Steric control in the metal-ligand electron transfer of iminopyridine-ytterbocene complexes

International audienceA systematic study of reactions between Cp*Yb-2(THF) (Cp* = eta(5)-C5Me5, 1) and iminopyridine ligands (IPy = 2,6-(Pr2C6H3N)-Pr-i=CH(C5H3N-R), R = H (2a), 6-C4H3O (2b), 6-C4H3S (2c), 6-C6H5 (2d)) featuring similar electron accepting properties but variable denticity and steric demand, has provided a new example of steric control on the redox chemistry of ytterbocenes. The reaction of the unsubstituted IPy 2a with 1, either in THF or toluene, gives rise to the paramagnetic species Cp*Yb-2(III)(IPy)(center dot-) (3a) as a result of a formal one-electron oxidation of the Yb-II ion along with IPy reduction to a radical-anionic state. The reactions of 1 with substituted iminopyridines 2b-d, bearing aryl or hetero-aryl dangling arms on the 6 position of the pyridine ring occur in a non-coordinating solvent (toluene) only and afford coordination compounds of a formally divalent ytterbium ion, coordinated by neutral IPy ligands Cp*Yb-2(II)(IPy)(0) (3b-d). The X-ray diffraction studies revealed that 2a-c act as bidentate ligands; while the radical-anionic IPy in 3a chelates the Yb-III ion with both nitrogens, neutral IPy ligands in 3b and 3c participate in the metal coordination sphere through the pyridine nitrogen and O or S atoms from the furan or thiophene moieties, respectively. Finally, in complex 3d the neutral IPy ligand formally adopts a monodentate coordination mode. However, an agostic interaction between the Yb-II ion and an ortho C-H bond of the phenyl ring has been detected. Imino-nitrogens in 3b-d are not involved in the metal coordination. Variable temperature magnetic measurements on 3a are consistent with a multiconfigurational ground state of the Yb ion and suggest that the largest contribution arises from the 4f(13)-radical configuration. For complexes 3b and 3c the data of magnetic measurements are indicative of a Yb-II-closed shell ligand electronic distribution. Complex 3d is characterized by a complex magnetic behavior which does not allow for an unambiguous estimation of its electronic structure. The results are rationalized using DFT and CSSCF calculations. Unlike diazabutadiene analogues, 3a does not undergo a solvent mediated metalligand electron transfer and remains paramagnetic in THF solution. On the other hand, complexes 3b-d readily react with THF to afford 1 and free IPy 2b-d

Styrene-ethylene stereoselective copolymerization catalysis for sPSE materials - Molecular modelling method

Le polystyrène syndiotactique est un matériau attractif pour divers domaines d’application, notamment ceux de l’emballage ou de l’électronique. En revanche des inconvénients peuvent limiter sa production industrielle : un procédé de synthèse à température élevée et une fragilité qui pose problème dans des applications où les propriétés mécaniques sont importantes. L’amélioration du procédé de fabrication et des propriétés physico-chimiques du polystyrène syndiotactique peut se faire par l’incorporation d’un co-monomère, comme l’éthylène, durant la polymérisation stéréosélective du styrène. Les systèmes catalytiques à base de métaux du groupe 3 présentent une forte syndiospécificité et semblent prometteurs pour la copolymérisation styrène-éthylène. L’optimisation par modélisation moléculaire de tels systèmes permettra à terme de concevoir un procédé moins énergivore et satisfaisant les exigences industrielles pour la production de matériaux haute performance. C’est dans ce contexte que s’inscrivent les travaux de cette thèse, qui présente l’étude de la réaction de copolymérisation stéréosélective du styrène avec l’éthylène catalysée par des complexes de métaux du groupe 3 par une approche théorique au niveau DFT. Cette thèse a été réalisée en collaboration avec un laboratoire expérimental et suivie par un groupe industriel.Syndiotactic polystyrene is an attractive material used in several fields, in particular packaging or electronics. Its industrial production may be restricted by: a high temperature synthesis process and its brittleness, which is a drawback for applications with mechanical requirements. The improvement of the production process and the physicochemical properties of the syndiotactic polystyrene can be achieved by copolymerization with ethylene. Catalytic systems based on group 3 metals exhibit a high syndiospecificity and seem promising for styrene-ethylene copolymerization. By using molecular modelling, the optimization of such systems will allow to design a less energy-consuming process that fulfils the industrial requirements for the production of high performance materials. In this context, the work presented within this thesis is a theoretical study of styrene-ethylene stereoselective copolymerization catalysis by using DFT calculations. This PhD thesis was conducted in collaboration with an experimental team and followed by an industrial group

