Phosphine-substituted and phosphido-bridged metal cluster in homogeneous catalysis. IV. Selective hydrogenation of diphenylacetylene and isomerization of cis-stilbene in the presence of Ru3(CO)12-n(PPh2H)n (n=2,3), HRu3(CO)10(μ-PPh2), HRu3(CO)9(μ-PPh2) and HRu3(CO)7(μ-PPh2)3

Article abstract of DOI:10.1016/0022-328X(89)85191-5

The cluster Ru3(CO)_12-n(PPh2H)_n (n=2,3), HRu3(CO)10(μ-PPh2), HRu3(CO)9(μ-PPh2) and HRu3(CO)7(μ-PPh2)3 show considerable activity in the selective hydrogenation of diphenylacetylene to stilbenes; the phosphine-substituted derivatives are also very efficient in the isomerization of cis-stilbene to trans-stilbene.The latter product is often found as a precipitate in the vials after the hydrogenation or isomerization experiments.Different cis/trans-stilbene ratios in the hydrogenation solutions have been found for the phosphine-substituted and the phosphido-bridged clusters; this points to different reaction patterns and/or intermediates.A comparison of the behaviour of C2Ph2, C2Et2 and HC2Bu^t under the same conditions and in the presence of the same phosphido-bridged cluster has been made; the nature of the alkyne has an important influence on the hydrogenation rate and the formation of reaction intermediates.