Insertion vs Ligand Exchange: Reactivity of Distanna Ansa Half-Sandwich Complexes of Molybdenum and Tungsten toward Isocyanide and Phosphine Complexes of Nickel and Palladium

Addition of [Ni(CNtBu)4] or [Ni(PEt3)4] to the molybdenum and tungsten distanna ansa half-sandwich complexes [{κ1-SntBu2SntBu2(η5-C5H4)}M(CO)3] (M = Mo, W) leads to carbonyl−isocyanide and carbonyl−phosphine exchange, respectively, resulting in enhanced reactivity toward chalcogen insertion in the case of the isocyanide compounds 8 and 9. Additionally, the first examples of oxidative addition of a half-sandwich ansa bridge toward zerovalent transition metals are presented by preparing the novel 1,3-distanna-2-pallada ansa half-sandwich complexes 17−20 by addition of [Pd(CNtBu)2].