Formation of Difluoromethylene−Arenium Complexes by Consecutive Aryl−CF3C−C Bond Activation and C−F Bond Cleavage

Oxidative addition of one of the strongest C−C bonds, Aryl−CF 3, to Rh(I) takes place upon treating 1-CF 3 -2,6-(CH 2 P t Bu 2 ) 2 -C 6 H 3 ( 1, PCP) with [RhClL 2 ] 2 (L = C 2 H 4 or C 8 H 14 ) in dioxane or toluene at elevated temperatures leading to quantitative formation of Rh(CF 3 )(2,6-(CH 2 P t Bu 2 ) 2 -C 6 H 3 )Cl ( 2 -Cl). The iodide analogue 2 -I was prepared by reacting Rh( η 1 -N 2 )(2,6-(CH 2 P t Bu 2 ) 2 -C 6 H 3 ) ( 3 ) with CF 3 I at room temperature. ArCF 2 −F bond cleavage was not observed in parallel to the C−C bond activation. Treating a dioxane solution of the thermally stable Rh III −CF 3 complexes 2 -Cl,I with excess trifluoromethanesulfonic acid (HOTf) at room temperature resulted in C F bond cleavage and selective formation of the unique difluoromethylene−arenium complexes [Rh(1-CF 2 -2,6-(CH 2 P t Bu 2 ) 2 -C 6 H 3 )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 BF 3 or Ph 3 CBF 4 (trityl cation) also resulted in C−F bond cleavage to give [Rh(1-CF 2 -2,6-(CH 2 P t Bu 2 ) 2 -C 6 H 3 )Cl]BF 4 ( 10 ).