Electronic vs. steric effects in octahedral cobaloximes. Molecular structure of trans-chlorobis(dimethylglyoximato)tributylphosphinecobalt(III) and transchlorobis(dimethylglyoximato)trimethylphosphitecobalt(III)

Abstract

Crystal data of the title compounds have revealed that crystals of trans-chlorobis(dimethylglyoximato)tributylphosphinecobalt(III), (I), are monoclinic, space group P2 1/c with a = 21.494(9), b = 15.362(5), c = 18.240(7) Å, β = 116.94(8)°, Z = 8 and crystals of trans-chlorobis(dimethylglyoximato)trimethylphosphitecobalt(III), (II), are orthorhombic, space group Pca2 1 with a = 17.210(7), b = 13.598(5) and c = 16.600(7) Å, Z = 8. The structures have been solved by three-dimensional Patterson and Fourier methods and refined by the least-squares technique. The final R values were 0.041 for (I) and 0.050 for (II), calculated on the basis of 4562 and 1613 independent reflections respectively. In both (I) and (II) the two crystallographically independent molecules have a similar structure with some differences in the CoPR 3 grouping geometry. The CoP bond lengths, as well as the deformations in the equatorial moiety, for the series R 3PCo(dmgH) 2X, where X =Cl or C-bonded group, and R = OMe, Bu n, Ph, Chx, are compared. The observed Co P bond lengths may be rationalized in terms of steric and electronic effects, which appear to be additive to a large extent.