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.