Tripodal Iminophenolate Ligand Complexes of Gallium(III), Indium(III), and Thallium(III)

The polydentate tripodal Schiff base ligand H3L has been prepared by treating a methanolic solution of tris(aminoethyl)amine and 5-bromosalicylaldehyde. This ligand, and its complexes with group-13 metal ions (GaIII, InIII, and TlIII) have been characterized by elemental analysis, NMR spectroscopy, FAB+-MS, and X-ray diffraction analysis. The ligand, not preorganized in the solid state, acts as a hexadentate N3O3 ligand in all cases to form octahedral structures, the apical nitrogen not being involved in the chelation even for the [Tl(L)] complex. NMR studies reveal that the intact and rigid structures of the complexes are maintained in solution. For the [Tl(L)] complex, long-range thallium isotope effect on the chemical shift (δH and δC) and on the coupling constants (JTl-H and JTl-C) has been observed, confirming a strong and stable bond between TlIII and H3L.