Highly efficient P–N nickel(<scp>ii</scp>) complexes for the dimerisation of ethylene

Buchard, Antoine; Auffrant, Audrey; Klemps, Christian; Vu-Do, Laurence; Boubekeur, Leïla; Goff, Xavier F. Le; Floch, Pascal Le

doi:10.1039/b618401d

Cited by 53 publications

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References 16 publications

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“…With the aim of (partially) filling this lack, we present in this article a detailed analysis on the influence of the exchange-correlation functionals on the mechanism of ethylene dimerization catalyzed by a mixed (P,N)-Nickel(II) complexes 13 ( Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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How the choice of a computational model could rule the chemical interpretation: The Ni(II) catalyzed ethylene dimerization as a case study

Tognetti¹,

Floch²,

Adamo³

2009

J Comput Chem

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In this article, we present a critical study of the theoretical protocol used for the determination of the nickel(II) catalyzed ethylene dimerization mechanism, considered as a representative example of the various problems related to the modeling a catalytic cycle. The choice of an appropriate computational procedure is indeed crucial for the validity of the conclusions that will be drawn from the computational process. The influence of the exchange-correlation functional on energetic profiles and geometries, the role of the basis set describing the metal atom, as well as the importance of the chosen molecular model, have been thus examined in details. From the obtained results, some general conclusions and guidelines are presented, which could constitute useful warnings in modeling homogenous catalysis. Besides, the database constituted by our high-level calculations can be used within benchmarking procedures to assess the performances of new computational methods based on density functional theory.

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Section: Introductionmentioning

confidence: 99%

“…Indeed, we recall that experimentally the proportions are as follows: more than 93% of butene, 7% of hexene, and none superior oligomers. 13 The experimental prototype of these complexes is the one bearing phenyl groups on the phosphorus atoms and a para-metoxybenzyle on nitrogen (Fig. 1).…”

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confidence: 99%

How the choice of a computational model could rule the chemical interpretation: The Ni(II) catalyzed ethylene dimerization as a case study

Tognetti¹,

Floch²,

Adamo³

2009

J Comput Chem

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“…[3b, 8] The hybridization of the nitrogen atoms is also of prime importance since it may influence the oxidation site, the spin state of the metal, and the magnetic interactions within the molecule. [5b, 9] Astonishingly, despite numerous structural variations proposed for salen ligands, the introduction of heteroatoms into their backbone was rarely investigated.[10] As we are interested in iminophosphorane (P=N) based ligands as an alternative to conventional imine-based ligands, [11] we developed a new class of ligands featuring iminophosphorane units, which we termed phosphasalen (or Psalen). We have recently demonstrated that these ligands are more flexible and electron-donating than their carbon analogues [12] and that they provide efficient and selective initiators for rac-lactide polymerization.…”

