The preparation and reactions of hydridochlorotris(triphenylphosphine)ruthenium(II) including homogeneous catalytic hydrogenation of alk-1-enes
The complex hydridochlorotris(triphenylphosphine)ruthenium(II) as a benzene solvate, RuClH(PPh3)3,C6H6, has been obtained by the interaction of the dichloride, RuCl2(PPh3)3, with molecular hydrogen at ambient temperature pressure in the presence of a base such as triethylamine; other preparative methods are described. The corresponding bromide, RuBrH(PPh3)3,C6H6, has been prepared. From the chloride by interaction with norbornadiene and 2,2′-bipyridyl, the complexes RuClH(C7H8)(PPh3)2 and [RuClH(bipyr)(PPh3)2]2 respectively have been obtained; the complex RuH2(CO)(PPh3)3 has also been prepared.
The complex RuClH(PPh3)3 is the most active catalyst yet discovered for the homogeneous hydrogenation of alk-1-enes in benzene or toluene solution. The interaction is highly specific and rates for other types of alkene are slower by a factor of at least 2 × 103. The inherent difficulties of the system however preclude detailed kinetic study and it is shown that slow poisoning of the catalyst occurs under hydrogenation conditions.
N.m.r. studies of the hydrido-complex and its deuteride have allowed hydrogen atom exchange studies to be made. Isomerisation of alkenes is studied. The slow exchange between molecular hydrogen and the α-proton of a phenyl group on the phosphine is demonstrated.