(Indenyl)rhodacarboranes. Electronic versus steric effects on the conformation of cyclic ligands

(Indenyl)rhodacarboranes 1,2-R2-3-(η5-indenyl)-3,1,2-RhC2B9H9 (2a: R = H; 2b: R = Me) and 3-(η5-indenyl)-4-SMe-3,1,2-RhC2B9H10 (3) were synthesized by reactions of the iodide complex [(η5-indenyl)RhI2]n (1b) with Tl[Tl(η-7,8-R2-7,8-C2B9H9)] or Tl[9-SMe2-7,8-C2B9H10]. The formation of 3 is accompanied by monodemethylation of the SMe2 substituent. The structures of rhodacarboranes 2b, 3 and the half-sandwich complex (η5-indenyl)RhBr2(dmso) were determined by X-ray diffraction. Rhodacarborane 2b has the sterically unfavorable eclipsed cisoid conformation, in which the bridgehead carbon atoms of the indenyl ligand are arranged close to the carborane cage carbon atoms. The thermal stability of conformers for 2b was analyzed by the DFT calculations. © 2018 Elsevier B.V.