Photochemical reactions of [CH2(η5-C 5H4)2][Rh(C2H4) 2]2 with silanes: Evidence for Si-C and C-H activation pathways

Article abstract of DOI:10.1039/b417171c

Photochemical reaction of [CH₂(η^5-C ₅H₄)₂][Rh(C₂H₄) ₂]₂ 1 with dmso led to the stepwise formation of [CH ₂(η⁵-C₅H₄)₂] [Rh(C₂H₄)₂][Rh(C₂H ₄)(dmso)] 2a and [CH₂(η⁵-C ₅H₄)₂][Rh(C₂H₄)(dmso)] ₂ 2b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH₂(η⁵-C₅H ₄)₂][Rh(CH₂=CHSiMe₃) ₂]₂, 3a,3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d ₆-benzene, H/D exchange between the solvent and the α-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH₂(η⁵-C₅H ₄)₂][Rh(C₂H₄)₂][Rh(C ₂H₄)(η²-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et₃SiH yielded the sequential substitution products [CH₂(η⁵-C₅H₄) ₂][Rh(C₂H₄)₂][Rh(C₂H ₄)(SiEt₃)H] 4a, [CH₂(η⁵-C ₅H₄)₂][Rh(C₂H₄)(SiEt ₃)H]₂ 4b, [CH₂(η⁵-C ₅H₄)₂]-[Rh(C₂H₄) (SiEt₃)H][Rh(SiEt₃)₂(H)₂] 4c and [CH₂(η⁵-C₅H₄) ₂][Rh(SiEt₃)₂(H)₂]₂ 4d; deuteration of the α-ring proton sites, and all the silyl protons, of 4d was demonstrated in d₆-benzene. This reaction is further complicated by the formation of two Si-C bond activation products, [CH₂(η ⁵-C₅H₄)₂][RhH(μ-SiEt ₂)]₂ 5 and [CH₂(η⁵-C ₅H₄)₂][(RhEt)(RhH)(μ-SiEt₂) ₂] 6. Complex 5 was also produced when 1 was photolysed with Et ₂SiH₂. When the photochemical reactions with Et ₃SiH were repeated at low temperatures, two isomers of the unstable C-H activation products, the vinyl hydrides [CH₂(η⁵- C₅H₄)₂][{Rh(SiEt₃)H}{Rh(SiEt ₃)}(μ-η¹,η²-CH=CH₂)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(η⁵-C₅H₄)CH ₂(C₅H₃SiEt₃)][Rh(SiEt ₃)₂(H)₂]₂ 8 while 4b formed [CH ₂(C₅H₃SiEt₃)₂] [Rh(SiEt₃)₂(H)₂]₂ (9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me₃SiH yielded the expected products [CH₂(η ⁵-C₅H₄)₂][Rh(C₂H ₄)₂][Rh(C₂H₄)(SiMe₃)H] 10a, [CH₂(η⁵-C₅H₄) ₂][Rh(C₂H₄)(SiMe₃)H]₂ 10b, [CH₂(η⁵-C₅H₄) ₂][Rh(C₂H₄)(SiMe₃)H][Rh(SiMe ₃)₂(H)₂] 10c and [CH₂(η ⁵-C₅H₄)₂][Rh(SiMe₃) ₂(H)₂]₂ 10d. However, three Si-C bond activation products, [CH₂(η⁵-C₅H ₄)₂][(RhMe)(RhH)(μ-SiMe₂)₂] 11, [CH₂(η⁵-C₅H₄) ₂][(Rh{SiMe₃})(RhMe)(μ-SiMe₂)₂] 12 and [CH₂(η⁵-C₅H₄) ₂][(Rh{SiMe₃})(RhH)(μ-SiMe₂)₂] 13 were also obtained in these reactions. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b417171c

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
5
Photochemical reactions of [CH (g -C H ) ][Rh(C H ) ] with
2
5
4 2
2
4 2 2
silanes: evidence for Si–C and C–H activation pathways†
Jenny L. Cunningham and Simon B. Duckett*
Department of Chemistry, University of York, Heslington, York, UK YO10 5DD
Received 11th November 2004, Accepted 14th December 2004
First published as an Advance Article on the web 18th January 2005
5
Photochemical reaction of [CH
2
(g -C
5
H
4
)
2
][Rh(C
)(dmso)] 2a and [CH
vinyltrimethylsilane ultimately yields three isomeric products of [CH
c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in
-benzene, H/D exchange between the solvent and the a-proton of the vinylsilane is revealed. In addition evidence
2
H
4
)
2
]
2
1 with dmso led to the stepwise formation of
5
5
[CH
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H
4
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
)(dmso)]
][Rh(CH
2
2b. Photolysis of 1 with
=CHSiMe
, 3a,3b and
5
2
(g -C
5
H
4
)
2
2
3
)
2 2
]
3
d
6
5
2
for two isomers of the solvent complex [CH
related experiments when the photolysis was completed at low temperature without substrate, although no evidence
for H/D exchange was observed. Photolysis of 1 with Et SiH yielded the sequential substitution products
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H )(g -toluene)] was obtained in these and
4
3
5
5
5
[CH
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H
4
)(SiEt
3
)H] 4a, [CH
2
(g -C
][Rh(SiEt
-benzene. This reaction is further complicated by the
(g -C ][RhH(l-SiEt )] 5 and
] 6. Complex 5 was also produced when 1 was photolysed with Et
When the photochemical reactions with Et SiH were repeated at low temperatures, two isomers of the unstable C–H
activation products, the vinyl hydrides [CH
were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products
5
H
4
)
2
][Rh(C
2
H
4
)(SiEt
3
)H]
2
4b, [CH
2
(g -C
5
H
4
)
2
]-
5
[
Rh(C
2
H
4
)(SiEt
3
)H][Rh(SiEt
3
)
2
(H)
2
] 4c and [CH
2
(g -C
5
H
4
)
2
3
)
2
(H)
]
2 2
4d; deuteration of the a-ring proton
sites, and all the silyl protons, of 4d was demonstrated in d
6
5
formation of two Si–C bond activation products, [CH
2
5
H
4
)
2
2
2
5
[CH
2
(g -C
5
H
4
)
2
][(RhEt)(RhH)(l-SiEt
2
)
2
2
SiH
2
.
3
5
1
2
H
4
)
2
][{Rh(SiEt
3
)H}{Rh(SiEt
3
)}(l-g ,g -CH=CH
2
)] 7a and 7b,
2
(g -C
5
5
[
(g -C
5
H
4
)CH
2
(C
5
H
3
SiEt
3
)][Rh(SiEt
3
)
2
(H)
2
]
2
8 while 4b formed [CH
2
(C SiEt
5
H
3
3
)
2
][Rh(SiEt
SiH yielded the expected products
)(SiMe )H] 10b,
(H)
3
)
2
(H)
2
] (9a and 9b) upon
2
reaction with excess silane. The corresponding photochemical reaction with Me
3
5
5
[
[
CH
CH
2
(g -C
5
H
H
4
)
)
2
][Rh(C
][Rh(C
2
H
H
4
)
2
][Rh(C
2
H
4
)(SiMe
3
)H] 10a, [CH
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
3
2
5
5
2
(g -C
5
4
2
2
4
)(SiMe )H][Rh(SiMe
three Si–C bond activation products, [CH
3
3
)
2
(H)
2
] 10c and [CH
2
(g -C
5
H
4
)
2
][Rh(SiMe
3
)
2
2
] 10d. However,
2
5
2
(g -C
5
H
4
)
2
][(RhMe)(RhH)(l-SiMe
2
)
2
] 11,
5
5
[
CH
2
(g -C
5
H
4
)
2
][(Rh{SiMe
3
})(RhMe)(l-SiMe
2
)
2
] 12 and [CH
2
(g -C
5
H
4
)
2
][(Rh{SiMe
3
})(RhH)(l-SiMe
2
) ] 13 were
2
also obtained in these reactions.
Introduction
In 1965, Chalk and Harrod proposed a mechanism for the
7
metal catalysed hydrosilation of olefins. The mechanism of
this reaction involves hydride migration onto the bound alkene,
5
Since CpFe(CO)
a transition metal silyl complex, was reported by Wilkinson
in 1956, the number of such complexes has grown rapidly.
2
SiMe
3
(Cp = (g -C
5
H ), the first example of
1
5
in a H–M–SiR complex, followed by reductive elimination
3
2
of the alkyl and silyl groups to form an alkylsilane. Many
transition metal complexes have since been found to catalyse the
There continues to be much interest in this area because
transition metal complexes are used to catalyse organosilane
based transformations such as hydrosilation and polysilane
8
hydrosilation reaction including some containing Cp or Cp*
5
(
where Cp* = g -C
5
Me
5
) ligands. For example, in 1981, Maitlis
(l-Cl) ] catalysed the
3
formation. A popular route to complexes containing a silyl
9
et al. demonstrated that [(Cp*RhCl)
2
2
ligand involves the oxidative addition of the Si–H bond of a
hydrosilation and dehydrogenative silation of alkenes. During
2a
silane by a coordinatively unsaturated transition metal centre.
10
these studies, Cp*Rh(SiEt)
2
(H)
were characterised. Extended studies then showed that
Cp*Rh(SiEt (H) and Cp*Rh(C catalysed the conversion
of ethene with Et SiH to a 3 : 1 mixture of CH and
=CHSiEt
Si. At the same time, Perutz et al. showed that irradiation
of CpRh(C with R
SiH (where R = Me, Et) led to
CpRh(C )H and CpRh(SiR (H) , and the hydrosila-
tion products EtSiR and CH
=CHSiR3. In contrast to the Cp*
analogues, CpRh(C and CpRh(SiR (H) were not found
to be active hydrosilation catalysts but CpRh(C )(SiR )H
was shown to be involved. Deuterium labelling studies were
used to suggest a role for CpRh(C )(SiR )H which begins
with a [1,3]-H shift to generate CpRh(SiR )Et, and is followed
2
and Cp*Rh(C
2
H
4
)(SiEt
3
)H
4
Harris et al. have used ultrafast IR spectroscopy and ab initio
11
methods to investigate the process of Si–H bond activation. They
3
)
2
2
2
H
)
4 2
studied the photochemical reactions of CpM(CO)
Mn, Re) in neat Et SiH. Following irradiation, these tricarbonyl
complexes lose CO to generate the dicarbonyl species CpM(CO)
which were solvated by either the Si–H bond or the C–H bond
of the ethyl group of the Et SiH (solvent) prior to forming
CpM(CO) (SiEt )(H). While the Re product contains Re–H
and Re–Si 2-centre 2-electron bonds, the Mn species contains
3
(where M =
3
2
3
3
12
13
Et
4
2
2
H
4
)
2
3
2
H
4
)(SiR
3
3
)
2
2
3
3
2
2
3
2
H
4
)
2
3
)
2
2
2
H
4
3
5
a Mn–H–SiR
3
, 3-centre 2-electron bond. Kubas et al. have
14
shown that ‘incomplete’ and ‘complete’ silane oxidative addition
products can exist in equilibrium with each other in the case
2
H
4
3
3
of Mo(SiH
4
)(CO)(Et
2
PC
2
H
4
PEt
2
)
2
. One other example of the
by silyl migration onto the alkene. Seitz and Wrighton had
earlier proposed a similar mechanism for hydrosilation by
‘complete’ oxidative addition of Si–H bonds is provided by the
6
work of Graham who reported on the reaction of CpRh(CO)
with R , CH ). He observed that loss
SiH (where R = C
of CO led to the formation of CpRh(CO)(SiR )(H).
2
15
16
Co(CO)
4
(SiMe
3
). More recently, Brookhart et al. showed
)CH CH
catalysed the hydrosilation of 1-hexene by Et SiH
via a similar silyl migration. Brookhart et al. have also reported
that Cp*Co(SiPh H) (H) is formed by thermal reaction of
Cp*Co(CH (where R = H, SiMe ) with Ph SiH
=CHR)
3
6
H
5
2
C
6
H
5
that the cationic Co(III) complex [Cp*Co(P(OMe)
3
2
2
-
3
+
ꢀ −
4
l-H] BAr
3
17
†
Electronic supplementary information (ESI) available: NMR charac-
2
2
2
terisation of 1–14. See http://www.rsc.org/suppdata/dt/b4/b417171c/
2
2
3
2
2
.
7
4 4
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5

View Article Online
The reported catalytic utility of related Group 9 metal
systems has been expanded further in recent years, with (g -
a J. Young valve, in the glove box. Solvents were introduced by
vacuum transfer.
5
C
9
H
7
)Rh(C
to ethene i.e. hydroacylation. Brookhart et al. showed that
Cp*Co(CH was also an active hydroacylation
=CHSiMe
catalyst for the addition of aliphatic aldehydes to vinylsilanes. In
2
H
4
)
2
proving to catalyse the addition of aldehydes
18 19
Synthesis of Na(DME)Cp
2
)
3 2
Na(DME)Cp was synthesised according to the method of
29
20
Smart and Curtis. 300 ml of DME was added to 20 g
the same year, Berry et al. reported the formation of arylsilanes
◦
of Na dispersion at −78 C (dry-ice/acetone bath). To this
via thermal dehydrocoupling of C
H, CH , Cl, Br) with Et
and the Rh catalyst Cp*Rh(SiEt
have also revealed that Cp*Rh(CH
addition of alkenes to aromatic ketones. A further example of
6
H
5
X (where X = CF
3
, F,
t
stirred solution cyclopentadienyl (30 ml), freshly distilled from
dicyclopentadienyl, was slowly added to maintain a gentle
evolution of H . The mixture was refluxed for 2–3 h. The pale-
pink solid was then collected by filtration on a glass frit, washed
with several portions of hexane (3 × 10 ml) and dried under
vacuum. Typical yield = 150–200 g.
3
3
SiH in the presence of Bu-ethylene
21
3
)
2
(H)
2
. Brookhart et al.
catalyses the
=CHSiMe
)
2
2
3 2
22
the use of such complexes is provided by Hartwig et al. who
demonstrated a role for Cp*Rh complexes in the formation of
boron functionalised linear alkanes and functionalised arenes.
23
Synthesis of CH
CH (C was synthesised using a modification of the method
described by Schaltegger et al., in which the CH
obtained via distillation. Na(DME)Cp (8 g) was stirred in 50 ml
of THF. A solution of CH Cl (7.5 ml) in 10 ml of THF was
2
(C
5
H
5
)
2
Approximately 20 years ago, Bergman et al. reported the
5
preparation of the dicobalt complex [CH
via reaction of [CH (C ] with Co (CO)
Na and reaction with MeI generated the M–M bond contain-
2
(g -C
5
H
4
)
2
][Co(CO)
2
],
2
5
H
)
5 2
2
5
H
5
)
2
2
8
. Reduction with
30
2
Cp was
2
5
ing species [CH
2
(g -C
et al. synthesised [CH
related dinuclear rhodium complexes, and reported on a number
5
H
4
)
2
5
][Co(Me)(l-CO)]
2
. In 1985, Werner
2
2
24
2
(g -C
5
H
4
)
2
][Rh(C
2
H
4
)
]
2 2
(1) and several
prepared. Half the solution was transferred, via cannula, to the
main reaction vessel and the mixture was gently refluxed for
h. The mixture was allowed to cool prior to addition of the
solution and then refluxed for a further 3–
h. After cooling to 0 C, degassed distilled water (15 ml) was
added via syringe and the mixture shaken. The THF layer was
dried twice over MgSO , transferred into a clean Schlenk tube
and concentrated under vacuum.
