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

The carbonylruthenium(0) complex Ru(CO){PCyp<sub>2</sub>(η<sup>2</sup>-C<sub>5</sub>H<sub>7</sub>)}<sub>2</sub> (<b>4</b>) has been prepared by reaction of RuH<sub>2</sub>{PCyp<sub>2</sub>(η<sup>2</sup>-C<sub>5</sub>H<sub>7</sub>)}<sub>2</sub> (<b>3</b>) with an excess of <i>tert</i>-butylethylene in the presence of ethanol. Decarbonylation of ethanol is also observed when reacting the bis(dihydrogen) complex RuH<sub>2</sub>(η<sup>2</sup>-H<sub>2</sub>)<sub>2</sub>(PCyp<sub>3</sub>)<sub>2</sub> (<b>1</b>) with 2 equiv of ethanol. The reaction results formally in the substitution of one dihydrogen ligand by a carbonyl, and the corresponding complex RuH<sub>2</sub>(η<sup>2</sup>-H<sub>2</sub>)(CO)(PCyp<sub>3</sub>)<sub>2</sub> (<b>5</b>) was isolated. An excess of <i>tert</i>-butylethylene reacted with <b>5</b> to give RuH<sub>2</sub>(CO){PCyp<sub>2</sub>(η<sup>2</sup>-C<sub>5</sub>H<sub>7</sub>)}(PCyp<sub>3</sub>) (<b>6</b>), which corresponds to the formal loss of 2 equiv of dihydrogen: loss of the dihydrogen ligand and dehydrogenation of one cyclopentyl ring. The dihydride <b>6</b> can be dehydrogenated further by reaction with ethylene, affording the ruthenium(0) complex Ru(η<sup>2</sup>-C<sub>2</sub>H<sub>4</sub>)(CO){PCyp<sub>2</sub>(η<sup>2</sup>-C<sub>5</sub>H<sub>7</sub>)}(PCyp<sub>3</sub>) (<b>7</b>). Finally, the dicarbonyl complex RuH<sub>2</sub>(CO)<sub>2</sub>(PCyp<sub>3</sub>)<sub>2</sub> (<b>8</b>) was isolated by exposing <b>1</b> to 3 bar of CO. <b>8</b> and the new complexes <b>4</b>−<b>7</b>, 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.