Aminodimethylalanes (R1R2NAlMe2) as Useful Synthetic Precursors of Aminoalane Difluorides Using Trimethyltin Fluoride: Crystal Structures of (2,6-i-Pr2C6H3)N(SiMe3)AlMe2 and (2,6-i-Pr2C6H3)N(SiMe3)AlF2

Abstract

Aminodimethylalanes R1R2NAlMe2 (R1 = 2,6-i-Pr2C6H3, 2,6-Me2C6H3; R2 = SiMe3, Si(i-Pr)Me2, Si(t-Bu)Me2, Si(2,4,6-Me3C6H2)Me2) are prepared in high yield via reaction of the respective amine R1R2NH with trimethylaluminum in n-hexane. Further reaction of (2,6-i-Pr2C6H3)N(SiMe3)AlMe2 with 2 equiv of trimethyltin fluoride in toluene affords the aminoalane difluoride (2,6-i-Pr2C6H3)N(SiMe3)AlF2. An X-ray structural determination of (2,6-i-Pr2C6H3)N(SiMe3)AlMe2 shows it to be dimeric with bridging methyl and terminal amino groups. The aminoalane difluoride (2,6-i-Pr2C6H3)N(SiMe3)AlF2 is trimeric with a six-membered alternating aluminum−fluorine ring. Terminal fluorine atoms are located above and below the ring. Reactions of aminoalanes R1R2NAlMe2 with 2 equiv of trimethyltin fluoride in THF yield the monomeric THF adducts R1R2NAlF2·THF.