Syntheses and structures of novel zerovalent ruthenium monodentate amine complexes†

Abstract

Novel ruthenium(0) monodentate amine (primary, secondary, and tertiary) and pyridine complexes, [Ru(η⁶-cot)(η²-dmfm)(L)] (cot = cycloocta-1,3,5-triene, dmfm = dimethyl fumarate; L = propylamine, benzylamine, dimethylamine, morpholine or pyridine), were prepared by the reaction of [Ru(η⁶-cot)(η²-dmfm)₂] with the corresponding amine in high yields. The structures of three of the complexes were determined by X-ray analyses and the co-ordination geometry around the central ruthenium atom is a highly distorted trigonal bipyramid. The nitrogen atom and one carbon–carbon double bond of the cyclooctatriene occupy the two axial positions, and the other two olefinic bonds of the cyclooctatriene and dimethyl fumarate the equatorial positions. The propylamine complex is in equilibrium with [Ru(η⁴-cot)(η²-dmfm)(PrNH₂)₂] in the presence of an excess of propylamine. The structure of this complex was confirmed by X-ray analysis. The position of the second amine is equatorial and the cyclooctatriene co-ordinated in a 1–2∶5–6-η bonding mode. When it was dissolved in CD₂Cl₂, propylamine at the equatorial position was dissociated, changing the η⁴-cyclooctatriene to the η⁶ mode to give [Ru(η⁶-cot)(η²-dmfm)(PrNH₂)].