Low coordinate Zn(II) organocations bearing extremely bulky NHC ligands: structural features, air-/water-tolerance and use in hydrosilylation and hydrogenation catalysis.

This work details the synthesis and characterization of low-coordinate Zn(II)-based organocations [(NHC)Zn(R)]+ incorporating extremely bulky NHCs [ITr] and [IAd] ([ITr] = ([ITr] = [(HCNCPh3)2C:]; [IAd] = [(HCNAd)2C:], Ad = adamantyl)). Their structural features and particularities are thoroughly assessed as well as their air and water tolerance. Neutral ITr and IAd adducts [(ITr)Zn(R)2] (1, R = Me; 2, R = Et) and [(IAd)Zn(R)2] (3, R = Me; 4, R = Et) were synthesized by reaction of carbene [ITr] or [IAd] with a stoichiometric amount of [ZnR2] and isolated in good yields. Despite the steric bulk of [ITr] and [IAd], neutral compounds 1-4 are robust and the solid state structure of adduct 3 was established through X-ray crystallographic studies as a trigonal monomer Zn(II) species. Adducts 1-4 may readily be ionized by [Ph3C][B(C6F5)4] to afford two-coordinate Zn(II) alkyl cations [(ITr)Zn(Me)]+ ([5]+) and [(ITr)Zn(Et)]+ ([6]+), [(IAd)Zn(Me)]+ ([7]+) and [(IAd)Zn(Me)]+ ([8]+), all isolated in high yields (>80%) as [B(C6F5)4]- salts, which were fully characterized. Remarkably, cation [(ITr)Zn(C6F5)]+ ([9]+), prepared by reaction of [5][B(C6F5)4] with [B(C6F5)3], features π-arene interactions with the electrophilic Zn(II), as deduced from solid state data and further completed by DFT-estimated non-covalent interactions (NCI), indicating that [ITr] may provide substantial steric and electrostatic stabilization. The latter certainly explains the remarkable stability of [(ITr)Zn(C6F5)]+ ([9]+) towards hydrolysis at RT, as it only coordinates H2O to afford an unprecedented stable Zn-OH2 organocation [10]+. Also noteworthy, H2O coordination is reversible allowing recovery of [(ITr)Zn(C6F5)]+ cation, even after prolonged air exposure. Yet, controlled hydrolysis of [(ITr)Zn(C6F5)]+ may occur upon heating with selective protonolysis of the Zn-C6F5 bond to afford structurally characterized dication [(ITr)Zn(OH)]22+ [11]2+. Interestingly, despite steric hindrance, the air-/water-tolerant cation [(ITr)Zn(C6F5)]+ is an effective CO2 hydrosilylation catalyst, and was also shown to mediate imine hydrogenation catalysis.

[Rethinking the management of elderly cancer patients : Proposals from the Age Cancer Priorities French Group]. / Repenser la prise en charge des sujets âgés atteints d'un cancer : propositions du groupe Priorités Âge Cancer.

The growing incidence of cancer associated with an aging population implies important health challenges that require questioning on the care management of older adults with cancer. There is a need to rethink the care management of older cancer patients with patient-centered decisions and an adjustment of the care pathway for this population. The Priorities Age Cancer (PAC) French group, made up of physicians, pharmacists and researchers in geriatric oncology, set up proposals to answer this need. First, the heterogeneity and the specificities of older adults as well as their preferences regarding cancer treatment goals, care management decisions must be patient-centered. The frailty screening tools should be generalized in clinical practice to provide geriatric assessment-guided recommendations and help for treatment decisions, and patients' involvement and shared decision should be developed. Second, older adults with cancer confront a complex health care system that demands a high level of health literacy. The caregivers, playing an essential role, may not be prepared for all these challenges. Thus, there is a need to promote health literacy by patient education, and patient-experts should be involved in health pathway. Third, there is a need to deal with dedicated partners and adjust the care pathway. New pathway careers as case-management nurses and specialized pharmacists should be involved in patient care and may play a central role together with other careers. Community-Hospital coordination should also be reinforced.

Towards Naked Zinc(II) in the Condensed Phase: A Highly Lewis Acidic ZnII Dication Stabilized by Weakly Coordinating Carborate Anions.

