Synthesis and thermal behaviour of some oxalate complexes of bivalent metals Mn, Co, Ni, Cu, Zn and Cd

Abstract

The reaction of M( II) oxalate (M = Mn, Co, Ni, Zn or Cd) with monomethylammonium oxalate in the presence of monomethylamine gives different compounds, depending on the metal atom. For M = Ni, Co or Zn double oxalates with the general empirical formula (CH 3NH 3) 4M(C 2O 4) 3· nH 2O (where n = 2 for Zn and Co, and n = 1 for Ni) are obtained, whilst for M = Cd or Mn the monomethylamine complexes (CH 3NH 3) 2Cd(C 2O 4) 2·(CH 3NH 2)·H 2O and (CH 3NH 3) 2Mn(C 2O 4) 3·(CH 3NH 2) 2·H 2O, respectively, are obtained. Dissolution of Cu(II) oxalate in concentrated ammonia gives diammine Cu(II) oxalate dihydrate. X-ray powder-diffraction patterns show that the complexes have different structures, except for the complexes of Co and Zn which are isostructural. Differential thermal analysis and thermogravimetry show that the compounds obtained undergo different modes of thermal decomposition.