Crystal and molecular structure of the bis(tetramethylammonium) octa-µ3-carbonyl-hexacarbonyl-octahedro-dinickeltetracobaltate(2–)

Abstract

Crystals of the title compound (NMe₄)₂[Co₄Ni₂(CO)₁₄], are trigonal, a= 11·283(6), c= 21·106(12)Å(hexagonal axes), space group R, Z= 3. The structure was determined by Patterson and Fourier methods from X-ray counter data and refined by full-matrix least-squares calculations to R 0·033 for 725 significant reflections. The anion has S₆ crystallographic symmetry. The metal atoms are statistically distributed at the corners of a lightly stretched octahedron, with independent M–M distances 2·487(1) and 2·519(1)Å. Six of the carbonyl ligands are bonded in terminal positions and eight are bridging on the octahedron faces. The M–C and C–O distances for the linear groups are 1·757(3), 1·129(5), Å and the mean values for the bridging ones 2·10(1), 1· 154(7)Å. The molecular geometry of the anion is compared with those of the isoelectronic species [Co₆(CO)₁₅]^2– and [Co₆(CO)₁₄]^4–.