Perfluoroaryl Zinc Catalysts Active in Cyclohexene Oxide Homopolymerization and Alternating Copolymerization with Carbon Dioxide

Abstract

The zinc complex Zn(C6F5)2(toluene) (1) behaves as a very active and selective catalyst in cyclohexene oxide (CHO) polymerization to produce poly(cyclohexene oxide) (PCHO) by the trans-ring-opening of CHO with remarkable TOF values at room temperature. The ring-opening copolymerization (ROCOP) of CO2 with CHO catalysed by 1 yields poly(cyclohexene carbonate) (PCHC) when using benzyl alcohol (BnOH) as an initiator at 120°C. The 1H NMR monitoring of the in situ reaction of 1 with BnOH highlighted the formation of the dinuclear species [(C6F5)2Zn2(BnO)2 (2) that was isolated and found an active catalyst in the ROCOP of CO2 with CHO in the absence of initiators. Interestingly, PCHCs by 2 in solventless conditions show polydispersity index (Mw/Mn) values close to 2, corresponding to those expected for a single-site catalyst; on the contrary, a broader polydispersity index of the polymer products was found in toluene solution, suggesting the formation of new zinc catalysts during the polymerization reaction.

Synthesis of Mono- and Dinuclear Aluminum Complexes Bearing Aromatic Amino-Phenolato Ligands: A Comparative Study in the Ring-Opening Polymerization of Cyclohexene Oxide

“…Three main signals were found in the 13 C NMR spectrum (C 6 D 6 , 101 MHz) with the methine carbon atoms at 78.7, 78.1, and 76.7 ppm, suggesting a ratio of ca. 1:1:1 for isotactic ( mm ), heterotactic ( mr and rm ), and syndiotactic ( rr ) triads, which is similar to polyethers obtained with bis­(perfluoroaryl) zinc complex as initiator . These results revealed that the PCHO obtained is atactic and the polymerization of CHO initiated by 2 has no stereocontrol.…”

“…1:1:1 for isotactic (mm), heterotactic (mr and rm), and syndiotactic (rr) triads, which is similar to polyethers obtained with bis-(perfluoroaryl) zinc complex as initiator. 31 These results revealed that the PCHO obtained is atactic and the polymerization of CHO initiated by 2 has no stereocontrol.…”

Ring-Opening Polymerization of Cyclohexene Oxide and Cycloaddition with CO2 Catalyzed by Amine Triphenolate Iron(III) Complexes

“…Notably, the NMR spectra of the polymerized products showed three different structures, indicating that the iron complex used for the ring-opening polymerization of CHO lacked selectivity. This finding is consistent with the results of Sokolovicz et al [45], who observed a similar lack of selectivity in the reaction catalyzed by Zn-based complexes to produce PCHO.…”

Zinc-Catalyzed Enantioselective [3 + 3] Annulation for Synthesis of Chiral Spiro[indoline-3,4′-thiopyrano[2,3-b]indole] Derivatives

“…The Friedel–Crafts reaction [ 12 , 13 ] has emerged as a powerful chemical tool for the construction of new C–C bonds, and it has been widely used to realize asymmetric transformations of aromatics and heteroaromatics [ 14 , 15 ]. In the past few years, dinuclear metal-ProPhenol catalysts, which feature both Lewis acidic and Brønsted basic sites, have emerged as a powerful chemical tool for asymmetric transformations and attracted much attention in this field [ 16 , 17 , 18 ]. For instance, the Trost group [ 19 ] first reported the use of a dinuclear zinc complex in Friedel–Crafts alkylations of unprotected pyrroles with nitroalkenes via deprotonation of the amino group in 2008.…”