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Pd‐catalyzed carboxylation of ethylene into sodium acrylate is an industrially relevant reaction that has gained increasing attention in the last years. By this process, CO2 can be transformed into a value‐added molecule in a single, high atom economy step. However, there is still some room for improvement since the productivity of the reference catalyst is rather low. A key aspect to achieve this goal concerns the good understanding of reaction mechanism. Herein, we combine experimental and DFT studies to gain some knowledge on the reactivity and catalytic performance of the Pd/dicyclohexylphosphinoethane (dcpe) system. First, we were able to understand the influence of the solvent on the reaction, and we demonstrated that DMF was the best candidate due to the more efficient formation of the Pd‐metallalactone. Moreover, we have demonstrated that highly available and less costly PdBr2 can be a suitable precursor, as PdII is reduced in situ in DMF in the presence of an excess of NaOtBu. Finally, the role of different monophosphine additives has been elucidated, which permitted us to rationally improve the catalytic performance. [ABSTRACT FROM AUTHOR]

Magnetically induced catalysis can be promoted taking advantage of optimal heating properties from the magnetic nanoparticles to be employed. However, when unprotected, these heating agents that are usually air‐sensitive, get sintered under the harsh catalytic conditions. In this context, we present, to the best of our knowledge, the first example of air‐stable magnetic nanoparticles that: 1) show excellent performance as heating agents in the CO2 methanation catalyzed by Ni/SiRAlOx, with CH4 yields above 95 %, and 2) do not sinter under reaction conditions. To attain both characteristics we demonstrate, first the exchange‐coupled magnetic approach as an alternative and effective way to tune the magnetic response and heating efficiency, and second, the chemical stability of cuboctahedron‐shaped core–shell hard CoFe2O4–soft Fe3O4 nanoparticles. [ABSTRACT FROM AUTHOR]

Induction heating of magnetic nanoparticles (NPs) is a method to activate heterogeneous catalytic reactions. It requires nano‐objects displaying high heating power and excellent catalytic activity. Here, using a surface engineering approach, bimetallic NPs are used for magnetically induced CO2 methanation, acting both as heating agent and catalyst. The organometallic synthesis of Fe30Ni70 NPs displaying high heating powers at low magnetic field amplitudes is described. The NPs are active but only slightly selective for CH4 after deposition on SiRAlOx owing to an iron‐rich shell (25 mL min−1, 25 mT, 300 kHz, conversion 71 %, methane selectivity 65 %). Proper surface engineering consisting of depositing a thin Ni layer leads to Fe30Ni70@Ni NPs displaying a very high activity for CO2 hydrogenation and a full selectivity. A quantitative yield in methane is obtained at low magnetic field and mild conditions (25 mL min−1, 19 mT, 300 kHz, conversion 100 %, methane selectivity 100 %). [ABSTRACT FROM AUTHOR]

The synthesis of water-soluble η3-allyl Pd(II) complexes containing sulfonated N-heterocyclic carbene (NHC) ligands of general formula [Pd(NHC)n(η3-allyl)Cl2-n] is reported (n = 1 (1) or 2 (8)). Monocarbene complexes were obtained with the most sterically hindered NHC ligands, and biscarbenes with the less sterically hindered NHCs. The behavior of the isolated complexes in water under acidic, neutral, or alkaline conditions has been studied. The complexes are rather stable in water under neutral or alkaline conditions, although displacement of the chlorido ligand by water or hydroxide occurs under these conditions. In acidic media, Pd-NHC bonds are protolysed, and it is especially noteworthy that this protolysis occurs preferentially to that of the Pd-allyl bonds in the case of the complexes with the less-sterically hindered NHC ligands. This behavior contrasts with that observed in dimethyl sulfoxide (dmso), where the Pd-allyl bonds are selectively broken upon treatment with Brönsted acids. In addition, Pd-NHC bond breaking was promoted by the addition of a strong σ-donor ligand such as cyanide. Complex 1a is an active catalyst for the Suzuki-Miyaura cross-coupling of water-soluble aryl chlorides in neat water under moderate conditions (typically, 0.5 mol % Pd and 60 °C). [ABSTRACT FROM AUTHOR]

The coordination of N-heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC PdII complex. NMR studies after 13CO adsorption established that the KS shifts the 13C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight-shifted to 600 ppm for 13C-labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car-Purcell-Meiboom-Gill (CPMG) echo train acquisition NMR experiments. [ABSTRACT FROM AUTHOR]

Activation of H-H, Si-H, and C-H bonds through σ-bond coordination has grown in the past 30 years from a scientific curiosity to an important tool in the functionalization of hydrocarbons. Several mechanisms were discovered via which the initially σ-bonded substrate could be converted: oxidative addition, heterolytic cleavage, σ-bond metathesis, electrophilic attack, etc. The use of metal nanoparticles (NPs) in this area is a more recent development, but obviously nanoparticles offer a much richer basis than classical homogeneous and heterogeneous catalysts for tuning reactivity for such a demanding process as C-H functionalization. Here, we will review the surface chemistry of nanoparticles and catalytic reactions occurring in the liquid phase, catalyzed by either colloidal or supported metal NPs. We consider nanoparticles prepared in solution, which are stabilized and tuned by polymers, ligands, and supports. The question we have addressed concerns the differences and similarities between molecular complexes and metal NPs in their reactivity toward σ-bond activation and functionalization.

Objectives: To compare the safety and efficacy of the new cobalt-chromium bioactive stent Titan Optimax ® (Hexacath, France) with its predecessor, Titan-2 ® ., Background: The TIOMAX registry includes 784 patients who underwent percutaneous coronary intervention with these stents in 21 Spanish hospitals., Methods: Analysis of all patients in the registry without exclusion criteria, candidates for revascularization (March-2013/July-2014). Initially 273 patients received Titan-2 ® , and the next 511 received the Optimax ® after its launch., Results: Mean age was 65.8 ± 13.0 (78.1% men); 49.2% were STEACS patients (n = 322), 29.8% NSTEACS, and 27.3% had stable angina or silent ischemia. Most STEACS patients (76.4% of n = 322) were treated <24 hr after developing symptoms. All-cause death (D), cardiac death (CD), acute myocardial infarction (AMI), and stent thrombosis (ST) at 1 month were 1.1, 0.8, 0.1, and 0.5%, respectively, with no significant differences between groups. At 1 year, the death rate was 5.5% for Titan-2 vs. 4.1% for Optimax ® , CD was 1.8% for both groups, ST 1.1 vs. 0.6%, new AMI 3.3 vs. 2.5% and target lesion revascularization (TLR) 3.7 vs. 2.9%. The primary endpoint of the composite event (CE) of D/AMI/TLR/ST occurred in 10.3% vs. 7.6% (p = 0.211). Patients with STEACS (N = 322: Titan-2/Optimax: 103/209) had better outcomes for secondary events, device-oriented failure CD/AMI/TLR (7.8% vs. 5.0%; p = 0.330), and non-fatal CE of AMI/ST/TLR (7.8% vs. 2.7%, p = 0.039)., Conclusions: The Titan Optimax retains the efficacy and safety of Titan 2. It appears to perform better in the subgroup of STEACS patients, by reducing the non-fatal CE of AMI/ST/TLR., (© 2017 Wiley Periodicals, Inc.)