Syntheses of Heterometallic Neodymium–Zinc Complexes and Their Performance in the Copolymerization of CO₂ and Cyclohexene Oxide

Abstract

A series of Nd−Zn heterometallic complexes bearing o-phenylenediamine-bridged tris(phenolato) ligands (L) were synthesized and characterized. By tuning the backbones of ancillary tris(phenolato) ligands and initiating benzyloxy groups, a Nd−Zn heterometallic complex 12 ( Cl LNdZnOBn CF3 ) was found to be highly active for the copolymerization of CO 2 and cyclohexene oxide (CHO) to produce perfect alternating poly-(cyclohexene carbonate) with a high turnover frequency up to 5640 h −1 under the polymerization of 90 °C and 20 bar CO 2 pressure. The kinetics study showed that CO 2 /CHO copolymerization catalyzed by 12 was the first order dependence of 12 and CHO concentration and the zero-order dependence of CO 2 pressure. The reaction of 12 with CO 2 generated a carbonate-coordinated [NdZnNd] trinuclear complex 13, which was believed to be the key intermediate to initiate CO 2 /CHO copolymerization. On the basis of some experiments, a plausible synergistic polymerization mechanism was proposed.

Non-covalent interactions in molecular architectures and solvent-free catalytic activity towards CO2 fixation of mononuclear Co(iii) complexes installed on modified Schiff base ligands

“…Among them, the most eminent and economically reliable method, especially in terms of maximum atom economy, is CO 2 fixation to epoxides. 24–27 A number of metal-complex catalysts such as zinc, 28–32 cobalt, 33–65 b chromium, 66–69 magnesium, 70–72 iron, 73–75 c nickel, 76–78 and rare-earth metal 79–81 based catalysts have been developed for CO 2 fixation. Among these, cobalt salen complexes are well known for their enhanced activity and selectivity towards CO 2 fixation.…”

Water-soluble chiral coordination polymers of Li+, Na+, K+, and Ba2+ with an anionic iron(iii) complex of a l-threonine derivative and a significant red shift of visible spectra with Al3+ salt

“…15,[17][18][19][20][21][22] In this regard, Zn(II) and alkali ions were used to bridge between smaller units in both types of materials. 16,[23][24][25] Thus, a soluble network out of an anionic metal complex binding to different metal ions, such as alkali metal ions, can be useful. If it forms a three-dimensional network, it might be able to generate porous structures necessary for trapping reagents.…”

Cationic tetranuclear macrocyclic CaCo3 complexes as highly active catalysts for alternating copolymerization of propylene oxide and carbon dioxide

“…1a), but they also contain significant amounts of CO 2 upon treatment with commercially available inexpensive comonomers such as propylene oxide (PO), for which the content of CO 2 reaches 43% wt of the resulting polypropylenecarbonate (PPC). 1–3 Thus, such an efficient CO 2 capturing system has prompted many researchers to develop more efficient catalysts, including mononuclear salen complexes, 3 j ,4 mononuclear porphyrin and corrole complexes, 5 homo- and hetero-dinuclear complexes, 6–8 and hetero-multinuclear complexes, 9 with improved catalytic activity, polymer selectivity, and carbonate linkage. Among these complexes, dinuclear complexes together with tetranuclear complexes supported by alkoxide bridged skeletons (Fig.…”

“…1b) are investigated most often because of their advantages for catalysing the alternating copolymerization, even under lower CO 2 pressure. 6–9…”