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 (DAD2–) or radical anions (DAD•−), respectively. The subsequent salt metathesis between LnCl3 (Ln = Tb or Er) and the above dianions affords dimeric monochlorido complexes [(DAD2–)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.