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THF
Terms modified by THF Selected AbstractsA Reference Electrode for Electrochemical and Cryoelectrochemical Use in Tetrahydrofuran SolventELECTROANALYSIS, Issue 21 2005Christopher Abstract We report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc+) are prepared to give a 4,mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4,mM to 40,,M and 20,°C to ,45,°C respectively. In addition, it is shown by steady,state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc+) otherwise seen in THF is suppressed by ion-pairing with PF using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte. [source] Immobilized Cytochrome c Sensor in Organic/Aqueous Media for the Characterization of Hydrophilic and Hydrophobic AntioxidantsELECTROANALYSIS, Issue 18 2003Moritz Beissenhirtz Abstract A method for the characterization of antioxidants is introduced, which allows the measurement of pure hydrophilic and hydrophobic substances as well as complex cosmetic creams. The sensor is based on cytochrome c covalently immobilized on a gold wire electrode working in mixtures of phosphate buffer and organic solvents. It is combined with a superoxide generating enzyme system. The decrease of the superoxide concentration in the test solution by the added antioxidants is detected and used for the quantification of their antioxidative efficiency. Electrochemical properties of immobilized cytochrome c, such as formal potential and heterogeneous electron transfer rate constant, have been investigated in mixtures of aqueous buffer and DMSO, methanol, butanediol, and THF. The maximum organic solvent content for quasi-reversible electrode behavior was correlated to spectroscopic measurements. The activity of the radical producing enzyme in such media was determined and the radical generation characterized. The antioxidative properties of pure substance such as ascorbic acid and Biochanin A as well as of five anti-ageing cosmetic creams were studied. This showed also the influence of matrix composition on the efficiency of antioxidative supplements. [source] Fast determination of prominent carotenoids in tomato fruits by CEC using methacrylate ester-based monolithic columnsELECTROPHORESIS, Issue 22 2007Ana Maria Adalid Abstract In this study, the major carotenoids (,-carotene and lycopene) present in tomato fruits were analyzed by CEC with a methacrylate ester-based monolithic column. The effects of the porogenic solvent ratio, and the hydrophobicity of bulk monomer employed were examined on carotenoids separations. A fast separation of these analytes was achieved in less than 5.0,min in a mobile phase containing 35% THF, 30% ACN, 30% methanol, and 5% of a 5,mM Tris aqueous buffer, pH,8, with lauryl methacrylate-based monoliths. The CEC method was evaluated in terms of detection limit and reproducibility (retention time, area, and column preparation) with values below 1.6,,g/mL and 7.2%, respectively. The proposed procedure was successfully applied to the determination of both carotenoids in fruits of several tomato-related species and its usefulness to analyze large series of samples for nutritional quality screening trials in tomato breeding programs is demonstrated. To our knowledge, this is the first work that exploits the powerful and user-friendly monolithic technology for quality breeding and germplasm evaluation program purposes. [source] Decreased cortisol production in male type 1 diabetic patientsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2003M. N. Kerstens Abstract Background It is unclear whether cortisol production and the 11,HSD-mediated cortisol to cortisone interconversion are different between type 1 diabetic patients and healthy subjects. Materials and methods Fourteen male, nonobese, normotensive type 1 diabetic patients without severe complications (HbA1c < 8·5%) were studied twice during a daily sodium intake of 50 and 200 mmol, and were then compared with 14 individually matched healthy subjects. Cortisol production was assessed by the sum of urinary cortisol metabolite excretion. Urinary ratios of (tetrahydrocortisol + allo-tetrahydrocortisol)/tetrahydro-cortisone [(THF + allo-THF)/THE] and of free cortisol/free cortisone [UFF/UFE] were determined as parameters of 11,HSD activity. Results Sum of urinary cortisol metabolite excretion during low- and high-salt diet was 7·4 ± 2·5 vs. 7·7 ± 2·3 nmol min,1 m,2 (NS) in diabetic patients and 9·7 ± 2·1 vs. 11·2 ± 4·1 nmol min,1 m,2 (NS) in healthy subjects, respectively (P < 0·05 vs. healthy subjects at both diets). The allo-THF excretion and allo-THF/THF ratios were lower in the diabetic than in the healthy males during both diets (P < 0·05). Urinary (THF + alloTHF)/THE and UFF/UFE were similar in both groups and remained unchanged after salt loading. Conclusions The sum of urinary cortisol metabolite excretion as a measure of cortisol production is lower in nonobese, normotensive