Reactivity studies of highly electrophilic ruthenium complexes

Abstract

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(C CPh)(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 H 2 across the Ru–C bond. The 16-electron complex also reacts with HSiCl 3 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 H 2 to afford the corresponding dihydrogen complex trans-[Ru(η 2-H 2)(P(O)(OH) 2)(dppe) 2][OTf] ( 5- H 2 ). 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(η 2-HD)(P(O)(OH) 2)(dppe) 2][OTf] ( 5- HD).