Reactivity and Derivatization of Five-Coordinate, Chelated Aluminum

The convenient five-coordinate starting materials, Salen(tBu)AlCl (Salen(tBu) = N,N‘-alkylene (or arylene) bis
(3,5-di-tert-butyl-2-hydroxybenzylideneamine) (1−4) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN3
(L = Salen(tBu) (5), Salpen(tBu) (6), and Salomphen(tBu) (7)) through trimethylsilylhalide elimination. The
decomposition of the azides produce first hydroxide (LAlOH (L = Salen(tBu) (8)) and, subsequently in the presence
of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe3 (L = Salen(tBu) (9), Salpen(tBu) (10), and
Salomphen(tBu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced
by the formation of Salomphen(tBu)AlOSiPh3 (12). Additionally, the first structurally characterized five-coordinate
monomeric amide, Salcen(tBu)AlN(SiMe3)2 (13), can prepared by a salt elimination utilizing Salcen(tBu)AlCl
(4). The compounds were characterized by spectroscopic methods (1H and 27Al NMR, MS, and IR) and, in the
case of 2 (Salpen(tBu)AlCl), 3 (Salomphen(tBu)AlCl) 9, 11, 12, and 13, by X-ray analysis. Several of the compounds
were explored as potential catalysts for the living polymerization of propylene oxide.