25
of their thermal reactions. Here we describe how the dinuclear
1
5
rhodium complex [CH
2
(g -C
5
H
4
)
2
][Rh(C
SiH
2
H
4
)
2
]
2
1 reacts with
3
remaining CH
4
2
Cl
2
dmso, CH , Et
2
=CHSiMe
3
3
SiH, Et
2
2
and Me SiH under
◦
photochemical conditions. A number of novel reaction products
that are formed via C–H and Si–C bond activation pathways are
described.
4
Synthesis of CH
CH [(C )Tl]
Bitterwolf. TlOEt (11 g) was added, dropwise, to a stirred THF
solution of CH (C . The resulting yellow suspension was
stirred for a further hour. The yellow precipitate was washed
with THF and hexane (3 × 5 ml) on a glass frit, dried and stored
in the freezer in the glove box.
2
[(C
5
H
4
)Tl]
2
Experimental
2
5
H
4
31
2
was synthesised according to the method of
All the syntheses and manipulations, except where specifically
stated, were carried out under inert atmosphere conditions using
standard Schlenk techniques or an Alvic Scientific Gas Shield
2
5
H
)
4 2
◦
glove box equipped with freezer (at −32 C), vacuum pump
and N purge facilities. Celite (Aldrich) was dried under vacuum
2
prior to use. NMR tubes were purchased from Wilmad (5 mm
5
28 Grade) and fitted with a concentric PTFE Young’s valve.
Chemicals were obtained from the following sources: Non-
Synthesis of [CH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
]
2
1
deuterated solvents: benzene, diethyl ether, dimethyl sulfoxide,
pentane, toluene, hexane and THF were obtained from Fisons.
Aromatic and ethereal solvents were dried by refluxing with
[Rh(C H ) (l-Cl)] was first synthesised according to the method
2
4
2
3
2
2
of Cramer. [CH (C H ) ][Rh(C H ) ] was synthesised using
2
5
4
2
2
4 2 2
3
3
a modification of the method described by Werner et al.
◦
sodium/benzophenone. Deuterated solvents: d
6
-benzene and
[Rh(C H ) (l-Cl)] (0.5 g) was added to a cooled (−78 C)
2
4
2
2
d
8
-toluene were stored over a potassium mirror and used via vac-
Schlenk tube containing CH [(C H )Tl] (0.99 g). THF (30 ml)
2
5
4
2
˚
uum transfer. d
stored under N
6
-dmso was dried over 4 A molecular sieves and
. Sodium, magnesium (turnings and powder)
was slowly transferred into the Schlenk tube with continual
stirring and the solvent removed after 30 minutes. The residue
was then extracted into pentane, prior to filtration through
Celite. Removal of the pentane yielded 1 as a yellow solid which
2
and potassium were purchased from Fisons. Triethylsilane and
trimethylchlorosilane were obtained from Fluka. Diethylsilane
and thallium ethoxide were obtained from Aldrich.
Multinuclear NMR spectra were acquired on a Bruker
DRX400 spectrometer and referenced to the residual protio
solvent peaks: benzene (d 7.15), toluene (d 2.1) and dmso (d 2.6).
◦
was then stored at −30 C. The NMR and mass spectroscopic
characterisation of 1 is described in the text.
Reaction of 1 with h -dmso
6
1
3
C spectra (100.62 MHz) were referenced according to: benzene
1
1
31
An NMR tube containing 1 dissolved in d -benzene was taken
6
(
d 128.7), toluene (d 20.4) and dmso (d 39.6). 1D H, H{ P},
C{ H}, P{ H}, F, DEPT and 2D H– C, H– Si, H– P,
H– Rh HMQC and H– H COSY NMR experiments were
1
3
1
31
1
19
1
13
1
29
1
31
into the glove box and a 12-fold excess of h -dmso added by
6
1
103
1
1
syringe. The tube was then degassed and photolysed under
vacuum.
26
27
performed using standard pulse sequences. 1D NOESY and
2
(
1
1
28
29
D H– H NOESY were performed as described. Si spectra
79.49 MHz) were referenced to TMS (d 0.0). Rh spectra
103
Low temperature in-situ photolysis of 1 in d
8
-toluene
were referenced relative to 12.64 MHz. Mass spectrometry was
performed on a VG Autospec instrument in either EI or CI mode
where initial GC separations were achieved on a CARBOWAX
An NMR tube containing 1 (5 mg) dissolved in d
8
-toluene
was degassed and introduced to the NMR probe, which was
then cooled to 203 K. The tube was photolysed in-situ via
the utilisation of a mirror and UV transmitting light guide
in conjunction with the Oriel lamp. This system has been
described previously for the case where a 325 nm laser source was
2
0M column. Photochemical studies were performed using an
Oriel 350 Watt High Pressure Xenon Arc Lamp.
34
employed as the photolysis source. This approach enabled the
photochemical reaction to be monitored at low temperature by
multinuclear NMR spectroscopy without the sample warming
up.
General method for preparation of NMR samples
Approximately 20 mg (unless stated otherwise) of the appro-
priate complex was introduced into an NMR tube, fitted with
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 4 5

View Article Online
Addition of Et
samples
3
SiH, Et
2
SiH
2
and CH
2
CHSiMe
3
to NMR
contained five signals, which arose from two types of C
protons (d 4.93 and 4.70), two types of ethene protons (d 2.74
and 1.21) and the apparently equivalent CH bridge proton pair
d 2.71). Both the signals at d 4.93 and 4.70 appeared as virtual
5
H ring
4
2
Et
3
SiH, Et
2
SiH
2
and CH
2
=CHSiMe
3
were stored in ampoules
(
under an atmosphere of N
2
. Addition of the required excess of
triplets (JH,H = 2.1 Hz), with the smaller splittings of 0.38 and
the silane to the NMR tubes containing 1 was achieved via a
suitable syringe. The NMR tubes were subsequently degassed
prior to photochemical or thermal treatment.
1
03
0
1
2
.64 Hz respectively due to rhodium coupling ( Rh, 100%, I =
. The corresponding 1D C{ H} NMR spectrum established
13
1
)
the presence of five different carbon environments in complex
1
103
1
and a 2D H– Rh HMQC NMR experiment, using the ring
103
Photochemical reaction of 1 with Et
12-cyclohexane
3
SiH in d -benzene and
6
and ethene proton couplings, located a single Rh signal at d
d
1
−
929. Although these data correspond to the fundamental H,
C and Rh signatures for 1, they are insufficient to attribute
resonances to specific ligand positions. The C chemical shifts
The NMR samples were prepared as described above, with the
excess of Et SiH to 1 being varied between 5- and 12-fold. In
13
103
13
3
order to generate only the Rh(III) species, a filter (k > 435 nm)
was used to allow selective irradiation of the Rh(I) precursor. The
filter was removed to enable irradiation of the Rh(III) products
which then produced the Rh(V) complexes. Upon completion
of the photochemical reactions, the volatiles were removed on a
were, however, easily assigned to a ligand position via short- and
1
13
long-range 2D H– C HMQC NMR experiments. Notably, in
the long-range experiment the CH bridge proton resonance
d 2.71) showed connections to the ipso and a-ring carbon
resonances, at d 105.28 and d 87.53 respectively. On the basis of
2
(
high-vacuum line and C
purposes of recording H NMR spectra.
6
H
6
was condensed into the tube for the
1
these observations it can be concluded that the a-C
5
H
4
H and
2
13
C nuclei give rise to the signals at d 4.93 and 87.53 respectively.
This deduction was further confirmed by a 2D H– H NOE
spectrum which revealed that the H resonances at d 2.71 and
1
1
Low temperature studies with Et
3
SiH and Et
2
SiH
2
1
An NMR tube containing 1 dissolved in d
8
-toluene and an excess
4.93 arise from groups that are close in space.
of silane was photolysed at 213 K. This was achieved by placing
the NMR tube in a partially silvered glass dewar which was
Positive cross-peaks, arising from chemical exchange, were
also detected in this NOE spectrum between the proton res-
onances for the ethene ligands which appear at d 2.74 and
1.21. This confirms that the ethene ligands of 1 exchange
positions by rotation about the rhodium–ethene bond and,
cooled, via a flow of liquid N vapour to 213 K. The lamp was
2
situated next to this dewar to enable photolysis. Meanwhile, the
NMR probe was cooled to 213 K. After 2 h irradiation, the
tube was rapidly transferred into the NMR machine to ensure
minimal variation in sample temperature.
1
03
since the Rh coupling remains throughout, the process can
be confirmed as intra-molecular. EXSY spectroscopy allowed
the rate constant for ethene rotation in 1 to be determined
Thermal reactions of 4a and 4b with Et
An NMR tube containing 1 dissolved in d
-fold excess of Et SiH was photolysed at 296 K. After 3.5 h
irradiation, H NMR spectroscopy confirmed the presence of
a and 4b as the major species. All the volatiles were removed
3
SiH
−1
as a function of temperature (e.g. 13.15 s at 286 K). The
‡
‡
‡
corresponding activation parameters, DH , DS and DG 296, were
6
-benzene and an
−
1
−1
−1
determined to be 66.8 ± 6.7 kJ mol , 10.6 ± 24.4 J K mol
and 63.7 ± 0.5 kJ mol respectively. This is consistent with the
values reported by Rausch et al. for the ethene rotation in the
8
3
−
1
1
35
4
‡
analogue of 1, [C
1
5
H
4
–C
5
H
4
][Rh(C
2
H
4
)
2
]
2
, where DG 296 = 65 ±
under vacuum and d
followed by Et
6
-benzene was condensed into the tube
◦
−1
36
kJ mol and by Cramer et al. for the mononuclear analogue
3
SiH. The resultant thermal reaction at 70
C
‡
−1
CpRh(C
2
H
4
)
2
, where DG 296 = 65.7 kJ mol .
was then monitored (the tube was kept dark to ensure that
no photochemical reaction took place). The ethene and ethane
generated during this process was removed by regular degassing.
The fluxionality of 1 is, however, further complicated by the
potential for it to exist in two extreme conformations with cis
and trans arrangements of the rhodium centre relative to the
1
Synthesis of Me
An ampoule containing LiAlH
connected to the high-vacuum line and degassed. The contents
3
SiH
methylene bridge (Fig. 1). Even at 177 K, however, the H NMR
spectrum of 1 in d
two sets of ring protons, two sets of ethene protons and one
set of CH bridge protons. The CH bridge proton resonance
8
-toluene still contains resonances for only
4
(3 g) and 5 ml of THF was
2
2
were frozen and SiMe
3
Cl (3 ml) condensed into this ampoule.
◦
does, however, show a substantial temperature variation in
its chemical shift, moving from d 2.73 at 317 K to d 2.35
at 177 K. Since only one set of resonances are still seen at
low temperature, rapid inter-conversion of the two rotamers is
necessary but the relatively large (0.38 ppm) variation in the
Upon thawing, the reaction mixture was stirred at −78 C. The
valve was periodically opened to allow the pressure increase to be
followed by a manometer. On completion, the resulting Me
3
SiH
gas was condensed into a large ampoule by liquid N . The vapour
2
was then purified by passing it through a dry-ice/acetone trap,
before being condensed back into the large ampoule where it
was stored prior to use.
CH bridge proton chemical shift indicates that the time spent
2
in any one orientation varies with temperature. 1D NOE spectra
recorded between 242 K and 183 K, where there is no ethene
rotation, revealed that the ethene protons yielding the signal at
d 1.21 (as observed at 296 K) show progressively reduced NOE
interactions to the ring protons, until at 198 K no interaction
is detected. In contrast, the ethene protons resonating at d 2.74
Reactions of 1 with Me
All NMR samples were prepared using the general methods de-
scribed previously, except for addition of the silane, Me SiH. The
excess of Me SiH to 1 was varied between 4- and 15-fold. The
NMR samples were degassed prior to study.
