Guanine complexes with 3d metal perchlorates

Abstract

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) 2 ClO 4 , Fe(xn) 2 (xnH) 2 ClO 4 ·H 2 O, M(xn)(xnH) 2 ClO 4 ·H 2 O (M = Fe, Co, Ni) and M(xn)(xnH) 2 ClO 4 · 2H 2 O (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 2 O; Fe 2+ , Co 2+ , Ni 2+ OClO 3 , H 2 O; Mn 2+ , Zn 2+ two aqua ligands. Probable binding sites of bidentate bridging xn − and unidentate terminal xnH and xn − are discussed.