A Neutral Cluster Cage with a Tetrahedral [Pd12IIL6] Framework: Crystal Structures and Host–Guest Studies

A charge-neutral tetrahedral [(Pd3X)4L6] cage assembly built from a trinuclear polyhedral building unit (PBU), [Pd3X]3+, cis-blocked with an imido P(V) ligand, [(NiPr)3PO]3– (X3–), and oxalate dianions (L2–) is reported. Use of benzoate or ferrocene dicarboxylate anions, which do not offer wide-angle chelation as that of oxalate dianions, leads to smaller prismatic clusters instead of polyhedral cage assemblies. The porosity of the tetrahedral cage assembly was determined by gas adsorption studies, which show a higher uptake capacity for CO2 over N2 and H2. The tetrahedral cage was shown to encapsulate a wide range of neutral guest solvents from polar to nonpolar such as dimethyl sulfoxide, benzene, dichloromethane, chloroform, carbon tetrachloride, and cyclopentane as observed by mass spectral and single-crystal X-ray diffraction studies. The 1H two-dimensional diffusion ordered spectroscopy NMR analysis shows that the host and guest molecules exhibit similar diffusion coefficients in all the studied hos...