P-31 NMR AND RAMAN-SPECTROSCOPIC STUDIES ON BINDING ISOMERISM AND ISOMERIZATION EQUILIBRIUM OF ALUMINUM COMPLEXES OF MONOMERIC PHOSPHORUS OXOANIONS IN SOLUTION

The binding isomerism of Al3+-phosphinate, -phosphite and -phosphate complexes was investigated by using P-31 NMR and Raman spectroscopies in solution. It was found that there are two types of binding mode in the complexes: a non-chelate binding mode in which the monomeric phosphorus oxoanions coordinate to the aluminium ion as monodentate ligands, and a chelate binding mode in which the monomeric phosphorus oxoanions coordinate to the aluminium ion as bidentate ligands. Furthermore, an isomerization equilibrium analysis was made on the chelate and the non-chelate isomers. The isomerization constants, K(non-chel)chel, for formation of the chelate isomer from the non-chelate one, were evaluated to be 2.8 for the AlPH2O2(2+) complex, 3.7 for the AlPHO3+ complex and 3.9 for the AlPO4 complex.