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Multinuclear NMR Spectroscopy (multinuclear + nmr_spectroscopy)
Selected AbstractsSolid-State Structure and Tautomerism of 2-Aminotroponimines Studied by X-ray Crystallography and Multinuclear NMR SpectroscopyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2004Rosa M. Claramunt Abstract Structural studies in the solid state by X-ray crystallography and by 13C and 15N CPMAS NMR spectroscopy carried out on a series of 2-aminotroponimine derivatives 2,5 has allowed to establish the existence of hydrogen bonding and to determine the most stable tautomer. Almost all the structures reflect the classical double-well potential function for the N,H···N hydrogen bonds. Only in the case of the compound N -(pyrrol-1-yl)-2-(pyrrol-1-ylamino)troponimine (5) the crystal structure shows two independent molecules, one with a classical hydrogen bond and another with either a single-well or a low-barrier hydrogen bond. The structure of this compound is discussed with the use of the solid-state NMR spectroscopic data. 2-Aminotropones, as intermediates to the 2-aminotroponimines, show the oxo-tautomer as the stable form. B3LYP/6-31G* calculations are used to rationalise the experimental results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Boron,Nitrogen Adducts of 1,3,5-Triaza-7-phosphaadamantane (PTA): Synthesis, Reactivity, and Molecular StructureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006Brian J. Frost Abstract Addition of BH3 to 1,3,5-triaza-7-phosphaadamantane (PTA) leads to the formation of the first coordination complex of PTA in which a nitrogen and not the phosphorus of PTA is involved in the bonding. Multinuclear NMR spectroscopy, X-ray crystallography, and computational chemistry are utilized in the characterization of the products. Crystal structures of PTA,BH3 (1) and O=PTA,BH3 (2) adducts are described. In addition a coordination polymer, [CpRu(PTA)2Cl(Ph3B3O3)]n (3), resulting from Lewis acid,base adduct formation between the PTA ligands of CpRu(PTA)2Cl and the product of the cyclocondensation of phenylboronic acid is described. The polymeric compound 3 was also characterized by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Rh(I) and Pd(II) complexes of methoxy functionalized heterocyclic carbene: Synthesis and characterizationCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2006M. E. Günay Abstract A new methoxy functionalized 2-(trichloromethyl)-1,3-diarylimidazolidin (6) was synthesized as the precursor for N-heterocyclic carbene complexes of Pd(II) and Rh(I) by the condensation of N,N'-bis(2,4-dimethoxyphenyl)-1,2-diaminoethane with chloral. The structures of all compounds have been elucidated by a combination of multinuclear NMR spectroscopy, elemental analysis and in one instance, by single crystal X-ray diffraction. Compound 8, C27H34N2O4ClRh, crystallizes in the triclinic space group P-1 with cell dimensions a = 9.7642(12)Å, b = 11.1914(11)Å, c = 13.0102(14)Å, , = 104.034(9)°, , = 106.658(9)°, , = 99.658(9)° with Z = 2. The molecular structure of 8 shows the geometry around the Rh metal to be a slightly distorted square planar. The crystal structure shows the formation of centrosymmetric dimers via intermolecular C-H...Cl hydrogen bonds. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An Unusual Anion,, Interaction in an ;rido Organometallic Assembly: Synthesis, First Crystal Structure, and Computational StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2009Jamal Moussa Abstract The organometallic assembly [Cp*Ir(,6 -C6H2O4)(BF2)2(CF3SO3)][Cp*Ir(,-Cl)3IrCp*] (3) was prepared from [Cp*Ir(solvent)3][OTf]2 (2) and 1,2,4,5 tetrahydroxybenzene (THB, 1) in acetone, in the presence of an excess amount of BF3·2H2O. Assembly 3 was fully characterized by multinuclear NMR spectroscopy. Remarkably, the X-ray molecular structure of 3 shows that an anion,, interaction occurs between the neutral component Cp*Ir(,6 -C6H2O4)(BF2)2 of the assembly and the CF3SO3 anion of the cationic species [Cp*Ir(,-Cl)3IrCp*]. Computational analysis was carried out on 3 to unravel the nature