Cyclopalladated Azo–linked Porous Polymers in C–C Bond Forming Reactions

We designed a new cyclopalladated porous polymer (cyclo-Pd(II)/PP-2) with up to 20.7 wt% of Pd and investigated it as a heterogeneous catalyst for C–C bond-forming transformations. It was also shown to be an effective scavenger for Pd2+ in solution. The palladacycles formed along the backbone of the azo-linked porous polymer (PP-2) with (Pd–N) and (Pd–C) bonds as were confirmed by a combination of spectroscopies. The cyclo-Pd(II)/PP-2 decomposed when used for Suzuki and Heck cross-coupling reactions, and acyclic-Pd/PP-2 formed with Pd nanoparticles (NPs) bound to the PP-2. The Suzuki couplings were highly efficient in water and exhibited excellent recyclability. The cyclo-Pd(II)/PP-2 was also an effective heterogeneous Lewis-acid catalyst for stereoselective carbocyclization reactions.