Catalyse de polymérisation stéréosélective du styrène avec l'éthylène pour la production de matériaux sPSE - Approche par modélisation moléculaire

Syndiotactic polystyrene is an attractive material used in several fields, in particular packaging or electronics. Its industrial production may be restricted by: a high temperature synthesis process and its brittleness, which is a drawback for applications with mechanical requirements. The improvement of the production process and the physicochemical properties of the syndiotactic polystyrene can be achieved by copolymerization with ethylene. Catalytic systems based on group 3 metals exhibit a high syndiospecificity and seem promising for styrene-ethylene copolymerization. By using molecular modelling, the optimization of such systems will allow to design a less energy-consuming process that fulfils the industrial requirements for the production of high performance materials. In this context, the work presented within this thesis is a theoretical study of styrene-ethylene stereoselective copolymerization catalysis by using DFT calculations. This PhD thesis was conducted in collaboration with an experimental team and followed by an industrial group.Le polystyrène syndiotactique est un matériau attractif pour divers domaines d’application, notamment ceux de l’emballage ou de l’électronique. En revanche des inconvénients peuvent limiter sa production industrielle : un procédé de synthèse à température élevée et une fragilité qui pose problème dans des applications où les propriétés mécaniques sont importantes. L’amélioration du procédé de fabrication et des propriétés physico-chimiques du polystyrène syndiotactique peut se faire par l’incorporation d’un co-monomère, comme l’éthylène, durant la polymérisation stéréosélective du styrène. Les systèmes catalytiques à base de métaux du groupe 3 présentent une forte syndiospécificité et semblent prometteurs pour la copolymérisation styrène-éthylène. L’optimisation par modélisation moléculaire de tels systèmes permettra à terme de concevoir un procédé moins énergivore et satisfaisant les exigences industrielles pour la production de matériaux haute performance. C’est dans ce contexte que s’inscrivent les travaux de cette thèse, qui présente l’étude de la réaction de copolymérisation stéréosélective du styrène avec l’éthylène catalysée par des complexes de métaux du groupe 3 par une approche théorique au niveau DFT. Cette thèse a été réalisée en collaboration avec un laboratoire expérimental et suivie par un groupe industriel

Catalyse de polymérisation stéréosélective du styrène avec l'éthylène pour la production de matériaux sPSE - Approche par modélisation moléculaire

Syndiotactic polystyrene is an attractive material used in several fields, in particular packaging or electronics. Its industrial production may be restricted by: a high temperature synthesis process and its brittleness, which is a drawback for applications with mechanical requirements. The improvement of the production process and the physicochemical properties of the syndiotactic polystyrene can be achieved by copolymerization with ethylene. Catalytic systems based on group 3 metals exhibit a high syndiospecificity and seem promising for styrene-ethylene copolymerization. By using molecular modelling, the optimization of such systems will allow to design a less energy-consuming process that fulfils the industrial requirements for the production of high performance materials. In this context, the work presented within this thesis is a theoretical study of styrene-ethylene stereoselective copolymerization catalysis by using DFT calculations. This PhD thesis was conducted in collaboration with an experimental team and followed by an industrial group.Le polystyrène syndiotactique est un matériau attractif pour divers domaines d’application, notamment ceux de l’emballage ou de l’électronique. En revanche des inconvénients peuvent limiter sa production industrielle : un procédé de synthèse à température élevée et une fragilité qui pose problème dans des applications où les propriétés mécaniques sont importantes. L’amélioration du procédé de fabrication et des propriétés physico-chimiques du polystyrène syndiotactique peut se faire par l’incorporation d’un co-monomère, comme l’éthylène, durant la polymérisation stéréosélective du styrène. Les systèmes catalytiques à base de métaux du groupe 3 présentent une forte syndiospécificité et semblent prometteurs pour la copolymérisation styrène-éthylène. L’optimisation par modélisation moléculaire de tels systèmes permettra à terme de concevoir un procédé moins énergivore et satisfaisant les exigences industrielles pour la production de matériaux haute performance. C’est dans ce contexte que s’inscrivent les travaux de cette thèse, qui présente l’étude de la réaction de copolymérisation stéréosélective du styrène avec l’éthylène catalysée par des complexes de métaux du groupe 3 par une approche théorique au niveau DFT. Cette thèse a été réalisée en collaboration avec un laboratoire expérimental et suivie par un groupe industriel