of this noncovalent interaction. Such an example could serve as a model to explain the important role of anions in organometallic chemistry and asymmetric catalysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] The Variable Binding Modes of Phenylbis(pyrid-2-ylmethyl)phosphane and Bis(pyrid-2-ylmethyl) Phenylphosphonite with AgI and CuIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009Fernando Hung-Low Abstract A series of new bridging phosphane and phosphonite structures forming three- and six-membered rings with the metal centers were synthesized and characterized. The resulting compounds of phenylbis(pyrid-2-ylmethyl)phosphane (1) with the silver(I) salts of trifluoroacetate (tfa,), tetrafluoroborate (BF4,), and trifluoromethanesulfonate (OTf,), and copper tetrakis(acetonitrile) hexafluorophosphate (PF6,) shows the flexibility of the ligand by displaying different coordination modes associated with the electronic and structural characteristics of the corresponding anion. Accordingly, ligand 1 in these complexes displays two different binding modes. With Agtfa and AgBF4 compounds 3 and 4 are obtained where the ligand chelates to two silver atoms that exhibit normalAg,Ag contacts in the range of 2.9 Å. When AgOTf or Cu(NCCH3)4PF6 are used, one molecule of 1 bridges the metal centers through a phosphorus atom while another is terminally bound. This induces short M,M distances of 2.6871 and 2.568 Å for 5 and 6, respectively. Similarly, the coordination behavior of the heterofunctional bis(pyrid-2-ylmethyl) phenylphosphonite ligand (2) is reported with Cu(NCCH3)4PF6 (7) and AgBF4 (8) to form two novel discrete molecules. In these complexes 2 coordinates through the P and N atoms, with the difference that in 7 the O atom of one of the carbinol arms is also bound to the Cu. Elemental analysis, variable-temperature multinuclear NMR spectroscopy, single-crystal X-ray diffraction, and low-temperature luminescence studies were carried out to fully characterize the compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] O -Acylated 2-Phosphanylphenol Derivatives , Useful Ligands in the Nickel-Catalyzed Polymerization of EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2009Dmitry G. Yakhvarov Abstract The title ligands were prepared by O -acylation of 2-diphenylphosphanyl-4-methylphenol (1) or directly by double lithiation of 2-bromo-4-methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O)Cl (R = Me, tBu, Ph, 4-MeOC6H4) to afford diphenylphosphinate 2 and carboxylic esters 3a,d. X-ray crystal structure analyses of 3b,d show conformations in which the P -phenyl substituents are rotated away from the ester group and the C(O)O , planes are nearly perpendicular to the phenol ring , plane. O -Acylated phosphanylphenols 2 and 3a,d form highly active catalysts with Ni(1,5-cod)2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O -acyl bond upon heating with nickel(0) precursor compounds in the presence of ethylene. The precursors are P-coordinated Ni0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 (in a 2:1 molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the precatalysts are activated. Catalysts 2Ni and 3a,dNi convert ethylene nearly quantitatively, 2Ni slowly, and 3a,dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0 into the O,C(O)R bond of 3a,d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by ,-hydride elimination changes the mechanism to the phosphanylphenolate,NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a,dNi catalysts relative to that observed for 1Ni and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Oxidative Addition of B,Br Bonds to Pd0: Synthesis and Structure of trans -Bromo(boryl)palladium ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2008Holger Braunschweig Abstract The oxidative addition of several bromoboranes to the Pd0 species [Pd(PCy3)2] yielded the novel palladium boryl complexes trans -[(Cy3P)2Pd(Br)(BCat)] (1) (Cat = 1,2-dioxophenylene), trans -[(Cy3P)2Pd(Br)(BCat,)] (2) (Cat, = Cat-4- tBu) and trans -[(Cy3P)2Pd(Br){B(X)X,}] {X = Br, X, = NMe2 (3), Pip (4) (Pip = NC5H10), Mes (5) [Mes = 2,4,6-(CH3)3C6H2]}. Compounds 1,5 were characterized by multinuclear NMR spectroscopy in solution; single crystals for X-ray analyses were acquired from 2 and 3, which thus allowed comparison of the structural data. The few palladium boryl complexes published so far were obtained by ,-bond metathesis; the oxidative addition of the corresponding bromoboranes to Pd0 has not yet been reported.