Chemistry of Bismuth, Chromium and Magnesium Complexes and Their Applications in the Ring-Opening Polymerization of Cyclic Esters and Epoxides.

摘要

Over the counter oral relief aids and dietary supplements were investigated as a catalyst for the ring opening polymerization, ROP, of lactide (LA) and caprolactone (CL). Among these catalysts, the activity of the Pepto-Bismol (the active ingredient bismuth subsalicylate) for ROP is comparable to the industrial ROP catalyst, Sn(Oct)2. A series of bismuth complexes in the form of SalenBiX, where X = alkoxides, halides, etc., were synthesized and employed for the ROP of LA and these are more reactive than the related Al complexes. Further studies of porphyrin-Bi-alkoxides lead to the discovery of the shortest Bi-Li bond containing complexes.;The reaction of propylene oxide, PO, and rac-LA, by TPPMX/PPN+Cl- catalyst, where M = Cr or Al, and X = chloride or alkoxide, produces isotactic polylactide, PLA, at room temperature and at higher temperature favors the formation of small molecules of 3,6-dimethyl-1,4-dioxan-2-one. The mechanistic pathway for the formation of PLA and 3,6-dimethyl-1,4-dioxan-2-one were investigated by GCMS, NMR and MALDI studies.;Several modified beta-dikitiminate ligands containing Mg complexes were synthesized and employed for the ROP of LA, CL and epoxides (propylene oxide, cyclohexene oxide and styrene oxide). All the Mg complexes are active for the polymerization of LA, CL and epoxides. Among these catalysts, BDI(Ph)Mg nBu(THF) is the fastest catalyst ( kp = 14.47 M-1s-1 ) for the ROP of LA for the magnesium complexes.