AB-INITIO XRPD STRUCTURE DETERMINATION OF METAL-CARBONYL CLUSTERS - THE CASE OF [HGRU(CO)4]4

The crystal and molecular structure of the new [HgRu(CO)4]4 cluster has been determined exclusively from X-ray powder diffraction data from standard laboratory equipment and refined with a (modified) Rietveld procedure. The title compound crystallizes in the monoclinic space group P2(1)/n, with a = 13.032(1) angstrom, b = 18.293(2) angstrom, c = 6.501 (1) angstrom, beta = 111.81(2)-degrees, V = 1438.9(4) angstrom3, and Z = 2; the final refinement converged to R(p) and R(wp) values of 0.097 and 0. 126, respectively, for 3351 data collected (Cu Kalpha) at room temperature in the 18-85-degrees (20) range. [HgRu(CO)4]4 consists of a planar, centrosymmetric, eight-membered ring of alternating Hg and cis-Ru(CO)4 units of idealized D4h symmetry. XRPD is shown to be a powerful tool to obtain useful structural information on moderately complex organometallic systems, when single crystals cannot be grown, if all the available chemical knowledge is included in the refinement through constraints.