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Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
Photochemical reactions of [CH2(C5H4)2][Rh(C2H4)2]2 with silanes: evidence for Si-C and
C-H activation pathways.
Jenny L. Cunningham and Simon B. Duckett.*
Department of Chemistry, University of York, YO10 5DD, United Kingdom
Supporting Information
Mass spectroscopic data for [CH2(C5H4)2][Rh(C2H4)2] 2 1
M/z
460
432
404
376
374
348
346
218
168
Fragment
M+
M+-C2H4
M+-2C2H4
M+-3C2H4
[C11H8Rh2(C2H4)]+
M+-4C2H4
[C11H8Rh2]+
[C9H7Rh]+
[C5H5Rh]+
Photochemical reaction of [CH2(C5H4)2][Rh(C2H4)2]2 1 with dmso. In order to investigate the
photochemical reactivity of 1, a solution of 1 in dmso-d6 was photolysed using broad band UV
irradiation from a 350 W Xe arc and the reaction monitored by 1D and 2D NMR spectroscopic
methods. After 15 min irradiation, a 1H NMR spectrum recorded at 300 K revealed the presence of
free ethene ( 5.41) and two new peaks at  2.72 (major) and 2.68 (minor) corresponding to the CH2
bridge protons of two metal-based photoproducts; such CH2 bridge 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 analogue of 1, CpRh(C2H4)2, is photolysed
with dmso the mono-substituted product CpRh(C2H4)(dmso) is obtained.Error! Bookmark not
defined. It was therefore expected that products corresponding to the successive loss of one ethene
ligand from each metal centre, namely [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)] 2a and
[CH2(C5H4)2][Rh(C2H4)(dmso)]2 2b, would be formed. Complex 2a contains two distinct C5H4
rings, in agreement with the fact that the CH2 bridge 1H resonance for this species at  2.72
connects to two ipso carbon resonances, at  101.52 and 104.84, and two  C5H4 carbons, at 
85.42 and 87.40 in the long-range 1H-13C NMR spectrum. It should be noted that the carbon
resonances at  87.40 and 104.84 are very similar to those observed for 1, in dmso, and hence can
1
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be attributed to the ring carbons of the [Rh(C2H4)2] moiety. Subsequently, direct one-bond
couplings between the
13
C signals at  85.42 and 87.40, and 1H resonances at  5.08 and 5.32
respectively located the -C5H4 proton resonances in 2a. The corresponding -C5H4 protons were
located at  5.23 and 5.05 in a similar way while 2D 1H-103Rh NMR spectroscopy revealed the
presence of two 103Rh resonances for 2a at  -929 and -613.
Upon extended photolysis [CH2(C5H4)2] [Rh(C2H4)(dmso)]2 2b became the sole product.
This product yields 1H NMR peaks at  5.07 and 5.21 (for the two sets of C5H4 protons), 2.68 (for
the CH2 bridge) and, 2.27 and 1.67 (for the ethene protons). Furthermore, a single 103Rh signal was
observed at  -617. Full NMR data for these two species is presented in Table 1.
A key feature in the 1H NMR spectra of both 2a and 2b was the observation of fine structure
for the ethene signals (at  2.28 and 1.67, 2a;  2.27 and 1.67, 2b). This indicates that there is now a
substantial barrier to alkene rotation in the dmso substituted centre. In the 1H-1H nOe spectrum,
much stronger interactions connect the -C5H4 ring protons ( 5.08 and 5.07) to the ethene ligand
protons than the -ring protons ( 5.23 and 5.21) and hence indicate that these ethene ligands spend
the majority of the time on the ‘internal face’ of the complex and the dmso ligands ‘on the outer
face’, with the ethene protons resonating at  2.28 and 2.27 pointing towards the rings. In order to
determine the orientation and binding mode of the dmso ligands in 2a and 2b a d6-benzene solution
of 1 was photolysed in the presence of a 12-fold excess of dmso-h6 until 1H NMR spectra recorded
at 300 K revealed the formation of both the mono- and di-substituted products. A 2D 1H-13C NMR
experiment then connected the methyl 1H and
13
C resonances of free dmso ( 1.78, 39.59), the
monosubstituted product ( 2.49, 53.71) and the disubstituted product ( 2.53, 53.63).
The
downfield shift of the 13C resonances (with respect to the free dmso) has previously been shown to
be indicative of dmso binding through the S atom in both products.1 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.
Low temperature in-situ photolysis of [CH2(C5H4)2][Rh(C2H4)2]2 1 in d8-toluene
A sample of complex 1 (5 mg) was dissolved in d8-toluene, in a 5 mm NMR tube, and placed into
the NMR spectrometer. The NMR probe, designed specifically for in-situ photolysis, was then
cooled to 203 K and a 1H NMR spectrum was recorded. The sample was then photolysed in-situ
and 1H NMR spectra recorded at regular intervals to monitor any photochemical reactions that were
occurring. After 2 hrs irradiation, there was evidence for a new species in the 1H NMR spectrum,
most notably via the observation of a new CH2 resonance, corresponding to the bridging methylene
2
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group, at  2.35. Free ethene was detected at  5.31 and no hydride resonances were observed in
the region  -5 to -25.
On the basis of these data, the new species described here was assigned to the solvent complex
[CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(2-toluene)]. Two possible isomers for this complex might be
expected, as shown in Figure 1.
Rh
R
Rh
Rh
Rh
R
Figure 1: Structures of the possible isomers of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(2-toluene)]
(where R = CD3).
