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 1(2-) have been isolated by one- and two-electron reduction of the azo compound 1 (ArNNAr, Ar = 4-CN-2,6-Pr-i(2)-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 pi* orbital of the N-N double bond of 1 leads to a half-double N-N bond in 1(2-) and a single N-N bond in 1(.2-). The uncoordinated nature of these reduced species enables them to activate CO2. The exposure of 1(.-) solution to CO2 led to the formation of oxalate anion C2O42-, while that of 1(2-) solution to CO2 afforded the hydrazine dicarboxylate dianion [1-2CO(2)](2-), which reversibly dissociated back to 1 and CO2 upon oxidation.