Home About us Contact
|
Home About us Contact | ||
|
|
||
One Equivalent (one + equivalent)
Selected AbstractsAminopyridinate-Stabilized Lanthanoid Complexes: Synthesis, Structure and Polymerization of Ethylene and IsopreneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010Christian Döring Abstract A series of aminopyridinate-stabilized dialkyl-lanthanoid complexes has been synthesized and characterized. The complexes were prepared by alkane elimination reacting [Ln(CH2SiMe3)3(thf)2] (Ln = Er, Yb, Lu) or [Ln(CH2Ph)3(thf)3] (Ln = Y, Er, Lu) with one equivalent of the bulky aminopyridine (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine. Single-crystal X-ray analyses were carried out for all of the benzyl derivatives. The reaction of these compounds with ammonium borate leads to the elimination of one of the two alkyl functions and affords organolanthanoid cations. The aminopyridinate-stabilized dialkyl-lanthanoid compounds can initiate the polymerization of isoprene after activation with perfluorinated tetraphenyl borates. The obtained polymers have a 3,4-content of 60,95,%. The metal ion size as well as the addition of alkylaluminium compounds influences the microstructure of the obtained polymer. Aminopyridinate-stabilized organolanthanoid cations of Sc, Lu, Er and Y can polymerize ethylene in the presence of alkylaluminium compounds. The Lu, Er and Y complexes act as a CCTP catalyst and the erbium compound exhibits the highest activity. [source] Developing the Kharasch Reaction in Aqueous Media: Dinuclear Group 8 and 9 Catalysts Containing the Bridging Cage Ligand Tris(1,2-dimethylhydrazino)diphosphane,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2008Alba E. Díaz-Álvarez Abstract The dinuclear complexes [{RuCl2(,6 - p -cymene)}2(,-THDP)] (4) and [{MCl(,4 -cod)}2(,-THDP)] [M = Rh (5), Ir (6)], containing the bridging cage-type ligand tris(1,2-dimethylhydrazino)diphosphane (THDP), have been synthesized in high yields (89,95,%) by treatment of dimers [{RuCl(,-Cl)(,6 - p -cymene)}2] (1) and [{M(,-Cl)(,4 -cod)}2] [M = Rh (2), Ir (3)] with one equivalent of THDP. The structure of the (,6 -arene)ruthenium(II) derivative 4 has been unequivocally confirmed by means of X-ray diffraction methods. All these complexes have been found to be active catalysts for the atom-transfer radical addition of bromotrichloromethane to olefins (Kharasch reaction) in heterogeneous aqueous media under mild conditions (room temp.).(© 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] Synthesis of a Hexadentate Hexameric Aluminum Imide and Its Metathesis ReactionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2003N. Dastagiri Reddy Abstract The reaction of AlH3·NMe3 with one equivalent of 2-cyanothiophene in toluene afforded [HAlNCH2(C4H3S)]6 (2) in good yield. Treatment of 2 with SiMe3Br and SiMe3Cl in toluene under refluxing conditions resulted in the formation of compounds [BrAlNCH2(C4H3S)]6 (3) and [ClAlNCH2(C4H3S)]6 (4), respectively. In a similar way [PhC,CAlNCH2(C4H3S)]6 (5) was readily obtained from the reaction between 2 and PhC,CH. When 2 was treated with PhSH the Al-N cluster core dissociated and a four-membered ring compound [(PhS)2AlNHCH2(C4H3S)]2 (6) was formed. In contrast, a similar hexameric aluminum imide (HAlNCH2Ph)6 (1) retains its Al-N network when treated with PhSH to yield (PhSAlNCH2Ph)6 (7). An exchange of ethyl groups and hydrides occurred when 2 was treated with excess of ZnEt2, forming [EtAlNCH2(C4H3S)]68. Compounds 2,4 and 6,8 were characterized by X-ray single-crystal analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Synthesis and Physicochemical Characterization of meso -Functionalized Corroles: Precursors of Organic,Inorganic Hybrid MaterialsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2005Jean-Michel