Combining NHC bis-Phenolate Ligands with Oxophilic Metal Centers: A Powerful Approach for the Development of Robust and Highly Effective Organometallic Catalysts:

The present paper describes an overview of a novel family of tridentate NHC pincer ligand in which two phenoxide moieties are directly connected to the nitrogen atoms of a central N-heterocyclic carbene. It was envisioned that such a structure might be suitable for coordination to a variety of metal centers across the periodic table, including oxophilic metals. Various metal complexes bearing such ligand are indeed readily accessible in high yields via straightforward routes. Interestingly, a robust zirconium-NHC complex was found to polymerize rac-lactide in a highly controlled, living and stereoselective manner to afford heterotactic PLA

Dépistage des troubles visuels et auditifs chez l'enfant. Application des recommandations chez les médecins généralistes du Maine-et-Loire

Dépister précocement les troubles visuels et auditifs chez le nourrisson permet une meilleure prise en charge thérapeutique. Ce rôle est en grande partie dévolu aux médecins généralistes et obligatoires lors des examens de santé du 9e et du 24e mois. Nous avons réalisé une enquête prospective auprès de l’ensemble des médecins généralistes d’un département français, afin de connaître leurs habitudes pratiques cliniques en matière de dépistage des troubles sensoriels. Le taux de réponses de 49 % a permis d’exploiter 321 questionnaires. Nous constatons que l’examen clinique n’est pas systématique et qu’il est principalement effectué lors des examens des 4e, 9e et 24e mois ou en cas de doute parental. Si les signes d’alerte sont, dans leur ensemble, bien connus des médecins généralistes, les facteurs de risque sont recherchés de façon incomplète. L’examen clinique reste sommaire avec la réalisation des principaux réflexes pour l’appareil visuel, mais une recherche superficielle du strabisme ou de l’amblyopie. Le dépistage auditif est réalisé principalement avec la voix ou le claquement des mains, bien que deux tiers d’entre eux possèdent des jouets calibrés. L’âge minimum de prise en charge est mal connu des praticiens et cela peut être préjudiciable à la bonne prise en charge des déficits sensoriels. Le nouveau carnet de santé devrait permettre un dépistage plus pertinent des troubles sensoriels chez le nourrisson : une plus large diffusion des informations et des conduites à tenir est nécessaire

Outcome of Ph negative myeloproliferative neoplasms transforming to accelerated or leukemic phase

Myeloproliferative neoplasms (MPN) are chronic disorders that can sometimes evolve into accelerated or leukemic phases. We retrospectively identified 122 patients with such blastic phases. The overall median survival was four months: 10.2 months for patients treated with intensive treatments compared to three months for best supportive care (p = .005). Azacytidine, intensive chemotherapies, or allogeneic stem cell transplantation gave the highest median survivals with 9, 10.2, and 19.4 months, respectively. Accelerated phases (AP) had a longer median survival compared to acute leukemia (4.8 months vs. 3.1 months; p = .02). In this retrospective and observational study, we observe that the longest survivals are seen in patients eligible for intensive treatments. Azacytidine shows interesting results in patients non-fit for intensive chemotherapy. Supportive care should probably be restricted to elderly patients and those with unfavorable karyotype. An early diagnosis of AP could also result in a better survival rate

Bis[bis(oxazolinato)] Complexes of Yttrium and Lanthanum: Molecular Structure and Use in Polymerization of (D,L)-Lactide and (D,L)-Γ-Butyrolactone

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Perfluoroaryl Zinc Catalysts Active in Cyclohexene Oxide Homopolymerization and Alternating Copolymerization with Carbon Dioxide

The zinc complex Zn(C6F5)(2)(toluene) (1) behaves as a very active and selective catalyst in cyclohexene oxide (CHO) polymerization to produce poly(cyclohexene oxide) (PCHO) by the trans-ring-opening of CHO with remarkable TOF values at room temperature. The ring-opening copolymerization (ROCOP) of CO2 with CHO catalysed by 1 yields poly(cyclohexene carbonate) (PCHC) when using benzyl alcohol (BnOH) as an initiator at 120 degrees C. The H-1 NMR monitoring of the in situ reaction of 1 with BnOH highlighted the formation of the dinuclear species [(C6F5)(2)Zn-2(BnO)(2)] (2) that was isolated and found an active catalyst in the ROCOP of CO2 with CHO in the absence of initiators. Interestingly, PCHCs by 2 in solventless conditions show polydispersity index (M-w/M-n) values close to 2, corresponding to those expected for a single-site catalyst; on the contrary, a broader polydispersity index of the polymer products was found in toluene solution, suggesting the formation of new zinc catalysts during the polymerization reaction

