Configurations of solvated complex ions of first transition metals in hexamethylphosphoric triamide as inferred from their absorption spectra and Stokes radii.

The absorption spectra and Stokes radii of solvated complex ions of first transition metals (Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)) were observed in hexamethylphosphoric triamide (HMPA) in order to determine their configurations. It seems that the Stokes radii of complex ions are sensitive to the configurational change, since the diameter of an HMPA molecule is very large as compared with the crystallographic diameters of central metal ions. As to the result, metal ions are tetrahedrally solvated in the cases of Mn(II), Fe(II), Co(II), and Cu(II), while in the case of Ni(II), equilibria are established among octahedral, square planar and tetrahedral solvated species. Zn(II) forms probably a complex ion solvated octahedrally by HMPA.