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Selective Hydrosilation of CO 2 to a Bis(silylacetal) Using an Anilido Bipyridyl‐Ligated Organoscandium Catalyst
Author(s) -
LeBlanc Francis A.,
Piers Warren E.,
Parvez Masood
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201309094
Subject(s) - carboxylate , chemistry , catalysis , ligand (biochemistry) , silane , medicinal chemistry , alkane , aryl , stereochemistry , polymer chemistry , organic chemistry , alkyl , biochemistry , receptor
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 CH 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 ScC 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.