Organoaluminum-nitrogen compounds

The presence of both donor and acceptor binding sites in organoaluminum amides makes them ideally suited for supramolecular self-assembly by dative bonding. Indeed, aminoalanes can occur either as monomeric molecules, 51, or as cyclic dimeric, 52, or trimeric, 53, supermolecules [R2A1NR R ] [n — 1,2, or 3), depending mostly on the steric properties of the organic groups. 

These compoimds, and their gallium and indium analogs, serve as precursors for Group 13 nitride materials (AIN, GaN, InN) [117]. Because aluminum-nitrogen compounds have been reviewed [118-121], selected recent examples only will be discussed here. It is worth mentioning that recent mass spectral measurements show that the dimeric aggregates are preserved even in the gas phase, with partial disso- 

The influence of organic groups on the extent of association of aminoalanes [R2A1NR R ] is illustrated by the list given in Table 3.2 [118]. 

It is obvious that small groups favor the formation of trimeric associates and bulky groups facilitate the formation of dimers. 

The thermolysis of some aluminum-nitrogen dimers oceurs with the formation of self-assembled supermoleeules (rings and cages) based upon the AI2N2 ring, which seems to be readily formed [131], 

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Pipes for pure aluminumtrialkyls should be short and mounted so that the product flows freely and completely (no "pockets" tilted towards the storage container). Pipings for organoaluminum compounds should be located at a distance from those for other reactive substances, water and vapour. The production of organoaluminum compounds requires apparatuses without lower drains the product can be sent from one apparatus into another by nitrogen flow through immersed pipes. 

Because organoaluminum compounds react readily with all types of Brpnsted acids and with atmospheric oxygen or peroxides, hydroalumination reactions must be conducted anhydrous in an atmosphere of pure nitrogen, and in deoxygenated solvents. Detailed experimental directions for the manipulation and transfer of aluminum alkyls and hydrides are available. °... 

Polar compounds (water, oxygen-, nitrogen-, and sulfur-containing compoimds). They react with the organoaluminum co-catalyst (water, alcohols, amines, thiols), complex the aluminum center in a Lewis acid/base interaction (ketones, ethers, thioefhers), or coordinate strongly to the nickel catalytic center (amines, sulfur compounds). They reduce the concentration of the active species and may be responsible of the formation of sludges in the reaction section. 

Aluminum tetraphenylporphyrin with axial bound chloride, (TPP)AICI, Ic is an effective initiator for the anionic ringopening polymerization of epoxides (11). - - This complex can be easily synthesized by reacting free-base tetraphenylporphyrin, (TPP)H2, with chlorodiethylaluminum in CH2CI2 under nitrogen, where the reaction proceeds rapidly and quantitatively at room temperature with evolution of two equivalents of ethane with respect to (TPP)H2-According to Scheme 1, a variety of aluminum porphyrins can be synthesized using some organoaluminum compounds and they are easily identified by H NMR (Table 2). 

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