The two structures drawn in Figure 1 would be expected to yield at least sixteen ring proton
resonances. After 18 hrs irradiation, 50 % conversion to this species was observed and over 50 hrs
of spectrometer time were used to characterise this solvent complex. In the 1H NMR spectrum,
peaks at  4.08, 4.14, 4.54, 4.61, 4.85, 5.05 and 5.12, corresponding to C 5H4 ring protons, and  0.18, 1.42, 2.53 and 2.89, attributed to ethene protons respectively, were readily visible. It was
noted that the peak at  4.54 was more intense than the other ring resonances. A 2D NOESY NMR
experiment located exchange cross-peaks between some of the observed resonances and hence
confirmed the presence of dynamic behaviour.
In these complexes, movement of the arene in an 2-2 fashion is possible which would lead to an
apparent plane of symmetry in each isomer and hence halve the number of ring proton resonances
to eight (four for each isomer). Arene rotation, which interconverts the two forms, and ethene
rotation is also possible. The reduced number of ring proton resonances observed supports the
former suggestion and, in addition, the fact that positive cross-peaks were observed between signals
at  4.08 and 4.61,  4.14 and 4.85, and  5.05 and 5.12 due to the interconversion of six
inequivalent ring proton environments at 203 K would indicate that arene rotation occurs.
Additionally, the nOe NMR spectrum also revealed rapid exchange between all four ethene proton
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signals  1.42 and -0.18, and  2.89 and 2.53. This supports the idea that both the arene and alkene
rotate. However, the signals at  1.42 and 2.89 had a weak doublet splitting, in contrast to the two
at  -0.18 and 2.53, which were broader. This indicated that the former two signals corresponded to
the more stable isomer. At 183 K nOe interactions were detected between the resonances at  2.53
and 2.89 and the ring protons which confirmed that the two signals arose from ethene protons
pointing up towards the C5H4 rings.
These nOe NMR spectra also located two ethene resonances at  1.34 and 2.81, which also
interconverted, due to the Rh(C2H4)2 units. (Overlap with the corresponding ethene resonances in
the starting material masked these signals in the 1D 1H NMR spectrum). These signals connected
to resonances at  5.12, 5.05 and 4.54 due to the corresponding C5H4 ring protons.
The CH2 bridge proton resonance showed nOe interactions to four ring signals at  5.12, 5.05, 4.85
and 4.14, which is consistent with these resonances arising from the -C5H4 protons. Connections
from these resonances then confirmed the identity of the -C5H4 protons;  5.12  4.54,  5.05 
4.54,  4.85  4.61 and  4.14  4.08. These observations are illustrated in Figure 2. It should be
noted that although resonances have been assigned for each isomer, the actual orientation of the
toluene ligand cannot be determined i.e. it is not possible to assign the up or down isomer.
Exchange observed:
4.61  4.08
4.85  4.14
5.05  5.12
1.42  2.89, -0.18, 2.53
2.89  1.42, 2.53, -0.18
1.34  2.81
4.85
2.35
4.61
Rh
2.89
1.42
5.05
4.14
4.54
2.35
4.08
R
Rh
Rh
1.34
2.81
2.53
-0.18
R
4
5.12
4.54
Rh
1.34
2.81
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Figure 2: 1H chemical shifts (ppm) in the two isomers of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(2toluene)] 3. (Note that the chemical shifts are placed nearest to the carbon atoms to which the
corresponding protons are attached).
We conclude that two isomeric forms of the solvent complex exist and they are interconverting.
It should be noted that although the two isomers give rise to a common CH2 bridge 1H signal at 
2.35, in the corresponding 2D 1H-13C correlation, this proton connects to two carbon resonances at 
24.75 and 23.78. These data demonstrate that the exchange rate is sufficiently rapid at 198 K for an
average signal to be seen for the CH2 bridge protons, but insufficient to average the corresponding
13
C peaks. In addition, 13C resonances were identified for the [CH2(C5H4)] unit bound to a rhodium
centre with ethene and toluene ligands;  93.15 (connected to the 1H at  4.08), 89.39 (4.14) and
101.86 (ipso carbon). The ipso and 
13
C resonances for the ring nuclei of the [Rh(C2H4)2] side
were located at  103.86, 88.00 (5.12) and 87.87 (5.05) via long-range connections to the CH2
bridge 1H signal at  2.35. This data is summarised in Table 1.
