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

The carbonylruthenium(0) complex Ru(CO){PCyp 2 (η 2 -C 5 H 7 )} 2 ( 4 ) has been prepared by reaction of RuH 2 {PCyp 2 (η 2 -C 5 H 7 )} 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 RuH 2 (η 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 RuH 2 (η 2 -H 2 )(CO)(PCyp 3 ) 2 ( 5 ) was isolated. An excess of tert -butylethylene reacted with 5 to give RuH 2 (CO){PCyp 2 (η 2 -C 5 H 7 )}(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(η 2 -C 2 H 4 )(CO){PCyp 2 (η 2 -C 5 H 7 )}(PCyp 3 ) ( 7 ). Finally, the dicarbonyl complex RuH 2 (CO) 2 (PCyp 3 ) 2 ( 8 ) was isolated by exposing 1 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.