Tetrakis(thiadiazole)porphyrazines. 7. Synthesis and structure of mu-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)]

The complex mu-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)], [(TTDPzAl)(2)O], has been obtained from the corresponding mononuclear Al(III) hydroxo-complex, [TTDPzAlOH], by refluxing a solution of this latter in alpha-chloronaphthalene or by heating the solid hydroxo species (250-300 degrees C) under vacuum (10(-2) mmHg). The complex, which appears as a stable species in air, shows a typical IR absorption at 983 cm(-1), assigned as nu(as)(Al-O-Al). Contact with water determines disappearance of this absorption consequent to the formation of the related hydroxide. [(TTDPzAl)(2)O], insoluble in most organic non-donor solvents, and very scarcely soluble in dimethylsulfoxide and dimethylformamide, shows some instability in pyridine, with probable breaking of the mu-oxo bridge and formation of the mononuclear hydroxide. Single crystals suitable for X-ray analysis were obtained by subliming [(TTDPzAl)(2)O] under vacuum at 500 degrees C under a continuous N(2) flow. Crystal data for [(TTDPzAl)(2)O], C(32)Al(2)N(32)OS(8): a = 7.613(2) angstrom, b = 11.280(2) angstrom, c = 23.363(5) angstrom, beta = 96.869(3)degrees, space group P2(1)/c (n. 14), U = 1991.9(7) angstrom(3), Z = 2, R(F)(a) = 0.0492, wR(F(2)) = 0.1024. The mu-oxo bridged complex has a central linear Al-O-Al bond system, with the Al(III) atoms displaced out of the respective N(4) square planar coordination sites by 0.441 angstrom and the two TTDPz planes lying in an eclipsed position, the overall structure of the complex approaching closely that of the related phthalocyaninato complex [(PcAl)(2)O]. Intermolecular contacts, instead, are definitely different for the two species, the type found present in [(TTDPzAl)(2)O] highly reminiscent of those of other previously reported "thiadiazole-porphyrazine" macrocycles, with the observed short inter-unit contacts between adjacent TTDPz macrocycles again determined by the presence in the TTDPz framework of the annulated peripheral (S,N)-containing heterocycles.