Descriptions of mass spectroscopic studies on the photoprod-
ucts produced during the reaction of 1 with Me SiH, and GCMS
3
SiH
3
3
show stronger NOE interactions to the ring protons and the CH
bridging group at 198 K. This suggests that the resonance at d
.74 arises from the ethene protons that point towards the C
2
2
5
H
4
3
rings. Those pointing away from the rings therefore resonate
at d 1.21. The increased interaction between the up-ethene
protons and the methylene bridge implies that the contribution
of structure B increases with decrease in temperature. These data
are important in the context of the work presented in this paper
because they reveal that the metal centres can potentially react
independently of one another (B) or show cooperative effects
(A). It should be noted that in the rest of the paper compounds
have been drawn with structure A, this does not mean that
analysis of the organic products, can be found in the ESI.†
Results and discussion
Dynamic behaviour of [CH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
2
] 1
In order to facilitate this study, 1 was first characterised by NMR
spectroscopy; full NMR spectroscopic data for 1 is presented in
1
Table 1. The 1D H NMR spectrum of 1, in d
6
-benzene at 296 K,
7
4 6
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
1
13
1
29
1
103
Table 1 H, C{ H}, Si{ H} and Rh NMR data for complexes 1–14 in C
6 6
D and at 296 K unless specified otherwise
1
13
1
29
1
103
Species
d H (J/Hz)
d
C{ H} (J/Hz)
d
Si{ H} (J/Hz)
d
Rh (J/Hz)
1
4.93 (vt, 4H, JHH = 2.1, a-C
5
H
H
4
)
)
105.28 (d, JRhC = 3.9, ipso-C
5
H
4
)
—
—
−929
4
2
1
2
.70 (vt, 4H, JHH = 2.1, b-C
5
4
87.53 (d, JRhC = 3.9, a-C
86.13 (d, JRhC = 4.1, b-C
38.00 (d, JRhC = 13.4, C
25.27 (s, CH bridge)
5 4
H )
.74 (br, 8H, up-C
.21 (br, 8H, down-C
.71 (s, 2H, CH
2
H
2
4
)
H
5
H
4
)
4
)
2
H
4
)
2
bridge)
2
b
b
a
a
2
3
a (d
6
-dmso, 5.32 (vt, 2H, JHH = 2.0, a-C
5
H
4
)
104.84 (d, JRhC = 5.2, ipso-C
101.52 (d, JRhC = 5.2, ipso-C
5
5
H
H
4
4
)
)
−613 (Rh )
00 K)
a
a
b
5
5
.23 (vt, 2H, JHH = 2.0, b-C
5
H
H
H
4
)
)
−929 (Rh )
b
.08 (vt, 2H, JHH = 2.0, a-C
.05 (vt, 2H, JHH = 2.0, b-C
.72 (s, 2H, CH bridge)
5
4
87.40 (d, JRhC = 4.4, a-C
5 4
H )
b
a
5
2
2
1
2
2
1
5
4
)
85.64 (d, JRhC = 4.4, b-C
5 4
H )
b
2
85.58 (m, JRhC = 4.4, b-C
5
H
4
)
a
b
.62 (br, 2H, C
.00 (br, 2H, C
2
H
H
4
)
)
85.42 (d, JRhC = 5.2, a-C
5
H
4
)
b
2
4
53.71 (s, Me)
b
.49 (s, 6H, Me)
.28 (m, 2H, up-C
.67 (m, 2H, down-C
37.10 (br, C
2
H
4
)
a
a
2
H
2
4
)
32.27 (d, JRhC = 30, C
2
H
4
)
a
H
4
)
24.64 (s, CH bridge)
2
2
b (d
6
-dmso, 5.21 (vt, 4H, JHH = 2.0, b-C
5
H
4
)
)
101.56 (d, JRhC = 6.0, ipso-C
5
H
4
)
—
−617
−782
3
00 K)
5
2
2
2
1
.07 (vt, 4H, JHH = 2.0, a-C
.68 (s, 2H, CH bridge)
.53 (s, 12H, Me)
.27 (m, 4H, up-C
.67 (m, 4H, down-C
5
H
4
85.43 (d, JRhC = 5.0, a-C
5 4
H )
2
85.52 (d, JRhC = 5.0, b-C
5
H
4
)
53.63 (s, Me)
2
H
2
4
)
H
32.38 (d, JRhC = 30, C
2
H
4
)
4
)
25.00 (s, CH bridge)
2
2
3
a
5.52 (dt, 2H, JHH = 1.5, 1.2, b-C
5
H
4
) 107.92 (ipso-C
5
H
4
1
)
)
)
3
0.30 (s, SiMe )
4
5
.13 (br, 2H, a-C
5
H
4
)
87.89 (m, a-C
5
H
4
1
4
4
4
3
2
2
0
−
.87 (q, 2H, JHH = 2, a-C
5
H
H
4
3)
87.75 (m, a-C
5
H
4
2
3
.36 (q, 2H, JHH = 2, b-C
5
4
)
85.34 (d, JRhC = 8.0, b-C
5
5
H
H
4
4
)
)
.58 (s, 2H, CH
2
bridge)
85.27 (d, JRhC = 8.0, b-C
5
.58 (d, 4H, JHH = 12, H )
53.72 (m, CH
2
=CHSiMe
3
)
)
6
.46 (d, 4H, JHH = 10, H )
43.05 (m, CH
28.20 (s, CH
0.40 (s, SiMe
2
=CHSiMe
3
.14 (s, 12H, SiMe
3
)
2
bridge)
3
)
7
0.250 (dd, 4H, JHH = 12, 10, H )
2
3
b
5.48 (dt, 2H, JHH = 1.5, 1.2, b-C
5
H
4
) 108.26 (ipso-C
5
H
4
4
)
)
)
0.27 (s, SiMe
3
)
−780
4
5
4
4
3
3
2
2
0
.20 (br, 2H, a-C
5
H
4
)
87.89 (m, a-C
87.75 (m, a-C
5
H
4
1
1
.76 (q, 2H, JHH = 2.2, a-C
5
H
4
3)
)
5
H
4
3
2
.41 (q, 2H, JHH = 2.2, b-C
5
H
4
85.60 (d, JRhC = 8.0, b-C
5
5
H
H
4
4
)
)
.74 (d, 1H, JHH = 15.7, CH
2
bridge) 85.07 (d, JRhC = 8.0, b-C
.50 (d, 1H, JHH = 15.7, CH
2
bridge) 53.72 (m, CH
43.05 (m, CH
28.26 (s, CH
0.40 (s, SiMe
2
=CHSiMe
3
)
)
5
.60 (d, 4H, JHH = 12, H )
2
=CHSiMe
3
6
.44 (d, 4H, JHH = 10, H )
2
bridge)
3
)
.13 (s, 12H, SiMe
3
)
7
−
0.246 (dd, 4H, JHH = 12, 10, H )
9
4
b
b
3
c
5.51 (m, 1H, b-C
5
H
H
4
2)
87.56 (a-C
87.38 (a-C
87.26 (b-C
5
5
H
H
H
H
4
)
0.89 (s, Rh )
0.30 (s, Rh )
−736 (Rh )
1
a
a
5
5
.23 (br, 1H, b-C
.20 (m, 1H, a-C
5
4
)
4
2)
−782 (Rh )
7
5
H
4
)
5
4
)
)
3
3
5
4
4
4
4
3
3
2
2
2
1
2
0
0
0
−
.15 (m, 1H, b-C
5
H
4
)
87.15 (b-C
5
4
10
.88 (q, 1H, JHH = 2.2, a-C
5
H
4
)
53.72 (trans-CH
2
=CHSiMe
3
)
1
.74 (m, 1H, a-C
.69 (m, 1H, a-C
5
H
H
4
)
50.24 (cis-CH
45.79 (cis-CH
2
=CHSiMe
3
)
)
4
8)
2
=CHSiMe
3
5
4
.40 (m, 1H, b-C
5
H
4
)
43.05 (trans-CH
2
=CHSiMe
3
)
a
.55 (d, 1H, JHH = 15.8, CH
2
2
bridge) 0.40 (s, SiMe
bridge) 85.29 (b-C
3
8)
.68 (d, 1H, JHH = 15.8, CH
5
5
5
5
H
H
4
4
)
)
)
14
9
7
.77 (dd, 2H, JHH = 12, JRhH = 2, H ) 84.89 (b-C
11
.61 (d, 2H, JHH = 12, H )
86.80 (a-C
87.84 (a-C
H
H
4
12
10
.46 (m, 2H, H )
4
)
.64 (ddd, 2H, JHH = 14, 12, JRhH
=
107.16 (ipso-C
5
H
4
4
)
)
15
, H )
a
.145 (s, 6H, SiMe
.144 (s, 6H, SiMe
.77 (dd, 2H, JHH = 14, 12, H )
3
3
)
)
108.21 (ipso-C
5
H
b
b
0.55 (SiMe
3
)
16
13
0.26 (m, 2H, H )
4
a
4.88 (br, 1H, a-C
5
H
H
4
4
–Rh(I))
–Rh(I))
105.10 (d, JRhC = 4.0,
ipso-C –Rh(I))
87.80 (d, JRhC = 4.0, a
–Rh(I))
–Rh(I)) 86.56 (d, JRhC = 4.0, b
–Rh(I))
38.27 (d, JRhC = 13.4,
–Rh(I))
25.71 (s, CH
41.35 (d, JRhSi = 23.3, SiEt
3
)
−929 (s, Rh(I))
5
H
4
4
4
2
1
.86 (br, 1H, a-C
5
−1483 (s, Rh(III))
5 4
C H
.71 (t, 2H, JHH = 1.9, b-C
5 4
H
5 4
C H
.74 (br, 4H, C
.21 (br, 4H, C
2
H
H
4
–Rh(I))
–Rh(I))
2 4
C H
2
4
2
bridge)
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 4 7

View Article Online
Table 1 (Continued)
1
13
1
29
1
103
Species
d H (J/Hz)
d
C{ H} (J/Hz)
d
Si{ H} (J/Hz)
d
Rh (J/Hz)
2
4
5
2
2
.73 (s, 2H, CH
.91 (br, 2H, a-C
.06 (br, 2H, b-C
2
bridge)
110.30 (d, JRhC = 4.0,
ipso-C –Rh(III))
89.15 (d, JRhC = 4.0,
a-C –Rh(III))
90.56 (d, JRhC = 4.0,
a-C –Rh(III))
84.97 (d, JRhC = 4.0,
b-C –Rh(III))
33.81 (br, JRhC = 13.4,
–Rh(III))
11.83 (s, CH
9.83 (s, CH
5
H
4
5
H
4
–Rh(III))
5
H
4
5
4
H –Rh(III))
5
H
4
.36 (br, 2H, C
.16 (br, 2H, C
2
2
H
H
4
4
–Rh(III))
–Rh(III))
5
H
4
2 4
C H
1
0
.06 (t, 9H, JHH = 9, CH
.73 (q, 6H, JHH = 8.6, CH
14.62 (d, 1H, JRhH = 33.5, JSiH
4, Rh–H)
3
)
3
)
2
)
2
)
−
=
=
1
4
b
4.93 (br, 4H, a-C
5
H
H
H
4
)
)
)
110.00 (d, JRhC = 4.0, ipso-C
5
H
4
)
41.43 (d, JRhSi = 23.3, SiEt
3
)
−1480 (s, Rh(III))
5
5
2
2
2
1
0
.09 (br, 2H, b-C
.05 (br, 2H, b-C
.77 (s, 2H, CH
5
4
90.60 (d, JRhC = 4.0, a-C
88.93 (d, JRhC = 4.0, a-C
5
5
H
H
H
4
4
)
5
4
)
)
)
2
bridge)
84.84 (d, JRhC = 4.0, b-C
5
4
.36 (br, 4H, C
.16 (br, 4H, C
2
H
H
4
)
)
33.81 (br, JRhC = 13.4, C
H
2 4
2
4
25.87 (s, CH
11.83 (s, CH
2
3
bridge)
)
.06 (t, 18H, JHH = 9, CH
.73 (q, 12H, JHH = 9, CH
14.65 (d, 2H, JRhH = 33.5, JSiH
4, Rh–H)
3
)
2
)
2
9.83 (s, CH )
−
1
4
c
4.89 (br, 2H, a-C
5
H
4
–Rh(III))
110.00 (d, JRhC = 4.0,
ipso-C –Rh(III))
90.60 (d, JRhC = 4.0,
a-C –Rh(III))
88.93 (d, JRhC = 4.0,
a-C –Rh(III))
84.84 (d, JRhC = 4.0,
b-C –Rh(III))
33.81 (d, JRhC = 13.4,
–Rh(III))
41.35 (d, JRhSi = 23.3, SiEt
40.05 (d, JRhSi = 16.3, SiEt
3
3
–Rh(III)) −1477 (s, Rh(III))
–Rh(V)) −1872 (s, Rh(V))
5
H
4
5
3
2
2
.05 (br, 2H, b-C
.17 (s, 2H, CH
H –Rh(III))
5 4
5
H
4
2
bridge)
5
H
4
.33 (br, 2H, C
.21 (br, 2H, C
2
2
H
H
4
4
–Rh(III))
–Rh(III))
5
H
4
2 4
C H
1
0
.08 (t, 9H, JHH = 9, CH
.72 (q, 6H, JHH = 9, CH
14.64 (d, 1H, JRhH = 33.5, JSiH
4, Rh(III)–H)
.90 (br, 2H, a-C
3
–Rh(III))
28.24 (s, CH
11.83 (s, CH
9.83 (s, CH –Rh(III))
2
2
bridge)
)
2
–Rh(III))
3
−
=
1
4
5
H
4
–Rh(V))
110.51 (d, JRhC = 4.0,
ipso-C –Rh(V))
92.17 (d, JRhC = 2.18, a
–Rh(V))
–Rh(V)) 87.67 (d, JRhC = 1.89,
b-C –Rh(V))
–Rh(V)) 13.72 (s, CH
5
H
4
5
1
0
.06 (br, 2H, b-C H –Rh(V))
5 4
5 4
C H
.07 (t, 18H, JHH = 7.8, CH
3
5
H
4
.82 (q, 12H, JHH = 7.8, CH
2
2
)
−
14.08 (d, 2H, JRhH = 38.5, JSiH
=
3
9.16 (s, CH Rh(V))
1
4, Rh(V)–H)
4
5
d
5.06 (vt, 4H, JHH = 1.89, a-C
5
H
4
)
)
110.51 (d, JRhC = 4.0, ipso-C
92.17 (d, JRhC = 2.18, a-C
5
4
H
)
)
4
)
40.15 (d, JRhSi = 16.3, SiEt
3
)
−1873 (s, Rh(V))
4
3
1
0
.91 (vt, 4H, JHH = 1.89, b-C
.47 (s, 2H, CH bridge)
.06 (t, 36H, JHH = 7.8, 36H, CH
5
H
4
5
H
2
87.67 (d, JRhC = 1.89, b-C
5
H
4
3
)
28.11 (s, CH
13.72 (s, CH
2
2
bridge)
)
.83 (q, 24H, JHH = 7.8, 24H, CH
2
)
−
14.09 (d, 4H, JRhH = 38.5, JSiH
.9, 4H, Rh–H)
=
9.16 (s, CH
3
)
8
5.27 (vt, 4H, JHH = 1.89, b-C
5
H
4
)
)
91.52 (t, JRhC = 2.2, a-C
5
H
4
)
205.9 (t, JRhSi = 37.3, SiEt
2
)
−2033 (m,
J
RhRh = 16.5)
4
3
1
1
1
1
.79 (vt, 4H, JHH = 1.89, a-C
.64 (s, 2H, CH bridge)
.43 (q, 4H, JHH = 7.8, CH
5
H
4
85.40 (t, JRhC = 1.9, b-C
5
H
4
2
84.70 (t, JRhC = 1.0, ipso-C
5
4
H )
2
‘up’)
)
27.84 (s, CH bridge)
2
.25 (t, 6H, JHH, = 7.5, CH
3
26.00 (t, JRhC = 1.0, CH
2
2
‘up’)
‘down’)
.24 (m, 6H, JHH = 7.4, CH
.23 (m, 4H, JHH = 7.8, CH
3
)
18.94 (t, JRhC = 3.0, CH
2
‘down’) 10.98 (s, CH
3
3
)
)
−
14.40 (m, 2H, JRhH = 39, 0.8,
10.51 (s, CH
hydride)
a
a
a
a
6
4.96 (vt, 2H, JHH = 1.9, a-C
5
H
4
)
)
94.45 (m, a-C
5
H
4
)
)
220.00 (dd, JRhSi = 29.7, 37.6, SiEt
2
)
−1342 (d,
a
J
RhRh = 15, Rh )
5
.02 (vt, 2H, JHH = 1.9, b-C
.43 (t, 2H, JHH = 7.8, CH
.33 (q, 3H, JHH = 7.8, CH
5
H
4
92.20 (m, b-C
5
H
4
−2019 (d,
b
J
RhRh = 15, Rh )
a
1
2
(Rh–Et)) 85.30 (m, ipso-C
(Rh–Et)) 26.70 (s, CH
5
4
H )
1
1
3
2
CH
3
(Rh–Et))
.60 (dq, 1H, JHH = 5.0, 7.0,
−9.80 (d, JRhC = 22, CH
2 3
CH
SiCH
2
CH
CH
3
)
)
(Rh–Et))
1
.31 (dq, 1H, JHH = 5.0, 7.0,
2 3
25.67 (s, SiCH CH )
SiCH
2
3
7
4 8
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
Table 1 (Continued)
1
13
1
29
1
103
Species
d H (J/Hz)
d
C{ H} (J/Hz)
d
Si{ H} (J/Hz)
d
Rh (J/Hz)
1
1
.22 (t, 6H, JHH = 7.0, SiCH
.26 (dq, 1H, JHH = 5.0, 7.0,
2
CH
3
)
)
10.13 (d, JRhC = 3, SiCH
2
CH
3
‘up’)
15.08 (dd, JRhC = 4, 2, SiCH
2
CH
3
SiCH
1
SiCH
1
3
4
5
−
2
CH
3
)
‘up’)
9.37 (s, SiCH
.07 (dq, 1H, JHH = 5.0, 7.0,
