Dehydrogenation and demethanation of 2-methylpropane and propane in the gas-phase by the 16-electron complex [Ru(bipy)2(CO)]2+* chemically activated by the association of [Ru(bipy)2]2+ and CO

Abstract

The reactions of [Ru(bipy)₂]²⁺ with 2-methylpropane, propane, and propene have been investigated in the ICR cell of a mass spectrometer. In these reactions, the association of one molecule of each hydrocarbon was observed. When [Ru(bipy)₂]²⁺ was ligated with CO, and the newly formed [Ru(bipy)₂(CO)]²⁺ was allowed to react with 2-methylpropane and propane both dehydrogenation and demethanation were observed among association and substitution products. Density functional calculations were used to help elucidate the mechanism and the energy requirement for the dehydrogenation and demethanation reactions of 2-methylpropane mediated by [Ru(bipy)₂(CO)]²⁺*. These very interesting elimination reactions of [Ru(bipy)₂(CO)]²⁺ are attributed to a hot 16-electron intermediate, [Ru(bipy)₂(CO)]²⁺*, formed upon ligation of [Ru(bipy)₂]²⁺ with CO which has no efficient means of dissipating its internal energy in the low-pressure confines of the ICR cell. The reactions were concluded to occur via a concerted elimination mechanism rather than by oxidative addition/reductive elimination following the dissociation of one Ru–N bond.