Zeolite effect in the enantioselective transhydrogenation over a Co‐salen “ship‐in‐the‐bottle” complex

Our investigations were focused on the transhydrogenation of carbonyl groups using Co(II)‐salen complexes entrapped in zeolites. The Co‐salen 1 complex was occluded in the zeolite as a “ship‐in‐the‐bottle” (SIB) catalyst, as could be demonstrated by means of DRIFT‐IR spectra, DTG, nitrogen adsorption isothermes and soxhlet extraction. The results of the test reactions show that an immobilization of the Co‐salen 1 complex in the zeolite as a “SIB” complex results in an enantiomeric excess as high as in the homogeneous case. The Co‐salen 1 USY SIB catalyst shows its best ee‐value at higher temperature (25°C) than the homogeneous one (-10°C). The reason could be the steric constraints of the Co‐salen complex in the zeolite framework.