Organoaluminum-oxygen derivatives

Although organoaluminum-oxygen derivatives (alumoxanes) are extremely important compounds in Ziegler-Natta polymerization of olefins and molecular precursors for ceramic materials [70, 71], their structure was considered an enigma as recently as 1994 [72] although considerable experimental data indicating association 

The sum of the covalent bond radii for the Al-0 pair is 1.84 A and the values observed should be compared with this value. Indeed, observed covalent A1 -O bonds are close to it and slightly longer bonds can be regarded as dative. 

Another cyclic dimer is the dialumoxane anion [Me3A10AIMe2]2, 36, (Al-O 1.78 and 1.80 A) this has been structurally characterized as tetramethylammonium salt [85]. 

3-dihydroxodialumoxane (HO)RAIOAIR(OH) [R = C(SiMe3)2] self-assembles into dimeric supermolecules with an adamantane-like structure [85a]. 

Trialumadioxane [Mes (Et)A10AlEt2(Mes A10)]2 (Mes = 2,4,6-Bu C6H2), 37, has a ladder-like supramolecular structure [86] of a type frequently observed in organotin-oxygen compounds. 

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Overall, the isolation and full characterization of products derived from the oxygenation of organoaluminum complexes has proved very rare. In one example, the reaction of the tetranuclear cluster [Al4(p3-8-quinolylimide)2Meg with molecular oxygen selectively afforded the monoalkoxide cluster [Al4(p3-8-... 

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