Halogenated β‐diketiminato magnesium complexes: Preparation, characterization, and catalysis for ring‐opening polymerization of aliphatic lactones. (17th February 2022)

• Record Type: Journal Article
• Authors: Mou, Zehuai; Xing, Fangyu; Gu, Jialu
• Is Part Of: Bulletin of the Korean Chemical Society. Volume 43:Number 5(2022)
• Page Start: 697
• Page End: 703
• Publication Date: 2022-02-17
• Subjects: halogenated β‐diketiminate -- lactones -- magnesium complex -- ring‐opening polymerization; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/bkcs.12510
• Languages: English
• ISSNs: 0253-2964

Abstract

Abstract: The halogenated β ‐diketiminato magnesium butyl complexes L X MgBu(THF) (X = Cl (1 ), Br (2 )) and allyl complexes L X Mg(allyl)(THF) (X = Cl (3 ), Br (4 )) (L Cl = ((2, 6‐Cl2 C6 H3 )N═C(Me)CH═C(Me)N(2, 6‐Cl2 C6 H3 )), L Br = ((2, 6‐Br2 C6 H3 )N═C(Me)CH═C(Me)N(2, 6‐Br2 C6 H3 )) were prepared and characterized. The treatment of butyl complex 2 with (S)‐1‐phenylethanol gave the corresponding alkoxide complex [L Br MgOCHMePh]2 (5 ), the dimeric structure of which was confirmed by single‐crystal x‐ray diffraction. When bulky diphenylmethanol was employed to react with Complex 2, THF‐ligated monomeric complex L Br MgOCHPh2 (THF) (6 ) was afforded. The catalytic performances of these magnesium complexes for ring‐opening polymerization of ε ‐caprolactone ( ε ‐CL), δ ‐valerolactone ( δ ‐VL), and γ ‐butyrolactone ( γ ‐BL) were evaluated. Abstract : β ‐Diketiminato ligands bearing alkyl groups (Me, Et, and i Pr) on the N ‐aryl moieties have been widely investigated in the organometallic chemistry and the ring‐opening polymerization (ROP) of cyclic esters, while halogenated β ‐diketiminate ligands have been far less unexplored. In this contribution, a series of halogenated β ‐diketiminato magnesium complexes with various initiating groups have been synthesized and characterized, among them a dimeric alkoxide complex was confirmed with single‐crystal x‐ray diffraction. These complexes could efficiently initiate the ROP of ε ‐CL and δ ‐VL at ambient temperature, where the alkoxide complexes (MgO bond) exert better control than the hydrocarbyl complexes (MgC bond). Moreover, these complexes could catalyze the ROP of nonstrained γ ‐BL at −40 °C.