Synthesis and reactivity of bis(heptamethylindenyl) yttrium (Ind*2Y) complexes containing alkyl and hydride ligands: crystal structure of Ind*2YCl(THF)

The syntheses and reactivities of yttrium alkyl and hydride complexes containing a sterically demanding, bis(heptamethylindenyl) ligand set are reported. The chloride complex Ind*2YCl(THF) (2, Ind* = heptamethylindenyl) was prepared by the reaction of Ind*Na (1, 2 equiv) with YCl3 in THF. Compound 2 was structurally characterized. Complex reaction mixtures were obtained when compound 2 was treated with KSi(SiMe3)3 or (THF)3LiSi(SiMe3)3, although 2 reacted readily with MeLi to yield the methyl complex Ind*2YMe(THF) (3). Treatment of 3 with H2 or PhSiH3 gave the base-stabilized hydride complex Ind*2YH(THF) (4). The base-free chloride complex Ind*2YCl (5) was synthesized by the reaction of 1 (2 equiv) with YCl3 in toluene. Treatment of 2 with LiCH(SiMe3)2 yielded the base-free alkyl complex Ind*2YCH(SiMe3)2 (6). No reaction was observed between 6 and CH4, and complex reaction mixtures were obtained when 6 was treated with H2 or PhSiH3. However, when 6 was treated with H2 in the presence of THF, the transient hydride Ind*2YH was trapped as complex 4. The increased steric bulk of 6 leads to a slower reaction with PhSiH3 as compared to Cp*2YCH(SiMe3)2 (7).