The employment of the hexyl-substituted anion [HexCB11 Cl11 ]- allowed the synthesis of a ZnII species, Zn[HexCB11 Cl11 ]2 , 3, in which the Zn2+ cation is only weakly coordinated to two carborate counterions and that is soluble in low polarity organic solvents such as bromobenzene. DOSY NMR studies show the facile displacement of at least one of the counterions, and this near nakedness of the cation results in high catalytic activity in the hydrosilylation of 1-hexene and 1-methyl-1cyclohexene. Fluoride ion affinity (FIA) calculations reveal a solution Lewis acidity of 3 (FIA=262.1 kJ mol-1 ) that is higher than that of the landmark Lewis acid B(C6 F5 )3 (FIA=220.5 kJ mol-1 ). This high Lewis acidity leads to a high activity in catalytic CO2 and Ph2 CO reduction by Et3 SiH and hydrogenation of 1,1-diphenylethylene using 1,4-cyclohexadiene as the hydrogen source. Compound 3 was characterized by multinuclear NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, and DFT studies.

Normal-to-Abnormal NHC Rearrangement of Al(III) , Ga(III) , and In(III) Trialkyl Complexes: Scope, Mechanism, Reactivity Studies, and H2 Activation.

The present contribution reports experimental and theoretical mechanistic investigations on a normal-to-abnormal (C2-to-C4-bonded) NHC rearrangement processes occurring with bulky group 13 metal NHC adducts, including the scope of such a reactivity for Al compounds. The sterically congested adducts (nItBu)MMe3 (nItBu=1,3-di-tert-butylimidazol-2-ylidene; M=Al, Ga, In; 1 a-c) readily rearrange to quantitatively afford the corresponding C4-bonded complexes (aItBu)MMe3 (4 a-c), a reaction that may be promoted by THF. Thorough experimental data and DFT calculations were performed on the nNHC-to-aNHC process converting the Al-nNHC (1 a) to its aNHC analogue 4 a. A nItBu/aItBu isomerization is proposed to account for the formation of the thermodynamic product 4 a through reaction of transient aItBu with THF-AlMe3 . The reaction of benzophenone with (nItBu)AlMe3 afforded the zwitterionic species (aItBu)(CPh2 -O-AlMe3 ) (6), reflecting the unusual reactivity that such bulky adducts may display. Interestingly, the nItBu/Al(iBu)3 Lewis pair behaves like a frustrated Lewis pair (FLP) since it readily reacts with H2 under mild conditions. This may open the way to future reactivity developments involving commonly used trialkylaluminum precursors.

High-throughput screening of metal-N-heterocyclic carbene complexes against biofilm formation by pathogenic bacteria.

A set of molecules including a majority of metal-N-heterocyclic carbene (NHC) complexes (metal=Ag, Cu, and Au) and azolium salts were evaluated by high-throughput screening of their activity against biofilm formation associated with pathogenic bacteria. The anti-planktonic effects were compared in parallel. Representative biofilm-forming strains of various genera were selected (Listeria, Pseudomonas, Staphylococcus, and Escherichia). All the compounds were tested at 1 mg L(-1) by using the BioFilm Ring Test. An information score (IS, sum of the activities) and an activity score (AS, difference between anti-biofilm and anti-planktonic activity) were determined from normalized experimental values to classify the most active molecules against the panel of bacterial strains. With this method we identified lipophilic Ag(I) and Cu(I) complexes possessing aromatic groups on the NHC ligand as the most efficient at inhibiting biofilm formation.

First example of an enantiopure planar chiral ligand built on a (eta5-cyclohexadienyl)Mn(CO)3 scaffold.

The synthesis of (eta5-cyclohexadienyl)Mn(CO)3-based planar chiral ligands is realized by an efficient lithiation/electrophilic quench procedure, and the coordinating properties of one of them are highlighted together with its optical resolution.

Synthesis, characterization, and PGSE (1H and 19F) NMR diffusion studies on cationic (eta6- arene)Mn(CO)3+ complexes: boron counterion, ion pairing, and solvent dependences.

The synthesis, characterization, and PGSE ((1)H and (19)F) NMR diffusion studies on the cationic [(eta(6)-arene)Mn(CO)(3)][X] (arene = anisole, 4-chloroanisole, and 1,3,5-trimethoxybenzene; X = BPh(4) and BArF) are reported. The tetraphenyl borate complexes of anisole and 4-chloroanisole show surprisingly strong ion pairing in dichloromethane solution, whereas the BArF salts do not. (1)H,(1)H-NOESY data support this anion selectivity. In chloroform solution one finds the usual strong ion pairing for both anions. The solid-state structure of [(eta(6)-1,3,5-trimethoxybenzene)Mn(CO)(3)][BPh(4)] has been determined. (13)C NMR and IR data for the new complexes are reported. The observed IR frequencies are higher for the BArF complexes than for the BPh(4) complexes.