Metal ions-nucleobases interactions: preparation and crystal structures of trichloroadeninium zinc(ii)(form ii) and a similar zinc complex of arprinocid [6-amino-9-(2-chloro-6-fluorobenzyl)purine]

Two zinc complexes—trichloroadeninium zinc(II)(Form 11), C₅H₆N₅Cl₃Zn [structure(I)] and a similar complex of Arprinocid, (6-amino-9-(2-chloro-6-fluorobenzyl)purine], C₁₂H₁₀N₅FCl₄Zn [structure(II)]—have been prepared Structure(I) crystallizes in the space group P2₁/c with a = 8.223(1)Å, b = 6.755(1) Å, c = 18.698(3) Å, β = 96.10(2)°,and Z = 4. Structure(II) crystallizes in the space group P2₁/c with a = 8.209(2) Å, b = 6.421(8) Å, c = 31.794(8) Å, β = 90.76(2)°, and Z = 4. Both of these structures were solved by the heavy atom method using diffractometric data and refined to R = 0.028 [structure(I)] and 0.038 [structure(II)]. Zinc with a distorted tetrahedral coordination having three chlorines and N(7) as ligators, protonation of the adenine moiety at N(1), dissymmetry of exocyclic angles at N(7), and an interligand hydrogen bond (“indirect chelation”) involving one of the three chlorines, coordinated to zinc and a proton of the exocylic amino group are the striking features common to both structures. Similar types of indirect chelation as observed in the different complexes of purines have been discussed. The zinc ion deviates from the imidazole plane by 0.412 Å in structure(I) and 0.524 Å in Structure(II). The imidazol and pyrimidine planes fold about the C(4)-C(5) bond by 2.4° in strctur(I) and 3.8° in structure(II). In structure(I), inversion related molecules are paired through N(9)-H…N(3) hydrogen bonds. N-H…Cl hydrogen bonds and C(8)-H…Cl interactions have been observed in both structures.     

Coordination chemistry of 7,9-disubstituted 6-oxopurine metal compounds. 4. Platinum(II) coordination at N(1). Molecular and crystal structure of [(ethylenediamine)bis(7,9-dimethylhypoxanthine)platinum(II)] hexafluorophosphate

The preparation and molecular and crystal structure of the complex [(ethylenediamine)bis(7,9,-dimethylhypoxanthine)platinum(II)] hexafluorophosphate, [Pt(C₂H₈N₂)(C₇H₈N₄O)₂] (PF₆)₂, are reported. The complex crystallizes in the monoclinic system, space group C2/c, with a = 12.334(2)Å, b = 10.256(2)Å, c = 22.339(3)Å, β = 101.31(1)°, V = 2771.0ų, Z = 4, D_measd = 2.087(3) g cm^?3, D_calc = 2.094 g cm^?3. Intensities for 3992 symmetry-averaged reflections were collected in the θ-2o scan mode on an automated diffractometer employing graphite-monochromatized MoKα radiation. The structure was solved by standard heavy-atom Patterson and Fourier methods. Full matrix least-squares refinement led to a final R value of 0.051. Both the ethylenediamine chelate and the PF₆^? anion are disordered. The primary coordination sphere about the Pt(II) center is approximately square planar with the bidentate ethylenediamine ligand and the N(1) atoms [Pt(II) ? N(1) = 2.020(5)Å] of two 7,9-dimethylhypoxanthine bases (related by a crystallographic twofold axis of symmetry) occupying the four coordination sites. The exocyclic O(6) carbonyl oxygen atoms of the two 7,9-dimethylhypoxanthine ligands participate in intracomplex hydrogen bonding with the amino groups of the ethylenediamine chelate [N(ethylenediamine) ? O(6) = 2.89( )Å]. The observed Pt ? O(6) intramolecular distances of 3.074(6)Å are similar to those found in other Pt(II) N(1)-bound 6-oxopurine complexes and in several Pt(II) N(3)-bound cytosine systems.     

