Diethyl acetylphosphonate complexes with 3 d metal perchlorates[1

Abstract

Complexes of diethyl acetylphosphonate(deap) with 3 d metal perchlorates were synthesized and characterized by means of IR and electronic spectral, magnetic susceptibility and conductance studies. The final solid products obtained during interaction of deap and metal salt in triethyl orthoformate are of the general type [M(deap) 3](ClO 4) n ·H 2O (MMn 2+, Fe 2+, Fe 2+, Co 2+, Ni 2+, Zn 2+; n = 2 o 3), involving a tris-chelate complex cation, in which deap coordinates as a bidentate ligand through the PO and CO oxygens; these metal chelates contain also exclusively ionic perchlorate and lattice water. In some cases (MMn 2+, Co 2+) the preceding chelates are precipitated directly from the ligand-salt reaction mixture in triethyl orthoformate. In other cases (MFe 2+, Fe 3+, Ni 2+, Zn 2+), however, viscous oily precipitates of the type [M(deap) 3(OH 2) 3](ClO 4) n · xH 2O ( n = 2 or 3; x = 1–3) are initially obtained. These oily products, in which deap functions as unidentate, coordinating only through the PO oxygen, are then converted to solid [M(deap) 3](ClO 4) n ·H 2O tris-chelates, by treatment with additional triethyl orthoformate (and diethyl ether). The competition between deap and aqua ligands for the inner coordination sphere of the metal ion is due to the fact that deap is a relatively weak ligand, giving rise to a ligand field of about equal strength to that generated by the aqua group.