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