Carbon-carbon bond activation of 2,2,6,6-tetramethyl-piperidine-1-oxyl by a Rh(II) metalloradical: a combined experimental and theoretical study

Journal of the American Chemical Society
Kin Shing ChanBas de Bruin

Abstract

Competitive major carbon-carbon bond activation (CCA) and minor carbon-hydrogen bond activation (CHA) channels are identified in the reaction between rhodium(II) meso-tetramesitylporphyrin [Rh(II)(tmp)] (1) and 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) (2). The CCA and CHA pathways lead to formation of [Rh(III)(tmp)Me] (3) and [Rh(III)(tmp)H] (5), respectively. In the presence of excess TEMPO, [Rh(II)(tmp)] is regenerated from [Rh(III)(tmp)H] with formation of 2,2,6,6-tetramethyl-piperidine-1-ol (TEMPOH) (4) via a subsequent hydrogen atom abstraction pathway. The yield of the CCA product [Rh(III)(tmp)Me] increased with higher temperature at the cost of the CHA product TEMPOH in the temperature range 50-80 degrees C. Both the CCA and CHA pathways follow second-order kinetics. The mechanism of the TEMPO carbon-carbon bond activation was studied by means of kinetic investigations and DFT calculations. Broken symmetry, unrestricted b3-lyp calculations along the open-shell singlet surface reveal a low-energy transition state (TS1) for direct TEMPO methyl radical abstraction by the Rh(II) radical (SH2 type mechanism). An alternative ionic pathway, with a somewhat higher barrier, was identified along the closed-shell singlet surfa...Continue Reading

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Citations

Apr 28, 2011·Inorganic Chemistry·Wojciech I DzikBas de Bruin
Dec 8, 2015·Journal of the American Chemical Society·Christian GodemannTorsten Beweries
Jun 14, 2017·Accounts of Chemical Research·Ching Tat To, Kin Shing Chan
Jul 22, 2017·Dalton Transactions : an International Journal of Inorganic Chemistry·Chun Meng TamKin Shing Chan
Jun 5, 2008·Chemistry : a European Journal·Wojciech I DzikBas de Bruin
May 11, 2010·Dalton Transactions : an International Journal of Inorganic Chemistry·Lin ChengZhijian Wu
Sep 8, 2010·Dalton Transactions : an International Journal of Inorganic Chemistry·Tsun-Ren ChenKelvin H-C Chen
Mar 23, 2019·Chemical Society Reviews·Paramasivam SivaguruXihe Bi
May 4, 2011·Angewandte Chemie·Ludger Tebben, Armido Studer
Dec 12, 2012·Chemical Communications : Chem Comm·Zhen LingXuefeng Fu
Nov 26, 2019·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Jialin WangJiani Ma
Jul 1, 2014·Organic Chemistry Frontiers : an International Journal of Organic Chemistry·Alpay DermenciGuangbin Dong
Dec 1, 2017·Chemical Society Reviews·Samuel J ThompsonGuangbin Dong
May 6, 2010·Journal of the American Chemical Society·Yun Wai Chan, Kin Shing Chan
Jul 23, 2021·Journal of the American Chemical Society·Jingjing XieX Peter Zhang
Jul 21, 2021·Journal of the American Chemical Society·Xiaoxu WangX Peter Zhang
Aug 5, 2010·Journal of the American Chemical Society·Wojciech I DzikBas de Bruin
May 12, 2018·Journal of the American Chemical Society·Jiajing ZhangHuayi Fang
Dec 7, 2013·The Journal of Organic Chemistry·Xiting ZhangCunyuan Zhao
Apr 11, 2020·Journal of the American Chemical Society·Stavros K KariofillisAbigail G Doyle

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