Preparation and structural characterization of di-μ-azido-bis[azido(2-aminopyridine)aquo]dicopper(II), [Cu(2-ampy)(N3)2(H2O)]2

Di-μ-azido-bis[azido(2-aminopyridine)aquo]dicopper(II), [Cu(2-ampy)(N₃)₂(H₂O)]₂, was synthesized and characterized by X-ray crystallography. The crystals are triclinic, space group P$\text{1}$, with a = 7.142(1), b = 7.812(1), c = 9.727(1) Å, a = 96.52(1), β = 95.52(1), γ = 113.47(1)°, and Z = 1. The structure was refined to R_F = 0.030 for 1960 observed MoKα diffractometer data. The dimeric molecule, which possesses a crystallographic inversion center, contains both terminal and μ(1)-bridging azido groups. Each copper(II) atom is further coordinated by a 2-aminopyridine ligand (via its ring N atom) and a water molecule to give a distorted square pyramid, with the metal atom raised by 0.17 Å above the N₄ basal plane [CuN (ring) = 2.001(2), CuN (azide) = 1.962(3)–2.018(2) Å] towards the apical aquo ligand [CuO = 2.371(2) Å]. Each water molecule forms an intramolecular O?HN (amine) acceptor hydrogen bond, and is linked by two OH?N (terminal azide) intermolecular donor hydrogen bonds to adjacent dimeric complexes to yield a layer structure parallel to (001). Infrared and electronic spectral data are presented and discussed.     

Characterization of a mononuclear copper carboxylate complex: Bis(acetylsalicylato)bis(pyridine)copper(II)

The preparation, spectral properties, and crystal structure of a mononuclear copper(II) complex of acetylsalicylate and pyridine are reported. The complex exists as bis(acetylsalicylato)bis(pyridine)copper(II) both in the solid state and in chloroform solution. The crystal is monoclinic, space group P2₁/n, with a = 17.823(5), b = 10.903(4), c = 6.598(2) Å, β = 95.74(2)°. The final refinement used 1472 observed reflections and gave an R of 0.046. The copper atom is surrounded by four atoms in a trans square planar arrangement with two short CuO distances of 1.949(3) Å and two CuN distances of 2.003(4) Å. Two longer CuO distances of 2.623(3) Å are made with the remaining oxygen atoms of the aspirin carboxylate groups.     

Synthesis,structural characterization,and properties of the organothorium alkylthiolate complex [(CH3)5C5]2Th(SCH2CH2CH3)2

This contribution reports the synthesis and characterization of the organothorium alkylthiolate complex [(CH₃)₅C₅]₂Th(SCH₂CH₂CH₃)₂. This compound crystallizes in the monoclinic space group C2/c (#15) with four molecules in a cell of dimensions a=19.066(2), b=11.603(1), c=16.379(2) Å, and β=130.08(1)°. Least-squares refinement led to a value for the conventional R index (on F_o) of 0.040 for 132 variables and 2030 observations having F_o²⩾3σ(F_o²). The molecular structure consists of an unexceptional ‘bent sandwich’ [(CH₃)₅C₅]₂Th fragment coordinated to two n-propylthiolate ligands. The ThS bond distance is 2.718(3) Å; the SC(α) distance, 1.78(2) Å; the ThSC(α) angle, 108.3(5)°; and the SThS′ angle, 102.5(2)°. Contrasts are drawn with the structures of analogous actinide alkoxides     

f-Element/crown ether complexes. 16. Synthesis,crystallization and crystal structure of [Dy(OH2)8]Cl3·18-crown-6·4H2O

When crystals of [Dy(OH₂)₇(OHMe)] [DyCl(OH₂)₂(18- crown-6)]₂Cl₇·2H₂O [1] are allowed to warm from 5 °C to ambient temperature (22 °C) under the original solvent mixture (1:3 CH₃OH: CH₃CN), they redissolve and the title complex can be isolated by slow evaporation of the resulting solution. The crystal structure of this complex, [Dy(OH₂)₈]Cl₃·18-crown-₆·4H₂O, has been determined. It crystallizes in the monoclinic space group, P2₁/c, with a = 10.395(1), b = 18.684(1), c = 16.259- (3) Å, β= 102.56(1)°, and D_calc = 1.61 g cm⁻³ for Z = 4. A final conventional R value of 0.041 was obtained by least-squares refinement using 3453 independent observed [F_o⩾5σ(F_o)] reflections. The [Dy(OH₂)₈]³⁺ cations and crown ether molecules are hydrogen bonded in a polymeric chain with the crown molecules separating the cations and a total of seven DyOH₂···O(crown ether) hydrogen bonds. The chains are connected by a hydrogen bonding network consisting of the cations, chloride ions, and uncoordinated water molecules. The geometry of the cation is best described as a bicapped trigonal prism with distortions on the reaction pathway toward dodecahedral symmetry. The two capping atoms average 2.41(1) Å from Dy, the remaining DyO distances average 2.38(2) Å. The 18-crown-6 molecule has the D_3d conformation normally observed except for a distortion of one OCCO unit containing the oxygen atom accepting two hydrogen bonds.     

