Copper N-heterocyclic carbenes (NHCs) are an emerging area of focus for catalysis and other applications. Using a straightforward methodology, a new and highly modifiable tetradentate copper­(II) NHC complex was generated and characterized using X-ray crystallography, UV–vis and EPR spectroscopy, cyclic voltammetry, and ESI-MS. This copper­(II) NHC complex adopted a distorted 4-coordinate coordination mode and demonstrates a unique absorption spectrum for a copper­(II) species, but more interestingly, its redox properties indicate that it can readily access all three common copper oxidation states under atmospheric conditions. The tetradentate copper­(II) NHC complex was used to catalytically generate new C–N bonds from a series of phenylboronic acids and amines. Once this CEL methodology was refined, moderate to high yields were achieved using catalytic amounts of the copper­(II) complex to couple phenylboronic acids to a series of aniline derivatives. Substituted phenylboronic acids and anilines had minimal impact on the catalytic capabilities of this copper complex; however, there is some indication that steric interactions between catalyst and substrates may have an impact on efficient catalysis. The straightforward synthesis of this framework and the utilization of an inexpensive, first-row transition metal center in this system highlight the usefulness of copper­(II) NHCs as catalyst for cross-coupling reactions.

Arylboronic acids are commonly used in modern organic chemistry to form new C–C and C–heteroatom bonds. These activated organic synthons show reactivity with heteroatoms in a range of substrates under ambient oxidative conditions. This broad reactivity has limited their use in protic, renewable solvents like water, ethanol, and methanol. Here, we report our efforts to study and optimize the activation of arylboronic acids by a copper(II) N-heterocyclic carbene (NHC) complex in aqueous solution and in a range of alcohols to generate phenol and aryl ethers, respectively. The optimized reactivity showcases the ability to make targeted C–O bonds, but also identifies conditions where water and alcohol activation could be limiting for C–C and C–heteroatom bond-forming reactions. This copper(II) complex shows strong reactivity toward arylboronic acid activation in aqueous medium at ambient temperature. The relationship between product formation and temperature and catalyst loading are described. Additionally, the effects of buffer, pH, base, and co-solvent are explored with respect to phenol and ether generation reactions. Characterization of the new copper(II) NCN-pincer complex by X-ray crystallography, HR-MS, cyclic voltammetry, FT-IR and UV-Vis spectral studies is reported.

Development of high hardness steels (HHS) for use in armor, shipbuilding, construction and automotive requires investigation into their sensitivity to hydrogen embrittlement. Hydrogen embrittlement, often caused by environmental corrosion, significantly impairs the mechanical properties of steel, producing increased local hardness and increased likelihood of catastrophic brittle failure. Mitigation of embrittlement can employ the introduction of hydrogen traps or phase barriers into the steel. In this work, we employed the Devanathan-Stachurski method to investigate the diffusion of hydrogen atoms through a steel membrane. The effect of strong hydrogen trapping was observed as an apparent change in hydrogen diffusivity from the initial and subsequent diffusion trials. We compared three different high hardness steel samples and used two methods to determine the apparent diffusivity and number of strong and weak hydrogen traps. Metallographic analysis of the samples illustrates the effect of composition on the diffusivity data. Figure 1