Synthesis of [Ru(CO)2(PPh3)(SP)] and [Ru(CO)(PPh3)2(SP)] and their catalytic activities for the hydroamination of phenylacetylene

The reaction of [Ru(CO)2(PPh3)3] (1) with o-styryldiphenylphophine (SP) (2) gave [Ru(CO)2(PPh3)(SP)] (3) in 83% yield. This styrylphosphine ruthenium complex 3 can also be synthesized by the reaction of [Ru(p-MeOC6H4NN)(CO)2(PPh3)2]BF4 (4) with NaBH4 and 2 in 50% yield. When “Ru(CO)(PPh3)3” generated by the reaction of [RuH2(CO)(PPh3)3] (8) with trimethylvinylsilane reacted with 2, [Ru(CO)(PPh3)2(SP)] (10) was produced in moderate yield as an air sensitive solid. The spectral and X-ray data of these complexes revealed that the coordination geometries around the ruthenium center of both complexes corresponded to a distorted trigonal bipyramid with the olefin occupying the equatorial position and the C–C bonding in the olefin moiety in 3 and 10 contained a significant contribution from a ruthenacyclopropane limiting structure. Complexes 3 and 10 showed catalytic activity for the hydroamination of phenylacetylene 11 with aniline 12. Ruthenium complex 3 in the co-presence of NH4PF6 or H3PW12O40 proves to be a superior catalyst system for this hydroamination reaction. In the case of the reaction using H3PW12O40 as an additive, ketimines (13) was obtained in 99% yield at a ruthenium-catalyst loading of 0.1 mol%. Some aniline derivatives such as 4-methoxy, 4-trifluoromethyl-, and 4-bromoanilines can also be used in this hydroamination reaction.