Table
1:
NMR
spectroscopic
data
2
[CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)( -toluene)]
2
for
the
3
1
4
a
Rh
Rh
1
H NMR
(d8-toluene,
203 K)
R
/ppm (multiplicity)
(i) 4.85 (br)
(ii) 4.14 (br)
(i) 4.61 (br)
(ii) 4.08 (br)
(i) 1.42 (br, down),
2.89 (br, up)
(ii) -0.18 (br, down), 2.53
(br, up)
2.35 (br)
(i) 5.05 (br)
(ii) 5.12 (br)
5
b
assignment
-C5H42
-C5H41
C2H4a
CH2 bridge
-C5H43
two
isomers
of
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4.54 (br)
1.34 (br), 2.81 (br)
13
C NMR
(ii) 89.39 (m)
(ii) 93.15 (m)
101.86 (m)
24.75 (s), 23.78 (s)
(i) 87.87 (m)
(ii) 88.00 (m)
103.86 (m)
-C5H44
C2H4b
-C5H42
-C5H41
ipso C5H4a
CH2 bridge
-C5H43
Ipso-C5H4b
NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(CH2=CHSiMe3)2]2 3a, 3b and 3c
R
R
R
Rh
Rh
R
R
R
Rh
Rh
R
R
3b
3a
R
R
Rh
Rh
R
R
3c
Complex 3a yields a singlet at  3.58 in the 1D 1H NMR spectrum corresponding to the equivalent
CH2 bridge protons. In the long-range 2D 1H-13C NMR spectrum, this signal shows connections to
one ipso carbon resonating at  107.92, and two  C5H4 carbon resonances at  87.89 and 87.75,
which in turn couple to two  1H resonances at  4.87 and 5.13 respectively. These observations
support the symmetrical structure for 3a. 2D NOESY spectra confirmed the identities of the C5H4
protons, which give rise to 1H resonances at  4.87 (), 5.52 (), 4.36 () and 5.13 (). In addition,
three vinylsilane CH 1H signals are visible at  2.58 (), 2.46 () and -0.25 (). Comparison of
these chemical shifts with those observed for analogous complexes suggests that the vinylsilane
ligands in 3a are in a trans orientation. Strong nOe interactions between the vinyl resonance at 
2.58 and the CH2 bridge and four C5H4 resonances confirm that this vinyl proton points upwards,
towards the C5H4 rings. A 1H signal at  0.14, corresponding to the SiMe3 protons, also shows
strong nOe interactions with the ring protons, as well as with the vinyl signal at  2.58. The other
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vinyl 1H signals at  -0.25 and 2.46 show no nOe interactions with the ring or bridging protons, but
are close in space to each other, with the resonance at  2.46 also showing nOe interactions to the
proton resonating at  2.58. In the 2D 1H-29Si NMR spectrum a 29Si resonance at  0.30 connects to
the 1H signal at  0.14. These observations confirm the orientation of the vinyl ligands with the
SiMe3 units pointing towards the C5H4 rings. The remaining
short-range 2D 1H-13C experiment. Notably, the vinyl
13
13
C resonances were located via a
C signals were identified at  53.72 and
43.05 via connections to signals at  -0.25, and  2.58 and 2.46 respectively. A single
103
Rh signal
for 3a was identified at  -782 in the corresponding 1H-103Rh NMR spectra, via connections to the
vinyl and C5H4 protons.
Complex 3b contains inequivalent CH2 bridge protons, which give rise to 1H signals at  3.74 and
3.50 corresponding to an AB pattern where JH,H = 15.7 Hz. Similarly to complex 3a, one ipso
carbon was identified at  108.26, and four C5H4 protons were located at  4.76 (), 5.48 (), 4.41
() and 5.20 (). On the basis of these observations it can be concluded that the two halves of 3b
are identical. The vinyl ligands in this complex produce 1H resonances at  2.60, 2.44, 0.13 (SiMe3)
and -0.246, and similar interactions to those observed in complex 3a were detected. For example,
the 1H resonance at  2.58 shows nOe interactions with resonances at  3.74, 3.50 (CH2 bridge) and
the four C5H4 protons, confirming that the protons giving rise to this signal point towards the rings.
The 29Si and
Rh resonances were identified at  0.27 and -780 respectively in the corresponding
103
2D correlations, and the remaining
13
C resonances were located via a short-range 2D 1H-13C
experiment.
Weak 1H resonances for the third isomer 3c appear at  3.55 and 3.68, for the inequivalent CH2
bridge protons,  2.61, 2.46, -0.26 and 0.145 (SiMe3), for the trans vinylsilane ligands, and  2.77,
1.64, 0.77 and 0.144 (SiMe3), for the cis vinylsilane ligands. The observation of eight C5H4 ring 1H
resonances at  5.51, 5.23, 5.20, 5.15, 4.88, 4.74, 4.69 and 4.40 supports the absence of symmetry
in 3c. In the 2D NOESY spectra, the 1H resonances at  3.68 and 3.55 show nOe interactions with
the four  C5H4 protons, at  5.20, 4.88, 4.74 and 4.69, and the vinyl protons resonating at  2.61
and 2.77. Long-range 2D 1H-13C NMR spectra enabled characterisation of the ring and vinyl
ligands in 3c. The corresponding 29Si chemical shifts of the SiMe3 groups appear at  0.30 and 0.89
in the 2D 1H-29Si NMR spectrum, and the two rhodium centres yield 103Rh resonances at  -782 and
-736 in the 2D 1H-103Rh spectrum.
7
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NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2] 4c
Et3Si
Rh
H Rh SiEt3
H
Et3Si
H
4c
Key 1H NMR spectroscopic features arising from complex 4c include two hydride resonances at  14.64 (d, JRh,H = 33.5 Hz) and -14.08 (d, JRh,H = 38.5 Hz), with
103
Rh couplings indicating the
presence of a Rh(III) and a Rh(V) centre respectively, and a CH2 bridge 1H resonance at  3.17. In
the corresponding long-range 2D 1H-13C NMR spectrum the CH2 bridge protons connect to two
ipso carbons resonating at  110.00 and 110.51, and three  ring carbons at δ 88.93, 90.60 and
92.17, which confirms that 4c contains two distinct rings. In this NMR experiment, the identified 
carbons show direct one bond couplings to protons resonating at  4.89 (δ 88.93 and 90.60) and
4.90 (δ 92.17). Due to the complexity of the NMR spectra, the corresponding  ring resonances
were located via a combination of short- and long-range 1H-13C NMR experiments. NOe data
confirmed the 1H assignments for the [CH2(C5H4)2] moiety and the 29Si NMR chemical shifts of the
silyl ligands ( 41.35 and 40.05) were located via connections to the hydride and ethyl proton
signals in the 2D 1H-29Si NMR spectrum. In the corresponding 1H-103Rh NMR experiment, the
Rh(III) and (V) resonances were located at  -1477 and -1872 respectively via the large RhH
couplings. The remaining 13C resonances were located via connections in a short-range 1H-13C 2D
correlation.
NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(SiEt3)2(H)2]2 4d
Et3Si Rh H
H SiEt3
H Rh SiEt3
Et3Si
H
4d
8
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The symmetrical complex 4d gives rise to only six signals in the 1D 1H NMR spectrum, which
correspond to the two types of C5H4 protons ( 5.06 and 4.91), the equivalent CH2 bridge protons (
3.47), the CH3 ( 1.06) and CH2 ( 0.83) groups of the silyl ligands and the hydrides ( -14.09).
The latter resonance shows a characteristic Rh(V) splitting of 38.5 Hz. In the long-range 2D 1H-13C
NMR spectrum, the methylene 1H signal at  3.47 showed connections to one ipso carbon at 
110.51 and one  ring carbon at  92.17, which confirms that 4d contains a symmetrical ligand
array. The  carbon resonance shows a direct one bond coupling to the 1H resonating at  5.06.
The remaining 1H resonance, at  4.91, therefore corresponds to the  proton, which connects to a
C signal at  87.67 via a one bond coupling. NOe data confirmed these 1H assignments and the
13
ethyl 1H signals were identified via connections to a 29Si resonance at  40.15 in a 2D 1H-29Si NMR
experiment. The corresponding 2D 1H-103Rh NMR spectrum contains a single 103Rh resonance at 
-1873.
NMR spectroscopic characterisation of [CH2(C5H4)2][RhH(-SiEt2)]2 5
Rh
Et
Et
H
Rh
Si
H
Si Et
Et
5
The 1H NMR spectrum of complex 5 contains a second order hydride resonance centred at  -14.40.
This second order pattern is attributed to the fact that each hydride ligand couples to two
magnetically distinct rhodium centres that collectively belong to an [AX] 2 spin system; simulation
of the hydride resonance as an [AX]2 multiplet revealed that JRhH = 39 Hz and -0.8 Hz, while JHH =
-1.2 Hz and JRhRh = 16.5 Hz which confirms the presence of a Rh-Rh bond. In the 2D 1H-29Si NMR
spectrum of 5, a triplet centred at  205.9 (JRhSi = 37.3 Hz) was observed first to connect to the
second order hydride resonance and then to two CH2 resonances. The chemical shift of the triplet
and equal coupling to two equivalent rhodium nuclei is characteristic of a bridging silyl group. As
can be seen from the picture above, the bridging silylene ligands each have two distinct ethyl
groups bound to them which accounts for the observation of two connections in the 2D 1H-29Si
NMR spectrum. A 2D 1H-1H nOe spectrum also confirmed the presence of the two inequivalent
9
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ethyl groups in each SiEt2 unit; one pointing towards and one pointing away from the rings, with
integrals confirming the presence of single SiEt2 and hydride units for each C5H4 group.
Furthermore, it located both the CH2 bridge proton resonance at  3.64 and the  ring proton
resonance at  4.79 via connections to the CH2 protons of the ethyl groups, in the SiEt2 units, which
point up towards the rings. The remaining 1H resonance, at  5.27 in the 1D 1H NMR spectrum,
arises from the  C5H4 protons. As expected for a symmetrical species of this type, the CH2 bridge
proton resonance ( 3.64) connects to a single ipso carbon resonating at  84.70 and one  C5H4
carbon at  91.52 in the long-range 1H-13C NMR spectrum. Connections in a short-range 2D 1H-13C
NMR experiment enabled the remaining
13
C resonances to be identified. The single rhodium
chemical shift for 5 was identified at  -2033 in the 2D 1H-103Rh NMR spectrum.
NMR spectroscopic characterisation of [CH2(C5H4)2][(RhEt)(RhH)(-SiEt2)2] 6
Et
a Et
Rh
Et
b
Rh
Si
Si Et
H
Et
6
In the 1H NMR spectrum complex 6 yields a doublet hydride resonance at  -14.60, with JRh,H = 40
Hz, along with a singlet at  3.47 for the CH2 bridge protons and eight signals corresponding to the
ethyl groups. The observation of four ring proton resonances and two rhodium environments
supports the structure shown above. In the long-range 2D 1H-13C NMR spectrum the CH2 bridge
protons connect to two ipso carbons resonating at  85.30 and 87.00, and two  ring carbons at δ
94.45 and 91.40, confirming that 6 contains two distinct rings. Connections in the corresponding
short-range 2D 1H-13C NMR spectrum established that the  ring protons resonate at  4.96 and
4.77. The remaining two C5H4 signals, at  5.02 and 5.17, therefore correspond to the  positions in
the ring. In the
29
Si{1H} NMR spectrum, a signal centred at  220 with doublet of doublet
multiplicity was observed, which confirms the presence of a bridging silylene unit that couples to
two inequivalent rhodium nuclei. The corresponding 2D 1H-103Rh NMR spectra of 6 contain
signals at  -2019 and -1342, which both show Rh-Rh splittings of 15 Hz, indicating the presence of
a metal-metal bond. Notably, the former shows a connection to the hydride resonance at  -14.60.