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confidence: 99%

A Tetracoordinated Phosphasalen Nickel(III) Complex

et al. 2013

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The oxidation of a Ni II complex bearing a tetradentate phosphasalen ligand, which differs from salen by the presence of an iminophosphorane (P = N) in place of an imine unit, was easily achieved by addition of a silver salt. The site of this oxidation was investigated with a combination of techniques (NMR, EPR, UV/Vis spectroscopy, X-ray diffraction, magnetic measurements) as well as DFT calculations. All data are in agreement with a high-valent Ni III center concentrating the spin density. This markedly differs from precedents in the salen series for which oxidation on the metal was only observed at low temperature or in the presence of additional ligands or anions. Therefore, thanks to the good electron-donating properties of the phosphasalen ligand, [Ni(Psalen)]+ represents a rare example of a tetracoordinated high-valent nickel complex in presence of a phenoxide ligand.N,N' -ethylenebis(salicylimine) (salen) derivatives constitute a very successful class of ligands that have found numerous applications in inorganic chemistry and catalysis. [1] Their extraordinary popularity comes from their easy synthesis, allowing a variety of skeleton variations, and their ability to coordinate to a great number of different metal ions. Moreover the presence of two phenoxide and imine functions is reminiscent of the coordination environment generated by two histidine and two tyrosine residues, encountered in several enzymes. Thus, in 1998, the one-electron oxidation of a (salen)copper(II) complex was described, and the resulting persistent phenoxy radical was established as a biomimetic functional model of galactose oxidase.[2] Since then, one-electron-oxidized metal salen complexes of firstrow transition metals have received considerable attention. [3] Depending on the nature of the redox-active orbitals, oxidation of salen complexes leads either to high-valent metal centers (metal-centered oxidation) or to species where the ligand is oxidized to a radical (ligand-centered oxidation). Therefore, various factors may affect the oxidation site, as it was nicely illustrated in the case of nickel salen complexes. In noncoordinating solvents, one-electron oxidation occurs on the ligand, and the unpaired electron is highly delocalized over the salen moiety with a small contribution of the nickel orbitals.[3b, 4] However, in coordinating solvents, or in the presence of exogenous ligands such as pyridine or coordinating anions, the geometry of the complex is modified and so is the site of the oxidation, allowing the formation of Ni III complexes.[4a,b, 5] Temperature-dependent behavior, that is, valence tautomerism, was also described in a few examples.[5b, 6] Moreover, the overall electronic distribution may be finely tuned by the substituents of the phenoxide rings. They influence not only the site of the oxidation (which takes place at the most electron-rich phenoxide ring) as evidenced with complexes featuring unsymmetrical salen, [3c, 7] but also the extent of radical delocalization. [3b, 8] The hybridization o...

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“…Titanium‐based Ziegler‐Natta systems are certainly the most widespread catalysts for this transformation 20, but some other approaches have been developed over the last decade, such as those based, for instance, on nickel catalysts. These last catalysts show an excellent activity (more than 90% of butene and turn‐over frequencies superior to 60,000 mol C2H4 mol Ni −1 h −1 ) 18 but mechanistical insigths have been given only recently (Tognetti et al, in preparation). More precisely, we have recently investigated the Cossee mechanism 21 of the ethylene dimerization (Fig.…”

Section: The Nickel(ii) Ethylene Dimerizationmentioning

confidence: 99%

“…In this article, we explore the combined use of these two approaches, Conceptual DFT and QSPR, to study catalytic transformations, namely nickel(II) catalyzed ethylene dimerization 18.…”

Section: Introductionmentioning

confidence: 99%

Can molecular quantum descriptors predict the butene selectivity in nickel(II) catalyzed ethylene dimerization? A QSPR study

Tognetti¹,

Fayet²,

Adamo³

2009

Int J of Quantum Chemistry

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ABSTRACT:In this article, we assess the ability of common molecular descriptors issued from quantum chemistry calculations (geometrical parameters, atomic charges, isodesmic energies, polarizabilities, and descriptors from conceptual DFT) to predict the butene selectivity in the mixed (P,N)-nickel(II) catalyzed ethylene dimerization process. To this aim, 29 active species are considered, characterized by different substitution patterns on the nitrogen and phosphorus atoms. For each of them, the Gibbs energy difference between the transition states for the third ethylene insertion and for the butene elimination is computed to characterize the selectivity. Our results show that, in contrast to previously reported catalysts, the studied descriptors did not show any significant correlations with the property to predict and their integration in a multivariate analysis was not more efficient for the considered catalytic systems.

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Highly efficient P–N nickel(ii) complexes for the dimerisation of ethylene

Abstract: New P-N ligands featuring a phosphino group and an iminophosphorane moiety were successfully employed in the nickel-catalysed dimerisation of ethylene.

Cited by 53 publications

References 16 publications

How the choice of a computational model could rule the chemical interpretation: The Ni(II) catalyzed ethylene dimerization as a case study

How the choice of a computational model could rule the chemical interpretation: The Ni(II) catalyzed ethylene dimerization as a case study

A Tetracoordinated Phosphasalen Nickel(III) Complex

Can molecular quantum descriptors predict the butene selectivity in nickel(II) catalyzed ethylene dimerization? A QSPR study

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