SYNTHESIS, STRUCTURE AND HYDROGENATION CATALYTIC ACTIVITY OF [RU3(MU(3),ETA(2)-AMPY)(MU,ETA(1)-ETA(2)-PHC=CHPH)(CO)6(PPH3)2] (AMPY = 2-AMINO-6-METHYLPYRIDINE)

The compound [Ru3(mu3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(CO)6(PPh3)2] (1) (ampy = 2-amino-6-methylpyridinate) has been prepared by reaction of [Ru3(mu3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(CO)7(PPh3)] with triphenylphosphine at room temperature. However, the reaction of [Ru3(mu-H)(mu3,eta2-ampy)(CO)7(PPh3)2] with diphenylacetylene requires a higher temperature (110-degrees-C) and does not give complex 1 but the phenyl derivative [Ru3(mu3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(mu-PPh2)(Ph)(CO)5(PPh3] (2). The thermolysis of complex 1 (110-degrees-C) also gives complex 2 quantitatively. Both 1 and 2 have been characterized by X-ray diffraction methods. Complex 1 is a catalyst precursor for the homogeneous hydrogenation of diphenylacetylene to a mixture of cis- and trans-stilbene under mild conditions (80-degrees-C, 1 atm. of H-2), although progressive deactivation of the catalytic species is observed. The dihydride [Ru3(mu-H)2(mu3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(CO)5(PPh3)2] (3), which has been characterized spectroscopically, is an intermediate in the catalytic hydrogenation reaction.