Theoretical Treatment of the Redox Chemistry of Low Valent Lanthanide and Actinide Complexes

Kefalidis, Christos E.; Castro, Ludovic; Yahia, Ahmed; Perrin, Lionel; Maron, Laurent

doi:10.1002/9781118688304.ch13

Cited by 6 publications

(3 citation statements)

References 141 publications

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“…12,14,19,23 Perrin, Maron, and Eisenstein have used this strategy intensively and fruitfully in mechanistic studies involving lanthanide(III) complexes, including polymerization reaction studies. 20,24,25 Notation. L_NdR refers to the neodymocene complex (C 5 Me 5 ) 2 NdR for L = 1 and Me 2 Si(C 13 H 8 ) 2 NdR for L = 2.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Owing to the concerted character of monomer insertion, the Nd oxidation state remains constant at its +III oxidation state during polymerization. In addition, it has been demonstrated that 4f orbitals and electrons have little to no influence on the lanthanide–ligand chemical bonds and their reactivity. − As a result, the 4f shell was implicitly considered by using a large-core 49-electron quasi-relativistic effective core potential (ECP) and its polarized associated basis set. , The choice of density functional (B3PW91), basis sets (6-311G(d,p)), and solvent (SMD-toluene) and dispersion corrections (D3-BJ) have already been discussed in previous communications. ,,, Perrin, Maron, and Eisenstein have used this strategy intensively and fruitfully in mechanistic studies involving lanthanide(III) complexes, including polymerization reaction studies. ,, …”

Section: Resultsmentioning

confidence: 99%

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Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

et al. 2018

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A range of dialkenylmagnesium compounds ([CH2CH(CH2) n ]2Mg; n = 1–6) were synthesized and used as chain transfer agents (CTA) with either (C5Me5)2NdCl2Li(OEt2)2 (1) or [Me2Si(C13H8)2Nd(BH4)2Li(thf)]2 (2) neodymium precursors for the polymerization of ethylene. In all cases, the systems followed a controlled coordinative chain transfer polymerization mechanism. The intramolecular insertion of the vinyl group on the CTA in growing chains is possible and led to the formation of cyclopentyl, cyclohexyl, and possibly cycloheptyl chain ends. While the production of cyclopentyl- or cyclohexyl-capped polyethylene chains can be quantitative (n = 2–5), the integrity of this double bond can also be kept if n is higher than 6. In comparison to 1/CTA catalytic systems, 2/CTA catalytic systems showed a higher propensity to produce cycloalkyl chain ends. This was ascribed to the lower steric demand around the active site, as shown by DFT calculations. In addition, the formation of bis(cyclopentylmethyl)magnesium from dipentenylmagnesium using a catalytic amount of 2 was shown.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

et al. 2018

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“…When it comes to chemical space, the Pople diagram is a two-dimensional display of the relationship of the size of any molecule and level of theory . Pople diagrams can easily be extended to accommodate additional or other dimensions such as relativistic effects or accuracy . In this study, we apply the idea of a Pople diagram to combine varying levels of theory in the training set of QML models (see Figure for the general idea).…”

Section: Introductionmentioning

confidence: 99%

Boosting Quantum Machine Learning Models with a Multilevel Combination Technique: Pople Diagrams Revisited

Zaspel

Huang

Harbrecht

et al. 2018

J. Chem. Theory Comput.

107

184

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Inspired by Pople diagrams popular in quantum chemistry, we introduce a hierarchical scheme, based on the multi-level combination (C) technique, to combine various levels of approximations made when calculating molecular energies within quantum chemistry. When combined with quantum machine learning (QML) models, the resulting CQML model is a generalized unified recursive kernel ridge regression which exploits correlations implicitly encoded in training data comprised of multiple levels in multiple dimensions. Here, we have investigated up to three dimensions: Chemical space, basis set, and electron correlation treatment. Numerical results have been obtained for atomization energies of a set of ∼7'000 organic molecules with up to 7 atoms (not counting hydrogens) containing CHONFClS, as well as for ∼6'000 constitutional isomers of C 7 H 10 O 2 . CQML learning curves for atomization energies suggest a dramatic reduction in necessary training samples calculated with the most accurate and costly method. In order to generate milli-second estimates of CCSD(T)/cc-pvdz atomization energies with prediction errors reaching chemical accuracy (∼1 kcal/mol), the CQML model requires only ∼100 training instances at CCSD(T)/cc-pvdz level, rather than thousands within conventional QML, while more training molecules are required at lower levels. Our results suggest a possibly favorable trade-off between various hierarchical approximations whose computational cost scales differently with electron number.

