Transition metal complexes of tris(aminomethyl) phosphine oxide (tampo) - Thermodynamic and X-ray diffraction studies
Abstract
The coordination behaviour of tris(aminomethyl) phosphine oxide (tampo) to selected transition metal ions was studied. In the case of Co(III), Ni(II) and Cu(II) complexes with metal-to-ligand 1: 2 stoichiometry, bis(tripodal) tampo coordinations forming octahedral coordination spheres (in the case of Cu(II) complex with significant Jahn-Teller distortion) were found by X-ray diffraction analysis.
Based on the potentiometric study, the tripodal coordination of the title ligand is also expected in solution. The stability of the metal complexes follows the Irving-Williams trend.
Compared with the structurally "parent" 1,1,1-tris(aminomethyl) ethane (tame) ligand, the complexation of tampo occurs at a lower pH as the consequence of low ligand basicity [logK(1) = 6.72(1), logK(2) = 5.34(1) and logK(3) = 3.82(1)], although the values of the stability constants of the metal complexes are relatively low.