STRUCTURAL STUDY OF STERIC EFFECTS IN COBALT DIMETHYLGLYOXIMATES CONTAINING PHOSPHINE LIGANDS - STRUCTURE OF TRANS-BIS(DIMETHYLGLYOXIMATO)METHYLTRIPHENYLPHOSPHINECOBALT(III) AND OF TRANS-BIS(DIMETHYLGLYOXIMATO)CHLOROTRICYCLOHEXYLPHOSPHINECOBALT(III) TOLUENE SOLVATE

The crystal and molecular structure of the title compounds has revealed that crystals of trans-bis(dimethylglyoxinate)methyltriphenylphosphinecobalt(Ill) (I) are monoclinic space group P21 with a = 10.4061(8), b = 15.54(1), c = 8.963(5) Å β = 108. 75(7)°, Z = 2 and crystals of trans-bis (dimethylglyoximate)chlorotricyclohexylphotphinecobalt(1II) (II) are monoclinic, space group P21/c with a = 9.501(7), b = 29.33(1), c = 12.98(1) Å β = 99.0(1)°, Z = 4. The structures have been solved by three-dimensional Patterson and Fourier methods and refined by the least-squares technique. The final R values were 0.032 for (I) and 0.072 for (II), calculated on the basis of 1850 and 1651 independent reflections respectively. In (I) the Co-P bond length of 2.418(1) Å is the largest value so far reported and confirms the strong trans-influence of the methyl group (Co--CH3, 2.026(6)Å). The coordinated N atoms are coplanar within ±0.015 Å; the cobalt is displaced of O. 112 Å above their mean plane towards the phosphine. The two dmgH units are bent away from the photphine ligand and their mean planes make an angle of 13. 6°. The axial bond lengths in (II) are: Co-P 2.369(5) Å, Co-CI 2.294(5) Å. The coordinated N atoms are coplanar within 0.007 Å with Co displaced of O. 10 Å towards phosphine ligand, whereas the two dmgH mean planes make an angle of 15.7°. These results are discussed in terms of steric factors. Correlation with experimental cone angles and n.m.r. results is discussed. © 1979.