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 [eta(5):sigma-(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-C-alkyl insertion products [eta(5):sigma-(C9H6)C2B10H10]Ln-(eta(2)(RN)(2)C(CH2C6H4-o-NMe2)](THF) (R = TMS, Ln = Y (2a), Gd (2b); R = Bu-t, Ln = Y (2a), Gd (2b); R = Bu-t, Ln = Y (3a)) or [eta(5):sigma-(C9H6)C2B10H10]Dy[eta(2)-(2,6-Me2C6H3)NC(CH2C6H4-o-NMe2)S](THF)(2) (4c). Treatment of 2a with I equiv of R'N=C=NR' to give the Y-C-cage insertion complexes [eta(5):sigma-(C9H6){N(R')C(=NR')}C2B10H10]Y[eta(2)-{(TMS)N}(2)C(CH2C6H4-o-NMe2)] (R' = Cy (5a), Pr-i (6a)). Similarly, unsaturated compounds Ph2C=C=O and PY2C=O (Py = 2-pyridyl) also inserted into the Y-C-cage bond in 2a to yield [eta(5):sigma-(C9H6){OC(=CPh2)}C2B10H10]Y[eta(2)-{(TMS)N}(2)C(CH2C6H4-o-NMe2)] (7a) and [eta(5):sigma-(C9H6){OC(Py)(2)}C2B10H10]Y[eta(2)-{(TMS)N)}(2)C(CH2C6H4-o-NMe2)](THF) (8a), respectively. In sharp contrast to the earlier reports that the nontraditional metal-C-cage sigma bonds in metal carboranyl complexes are generally inert toward electrophiles, the insertion of unsaturated molecules into the Y-C-cage sigma 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.