The synthesis of two bridgehead-substituted nitrosamines, di-1-adamantylnitrosamine (1) and di-1-norbornylnitrosamine (2), is described, and their solid state crystal structures are reported. Large bridgehead substituents increase the NNO angle of the nitrosamine (compared to that found for dimethylnitrosamine) without deconjugating the NNO pi system significantly. This structural change correlates with a red-shifted optical absorption, a diminished N,N rotational barrier, and a greater ease of oxidation of these hindered nitrosamines than is observed for dimethylnitrosamine. The electronic basis of these structure/function correlations is examined. It is concluded that 1 is more strained than N-nitroso-2,2,6,6-tetramethylpiperidine (3) which is more strained than 2 and that a raised (in energy) NO n orbital is primarily responsible for the extreme properties of the former.

This report provides the first examples of solution-stable azodioxide radical cations and describes their direct spectroscopic observation and, in one case, their thermal chemistry. The formal oxidation potentials, E°', for i\yV '-dioxo-2,3-diazabicyclo[2.2.2]oct-2-ene (3), /VJV'-dioxo-2,3-diazabicyclo[2.2.1]hept-2-ene (4), and AyV-dioxo-1,1 '-azobis(norbomane) (5) are 1.65,1.68, and 1.54 V vs SCE, respectively. ESR spectroscopy shows the intermediate cations to be radicals. Radical cation 5,+ (red, Am 510 nm) has a five-line ESR spectrum of (2 ) 1.1 G, while 3,+ (bronze) has a nine-line ESR spectrum simulated as (4 ) 0.86 and o(2N) 1.22 G. Both 3,+ and 5,+ decay in seconds to minutes at room temperature. Thermal decomposition of 5,+ results in C,N and N,N bond cleavage, yielding 1-norbomyl cation (trapped by solvent) and NO+ (trapped in low yield by the oxidant under chemical oxidation conditions). Two viable mechanisms are presented for 5,+'s thermal decay, both of which invoke nitrosoalkane monomer 5m as an intermediate. In a related study, oxidation of nitrosoalkane 2m is found to mediate its facile denitrosation. This work affords the first examples of electron-transfer-mediated C,N bond cleavage of azodioxides and of nitrosoalkanes. Substantial bond weakening is shown to accompany electron loss from these substrates. For 5, oxidation leads ultimately to C,N bond activation.

No abstract

No abstract

2-Thioxoethen-I-one (8) can thus be generated in a photochemically induced addition of CS to CO. This reaction is reversible. C,OS, which probably possesses a triplet ground state, is stable under matrix conditions. Our results are in accordance with the findings of Schwarz et al., who by neutralization reionization mass spectrometry identified C,0Sr"] but not C202[121 as a viable species in the gas phase.