The crystal structure of 2-deoxy-β-d-arabino-hexopyranose at −150°

2-Deoxy-β-d-arabino-hexopyranose, C₆H₁₂O₅, is orthorhombic, P2₁2₁2₁, with cell dimensions at ?150° [20°], a = 6.484(2) [6.510(3)], b = 10.364(2) [10.427(4)], c = 11.134(3) [11.153(5)] Å, V = 748.2 [757.1] ų, Z = 4, D_x = 1.457 [1.440], and D_m = [1.455] g.cm^?3. The intensities of 1269 reflections were measured by using MoKα radiation. The structure was solved by direct methods, and refined by full-matrix least-squares, with anisotropic, thermal parameters for the carbon and oxygen atoms, and isotropic parameters for the hydrogen atoms. The pyranose has the ⁴C₁(d) conformation, with puckering parameters Q = 0.563 Å, θ = 3.9°, and ? = 350.3°. The departure from ideality is very small, and less than that in β-d-glucopyranose, Q = 0.584 Å and θ = 6.9°. The β-glycosidic, CO bond is short, 1.383(4) Å, and the OCOH torsion angle is ?87°, consistent with the anomeric effect. The hydrogen-bonding scheme consists of infinite chains, with side chains terminating at a ring-oxygen atom.     

Sodium binding to d-glucuronate residues: Crystal structure of sodium d-glucuronate monohydrate

Three-dimensional X-ray diffraction data were used to determine the crystal structure of sodium β-d-glucuronate monohydrate, a model system for investigating the factors involved in the binding of sodium ions to d-glucuronate residues of glycosaminoglycans. Crystals of the salt are monoclinic, space group P2₁, with a = 9.206(3) Å, b = 7.007(2) Å, c = 7.378(3) Å, β = 96.84(3)°, and Z = 2. Intensity data for 858 reflections were measured with an automated diffractometer. A trial structure, obtained by direct methods, was refined by least squares to R = 0.035. An outstanding feature of the crystal packing is the interaction of d-glucuronate anions with sodium ions. The sodium ion is coordinated to three symmetry-related $\text{d}$-glucuronate anions and to one water molecule. The d-glucuronate anion binds sodium cations through the three following sites: one that involves a carboxyl oxygen atom combined with ring oxygen O-5; one that includes a single carboxyl oxygen atom, and one composed of the O-3–O-4 pair of hydroxyl groups.     

Preparation and crystal structure of the hydroxo-bridged complex biscyclo-tri-μ-hydroxo-tris[(trans-1,2-diaminocyclohexane)platinum(II)] tris

The title compound, [C₁₈H₄₅N₆O₃Pt₃]2(SO₄)₃·14H₂O, belongs to space group C2/c, with a = 25.90(2) Å, b = 14.33(2) Å, c = 23.74(3) Å, β = 122.88(7)°, and Z = 4. The structure was refined on 2899 independent nonzero reflections to an R factor of 0.042. The crystal contains hydroxobridged cyclic [Pt₃(OH)₃(C₆H₁₄N₂)₃]³⁺ ions, in which the Pt₃O₃, ring has a chair conformation. The coordination around each Pt atom is square planar and the cyclohexyl ring lies roughly in the same plane. A large cavity between two trimeric ions related by a twofold axis is filled with one SO₄^2- ion and five water molecules, which participate in an intricate network of hydrogen bonds among themselves and with the hydroxo and amino groups of the complex cation. These units are held together in the crystal by stacking interactions between Pt(OH)₂(C₆H₁₄N₂) “planes” belonging to adjacent molecules, as well as by hydrogen bonds involving the remaining SO₄^2- ions and water molecules. The presence of the cyclohexane ring precludes λ-δ interconversion in the chelate ring and imparts rigidity to the Pt(trans-dach)²⁺ unit.     

An assessment of the cis-influence in coenzyme B12 Models. The structure of the mixed schiff-base/oxime complex: Aquo(3,9-dimethyl-2,10-diethyl-1,4,8,1 1-tetra-azaundeca-1,3,8,10-tetraen-11-ol-1-olato)(methyl)cobalt(III)hexafluorophosphate

The title compound is the first accurately determined structure in the general class of ‘Costa’ B₁₂ models. The data permit comparisons of structural results to other relevant B₁₂ models and the construction of a cis effect series.Crystal Data: C₁₄H₂₀CoF₆N₄O₃P, M = 504.4, monoclinic, space group P2₁/c, a = 14.316(3), b = 6.819(1), c = 22.741(5) Å and β = 99.91(2)°, V = 2186.9 ų, D_m = 1.52, Z = 4, D_c = 1.53 g cm^?3, μ(MoKα) = 9.2 cm^?1, λ(MoKα) = 0.7107 Å. Unit cell parameters were refined and intensity data collected on a CAD4 computer-controlled diffractometer, using graphite-monochromated MoKα radiation. A total of 5803 reflections were collected and corrected for Lorentz-polarization factor, 2802 independent reflections with I > 3σ(I) being used in the subsequent calculations.The CoO bond length to the axial water is 2.102- (3) Å. This value places the Costa model structural cis influence as being comparatively close to corrin based systems, somewhat greater than cobaloximes and definitely lower than Schiff-base complexes.     

