Open AccessOrigin of the Difference in Reactivity between Ir Catalysts for the Borylation of C–H Bonds
Author(s) -
Raphael J. Oeschger,
Matthew A. Larsen,
Alessandro Bismuto,
John F. Hartwig
Publication year - 2019
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.9b08920
Subject(s) - chemistry , catalysis , reactivity (psychology) , borylation , stoichiometry , dissociation (chemistry) , photochemistry , medicinal chemistry , organic chemistry , medicine , alkyl , alternative medicine , pathology , aryl
A mechanistic study on the origin of the difference in reactivity between Ir catalysts for C-H borylation reactions is reported. Catalytic reactions of B 2 pin 2 with a series of substrates that require high temperatures and long reaction times were conducted. These reactions catalyzed by the combination of [Ir(COD)(OMe)] 2 and 3,4,7,8-tetramethylphenanthroline (tmphen) occur in yields that are substantially higher than those of reactions catalyzed by [Ir(COD)(OMe)] 2 and 4,4'-di- tert -butylbipyridine (dtbpy). The electronic properties of Ir catalysts ligated by dtbpy or tmphen and their stoichiometric reactivity were investigated. It was found that a longer lifetime rather than higher reactivity of the catalyst leads to higher yields of reactions catalyzed by Ir-tmphen. The catalyst ligated by dtbpy decomposes principally by dissociation of the ligand and rapid borylation at the positions alpha to nitrogen. Thus, the greater stability of the catalyst containing tmphen results from its greater binding constant.