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)2C6H3)­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 I2 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 tBu­(L-PdTFA) is
an ineffective catalyst owing to decomposition under the catalytic
conditions, highlighting the beneficial effects of immobilization.

一种多孔金属-有机框架（metal–organic framework）Zr₆O₄(OH)₄(L-PdX)₃(1-X)，由钯双亚膦酸酯钳形配合物([L-PdX]⁴– = [(2,6-(OPAr₂)₂C₆H₃)PdX]⁴–，其中Ar为p-C₆H₄CO₂–，X为Cl或I)构筑得到。将1-X与PhI(O₂CCF₃)₂进行反应，可实现I–与CF₃CO₂–的配体交换，生成1-TFA与可溶性副产物I₂。1-TFA可作为活性且可循环使用的催化剂，以甲酸为氢源催化苯甲醛的转移氢化反应。与之相比，其均相类似物tBu(L-PdTFA)在催化条件下易发生分解，因此催化性能不佳，这凸显了固载化策略的有益作用。