Synthesis and structures of mono(1-aza-allyl) complexes of aluminum

The synthesis and structures of new aluminum complexes using the 1-aza-allyl ligand R (R = [N(SiMe3)C(Ph)C(SiMe3)(2)](-)) are described. The reaction of RLi . THF with AlMe2Cl, AlMeCl2, AlCl3, and AlBr3 in diethyl ether or n-hexane, after workup, afforded RAlMe2 (1), RAlMeCl (2), RAlCl2 (3), and RAlBr2 (4), respectively, while [RAlF(mu-F)](2) (5) or RAlI2 (6) was prepared in high yield by the reaction of RAlMe2(1) with 2 equiv of Me3SnF or I-2, respectively, in toluene. The complex 2 or 3 reacts with an excess of THF to give the corresponding THF adduct RAlClMe . THF (7) or RAlCl2. THF (8). Compounds 7 and 8 are not stable; the coordinated THF can be easily removed in vacuo at ambient temperature. The molecular structures of 3, 5, and 8 have been established by X-ray crystallography. Compound 3 is a monomer with a chelating eta(3) 1-aza-allyl ligand, while compound 8 forms an open structure with an eta(1) pendant ligand. Compound 5 is the first example of a dimeric aluminum difluoride, in which two bridging F atoms reside on the pseudo 2-fold axis of the approximately C-2 symmetric molecule. The two pentacoordinated aluminum atoms can be described as having distorted trigonal-bipyramidal geometries, which have in common one bridging F atom in an apical position and the other bridging F atom in an equatorial position.