THE CRYSTAL-STRUCTURE AND LOW-TEMPERATURE C-13 NMR-SPECTRUM OF THE 7-COORDINATE COMPLEX OF TUNGSTEN(II), [WI2(CO)(3)(NCPH)(2)]

The crystal structure of [WI2(CO)(3)(NCPh)(2)] (1) has been determined by X-ray methods. The crystals are orthorhombic, space group Pnam, a = 7.815(3), b = 13.839(5), c = 18.475(3) Angstrom, Z = 8, R = 0.0346 f or 1497 observed data. The complex [WI2(CO)(3)(NCPh)(2)] has a seven-c oordinate geometry, which may be described as a distorted capped octah edron, with the two iodo-ligands mutually trans, while each nitrile is trans to a carbonyl group. The capped octahedral geometry consists of a capping carbonyl {C(10)} on the face defined by I(1), C(20) and C(2 0)#. However, the geometry may also be described as a capped trigonal prism, which has one triangular face occupied by three carbonyl groups and the second triangular face occupied by N(1), N(1)# and I(1) atoms , respectively. The iodide 1(2) occupies the capping position on the r ectangular face defined by the atoms C(20), C(20)#, N(1), and N(1)#. T he low temperature C-13 NMR spectrum (203 K, CD2Cl2) of 1 shows a sing le carbonyl resonance at 219.27 ppm which indicates that the complex i s undergoing a rapid fluxional process in solution at 203 K.