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(SiMe 3 )C(Ph)C(SiMe 3 ) 2 ] - ) are described. The reaction of RLi·THF with AlMe 2 Cl, AlMeCl 2, AlCl 3, and AlBr 3 in diethyl ether or n -hexane, after workup, afforded RAlMe 2 ( 1 ), RAlMeCl ( 2 ), RAlCl 2 ( 3 ), and RAlBr 2 ( 4 ), respectively, while [RAlF( μ -F)] 2 ( 5 ) or RAlI 2 ( 6 ) was prepared in high yield by the reaction of RAlMe 2 ( 1 ) with 2 equiv of Me 3 SnF 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 RAlCl 2 ·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 η 3 1-aza-allyl ligand, while compound 8 forms an open structure with an η 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 .