Thiocyanate and Dicyanamide Anion Controlled Nuclearity in Mn, Co, Ni, Cu, and Zn Metal Complexes with Hemilabile Ligand 2-Benzoylpyridine

Two pseudohalides thiocyanate and dicyanamide have been employed to synthesize complexes of Mn^II, Co^II, Ni^II, Cu^II, and Zn^II in the presence of a hemilabile ligand 2-benzoylpyridine (Phpyk). With thiocyanate all the aforesaid metal ions (except for Co^II, of which suitable single crystals for X-ray analysis were not obtained) produce mononuclear complexes having general composition of [M^II(NCS)₂(Phpyk)₂]. The structure determination reveals that Mn and Zn complexes (1, 4) are isomorphous and isostructural (crystallizing in space group C2/c), while Ni and Cu complexes (2, 3) crystallize in space groups P1̅ and P2₁/n, respectively. Interestingly, no complex has been obtained with a configuration having the N of one Phpyk trans to the O of the other chelating ligand and among the four complexes only in complex 3 the two thiocyanato ligands are in trans-configuration. On the other hand, complexes 5–8 are isomorphous and crystallize in orthorhombic chiral space group P2₁2₁2₁. The bridging mode of dicyanamide anions helps to generate a three-dimensional covalently bonded polymeric network of 6⁶ topology for all the polynuclear complexes. By using 8 as sole precursor, we have pyrolytically synthesized triangular shaped ZnO nanoparticles.