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Interactions of Cationic Palladium(II)- and Platinum(II)-,3 -Allyl Complexes with Fluoride: Is Asymmetric Allylic Fluorination a Viable Reaction?EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Lukas Hintermann Abstract The complex cations [M(,3 -R2All)(PPFPz{3- tBu})]+ (M = PdII, R2All = 1,3-diphenylallyl, 1,3-dicyclohexylallyl, indenyl; M = PtII, R2All = 1,3-diphenylallyl; PPFPz-{3- tBu} = 3- tert -butyl-1-{1-[2-diphenylphosphanyl-ferrocenyl]ethyl}-1H -pyrazole)have been prepared as salts with PF6, or SbF6,. They have been characterized by NMR spectroscopy in solution and by X-ray crystallography in the solid state. Their reactions with sources of nucleophilic and "naked" fluoride have been investigated by multinuclear NMR spectroscopy. The PdII complexes did not undergo any nucleophilic substitution with concomitant release of allyl fluorides. The dicyclohexylallyl fragment was released as a 1,3-diene by elimination, but with other allyl complexes nonspecific decomposition reactions predominated. The complex [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]PF6 underwent an anion exchange with Me4NF to give [Pt(1,3-Ph2C3H3)(PPFPz{3- tBu})]F which existed as a mixture of interconverting allyl isomers in solution at ambient temperature. For the bromide salt, [Pt(,3 -1,3-Ph2C3H3)(PPFPz{3- tBu})]Br, allyl isomerization was slow at ambient temperature. Precursors of Pt0 reacted with bromo-1,3-diphenylprop-2-ene to give [Pt2(,-Br)2(,3 -1,3-Ph2All)2] and precursors of Pd0 underwent oxidative additions with bromo- and fluoro-1,3-diphenyl-2-propene to give 1,3-diphenylallyl complexes of PdII. Therefore, the nucleophilic attack of fluoride on the allyl fragment of PdII complexes is endergonic, and the high energy barrier of this step is difficult to overcome in a catalytic allylic fluorination reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis, Solution-State and Solid-State Structural Characterization of Monocationic Nitrido Heterocomplexes [M(N)(DTC)(PNP)]+ (M = 99Tc, Re; DTC = Dithiocarbamate; PNP = Heterodiphosphane)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004Cristina Bolzati Abstract Mono-cationic nitrido heterocomplexes of general formula [M(N)(DTC)(PNP)]+ (where M is 99Tc or Re, DTC is the mono-anionic form of a dithiocarbamate ligand, and PNP is a diphosphane ligand with a tertiary amine-containing five-membered spacer) were prepared by ligand-exchange reactions with the labile precursors [M(N)Cl2(PPh3)2] in dichloromethane/alcohol mixtures. The molecular structure of the representative rhenium complex [Re(N)(dedc)(pnp2)][PF6] (1) displays a distorted, square-pyramidal geometry with the dithiocarbamate sulfur and the diphosphane phosphorus atoms spanning the four coordination positions on the equatorial plane. If the additional interactions between the nitrido nitrogen and the weakly bonded transN -diphosphane heteroatom, the molecular geometry can be viewed as pseudo-octahedral. The structure in solution, as established by multinuclear NMR spectroscopy and ESI spectrometry, is monomeric, and identical to that shown in the solid state. Replacement of the phenyl groups on the phosphorous atoms in complexes 1, 2, 5, and 6 with alkyl groups modified neither the course of the reaction nor the composition of the resulting complexes. These results, together with the observation that no symmetrical complexes containing two identical bidentate ligands were produced in these reactions, strongly supports the conclusion that a mixed coordination sphere, composed by a combination of ,-donor and ,-acceptor atoms around the [M,N]2+ group, constitutes a highly stable system. Compounds