10
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Four different SiCH2 proton signals were observed for this product with the corresponding pairs of
inequivalent ethyl groups pointing towards and away from the rings respectively, as demonstrated
by nOe interactions. Two additional 1H signals at  1.43 (CH2) and 1.33 (CH3) arise from the
rhodium-ethyl group. In the 2D 1H-13C NMR spectrum, 13C resonances at  -9.80 (CH2) and 26.70
(CH3) were observed for this ligand; the former signal showing a
103
Rh coupling of 22 Hz that is
indicative of a direct one bond Rh-C coupling. When the volatiles were removed from this sample,
mass spectral analysis yielded an M/z peak at 492 due to M+-EtH.
NMR spectroscopic
characterisation
of
[CH2(C5H4)2][{Rh(SiEt3)H}{Rh(SiEt3)}(-1,2-
CH=CH2)] 7a and 7b
H
Et3Si
Rh
H
Rh
H
SiEt3
Et3Si
H
H
Rh
Rh
SiEt3
H
H
7a
H
7b
Complex 7a gives rise to vinyl signals at  9.58, 3.65 and 2.41, along with a hydride signal at 
-15.50 (dd, JRh,H = 3.7, 35.4 Hz), which has doublet of doublet multiplicity indicating the presence
of two inequivalent rhodium centres. In the corresponding 2D 1H-103Rh NMR spectrum, this
hydride signal connects to two rhodium centres, resonating at  -779 and -1407, with JRhRh = 14 Hz
indicating the presence of a metal-metal bond. In addition, this experiment confirms the presence
of a vinyl ligand; the signal at  -779 shows strong connections to protons resonating at  3.65 and
2.41, while the signal at  -1407 couples to the three proton resonances at  9.58, 3.65 and 2.41.
The large chemical shift difference between the
103
Rh centres suggests that they have significantly
different electronic environments. Other notable features include the observation of inequivalent
CH2 bridge protons, resonating at  3.41 and 2.95, and the identification of eight separate ring
proton environments - yielding resonances at  5.39, 5.19, 5.03, 4.79, 4.71, 4.43, 4.29 and 4.08 - via
nOe experiments; both of which support an unsymmetrical structure for 7a. 2D 1H-29Si NMR
experiments established the presence of two terminal SiEt3 ligands, with 29Si resonances at  35.21
(d, JRh,Si = 27 Hz) and  43.45 (d, JRh,Si = 35 Hz), which in turn coupled to signals at  1.21 and
11
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0.97, and  1.07 and 0.74 due to the CH3 and CH2 protons in each terminal SiEt3 ligand
respectively. The pairs of  ring protons for the inequivalent C5H4 units appear at  4.08 and 4.79,
and  5.19 and 4.29 respectively. A 2D 1H-1H COSY NMR experiment confirmed the vinyl and
ring proton assignments. The nOe experiment also showed that the vinyl proton giving rise to the
signal at  9.58 is close in space to the ring protons yielding signals at  4.08 and 4.29, which
indicates that this vinyl proton is orientated such that it is next to the C5H4 rings. The vinyl proton
at  3.65 also shows an nOe connection, although weak, to a  C5H4 proton, at  4.43. On the basis
of these observations it can be concluded that the vinyl ligand is orientated such that it points
upwards, towards the rings. In addition, the vinyl signals at  3.65 and 2.41 show nOe interactions
to peaks at  1.23 and 0.74, corresponding to one of the terminal silyl ligands. Connections also
indicate that the ring bridge proton yielding the resonance at  2.95 is close in space to the silyl
ligand protons resonating at  1.23, and the  C5H4 protons resonating at  4.29 and 4.08. In
contrast the hydride signal connects with ring proton resonances at  4.71 and  5.19. It is therefore
possible to conclude that the silyl ligand in on the same side of the complex as the vinyl group.
In the long-range 2D 1H-13C NMR spectrum, four  and four 
13
C ring resonances were located,
although the ipso carbons were too weak to assign. Connections in a short-range 2D 1H-13C NMR
experiment enabled identification of the vinyl and CH2 bridge 13C resonances.
Complex 7b appears to contain an identical ligand array to 7a; in the 1H NMR spectrum 7b yields
signals at  8.58, 4.19 and 4.13, for the vinyl ligand, and  -15.19 (dd, JRh,H = 10.7, 33.3 Hz) for the
hydride. The low temperature 2D 1H-103Rh NMR experiment revealed the presence of two rhodium
centres, at  -666 and -1399, which both couple to the vinyl signals, and are connected by a Rh-Rh
bond (JRh,Rh = 14 Hz). In the 2D 1H-29Si NMR spectra,
29
Si resonances corresponding to two
terminal SiEt3 ligands arose at  42.08 (d, JRh,Si = 33 Hz) and  43.16 (d, JRh,Si = 37 Hz). However,
in contrast to 7a, the CH=CH2 vinyl proton, at  8.58, in 7b now connects to the hydride resonance.
In view of this, it can be concluded that the vinyl ligand is orientated such that it points down, away
from the silyl group. Complex 7b is unstable, and disappears from the spectrum overnight even
when they are recorded at 213 K. Only partial NMR data is therefore available for this complex.
