tert-amyl compounds of aluminum and gallium: Halides, hydroxides, and chalcogenides

The reaction of AlCl3 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(mu-OH)](3) (4), which is converted to the dimer [(Me(2)EtC)(2)Al(mu-OH)](2) (5) upon heating. The reaction of Al(CMe(2)Et)(3) with H2S at room temperature yields the cubane compound [(Me(2)EtC)Al(mu(3)-S)](4) (6). If the reaction is carried out at 0 degrees C, then the hexamer [(Me(2)EtC)Al(mu(3)-S)](6) (7) may be isolated along with compound 6. The selenide analog of 6, [(Me(2)EtC)Al(mu(3)-Se)](4) (8), is prepared directly from the reaction of compound 1 with H2Se, while the telluride analog, [(Me(2)EtC)Al(mu-Te)](4) (9), is prepared by the direct reaction of compound 1 with tellurium metal. The gallium cubane compounds [(Me(2)EtC)Ga(mu(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(mu(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(mu(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.