Correlation of intra and intermolecular hydrogen bridges in bis(dimethylglyoximato)cobalt(III)complexes

The solid state structures of the complexes Co(Hdmg)(2)(NCS)(NH3) (Hdmg = dimethylglyoximate) and CoCl(Hdmg)(2)(H2O) were determined by single crystal X-ray diffraction. The thiocyanato complex crystallizes in the orthorhombic space group Pnma with lattice constants a = 14.626(3) A, b = 9.222(3) A, c =11.575(3) A, V = 1561.2(7) A(3) and Z = 4 while the chloro complex is monoclinic. space group P2(1)/m with lattice constants a = 7.572(2) A, b = 8.820(4) A, c = 10.351(5)A, beta = 96.39(3)degrees, V = 687.2(5) A(3) and Z = 2. In these coordination compounds the pseudooctahedral molecules are located on crystallographic mirror- planes; both bridging hydrogen atoms in each complex are close to one of the chelating ligands whereas chemical intuition would rather suggest two monoprotonated Hdmg moieties. This conflict is resolved when the correlation between intra and inter-molecular hydrogen bonds is taken into account.