Abstract
Addition of primary alcohols, RCH{sub 2}OH (> 6 equiv), to hydrocarbon solutions of M{sub 2}(O-t-Bu){sub 6} compounds has led to the isolation of the first homoleptic series of cluster alkoxides M{sub 4}(OCH{sub 2}R){sub 12} for both M = Mo and W where R = i-Pr, Cy (Cy = cyclohexyl), Cp (Cp = cyclopentyl), and c-Bu (c-Bu = cyclobutyl). The NMR data ({sup 1}H and {sup 13}C) indicate a common structural unit for this class of compounds containing a molecular mirror plane. For each M{sub 4}(OCH{sub 2}R){sub 12} compound there are eight types of alkoxide ligands in the integral intensity 2:2:2:2:1:1:1:1. Those having integral intensity two possess diastereotopic methylene protons, indicating that they do not lie on the mirror plane, whereas the other four alkoxides (1:1:1:1) are contained within the mirror plane. Though these compounds yield crystals from 1,2-dimethoxyethane, they failed to diffract beyond 10{degree} indicating a molecular disorder within hexagonal packing of M{sub 4} units. However, the cyclobutylmethoxide derivatives crystallize with an additional molecule of alcohol, M{sub 4}(CH{sub 2}-c-Bu){sub 12}(HOCH{sub 2}-c-Bu), and the molecular structure of the molybdenum compound was determined by an X-ray study. Crystal data for Mo{sub 4}(OCH{sub 2}-c-Bu){sub 12}(HOCH{sub 2}-c-Bu) at {minus}156{degree}C: a = b = 19.952more » (7) {angstrom}, c = 34.755 (16) {angstrom}, Z = 8, d{sub calcd} = 1.43 g cm{sup {minus}3}, and space group Pr{sub 1}. The unit cell contains two crystallographically independent molecules that are essentially equivalent with respect to M-M and M-O distances and angles. In each there is a central Mo{sub 4} butterfly with a dihedral angle between the Mo{sub 3} triangles of 132.5{degree}.« less
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