Synthesis, structure, dynamic properties, and indenyl transfer reactions of {AlMe₂(THF) (indenyl)}₂SiMe₂

The reaction of Li₂SBI (SBI = Me₂Si(1-indenyl)₂) with 2 equiv of AlMe₂Cl in Et₂O, followed by treatment with THF, affords {AlMe₂(THF)(indenyl)}₂-SiMe₂ (1), which is isolated as a ca. 1/1 mixture of rac and meso isomers, from which rac-1 is obtained by crystallization from toluene. An X-ray crystallographic analysis establishes that rac-1 exists as the 1,3 isomer, i.e., (1-{AlMe₂(THF)-1-indenyl)}(3-{AlMe ₂(THF)}-1-indenyl)SiMe₂, in the solid state. NMR studies establish that in toluene-d₈, rac-1 exists as a 2/1 mixture of 1,3 and 1,1 Al-indenyl isomers which interconvert rapidly on the NMR time scale at room temperature. Rac-1 undergoes slow isomerization to a 1/1 rac/meso mixture (3 days, 23°C, benzene) and also undergoes slow partial disproportionation by ligand redistribution (28% conversion, 2 days, 23°C, benzene). Compound 1 (1/1 to 1.4/1 rac/meso mixture) reacts with Zr(NMe₂)₄ and Hf(NMe₂)₄ under mild conditions to yield (SBI)Zr(NMe₂)₂ in >90% NMR yield (rac/meso = 4.5/1) and rac-(SBI)Hf(NMe₂)₂ in 61% isolated yield, respectively.