Studies of the Ligand Effect on the Synthesis of Dialuminoxanes by Various β-Diketiminato Ligands

Reactions of LH (L = HC­[C­(Me)­N­(2,6-Me2C6H3)]2) with MenAlCl3–n in diethyl ether afforded the adducts LH·AlMen(Cl)3–n (n = 2, 3; 1, 4; 0, 5) in good yields. Treatment of 3 at elevated temperatures in toluene resulted in LAlMeCl (2) by intramolecular elimination of methane. The controlled hydrolysis of LAlMeCl (2) with equimolar amounts of water in the presence of N-heterocyclic carbene (NHC) gave a mixture of [LAl­(Me)]2(μ-O) (7) and dimeric [LAlMe­(μ-OH)]2 (8). A convenient route for the preparation of [LAlMe­(μ-OH)]2 (8) was the NHC-assisted controlled hydrolysis of LAlMeI (9). Stepwise hydrolysis of LAlH2 (11) gave dialuminoxane hydride [LAl­(H)]2(μ-O) (12) and dialuminoxane hydroxide [LAl­(OH)]2(μ-O) (13), respectively. Anhydrous treatment of LAlCl2 (1) or LAlMeCl (2) with Ag2O afforded chlorinated dialuminoxane [LAl­(Cl)]2(μ-O) (14) and [LAl­(Me)]2(μ-O) (7), respectively.