Ruthenium(II)−MeO−Biphep−Arene Dications:  Acetylene Reactions and Unexpected Cyclometalation

Reactions of [Ru(arene)(MeO−Biphep)](SbF 6 ) 2 (arene = p -cymene, 4, or benzene, 5; MeO−Biphep = (6,6‘-dimethoxybiphenyl-2,2‘-diyl)bis(diphenylphosphine)) with several terminal acetylene compounds lead to products derived from cyclometalation of one of the P-phenyl rings, followed by insertion of the acetylene derivative into the new Ru−C bond. The solid-state structure of one of these compounds, an η 6 -benzene complex derived from phenylacetylene, has been determined by X-ray diffraction. The dicationic complexes 4 and 5 catalyze the reaction of benzoic acid with 1-pentyne or 1-octyne to form enol-ester organic products. Using octyne- d 1, deuterium-labeling experiments show scrambling of the deuterium atom. A new Ru−carbene complex was prepared and used in the catalytic reaction.