Extremely Congested Hydrazine Radical Cations

Article abstract of DOI:10.1021/jo00330a014

Addition of tert-butyllithium to the N2 tert-butylated diazenium cations derived from bicyclic azo compounds gave 2,3-di-tert-butyl-2,3-diazabicyclo<2.2.1>heptane (6), its 7,7-spirocyclopropyl analogue (9), and its bicyclo<2.2.2>octane analogue (10).These very hindered tetraalkylhydrazines are unusually sensitive to both air and heat, and their radical cations decompose thermally at 25 deg C with rate constants of approximately 1, 0.1, and 10 s^-1, respectively, undergoing de-tert-butylation.Despite their kinetic instability, these radical cations are thermodynamically slightly easier to form by one-electron removal from the neutral hydrazine than are analogues with the tert-butyl groups replaced by methyl groups.Destabilization of the neutral form by the bulky tert-butyl substituents almost exactly balances destabilization of the radical cationic form, leading to very small changes in E⁰' as the size of alkyl groups is increased.