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Facile CO Cleavage by a Multimetallic CsU₂ Nitride Complex

et al. 2016

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Uranium nitrides are important materials with potential application as fuel for nuclear power generation, and as highly active catalysts. Molecular nitride compounds could provide important insight into the nature of the uranium-nitride bond, but currently little is known about their reactivity. Here we find that a complex containing a nitride bridging two uranium centres and a cesium cation readily cleaves the C≡O bond (one of the strongest bonds in nature) under ambient conditions. The product formed has a [CsU2(μ-CN)(μ-O)] core indicating that the three cationsUranium nitrides are of great interest because of the potential applications in both stoichiometric and catalytic transformations and in materials science and engineering.[1] The recent discovery and characterization of stable mononuclear and dinuclear uranium nitride complexes [2] has now rendered the investigation of the reactivity of these species accessible. Carbon monoxide is an inexpensive and readily available C1 feedstock used in industry for the production of a wide variety of chemicals such as methanol, acetic acid, phosgene and hydrocarbons.[3] A key step in the Fischer-Tropsch hydrocarbon production from CO and H2 is the cleavage of the CO triple bond, which is the strongest bond in chemistry (dissociation energy at 298 K =1076 kJ mol -1). This process requires the use of heterogeneous transition-metal catalysts at elevated temperatures.[4] The cleavage of the CO bond under mild conditions is an important fundamental challenge in the search of new routes for the production of functionalized organic molecules from CO. The direct addition of CO to a metal-nitride is a rare event observed only for highly nucleophilic nitride complexes of d-block transition metals such as V, Fe and Hf.[5] Notably, a few terminal monometallic nitrido complexes and only one exemple of nidridebridged dimetallic complex[5f] effect nitrogen atom transfer to CO affording cyanate which in some case is spontaneously extruded.[5d] Reductive carbonylation of monometallic U(V) and U(VI) nitrides by CO affording the isocyanate ligand has also been recently reported.[5e] However complete cleavage of CO by a nitride complex has not been reported so far. Several examples of CO cleavage by metal complexes have been reported, [6] and these reactions often yield metal-carbide complexes and oxo clusters. The binding [7] and the reduction [8] of CO by uranium(III) complexes has been demonstrated. Several examples of CO reductive homologations effected by uranium(III) systems, yielding deltate, [9] squarate [9b, 10] or ethynediolate dianions [9b, 11] have also been identified. However, uranium compounds that effect the deoxygenation of CO have not yet been identified. We recently demonstrated the unusually high nucleophilic character of the nitride-bridged di-uranium complex Cs [{U(OSi(OtBu)3)3}2(μ-N)], (1) [2d, 12] , that reacts in ambient conditions with CO2 and CS2 leading to N-C bond formation yielding cyanate and thiocyanate and unprecedented dicarbamate species....

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Theoretical Treatment of the Redox Chemistry of Low Valent Lanthanide and Actinide Complexes

Cited by 6 publications

References 141 publications

Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

Boosting Quantum Machine Learning Models with a Multilevel Combination Technique: Pople Diagrams Revisited

Facile CO Cleavage by a Multimetallic CsU₂ Nitride Complex

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Theoretical Treatment of the Redox Chemistry of Low Valent Lanthanide and Actinide Complexes

Cited by 6 publications

References 141 publications

Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

Dialkenylmagnesium Compounds in Coordinative Chain Transfer Polymerization of Ethylene. Reversible Chain Transfer Agents and Tools To Probe Catalyst Selectivities toward Ring Formation

Boosting Quantum Machine Learning Models with a Multilevel Combination Technique: Pople Diagrams Revisited

Facile CO Cleavage by a Multimetallic CsU2 Nitride Complex

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Facile CO Cleavage by a Multimetallic CsU₂ Nitride Complex