NMR spectroscopic characterisation of [(C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]2 8
Et3Si
Et3Si Rh H
12
H SiEt3
H Rh SiEt3
Et3Si
H
8
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
Complex 8 gives rise to two hydride resonances at  -13.92 (d, JRh,H = 37 Hz) and  -14.06 (d, JRh,H
= 38 Hz). Both reveal doublet splittings in accordance with coupling to Rh(V) centres. In the longrange 2D 1H-13C NMR spectrum, the CH2 bridge proton resonance at  3.61 connects to two ipso
carbons resonating at  110.60 and 111.40, which confirms the presence of two distinct rings.
Furthermore, four sets of 
13
C and 1H resonances were identified for these rings at  91.89/5.06,
91.62/5.12, 91.88/5.28 and 98.31/5.30 respectively. Further connections within the 2D 1H-13C
NMR spectrum reveal that the pair of  protons resonating at  5.06 and 5.12 in one ring are next to
 13C nuclei that resonate at  87.40 and 87.50; these in turn couple directly to  ring protons at 
4.90 and 4.93. In the second ring, the 1H resonances at  5.30 and 5.28 show connections to 
carbons at  95.50 and 95.63. In the short-range 2D 1H-13C NMR spectrum, the  13C resonance at
 95.50 connects to a 1H resonance at  5.10. However, no corresponding connection to a  proton
is observed for the carbon giving rise to the signal at  95.63. A DEPT experiment confirmed that
the carbon resonance at  95.50 arises from a CH group, while that at  95.63 proved to have no
protons attached. A similar situation would exist if a SiEt3 ligand replaced the proton. In addition,
this ring carbon showed a connection to a 1H signal at  0.78, attributed to the methylene protons in
a SiEt3 ligand. In the corresponding 1H-1H NOESY spectrum, nOe interactions were observed
between the ring protons and two distinct ethyl groups; resonances at  0.915 (CH2) and 1.12 (CH3),
for one type of ethyl, and  0.78 (CH2) and 1.044 (CH3) for the second. In the 2D 1H-29Si NMR
spectrum, the corresponding
29
Si resonances were identified, via connections to these ethyl
resonances, at  36.70 (JRhSi = 17 Hz), Rh-SiEt3, and -0.87, C5H3SiEt3, respectively. A 2D 1H-103Rh
experiment located the 103Rh resonances at  -1850 and -1836 via connections to the hydride signals
at  -14.06 and -13.92 respectively. The 1H and
29
Si chemical shifts of the SiEt3 ligands in the
(C5H4)Rh(SiEt3)2(H)2 moiety were detected via a combination of nOe interactions with the ring
protons and 2D 1H-29Si NMR spectra. Connections in a short-range 2D 1H-13C NMR experiment
enabled the remaining 13C resonances to be identified.
13
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
NMR spectroscopic characterisation of [CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2 9a and 9b
Et3Si
Et3Si Rh H
H SiEt3
H
Et3Si
SiEt3
Rh
9a
SiEt3
H
SiEt3
9b
Et3Si
Et3Si Rh H
H SiEt3
H Rh SiEt3
Et3Si
H
Complex 9a yields a single hydride signal at  -13.89 (d, JRh,H = 37 Hz) in the 1D 1H NMR
spectrum, with the rhodium coupling of 37 Hz indicating the presence of a Rh(V) centre. In the
long-range 1H-13C NMR spectrum, the CH2 bridge proton resonance at  3.71 connects to one ipso
carbon resonating at  111.90, which is indicative of a symmetrical product, and two  carbons at 
98.84 and 92.08. The corresponding  1H signals appear at  5.26 and 5.27, which in turn couple to
 ring carbons resonating at  95.66 and 95.48. In an analogous manner to 8, one of the 
13
C
signals arises from a CH group ( 95.48), while the other ( 95.66) proves to arise from a carbon
that has a SiEt3 group attached. Similarly to 8, nOe interactions also confirm the presence of two
distinct types of SiEt3 ligands in 9a; one coordinated to the rings, C5H3SiEt3 (with 1H resonances at
 0.771 (CH2) and 1.040 (CH3)) and the other coordinated to the metal centre, Rh-SiEt3 (with 1H
resonances at  0.917 (CH2) and 1.133 (CH3)). Connections in the corresponding 2D 1H-29Si NMR
spectrum enabled assignment of the
103
29
Si resonances at  -0.702 and 36.52 respectively. A single
Rh resonance was identified at  -1837 in the 2D 1H-103Rh spectrum, via connections to the
hydride signal. The remaining
13
C chemical shifts were located in the short-range 1H-13C NMR
experiment.
Complex 9b gives rise to very similar features to 9a. The key to distinguishing between these two
structures is in the CH2 bridge 1H signals; in structure 9a the methylene bridge protons are
inequivalent, whereas those in structure 9b are equivalent. Close inspection of the 1H NMR
spectrum reveals that the CH2 bridge signal at  3.71 is marginally broader than the other at  3.76,
which indicates a slight inequivalence of the two protons giving rise to the peak at  3.71. This
supports the structural assignment of 9a and 9b.
14
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a,
[CH2(C5H4)2][Rh(C2H4)(SiMe3)H]2 10b,
[CH2(C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2]
10c and [CH2(C5H4)2][Rh(SiMe3)2(H)2]2 10d.
