Convenient syntheses of the square-bipyramidal cluster, [Co4(µ-4-GeMe)2(CO)11] and the formation of [Co4(µ4-GeMe)-{µ4-GeCo(CO)4}(CO)11] and [Co4{µ4-GeMn(CO)5}-{µ4-GeCo(CO)4}(CO)11]: new Ge2Co4 clusters containing the square-bipyramidal skeleton; and the crystal structure of [Co4(µ4-GeMe){µ4-GeCo(CO)4}(CO)11]

Abstract

The compound [Co₄(µ₄GeMe)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{µ-Ge(Me)Co(CO)₄}₂(CO)₆]3, at 40–45 °C. The compound [Co₂(CO)₈] reacts with GeMeH₂GeMeH₂ to give a modest yield of 1a and with GeMeH₂GeH₃ forms [Co₄(µ₄-GeMe)-{µ₄-GeCo(CO)₄}(CO)₁₁]4a, also formed from the reaction of [µ₄-Ge{Co₂(CO)₆(µ-GeMeH)}{Co₂(CO)₇}]5 with [Co₂(CO)₈]. The molecular structure of compound 4a, was determined by X-ray crystallography [monoclinic, space group, I2/a(non-standard C2/c), a= 12.852(3), b= 14.528(5), c= 26.566(8)Å, β= 90.32(2)°, R= 0.0699 for 1660 data with I > 2σ(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.