The crystal and molecular structure of the diphenylethylphosphine oxide adduct of tetrakis-(μ3-hydroxotricarbonylhydridotungsten), [W(OH)(CO)3H]4·4 OPPh2Et

The compound [W(OH)(CO)3H]4·4 OPPh2Et crystallizes in the monoclinic space group C2/c with the following unit cell constants: a = 25.06(2), b = 14.08(1), c = 24.60(2) A, β = 120°20′(10′) and Z = 4. The structure has been determined from a set of 1246 independent non-zero reflections, measured with counter methods, and refined by least-squares to a final R index of 0.049. It consists of tetrameric units [W(OH)(CO)3H]4, lying around the two-fold crystallographic axes. The tungsten atoms, which occupy the corners of a regular tetrahedron, are held together by four μ3-hydroxo groups, so that the W4O4 moiety forms a distorted cube. The W…W distances (mean value 3.48 A) are definitely non-bonding. The stereochemical arrangement of the ligands around the tungsten atoms identifies the hydridic hydrogen positions. The resulting coordination polyhedron in each (OH)3W(CO)3H moiety can be described as a combination, by apex sharing, of one triangular and one square pyramid, the triangle being formed by the OH oxygen atoms and the square by the CO carbon atoms plus the hydridic hydrogen. The four OPPh2Et molecules are joined to the tetramer through strong hydrogen bonds with the μ3-hydroxo groups (O…O contacts of 2.47 and 2.48 A).