A sample of 1 (20 mg) was photolysed in C6D6, at 296 K, in the presence of a 9 fold excess of
Me3SiH. 1H NMR spectra recorded after 30 min showed several new resonances - free ethene was
detected at  5.24 and two hydride resonances at  -14.57 (major) and -14.60 (minor), which were
both split into doublets of 34.08 Hz due to
103
Rh coupling. This indicates that they were produced
by Rh(III) complexes. This suggested that oxidative addition of a Si-H bond of Me3SiH had
occurred at two rhodium centres, following the photochemical elimination of ethene. Two singlets
at  2.74 and 2.78, for the CH2 bridge protons, and other resonances in the C5H4 and aliphatic 1H
regions
were
also
observed.
These
two
complexes
were
identified
as
[CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a and [CH2(C5H4)2][Rh(C2H4)(SiMe3)H]2 10b,
with the structures illustrated below.
Rh
Rh
Me3Si Rh
H
SiMe3
H
Rh
SiMe3
H
Structures
of
[CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H]
[CH2(C5H4)2][Rh(C2H4)(SiMe3)H] 2 10b.
10a
and
These complexes were characterised in a similar manner to that described for 4a and 4b. It should
be noted that the methyl groups of the silyl ligands, which were first located using a 2D 1H-29Si
NMR experiment, showed nOe interactions with the ring and ethene protons of the Rh(III) side of
complex 10a.
After another 20 min irradiation, three further hydride signals at  -14.59, -13.74, and -13.75 were
visible in the
1
H NMR spectrum.
These were assigned to the hydride resonances in
[CH2(C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2] 10c and [CH2(C5H4)2][Rh(SiMe3)2(H)2]2 10d
respectively. The latter two signals had a doublet multiplicity, with a
15
103
Rh coupling of 39.94 Hz,
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
confirming the presence of Rh(V) metal centres. In addition, the hydride resonance at  -14.59 was
identified as arising from the proton attached to the Rh(III) centre in complex 10c.
NMR
spectroscopic data for complexes 10a - 10d are listed in Table 1 of the manuscript.
Me3Si Rh H
H SiMe3
Rh
SiMe3
H
Me3Si Rh H
H Rh SiMe3
H SiMe3 Me3Si H
Structures
of
[CH2(C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2]
[CH2(C5H4)2][Rh(SiMe3)2(H)2] 2 10d.
10c
and
These four species are analogous to complexes 4a - 4d, generated when 1 was photolysed with
Et3SiH, with a similar stepwise progression of photoproducts from 10a to 10b to 10c to 10d being
observed.
An identical sample of 1 in protio-benzene was prepared and photolysed in the presence of Me3SiH.
1
H NMR spectra were recorded regularly to follow the reaction and small samples were taken out
for mass spectroscopic analysis after 10, 30, 45 and 75 min irradiation i.e. after the formation of
10a, 10b, 10c and 10d was observed in the 1H NMR spectra. It was noted that, although no
molecular ion peaks were visible, there appeared to be a trend in the mass spectra; in the first
sample a peak at m/z 374 was detected, which corresponded to the fragment [C11H8Rh2Si]+. At
longer photolysis times, this peak was observed to decrease in intensity, with other peaks at m/z 400
and 430 growing in as 10b and 10c were being generated. These corresponded to the fragments
[C11H6Rh2Si2]+ and [C11H8Rh2Si3]+. In the final mass spectrum, the peaks at m/z 374, 400 and 430
were found to be depleted and the major fragment was detected as [C11H10Rh2Si4]+ (m/z 460).
Additionally, there was evidence for peaks differing in mass by 15, which indicated the loss of
methyl groups. At this point, the ratio of 10a:b:c:d was 71:22:5:2 % i.e. the dominant species were
those containing Rh(III) centres.
16
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
NMR spectroscopic characterisation of [CH2(C5H4)2][(RhMe)(RhH)(-SiMe2)2]
11,
[CH2(C5H4)2][(Rh{SiMe3})(RhMe)(-SiMe2)2] 12 and [CH2(C5H4)2][(Rh{SiMe3})(RhH)(SiMe2)2] 13
Me
Rh
Me
Rh
Si
Si Me
Me
Me
Rh
Si
Me
Si Me
Me
Rh
H
Me3Si
Me
Me
11
12
Me
Rh
Me
Rh
Si
Si Me
Me3Si
H
Me
13
Key H NMR spectroscopic features for complex 11 include a hydride resonance at  -14.19 (m,
1
JRh,H = 40.8 Hz) and a singlet at  3.54 corresponding to the CH2 bridge protons. In the long-range
2D 1H-13C NMR spectrum, the CH2 bridge 1H resonance couples to two ipso carbons ( 85.83 and
86.68) and two  ring carbons ( 93.68 and 91.81), which confirms that 11 contains two distinct
rings. Further connections in this experiment enabled the corresponding  1H resonances ( 4.90
and 4.77) and 
13
C/1H resonances ( 91.41/4.93 and 85.49/5.21) to be assigned. The 2D 1H-29Si
NMR spectrum contains a
29
Si signal at  204.67 (dd, JRh,Si = 34.9, 46.0), which is indicative of a
bridging silylene group that couples to two inequivalent rhodium centres. Interestingly, this
29
Si
resonance connects to two distinct methyl groups in the SiMe2 unit, which resonate at  1.13 and
0.77. One methyl group ( 1.13) points towards the rings and shows nOe interactions with the 
ring protons, and the other ( 0.77) points away from the rings and hence shows no nOe interactions
to the C5H4 protons. Furthermore, the 1H-1H nOe experiment revealed an nOe connection between
the down-methyl 1H resonance at  0.77 and a signal at  0.20, assigned to the Rh-Me ligand. In the
2D 1H-13C NMR spectrum, a resonance at  -31.23 (d, JRh,C = 27.5 Hz) in the
13
C dimension was
observed, indicating direct bonding between the rhodium nucleus and this methyl group. The 2D
17
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
1
H-103Rh NMR spectra located the two metal centres in 11, which give rise to
Rh signals at  -
103
1424 and -2008, via connections to the methyl and hydride resonances respectively.
