Hexakis(tris(hydroxymethyl)phosphine oxide)metal(II) and (III) perchlorates [1

Abstract

Complexes of tris(hydroxymethyl)phosphine oxide (thpo) with various metal perchlorates were prepared by interaction of ligand and salt in triethyl orthoformate. Characterization of the new complexes by means of spectral, magnetic and conductance studies led to their formulation as [M(thpo) 6](ClO 4) n (M = Mg 2+, Cr 3+, Mn 2+, Fe 2+, Fe 3+, Co 2+, Ni 2+, Cu 2+, Zn 2+, Cd 2+, Nd 3+; n = 2 or 3), involving low symmetry hexacoordinated complex cations and exclusively ionic perchlorate. Thpo acts as a unidentate ligand, coordinating through the PO oxygen. The tendency of thpo to form 6:1 cationic metal complexes, in contrast to other phosphine oxides, which yield 4:1 or 5:1 complexs with the same metal perchlorates, is attributed to its lower ligand-field strength. The metal-thpo bonds are weaker than the corresponding bonds in the complexes of other phosphine oxides. This leads to a less sterically crowded environment around the central metal ion, and allows the accommodation of six thpo molecules in the first coordination sphere.