containing dangling alkyl-substituted groups in the outer sphere (3, 4, 7, and 8) were fully characterized by multinuclear NMR spectroscopy and ESI mass spectrometry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Coordination Modes of 9-Methyladenine in cis -Platinum(II) Complexes with Dimethyl(phenyl)phosphanes as Ancillary Ligands , Synthesis and Characterization of cis -[PtL2(9-MeAd)2](NO3)2, cis -[PtL2{9-MeAd(,H)}]3(NO3)3, and cis -[L2Pt{9-MeAd(,H)}PtL2](NO3)3EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2003Bruno Longato Abstract Treatment of 9-methyladenine (9-MeAd) with cis -[PtL2(NO3)2] (1) (L = PMe2Ph) in a 2:1 molar ratio generated the bis(adduct) cis -[PtL2(9-MeAd)2](NO3)2 (2), which was isolated and fully characterized by multinuclear (1H, 31P, 13C, 195Pt and 15N) NMR analysis, which showed that the two nucleobases are selectively coordinated through the N1 atom. Small amounts of a mono(adduct) cis -[PtL2(S)(9-MeAd)]2+ (3) (S = solvent) and of a diplatinated species cis -[L2Pt(S){9-MeAd(,H)}PtL2]3+ (4) are formed in DMSO solution when 9-MeAd is present in smaller quantities than 1. Complex 3 is platinated at N1, with a solvent molecule representing the fourth ligand around the metal center. Complex 4 contains an adenine molecule deprotonated and platinated at N1,N6,N7, with two cis -L2Pt units bonded to nitrogen atom N1 and to nitrogen atoms N6 and N7, respectively. With increasing relative concentration of the nucleobase, both complexes 3 and 4 progressively convert into the bis(adduct) 2, the only species detectable in solution when the Ad/Pt molar ratio is 2:1. The trinuclear compound cis -[L2Pt{9-MeAd(,H)}]3(NO3)3 (5) (L = PMe2Ph), containing an NH2 -deprotonated nucleobase bridging the metal centers through the N1 and N6 atoms, is quantitatively formed when the dinuclear hydroxo complex cis -[Pt(,-OH)L2]2(NO3)2 (6) reacts with 9-MeAd in CH3CN solution. The isolated complex was fully characterized by multinuclear NMR spectroscopy and mass spectrometry. It appears to be stable in solution in CH3CN and chlorinated solvents, whereas in DMSO it partially converts into a new species, probably the dinuclear analog cis -[PtL2{9-MeAd(,H)}]2(NO3)2, in which the adenine maintains its coordination mode. At equilibrium the trinuclear/dinuclear species molar ratio is 20:1. Through the addition of a stoichiometric amount of nitrate 1 to a DMSO solution of 5 we were able to generate the diplatinated compound 4 in high yield. Complex 4 displays a new coordination mode for the adeninate ion, with N1 bonded to one platinum atom whereas N6 and N7 are chelated to a second one. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] The Synthesis and Reactivity of Group 4 Zwitterionic Complexes of the Type Mt+CH2AlCl3,: One-Component Stereoselective Polymerization and Oligomerization Catalysts for Olefins and AcetylenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2004John J. Eisch Abstract A reinvestigation of the interaction of TiCl4 with 2 equiv. of Me3Al in toluene between ,78 °C and 25 °C over 24 h has now established that the ultimate black product obtained is an associated zwitterion of the type [Ti+,CH2,AlCl3,]n, supported by multinuclear NMR spectroscopy and mass spectrometric and gasometric analyses of the gases evolved (CH4, H2) upon its protolysis. Chemical reactions of the zwitterion have corroborated specific aspects of its proposed structure: 1) its methylene character, by its transformation of benzophenone into 1,1-diphenylethylene; 2) its divalent titanium content, by the substantial reductive dimerization of benzophenone to tetraphenylethylene, and 3) its Lewis acidic Ti center, by its catalytic isomerization of trans -stilbene oxide to 1,1-diphenylacetaldehyde. Similar individual reactions of ZrCl4 or HfCl4 with Me3Al have led to the analogous zwitterions [Zr+,CH2,AlCl3,]n and [Hf+,CH2,AlCl3,]n, respectively. These zwitterions of Ti, Zr and Hf have been proven to be capable of the cyclotrimerization and/or polymerization of acetylenes with varying facility, as evidenced by their catalytic action on 1-hexyne, phenylacetylene, di- n -butylacetylene, and diphenylacetylene. Furthermore, all three zwitterions were able to polymerize ethylene, without any added cocatalyst, with an activity following the order Zr > Ti > Hf. The Ti and Zr zwitterions effected the stereoselective polymerization of propylene to yield 50% of isotactic polymer, and all three catalysts induced the polymerization of 1-hexene to yield 85% (Zr, Hf) or 100% (Ti) of isotactic polymer. These oligomerizations and stereoselective polymerizations of acetylenes and olefins can be rationalized through a model for the active site resembling a three-membered metallacyclopropa(e)nium ion intermediate formed from the attack of the Group 4 metal zwitterion on the unsaturated hydrocarbon. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Mechanism of the protective effect of hypothermia on ammonia toxicity in astrocytesJOURNAL OF NEUROCHEMISTRY, Issue 2002C. Zwingmann Ammonia is a key factor in the pathogenesis of hepatic encephalopathy (HE). Acute ammonia treatment causes energy failure of astrocytes, which are able to compensate partly by increased anaerobic metabolism as a means of making up for the energetic shortfall. As hypothermia offers protection from severe encephalopathy and lactate accumulation in liver failure, we investigated the mechanism by which hypothermia protects against ammonia toxicity by multinuclear NMR spectroscopy. 12 h exposure to 5 mm NH4CL decreased the phosphocreatine (PCr)/creatine (Cr) and ATP/ADP ratios to 65 and 76% of control, increased synthesis and release of glutamine to 200,250% and led to a significant stimulation of glycolytic activity reflected by increased uptake and consumption of glucose and accumulation of de novo synthesized intra- and extracellular lactate to 161 and 230% of control. The protective effect of mild hypothermia was evident from inhibiton of lactate accumulation and restoration of ammonia-induced depletion of PCr/Cr. Moderate hypothermia led to an increase of PCr/Cr ratio and inhibited lactate synthesis to 14% of normothermic control, but did not prevent the ATP decrease. While hypothermia inhibited glycolytic flux, intracellular glutamine remained elevated. The results suggest that hypothermia-induced protection against ammonia toxicity results from reduction of cellular energy demand leading to inhibition of anaerobic glucose metabolism and a compensatory stimulation of mitochondrial energy production. Acknowledgements:, Funded by CIHR Canada. [source] Synthesis and Characterization of 1-Azido-2-Nitro-2-Azapropane and 1-Nitrotetrazolato-2-Nitro-2-AzapropanePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 4 2006Roland Boese Abstract 1-Azido-2-nitro-2-azapropane (1) was synthesized in high yield from 1-chloro-2-nitro-2-azapropane and sodium azide. 1-Nitrotetrazolato-2-nitro-2-azapropane (2) was synthesized in high yield from 1-chloro-2-nitro-2-azapropane and silver nitrotetrazolate. The highly energetic new compounds (1 and 2) were characterized using vibrational (IR and Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N), elemental analysis and low-temperature single crystal X-ray diffraction. 1-Azido-2-nitro-2-azapropane (1) represents a covalently bound liquid energetic material which contains both a nitramine unit and an azide group in the molecule. 1-Nitrotetrazolato-2-nitro-2-azapropane (2) is a covalently bound room-temperature stable solid which contains a nitramine group and a nitrotetrazolate ring unit in the molecule. Compounds 1 and 2 are hydrolytically stable at ambient conditions. The impact sensitivity of compound 1 is very high (<1,J) whereas compound 2 is less sensitive (<6,J). [source] Energetic, Low-Melting Salts of Simple HeterocyclesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 4 2003Gregory Drake The synthesis of three new families of heterocyclic-based salts was undertaken and accomplished. Three triazole systems, 1H-1,2,4-triazole, 4-amino-1,2,4-triazole, and 1H-1,2,3-triazole, were used as proton bases with nitric (HNO3), perchloric (HClO4), and dinitramidic (HN(NO2)2) acid systems. In all cases, stable salts were recovered