Bioactive peptides: Conformational studies of [TYR4] cyclolinopeptide A

The solid state conformational analysis of [Tyr⁴] cyclolinopeptide A has been carried out by x-ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane-water mixture [a = 9.849 (5) Å, b = 20.752 (4) Å, c = 16.728 (5) Å, β = 98.83 (3)°, space group P2₁, Z = 2], shows the presence of five intramolecular N-H? O?C hydrogen bonds, with formation of one C₁₇ ring structure, one α-turn (C₁₃), one inverse γ-turn (C₇), and two β-turns (C₁₀, one of type III and one of type 1). The Pro¹-Pro² peptide unit is cis (ω = 5°) all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 Å. © 1995 John Wiley & Sons, Inc.     

Metal-phenoxyalkanoic acid interactions. Part 15. The crystal structures of diaquabis(phenoxyacetato)cadmium(II) and catena-μ-[aquabis(phenoxyacetato-O)lead(II)-bis(phenoxyacetato)lead(II)]

The crystal structures of the cadmium(II) and lead(II) complexes of phenoxyacetic acid (PAH) have been determined by single crystal X-ray diffraction techniques. The cadmium complex, [Cd(PA)₂(H₂O)₂] (1), space group C2, with Z = 2 in a cell of dimensions, a = 11.801(2), b = 5.484(1), c = 13.431(3) Å, β = 100.87(2)°, possesses a distorted trapezoidal bipyramidal coordination around the metal atom, involving two water oxygens [2.210(5) Å] and four carboxyl oxygens from two symmetrical bidentate phenoxyacetate ligands [2.363(4), 2.365(4) Å] with Cd lying on the crystallographic two- fold axis. The lead complex, [Pb₂(PA)₄(H₂O)]_n(2) is triclinic, space group P$\text{1}$, Z = 2, with a cell of dimensions, a = 10.135(4), b = 10.675(3), c = 19.285(9) Å, α = 114.66(3), β = 91.94(3) and γ = 114.99(3)°. (2) is a two-dimensional polymer with a repeating dimer sub-unit. The first lead [Pb(1)] has an irregular MO₈ coordination [2.34?2.96(2) Å: mean, 2.63(2) Å] involving the water molecule, two oxygens from an asymmetric bidentate carboxylate group, two from a bidentate chelate [O(ether), O(carboxylate)] group and three from bridging oxygens, one of which also provides a polymer link to another symmetry generated lead. The second lead [Pb(2)] is irregular seven-coordinate [PbO, 2.48?2.73(2) Å: mean, 2.61(2) Å] with three bonds from the bridging groups, two from an unsymmetrical bidentate carboxylate (O, O′) group and one from a second carboxyl group which also bridges two Pb(2) centres in the polymer.     

Synthesis and coordination chemistry of tripodal dialkyl[1,2-bis(diethylcarbamoyl)ethyl]phosphonates with lanthanide nitrates

