Access to Ruthenium(0) Carbonyl Complexes via Dehydrogenation of a Tricyclopentylphosphine Ligand and Decarbonylation of Alcohols

The carbonylruthenium(0) complex Ru(CO){PCyp22-C5H7)}2 (4) has been prepared by reaction of RuH2{PCyp22-C5H7)}2 (3) with an excess of tert-butylethylene in the presence of ethanol. Decarbonylation of ethanol is also observed when reacting the bis(dihydrogen) complex RuH22-H2)2(PCyp3)2 (1) with 2 equiv of ethanol. The reaction results formally in the substitution of one dihydrogen ligand by a carbonyl, and the corresponding complex RuH22-H2)(CO)(PCyp3)2 (5) was isolated. An excess of tert-butylethylene reacted with 5 to give RuH2(CO){PCyp22-C5H7)}(PCyp3) (6), which corresponds to the formal loss of 2 equiv of dihydrogen: loss of the dihydrogen ligand and dehydrogenation of one cyclopentyl ring. The dihydride 6 can be dehydrogenated further by reaction with ethylene, affording the ruthenium(0) complex Ru(η2-C2H4)(CO){PCyp22-C5H7)}(PCyp3) (7). Finally, the dicarbonyl complex RuH2(CO)2(PCyp3)2 (8) was isolated by exposing 1 to 3 bar of CO. 8 and the new complexes 47, resulting from partial dehydrogenation of one or two cyclopentyl rings of the tricyclopentylphosphines and/or decarbonylation of alcohol, were characterized by multinuclear NMR, IR, elemental analysis, and X-ray diffraction.