type 1 diabetic males with adequate glycaemic control and without severe complications, irrespective of sodium intake. We suggest that this is at least in part as result of diminished 5, reductase activity, resulting in a decreased cortisol metabolic clearance. In type 1 diabetic and in healthy males, the 11,HSD setpoint is not affected by physiological variations in sodium intake. [source] 11b-hydroxysteroid dehydrogenase activity in proteinuric patients and the effect of angiotensin-II receptor blockadeEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 7 2002M. N. Kerstens Abstract Background It has been suggested that an altered setpoint of the 11,HSD-mediated cortisol to cortisone interconversion towards cortisol contributes to sodium retention in nephrotic syndrome patients. We studied the parameters of 11,HSD activity in proteinuric patients, in particular its activity at the kidney level. We also studied the effect of angiotensin-II receptor blockade on the parameters of 11,HSD activity. Materials and methods Serum cortisol/cortisone ratio and the urinary ratios of (tetrahydrocortisol + allo-tetrahydrocortisol)/tetrahydrocortisone [(THF + allo-THF)/THE] and of urinary free cortisol/free cortisone (UFF/UFE) were measured in eight proteinuric patients and compared with eight matched, healthy subjects. Patients were subsequently studied after 4 weeks' treatment with losartan 50 mg day,1 and placebo, respectively. Results No significant differences between the proteinuric patients and the healthy subjects were observed in the serum cortisol, serum cortisone, serum cortisol to cortisone ratio, or in the urinary excretions of THF, allo-THF, THE, sum of cortisol metabolites, or the (THF + allo-THF)/THE ratio. Urinary free cortisol excretion and the UFF/UFE ratio were lower in the proteinuric patients than in the healthy subjects (56 ± 21 vs. 85 ± 24 pmol min,1, P < 0·05, and 0·39 ± 0·07 vs. 0·63 ± 0·28, P < 0·05, respectively). Mean arterial pressure and proteinuria were reduced significantly during losartan treatment, but without concomitant changes in peripheral cortisol metabolism. Conclusions Increased renal inactivation of cortisol in proteinuric patients does not support the contention that altered 11,HSD activity contributes to sodium retention in patients with nephrotic syndrome. Losartan 50 mg d.d. reduces mean arterial pressure and proteinuria, but does not exert a significant effect on the cortisol to cortisone interconversion. [source] Ketiminate-Supported LiCl Cages and Group 13 ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2010Audra F. Lugo (née Gushwa) Abstract The coordination preferences of the ketiminato ligands L1H, {[RN(H)(C(Me))2C(Me)=O], R = 2,6-diisopropylphenyl (Dipp) or 2,6-dimethylphenyl (Dmp)} and L2H {[RN(H)C(Me)CHC(Me)=O], R = C2H4NEt2} with group 13 elements were investigated. The expected N,O -chelated products [DmpL1BF2] (1), [L2Al(Me)Cl] (2A and 2B), and [L2InMe2] (6), were obtained from reactions with BF3·OEt2, AlMe2Cl and InMe3 respectively, but the reaction of DippL1 with GaCl3 afforded a metal-halide, neutral ligand adduct, [GaCl3·DippL1H] (3). More interestingly the reactions of DippL1 with InMe3, formed in situ from InCl3 and MeLi, led to the isolation of two ketiminate-supported LiCl cages[InMe2Li7Cl5(DippL1,)2(DippL1)(THF)3] (4) and [Li5(Cl)(DippL1)4]·2PhMe (5). The lithium cage 4 features reaction of InMe3 with one backbone methyl group from each of two DippL1 ligands, to afford a tetraalkylindate moiety in the framework of two doubly deprotonated ligands (L,). [source] Electron-Sponge Behavior, Reactivity and Electronic Structures of Cobalt-Centered Cubic Co9Te6(CO)8 ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008Mustapha Bencharif Abstract Extended investigations of the reaction sequence [Cp,2Nb(Te2)H]/CH3Li/[Co2(CO)8] (Cp, = tBuC5H4) led to the identification of Lin[3] {3 = [Co9Te6(CO)8]; n = 1, 2} salts through their transformation with [PPN]Cl into [PPN]n[3] (PPN = Ph3PNPPh3). These compounds form in the solid state columnar ([PPN][3]) or undulated 2D ([PPN]2[3]) supramolecular networks. Electrochemical studies of [Cp*2Nb(CO)2][3] (Cp* = C5Me5) or [Na(THF)6][3] revealed the presence of the redox couples [3],/[3]2,/[3]3,/[3]4,/[3]5, regardless of the nature of the cation, whereas in the anodic part oxidative degradation of the cluster takes place. This behavior is in agreement with the observation that [3], containing salts form with PPh3AuCl or dppe decomposition products like [(PPh3)2Au][CoCl3PPh3] or [Co(CO)2dppe]2(,-Te). A neutral cluster comprising the Co@Co8(,4 -Te)6 core formed in the reaction of [Cp*2Nb(CO)2][Co11Te7(CO)10] with PPh3AuCl, which gave [Co9Te6(CO)4(PPh3)4] (4) after oxidative cluster degradation and CO substitution. 