner to 3.
Anal. Found: C, 67.0; H, 5.3. C49H47ClOPRhSi2.
Anal. Found: C, 54.2; H, 5.7. C26H33ClOPRhSi2.
1
Calc. C, 67.1; H, 5.4%. H-NMR (C7D8, 298 K, 500
1
Calc. C, 53.2; H, 5.7%. H-NMR (CD2Cl2, 241 K, 500
MHz): l 2.02 (s, MeC6H4, 9H), 2.81 (d, H2, 2H),
3.16 (dd, H1, 2H), 4.12 (d, H3, 2H), 6.75–7.82 (m,
MeC6H4, 12H), 7.01–8.15 (m, Ph, 20H), 3J(1H1–
1H2)=10.6 Hz, 3J(1H1–1H3)=13.9 Hz. 13C{1H}-
MHz): l −0.03 (s, Mee, 6H), 0.45 (s, Mea, 6H),
1.5–2.6 (m, Cy, 33H), 2.23 (d, H2, 2H), 2.49 (dd, H1,
3
3
2H), 2.87 (d, H3, 2H), J(1H1–1H2)=10.6 Hz, J(1H1–
1H3)=14.0 Hz. 31P{1H}-NMR (C7D8, 303 K, 32 MHz):
l 48.9 (d), J(31P–103Rh)=176 Hz.
1
NMR (C7D8, 298 K, 125.8 MHz):
l 21.3 (s,
MeC6H4), 57.8 (d, C1), 65.3 (d, C2), 128.8–139.9 (m,
1
MeC6H4), 128.3–137.1 (m, Ph), J(13C1–103Rh)=12.4
3.5. Synthesis of [Rh{(ViSiMe2)2O}P(C6H4Me-p)3Cl]
(5)
Hz, 1J(13C2–103Rh)=10.3 MHz. 29Si{1H}-NMR
(C7D8, 298 K, 99.4 MHz) l −11.9 (dd), 3J(29Si–
2
31P)=1.7 Hz, J(29Si–103Rh)=1.8 Hz. 31P{1H}-NMR
The yellow–orange crystalline complex 5 (0.32 g,
0.50 mmol, 73%), m.p. 179–181°C, was prepared in a
similar manner to 3.
1
(C7D8, 298 K, 101 MHz): l 49.7 (d), J(31P–103Rh)=
179 Hz.

374
C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
Table 4
3.7. Synthesis of [{Rh(Vi2SiMe2)(v-Cl)}2] (7)
Crystal data and structural refinement parameters for 1, 2 and 7
Divinyldimethylsilane (0.5 ml) was added to a
rapidly stirring suspension of [{Rh(C2H4)2(m-Cl)}2]
(0.17 g, 0.44 mmol) in toluene (5 ml). The reaction
mixture was allowed to stir for 3 h. The solvent and
ethylene were removed under reduced pressure. The
residual orange–red solid was dissolved in toluene (5
ml), filtered through Celite and washed with toluene
(5 ml). The combined filtrate and washings were con-
centrated under reduced pressure to ca. 2 ml and
stored at −30°C for 48 h, to yield orange red crys-
tals of 7 (0.14 g, 0.28 mmol, 64%), m.p. 96–98°C.
X-ray quality crystals were grown from n-pentane.
Anal. Found: C, 28.8; H, 4.8. C12H24Cl2Rh2Si2.
1
2
7
Formula
C16H36Cl2O2Rh2Si4 C56H52Cl2O2Rh2Si4 C12H24Cl2Rh2Si2
M
649.5
1146.1
501.2
Crystal system Triclinic
Monoclinic
15.118(5)
16.305(5)
21.784(6)
Monoclinic
10.486(3)
14.339(3)
12.202(2)
,
a (A)
6.417(2)
8.290(4)
13.197(3)
72.91(3)
86.94(2)
78.52(2)
656.9
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
107.30(3)
90.30(2)
3
,
U (A )
5125.3
4
1834.7
Z
1
4
Dcalc. (g cm−3
Space group
qmax for data
)
1.64
1.48
P21/c
25
1.82
(
P1 (no. 2)
P21/c (no. 14)
1
25
Calc. C, 28.8; H, 4.8%. H-NMR (C7D8, 298 K, 500
collection (°)
Unique
MHz): l −0.37 (s, Mee, 3H), 0.54 (s, Mea, 3H), 2.58
(m, H3, 2H), 3.24 (dd, H1, 2H), 3.58 (m, H2, 2H),
3J(1H1–1H2)=11.2 Hz, 3J(1H1–1H3)=15.4 Hz,
2J(1H2–103Rh)=1.4 Hz, 2J(1H3–103Rh)=1.3 Hz.
