PREPARATION AND CHARACTERIZATION OF A HETERONUCLEAR MU-ALKYNE COMPLEX- X-RAY CRYSTAL-STRUCTURE OF MOCO(CO)(4)(PPH(3))(MU-HC-CSIME(3))(ETA(5)-C5H5)

Reaction of MoCo(CO)(5)(Ph(3))(2)(eta(5)-C5H5) (1a) with trimethylsily lacetylene in tetrahydrofuran at 58 degrees C yielded two acetylene br idged heterobimetallic compounds, MoCo(CO)(4)(PPh(3)){mu-HC=CSiMe(3)} (eta(5)-C5H5) (4) and MoCo(CO)(5){mu-HC=CSiMe(3)} (eta(5)-C5H5) (5). ( 4) was characterized by mass, infrared, H-1, C-13 and P-31 NMR spectra . The X-ray crystal structure of (4) was determined: triclinic, P-1, a = 8.821(1) Angstrom, b = 11.315(3) Angstrom, c = 17.029(2) Angstrom, alpha = 70.73(1)degrees, beta = 78.72(1)degrees, gamma = 86.10(2)degre es, V = 1573.4(6) Angstrom(3), Z = 2, R = 3.92%, R(w) = 6.06% for 4285 (F > 4 sigma(F)) observed reflections. The core of this molecule is a quasi-tetrahedron containing Mo, Co and two carbons of acetylene. The triphenylphosphine ligand is attached to cobalt rather than molybdenu m center.