Cyclometalated phosphine-based pincer complexes: Mechanistic insight in catalysis, coordination, and bond activation

Conversion of Biomass into Chemicals over Metal Catalysts

The Golden Age of Transfer Hydrogenation

Research interest in biomass conversion to fuels and chemicals has increased significantly in the last decade as the necessity for a renewable source of carbon has become more evident. Accordingly, many different reactions and processes to convert biomass into high-value products and fuels have been proposed in the literature. Special attention has been given to the conversion of lignocellulosic biomass, which does not compete with food sources and is widely available as a low cost feedstock. In this review, we start with a brief introduction on lignocellulose and the different chemical structures of its components: cellulose, hemicellulose, and lignin. These three components allow for the production of different chemicals after fractionation. After a brief overview of the main reactions involved in biomass conversion, we focus on those where bimetallic catalysts are playing an important role. Although the reactions are similar for cellulose and hemicellulose, which contain C6 and C5 sugars, respectively, different products are obtained, and therefore, they have been reviewed separately. The third major fraction of lignocellulose that we address is lignin, which has significant challenges to overcome, as its structure makes catalytic processing more challenging. Bimetallic catalysts offer the possibility of enabling lignocellulosic processing to become a larger part of the biofuels and renewable chemical industry. This review summarizes recent results published in the literature for biomass upgrading reactions using bimetallic catalysts.

Bimetallic catalysts for upgrading of biomass to fuels and chemicals

and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

Hydrogenolysis of glycerol to glycols over ruthenium catalysts: Effect of support and catalyst reduction temperature

Converting CO2 and H2 O into carbon-based fuel by IR light is a tough task. Herein, compared with other single-component photocatalysts, the most efficient IR-light-driven CO2 reduction is achieved by an element-doped ultrathin metallic photocatalyst-Ni-doped CoS2 nanosheets (Ni-CoS2 ). The evolution rate of CH4 over Ni-CoS2 is up to 101.8 μmol g-1  h-1 . The metallic and ultrathin nature endow Ni-CoS2 with excellent IR light absorption ability. The PL spectra and Arrhenius plots indicate that Ni atoms could facilitate the separation of photogenerated carriers and the decrease of the activation energy. Moreover, in situ FTIR, DFT calculations, and CH4 -TPD reveal that the doped Ni atoms in CoS2 could effectively depress the formation energy of the *COOH, *CHO and desorption energy of CH4 . This work manifests that element doping in atomic level is a powerful way to control the reaction intermediates, providing possibilities to realize high-efficiency IR-light-driven CO2 reduction.

Efficient Infrared-Light-Driven CO2 Reduction Over Ultrathin Metallic Ni-doped CoS2 Nanosheets.

One-pot synthesis of 2-substituted benzo[b]furans via Pd–tetraphosphine catalyzed coupling of 2-halophenols with alkynes

Hydrous zirconia supported iridium nanoparticles: An excellent catalyst for the hydrogenation of haloaromatic nitro compounds

