Chiral Pt(II)-V(V) Bimetallic Cages and Guest-Induced Allosteric Regulation of Catalytic Asymmetric Sulfoxidation

Flexible metal-organic cages can provide confined active metal sites and show promise in mimicking metalloenzymes. In this study, we synthesized two flexible chiral bimetallic coordination cages, [(PEt₃)₆Pt₃(R,R,R-VL)₂]⁶⁺ and its enantiomer, through the self-assembly of platinum(II) precursors with enantiopure tripodal vanadium(V) complexes bearing pendant pyridyl groups (VL). The cages show guest binding with chiral camphorsulfonate anions, concomitant with changes in the cage conformation. The catalytic properties of the cage for oxidizing thioethers into chiral sulfoxides were investigated in comparison with a simple chiral vanadium(V) complex. While the simple complex, either alone or along with camphorsulfonate, does not show any enantioselectivity, the cage alone enables enantioselective oxidation even though the enantiomeric excess is low. The stereoselectivity is significantly improved after the camphorsulfonate guest is introduced to the cage. The chiral guest acts like an allosteric effector for enzymes to modulate the cage conformation and the local microenvironment around the catalytic site in favor of chiral induction. This work highlights the potentials of leveraging cage-confined catalytic sites and host-guest interactions for advancing supramolecular asymmetric catalysis.