Magnesium tetraorganyl derivatives of group 13 metals as intermediate products in the synthesis of group 13 metal alkyls and aryls

Reactions of organomagnesium halides with group 13 metal halides lead to the formation of R3M type compounds (R = alkyl, aryl; M = Al, Ga, In) and are considered as the simplest methods of R3M compound syntheses. These seemingly simple reactions reveal a much more complex chemistry involving mixed magnesium-group 13 metal compounds. To elucidate the reaction course of reactions of organomagnesium halides with group 13 metal halides, we have studied reactions of R3M with organomagnesium halides. The interaction of Et3M with R1MgX led to the formation of following products being mixtures of crystalline ionic complexes with the general composition of [Et4-nR1nM]−[XMg (thf)5]+·(thf): [Et2.2Al(CH=CH2)1.8]−[BrMg (thf)5]+·(thf) (1), [Et3Ga(CH=CH2)]−[BrMg (thf)5]+·(thf) (2), [Et4Al]−[BrMg (thf)5]+·(thf) (3), [Et4Ga]−[BrMg (thf)5]+·(thf) (4), [Et2.9Al(C6H5)1.1]−[BrMg (thf)5]+·(thf) (5), [Et2.9Ga(C6H5)1.1]−[BrMg (thf)5]+·(thf) (6), [Et3.4GaMe0.6]−[IMg (thf)5]+·(thf) (7) and [Et4In]−[BrMg (thf)5]+·(thf) (8). A comparison of the production course of group 13 metal trialkyls R3M with a thermal decomposition of 1–8 products showed that reactions of MX3 with RMgX (X = Br, I; R = alkyl, aryl) yield initially intermediate ionic compounds, which must then be thermally decomposed to obtain pure R3M compounds. If group 13 metal bromides and iodides, and alkyl (aryl)magnesium bromides and iodides in thf are used, only intermediate products with the [R4M]−[XMg (thf)5]+·(thf) structure are formed.