Matches in SemOpenAlex for { <https://semopenalex.org/work/W2171652157> ?p ?o ?g. }
- W2171652157 endingPage "2802" @default.
- W2171652157 startingPage "2792" @default.
- W2171652157 abstract "A series of group 4 metal tetracarbamates M(O(2)CNR(2))(4) (M = Ti, R = Et, 1a; M = Zr, R = Et, 1b; (i)Pr, 1c; M = Hf, R = Et, 1d; R = (i)Pr, 1e) were studied as catalytic precursors in the solution polymerization of rac-lactide. The titanium complex but not the zirconium and hafnium ones increase the activity by addition of (i)PrOH. The structure of the carbamato ligand markedly influences the molar mass of polymer; the complexes with isopropyl carbamato ligands produced PLA with molar masses up to 94,000 g mol(-1). The main mechanistic aspects of the initial stages of the polymerization reactions were outlined by spectroscopic and computational analyses. In the case of zirconium and hafnium complexes, an interaction between a carbamato ligand and the CH unit of one lactide molecule is established at room temperature. This interaction is followed by the high temperature proton transfer from the lactide to the carbamato O-atom, affording a catalytic active alkoxy complex with release of CO(2) and NHR(2). The polymerization mediated by Ti(O(2)CNEt(2))(4) involves the release of a radical fragment [O(2)CNEt(2)]˙, with consequent generation of a Ti(III) center. The propagating chain is an alcoholate ligand coordinated to a Ti(IV) centre and containing a radical mainly localized at the tail of the chain (DFT, EPR)." @default.
- W2171652157 created "2016-06-24" @default.
- W2171652157 creator A5006684926 @default.
- W2171652157 creator A5026664836 @default.
- W2171652157 creator A5030844947 @default.
- W2171652157 creator A5032937484 @default.
- W2171652157 creator A5053942420 @default.
- W2171652157 creator A5062096538 @default.
- W2171652157 date "2013-01-01" @default.
- W2171652157 modified "2023-10-18" @default.
- W2171652157 title "Ring opening polymerization of rac-lactide by group 4 tetracarbamato complexes: activation, propagation and role of the metal" @default.
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