2
CH
3
)
2
CH3)
.26 (t, 6H, JHH = 7.0, SiCH
.47 (s, 2H, CH bridge)
.77 (vt, 2H, JHH = 1.9, a-C
2
CH
3
27.13 (s, CH
91.40 (m, a-C
84.90 (m, b-C
87.00 (m, ipso-C
2
bridge)
b
2
5
H
H
4
b)
)
b
5
H
H
4
b)
)
5
4
b
.17 (vt, 2H, JHH = 1.9, b-C
5
4
5
H
4
)
14.60 (d, 1H, JRhH = 40, hydride)
12
11
13 11
H
b
a
7
a
8
9.58 (dd, J
H )
H
H
= 16, J
H
= 9,
146 (br, CH=CH
2
)
43.45 (d, JRhSi = 35 SiEt
35.21 (d, JRhSi = 27 SiEt
3
3
)
)
−779 (d JRhRh =
11
a
(
d
-toluene,
13.8, Rh )
2
13 K)
3
1
3
5
5
.39 (m, b-C
5
H
4
)
97.41 (m, b-C
5
H
4
)
−1407 (d JRhRh
=
b
1
3.8, Rh )
.19 (m, a-C
.03 (m, b-C
.79 (m, a-C
5
H
4
)
)
95.80 (m, CH=CH
2
)
7
8
7
5
4
4
4
4
4
3
3
2
5
H
4
90.80 (m, b-C
5
H
4
)
)
4
5
5
H
4
2)
88.71 (m, a-C
88.67 (m, a-C
5
5
H
H
4
4
.71 (m, b-C
.43 (m, b-C
5
5
H
H
4
4
)
)
)
)
6)
6
88.42 (m, b-C
87.02 (m, a-C
85.38 (m, b-C
82.96 (m, a-C
5 4
H
)
4
1
.29 (m, a-C
.08 (m, a-C
5
5
H
H
4
5
H
4
2)
5
4
13
5
H
4
)
)
11
13
8
.65 (m, J = 9, H )
.41 (d, JHH = 13.70, CH
.95 (d, JHH = 13.70, CH
H
H
5
H
4
9
2
bridge, H ) 25.64 (s, CH
bridge,
2
bridge)
2
10
H )
11
12
12
2
1
1
0
0
.41 (m, J
H
H
= 16, H )
b
.23 (m, CH
.07 (m, CH
.97 (m, CH
.74 (m, CH
3
3
2
2
, SiEt
, SiEt
, SiEt
3
3
3
3
)
)
)
)
a
a
b
, SiEt
b
a
−
15.50 (dd, JRh
.0, hydride)
H
= 35.4, JRh
H
=
3
2
1
3
1
a
7
b
8
8.58 (dd, J
H
H
= 7.6, J
H
H
= 12.6,
—
43.16 (d, JRhSi 37 SiEt
42.08 (d, JRhSi 33 SiEt
3
3
)
666 (d JRhRh 14
1
a
(
d
-toluene,
H )
Rh )
2
13 K)
1
2
2
3
3
2
b
4
H )
.12 9 (dd, J
H
H
H
H
= 7.6, J
H
H
1
= 16.3,
)
−1399 (d JRhRh 14
b
Rh )
3
4
H )
.13 3 (dd, J
= 16.3, J
H
H
= 12.6,
3
3
1
1
0
.39 (d, JHH = 13.8, CH
2
bridge)
bridge)
.01 (d, JHH = 13.8, CH
2
a
.21 (m, CH
.26 (m, CH
.85 (m, CH
3
3
2
, SiEt
, SiEt
, SiEt
3
3
3
)
)
b
b)
b
a
−
15.19 (dd, JRh
0.7, hydride)
H
= 33.3, JRh
H
=
1
1
7
4
0
6
b
a
8
5.30 (m, 1H, a-C
5
5
5
H
H
H
H
H
H
H
4
4
4
)
111.40 (d, JRhC = 3.0, ipso-C
110.60 (d, JRhC = 2.6, ipso-C
5
5
H
H
)
)
)
)
)
4
4
)
)
39.86 (d, JRhSi = 16.5 SiEt
36.70 (d, JRhSi = 17, SiEt
−0.87 (s, C SiEt
3
)
−1836 (Rh )
5
a
b
5
5
5
5
4
4
3
1
1
1
0
0
0
.28 (m, 1H, a-C
.12 (m, 1H, a-C
)
3
)
−1850 (Rh )
10
9)
98.31 (d, JRhC = 3.0, a-C
5
H
4
5
H
3
3
)
8
.10 (m, 1H, b-C
.06 (m, 1H, a-C
5
4
)
95.63 (d, JRhC = 3.0, b-C
95.50 (d, JRhC = 3.0, b-C
5
5
H
H
4
4
1
9
1
7
5
4
3)
.93 (m, 1H, b-C
.90 (m, 1H, b-C
5
4
)
)
91.89 (d, JRhC = 2.8, a-C
91.88 (d, JRhC = 3.0, a-C
5
5
H
H
4
4
2
5
4
4
.61 (s, 2H, CH
2
bridge)
91.62 (d JRhC = 3.0, a-C
5
H
4
)
a
3
.12 (m, CH , SiEt
3
3
)
87.50 (d, JRhC = 3.0, b-C
87.40 (d, JRhC = 3.0, b-C
5
H
H
4
4
)
2
b
.096 (m, CH
.044 (m, CH
.915 (m, CH
.846 (m, CH
3
3
2
2
, SiEt
, C
, SiEt
, SiEt
3
)
5
)
5
H
3
3
3
SiEt
3
)
27.72 (s, CH
13.68 (s, CH
13.62 (s, CH
2
2
2
bridge)
a
b
)
)
, SiEt
, SiEt
3
)
)
b
a
3
.78 (m, CH
2
, C
5
H
3
SiEt
3
)
6.88 (s, CH
6.77 (s, CH
3
, C
, SiEt
5
H
3
3
SiEt
)
3
)
)
b
−
13.92 (d, 2H, JRhH = 37, JSiH
=
3
a
1
1.6, hydride )
−
14.06 (d, 2H, JRhH = 38, JSiH
=
5.29 (s, CH
2
, C
5
H
3
SiEt
3
b
1
3.9, hydride )
4
1
5
9
a
5.27 (br, 2H, a-C
5
H
H
H
4
4
)
111.90 (d, JRhC = 3.0, ipso-C
5
H
4
)
36.52 (d, JRhSi = 17 SiEt
−0.702 (C SiEt
3
)
−1837
1
5
5
3
1
1
0
.26 (br, 2H, a-C
.07 (br, 4H, b-C
.71 (br, 2H, CH
5
3)
98.84 (d, JRhC = 3.0, a-C
5
H
4
2)
5
H
3
3
)
5
4
)
95.66 (d, JRhC = 3.0, b-C
95.48 (d, JRhC = 3.0, b-C
5
5
H
H
4
4
)
3
2
bridge)
)
4
)
.133 (t, JHH = 7.3, CH
3
, SiEt
, C
, SiEt
3
)
92.08 (d, JRhC = 3.0, a-C
5
H
4
.040 (t, JHH = 7.8, CH
3
5
H
3
SiEt
3
)
27.49 (s, CH
13.62 (s, CH
2
2
bridge)
, SiEt
.917 (q, JHH = 7.3, CH
2
3
)
3
)
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 4 9

View Article Online
Table 1 (Continued)
1
13
1
29
1
103
Species
d H (J/Hz)
d
C{ H} (J/Hz)
d
Si{ H} (J/Hz)
d
Rh (J/Hz)
0
.771 (q, JHH = 7.8, CH
13.89 (d, 4H, JRhH = 37, JSiH
0.13, hydride)
2
, C
5
H
3
SiEt
=
3
)
8.90 (s, CH
5.29 (s, CH
3
, SiEt
3
)
−
2
, C
5
H
3
SiEt
3
)
)
1
6
.78 (s, CH
3
, C
5
H
3
SiEt
3
1
5
9
b
5.34 (t, 4H, JHH = 1.5, a-C
5
H
4
)
)
111.70 (d, JRhC = 3.0, ipso-C
5
H
4
)
36.55 (d JRhSi = 17, SiEt
3
)
−1832
4
1
5
5
.255 (br, 2H, a-C
5
H
4
)
98.94 (d, JRhC = 3.0, a-C
5
H
4
2)
−0.815 (C SiEt
5
H
3
3
)
3
.03 (t, 2H, JHH = 2.0, b-C
5
H
4
95.64 (d, JRhC = 3.0, b-C
95.38 (d, JRhC = 3.0, b-C
5
5
H
4
4
)
3
3
1
1
0
0
.76 (s, 2H, CH bridge)
2
H
)
)
4
.132 (t, JHH = 7.3, CH
.040 (t, JHH = 7.8, CH
3
3
, SiEt
, C
3
)
92.14 (d, JRhC = 3.0, a-C
5
H
4
5
H
3
SiEt
3
)
27.80 (s, CH
13.62 (s, CH
2
2
bridge)
, SiEt
.92 (q, JHH = 7.3, CH
2
, SiEt
, C
13.92 (d, 4H, JRhH = 37, JSiH
1.6, hydride)
3
)
3
)
.778 (q, JHH = 7.8 CH
2
5
H
3
SiEt
3
)
9.00 (s, CH
5.30 (s, CH
3
3
, SiEt )
−
=
2
, C
5
H
3
SiEt
3
3
)
)
1
6
.79 (s, CH
3
, C
5
H
3
SiEt
1
0a
4.87 (vt, 2H, JHH = 2.0,
a-C –Rh(I))
.69 (vt, 2H, JHH = 2.0,
b-C –Rh(I))
87.60 (d, JRhC = 4, a-C
86.22 (d, JRhC = 4, b-C
104.85 (ipso-C –Rh(I))
5
H
4
–Rh(I)) 23.64 (d, JRhSi = 23.29, SiMe
3
)
−929 (Rh(I))
5
H
4
4
5
H
4
–Rh(I))
−1450 (Rh(III))
5
H
4
2
1
.74 (br, 4H, C
.20 (br, 4H, C
2
H
H
4
–Rh(I))
–Rh(I))
5 4
H
2
4
38.05 (d, JRhC = 13.5,
–Rh(I))
25.64 (s, CH
89.24, 90.56 (m, a-C
87.38 (m, b-C –Rh(III))
110.03 (ipso-C –Rh(III))
34.23 (br, C –Rh(III))
8.18 (s, CH
2 4
C H
2
5
4
4
2
2
0
−
.74 (s, 2H, CH
.01 (br, 1H, a-C
.85 (br, 1H, a-C
2
bridge)
2
bridge)
5
H
H
H
4
–Rh(III))
–Rh(III))
–Rh(III))
5 4
H –Rh(III))
5
4
5
H
4
.76 (br, 2H, b-C
5
4
5 4
H
.40 (br, 2H, C
.16 (br, 2H, C
2
H
H
4
–Rh(III))
–Rh(III))
2 4
H
2
4
3
)
3
.37 (s, 9H, CH )
14.57 (d, 1H, JRhH = 34.1, hydride)
1
1
0b
0c
5.01 (br, 2H, a-C
5
H
H
H
4
4
)
)
)
109.95 (ipso-C
5
H
4
)
23.64 (d, JRhSi = 23.29 SiEt
3
)
−1449
4
4
2
2
2
0
.85 (br, 2H, a-C
.76 (br, 4H, b-C
.78 (s, 2H, CH
5
4
89.10 (m, a-C
90.50 (m, a-C
5
H
H
4
)
)
)
5
5
4
2
bridge)
87.30 (m, b-C
34.20 (br, C
25.85 (s, CH
8.18 (s, CH
5 4
H
.38 (br, 4H, C
.16 (br, 4H, C
2
H
H
4
)
)
2 4
H )
2
4
2
bridge)
.37 (s, 18H, CH
3
)
3
)
−
14.60 (d, 2H, JRhH = 34.1, hydride)
5.01 (m, 2H, a-C
5
H
4
–Rh(III))
90.44 (m, a-C
5
H
4
–Rh(III))
–Rh(III))
23.64 (d, JRhSi = 23.3, SiMe
Rh(III))
19.83 (d, JRhSi = 23.4, SiMe
3
3
,
−1450 (Rh(III))
4
3
.76 (m, 2H, b-C
.07 (s, 2H, CH
5
H
bridge)
4
–Rh(III))
89.24 (m, b-C
110.18 (ipso-C
34.20 (m, C
26.88 (s, CH
8.18 (s, CH , Rh(III))
110.90 (ipso-C –Rh(V))
5
H
4
, Rh(V)) −1731 (Rh(V))
2
5
H
)
4
–Rh(III))
2
2
0
−
.39 (br, 2H, C
.16 (br, 2H, C
.40 (s, 9H, CH
14.59 (d, 1H, JRhH = 34.1,
hydride-Rh(III))
2
2
H
H
4
4
)
)
2 4
H
2
bridge)
3
–Rh(III))
3
5 4
H
4
4
0
−
.96 (m, 2H, a-C
.87 (m, 2H, b-C
.51 (s, 18H, CH
13.74 (d, 2H, JRhH = 39.9,
hydride-Rh(V))
5
H
H
, Rh(V))
4
–Rh(V))
–Rh(V))
91.94 (m, a-C
88.00 (m, b-C
3
12.00 (s, CH –Rh(V))
5
H
4
–Rh(V))
5
4
H –Rh(V))
5 4
3
1
1
0d
1
4.98 (vt, 4H, JHH = 1.9, a-C
5
H
H
4
)
)
91.98 (m, a-C
87.59 (m, b-C
111.12 (ipso-C
5
H
H
5 4
4
)
)
19.83 (d, JRhSi = 23.39 SiMe
3
)
−1732
4
.87 (vt, 4H, JHH = 1.9, b-C
.34 (s, 2H, CH bridge)
.51 (s, 36H, CH
5
4
3
0
2
5
H
4
)
3
)
27.80 (s, CH
2
bridge)
−
13.75 (d, 4H, JRhH = 39.9, hydride) 12.18 (s, CH
3
)
a
a
a
4.90 (m, 2H, a-C
5
H
4
)
93.68 (d, JRhC = 2.0, a-C
5
H
4
)
)
204.67 (dd, JRhSi = 34.9, 46.0, SiMe
2
)
−1424 (d,
a
J
RhRh = 15, Rh )
a
4
0
.93 (m, 2H, b-C
5
H
4
)
91.41 (d, JRhC = 2.0, b-C
5
H
4
−2008 (d,
b
J
RhRh = 15, Rh )
a
.20 (s, 3H, Rh–Me)
85.83 (ipso-C
5
H
4
)
1
0
3
4
5
.13 (m, 6H, SiCH
.77 (m, 6H, SiCH
3
3
‘up’)
26.96 (s, CH
20.18 (m, SiCH ‘up’)
12.54 (m, SiCH ‘down’)
2
bridge)
‘down’)
.54 (s, 2H, CH
.77 (m, 2H, a-C
.21 (m, 2H, b-C
2
bridge)
b
5
H
4
b)
−31.23 (d, JRhC = 27.5, Rh–Me)
b
5
H
4
)
91.81 (d, JRhC = 3.0, a-C
5
H
4
)
)
b
−
14.19 (m, 1H, JRhH = 40.8, hydride) 86.68 (ipso-C
5
H
4
)
b
8
5.49 (d, JRhC = 4.0, b-C
5 4
H
a
a
1
2
4.73 (m, 2H, a-C
5
H
4
)
94.30 (m, a-C
5
H
4
)
212.39 (dd, JRhS = 35.65, 46.18,
SiMe
−1957 (d, JRhRh
=
a
2
)
14.7, Rh )
7
5 0
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
Table 1 (Continued)
1
13
1
29
1
103
Species
d H (J/Hz)
d
C{ H} (J/Hz)
d
Si{ H} (J/Hz)
d
Rh (J/Hz)
a
a
4
3
.97 (m, 2H, b-C
5
H
4
)
90.58 (m, b-C
5
H
4
)
15.41 (d, JRhSi = 40.53, SiMe
3
)
−1350 (d, JRhRh
=
b
1
4.7, Rh )
a
.44 (s, 2H, CH
2
bridge)
95.33 (m, ipso-C
26.05 (s, CH
5
H
4
)
1
0
0
4
4
0
.04 (m, 6H, SiCH
.69 (m, 6H, SiCH
3
‘up’)
’down’)
2
bridge)
‘up’)
‘down’)
3
21.71 (s, SiCH
12.91 (s, SiCH
3
.47 (s, 9H, Rh–SiMe
3
)
3
b
.89 (m, 2H, a-C
.77 (m, 2H, b-C
.15 (s, 3H, Rh–Me)
5
H
4
b)
10.43 (d, JRhC = 2.0, Rh–SiMe
3
)
b
5
H
4
)
93.62 (m, a-C
5
H
4
)
)
b
5 4
91.01 (m, b-C H
8
b
5 4
7.96 (m, ipso-C H )
−
27.51 (d, JRhC = 27.5, Rh–Me)
a
a
a
1
3
4.71 (vt, 2H, JHH = 2.2, a-C
5
H
4
)
)
93.86 (d, JRhC = 2.0, a-C
5
H
4
)
197.44 (dd, JRhSi = 29.1, 46.6, SiMe
13.74 (d, JRhSi = 34.7, SiMe
2
)
−1965 (d, JRhRh
=
=
a
1
4.8, Rh )
a
5
.02 (vt, 2H, JHH = 2.2, b-C
.58 (s, 2H, CH bridge)
5
H
4
92.65 (ipso-C
5
H
4
)
3
)
−1952 (d, JRhRh
b
1
4.8, Rh )
a
3
1
0
0
5
4
2
90.79 (d, JRhC = 2.5, b-C
26.76 (s, CH bridge)
20.83 (s, SiCH
17.83 (s, SiCH
5 4
H
)
.02 (s, 6H, SiCH
.94 (s, 6H, SiCH
.49 (s, 3H, Rh–SiMe
3
‘up’)
2
3
‘down’)
3
‘up’)
3
)
3
‘down’)
b
b
.13 (vt, 2H, JHH = 2.0, b-C
5
H
H
4
)
)
11.70 (d, JRhC = 2.0, Rh–SiMe
3
)
b
.77 (vt, 2H, JHH = 2.0, a-C
5
4
91.61 (d, JRhC = 3.0, a-C
5
H
4
)
b
−
14.19 (m, 1H, JRhH = 40.8,
85.99 (ipso-C
5
H
4
)
hydride)
b
8
5.34 (d, JRhC = 4.0, b-C
5 4
H
)
a
a
a
1
4
8
5.08 (m, 2H, a-C
5
H
4
)
)
)
H
98.57 (ipso-C
5
H
4
)
20.91 (d, JRhSi = 23.71 SiMe
3
)
−1052 (Rh )
(
d
-toluene,
2
13 K)
a
a
b
4
2
1
.26 (m, 2H, b-C
.68 (br, 2H, up-C
.89 (br, 2H, down-C
5
H
2
4
89.32 (m, a-C
88.55 (m, b-C
36.67 (m, C
32.41 (s, CH
5
H
H
5 4
4
a)
)
−1608 (Rh )
H
4
2
4
)
2 4
H )
−
12.97 (dd, 2H, JRhH = 17.4,
2
bridge)
2
2
4
4
0
5.7, hydride)
b
.59 (s, 2H, CH
2
bridge)
92.89 (m, a-C
112.9 (ipso-C
3
11.65 (SiMe )
5
H
4
)
b
b
.89 (m, 2H, a C
.78 (m, 2H, b-C
.62 (s, 18H, SiMe
5
H
4
b)
5 4
H )
5
H
4
)
3
)
1
form A dominates but rather it simply reflects a useful pictorial
fact that the CH
2
bridge H resonance for this species at d
representation.
