Gallium Lewis acid compounds

Gallium chloride, as Lewis acid, 9, 741 Gallium compounds... 

The tendency of the aluminium atom to complete its electron octet is manifested as the Lewis acidity of organoaluminium compounds. This is demonstrated by the formation of 1 1 complexes of trialkylaluminium with anions or bases such as ethers and amines. Organoaluminium compounds are generally more acid than the organoderivatives of boron, indium and gallium. For steric reasons, complex formation is more difficult in compounds of... 

The racemisation of 1-phenylethylchloride catalysed by various Lewis acids in diethyl ether at 25 °C was studied by Evans and Satchell Gallium, aluminium and boron chlorides as well as boron fluoride induced a clean first-order loss of optical activity and the rate of this process was found to be directly proportional to the catalyst concentration. The effect of added water was investigated quantitatively in the case of gallium chloride and the retarding role of this compound followed the kinetic expression ... 

The literature reveals a paucity of compounds containing the Ga-Sb bond. However, antimony seems to behave in a fashion similar to that of its lighter congeners. For example it can readily for Lewis acid-base adducts, (Bu )3GaSb(Et3). " Trimers such as [Me2GaSb (SiMe3)2]3 have also been reported. The coordination of gallium in both of these compounds is unremarkable four-coordinate tetrahedral. 

The polycondensation of BHET to PET proceeds in the melt at temperatures of 270-305 °C, under vacuum (< 1 mbar absolute pressure) and in the presence of Lewis acid metal compounds, such as titanium alkoxides, dialkyltin oxide, gallium oxide, germanium oxide, thallium oxide, lanthanide salts, and most commonly, antimony oxide [1,2, 22-26]. Under polymerization reaction conditions, these catalysts are generally converted to their alkoxides with ethylene glycol. Typical of such alkoxides is antimony(III) glycolate, the active catalyst for the majority of the world s PET production [27] (cf. Structure 1). 

Some adducts of stannylenes with Lewis acids, such as boron compounds" and AlClg are known. More common are adducts of stannylenes with Lewis bases, such as 1,4-dioxane or phosphines. Stannylenes form adducts with carbenes (Scheme 2.8.5) and with carbene analogs, such as gallium(I) derivatives or even other stannylenes. In the latter adducts between two tin(II) atoms, one stannylene acts as a Lewis base and the other one as a Lewis acid. 

The preparation and use of indium trichloride, gallium trichloride, and zinc chloride supported on MCM-41 as Lewis acids in the Friedel-Crafts acylation of aromatics with acyl chlorides was investigated. The support itself shows no catalytic activity in the benzoylation of benzene with BC, whereas the highest activity is showed by the supported indium trichloride. The order for acylation activity of the supported metal chloride (indium trichloride > gallium trichloride zinc chloride) is quite similar to that of the redox potential of the metals [E , +/, (-0.34 V) > E°Ga /Ga ( 0.53 V) > E 2n +/zn ( 0.74 V)] and confirms a possible relationship between the redox potential and the catalytic activity of the supported metal chloride. The reaction can be efficiently applied to a variety of aromatic compounds, including toluene, para-xylene, mesitylene, anisole, and 2-MN (70%-90% yield), confirming the moisture insensitivity of the catalyst. ... 

Aluminum alkyls are stronger Lewis acids than the trialkyls of boron and gallium, and complex formation in the presence of Lewis bases is an important aspect of the reaction chemistry of organoaluminum compounds. The Lewis acidity of organoaluminum compounds accounts for the strong association of aluminum alkyls and hydrides by three-center two-electron bonds, as well as association of organoaluminum... 

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