Issue 4, 2005
From the journal:

Dalton Transactions

Photochemical reactions of [CH2(η5-C5H4)2][Rh(C2H4)2]2 with silanes: evidence for Si–C and C–H activation pathways†

Jenny L. Cunninghama  and  Simon B. Duckett*a  

* Corresponding authors

a Department of Chemistry, University of York, Heslington, York, UK

Abstract

Photochemical reaction of [CH2(η5-C5H4)2][Rh(C2H4)2]21 with dmso led to the stepwise formation of [CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)] 2a and [CH2(η5-C5H4)2][Rh(C2H4)(dmso)]22b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(η5-C5H4)2][Rh(CH2[double bond, length as m-dash]CHSiMe3)2]2, 3a,3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d6-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-C5H4)2][Rh(C2H4)2][Rh(C2H4)(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(C2H4)(SiEt3)H] 4a, [CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H]24b, [CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2] 4c and [CH2(η5-C5H4)2][Rh(SiEt3)2(H)2]24d; 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(η5-C5H4)2][RhH(μ-SiEt2)]25 and [CH2(η5-C5H4)2][(RhEt)(RhH)(μ-SiEt2)2] 6. Complex 5 was also produced when 1 was photolysed with Et2SiH2. When the photochemical reactions with Et3SiH 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(SiEt3)}(μ-η1,η2-CH[double bond, length as m-dash]CH2)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(η5-C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]28 while 4b formed [CH2(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(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a, [CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H]210b, [CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2] 10c and [CH2(η5-C5H4)2][Rh(SiMe3)2(H)2]210d. However, three Si–C bond activation products, [CH2(η5-C5H4)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.

Graphical abstract: Photochemical reactions of [CH2(η5-C5H4)2][Rh(C2H4)2]2 with silanes: evidence for Si–C and C–H activation pathways

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Article information

DOI
https://doi.org/10.1039/B417171C
Article type
Paper
Submitted
11 Nov 2004
Accepted
14 Dec 2004
First published
18 Jan 2005

Dalton Trans., 2005, 744-759

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Photochemical reactions of [CH2(η5-C5H4)2][Rh(C2H4)2]2 with silanes: evidence for Si–C and C–H activation pathways

J. L. Cunningham and S. B. Duckett, Dalton Trans., 2005, 744 DOI: 10.1039/B417171C

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