113Cd NMR Determination of the Binding Parameters of Alicyclic Epoxides to [Hydrotris(3-phenylpyrazol-1-yl)borate]Cd(II) Acetate

Steric and electronic factor comparisons in hydrotris(3-phenylpyrazolyl)borate nickel(II) aryloxides

Hydrotris(pyrazolyl)borate (Tp) ligands, also known as scorpionates, are potent tridentate donors that effectively bind metal ions in a face-capping array. Hydrotris(3-phenylpyrazolyl)borate enforces a tetrahedral environment on Ni^II to model metalloenzymes. The syntheses and structural characterizations of a number of [hydrotris(3-phenylpyrazolyl)borato]nickel(II) aryloxides were performed to provide insight into the environment of the model active site; these compounds are chlorido[hydrotris(3-phenylpyrazolyl-κN²)borato](3-phenyl-1H-pyrazole-κN²)nickel(II) chloroform monosolvate, [Ni(C₂₇H₂₂BN₆)Cl(C₉H₈N₂)]·CHCl₃, (2), [hydrotris(3-phenylpyrazolyl-κN²)borato](phenolato-κO)nickel(II), [Ni(C₂₇H₂₂BN₆)(C₆H₅O)], (3), (2,6-dimethylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN²)borato]nickel(II) [Ni(C₂₇H₂₂BN₆)(C₈H₉O)], (4), (4-tert-butylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN²)borato]nickel(II), [Ni(C₂₇H₂₂BN₆)(C₁₀H₁₃O)], (5), and [hydrotris(3-phenylpyrazolyl-κN²)borato](phenolato-κO)(tetrahydrofuran-κO)nickel(II) tetrahydrofuran monosolvate, [Ni(C₂₇H₂₂BN₆)(C₆H₅O)(C₄H₈O)]·C₄H₈O, (6). Alkyl groups, e.g. tert-butyl in (5) and methyl in (4), electronically activate the aryloxide group to intramolecular π-π stacking but can be frustrated by steric encumbrance at the interacting ring faces. The flexibility at the nickel coordination site, afforded by the uncrowded B atom of the Tp^Ph ligand, allows tetrahydrofuran coordination in the phenolate compound.

Catalysts for CO2/epoxide ring-opening copolymerization

This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research.

Highly active Cr(iii) catalysts for the reaction of CO2 with epoxides

This paper describes the synthesis and characterization of [Cr(babhq)OAc^F(EtOH)] (OAc^F− = CF₃CO₂⁻) as well as the application of the complex as the catalyst in the reaction of CO₂ with epoxides.