Studies on the metal—amide bond. XVII. The crystal and molecular structure of the α-form of aqua[N,N′-bis(2′-pyridinecarboxamido)-1,3-propane] copper(II) dihydrate

α-Aqua[N,N′-bis(2′-pyridinecarboxamido)-1,3-propane]copper(II) dihydrate, C₁₅H₂₀N₄O₅Cu, is monoclinic, space group P2₁/c, with a = 11.719(2), b = 13.092(2), c = 12.663(2) Å, β = 119.56(1)°, Z = 4. The structure was refined to R = 0.026 for 2398 diffractometer data using full-matrix least-squares methods. The copper atom is five-coordinate with the N₄-tetradentate ligand encompassing the base of a distorted square-based pyramid which is appreciably distorted towards a trigonal bipyramid [average Cu-N(amide) 1.950(2), Cu-N(pyridine) 2.043(2) Å, N(amide)-Cu-N(amide) 94.5(1), N(pyridine)-Cu-N(pyridine) 100.2(1)°] and with the copper atom lying 0.27 Å above the N₄ plane towards the apical water molecule [Cu-O 2.236(2) Å]. The central six-membered chelate ring adopts a skewed boat conformation and the enforced strain in the molecule results in non-planar distortions in the pyridine rings with only small distortions in the amide groups. The molecules pack in sheets parallel to (10$\text{1}$) and the hydrogen-bonding network involves the water molecules and the amide oxygen atoms of the ligand.     

N,N-diisopropylcarboxylic acid amide complexes of thorium(IV) and uranium(IV) N-thiocyanates; the crystal structure of tetraisothiocyanato tetrakis(N,N-diisopropylacetamide-O)uranium(IV)

The complexes M(NCS)₄·xL (x = 2, M = U, L = Me₃CCON(Prⁱ)₂(dippva); x = 3, M = Th, L = Me₂CHCON(Prⁱ)₂(dipiba) and dippva, M = U, L = EtCON(Pr¹)₂(dippa), dipiba and dippva; x = 4, M = Th, L = MeCON(Prⁱ)₂(dipa), dippa and dipiba, M = U, L = dipa, dippa) and the solvates M(NCS)₄·4dipa·CH₂Cl₂ (M = Th, U) have been prepared. Their i.r. and u.v.-visible (M = U only) spectra are reported. The crystal and molecular structure of U(NCS)₄(dipa)₄· CH₂Cl₂ has been determined by the heavy-atom method from X-ray diffractometer data and refined by least squares to R 0.029 for 1135 independent reflections. The crystal is tetragonal, space group P$\text{4}$2₁c, with Z = 2, a = 15.663(4) and c = 10.512(3) Å. The coordination geometry about the 8-coordinate uranium atom is dodecahedral with the N atoms of the NCS groups occupying the dodecahedral A sites and the ‘dipa’ O atoms the B sites. The bonding distances of UO and UN are 2.363(8), and 2.444(11) Å respectively.     

6-Azauridine, a nucleoside with unusual ribose conformation. The molecular and crystal structure

