STRUCTURE OF MU-OXO-MU-CHLORO-DI-MU-PROPIONATO-BIS(CHLOROTRIPHENYLPHOSPHINERHENIUM) . A NEW METAL-METAL BOND

The crystal and molecular structures of one of the substances reported by Rouschias and Wilkinson to have the general formula Re2Cl3(O2CR)2[P(C6H5)3]2, namely, the one with R = C2H5, have been determined in an X-ray crystallographic study; It was found that the formula as previously given is incorrect, lacking one oxygen atom. The Re2OCl3(O2CC2H5)2- [(C6H5)3]2 molecule consists of two structurally equivalent Re atoms each surrounded by six ligand atoms at the vertices of a slightly distorted octahedron. The octahedra are joined on a common edge formed by bridging O and Cl atoms. The other two CI atoms occupy positions trans to the bridging O atom, and the P atoms occupy positions trans to the bridging Cl atom. The pairs of vertices above and below the plane defined by these six ligand atoms and the two Re atoms are occupied by bridging bidentate C2H5COO groups. The symmetry of the two Re atoms and the ten atoms coordinated to them is C2v neglecting small packing distortions. The Re-Re distance is 2.514 (1) Å. The entire structure is nearly identical with that of Re2OCl3(O2CC2H5)[P(C6H5)3]2 except for the replacement of two CI atoms by a propionato group. The crystals studied belong to space group P21/c with dimensions a = 14.059 ± 0.003 Å, b = 17.477 ± 0.003 Å, c = 17.556 ± 0.003 Å, and β = 97.80 ± 0.01°. The observed and calculated densities were 1.81 + 0.01 and 1.82 g cm- (for Z = 4), respectively. The structure was solved and refined using 2125 statistically significant independent reflections. Refinement was by a full-matrix, least-squares program in which the phenyl groups were treated as rigid bodies with separate isotropic temperature parameters for each carbon atom; anisotropic temperature parameters were used for Re, CI, and P atoms. Final weighted and unweighted discrepancy indexes were 0.034 and 0.031, respectively. Mean values of bond lengths to rhenium atoms are (Å): Re-Cl(terminal), 2.360 (3); Re-Cl(bridge), 2.403 (3); Re-P, 2.455 (3); Re-O(carboxyl), 2.108 (5); Re-O(bridge), 1.916 (6). © 1969, American Chemical Society. All rights reserved.