STRUCTURE OF C5H5)(2)RU2FE2(CO)(8)(MU(2)-CO)(MU(4)-ETA(6)-C6H6) - AN UNUSUAL MIXED-METAL COMPOUND CONTAINING A BRIDGING DIALLYL LIGAND DERIVED BY UNSYMMETRICAL COUPLING OF 2 ALLENYL GROUPS

The heteronuclear compound C5H5)(2)Ru2Fe2(CO)(8)(mu(2)-CO)(mu(4)-eta(6 )-C6H6) (1), Obtained by reaction of (eta(5)-C5H5)(CO)(2)RuCH=C=CH2 wi th Fe-2(CO)(9), displays unusually complex H-1 and C-13 NMR spectra, A ll nine CO ligands, as well as all six carbon and hydrogen atoms of C6 H6, afford separate resonance signals. The structure of 1 was determin ed by X-ray diffraction techniques. The complex crystallizes from hexa ne (as a 3.1 cluster:solvate complex) in the centrosymmetric triclinic space group P (1) over bar with a = 7.852(1) Angstrom, b = 23.487(5) Angstrom, c = 24.144(4) Angstrom, alpha = 74.47(2)degrees, beta = 84.7 9(1)degrees, gamma = 86.69(1)degrees, V = 4269.8(14) Angstrom(3). The unit cell contains six polynuclear Ru2Fe2-containing molecules and two molecules of hexane. X-ray diffraction data (Mo K alpha, 2 theta = 7. 0-40.0 degrees) were collected with a Siemens R3m/V diffractometer and the structure was refined to R = 6.56% for all 7987 independent refle ctions (R = 2.90% for those 4844 reflections with \F-o\ > 6 sigma(\F-o \)). The organometallic molecule is based upon an unusual CH-C(CH2)-C H-C-CH2 fragment, which is derived from a beta-gamma coupling of two allenyl moieties and which forms pi-allyl linkages to the two iron ato ms and sigma-bonds (via the starred carbon atoms) to (eta(5)-C5H5)Ru m oieties. The metal atoms are arranged as a linear Ru(1)-Fe(2)-Fe(3) sy stem and a lone Ru(4) atom. Dimensions in the three independent molecu les are internally consistent, with carbonyl-bridged Ru(1)-Fe(2) dista nces of 2.687(1), 2.679(1) and 2.687(1) Angstrom and Fe(2)-Fe(3) dista nces of 2.895(2), 2.871(2) and 2.906(2) Angstrom.