and fully characterized by vibrational spectra (IR, Raman), multinuclear NMR spectroscopy, material balance, density measurements, and elemental analyses, as well as DSC, TGA and initial safety testing (impact). Many of these salts have melting points well below 100,°C, yet high decomposition onsets, defining them as new, highly energetic members of the well known class of materials identified as ionic liquids. Additionally, the single crystal X-ray diffraction study of 1,2,4-triazolium perchlorate was investigated, revealing the expected structure. [source] 2,2,2-Trifluoro- N -(1a,2,7,7a-tetrahydronaphtho[2,3- b]oxiren-3-yl)acetamide by X-ray powder diffractionACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Mwaffak Rukiah The title compound, C12H10F3NO2, an important precursor in the preparation of benzovesamicol analogues for the diagnosis of Alzheimer's disease, was prepared by the epoxidation of 5,8-dihydronaphthalen-1-amine using 3-chloroperoxybenzoic acid. The structure was determined by X-ray powder diffraction, multinuclear NMR spectroscopy and FT,IR spectroscopy. A pair of molecules form intermolecular N,H...O hydrogen bonds, involving the amino and oxirene groups, to produce a dimer. [source] New chiral phosphinite ligands with C2 -symmetric axis and their possible applications in Ru-catalyzed asymmetric transfer hydrogenationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Murat Aydemir Abstract The new chiral ligands N,N,-bis-[(1R)-1-ethyl-2- O -(diphenylphosphinite)ethyl]ethanediamide, 1, and N,N,-bis-[(1S)-1-isobutyl-2- O -(diphenylphosphinite)ethyl]ethanediamide, 2, and the corresponding ruthenium complexes 3 and 4 were prepared and their structures were elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. Following activation by NaOH, these chiral ruthenium complexes serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iPrOH. The complexes 3 and 4 showed high catalytic activity but low selectivity in asymmetric transfer hydrogenation reactions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis and molecular structures of 1-chloro-1-silacyclopent-2-enes.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 20091-organoboration, 2-hydroboration, Combination of , protodeborylation Abstract The reaction of alkyn-1-yl(chloro)(methyl)vinyl- and alkyn-1-yl(chloro)(phenyl)-vinylsilane with 9-borabicyclo[3.3.1]nonane (9-BBN) afforded selectively 1-silacyclopent-2-ene derivatives containing a SiCl function, as a result of consecutive 1,2-hydroboration and 1,1-organoboration. Protodeborylation with acetic acid left the SiCl functions in various 1-silacyclopent-2-enes untouched, whereas acetic acid in the presence of dipropylamine led to conversion of the SiCl into the SiOAc function. New starting materials and all products were characterized in solution by multinuclear NMR spectroscopy (1H, 11B, 13C and 29Si NMR), and the molecular structures of two 1-silacyclopent-2-ene derivatives were determined by X-ray analysis. The gas phase geometries of 1-silacyclopent-2-enes were optimized by DFT calculations [B3LYP/6-311 + G(d,p) level of theory], found to be in reasonable agreement with the results of the crystal structure determination, and NMR parameters were calculated at the same level of theory. Copyright © 2009 John Wiley & Sons, Ltd. [source] Aqueous phase carbon dioxide and bicarbonate hydrogenation catalyzed by cyclopentadienyl ruthenium complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2007Sylvain S. Bosquain Abstract The water-soluble ruthenium(II) complexes [Cp,RuX(PTA)2]Y and [CpRuCl(PPh3)(mPTA)]OTf (Cp, = Cp, Cp*, X = Cl and Y = nil; or X = MeCN and Y = PF6; PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA = 1-methyl-1,3,5-triaza-7-phosphaadamantane) were used as catalyst precursors for the hydrogenation of CO2 and bicarbonate in aqueous solutions, in the absence of amines or other additives, under relatively mild conditions (100 bar H2, 30,80 °C), with moderate activities. Kinetic studies showed that the hydrogenation of HCO3, proceeds without an induction period, and that the rate strongly depends on the