“…Employing 5 a (0.1 mmol), H 2 (50 bar), 40 °C, and dichloromethane as a solvent, a series of previously established organometallic arene‐hydrogenation pre‐catalysts such as [Rh‐CAAC(COD)Cl] (CAAC=cyclic (alkyl)(amino)carbene, COD=1,5‐cyclooctadiene) ( 1 ), [24] [Rh(COD)Cl] 2 ( 2 ), [( η 5 ‐C 5 Me 5 )Rh(ppy)H] ( 3 ), and [Ru( p ‐cymene)Cl 2 ] 2 ( 4 ) were chosen for hydrogenation. Our group, [21a, 22, 23, 25] Zeng, [20, 26] Bullock, [27] and others [28] have established several arene hydrogenation catalytic systems utilizing complex 1 and its analogs as pre‐catalysts. Lately, it is well‐established that complex 1 , in the presence of molecular sieves or silica and hydrogen, generates the supported Rh 0 ‐nanoparticles in situ which further catalyze the arene‐hydrogenation reaction [23, 25a] .…”