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 · 6H2O in a 2:1 molar ratio in EtOH affords the complex [CuII(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 [CuII(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 {[CuII(pyppt)2](ClO4)2 · EtOH}∞ (3). The structures of both complexes have been determined by single crystal X-ray diffraction.