pH of the reaction medium. High-pressure multinuclear NMR spectroscopy revealed that the ruthenium(II) chloride precursors are quantitatively converted into the corresponding hydrides under H2 pressure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Sterically Crowded peri -Substituted Naphthalene Phosphines and their PV DerivativesCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2010Fergus Abstract Three sterically crowded peri -substituted naphthalene phosphines, Nap[PPh2][ER] (Nap=naphthalene-1,8-diyl; ER=SEt, SPh, SePh) 1,3, which contain phosphorus and chalcogen functional groups at the peri positions have been prepared. Each phosphine reacts to form a complete series of PV chalcogenides Nap[P(E,)(Ph2)(ER)] (E,=O, S, Se). The novel compounds were fully characterised by using X-ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. X-ray data for 1, 2, n,O, n,S, n,Se (n=1,3) are compared. Eleven molecular structures have been analysed by naphthalene ring torsions, peri -atom displacement, splay angle magnitude, X,,,E interactions, aromatic ring orientations and quasi-linear arrangements. An increase in the congestion of the peri region following the introduction of heavy chalcogen atoms is accompanied by a general increase in naphthalene distortion. P,,,E distances increase for molecules that contain bulkier atoms at the peri positions and also when larger chalcogen atoms are bound to phosphorus. The chalcogenides adopt similar conformations that contain a quasi-linear E,,,PC fragment, except for 3,O, which displays a twist-axial-twist conformation resulting in the formation of a linear O,,,SeC alignment. Ab initio MO calculations performed on 2,O, 3,O, 3,S and 3,Se reveal Wiberg bond index values of 0.02 to 0.04, which indicates only minor non-bonded interactions; however, calculations on radical cations of 3,O, 3,S and 3,Se reveal increased values (0.14,0.19). [source] Self-Assembly of a Triangle-Shaped, Hexaplatinum-Incorporated, Supramolecular Amphiphile in Solution and at InterfacesCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2009Umamageswaran Maran Dr. Abstract The self-assembly and characterization of a novel supramolecular amphiphile built from a new 60° amphiphilic precursor that incorporates hydrophilic platinum(II) metals and hydrophobic dioctadecyloxy chains is reported. The amphiphilic macrocycle and its precursor compound have been characterized by multinuclear NMR spectroscopy, ESI-MS, and other standard techniques. The coacervate morphology of the amphiphile at the liquid,liquid interface has been studied by using confocal optical microscopy and in situ Raman spectroscopy. The self-assembly of the amphiphilic macrocycle at the air,water interface has been investigated through Langmuir-trough techniques. The study indicates the possible formation of surface micelle-like aggregates. The disparity between the experimental molecular areas and those derived from molecular models support the idea of aggregation. AFM images of the surface aggregates show the formation of a flat topology with arbitrary ridgelike patterns. Reasonable molecular-packing arrangements are proposed to explain the molecular organization within the observed structures. [source] Cationic P,S,X cages (X=Br, I)CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2006Marcin Gonsior Dr. Abstract The first condensed-phase preparation of ternary P,Ch,X cations (Ch=O,Te, X=F,I) is reported: [P5S3X2]+, [P5S2X2]+, and [P4S4X]+ (X=Br, I). [P5S3X2]+ is formed from the reaction of the Ag+/PX3 reagent with P4S3. The [P5S3X2]+ ions have a structure that is related to P4S5 by replacing PS by P+X and S in the four-membered ring by P(X). We provide evidence that the active ingredient of the Ag+/PX3 reagent is the (H2CCl2)Ag,X,PX2+ cation. The latter likely reacts with the HOMO of P4S3 in a concerted HOMO,LUMO addition to give the P5S3X2+ ion as the first species visible in situ in the low-temperature 31P NMR spectrum. The [P5S3X2]+ ions are metastable at ,78,°C and disproportionate at slightly higher temperatures to give [P5S2X2]+ and [P4S4X]+, probably with the