Gallium, dimer reactions

The halides, GaQs, AlBrs, A1C13, and FeCl3, very probably also exist in dimeric form. With these halides, however, the complexation reaction with the azide is the fast step so that no square-root term is found in the kinetic equation. Arsenic trichloride, arsenic tribromide, phosphorus trichloride, and phosphorus pentachloride were without effect on the rate of decomposition of benzoyl azide. Finally, the authors have observed that the catalytic influence of boron tribromide was much higher than all the other halides. Its rate constant was estimated to be about 18 times larger than that for gallium chloride. 

It is anticipated that all of the complex reactions observed in the boron system and in the studies on indium and gallium derivatives to be discussed below will be found in alkylaluminum systems. There also will be some additional complications which arise from the fact that the A1R3 moiety often occurs in a dimeric form which will alter the energetics of the reaction and may in some instances govern the mechanism of exchange as observed for alkyl group transfer. 

In 2001, Chisholm s group reported a (3-diiminate (BDI) gallium-OSiMe3 complex which was unreactive for LA ROP the authors cited substrate binding as the limiting step [76]. Recently, a gallium alkoxide initiator (11) has been reported as an efficient polymerization initiator [72]. The dimeric complex was formed by reaction of GaMe3 with (A)-methyl lactate (Fig. 15). 

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