2.72 connects to two ipso carbon resonances, at d 101.52 and
04.84, and two a-C carbons, at d 85.42 and 87.40 in the
long-range H– C NMR spectrum. Upon extended photolysis
CH (C ][Rh(C )(dmso)] 2b became the sole product.
This product yields H NMR peaks at d 5.07 and 5.21 (for the
two sets of C protons), 2.68 (for the CH bridge) and, 2.27
1
5
H
4
1
13
[
2
5
H
4
)
2
2
1
H
4
2
5
H
4
2
1
03
and 1.67 (for the ethene protons). Furthermore, a single Rh
signal was observed at d −617. Full NMR data for these two
species are presented in Table 1.
1
Fig. 1 Extreme conformations of 1.
A key feature in the H NMR spectra of both 2a and 2b
was the observation of fine structure for the ethene signals (at
d 2.28 and 1.67, 2a; d 2.27 and 1.67, 2b). This indicates that
there is now a substantial barrier to alkene rotation in the dmso
substituted centre. In order to determine the orientation and
Photochemical reaction of [CH
with dmso
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2 2
]
1
In order to investigate the photochemical reactivity of 1, a
solution of 1 in d -dmso was photolysed using broad band UV
binding mode of the dmso ligands in 2a and 2b a d -benzene
6
6
solution of 1 was photolysed in the presence of a 12-fold excess
1
irradiation from a 350 W Xe arc and the reaction monitored
by 1D and 2D NMR spectroscopic methods. After 15 min
of h -dmso until H NMR spectra recorded at 300 K revealed the
6
formation of both the mono- and di-substituted products. A 2D
1
1
13
1
13
irradiation, a H NMR spectrum recorded at 300 K revealed
H– C NMR experiment then connected the methyl H and C
the presence of free ethene (d 5.41) and two new peaks at d
resonances of free dmso (d 1.78, 39.59), the monosubstituted
product (d 2.49, 53.71) and the disubstituted product (d 2.53,
2
.72 (major) and 2.68 (minor) corresponding to the CH
2
bridge
bridge
1
3
protons of two metal-based photoproducts; such CH
2
53.63). The downfield shift of the C resonances (with respect
to the free dmso) has previously been shown to be indicative
proton resonances proved to be a firm indicator of the number
of products that were produced in the reactions described here.
It should be noted at this stage, that when the mononuclear
37
of dmso binding through the S atom in both products. These
observations demonstrate that UV irradiation of 1 in solution
provides a facile route to complexes resulting from the loss of a
single ethene molecule per rhodium centre.
analogue of 1, CpRh(C
mono-substituted product CpRh(C
2
H ) , is photolysed with dmso the
4
2
41
2
H )(dmso) is obtained.
4
It was therefore expected that products corresponding to the
successive loss of one ethene ligand from each metal cen-
Low temperature in-situ photolysis of [CH
in d -toluene
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2 2
]
1
8
tre, namely [CH
CH (C ][Rh(C
a contains two distinct C
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H )(dmso)] 2a and
4
[
2
5
H
4
)
2
2
H
4
)(dmso)]
2
2b, would be formed. Complex
rings, in agreement with the
Perutz et al. used laser flash photolysis to demonstrate the
existence of two transient intermediates, [CpRh(C )] and
2
5
H
4
2
H
4
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 5 1

View Article Online
CpRh(C
of CpRh(C
group has also reported evidence for the solvent complexes
2
H
4
)(solv) (where solv = solvent), following irradiation
NOE connections were consistent with the chemical shift data
included in Fig. 2. It should be noted that the actual orientation
34,38
2
H
)
4 2
in cyclohexane and benzene. The same
of the d
8
-toluene ligand in these species cannot be determined
2
41
CpRh(C
stitution products that are formed by photolysis of CpRh(C
in the presence of a suitable ligand therefore originate from either
CpRh(C ) or CpRh(C )(solv). We recently expanded on
these studies by completing an NMR based in-situ photolysis
2
H
4
)(MeCN) and CpRh(C
2
H
4
)(g -toluene). The sub-
i.e. it is not possible to distinguish the up or down isomers.
2
H
)
4 2
Photochemical reaction of [CH
vinyltrimethylsilane
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
2
] 1 with
2
H
4
2
H
4
41
34
Perutz et al. have previously reported that photolysis of the
mononuclear analogue of 1, CpRh(C , with vinyltrimethyl-
silane led to the formation of CpRh(C
and the double substitution product CpRh(CH
study of this system at 193 K. This revealed that the photo-
2
2
H
4 2
)
2
product CpRh(C
that interconvert on the NMR timescale. It should be noted that
the related species CpIr(C )(C ) has also been shown to
exist in two isomeric forms, where the metal binds to the p-face
2
H
4
)(g -toluene) exists in two isomeric forms
H
4
)(CH
2
=CHSiMe
3 2
3
)
,
=CHSiMe
)
2
2
H
4
6
F
6
where the latter complex exists in cis and trans forms that are
2
differentiated by the relative orientations of the vinyl ligands.
in an g -fashion and the C plane points towards or away from
6
39
Exhaustive photolysis of a solution of 1 in d -benzene in the
6
the cyclopentadienyl ring. We now expand on the previously
presence of an 8-fold excess of vinyltrimethylsilane yielded
three major products which were subsequently assigned to
communicated data obtained from the low temperature in-situ
photolysis of 1 with d
A sample of complex 1 (5 mg) was dissolved in d
a 5 mm NMR tube, and placed into the NMR spectrometer.
8
-toluene.
the disubstituted species [CH
2
(C
5
H
4
)
2
][Rh(CH
2
=CHSiMe
3
)
2
]
2
8
-toluene, in
3a,3b and 3c (Fig. 3). This observation demonstrates that the
1
substitution of both the ethene ligands on each rhodium centre
in 1 is possible.
The sample was then photolysed in-situ at 203 K and
H
NMR spectra recorded at regular intervals. After 18 h of
irradiation, there was evidence for a single new species in the
1
H NMR spectrum, most notably via the observation of a CH
2
resonance, corresponding to the bridging methylene group, at
d 2.35 with equal intensity to the analogous resonance of 1.
Free ethene was detected at d 5.31, but no hydride resonances
were observed in the region d −5 to −25. On the basis of
these data, the new species was expected to be the solvent
2
complex [CH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H
4
)(g -toluene)]. Two
rotamers, as drawn in Fig. 2, would be expected for this species
and hence sixteen ring proton resonances could potentially be
observed. In the H NMR spectrum, only seven peaks at d 4.08,
Fig. 3 Structures of [CH
indicated by NMR spectroscopy (where R = SiMe
2
(C
5
H
4
)
2
][Rh(CH
2
=CHR)
2
2
] 3a, 3b and 3c as
1
3
).
4
.14, 4.54, 4.61, 4.85, 5.05 and 5.12, corresponding to C
5
4
H ring
protons, and d −0.18, 1.42, 2.53 and 2.89, attributed to ethene
protons respectively were readily visible. It was noted that the
peak at d 4.54 was twice as intense as the other ring proton
resonances.
A brief description of how the NMR data supports this
deduction follows (Table 1). The dominant products 3a and
1
3b yield vinyl H signals at d −0.250, 2.46 and 2.58, for 3a,
and d −0.246, 2.44 and 2.60, for 3b and are indicative of the
ligand orientations. Previously, the relative orientation of the
vinylsilane ligands in CpRh(CH
affect the chemical shift of H , which appears at d 0.68 in the
2
=CHSiMe
3
)
2
was shown to
a
41
cis form and d −0.40 in the trans form. This implies that the
vinylsilane ligands on each rhodium centre in 3a and 3b are
orientated trans to one another. There are two possible ways of
achieving this; the pairs of vinylsilane ligands can themselves
be either in a cis or trans arrangement. The distinction between
these two forms was simple to achieve since the symmetrical
Fig.
2
H
H
Structures
of
two
isomers
of
2 5 4 2
[CH (C H ) ]-
[
[
Rh(C
Rh(C
2
2
4
4
)
2
]-
product 3a yields a single CH
while the unsymmetrical form 3b gives rise to an AB pattern
for the CH group with resonances at d 3.50 and 3.74; this is
2
bridge proton resonance at d 3.58
2
1
)(g -toluene)] (where R = CD
3
) with key H resonances
indicated.
2
achieved by a trans arrangement of the pairs of vinyl ligands.
Species 3a and 3b each yield four ring H resonances with NOE
2
2
1
Ring-walk of the unsymmetrical arene, in a series of g -g
steps, would lead to an apparent plane of symmetry in each
of these rotamers and hence halve the number of ring proton
resonances expected for each isomer to four. The observation of
eight ring proton resonances is consistent with this hypothesis.
Positive cross-peaks were observed between signals at d 4.08 and
measurements confirming that the SiMe
3
groups point towards
the C rings. Unambiguous assignment of 3a and 3b was
5
H
4
1
13
29
103
achieved via H– C, Si and Rh 2D correlations.
In contrast, complex 3c yields six H resonances due to
1
the vinylsilane core, with the three at d 2.61, 2.46 and −0.26
corresponding to a pair of trans vinylsilane ligands on one
metal centre, and the remaining three, at d 2.77, 1.64 and 0.77,
corresponding to a pair of cis ligands on the second metal centre.
Thus, 3c possesses a trans/cis arrangement of the vinylsilane
ligand pairs and has the structure shown in Fig. 3. The ratio of
3a : 3b : 3c was 4 : 1.7 : 1.
4
.61, d 4.14 and 4.85, and d 5.05 and 5.12 in the corresponding
EXSY spectrum. These data correspond to the observation of
the pairwise interconversion of the six distinct ring proton sites at
2
03 K and prove that the two proposed rotamers interconvert by
40
arene rotation. The observation of further EXSY connections
between the four ethene proton signals at d 1.42 and −0.18, and
d 2.89 and 2.53 further complicates these spectra, but indicates
that the alkene ligands bound to the substituted rhodium centre
also rotate. These NOE spectra enabled the location of two
further ethene resonances, at d 1.34 and 2.81 (which correspond
to ligand sites that also interchanged positions) due to the
units of the unsubstituted ring. (Overlap with the
corresponding ethene resonances in the starting material masked
these signals in the initial 1D H NMR spectrum.) These
It is important to note that these spectra were complicated
by the fact that H/D exchange was observed between the
solvent, d
6
-benzene, and free and bound vinyltrimethylsilane.
Free vinyltrimethylsilane yields NMR signals at d 6.16 (dd,
a
b
J
H,H = 14.7, 20.3, H ), 5.90 (dd, JH,H = 3.9, 14.7, H ), 5.65
c
Rh(C
2
H
4
)
2
(dd, JH,H = 3.9, 20.3, H ) and 0.05 (s, SiMe
3
), however, after 5 h
photolysis, signals with a doublet of 1 : 1 : 1 triplet multiplicity
1
were present at d 5.90 and 5.65. The d 6.16 resonance then proved
7
5 2
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
Scheme 1 Structures of products formed during photochemical reactions of 1 with HSiEt
3
, HSiMe
3
and H
2
SiEt
2
.
to be reduced in intensity by 50% of the expected integral value;
two ipso carbons at d 105.10 and 110.30, and three a-ring carbons
at d 87.80, 89.15 and 90.56. This confirms that the associated
2
b
c
the H couplings are 2.2 (JD,H ) and 3.2 (JD,H ) Hz respectively.
A 1 : 1 : 1 triplet, centred at d 139.8 (JD,C = 21 Hz), was observed
complex contains two distinct C
5
4
H rings. The remaining bridge
1
3
in the corresponding C NMR spectrum in accord with the fact
proton resonance at d 2.77 for 4b connects to a single ipso
carbon at d 110.00, and two distinct a-ring carbons at d 88.93
and 90.60, which confirms that 4b is a symmetrical product.
This information, in conjunction with the corresponding NOE
a
1
that H becomes deuterated. GCMS and H NMR integrations
2
both agreed with 50% H incorporation into the alpha proton
site of both free and bound vinyltrimethylsilane. Similar H–D
42
1
exchange has been seen with Cp*Rh(CH
2
=CHSiMe
3
).
data, enabled the complete assignment of the H resonances
This reaction should be noted for three reasons, (i) the
dominant species 3a possesses a trans/trans arrangement of
vinylsilane ligands, with the silyl groups orientated such that
they are furthest away from each other-presumably due to steric
reasons, (ii) in contrast to the reaction with dmso, exhaustive
photolysis of 1 with vinylsilane now results in the substitution
of all four ethene ligands and (iii) evidence for a C–H bond
activation pathway has been obtained.
for the corresponding Rh(I) and Rh(III) rings in these species.
1
29
29
The corresponding 2D H– Si NMR spectrum located the Si
chemical shifts for the silyl ligands in 4a (d 41.35) and 4b (d
41.43) via connections to the corresponding hydride and ethyl
1
103
proton signals, while the 2D H– Rh NMR spectrum located
1
03
the corresponding Rh resonances at d −929 and −1483 in 4a,
1
and d −1480 in 4b via connections to the ethene H resonances.
