Tungstotellurates of the imidazolium and 4-methylimidazolium cations

Tungstotellurates of the organic imidazolium and 4-methyl-imidazolium cations have been prepared and characterized by X-ray diffraction and i.r. spectroscopy. The [TeW₆O₂₄]^6– anion is formed by close packing of oxygen atoms with Te and W atoms in distorted octahedral voids. In both compounds the organic cations are involved in hydrogen bonds, to the [TeW₆O₂₄]^6– anion in [H₂imz]₆[TeW₆O₂₄] · 2(Himz) (1) and to Te(OH)₆ units in [4-H₂-methyl-imz]₆[TeW₆O₂₄] · Te(OH)₆ (2). Solution studies of (1) and (2) by ¹H-, ¹⁸³W- and ¹²⁵Te-n.m.r. have been carried out. Thermogravimetric (t.g.) and calorimetric (d.s.c.) analyses were performed for both compounds.     

A series of novel lanthanide polyoxometalates: condensation of building blocks dependent on the nature of rare earth cations

A series of novel lanthanide polyoxomolybdates was synthesized by reaction of lanthanide cations with the Anderson type anion (TeMo(6)O(24))(6-). The polyoxometalates K(6n)(TeMo(6)O(24))(n)[(Ln(H(2)O)(7))(2)(TeMo(6)O(24))](n)[middle dot]16nH(2)O (Ln = Eu, Gd) and K(3n)[Ln(H(2)O)(5)(TeMo(6)O(24))](n)[middle dot]6nH(2)O (Ln = Tb, Dy, Ho, Er) were characterized by X-ray structure analysis, elemental analysis and IR spectroscopy. We found that the solid-state structures of Ln/(TeMo(6)O(24))(6-) compounds are strongly dependent on the lanthanide cations, and therefore represent a rare example for different arrangements of building units depending on the nature of the rare earth cations. While the Eu(3+) and Gd(3+) cations achieve ninefold coordination by seven water molecules and two terminal oxygen atoms of the (TeMo(6)O(24))(6-) anions, the Tb(3+), Dy(3+), Ho(3+) and Er(3+) cations are coordinated by five water molecules, two terminal oxygen atoms and one molybdenum-bridging oxygen atom belonging to the (TeMo(6)O(24))(6-) anion. The europium and gadolinium substituted compounds contain infinite one-dimensional [(Ln(H(2)O)(7))(2)(TeMo(6)O(24))](n) chains; the terbium, dysprosium, holmium and erbium compounds contain infinite one-dimensional [Ln(H(2)O)(5)(TeMo(6)O(24))](n)(3n-) chains.     

Synthesis,properties and crystal structure of a heteropoly compound containing titanium

K4H2CoW12O40·2TiO2·9H2O crystallizes from an aqueous solution of Na2WO4, Co(OAc)2 and Ti(SO4)2. The compound has very similar i.r. and u.v. spectra to those of [CoW12O40]6– and [CoW11TiO40]8– but its polarographic behaviour is different from that of [CoW11TiO40]8– and exhibits only reduction of tungsten(VI). A single crystal structural analysis indicates that this compound consists of the heteropolyanion [CoW12O40]6–, titanium–oxygen chain, potassium ions and water molecules.     

Synthesis and Structures of New Enaminones

Two isomeric enaminones were obtained by reaction of ethyl 2-hydroxy-4-(4-hydroxy-6-methyl2H-pyran-2-on-3-yl)-4-oxo-2-butenoate (1) and amines (aniline, benzylamine, butylamine and tyramine) in ethanol. The structures of isomers were studied by ¹³C and ¹H NMR spectra, whereas in the case of isomers 2b, 3a, and 4a (Scheme 1), the crystal structures have been determined by single crystal X-ray diffractometry. The compounds 2b and 3a exist in the solid state as N–C=C–C=O, whereas 4a is in the N–C=C–C–OH tautomeric form (Scheme 2, form A and B, respectively). All three structures exhibit very short intramolecular hydrogen bonds of O–H···O [in the range 2.396(3) – 2.448(3) Å] and N–H···O [in the range 2.580(5) – 2.679(3) Å] type, that are reinforced by delocalization. The crystal structures are in addition stabilized by C–H···O weak hydrogen bonds. In 2b and 3a, the discrete dimers are formed by eight-membered ring containing hydrogen bonds; in 4a, the infinite chains along [1 0 1] direction are formed.     

