Bismuth Compounds React With a Nitrone: Lewis Pair Formation and Quantification of Radical Trapping

ABSTRACT Reactions of the Lewis acidic, cationic bismuth compound [BiMe 2 (SbF 6 )] ( 1 ) with the spin trap α‐phenyl‐ N ‐ tert butyl‐nitrone (PBN) yield simple Lewis acid/base adducts [BiMe 2 (PBN)(SbF 6 )] ( 2 ) and [BiMe 2 (PBN) 2 ][SbF 6 ] ( 3 ). Such adducts have, for the first time, been fully characterized for the frequently used spin trap PBN. The ability of 2 and 3 to release PBN‐trapped methyl radicals under thermal conditions is investigated. This is compared to the ability of a small series of simple neutral organobismuth compounds BiR 3 (R = Me, n Bu, i Pr, t Bu, CF 3 ) and one mixed aryl/alkyl‐substituted bismuth complex to transfer carbon‐based radicals to PBN. Applied analytical techniques include NMR spectroscopy, elemental analysis, mass spectrometry, single‐crystal X‐ray diffraction analysis, and EPR spectroscopy.