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Metallocene complex (Cp2ZrCl2)-Zr-tt (Cp-tt = eta(5)-1,3-(Bu2C5H3)-Bu-t) (1) has been prepared from the reaction of LiCptt with ZrCl4 in good yield. Reactions of 1 with dilithium dichalcogenolate o-carboranes afforded new type of half-sandwich compounds with dichalcogenolate o-carboranyl ligands [Li(THF)(4)][(CpZr)-Zr-tt(E2C2B10H10)(2)] (E = S, 2a; E = Se, 2b) in which only one cyclopentadienyl ring ligand existed. Complexes 1 and 2a were structurally characterized by X-ray analyses. In complex 2a, the Zr(IV) ion is eta(5)-bound to one 1,3-di-tert-cyclopentadienyl ring and a-bound to four mu(2)-sulfur atoms of two dithio-carboranes. The zirconium atom and four sulfur atoms form a distorted pyramid. The coordination sphere around the zirconium atom resembles in a piano stool structure with four legs of sulfur atoms and the fulcrum at the zirconium atom.

The title complex was synthesized and characterized by H-1, C-13, Sn-119 NMR and IR spectra. A single crystal X-ray diffraction study confirmed its molecular structure and revealed that 3,4,5-trimethoxy-benzoyl salicylahydrazone was a tridentate and approximately planar ligand. The complex crystallizes in the triclinic space group P1BAR with a = 9.208(3), b = 12.536(2), c = 12.187(4) angstrom, alpha = 113.12(2), beta = 90.58(2), gamma = 81.42(2), V = 1277.5(6) angstrom, Z = 2. The structure was refined to R = 0.033 and R(w) = 0.041 for 3944 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. The Sn-C bond lengths are 2.129(5) and 2.113(5) angstrom (av. 2.121(5) angstrom), the C-Sn-C angle is 123.3(2); the bond length between the tin atom and the chelating nitrogen is 2.173(3) angstrom. Two chain carbon atoms and the chelating nitrogen atom occupy the basal plane. The skeleton of two erect oxygen atoms and the tin atom is bent (O-Sn-O angle = 153.5(1)). In the complex, the ligand exists in the enol-form.

The crystal structures of three Schiff base metal complexes of 1-aminocyclopropanecarboxylic acid (ACC), a precursor of the plant hormone ethylene, [Cu(PLACC)(H2O)]·(NO3)·H2O (1), [Ni(PL- ACC)(H2O)2]·(NO3)·H2O(2) and [Cu(PLPACC)(H2O)]2·4H2O(3)(PL=pyridoxal and PLP =pyridoxal 5′-phosphate), have been determined by X-ray diffraction. 1 and 2 are quasi-isostructural to each other, with a minor difference in the coordination geometry, i.e. square-pyramidal copper(II) and square-bipyramidal nickel(II): the basal plane is defined by the imino nitrogen, the phenolic and the carboxylate oxygens of the Schiff base ligand, and a water molecule, and the apical position(s) occupied by the hydroxymethyl oxygen of a neighboring molecule (plus a water for 2), thus forming a one- dimensional polymer. 3 involves two crystallographically independent [Cu(PLPACC)(H2O)] structural units, A and B, which differ only in the phosphate conformation. The environment of each copper atom is similar to that in 1 except for the axial coordination of one of the phosphate oxygens of a neighboring molecule, thus creating an analogous polymeric chain structure, -A-B-A-B-. These three compounds may serve as a model for a Schiff base derived from pyridoxal and 1-aminocyclopropa- necarboxylate, a reaction intermediate in ethylene biosynthesis, in accordance with Dunathan's hypothesis. Crystallographic data: 1, space group P21/a, a=13.222(3), b=10.820(2), c=11.821(3) A, β=110.51(2)°, V=1583.9(7) A3, Z=4 and R=0.044 for 2034 observed reflections; 2, space group P21/c, a=12.896(2), b=10.667(2), c=12.628(3) A, β=111.23(2), V=1619.3(6) A3, Z=4 and R=0.043 for 1603 observed reflections; 3, space group P 1 , a=15.700(2), b=11.738(1), c=9.281(1) A3, α=98.61(1), β=97.34(1), γ=98.16(1)°, V=1654.4(3) A3, Z=2 and R=0.038 for 4732 observed reflections.

The crystal structure of [Mn(thiamine)Cl2(H2O)]2[thiamine]2Cl4·2H2O has been determined by X-ray diffraction methods. The compound contains a cyclic dimer of a complex cation with two thiamine ligands bridged by two Mn(II) ions across a crystallographic center of symmetry. Each Mn(II) is coordinated by two chloride atoms, a water molecule, a N(1′) atom of the pyrimidine from a thiamine and an O(53) atom of the hydroxyethyl side chain from another thiamine. There are two free-base thiamine molecules related by a center of symmetry in the unit cell, which form a base-pair through the hydrogen bonds. Both the independent thiamine molecules in the asymmetric unit assume the common F conformation with φT=10.0(9) and 3.6(10) and φP=85.6(7) and 79.6(7), respectively. The compound provides a possible model for a metal-bridged enzyme-coenzyme complex in thiamine catalysis. Crystallographic data: triclinic, space group P 1 , a=12.441(4), b=13.572(4), c=11.267(3) A, α=103.15(2), β=89.03(3), γ=115.64(2)°, Z=1, Dcalc=1.524 g cm−3, and R=0.050 for 3019 observed reflections with I>3σ(I).

The crystal structures of Co(thiamine)Cl3·0.4H2O (1) and Zn(thiamine)Br3·0.2H2O (2) have been determined by X-ray diffraction. The compounds are isomorphous to each other. Each compound forms a discrete M(thiamine)X3 (M=Co(II) and X=Cl−; M=Zn(II) and X=Br∝-) structure with the tetrahedral M(II) atom being bonded by the three halide atoms and the N(1′) atom of the pyrimidine ring. The thiamine ligand adopts the S conformation: oT and oP=128.9(3) and 111.8(4)° for 1 and 130.5(9) and 113.5(9)° for 2. A ‘two-point’ halide bridge between the pyrimidine and the thiazolium moieties of the same molecule through an N(4′α)H···X(1) hydrogen bond and an X(2)···thiazolium electrostatic contact is a factor that affects the S conformation. Crystal data: 1, monoclinic, space group C2/c, a=25.767(9), b=8.490(2), c=17.539(6) A, β=106.24(1)°, Z=8, Dcalc=1.579 g cm−3 and R=0.045 for 3508 observed reflections; 2, monoclinic, space group C2/c, a=26.388(5), b=8.563(1), c=17.753(3) A, β=105.95(1)°, Z=8, Dcalc=1.977 g cm−3 and R=0.051 for 1991 observed reflections.

The crystal structure of the title compound was determined by X-ray diffraction. The dysprosium ion is eight-coordinated by three oxygen atoms and three nitrogen atoms from three picolinato ions and two water oxygen atoms. The nitrogen atom and one carboxyl oxygen atom of each picolinato ion are coordinated to the same dysprosium ion to form a five-membered chelating ring. The title compound exists as discrete molecules in the crystal structure.