A New Supporting Ligand in Actinide Chemistry Leads to Reactive Bis(NHC)borate-Supported Thorium Complexes

A versatile, monoanionic, chelating (bis)­carbene ligand (2) was used to prepare a thorium dihalide complex (3) and a direduced-bpy derivative (4). CASSCF calculations suggest the involvement of a multiconfigurational open-shell singlet, with the main configuration corresponding to a Th­(III)-bpy(−1) (f1π*1) electronic structure. The reactivity of 4 was explored in various transformations, including reactions with carbonyls and organic azides; the latter gave rise to an unusual terminal Th-imido bpy complex (6).