Search results for "Reactivity"
showing 10 items of 880 documents
Formation and Reactivity of the [Cp‘2Ta(H)2]+ Cation (Cp‘ = η5-tBuC5H4)
1999
The complex Cp‘2Ta(H)(OCOCF3)2 (2) is synthesized by the acidolysis of Cp‘2TaH3 (1) (Cp‘ = η5-tBuC5H4) in the presence of an excess of trifluoroacetic acid. 1 undergoes a loss of H- upon the reacti...
Reactivity of bimetallic dibridged complexes Cp2Ta(H)(μ-H)(μ-PMe2)M′(CO)4 (M′ = Cr, Mo, W) toward two-electron donor ligands L (L = PR3, Me2P(CH2)nPM…
1998
Abstract The reaction of the heterobimetallic phosphido- and hydrido-bridged complexes Cp 2 TaH(μ-H)(μ-PMe 2 )M′(CO) 4 (M′ = Cr, Mo, W) ( 1–3 ) with phosphines (L = PPh 2 Me, PMe 2 Ph) or diphosphines (L = dmpm, dmpe) leads to Cp 2 Ta(H) 2 (μ-PMe 2 )M′(CO) 4 (L) ( 1a, 1b, c, d-3b, c, d ) with L regiospecifically coordinated to M′. Except for L = PPh 2 Me, the reaction is stereospecific, since a cis arrangement (with respect to the PMe 2 bridge) on the M′ site is obtained. The new compounds Cp 2 Ta(H) 2 (μ-PMe 2 )M′ (CO) 4 (Me 2 P(CH 2 ) 2 PMe 2 ) (M′ = Mo, W) are able to bind [Cr(CO) 5 ] fragments affording the linear trinuclear chain compounds Cp 2 Ta(H) 2 (μ-PMe 2 )M′(CO) 4 (Me 2 P(CH 5 )…
Influence of structural factors and enzyme type on the reactivity and enantioselectivity of the enzymatic esterification of bicyclic meso dialcohols
1992
The meso dialcohols 1–7, obtained from the Diels-Alder adducts furan/maleic anhydride, furan/dimethyl acetylenedi-carboxylate, and cyclopentadiene/maleic anhydride, were subjected to enzymatic esterification in organic solvents. A mixture of the corresponding chiral monoacetates and the meso diacetates was obtained. It has been found that reaction rate and enantioselectivity markedly depend on substrate structure, temperature, enzyme type, and nature of the solvent. The presence of an oxygen bridge and an exo configuration are the two structural features which lead to the highest enantioselectivity values.
Syntheses and reactivity of aminobis(diorganylamino)phosphanes
1996
Aminobis(diorganylamino)phosphanes (R2N)2PNH2 (R = iPr, c-Hex, Ph) (2a–c), were obtained by treatment of the corresponding chlorobis(diorganylamino)phosphanes 1a–c with lithium amide in liquid ammonia. The transition metal phosphane complex (R2N)2(H2N)PNi(CO)3 (3) was prepared by reaction of 2a with tetracarbonylnickel. N-Complexation of 2a with trimethylalane affords the iminophosphorane-alane adduct (R2N)2HP=N(H)AlMe3 (4) by 1,2-H shift from the nitrogen to the phosphorus atom. The corresponding reaction with aluminium trichloride leads to the formation of the salt [(R2N)2HP=N(H)]2AlC12+[AlC14]− (5), in which two iminophosphorane moieties are linked by an AlCl2 bridge. Lithiation of 2a an…
Synthesis and Electrochemical Reactivity of sigma-Bonded and N-Substituted Cobalt Porphycenes.
