Xanthine complexes with 3d metal perchlorates

Abstract

Complexes of xanthine (xnH) with 3d metal perchlorates were prepared by refluxing mixtures of ligand and metal salt in ethyl acetate-triethyl orthoformate. In all cases, partial substitution of anionic xn − for ClO 4 − groups occurs, and the solid complexes isolated also contain invariably two neutral xnH ligands per metal ion, viz. Cr(xn) 2(xnH) 2ClO 4, Fe(xn) 2(xnH) 2ClO 4·H 2O, M(xn)(xnH) 2ClO 4·H 2O (M = Fe, Co, Ni) and M(xn)(xnH) 2ClO 4· 2H 2O (M = Mn, Zn). The new complexes are generally hexacoordinated and appear to be linear chainlike polymeric species characterized by a (-Mxn-) n single-bridged backbone. Four terminal ligands per metal ion, including two xnH groups in all cases, complete its inner coordination sphere; the remaining two terminal ligands differ from complex to complex as follows: M = Cr 3+ xn −, -OClO 3; Fe 3+ xn −, H 2O; Fe 2+, Co 2+, Ni 2+OClO 3, H 2O; Mn 2+, Zn 2+ two aqua ligands. Probable binding sites of bidentate bridging xn − and unidentate terminal xnH and xn − are discussed.