Structural features of group V A xanthates. The crystal and molecular structures of tris(O-isopropylxanthatoarsenic(III), antimony(III) and -bismuth(II)

The crystal structures of the title compounds, M(S₂COⁱC₃H₇)₃, M = As(III), (1); Sb(III), (2); and Bi(III), (3) have been determined by three dimensional X-ray diffraction techniques and refined by a least square method. Crystals of (1) and (2) are isomorphous and both crystallize in the rhombohedral space group R$\text{3}$, with unit cell parameters for (1) a_hex = 11.559(2), c_hex = 28.131(3) Å and for (2) a_hex = 11.696(2) and c_hex = 28.135(2) Å, Z = 6. The central metal atom in both (1) and (2) is coordinated by three asymmetrically chelating xanthate ligands [AsS 2.305(2) and 2.978(2) Å and SbS 2.508(1) and 3.006(1) Å] which form a distorted octahedral environment consistent with the presence of a stereochemically active lone pair of electrons. Crystals of (3) are orthorhombic, space group Pnma, Z = 4 with dimensions a = 11.003(3), b = 20.833(4) and c = 9.428(2) Å. The environment of the bismuth atom in (3) is seven coordinate and is comprised of six sulphur atoms, derived from three asymmetrically coordinating xanthate ligands, and a bridging sulphur atom from a neighbouring molecule which results in the formation a polymeric array. For (1) final R and R_W 0.050 and 0.047 respectively for 936 reflections [I ? 3σ(I); (2) R 0.040, R_w 0.040 for 1455 reflections I ? 2σ(I)]; and (3) R 0.052, R_w 0.039 for 1796 reflections [I ? 2σ(I).     

The crystal and molecular structure of O-ethylxanthato-bis(quinolin-8-olato)antimony(III) and a redetermination for tris(O-ethylxanthato)antimony(III)

The crystal structures of the title compounds Sb(C₉H₆NO)₂(S₂COC₂H₅) (1) and Sb(S₂COC₂H₅)₃ (2) have been determined by three dimensional X-ray diffraction techniques and refined by a least squares method; final R 0.049 for 2911 reflections [I ? 3σ(I)] for (1) and R 0.047, R_w 0.046 for 846 reflections [I ? 2σ(I)] for (2). Crystals of (1) are triclinic, space group P1, a = 10.825(2), b = 11.131(2), c = 8.911(1) Å, α = 109.45(1), β = 95.92(1) and γ = 93.02(1)° with Z = 2. Crystals of (2) are rhombohedral, space group R$\text{3}$, a_rhomb = 10.138(3) Å and α = 103.43(2)°. The environment of the Sb atom in (1) is based on a pentagonal bipyramidal geometry consisting of the six donor atoms of the three chelating ligands and a stereochemically active lone-pair of electrons which occupies the remaining axial position. The xanthate ligand chelates the Sb atom almost symmetrically with two long SbS bonds of 3.059(2) and 3.171(2) Å. In contrast the xanthate ligands in (2) chelate the Sb atom with asymmetric SbS bonds of 2.511(2) and 3.002(3) Å.     

The crystal and molecular structure of O-(β-D-xylopyranosyl)-L-serine and its copper (II) complex and some of their reactions

The interatomic distances and angles have been evaluated in xylosyl serine and its Cu(II) complex by X-ray crystal analysis. Physical data are provided for the acid and alkaline degradation of the former, together with evidence for the catalytic effect on Cu(II) on its alkaline elimination.     

The crystal and molecular structure of tetrakis(biuret)strontium(II) perchlorate

Crystals of tetrakis(biuret)strontium(II) perchlorate, [Sr((NH₂CO)₂NH)₄](ClO₄)₂, are monoclinic with a = 11.21(1), b = 7.30(1), c = 14.52(1) A, β = 98.2(2)°, D_obs = 1.976, D_calcd(Z = 2) = 1.973 g/cm³, space group P2/c. 1526 independent reflections recorded photographically by the equi-inclination. Weissenberg technique using CuKα, the intensities of which were estimated visually, were used in the structure determination. The structure was solved by Patterson and Fourier methods and refined anisotropically by diagonal least squares to an R factor of 0.094. The strontium atoms are located at special positions related by inversion. The perchlorate moieties are ionic although extensive hydrogen bonding exists between them and the primary and secondary amines of biuret. The two biuret ligands in the asymmetric unit are bonded to strontium as bidentates via the carbonyl oxygens with a small twist (10.9, 12.0°) about the oxygen-oxygen line. The six membered rings formed by the chelate ligands with strontium are folded (49.6, 1.8°) about the oxygen-oxygen line. This is attributed to packing considerations. The co-ordination polyhedron is best described as approximately D₂-222 distorted square antiprism with the bidentate ligands spanning opposite edges of the rectangular faces. To our knowledge this complex presents the first case of an eight co-ordinate non-transition metal complex, characterized by x-rays, where all of the ligands are non-ionic chemically identical oxygen donor bidentates.     

