Access to ruthenium(0) carbonyl complexes via dehydrogenation of a tricyclopentylphosphine ligand and decarbonylation of alcohols

The carbonylruthenium(0) complex Ru(CO){PCyp(2)(eta(2)-C5H7)}(2) (4) has been prepared by reaction of RuH2 {PCyp(2)(eta(2)-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 RuH2(eta(2)-H-2)(2)(PCyp(3))(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 RuH2(eta(2) H-2)(CO)(PCyp(3))(2) (5) was isolated. An excess of tert-butylethylene reacted with 5 to give RuH2(CO) {PCyp(2)(eta(2)-C5H7)}(PCyp(3)) (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(eta(2)-C2H4)(CO){PCyp(2)(eta(2)-C5H7)}(PCyp(3)) (7). Finally, the dicarbonyl complex RuH2(CO)(2)(PCyp(3))(2) (8) was isolated by exposing I to 3 bar of CO. 8 and the new complexes 4-7, 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.