Improved Catalytic Activity and Stability of a Palladium Pincer Complex by Incorporation into a Metal-Organic Framework

A porous metal-organic framework Zr6O4(OH)(4)(L-PdX)(3) (1-X) has been constructed from Pd diphosphinite pincer complexes ([L-PdX](4-) = [(2,6-(OPAr2)(2)C6H3)PdX](4-), Ar = p-C6H4CO2-, X = Cl, I). Reaction of 1-X with PhI(O2CCF3)(2) facilitates I-/CF3CO2- ligand exchange to generate 1-TFA and I-2 as a soluble byproduct. 1-TFA is an active and recyclable catalyst for transfer hydrogenation of benzaldehydes using formic acid as a hydrogen source. In contrast, the homogeneous analogue Bu-t(L-PdTFA) is an ineffective catalyst owing to decomposition under the catalytic conditions, highlighting the beneficial effects of immobilization.