Barbe Abstract Cobalt(III) corroles exhibit an infinite selectivity for the coordination of carbon monoxide towards dioxygen and dinitrogen. This peculiar property thus allows their use as sensing devices for CO detection. Here are described the syntheses and physico-chemical characterization of meso mono-, bis- and tris(triethoxysilyl)-functionalized corroles, precursors of organic,inorganic materials. The corrole ring formation was achieved in every case using the "2+1" method involving the reaction of two equivalents of an encumbered dipyrromethane with one equivalent of an aromatic aldehyde in the presence of a catalytic amount of trifluoroacetic acid. The functionalization of the corrole by triethoxysilyl chains was carried out by a condensation reaction of an isocyanate, bearing a triethoxysilyl termination, either on an amino or hydroxy group. Each final compound and intermediate were characterized by various physico-chemical techniques such as 1H NMR, UV/Vis, MALDI/TOF or EI mass spectrometry and elemental analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] An Efficient Solvent-Free Route to Silyl Esters and Silyl EthersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Yuko Ojima Abstract Dinuclear metal complexes, especially (p -cymene)ruthenium dichloride dimer {[RuCl2(p -cymene)]2}, have been found to exhibit high catalytic performance for the dehydrosilylation of various kinds of carboxylic acids and alcohols. The dehydrosilylation with [RuCl2(p -cymene)]2 proceeded efficiently with only one equivalent of silane with respect to substrate (carboxylic acids or alcohols) under solvent-free conditions to give the corresponding silyl esters and ethers in excellent yields with a high turnover number (TON) and frequency (TOF). The 1H,NMR spectrum of a toluene- d8 solution of [RuCl2(p -cymene)]2 and a silane showed a signal assignable to the ruthenium hydride species. In contrast, no new signals were detected in the 1H,NMR spectrum of a toluene- d8 solution of [RuCl2(p -cymene)]2 and a carboxylic acid or an alcohol. Therefore, the ruthenium metal in [RuCl2(p -cymene)]2 activates a silane to afford the hydride intermediate, possibly a silylmetal hydride species. Then, the nucleophilic attack of a substrate (carboxylic acid or alcohol) to the hydride intermediate proceeds to give the corresponding silylated product. The present dehydrosilylation with an optically active silane proceeded exclusively under inversion of stereochemistry at the chiral silicon center, suggesting that the nucleophilic attack of a substrate to the hydride intermediate occurs from the backside of the ruthenium-silicon bond. [source] A Bimetallic Ruthenium Complex as a Catalyst Precursor for the Atom Transfer Radical Polymerization of Methacrylates at Ambient TemperatureADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4-5 2006Michel Haas Abstract The bimetallic ruthenium complex [(1,3,5- i -Pr3C6H3)Ru(,-Cl)3RuCl(C2H4)(PCy3)] has been synthesized by reaction of [(1,3,5- i -Pr3C6H3)RuCl2)]2 with one equivalent of PCy3 in the presence of ethylene. It can be used as a catalyst precursor for the controlled atom transfer radical polymerization of methacrylates at 35,°C. The resulting polymers show low polydispersities. [source] Reaction of 4,5,6-triaminopyrimidine and 2,4,5,6-tetraaminopyrimidine with 3-dimethylaminopropiophenones.