Distinct Reactivity Modes of a Copper Hydride Enabled by an Intramolecular Lewis Acid

Abstract

We disclose a 1,4,7-triazacyclononane (TACN) ligand featuring an appended boron Lewis acid. Metalation with Cu­(I) affords a series of tetrahedral complexes including a boron-capped cuprous hydride. We demonstrate distinct reactivity modes as a function of chemical oxidation: hydride transfer to CO2 in the copper­(I) state and oxidant-induced H2 evolution as well as alkyne reduction.

Enzyme-inspired catalysts with high activity and selectivity for oxidative polymerization of 2-phenylphenol

“…The structure consists of a five-coordinated Cu unit adopting a distorted tetragonal pyramidal geometry constructed by the coordination of an N 3 O 2 donor set: namely, one N atom with the t Bu group occupying the apical position; two N atoms with the t Bu and n Bu groups and two O atoms of the SO 4 2− ion equatorially situated due to the Jahn–Teller effect. A Cu( i ) complex with t Bu 2 n Butacn, [Cu( t Bu 2 n Butacn)(OSO 2 CF 3 )], has been very recently reported as a comparative example for alkyne reduction, 22 which is not related to oxidative polymerization at all.…”

“…To examine the steric effect of the R 1-3 substituents on the Cu(R 1 R 2 R 3 tacn)-catalyzed oxidative polymerization of 2-PhP, the tacn ligands having one and two bulky t Bu group(s) in R 1-3 , t Bu i Pr 2 tacn and t Bu 2 n Butacn, were prepared, as well as been very recently reported as a comparative example for alkyne reduction, 22 which is not related to oxidative polymerization at all. Cu complexes with t Bu 3 tacn have been previously reported as four-coordinated Cu(I)(MeCN) and five-coordinated Cu(II) 2 (μ-η 2 :η 2 -peroxido) complexes.…”

Zinc-Catalyzed Hydroboration of Carbon Dioxide Amplified by Borane-Tethered Heteroscorpionate Bis(Pyrazolyl)methane Ligands

“…Bercaw and co-workers used a borane–phosphine ligand to activate carbonyl ligands in rhenium complexes, while Klankermayer used the same ligand to activate Ru–H bonds . Szymczak and co-workers presented several works containing transition metal complexes of multidentate nitrogen-based ligands, based on pyridinepyrazolyl or 1,4,7-triazacyclononane derivatives functionalized with boranes, with applications in the stoichiometric activation of small molecules . Drover and co-workers prepared late-transition metal complexes of borane-functionalized 1,2-bis­(phosphino)­ethanes .…”

Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

“…Our group previously reported the utility of appended Lewis acids to cooperatively interact with substrates and their ability to impart divergent chemical reactivity including small-molecule activation, C–H activation, and hydride transfer. − In these studies, we uncovered that substrate binding and subsequent reactivity are governed by (1) Lewis acid strength, (2) Lewis acid denticity (mono- vs ditopic), and (3) tether length/rigidity of the appended borane. Herein, we leverage these design principles to enable direct aerobic oxidation of Ni­(II) on a high-spin, tetrahedral platform and show that the high-valent Ni–O 2 intermediates are catalytically competent for electrophilic oxidation of PPh 3 and phenols.…”