Nitrene Insertion into Aromatic and Benzylic C−H Bonds Catalyzed by Copper Complexes of Fluorinated Bis‐ and Tris(pyrazolyl)borates

Fluorinated bis‐ and tris(pyrazolyl)boratocopper complexes catalyze the nitrene insertion to C−H bonds of aromatic hydrocarbons efficiently producing amination products in good to excellent yields at room temperature. Imidoiodanes, PhI=NTs (Ts= p ‐toluenesulfonyl) and PhI=NNs (Ns= p ‐nitrophenylsulfonyl) serve as the nitrene source. The bis(pyrazolyl)borate catalyst [H 2 B(3,5‐(CF 3 ) 2 Pz) 2 ]Cu(NCMe) with PhI=NNs produced the arene C−H functionalized product of mesitylene in 87 % yield with only trace amounts of benzylic C−H insertion. The use of [H 2 B(3,5‐(CF 3 ) 2 ‐4‐(NO 2 )Pz) 2 ]Cu(NCMe) that has an even weakly donating pyrazolate generated the arene C−H insertion product exclusively. The tris(pyrazolyl)borate complex [HB(3,5‐(CF 3 ) 2 Pz) 3 ]Cu(NCMe), in contrast, generated the benzylic amination product from mesitylene and PhI=NNs in 82 % yield with only very minor amounts of arene C−H functionalization. DFT calculations suggest that Cu‐nitrene moiety generated from [HB(3,5‐(CF 3 ) 2 Pz) 3 ]Cu(NCMe) and PhI=NNs activates the benzylic C−H bond of mesitylene via a hydrogen atom abstraction (HAA) followed by a radical rebound (RR) pathway, whereas the functionalization of sp 2 C−H bonds of mesitylene by [H 2 B(3,5‐(CF 3 ) 2 Pz) 2 ]Cu(NNs) ensues possibly via a nitrene addition to the arene core.