CRYSTAL AND MOLECULAR STRUCTURE OF DIIODO [BIS(O-METHYLTHIOPHENYL)PHENYLPHOSPHINE]NICKEL(2), NI(C20H19PS2)I2

A three-dimensional X-ray structure determination of Ni(DSP)I2 (DSP = bis(o-methylthiophenyl)phenylphosphine) is reported. The compound crystallizes in the space group D2h15-Pbca with eight formula units in a cell of dimensions a = 13.95 (2), b = 17.97 (2), and c = 18.12 (2) Å. The calculated density (1.95 g/cm3) is in excellent agreement with the observed density of 1.95 ± 0.01 g/cm8. Data were collected by the equiinclination Weissenberg technique and intensities were estimated visually. The structure has been refined by full-matrix least-squares methods to a final conventional R factor of 8.3% for 1100 observed reflections. The structure has discrete squarepyramidal Ni(DSP)I2 molecules in which the phosphorus, one sulfur, and two iodine atoms form the basal plane and the other sulfur atom is the apex. This structure is unique among squarepyramidal complexes of the first transition series in that the central metal lies only slightly (0.09 Å) above the basal plane. The specific arrangement of donor atoms and the long Ni-S apical bond are interpreted in terms of maximum metal to ligand π-back-bondmg and the prolate nature of the 3d-electron density along the z axis in a d8 low-spin, squarepyramidal complex. © 1969, American Chemical Society. All rights reserved.