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

We report the design of a bifunctional metal-organic layer (MOL), Hf-12-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 Hf-12 secondary building unit (SBU) as a hydrogen-transfer catalyst. Hf-12-Ru-Co efficiently catalyzed acceptorless dehydrogenation of indolines and tetrahydroquinolines to afford indoles and quinolones. We extended this strategy to prepare Hf-12-Ru-Co-OTf MOL with a [Ru(DBB)(bpy)(2)](2+) photosensitizer and Hf-12 SBU capped with triflate as strong Lewis acids and PPA-Co as a hydrogen transfer catalyst. With three synergistic active sites, Hf-12-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.

Automated summary

The study introduced the design of a bifunctional metal-organic layer (MOL) combining a photosensitizer and a hydrogen-transfer catalyst, which efficiently catalyzed acceptorless dehydrogenation reactions of indolines and tetrahydroquinolines, as well as dehydrogenative tandem transformations of indolines with alkenes or aldehydes. With the potential of MOLs in constructing novel multifunctional heterogeneous catalysts demonstrated, this research contributes to the development of catalytic systems for organic transformations.