Synthesis, Structural Characterization, and Reactivity of Organolanthanide Complexes Derived from a New, Versatile Boron-Bridged Ligand, iPr2NB(C9H7)(C2B10H11)

New boron-bridged ligands incorporating both indenyl and carboranyl moieties have been prepared. Reaction of i Pr 2 NB(C 9 H 7 )Cl with 1 equiv of Li 2 C 2 B 10 H 10 gave, after treatment with 1 equiv of n -BuLi, the dilithium salt [ i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]Li 2 (OEt 2 ) 2 ( 1 ), which was conveniently converted into its neutral counterpart i Pr 2 NB(C 9 H 7 )(C 2 B 10 H 11 ) ( 2 ) via reaction with excess C 5 H 6 . Mixing 1 and 2 in a 1:1 molar ratio quantitatively afforded the monolithium salt [ i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 11 )]Li(THF) 2 ( 3 ). Treatment of LnI 2 with 1 equiv of 1 generated the trivalent organolanthanide complexes meso -[{ η 5: σ - i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )} 2 Ln][Li(S) n ] (Ln = Sm, Yb; S = THF, n = 4; S = DME, n = 3), which was also prepared in a much higher yield by reaction of LnI 2 with 1 equiv of 1 followed by treatment with 1 equiv of 3 . Both inter- and intramolecular electron-transfer pathways are proposed for these reactions. Reaction of LnCl 3 with 1 or 2 equiv of 1 gave the same ionic complexes meso -[{ η 5: σ - i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )} 2 Ln][Li(S) n ] (Ln = Nd, Y, Yb; S = THF, n = 4; S = DME, n = 3). Silylamine elimination reactions of 2 and Ln[N(SiHMe 2 ) 2 ] 3 (THF) 2 resulted in clear formation of [ η 5: σ - i Pr 2 NB(C 9 H 6 )(C 2 B 10 H 10 )]LnN(SiHMe 2 ) 2 (THF) 2 (Ln = Nd ( 8 ), Er ( 9 ), Y ( 10 )). Treatment of 8 with Me 3 NHCl or Me 3 SiCl led to the isolation of 2 and NdCl 3 (DME) 2 ( 11 ), respectively. The new complexes were fully characterized by various spectroscopic data and element analyses. Some were further confirmed by single-crystal X-ray analyses. Complex 8 is an active catalyst for the polymerization of methyl methacrylate (MMA) in toluene, affording syn-rich poly(MMA)s.