Uncovering Factors Controlling Reactivity of Metal‐TEMPO Reaction Systems in the Solid State and Solution

Abstract

Nitroxides find application in various areas of chemistry, and a more in‐depth understanding of factors controlling their reactivity with metal complexes is warranted to promote further developments. Here, we report on the effect of the metal centre Lewis acidity on both the distribution of the O‐ and N‐centered spin density in 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) and turning TEMPO from the O‐ to N‐radical mode scavenger in metal‐TEMPO systems. We use Et(Cl)Zn/TEMPO model reaction system with tuneable reactivity in the solid state and solution. Among various products, a unique Lewis acid‐base adduct of Cl2Zn with the N‐ethylated TEMPO was isolated and structurally characterised, and the so‐called solid‐state 'slow chemistry' reaction led to a higher yield of the N‐alkylated product. The revealed structure‐activity/selectivity correlations are exceptional yet are entirely rationalised by the mechanistic underpinning supported by theoretical calculations of studied model systems. This work lays a foundation and mechanistic blueprint for future metal/nitroxide systems exploration.

Fresh Impetus in the Chemistry of Calcium Peroxides

“…Based on our vast expertise in the oxygenation of organometallics with redox-inactive metal centers − ,, and the multifaced chemistry of organometallic/TEMPO systems, ,, we envisioned that the marriage of these two fertile landscapes might be a new vista for the O 2 activation (Scheme ). As proof of concept, we present the preparation and structural characterization of the first Ca complex incorporating a TEMPO anion and reveal its reactivity toward O 2 , leading to unique Ca-hydroperoxide and heterometallic Ca/K peroxide complexes.…”