Molecular Recognition and Chirality Sensing with Metallocene Dichloride Complexes.

The utility of well-defined transition-metal coordination complexes for separation-free enantioselective optical analysis has received significant traction due to its promise to speed up chiral compound screening workflows. Herein, chiroptical sensing of a broad selection of carboxylic acids with metallocene dihalides is introduced. Cp2TiCl2 and Cp2MoCl2 undergo smooth chloride exchange under mild conditions toward carboxylate complexes, displaying quantifiable circular dichroism signals at long wavelengths. Spectroscopic titration experiments and crystallographic analysis show that both chlorides in Cp2TiCl2 are readily displaced, while Cp2MoCl2 forms a monocarboxylate complex. In either case, characteristic CD inductions are observed that allow accurate er analysis across a wide range of enantiomeric compositions.