Coordination-Driven Self-assembly of Cyclopentadienyl-Capped Heterometallic Zr–Pd Cages

Abstract

A series of heterometallic Zr3Pd3-trigonal bipyramidal compounds (1–4) was synthesized by two-component coordination-driven self-assembly of cis-protected palladium(II) 90° acceptors with trinuclear carboxylate-bridged zirconocene-based tripodal metallo-ligands. To avoid multiple product formation using two different metal acceptors, we chose trinuclear Zr(IV) metallo-ligands as donors. All the compounds were characterized by NMR and single crystal X-ray diffraction. Among the compounds, the water-soluble compound 2 is capable to encapsulate aromatic guests such as naphthalene and 2-naphthaldehyde. The encapsulation of the guests was confirmed by NMR and UV–vis spectrometry. The binding constants as well as corresponding Gibbs free energy changes were calculated separately from the 1H NMR titration of compound 2 with guests (naphthalene/2-naphthaldehyde).