Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis

Abstract

We report the design of a bifunctional metal-organic layer (MOL), Hf₁₂ -Ru-Co, composed of [Ru(DBB)(bpy)₂ ]²⁺ [DBB-Ru, DBB=4,4'-di(4-benzoato)-2,2'-bipyridine; bpy=2,2'-bipyridine] connecting ligand as a photosensitizer and Co(dmgH)₂ (PPA)Cl (PPA-Co, dmgH=dimethylglyoxime; PPA=4-pyridinepropionic acid) on the Hf₁₂ secondary building unit (SBU) as a hydrogen-transfer catalyst. Hf₁₂ -Ru-Co efficiently catalyzed acceptorless dehydrogenation of indolines and tetrahydroquinolines to afford indoles and quinolones. We extended this strategy to prepare Hf₁₂ -Ru-Co-OTf MOL with a [Ru(DBB)(bpy)₂ ]²⁺ photosensitizer and Hf₁₂ SBU capped with triflate as strong Lewis acids and PPA-Co as a hydrogen transfer catalyst. With three synergistic active sites, Hf₁₂ -Ru-Co-OTf competently catalyzed dehydrogenative tandem transformations of indolines with alkenes or aldehydes to afford 3-alkylindoles and bisindolylmethanes with turnover numbers of up to 500 and 460, respectively, illustrating the potential use of MOLs in constructing novel multifunctional heterogeneous catalysts.