Synthesis and structure of chloro(ligand)bis(glyoximato)cobalt(III) complexes: structural evidence of an electronic effect on the structure of the dimethylpyrazine ligand

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The synthesis and characterization of trans-chloroligandbis(glyoximato)cobalt(III) complexes (ligand=2,6-dimethylpyrazine, β-picoline and γ-picoline) are presented. X-ray crystal structure determination of the dimethylpyrazine derivative, [CoCl(gH) 2(Me 2pz)] ( 1), has been carried out, and two important structural features found: a significant change in bond distances within the aromatic nitrogen donor upon substitution of a methyl group of the equatorial dioximato ligand by a hydrogen, and a conformational preference for the axial ligand which appears to be oriented parallel to the equatorial CC bonds, indicating that the substituents of the dioximato ligand are not important in determining that conformation. Changes in the bond angles of the glyoxime ligands upon coordination are due to chelation and hydrogen bond formation. Compound 1 is monoclinic, space group P2 1/ n, with Z=4 and unit cell parameters a=14.973(3), b=10.790(2) and c=10.844(2) Å and β=90.92(2)°.