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Jeanet Conradie - One of the best experts on this subject based on the ideXlab platform.
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Characterisation and mechanistic study of the Oxidative Addition Reactions of [Ir(cod)(sacac)]
Journal of Organometallic Chemistry, 2015Co-Authors: Walter Purcell, Jeanet Conradie, Sumit Kumar, Johan A. VenterAbstract:Abstract [Ir(cod)(sacac)] (sacac = thioacetyl acetonato) complexes were successfully synthesized and characterised using 1 H and 13 C NMR, IR and micro elemental analyses. The formation of isosbestic points in different solvents clearly indicate the formation of only one product, while the kinetic results for all of the complexes (except for chlorobenzene) showed simple second order kinetics with a zero intercept (within experimental error). The rate of Oxidative Addition showed little or no change with a solvent variation even with a large difference in polarity for the selected solvents, varying between 1.78 × 10 −3 and 5.2(3) M −1 s −1 for chlorobenzene and acetonitrile respectively. Activation volumes were determined in four of the solvents, which varied between +10.2(9) for chloroform to −18(1) cm 3 mol −1 for acetonitrile. This solvent variation obeyed the Kirkwood equation with an intrinsic volume of activation of −21(3) cm 3 . A DFT analysis of the Oxidative Addition Reaction shows that the trans Addition is energetically favoured and that the trans [Ir(cod) (sacac) (CH 3 ) (I)]-alkyl product is more stable than the four possible cis [Ir(cod) (sacac) (CH 3 ) (I)]-alkyl products.
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Oxidative Addition of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH_2)_3CCH_3)]: an experimental and computational study
Central European Journal of Chemistry, 2012Co-Authors: Johannes J. C. Erasmus, Jeanet ConradieAbstract:The Reaction rate of the Oxidative Addition and CO insertion steps of methyl iodide with [Rh(PhCOCHCOPh)(CO)(P(OCH_2)_3CCH_3)] are presented. Large negative experimental values for the activation entropy and results from a density functional theory computational chemistry study indicated trans Addition of the CH3I to [Rh(PhCOCHCOPh)(CO)(P(OCH_2)_3CCH_3)]. A study of the molecular orbitals gives insight into the flow of electrons during the Oxidative Addition Reaction. CO insertion leads to a square pyramidal [Rh(PhCOCHCOPh)(P(OCH_2)_3CCH_3)(COCH_3)(I)] acyl product with the COCH3 moiety in the apical position. The strong electron donation of the P(OCH_2)_3CCH_3 ligand accelerates the oxidation Addition step of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH_2)_3CCH_3)] by ca . 265 times faster (at 35°C) than that of the Monsanto catalyst, but inhibits the CO insertion step.
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methyl iodide Oxidative Addition to rh acac co pph3 an experimental and theoretical study of the stereochemistry of the products and the Reaction mechanism
Dalton Transactions, 2011Co-Authors: Marrigje M Conradie, Jeanet ConradieAbstract:Density functional theory was used to investigate the Oxidative Addition and subsequent carbonyl insertion and deinsertion steps of the Reaction of methyl iodide to a rhodium(I) acetylacetonato complex of the formula [Rh(acac)(CO)(PPh3)] (Hacac = acetylacetone). This process has been studied experimentally for many rhodium β-diketonato complexes, but, to the best of our knowledge, this is the first systematic computational study of the complete Reaction sequence. Experimental 1H techniques complement the theoretical results on the stereochemistry of the Reaction intermediates and products. 1H NMR also revealed the existence of a second rhodium(III)–acyl product, which has not been previously observed in this Reaction. The calculated Gibbs free energy of activation of the Oxidative Addition Reaction is 71 kJ mol−1, which is in agreement with the experimental value of 82(1) kJ mol−1. The DFT-calculated Oxidative Addition corresponds to an associative SN2 nucleophilic attack by the rhodium metal centre on the methyl iodide, which is in agreement with calculated and experimental (in brackets) activation parameters of the Reaction, 27 (38.8) kJ mol−1 for ΔH≠ and −147 (−146) J K−1 mol−1 for ΔS≠.
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stereochemistry of the Reaction products of the Oxidative Addition Reaction of methyl iodide to rh c4h3s cochcor co pph3 a nmr and computational study r cf3 c6h5 c4h3s
Inorganica Chimica Acta, 2009Co-Authors: Marrigje M Conradie, Jeanet ConradieAbstract:Abstract A NMR study of the Reaction mixture of the square planar [Rh((C 4 H 3 S)COCHCOR)(CO)(PPh 3 )] complex and CH 3 I, where R = CF 3 , C 6 H 5 or C 4 H 3 S, revealed that two types of alkyl and one (R = CF 3 ) or two (R = C 6 H 5 or C 4 H 3 S) types of acyl species exist in the system. Two isomers of each species with an unsymmetrical β-diketonato ligand were observed. 1 H– 1 H NOESY NMR unambiguously showed that the PPh 3 group is in the apical position in the more stable Rh III -alkyl product. Theoretical computations of the equilibrium geometry of the possible Reaction products, consistent with experimental observations, revealed that the first alkyl product results from trans Addition to Rh I and that the second thermodynamic alkyl product adopts an octahedral geometry with the PPh 3 group and the iodide above and below the square planar plane. Theoretical computations also revealed that the thermodynamic acyl product adopts a square-pyramidal geometry with the COCH 3 group in the apical position.
