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.