Solving simple organometallic structures solely from x-ray powder diffraction data: The case of polymeric [{Ru(CO)4}n]

The crystal and molecular structure of [{Ru(CO)4}n] has been determined solely from X-ray powder diffraction data using standard laboratory equipment and refined with a (modified) Rietveld procedure. The compound crystallizes in the orthorhombic space group Ibam, with a = 14.147(4), b = 7.060(2) and c = 5.720(1) Å, Z = 4; the final refinement (19 variables) converged to Rp, Rwp and RBragg of 0.077, 0.102 and 0.025, respectively, for 4001 data collected at room temperature in the 5-85° (2θ) range. The structure, which consists of a polymeric stack of staggered trans-D4h Ru(CO)4 fragments separated by a Ru-Ru contact of 2.860(1) Å, is the first polymeric binary metal carbonyl compound so far characterized. Strain and particle-size broadening effects have been observed, and the microstructural properties of the compound are discussed.