The cytostatic analogue ribo-6-azauridine crystallizes in the orthorhombic space group P2₁2₁2₁ with eight molecules per unit cell of dimensions $\text{a = 20.230, b = 7.709, c = 12.863}\text{A}\text{?}$. A trial structure was obtained by direct methods. Least-squares refinement of co-ordinates and anisotropic thermal parameters based on 1998 reflections measured on a four-circle diffractometer led to a discrepancy index R = 4.0%. Like uridine, 6-azauridine has the anti conformation about the glycosidic bond and a C(3′)-endo sugar pucker. Unlike uridine, it exhibits a close approach of N(6) to C(2′) at only 2.814 and 2.844 Å in the two independent molecules, and a C(5′)(5′) bond that is gauche to C(4′)O(1′) but trans to C(4′)C(3′); this conformation about a C(4′)C(5′) bond has never been observed before for C(3′)-endo puckered riboses in the crystalline state. The crystal structure displays a pseudo-A face centering and very similar conformational parameters for the two independent molecules. Every OH and NH group in the structure serves as a proton donor in a hydrogen bond, including an unusual N(3)—H(3) … O(1′) link. Molecular orbital calculations by the extended Hückel method indicate that from uridine to 6-azauridine the net charge changes sign at ring positions 5 and 6 and disappears at 1.     

Crystal structure of the low-dimensional uranium pentatelluride: UTe5

The crystal structure of UTe₅ (a = 17.915(5), b = 10.407(3), c = 4.220(2) Å, Pnma, Pn2₁a, Z =4) was refined from 822 intensities with I>3σ(I) to a conventional R factor of 0.060. The uranium coordination polyhedron is a three capped tellurium trigonal prism, and all the Te atoms are involved in TeTe bonds. The structure is built up with infinite chains of prisms stacked in the $\text{c}$ direction. The chains are linked into (b, c) layers by a single Te atom which exhibits some positional disorder.     

Corrections to Nomenclature of Phosphorus-Containing Compounds of Biochemical Importance

Crystals of cholesteryl oleate (C₄₅H₇₈O₂) are monoclinic, space group P2₁, with $\text{a = 12.65(3), b = 9.13(3), c = 18.79(5)}\text{A}\text{?}\text{, β = 93.3(3)°}$ and have 2 molecules in the unit cell. The crystal structure has been determined by Patterson and Fourier methods at a resolution $\text{d}{}_{\mathrm{<mtext>min</mtext>}}\text{= 1.1}\text{A}\text{?}$, using 799 X-ray intensities (CuKα) measured by a diffractometer. Structure refinement by block-diagonal least squares gave R = 0.12. The oleate chains are almost straight except for a kink at the cis-double bond. The chains pack side by side but without a regular sub-cell structure, in a manner which might be similar to the arrangement within biological membranes. As in cholesteryl octanoate, the cholesteryl ring systems pack together with extensive overlap of anti-parallel nearest neighbours. Projecting methyl groups interlock.     

The molecular structures of pyridine-chromiumpentacarbonyl and bis(pyridine)-chromiumtetracarbonyl

The structures of pyridinechromiumpentacarbonyl, (1), and bis(pyridine)chromiumtetracarbonyl,(2) have been determined. (1) crystallizes in the space group Pbam with a = 15.289(3) Å, b = 19.276(5) Å and c = 7.677(6) Å. (2) crystallizes in the space group P$\text{1}$ with a = 7.365(2) Å, b = 8.136(2) Å, c = 13.491(4) Å, α = 89.49(2)°, β = 88.89(2)°, and γ = 63.09(2)°. The structures refined to R_w values of 0.020 and 0.034 for (1) and (2), respectively. In both cases the pyridine rings are planar and stagger the cis CrCO bonds. A comparison of the structural results from these two compounds to piperidinechromiumpentacarbonyl and Cr(CO)₆ seems to indicate that the pyridine ligand is a weaker σ-donor and stronger π-acceptor than the saturated analog, piperidine.     

Preparation,crystal and molecular structure of aquadichlorobis(ethylpyridine)-oxovanadium

The compound VOCl₂·2(3-Etpy)·H₂O (Etpy = ethylpyridine) was prepared by slow hydrolysis of the toluene suspension obtained from the reaction of VCl₄ with 3-ethylpyridine The crystal was found to be monoclinic C2/c, Z = 4, ϱ(calc.) = 1.426 × 10³ kg m⁻³, a = 13.281(5), b = 13.989(7), c = 9.277(8) Å, V = 1723(2) ų β = 90.53(5)°.Final full matrix least-square refinement with anisotropic thermal parameters for all non-hydrogen atoms gave R = 0.039, R_w = 0.042, R_g = 0.053. The vanadium atom is hexacoordinate with the pyridine ligands in mutually trans positions in the plane containing the Cl atoms. The O vanadyl atom is in an axial position trans to the coordinated H₂O molecule, and the OVO line is a binary axis for the molecule.