The novel mixed-ligand metal succinate (suc) complexes with 1, 10-phenanthroline (phen) and ethylenediamine (en) have been synthesized and characterized by elemental analyses, magnetic moments, UV-VIS and IR spectra. Thermal reactivity of the complexes was studied in air using DTA and TG, and decomposition of the complexes resulted in the formation of corresponding metal oxides. The crystal structure of the [Co(suc)(H2O)(phen)(2)] . 1.5H(2)O . C4H10O complex was determined by x-ray diffraction. The Co(II) complex crystallizes as a monobutanol solvate. In the complex, the cobalt ion lies on an inversion center and displays a distorted octahedral coordination with one aqua, one suc and two phen ligands. The suc ligand acts as a monodentate ligand through one of the negatively charged O atoms, while phen behaves as N-donor bidentate ligand. The crystal also contains disordered lattice water molecules and the structure is stabilized by extensive hydrogen bonding to form a three-dimensional infinite network.