Trifunctional dialkyl [1,2-bis(diethylcarbamoyl)- ethyl] phosphonates, (RO)₂P(O)CH[C(O)N(C₂H₅)₂]- [CH₂C(O)N(C₂H₅)₂] R  CH₃, C₂H₅, i-C₃H₇, n-C₆H₁₃ were prepared from the respective sodium salts, Na[(RO)₂P(O)CHC(O)N(C₂H₅)₂] and N,N- diethylchloroacetamide, and they were characterized by elemental analysis, mass, infrared and NMR spectroscopy. The molecular structure of (i-C₃H₇O)₂- P(O)CH[C(O)N(C₂H₅)₂][CH₂C(O)N(C₂H₅)₂] was determined by single crystal X-ray diffraction analysis and found to crystallize in the monoclinic space group P2₁/c with a=15.589(6), b=9.783(4), c= 16.283(7) Å, β = 110.90(3)°, Z = 4 and V= 2320(2) ų. The structure was solved by direct methods and blocked least-squares refinement converged with Rf = 5.7% and R_wF= 4.4% on 2266 unique data with F>4σ(F). Important bond distances include PO 1.459(3) Å, CHCO 1.228(3) Å and CHCH₂CO 1.223(3) Å. The coordination chemistry of the ligand with several lanthanides was examined, and the structure of the complex Gd(NO₃)₃{[(i-C₃H₇O)₂P(O)CH[C(O)N(C₂H₅)₂][CH₂C(O)N(C₂H₅)₂]}₂·H₂O was determined. The complex crystallized in the monoclinic space group P2₁/n with a = 13.524(5), b = 22.033(4), c = 19.604(4) Å β = 106.22(2)°, Z = 4 and V= 5609(3) ų. The structure was solved by heavy atom techniques and blocked least-squares refinement converged with R_F = 5.9% and R_wF = 4.1% on 5275 reflections with F > 4σ(F). Both trifunctional ligands were found to bond to Gd(III) through only the phosphoryl oxygen atoms. The remainder of the Gd coordination sphere was composed of three bidentate nitrate oxygen atoms and an oxygen bonded water molecule. Several important bond distances include GdO(phosphoryl)_av = 2.343(5) Å, GdO(nitrate)_av = 2.475(7) Å, GdO(water) = 2.354(5) Å, PO(phosphoryl)_av = 1.467(6) Å, CHCO_av = 1.242(10) Å and CHCH₂CO_av = 1.209(11) Å.     

Synthesis and characterization of technetium(V) complexes with tridentate schiff base ligands. X-ray crystal structure of chloro[N-(2-hydroxyphenyl)salicylideneiminato]oxotechnetium(V)

Five-coordinate technetium(V) complexes of the form TcO(L)Cl where L is one of the two tridentate Schiff base ligands N-(2-oxidophenyl)salicylideneiminate or N-(2-mercaptophenyl)salicylideneiminate have been synthesized and characterized. These neutral complexes precipitate from methanol upon reaction of the Schiff base ligand with TcOCl₄^?. A single crystal X-ray structure determination shows that the chloro [[N-(2-oxidophenyl)salicylideneiminato](2?)-N,O,O′]oxotechnetium(V) complex, [TcO(C₁₃H₉NO₂)Cl], formula weight 362, has a distorted square pyramidal coordination geometry with the oxo ligand in the axial position. The steric requirements of the oxo group cause the Tc atom to be displayed 0.67 Å out of the mean equatorial plane of the other four donor atoms. This complex crystallizes in the monoclinic space group P2₁/a with a = 13.423(6) Å, b = 12.570(5) Å, c = 7.769(3) Å, β = 106.53(5)°, V = 1256.7(9) ų, and Z = 4. The structure has been refined to R = 0.047 for 1775 observed reflections.     

Coordination chemistry of lanthanides with cryptands. An X-ray and spectroscopic study of the complex Nd2(NO3)6 [C18H36O6N2]·H2O

By reacting neodymium nitrate hexahydrate with the cryptand 〈222〉 in methanol, the complex Nd₂-(NO₃)₆[C₁₈H₃₆O₆N₂]·H₂O was obtained and analyzed by single-crystal X-ray diffraction. The cell is triclinic P$\text{1}$ with a = 14.870(2) Å, b = 13.261(2) Å, c = 8.832(1) Å, α = 91.2(1)°, β = 93.4(1)°, γ = 87.6(1)°, Z = 2 and U = 1736.6 ų. The structure was refined by least-squares methods to the conventional R = 0.039 for 6177 observed reflections. The compound contains the cations [Nd〈222〉(NO₃)]²⁺ and the anions [Nd(NO₃)₅·H₂O]^2?, and is isostructural with the samarium analogue. Solid state fluorescence spectra of the title complex were measured at room and liquid nitrogen temperature, and the transitions ⁴F_3/2 → ⁴I_9/2 and ⁴F_3/2 → ⁴I_11/2 analyzed.     

Crystal structure of 4-(N-acetyl,2,3,4-tri-O-acetyl-β-l-arabinopyranosylamino)azobenzene

The crystals of the title compound, C₂₅H₂₇N₃O₈ (M_r497.55), are monoclinic, space group P2₁ with a = 11.680(2), b = 8.089(1), c = 13.804(3) Å, β = 92.52(2)°, V = 1302.7 ų, and Z = 2; D_c = 1.27 g.cm⁻³. The structure was solved by using direct methods. The refinement of all non-hydrogen atom parameters yielded R = 0.050. The compound has normal geometry with the ¹C₄ conformation of the pyranoid ring and the extended trans conformation of the azobenzene moiety.     