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methyl iodide Oxidative Addition to rhodium i complexes a dft and nmr study of rh fccochcocf 3 co pph 3 and the rhodium iii Reaction products
South African journal of chemistry, 2008Co-Authors: Marrigje M Conradie, Jeanet ConradieAbstract:A theoretical (DFT) study of the equilibrium geometry of the possible Reaction products of the Oxidative Addition Reaction [Rh(FcCOCHCOCF 3 )(CO)(PPh 3 )] + CH 3 I (Fc = ferrocenyl), consistent with experimental observations, revealed that the first alkyl product results from trans Addition to RhI. Isomerization via an acyl intermediate leads to a second octahedral alkyl product with the PPh 3 group and the iodide above and below the square plane. Theoretical computations also revealed that the thermodynamic acyl product adopts a square-pyramidal geometry with the COCH 3 group in the apical position. Keywords: DFT, computational, rhodium, β-diketone, NMR PDF and Supplementry file attached
Mats Svensson - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical study of Oxidative Addition Reaction of nickel atom to o h bond of water
Journal of Chemical Physics, 1994Co-Authors: Steven A Mitchell, Per E M Siegbahn, Mark A Blitz, Mats SvenssonAbstract:The Reaction of atomic nickel with water in the gas phase has been investigated by kinetic studies under static pressure conditions near room temperature, and by accurate quantum chemical calculations. Experimental and theoretical results are consistent with a Reaction mechanism involving formation of a weakly bound nickel–water adduct, which may react further by Oxidative Addition of nickel to the O–H bond of water to form the insertion product HNiOH. Experimental estimates of Reaction energetics have been made by using unimolecular Reaction theory calculations to model rate coefficients obtained by fitting kinetic data to a simple rate equations model. These experimental estimates are in agreement with the theoretical results, and indicate that the insertion product is bound by at least 20–25 kcal/mol, relative to nickel plus water. There is also agreement that the barrier to Oxidative Addition is no greater than 1–2 kcal/mol, and may be smaller. This theoretical result was obtained only at the highest ...
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the effects of covalent ligands on the Oxidative Addition Reaction between second row transition metal atoms and methane
Journal of the American Chemical Society, 1993Co-Authors: Per E M Siegbahn, Margareta R A Blomberg, Mats SvenssonAbstract:Calculations including electron correlation of all valence electrons have been performed to study covalent ligand effects in the Oxidative Addition Reaction of methane to second-row transition-metal complexes. Both Reaction energies and barrier heights have been determined. As a comparison the Reaction energies for the Oxidative Addition of the hydrogen molecule have also been evaluated. The entire sequence of second-row transition metals from yttrium to palladium has been studied. Hydrogen ligands have been added to systematically saturate all valencies of each metal, which means that results for 23 different Reactions each for the Oxidative Addition of methane and of molecular hydrogen have been obtained
Jianhui Wang - One of the best experts on this subject based on the ideXlab platform.
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improved visible photocatalytic activity on titania modified with o pd cl species assisted by Oxidative Addition Reaction of pd0
Journal of Physical Chemistry C, 2017Co-Authors: Yajun Yang, Yanlong Yu, Chunling Zhang, Jianhui WangAbstract:We introduce the idea of Pd catalysis used in cross-coupling Reactions into photocatalysis. The −O–Pd–Cl surface species modified on nanoscale TiO2 can remarkably enhance the photocatalytic activity under visible-light irradiation in the degradation of 4-bromophenol. It is revealed that the catalytically active Pd0 is in situ generated by the reduction of photogenerated electrons from TiO2. The −O–Pd0–Cl species can react with 4-bromophenol to form hydroxyphenyl radicals via an Oxidative Addition Reaction. The photocatalytic mechanism assisted by the Oxidative Addition Reaction on −O–Pd–Cl species is also demonstrated. We were hence able to rationally tailor the coordination environment of Pd on the TiO2 surface to obtain high photocatalytic activity and selectivity.
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Improved Visible Photocatalytic Activity on Titania Modified with −O–Pd–Cl Species Assisted by Oxidative Addition Reaction of Pd0
Journal of Physical Chemistry C, 2016Co-Authors: Yajun Yang, Yanlong Yu, Chunling Zhang, Jianhui WangAbstract:We introduce the idea of Pd catalysis used in cross-coupling Reactions into photocatalysis. The −O–Pd–Cl surface species modified on nanoscale TiO2 can remarkably enhance the photocatalytic activity under visible-light irradiation in the degradation of 4-bromophenol. It is revealed that the catalytically active Pd0 is in situ generated by the reduction of photogenerated electrons from TiO2. The −O–Pd0–Cl species can react with 4-bromophenol to form hydroxyphenyl radicals via an Oxidative Addition Reaction. The photocatalytic mechanism assisted by the Oxidative Addition Reaction on −O–Pd–Cl species is also demonstrated. We were hence able to rationally tailor the coordination environment of Pd on the TiO2 surface to obtain high photocatalytic activity and selectivity.
