Syntheses, structure, and a Mössbauer and magnetic study of Ba(4)Fe(2)I(5)S(4)

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U appears to be essential for the formation of single crystals suitable for X-ray diffraction studies. Ba4Fe2I5S4 crystallizes in a new structure type with two formula units in space group I4/m of the tetragonal system. The structure consists of a Ba-I network penetrated by (1)infinity[Fe2S4] chains. Each Fe atom, which is located on a site with 4 symmetry, is tetrahedrally coordinated to four S atoms. The FeS4 tetrahedra edge-share to form linear (1)infinity[Fe2S4] chains in the [001] direction. The Fe-Fe interatomic distance in these chains is 2.5630(4) A, only about 3% longer than the shortest Fe-Fe distance in -Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is +2.5. The M?ssbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfine parameters consistent with an average Fe oxidation state of +2.5. The M?ssbauer spectrum obtained at 4.2 K consists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent with rapid electron delocalization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba4Fe2I5S4, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensional ferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between the chains at lower temperatures.     

X-ray structure of (N-heterocyclic)(η4-diene)-dicarbonyliron(0) compounds

(N-Heterocyclic)(η⁴-diene)dicarbonyliron(0) compounds, where the N-heterocycles are quinoline and pyrazine and the diene is the diethyl ester of the hexa-2,4-dien-1,6-dioic acid (diethyl muconate) were studied by X-ray diffraction. The measurements demonstrated that the N-heterocycle occupies different positions of a tetragonal pyramid in these compounds. Quinoline occupies a basal position and pyrazine an apical position. This is discussed in terms of the π-bonding ability of the ligands.     

Molecular structure of tetrakis[benzenethiolatotrimethylplatinum(IV)], (μ3-SPh)4(PtMe3)4

The crystal structure of the title compound is reported, and the geometry and symmetry of the three-fold bridging by the arylthiolate ligand with two-fold symmetry is assessed. PtS bond lengths are differentiated by only 0.04Å. Crystal data: C₃₆H₅₆Pt₄S₄, M = 1897.4, tetragonal, space group P4₃2₁2, a = 14.187(1), c = 40.399(6)Å, U = 8131.11ų, Z = 8.     

Crystal and molecular structure of 4(3-acryloyloxy)octyloxy- and 4(3-acryloyloxy)hexyloxy-4′-cyanobiphenyls

The molecular and crystal structures of N≡C-C₆H₄-C₆H₄-O-(CH₂)₈-O-CO-CH=CH₂ (4(3-acryloyloxy)octyloxy-4′-cyanobiphenyl) (I) and N≡C-C₆H₄-C₆H₄-O-(CH₂)₆-O-CO-CH=CH₂ (4(3-acryloyloxy)hexyloxy-4′-cyanobiphenyl) (II) were determined by X-ray diffraction. The structures of I and II are stereotype. The space group of I and II is C2/c, Z = 8; lattice parameters I: a = 34.677(7)?, b = 9.452(2)?, c = 13.004(3) ?, β = 99.30(3)°; II: a = 30.858(6) ?, b = 9.504(2) ?, c = 13.082(2) ?, β = 92.78(3)°. The planar extended molecules I and II are packed in the unit cell to give clearly differentiated aliphatic and aromatic regions throughout the whole crystal. All intermolecular contacts are concentrated in the aromatic region. The molecular packing is very loose but the aromatic areas of I and II fully coincide. The only free parameter of the structure is the length of the aliphatic chain (CH₂)n (n = 8 and 6). According to DSC data, compound I possesses enantiotropic mesomorphism and II possesses monotropic mesomorphism.     

Synthesis and structure of a ‘4 + 1’ oxorhenium(V) complex containing imidazole derivatives

The ‘4?+?1’ concept was used to prepare the complex salt [ReO(iao)Br]Br (1) from the reaction of (n-Bu₄N)[ReOBr₄(OPPh₃)] with the ligand bis{2′-methyl(1′-methylimidazole)}-2-aminoethanol (Hiao) in methanol. The single-crystal X-ray crystal structure of 1 shows that iao acts as a monoanionic, tetradentate, N₃O-donor chelate. When the reaction was carried out in acetonitrile, the neutral complex [ReO(iao)Br₂] (2) was isolated. Elemental analyses and IR data suggest that iao acts as a tridentate, N₂O-donor ligand in 2.     

