Selective Hydrosilation of CO₂ to a Bis(silylacetal) Using an Anilido Bipyridyl‐Ligated Organoscandium Catalyst

A rigid anilido bipyridyl ligand has been designed for use in an organoscandium‐based carbon dioxide hydrosilation catalyst. Ligand attachment by alkane elimination results in metalation of an aryl CH bond in a 3,5‐di‐ tert ‐butylphenyl group installed on the pyridyl unit, thus rendering the ligand tetradentate. Insertion of CO 2 into the newly formed ScC bond leads to a κ 1 carboxylate which, when treated with the borane B(C 6 F 5 ) 3 , becomes hemilabile. In addition to activating the catalyst, the k 1 carboxylate effectively sequesters free B(C 6 F 5 ) 3 and the ensemble is able to effectively hydrosilate CO 2 , in the presence of excess Et 3 SiH, almost exclusively to R 3 SiOCH 2 OSiR 3 . A maximum turnover number of about 3400 (conversion of silane) is observed. Mechanistic experiments suggest that the sequestration of free B(C 6 F 5 ) 3 by the hemilabile carboxylate contributes to the selectivity observed and prevents over reduction to methane.