Radical polymerization of styrene in the presence of Tin(IV) catecholate complexes

The synthesis of PS in the presence of diethyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate and diphenyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate has been studied. It has been found that such tin catecholates can act as chain length regulators in the polymerization of styrene and ensure a linear increase in molecular mass with conversion. Using the macroinitiators obtained in the presence of diphenyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate, the postpolymerization of styrene has been carried out.     

Complexes of germanium(IV) fluoride with phosphane ligands: structural and spectroscopic authentication of germanium(IV) phosphane complexes

The first phosphane complexes of germanium(iv) fluoride, trans-[GeF(4)(PR(3))(2)] (R = Me or Ph) and cis-[GeF(4)(diphosphane)] (diphosphane = R(2)P(CH(2))(2)PR(2), R = Me, Et, Ph or Cy; o-C(6)H(4)(PR(2))(2), R = Me or Ph) have been prepared from [GeF(4)(MeCN)(2)] and the ligands in dry CH(2)Cl(2) and characterised by microanalysis, IR, Raman, (1)H, (19)F{(1)H} and (31)P{(1)H} NMR spectroscopy. The crystal structures of [GeF(4)(diphosphane)] (diphosphane = Ph(2)P(CH(2))(2)PPh(2) and o-C(6)H(4)(PMe(2))(2)) have been determined and show the expected cis octahedral geometries. In anhydrous CH(2)Cl(2) solution the complexes are slowly converted into the corresponding phosphane oxide adducts by dry O(2). The apparently contradictory literature on the reaction of GeCl(4) with phosphanes is clarified. The complexes trans-[GeCl(4)(AsR(3))(2)] (R = Me or Et) are obtained from GeCl(4) and AsR(3) either without solvent or in CH(2)Cl(2), and the structures of trans-[GeCl(4)(AsEt(3))(2)] and Et(3)AsCl(2) determined. Unexpectedly, the complexes of GeF(4) with arsane ligands are very unstable and have not been isolated in a pure state. The behaviour of the germanium(iv) halides towards phosphane and arsane ligands are compared with the corresponding silicon(iv) and tin(iv) systems.     

A facile route to germanium(IV) binaphthoxide complexes: crystal structure of a chiral resolved germanium(IV) binaphthoxide

A method for the facile synthesis of chiral germanium(IV) binaphthoxide complexes from the corresponding binaphthols and an organogermanium trichloride has been developed, which allows these unusual types of compounds to be synthesized in high yields. The crystal structure of one such complex, (S)-[Ge{O2C20H10(SiMe3)2-3,3'}{Cl}{Ph}], has been determined.     

New lead(II) catecholate and o-semiquinone complexes

Lead(II) catecholate complexes were prepared by reduction of 3,6-di-tert-butyl-o-benzoquinone and its derivatives with lead metal in THF. The molecular structure of the (CatPb)₄·(PbO)₂·6C₃H₆O complex (Cat is the dianion of 3,6-di-tert-butylcatechol), which was synthesized by hydrolysis of lead 3,6-di-tert-butylcatecholate in acetone, was established by X-ray diffraction. A series of lead(II) o-semiquinone complexes, which were prepared by the addition of the phenoxyl radical to lead catecholates or by oxidation of the latter with mercury(II), copper(II), or silver(I) halides, were studied by the ESR method. Lead(II) mono-o-semiquinolate complexes undergo symmetrization to form stable bis-o-semiquinolates, which were isolated and characterized in individual state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1103–1111, July, 2006.     

Specific features of the structure of germanium(IV) complexes with polybasic acids

The specific features revealed in the structure of germanium(IV) compounds with ligands in the form of anions of polybasic acids (monoamine, diamine, and triamine complexones, i.e., hydroxyethylidene-diphosphonic and carboxylic acids) have been considered. The influence of the individuality of specific acids on the structure type (mononuclear, binuclear, trinuclear, hexanuclear, polynuclear), the coordination mode of monodentate ligands and donor atoms of polydentate ligands (terminal, bridging, chelating, chelating-bridging), and variants of the coordination of polydentate ligands, i.e., anions of polybasic acids, with metal atoms (germanium, rare-earth elements, copper, barium), as well as on the dependence of the Ge-O bond length on the individual nature of ligands (OH, H₂O, O(oxo)) and donor atoms of polydentate ligands α- and β-O(carb), O(hydr), O(P)] and their function in the structure (terminal, bridging, chelating, chelating-bridging), has been analyzed using 28 homometallic and heterometallic complexes as an example.     

Le nitrure de germanium (IV)

Literature data on preparation and structure of germanium nitride Ge₃N₄ as well as on its thermodynamic, physical and chemical properties and applications of the material are reviewed.     

