Search results for "Reactivity"
showing 10 items of 880 documents
Synthesis and characterization of triphenyltin(IV) 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates. Crystal and molecular structures of Ph3Sn{O2CC6H3-…
2005
Abstract Triphenyltin 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoate, Ph3SnL2H, has been prepared and characterized, its structure determined by X-ray crystallography, and the structure compared with those of its homologues. Two polymorphs were isolated from the same crystallization attempt. The reactivity of tetrahedral Ph3SnL1H (L1H = 5-[(E)-2-(2-methylphenyl)-1-diazenyl]-2-hydroxybenzoate) towards 2,2′-bipyridine (bipy) has been investigated to ascertain the ability of bipy to coordinate to the Sn-complex and the resultant changes in the molecular architecture. The crystal structure of the product revealed that the bipy moiety does not coordinate to the Sn atom, but forms a cycl…
Synthesis and Reactivity of New Complexes of Rhodium and Iridium with Bis(dichloroimidazolylidene) Ligands. Electronic and Catalytic Implications of …
2006
The preparation of a new bis(dichloroimidazolylidene) ligand has provided chelate-N-heterocyclic complexes of Rh(I) and Ir(I), which have been fully characterized. The crystal structures of three of the new complexes are described. The study of the electronic properties of the new ligands was made on the basis of the ν(CO) stretching frequencies of the carbonyl derivatives, showing that the chloroimidazolylidene ligand is significantly less σ-donating than the related nonchlorinated analogue. This electronic modification of the ligand has important implications for the catalytic properties of the compounds obtained, as observed from enhanced activity shown in catalytic hydrosilylation of te…
Synthesis and Reactivity toward Isonitriles of (2-Aminoaryl)palladium(II) Complexes
2001
Mixtures of “Pd(dba)2” (dba = dibenzylideneacetone) and 2,2‘-bipyridine (bpy; 1:2) or N,N,N‘,N‘-tetramethylethylenediamine (tmeda; 1:1) react with 2-bromo-4-nitroaniline to give [Pd{C6H3NH2-2-NO2-5}Br(N−N)] (N−N = bpy (1b), tmeda (1b‘)). Reactions of 2-iodoaniline with mixtures of “Pd(dba)2” and isonitriles RNC (R = C6H3Me2-2,6 (Xy), 2:1:2 molar ratios; R = tBu, 2.9:1:2 molar ratios) result in the formation of the complexes [Pd{κ2C,N-C(NXy)C6H4NH2-2}I(CNXy)] (2a) and trans-[Pd{C(NtBu)C6H4NH2-2}I(CNtBu)2] (3a*). The reactions of [Pd{C6H4NH2-2}I(bpy)] and 1b‘ with RNC give the complexes trans-[Pd{C(NR)C6H3NH2-2-Y-5}}X(CNR)2] (Y = H, X = I, R = Xy (3a), tBu (3a*); Y = NO2, X = Br, R = Xy (3b),…
Four-, five- and six-coordinated Zn-II complexes of OH-containing ligands: Syntheses, structure and reactivity
2002
Four-, five- and six-coordinated complexes of Zn-II with OH-rich molecules possessing an ONO binding core were synthesized, characterized and their structures were established by single-crystal X-ray diffraction, The corresponding metal ion geometries were found to be distorted tetrahedral, square pyramidal and octahedral, respectively. The complexes exhibit interesting lattice structures such as layered and corrugated sheets owing to the presence of a number of weak intermolecular interactions. The five-coordinated, water-bound Zn-II complex was studied because of its putative hydrolysis property towards p-nitrophenyl acetate. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Syntheses and reactivity of oxo niobocene complexes Cp*2Nb(O)X (X=H, OCH3) and crystal structures of [Cp*2Nb(OH)F]BF4 and Cp*2Nb(O)OC(O)H (Cp*=η5-C…
1998
Abstract Reaction of Cp*2NbCl2 (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF forms the complexes Cp*2Nb(O)X (X=Cl: 2, H: 3). The ratio of 2 and 3 depends on the stoichiometry. If NaOMe is added or MeOH in solution Cp*2Nb(O)OMe 4 is formed in good yields. Reactivity studies with 3 and 4 show that the NbO as well as the Nb–X unit behave as chemically active sites. Protonation of 3 or 4 with HBF4 is followed by an attack of fluoride (from BF4− anion) to give [Cp*2Nb(OH)F]BF4 6 and [Cp*2NbF2]BF4 7. In contrast the reaction of 3 or 4 with HCO2H results in an exchange of X− by formate to give Cp*2Nb(O)OC(O)H 8. The crystal structures of 6 and 8 are reported. Electrochemical investigations of…