Crystal structure of a μ-oxo-bridged dimeric iron(III) complex

A dimeric [{Fe(5-ClL1)}₂(μ-O)], [H₂-5-ClL1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.     

Crystal structure of [Cu4(pytp)2(SO4)2(H2O)10](SO4)2 · 4H2O. A tetranuclear copper(II) complex with a new asymmetric ligand,pytp*, as a bridge

A new asymmetric bridge ligand, pytp, was prepared and characterized systematically by f.t.i.r., u.v.–vis., ¹H-n.m.r. and by FAB-MS spectroscopy. A tetranuclear Cu^II complex [Cu₄(pytp)₂(SO₄)₂(H₂O)₁₀](SO₄)₂·4H₂O (1) was prepared and characterized by elemental analysis and u.v.–vis. spectroscopy. A crystal structure analysis indicates that there are two different coordination spheres in (1) and that two of the copper centers are bridged by two ₂-SO₄ entities, creating a most unusual sulphate bridge.     

Like (CO)4, Do (CS)4 and (CSe)4 Have a Triplet Ground State?

Cyclobutane‐1,2,3,4‐tetraone, (CO)₄, was computationally predicted and, subsequently, experimentally confirmed to have a triplet ground state, in which a b_2g σ MO and an a_2u π MO were each singly occupied. In contrast, the (U)CCSD(T) calculations reported herein found that cyclobutane‐1,2,3,4‐tetrathione, (CS)₄, and cyclobutane‐1,2,3,4‐tetraselenone, (CSe)₄, both had singlet ground states, in which the b_2g σ MO was doubly occupied and the a_2u π MO was empty. Our calculations showed that both the longer C?X distances and smaller coefficients on the carbon atoms in the b_2g and a_2u MOs of (CS)₄ and (CSe)₄ contributed to the difference between the ground states of these two molecules and the ground state of (CO)₄. An experimental test of the prediction of a singlet ground state for (CS)₄ is proposed.     

Crystal structure of N-(β-acetoxyethyl)-4-methylpyridinium bromide

In continuation of previous studies [1] on structures of compounds differing from acetylcholine and choline by having a pyridine ring instead of the quaternary N atom, the x-ray structure of N-(-acetoxyethyl)-4-methylpyridinium bromide, which has cholinergic activity [2], is solved.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1813–1816, August, 1991.     

Crystal structure and magnetic properties of a nitronyl nitroxide complex {[Co2(NIT4Py)4(fum)2(H2O)4] · (H2O)2} n

The title compound {[Co₂(NIT4Py)₄(fum)₂(H₂O)₄] · (H₂O)₂} _n , where NIT4Py = 2-(4′-pyridinyl)-4,4,5,5-tetra-methylimidazoline-1-oxyl-3-oxide and fum = fumarate, was prepared and structurally characterized by X-ray diffraction. It crystallizes in triclinic, space group P 1 with a = 9.8853(9) Å, b = 13.2167(13) Å, c = 13.8481(12) Å, α = 68.5400(10)°, β = 73.467(2)°, γ = 74.596(2)°, V = 1587.6(3) ų, Z = 1, and R ₁ [I > 2σ(I)] = 0.0662. The complex consists of two kinds of neutral infinite 1-D chains, in which [Co(NIT4Py)₂(H₂O)₂] moieties are connected by fumarate anions in a bis-monodentate mode. These 1-D chains are further connected by hydrogen bonds, generating a 2-D network. The variable temperature magnetic susceptibility measurement reveals that the magnetic couplings between Co(II) and NIT4Py are weak antiferromagnetic interactions.     