4 was characterized by X-ray crystallography. DFT calculations carried out on all members of the [3]n (n = +1 to ,5) family and on related species indicate that there is no significant Jahn,Teller distortion (and therefore no connectivity change) for any of the considered electron counts. Magnetic investigations on [PPN][3] show that the ground state of [3], is a spin triplet with spins interacting antiferromagnetically in a 1D space.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis and Reactions of Polynuclear Polyhydrido Rare Earth Metal Complexes Containing "(C5Me4SiMe3)LnH2" Units: A New Frontier in Rare Earth Metal Hydride ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Zhaomin Hou Abstract A series of tetranuclear octahydrido rare earth metal complexes of general formula [(C5Me4SiMe3)Ln(,-H)2]4(THF)n (Ln = Sc, Y, Gd, Dy, Ho, Er, Tm, Lu; n = 0, 1, or 2) that contain C5Me4SiMe3 as an ancillary ligand have been prepared and structurally characterized. These hydride clusters are soluble in common organic solvents such as THF, toluene, and hexane, and maintain their tetranuclear framework in solution. Such polynuclear polyhydrido complexes exhibit extremely high and unique reactivity toward a variety of unsaturated substrates including CO, CO2, and nitriles. The reaction of these neutral polyhydrides with one equivalent of [Ph3C][B(C6F5)4] affords the corresponding cationic hydride clusters [(C5Me4SiMe3)4Ln4H7(THF)n][B(C6F5)4], which can act as catalysts for the syndiospecific polymerization of styrene and regio- and stereospecific cis -1,4-polymerization of 1,3-cyclohexadiene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Trinuclear Aqua Cyano-Bridged Ruthenium Complex [{(,5 -C5H5)(PPh3)2Ru(,-CN)}2RuCl2(PPh3)(H2O)]PF6: Synthesis, Characterization and Crystal StructureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Viatcheslav Vertlib Abstract The organometallic trinuclear aqua cyano-bridged complex [{(,5 -C5H5)(PPh3)2Ru(,-CN)}2RuCl2(PPh3)(H2O)]PF6 (1), in which the fragment [RuCl2(PPh3)(H2O)] acts as a bridge and an acceptor group between the two terminal cyclopentadienyl ruthenium cyano moieties, was isolated in moderate yield from the reaction of [(,5 -C5H5)(PPh3)2RuCN] with [RuCl2(PPh3)3] in THF. To the best of our knowledge, compound 1 is one of the few examples of a trinuclear array of ruthenium fragments bridged by the nitrogen atom of the,C,N, group (Ru,C,N,Ru,,N,C,Ru) with a Ru-coordinated water molecule. The new aqua complex was structurally characterized by FTIR, 1H, 13C, and 31P NMR spectroscopy, mass spectrometry, elemental analysis, single-crystal X-ray diffraction, and cyclic voltammetry. The title complex crystallizes in a triclinic unit cell a = 17.3477(6) Å, b = 17.8551(5) Å, c = 18.2460(7) Å, , = 95.693(2)°, , = 111.648(2)°, and , = 97.839(2)° in the space group P with Z = 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Cationic Brønsted Acids for the Preparation of SnIV Salts: Synthesis and Characterisation of [Ph3Sn(OEt2)][H2N{B(C6F5)3}2],[Sn(NMe2)3(HNMe2)2][B(C6F5)4] and [Me3Sn(HNMe2)2][B(C6F5)4]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2006Yann Sarazin Abstract Ph3SnN(SiMe3)2 (1) was prepared in good yields by reaction of [{NaN(SiMe3)2}2·THF] (2) with Ph3SnF. Treatment of 1 with [H(OEt2)2][H2N{B(C6F5)3}2] (4) in dichloromethane afforded the stannylium cation [Ph3Sn(OEt2)][H2N{B(C6F5)3}2] (5), which was characterised by 1H, 13C{1H}, 11B, 19F and 119Sn NMR spectroscopy. The reaction of Sn(NMe2)4 with [Ph2MeNH][B(C6F5)4] (3) gave the amidotin(IV) compound [Sn(NMe2)3(HNMe2)2][B(C6F5)4] (6) which proved very stable towards ligand substitution and resisted treatment with Et2O, THF, TMEDA and pyrazine. Two new Brønsted acid salts [H(NMe2H)2][B(C6F5)4] (7) and [(C4H4N2)H·OEt2][H2N{B(C6F5)3}2] (8) were synthesised. The reaction of 7 with Sn(NMe2)4 in Et2O allowed the preparation of 6 in a much improved yield (83,%). The treatment of 7 with Me3SnN(SiMe3)2 in Et2O yielded [Me3Sn(HNMe2)2][B(C6F5)4] (9) nearly quantitatively. Compounds 1, 2, 6, 8 and 9 were characterised by single-crystal X-ray diffraction analyses; 6 is the first example of a structurally characterised amidotin(IV)cation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] The First Metal-Oxo Cluster Containing Lithium and BismuthEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Michael Mehring Abstract The reaction of [Bi(OtBu)3] with LiOSiMe3 gave the heterobimetallic bismuth-oxo cluster [Bi3Li5(,5 -O)2(,3 -OSiMe3)2(,3 -OtBu)2(,2 -OtBu)6] (1) after elimination of Me3SiOSiMe3. The cage compound 1 is the first example of a mixed-metal alkoxide/siloxide composed of lithium and bismuth. Crystals of 1·2 C7H8 and 1·1.5 THF suitable for X-ray single crystal structure analysis were obtained by crystallisation from toluene and THF, respectively. Both solvates crystallise in the orthorhombic space group Pmmn with Z = 2. The lattice constants are a = 16.267(3) Å, b = 17.126(3) Å and c = 12.155(2) Å (1·2 C7H8) and a = 16.353(2) Å, b = 17.156(1) Å and c = 12.256(1) Å (1·1.5 THF). In both compounds the solvent molecules occupy channels along the c -axis. The