Redox reactions involving the indium(III) catecholate complexes

Indium catecholate complexes 3,6-CatInR (3,6-Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion (3,6-Q), R = Me (I) and Et (II)) are synthesized by the exchange reaction between RInI₂ and thallium catecholate 3,6-CatTl₂. Compounds I and II are trimeric in both the solution and crystalline state. The oxidation of compound I and earlier described complex [3,6-CatInI(THF)]₂ (THF is tetrahydrofuran) by various substrates (iodine, 3,6-Q, and tetramethylthiuram disulfide) is studied. Different indium(III) o-semiquinone complexes are the reaction products, depending on the reaction conditions.     

N-substituted salicylaldimines derivatives of germanium(IV)

Hexa-coordinatedSchiff base complexes of germanium of the general type Ge(OC₂H₅)₂(SB)₂ (SB^– is the anion of the monofunctional bidentateSchiff base,SBH) have been synthesized by the reaction between ethyl-orthogermanate and theSchiff base in benzene medium. Always a 12 complex is obtained irrespective of the molar ratios in which the reactants are used. The resulting new complexes have been characterized by elemental analysis, molecular weight determinations, infrared and proton magnetic resonance spectra and found to be non-electrolytes inDMF.

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N-Substitwierte Salicylaldimin-Komplexe des Germanium(IV)

Zusammenfassung Es wurden hexa-koordinierteSchiff-Basen Komplexe des Germanium(IV), vom generellen Typ Ge(OC₂H₅)₂(SB)₂ (SB ^– ist das Anion der monofunktionellen, zweizähnigenSchiff-BaseSBH), über die Reaktion von Ethylorthogermanat mit der entsprechendenSchiff-Base hergestellt. Es wurden durchwegs 12-Komplexe erhalten. Elementaranalyse, Molgewichtsbestimmung und IR- und NMR-Spektroskopie wurden zur Charakterisierung der Komplexe herangezogen.

     

Beta-nitro derivatives of germanium(IV) corrolates

The reaction between germanium(IV) meso-triphenylcorrolates and nitrate salts affords the corresponding beta-nitro substituted corroles in good yield. Chromatographic separation of the crude reaction mixtures enables isolation of a mu-oxo dimer along with the corresponding monomers bearing a hydroxy or methoxy group at an axial position of the germanium central metal ion. Depending on the reaction conditions, mono- or dinitro substituted complexes can be obtained. The substitution is highly regioselective in each case, giving only the 3-nitro or 3,17-dinitro derivative among the different possible isomers. Five of the synthesized complexes were examined by cyclic voltammetry and UV-visible spectroelectrochemistry in dichloromethane, and the dinitro mu-oxo dimer is structurally characterized.     

Novel platinum(II) and (IV) complexes of naphthaldimine schiff bases

Naphthaldimines containing N₂O₂ donor centers react with platinum(II) and (IV) chlorides to give two types of complexes depending on the valence of the platinum ion. For [Pt(II)], the ligand is neutral, [(H₂L¹)PtCl₂]·3H₂O (1) and [(H₂L³)₂Pt₂Cl₄]·5H₂O (3), or monobasic [(HL²)₂Pt₂Cl₂]·2H₂O (2) and [(HL⁴)₂Pt]·2H₂O (4). These complexes are all diamagnetic having square-planar geometry. For [Pt(IV)], the ligand is dibasic, [(L¹)Pt₂Cl₄(OH)₂]·2H₂O (5), [(L²)Pt₃Cl₁₀]·3H₂O (6), [(L³)Pt₂Cl₄(OH)₂]·C₂H₅OH (7) and [(L⁴)Pt₂Cl₆]·H₂O (8). The Pt(IV) complexes are diamagnetic and exhibit octahedral configuration around the platinum ion. The complexes were characterized by elemental analysis, UV-Vis and IR spectra, electrical conductivity and thermal analyses (DTA and TGA). The molar conductances in DMF solutions indicate that the complexes are non-ionic. The complexes were tested for their catalytic activities towards cathodic reduction of oxygen.     

