129176-24-5Relevant articles and documents
η4-Siloles as ligands for cationic cobalt and rhodium phosphine complexes
Dufour,Dartiguenave,Dartiguenave,Dubac
, p. 2832 - 2836 (2008/10/08)
Reaction of 1-R-1-R′-3,4-dimethylsiloles (R = R′ = Me, 1; R = Me; R′ = Ph, 2; R = Me, R′ = allyl, 3; R = R′ = allyl, 4) with CoBr(PMe3)3 afforded the 18e [Co(silole)(PMe3)3]+ complexes, which were precipitated as BPh4 salts. Only one isomer was observed in which the larger substituent at Si was located in an exo position. Even when the silicon atom bore two allyl groups, no coordination of the endo allyl function to cobalt was apparent. This is in agreement with the higher nucleophilicity of PMe3 compared to that of alkene. Complexation with the 12e rhodium fragment [Rh(PPh3]2]+ occurred when an excess of silole was added to a hydrogenated solution of [Rh(COD)(PPh3)2]PF6 in THF. The cationic complexes [Rh(silole)(PPh3)2]PF6 that precipitated were characterized by 1H, 13C, and 31P NMR spectroscopy and elementary analysis. As for cobalt, only one isomer was present and no coordination of the allyl group in an endo position to rhodium was observed. Comparison of the 13C and 1H chemical shifts of the carbon and proton atoms of the ring indicated that the distortion of the ring on coordination is larger in cobalt than in rhodium, in agreement with the lower nucleophilic character of Co compared to that of Rh.