Synthesis and crystal structure of tetrakis(dimethylsulfoxide) platinum(II) bis(triflouromethanesulfonate)

Crystals of Pt(DMSO)₄(TFMS)₂ have been prepared by dissolution of platinum(II) hydroxide in a solution of CF₃SO₃H in DMSO and subsequent evaporation. The structure was determined by use of a CAD-4 diffractometer with monochromatic Mo Kα radiation. The space group is P with Z = 2, a = 8.630(2), b = 9.557(3), c = 16.659(3) Å, α = 73.33(2), β = 77.38(2) and γ = 79.19(3)°. The refinement converged to R = 0.056. The coordination around platinum is distorted square-planar with two S- and two O-bonded DMSO ligands in a cis-arrangement. The four donor atoms and the platinum are coplanar within 0.03 Å. There is a severe steric crowding between the two S-bonded DMSO molecules, which gives rise to a distortion of the bond angles around the platinum. The crowding is minimized as much as possible by a staggered arrangement of oxygen atoms and methyl groups of adjacent ligands. Pt---S bond lengths 2.208(3) and 2.205(4) Å are significantly shorter that those in the corresponding palladium complex, in accordance with a much stronger bond in the case of platinum. Bond length comparisons also indicate that ground state transinfluence of S-bonded DMSO probably is about the same in platinum and palladium complexes.     

Preparation and crystal structure of bis(acetato)(trans-1,2-diaminocyclohexane)platinum(II)

The structure of the complex [Pt(trans-1,2-di- aminocyclohexane) (acetate)₂]·H₂O has been determined by X-ray diffraction. This racemic compound is orthorhombic, space group Aba2, a = 20.813(9), b = 7.926(5), c = 17.296(8) Å, Z = 8. The structure was refined on 1214 nonzero Cu Kα reflections to R = 0.028. The square planar environment of Pt includes the amino groups of the diamine in cis positions and oxygens from two monodentate acetates. The PtN and PtO distances average 2.00(3) and 2.02(3) Å, respectively. The bite of the diamine ligand imposes a NPtN angle of 85(1)°, whereas the small OPtO angle of 85(1)° probably results from packing effects. The average plane through the puckered cyclohexyl ring makes an angle of 19° with the PtN₂O₂ plane. The molecules are stacked by pairs along the b axis. The two molecules of each pair are 180° apart about the stacking axis, and form altogether four NH···O hydrogen bonds.     

The preparation and crystal structure analysis of bis(L-Arginine)Cu(II)(acetate)2trihydrate

The crystal structure of bis(L-arginine)Cu(II)(acetate)₂trihydrate has been determined by X-ray analysis. The complex crystallizes in the monoclinic space group P2₁, with cell dimensions a = 15.948(2), b = 16.878(2), c = 10.378(2) Å, β = 108.47(1)°, Z = 4. There are two independent formula units in the asymmetric unit. The Cu atoms were located from a Patterson synthesis and the remaining atoms from difference Fourier syntheses. The structure was refined by least-squares to R = 0.079 and R = 0.11. Each copper atom has an essentially square planar coordination with the two arginine molecules chelated via the carboxy oxygens and the α-amino nitrogens, but with distorted six-fold coordinations completed by weak Cu…O (acetate) interactions. Electrostatic interactions between the acetates and the protonated ends of the amino acid residues link the two independent [Cu(L-arginine)₂(acetate)₂] units into dimers, which are then connected via hydrogen bonds, also involving the water molecules, into an infinite network.     

Binuclear diorganotin(IV) complexes with bis(O,O′-4-acyl-5-pyrazolonato) bis(bidentate) ligands

Syntheses, spectroscopic and thermal characterization are reported for the potentially tetradentate bis(O,O′-4-acyl-5-pyrazolone) pro-ligands HQ3QH and HQ4QH (in detail HQ3QH: 1,5-bis(5-hydroxy-1-phenyl-3-methyl-1H-pyrazol-4-yl)pentane-1,5-dione, HQ4QH: 1,6-bis(5-hydroxy-1-phenyl-3-methyl-1H-pyrazol-4-yl)hexane-1,6-dione) and their di-n-butyltin(IV) derivatives and . Single crystal X-ray structural characterizations of the proligand HQ4QH and of the binuclear tin(IV) complex are also reported; both the ligand and complex molecules are centrosymmetric, the latter having two independent molecules in the structure. Sn-C, O(acyl), O(pz) distances (〈 〉) are 2.121(3), 2.119(6) and 2.37(4) Å.     

Macrocyclic nickel(II) complexes: Spectroscopic studies and crystal structure of bis(difluoroboron-alpha-furilglyoximato)nickel(II)

Bis (difluoroboron - α - furilglyoximato) nickel (II), C₂₀H₁₂O₈N₄B₂F₄Ni, was prepared by cyclization of its hydrogen-bonded precursor with BF₃·OEt₂. The compound crystallizes in the space group P2₁/_c with a = 11.162(2), b = 5.569(2), c = 19.527(3) Å, β = 100.08(1)°, U = 1195.1(3) ų, and Z = 2. The structure was refined to an R value of 0.033 using 2371 unique reflections collected with a CAD4-SDP diffractometer system. Unlike the corresponding planar macrocyclic as well as hydrogen-bonded dimethylglyoximates, the title compound neither dimerizes not exhibits columnar stacked structure. The 14-member macrocycle is planar except the B atoms, and no metal-metal interactions are observed in this compound. The complexation and cyclization reactions were investigated using spectral data. The structure is compared with other macrocyclic complexes.     