1998
The first synthesis and characterization of sigma-bonded and N-substituted cobalt porphycenes is reported. The investigated compounds are represented as (Pc)Co(R) and (N-CH(3)OEPc)CoCl, where R is CH(3) or C(6)H(5), Pc is the dianion of 2,3,6,7,12,13,16,17-octaethylporphycene (OEPc), 2,7,12,17-tetrapropylporphycene (TPrPc), or 2,7,12,17-tetraethyl-3,6,13,16-tetramethylporphycene (EtioPc), N-CH(3)OEPc is the monoanion of N-methyl-2,3,6,7,12,13,16,17-octaethylporphycene. Each sigma-bonded (Pc)Co(R) derivative can be reversibly reduced or oxidized by two electrons, but a slow migration of the sigma-bonded R group occurs following electrogeneration of [(Pc)Co(R)](+)()(*)() leading, as a final p…
New Insights into the Stoichiometric and Catalytic Reactivity of Unsaturated Pd 3 (dppm) 3 CO n + Clusters ( n = 0, 1) Towards Halocarbons – First Ev…
2005
The title clusters, Pd 3 (dppm) 3 (CO) + and Pd 3 (dppm) 3 (CO) 0 can be electrochemically generated from the 1- and 2-electron reductions, respectively, of the Pd 3 (dppm) 3 (CO) 2 + cluster [dppm = bis(diphenylphosphanyl)methane; Pd 3 2 + ]. Pd 3 + reacts in a stoichiometric ratio with methyl iodide, MeI, and benzyl bromide, BzBr, in THF to provide the corresponding Pd 3 (X) + adducts (X = I, Br respectively) as inorganic products. Other products are Bz 2 and PhMe for BzBr but, for MeI, no organic product was observed (since they are too volatile). In the presence of the same substrates, Pd 3 0 also reacts in a stoichiometric ratio to form the same organics and the Pd 3 -(X) + adducts (X …
Formation and Reactivity of a Tantalocene Trihydride Containing an Aminoethyl‐Functionalised Ligand
2003
The complex [Cp*{C5H4(CH2CH2NMe2)}TaCl2] (1) was synthesised by reaction of the lithium salt LiC5H4(CH2CH2NMe2) with the tantalum compound [Cp*TaCl3(PMe3)]. Reduction of 1 with NaAl(H)2(OCH2CH2OMe)2 leads to the trihydride derivative [Cp*{C5H4(CH2CH2NMe2)}TaH3] (2). The oxidation of 2 in THF with ferrocenium ion leads to a cationic dihydride intermediate [Cp*{C5H4(CH2CH2NMe2)}TaH2]PF6 (3) with an intramolecular stabilization by the aminoethyl side-chain of the cyclopentadienyl ligand. The hemilabile character of the functionalised cyclopentadienyl ligand was checked by treating 3 with electron-donating ligands (e.g. phosphanes, sulfides, anions); in all cases, no displacement of the amino g…
Experimental and theoretical study using DFT method for the competitive adsorption of two cationic dyes from wastewaters
2016
Abstract The adsorption of cationic dyes, Basic Yellow (BY28) and Methylene Blue (MB) on a new activated carbon from medlar species were studied in both single and binary system. Some experimental parameters, namely, pH, amount of adsorbent and contact time are studied. Quantum chemical results indicate that the adsorption efficiency was directly related to the dye electrophilicity power. Some theorical parameters were calculated and proved that MB is more electrophilic than BY28, than greatest interaction with surface sites. Kinetic study showed that the adsorption follows the pseudo-second-order model and Freundlich was the best model to describe the phenomenon in the single and binary sy…
Copper(I) Complexes of Bis(2-(diphenylphosphino)phenyl) Ether: Synthesis, Reactivity, and Theoretical Calculations
2007
The tricoordinated cationic Cu-I complex [Cu(kappa(2)-P,P'-DPEphos)(kappa(1)-P-DPEphos)][BF4] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl) ether) containing a dangling phosphorus center was synthesized from the reaction of [Cu(CH3CN)(4)][BF4] with DPEphos in a 1:2 molar ratio in dichloromethane. When complex 1 is treated with MnO2, elemental sulfur, or selenium, the uncoordinated phosphorus atom undergoes oxidation to form a PE bond resulting in the formation of complexes of the type [Cu(kappa(2)-P,P'-DPEphos)(kappa(2)-P,E-DPEphos-E)][BF4] (2, E = O; 3, E = S; 4, E = Se) containing a Cu-E bond. The zigzag polymeric Cu-I complex [Cu(kappa(2)-P,P'-DPEphos)(mu-4,4'-bpy)](n)[BF4](n) (5) was …
Di-n-butyltin(IV)-catalyzed dimethyl carbonate synthesis from carbon dioxide and methanol: An in situ high pressure 119Sn{1H} NMR spectroscopic study
2011
The reactivity of five di-n-butyltin(IV) complexes, n-Bu2Sn(OR)(2) (1), n-Bu2SnO (3), [n-Bu2Sn(OR)](2)O (4), (n-Bu2SnO)(2)(CO2) (6) and (n-Bu2SnO)(6)[(n-Bu2SnOR)(2)(CO3)](2) (7) (R = CH3), with CO2, suggested as possible catalyst precursors and key-intermediates for the direct synthesis of dimethyl carbonate from carbon dioxide and methanol, has been investigated using high-pressure Sn-119{H-1} NMR (HP-NMR) spectroscopy. Four of the five precursors studied, i.e. 3, 4, 6 and 7 give rise to an identical Sn-119{H-1} NMR pattern which can be explicitly attributed to the fingerprint of the dimeric form of the 1-methoxy-3-methylcarbonatotetrabutyldistannoxane {5}(2). However, with 1, a new pair o…