Heterogeneous catalytic systems for asymmetric reactions are fascinating because of their potential in synthetic applications. However, because of the high substrate specificity of these catalysts, the complexity of the task at hand, and the difficulties in understanding and designing the catalytic reactions, there have been just three established systems reported. One system identified for asymmetric hydrogenation is the cinchona-modified Pt/Al2O3 for asymmetric hydrogenation of a-keto esters, which was developed by Orito et al. in 1979. Baiker et al. successfully used this catalyst in the asymmetric hydrogenation of activated aromatic ketones. However, when considering the asymmetric hydrogenation of simple aromatic ketones and derivatives, which are among the most fundamental subjects in modern synthetic chemistry, few successful heterogeneous catalytic examples are reported. Chiral modifiers are the origin of the enantioselectivity in most heterogeneous catalytic reactions, and natural cinchona alkaloids and their derivatives have been widely used as versatile chiral catalysts, ligands, column packing, and chiral shift reagents. Two of the three most well-known heterogeneous catalytic systems in asymmetric reactions are based on natural cinchona alkaloids and their derivatives as the chiral modifiers. 5] Stabilizers, which are widely used in preparing nanometal catalysts, including amines, phosphines, and thiols, have been gradually introduced into supported catalysts in recent years. We previously reported polyvinylpyrrolidone (PVP) and cinchona-stabilized Rh in the asymmetric hydrogenation of a-keto esters, in which moderate to good enantioselectivities were obtained. Meanwhile, little attention has been paid to the preparation of supported metal catalysts stabilized by phosphines. Reported herein is a Ph3Pstabilized Ir/SiO2 catalyst system modified by a chiral diamine, derived from cinchona alkaloids, for the asymmetric hydrogenation of simple aromatic ketones and their derivatives; the results are compared to known homogeneous catalysts. To the best of our knowledge, this is the first report of the asymmetric hydrogenation of simple aromatic ketones with a greater than 95 % ee by using a new heterogeneous catalyst. This report is also the first successful example of the asymmetric hydrogenation of simple aromatic ketones employing Ir and H2. The high-resolution transmission electron microscopy (HRTEM) picture (Figure 1 in the Supporting Information) of 3%Ir/SiO2/2tpp (tpp = triphenylphosphine) showed that Ir is highly dispersed on the SiO2 as an amorphous agglomerate. The X-ray photoelectron spectroscopy (XPS) analysis indicated that the metal component is present in a reduced state (Ir 4f7/2 core level centered at 61.6 eV) compared to Ir 0 (Ir 4f7/2 core level centered at 60.8 eV), and the binding energy (103.5 eV) of Si2p is similar to the expected value (103.4 eV) for the corresponding SiO2. [12] The full range XPS spectra indicated that the amount of Ir supported on the SiO2 is 3% wt/wt. The catalysts are remarkably stable in the solid state and can be stored open to air. IR and P solid state NMR (PMAS NMR) spectra are effective for the investigation of the mutual ligand–metal– support interactions of solid catalysts. Information on the interaction between the metal and the phosphine was first confirmed by FTIR methods in which the red shift of the P C6H5 deformation around 1434 cm 1 in 3%Ir/SiO2/2tpp is an indication of the coordination of PPh3 to the metal. Interaction between the cinchona alkaloid and the metal was also confirmed by FTIR analysis in which the blue shift of the N H deformation around 3366 cm 1 in 3 %Ir/SiO2/2tpp/ diamine 2 is an indication of the coordination of the amine with the metal. Furthermore, the interactions between PPh3, Ir, 2, and SiO2 were detected by PMAS NMR spectroscopy (Figure 1); the broad signal at d = 5.4 ppm in Figure 1a was assigned to the PPh3 supported on the SiO2 on the basis of literature reports. The broad signal at d = 37.4 ppm may be attributed to a strong P···Si interaction on acidic SiO2 (Figure 1a), which is similar to phenomena observed in previous reports. The broad signals at d = 8.2 ppm and d = 26.0 ppm in Figure 1c are new, and appear during the catalyst (3%Ir/SiO2/2tpp) preparation, whereas the signal for the PPh3 supported on SiO2 disappeared and the signal for the P···Si interaction was enhanced. When diamine 2 was added to the 3 %Ir/SiO2/2tpp catalyst (Figure 1 d), two new signals appeared (d = 13.5 and 30.3 ppm) and the signal of the P···Si [*] H.-y. Jiang, C.-f. Yang, C. Li, H.-y. Fu, Prof. H. Chen, Prof. R.-x. Li, Prof. X.-j. Li Key Lab of Green Chemistry and Technology, Ministry of Education, The Institute of Homogeneous Catalysis, College of Chemistry, Sichuan University No. 29 Wang jiang Road, Chengdu 610064 (PR China) Fax: (+ 86)28-8541-2904 E-mail: scuhchen@163.com Homepage: http://chem.scu.edu.cn/professor/chenhua.htm

Ruixiang Li

Papers

Hydrogenolysis of glycerol to glycols over ruthenium catalysts: Effect of support and catalyst reduction temperature

Efficient Infrared-Light-Driven CO2 Reduction Over Ultrathin Metallic Ni-doped CoS2 Nanosheets.

One-pot synthesis of 2-substituted benzo[b]furans via Pd–tetraphosphine catalyzed coupling of 2-halophenols with alkynes

Hydrous zirconia supported iridium nanoparticles: An excellent catalyst for the hydrogenation of haloaromatic nitro compounds

Heterogeneous Enantioselective Hydrogenation of Aromatic Ketones Catalyzed by Cinchona‐ and Phosphine‐Modified Iridium Catalysts