Trimethylsilyl Chloride Aids in Solubilization of Oxidative Addition Intermediates from Zinc Metal

Trimethylsilyl chloride (TMSCl) is commonly used to “activate” metal(0) powders toward oxidative addition of organohalides, but knowledge of its mechanism remains limited by the inability to characterize chemical intermediates under reaction conditions. Here, fluorescence lifetime imaging microscopy (FLIM) overcomes these prior limitations and shows that TMSCl aids in solubilization of the organozinc intermediate from zinc(0) metal after oxidative addition, a previously unknown mechanistic role. This mechanistic role is in contrast to previously known roles for TMSCl before the oxidative addition step. To achieve this understanding, FLIM, a tool traditionally used in biology, is developed to characterize intermediates during a chemical reaction—thus revealing mechanistic steps that are unobservable without fluorescence lifetime data. These findings impact organometallic reagent synthesis and catalysis by providing a previously uncharacterized mechanistic role for a widely used activating agent, an understanding of which is suitable for revising activation models and for developing strategies to activate currently unreactive metals.     

Spectroscopic insights into adhesion failure at the buried epoxy-metal interphase using AFM-IR

Local AFM-IR analysis is performed on the organic coating residues remaining on carbon steel substrates after pull-off adhesion tests. This approach provides unique spectral information, because scattering from these rough substrates has previously prohibited transflectance FTIR analysis of such regions. The AFM-IR spectra of epoxy-amine residues display characteristic oxidation bands, which can only be detected by ATR-FTIR spectroscopy of intact coatings after thermal aging. These oxidation bands are shown to be more intense for thinner coating remnants and dominate the spectra of residue left by coatings removed after thermal aging at 70°C for 4 weeks. This, alongside distinctive changes in the macroscopic adhesion behavior after thermal aging, provides direct evidence that rapid oxidation occurs in the buried polymer-metal interphase during thermal aging.     

Nickel‐Catalyzed Cascade Annulation for the Rapid Synthesis of Carbocyclic Nitriles

We report a Ni‐catalyzed cascade annulation reaction that proceeds through two sequential carbometallation steps followed by C?CN reductive elimination. This reaction transforms two simple starting materials into complex, carbocyclic nitriles.