Jim Patel

CH activation at the 3-position of pentane chains to form [NC(sp3)N]− complexes incorporating six-membered pallada(II)cyclic rings and pyridine, pyrazole and N-methylimidazole donor groups. Structural studies and comparison with [NC(sp2)N]− complexes

Abstract Alkylpalladium complexes bearing the [NC(sp3)N]− donor motif and two six-membered palladacycles are generated on activation of C(sp3)H bonds by palladium(II) acetate. Cyclopalladation of the new reagents 1,5-bis(pyridin-2-yl)pentane [CH2(CH2CH2py)2] (1), 1,5-bis(pyrazol-1-yl)pentane [CH2(CH2CH2pz)2] (2) and 1,5-bis(N-methylimidazol-2-yl)pentane [CH2(CH2CH2mim)2] (3), followed by reaction with lithium chloride afford the palladium(II) complexes Pd{CH(CH2CH2py)2-N,C,N′}Cl (5), Pd{CH(CH2CH2pz)2-N,C,N′}Cl (6) and Pd{CH(CH2CH2mim)2-N,C,N′}Cl (7), respectively. Abstraction of chloride from 6 with AgBF4 in acetone generates the cationic acetone complex [Pd{CH(CH2CH2pz)2-N,C,N′}(OCMe2)][BF4] (8). X-ray crystal structures of 5, 6 and 8 reveal tridentate [NC(sp3)N′]− intramolecular coordination of the ligands. These structures are compared with that of a closely related [NC(sp2)N]− system in [Pd{2,6-(pzCH2)2C6H3-N,C,N′}(OH2)][BF4] (10), obtained on cyclopalladation of 1,3-bis(pyrazol-1-ylmethyl)benzene followed by derivatisation to form the aqua complex.

An Evaluation of Some Hindered Diamines as Chiral Modifiers of Metal-Promoted Reactions

Diamino analogues of the C2-symmetric chiral diphosphine ligands DuPHOS and BPE have been prepared and evaluated as chiral modifiers of the osmium tetraoxide dihydroxylation of stilbene. NMR experiments showed that these ligands were too bulky to coordinate to osmium. Less hindered analogues of these ligands were prepared and some were shown to act as ligands in dihydroxylation reactions but with poor enantioselectivity (e.e. < 10%). The diamines have also been briefly evaluated as ligands in rhodium-catalyzed hydroformylation and copper-catalyzed phenolic coupling reactions. Once again, only low enantioselectivity was obtained.

Mono(p-tolyl)platinum(II) and bis(p-tolyl)platinum(II) complexes of diethylsulfide as reagents for organoplatinum synthesis. Structures of [Pt(p-Tol)2(μ-SEt2)]2 and PtCl(p-Tol)(bpy) (bpy = 2,2'-bipyridine)

Abstract The complex trans-PtCl(p-Tol)(SEt2)2 is obtained from the reaction of [Pt(p-Tol)2(SEt2)]2 with PtCl2(SEt2)2 and SEt2 in mole ratio 1:2:2. The mono(p-tolyl)platinum(II) and bis(p-tolyl)platinum(II) complexes of diethylsulfide react with 2,2′-bipyridine to form the complexes PtX(p-Tol)(bpy) (X=p-Tol, Cl) and are useful reagents for organoplatinum chemistry. X-ray crystal structures are presented for square planar PtCl(p-Tol)(bpy) and the centrosymmetric dimer [Pt(p-Tol)2(μ-SEt2)]2.

Sustainable options for the utilization of solid residues from wine production

The efficient use of solid organic waste materials is an issue of particular importance for the wine industry. This paper focuses on the valorization of grape marc, the major component of winery organic waste (60-70%). Two methods were designed and compared: combustion to generate electricity, and the pyrolysis for the production of bio-char, bio-oil, and bio-gas. Each of these processes was analysed to determine their economic and environmental viability. The flow-sheeting software, ASPEN PLUS, was used to model the two cases. Data from the simulations was used to inform techno-economic and environmental analyses. Pyrolysis was found to be the superior method of utilizing grape marc from both economic and environmental perspectives. Both pyrolysis and combustion exploit the energy content of the waste, which is not recovered by the traditional treatments, composting or distillation. In addition to the production of energy, pyrolysis yielded 151kg of bio-char and 140kg of bio-oil per tonne of grape marc. These products may be used in place of fossil fuels, resulting in a net reduction of carbon dioxide emissions. However, the potential deleterious effects resulting from the replacement of the traditional treatments was not considered. Investment in either pyrolysis or combustion had a negligible impact on the price of the wine produced for wineries with an annual grape crush larger than 1000 tonnes. Composting has significant economic advantages in wineries with a small grape crush of less than 50 tonnes.