1
3
The remaining C resonances were located via connections in a
1
13
short-range H– C 2D correlation. The full NMR spectroscopic
data for complexes 4a and 4b obtained in this way are presented
in Table 1.
Photochemical reactions of [CH
Et SiH and Et SiH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
2
] 1 with
3
2
2
1
Upon further irradiation, the H resonances due to 4b were
When a solution of 1 in d
6
-benzene was photolysed at 296 K,
observed to consistently grow in intensity whilst those arising
from 4a initially grew and were then depleted. Subsequently,
resonances for 4b began to disappear, and new signals for
four new hydride containing species, identified by NMR spec-
using a k > 400 nm filter, in the presence of a 5-fold excess of
1
Et SiH, the H NMR spectrum recorded after 30 min irradiation
3
contained a signal at d 5.24, corresponding to free ethene,
and two new hydride resonances at d −14.62 (major) and d
troscopy as [CH
4c, [CH (C ][Rh(SiEt
SiEt )] 5 and [CH (C
2
(C
5
H
4
)
2
][Rh(C
2
H
2
4
)(SiEt
4d, [CH
3
)H][Rh(SiEt
3
)
2
(H) ]
2
−
14.65 (minor). Both these resonances were split into doublets
of 33.5 Hz due to coupling to Rh; this value proved to be
2
5
H
4
)
2
3
)
2
(H)
2
]
2
(C
5
H
4
)
2
][RhH(l-
] 6 were
1
03
2
2
2
5
H
4
)
2
][(RhEt)(RhH)(l-SiEt
2
)
2
indicative of a Rh(III) centre in the analogous CpRh system.1
3b
observed. NMR resonances for these products were unambigu-
ously assigned using the methods described for complexes 4a and
4b (see ESI† and Table 1). The formation of 4c and 4d is consis-
tent with the expected stepwise photochemical displacement of
ethene from 4a and 4b, as illustrated in Scheme 2, however, the
generation of 5 and 6, corresponding to Si–C bond activation
products, was somewhat unexpected (structures indicated in
Scheme 1).
Thus the species giving rise to these hydride signals were assigned
as [CH (C ][Rh(C ][Rh(C )(SiEt )H] 4a, the primary
photoproduct, and [CH (C ][Rh(C )(SiEt )H] 4b, the
2
5
H
4
)
2
2
H
4
)
2
2
H
4
3
2
5
H
4
)
2
2
H
4
3
2
secondary product, respectively. The structures of these species
are indicated in Scheme 1.
1
While the resultant H NMR spectrum is extremely complex
between 4 and 6 ppm, three resonances that were attributable to
the CH
were easily distinguished at d 2.71, 2.73 and 2.77 respectively. The
.04 ppm separation of the latter two signals proved sufficient
2
bridge protons of 1 and the photoproducts 4a and 4b
The ratio of 4d : 5 : 6 observed after 4 h of photolysis proved
1
to be 72 : 16 : 12, although, inspection of the H NMR spectra
0
as a function of irradiation time revealed that 6 was generated
prior to 5. Interestingly, the proportion of 5 and 6 relative to 4d
1
to enable the identification of 4a and 4b via long-range 2D H–
1
3
C and 2D NOE measurements. Significantly, the CH
2
bridge
increased in experiments where the initial excess of Et SiH used
3
protons of the major product resonate at d 2.73 and connect to
relative to 1 was reduced. Upon exhaustive photolysis of these
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 5 3

View Article Online
the presence of two inequivalent ethyl groups on each of the
SiEt units; one pointing towards and one pointing away from
2
the rings (Scheme 1).
Key features arising from the unsymmetrical silylene bridged
1
3
complex 6, include eight CH C resonances, corresponding to
the a and b positions of two distinct C rings, and two ipso
carbon signals. A single hydride resonance, a rhodium coupled
5
H
4
2
9
doublet, was observed at d −14.60 while the corresponding Si
resonance appears as a doublet of doublets at d 220 (JSiRh
9.7, 37.6 Hz). This confirms that 6 contains a hydride ligand,
=
2
1
03
and silicon centre that bridges two inequivalent Rh nuclei,
which were subsequently found to yield signals at d −2019 and
−
1342. The remaining site was identified via the observation of
13
a methylene C signal for a RhEt ligand that was split by a
1
03
direct, one bond, Rh coupling of 22 Hz. Both 5 and 6 contain
Rh–Rh bonds, as demonstrated by values for JRhRh of 16.5 and
1
5 Hz determined for these species respectively.
The reactions with Et SiH revealed that the corresponding 16-
electron fragments formed by ethene loss were able to break a
Si–H bond and form the corresponding Rh(III)(C )(SiEt )(H)
products. The corresponding JSiH coupling constants for 4a and
b proved to be 14 Hz in each case (Table 1) which suggests
3
2
H
4
3
2
4
that there is no 3-centre bonding interaction in these species.
These Rh(III) centres also proved to undergo photochemically
driven ethene loss to yield formal Rh(V) centres of the type
Rh(SiEt
3
)
2
(H) by the addition of a second molecule of silane.
2
2
Scheme 2 Conversion of 1 to 4a, 4b, 4c, 4d, 5 and 6.
Again, the size of the JSiH couplings observed for 4c and 4d
suggested that there were no 3-centre-2-electron interactions
present in these complexes. This is consistent with the fact that
samples only complexes 4d (71%) and 5 (29% in the case above)
remain; this confirms that 6 transforms into 5 upon photolysis
the 16-electron fragment Rh(III) [(C
5
H
4
)R][Rh(SiEt )H] (where
3
(
Scheme 2). Complex 5 could be generated independently when
was photolysed with a 4-fold excess of Et SiH in d -benzene
at 296 K.
It should be noted that when this reaction was completed
in d -benzene, only one ring proton resonance, at d 4.91, was
observed for 4d. However, when the irradiation of 1 was repeated
R = [CH
2
(C )][Rh(C )(SiEt )H]) appears to be sufficiently
5
H
4
2
H
4
3
1
2
2
6
electron rich to be able to activate both the Si–C bonds of
bound silyl groups and the C–D bonds of aromatic and aliphatic
solvents. A similar deduction has been made by Berry on a
20
6
related Cp*Rh system.
1
on an NMR scale in neat Et SiH, H NMR spectroscopy
3
Low temperature studies with Et
3
SiH and Et
2
SiH : Generation
2
revealed peaks corresponding to a single product, 4d. Under
these conditions, the formation of 5 was suppressed and two
resonances of equal intensity were observed for the two types of
of r,p vinyl complexes
In order to probe the C–H activation potential of these binuclear
rhodium systems further, a series of photochemical studies were
performed using the in-situ photochemical approach described
C
5
H ring protons of 4d at d 5.06 and 4.91. Ultimately this effect
4
1 13
was explained by the observation in a long-range 2D H– C
correlation spectrum that the signal at d 4.91 connected to a b
earlier at low temperature where any C–H/C–D bond activation
1
3
34
C resonance which appeared as a 1 : 1 : 1 triplet of 28 Hz in
products might be stabilised. A solution of 1 in d
8
-toluene was
1
3
the C domain. This is consistent with deuteration of the a-ring
therefore photolysed at 213 K in the presence of a 4-fold excess of
1
1
positions in 4d. The H NMR spectrum for the reaction product
Et SiH. H NMR spectra recorded at 213 K after 2 h irradiation
3
formed in d
6
-benzene contained a peak at d 5.06 with only 10%
revealed the presence of free ethene and 4a as the dominant
species, while 4b was observed as a minor component. Two
further photoproducts were generated during this reaction as
demonstrated by the observation of hydride signals at d −15.50
(dd, JRh,H = 3.7, 35.4 Hz) 7a and d −15.19 (dd, JRh,H = 10.7,
33.3 Hz) 7b which were approximately 10% of the intensity
of the expected intensity suggesting that 90% deuteration of the
a-ring proton site was achieved. Examination of this sample by
2
H NMR spectroscopy revealed broad peaks at d 5.06, 1.08,
2
0
.83 and −14.10 that are consistent with H labeling of the
a-ring position, the ethyl groups of the silyl ligands and the
1
hydride site. In order to explore this effect further we photolysed
of the hydride signals arising from 4a. Additional H signals
1
with Et
3
SiH in d12-cyclohexane rather than d
6
-benzene. Under
were also visible at d 9.58, 8.58, 4.19, 4.13, 3.65 and 2.41, with
the corresponding integrals suggesting that the resonances at
d 9.58, 3.65 and 2.41 arose from one species while those at d
8.58, 4.19 and 4.13 corresponded to a second product. Based
on integrals of the d 9.58 and d 8.58 signals these materials
were initially produced in a 1 : 1 ratio, although 7b proved to be
dramatically less stable than 7a with the associated NMR signals
these conditions the level of deuteration of the a-ring site fell
to 80%. These observations suggest that while aromatic C–
H/D activation and exchange is more facile, aliphatic C–H/D
activation and exchange occurs with only slightly less propensity.
Descriptions of how the structures of 5 and 6 fit with their
NMR data can be found in the ESI.† However, important
features worthy of note for 5 are the appearance of the
◦
disappearing over night at −50 C. Similar resonances have
2
9
103
corresponding hydride, Si and Rh resonances. The hydride
been reported for the vinyl-bridged binuclear iridium complexes
1
2
1
2
signal of 5, at d −14.40, is the most diagnostic feature since a
[(C
5
H
5
)Ir(l-g , g -CH=CHtBu)]
2
and [CH
2
(C
5
H
4
)
2
][Ir (l-g , g -
2
second order pattern, corresponding to an [AX]
2
spin system
CH=CHtBu)
2
], which suggested that 7a and 7b also contain
1
2
44
is observed (from simulation JRh,H = 39 and −0.8 Hz, while
l-g , g -vinyl ligands. This was subsequently confirmed, with
the complexes being shown by NMR spectroscopy to have
identical ligand spheres, differing only in the relative vinyl group
orientations as determined by NOE spectroscopy. The structures
of 7a and 7b and a suggested route to their formation are
shown in Fig. 4. These species differ according to the relative
2
9
J
H,H = −1.2 Hz and JRh,Rh = 16.5 Hz). In addition, the Si
resonance for this species appears as a rhodium coupled triplet
at d 205.9 (JRh,Si = 37.3 Hz) which is characteristic of a bridging
43
103
silyl group. The corresponding Rh resonance for 5 was
located at d −2033. Significantly, NOE measurements confirmed
7
5 4
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
These signals were subsequently shown to arise from the ring-
substituted products [(C
5
H
4
)CH
2
(C
5
H
3
SiEt
3
)][Rh(SiEt
3
)
2
(H)
2
]
2
8
and [CH (C SiEt ][Rh(SiEt
2
5
H
3
3
)
2
3
)
2
(H)
]
2 2
, with the latter species
existing as isomers 9a and 9b. The structures of these materials
are shown in Scheme 1.
A full description of the NMR spectroscopic characterisation
of 8, 9a and 9b is given in the ESI,† and their NMR data
are presented in Table 1. Key resonances for these new species
1
appeared in the CH
2
bridge region of the H NMR spectrum
1
13
103
29
at d 3.61, 3.71 and 3.76. Tracing the H, C, Rh and Si
resonance connectivity within these products was achieved via
1
13
1
103
1
29
appropriate high-resolution H– C, H– Rh and H– Si 2D
1
1
HMQC correlations, coupled with appropriate H– H NOE
data. In the case of the complex giving rise to the methylene
bridge proton resonance at d 3.61, two ipso carbon signals were
located at d 110.60 and 111.40. This required the corresponding
product to contain two distinct rings. Four sets of a C and
H resonances were identified for these rings at d 91.89/5.06,
1
3
1
9
1.62/5.12, 91.88/5.28 and 98.31/5.30 respectively. Further
1 13
connections within the 2D H– C NMR spectrum revealed that
Fig. 4 Generation of vinylic C–H activation products 7a and 7b.
the pair of inequivalent aprotons resonating at d 5.06 and 5.12 in
one ring were next to b-ring C nuclei that resonated at d 87.40
1
3
orientations of the silyl and hydride ligands on the higher
oxidation state rhodium centre.
and 87.50 which in turn coupled directly to b-ring protons at d
1
4
5
.90 and 4.93. In the second ring, H resonances at d 5.30 and
.28 were found to connect to b-ring carbon signals at d 95.50
1
03
It should be noted, the Rh spectra of these complexes
proved to be very helpful in their characterisation. The doublet
of doublet multiplicity of each hydride resonance required
both these species to contain inequivalent rhodium centres,
which were subsequently shown to yield signals at d −779
1
3
and 95.63. However, direct C detection demonstrated that the
carbon resonance at d 95.50 arose from a CH group while that
at d 95.63 proved to arise from a carbon centre with no protons
attached. This situation would exist if an SiEt group replaced
3
1
03
and −1407 for 7a and d −666 and −1399 for 7b. The Rh
spectra subsequently revealed Rh–Rh splittings of ca. 14 Hz
which indicates the products contain metal–metal bonds, with
the proton and hence this species corresponded to a silylated
ring substitution product.
The presence of this silyl group was confirmed by three
separate NMR spectroscopic procedures. First, in the long-
1
03
the large chemical shift difference between the Rh signals
further indicating that the two metal centres have different
environments. Full NMR spectroscopic data for 7a and partial
data for 7b are included in Table 1, a description of their
detailed NMR assignments is presented in the ESI.† The
relative amount of 7a and 7b formed in this reaction proved
1
13
range 2D H– C NMR spectrum, a connection between the
CH (d 0.78) proton signal of the SiEt group and the ring
2
3
1
carbon (d 95.63) was observed. In the second method, a H–
1
H NOESY spectrum revealed NOE interactions between the
ring protons and two distinct ethyl group resonances at d
to increase as the initial excess of Et SiH relative to 1 was
3
0
.915 (CH
2
) and 1.12 (CH
) for the second. In the third procedure,
a H– Si correlation was found to contain resonances that
3
), for one type of ethyl, and d 0.78
reduced. Furthermore, both these complexes proved to be
thermally unstable, apparently transforming into 4a and 4b on
warming. Interestingly, the analogous low temperature reaction
(CH ) and 1.044 (CH
2
3
1
29
2
9
connected these ethyl proton resonances to Si signals at d 36.70
RhSi = 17 Hz, Rh–SiEt ) and −0.87 (C SiEt ) respectively.
The full NMR spectroscopic data for complex 8, identified as
(C )CH (C SiEt )][Rh(SiEt (H) , are listed in Table 1.
The remaining two methylene bridge H signals, located
at d 3.71 (br) and 3.76, coupled to single ipso carbon
with Et
2
SiH generated 5 alone.
2
(
J
3
5
H
3
3
Thermal reactions of [CH
SiEt )H] 4a and [CH (C
Et SiH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh (C
2
H
4
)-
[
5
H
4
2
5
H
3
3
3
)
2
]
2 2
(
3
2
5
H
4
)
2
][Rh(C )(SiEt
2
H
4
3
)H] 4b with
2
1
3
1
13
It has been reported that CpRh(C
mally with R
SiH (where R = Me, Et) to generate the
tri(silyl)hydride complex CpRh(SiR H and ethane. However,
the CpRh(SiR H product proved to be unstable and reacted
further to generate the ring-substituted product [C (SiR )][Rh
SiR (H) ] via silyl migration to the capping cyclic polyene.