Tridentate complexes of group 10 bearing bis-aryloxide N-heterocyclic carbene ligands: Synthesis, structural, spectroscopic, and computational characterization

A series of group 10 complexes featuring chelating tridentate bis-aryloxide N-heterocyclic carbenes were synthesized and characterized by using different techniques. Ni(II), Pd(II), and Pt(II) complexes were isolated in good yields by straightforward direct metalation of the corresponding benzimidazolium or imidazolium precursors in a one-pot procedure. All of the compounds were fully characterized, including single-crystal X-ray diffractometric determination for three of the derivatives. In the solid state, the complexes adopt a typical square-planar coordination geometry around the platinum atom, sizably distorted in order to comply with the geometrical constraints imposed by the bis-aryloxide N-heterocyclic carbene ligand. For platinum and palladium derivatives, a joint experimental and theoretical characterization was performed in order to study the optical properties of the newly prepared complexes by means of electronic absorption and steady-state and time-resolved photophysical techniques as well as density functional theory (DFT) and time-dependent DFT in both vacuum and solvent. When the temperature was lowered to 77 K in frozen glassy matrix, three platinum complexes showed broad and featureless, yet weak, photoluminescence in the green region of the visible spectrum with excited-state lifetimes on the order of a few microseconds. On the basis of joint experimental and computational findings and literature on platinum complexes, such emission was assigned to a triplet-manifold metal-ligand-to-ligand charge transfer (3MLLCT) transition

Unusual Benzyl Migration Reactivity in NHC-Bearing Group 4 Metal Chelates: Synthesis, Characterization, and Mechanistic Investigations

International audienceThe reaction of 1 equiv of [M(CH2Ph)4] (M = Zr, Hf) and 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)imidazolinium chloride [tBu(OCO)H3, 1] cleanly yielded the corresponding M-NHC chloro benzyl derivatives [[tBu(OCO)]M(Cl)(CH2Ph)] (2Zr and 2Hf) along with 3 equiv of toluene. For both metal complexes, the effective formation of a (κ3-OCO) metal chelate and the coordination of a benzyl ligand onto the M(IV) metal center were established by NMR and elemental analysis. In contrast, under identical conditions, the reaction of Ti(CH2Ph)4 with the imidazolinium proligand 1 yielded the unexpected rearranged dimer product 3Ti, arising from the migration of the Ti-Bn group from the metal center to the Ccarbene atom. The molecular structure of 3Ti was established by analogy with the X-ray-determined Zr analogue 3Zr. Compound 3Zr quantitatively formed upon heating a benzene solution of 2Zr at 60 °C. In the solid state, compound 3Zr consists of two seven-coordinate mononuclear Zr fragments that are associated by two bridging μ2-chloride atoms, confirming the migration of the Zr-Bn moiety from the metal center to the Ccarbene atom. Carrying out the reaction of [M(CH2Ph)4] (M = Ti, Zr, Hf) with imidazolinium proligand 1 in THF led to the quantitative formation of the corresponding rearranged monomeric THF adduct [[tBu(OC(Bn)O)]M(Cl)(THF)] (4Ti-THF, 4Zr-THF, and 4Hf-THF), as established by X-ray crystallographic studies in the case of 4Ti-THF. Such a THF-promoted benzyl migration was also observed with the dibenzyl Zr and Hf complexes [[tBu(OCO)]M(CH2Ph)2] (5Zr and 5Hf), leading to the formation of the corresponding THF-rearranged products [[tBu(OC(Bn)O)]M(CH2Ph)(THF)] (6Zr-THF and 6Hf-THF). The addition of 1 equiv of methylmagnesium bromide (CH3MgBr) or phenylmagnesium bromide (PhMgBr) to 1 equiv of the zirconium dichloro NHC complex [[tBu(OCO)]Zr(Cl)2(THF)] (8) in THF yielded the rearranged products [[tBu(OC(Me)O)]M(Cl)(THF)] (9Me) and [[tBu(OC(Ph)O)]M(Cl)(THF)] (9Ph), respectively, as deduced from NMR data. Kinetic studies were carried out on the THF-promoted rearrangement reaction of the benzyl chloro Hf derivative 2Hf in the presence of THF to produce 4Hf-THF. These data are consistent with the reaction rate law being first order both in THF and in the THF adduct 2Hf-THF. DFT calculations on the Ti, Zr, and Hf systems support a benzyl migration reaction occurring at a transient heptacoordinated bis-THF adduct species of the type [[tBu(OCO)]M(Cl)(Bn)(THF)2], which may readily form upon THF coordination to 2Hf-THF. © 2015 American Chemical Society