Organoaluminum and -gallium Formamidinate Complexes



Dialuminum formamidinate complexes [Me2Al(μ-Form)(μ-Me)AlMe2] [Form (ArNCHNAr) = EtForm (Ar = 2,6-Et2C6H3) or DippForm (Ar = 2,6-iPr2C6H3)] were obtained in good yields by treatment of formamidines (FormH) with trimethylaluminum in a 1:3 stoichiometry. The products contain both a bridging Form ligand and a bridging methyl group between the two aluminum centers. [M(Form)Me2] (M = Al, Form = DippForm, EtForm; M = Ga, Form = DippForm) were prepared in high yields by the protonolysis reactions of MMe3 (M = Al, Ga) with formamidines (FormH) in a 1:1 stoichiometry. [Al(DippForm)Me2] was also synthesized by other methods including concentration of the tetrahydrofuran/n-hexane solution of [Me2Al(μ-DippForm)(μ-Me)AlMe2] to dryness and also by reaction of AlMe3 with [Ga(DippForm)Me2] in a 1:1 ratio. Partial dissociation of the dialuminum to monoaluminum complexes was detected in the 1H NMR spectra of [Me2Al(μ-Form)(μ-Me)AlMe2] complexes. All complexes exhibit a distorted tetrahedral stereochemistry of the Group 13 metal atoms.