Hydrocarbon complexes of ruthenium. Part V. Reactions of trimethylsilyl- and trimethylgermyl-carbonylruthenium complexes with cyclo-heptatrienes

Abstract

On reaction of [Ru(MMe₃)₂(CO)₄](I; M = Si or Ge) with cycloheptatriene, migration of MMe₃ groups occurs to yield cycloheptadienyl complexes [Ru(MMe₃)(CO)₂(1–5-η-C₇H₈MMe₃-6)], identified by ¹H and ¹³C n.m.r. spectroscopy. The molecular structure of [Ru(SiMe₃)(CO)₂(1–5-η-C₇H₇(SiMe₃-6)(C₆F₅-7)}], prepared from 7-C₆F₅·C₇H₇ and (I; M = Si), reveals an exo configuration for migrant SiMe3(with respect to ruthenium), while a mechanistic experiment suggests a substantially intramolecular migration. Reactions of [{Ru(MMe₃)(CO)₄}₂](II; M = Si or Ge) with C₇H₈ in heptane give [Ru(MMe₃)(CO)₂(1–5-η)-C₇H₈MMe₃-6)] and [Ru₃(CO)₆(C₇H₇)-(C₇H₆)] in low yields, with bridging cycloheptatrienyl complexes [Ru₂(MMe₃)(CO)₅(1–2,3–4-η : 5–7-η-C₇H₉)] as the major products. A minor product, [Ru₂(SiMe₃)(CO)₅(1–2,3–4-η : 5–7-η-C₇H₆SiMe₃-7)], formed by SiMe₃ migration, has been identified from the reaction of (II; M = Si) with C₇H₈. The C₇H₇ rings in the complexes [Ru₂(MMe₃)(CO)₅(η-C₇H₇)] are fluxional even at –90 °C. The preparation and n.m.r. study of derivatives [Ru₂(SiMe₃)(CO)₅(η-C₇H₆R)](R = Me, Ph, C₆F₅, or SiMe₅) is also described. In a sealed tube at 150 °C, (II; M = Si) and C₇H₈ react differently, affording the SiMe₃-migration product [Ru(CO)₃(1–2 : 3–4-η-C₇H₉SiMe₃-2)] and Ru₃(CO)₁₂.