It was therefore expected that thermal reactions of 4a and
b might provide access to the corresponding trisilyl hydride
2
H
4
)(SiR
3
)H reacts ther-
signals in the long-range 2D H– C NMR spectrum at d
3
111.99 and 111.70 respectively. This reveals that both these
45
3
)
3
products are symmetrical about the CH bridge. Using the
2
3
)
3
same NMR spectroscopic methods described for 8, these two
species were deduced to correspond to the ring-substituted
5
H
4
3
(
3
)
2
2
products [CH
differ only in the relative orientations of the ring substituents
(Scheme 1). It should be noted that, in isomer 9a, the CH
bridge protons should be slightly inequivalent in accordance
2
(C
5
H
3
SiEt
3
)
2
][Rh(SiEt
3
)
2
(H)
2
2
] 9a and 9b which
4
2
or silyl ring substitution products, or even the Si–C bond
activation products 5 and 6. A solution was therefore prepared
with the correspondingly broad CH bridge proton signal at
d 3.71.
2
that contained both 4a and 4b in d
6
-benzene and a greater
than 5-fold excess of Et SiH. The resulting thermal reaction
3
In a further reaction, where the isolation of 4d was attempted,
a 5 mm NMR tube containing 20 mg of 1 in neat Et SiH was
photolysed for 5 h. Upon removal of the volatiles, redissolving in
1
was then monitored by H NMR spectroscopy which revealed
that all resonances arising from 4a and 4b disappeared, with
new signals for 4d, 5 and 6 (in a ratio of 59 : 24 : 17)
becoming visible; the most diagnostic features seen in these
spectra were the corresponding hydride resonances at d −14.09,
3
1
d -benzene, and recording a H NMR spectrum, the apparently
6
selective formation of 4d was confirmed. This reaction was then
scaled up, with a 100 mg sample of 1 being dissolved in neat
−
14.40 and −14.60 respectively. On the basis of these obser-
Et
3
SiH and photolysed for 10 h. The sample was then dried
1
vations it can be concluded that the formation of the Si–C
bond activation products is possible under thermal conditions.
This situation is, however, complicated by the observation of
further hydride resonances at d −14.06 (d, JRh,H = 38 Hz),
under vacuum, dissolved in d -benzene and a H NMR spectrum
6
obtained. Examination of the hydride region of the NMR
spectrum revealed the presence of the three hydride containing
products 8, 9a and 9b as the major products. The formation of
4d was therefore suppressed in this system when the conditions
−
13.92 (d, JRh,H = 37 Hz) and −13.89 (d, JRh,H = 37 Hz).
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 5 5

View Article Online
1
employed were meant to ensure the selective formation of
d.
a 4-fold excess of Me SiH. H NMR spectra recorded after 3 h
3
4
irradiation revealed the presence of free ethene and resonances
corresponding to 10a (major), 10b, 10c and 10d. Two additional
photoproducts were also observed in this reaction—one yielding
a hydride signal at d −12.97 (dd, JRh,H = 17.4, 25.7 Hz), and
Photochemical reactions of [CH
Me SiH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
2
] 1 with
3
tentatively assigned as [CH
H)
d −19.00, and hence assigned as [CH
5. The ratio of 10a : 14 : 15 at this point proved to be 88 : 4 : 8.
A description of the NMR characterisation of 14, which
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)][Rh(SiMe
3
)
2
](l-
In order to explore whether these reactions depended on
the identity of the silane, a d -benzene solution of 1 was
photolysed at 296 K, using a k > 400 nm filter, in the
2
14, and the second yielding a second order resonance at
(C ][RhH(l-SiMe )]
6
2
5
H
4
)
2
2
2
1
1
presence of a 9-fold excess of Me
recorded after 30 min revealed the presence of free ethene
d 5.24) and two rhodium coupled hydride resonances at
3
SiH. H NMR spectra
has the structure shown in Scheme 3, is given in the ESI.†
However, important features that should be noted include the
doublet of doublet multiplicity (17.42 and 25.65 Hz) seen for
the hydride signal. This confirms the presence of two distinct
rhodium centres and a pair of equivalent bridging hydrides.
(
d −14.57 (major) and −14.60 (minor). These observations
suggest that this reaction follows an analogous path to that
described previously with Et
these signals are [CH (C
0a and [CH (C ][Rh(C
pected, extended irradiation did result in the formation
of [CH (C ][Rh(C )(SiMe )H][Rh(SiMe (H) ] 10c and
CH (C ][Rh(SiMe (H) 10d. The NMR characteristics
3
SiH and hence the species yielding
][Rh(C ][Rh(C )(SiMe )H]
)(SiMe )H] 10b. As ex-
2
5
H
4
)
2
2
H
4
)
2
2
H
4
3
1
13
In the long-range 2D H– C NMR spectrum, the CH
protons couple to two ipso carbons, which confirms the presence
of two distinct C rings, and two a-ring carbons, which sup-
ports a symmetrical ligand arrangement about each (C )Rh
2
bridge
1
2
5
H
4
)
2
2
H
4
3
2
5
H
4
2
5
H
4
)
2
2
H
4
3
3
)
2
2
5
H
4
[
2
5
H
4
)
2
3
)
2
]
2 2
1
29
moiety. Furthermore, 2D NOE and H– Si experiments provide
unambiguous evidence for the presence of bound ethene and
of complexes 10a–10d are listed in Table 1 and a description of
the assignment process can be found in the ESI.† Three new
Rh–SiMe ligands in 14.
3
bridged species, identified as [CH
SiMe ] 11, [CH (C
][(Rh{SiMe
and [CH (C })(RhH)(l-SiMe
][(Rh{SiMe
2
(C
})(RhMe)(l-SiMe
] 13 were also
5
H
4
)
2
][(RhMe)(RhH)(l-
1 103
In the 2D H– Rh NMR spectrum, the hydride signal at d
19.00 due to 15 couples to a single rhodium centre resonating
2
)
2
2
5
H
4
)
2
3
)
2 2
] 12
−
2
5
H
4
)
2
3
)
2 2
1
29
at d −1420, and the corresponding 2D H– Si NMR spectrum
formed in this reaction. The structures of these materials are
shown in Scheme 3. At the point when all the Rh(I) and Rh(III)
centres were consumed, the ratio of 10d : 11 : 12 : 13 in solution
proved to be 18 : 34 : 27 : 21.
2
9
contains a triplet at d 204.96 in the Si dimension. These
observations suggested the formation of an analogous species
to 5, with bridging silylene and hydride ligands which couple
to two magnetically distinct rhodium centres. Furthermore, the
2
9
1
Si resonance couples to two peaks in the H dimension at d
1
.16 and 0.86, which indicates the presence of two inequivalent
methyl groups in the SiMe ligands. However, 15 was found to be
2
unstable, and hence the full NMR based characterisation of this
species was not possible. These data however serve to indicate
that the reactivity of 1 towards silanes is highly dependent on
the identity of the silane.
Hydrosilylation
The mononuclear CpRh(C
2
H
4
)(SiR )H Rh(III) systems have
3
been shown to be precursors to catalytically active species
14
Scheme 3 Additional products formed during the photochemical
involved in the hydrosilation of ethene with R
irradiation of complex 1 in d -benzene in the presence of Et
the volatiles were subjected to GCMS analysis which revealed
that Et SiH, Et Si and CH were present. The same
=CHSiEt
analysis was carried out on the volatiles from the analogous
reaction of complex 1 with Me SiH. The GCMS results now
detected EtSiMe , CH and the double insertion
=CHSiMe
product SiMe CH CH SiMe . Hydrosilation of CH
=CHSiMe
SiMe
3
SiH. Following
3
reactions of 1 with HSiMe .
6
3
SiH,
Species 11, 12 and 13 all contain two distinct C
5
H
4
rings,
and produce signals in the corresponding Si NMR spectrum
at d 204.67 (dd, JRh,Si = 34.9, 46.0 Hz), 212.39 (dd, JRh,Si
3
4
2
3
2
9
=
3
3
5.7, 46.2 Hz) and 197.44 (dd, JRh,Si = 29.1, 46.6 Hz) respec-
3
2
3
tively which are characteristic of bridging silyl ligands. These
products are differentiated by their terminal 1-electron donor
3
2
2
3
2
3
would explain the generation of SiMe
3
CH
2
CH
2
3
.
ligands, which correspond to Me/H, SiMe
3
/Me and SiMe /H
3
respectively. A full description of how the NMR spectroscopic
characterisation of 11, 12 and 13 was achieved can be found in
the ESI.†
Conclusions
The work presented in this paper has employed 1D and
D NMR methods to unambiguously characterise a num-
ber of dinuclear rhodium complexes that were formed when
In view of the observations made during the analogous
2
reaction with Et
was expected to yield the Rh(V) species 10d alone. However,
the silylene-bridged complex 13 containing SiMe and H ter-
minations was generated when a sample of 1 was photolysed
in d -benzene with a 10-fold excess of silane for 4 h. Upon
replacing the d -benzene with C , and examining the sample
by H NMR spectroscopy, signals in the methyl region revealed
3
SiH, exhaustive photolysis of 1 with Me
3
SiH
[
CH
2
(C
5
H
2
4
)
2
][Rh(C
2
H
4
)
2
]
2
1 was photolysed in the presence of
3
dmso, CH
=CHSiR
3
and R
3
SiH [R = Me, Et]. These reactions
proved to be relatively unselective, with the presence of two
independent metal centres dramatically increasing the complex-
ity of the situation over that found when the corresponding
mononuclear systems have been examined. The preliminary
NMR spectroscopic studies on 1 revealed dynamic behaviour
6
6
6
H
6
2
2
H labelling of the SiMe
3
and SiMe groups in 13. There was no
2
2
evidence for H incorporation in the rings, which was confirmed
in the H NMR spectrum—the signals at d 4.71, 4.77, 5.02 and
1
via the observation of dramatic variations in the H chemical
shift of the CH
attributed to rotation about the CH
1
2
bridge protons with temperature. This was
–C bond and suggested
5
.13 were all of equal intensity.
2
5
H
4
that the populations of the two extreme conformations available
in solution changed with temperature. Fig. 1 illustrates the
two situations and would suggest that the two metal centres
might react totally independently of one another (B) or show
Low temperature studies with Me
In order to probe these reactions at low temperature, a solution
of 1 in d -toluene was photolysed at 213 K in the presence of
3
SiH
8
7
5 6
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
2
cooperative effects (A). Evidence for both these situations has
been obtained during these studies.
Photochemical studies on the reaction of 1 in dmso have
revealed that one of the ethene ligands of each rhodium centre in
in toluene, no phenyl hydride or g -arene containing complexes
were detected. However, deuterium incorporation into 4d and
10d provided evidence for the transient existence of such
products. The enhanced stability of 7a over 7b is most likely a
result of the relative orientations of the hydride and silyl ligands
on the rhodium centre with the higher oxidation state.
1
can be readily replaced with dmso. This led to the stepwise for-
mation of [CH (C ][Rh(C ][Rh(C )(dmso)] 2a and
CH (C ][Rh(C )(dmso)] 2b, where the dmso ligand is
bound through the sulfur atom. This deduction was based on
2
5
H
4
)
4
2
2
H
2
4
)
2
2
H
4
[
2
5
H
4
)
2
2
H
Similar H/D exchange processes have been observed be-
fore. For example, Maitlis et al. observed H/D exchange
(H) , a known thermal source of [Cp*Rh-
(SiEt )H], was heated in d -benzene. Later, Berry et al.
revealed that this complex was an active catalyst for the
formation of arylsilanes. However, it should be noted that there
was no evidence to suggest that similar functionalised aryl
species were generated here. The detection of the silylene-bridged
species 5 and 6, following the photochemical reaction of 1 with
1
3
the downfield shift of the corresponding C methyl resonances
when Cp*Rh(SiEt
3
)
2
2
1
1
2
0
(
with respect to that of free dmso) which matches the findings
3
6
37
in related species.
Low temperature in-situ photochemical studies where
was irradiated in d -toluene in the absence of sub-
strate enabled the detection of the labile solvent com-
1
8
2
plex [CH
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)
2
][Rh(C
2
H )(g -toluene)] which
4
was found to exist in two interconverting isomeric forms that
differ only in the relative orientation of the g -toluene ligand. The
Et
is [CH
3
SiH is, however, significant since it confirms that not only
(C ][Rh(C )(SiEt )H][Rh(SiEt )H] able to C–H
2
2
5
H
4
)
2
2
H
4
3
3
photochemical substitutions are therefore likely to first involve
the generation of an unstable solvent complex. No evidence for
H/D exchange with the solvent was observed in this experiment.
The photochemical reaction of 1 with vinyltrimethylsilane
demonstrated that three isomeric forms of the double substi-
and Si–H bond activate, but that Si–C bond activation is also
possible. Notably, when the photolysis was completed at low
temperature, these silylene bridged complexes are not observed,
but the corresponding vinyl activation species are produced.
This indicates that there is a higher activation barrier for Si–C
cleavage and the products of this process are relatively stable.
The H resonances corresponding to free ethene and ethane
generated in these experiments showed no signs of splitting due
to deuterium incorporation.
tution product [CH
c) could be obtained after exhaustive photolysis. These differ in
the relative orientations of the SiMe substituents as illustrated
in Fig. 3. Examination of the NMR spectra obtained for
these samples revealed H/D exchange between the solvent, d
2
(C
5
H
4
)
2
][Rh(CH
2
=CHSiMe
3
)
2
]
2
(3a, 3b and
1
3
3
6
-
It is interesting to note the variability in the bridged sily-
lene products that were formed at room temperature.
benzene, and the aproton of free vinyltrimethylsilane. Brookhart
et al. have previously observed deuterium incorporation into
With Et
[CH (C
(RhEt)(l-SiEt
bridged species are observed; [CH
SiMe ] 11, [CH (C
][(Rh{SiMe
and [CH (C })(RhH)(l-SiMe
][(Rh{SiMe
mation of the (H)(Et) and (H)(Me) analogues suggests that the
source of the Rh–Et ligand in [CH (C ][(RhH)(RhEt)(l-
3
SiH, two silylene bridged complexes are generated;
][Rh(l-SiEt )H] and [CH (C ][(RhH)-
6. While for Me SiH, three silylene
(C ][(RhMe)(RhH)(l-
})(RhMe)(l-SiMe ] 12
] 13. The for-
the vinylic sites of the olefin ligands of Cp*Co(CH
2
=CHR)
2
2
5
H
4
)
2
2
2
5
2
5
H
)
4 2
(
where R = H, SiMe
3
) following heating of these complexes
2
)
2
]
3
46
47
in d
6
-benzene. Earlier studies by Seiwell found similar H/D
2
5
H
)
4 2
5
exchange with (g -C
they were heated in d
involving solvent coordination to the coordinatively unsaturated
M(olefin)] fragment, followed by H/D exchange with the
olefin and subsequent elimination of C H was proposed.
Brookhart et al. have also prepared the analogous rhodium
5
R
5
)Rh(C
2
H
4
)
2
(where R = H, Me) when
2
)
2
2
5
H
4
)
2
3
)
2 2
6
-benzene. In both cases, a mechanism
2
5
H
4
)
2
3
)
2 2
[C
5
R
5
2
5
H
)
4 2
6
D
5
42
complexes Cp*Rh(CH
2
=CHR)
2
(where R = SiMe
3
, SiMe OEt,
2
i
i
Si(O Pr)
3
, SiMe(OSiMe , SiPh
3
)
2
2
O Pr) and seen similar effects,
as have Perutz et al. during their photochemical studies of
41
CpRh(C
2
H
4
)
2
.
The photochemical studies with Et
3
SiH and Me SiH have
3
demonstrated that upon ethene loss, complex 1 is able to activate
the Si–H bonds of the trialkylsilanes as shown in Scheme 2.
The primary photoproducts of these reactions contain both
Rh(I) and Rh(III) centres but upon extended photolysis, the
stepwise replacement of ethene is observed. This enabled the
corresponding Rh(III)/(III), Rh(III)/(V) and Rh(V)/(V) species, to
2
be characterised. The small values of the JSi
–
hydride coupling
H
constants determined for the SiEt containing complexes 4a
3
(
J
SiH = 14 Hz), 4b (JSiH = 14 Hz) and 4d (JSiH = 9 Hz) imply
that full oxidative addition of the Si–H bond has occurred.
