Solvent Dependence of the Structure of Ethylzinc Acetate and Its Application in CO2/Epoxide Copolymerization

Octanuclear Zinc Clusters in Microporous Organic Polymers: Network-Enhanced Reductive CO2 Fixation to Formamides at Room Temperature

A building block containing eight zincs and eight iodo groups (8 Zn) is obtained by the Zn complexation of a salen ligand bearing two additional hydroxy groups. Through the Sonogashira-Hagihara coupling of 8 Zn with 1,3,5,7-tetra(4-ethynylphenyl) adamantane, microporous organic polymers bearing octanuclear zinc clusters (MOP-8 Zn) are prepared, exhibiting a high surface area of 562 m2 g-1, microporosity, and a particulate morphology with an average diameter of 249 nm. The MOP-8 Zn exhibits significantly enhanced catalytic performance, compared to molecular counterparts, in the reductive carbon dioxide fixation to formamides, possibly due to the cooperative adsorption and confinement effect of networks on substrates.

Polynuclear alkoxy-zinc complexes of bowl-shaped macrocycles and their use in the copolymerisation of cyclohexene oxide and CO2

The reactions between alcohols and the tetranuclear ethyl-Zn complexes of an ortho-phenylene-bridged polypyrrole macrocycle, Zn4Et4(L1) 1 and the related anthracenyl-bridged macrocyclic complex, Zn4Et4(THF)4(L2) 2 have been studied. With long-chain alcohols such as n-hexanol, the clean formation of the tetranuclear hexoxide complex Zn4(OC6H13)4(L1) 3 occurs. In contrast, the use of shorter-chain alcohols such as i-propanol results in the trinuclear complex Zn3(μ2-OiPr)2(μ3-OiPr)(HL1) 4 that arises from demetalation; this complex was characterised by X-ray crystallography. The clean formation of these polynuclear zinc clusters allowed a study of their use as catalysts in the ring-opening copolymerisation (ROCOP) reaction between cyclohexene oxide and CO2. In situ reactions involving the pre-catalyst 1 and n-hexanol formed the desired polymer with the best selectivity for polycarbonate (90%) at 30 atm CO2, whilst the activity and performance of pre-catalyst 2 was poor in comparison.

Selective aerobic oxidation of halides and amines with an inorganic-ligand supported zinc catalyst

A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.

Copolymerization of CO2 and epoxides mediated by zinc organyls

Herein we report the copolymerization of CHO with CO2 in the presence of various zinc compounds R2Zn (R = Et, Bu, iPr, Cy and Ph). Several zinc organyls proved to be efficient catalysts for this reaction in the absence of water and co-catalyst. Notably, readily available Bu2Zn reached a TON up to 269 and an initial TOF up to 91 h-1. The effect of various parameters on the reaction outcome has been investigated. Poly(ether)carbonates with molecular weights up to 79.3 kg mol-1 and a CO2 content of up to 97% were obtained. Under standard reaction conditions (100 °C, 2.0 MPa, 16 h) the influence of commonly employed co-catalysts such as PPNCl and TBAB has been investigated in the presence of Et2Zn (0.5 mol%). The reaction of other epoxides (e.g. propylene and styrene oxide) under these conditions led to no significant conversion or to the formation of the respective cyclic carbonate as the main product.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

Organometallic and metal amide reagents react with –OH groups to generate metal–oxygen connectivity, yielding metal-oxo heterobimetallics, clusters and nanoparticles.

Simple phosphinate ligands access zinc clusters identified in the synthesis of zinc oxide nanoparticles

The bottom-up synthesis of ligand-stabilized functional nanoparticles from molecular precursors is widely applied but is difficult to study mechanistically. Here we use ³¹P NMR spectroscopy to follow the trajectory of phosphinate ligands during the synthesis of a range of ligated zinc oxo clusters, containing 4, 6 and 11 zinc atoms. Using an organometallic route, the clusters interconvert rapidly and self-assemble in solution based on thermodynamic equilibria rather than nucleation kinetics. These clusters are also identified in situ during the synthesis of phosphinate-capped zinc oxide nanoparticles. Unexpectedly, the ligand is sequestered to a stable Zn₁₁ cluster during the majority of the synthesis and only becomes coordinated to the nanoparticle surface, in the final step. In addition to a versatile and accessible route to (optionally doped) zinc clusters, the findings provide an understanding of the role of well-defined molecular precursors during the synthesis of small (2–4 nm) nanoparticles.

Ligands and surfactants play an important part in the synthesis of nanoparticles from molecular precursors although their exact roles are poorly understood. Here, the authors isolate a range of intermediate sized zinc clusters and are able to spectroscopically probe the self-assembly and ligand effects.

A one-step Cu/ZnO quasi-homogeneous catalyst for DME production from syn-gas

Colloidal Cu/ZnO nanoparticles combine with γ-Al₂O₃ to form promising hybrid catalysts for the direct synthesis of dimethyl ether (DME) in liquid phase, showing high activity, selectivity and stability.

Comparing a series of 8-quinolinolato complexes of aluminium, titanium and zinc as initiators for the ring-opening polymerization of rac-lactide

The preparation, characterization and properties of a series of 8-hydroxy quinolinolate complexes of Ti(iv), Al(iii) and Zn(ii) are presented. The complexes are active initiators for rac-lactide polymerizations: their performances are compared.

Conversion Between Doubly and Triply Carboxylate-Bridged Di(ethylzinc) Complexes and Formation of the (μ-Oxo)tetrazinc Carboxylate [Zn4O(ArTolCO2)6]

Ethylzinc 2,6-bis(p-tolyl)benzoate converts between two forms in solution. Through NMR spectroscopic techniques and X-ray crystallography, the species in equilibrium were identified as [Zn₂(Ar^TolCO₂)₂(Et)₂(THF)₂] (1), [Zn₂(Ar^TolCO₂)₃(Et)(THF)] (2), and diethylzinc (Ar^Tol = 2,6-bis(p-tolyl)phenyl). The equilibrium provides a model for understanding the speciation between doubly and triply m-terphenylcarboxylate bridged diiron(II) and mononuclear iron(II) complexes. Evidence is presented for the occurrence of coordinatively unsaturated trigonal zinc species in solution. Both 1 and 2 decompose in air to form the T-symmetric oxozinc carboxylate [Zn₄O(Ar^TolCO₂)₆] (3).

Synthesis of cyclic carbonates catalysed by aluminium heteroscorpionate complexes

A trimetallic aluminium complex catalyses the synthesis of cyclic carbonates from epoxides and CO₂ at room temperature and pressure.