Synthesis, structure and spectroscopy of clathrate inclusion compounds of cobalt(II), cadmium(II) and zinc(II) trans-4-styrylpyridine nitrates as host with trans-4-styrylpyridine as guest (2 : 1)

New clathrate inclusion compounds with the general formula, MA(3)X(2) . 1/2 G (M = Co(II)( 1), Cd(II)(2), and Zn(II)(3), X = NO3- and A and G = trans-4 -styrylpyridine), differing from the usual Werner clathrates, MA(4)X(2) . 2 G, have been prepared and characterized by elemental and thermal analyses, IR and electronic spectroscopy and X-ray crystallography. Two representativ e compounds [Co(stpy)(3)(NO3)(2)] . 1/2stpy (1) and [Cd(stpy)(3)(NO3)(2)] . 1/2 stpy (2) are investigated by single crystal X-ray diffraction. Compoun d (1) crystallizes in the triclinic space group P (1) over right arrow with a = 10.966(2), b = 12.802(4), c = 16.063(5) Angstrom alpha = 83.38(3), bet a = 71.30(2), gamma = 76.88(3) degrees, Z = 2. The structure is made up of discrete molecules of [Co(stpy)(3)(NO3)(2)]. The central Co(II) is surround ed by three stpy nitrogen atoms and four oxygen atoms of two asymmetrically coordinated bidentate nitrate ligands. One of the oxygens is semicoordinat ed leading to a distorted octahedral geometry for Co(II). Compound (2) crys tallizes in the monoclinic space group P2(1)/n with a = 15.597(3), b = 18.3 13(5), c = 16.188(3) Angstrom beta = 115.998(14)degrees and Z = 4. The stru cture consists of neutral molecules of [Cd(stpy)(3)(NO3)(2)]. The geometry around Cd(II) is best described as pentagonal bipyramid with four oxygen at oms from symmetrical bidentate nitrate groups and one stpy nitrogen atom in the equatorial positions. Two other nitrogen atoms from stpy ligands occup y the axial positions. The guest stpy molecules are trapped in the centrosy mmetrical cavities in lattices of both 1 and 2. Compound 3 is found to be i somorphous with 2. A large splitting of the symmetric and asymmetric NO2 st retching vibrations reveals the presence of bidentate nitrate ligands. Ther mogravimetric and DTA studies on the Cd(II) compound, show it to be a therm ally stable inclusion compound.