SYNTHETIC AND STRUCTURAL STUDIES OF A NEW NICKEL-ANTIMONY ALKOXIDE - NI6SB4O4(OET)16(HOET)4

A Ni-Sb alkoxide of the formula Ni6Sb4O4(OEt)16(HOEt)4 has been prepared by reacting anhydrous NiBr2 with 2KOEt and Sb(OEt)3 in a toluene/ethanol solution under a dry, oxygen-free atmosphere. Ni6Sb4O4(OEt)16(HOEt)4 crystallizes with the centrosymmetric tetragonal space group symmetry P4(2)/n, with a = 13.003(1) angstrom, c = 19.332(3) angstrom, V = 3269(1) angstrom3, Z = 2, D(x) = 1.833(l) g/cm3, and M = 1808.6. The crystal structure was refined to R = 0.036 (R(w) = 0.039) for the 3005 most significant single-crystal X-ray diffraction intensities collected with Mo Kalpha radiation lambda(Mo Kalpha) = 0.7107 angstrom, mu(Mo Kalpha) = 34.0 cm-1) at 170(l) K. The packing of the molecules can be considered as body-centered cubic. The trivalent Sb atoms are 5-coordinated by oxygen atoms; the stereoactive lone pair completes an octahedral coordination geometry. The nickel atoms are approximately octahedrally coordinated by the oxygen atoms. Strong intramolecular hydrogen bonds, involving the hydroxyl groups of the ethanol molecules, apparently affect the molecular geometry. Extended Huckel molecular orbital calculations further support the assignment of the intramolecular hydrogen bond. An analysis of the thermal vibrational parameters indicates that all the metal and oxygen atoms in the molecule can be considered as constituting an essentially rigid body, while the thermal motions of the ethyl groups are more uncorrelated.