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The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)‐BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N‐heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst. [ABSTRACT FROM AUTHOR]

A novel one‐pot iridium‐catalyzed domino hydroxymethylation of olefins, which relies on using two different ligands at the same time, is reported. DFT computation reveals different activities for the individual hydroformylation and hydrogenation steps in the presence of mono‐ and bidentate ligands. Whereas bidentate ligands have higher hydrogenation activity, monodentate ligands show higher hydroformylation activity. Accordingly, a catalyst system is introduced that uses dual ligands in the whole domino process. Control experiments show that the overall selectivity is kinetically controlled. Both computation and experiment explain the function of the two optimized ligands during the domino process. [ABSTRACT FROM AUTHOR]

In catalysis science, the electronic structure of the active site determines the structure–activity relationship of the catalyst to a large extent. Therefore, modulating the electronic structure has become a main route for the rational design of metal‐based catalyst materials. In this work, we prepared a LaCoSiHx material that has more electronegativity and a lower workfunction than traditional supported Co‐based catalysts. Using CO2 methanation as a model catalytic reaction, the facile dissociation of CO2 and CO (a key reaction intermediate) on the surface of the LaCoSiHx catalyst is observed by various experimental methods (e.g., in situ Raman and FTIR) at room temperature. Moreover, theoretical calculation results further show that LaCoSiHx has a much stronger capacity for carbon–oxygen bond activation than the Co surface. The intrinsic mechanism is attributed to the marked electron transfer from catalysts into the antibonding orbital of CO2 and CO. [ABSTRACT FROM AUTHOR]

An in‐depth theoretical study has been performed to investigate the mechanism of alkene dehydrogenative silylation catalyzed by the bis(imino)pyridine cobalt methyl complex (MesPDI)Co(CH3) on the singlet, triplet and open‐shell singlet potential energy surfaces as well as the corresponding minimum energy crossing points. The formation of active catalyst [(MesPDI)Co(CH3)+HSiR3→(MesPDI)Co−[Si]+CH4] follows an open‐shell singlet potential energy surface, while the active catalyst has a triplet ground state. For 1‐butene as substrate, the formation of E/Z‐allylsilanes follows the singlet surface; and the E‐allylsilane is more favored than the Z‐allylsilane kinetically, and the expected ratio agrees with the experiment. For bulky 4,4‐dimethyl‐1‐pentene as substrate, the selectivity of allylsilane and vinylsilane is thermodynamically determined and this is supported by the need of low silane/olefin ratio (1/4) in experiment. [ABSTRACT FROM AUTHOR]

A general and atom‐economical synthesis of 1,1‐diborylalkanes from alkenes and a borane without the need for an additional H2 acceptor is reported for the first time. The key to our success is the use of an earth‐abundant zirconium‐based catalyst, which allows a balance of self‐contradictory reactivities (dehydrogenative boration and hydroboration) to be achieved. Our method avoids using an excess amount of another alkene as an H2 acceptor, which was required in other reported systems. Furthermore, substrates such as simple long‐chain aliphatic alkenes that did not react before also underwent 1,1‐diboration in our system. Significantly, the unprecedented 1,1‐diboration of internal alkenes enabled the preparation of 1,1‐diborylalkanes. [ABSTRACT FROM AUTHOR]

The electrochemical conversion of N2 at ambient conditions using renewably generated electricity is an attractive approach for sustainable ammonia (NH3) production. Considering the chemical inertness of N2, rational design of efficient and stable catalysts is required. Therefore, in this work, it is demonstrated that a C‐doped TiO2/C (C‐TixOy/C) material derived from the metal–organic framework (MOF) MIL‐125(Ti) can achieve a high Faradaic efficiency (FE) of 17.8 %, which even surpasses most of the established noble metal‐based catalysts. On the basis of the experimental results and theoretical calculations, the remarkable properties of the catalysts can be attributed to the doping of carbon atoms into oxygen vacancies (OVs) and the formation of Ti−C bonds in C‐TixOy. This binding motive is found to be energetically more favorable for N2 activation compared to the non‐substituted OVs in TiO2. This work elucidates that electrochemical N2 reduction reaction (NRR) performance can be largely improved by creating catalytically active centers through rational substitution of anions into metal oxides. [ABSTRACT FROM AUTHOR]

Hydrogenation of esters to alcohols with a well-defined iron iPr2PNP pincer complex has been recently reported by us and other groups. We now introduce a novel and sterically less hindered Et2PNP congener that provides superior catalytic activity in the hydrogenation of various carboxylic acid esters and lactones compared to the known complex. Successful hydrogenation proceeds under relatively mild conditions (60 °C) with lower catalyst loadings. [ABSTRACT FROM AUTHOR]

An efficient procedure for the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively, with molecular oxygen under ambient conditions has been achieved. By applying catalytic amounts of Pd(OAc)2 in the presence of tertiary phosphine oxides (OPR3) as ligands, a variety of substrates are selectively oxidized without formation of ester byproducts. Spectroscopic investigations and DFT calculations suggest stabilization of the active palladium(II) catalyst by phosphine oxide ligands. [ABSTRACT FROM AUTHOR]

The article presents the molecular structure of the reactivity and stability of CpCoI complexes as catalysts for cycloaddition reactions using systematic ligand variations.

