α-Diimine-mediated C-H functionalization of arenes for aryl-aryl cross-coupling reactions

Easily accessible methods for direct C-H arylation of arenes have been explored in the presence of transition metal catalysts to facilitate C-C bond formation; however, the absence of transition-metal impurities is a significant concern in the preparation of active pharmaceutical ingredients (APIs). Herein, we examine the use of bis(imino)acenaphthene (BIAN) as a potential single-electron transfer initiator in transition metal-free C-C bond-forming reactions. Using this approach, arenes are coupled to several aryl and heteroaryl halides. Based upon preliminary mechanistic evidence and crystallographic probation of an active initiator species, we tentatively propose a potassium-stabilized 'metal-free' radical pathway is in operation.

Synthesis of zirconocene complexes and their use in slurry-phase polymerisation of ethylene

A new family of zirconocene complexes of the type (^3-RInd^#)₂ZrX₂ (where Ind^# = C₆Me₅H and R = Me, Et and Ph) have been synthesised and fully characterised. Six new crystal structures have been reported (meso-(^3-EtInd^#)₂ZrBr₂, rac-(^3-EtInd^#)₂ZrCl₂, rac-(^3-EtInd^#)₂Zr(CH₂Ph)₂, meso-(^3-EtInd^#)₂Zr(CH₂Ph)₂, meso-(^3-MeInd^#)₂ZrBr₂ and meso-(^3-MeInd^#)₂Zr(CH₂Ph)₂). The complexes were studied for slurry-phase ethylene polymerisation when immobilised on solid polymethylaluminoxane (sMAO). Variation in the initiation group was found to have greater influence over polymerisation activity for meso-catalysts than rac-catalysts, with meso-alkyl catalysts showing higher polymerisation activities than meso-halide. Below 70 °C, polymerisation activity follows the order sMAO-meso-(^3-EtInd^#)₂Zr(CH₂Ph)_2, sMAO-meso-(^3-EtInd^#)₂ZrCl₂ and sMAO-meso-(^3-EtInd^#)₂ZrBr₂ (activities of 657, 561, and 452 kg_PE mol_M⁻¹ h⁻¹ bar⁻¹, respectively). sMAO-meso-(^3-EtInd^#)₂ZrBr₂ produces HDPE with the highest molecular weight, followed by sMAO-meso-(^3-EtInd^#)₂ZrCl₂ and sMAO-meso-(^3-EtInd^#)₂Zr(CH₂Ph)₂ (M_w of 503, 406, and 345 kg mol⁻¹, respectively, at 50 °C). sMAO-meso-(^3-MeInd^#)₂ZrBr₂ produced HDPE with almost identical molecular weights to sMAO-meso-(^3-EtInd^#)₂ZrCl₂ (395 kg mol⁻¹ at 50 °C).

A new family of zirconocene complexes of the type (^3-RInd^#)₂ZrX₂ (where Ind^# = C₆Me₅H and R = Me, Et and Ph) have been synthesised and fully characterised.

Synthesis of ultra-high molecular weight poly(ethylene)-co-(1-hexene) copolymers through high-throughput catalyst screening

A family of permethylindenyl titanium constrained geometry complexes, Me₂SB(^R′N,^3-RI*)TiX₂ ((3-R-η⁵-C₉Me₅)Me₂Si(^R′TiX₂)), supported on solid polymethylaluminoxane (sMAO) are investigated as slurry-phase catalysts for ethylene/H₂ homopolymerisation and ethylene/1-hexene copolymerisation by high-throughput catalyst screening. Me₂SB(^tBuN,I*)TiCl₂ supported on sMAO [sMAO-Me₂SB(^tBuN,I*)TiCl₂] is responsive to small quantities of H₂ (<1.6%), maintaining high polymerisation activities (up to 4900 kg_PE mol_Ti⁻¹ h⁻¹ bar⁻¹) and yielding polyethylenes with significantly decreased molecular weight (M_w) (from 2700 to 41 kDa with 1.6% H₂). In slurry-phase ethylene/1-hexene copolymerisation studies, a decrease in polymerisation activity and polymer molecular weights compared to ethylene homopolymerisation is observed. Compared to many solid supported system, these complexes all display high 1-hexene incorporation levels up to a maximum incorporation of 14.2 mol% for sMAO-Me₂SB(^iPrN,I*)TiCl₂). We observe a proportionate increase in 1-hexene incorporation with concentration, highlighting the ability of these catalysts to controllably tune the amount of 1-hexene incorporated into the polymer chain to produce linear low-density polyethylene (LLDPE) materials.