13C{1H}-NMR (C7D8, 313 K, 125.8 MHz): l 1.2 (s,
9308
1898
6080
4828
3226
1991
reflections
Reflections
with I\2|(I)
R1 [for I\2|(I)] 0.039
wR2 0.04
(for all data)
0.085
0.044
0.086
0.2159
Table 3
,
Bond lengths (A) and angles (°) for [(Rh(CH2ꢀCH)2SiMe2(m-Cl)}2]
a
(7)
,
Bond lengths (A)
1
Mee), 6.3 (s, Mea), 57.2 (s, C1), 72.0 (d, C2), J(13C2–
103Rh)=14.0 Hz. 29Si{1H}-NMR (C7D8, 298 K, 99.4
MHz): l −4.2 (s).
Rh(1)–Cl(1)
Rh(1)–M(2)
Rh(1)–C(1)
Rh(1)–C(3)
Rh(2)–Cl(1)
Rh(2)–M(3)
Rh(2)–C(7)
Rh(2)–C(9)
Rh(1)···Rh(2)
Si(1)–C(3)
Si(1)–C(1)
Si(2)–C(11)
Si(2)–C(9)
C(3)–C(4)
C(9)–C(10)
2.389(2)
2.024(9)
2.146(8)
2.141(8)
2.385(2)
2.019(9)
2.145(8)
2.135(8)
3.133(1)
1.852(9)
1.867(8)
1.850(9)
1.865(9)
Rh(1)–Cl(2)
Rh(1)–M(1)
Rh(1)–C(2)
Rh(1)–C(4)
Rh(2)–Cl(2)
Rh(2)–M(4)
Rh(2)–C(8)
Rh(2)–C(10)
Si(1)–C(6)
2.376(2)
2.026(10)
2.134(10)
2.135(9)
2.385(2)
2.020(9)
2.123(9)
2.135(9)
1.847(8)
1.856(8)
1.850(8)
1.850(9)
1.384(12)
1.387(12)
3.8. X-ray structure determinations for 1, 2 and 7
Intensities were measured on an Enraf–Nonius
CAD 4 diffractometer (1 and 7) or a Mar Research
Image Plate system for 2 at 293 K with monochro-
Si(1)–C(5)
Si(2)–C(12)
Si(2)–C(7)
,
matic Mo–Ka radiation (u=0.71071 A). Corrections
C(1)–C(2)
for absorption were applied using DIFABS for 1 and
using psi-scan measurements for 2 and 7. Refinement
was by full-matrix least-squares on F, using Enraf–
Nonius MOLEN programs for 1 and on F2 using all
reflections and SHELX-93 for 2 and 7. Non-hydrogen
atoms were refined anisotropically. For 1, hydrogen
atoms were fixed at calculated positions, except for
the vinyl H atoms which were freely refined. For 2
and 7, H atoms were included in riding mode (Table
4).
1.381(19) C(7)–C(8)
1.380(19)
Bond angles (°)
M(2)–Rh(1)–M(1)
M(1)–Rh(1)–Cl(2)
M(1)–Rh(1)–Cl(1)
M(3)–Rh(2)–M(4)
M(4)–Rh(2)–Cl(2)
M(4)–Rh(2)–Cl(1)
Rh(2)–Cl(1)–Rh(1)
C(6)–Si(1)–C(3)
C(3)–Si(1)–C(5)
C(3)–Si(1)–C(1)
C(12)–Si(2)–C(11)
C(11)–Si(2)–C(7)
C(11)–Si(2)–C(9)
C(2)–C(1)–Si(1)
C(8)–C(7)–Si(2)
89.1(3)
175.4(3)
92.7(3)
89.6(3)
92.2(3)
175.1(3)
M(2)–Rh(1)–Cl(2)
92.5(3)
177.9(3)
85.69(8)
177.7(3)
92.7(3)
85.59(8)
82.31(7)
111.1(4)
116.1(4)
108.8(4)
115.9(4)
113.9(4)
93.4(7)
M(2)–Rh(1)–Cl(1)
Cl(2)–Rh(1)–Cl(1)
M(3)–Rh(2)–Cl(9)
M(3)–Rh(2)–Cl(1)
Cl(2)–Rh(2)–Cl(1)
82.03(7) Rh(1)–Cl(2)–Rh(2)
116.2(4)
109.1(4)
94.3(4)
109.8(4)
111.3(4)
111.7(4)
124.7(7)
121.6(7)
C(6)–Si(1)–C(5)
C(6)–Si(1)–C(1)
C(5)–Si(1)–C(1)
C(12)–Si(2)–C(7)
C(12)–Si(2)–C(9)
C(7)–Si(2)–C(9)
C(4)–C(3)–Si(19)
C(10)–C(9)–Si(2)
Acknowledgements
194.5(7)
191.0(7)
We thank the EPSRC and Dow Corning Ltd.
(Barry) for the awards of CASE studentships to C.
MacBeath and N.J.W. Warhurst and Dr Peter Hu-
pfield for his interest and encouragement.
a M1, M2, M3 and M4 are the midpoints of the C(1)–C(2),
C(3)–C(4), C(7)–C(8) and C(9)–C(10) bonds, respectively.

C.J. Cardin et al. / Journal of Organometallic Chemistry 584 (1999) 366–375
375
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