Effect of a Swelling Agent on the Performance of Ni/Porous Silica Catalyst for CH4–CO2 Reforming

Hierarchical porous materials are of great interest in various industrial applications because of their potential to overcome the mass transport limitations typically encountered for single-mode porous materials. This report describes the synthesis of a hierarchical trimodal porous silica-based material using a 7.5 molar ratio of a relatively inexpensive nonionic surfactant template, triblock copolymer P123, EO20PO70EO20. The pore size distribution curve shows the presence of three types of pores with average diameters of ∼8, 25, and 89 nm. Electron microscope images confirm the existence of smaller ordered mesopores (first mode), larger ordered mesopores (second mode), and macropores (third mode). Ni nanoparticles dispersed on this trimodal porous silica produce a material that exhibited excellent catalytic performance for the CO2 reforming of CH4. This research provides new insights that will facilitate the development of trimodal porous silica (TMS) materials for a variety of applications. The results demonstrated that the presence of large pores (second and third mode pores) in TMS material increased the number of accessible active Ni sites, which led to the high activity observed for Ni/TMS catalyst.

Combining additive manufacturing and catalysis: a review

This review presents an insight into additive manufacturing (AM) technologies as they are applied to heterogeneous catalysis; the combination of these fields presents opportunities but also comes with challenges. AM enables greater design complexity, rapid prototyping, control over reactant stoichiometry and unique catalyst immobilisation options. The challenges to applying AM in heterogeneous catalysis are associated with limited material choices, quasi-stable printed materials and chemical interfacing of the catalyst system with cthese printed materials. AM printing technologies are introduced to the heterogeneous catalysis research community with a focus on the many benefits they offer in this growing field.

Revisiting the Aufbau reaction with acetylene: growth at aluminium producing a unique oligomer distribution.

The possibility of using aluminum alkyls for the growth of acetylene oligomerization was studied utilizing an addition reaction different from the Aufbau reaction of ethylene. The investigations included exposing toluene solutions of AlEt 3 to acetylene at a pressure of 1 bar gauge, which resulted in double insertion in Al-hexadienyl groups. AlMe 3 exposed to acetylene under the conditions of 100°C and 1 brag acetylene show a dominant oligomer distribution made up of propane, 1,3-pentadiene, C 9, C 13, and C 17 products. It is also found that oligomerization of AlEt 3 follows removal of the volatiles under vacuum and formation of C 10+ fractions as a yellow liquid. The distribution of oligomers can be explained by a model whereby the rate of addition across the double bond is significantly greater than that for insertion.

Mesoporous carbon-supported Cu/ZnO for methanol synthesis from carbon dioxide

Catalysts based on Cu/CuO–ZnO supported on mesoporous carbon (FDU-15) were synthesised and tested for methanol production from CO2 and H2. The catalytic activity was strongly dependent on the method by which the Cu and Zn components were loaded onto the carbon support. Three synthetic methods were trialled and the materials produced were characterised by various techniques. The materials with better contact between the Cu/CuO and ZnO particles were catalytically more active towards methanol production (CZC-3 > CZC-2 > CZC-1). The methanol production rate for CZC-3 (7.3 mmol g–1 h–1) was higher, on a catalyst weight basis, than that of a commercial catalyst (5.6 mmol g–1 h–1). Also, CZC-3 had a higher turnover frequency (1.8 × 10–2 s–1) than the commercial catalyst (0.2 × 10–2 s–1). This work demonstrates that Cu/CuO and ZnO particles supported on mesoporous carbon, prepared by an appropriate method, are promising catalysts for methanol synthesis from carbon dioxide.

DFT study of nickel-catalyzed low-temperature methanol synthesis

Low‐temperature methanol synthesis (CO+2 H2→CH3OH) catalyzed by a homogeneous nickel/alkali metal alkoxide system has been studied theoretically. Two broad mechanistic possibilities, the direct hydrogenation of CO by nickel formyl species and indirect hydrogenation via methyl formate formation, have been examined. The most favorable mechanism involves the methanolysis of CO to methyl formate catalyzed by an ether complex of sodium methoxide followed by the stepwise hydrogenation of methyl formate to formaldehyde and then to a nickel methoxide, in which both steps are mediated by a nickel hydride. In the final step the nickel methoxide is hydrogenated to release methanol. The conversion of methyl formate to the nickel methoxide is predicted to be rate limiting, and the nickel hydride is the most likely catalyst resting state. The theoretical results are discussed in the context of existing experimental observations, and a good agreement with past studies was obtained.