Binuclear complexes of Co(III) containing extended conjugated bis(catecholate) ligands

Binuclear complexes of cobalt(III) have been prepared with 3,3',4,4'-tetrahydroxy-benzaldazine (H4thB), 3,3',4,4'-tetrahydroxy-5,5'-dimethoxybenzaldazine (H4thM), and 3,3',4,4'-tetrahydroxydimethylbenzaldazine (H4thA) as bis(catecholate) ligands that link metal ions separated by 16 A through a conjugated bridge. In one case, [Co2(bpy)4(thM)]2+, stereodynamic properties observed in solution by 1H NMR are associated with valence tautomerism, with formation of a labile hs-Co(II) species by electron transfer from the catecholate regions of the bridge. Electrochemical oxidation of the complexes occurs at the bridges as two closely spaced one-electron couples. Chemical oxidation of [Co2(bpy) 4(thB)]2+ with Ag+ is observed to occur as a two-electron process forming [Co2(bpy) 4(thB(SQ,SQ))]4+. Attempted crystallization in the presence of air was observed to result in formation of the [Co(bpy)2(BACat)]+ (H2BACat, 3,4-dihydroxybenzaldehyde) cation by aerobic oxidation. Structural characterization is provided for the H4thM ligand and [Co(bpy)2(BACat)](BF4).     

Pentamethylcyclopentadienylplatinum(IV) complexes

Reaction of dichloro(η⁴-pentamethylcyclopentadiene)platinum with bromine yields a η⁵-pentamethylcyclopentadienylplatinum(IV) complex which is formulated as [C₅Me₅PtBr₃PtC₅Me₅]Br₃.     

Synthesis and characterization of germanium (IV) and silicon (IV) complexes derived from 9-hydroxyphenalenone: X-ray crystal and molecular structure of tris-(9-oxophenalenone)-germanium (IV) and silicon (IV) salts

The germanium (IV) and silicon (IV) complexes, tris-(9-oxophenalenone)-germanium (IV) tetrakis[3,5-bis(trifluoromethyl) phenyl] borate (7⁺TFPB⁻) and tris-(9-oxophenalenone)-silicon (IV) tetrakis[3,5-bis(trifluoromethyl) phenyl] borate (8⁺TFPB⁻), derived from 9-hydroxyphenalenone have been synthesized and characterized by elemental analyses, infrared spectra and as well as by single crystal X-ray study. The crystal structure of 7⁺TFPB⁻ and 8⁺TFPB⁻ shows a one-dimensional chain like structure and π-overlap between the neighbouring phenalenyl planes. The cyclic voltammograms of 7⁺TFPB⁻ and 8⁺TFPB⁻ show three reversible one-electron reduction steps due to the formation of the radical, anion and dianion as each phenalenyl moiety accepts an electron.     

Titanocene(IV) and vanadocene(IV) complexes of dicyanomethanidobenzoate

The new titanocene and vanadocene complexes of the non-linear pseudohalides Cp₂Ti(dcmb)₂, Cp₂VCl(dcmb), (η⁵-C₅H₄Me)₂VCl(dcmb) and Cp₂V(dcmb)₂ were prepared by reaction of titanocene dichloride (Cp₂TiCl₂) and vanadocene dichlorides (Cp₂VCl₂, (η⁵-C₅H₄Me)₂VCl₂) with dicyanomethanidobenzoic acid (dcmbH, PhC(OH)C(CN)₂). These reactions have proven that the dcmb ligand could be coordinated to the central metal by oxygen or nitrogen donor atoms. The bonding mode of the dcmb ligand reflects properties of the central metal. The strongly oxophilic titanium(IV) shows the bonding through oxygen atom while bonding through nitrogen atom was observed for less oxophilic vanadium(IV). The bonding fashion of the dcmb ligands was determined by spectroscopic methods. X-ray diffraction analysis was used for the structure determination of the compounds dcmbH·H₂O, Cp₂Ti(dcmb)₂·CH₂Cl₂, (η⁵-C₅H₄Me)₂VCl(dcmb) and [Cp₂V(OC(Ph)C(CN)C(OMe)NH)][dcmb].     

Heterodimetallic germanium(IV) complex structures with transition metals

The hydrothermal synthesis and structural characterization of a number of complex compounds containing the divalent tris(oxalato-O,O')germanate anion, [Ge(C2O4)3]2-, or the neutral bis(oxalate-O,O')germanium fragment, [Ge(C2O4)2], with transition-metal (M) cationic complexes of 1,10'-phenanthroline (phen) is reported: [M(phen)3][Ge(C2O4)3].xH2O [where M2+ = Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), Co2+ (4); x = 0.2 for 2b], [MGe(phen)2(mu2-OH)2(C2O4)2] [where M2+ = Cd2+ (5) and Cu2+ (6)]. The isolation of two polymorphs with Cu2+ (1a and 1b) and other pseudo-polymorphs for Fe2+ (2a and 2b) was rationalized based on slightly different molar ratios for the starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basis of single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series of compounds was discussed on the basis of the various intermolecular interactions present (strong C-H...pi and weak C-H...O hydrogen-bonding interactions, C-H...pi and pi-pi contacts).