SUBSTITUTED CYCLOPENTADIENYL LIGANDS .10. INTRAMOLECULAR STERIC INTERACTIONS IN [(ETA(5)-C5H3(SIME(3))(2))MO(CO)(2)(L)I]

Reaction of C5H4(SiMe(3))(2) with Mo(CO)(6) yielded [(mu(5)-C5H3(SiMe( 3))(2))Mo(CO)(3)](2), which on addition of iodine gave [(eta(5)-C5H3(S iMe(3))(2))Mo(CO)(3)I]. Carbonyl displacement by a range of ligands : [L = P(OMe)(3), P(OPri)(3), P(O-o-tol)(3), PMe(3), PMe(2)Ph, PMePh(2), PPh(3), P(m-tol)(3)] gave the new complexes [(eta(5)-C5H3(SiMe(3))(2) )Mo(CO)(2)(L)I]. For all L the trans isomer was the dominant, if not e xclusive: isomer formed in the reaction. An NOE spectral analysis of [ (eta(5)-C5H3(SiMe(3))(2))Mo(CO)(2)(L)I] [L = PMe(2)Ph, P(OMe)(3)] reve aled that the L group resided on the sterically uncongested side of th e cyclopentadienyl ligand and that the ligand did not access the conge sted side of the molecule. Quantification of this phenomenon [L = P(OM e)(3)] was achieved by means of the vertex angle of overlap methodolog y. This methodology revealed a steric preference with the trans isomer (less congestion of CO than I with an SiMe(3) group) being the more s table isomer for L = P(OMe)(3). Copyright (C) 1996 Elsevier Science Lt d