Diazadienes in lanthanide chemistry: a new insight into old ligands. Synthesis, structures, and properties of complexes {[(R)CNC6H3Pri 2]2}Lu(THF)2(μ-Cl)2Li(THF)2 (R = CH3 or CH2)

The reaction of the dianionic derivative [DADLi2] (DAD is 1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diazabuta-1,3-diene), which was synthesized in situ by reduction of the corresponding DAD with an excess of metallic lithium in THF, with anhydrous LuCl3 (1: 1) affords the metallacyclic complex {[(Me)CNC6H3Pri 2]2}Lu(THF)2(μ-Cl)2Li(THF)2 (1) containing the enediamide fragment N-C(Me)=C(Me)-N. The treatment of DAD with 2 equiv. of BuLi in a diethyl ether-hexane mixture at 20 °C results in the C-H bond activation of the methyl substituents at the imine carbon atom. The reaction of the in situ formed dilithium derivative [DAD−2HLi2] with LuCl3 in THF afforded the complex {[(CH2)CNC6H3Pri 2]2}-Lu(THF)2(μ-Cl)2Li(THF)2 (2) with the diamide ligand N-C(=CH2)-C(=CH2)-N. The structures of complexes 1 and 2 were established by X-ray diffraction.