extrusion of 1/n,(PX)n (X=Br, I). All six new cage compounds have been characterized by multinuclear NMR spectroscopy and, in part, by IR or Raman spectroscopy. The [P5S2X2]+ salts have a nortricyclane skeleton and were also characterized by X-ray crystallography. The structure of the [P4S4X]+ ion is related to that of P4S5 in that the exo -cage PS bond is replaced by an isoelectronic P+X moiety. [source] Platinum Complexes of Dibenzo[1,2]Dithiin, Dibenzo[1,2]Dithiin Oxides and Related Polyaromatic Hydrocarbon LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2006Stephen M. Aucott Dr. Abstract The synthesis of platinum bisphosphine complexes of biphenyl- 2,2,-dichalcogenates and the oxides of dibenzo[1,2]dithiin and related ligand systems by oxidative addition to [Pt(PPh3)4] is reported. We also describe the synthesis of a new compound, dibenzothiophen-4-yldiselenide and its simple platinum complex (obtained by oxidative addition). All complexes have been fully characterised, principally by using multinuclear NMR spectroscopy and in six cases by means of single-crystal X-ray diffraction studies. The majority are simple S/S or Se/Se complexes, however the addition of dibenzo[1,2]dithiin trioxide to [Pt(PPh3)4] gives a bimetallic system, [Pt{2-[S(O)],2,-[S(O)2]-biphen}(PPh3)]2, containing a central Pt2S2O2 core in which the ligand behaves as a tridentate S,S,O donor. [source] Insights into CO/Styrene Copolymerization by Using PdII Catalysts Containing Modular Pyridine,Imidazoline LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Amaia Bastero Dr. Abstract Continuing our studies into the effect that NN, ligands have on CO/styrene copolymerization, we prepared new C1 -symmetrical pyridine,imidazoline ligands with 4,,5,- cis stereochemistry in the imidazoline ring (5) and 4,,5,- trans stereochemistry (6,10) and compared them with our previously reported ligands (1,4). Their coordination to neutral methylpalladium(II) (5,a,10,a) and cationic complexes (5,b,10,b), investigated in solution by NMR spectroscopy, indicates that both the electronic and steric properties of the imidazolines determine the stereochemistry of the palladium complexes. The crystal structures of two neutral palladium precursors [Pd(Me)2,nCln(NN,)] (n=1 for 8,a; n=2 for 9,a,) show that the PdN coordination distances and the geometrical distortions in the imidazoline ring depend on the electronic nature of the substituents in the imidazoline fragment. Density functional calculations performed on selected neutral and cationic palladium complexes compare well with NMR and X-ray data. The calculations also account for the formation of only one or two stereoisomers of the cationic complexes. The performance of the cationic complexes as catalyst precursors in CO/4- tert -butylstyrene copolymerization under mild pressures and temperatures was analyzed in terms of the productivity and degree of stereoregularity of the polyketones obtained. Insertion of CO into the PdMe bond, which was monitored by multinuclear NMR spectroscopy, shows that the N ligand influences the stereochemistry of the acyl species formed. [source] New Insights into the Formation and Reactivity of Molecular Organostannonic AcidsCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2010S. Usman Ahmad Abstract The controlled base hydrolysis of 2,6-Mes2C6H3SnCl3 (1; Mes=mesityl) provided 2,6-Mes2C6H3Sn(OH)Cl2,H2O (2) and the trinuclear organostannonic acid trans -[2,6-Mes2C6H3Sn(O)OH]3 (3), respectively. In moist C6D6, 3 reversibly reacts with water to give the monomeric organostannonic acid 2,6-Mes2C6H3Sn(OH)3 (3,a). The reaction of 3 with (tBu2SnO)3, Ph2PO2H, and NaH, gives rise to the multinuclear hypercoordinated organostannoxane clusters [tBu2Sn(OH)OSnR(OH)2OC(OSntBu2OH)2(O)SnR(OH)(H2O)]2 (5), [RSn(OH)2(O2PPh2)]2 (6), and Na3(RSn)4O6(OH)3 (7), respectively (R=2,6-Mes2C6H3). The characterization of the new compounds is achieved by multinuclear NMR spectroscopy and electrospray mass spectrometry in solution and 119Sn MAS NMR spectroscopy, IR spectroscopy, and X-ray crystallography in the solid-state. [source] | |||||||||||||