Mono- and dichlorido terbium(III) and erbium(III) complexes coordinated by diazabutadiene ligands in different redox states

Treatment of 1,4-diazabutadienes (DADs) of formula DippN=C(R)C(R)=NDipp (Dipp = 2,6-Pr₂ⁱC₆H₃, R = H or Me) with 2 or 1 equiv. of potassium metal in THF leads to the corresponding dianions (DAD^2–) or radical anions (DAD^•−), respectively. The subsequent salt metathesis between LnCl₃ (Ln = Tb or Er) and the above dianions affords dimeric monochlorido complexes [(DAD^2–)Ln(THF)₂(μ-Cl)]₂ with bridging chlorine atoms between the lanthanides. The reaction of the radical anion species with LnCl₃, if R = H, gives monomeric dichlorido complexes (DAD^•−)Ln(THF)₂Cl₂; however, if R = Me, the activation of one methyl group occurs, which in the reaction with TbCl3 leads to the formation of a product with shifted double bonds [DippN=C(Me)C(=CH₂)N(Dipp)]Tb(THF)₂Cl₂.