Diazadienes in lanthanide chemistry: transformation in the diamide and enamine amide ligand systems. Synthesis, structures, and properties of complexes (2,6-Pri2C6H3N-C(=CH2)C(=CH2)-NC6H3Pri2-2,6)-Yb(THF)2(μ-Cl)2Li(THF)2 and (2,6-Pri2C6H3N(H)C(Me)=C(Me)-NC6H3Pri2-2,6)GdCl(THF)(μ-Cl)2Li(THF)2

The reaction of lithium amide derivative [2,6-Pri 2C6H3N-C(=CH2)C(=CH2)-NC6H3Pri 2-2,6][Li(THF) n ]2, which was obtained in situ by the interaction of 1,4-bis(2,6-di-isopropylphenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene with two equivalents of BunLi, with anhydrous YbCl3 (1: 1) affords metallacyclic ate-complex [2,6-Pri 2C6H3N-C(=CH2)C(=CH2)-NC6H3Pri 2-2,6]Yb(THF)2(μ-Cl)2Li(THF)2 (1) containing diamide fragment [N-C(=CH2)-C(=CH2)-N]Yb. The reaction of dilithium derivative [(2,6-Pri 2C6H3NC(Me)=C(Me)NC6H3Pri 2-2,6)]2−[Li+(THF) n ]2 with GdCl3 in THF (molar ratio 1: 1) does not result in the formation of a gadolinium complex with the dianionic enediamide ligand but proceeds via the protonation of one of the M-N bonds to form complex [2,6-Pri 2C6H3N(H)C(Me)=C(Me)NC6H3Pri 2-2,6]GdCl(THF)(μ-Cl)2Li(THF)2 (2) bearing the monoanionic enamine amide fragment. The structures of complexes 1 and 2 were determined by X-ray diffraction analysis.