In or out? Adaptive metal binding by a diphosphine-based Zr metal-organic cage

Abstract

A lantern-type Zr metal-organic cage (MOC), Zr-P₂N₂, has been synthesized using ditopic carboxylate linkers based on the 1,5-diaza-3,7-diphosphacyclooctane (P₂N₂) ligand platform. Single-crystal X-ray diffraction shows that the diphosphine groups of the P₂N₂ linkers point into the confined MOC cavity. Postsynthetic metalation of the diphosphine groups with Pd and Pt precursors generates the heterobimetallic cages Zr-P₂N₂-PdCl₂ and Zr-P₂N₂-PtCl₂. Structural characterization reveals that the linkers flip to accommodate metal chelation, resulting in outward facing metal diphosphine groups. Conversely, reaction of Zr-P₂N₂ with AgPF₆ results in formation of Zr-P₂N₂-Ag, which contains hexasilver core supported by phosphine complexation within the cage interior. This work highlights the adaptive structural behavior of Zr-P₂N₂ which provides new opportunities for designing responsive MOCs.