Reactivity and Derivatization of Five-Coordinate, Chelated Aluminum

Abstract

The convenient five-coordinate starting materials, Salen((t)Bu)AlCl (Salen((t)Bu) = 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, LAlN(3) (L = Salen((t)Bu) (5), Salpen((t)Bu) (6), and Salomphen((t)Bu) (7)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen((t)Bu) (8)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe(3) (L = Salen((t)Bu) (9), Salpen((t)Bu) (10), and Salomphen((t)Bu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen((t)Bu)AlOSiPh(3) (12). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen((t)Bu)AlN(SiMe(3))(2) (13), can prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4). The compounds were characterized by spectroscopic methods ((1)H and (27)Al NMR, MS, and IR) and, in the case of 2 (Salpen((t)Bu)AlCl), 3 (Salomphen((t)Bu)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.

Synthesis and Reactivity of Rare Earth Metal Alkyl Complexes Stabilized by Anilido Phosphinimine and Amino Phosphine Ligands

“…The geometry of the central metal atom is five-coordinate trigonal-bipyramidal with a distortion value of t = 0.61. [17] The YÀN bond lengths, which range from 2.215(3) to 2.232 , are comparable to those in 2 and are reasonable for rare earth metal-nitrogen bonds. Coordination of the THF molecule increases the steric crowding of complex 5 a, so that the N2-Y1-N3 bond angle of 103.04(9)8 is much Catalytic activity towards polymerization of lactide: Biodegradable polymers have long been considered as an alternative to polyolefins, among which linear aliphatic polyesters are particularly attractive and widely used.…”

Five‐coordinated active species in the stereoselective polymerization of rac‐lactide using N,N′‐(2,2‐dimethyl‐1,3‐propylene) bis(3,5‐di‐tert‐butyl‐salicylideneimine) aluminum complexes

“…The s value of LAlOCH(CH 3 )COOCH 3 (0.86) is significantly higher than those of complexes LAlEt (0.76) and LAlO i Pr (0.78), 20,21 which indicates that the Al center adopts a more TBP geometry than those of LAlEt and LAlO i Pr. 24 The atoms N2 and O1 occupy the axial sites and form an angle of 172.52(14)8, the N1, O2, and O3 atoms occupy the equatorial plane that form angles 121.65(14)8 (O2À ÀAlÀ ÀO3), 121.15(13)8 (N1À ÀAlÀ ÀO2), and 116.31(14)8 (O3À ÀAlÀ ÀN1). These do not significantly differ from LAlO i Pr.…”

Five-coordinate organoaluminum acetylides and crystal structure of the hydrosylate, [Salophen(tBu)Al]2O

“…The 27 Al NMR shifts in the range 43-57 ppm unambiguously confirm the existence of five-coordinate aluminum atoms in these compounds. Depending on the nature of the connection between the two nitrogen atoms of the ligand (the ''backbone'' of the ligand) [18], the compounds are either square pyramidal (with aryl backbones) or trigonal bipyramidal (with alkylene backbones). The acetylides 5-8 can be prepared in high yields by combining 1-4 with LiCBCPh in THF at )78°C (Scheme 1).…”

“…Like Salen aluminum amides [9] and azides [18], 5-8 are very moisture sensitive. In the presence of trace amounts of water, acetylides 5-8 hydrolyze to form aluminum hydroxides (e.g., Salophen( t Bu)AlOH (Scheme 2)).…”