A new polymorph of (O‐ethyl dithio­carbonato‐κ2S,S′)­bis­(tri­phenylphosphine‐κP)silver(I)

A new triclinic polymorphic modification of the title compound, [Ag(C₃H₅OS₂)(C₁₈H₁₅P)₂], has been found and compared with the previously known orthorhombic modification [Tiekink (1988). Coord. Chem. 17 , 239–243]. The two polymorphs have the same molecular shape, viz. a distorted tetrahedral geometry, with a chelating di­thio­carbonate (xanthate) and two PPh₃ ligands bonded to the Ag atom. However, in this new polymorph, the xanthate ligand is bonded asymmetrically to the Ag atom, with Ag—S distances of 2.5489 (6) and 2.8055 (7) Å, while for the orthorhombic polymorph these distances are 2.686 (4) and 2.601 (4) Å. The Ag—P distances are similar in both structures.     

Metal-free synthesis of azacalix[4]arenes

The facile preparation of N(H)-bridged azacalix[4]arenes has been achieved by stepwise nucleophilic aromatic substitutions assisted by hydrogen bonding interactions. The synthesis is uncatalyzed and affords previously unknown tetranitroazacalix[4]arenes.     

K2M(H2P2O7)2·2H2O (M = Ni,Cu, Zn): ortho­rhom­bic forms and Raman spectra

The crystal structures of three isotypic ortho­rhom­bic dihydrogendiphosphates, namely dipotassium copper(II)/nickel(II)/zinc(II) bis­(dihydrogendiphosphate) dihydrate, K₂M(H₂P₂O₇)₂·2H₂O (M = Cu, Ni and Zn), have been refined from single‐crystal data. The M²⁺ and K⁺ cations are located at sites of m symmetry, and the P atoms occupy general positions. These compounds also exist in triclinic forms with very similar structural features. The structures of both forms are compared, as well as the geometry of the MO₆ octa­hedron, which is considerably elongated towards the water mol­ecules for M = Ni and Cu. Such elongation has not been observed among the other representatives of the family. A Raman study of the whole series K₂M(H₂P₂O₇)₂·2H₂O (M = Mn, Co, Ni, Cu, Zn and Mg) is reported.     

Synthesis and characterization of ethylxanthato complexes of zinc(II) with P-donor ligands

Monomeric, five-coordinated bis(ethylxanthato)Zn^II(phosphine) complexes [phosphine = PPh₃, P(o-tolyl)₃, P(CH₂Ph)₃] have been synthesized by addition of the phosphine ligand (1:1 molar ratio) to CH₂Cl₂ solutions of [Zn(S₂COEt)₂]. Bidentate ligands Ph₂PCH₂CH₂PPh₂ (dppe) and Ph₂P(CH₂)₄PPh₂ (dppb) reacted in a 1:2 molar ratio to form dinuclear phosphine-bridged complexes. The Zn—P bonds are very labile and are probably broken in solution. The characterization of all the compounds has been carried out by elemental analyses and spectroscopic methods (i.r. and n.m.r.). The structure of binuclear [(S₂COEt)₂Zn(-dppb)Zn(S₂COEt)₂], determined by X-ray crystallography, shows a distorted trigonal bipyramidal environment for the Zn atoms, formed by two chelating xanthate and a bridging dppb ligand.     

AErP<Subscript>2</Subscript>O<Subscript>7</Subscript> (A = Rb,Cs) and HEuP<Subscript>2</Subscript>O<Subscript>7</Subscript>·3H<Subscript>2</Subscript>O: Crystal Structures,Vibrational Studies and Thermal Behaviours

Abstract  

New diphosphates AErP₂O₇, A = Rb (1), Cs (2), and HEuP₂O₇·3H₂O (3) have been prepared via soft chemistry route from evaporation of aqueous solution. Their crystal structures have been solved by single crystal diffraction data. The compounds (1) and (2) crystallize in the monoclinic space group P2₁/c with the following unit cell dimensions: (1) a = 7.7248(4) ?, b = 10.9342(6) ?, c = 8.6716(3) ?, β = 105.434(4)° and Z = 4; (2) a = 7.9192(4) ?, b = 10.8606(4) ?, c = 8.7684(5) ?, β = 104.317(5)° and Z = 4. Compound (3) crystallises in the triclinic space group P − 1, with the unit cell parameters: a = 6.4036(5) ?, b = 6.8753(6) ?, c = 9.7964(8) ?, α = 81.706(7)°, β = 80.218(7)°, γ = 88.381(7)°. Crystal structure of (1) and (2) consists of 3D open framework built from [ErO₆] octahedra sharing corners with [P₂O₇] units, leading to the formation of channels running along c direction in which A⁺ [A = Rb(1), Cs(2)] ions are located. The compound (3), on the other hand, exhibits a lamellar structure, in which edge-sharing polyhedra of eightfold coordinated europium form chains along [010]. These chains are joined in turn to each others using diphosphates bridges. A network of O–H···O hydrogen bonds reinforces the cohesion of the structure of (3). The diphosphate groups in (1), (2) and (3) adopts an eclipsed configuration. IR and Raman spectra of the three new phosphates show usual signals related to the P₂O₇ diphosphate group and the water molecule. TG and DTA studies were carried out on crystals of (3). The data are correlated to the crystal structures ones.     

