Radical ions. 36. Structural changes accompanying the one-electron oxidation of hydrazine and its silyl derivatives

Mechanistic studies on oxidation of hydrazine by a µ-oxo diiron(iii,iii) complex in aqueous acidic media—proton coupled electron transfer

“…85 The N-N bond length is also shortened significantly. 60,86 This significant structural change is in qualitative agreement with the low self-exchange rate constant for the couple N 2 H 4 /N 2 H 4 + and it might also predict a slower one-electron oxidation of N 2 H 4 that is found in many of its reactions particularly when the oxidizing agent is not so powerful 20 such as in the present situation. PCET reduces the activation barrier for the energetically unfavourable one-electron oxidation of hydrazine by the dinuclear iron(III,III) under reference-the net reaction thus becomes thermodynamically downhill and ultimately it leads to gaseous N 2 by successive oxidation of N 2 H 4 + radical.…”

Odd‐Electron Bonds

“…Even thougho dd-electron bonds are important in radicalr eactivity,e lectrochemistry and catalysis, it is remarkable how unfamiliar these principles have remained. Above all, much of the late Dieter Asmus' seminalw ork [4][5][6][7][8][9][10][11][12][13] has apparently been forgotten, [72] but also the pioneering experimental studies of Meot-Ner, [19] Pauling [3] and Hiberty's [29] rationalization of oddelectron bond energiesi nt erms of valence-bond theory and Bock [34] and Nelsen's [35] fundamental studies on three-electron p-bonds are apparently no longerp resenti no ur general picture of bondingt heory.T his short review attempts to remind us of these classical examples of physicalo rganic chemistry, which taken on an even more importantr ole as the importance of radicals and radical ions is increasingly recognized in both biology and photovoltaics and whose importance in transition-metal chemistry has recently been reviewed. [73] Computational Section All calculations used the Gaussian 09 series of programs.…”

“…One of the early successes of theory was Bock's prediction [34] that the hydrazine radicalc ation,N H 2 NH 2 + C,s hould be planar with at hree-electron p-bond. This was accompanied by an increasingb ody of experimental information [35] that pointed towards al arge change in structure on one-electrono xidation of hydrazines.T he rotation barrier of at etraalkyl-hydrazine radical cation (22-23 kcal mol À1 )w as measured in solution af ew years later [36] and was found to be lower than the calculated (MP2/6-31G(d)) barrier( 30 kcal mol À1 )f or parent NH 2 NH 2 + C In the following years, hydrazine radical cations becamew orkhorses of experimental electron-transfer chemistry because of their large reorganization energy,w hich slows electron-transfer reactions to make them amenable to study by av ariety of methods.…”

Boratome als Spinträger in zwei‐ und dreidimensionalen Systemen

“…B. für ausgedehnte magnetische Systeme, ähnlich wie Organoborane seit kurzem in Materialien mit möglichen optischen und elektrochemischen (Sensor-)Anwendungen eingesetzt werden. [7] Grundsätzlich ist Bor ein ausgezeichnetes Element zur Untersuchung von Spinverteilung in paramagnetischen Verbindungen, weil beide stabilen Isotope, 10 B (19.8 %, I = 3) und 11 B (80.2 %, I = 3/2), einen Kernspin und ausreichende magnetische Momente (m( 10 B)/m( 11 B) = 0.335) aufweisen. [8] Die…”

“…Paramagnetische Verbindungen mit mindestens teilweise borzen- Kombination beider Isotope mit ihren relativ hohen I-Werten kann jedoch zu einer großen Zahl von Hyperfeinaufspaltungslinien führen, wenn mehrere Boratome und andere aktive Kerne mit dem Elektronenspin wechselwirken, [9,10] was zu einem teilweisen oder sogar vollständigen Verlust der Information aus EPR-Spektren führen kann. In solchen Fällen haben sich andere Methoden wie ENDOR(Electron-NuclearDouble-Resonance)-oder TRIPLE-Spektroskopie bewährt (siehe Abbildung 3 in Abschnitt 2.3).…”