Homo- and heteroalumoxane silicates

Abstract

Acid–base reactions of LAl(OH)(μ-O)Si(OH)(OtBu)₂ (L = HC[CMeNAr]₂⁻, Ar = 2,6-iPr₂C₆H₃) (1) with nBuLi, AlMe₃, GaMe₃, and ZnMe₂ led to the isolation of several homo and heterometallic systems containing either the hydroxo Al–OH–M or alumoxane Al–O–M unit stabilized by a silicate moiety. In reactions with AlMe₃, the stepwise deprotonation of 1 could be observed and leads to the first example of a covalent Al₂SiO₃ alumoxane ring and furthermore the multimetallic compounds LAl(μ-O)(μ-AlMe₂)(μ-O)Si[(μ₃-O)(AlMe₂)](μ-OtBu)(OtBu) and LAl(μ₃-O)(AlMe₃)(μ-AlMe₂)(μ-O)Si[(μ₃-O)(AlMe₂)](μ-OtBu)(OtBu) are formed in the presence of two or more equivalents of AlMe₃. These compounds represent molecular models for a “pure” and “real” MAO and a rare case of a “free” AlMe₃ molecule coordinated to an alumoxane moiety. The molecular structures of all compounds have been determined using single crystal X-ray diffraction.