The rapid synthesis of the heteropolyoxometalate-pillared layered double hydroxide Zn2Al(OH)6[SiW11O39Co(H2O)]1/6 · 4H2O by the action of ultrasound

The ion-exchange between the transition metal monosubstituted heteropolyoxometalate anion [SiW11O39-Co(H2O)]6– and the anionic clay Zn2Al(OH)6NO3· xH2O by the action of ultrasound gave the heteropolyanion-pillared layered double hydroxide Zn2Al-(OH)6[SiW11O39Co(H2O)]1/6·4H2O within 7 min. The product was characterized by powder X-ray diffraction, i.r. spectroscopy and elemental analysis. The results show that the gallery height of the complex is 1.00±0.02 nm and the heteropolyanion [SiW11O39-Co(H2O)]6– entering the layer retains the integrity of the Keggin structure. Experimentally, the atomic ratio of each element in the formula is Zn:Al = 2.1:0.95 and Si:W:Co = 0.96:10.90:0.98.     

Cobalt(III) α-Dimethylglyoximates [Co(DH)2(Py)2]2SiF6 · 10H2O and [Co(DH)2(Thio)2]2SiF6 · 2H2O · C2H5OH: Synthesis and Structure

[Co(DH)₂(Py)₂]₂SiF₆ · 10H₂O and [Co(DH)₂(Thio)₂]₂SiF₆ · 2H₂O · C₂H₅OH complexes are synthesized and characterized by X-ray diffraction analysis. Two radicals of -glyoxime linked by hydrogen O–H···O bonds lie in the equatorial plane of the octahedral Co(III) complexes. Intramolecular (– and N–H···O) and intermolecular (O–H···F, O–H···O, N–H···F, N–H···O, N–H···S) interactions are discovered in the crystal. The influence of nonvalence interactions on the structures is discussed.     

Complexation in the CuCl2-C2H5OH-H2O system

Depending on the ethanol-water ratio, five individual compounds of copper(II) of the following compositions are formed in the CuCl₂-C₂H₅OH-H₂O system: [CuCl₂(C₂H₅OH)_4] (I), cis-[CuCl₂(C₂H₅OH)₂·(H₂O)₂] (II), trans-[CuCl₂(C₂H₅OH)₂· (H₂O)₂](III), [Cu(H₂O)₆]²⁺ (IV), and [Cu(OH)₂(H₂O)₄] (V).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2725–2729, December, 1990.     

Redox chemistry of [Fe2(CN)10]4−. Part 5. Reaction with thiourea

The reaction of the dimeric iron(III) complex [Fe2(CN)10]4– with a large excess of thiourea, tu, takes place in a series of stages, the first two of which have been examined in detail. The first stage is a one equivalent outer sphere electron transfer to form [Fe2– (CN)10]5– and the radical cation tu+· which dimerises to form the disulfide tu22+. There is kinetic evidence for the formation of a significant proportion of a precursor complex [Fe2(CN)10]4–·tu at high concentrations of tu. The second stage involves cleavage of the mixed valence dimer to yield [Fe(CN)5tu]2– and [Fe(CN)5H2O]3–. On standing, substitution of H2O by tu and oxidation by air occurs slowly, and finally all of the original iron is observed as [Fe(CN)5tu]2–.     

Clathrate forming ability of some [MgA4X2] complexes where A=4-methylpyridine or pyridine and X=halogen or NCS

Three new compounds have been synthesized: [Mg(4-MePy)₄(NCS)₂]·0.67(4-MePy)·xH₂O (x=0.07–0.24 [Mg(4-MePy)₄(NCS)₂]·(4-MePy) and [MgPy₄(NCS)₂]·2Py·2H₂O. Their structures have been investigated by Raman spectroscopy and the first two compounds have been shown to be isostructural with the clathrates [Cu(4-MePy)₄(NCS)₂]·0.67(4-MePy)·0.33H₂O and [Ni(4-MePy)₄(NCS)₂]·(4-MePy). Thermal and other properties have been studied. It was concluded from an analysis of the literature that pyridine complexes of Mg and Ca are capable of forming clathrates with Py as guest molecule, although these compounds have not been examined before from the point of view of clathrate chemistry.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 66–73, March–April, 1993.     

Intramolecular Hypervalent X←X Interaction in Heteropentalene Compounds Containing S and O Atoms

Chalcogen-containing heteropentalene and quasimonocyclic compounds having O–O–O and S–S–S triads or O–O and S–S diads were studied by the ab initio [MP2(full)/6-31G** and MP2(fc)/ 6-31+G**] and DFT (B3LYP/6-31G**) methods. The oxygen-containing compounds are characterized by strong O···O repulsion which destabilize the pentalene structure. The molecule of 3-thioxo-1-propenesulfenyl fluoride, in contrast to 3-mercapto-2-propenethial, is more stable in the cis-s-cis conformation with an appreciably shortened S–S contact [2.274 Å (MP2), 2.503 Å (B3LYP)] which approaches the length of a standard S–S covalent bond.     

