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Updated: May 15, 2026

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Magnesium catalysis of imine hydroboration
Merle Arrowsmith1, Michael S Hill, Gabriele Kociok-Köhn
1Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Abstract:
The β-diketiminato magnesium alkyl complex [LMgnBu] (L=CH{CMe(NDipp)}(2), Dipp=diisopropylphenyl) is shown to be a highly effective precatalyst for the hydroboration of alkyl and aryl substituted aldimines and ketimines with pinacol borane (HBpin). Catalysis is proposed to occur through a sequence of Mg-N/B-H metathesis and rate-determining Mg-H/N=C insertion steps, a proposal strongly supported by stoichiometric studies and kinetic analysis. The reactions are observed to proceed through the intermediacy of well-defined magnesium amides, two examples of which have been isolated and structurally characterized. Mechanistic investigations suggest that the catalytic rate-determining process occurs at an isolated magnesium center and requires the presence of two molecules of the imine substrate for effective turnover. This latter observation is rationalized as a requirement for the secondary substrate molecule to displace HBpin from the coordination sphere of the catalytic magnesium center.
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