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

The compound mu3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(CO)6(PPh3)2] (1) (a mpy = 2-amino-6-methylpyridinate) has been prepared by reaction of (mu 3,eta2-ampy)(mu,eta1:eta2-PhC=CHPh)(CO)7(PPh3)] with triphenylphosphin e at room temperature. However, the reaction of [Ru3(mu-H)(mu3,eta2-am py)(CO)7(PPh3)2] with diphenylacetylene requires a higher temperature (110-degrees-C) and does not give complex 1 but the phenyl derivative py)(mu,eta1:eta2-PhC=CHPh)(mu-PPh2)(Ph)(CO)5(PPh3] (2). The thermolysi s of complex 1 (110-degrees-C) also gives complex 2 quantitatively. Bo th 1 and 2 have been characterized by X-ray diffraction methods. Compl ex 1 is a catalyst precursor for the homogeneous hydrogenation of diph enylacetylene to a mixture of cis- and trans-stilbene under mild condi tions (80-degrees-C, 1 atm. of H-2), although progressive deactivation of the catalytic species is observed. The dihydride mu3,eta2-ampy)(mu ,eta1:eta2-PhC=CHPh)(CO)5(PPh3)2] (3), which has been characterized sp ectroscopically, is an intermediate in the catalytic hydrogenation rea ction.