Ruthenium(II)-MeO-Biphep-arene dications: Acetylene reactions and unexpected cyclometalation

Reactions of [Ru(arene)(MeO-Biphep)](SbF6)(2) (arene = p-cymene, 4, or benz ene, 5; MeO-Biphep = (6,6 ' -dimethoxybiphenyl-2,2 ' -diyl)bis(diphenylphos phine)) 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 eta (6)-benzene complex derived from phenyla cetylene, has been determined by X-ray diffraction, The dicationic complexe s 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.