Synthesis and properties of podands with 4-antipyryliminomethine groups

Novel podands with 4-antipyryliminomethine groups on benzenes and various numbers of ethers are prepared. According to UV spectroscopy, these compounds form complexes with alkali, alkaline earth, and transition metals. Extraction of metal picrates demonstrated that the podands selectively form extractable complexes with these salts. A lead-selective electrode with an electrode function 22–24 mV/pPb is based on 1,8-bis[2-(4-antipyryliminomethine)phenoxy]-3,6-dioxaoctane. This enables 1·10^–6–1·10^–2 M Pb to be determined in the pH range 3.5–5.5. The electrode is highly selective for Pb in the presence of alkali and alkaline earth metals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2099–2102, September, 1990.     

Syntheses,crystal structures and properties of copper(II) complexes of 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino]propan-2-ol and 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino] propane

The syntheses of two polydentate ligands comprising imidazole donors, 1,3-bis[(4-methyl-5-imidazol-1-yl) ethylideneamino]propan-2-ol (BIPO), 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino]propane (BIP), and their copper(II) complexes [Cu(BIPO)(ClO₄)(H₂O)] (NO₃) · H₂O (1) and [Cu(BIP)(ClO₄)](ClO₄) · 2H₂O (2) are reported. Single-crystal structural analyses show that (1) adopts an elongated octahedral geometry with the axial positions occupied by a perchlorate oxygen atom and an aqua ligand, while (2) adopts a distorted square-pyramidal geometry with the axial positions occupied by a perchlorate oxygen atom. Electronic spectra in aqueous solution indicate that both (1) and (2) adopt square-pyramidal geometry. Cyclic voltammetry in aqueous solution gives reduction waves at –0.07 and –0.08 V versus s.c.e. for (1) and (2), respectively. The low reduction potential and general reversibility of the redox reaction of (1) and (2) indicate that BIPO and BIP are flexible enough to stabilize both Cu^II and Cu^I forms of the complexes.     

Synthesis and Structure of Co(III) Coordination Compounds [Co(DH)2(Anil)2][BF4] and [Co(DH)2(Py)2][BF4]

The complex compounds [Co(DH)₂(Anil)₂][BF₄] and [Co(DH)₂(Py)₂][BF₄] were synthesized from Co(BF₄)₂ · 6H₂O–DH₂–A–alcohol–water systems (DH₂ is dimethylglyoxim and A is pyridine (Py) or aniline (Anil)), and their crystal structures were determined using X-ray diffraction analysis. In octahedral Co(III) complexes, two dimethylglyoxime radicals lie in the equatorial plane and are joined via the intramolecular hydrogen bond O–H···O. The complexes with pyridine and aniline have similar configurations but different crystal structures.     

Ionothermal syntheses of six three-dimensional zinc metal-organic frameworks with 1-alkyl-3-methylimidazolium bromide ionic liquids as solvents

We have performed ionothermal reactions between Zn(NO3)2 and H3BTC in 1-alkyl-3-methylimidazolium bromide ionic liquids with the alkyl group varying from ethyl to amyl. Six 3-D metal-organic frameworks (MOFs), including two isomeric compounds [Zn3(BTC)2(H2O)2] x 2H2O (1 and 2) (H3BTC = 1,3,5-benzenetricarboxylate acid), [EMI][Zn(BTC)] (3) (E = ethyl, MI = 3-methylimidazolium), [PMI][Zn(BTC)](4) (P = propyl), [BMI]2[Zn4(BTC)3(OH)(H2O)3] (5) (B = butyl), and [AMI][Zn2(BTC)(OH)Br] (6) (A = amyl), have been synthesized and structurally characterized. Compounds 1 and 2 are isomeric compounds, in which the coordination modes of Zn atoms and the BTC3- ligands are considerably different. Compounds 3-6 crystallize with the corresponding ionic liquid cations incorporated in the frameworks. Their crystal structures show various features including various coordination geometries of Zn2+ and various bridging modes of the BTC3- ligands. The incorporated cations appear to have strong interactions with the frameworks.     