basic molecular unit is best described as a face-sharing double cubane [BiLi5(,4 -O)2(,3 -OSiMe3)2(,3 -OtBu)2] which is coordinated by two [Bi(OtBu)3] molecules. The compound is kinetically labile in solution and readily decomposes in 1,1,2,2-tetrachloroethane with elimination of 1,1,2-trichloroethylene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Single-Electron-Transfer Reactions of ,-Diimine dpp-BIAN and Its Magnesium Complex (dpp-BIAN)2,Mg2+(THF)3EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Igor L. Fedushkin Abstract The reactions of (dpp-BIAN)Mg(THF)3 (1) {dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene} with ethyl halides EtX (X = Cl, Br, I) in hexane proceed by single-electron transfer (SET) from the metal complex to the organic halide. Complexes [(dpp-BIAN)(Et)]MgX(THF)n [X = Cl, n = 0 (2); X = Br, n = 2 (3); X = I, n = 1 (4)] are the products of ethyl transfer to an imine carbon atom of a coordinated diimine ligand. The compound [(dpp-BIAN)(Et)]MgBr (3a) was obtained from the reaction of free dpp-BIAN with ethylmagnesiumbromide in hexane. In this case SET from the Grignard reagent to the neutral diimine takes place. Compounds 2,4 and 3a were isolated as crystals and characterized by 1H NMR spectroscopy. The molecular structure of 3 was determined by single-crystal X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Chelate [2-(Iminoethyl)pyridine N -oxide]metal Complexes , Synthesis and Structural Comparison with Their Chemically Related 2-(Iminoethyl)pyridine-Derived SystemsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006Katrin Nienkemper Abstract The N,O-chelate ligands 2-(iminoethyl)pyridine N -oxide (2a) and 2-(iminoethyl)-6-isopropylpyridine N -oxide (2b) were prepared by conventional synthetic routes, the latter involving a variant of the Reissert,Henze reaction. Treatment of 2a with FeCl2 resulted in a deoxygenation reaction of the ligand and formation of the salt [bis{2-(iminoethyl)pyridine}FeCl]+[FeCl4], (18a). In contrast, the reaction of 2a with PdCl2 or CoCl2 cleanly furnished the six-membered chelate [,N,O -2(iminoethyl)pyridine N -oxide]MCl2 complexes (19a, M = Pd) or (20a, M = Co), respectively, which were both characterised by X-ray diffraction. Treatment of 2b with [NiBr2(dme)], followed by crystallisation from THF, gave the complex [(,N,O - 2b)NiBr2(THF)] (21b), which features a distorted trigonal-bipyramidal coordination geometry of the central metal atom. The reaction of 2a with [NiBr2(dme)] gave the structurally related complex [(,N,O - 2a)NiBr2(,O - 2a)] (21a). The N,O-chelate Pd complex 19a was shown to be an active catalyst for the Suzuki coupling reaction. The ligand systems 2a,b and their related 2-(iminoethyl)pyridines 3a,b and a variety of metal complexes of ligands 3 were also prepared and characterised for comparison by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Structural Relationships in High-Nuclearity Heterobimetallic Bismuth-Oxo ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Michael Mehring Abstract The novel heterobimetallic sodium-bismuth-oxo clusters [Bi2Na4O(OSiMe3)8] (1), [Bi10Na5O7(OH)6(OSiMe3)15]·1.5C7H8 (2·1.5C7H8), [Bi15Na3O18(OSiMe3)12]·C7H8 (3·C7H8) and [Bi14Na8O18(OSiMe3)14(THF)4]·C6H6 (4·C6H6) were prepared starting from BiCl3 and NaOSiMe3. Compound 1 crystallises in the trigonal space group Rc with the lattice constants a = 12.8844(3) Å and c = 54.6565(3) Å, compound 2·1.5C7H8 crystallises in the triclinic space group P with the lattice constants a = 15.0377(2) Å, b = 16.0373(2) Å, c = 27.8967(5) Å, , = 87.1321(6)°, , = 86.6530(7)° and , = 63.6617(6)°, compound 3·C7H8 crystallises in the monoclinic space group C2/c with the lattice constants a = 54.311(11), b = 19.846(4), c = 22.885(5) Å and , = 112.32(3)°, and compound 4·C6H6 crystallises in the trigonal space group R with the lattice constants a = 15.9786(4) Å and c = 46.8329(17) Å. The formation of M,O,M bonds results from both partial hydrolysis followed by condensation as well as from elimination of Me3SiOSiMe3 from M,OSiMe3 groups. The hexanuclear metal-oxo silanolate 1 is more conveniently synthesised by the addition of NaOSiMe3 to a toluene solution of in situ-prepared [Bi(OSiMe3)3]. The metal-oxo(hydroxo) silanolates differ significantly in composition, but show similar building units. Thermal decomposition of the metal-oxo silanolates in the solid state gave heterogeneous decomposition products containing bismuth silicates. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Generation and Reactions of Overcrowded Diaryldilithiostannane and DiaryldipotassiostannaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2005Tomoyuki Tajima Abstract Exhaustive reduction of an overcrowded dibromostannane bearing two bulky aromatic substituents, Tbt(Dip)SnBr2 {Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl; Dip = 2,6-diisopropylphenyl}, with an excess amount of lithium naphthalenide in THF at ,78 °C gave the corresponding dilithiostannane, Tbt(Dip)SnLi2, the generation of which was confirmed by trapping experiments with some electrophiles together with 119Sn and 7Li NMR spectroscopy. The diaryldilithiostannane was found to be stable in solution under an inert gas below ,25 °C. The potassium analogue, Tbt(Dip)SnK2, was also generated by the reduction of the dibromostannane in THF at ,78 °C by the use of KC8 as a reductant. The reactions of dilithiostannane and dipotassiostannane obtained with o -dibromobenzene did not give a stannacyclopropabenzene derivative but an unexpected cyclization product, a stannacyclobutabenzene derivative, in contrast to thereactions of the corresponding dilithiosilane and dilithiogermane, Tbt(Dip)ELi2 (E = Si, Ge), with o -dibromobenzene leading to the formation of the corresponding metallacyclopropabenzenes as stable crystalline compounds. A preliminary result of the synthesis of a tin,tellurium double-bond compound from the dilithiostannane is also presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Nitrate- and Nitrite-Assisted Conversion of an Acetonitrile Ligand Into an Amidato Bridge at an {Mo2(Cp)2(,-SMe)3} Core: Electrochemistry of the Amidato Complex [Mo2(Cp)2(,-SMe)3{,-,1,,1 -OC(Me)NH}]+EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2005Marc Le Hénanf Abstract Treatment of [Mo2(Cp)2(,-SMe)3(MeCN)2]+ (1+) with NO3, or NO2, results in the conversion of one terminally bound acetonitrile ligand into an amidato bridge. The reaction produces [Mo2(Cp)2(,-SMe)3{,-,1,,1 -OC(Me)NH}]0/+ (20/+) and involves the formation of an intermediate, which was detected by cyclic voltammetry but which could not be isolated, and which likely arises from the substitution of the NOx anion for one MeCN ligand. The electrochemical behaviour of 2+ was studied by cyclic voltammetry in THF and MeCN. The reduction of 2+ in the presence of acid (HBF4/H2O or HBF4/Et2O) in these solvents leads to the release of the amidate bridge. Controlled-potential electrolysis of 2+ in MeCN in the presence of acid produces 1+ quantitatively; the charge consumed (>1 F,mol,1 of 1+) indicates that electrons are also used to reduce protons. This was confirmed by the formation of 2+ (in variable amounts depending on the conditions) on treating 2 with acid. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Solvent-Mediated Redox Transformations of Ytterbium Bis(indenyl)diazabutadiene ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2005Alexander A. Trifonov Abstract The reactions of diamagnetic [(C9H7)2Yb(THF)2] (2) and [rac -(CH2 -1-C9H6)2Yb(THF)2] (3) with tBuN=CH,CH=NtBu (DAD) in toluene result in the formation of the paramagnetic complexes [(C9H7)2Yb(DAD)] (4) and [rac- (CH2 -1-C9H6)2Yb(DAD)] (5), respectively. The IR, UV/Vis, and 1H NMR spectroscopic data, the magnetic properties, and the single-crystal X-ray diffraction studies of 4 and 5 indicate that in the solid state and in noncoordinating media both complexes are ytterbium(III) derivatives containing the DAD radical-anion, whereas the 1H NMR and UV/Vis spectra of solutions of 4 and 5 in the coordinating solvent THF give evidence for divalent ytterbium. Recrystallization of 4 and 5 from THF/hexane results in the recovery of the starting ytterbium complexes 2 and 3 due to an unusual redox substitution of the radical anion of diazabutadiene by THF in the coordination sphere of ytterbium. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Preparation and Coordination Chemistry of n -AllylaminophosphaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2005Alexandra M. Z. Slawin Abstract Reaction of allylamine with 1 equiv. of Ph2PCl in the presence of NEt3, proceeds in THF to give (allylamino)phosphane 1. 1 has been coordinated as a monodentate P ligand with Au, Pd, Pt, Ru, Rh, Ir and as a bidentate P,allyl ligand to Pt. Reaction of KOtBu with [PtCl2{Ph2PNH(C3H5)}2] in methanol gives [Pt{Ph2PNH(C3H8O)}2]. The X-ray structures of 1.Se and four demonstrative monodentate complexes all reveal intramolecular N,H···Cl hydrogen bonding. The structure of [Pt{Ph2PNH(C3H8O)}2] consists of an N,H···O hydrogen-bonded dimer in the solid state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Diastereomeric Halfsandwich Rhenium Complexes Containing Hemilabile Phosphane LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Stefan Dilsky Abstract The syntheses and some typical reactions of diastereomeric rhenium complexes [CpRe(NO)(CO){P(Ph)(R)(R,)}]BF4 (R = Me, Ph; R, = 2-C6H4OMe, CH2C4H3S, CH2C4H7O) (3a,e) are described. Reduction of the carbonyl ligand with NaBH4 in THF gave the corresponding methyl complexes [CpRe(NO){P(Ph)(R)(R,)}(CH3)] (4a,e). Acid treatment of the methyl complexes leads to liberation of methane and coordination of the additional donor site of the potentially bidentate phosphane ligand. Of the chelate complexes 5a,e, those with R, = 2-C6H4OMe (5a, d) decomposed in solution at room temperature. In donor solvents, the chelate ring opens giving the stable solvated complexes [CpRe(NO){P(Ph)(R)(R,)}](solvent)]BF4 (solvent = CH3CN, THF) (6b,e, 7d). The new compounds are thus suitable starting materials for the syntheses of diastereomeric rhenium complexes [CpRe(NO){P(Ph)(R)(R,)}(L)]BF4. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis of (Vinylidene)- and (Cyclopropenyl)ruthenium Complexes Containing a Tris(pyrazolyl)borato (Tp) LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004Yih-Hsing Lo Abstract A convenient high-yield route to [Ru(C,C,Ph)(Tp)(PPh3)2] [2; Tp = HB(pz)3, pz = pyrazolyl] has been found through the intermediacy of [RuCl2(Hpz)2(PPh3)2] (1). This complex is readily obtained on treatment of [RuCl2(PPh3)3] with 2 equiv. of pyrazole in boiling THF. The molecular structures of complexes 1 and 2 have been confirmed by single-crystal X-ray diffraction analysis. A number of new cationic vinylidene complexes [Ru{=C=C(Ph)CH2R}(Tp)(PPh3)2]+ [3a, R = CN; 3b, R = HC=CH2; 3c, R = CH=C(CH3)2; 3d, R = Ph; 3e, R = C(O)OMe] have been prepared by electrophilic addition of organic halides to complex 2. The deprotonation reaction of 3a yields the cyclopropenyl complex 4a. One phosphane ligand of 4a is remarkably labile, being replaced by donor ligands L to yield diastereomeric mixtures of the cyclopropenyl complexes 5a,5d mostly in an approximate 4:1 ratio. The cyclopropenyl rings in 4a and 5a are susceptible to ring opening by I2. In addition, treatment of 4a with nBuNC in the presence of MeOH results in substitution of a phosphane ligand by nBuNC followed by protonation of the three-membered ring by MeOH. This is then followed by addition of methoxide to give the vinyl ether complex [Ru{C(OMe)=C(Ph)CH2CN}(Tp)(PPh3)(nBuNC)] (8a). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Binary Neodymium Alkoxide/Dialkylmagnesium Polymerization Systems: Studies on the Nature of the Reaction Intermediates and Active SpeciesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2004Jérôme Gromada Abstract Attempts to identify the intermediates and/or active species generated from binary combinations of a lanthanide alk(aryl)oxide with a dialkylmagnesium reagent, which behave as efficient olefin polymerization systems, are reported. The well-defined trinuclear complex [Nd3(,3 -OtBu)2(,2 -OtBu)3(,-OtBu)4(THF)2] (1) and the monomeric precursor [Nd(OC6H2tBu2 -2,6-Me-4)3(THF)] (2) were used in association with [Mg(CH2SiMe3)2(Et2O)] (3). The new heterodimetallic complex [(THF)Nd(,3 -OtBu)2(,2 -OtBu)2(OtBu)Mg2(CH2TMS)2] (4) and the alkyllanthanide complex [Nd(OC6H2tBu2 -2,6-Me-4)2(CH2SiMe3)(THF)2] (5) have been isolated and characterized in the solid state and in solution. Complex 4 is proposed to be a reaction intermediate in the active species formation, while complex 5 is the first alkyllanthanide species isolated from an "Ln(OR)3"/MgR2 mixture, consistent with the observed behavior of these combinations in olefin polymerization. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Characterization of Cubane-Like Cr4E4 (E = S, Se) Clusters , Molecular Structures of (,5 -RC5H4)4Cr4E4 (E = S, R = MeCO, MeO2C, EtO2C; E = Se, R = H)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2004Li-Cheng Song Abstract Treatment of the Cr,Cr singly-bonded dimers [,5 -RC5H4Cr(CO)3]2 (1, R = MeCO; 2, R = MeO2C; 3, R = EtO2C) with excess sulfur in refluxing THF gave the cubane Cr4S4 clusters (,5 -RC5H4)4Cr4S4 (4, R = MeCO; 5, R = MeO2C; 6, R = EtO2C). The cubane Cr4S4 cluster 4 reacted with excess 2,4-dinitrophenylhydrazine to produce the hydrazone derivative [,5,2,4-(NO2)2C6H3NHN=C(Me)C5H4]4Cr4S4 (7). The singly-bonded dimers of [,5 -RC5H4Cr(CO)3]2 (8, R = Me; 9, R = EtO2C), in the presence of excess selenium, reacted similarly to the linear Cr2Se complexes [,5 -RC5H4Cr(CO)2]2Se (10, R = Me; 11, R = EtO2C), which reacted with an equimolar quantity of selenium to afford the cubane Cr4Se4 clusters (,5 -RC5H4)4Cr4Se4 (12, R = Me; 13, R = EtO2C). A particularly interesting phenomenon is the cross-assembled reaction of the linear Cr2Se complexes [,5 -MeC(O)C5H4Cr(CO)2]2Se (14) and [CpCr(CO)2]2Se (15) in the presence of excess selenium in THF that gave rise to a series of cubane Cr4Se4 clusters [,5 -MeC(O)C5H4]nCp4,nCr4Se4 (16, n = 0; 17, n = 1; 18, n = 2; 19, n = 3; 20, n = 4). The possible pathway for the cross-assembled reaction is suggested. Furthermore the new clusters were characterized by elemental analysis and spectroscopy, and in the case of 4,6 and 16 also by X-ray diffraction techniques. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Neutral and Cationic Methylaluminium Complexes of 2-Anilinotropone Ligands: Synthesis, Characterization, and Reactivity toward EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2004Daniela Pappalardo Abstract Some new aluminium complexes bearing bidentate monoanionic 2-anilinotroponate ligands have been synthesized and characterized. Reaction of 2-(2,6-diisopropylanilino)tropone or 2-(perfluoroanilino)tropone with AlMe3 (1 equiv.) gave, by methane elimination, compounds [2-(2,6-diisopropylanilino)tropone]AlMe2 (1) and [2-(perfluoroanilino)tropone]AlMe2 (2), respectively, as yellow solids. Reaction of 1 with 1 equiv. of the ligand furnished, by protodealumination of a second Al,CH3 bond, the [2-(2,6-diisopropylanilino)tropone]2AlMe derivative 3. The structure of 3 has been determined by single-crystal X-ray diffraction, showing a five-coordinate aluminium atom with a distorted trigonal-bipyramidal geometry. Compounds 1 and 3 underwent methyl abstraction reactions with B(C6F5)3; the resulting cationic species was trapped in the presence of THF in dichloromethane solution. The reactivity of the synthesized compounds in ethylene polymerisation has also been explored. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Dinuclear Potassium-Chromium and Potassium-Tungsten Carbonyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Vladimir Kirin Abstract The tetracarbonyl complexes [M(CO)4{,2 -(Ph2P)2NH}] [M = Cr (1a), W (1b)] have been synthesised by reaction of M(CO)6, Me3NO·2H2O, and (Ph2P)2NH. Subsequent treatment of complexes 1a,b with an excess of KH in THF at room temperature yields the potassium salts [Cr(CO)4{,2 -(Ph2P)2N}K(THF)3]n (2a) and [W(CO)4{,2 -(Ph2P)2N}K(THF)2]n (2b), respectively, in almost quantitative yields. The ionic compounds 2a,b are stable at room temperature. All four compounds 1a,b and 2a,b were characterised by single-crystal X-ray diffraction. Compounds 2a,b form infinite chains via isocarbonyl bridges in the solid state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Sodium Hydro(isothiocyanato)borates: Synthesis and StructuresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2004Heinrich Nöth Abstract Sodium thiocyanate reacts in THF solution with 18-crown-6 to give the molecular compound Na(18-crown-6)(THF)NCS (3) with the N atom of the NCS anion oriented towards Na+. The same reaction with 15-crown-5 yields the ion pair Na(15-crown-5)NCS (4). In contrast, Na(NCS)(py)4, obtained by treating a solution of Na(H3BNCS) in THF with pyridine, yields Na(py)4(NCS) (5), which has a chain structure with hexacoordinate Na atoms coordinated to five N atoms and an S atom. Na(NCS) in THF adds 1 equiv. of BH3 to give Na(H3BNCS)·nTHF. Addition of 18-crown-6 to this solution yields crystals of the salt [Na(18-crown-6)(THF)2][H3BNCS] (1), as shown by X-ray crystallography. Both the cation and the anion show site disorder. However, when 15-crown-5 is used for complexation, the salt [Na(15-crown-5)(THF)][H3BNCS] (2) can be isolated. Its anion shows an almost linear B,N,C,S unit. Only a mixture of (catecholato)(isothiocyanato)borates results on treating Na(NCS) in THF with catecholborane. However, the borate Na[catB(NCS)2] is readily formed by adding Na(NCS) to B -(isothiocyanato)catecholborane. Single crystals of this compound were obtained as the salt [Na(18-crown-6)(THF)2][catB(NCS)2] (6). On the other hand, the reaction of Na(NCS) with 9-borabicyclo[3.3.1]nonane (9-BBN) in THF yields Na[(9-BBN)NCS)]·nTHF, and, on addition of 18-crown-6, the complex [Na(18-crown-6)(THF)2][(9-BBN)NCS] was isolated. Suitable crystals for X-ray structure determination were, however, only obtained by crystallization from tetrahydropyran. This solvate has the rather unusual structure [Na(18-crown-6)(thp)2][{(9-BBN)NCS}2Na(thp)4] (8). The sodiate anion has an Na atom coordinated by two S and four O atoms. DFT calculations support these experimental results: The (isothiocyanato)borates are more stable than the thiocyanato isomers. For the latter a bent structure of the B,S,C,N unit with a B,S,C bond angle of 105.7° is predicted. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Reaction of MnII Iodides Bearing the ,-Diketiminate Ligand: the First Divalent Manganese N-Heterocyclic Carbene Complexes [{HC(CMeNAr)2}MnI{C[N(iPr)CMe]2}] and [{HC(CMeNAr)2}MnNHAr{C[N(iPr)CMe]2}] (Ar = 2,6- iPr2C6H3)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2003Jianfang Chai Abstract The manganese mono-iodide [HC(CMeNAr)2]MnI(THF) (Ar = 2,6- iPr2C6H3) (3) was prepared in good yield from the reaction of [HC(CMeNAr)2]K with MnI2 in THF. Treatment of 3 under reflux in toluene and removing all the volatiles in vacuo afforded the dimeric compound [{HC(CMeNAr)2}Mn]2(,-I)2 (4). Displacement of the coordinated THF in 3 by a strong Lewis base C[N(iPr)CMe]2 or by adding C[N(iPr)CMe]2 to the toluene solution of 4 readily gave the N-heterocyclic carbene adduct [{HC(CMeNAr)2}]MnI{C[N(iPr)CMe]2} (5). Reduction of 5 with sodium/potassium alloy at room temperature unexpectedly resulted in the formation of the monomeric compound [{HC(CMeNAr)2}]MnNHAr{C[N(iPr)CMe]2} (6). Alternatively 6 was obtained by the salt elimination reaction of 5 with LiNHAr. Compounds 5 and 6 are the first examples of divalent manganese N-heterocyclic carbene adducts and the first manganese non-carbonyl carbene complexes. The single crystal X-ray structural analyses reveal that compounds 3 and 6 are monomeric and compound 4 is dimeric in the solid state. The manganese centers in these compounds exhibit a distorted tetrahedral geometry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] The First Structurally Characterized DiorganoaluminateEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2003Colin Eaborn Abstract The first structurally characterized dialkylaluminate [{Li(THF)}(AltBu{C(SiMe3)3}H2)]2 (3) is dimeric in the solid state with [Li(THF)]+ and [AltBu{C(SiMe3)3}H2], fragments linked by Li···H,Al bridges. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Structural Studies of Lithium Telluro- and Seleno-Phosphorus CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2003Robert P. Davies Abstract Lithium tellurophosphinite [Ph2PTe][Li(TMEDA)1.33(THF)1.33] (4), ditellurophosphinate, [Ph2PTe2][Li(THF)3.5(TMEDA)0.25] (5), and selenotellurophosphinate [Ph2P(Se)Te][Li(THF)2(TMEDA)] (6) complexes have been prepared from the insertion/oxidation reactions of lithiated secondary phosphanes with elemental chalcogens and characterised by X-ray crystallography. Compounds 4,6 contain no tellurium,lithium bonding interactions in the solid state, instead existing as ion-separated species with THF/TMEDA-solvated lithium cations. Reaction of dilithiated primary phosphanes with more than three equivalents of elemental selenium gives [{(c -C6H11)P(Se)(SeLi)}2·2TMEDA] (7) via a phosphorus-phosphorus coupling reaction. Solid state characterisation of 7 reveals the organo groups in the tetradentate tetraselenohypodisphosphinate ligand to be in an anti conformation to one another and each lithium atom to be coordinated by two selenium atoms, one from each of the diselenophosphinate groups. Multinuclear NMR spectroscopic data are consistent with retention of the solid-state structures of 4,7 in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Regiospecific Cyclometalation of Diphenyl(2-substituted phenyl)phosphane with Methyltetrakis(trimethylphosphane)cobalt(I)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2003Hans-Friedrich Klein Abstract The pre-chelate molecules 2-(diphenylphosphanyl)- N,N -dimethylaniline, [2-(diphenylphosphanyl)benzyl]dimethylamine, 1-(diphenylphosphanyl)-2-ethylbenzene, 1-(diphenylphosphanyl)-2-isopropylbenzene, and 2-(diphenylphosphanyl)benzonitrile, in a reaction with [CoMe(PMe3)4], eliminate methane to afford the selectively 6- ortho -metalated complexes 1,5 that contain four-membered metallacycles. The molecular structure of 3 shows a tbp-coordinated cobalt atom, with axial C and PMe3 donor groups. Metalation in the aliphatic side-chain occurs with 2-(diphenylphosphanyl)toluene, giving complex 6 that contains a five-membered metallacycle. Benzyldiphenylphosphane is selectively ortho -metalated in the benzyl group, affording 7. As shown by the molecular structures, complex 7 is a true ligand isomer of 6. Substitution of a trimethylphosphane group in compounds 4 and 6 by ethene gives the pentacoordinate complexes 8 and 9, respectively. The ethene ligand is ,-coordinated in the equatorial plane of a trigonal bipyramid. Under 1 bar of CO, complex 6 forms monocarbonyl complex 10. Carbonylation of complexes 3 and 4 proceeds by insertion of CO into the Co,C bond under ring expansion, affording the aroylcobalt complexes 11 and 12, respectively. Complex 6 reacts with iodomethane in an oxidative substitution reaction yielding a structurally characterized octahedral complex mer - 13, which eliminates a methyl group in THF at 20 °C to form a pentacoordinate cobalt(II) complex 14. Complex 3 oxidatively adds iodomethane in a stereoselective cis addition to give the cobalt(III) complex mer - 15, which retains its four-membered metallacycle and the CoCH3 group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Enantioselective CpRu-Catalyzed Carroll Rearrangement , Ligand and Metal Source ImportanceEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008David Linder Abstract The addition of unstabilized carbonyl nucleophiles to unsymmetrical allyl-metal fragments still represents a challenge to generate stereogenic centers enantio- and regioselectively. In this context, the decarboxylative Carroll rearrangement of allyl ,-keto esters is particularly interesting, since chiral ,,,-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, with selected enantiopure pyridine-monooxazoline ligands, catalyze this transformation and afford complete conversions along with good levels of regioselectivity and enantioselectivity. Even more challenging (electron-poor) substrates react (up to 86,% ee, branched/linear ratio , 97:03). In addition, the use of an air-stable metal precursor, namely [CpRu(,6 -naphthalene)][PF6], allows the reaction to be carried out reproducibly evenin non-anhydrous THF with a catalyst loading as low as2 mol-%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | |||||||||||||||||||||||||||||||||||||