GAS-PHASE REACTIONS .89. RADICAL IONS .90. DI(TERT-BUTYL)DIAZOMETHANE - THERMAL-DECOMPOSITION AND ONE-ELECTRON REDOX REACTIONS

Di(tert-butyl)diazomethane is a potential precursor for the still unknown, presumably sterically overcrowded tetrakis(tert-butyl)ethane and, therefore, re-investigated. Its (HeI) photoelectron spectrum exhibits a low first vertical ionization energy of only 7.45 eV. Based on the ionization pattern, both the thermal decomposition above 600 K under nearly unimolecular conditions as well as the N2 elimination at the surface of contacts, [Ni(x)/C]infinity, [Rh4(CO)12/SiO2]infinity, [Rhx/SiO2]infinity, and [Ag2CO3]infinity are analyzed in a flow-system. Heterogeneously catalyzed, N2 is split off already at room temperature, but in contrast to results for sterically less shielded diazo compounds, no dimer is formed, and only mixtures of known di(tert-butyl)carbene-isomerization products are isolated. Cyclic voltammetry at 233 K using a glassy carbon electrode proves a reversible oxidation followed by N2 elimination at higher temperatures and an irreversible reduction. On chemical oxidation, however, no paramagnetic species can be detected, whereas chemical reduction at a potassium metal mirror in a THF solution containing (2.2.2)cryptand, yields the radical anion characterized by ESR spectroscopy. Without a cation-chelating ligand, the radical anion of a hitherto unknown dimer, ((CH3)3C)2C=N-N=N-N=C(C(CH3)3)2.theta, is generated, which dissociates at higher temperature, forming ((CH3)3C)2=N2.theta. This one-electron reduction product of di(tert-butyl)diazomethane can also be detected after quickly warming up a solution containing presumably the radical anion of the triphenylphosphane adduct ((CH3)3C)2C=N-N-PPh3.theta. In one of these reduction reactions, a N2 elimination is observed.