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The development of effective and low-energy-consumption catalysts for CO2 conversion into high-value-added products by constructing versatile active sites on the surface of heterogeneous compounds is an urgent and challenging task. In this study, a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co3[Co(CN)6]2), typical cobalt Prussian blue analogue (CoCo-PBA) modified with tetrabutylammonium bromide (TBAB), is proven to be the superior catalyst for CO2 and epoxide coupling to produce cyclic carbonates with > 99% yield under mild reaction conditions (1.0 MPa, 65 °C). Based on a series of characterizations, it is revealed that the CoCo-PBA structure can maintain relatively high thermal and chemical stability. Recycling experiments exhibited that the CoCo-PBA system could retain 98% of the original activity after six reaction rounds. The CoCo-PBA/TBAB catalytic system was also highly active for coupling CO2 with other industrial-grade epoxides. These results show the CoCo-PBA catalytic system potential flexibility and the generality of the catalyst preparation strategy.

The copolymerization of carbonyl sulfide (COS) with epoxides has been developed to be a facile method to synthesize well-defined sulfur-containing polymers. This work describes the steric effect of tertiary amines on the copolymerization of COS with propylene oxide (PO) via a zwitterionic approach, using triethyl borane (TEB) accompanied by various tertiary amines. N,N-Dimethylcyclohexylamine accompanied by TEB (1/1) showed an exceedingly high turnover frequency of up to 69 800 h−1 and a copolymer selectivity of up to >99% for organocatalytic COS/PO copolymerization at 60 °C under solvent-free conditions. The obtained poly(propylene monothiocarbonate)s (PPMTC)s have fully alternating sequences, regioregularity of >99% tail-to-head (T–H) content, and high-number average molecular weights of up to 221.8 kg mol−1 and narrow dispersities (1.1–1.3) within 1 min. We disclosed that tertiary amines (pKa values range from 8.19 to 10.80) with less steric hindrance exhibited higher catalytic activity for COS/PO copolymerization.

A series of tin(II) complexes supported by N₂O₂ bis(phenol)‐amine ligands were prepared from the reactions of the corresponding ligands with Sn[N(SiMe₃)₂]₂ in benzene at room temperature. The ligands were designed to have different substituted group at the ortho‐position on the aryl rings (R = ᵗBu, CH₃) and N‐containing side arm (E = CH₂NEt₂ and pyridine) giving a variation of tin(II) complexes (R = ᵗBu, E = CH₂NEt₂, 2a; R = ᵗBu, E = py, 2b; R = CH₃, E = CH₂NEt₂, 2c; R = CH₃, E = py, 2d). All complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. The single‐crystal X‐ray crystallography revealed that all complexes have a monomeric four‐coordinate tin center with a distorted seesaw structure. All complexes are active for solvent‐free polymerization of l‐lactide at 120 °C giving poly(l‐lactide) with narrow to moderate dispersity (Ð = 1.12–1.56). In the presence of benzyl alcohol during the polymerization, the resulting polymer was found to be linear having benzyl alcohol as the end group while, in the absence of benzyl alcohol, the polymer was cyclic. The large ᵗBu group at the ortho‐position was found to decrease polymerization activity while the more basic CH₂NEt₂ group was found to increase the polymerization activity. The polymerization of rac‐lactide under a similar condition gave PLA having a slight heterotactic bias for all catalysts. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2104–2112

The synthesis, structural characterization and reactivity of aluminum complexes supported by a novel tetradentate aminophenolate ligand containing furfuryl groups (LH), LAlMe2 (1), LAlMeCl (2) and LAlMeOtBu (3), are described. The molecular structures of ligand LH and complexes 1–3 are determined by X-ray structural analysis. Complexes 1–3 contain a four-coordinated mononuclear aluminum center. Activation of complex 1 with either B(C6F5)3 or [Ph3C][B(C6F5)4] afforded the corresponding cationic complex, [LAlMe][MeB(C6F5)3] or [LAlMe][B(C6F5)4], respectively. All cationic complexes were stable at room temperature in the absence of an external Lewis base over a week. The cationic complex [LAlMe][MeB(C6F5)3] decomposed upon heating at 70 °C, giving a neutral LAlMe(C6F5) complex. Complexes 1–3 were inactive for the ring-opening polymerization (ROP) of e-caprolactone (CL) at room temperature. However, only the cationic aluminum complex [LAlMe][MeB(C6F5)3] in the presence of benzyl alcohol was found to be active in the ROP of CL at room temperature in a well-behaved manner, giving a first-order reaction with respect to [CL].

The rapid one-pot catalytic synthesis of double-capped oligoesters was carried out by the ring-opening polymerization of various cyclic ester monomers (i.e. e -caprolactone ( e -CL), δ -valerolactone (DVL), γ -butyrolactone (GBL), and L -lactide ( L -LA)) followed by the transesterification reaction with a variety of alkyl esters as an end-capping agent. Simple metal amides were found to be an effective catalyst under mild condition. Among them, LiN(SiMe 3 ) 2 was shown to be the most active catalyst giving 94% conversion of double-capped oligo( e -caprolactone) within 5 min at room temperature. The average chain length of the oligoesters can be controlled by the adjustment of the ratio of an alkyl ester to monomer, the reaction time and reaction temperature.