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 20003-dihydropyrimido[, 4]diazepines, 5- b][, Synthesis of new 4-aryl- Several new 6-amino- and 6,8-diamino-4-aryl-2,3-dihydropyrimido[4,5- b][1,4]diazepines were obtained from the reaction of 4,5,6-triaminopyrimidine 1a and 2,4,5,6-tetraaminopyrimidine 1b with one equivalent of 3-dimethylaminopropiophenones 2 in absolute ethanol. Structure analysis of 6-amino- and 6,8-diamino-4-aryl-2,3-dihydropyrimido[4,5- b][1,4]diazepines 3a-i, determined by detailed nmr measurements, reveals a high regioselectivity of this reaction. [source] Molecular imprinting of AMP by an ionic-noncovalent dual approachJOURNAL OF SEPARATION SCIENCE, JSS, Issue 19 2009Florent Breton Abstract In order to mimic recognition properties of adenylate kinase, molecularly imprinted polymers (MIPs) were prepared for adenosine 5,-monophosphate (AMP), a substrate of the enzyme. Different functional monomers interacting with the phosphate moiety were tested, and the MIP giving the best specific binding of AMP was composed with one equivalent of 2-(dimethylamino)ethyl methacrylate and ten equivalents of acrylamide compared to AMP. Packed into solid phase cartridge, this polymer showed similar characteristics than the enzyme, since it was specific for AMP toward other nucleotides. [source] A novel trinuclear zinc(II) cluster with a tetrahedral ZnO4 coreACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Orde Q. Munro The reaction of 0.67 molar equivalents of the O,N,O,-tridentate zwitterionic Schiff base (2Z,4E)-4-[(2-hydroxyphenyl)iminio]pent-2-en-2-olate (H2L) with one equivalent of zinc(II) acetate in methanol affords a novel trinuclear ZnII cluster, di-,-acetato-1:2,2O:O,;2:3,2O:O,-dimethanol-1,O,3,O -bis{,-2-[(2E,3Z)-4-oxidopent-3-en-2-ylideneamino]phenolato}-1:2,4O2,N,O4:O4;2:3,4O4:O2,N,O4 -trizinc(II), [Zn3(C11H11NO2)2(C2H3O2)2(CH4O)2], (I), in which two bridging acetate ligands link the terminal square-based pyramidal ZnII ions to the approximately tetrahedral ZnII ion at the core of the cluster. The ZnO4 coordination group of the central ZnII ion is established by two bridging phenolate and two bridging acetate O atoms. The remaining four coordination sites of each terminal ZnII ion are occupied by methanol and deprotonated H2L. Furthermore, the Zn-bound methanol hydroxyl groups are involved in complementary hydrogen bonding with the Zn-bound enolate O atom of a neighbouring molecule, about an inversion centre in each case. The structure of (I) is therefore best described as an extended one-dimensional hydrogen-bonded chain of trinuclear ZnII clusters. [source] Squaraines as Reporter Units: Insights into their Photophysics, Protonation, and Metal-Ion Coordination BehaviourCHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2008Abstract The synthesis, photophysical properties, protonation, and metal-ion coordination features of a family of nine aniline-based symmetrical squaraine derivatives are reported. The squaraine scaffold displays very attractive photophysical properties for a signalling unit. These dyes show absorption and weakly Stokes-shifted, mirror-image-shaped emission bands in the visible spectral range and there are no hints of multiple emission bands. The mono-exponential fluorescence decay kinetics observed for all the derivatives indicate that only one excited state is involved in the emission. These data stress the interpretation that squaraines can be regarded as polymethine-type dyes. From a coordination chemistry point of view, the squaraines possess four potential binding sites; that is, two nitrogen atoms from the anilino groups and two oxygen atoms from the central C4O2 four-membered ring. These coordination sites are part of a cross-conjugated ,-system and coordination events with protons or certain metal ions affect the electronic properties of the delocalised ,-system dramatically, resulting in a rich modulation of the colour of the squaraines. The absorption band at around 640,nm is blue-shifted when coordination at the anilino nitrogen atoms occurs, whereas coordination to the C2O4 oxygen atoms results in the development