title: Aluminum complexes derived from a hexadentate salen-type Schiff base: synthesis, structure, and catalysis for cyclic carbonate synthesis.
abstract: Different aluminum complexes were synthesized by the reaction of aluminum alkyls with a hexadentate salen-type Schiff base. The reaction of N,N'-bis(3,5-di-tert-butylsalicylidene)-2,2'-(ethylenedioxy)dianiline (LH2) with one equiv. of AlMe3in toluene at 100 °C proceeded by methane elimination to produce the intermediate methyl complex [AlMeL] (1), and then subsequent intramolecular methyl migration to give the aluminum complex [AlL'] (2) [L' = (2-O-3,5-tBu2C6H2)CH[double bond, length as m-dash]NC6H4OCH2CH2OC6H4NCH(Me)(2'-O-3',5'-tBu2C6H2)]. The reaction of the same ligand with AlEt3under the same experimental conditions involved ethane elimination, ethylene elimination and intramolecular hydrogen migration, and led to the complex [AlL''] (3) [L'' = (2-O-3,5-tBu2C6H2)CH[double bond, length as m-dash]NC6H4OCH2CH2OC6H4NCH2(2'-O-3',5'-tBu2C6H2)]. However, the interaction of two equivalents of AlMe3and AlEt3afforded the corresponding binuclear complexes [(AlMe2)2L] (4) and [(AlEt2)2L] (5), respectively, and no methyl or hydrogen migration was found. The solid-state structures of aluminum complexes 1-3 were determined by single-crystal X-ray diffraction. It was found that complexes 2-5 show a very effective catalytic activity for the cycloaddition of epoxides and CO2in the presence of NBu4Br as a cocatalyst at atmospheric pressure.
authors.affiliation: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Dushu Lake Campus, Soochow University, Suzhou 215123, People's Republic of China. yrwang@suda.edu.cn yaoym@suda.edu.cn.
authors.forename: Ya
authors.initials: Y
authors.lastname: Xu
authors.forename: Dan
authors.initials: D
authors.lastname: Yuan
authors.forename: Yaorong
authors.initials: Y
authors.lastname: Wang
authors.forename: Yingming
authors.initials: Y
authors.lastname: Yao