Crystal structure of [chloro(diethyldithiocarbamato)butyl phenyl]tin(IV)

The crystal structure of the title compound, SnCl(C₆H₅)(C₄H₉)[S₂CN(C₂H₅)₂], was determined and refined to an R factor of 3.2% for 4876 reflections. The molecule contains five-coordinate tin in a distorted trigonal bipyramidal arrangement with the tin atom lying 0.20 Å below the equatorial plane formed by one of the sulphur atoms, S(1), and the donor carbons of the butyl and phenyl groups. The chlorine and the other sulphur atom, S(2), occupy axial sites, making a S(2)SnCl angle of 156.85(1)°. The SnS(2) bond is markedly elongated (2.764(1) Å) compared to the SnCl bond (2.449(1) Å) and the SnS(1) bond (2.454(1) Å). The structure resembles those of analogues such as (C₆H₅)₂Sn(glygly) in having both hydrocarbon ligands located in the equatorial plane. Crystal data: space group P$\text{1}$: a = 8.291(2) Å, b = 14.726(3) Å, c = 9.509(2) Å, α = 96.24(2)°, β = 107.02(3)°, γ = 116.70(2)°, Z = 2, R = 3.2% for 4876 independent reflections.     

Dioxo-, oxothio- and dithio-tungsten(VI) and tungsten(V) complexes of the ligand N,N′-Dimethyl-N,N′-bis(2-mercaptophenyl)ethylenediamine

Synthesis of complexes cis,cis-W^VOXL (X=Cl, NCS), cis,trans-W^VOXL (X=Cl, OPh, SPh) and cis,trans-W^VIE₂L (E₂=O₂, OS, S₂) of the title ligand LH₂ are reported. cis,cis-W^VOCIL crystallises in space group P2₁/c with a=13.6541(9) Å, b=7.1555(11) Å, c=18.198(2) Å, β=95.294(6)°, V=1770.4(3) ų and Z=4 while the cis,trans isomer crystallises in space group P2₁/n with a=10.361(3) Å, b=14.141(4) Å, c=12.213(5) Å, β=102.56(3)°, V=1747(2) ų and Z=4. cis,trans-W^VIS₂L crystallises in space group P2₁/n with a=10.645(2) Å, b=13.929(2) Å, c=12.189(2) Å, β=103.14(2)°, V=1760(1) ų and Z=4. A short CH₃···Cl distance of 3.067(7) Å and an acute OWCl angle of 94.1(2)° are seen in cis,cis-W^VOClL, which converts to the cis,trans form on heating in MeCN. The latter isomer features a CH₃···Cl distance of 3.38(2) Å and an OWCl angle of 105.1(8)°. Electrochemical and EPR data are reported. In particular, cis,trans-W^VIE₂L may be reduced to [W^VE₂L]^–. EPR properties of these anions and those of complexes W^VOXL are discussed in the context of W^V centres in tungsten enzymes.     

The synthesis of technetium(V) complexes containing sterically bulky thiolate ligands. The molecular structure of tetrabutylammonium oxotetrakis(2,4,6-trimethylbenzenethiolato)technetate(V)

The reactions between [TcOCl₄]⁻ and the sterically bulky thiols ArSH (Ar = 2,4,6-Me₃C₆H₂, 2,4,6- Prⁱ₃C₆H₂ and 2,6-Ph₂C₆H₃) in methanol afford complexes of formula [TcO(SAr)₄]⁻ which may be isolated as salts with bulky organic cations. The molecular structure of [Buⁿ₄N][TcO(2,4,6-Me₃C₆H₂S)₄] was determined by X-ray diffraction methods. The Tc(V) centre was found to adopt the expected square pyramidal geometry in which an oxo group occupies the apical site and the four thiolate sulphurs the basal sites. The TcO distance is 1.659(11) Å and the average TcS distance 2.38(2) Å. The average cis STcS, trans STcS and OTcS angles are respectively 82.7(6)°, 138.4(3)° and 110.8(4)°.     

