Preparation, dynamic NMR behavior and X-ray structure of a novel 1:1 complex of dimethyldivinylsilane and carbonylbis(triphenylphosphine)ruthenium

Abstract

Treatment of dihydridocarbonyltris(triphenylphosphine)ruthenium with a stoichiometric amount of styrene, followed by the addition of dimethyldivinylsilane, leads to a 1:1 complex: [Ph 3P] 2RuCO[η-(CH 2CH) 2Si(CH 3) 2]. This species has been characterized fully and its structure determined by X-ray crystallography at −100°C. The structure is unsymmetrical. The two triphenylphosphine ligands are not equivalent. Similarly, while both of the C–C double bonds of the dimethyldivinylsilane ligand are π-bonded to the ruthenium center, they are also dissimilar. In solution, the 1H- and 31P-NMR of this complex change with temperature. At low temperature, in the 1H-NMR the two methyl and the two vinyl groups bonded to silicon are each different. Similarly, in the 31P-NMR spectrum the two triphenylphosphine ligands are different. At high temperature, rapid equilibration occurs averaging the spectra. The Δ G ‡ for the exchange processes for the vinyl groups in the 1H-NMR and the 31P-NMR are both ∼12.7 kcal mol −1. The Δ G ‡ for the exchange process that averages the methyl groups in the 1H-NMR is ∼15.2 kcal mol −1.