Unveiling reactive metal sites in a Pd pincer MOF: insights into Lewis acid and pore selective catalysis

Abstract

A porous Zr metal-organic framework, 1-PdBF4 [Zr6O4(OH)4(OAc)2.4{(PNNNP)Pd(MeCN)}2.4(BF4)2.4; PNNNP = 2,6-(HNPAr2)2C5H3N; Ar = p-C6H4CO2-], has been synthesized via postsynthetic oxidative I-/BF4- ligand exchange using NOBF4. 1-PdBF4 enjoys markedly superior catalytic activity and recyclability to its trifluoracetate-exchanged analogue, 1-PdTFA, for the intramolecular cyclization of o-alkynyl anilines and the carbonyl-ene cyclization of citronellal. Moreover, 1-PdBF4 demonstrates a rare example of pore selective catalysis for the cyclization of 2-ethynyl aniline.