Barriers to rotation in ortho-substituted tertiary aromatic amides: Effect of chloro-substitution on resonance and distortion
2018
Planarity of the amide bond represents one of the most widely recognized properties of amides. Herein, we report a combined structural and computational study on the effect of ortho-substitution on resonance and barriers to rotation in tertiary aromatic amides. We demonstrate that ortho-chloro substitution in a class of benzamides that are important from the reactivity and medicinal chemistry perspective results in increased barriers to rotation around both the N-C(O) and C-C(O) axes. The effect of steric hindrance on structures, resonance energies, barriers to rotation, and proton affinities is discussed. The present study strongly supports the use of ortho-substitution in common benzamide…
Assessing the reactivity of sodium alkyl-magnesiates towards quinoxaline : single electron transfer (SET) vs. nucleophilic alkylation processes
2015
By exploring the reactivity of sodium butyl-magnesiate (1) supported by the bulky chelating silyl(bisamido) ligand {Ph2Si(NAr*)2}(2-) (Ar* = 2,6-iPr2-C6H3) towards Quinoxaline (Qx), the ability of this bimetallic system to effectively promote SET processes has been disclosed. Thus 1 executes the single-electron reduction of Qx affording complex (2) whose structure in the solid state contains two quinaxolyl radical anions Qx˙ stabilised within a dimeric magnesiate framework. Combining multinuclear NMR and EPR measurements with DFT calculations, new insights into the constitution of 2 in solution and its magnetic behaviour have been gained. Further evidence on the SET reactivity of 1 was foun…
Experimental and theoretical investigations for the tandem alkylation–isomerization reactions between unsaturated carboxylic acids and allyl halides
2003
Abstract—Alkylation of dienediolates from unsaturated carboxylic acids with allylic halides when followed by solventless thermaltreatment at 150 to 2008C afford rearranged products on a trend highly dependent on the acarbon substitution. Thus, 2,2-bisallylated acidswith H atoms at C-2 lead to its 1,3-shift, whereas 2-methyl-2,2-bisallylated acids lead to the corresponding Cope rearrangement product. Inthe latter case, this tandem allylation-Cope reaction lead, in a highly regio and diastereoselective way, to products not accessible from directalkylation. B3LYP/6-31G p energies for the compounds involved at these isomerizations are in reasonable agreement with the experiments,allowing to exp…
13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines
2005
Abstract: Chemical shifts of the para carbon atoms, δ(13C-4), in a series of aromatic amines were used to calculate the Ãp, ÃR and ÃOR substituent constants for different amino groups. 1-Pyrrolidino, N,N-di-n-butylamino and N,N-diethylamino groups were found to be the most strong electron-donors. ortho-Substitution decreases the donor properties of the amino group. The amino groups in 2,6-di-i-propylaniline and N,N-2,6-tetramethylaniline have very weak electron-donor properties. The nitrogen atom in benzoquinuclidine and N,N-dimethyl-2,6-di-i-propylaniline have an electron-acceptor character. The calculated substituent constants of the amino groups studied are consistent with the s…
Reactivity of dialkoxydibutylstannanes toward carbon dioxide: A DFT study of electronic and steric effects
2012
Abstract DFT calculations were performed for the reaction of CO 2 with the monomeric species, R′ 2 Sn(OR) 2 , (R = R′ = CH 3 ; R = CH 3 , CH 2 CH 3 , CH(CH 3 ) 2 , R′ = n -Bu) for assessing the role of electronic and steric effects in the kinetics and thermodynamics of CO 2 insertion into Sn–OR bonds. The reaction pathways are exothermic and involve the successive insertion into the two Sn–OR bonds. The driving force for insertion is ascribed to a charge-transfer between the HOMO of the complexes, mainly localized on the oxygen atom of the alkoxy ligands, and the LUMO of CO 2 . Interestingly enough, the energy barrier of the second insertion is much lower by around 27 kJ mol −1 , and quite…