Potential multifunctional anti-cancer metal complexes. I. Synthesis and x-ray structural studies of some dinuclear rhodium(II) carboxylate complexes with diamine-substituted acridine ligands in terminal coordination positions

The preparations are reported of [Rh(RCO₂)₂L]₂ [where R = CH₃, C₂H₅, and CH₃OCH₂; L = 6-chloro-2-methoxy-9-[2(NR′₂)ethyl]aminoacridine (R′ = H, CH₃)]. X-ray structural studies have been carried out on two of the compounds [ R = C₂H₅, R′ = H, (1); R = CH₃, R′ = CH₃, (2)]. Compound 1 is monoclinic, space group C2/c, with a = 20.864(11), b = 15.736(4), c = 14.402(4) Å, β = 93.14(4)°, V = 4721 ų, and Z = 4; 2 is monoclinic, space group P2₁/n, a = 8.861(2), b = 23.089(10), c = 12.014(2) Å, β = 105.84(2)°, V = 2365 ų, and Z = 2. Both compounds comprise the standard dinuclear rhodium(II) carboxylate unit with the substituted acridine ligands coordinated to rhodium in the axial positions, via the NH₂ group nitrogen in 1 and the N(CH₃)₂ nitrogen in 2.The dimethyl substitution on the tertiary amine group in 2, and an associated conformational change in the diamine chain, result in an increased separation of the acridine ligand from the metal centre. There is a pronounced acridine base stacking in 1 but not in 2.     

New preparations and molecular structures of cis-MCl2(Ph2PCH2PPh2)2, M = Ru,Os and trans-RuCl2(Ph2PCH2PPh2)2

The title compounds were made by reacting bis(diphenylphosphino)methane (dppm) with reduced solutions of OsCl₆^4? and Ru₂OCl₁₀^4?. The crystal and molecular structures of these compounds have been determined form three-dimensional X-ray study. The cis-isomers crystallize with one CHCl₃ per molecule of the complex. All three compounds crystallize in the monoclinic space group P2₁/n with unit cell dimensions as follows: Cis-OsCl₂(dppm)₂·CHCl₃: a = 13.415(4) Å, b = 22.859(4) Å, c = 16.693(3) Å, β = 105.77(3)°, V = 4926(3) ų, Z = 4. cis-RuCl₂(dppm)₂·CHCl₃: a = 13.442(3) Å, b = 22.833(7) Å, c = 16.750(4) Å, β = 105.53(2)°, V = 4953(3) ų, Z = 4. trans-RuCl₂(dppm)₂: a = 11.368(7) Å, b = 10.656(6) Å, c = 18.832(12) Å; β = 103.90(6)°, V = 2213(7) ų; Z = 2. The structures were refined to R = 0.044 (R_w = 0.055) for cis-OsCl₂(dppm)₂·CHCl₃; R = 0.065 (R_w = 0.079) for cis-RuCl₂(dppm)₂·CHCl₃ and R = 0.028 (R_w = 0.038) for trans-RuCl₂(dppm)₂. The complexes are six coordinate with stable four-membered chelate rings. The PMP angle in the chelate rings is ca. 71° in each case.     

The crystal and molecular structures of dioxo mo(VI) complexes of tripodal,tetradentate N,S-donor ligands

The crystal and molecular structures of the complexes MoO₂((SCH₂CH₂)₂NCH₂CH₂SCH₃), I and MoO₂((SCH₂CH₂)₂NCH₂CH₂N(CH₃)₂), II, have been determined from X-ray intensity data collected by counter methods. Compound I crystallizes in two forms, Ia and Ib. In form Ia the space group is P2₁/n with cell parameters a = 7.235(2), b = 7.717(2), c = 24.527(6) Å, β = 119.86(2)°, V = 1188(1) ų, Z = 4. In form Ib the space group is P2₁/c with cell parameters a = 14.945(5), b = 11.925(5), c = 14.878(4) Å, β = 114.51(2)°, V = 2413(3) ų, Z = 8. The molecules of I in Ia and Ib are very similar having an octahedral structure with cis oxo groups, trans thiolates (cis to both oxo groups) and N and thioether sulfur atoms trans to oxo groups. Average ditances are MoO = 1.70, MoS (thiolate) = 2.40, MoN = 2.40 and MoS (thioether) = 2.79 Å. Molecule II crystallizes in space group P2₁2₁2₁ with a = 7.188(1), b = 22.708(8), c = 7.746(2) Å, V = 1246(1) ų and Z = 4. The coordination about Mo is octahedral with cis oxo groups, trans thiolates and N atoms trans to oxo. Distances in the first coordination sphere are MoO = 1.705(2), 1.699(2), MoS = 2.420(1), 2.409(1) and MoN = 2.372(2), 2.510(2) Å. The conformational features of the complexes are discussed. Complex I displays MoO and MoS distances which are very similar to those found by EXAFS in sulfite oxidase. This similarity is discussed.     

