ORGANOMETALLIC CHALCOGEN COMPLEXES .17. PREPARATION AND STRUCTURAL CHARACTERIZATION OF A METAL-OXYGEN ATOM CLUSTER SYSTEM CO3(PI-C5H5)3(CO)(O)

A new metal-oxygen cluster system, Co3(π-C5H5)3(CO)(O), has been isolated in very low yield from prolonged ultraviolet irradiation of a Co(π-C5H5)(CO)2 solution. The compound presumably arises by oxidative and/or photolytic decomposition of the King compound Co3(π-C5H5)3(CO)3. The characterization of this complex was achieved from the X-ray structural determination. The molecular configuration of Co3(π-C5H5)3(CO)(O) consists of an equilateral triangle of cobalt atoms with triply bridging carbonyl and oxygen ligands symmetrically positioned above and below the tricobalt plane on the principal threefold molecular axis. The three cyclopentadienyl rings are perpendicularly disposed about the tricobalt plane such that with the assumption of cylindrical symmetry for each ring the molecule approximates C3v-3m symmetry. A stereochemical consequence of the necessity of electron-pair cobalt-cobalt bonds in order for each cobalt atom to attain a closed-shell electronic configuration is a single-bond Co-Co distance of 2.365 ° 0.004 Å which is similar to the metal-metal bond length of 2.358 ± 0.002 Å in the electronically equivalent and structurally analogous complex Ni2Co(π-C5H5)3(CO)2,. The structural features of Co3(π-C5H5)3(CO)(O) are also compared with those of the geometrically related Ni3(π-C5H5)3(CO)2 and Ni3(π-C5H5)3S2 complexes. Despite complications caused by a twinning of the hexagonal crystals and by a horizontal mirror plane crystal disordering of the cyclopentadienyl, carbonyl, and oxygen ligands, the structure was successfully elucidated by application of the Wei technique and refined by least squares to a final R1(F2) value of 6.4% and R2(F2) value of 10.4% for the diffractometry-collected intensity data. The single-crystal component contains two formula species in a hexagonal unit cell of symmetry P63/m and dimensions β = 9.077 ° 0.006 Å and c = 10.235 ± 0.006 Å the calculated and observed densities are both 1.89 g cm-3. © 1969, American Chemical Society. All rights reserved.