Pyridine-type complexes of transition-metal halides. III: Structural and thermal relationships among the cobalt(II) complexes with halide ions and 2-, 3-, and 4-Methylpyridine, the crystal structure of dibromotetrakis (3-methylpyridine)cobalt(II)

The correlation between structure and thermal properties of halogeno methylpyridine cobalt(II) is described. The ternary mixed tetrakis-derivatives and the tetrahedral bis-complexes of cobalt(II) chlorides and bromides formed with picolines are structurally very similar to the cadmium(II) and nickel(II) analogues, the iodides are somewhat different, however. On the basis of the characteristic correlation between the densities calculated from powder diffraction data and the molecular weights, the densities of a few thermal intermediates, which have not yet been prepared, are predicted. The square bipyramidal structure of dibromotetrakis(3-methylpyridine)cobalt(II) is described, and the deformation of the octahedra is discussed in detail. Structural study was extended by molecular mechanics (MM+ and MMX) and molecular orbital (SINDO1) calculations.