Electronic Structure of Manganese Complexes of the Redox‐Non‐innocent Tetrazene Ligand and Evidence for the Metal‐Azide/Imido Cycloaddition Intermediate

Abstract

The first synthetic manganese tetrazene complexes are described as a redox pair comprising anionic [Mn(N4 Ad2 )2 ](-) (1) and neutral Mn(N4 Ad2 )2 (2) complexes (N4 Ad2 =[Ad-N-N=N-N-Ad](2-) ). Compound 1 is obtained in two forms as lithium salts, one as a cationic Li2 Mn cluster, and one as a Mn-Li 1D ionic polymer. Compound 1 is electronically described as a Mn(III) center with two [N4 Ad2 ](2-) ligands. The one-electron oxidized 2 is crystalized in two morphologies, one as pure 2 and one as an acetonitrile adduct. Despite similar composition, the behavior of 2 differs in the two morphologies. Compound 2-MeCN is relatively air and temperature stable. Crystalline 2, on the other hand, exhibits a compositional, dynamic disorder wherein the tetrazene metallacycle ring-opens into a metal imide/azide complex detectable by X-ray crystallography and FTIR spectroscopy. Electronic structure of 2 was examined by EPR and XPS spectroscopies and DFT calculations, which indicate 2 is best described as a Mn(III) ion with an anion radical delocalized across the two ligands through spin-polarization effects.

Fe-N system at high pressure reveals a compound featuring polymeric nitrogen chains

“…Examples of transition metal complexes with tetraazadienes 58 , tetraaz-2-enes 59 or hexazene 60 , 61 ligands are known, and the longest cycle-containing chain has 11 N atoms in 1,1′-(triaz-1-ene-1,3-diyl)bis(1H-tetrazol-5-amine) 62 . However, we are unaware about the existence of linear nitrogen chains containing more than six nitrogen atoms, which have been reported hitherto.…”

Transition-metal-mediated reduction and reversible double-cyclization of cyanuric triazide to an asymmetric bitetrazolate involving cleavage of the six-membered aromatic ring

“…We intended to extrapolate our work on the formation of metallotetrazene species [34][35][36][37][38][39][40][41] from addition of azides at manganese centers to cyanuric triazide 50 by reaction with Mn(NR 2 ) 2 51 (R = SiMe 3 ). However, this experiment resulted in an entirely different type of chemical reaction.…”

“…23 Other cycloadditions of azide reactions are of interest as well. Our group 34,35 and others [36][37][38][39][40][41] have explored the cycloaddition of two azide units, coupled to metal-mediated extrusion of N 2 , to give ve-membered tetrazene metallacycles. In these complexes, a redox-non-innocent four-nitrogen chain of catenated nitrogen ligands acts as a bidentate ligand.…”

“…In these complexes, a redox-non-innocent four-nitrogen chain of catenated nitrogen ligands acts as a bidentate ligand. 34,35,[39][40][41] A highly relevant cycloaddition reaction of azide occurs on orthoazidoazines, viz., nitrogen-substituted benzene rings with an azide group ortho to a ring nitrogen. This species can undergo a reversible isomerization to a indole-like fused bicycle containing a tetrazole ring fused to the six-membered azine.…”

Hemicubane topological analogs of the oxygen-evolving complex of photosystem II mediating water-assisted propylene carbonate oxidation

“…4), a star-shaped cluster of six edgefused hemicubane features. The counterions are the wellknown [46][47][48][49][50] tris[bis(trimethylsilyl)amido]manganate(II) anionic complex:…”