Reactivity studies of highly electrophilic ruthenium complexes

The 16-electron, coordinatively unsaturated, dicationic ruthenium complex [Ru(P(OH)2(OMe))(dppe)2][OTf]2 (1a) brings about the heterolysis of the C–H bond in phenylacetylene to afford the phenylacetylide complex trans-[Ru(CCPh)(P(OH)2(OMe))(dppe)2][OTf] (2). The phenylacetylide complex undergoes hydrogenation to give a ruthenium hydride complex trans-[Ru(H)(P(OH)2(OMe))(dppe)2][OTf] (3) and phenylacetylene via the addition of H2 across the Ru–C bond. The 16-electron complex also reacts with HSiCl3 quite vigorously to yield a chloride complex trans-[Ru(Cl)(P(OH)2(OMe))(dppe)2][OTf] (4). On the other hand, the other coordinatively unsaturated ruthenium complex [Ru(P(OH)3)(dppe)2][OTf]2 (1b) reacts with a base N-benzylideneaniline to afford a phosphonate complex [Ru(P(O)(OH)2)(dppe)2][OTf] (5) via the abstraction of one of the protons of the P(OH)3 ligand by the base. The phenylacetylide, chloride, and the phosphonate complexes have been structurally characterized. The phosphonate complex reacts with H2 to afford the corresponding dihydrogen complex trans-[Ru(η2-H2)(P(O)(OH)2)(dppe)2][OTf] (5-H2). The intact nature of the H–H bond in this species was established using variable temperature 1H spin–lattice relaxation time measurements and the observation of a significant J(H,D) coupling in the HD isotopomer trans-[Ru(η2-HD)(P(O)(OH)2)(dppe)2][OTf] (5-HD).