Substitution effects in highly syndioselective styrene polymerization catalysts based on single-component allyl ansa-lanthanidocenes: A theoretical study

International audienc

SO2 and SO3 reactions with [(C5Me5)(2)Sm-O-Sm (C5Me5)(2)]: a DFT investigation and comparison with CO2 reactivity

bibtex: ISI:000403968300003 bibtex\location:'THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND',publisher:'ROYAL SOC CHEMISTRY',type:'Article',affiliation:'Maron, L (Reprint Author), Univ Toulouse, LPCNO, CNRS, INSA,UPS, 135 Ave Rangueil, F-31077 Toulouse, France. Louyriac, Elisa; Maron, Laurent, Univ Toulouse, LPCNO, CNRS, INSA,UPS, 135 Ave Rangueil, F-31077 Toulouse, France. Roesky, Peter W., KIT, Inst Inorgan Chem, Engesserstr 15, D-76131 Karlsruhe, Germany.','author-email':'[email protected] [email protected]',da:'2018-12-05','doc-delivery-number':'EY4SR',eissn:'1477-9234','journal-iso':'Dalton Trans.','keywords-plus':'CRYSTALLOGRAPHIC CHARACTERIZATION; SULFINATE COMPLEXES; ACTIVATION; OXO; LANTHANIDE; DITHIONITE; MECHANISM; DIOXIDE','number-of-cited-references':'20','research-areas':'Chemistry','times-cited':'3','unique-id':'ISI:000403968300003','usage-count-last-180-days':'3','usage-count-since-2013':'10','web-of-science-categories':'Chemistry, Inorganic & Nuclear'\Recently, it was shown that samarocene oxide [Cp*2SmO-SmCp*(2)] with Cp* = C5Me5 could react with organic and inorganic anhydrides. The reactions of [Cp*Sm-2-O-SmCp*(2)] with SO2 and SO3 are reported using DFT calculations and compared with the reactivity of CO2. These reactions exhibit similar features yielding [Cp*(2)-Sm-(mu-eta(1):eta(2)-OSO2)-SmCp*2] similar to [Cp*(2)-Sm(mu-eta(1):eta(2)-OCO2)-SmCp*(2)] and [Cp*(2)-Sm-(mu-eta(2):eta(2)-O2SO2)-SmCp*(2)] complexes

Divalent Ytterbium Complex-Catalyzed Homo- and Cross-Coupling of Primary Arylsilanes

International audienceRedistribution of primary silanes through C-Si and Si-H bond cleavage and reformation provides a straightforward synthesis of secondary silanes, but the poor selectivity and low efficiency severely hinders the application of this synthetic protocol. Here, we show that a newly synthesized divalent ytterbium alkyl complex exhibits unprecedentedly high catalytic activity toward the selective redistribution of primary arylsilanes to secondary arylsilanes. More significantly, this complex also effectively catalyzes the cross-coupling between electron-withdrawing substituted primary arylsilanes and electron-donating substituted primary arylsilanes to secondary arylsilanes containing two different aryls. DFT calculation indicates that the reaction always involve the exothermic formation of a hypervalent silicon upon facile addition of PhSiH3 to the Yb-E (E = C, H) bond. This hypervalent compound can easily either generate directly the Yb-Ph complex, or indirectly through the formation of Yb-H, that is the key complex for the formation of Ph2SiH2

Small molecule activation with divalent samarium triflate: a synergistic effort to cleave O 2

International audienc

Formation of a Uranium-Bound eta(1)-Cyaphide (CP-) Ligand via Activation and C-O Bond Cleavage of Phosphaethynolate (OCP-)

