Synthesis, structural characterization, and reactivity of organolanthanide complexes derived from a new, versatile boron-bridged ligand, (Pr2NB)-Pr-i(C9H7)(C2B10H11)

摘要

New boron-bridged ligands incorporating both indenyl and carboranyl moieties have been prepared. Reaction of (Pr2NB)-Pr-i(C9H7)Cl with 1 equiv of Li2C2B10H10 gave, after treatment with 1 equiv of n-BuLi, the dilithium salt [(Pr2NB)-Pr-i(C9H6)(C2B10H10)]Li-2(OEt2)(2) (1), which was conveniently converted into its neutral counterpart (Pr2NB)-Pr-i(C9H7)(C2B10H11) (2) via reaction with excess C5H6. Mixing 1 and 2 in a 1:1 molar ratio quantitatively afforded the monolithium. salt [(Pr2NB)-Pr-i(C9H6)(C2B10H11)]Li(THF)(2) (3). Treatment of LnI(2) with 1 equiv of 1 generated the trivalent organolanthanide complexes meso-[{eta(5):sigma-(Pr2NB)-Pr-i(C9H6)(C2B10H10)}(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-[{eta(5):sigma-(Pr2NB)-Pr-i(C9H6)(C2B10H10)}(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(SiHMe2)(2)](3)(THF)(2) resulted in clear formation of [eta(5):sigma-(Pr2NB)-Pr-i(C9H6)(C2B10H10)]LnN(SiHMe2)(2)(THF)(2) (Ln = Nd (8), Er (9), Y (10)). Treatment of 8 with Me3NHCl or Me3SiCl led to the isolation of 2 and NdCl3(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 (MALA) in toluene, affording syn-rich poly(MMA)s. [References: 67]