tert-Amyl Compounds of Aluminum and Gallium: Halides, Hydroxides, and Chalcogenides

The reaction of AlCl 3 with 3 equiv of the tert -amyl Grignard reagent (Me 2 EtC)MgCl yields the monomeric trialkyl compound Al(CMe 2 Et) 3 ( 1 ). Reaction of compound 1 with MeCN and [PPN]Cl yields the Lewis acid−base complexes Al(CMe 2 Et) 3 (MeCN) ( 2 ) and [PPN][AlCl(CMe 2 Et) 3 ] ( 3 ), respectively. The hydrolysis of Al(CMe 2 Et) 3 in hexane results in the formation of the trimeric hydroxide [(Me 2 EtC) 2 Al(μ-OH)] 3 ( 4 ), which is converted to the dimer [(Me 2 EtC) 2 Al(μ-OH)] 2 ( 5 ) upon heating. The reaction of Al(CMe 2 Et) 3 with H 2 S at room temperature yields the cubane compound [(Me 2 EtC)Al(μ 3 -S)] 4 ( 6 ). If the reaction is carried out at 0 °C, then the hexamer [(Me 2 EtC)Al(μ 3 -S)] 6 ( 7 ) may be isolated along with compound 6 . The selenide analog of 6, [(Me 2 EtC)Al(μ 3 -Se)] 4 ( 8 ), is prepared directly from the reaction of compound 1 with H 2 Se, while the telluride analog, [(Me 2 EtC)Al(μ 3 -Te)] 4 ( 9 ), is prepared by the direct reaction of compound 1 with tellurium metal. The gallium cubane compounds [(Me 2 EtC)Ga(μ 3 -E)] 4, (E = S ( 10 ), Se ( 11 ), Te ( 12 )) have been prepared from the reaction of Ga(CMe 2 Et) 3 with the appropriate element. The tert -amyl compounds are compared to their tert -butyl analogs, and the isolation of compound 7 is used as a precedent to prepare [( t Bu)Al(μ 3 -S)] 6 ( 13 ). A structural analysis is made of the M 4 E 4 cubane cores (M = Al, Ga, In; E = S, Se, Te), and a new topological method is proposed to predict the intracage bond angles in group 13 cage compounds, [(R)M(μ 3 -X)] n . The molecular structures of compounds 3, 6, 8, and 10 − 12 have been determined by X-ray crystallography, and a discussion of the crystallographic problems associated with the tert -amyl group is presented.