Hydrocarbon complexes of ruthenium. Part IV. Cyclic dienyl complexes

Abstract

Cyclopentadiene, cyclohexa-1,3-diene, and cyclohepta-1,3-diene yield dienyl complexes [Ru(MMe₃)(CO)₂(1–5-η-dienyl)](M = Si or Ge) on reaction with [Ru(MMe₃)₂(CO)₄](M = Si or Ge) or [{Ru(SiMe₃)(CO)₄}₂]. Cyclohexa-1,3-diene gives [Ru(CO)₃(1–2 : 3–4 η-C₆H₈)] as the major product with both ruthenium complexes, whereas Cyclopentadiene and cyclohepta-1,3-diene give the corresponding [Ru(CO)₃(1–2 : 3–4-η-diene)] complex only with [{Ru(SiMe₃)(CO)₄}₂]. In the Cyclopentadiene reactions, formation of [Ru(CO)₃(1–2 : 3–4-η-C₅H₆)] is deduced from observation of its decomposition product [RuH(CO)₂(η-C₅H₅)]. Both [Ru(CO)₃-(1–2 : 3–4-η-C₆H₈)] and [Ru(CO)₃(1–2 : 3–4-η-C₇H₁₀)] are best prepared by treating Ru₃(CO)₁₂ with the diene, and have been employed as source of the cations [Ru(CO)₃(1–5-η-C₆H₇)]⁺ and [Ru(CO)₃(1–5-η-C₇H₉)]⁺via hydride abstract ion with [Ph₃C][BF₄]. The interaction of the cations with several nucleophiles has been studied, revealing a wide variation in the site of attack. Thus X^–(X = Br or I), CN^–, OMe^–, and H^– attack [Ru(CO)₃(1–5-η-C₇H₉)]⁺ to yield respectively [RuX(CO)₂(1–5-η-C₇H₉)], [Ru(CO)₃(1-σ,3–5-η-C₇H₉CN-2)], [Ru(CO)₃-(1–2 : 3–4-η-C₇H₉OMe-5)], and a mixture of [Ru(CO)₃(1-σ,3–5-η-C₇H₁₀)] and [Ru(CO)₃(1–2 : 3–4-η-C₇H₁₀)].