bibtex: ISI:000416614700005 bibtex\location:'1155 16TH ST, NW, WASHINGTON, DC 20036 USA',publisher:'AMER CHEMICAL SOC',type:'Article',affiliation:'Meyer, K (Reprint Author), Friedrich Alexander Univ Erlangen Nurnberg FAU, Dept Chem & Pharm, Inorgan Chem, Egerlandstr 1, D-91058 Erlangen, Germany. Hoerger, Christopher J.; Heinemann, Frank W.; Meyer, Karsten, Friedrich Alexander Univ Erlangen Nurnberg FAU, Dept Chem & Pharm, Inorgan Chem, Egerlandstr 1, D-91058 Erlangen, Germany. Gruetzmacher, Hansjoerg, ETH, Dept Chem & Appl Biosci, Vladimir Prelog Weg 1, CH-8093 Zurich, Switzerland. Louyriac, Elisa; Maron, Laurent, Univ Toulouse, 135 Ave Rangueil, F-31077 Toulouse, France. Louyriac, Elisa; Maron, Laurent, CNRS, INSA, 135 Ave Rangueil, F-31077 Toulouse, France.','author-email':'[email protected]',da:'2018-12-05','doc-delivery-number':'FO2MZ',eissn:'1520-6041','funding-acknowledgement':'German Federal Ministry of Education and Research (BMBF) [02NUK012C, 02NUK020C]; Joint DFG-ANR projects [ME1754/7-1, ANR-14-CE35-0004-01]; FAU Erlangen-NUrnberg','funding-text':'This work was supported by funds of the German Federal Ministry of Education and Research (BMBF 2020+ support codes 02NUK012C and 02NUK020C), the Joint DFG-ANR projects (ME1754/7-1, ANR-14-CE35-0004-01), and the FAU Erlangen-NUrnberg. We thank Dr. Andreas Scheurer for assistance with the NMR measurements.','journal-iso':'Organometallics','keywords-plus':'ELECTRON-TRANSFER REACTIONS; EQUIVALENT-TO-P; E-U E; 2-PHOSPHAETHYNOLATE ANION; SODIUM PHOSPHAETHYNOLATE; CONVENIENT SYNTHESIS; COMPLEXES; REACTIVITY; CO2; CHEMISTRY','number-of-cited-references':'45','orcid-numbers':'Meyer, Karsten/0000-0002-7844-2998','research-areas':'Chemistry','researcherid-numbers':'Meyer, Karsten/G-2570-2012','times-cited':'5','unique-id':'ISI:000416614700005','usage-count-last-180-days':'2','usage-count-since-2013':'11','web-of-science-categories':'Chemistry, Inorganic & Nuclear; Chemistry, Organic'\Reaction of the trivalent uranium complex [(((ArO)-Ar-Ad,Me)(3)N]U(DME)] with [Na(OCP)(dioxane)(2.5)] and 2.2.2 -crypt yields the mu-oxo-bridged, diuranium complex [Na(2.2.2-crypt)]-[\(((ArO)-Ar-Ad,Me)(3)N)U(DME)\(mu-O)\(((ArO)-A r-Ad,Me)(3)N)U(CP)\] (1). Complex 1 features an asymmetric, dinuclear U-IV-O-U-IV core structure with a cyaphide (CP-) anion eta(I)-CP bound to one of the U ions, and a kappa(2)-O DME coordinated to the other. The CP- ligand is unprecedented in uranium chemistry and is formed through reductive C-O bond cleavage of the phosphaethynolate anion (OCP-). An analogous reaction was performed starting from the tetravalent uranium halide complex [(((ArO)-Ar-Ad,Me)N-3)U(DME)(C1)]. This salt metathesis approach with 2.70 [Na(OCP)(dioxane)(2.5)] results in formation of the mononuclear complex [(((ArO)-Ar-Ad,Me)(3)N)U(DME) (OCP) (2) with an OCP- anion bound to the uranium(IV) center via the oxygen atom in an eta(1)-OCP fashion

Cyaarside (CAs-) and 1,3-Diarsaallendiide (AsCAs2-) Ligands Coordinated to Uranium and Generated via Activation of the Arsaethynolate Ligand (OCAs-)

International audienceReaction of the trivalent uranium complex [(((ArO)-Ar-Ad,Me)(3)N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)(3)], in the presence of 2.2.2-crypt, yields [Na(2.2.2-crypt)][{(((ArO)-Ar-Ad,Me)(3)N)U-IV(THF)}(-O){(((ArO)-Ar-Ad,Me)(3)N)U-IV(CAs)}] (1), the first example of a coordinated (1)-cyaarside ligand (CAs-). Formation of the terminal CAs- is promoted by the highly reducing, oxophilic U-III precursor [(((ArO)-Ar-Ad,Me)(3)N)U(DME)] and proceeds through reductive C-O bond cleavage of the bound arsaethynolate anion, OCAs-. If two equiv of OCAs- react with the U-III precursor, the binuclear, -oxo-bridged U-2(IV/IV) complex [Na(2.2.2-crypt)](2)[{(((ArO)-Ar-Ad,Me)(3)N)U-IV}(2)(-O)(-AsCAs)] (2), comprising the hitherto unknown :(1),(1)-coordinated (AsCAs)(2-) ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs-. An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs-