Supplementary Material for Dalton Transactions

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 Fragment 460 M+ + 432 M -C2H4 + 404 M -2C2H4 + 376 M -3C2H4 + 374 [C11H8Rh2(C2H4)] + 348 M -4C2H4 + 346 [C11H8Rh2] + 218 [C9H7Rh] + 168 [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: Reference source not found 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

1 rings, in agreement with the fact that the CH2 bridge H 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 be attributed to the ring carbons of the [Rh(C2H4)2] moiety. Subsequently, direct one-bond couplings between the

1 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 13C 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.

1 This product yields H NMR peaks at  5.07 and 5.21 (for the two sets of C5H4 protons), 2.68 (for

103 the CH2 bridge) and, 2.27 and 1.67 (for the ethene protons). Furthermore, a single Rh 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

1 of 1 was photolysed in the presence of a 12-fold excess of dmso-h6 until H 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 13C 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 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 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

2 [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)( -toluene)]. Two possible isomers for this complex might be expected, as shown in Figure 1.

R Rh Rh Rh Rh

2 Figure 1: Structures of the possible isomers of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)( -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 C5H4 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.

3 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 Additionally, the nOe NMR spectrum also revealed rapid exchange between all four ethene proton 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 5.05 4.14 5.12 2.35 2.35 4.61 4.54 4.08 4.54

R Rh 2.89 Rh Rh 2.53 Rh

1.42 1.34 -0.18 1.34 2.81 2.81

4 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 1 2 Figure 2: H chemical shifts (ppm) in the two isomers of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)( - toluene)] 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.

1 It should be noted that although the two isomers give rise to a common CH2 bridge H 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 13 C peaks. In addition, C 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

13 101.86 (ipso carbon). The ipso and  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 for the two isomers of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4) (2-toluene)]

2 3 1 4

a b Rh Rh

R /ppm (multiplicity) assignment 1 2 H NMR (i) 4.85 (br) -C5H4 (ii) 4.14 (br) 1 (d8-toluene, (i) 4.61 (br) -C5H4 (ii) 4.08 (br) a 203 K) (i) 1.42 (br, down), C2H4 2.89 (br, up) (ii) -0.18 (br, down), 2.53 (br, up)

2.35 (br) CH2 bridge 3 (i) 5.05 (br) -C5H4 (ii) 5.12 (br)

5 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 4 4.54 (br) -C5H4 b 1.34 (br), 2.81 (br) C2H4 13 2 C NMR (ii) 89.39 (m) -C5H4 1 (ii) 93.15 (m) -C5H4 a 101.86 (m) ipso C5H4

24.75 (s), 23.78 (s) CH2 bridge 3 (i) 87.87 (m) -C5H4 (ii) 88.00 (m) b 103.86 (m) Ipso-C5H4

NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(CH2=CHSiMe3)2]2 3a, 3b and 3c

R R Rh R R Rh Rh Rh R R R R 3a 3b

R R R Rh Rh R 3c Complex 3a yields a singlet at  3.58 in the 1D 1H NMR spectrum corresponding to the equivalent

1 13 CH2 bridge protons. In the long-range 2D H- C 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,

1 towards the C5H4 rings. A H 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

6 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 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

13 SiMe3 units pointing towards the C5H4 rings. The remaining C resonances were located via a short-range 2D 1H-13C experiment. Notably, the vinyl 13C 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 103Rh signal for 3a was identified at  -782 in the corresponding 1H-103Rh NMR spectra, via connections to the vinyl and C5H4 protons.

1 Complex 3b contains inequivalent CH2 bridge protons, which give rise to H 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

1 are identical. The vinyl ligands in this complex produce H 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,

1 the H 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 103Rh resonances were identified at  0.27 and -780 respectively in the corresponding 2D correlations, and the remaining 13C resonances were located via a short-range 2D 1H-13C experiment.

1 Weak H 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 1.64, 0.77 and 0.144 (SiMe3), for the cis vinylsilane ligands. The observation of eight C5H4 ring H 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

29 ligands in 3c. The corresponding Si 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 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2] 4c

Rh Rh Et3Si H SiEt3 H Et3Si H 4c

Key 1H NMR spectroscopic features arising from complex 4c include two hydride resonances at 

103 -14.64 (d, JRh,H = 33.5 Hz) and -14.08 (d, JRh,H = 38.5 Hz), with Rh couplings indicating the

1 presence of a Rh(III) and a Rh(V) centre respectively, and a CH2 bridge H resonance at  3.17. In

1 13 the corresponding long-range 2D H- C 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

1 29 confirmed the H assignments for the [CH2(C5H4)2] moiety and the Si 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

Rh Rh Et3Si H H SiEt3 H SiEt3 Et3Si H 4d 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 (

8 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005

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 13C signal at  87.67 via a one bond coupling. NOe data confirmed these 1H assignments and the 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

Et Et Rh Rh H 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 29 -1.2 Hz and JRhRh = 16.5 Hz which confirms the presence of a Rh-Rh bond. In the 2D H- Si 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 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 13C 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

a Et Et b Rh Rh Et Si H Si Et Et 6

1 In the H 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

1 13 supports the structure shown above. In the long-range 2D H- C 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 29Si{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.

Four different SiCH2 proton signals were observed for this product with the corresponding pairs of

10 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 inequivalent ethyl groups pointing towards and away from the rings respectively, as demonstrated

1 by nOe interactions. Two additional H signals at  1.43 (CH2) and 1.33 (CH3) arise from the

1 13 13 rhodium-ethyl group. In the 2D H- C NMR spectrum, C resonances at  -9.80 (CH2) and 26.70

103 (CH3) were observed for this ligand; the former signal showing a 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.

1 2 NMR spectroscopic characterisation of [CH2(C5H4)2][{Rh(SiEt3)H}{Rh(SiEt3)}(- , -

CH=CH2)] 7a and 7b

H H Rh Rh Et3Si H Rh Rh SiEt Et3Si SiEt 3 H 3 H 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 103Rh 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

29 experiments established the presence of two terminal SiEt3 ligands, with Si 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 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

11 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 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  13C ring resonances were located, although the ipso carbons were too weak to assign. Connections in a short-range 2D 1H-13C NMR

13 experiment enabled identification of the vinyl and CH2 bridge C 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

1 29 29 bond (JRh,Rh = 14 Hz). In the 2D H- Si NMR spectra, 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 Rh Rh Et3Si H H SiEt3 H SiEt3 Et3Si H 8 12 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 long-

1 13 range 2D H- C 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  13C 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

1 1 a SiEt3 ligand. In the corresponding H- H NOESY spectrum, nOe interactions were observed between the ring protons and two distinct ethyl groups; resonances at  0.915 (CH2) and 1.12 (CH3),

1 29 for one type of ethyl, and  0.78 (CH2) and 1.044 (CH3) for the second. In the 2D H- Si NMR spectrum, the corresponding 29Si resonances were identified, via connections to these ethyl

1 103 resonances, at  36.70 (JRhSi = 17 Hz), Rh-SiEt3, and -0.87, C5H3SiEt3, respectively. A 2D H- Rh experiment located the 103Rh resonances at  -1850 and -1836 via connections to the hydride signals

1 29 at  -14.06 and -13.92 respectively. The H and 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.

NMR spectroscopic characterisation of [CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2 9a and 9b

Et3Si SiEt 9a Rh Rh 3 Et3Si H H SiEt3 H SiEt3 Et3Si H

SiEt3 9b 13 Et3Si Rh Rh Et3Si H H SiEt3 H SiEt3 Et3Si H Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005

1 Complex 9a yields a single hydride signal at  -13.89 (d, JRh,H = 37 Hz) in the 1D H NMR spectrum, with the rhodium coupling of 37 Hz indicating the presence of a Rh(V) centre. In the

1 13 long-range H- C 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  13C 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

1 distinct types of SiEt3 ligands in 9a; one coordinated to the rings, C5H3SiEt3 (with H resonances at

1  0.771 (CH2) and 1.040 (CH3)) and the other coordinated to the metal centre, Rh-SiEt3 (with H

1 29 resonances at  0.917 (CH2) and 1.133 (CH3)). Connections in the corresponding 2D H- Si NMR spectrum enabled assignment of the 29Si resonances at  -0.702 and 36.52 respectively. A single 103Rh resonance was identified at  -1837 in the 2D 1H-103Rh spectrum, via connections to the hydride signal. The remaining 13C 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

1 structures is in the CH2 bridge H 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.

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

1 Me3SiH. H 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 103Rh coupling. This indicates that they were produced

14 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 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

1 at  2.74 and 2.78, for the CH2 bridge protons, and other resonances in the C5H4 and aliphatic H 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 Rh Rh SiMe3 Me3Si SiMe3 H H H

Structures of [CH2(C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a and [CH2(C5H4)2][Rh(C2H4) (SiMe3)H]2 10b.

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

1 visible in the 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 103Rh coupling of 39.94 Hz, 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.

Rh Rh Rh Rh Me3Si H SiMe3 Me3Si H H SiMe3 H SiMe3 H H SiMe3 Me3Si H

Structures of [CH2(C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2] 10c and [CH2(C5H4)2] [Rh(SiMe3)2(H)2]2 10d.

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. 1H 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.

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 Me Me Me Rh Rh Rh Rh Si Me H Me3Si Si Me Si Me Si Me Me Me 11 12 Me Me Rh Rh Me3Si Si H Si Me 16 Me

13 Supplementary Material for Dalton Transactions This journal is © The Royal Society of Chemistry 2005 Key 1H NMR spectroscopic features for complex 11 include a hydride resonance at  -14.19 (m,

JRh,H = 40.8 Hz) and a singlet at  3.54 corresponding to the CH2 bridge protons. In the long-range

1 13 1 2D H- C NMR spectrum, the CH2 bridge H 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  13C/1H resonances ( 91.41/4.93 and 85.49/5.21) to be assigned. The 2D 1H-29Si

29 NMR spectrum contains a 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 29Si 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

1 1 to the C5H4 protons. Furthermore, the H- H 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

1 13 13 2D H- C NMR spectrum, a resonance at  -31.23 (d, JRh,C = 27.5 Hz) in the C dimension was observed, indicating direct bonding between the rhodium nucleus and this methyl group. The 2D 1H-103Rh NMR spectra located the two metal centres in 11, which give rise to 103Rh signals at  -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

1 29 29 a Rh-SiMe3 group on the basis of connections, in the 2D H- Si NMR spectrum, to a Si resonance of doublet multiplicity at  15.41. The latter 1H signal, assigned to a Rh-Me ligand, connects to the 103Rh resonance at  -1957 in the corresponding 1H-103Rh NMR spectrum. In the 2D 1H-13C NMR experiment, a 13C resonance at  -27.51, which connects to the methyl 1H resonance at  0.15, is 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 1 Rh resonance at  -1952. The second terminal ligand is a Rh-SiMe3 group, which yields H and

29 Si resonances at  0.49 and 13.74 (d, JRh,Si = 34.7 Hz) respectively.

Mass spectroscopic data for [CH2(C5H4)2][(Rh{SiMe3})(RhH)(-SiMe2)2] 13

M/z Fragment 538 M+ 523 M+-Me 508 M+-2Me + 464 M -Me3SiH

NMR spectroscopic characterisation of [CH2(C5H4)2][Rh(C2H4)][Rh(SiMe3)2](-H)2 14

Rh Rh H SiMe3 H SiMe3 14

1 Complex 14 yields a hydride resonance at  -12.97 (dd, JRh,H = 17.4, 25.7 Hz) in the 1D H 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

1 29 away from the C5H4 rings ( 1.89). The corresponding 2D H- Si NMR experiment revealed a

1 29 connection from the H signal at  0.62 to a Si nucleus resonating at  20.91 (d, JRh,Si = 23.7 Hz)

1 13 which indicates the presence of at least one terminal SiMe3 unit. Finally, in the 2D H- C NMR

1 spectra, connections from the CH2 bridge H 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

13 and a symmetrical ligand arrangement about each (C5H4)Rh moiety. The remaining C 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 M/z Fragment + Et3SiH 59 M -C4H9 87 M+-Et 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 M/z Fragment + EtSiMe3 87 M -Me + 73 [SiMe3] + 59 [SiMe2] 43 [SiMe]+ + CH2=CHSiMe3 100 M 85 M+-Me + 73 [SiMe3] + 59 [SiMe2] 43 [SiMe]+ + SiMe3CH2CH2 159 M -Me SiMe3 131 M+-SiMe + 86 M -SiMe4 + 73 [SiMe3]

19 1 . J. D. Fotheringham, G. A. Heath, A. J. Lindsay and T. A. Stephenson, J. Chem. Research 1986, 82.