Synthesis and characterisation of complexes formed between the ligand tris(2-pyridylmethyl)amine and the Group III metals gallium and thallium

Reactions of the Group III metals, gallium and thallium, with the ligand tris(2-pyridylmethyl)amine (TPA) leads to the formation of 1:1 metal to ligand complexes, but not the simple 1:1 complexes observed in the reactions between the Group I and II metals with TPA. One such complex, [Ga(TPA)(OH)]2(Cl)4·4H2O·2.956MeOH (1), has been structurally characterised and found to have a dimeric structure resulting from hydroxy bridging. The crystal structure of the thallium complex was also determined and was found to be [Tl(TPA)]2[H3O][NO3]3 (2), consisting of two different [Tl(TPA)]+ cations, one of which was disordered. The essential difference between the two cations is that one contains a four co-ordinate thallium cation while the second contains a seven co-ordinate thallium cation as a result of bonding to the three nitrate anions.