Formation of difluoromethylene-arenium complexes by consecutive Aryl- CF3 C-C bond activation and C-F bond cleavage

Milko van der Boom, Yehoshoa Ben-David, David Milstein

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Abstract

Oxidative addition of one of the strongest C-C bonds, Aryl-CF3, to Rh(I) takes place upon treating 1-CF3-2,6-(CH2P(t)Bu2)2-C6H3 (1, PCP) with [RhClL2]2 (L = C2H4 or C8H14) in dioxane or toluene at elevated temperatures leading to quantitative formation of Rh(CF3)(2,6- (CH2P(t)Bu2)2-C6H3)Cl (2-Cl). The iodide analogue 2-I was prepared by reacting Rh(η1-N2)(2,6-(CH2P(t)Bu2)2-C6H3) (3) with CF3I at room temperature. ArCF2-F bond cleavage was not observed in parallel to the C-C bond activation. Treating a dioxane solution of the thermally stable Rh(III)- CF3 complexes 2-Cl,I with excess trifluoromethanesulfonic acid (HOTf) at room temperature resulted in CF bond cleavage and selective formation of the unique difluoromethylene-arenium complexes [Rh(1-CF2-2,6-(CH2P(t)Bu2)2- C6H3)X][OTf] (4; X = Cl, I) which were characterized spectroscopically by NMR, UV/vis, and FD-MS. No reaction was observed with HCl. Reaction of 2-Cl with BF3 or Ph3CBF4 (trityl cation) also resulted in C-F bond cleavage to give [Rh(1-CF2-2,6-(CH2P(t)Bu2)2-C6H3)Cl]BF4 (10).

Original languageEnglish
Pages (from-to)6652-6656
Number of pages5
JournalJournal of the American Chemical Society
Volume121
Issue number28
DOIs
Publication statusPublished - Jul 21 1999

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ASJC Scopus subject areas

  • Chemistry(all)

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