of red-shifted bands. Addition of more than one equivalent of protons or metal cations could additionally entail mixed N,O - or N,N -coordinated complexes, manifested in the development of a broad band at 480,nm or complete bleaching in the visible range, respectively. Analysis of the spectrophotometric titration data with HYPERQUAD yielded the macroscopic and microscopic stability constants of the complexes. Theoretical modelling of the various protonated species by molecular mechanics methods and consideration of some of the title dyes within the framework of molecular chemosensing and molecular-scale "logic gates" complement this contribution. [source] Sodium Cation Migration Above the Diimine ,-System of Solvent Coordinated dpp-BIAN Sodium Aluminum Complexes (dpp-BIAN=1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene)CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2007Herbert Schumann Prof. Abstract The reactions of the disodium salt of the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN) ligand with one equivalent of Me2AlCl in diethyl ether, toluene, and benzene produced the complexes [Na(Et2O)2(dpp-BIAN)AlMe2] (1), [Na(,6 -C7H8)(dpp-BIAN)AlMe2] (2) and [Na(,6 -C6H6)(dpp-BIAN)AlMe2] (3), respectively. Recrystallization of 1 from hexane afforded solvent-free [{Na(dpp-BIAN)AlMe2}n] (4) or [Na(Et2O)(dpp-BIAN)AlMe2] (5) depending on the temperature of the solvent. The molecular structures of 1,5 have been determined by single-crystal X-ray diffraction. The sodium cation coordinates either one of the naphthalene rings (1) or the diimine part of the dpp-BIAN ligand (2,5). In the complexes 2 and 3, the sodium cation additionally coordinates the toluene (2) or benzene molecule (3) in an ,6 -fashion. [source] Synthesis and Reactivity of Rare Earth Metal Alkyl Complexes Stabilized by Anilido Phosphinimine and Amino Phosphine LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2007Bo Liu Abstract Anilido phosphinimino ancillary ligand H2L1 reacted with one equivalent of rare earth metal trialkyl [Ln{CH2Si(CH3)3}3(thf)2] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L1LnCH2Si(CH3)3(THF)] (1,a: Ln=Y; 1,b: Ln=Lu). In this process, deprotonation of H2L1 by one metal alkyl species was followed by intramolecular CH activation of the phenyl group of the phosphine moiety to generate dianionic species L1 with release of two equivalnts of tetramethylsilane. Ligand L1 coordinates to Ln3+ ions in a rare C,N,N tridentate mode. Complex l,a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL1)LnY(NHC6H3iPr2 -2,6)2] (2) selectively, that is, the CH activation of the phenyl group is reversible. When 1,a was exposed to moisture, the hydrolyzed dimeric complex [{(HL1)Y(OH)}2](OH)2 (3) was isolated. Treatment of [Ln{CH2Si(CH3)3}3(thf)2] with amino phosphine ligands HL2-R gave stable rare earth metal bis-alkyl complexes [(L2-R)Ln{CH2Si(CH3)3}2(thf)] (4,a: Ln=Y, R=Me; 4,b: Ln=Lu, R=Me; 4,c: Ln=Y, R=iPr; 4,d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4,a and 4,c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L2-R)Y(NHC6H3iPr2 -2,6)2(thf)] (5,a: R=Me; 5,b: R=iPr). Complexes 1,a,b and 4,a,d initiated the ring-opening polymerization of d,l -lactide with high activity to give atactic polylactides. [source] A New Fluorescent Probe for Zinc(II): An 8-Hydroxy-5- N,N -dimethylaminosulfonylquinoline-Pendant 1,4,7,10-TetraazacyclododecaneCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2006Shin Aoki Prof. Abstract A new fluorescent probe for Zn2+, namely, 8-hydroxy-5- N,N -dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L8), was designed and synthesized (cyclen=1,4,7,10-tetraazacyclododecane). By potentiometric pH, 1H NMR, and UV spectroscopic titrations, the deprotonation constants pKa1,pKa6 of L8,4,HCl were determined to be <2, <2, <2 (for amino groups of the cyclen and quinoline moieties), 7.19±0.05 (for 8-OH of the quinoline moiety), 10.10±0.05, and 11.49±0.05, respectively, at 25,°C with I=0.1 (NaNO3). The results of 1H NMR, potentiometric pH, and UV titrations, as well as single-crystal X-ray diffraction analysis, showed that L8 and Zn2+ form a 1:1 complex [Zn(H,1L8)], in which the 8-OH group of the quinoline ring of L8 is deprotonated and coordinates to Zn2+, in aqueous solution at neutral pH. On addition of one equivalent of Zn2+ and Cd2+, the fluorescence emission of L8 (5 ,M) at 512 nm in aqueous solution at pH 7.4 [10 mM HEPES with I=0.1 (NaNO3)] and 25,°C increased by factors of 17 and 43, respectively. We found that the cyclen moiety has the unique property of quenching the fluorescence emission of the quinolinol moiety when not complexed with metal cations, but enhancing emission when complexed with Zn2+ or Cd2+. In addition, the Zn2+,L8 complex [Zn(H,1L8)] is much more thermodynamically and kinetically stable (Kd{Zn(H,1L8)}=[Zn2+]free[L8]free/[Zn(H,1L8)]=8 fM at pH 7.4) than the Zn2+ complexes of our previous Zn2+ fluorophores ([Zn(H,1L2)] and [Zn(L3)]). Furthermore, formation of [Zn(H,1L8)] is much faster than those of [Zn(H,1L2)] and [Zn(L3)]. The staining of early-stage apoptotic cells with L8 is also described. [source] Generation of Cationic [Zr-{tert -Butyl Enolate}] Reactive Species: Methyl Abstraction versus Hydride AbstractionCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2004Bing Lian Dr. Abstract Treatment of the neutral methyl,Zr,enolate [Cp2Zr(Me){O(tBuO)CCMe2}] (1) with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] as a methyl abstractor in THF at 0,°C leads to the selective formation of the free ion pair complex [Cp2Zr(THF){O(tBuO)CCMe2}]+,[anion], (2) (anion=MeB(C6F5)3,, B(C6F5)4,), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20,°C in THF with release of one equivalent of isobutene to form the cationic Zr,carboxylate species [Cp2Zr(THF)(O2CiPr)]+ (3), through a proposed intramolecular proton transfer process from the tert -butoxy group to the enolate. The reaction of 1 with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] in CH2Cl2 leads to the direct, rapid formation of the dimeric ,-isobutyrato,Zr dicationic species [{Cp2Zr[,-(O2CiPr)]}2]2+ (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph3C][B(C6F5)4] is used to generate the cationic Zr,enolate species from 1 in CD2Cl2, a 15:85 mixture of dicationic complexes 4 and [{Cp2Zr[, -(O2CC(Me)CH2)]}2]2+[B(C6F5)4] (5 -[B(C6F5)4]2) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph3C+, as supported by the parallel production of Ph3CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2,5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies. [source] Coupling reaction of organoboronic acids with chloropyrimidines and trichlorotriazine,CHINESE JOURNAL OF CHEMISTRY, Issue 9 2004Jiu-Qing Tan Abstract Pd-catalyzed cross-coupling reactions of chloropyrimidines with alkenylboronic acids readily proceed to give the corresponding alkenylpyrimidines in high to excellent yields. The coupling reaction of 2,4-dichloropyrimidine or 2,4,6-trichloropyrimidine with one equivalent of alkenylboronic acid occurred more easily on 4-position than on 2-position, which implied that the reaction is highly regioselective. The reaction is stereospecific since the configuration of C=C remained intact. The preliminary study on the cross-coupling reactions of 2,4,6-trichlorotriazine with one equivalent of arylboronic acids showed that the reactions afforded the monosubstituted triazines in moderate yields. The effect of steric hindrance of the substitutents on the reactions was found. [source] | ||||||||||||||||||||||