Steric Influences in Octahedral Cohaloximes. The Crystal and Molecular Structure of trans-methylhis(dimethylglyoximato) (phosphite)cobalt(III) Complexs with Phosphite=P(OMe)2Ph and P(OMe)Ph2

The crystal structures of the title compounds, (P(OMe)2Ph)Co( DH)2Me (I) and (P(0Me)Ph2)Co(DH)2Me (II), are reported. Compound I crystallizes in the orthorhombic system, space group Pbca, with cell parameters a = 14.652(7), b = 26.45(1) and c = 11.330(6) A and z = 8; compound II crystallizes in the monoclinic system, space group P21 with cell parameters a = 9.423(7), b = 15.184(8), c = 8.948 (7) A and ~ = 100.50(9)0 , Z = 2. Both structures were solved by conventional Patterson and Fourier methods and refined by the block diagonal least-squares method to final R values of 0.033(1) and 0.034(II), using 2108 for I and 2063 for II independent reflections with I > 30\u27(1). In both compounds the cobalt atom has a distorted octahedral geometry, the two DH units occupying the equatorial positions and Me and the P-ligand the axial ones. The Co-C and Co- P bond lengths are 2.013(5) and 2.287(1) A in I and 2.019(6) and 2.352(1) A in II, respectively. Linear correlation between Co-P bond lengths and Tolman\u27s cone angles in the series RaPCo(DH)2Me is found, with the exception of the P(OMe)Ph2 derivative. Furthermore, the linear relationship between the above Co-P distances and those reported for analogous chloro-derivatives, already found for phosphines, is valid for I but not for II