Preparation and characterization of an unusual Di-cobalt complex; X-ray crystal structure of Co(CO)(2)(mu-CO)(mu:eta(2),eta(4)-C(4)Ph(4))Co(Co)(2)(PPh(3))

Reaction of [MoCo(CO)(5)(PPh(3))(2)(eta(5)-C5H5)] (1) With diphenylacetylene in tetrahydrofuran at 50 degrees C yielded two heterobimetallic compounds, [MoCo(CO)(4)(PPh(3)){mu-PhC = CPh}(eta(5)-C5H5)] (4) and [MoCo(CO)(5){mu-PhC = CPh}(eta(5)-C5H5)] (5). However, an unexpected product, Co(CO)(2)(mu-CO)(mu:eta(2),eta(4)-C(4)Ph(4))Co(CO)(2)(PPh(3)) (6), was observed while attempting to grow the crystals for structural determination of 4. The X-ray crystal structure of 6 was determined: triclinic, <P(1)over bar>, a = 11.654(2) Angstrom, b = 12.864(2) Angstrom, c = 13.854(2) Angstrom, alpha = 89.67(2)degrees, beta = 86.00(2)degrees, gamma = 83.33(2)degrees, V = 2057.9(6) Angstrom(3), Z = 2. In 6, two cobalt fragments are at apical and basal positions of the pseudo-pentagonal pyramidal structure, respectively. The electron count for the apical cobalt fragments is 20, which is rather unusual. It is believed that 6 was formed after the fragmentation and recombination of the fragmented species of 4.