New Chemistry from an Old Reagent: Mono- and Dinuclear Macrocyclic Uranium(III) Complexes from [U(BH4)3(THF)2]

A new robust and high-yielding synthesis of the valuable UIII synthon [U­(BH4)3(THF)2] is reported. Reactivity in ligand exchange reactions is found to contrast significantly to that of uranium triiodide. This is exemplified by the synthesis and characterization of azamacrocyclic UIII complexes, including mononuclear [U­(BH4)­(L)] and dinuclear [Li­(THF)4]­[{U­(BH4)}2(μ-BH4)­(LMe)] and [Na­(THF)4]­[{U­(BH4)}2(μ-BH4)­(LA)­(THF)2]. The structures of all complexes have been determined by single-crystal X-ray diffraction and display two new UIII2(BH4)3 motifs.