Direct Evidence for Neutral <i>N</i>-Pyrazolyl Radicals: Paddlewheel Dibismuthanes Bearing Pyrazolato Ligands with Very Short Bi–Bi Single Bonds

Abstract

Neutral N -pyrazolyl radicals [3,5-R 2 pz] • as reactive intermediates were generated by one-electron oxidization of the corresponding 3,5-disubstituted pyrazolato anions [3,5-R 2 pz] − (R = t Bu, Ph) with BiCl 3 and trapped by the use of 5,5-dimethyl-1-pyrroline- N -oxide as a spin trap, which was confirmed by electron paramagnetic resonance spectral analysis. With dimerization of the postulated pyrazolato low-valent Bi II radical species, two novel paddlewheel pyrazolatodibismuthanes [L 2 (Bi–Bi)L 2 ] [L = η 1,η 1 -3,5-R 2 pz; R = t Bu ( 5α, 5β, and 5γ ), Ph ( 6 )] were isolated and structurally characterized.