Self-assembled Pd6L4 cage and Pd4L4 square using hydrazide based ligands: synthesis, characterization and catalytic activity in Suzuki-Miyaura coupling reactions

摘要

A discrete Pd6L4 Td-symmetric molecular cage and a discrete Pd4L4 square assembly were obtained using a coordination-driven self-assembly technique. The assembly, Pd6L4, was prepared via a face-directed method, utilising a 'cis-clipped' palladium(II) species and a new C-3 symmetric tripodal hydrazinic ligand. The Pd4L4 square assembly was prepared via an edge directed method, using the 'cis-clipped'palladium(II) species and a new C-2 symmetric dipodal hydrazinic ligand. Both assemblies were characterised using multinuclear NMR and ESI-MS spectroscopic techniques and elemental analysis. The size of the assemblies were assigned from HR-TEM measurements, while DOSY NMR analysis established the presence of single component species in solution. Optimised structures obtained using Hartree-Fock calculations are in conformity with the experimental results. Both the assemblies show significant catalytic activity as heterogeneous catalysts for Suzuki-Miyaura coupling reactions under mild, aerobic and phosphine free conditions in aqueous ethanolic medium.