Catalytic Hydrodechlorination of Benzyl Chloride Promoted by Rh– N ‐heterocyclic Carbene Catalysts

The rhodium(I) complexes [Rh(Cl)(COD)(R‐NHC‐(CH 2 ) 3 Si(O i Pr) 3 )] [COD=cyclooctadiene; R=2,6‐diisopropylphenyl ( 1 a ); n ‐butyl ( 1 b )] are effective catalyst precursors for the homogeneous hydrodechlorination of benzyl chloride using HSiEt 3 as hydrogen source. This reaction is selective to the formation of toluene. However, in presence of a stoichiometric amount of potassium tert ‐butoxide (K t BuO) the formation of mixtures containing toluene together with 17–19 mol % of the CC homocoupling product, namely PhCH 2 CH 2 Ph, is observed. A mechanism proposal based on experimental insights and theoretical calculations at the DFT level that allows explanation of the experimental findings is included. Moreover, the heterogeneous catalytic system based on catalyst 1 a supported on MCM‐41 has been demonstrated to be effective for the solvent‐free hydrodechlorination of benzyl chloride using HSiEt 3 and HSiMe(OSiMe 3 ) 2 .