Metal-induced B-H activation.: Addition of phenylacetylene to Cp*Rh-, Cp*Ir-, (p-cymene)Ru- and (p-cymene)Os halfsandwich complexes containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolate ligand

The addition reactions of the 16e halfsandwich complexes Cp*M[S2C2(B10H10)] (1S M = Rh, 2S M = Ir) and eta(6)-(4-isopropyl-toluene)M[S2C2(B10H10)] (3S M = Ru and 4S M = Os) with phenylacetylene lead selectively to the 18e complexes 5S-8S, in which a metal-boron bond is present and the phenylacetylene is regio- and stereoselectively inserted into one of the M-S bonds, with one hydrogen atom transferred from the carborane cage to the terminal carbon of the alkyne, corresponding to ortho-metalation of the carborane cage. In all cases, the S-eta(2)-(Ph)CC and the C(1)B units are linked to the metal in cisoid positions. The analogous reaction of Cp*Ir[Se2C2(B10H10)] 2Se with phenylacetylene gives 6Se. Complex 5S undergoes an intramolecular rearrangement in solution to the isomer 9S, where the Rh-B bond is cleaved, the B-atom now bearing the organic substituent, and a metal-carbon sigma bond being formed together with a coordinative S-->Rh bond. In contrast, the p-cymene complexes 7S and 8S rearrange into isomers 10S and 11S, in which the S-eta(2)-(Ph)C-C and the C(1)-B(M) moieties occupy transoid positions, preventing further intramolecular rearrangements. The proposed structures in solution were deduced from NMR data (H-1-, B-11-, C-13-, Se-77-, and Rh-103-NMR) and X-ray structural analyses were carried out for 5S, 6Se, 9S and 10S. (C) 2000 Elsevier Science S.A. All rights reserved.