Polyoxometalate monolayers in Langmuir-Blodgett films

Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB film occur very quickly and are reversible. 2) The preparation of LB films based on magnetic polyoxometalates, such as the Keggin anions, [CoW12O40]6- and [SiMn(OH2)W11O39]6-, or containing magnetic clusters of increasing nuclearities such as [Co4(H2O)2(PW9O34)2]10- and [Co4(H2O)2(P2W15O62)2]16- based on a Co4O16 ferromagnetic cluster, and the polyoxometalates [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16- and [Ni9(OH)3-(H2O)6(HPO4)2(PW9O34)3]16- based on a nonanuclear M9O36 cluster. 3) The preparation of LB films of the giant heteropolyoxomolybdate, [Na3(NH4)12][Mo57Fe6(NO)6O174(OH)3-(H2O)24]76 H2O.     

Complexes of 2,5-dihydroxy-1,4-benzoquinone and chloranilic acid with second and third row transition elements

The synthesis of new 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ) and chloranilic acid (H2CA) complexes cis-[Mo2O5L2]2– (L = DHBQ, CA), [W2O5(DHBQ)2]2–, [WO2(CA)2]2–, trans-[UO2(DHBQ)]·H2O, and trans-[UO2(CA)2]2– is described. Raman, i.r., 1H and 13C n.m.r spectra of the ligands and their complexes are reported and their structures discussed.     

Infinite sheet structure of disodium tetra-μ-acetato- dichlorodirhodate(II) tetrahydrate

The binuclear rhodium(II) complex Na2[Rh2Cl2(OAc)4]· 4H2O has an infinite sheet structure. Binuclear anionic complexes [Rh2Cl2(OAc)4]2– are bound with cationic entities. The Na+ cation has pseudooctahedral coordination and is surrounded by two chloro ligands and two oxygen atoms of bridging acetato ligands of two [Rh2Cl2(OAc)4]2– anions and two water molecules. Both Cl and H2O are bridging ligands involved in formation of the Na+ chains. The remaining water molecules are located between sheets.     

Preparation and characterisation of copper(II) complexes with bis(1-pyrazolyl)propane

Summary The synthesis and characterisation of the coordination compounds of some copper(II) salts with bis (1-pyrazolyl)propane, Me₂Cpz₂, are reported. Coloured stable solid complexes of the type Cu(Me₂Cpz₂) X₂(X = Cl^–, Br^– or AcO^–), Cu(Me₂Cpz₂)(ClO₄)₂ · H₂O, [Cu(Me₂Cpz₂)SO₄ · 2 H₂O] · H₂O and [Cu(Me₂Cpz₂)₂X]X (X = NO ₃ ^– or ClO ₄ ^– ) have been isolated and characterised by elemental analysis, electronic, i.r. and magnetic measurements. Probable structures of the complexes are discussed on the basis of their spectral data.     

ESR spectra of copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones

ESR spectra of binuclear copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones (H₄L) [Cu₂L·2Py], in which the coordination polyhedra are linked by the polymethylene chain with different lengths (from one to five units), were studied. The spectra of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids exhibit weak exchange interactions between the paramagnetic sites. These interactions induce seven HFS lines from two equivalent copper nuclei with the constant 40·10^–4 cm^–1 in the ESR spectra of liquid solutions. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of the complex based on heptadioic acyldihydrazone contains the signal of four HFS lines with the constant 72·10^–4 cm^–1, which is common for the copper(ii) monomeric compounds.     

Tetranuclear copper complexes with new β-diketone and β-iminoketone-containing ligands

Novel tetranuclear copper complexes, Cu4(OH)2(ClO4)3 (HA)·H2O (1) and Cu4(ClO4)5(H3B)·3H2O (2), were synthesized by reacting 1,5-bis(1-phenyl-3-methyl-5-pyrazolone-4)-1 ,5-pentanedione with 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine in the presence of a template reagent copper ion. New [2+2] type open cyclic multidentate ligands are also obtained from the reaction (H4A and H6B stand for new compounds from 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine, respectively). They each contain five C = O, three C = N and one NH2 groups. The complexes were characterized by elemental analyses, conductivity, FT-i.r. (micro-i.r., deconvolution technique), FAB-MS, e.s.r., electronic spectra and extended X-ray absorption fine structure (EXAFS). Copper ions in (1) are basically four coordinate with tetragonal geometry. The average coordination bond distances of Cu–N and Cu–O are 1.91 Å and 2.05 Å. In (2), copper ions are primarily five coordinate with square-based pyramidal geometry. The average coordination bond distances of Cu–N and Cu–O are 1.93Å and 2.08Å. Four copper atoms in molecules may be arranged tetragonally. Both the ligand field and the coordination bonds in complex (1) are stronger than those in (2). Investigations on variable temperature susceptibilities show that some antiferromagnetic exchange interaction exist in the complexes. The plots of –1 versus T obey the Curie-Weiss law only at low temperature. Preliminary results of a bioassay indicate that the two complexes have some antitumour activity in vitro.