Organo-copper(II) complexes as products of radical atom transfer

Zerk, Timothy J. and Bernhardt, Paul V. (2017) Organo-copper(II) complexes as products of radical atom transfer. Inorganic Chemistry, 56 10: 5784-5792. doi:10.1021/acs.inorgchem.7b00402


Author Zerk, Timothy J.
Bernhardt, Paul V.
Title Organo-copper(II) complexes as products of radical atom transfer
Journal name Inorganic Chemistry   Check publisher's open access policy
ISSN 1520-510X
0020-1669
Publication date 2017-04-27
Sub-type Article (original research)
DOI 10.1021/acs.inorgchem.7b00402
Open Access Status Not yet assessed
Volume 56
Issue 10
Start page 5784
End page 5792
Total pages 9
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Subject 1606 Physical and Theoretical Chemistry
1604 Inorganic Chemistry
Abstract Copper complexes bearing polyamine chelate ligands are among the most widely used and highly active catalysts for atom transfer radical polymerization (ATRP). Copper(I) complexes of these ligands (CuL) react with an alkyl halide initiator (RX) in the atom transfer step to generate the higher oxidation state halido complex CuLX and the radical R. However, CuL present in the reaction also has the potential to react with the liberated radicals to generate the organometallic species CuLR (where R is formally a carbanion). The reversible association of radical and CuL would facilitate the operation of an alternate, competitive controlled radical polymerization pathway known as organometallic-mediated radical polymerization (OMRP). Recently this possibility has been proposed to occur for a number of different copper catalysts under ATRP conditions, but unequivocal evidence of this organometallic adduct is lacking. Herein we provide direct observation of this species, including an optical spectrum for two of the most commonly used copper catalysts. Furthermore, using cyclic voltammetry coupled to simulations, we are able to determine each of the key thermodynamic and kinetic steps involved in both the atom transfer and radical transfer pathways to assess the impact of ligand, solvent, and initiator on these.
Formatted abstract
Copper complexes bearing polyamine chelate ligands are among the most widely used and highly active catalysts for atom transfer radical polymerization (ATRP). Copper(I) complexes of these ligands (CuIL) react with an alkyl halide initiator (RX) in the atom transfer step to generate the higher oxidation state halido complex CuIILX and the radical R. However, CuIL present in the reaction also has the potential to react with the liberated radicals to generate the organometallic species CuIILR (where R is formally a carbanion). The reversible association of radical and CuIL would facilitate the operation of an alternate, competitive controlled radical polymerization pathway known as organometallic-mediated radical polymerization (OMRP). Recently this possibility has been proposed to occur for a number of different copper catalysts under ATRP conditions, but unequivocal evidence of this organometallic adduct is lacking. Herein we provide direct observation of this species, including an optical spectrum for two of the most commonly used copper catalysts. Furthermore, using cyclic voltammetry coupled to simulations, we are able to determine each of the key thermodynamic and kinetic steps involved in both the atom transfer and radical transfer pathways to assess the impact of ligand, solvent, and initiator on these.
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID DP150104672
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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Created: Fri, 05 May 2017, 11:32:14 EST by Mrs Louise Nimwegen on behalf of School of Chemistry & Molecular Biosciences