Two forms of a copper(II) complex of 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole:: a six-coordinate monomer versus a five-coordinate polymer

The reaction of the new bidirectional ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (pyppt) with Cu(ClO4)(2) (.) 6H(2)O in a 2:1 molar ratio in EtOH affords the complex [Cu-II(pyppt)(2)(ClO4)(2)] (.) H2O (1) as a microcrystalline turquoise solid. Recrystallisation of complex 1 from MeCN by vapour diffusion of Et2O gives blue crystals of the monomeric octahedral complex [Cu-II(pyppt)(2)(ClO4)(2)] (.) MeCN (2). In contrast, addition of EtOH to a solution of complex 1 in MeCN followed by slow evaporation yields blue crystals of the five-coordinate polymeric complex {[Cu-II(pyppt)(2)](ClO4)(2) (.) EtOH}(infinity) (3). The structures of both complexes have been determined by single crystal X-ray diffraction. (C) 2004 Elsevier B.V. All rights reserved.