A Tunable Trifluoromethyliodonium Reagent.

Four complexes of MCl4 (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 TiCl4 , an I-O bond cleavage occurs, leading to the formation of the trifluoromethyliodonium alcoholate complexes [Ti2 Cl6 (L)4 ]Cl2 (2 a) and Ti2 Cl8 (L) (2 b). Reactions with ZrCl4 and HfCl4 form the complexes ZrCl4 (L)2 (3) and HfCl4 (L)2 (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 ZrCl4 /HfCl4 <TiCl4 <2 TiCl4 . 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.