Do Cp(CO)<sub>2</sub>Mn Fragments Stabilize Radicals?

Groß, Renate; Kaim, Wolfgang

doi:10.1002/anie.198508561

Cited by 43 publications

(18 citation statements)

References 28 publications

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“…), perhaps the simplest organic nitrogen‐based radicals, are normally very unstable and short‐lived species 6. 7 Early claims8, 9 that certain metal complexes could be formulated as metal aminyls (Figure 1 a) proved to be incorrect 10. 11 In these and other cases,12 the metal aminyl formulation turns out to be of secondary importance, and these species are still best described as the more familiar metal amides (Figure 1 b).…”

Section: Methodsmentioning

confidence: 99%

Metal Complexes of Aminyl Radicals

Hicks

2008

Angew Chem Int Ed

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electronic structure · N ligands · nitrogen · radicals · transition metalsTransition-metal complexes with open-shell configurations typically have their spin density more or less confined to the metal ion: the unpaired electron (or electrons) resides in metal-based d orbitals, and there is minimal delocalization onto the ligands that comprise the inner coordination sphere of the complex. Metal complexes in which an unpaired electron resides on a ligand are relatively rare but are by no means unknown or unimportant. Semiquinone anions [1] and phenoxyls [2] are two examples of well-known radical ligands, both of which are delocalized p radicals which bind to metals through oxygen atoms. Both of these classes of radical ligands have attracted significant attention because of their importance in bioinorganic chemistry and their interesting physical properties.Radical ligands in which nitrogen atoms are the donors are also known. A variety of radical anion species fall into this group, [3] as do neutral radicals such as verdazyls [4] and thiazyls.[5] In most of these cases the unpaired electron is delocalized over the ligands conjugated p system, and the radicals enjoy some level of stability even as uncoordinated species: most are persistent in solution and some (e.g. verdazyls and thiazyls) are isolable compounds.Aminyl radicals (R 2 NC), perhaps the simplest organic nitrogen-based radicals, are normally very unstable and shortlived species. [6,7] Early claims [8,9] that certain metal complexes could be formulated as metal aminyls (Figure 1 a) proved to be incorrect. [10,11] In these and other cases, [12] the metal aminyl formulation turns out to be of secondary importance, and these species are still best described as the more familiar metal amides (Figure 1 b). Other complexes, in which the evidence for metal aminyl character was more compelling, were not sufficiently stable to be isolated, thereby limiting the studies of these complexes to in situ spectroscopic ones. [13] Thus it appeared that genuine, isolable metal aminyl radical complexes were elusive species, lost somewhere between the pitfalls of instability and conversion to the metal amide configuration (Figure 1 b).The first isolable aminyl radical complex was reported by Grützmacher and co-workers in 2005.[14] Deprotonation of the NH group of the cationic rhodium(I) amine compound 1 affords the neutral rhodium(I) amide complex 2 (Scheme 1).The latter can be easily oxidized (E 0 = À0.55 V vs. ferrocene/ ferrocenium in DMSO) and thus, treatment of 2 with ferrocenium cation generates cation 3 (as its CF 3 SO 3 À salt) as a stable entity in the solid state and in solution. EPR spectroscopy studies indicate that the majority of spin density resides on the nitrogen atom, supporting the formulation of 3 as a rhodium(I) complex of a neutral aminyl radical rather than a rhodium(II) amido compound. The EPR data are corroborated by DFT calculations, which predict a spin density of 57 % on nitrogen and 30 % on rhodium (Figure 2 a). The singly occupied molecular orbi...

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Section: Methodsmentioning

confidence: 99%

Metal Complexes of Aminyl Radicals

Hicks

2008

Angew Chem Int Ed

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“…Claims for the "stabilization of unusual molecules" such as radicals (e.g. R 2 NC) [19] or radical ions (e.g. CO 2 C À ) [20] by metal complexation require hard evidence for the individual oxidation states of metal and ligands.…”

Section: àmentioning

confidence: 99%

“…CO 2 C À ) [20] by metal complexation require hard evidence for the individual oxidation states of metal and ligands. For instance, the formation of metal-complex-stabilized aminyl radicals [19] has had a controversial history with respect to the…”

Section: àmentioning

confidence: 99%

N₂^.3−: Filling a Gap in the N₂ⁿ⁻ Series

Kaim

Sarkar

2009

Angew Chem Int Ed

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coordination chemistry · nitrogen · radical complexes · rare-earth metals · superoxide analoguesParallel to the elucidation of the heterogeneous catalytic reactions leading from adsorbed N 2 and H 2 to NH 3 under real or idealized conditions [1] and in addition to continued studies of enzymatic nitrogen fixation, [2] the primary products of N 2 reduction have received special attention as surface-or metalstabilized molecular ions. Thus, the one-electron addition to N 2 C À [3] and the stabilization of two-electron reduced diazenido(2À) ions ("pernitride", N 2 2À

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“…Die Feststellung einer "Metallkomplex-Stabilisierung ungewöhnlicher Moleküle" wie es Radikale (z. B. R 2 NC) [19] oder Radikalionen (z. B. CO 2 C À ) [20] sind, bedarf klarer Beweise für die individuellen Oxidationsstufen von Metallen und Liganden.…”

Section: àunclassified

“…B. CO 2 C À ) [20] sind, bedarf klarer Beweise für die individuellen Oxidationsstufen von Metallen und Liganden. Beispielsweise ergab sich hinsichtlich der Metallstabilisierung von Aminyl-Radikalen [19] eine nicht immer eindeutige Situation [19a] bezüglich der Alternativen…”

Section: àunclassified