STRUCTURE OF IRON DIRHENIUM TETRADECACARBONYL, [RE(CO)5FE(CO)4RE(CO)5]

Tetracarbonylbis(pentacarbonylrhenio)-iron, [FeRe2(CO)14], M(r) = 820.4, monoclinic, C2/m, a = 12.062 (1), b = 14.679 (1), c = 11.816 (1) angstrom, beta = 97.31 (1)-degrees, V = 2075.1 angstrom 3, Z = 4, D(x) = 2.626 g cm-3, lambda(Mo K-alpha) = 0.71073 angstrom, mu = 129 cm-1, F(000) = 1488, T = 295 K, R(F2) = 0.049 for 1580 reflections having F2 > sigma(F2), wR(F2) = 0.03. The asymmetric unit contains two crystallographically distinct molecules with symmetry 2/m, similar to those found in FeMn2(CO)14. Both molecules have linear arrangements of metal atoms without bridging carbonyl linkages, but differ in disposition of symmetry elements. The principal observations discussed are a shortening of the Re-Fe bond [0.027 (2) angstrom] and a torsional distortion of the Re(CO)5 and Fe(CO)4 groups from an idealized staggered configuration [45 --> 40.2 (5)-degrees] in one of the two independent molecules. These differences between the two molecules are attributed to differences in crystalline environment. Interatomic distances have also been reported but without discussion by Crocker, Mattson, Heinekey & Schulte [Inorg. Chem. (1988), 27, 3722-3729].