Phenylacetylene dimerization promoted by ruthenium(II) complexes

Article abstract of DOI:10.1016/0022-328X(91)86337-P

The complex Ru(CO)(CH=CHPh)Cl(C5H5N)(PPh3)2 and related alkenyl complexes react in methanol or ethanol to give (E,E)-1,4-diphenylbuta-1,3-diene and the ruthenium(II) hydride Ru(CO)H(Cl)(C5H5N)(PPh3)3.Futher reaction of this hydride with the butadiene results in 1,2-reduction to yield (E)-1,4-diphenyl-1-butene.However, the reaction of phenylacetylene with catalytic amounts of ruthenium hydrides gave the dimer (Z)-1,4-diphenylbuten-3-yne.On the other hand, the reaction of 1,2-diphenylethenylruthenium(II) derivatives in methanol or ethanol gave trans-stilbene rather than the butadiene.Several deuteration experiments were performed in order to elucidate the mechanism of formation of (E,E)-1,4-diphenylbuta-1,3-diene and ruthenium hydride from the corresponding alkenyl complexes.