Stable, yet “Naked”, Azo Radical Anion ArNNAr•– and Dianion ArNNAr2- (Ar = 4-CN-2,6-iPr2-C6H2) with Selective CO2 Activation
Azo radical anion 1•– and dianion 12- have been isolated by one- and two-electron reductions of the azo compound 1 (ArNNAr, Ar = 4-CN-2,6-iPr2-C6H2) with alkali metals, respectively. The reduced species have been characterized by single-crystal X-ray analysis, EPR, UV and FT-IR spectroscopy, as well as SQUID measurements. The filling of one and two electrons in the π* orbital of N–N double bond of 1 leads to a half-double N–N bond in 1•– and a single N–N bond in 12-. The uncoordinated nature enables these reduced species to activate CO2. The exposure of 1•– solution to CO2 led to the formation of oxalate anion C2O42-, while that of 12- solution to CO2 afforded the hydrazine dicarboxylate dianion [1-2CO2]2-, which reversiably dissociated back to 1 and CO2 upon oxidation.