A Tunable Trifluoromethyliodonium Reagent.

Four complexes of MCl (M=Ti, Zr, Hf) with the hypervalent trifluoromethyl iodine reagent trifluoromethyl-1,3-dihydro-3,3-dimethyl-1,2-benziodoxole (1,=L) are described. With TiCl , an I-O bond cleavage occurs, leading to the formation of the trifluoromethyliodonium alcoholate complexes [Ti Cl (L) ]Cl (2 a) and Ti Cl (L) (2 b). Reactions with ZrCl and HfCl form the complexes ZrCl (L) (3) and HfCl (L) (4), respectively, wherein the original I-O bond is retained and elongated compared to that in free 1. Therefore, the reactivity of 1 can be easily and practically fine-tuned by addition of different metal chlorides, following the order ZrCl /HfCl <TiCl <2 TiCl . Complexes 2 a, 3, and 4 are remarkably bench-stable forms of activated reagent 1, while 2 b is readily accessible in situ. 2 a and 2 b represent the first "real" trifluoromethyliodonium reagents derived from iodanes, that is, with the I-O bond being completely cleaved. The new complexes were shown to be useful for the trifluoromethylation of para-toluenesulfonate under aprotic conditions.