Reactivity of Traditional Metal–Carbon (Alkyl) versus Nontraditional Metal–Carbon (Cage) Bonds in Organo-Rare-Earth Metal Complexes [η5:σ-(C9H6)(C2B10H10)]­Ln(CH2C6H4‑o‑NMe2)(THF)2

Equimolar reaction of 1-indenyl-1,2-carborane with Ln­(CH2C6H4-o-NMe2)3 in THF gave highly constrained-geometry complexes [η5:σ-(C9H6)­C2B10H10]­Ln­(CH2C6H4-o-NMe2)­(THF)2 (Ln = Y (1a), Gd (1b), Dy (1c)). They reacted with RNCNR or 2,6-Me2C6H3NCS to generate the Ln–Calkyl insertion products [η5:σ-(C9H6)­C2B10H10]­Ln­[η2-(RN)2C­(CH2C6H4-o-NMe2)]­(THF) (R = TMS, Ln = Y (2a), Gd (2b); R = tBu, Ln = Y (3a)) or [η5:σ-(C9H6)­C2B10H10]­Dy­[η2-(2,6-Me2C6H3)­NC­(CH2C6H4-o-NMe2)­S]­(THF)2 (4c). Treatment of 2a with 1 equiv of R′NCNR′ to give the Y–Ccage insertion complexes [η5:σ-(C9H6)­{N­(R′)­C­(NR′)}­C2B10H10]­Y­[η2-{(TMS)­N}2­C­(CH2C6H4-o-NMe2)] (R′ = Cy (5a), iPr (6a)). Similarly, unsaturated compounds Ph2CCO and Py2CO (Py = 2-pyridyl) also inserted into the Y–Ccage bond in 2a to yield [η5:σ-(C9H6)­{OC­(CPh2)}­C2B10H10]­Y­[η2-{(TMS)­N}2C­(CH2C6H4-o-NMe2)] (7a) and [η5:σ-(C9H6)­{OC­(Py)2}­C2B10H10]­Y­[η2-{(TMS)­N)}2­C­(CH2C6H4-o-NMe2)]­(THF) (8a), respectively. In sharp contrast to the earlier reports that the nontraditional metal–Ccage σ bonds in metal–carboranyl complexes are generally inert toward electrophiles, the insertion of unsaturated molecules into the Y–Ccage σ bond in 2a represents the first example of this type of reactions. These results shed some light on how to activate the nontraditional metal–carbon (cage) bonds in metal–carboranyl complexes. All new complexes were characterized by spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.