Synthesis and Structure of Rare-Earth-Metal Dicarbollide Complexes with an Imidazolin-2-iminato Ligand Featuring Very Short Metal−Nitrogen Bonds

Several rare-earth-metal complexes involving both imidazolin-2-iminato and dicarbollide ligands were prepared by the reaction of imidazolin-2-iminato rare-earth-metal dichlorides [(ImArN)MCl2(THF)3] with 1 equiv of Na2[C2B9H11] in THF to afford the complexes [(ImArN)M(η5-C2B9H11)(THF)2] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) in high yields. Treatment of [(ImArN)M(CH2SiMe3)2(THF)n] with 1 equiv of the zwitterionic [nido-(Me2NHCH2CH2)C2B9H11] in THF afforded the donor-functionalized dicarbollide complexes [(ImArN)M{σ:η5-(Me2NCH2CH2)C2B9H10}(THF)] (4a, M = Sc; 4b, M = Y; 4c, M = Lu) in good yields. In a similar manner, complexes [(ImArN)Y{σ:σ:η5-(Me2NCH2)2C2B9H9}(THF)] (5) and [(ImArN)Y{σ:σ:η5-(Me2NCH2CH2)(MeOCH2CH2)C2B9H9}] (6) with two tethered donor moieties were synthesized. All complexes were characterized by various spectroscopic techniques and elemental analyses. Their structures were further confirmed by single-crystal X-ray analyses, revealing that the metal−nitrogen bonds in these complexes are either the shortest or among the shortest ever reported for scandium−, yttrium−, or lutetium−nitrogen systems.