Complexes 12 and 13 yield similar resonances to those observed for 11 and therefore their
characterisation was achieved as outlined above for 11. However, the difference between 11, 12
and 13 lies in the identity of the terminal ligands, which, in 11, correspond to methyl and hydride
ligands. Notably, for complex 12, 1H signals at  0.47 and 0.15 arise from protons which are close
in space to the methyls in the corresponding SiMe2 ligands. The former resonance was assigned to
a Rh-SiMe3 group on the basis of connections, in the 2D 1H-29Si NMR spectrum, to a 29Si resonance
of doublet multiplicity at  15.41. The latter 1H signal, assigned to a Rh-Me ligand, connects to the
103
Rh resonance at  -1957 in the corresponding 1H-103Rh NMR spectrum. In the 2D 1H-13C NMR
experiment, a
C resonance at  -27.51, which connects to the methyl 1H resonance at  0.15, is
13
split into a doublet with JRh,C = 27.5 Hz. Both the chemical shift of this resonance and its doublet
multiplicity confirm direct bonding between a rhodium centre and this methyl group. Similarly to
11, complex 13 gives rise to a hydride signal at  -14.19 (m, JRh,H = 40.8 Hz) which connects to a
103
Rh resonance at  -1952. The second terminal ligand is a Rh-SiMe3 group, which yields 1H and
Si resonances at  0.49 and 13.74 (d, JRh,Si = 34.7 Hz) respectively.
29
Mass spectroscopic data for [CH2(C5H4)2][(Rh{SiMe3})(RhH)(-SiMe2)2] 13
M/z
538
523
508
464
Fragment
M+
M+-Me
M+-2Me
M+-Me3SiH
NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(C2H4)][Rh(SiMe3)2](-H)2 14
18
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
Rh
H
H
Rh
SiMe3
SiMe3
14
Complex 14 yields a hydride resonance at  -12.97 (dd, JRh,H = 17.4, 25.7 Hz) in the 1D 1H NMR
spectrum. In the 2D 1H-103Rh NMR spectrum, this hydride couples to two rhodium centres at  1608 and -1052. The rhodium coupling constants of 17.42 and 25.65 Hz respectively are indicative
of a bridging hydride. This experiment revealed additional signals; peaks at  2.68 (ethene) and
1.89 (ethene) couple to the rhodium centre that resonates at  -1052, while resonances at  0.62
(CH3), 4.78 (C5H4) and 4.89 (C5H4) show connections to the rhodium at  -1608. Furthermore, in
the NOESY spectrum, nOe interactions between the resonance at  0.62 and signals at  -12.97,
5.19, 5.08, 4.89, 4.78 and 1.89, assigned to the hydride, four C5H4 proton resonances and an ethene
proton resonance are visible. Exchange peaks detected between the peaks at  2.68 and 1.89
confirms the presence of an ethene ligand, with protons pointing towards ( 2.68) and away from
the C5H4 rings ( 1.89). The corresponding 2D 1H-29Si NMR experiment revealed a connection
from the 1H signal at  0.62 to a
29
Si nucleus resonating at  20.91 (d, JRh,Si = 23.7 Hz) which
indicates the presence of at least one terminal SiMe3 unit. Finally, in the 2D 1H-13C NMR spectra,
connections from the CH2 bridge 1H resonance at  2.59 to two ipso carbons ( 98.57 and 112.9)
and two  ring carbons ( 89.32 and 92.89) confirms the presence of two distinct C5H4 rings and a
symmetrical ligand arrangement about each (C5H4)Rh moiety. The remaining 13C resonances were
assigned via a short-range 2D 1H-13C NMR spectrum.
The organic products produced in these reactions were analyzed by GC-MS. The following data
was obtained for systems starting with Et3SiH, and Me3SiH.
Mass spectroscopic data for Et3SiH, Et4Si and CH2=CHSiEt3
Compound
Et3SiH
M/z
Fragment
M+-C4H9
M+-Et
59
87
19
Supplementary Material for Dalton Transactions
This journal is © The Royal Society of Chemistry 2005
116
M+
Et4Si
59
[SiEtH2]+
87
[SiEt2H]+
115
[SiEt3]+
144
M+
CH2=CHSiEt3 57
M+-Et-2C2H4
85
M+-Et-C2H4
113
M+-Et
142
M+
Mass spectroscopic data for EtSiMe3 , CH2=CHSiMe3 and SiMe3CH2CH2SiMe3
Compound
EtSiMe3
CH2=CHSiMe3
SiMe3CH2CH2
SiMe3
87
73
59
43
100
85
73
59
43
159
M/z
Fragment
M+-Me
[SiMe3]+
[SiMe2]+
[SiMe]+
M+
M+-Me
[SiMe3]+
[SiMe2]+
[SiMe]+
M+-Me
131
86
73
M+-SiMe
M+-SiMe4
[SiMe3]+
1
. J. D. Fotheringham, G. A. Heath, A. J. Lindsay and T. A. Stephenson, J. Chem. Research 1986, 82.
20