CRYSTAL-STRUCTURE OF 2 ZINC THIOCYANATE H EXAMETHYLENETETRAMINE ADDUCTS, ZN(SCN)(2)CENTER-DOT(C6H12N4)(2), AND (ZN(SCN)(2)CENTER-DOT-C6H12N4-CENTER-DOT-2H2O)(N), WITH DIFFERENTLY COORDINATED ZINC IONS

Crystals of the adducts Zn(SCN)(2).(C6H12N4)(2) (1), and {Zn(SCN)(2).C 6H12N4.2H(2)O}(n) (2) were obtained by crystallization from aqueous so lutions containing hexamethylenetetramine, potassium thiocyanate and z inc nitrate or zinc sulfate, resp., under identical conditions, as two totally different products. 1 crystallizes orthorhombically, space gr oup P nmm, Z = 2, a = 622.4(5), b = 1152.3(7), c = 1394.0(9) pm; 2 is monoclinic, space group C2/c, a = 984.4(3), b = 1217.0(5), c = 1257.4( 6) pm, and beta = 111.69(5)degrees. The crystal structure of 1 contain s discrete molecules of the complex, in which the zinc ion is tetrahed rally coordinated by two NCS ligands, and two hexamethylenetetramine m olecules, which act as monodentate ligands. In 2 however, the zinc ion s are octahedrally coordinated. A ''supramolecular'' structure is form ed: The hexamethylenetetramine molecules act as bridging bidentate lig ands and connect [Zn(H2O)(2)(NCS)(2)] units forming zig-zag chains. Ad jacent chains are interconnected via hydrogen bends. The formation of the two compounds with different coordination may be due to the fact, that the educts Zn(NO3)(2).4H(2)O and ZnSO4.7H(2)O contain Zn(H2O)(4) and Zn(H2O)(6) moieties, resp., and that these species are retained in solution.