Unprecedented ligand anti-bis-benzylation upon thermolytic treatment of 2,3-diphenylbenzo[g]quinoxaline with (η1-benzyl) pentacarbonylmanganese

The treatment of 2,3-diphenylbenzo[g]quinoxaline with PhCH2Mn(CO)5 in boiling n-heptane affords substantial amounts of a biscyclomanganated 5,10-anti-bis-benzylation product, which structure was assessed by X-ray diffraction analysis. In toluene and under similar experimental conditions, the formation of the latter is inhibited and the major product is the corresponding bis-cyclomanganated 2,3-diphenylbenzo[g]quinoxaline. The bis-benzylation reaction seemingly results from a trapping of benzyl radicals formed upon homolytic cleavage of the C–Mn bond in PhCH2Mn(CO)5 by the metallated 2,3-diphenylbenzo[g]quinoxaline.