Discovering More Non‐Innocence: Triazenido versus Triazenyl Radical Ligand Function, and a Comment on [NO₂]ⁿ as a “Suspect” Ligand

Abstract

The unusual suspects: Depending on co-ligands L(n) and the effects of substituents (R), the well-known triazenides [N(NR)2](-) may act as EPR detectable coordinated triazenyl ligands, [N(NR)2](·). They are thus new non-innocent ligands and are related to the hitherto unused non-innocent nitrogen dioxide ligand, [NO2](·).

Non‐innocent Redox Behavior of Amidinato Ligands: Spectroscopic Evidence for Amidinyl Complexes

“…[1,2] Studies of quadruple [3] and quintuple [4] bonds have revealed effects of the high basicity of these ligands in comparison to carboxylato or carboxamido analogues. However, in contrast to recently reported related triazenido [5] or β-diketiminato (Nacnac -) [6] ligands the amidinato function has not yet been described as behaving non-innocently; amidinyl radicals as one-electron oxidation products of amidinato anions were described as transient species. [7] Nitrogen-centered radicals and their complexes have received increased attention recently because of their good accessibility under the proper conditions and due to their synthetic potential.…”

“…Parallel to the behavior of corresponding triazenide compounds, [5] the reversible one-electron oxidation processes of 1 + on one side and of 2 and 3 + on the other side yield a strikingly different spectroscopic response. The EPR signal of 1 2+ is that of a typical Ru III complex with d 5 configuration, being visible only at low temperatures where it displays an axial splitting of the considerably separated g factor components g 1 , g 2 , and g 3 in glassy frozen solution ( Figure 5A).…”

“…The compounds 1(PF 6 ), 2, and 3(PF 6 ) undergo two oneelectron oxidations ( Figure 4, Table 3) at potentials, which are slightly lower than those of corresponding triazenido complexes; [5] the second oxidation step is reversible for 1(PF 6 ) but irreversible for 2 and 3(PF 6 ). This result is attributed to the increased donor capacity of amidinates relative to triazenides.…”

“…[7] Nitrogen-centered radicals and their complexes have received increased attention recently because of their good accessibility under the proper conditions and due to their synthetic potential. [8] Following the surprisingly variable oxidation of triazenidoruthenium(II) complexes to yield triazenidoruthenium(III), triazenylruthenium(II), or mixed oxidation state species [5] we have employed the N,NЈ-bis (4-methoxyphenyl)acetamidinato (bmaa -) ligand in order to probe whether a similar redox ambiguity (Scheme 1) is feasible for the amidinato/amidinyl redox system.…”

Electrochemical triggered O-atom transfer reaction in nitrocarbonyl rhenium(I) complexes: An IR spectroelectrochemical investigation

“…Also, the redox ''non-innocent'' behavior of coordinated nitrosyl makes it an interesting ligand for investigation [15]. The nitrite ligand has also very important physiological properties [16,17], and recently it was proposed as a ''suspect ligand'' [18]. Then, reactivity studies in rhenium carbonyl complexes with biological relevant ligands, such as NO 2 À and NO, are fundamental.…”