The synthesis and crystal structure of a hydrated magnesium phosphate Mg3(PO4)2·4H2O

The synthesis and crystal structure of a novel hydrated magnesium phosphate is described. The crystal structure was solved from powder X-ray diffraction data. Mg₃(PO₄)₂·4H₂O crystallizes in the orthorhombic space group Cmc2₁ (No. 36) with a=8.41087(9) Å, b=17.3850(2) Å, c=12.8034(1) Å, V=1872.15(4) ų and Z=8. The structure consists of sheets stacked along [010], which are linked by edge sharing octahedral Mg₂O₆(H₂O)₄ dimers. Within the sheets there are infinite edge-sharing chains of Mg octahedra along [100]. The compound has been further characterized by ³¹P MAS NMR spectroscopy and thermogravimetric analysis. The crystal structure of two dehydrated variants existing around 200 (Mg₃(PO₄)₂·2.5H₂O) and 275 °C (Mg₃(PO₄)₂·2H₂O) remain unknown.     

Crystal structure of radical-cation salt β-(DOET)4CuBr4·PhCl

A new radical-cation salt β-(DOET)₄CuBr₄·PhCl (DOET = (1,4-dioxanediyl-2,3-dithio)ethylene-dithiotetrathiafulvalene) is synthesized by electrocrystallization in the dc mode (I = 0.12 μA), and its structure is studied. In the structure of the salt, the DOET radical cations are packed in layers parallel to ab. The average charge on DOET is equal to +0.5. The dioxane rings and ethylene groups of DOET, the tetrahedral CuBr ₄ ^2? -anion, and the chlorobenzene molecules are each disordered over two positions with a 50% probability, and the chlorine atoms of chlorobenzene are disordered over four positions with a 25% probability. The salt has semiconducting properties (E _a = 55 meV).     

Synthesis,spectra and crystal structure of a dinuclear manganese(χ) complex [(NTB)Mn(μ-O)]2(ClO4)4 · 2H2O

A novel dinuclear manganese(χ) complex [(NTB)Mn(μ-O)]₂(ClO₄)₄?·?2H₂O (1) (NTB?=?tris(2-benzimidazolylmethyl) amine) has been synthesized and characterized. The crystal structure is determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system, space group C2/c with a?=?18.3461(1), b?=?15.4170(1), c?=?21.0141(1)?Å, β?=?90.5290(1)°, V?=?5943.4(8)?ų, Z?=?4 and R ₁?=?0.0789 for 5729 observed reflections. Two manganese atoms are bridged by two oxygen atoms forming a dinuclear complex. The results of interaction between 1 and H₂O₂ indicated that hydrogen peroxide destroyed the Mn₂O₂ unit of 1.     

The structure of the VO2F3−4 ion: Crystal structure of (NH4)3VO2F4

The VO₂F³⁻₄ ion has a cis octahedral structure, as is shown by single crystal structure analysis of the title compound. The unit cell of (NH₄)₃VO₂F₄ (space group Immm or I222, a = 912.6(2), b = 1881.8(4), c = 626.4(1) pm, Z = 6) contains two symmetrically independent anions. One is rotationally disordered. Oxo and fluoro ligands cannot be distinguished. But the second one has a distorted cis octahedral structure with the lengths 170.0(4), 186.1(4), and 202.3(4) pm for the VO, VF (axial), and VF (equatorial) bonds. Infrared and Raman spectra as well as theoretical considerations support the crystallographic results. The phase transitions at 418 and 215 K were confirmed by variable temperature X-ray powder diffraction. Above 418 K the cubic cryolite type structure is adopted with a = 902.6(2) pm. Plausible mechanisms for the phase transitions are suggested.     

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6)

