Ligand-field control and hydrogen bonding as design elements in the assembly and crystallization of poly(azolyl)borate metal complexes: Chelate complexes versus coordination polymers and symmetrical versus distorted grid sheets

The 1- and 2-D coordination polymers [Mn{HB(C2H2N3)(3)}(2)(H2O)(2)]. 4H(2)O (11) and [Ni{H2B(CHN4)(2)}(2)(NH3)(2)] (13), respectively, and the chelate complex [Ni{H2B(C2H2N3)(2)}(2)(H2O)(2)]. 2H(2)O (12) were synthesized and structurally characterized. The compounds contain ambidentate poly(azolyl)borato ligands (azolyl = triazolyl or tetrazolyl), which can chelate or bridge metal centers. The metal-ligand structures in 11-13 differ from the known coordination modes of the poly(azolyl)borates towards other metal centers, We describe how a change in the metal and/or the conditions of crystallization affects the ligand-field stabilization energy and favors one type of nitrogen donor atom over the other for the poly(triazolyl)borato ligands. The crystal structures of 11 and 12 contain additional water of crystallization; this leads to hydrogen-bonded solvent substructures. In the case of the bis(tetrazolyl)borato ligand the water substructure is shown to function as a ''reinforcing bar'' that symmetrizes the metal-ligand grid sheet.