Cobaltoporphyrin-Catalyzed CO₂/Epoxide Copolymerization: Selectivity Control by Molecular Design

Abstract

A series of cobalt(III) chloride porphyrin complexes of the general formula 5,10,15,20-tetra(p-alkoxy)-phenylporphyrin cobalt chloride (4b−e) and the related 5,10,15,20-tetra(p-nitro)phenylporphyrin cobalt chloride (4f) are presented and their reactivity toward propylene oxide (PO)/CO 2 coupling/copolymerization is explored. While the nitro-substituted complex (4f), in conjunction with an onium salt, shows moderate activity toward cyclization, the 4b−e/ onium systems show superior copolymerization activity in comparison to tetraphenylporphyrin Co(III) chloride (4a) with high selectivity and conversion to poly(propylene carbonate) (PPC). A comprehensive copolymerization behavior study of the alkoxy-substituted porphyrin complexes 4b−e in terms of reaction temperature and CO 2 pressure is presented. Complexes bearing longer alkoxy-substituents demonstrate the highest polymerization activity and molecular weights, however all substituted catalyst systems display a reduced tolerance to increased temperature with respect to PPC formation. Studies of the resulting polymer microstructures show excellent head-totail epoxide incorporation and near perfectly alternating poly(carbonate) character at lower polymerization temperatures.

Metalated porous porphyrin polymers as efficient heterogeneous catalysts for cycloaddition of epoxides with CO2 under ambient conditions

“…The TSP was synthesized in a typical ''one-pot" reaction according to the literature [51]. Pyrrole (0.7 mL, 10 mmol) and 4-vinylbenzaldehyde (1.32 g, 10 mmol) were added to a flask containing propionic acid (100 mL) preheated to 140°C in air.…”

Biomimetic Nitration of Phenols Using Metalloporphyrins/H2O2/NO2 −

“…All metalloporphyrins were synthesized in our laboratory by Alder reaction according to the literature [19][20][21][22]. Other reactants, solvents and standard samples were purchased from commercial sources, and used without further purification.…”

Zinc Oxide Supported trans-CoD(p-Cl)PPCl-Type Metalloporphyrins Catalyst for Cyclohexane Oxidation to Cyclohexanol and Cyclohexanone with High Yield

“…The results are shown in Table 1. The support can behave like an electron-withdrawing substituent, that is, the electronic density of cobalt ions in supported metalloporphyrins changes with the support 28 . The support can behave like an electron-withdrawing substituent, that is, the electronic density of cobalt ions in supported metalloporphyrins changes with the support 28 .…”