posted on 1999-05-07, 00:00authored byChunming Cui, Herbert W. Roesky, Mathias Noltemeyer, Michael F. Lappert, Hans-Georg Schmidt, Haijun Hao
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(μ-F)]2 (5) or RAlI2 (6)
was prepared in high yield by the reaction of RAlMe2(1) with 2 equiv of Me3SnF or I2,
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 η3 1-aza-allyl ligand, while compound 8 forms
an open structure with an η1 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 C2 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.