Synthesis and X-ray powder diffraction characterization of tetra- and hexa-imidazole complexes of magnesium(II)

X-ray powder diffraction data for two ionic salts contg. imidazole (Him) complexes of the magnesium(II) ion, [Mg(Him)4(H2O)2]Cl2 and [Mg(Him)6](NO3)2, are reported. Their crystal and mol. structures were detd. by simulated annealing and full-profile Rietveld refinement methods. [Mg(Him)4(H2O)2]Cl2 was found to crystallize in the monoclinic system with space group C2/c, a=12.3980(3) A, b=11.0234(2) A, c=14.4691(3) A, and =107.024(1). [Mg(Him)6](NO3)2 crystallizes in the trigonal R-3 space group with a=b=12.4631(4) A and c=14.9449(6) A. Both species contain centrosym. complexes, and Mg is octahedrally coordinated by six imidazoles, as in [Mg(Him)6](NO3)2, or by four imidazoles and two water mols., as in [Mg(Him)4(H2O)2]Cl2. Addnl. analytic, thermogravimetric, calorimetric, and spectroscopic characterizations were also performed.