Abstract

The molecular and crystal structure of N-(4-n-butyloxybenzylidene)-4′-ethylaniline (4O.2) and the homologue N-(4-n-heptyloxybenzylidene)-4′-hexylaniline (7O.6) have been solved (at room temperature) by direct methods. The crystals of both compounds belong to the triclinic system with space group P1 with two molecules per unit cell. 4O.2: a = 5·531(2), b = 7·592(3), c = 19·746(7) Å, α = 86·66(2), β = 88·15(2), γ = 90·29(2)° 7O.6: a = 5·420(2), b = 8·307(3), c = 28·057(7) Å, α = 91·69(2), β = 89·76(2), γ = 108·02(2)°. The structures were refined by full-matrix least-squares calculations to R = 0·036 for 2297 observed reflections for 4O.2 and to R = 0·037 for 2150 reflections for 7O.6. The conformations in the asymmetric units of the two compounds differ considerably: The planes of the two phenyl rings of 4O.2, forming the mesogenic core of the molecule, are twisted at 61·2° to each other and the butoxy group contains a gauche conformation. In contrast the heptoxy chain of 7O.6 forms an all trans-conformation which lies almost in one plane with the two coplanar phenyl rings. The hexyl group also exists in an extended form, in a plane which is rotated against the plane of the mesogenic unit. The packing in the crystalline state of the two homologues exhibits a layered structure along c*; in 4O.2 these layers are separated, but in 7O.6 they are interdigitated. The compensation of the dipole moments of the C?O?C and C?N?C bonds occurs similarly in both structures: molecular orientations parallel to the a, c-plane in which the long axes of the molecules points in the same direction are packed in antiparallel fashion along b*.     

Molecular structure of compounds containing a 2,2′-bithienyl fragment (review)

The results of X-ray crystallographic investigations of compounds containing a 2,2-bithienyl fragment are summarized and analyzed. The structural characteristics of unsubstituted bithiophene, 5-monosubstituted, 5,5-, 3,3-, 4,4-, and 3,4-disubstituted, and more highly substituted bithiophenes and also the structure of -conjugated oligothiophene derivatives are considered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 725–760, June, 2000.     

The crystal structure of a novel basket binuclear silver (Ⅰ) cryptate

The metal complexes of polyaza cryptand have attracted much attentionowing to their special structure, unusual photo-chemical, electrical and catalyticproperties. Recently, Lehn and Nelson synthesized successively a series ofcryptands and crypatates with high yield by (2+3) schiff-base condensation of tris(2-aminoethyl)amine and aryl dialdehyde. But so far, little work about the analogueswith larger cavities and flexible chains condensed by tris (3-aminopropyl) amine (abbr.     

STM and voltammetric studies on the structure of a 4-pyridinethiolate monolayer chemisorbed on Au(100)-(1×1) surface

The structure for a 4-pyridinethiolate monolayer chemisorbed on the Au(100)-(1×1) single crystal surface was characterized by in situ scanning tunneling microscopy (STM) and cyclic voltammetry (CV). In situ STM observation showed a well-ordered p(√2 R 45°×5 R 53.1°) structure (abbreviated as √2×5) for the surface modified with either 4-pyridinethiol (4-PySH) or bis(4-pyridyl)disulfide (4,4′-PySSPy) in a 0.05 M HClO₄ solution. On the Au(100)-(1×1) surface, 4-PySH molecules formed a dimer structure with the S–S bond length of about 2.4 nm. The observed dimer structure is similar to that previously reported on the Au(111) surface, and the orientation of the pyridine ring is mostly perpendicular to the surface normal. However, the adsorbed molecules were more densely packed (√3/√2 times) on the Au(100) surface than on the Au(111) surface. The surface excess was estimated to be 5.8 (±0.2)×10⁻¹⁰ mol cm⁻² based on the voltammetric charge for the reductive desorption. This value is in good agreement with that (5.7×10⁻¹⁰ mol cm⁻²) calculated from the parallelogrammic (√2×5) unit cell. The Au(100)-(1×1) surface modified with 4-PySH gave a well-defined electrochemical response of cytochrome c.     

The synthesis and crystal structure of a copper-sulfur cluster [Cu4(S5)2(C5H5N)4]·S8

The cluster [Cu₄(S₅)₂(C₅H₅N)₄]·S₈ with cage structure has been obtained by reaction of copper powder with sulfur and K₂S _x in pyridine, and its structure was determined by X-ray crystallography. The crystal data for the title compound: triclinic, P (No. 2),Z = 2,a = 11.818(4) Å,b = 13.155(3) Å,c = 14.177(4) Å, = 93.79(2)°, = 96.68(2)°, = 115.76(2)°,V = 1954.52(1) ų. The structure was refined toR = 0.038R _w = 0.053) for 6444 data withI > 3.0(I).Dedicated to Professor Jiaxi Lu on the occasion of his 80th birthday.