Preparation and Characterization of a Heteronuclear μ-Alkyne Complex; X-Ray Crystal Structure of MoCo(CO)4(PPh3){μ-HCCSiMe3)(η5-C5H5)

Reaction of MoCo(CO)₅(PPh₃)₂(η⁵-C₅H₅) (1a) with trimethylsilylacetylene in tetrahydrofuran at 58° C yielded two acetylene bridged heterobimetallic compounds, MoCo(CO)₄(PPh₃){μ-HC?CSiMe₃}(η⁵-C₅H₅) (4) and MoCo (CO)₅{μ-HC?CSiMe₃}(η⁵-C₅H₅)(5). (4) was characterized by mass, infrared, ¹H, ¹³C and ³¹P NMR spectra. The X-ray crystal structure of (4) was determined:triclinic, P-1, a=8.821(1) Å, b=11.315(3) Å, c=17.029(2) Å, α=70.73(1)°, β=78 .72(1)°, γ=86.10(2)°,V =1573.4(6) ų, Z=2, R = 3.92%,R_w = 6.06% for 4285 (F > 4σ (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 molybdenum center.