Synthesis, spectroscopic characterization, and x-ray structural determination of W(CO)4(PR3)CNC6H4(PR3) (R = Ph, Et)

Two bimetallic complexes containing 1,4-diisocyanobenzene as a bridging ligand have been prepared and examined by x-ray crystallography and 13C NMR, 31P NMR, and infrared spectroscopies. W(CO)4(PEt3)CNC6H4NCW(CO)4(PEt3) (1) and W(CO)4(PPh3)CNC6H4NCW(CO)4(PPh3) (2) both crystallized in the same space group in very similar packing environments. Crystal data: for 1, monoclinic space group P21/n,a = 7.780 (2) angstrom, b = 15.930 (3) angstrom, c = 14.137 (6) angstrom, β = 99.56 (3)degree, Z = 2, R = 0.040; for 2, monoclinic space group P21/n, a = 11.641 (2) angstrom, b = 16.970 (2) angstrom, c = 12.463 (2), angstrom, β = 101.24 (1)degree, Z = 2, R = 0.047; NMR chemical shifts and vibrational frequencies for CNC6H4NC experience significant changes upon coordination, and the presence of an organophosphine ligand in the metal coordination sphere causes the diisocyanide to experience in-plane bends of 10.8 degrees for 1 and 4.2 degree for 2. In spite of strong evidence for the M-CNR back-bonding, the C-N bond length varies only negligibly among 1, 2, and CNC6H4NC, the free ligand. 20 references, 2 figures, 8 tables