Thermochemical and spectral properties of hydrates of Co(II), Ni(II) and Cu(II) maleate. Crystal structure of Co(II) maleate trihydrate

The crystal and molecular structure of Co(II) maleate trihydrate, Co(C4H2O4 ). 3H(2)O, was determined by direct method and Fourier techniques. The stru cture was refined by full-matrix least-squares methods to a weighted R fact or of 0.0263, based on independent reflections. The compound is a three-dim ensional coordination polymer with distorted octahedron geometry at each co balt(II) centre. Each cobalt atom is six-coordinated through two oxygen ato ms from water molecules and four oxygen atoms from four different maleate g roups, The thermal decompositions of Co(mal). 3H(2)O, Ni(mal). 3H(2)O and C u(mal).H2O (mal = maleate) have been investigated by means of TG, DTG, DSC and IR spectra. The release of volatile molecules after heating is either a three-step process for Co(mal). 3H(2)O and Ni(mal). 3H(2)O or a two-step p rocess for Cu(mal).H2O.