An elusive S=3/2 oxocobalt(IV) complex is stabilized by a Lewis acid interaction with a scandium(III) ion. The {CoIV‐O‐Sc}3+ unit, characterized by spectroscopic and DFT methods, is a stronger electron‐transfer and H‐atom abstraction agent but weaker oxo‐transfer agent than the corresponding {FeIVO} complex (see scheme; L=tris[2‐(N‐tetramethylguanidyl)ethyl]amine).

High–valent copper nitrene intermediates have long been proposed to play a role in copper catalyzed aziridination and amination reactions. However, such intermediates have eluded detection for decades, which prevents the unambiguous assignments of mechanisms. Moreover, the electronic structure of the proposed copper–nitrene intermediates has also been controversially discussed in the literature. These mechanistic questions and controversy have provided tremendous motivation for probing the accessibility and reactivity of CuIII–NR/CuIIN•R species. In this paper we report a breakthrough in this field by trapping a transient copper–tosylnitrene species 3–Sc in presence of scandium triflate. Sufficient stability of 3–Sc at −90 °C enabled its characterization with optical, resonance Raman, nuclear magnetic resonance, and x–ray absorption near edge (XANES) spectroscopies, which helped to establish its electronic structure as CuIIN•Ts (Ts = tosyl group) and not CuIIINTs. 3–Sc can initiate tosyl–amination of cyclohexane, thereby suggesting CuIIN•Ts cores as viable reactants in oxidation catalysis.

Nitrite (NO) and nitroso compounds (E-NO, E = RS, RO, and RN) in mammalian plasma and cells serve important roles in nitric oxide (NO) dependent as well as NO independent signaling. Employing an electron deficient β-diketiminato copper(II) nitrito complex [ClNN]Cu(κ-ON)·THF, thiols mediate reduction of nitrite to NO. In contrast to NO generation upon reaction of thiols at iron nitrite species, at copper this conversion proceeds through nucleophilic attack of thiol RSH on the bound nitrite in [Cu](κ-ON) that leads to S-nitrosation to give the S-nitrosothiol RSNO and copper(II) hydroxide [Cu]-OH. This nitrosation pathway is general and results in the nitrosation of the amine PhNH and alcohol BuOH to give PhNNO and BuONO, respectively. NO formation from thiols occurs from the reaction of RSNO and a copper(II) thiolate [Cu]-SR intermediate formed upon reaction of an additional equiv thiol with [Cu]-OH.

Ni(III)-intermediates are trapped by EPR and UV/Vis spectroscopy in the reaction of a Ni(II) salt with mCPBA. On the basis of their oxo-transfer and hydrogen-atom abstraction abilities the intermediates are assigned as the elusive terminal Ni(III)-oxo/hydroxo species. The findings suggest that Ni(III)-O(H) moieties are viable reactants in oxidation catalysis.

In the view of physiological significance, the transition-metal-mediated routes for nitrite (NO2 –) to nitric oxide (NO) conversion and phenol oxidation are of prime importance. Probing the reactivity of substituted phenols toward the nitritocopper­(II) cryptate complex [mC]­Cu­(κ2 -O2N)­(ClO4) (1a), this report illustrates NO release from nitrite at copper­(II) following a proton-coupled electron transfer (PCET) pathway. Moreover, a different protonated state of 1a with a proton hosted in the outer coordination sphere, [mCH]­Cu­(κ2 -O2N)­(ClO4)2 (3), also reacts with substituted phenols via primary electron transfer from the phenol. Intriguingly, the alternative mechanism operative because of the presence of a proton at the remote site in 3 facilitates an unusual anaerobic pathway for phenol nitration.