Coordination-Initiated Nitroxide-Mediated Polymerization (CI-NMP)

Abstract

Preparation of materials by nitroxide-mediated polymerization (NMP) is well known nowadays. To increase the possible usefulness of NMP for the production of hybrid materials or polymer-decorated complexes, coordination-initiated NMP (CI-NMP) was developed and investigated here. CI-NMP was exemplified using the instantaneous and spontaneous reaction of alkoxyamines carrying a pyridyl moiety on the alkyl group and the Zn(hfac)2 (hfac: hexafluoroacetylacetonate) complex as a metal centre. NMP of styrene and n-butyl acrylate was carried out with either previously or in situ-prepared complexes. Both approaches afforded NMP of the same quality. The positive influence of metal centre coordination is highlighted by efficient NMP at 90°C.

How intramolecular coordination bonding (ICB) controls the homolysis of the C–ON bond in alkoxyamines

“…10,11 Furthermore, formation of complexes of the Zn(hfac) 2 electron acceptor matrix with alkoxyamines has a positive effect on NMP because it enhances initiation efficiency. 12 As we have demonstrated earlier, [7][8][9] alkoxyamine-metal complexes undergo equilibrium dissociation in solution. One can shi this equilibrium by adding a complexation agent for zinc ions, e.g., pyridine (Py) or bi-pyridine.…”

Oxime radicals: generation, properties and application in organic synthesis

“…Oximes unsubstituted in α-position (R 2 = R 3 = H) also undergo this transformation (example 170d,l). Both various aromatic substituents (products 170e-g) and alkyl substituents (example 170h) may be present in the EBX reagent at R 6 . Under the same reaction conditions, γ,δ-unsaturated oximes give substituted cyclic nitrones (products 171a-e).…”

“…Stable N-oxyl radicals (mainly of the aminoxyl type, Figure 1, I) are used in the development of organic magnetic materials [1], organic batteries [2][3][4], in the preparation of polymers by living polymerization [5,6], in the studies of biomolecules and living systems by EPR [7] and NMR [8] techniques. Stable N-oxyl radicals occupy a central place in organic chemistry as scavengers of C-centered radicals [9] and selective oxidation organocatalysts (for example, in the oxidation of alcohols to the corresponding carbonyl compounds [10,11]).…”

New Variants of Nitroxide Mediated Polymerization

“…Later, NMP promoted by the protonation of the alkyl fragment of 7 was reported and exhibited the expected output from conventional NMP experiments [ 64 ]. CI-NMP was then developed using di(hexafluoroacetylacetonate) zinc ligand with 7 and showed an improvement in NMP features—linearity of Mn vs conversion and Ð vs conversion ( Figure 9 )—when low polymerization temperatures were applied [ 65 ].…”