Linear and pre-organized carboxylic acid picket porphyrins as bismuth chelators

New picket porphyrins delivering at least one carboxylic group around the coordination site of the macrocycle were synthesized for bismuth coordination. The influence of the number, the length, and the pre-organization of the carboxylic acid pickets on the stability of the bismuth complexes was explored. Their stabilities in acidic medium were compared with those of their precursors bearing ester pickets. The molecular structure of one of the bismuth complexes, which is the only monomeric bismuth porphyrin reported up to now, is discussed. At the opposite of what we initially reported, and in agreement with the theoretical calculations, the distortion of the macrocycle in this structure is mainly due to the number of water molecules in the first sphere of coordination of the bismuth.     

The coordination chemistry of FeCl3 and FeCl2 to bis[2-(2,3-dihydroxyphenyl)-6-pyridylmethyl](2-pyridylmethyl)amine: access to a diiron(III) compound with an unusual pentagonal-bipyramidal/square-pyramidal environment

Coordination of FeCl3 to the title ligand yields a mononuclear iron(III) complex 1, which was characterized by spectroscopic techniques and X-ray diffraction. The ligand is (kappa3-N) tridentate and the metal, which lies in a pseudo-octahedral environment, is bound to a phenolate group from the catechol substituent. The dichloroiron(II) complex 2 was easily obtained by metalation of the ligand with FeCl2 and characterized by various spectroscopic techniques. In their cyclic voltammograms both 1 and 2 display the same reversible FeII/FeIII wave at E1/2=10 mV (vs. SCE). Reduction of compound 1 with Zn/Hg yields 2', which displays identical properties to 2. Taken together, these findings indicate that in spite of the different oxidation state of the metal in 2, no major geometrical/structural change is observed at the metal center with respect to 1. The reaction of 2 with dioxygen in the absence of organic substrates proceeds extremely rapidly and yields compound 3, which is a diiron(III) derivative whose X-ray crystal structure is also reported. The possibility of a radical-based mechanism is discussed. Compound 3 displays an unusual geometry: one iron(III) center is seven-coordinate, whereas the other lies in a square-pyramidal environment. The two iron atoms are bridged by the catecholato substituents. To the best of our knowledge, 3 is the first example of a seven-coordinate iron(III) derivative with tris(2-pyridylmethyl)amine ligands.     

Flavone glycosides from Calycotome villosa Subsp. Intermedia

The known flavonoid chrysin-7-O-(beta-D-glycopyranoside) (chrysin glucoside,1) as a major fraction and a new glycoside flavone, chrysin-7-O-beta-D-[(6"-acetyl)glycopyranoside] (2) were isolated from the flowers and leaves of Calycotome Villosa Subsp. Intermedia, They were identified by UV-Vis, 1R, (1)H-, (13)C-NMR and ESI-MS.     

Bis(O‐ethyl di­thio­carbonato‐κ2S,S′)­palladium(II)

The Pd atom in the title compound, [Pd(C₃H₅OS₂)₂], lies on an inversion center and adopts a square‐planar coordination geometry defined by the four S atoms of the two di­thio­carbonate (xanthate) ligands. In the solid state, the mol­ecules aggregate into layers in which the rows of mol­ecules alternate their orientation to allow each Pd atom to interact with two symmetry‐equivalent S atoms of the xanthate ligands of adjacent mol­ecules, generating a pseudo‐octahedral environment around each Pd atom. This weak interaction of 3.3579 (7) Å can be classified as a closed‐shell electrostatic intermolecular interaction.     

Structure elucidation and vasodilator activity of methoxy flavonols from Calycotome villosa subsp. intermedia

Two flavonols identified as 3,5,7,4′-tetrahydroxy-3′-methoxyflavone (1) and 3,5,7,4′-tetrahydroxy-8-methoxyflavone (2) were isolated from the seeds of Calycotome villosa subsp. intermedia. The structure elucidation of the isolated compounds was performed by the spectroscopic methods (UV, IR, ¹H NMR, ¹³C NMR and MS) and also by a single crystal X-ray analysis in the case of compound (2). Vasodilator activity of compound (2) was demonstrated in isolated rat aorta contracted with high KCl or with noradrenaline.