Solution and solid state behavior of Co2+, Ni2+ and Zn2+ tosylaminoacidate systems: Crystal and molecular structure of bis(N-tosylglycinato)tetraaquocobalt(II) and bis(N-tosyl-β-alaninato)tetraaquozinc(II) complexes

The interactions between N-tosylamino acids and cobalt(II), nickel(II) and zinc(II) ions in aqueous solution and in the solid state have been investigated. From concentrated aqueous solutions, compounds of general formula [M(II)(N-tosylaminoacidato)₂(H₂O)₄](M = Co(II), Ni(II) and N-tosylaminoacidato = N-tosylglycinate (Tsgly^?), N-tosyl-α- and -β-alaninate (Ts-α- and Ts-β-ala^?); M = Zn(II) and N-tosylaminoacidate = Tsgly^?, Ts-β-ala^?) and [Zn(II)(N- tosylaminoacidato)₂(H₂O)₂] were isolated and characterized by means of thermogravimetric, electronic and infrared spectra. For two of them: [Co(Tsgly)₂(H₂O)₄](I) and [Zn(Ts-β-ala)₂(H₂O)₄](II) the crystal and molecular structures were also determined. Both compounds crystallize in the monoclinic space group P2₁/c, with two formula units in a cell of dimensions: a = 13.007(6), b = 5.036(2), c = 18.925(7) Å, β = 102.33(3)° for (I) and a = 14.173(6), b = 5.469(2), c = 17.701(7) Å, β = 106.63(3)° for (II). The structures were solved by the heavy-atom method and refined by least-squares calculations to R = 0.031 and 0.064 for (I) and (II) respectively. The cobalt and zinc atoms lie in the centers of symmetry, each bonded to two amino- acid molecules through a carboxylic oxygen atom and four water molecules in a slightly tetragonally distorted octahedral geometry. The second carboxylic oxygen atom is not involved in metal coordination. Electronic and X ray-powder spectra suggest that the tetrahydrate complexes of Co²⁺, Ni²⁺ and Zn²⁺ ions of the same amino acids are isomorphous and isostructural. No coordinative interactions between ligand and metal ions were found in aqueous solution on varying the pH values before hydroxide precipitation.     

Synthesis and crystal and molecular structure of a methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate complex

Bis-Methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate, Dy[O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂]₂(NCS) was prepared from the combination of ethanolic solutions of Dy(NCS)₃·xH₂O and (CH₃O)₂P(O)CH₂C(O)N(C₂H₅)₂. The complex was characterized by infrared and NMR spectroscopy, and single crystal X-ray diffraction methods. The crystal structure was determined at 25 °C from 3727 independent reflections by using a standard automated diffractometer. The complex was found to crystallize in the monoclinic space group P2₁/c with a = 13.282(4) Å, b = 19.168(5) Å, c = 9.648(2) Å, β = 90.09(2)°, Z = 4, V = 2456.4 ų and ?_cald = 1.72 g cm^?3. The structure was solved by standard heavy atom techniques, and blocked least-squares refinement converged with R_f = 4.7% and R_wF = 4.9%. The Dy atom is seven coordinate and bonded in a bidentate fashion to two anionic phosphonate ligands [O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂^?] through the carbonyl oxygen atoms and one of two phosphonate oxygen atoms. In addition, each Dy atom is coordinated to two phosphonate oxygen atoms from two neighboring complexes and to the nitrogen atom of a thiocyanate ion. This coordination scheme gives rise to a two-dimensional polymeric structure. Some important bond distances include DyNCS 2.433(8) Å, DyO(carbonyl)_avg 2.39(2) Å, DyO(equat. phosphoryl)_avg 2.303(8) Å, DyO(axial phosphoryl)_avg 2.25(2), PO(phosphoryl)_avg 1.493(3) Å and CO(carbonyl)_avg 1.25(1) Å.