Jannie C Swarts - One of the best experts on this subject based on the ideXlab platform.
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kinetic study of the Oxidative Addition Reaction between methyl iodide and rh fccochcocf3 co pph3 structure of rh fccochcocf3 co pph3 ch3 i
Polyhedron, 2007Co-Authors: Jeanet Conradie, Gert J Lamprecht, Andreas Roodt, Jannie C SwartsAbstract:Abstract The kinetics of Oxidative Addition of CH3I to [Rh(FcCOCHCOCF3)(CO)(PPh3)], where Fc = ferrocenyl and (FcCOCHCOCF3)− = fctfa = ferrocenoylacetonato, have been studied utilizing UV/Vis, IR, 1H and 31P NMR techniques. Three definite sets of Reactions involving isomers of at least two distinctly different classes of RhIII-alkyl and two different classes of RhIII-acyl species were observed. Rate constants for this Reaction in CHCl3 at 25 °C, applicable to the Reaction sequence below, were determined as k1 = 0.00611(1) dm3 mol−1 s−1, k−1 = 0.0005(1) s−1, k3 = 0.00017(2) s−1 and k4 = 0.0000044(1) s−1 while k−3 ≪ k3 and k−4 ≪ k4 but both ≠0. The indeterminable equilibrium K2 was fast enough to be maintained during RhI depletion in the first set of Reactions and during the RhIIIalkyl2 formation in the second set of Reactions. From a 1H and 31P NMR study in CDCl3, Kc1 was found to be 0.68, Kc2 = 2.57, Kc3 = 1.00, Kc4 = 4.56 and Kc5 = 1.65. Download : Download full-size image The above Reaction sequence represents a completely general Reaction sequence for the Oxidative Addition of iodomethane to any β-diketonato complex of the type [Rh(β-diketonato)(CO)(PPh3)], although the equilibrium K2 may not necessarily always be fast. A temperature dependence study in chloroform led to the activation enthalpies, ΔH#, and activation entropies, ΔS#, for both the first and second sets of Reactions. A solvent dependence study utilizing five different solvents showed the rate of the first set of Reactions are directly proportional to the dielectric constant of the solvent. The molecular formula of all the RhIII-alkyl and RhIII-acyl species are [Rh(FcCOCHCOCF3)(CH3)(CO)(PPh3)(I)] and [Rh(FcCOCHCOCF3)(COCH3)(PPh3)(I)], respectively (Fc = ferrocenyl), but the geometries of the two RhIII isomers and the initial RhI species all differ due to different coordination spheres. A crystal structure determination (Z = 4, monoclinic, P21/c) of [Rh(FcCOCHCOCF3)(CO)(PPh3)(CH3)(I)], an isomer of the RhIII-alkyl2 species, is also reported.
Per E M Siegbahn - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical study of Oxidative Addition Reaction of nickel atom to o h bond of water
Journal of Chemical Physics, 1994Co-Authors: Steven A Mitchell, Per E M Siegbahn, Mark A Blitz, Mats SvenssonAbstract:The Reaction of atomic nickel with water in the gas phase has been investigated by kinetic studies under static pressure conditions near room temperature, and by accurate quantum chemical calculations. Experimental and theoretical results are consistent with a Reaction mechanism involving formation of a weakly bound nickel–water adduct, which may react further by Oxidative Addition of nickel to the O–H bond of water to form the insertion product HNiOH. Experimental estimates of Reaction energetics have been made by using unimolecular Reaction theory calculations to model rate coefficients obtained by fitting kinetic data to a simple rate equations model. These experimental estimates are in agreement with the theoretical results, and indicate that the insertion product is bound by at least 20–25 kcal/mol, relative to nickel plus water. There is also agreement that the barrier to Oxidative Addition is no greater than 1–2 kcal/mol, and may be smaller. This theoretical result was obtained only at the highest ...
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the effects of covalent ligands on the Oxidative Addition Reaction between second row transition metal atoms and methane
Journal of the American Chemical Society, 1993Co-Authors: Per E M Siegbahn, Margareta R A Blomberg, Mats SvenssonAbstract:Calculations including electron correlation of all valence electrons have been performed to study covalent ligand effects in the Oxidative Addition Reaction of methane to second-row transition-metal complexes. Both Reaction energies and barrier heights have been determined. As a comparison the Reaction energies for the Oxidative Addition of the hydrogen molecule have also been evaluated. The entire sequence of second-row transition metals from yttrium to palladium has been studied. Hydrogen ligands have been added to systematically saturate all valencies of each metal, which means that results for 23 different Reactions each for the Oxidative Addition of methane and of molecular hydrogen have been obtained
