Search results for "Catalysis"

The Pd3(dppm)3(CO)2+ Cluster: An Efficient Electrochemically Assisted Lewis Acid Catalyst for the Fluorination and Alcoholysis of Acyl Chlorides.

2002

The dicationic palladium cluster Pd3(dppm)3(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCO…

First Example of Coexistence of Thermal Spin Transition and Liquid-Crystal Properties.

2001

The rodlike FeIII complex of an N-alkyloxysalicylidenyl-N'-ethyl-N-ethylenediamine ligand, shown as a computer model in the picture, is the first compound in which spin-crossover (SC) and liquid-crystalline (LC) properties coexist. This synergy should allow the magnetic and optical properties of SC compounds to be combined with the sensitivity of the LC state to electromagnetic fields.

A molecular electron density theory study of the Lewis acid–catalyzed decomposition reaction of nitroethyl benzoate using aluminum derivatives

2019

Hydrogen-Bond Cooperative Effects in Small Cyclic Water Clusters as Revealed by the Interacting Quantum Atoms Approach

2013

The cooperative effects of hydrogen bonding in small water clus- ters (H2O)n (n = 3-6) have been studied by using the partition of the electronic energy in accordance with the interact- ing quantum atoms (IQA) approach. The IQA energy splitting is comple- mented by a topological analysis of the electron density (1(r)) compliant with the quantum theory of atoms-in-mole- cules (QTAIM) and the calculation of electrostatic interactions by using one- and two-electron integrals, thereby avoiding convergence issues inherent to a multipolar expansion. The results show that the cooperative effects of hy- drogen bonding in small water clusters arise from a compromise between: 1) the deformation energ…

Unravelling the strain-promoted [3+2] cycloaddition reactions of phenyl azide with cycloalkynes from the molecular electron density theory perspective

2020

The strain-promoted [3+2] cycloaddition (SP-32CA) reactions of phenyl azide with a series of five strained cycloalkynes C5–C9 have been studied within molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These zwitterionic type SP-32CA reactions take place through a one-step mechanism, with activation enthalpies in acetonitrile between −4.2 and 19.9 kcal mol−1. An excellent linear correlation between the decrease in activation enthalpies and the ring size of this series of cycloalkynes can be established. The present study shows that the highly strained cycloalkynes C5 and C6 experience a different chemical reactivity than less strained cycloalkynes C7–C9,…

Partial Reduction and Selective Transfer of Hydrogen Chloride on Catalytic Gold Nanoparticles

2017

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim HCl in solution accepts electron density from Au NPs and partially reduces at room temperature, as occurs with other simple diatomic molecules, such as O2 and H2. The activation can be run catalytically in the presence of alkynes to give exclusively E-vinyl chlorides, after the regio- and stereoselective transfer of HCl. Based also on this method, vinyl chloride monomer (VCM) can be produced in a milder and greener way than current industrial processes.

The nature of inter- and intramolecular interactions in F2OXe…HX (X= F, Cl, Br, I) complexes

2015

Electronic structure of the XeOF2 molecule and its two complexes with HX (X= F, Cl, Br, I) molecules have been studied in the gas phase using quantum chemical topology methods: topological analysis of electron localization function (ELF), electron density, ρ(r), reduced gradient of electron density |RDG(r)| in real space, and symmetry adapted perturbation theory (SAPT) in the Hilbert space. The wave function has been approximated by the MP2 and DFT methods, using APF-D, B3LYP, M062X, and B2PLYP functionals, with the dispersion correction as proposed by Grimme (GD3). For the Xe-F and Xe=O bonds in the isolated XeOF2 molecule, the bonding ELF-localization basins have not been observed. Accord…

Similarities and differences between crystal and enzyme environmental effects on the electron density of drug molecules

2021

Abstract The crystal interaction density is generally assumed to be a suitable measure of the polarization of a low‐molecular weight ligand inside an enzyme, but this approximation has seldomly been tested and has never been quantified before. In this study, we compare the crystal interaction density and the interaction electrostatic potential for a model compound of loxistatin acid (E64c) with those inside cathepsin B, in solution, and in vacuum. We apply QM/MM calculations and experimental quantum crystallography to show that the crystal interaction density is indeed very similar to the enzyme interaction density. Less than 0.1 e are shifted between these two environments in total. Howeve…

Frontispiece: A Novel High‐Pressure Tin Oxynitride Sn 2 N 2 O

2020

Chemistry - a European journal 26(10), 2187-2194 (2020). doi:10.1002/chem.202081063

Theoretical study on the molecular mechanism of the [5 + 2] vs. [4 + 2] cyclization mediated by Lewis acid in the quinone system

2013

[EN] The thermal and Lewis acid (LA) catalyzed cyclizations of quinone 1 involved in the synthesis of Colombiasin A and Elipsaterosin B have been theoretically studied using DFT methods at the B3LYP/6-311G(d,p) computational level. B3LYP calculations suggest that the formal endo [4 + 2] cycloadduct allowing the synthesis of Colombiasin A is preferentially formed under thermal conditions, while in the presence of the BF3 LA catalyst the formal [5 + 2] cycloadduct is seen, allowing the synthesis of Elipsaterosin B. The BF3 LA catalyst not only accelerates the nucleophilic attack on the C2 carbon of the quinone framework through a more polar C-C bond formation, but also provokes a different el…