Trans-bis(benzo(1,3)-thiazole)bis(N,N-dimethylformamide)bis(N-thiocyanato)-cobalt(II): spectroscopy,thermal analysis and crystal structure

Disolution of Co(bzt)₂(NCS)₂ (bzt = benzo 1,3- thiazole) in dimethyl formamide (dmf) produces Co(bzt)₂(NCS)₂(dmf)₂. The stoichionmetry of the complex has been established by a combination of chemical (C, H, N) and thermal analysis. The comlex has an octahedral structure with pairs of ligands in trans configuration as well as a CoN₄O₂ coordination sphere with CoN distances of 2.185(2) Å (bzt); 2.082(2) Å (NCS) and CoN(dmf) of 2.118(2) Å. The infrared and electronic absorption spectra are consistent with this arrangement.     

The crystal and molecular structure of diethylenetriammonium hexachloro-antimonate(III)

A compound of the type [DenH₃]SbCl₆ (DenH₃ = diethylenetriammonium cation) was prepared and characterized by means of structural and vibrational measurements. The structure consists of monomeric SbCl₆^3? anions and triprotonated diethylenetriam-monium cations. The SbCl₆^3? anion has a strongly distorted octahedral geometry, presenting three short (2.415–2.495 Å) and three long (2.836–3.114 Å) SbCl bonds. The presence of multiple hydrogen bonds, mainly involving the counterion and the three long-bonded chlorine atoms, is considered to be responsible for the octahedral distortion. Vibrational properties of the complex are discussed in the light of its known crystal structure.     

The crystal and molecular structure of tri-o-ethylamylose (tea 3)

The crystal and molecular structure of a tri-O-ethylamylose polymorph, TEA 3, has been solved by stereochemical conformation and packing analysis, combined with X-ray fibre diffraction analysis. The unit cell is orthorhombic, space group P2₁2₁2₁, with a  15.36 (±0.03) Å, b  12.18 (±0.05) Å, and c (fibre repeat)  15.48 (±0.01) Å. The actual chain conformation is a 4₃ helix with the EtO-6 group in the tg position, as was found in the polymorph TEA 1.     

Copper(II) halide complexes of 2-aminobenzophenone. Crystal and molecular structure of bis(2-aminobenzophenone)dichlorocopper(II)

The complexes CuX₂L₂ (X = Cl, Br; L = 2-aminobenzophenone) were prepared and characterized by means of magnetic and spectroscopic measurements. For the Cl compound the crystal structure was also determined. Crystals are triclinic, space group P$\text{1}$, with a = 13.397(3), b = 10.752(2), c = 9.205(2) Å, α = 72.26(1)°, β = 91.58(1)°, γ = 106.86(1)°, and Z = 2. The structure was solved by the heavy-atom method and refined by least-squares calculations to R = 0.034 for 2581 counter data. It consists of discrete CuX₂L₂ monomers showing distorted trigonal bipyramidal coordination geometry about the copper ion. The amino nitrogens are axial ligands, with the equatorial positions occupied by two chlorine atoms and a carbonyl oxygen from one L molecule acting as a bidentate ligand. Infrared and ligand field spectroscopies and magnetic measurements, interpreted on the basis of the known crystal structure, also suggest a similar structure for the related Br compound.     

The crystal and molecular structure of cytosine-glycyl-glycine-copper(II) complex,a biologically important ternary coordination complex

The title compound was prepared and studied to gain some insight into the structural basis for the protein-nucleic acid-metal ion interaction. The crystal structure has been determined from three-dimensional diffractometer X-ray data using Cu Kα radiation. The crystals are monoclinic, space group $\text{P2}{}_1\text{c}$, with cell dimension; a=10.642(1)Å, b=8.081(1)Å, c=17.792(1)Å, β=124.29(1)^o, z=4. Amino and amide nitrogen, carboxyl O(8) of glycylglycine, N(3) of cytosine and O(2) of adjacent cytosine molecule coordinate to the central copper ion to form a square pyramid. An additional weak interaction in complex molecule between copper and O(2) of cytosine is also observed. The complex molecules are held together by hydrogen- and coordination-bonds in crystalline state.     

The use of bis(mercaptoacetato-S,O)hydroxoiron(III) complex for the determination of hydroxamates

A rapid, indirect, spectrophometric procedure for the determination of hydroxamates, based on the competition for ferric ions of the bis(mercaptoacetato-S,O)hydroxoiron(III) complex, has been developed. The assay is remarkably free of interferences by common ions, thus rendering it useful in the quantitative determination of hydroxamates in culture fluids and crude preparations.