Reaction of Me2Si(C9H7)Cl with 1 equiv of Li2C2B10H10 gave, after hydrolysis, the new versatile ligand Me2Si(C9H7)(C2B10H11) (1). 1 can be conveniently converted into the monoanion [Me2Si(C9H6)(C2B10H11)]-(2) and the dianion [Me2Si(C9H6)(C2B10H10)]2-(3) by treatment with 1 equiv or excess amounts of NaH, respectively. Treatment of SmI2 with 2 in THF gave the unexpected redox product [η5:η6-Me2Si(C9H6)(C2B10H11)]Sm(THF)2 (4). Reaction of SmI2 with 1 equiv of 3 in THF, followed by reaction with 2, gave the unexpected C-H bond reduction product [{η5:σ-Me2Si(C9H6)(C2B10H10)}2Sm][Na(THF)6] (5). In contrast, reaction of YbI2 with 1 or 2 equiv of 2 afforded [{η5-Me2Si(C9H6)(C2B10H11)}Yb(σ-I)(THF)2]2 (6) or [η5-Me2Si(C9H6)(C2B10H11)]2Yb(THF)2 (7), respectively. Treatment of YbI2 with 1 equiv of 3 in THF gave [η5:σ-Me2Si(C9H6)(C2B10H10)]Yb(THF)3 (8), which is the first mixed-ligand organolanthanide(II) complex containing both Ln-C ð and ó bonds to be reported. 8 can also be prepared from the reaction of 6 with excess NaH in THF. Reaction of 8 with 1 equiv of 2 in THF yielded [η5-Me2Si(C9H6)(C2B10H11)]Yb(THF)[(μ-η5):σ-Me2Si(C9H6)(C2B10H10)]Na-(THF)3 (9), which can also be prepared by reaction of 7 with 1 equiv of NaH in THF. These new complexes have been fully characterized by 1H, 13C, and 11B NMR, IR spectroscopy, and elemental analyses. The molecular structures of 4, 5, 8, and 9 have been further confirmed by single-crystal X-ray analyses.