Abstract: The reaction mechanism of thiophene hydrodesulfurization (HDS) on a Mo3S9 model catalyst has been investigated at the GGA level of density functional theory. On the basis of the computed energetic data, 2,5-dihydrothiophene has been identified as the most important intermediate of HDS processes, and it is responsible for the direct formation of butadiene as the principal product. Neither the stepwise formation of cis-2-butene nor that of butane is competitive. However, butene (or butane) can be obtained from the hydrogenation of the formed butadiene. [Copyright &y& Elsevier]

[Display omitted] • Solving the problem of metal leaching is a key scientific problem. • The metal leaching was effectively suppressed on CoGa intermetallic compound. • Ga atoms act as incompatible sites for CO molecules. • Ga atoms also act as anchor points for Co to separate continuous Co atoms. Metal leaching is an important obstacle for the development of CO-containing heterogeneous catalysis systems. The modulation of the metal surface could substantially influence the structural stability under a CO atmosphere. In this work, the inductively coupled plasma (ICP) results indicate that the leaching amount of cobalt in the CoGa intermetallic compound (CoGa IMC/SiO 2) catalyst is notably less than that of the Co/SiO 2 catalyst in hydroformylation reaction. The in situ Fourier Transform Infrared Spectroscopy (FTIR) results prove that aldehydes can be generated on CoGa IMC/SiO 2 by heterogeneous hydroformylation reaction without the formation of Co carbonyl species. Moreover, the analysis of metal bond interaction proves that although the Co-Ga bond has a weaker metal interaction strength in the bulk phase, it has higher structural stability than the Co-Co bond with the adsorption of CO molecules. Above all, this work provides a strategy to suppress metal leaching for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Locations of Al in the Al-Ge-ITQ-13 framework were regulated by adding different amounts of Ge and Al for the purpose of developing a potential methanol-to-propene catalyst. Ge had no significant influence on acid site number, strength, and type, but influenced acid site distribution and catalytic properties. The Al sited at T2, T5, and particularly T9 sites rapidly deactivated Al-Ge-ITQ-13, but attempts to locate Al at T3 and T6 by adjusting Ge and Al content remarkably increased its catalytic life and propene selectivity, by 686% and 44% respectively. A simple method for roughly estimating the great effects of acid site distribution and density on the catalytic life was developed by measuring the intensity of 27 Al MAS NMR signal around 51.4–53.4 ppm, even though changes in acid site density are always accompanied by alterations of acid site distribution. The hydrothermal treatment of Al-Ge-ITQ-13 confirms its potential for use in industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 Conversion to CH 4 and CH 3 OH on ZrO 2 support Ni catalysis was computed. • Metal-Metal and Metal-support Interaction was analysed. • Reaction Mechanisms, differently from metallic Ni, were identified. • Metal interaction determines structure of support Ni and reaction mechanisms. To better understand the metal-support interaction and structure–activity relationship, we computed the mechanisms of CO 2 hydrogenation to CH 4 and CH 3 OH on ZrO 2 supported Ni catalyst. On a supported irregular Ni 13 cluster, which exhibits a balanced metal–metal and metal-support interaction with surface Zr and O atoms covered, two preferred routes [CO 2 → CO → CHO → CH/CH 3 O → CH 3 → CH 4 /CH 3 OH] are found, and the rate-determining step is the CO 2 direct dissociation. Such mechanisms differ very strongly from those reported on flat metallic Ni(1 1 1) surface and Ni clusters supported on different metal oxides, demonstrating that different supports generate different metal-support interaction that simultaneously changes the metal structures and the reaction mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Ab initio atomistic thermodynamics is utilized to achieve the understanding of the surface structure and stability of χ-Fe5C2 under CO and synthesis gas (H2/CO) pretreatment conditions in catalyst activation for Fischer–Tropsch synthesis (FTS). On the basis of the computed surface free energy (γ) as a function of the carbon chemical potential (μ C) by considering temperature, pressure, and H2/CO ratios, it is found that CO pretreatment favors stable carbon-rich facets, while small amount of H2 added into CO leads to a large decrease in μ C and thus stabilizing carbon-poor facets. The high activity of surface carbon toward hydrogenation might explain the enhanced initial activity of the FTS catalysts activated from CO pretreatment. Moreover, under both CO and H2/CO pretreatments, either low temperature or low pressure can lead to stable carbon-rich facets. [Copyright &y& Elsevier]

Review: 60 refs. [ABSTRACT FROM AUTHOR]