In addition, the value of JRhH in 4a is 33.5 Hz and 4d is
38.5 Hz which allows the Rh(III) and Rh(V) centres to be
readily distinguished. There is also a systematic shift in the
1
03
Rh chemical shifts found for these complexes to higher field
on increasing the oxidation state from Rh(I) to (III) to (V). For
example, the values found for 1, 4a and 4d are d −929 (Rh(I)),
−
1483 (Rh(III)) and −1873 (Rh(V)).
The 16-electron fragment [(C
5 4
H
)R][Rh(SiEt
3
)H] (where R =
[CH (C )][Rh(C )(SiEt )H]), formed by photolysis in these
2
5
H
4
2
H
4
3
reactions, has also been shown at low temperature to activate
the C–H bonds of the ethene ligand attached to the second
Rh centre (Fig. 4). Two geometries of the corresponding vinyl
hydride product 7 were detected in solution. This information
demonstrates that the proximity of the second Rh centre can lead
to novel reaction chemistry. Here, activation of a ligand which
is remotely coordinated to the metal centre is demonstrated.
Although these reactions were undertaken at low temperature
Scheme 4 Pathways to the Si–C bond activation products observed
during the reactions of 10b with Me SiH.
3
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 5 7

View Article Online
−
1
SiEt
2
)
2
] is therefore Et
3
SiH, and not an ethene ligand, as
and Si–C 384 kJ mol ), it would seem plausible that reactions
1
−
−1
indicated in Scheme 4.
involving C–C (368 kJ mol ) or Si–Si (226 kJ mol ) bond
cleavage should also become feasible in these systems if suitable
groups can be brought together. We are currently exploring these
reactions.
The ratio of Rh(V) products to Si–C cleavage products
obtained in these reactions proved to be influenced by the excess
of silane relative to the corresponding unsaturated fragment.
Thus when 1 was photolysed on an NMR scale in neat Et SiH,
3
neither 5 nor 6 were observed—only the product of ethene loss
and Si–H activation, 4d, was generated. Consequently, as the
Acknowledgements
S. B. D. and J. L. C. are grateful to the EPSRC and Bruker UK for
support. A generous loan of rhodium trichloride from Johnson
Matthey PLC (“JM”) is acknowledged. Helpful discussions with
Prof. R. N. Perutz and Dr R. J. Mawby are also acknowledged.‘
concentration of Et SiH rises, the reaction pathways that lead
3
to the formation of the silylene bridged species are suppressed
because the rate of intra-molecular Si–C activation no longer
competes with inter-molecular Si–H activation of the free silane.
When the original excess of Et SiH relative to 1 was between 8
and 12-fold, the ratio of Rh(V) to silylene bridged species proved
3
References
1
2
3
T. S. Piper, D. Lemal and G. Wilkinson, Naturwissenschaften, 1956,
3, 129.
(a) J. Y. Corey and J. Braddock-Wilking, Chem. Rev., 1999, 99, 175;
to be approximately 7 : 3. However, when 1 was photolysed in
4
the presence of between a 6- and 8-fold excess of Me SiH, the
3
corresponding ratio proved to be approximately 2 : 8 in favour
of the Si–C activation products. This demonstrates that intra-
molecular Si–C bond activation of a Si–Me bond is more facile
than that of a Si–Et bond.
(
b) U. Schubert, Transition Met. Chem., 1991, 16, 136.
I. Ojima, The Chemistry of Organic Silicon Compounds, John Wiley
and Sons Ltd., New York, 1989, ch. 25, 1479.
4 (a) H. Yang, M. C. Asplund, K. T. Kotz, M. J. Wilkens, H. Frei and
C. B. Harris, J. Am. Chem. Soc., 1998, 120, 10154; (b) H. Yang, K. T.
Kotz, M. C. Asplund and C. B. Harris, J. Am. Chem. Soc., 1997, 119,
The low temperature photochemical studies with Me
also suggested that while the formation of similar vinyl hydride
species to those observed in the presence of Et SiH was
3
SiH
9
564.
3
5
X.-L. Luo, G. J. Kubas, C. J. Burns, J. C. Bryan and C. I. Unkefer,
J. Am. Chem. Soc., 1995, 117, 1159.
A. J. Oliver and W. A. G. Graham, Inorg. Chem., 1971, 10, 1.
possible, they were observed at only a 1% level, with Si–
C bond activation products dominating. This suggests that a
substantial contribution to the Si–C bond activation barrier is
steric in origin. The detection of the bridging hydride complex
6
7 A. J. Chalk and J. F. Harrod, J. Am. Chem. Soc., 1965, 87, 16.
8 J. L. Speier, Adv. Organomet. Chem., 1979, 17, 407.
9
A. Millan, E. Towns and P. M. Maitlis, J. Chem. Soc., Chem.
Commun., 1981, 673.
[
CH
ble silylene bridged species [CH
that is analogous to 5, supports this view.
2
(C
5
H
4
)
2
][Rh(C
2
H
4
)][Rh(SiMe
3
)
2
](l-H)
2
14, and the unsta-
)H] 15,
2
(C
5
H
4
)
2
][Rh(l-SiMe
2
2
1
1
0 M.-J. Fernandez and P. M. Maitlis, J. Chem. Soc., Chem. Commun.,
982, 310.
1 P. O. Bentz, J. Ruiz, B. E. Mann, C. M. Spencer and P. M. Maitlis,
1
43
A review by Ogina and Tobita reveals numerous examples
of similarly bridged silylene complexes which are generally
formed by the reaction of di-, tri- and tetra-hydrosilanes
with coordinatively unsaturated metal centres, although an
alternative approach involves the oxidative addition of both the
Si–H and Si–Si bonds of disilanes to metal centres. It appears
that the formation of such species via Si–C bond activation
J. Chem. Soc., Chem. Commun., 1985, 1374.
12 J. Ruiz, P. O. Bentz, B. E. Mann, C. M. Spencer, B. F. Taylor and
P. M. Maitlis, J. Chem. Soc., Dalton Trans., 1987, 2709.
1
3 (a) D. M. Haddleton and R. N. Perutz, J. Chem. Soc., Chem. Com-
mun., 1985, 1372; (b) S. B. Duckett, D. M. Haddleton, S. A. Jackson,
R. N. Perutz, M. Poliakoff and R. K. Upmacis, Organometallics,
1
988, 7, 1526.
48
is less common, although, Suzuki et al. have published data
on the reactions of (Cp*Ru) (l-H) with vinyltrimethylsilane.
They observed the l-dimethylsilylene, l-ethylidyne species
Cp*Ru) (l-SiMe )(l-CCH )(l-H), generated by double Si–C
bond activation. While Oskada et al. have reported that the
14 S. B. Duckett and R. N. Perutz, Organometallics, 1992, 11, 90.
15 F. Seitz and M. S. Wrighton, Angew. Chem., Int. Ed. Engl., 1988, 27,
2
4
2
89.
1
1
6 M. Brookhart and B. E. Grant, J. Am. Chem. Soc., 1993, 115, 2151.
7 M. Brookhart, B. E. Grant, C. P. Lenges, M. H. Prosenc and P. S.
White, Angew. Chem. Int. Ed., 2000, 39, 1676.
(
2
2
3
49
reaction of tris(2-phenylethyl)silane with [RhClL
2
] (where L =
1
8 T. B. Marder, D. C. Roe and D. Milstein, Organometallics, 1988, 7,
i
P( Pr)
3
) generated the species [Rh(H)
2
L(l-SiR
2
)]
2
as a result of
1451.
both Si–H and Si–C bond activation. Redistribution reactions
where silane substituents are exchanged represent an important
organosilicon based reaction that involves Si–C bond cleav-
age and reformation. Sabo-Etienne et al. have used this ap-
19 C. P. Lenges, P. S. White and M. Brookhart, J. Am. Chem. Soc., 1998,
1
20, 6965.
2
0 K. Ezbiansky, P. I. Djurovich, M. LaForest, D. J. Sinning, R. Zayes
and D. H. Berry, Organometallics, 1998, 17, 1455.
2
2
1 C. P. Lenges and M. Brookhart, J. Am. Chem. Soc., 1999, 121, 6616.
2 (a) K. M. Waltz, C. N. Muhoro and J. F. Hartwig, Organometallics,
2
2
2
2
proach to generate novel bridging silanes in Ru
2
4
H (l-g :g :g :g -
50
2
2
SiH
4
)(PCy
3
)
4
and Ru
2
H
2
(l-g :g -SiH
2
(Me)
2
)
3
(PCy ) . The cat-
3
2
1
999, 18, 3383; (b) H. Chen, S. Schlecht, T. C. Semple and J. F.
alytic formation of SiC bonds from CH and SiH containing
substrates provides an exciting opportunity for efficient catalytic
CH bond functionalisation.
Thermal reactivity studies on the Rh(III) complexes 4a and 4b
showed that they react to form 4c, 4d, 5 and 6 when the excess
of silane relative to the precursor is restricted to 10-fold or less.
However, this situation is complicated by the observation of the
Hartwig, Science, 2000, 287, 1995; (c) K. M. Waltz and J. F. Hartwig,
J. Am. Chem. Soc., 2000, 122, 11358; (d) K. Kawamura and J. F.
Hartwig, J. Am. Chem. Soc., 2001, 123, 8422; (e) Y. Kondo, D. Garc ´ı a-
Cuadrado, J. F. Hartwig, N. K. Boaen, N. L. Wagner and M. A.
Hillmyer, J. Am. Chem. Soc., 2002, 124, 1164.
51,52
2
3 (a) H. E. Bryndza and R. G. Bergman, J. Am. Chem. Soc., 1979, 101,
4
766; (b) N. E. Schore, C. S. Ilenda, M. A. White, H. E. Bryndza,
M. G. Matturo and R. G. Bergman, J. Am. Chem. Soc., 1984, 106,
7451.
SiEt
silane is present. During studies on the analogous mononuclear
systems, Perutz et al. observed that, CpRh(C )(SiEt )(H)
formed CpRh(SiEt (H) on reaction with two equivalents of
silane, and that species ultimately yielded the analogous complex
3
ring-substituted products 8 and 9 when a large excess of
2
2
4 H. Werner, H. J. Scholz and R. Zolk, Chem. Ber., 1985, 118, 4531.
5 H. Werner, M. Treiber, A. Nessel, F. Lippert, P. Betz and C. Kr u¨ ger,
Chem. Ber., 1992, 125, 337.
6 (a) S. Braun, H.-O. Kalinowski and S. Berger, S. 150 and More
Basic NMR Experiments, Wiley-VCH, New York, 2nd edn., 1998;
(b) A. E. Derome, Modern NMR Techniques for Chemistry Research,
Pergamon Press, Oxford, 1987.
2
H
4
3
)
3 3
2
45
(
C
5
H
4
SiEt
3
)Rh(SiEt
3
)
2
(H) as the only reaction product. The
2
role of a similar, but undetected, tri(silyl)hydride complex is
therefore suspected here.
2
7 K. Stott, J. Stonehouse, J. Keeler, T. L. Hwang and A. J. Shaka, J. Am.
Chem. Soc., 1995, 117, 4199.
Collectively, these observations reveal the accessibility of
intermolecular Si–H and C–H activation pathways, and in-
tramolecular Si–H, Si–C and C–H activation pathways. In
view of these findings, and consideration of the relative bond
2
2
3
8 R. Wagner and S. Berger, J. Magn. Reson., 1996, 123A, 119.
9 J. C. Smart and C. J. Curtis, Inorg. Chem., 1977, 16, 1788.
0 H. Schaltegger, M. Neuenschwander and D. Meuche, Helv. Chim.
Acta, 1965, 48, 955.
−
1
−1
dissociation energies (e.g. Si–H 318 kJ mol , C–H 435 kJ mol
31 T. E. Bitterwolf, J. Organomet. Chem., 1986, 312, 197.
7
5 8
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9

View Article Online
3
3
3
2 R. Cramer, Inorg. Synth., 1974, 15, 14.
Angew. Chem., 1991, 103, 999; (b) H. Werner, J. Wolf, A. Nessel,
A. Fries, B. Stempfle and O. N u¨ rnberg, Can. J. Chem., 1995, 73,
1050.
3 H. Werner, H. J. Scholz and R. Zolk, Chem. Ber., 1985, 118, 4531.
4 C. Godard, P. Callaghan, J. L. Cunningham, S. B. Duckett, J. A. B.
Lohman and R. N. Perutz, Chem. Commun., 2002, 2836.
5 M. D. Rausch, W. C. Spink, B. G. Conway, R. D. Rogers and J. L.
Atwood, J. Organomet. Chem., 1990, 383, 227.
45 S. B. Duckett and R. N. Perutz, J. Chem. Soc., Chem. Commun., 1991,
3
28.
46 C. P. Lenges, M. Brookhart and B. E. Grant, J. Organomet. Chem.,
1997, 528, 199.
47 L. P. Seiwell, J. Am. Chem. Soc., 1974, 96, 7134.
48 T. Takao, M. Amako and H. Suzuki, Organometallics, 2001, 20, 3406.
49 K. Osakada, T. Koizumi and T. Yamamoto, Bull. Chem. Soc. Jpn.,
1997, 70, 189.
50 R. B. Said, K. Hussein, J.-C. Barthelat, I. Atheaux, S. Sabo-Etienne,
M. Grellier, B. Donnadieu and B. Chaudret, Dalton Trans., 2003,
4139.
3
3
6 R. Cramer and J. J. Mrowca, Inorg. Chim. Acta, 1971, 5, 528.
7 J. D. Fotheringham, G. A. Heath, A. J. Lindsay and T. A. Stephenson,
J. Chem. Res., Synop., 1986, 82.
8 S. B. Belt, D. M. Haddleton, R. N. Perutz, B. P. Smith and A. J.
Dixon, J. Chem. Soc., Chem. Commun., 1987, 1347.
9 T. W. Bell, M. Helliwell, M. G. Partridge and R. N. Perutz,
Organometallics, 1992, 11, 1911.
3
3
4
4
4
0 C. L. Higgitt, A. H. Klahn, M. H. Moore, B. Oelckers, M. G.
Partridge and R. N. Perutz, J. Chem. Soc., Dalton Trans., 1997, 1269.
1 S. T. Belt, S. B. Duckett, D. M. Haddleton and R. N. Perutz,
Organometallics, 1989, 8, 748.
51 V. K. Diourmaev, L. J. Procopio, P. J. Carroll and D. H. Berry, J. Am.
Chem. Soc., 2003, 125, 8043.
52 (a) F. Kakiuchi, F. M. Matsumoto, K. Tsuchiya, K. Igi, T. Hayamizu,
N. Chatani and S. Murai, J. Organomet. Chem., 2003, 686, 134;
(b) F. Kakiuchi, K. Tsuchiya, M. Matsumoto, B. Mizushima and N.
Chatani, J. Am. Chem. Soc., 2004, 126, 12792.
2 C. P. Lenges, P. S. White and M. Brookhart, J. Amer. Chem. Soc.,
1
999, 121, 4385.
4
4
3 H. Ogina and H. Tobita, Adv. Organomet. Chem., 1998, 42, 223.
4 (a) Nessel, O. N u¨ rnberg, J. Wolf and H. Werner, Angew. Chem. Int.
Ed., 1991, 30, 1006; Nessel, O. N u¨ rnberg, J. Wolf and H. Werner,
D a l t o n T r a n s . , 2 0 0 5 , 7 4 4 – 7 5 9
7 5 9