CONVENIENT SYNTHESES OF THE SQUARE-BIPYRAMIDAL CLUSTER, [CO4(MU-4-GEME)2(CO)11]AND THE FORMATION OF [CO4(MU-4-GEME)-(MU-4-GECO(CO)4)(CO)11] AND [CO4(MU-4-GEMN(CO)5)-(MU-4-GECO(CO)4)(CO)11] - NEW GE2CO4 CLUSTERS CONTAINING THE SQUARE-BIPYRAMIDAL SKELETON - AND THE CRYSTAL-STRUCTURE OF [CO4(MU-4-GEME)(MU-4-GECO(CO)4)(CO)11]

The compound [Co4(mu-4-GeMe)2(CO)11] 1a results directly in high yield from the reaction of GeMeH3 with [Co4(CO)12] under mild conditions. It also forms near-quantitatively from the smooth decarbonylation of [Co2{mu-Ge(Me)Co(CO)4}2(CO)6] 3, at 40-45-degrees-C. The compound [Co2(CO)8] reacts with GeMeH2GeMeH2 to give a modest yield of 1a and with GeMeH2GeH3 forms [Co4(mu-4-GeMe)-{mu-4-GeCo(CO)4}(CO)11] 4a, also formed from the reaction of [mu-4-Ge{Co2(CO)6(mu-GeMeH)}{Co2(CO)7}] 5 with [Co2(CO)8]. The molecular structure of compound 4a was determined by X-ray crystallography [monoclinic, space group, 12/a (non-standard C2/c), a = 12.852(3), b = 14.528(5), c = 26.566(8) angstrom, beta = 90.32(2)-degrees, R = 0.0699 for 1660 data with I > 2-sigma-(I)] and is related to that of 1a by replacing one terminal Me by terminal Co(CO)4. Spectroscopic evidence indicates that other Ge2RH5 [R = Mn(CO)5 or Et] give analogues of 4a with the appropriate R terminal groups.