Permethylindenyl titanium CGCs supported on solid polymethylaluminoxane (sMAO) are investigated as slurry-phase catalysts by high-throughput catalyst screening (copolymerisation of ethylene/1-hexene with incorporation levels up to 14.2 mol%).

Polymethylaluminoxane organic frameworks (sMAOF) – highly active supports for slurry phase ethylene polymerisation

A series of modified solid polymethylaluminoxane (sMAO) catalyst supports have been developed for slurry phase ethylene polymerisation, using aryl di-ol modifier groups.

Correlations of acidity-basicity of solvent treated layered double hydroxides/oxides and their CO2 capture performance

The basicity and acidity of solvent-treated layered double hydroxide (ST-LDHs) and their layered double oxides (ST-LDOs) have been fully studied using Hammett titration, in situ FTIR, CO₂-TPD and NH₃-TPD. Five solvents (ethanol, acetone, isopropanol, ethyl acetate and 1-hexanol) were selected to treat [Mg_0.72Al_0.28(OH)₂](CO₃)_0.14 (Mg_2.5Al-CO₃ LDH) and compared with traditional LDH co-precipitated from water. The Brønsted basicity strength of the ST-LDHs and ST-LDOs increased but was accompanied by a decrease in basic site density. In addition, the Lewis acidity of ST-LDOs also changes significantly, with medium strength Lewis acid sites dissapearing after solvent treatment. We found that the CO₂ capture capacity of solvent treated LDOs is 50% higher than that of traditional co-precipitated LDO sample. The ethanol treated LDO exhibited the highest CO₂ uptake of 1.01 mmol g^-1. The observed CO₂ capture performance of the ST-LDOs correlates linearly with the ratio of total acid sites to total basic sites.

Novel M (Mg/Ni/Cu)-Al-CO3 layered double hydroxides synthesized by aqueous miscible organic solvent treatment (AMOST) method for CO2 capture

Layered double hydroxides (LDHs) have been intensively studied in recent years owing to their great potential in CO₂ capture. However, the severe aggregation between platelets and low surface area restricted it from exhibiting very high CO₂ adsorption capacity and CO₂/N₂ selectivity. In this research, we for the first time synthesized Ni-Al-CO₃ and Cu-Al-CO₃ LDHs using aqueous miscible organic solvent treatment (AMOST) method. The as-synthesized materials were evaluated for CO₂ adsorption at three different temperatures (50, 80, 120 °C) applicable to post-combustion CO₂ capture. Characterized with XRD, N₂ adsorption-desorption, TEM, EDX, and TGA, we found the newly synthesized Ni-Al-CO₃ LDH showed a nano-flower-like morphology comprising randomly oriented 2D nanoplatelets with both high surface area (249.45 m²/g) and pore volume (0.59 cc/g). Experimental results demonstrated that un-calcined Ni-Al-CO₃ LDH is superior in terms of CO₂ capture among the three LDHs, with a maximum CO₂ adsorption capacity of 0.87 mmol/g and the ideal CO₂/N₂ selectivity of 166 at 50 °C under 1200 mbar for typical flue gas CO₂/N₂ composition (CO₂:N₂ = 15:85, v/v). This is the first report of a delaminated Ni-Al-CO₃ LDH showing better CO₂ capture performance than the well-reported optimal Mg layered double hydroxide.

Group 4 permethylindenyl complexes for slurry-phase polymerisation of ethylene

Supported group 4 permethylindenyl based catalysts displayed extremely high ethylene polymerisation activity affording popcorn shaped low molecular weights polyethylenes.

Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems

Unsymmetrical permethylindenyl bent metallocene complexes have been synthesised and reacted with inorganic solid supports to afford catalysts for the slurry phase polymerisation of ethylene. Those supported on solid polymethylaluminoxane were both highly active catalysts and afforded polymers with a desirable, low aggregation, "popcorn" morphology.

Group 4 permethylindenyl constrained geometry complexes for ethylene polymerisation catalysis

The synthesis and characterisation of six permethylindenyl constrained geometry complexes is reported. Slurry phase ethylene polymerisation studies demonstrate that activities increase with increasing electron donating character of the amido fragment.

Metallocene supported core@LDH catalysts for slurry phase ethylene polymerisation

We report the synthesis of solid catalysts based on a zirconocene supported on either silica@AMO-LDH or zeolite@AMO-LDH for the slurry phase polymerisation of ethylene. The hybrid catalysts demonstrate synergistic effects in which the polymerisation activity is up to three times higher than the zirconocene supported on analogous single phase silica or zeolite supports.

Core-shell zeolite@aqueous miscible organic-layered double hydroxides

We report a general method for the synthesis of core-shell hybrid materials containing a microporous zeolite core with an aqueous miscible organic-layered double hydroxide (AMO-LDH) shell using a simple in situ coprecipitation method. For example, zeolite-HY@AMO-Mg2Al-CO3-LDH contains a 150 nm hierarchical AMO-Mg2Al-CO3-LDH surface coating on zeolite-HY. It exhibits a similar BET surface area (698 m2 g-1) as the parent zeolite-HY but this surface area has been re-allocated between microspores and mesopores. We believe that surface aluminium sites act as nucleation sites for the formation of the LDH coating and so robustly links it into the zeolite lattice. We expect that this new hybrid structure with micropores dominating in the core and mesopores populating the shell will provide a desirable new hybrid structure type for adsorption or catalysis.

Tungsten imido catalysts for selective ethylene dimerisation

A tungsten imido complex W(NDipp)Me₃Cl (Dipp = 2,6-ⁱPr-C₆H₃) is active for the selective dimerisation of ethylene to yield 1-butene under mild conditions. The catalyst supported on polymethylaluminoxane demonstrates higher activity and selectivity.

Raising the N-aryl fluoride content in unsymmetrical diaryliminoacenaphthylenes as a route to highly active nickel(ii) catalysts in ethylene polymerization

The title nickel systems, incorporating fluorine content on one N-aryl group, display superior productivity.

Tuneable ultra high specific surface area Mg/Al-CO3 layered double hydroxides

We report the synthesis of tuneable ultra high specific surface area Aqueous Miscible Organic solvent-Layered Double Hydroxides (AMO-LDHs). We have investigated the effects of different solvent dispersion volumes, dispersion times and the number of re-dispersion cycles specific surface area of AMO-LDHs. In particular, the effects of acetone dispersion on two different morphology AMO-LDHs (Mg3Al-CO3 AMO-LDH flowers and Mg3Al-CO3 AMO-LDH plates) was investigated. It was found that the amount of acetone used in the dispersion step process can significantly affect the specific surface area of Mg3Al-CO3 AMO-LDH flowers while the dispersion time in acetone is critical factor to obtain high specific surface area Mg3Al-CO3 AMO-LDH plates. Optimisation of the acetone washing steps enables Mg3Al-CO3 AMO-LDH to have high specific surface area up to 365 m(2) g(-1) for LDH flowers and 263 m(2) g(-1) for LDH plates. In addition, spray drying was found to be an effective and practical drying method to increase the specific surface area by a factor of 1.75. Our findings now form the basis of an effective general strategy to obtain ultrahigh specific surface area LDHs.

Synthesis and characterisation of permethylindenyl zirconium complexes and their use in ethylene polymerisation

We report here the synthesis, characterisation and use in solution and slurry phase ethylene polymerisation of new group 4 permethylindenyl complexes.