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 [(Im(Ar)N)MCl2-(THF)(3)] with 1 equiv of Na-2[C2B9H11] in THF to afford the complexes [(Im(Ar)N)M(eta(5)-C2B9H11)(THF)(2)] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) in high yields. Treatment of [(Im(Ar)N)M(CH2SiMe3)(2)(THF)] with 1 equiv of the zwitterionic [nido-(Me2NHCH2CH2)C2B9H11] in THF afforded the donor-functionalized dicarbollide complexes [(Im(Ar)NM{sigma:eta(5)-(Me2NCH2CH2)C2B9H10}(THF)] (4a, M = Sc; 4b, M = Y; 4c, M = Lu) in good yields. In a similar manner, complexes [(Im(Ar)N)Y{sigma:sigma:eta(5)-(Me2NCH2)(2)C2B9H9}(THF)] (5) and [(Im(Ar)N)Y{sigma:sigma:eta(5)-(Me2NCH2CH2)(MeOCH2CHDC2B9H9}] (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.