Manganese coordination chemistry of bis(imino)phenoxide derived [2 + 2] Schiff-base macrocyclic ligands

Yang, Wenxue; Zhao, Ke‐Qing; Wang, Bi‐Qin; Redshaw, Carl; Elsegood, Mark R. J.; Zhao, Jiang‐Lin; Yamato, Takehiko

doi:10.1039/c5dt03453a

Cited by 16 publications

(15 citation statements)

References 30 publications

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“…Very recently, Yang et al . synthesized manganese complexes of bis(imino)phenoxide derived macrocyclic ligands for the ROP of ϵ ‐CL . Unfortunately, only poor activity with low conversion was observed.…”

Section: Introductionsupporting

confidence: 55%

Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

et al. 2016

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Chlorides of group 4 metals containing the bis(imino)phenoxide ligand scaffold were synthesized from a direct reaction between the respective ligand and metal chlorides MCl 4 (M = Ti, Zr and Hf). These complexes were thoroughly characterized using various spectroscopic methods and single crystal X-ray diffraction studies. They are potent catalysts for the polymerization of rac-lactide (rac-LA), L-lactide (L-LA), e-caprolactone (e-CL), epoxides such as, rac-cyclohexene oxide (rac-CHO), racpropylene oxide (rac-PO), rac-styrene oxide (rac-SO) and ethylene, resulting in polymers with high number average molecular weights (M n ) and narrow molecular weight distributions (MWDs). The kinetic and mechanistic studies associated with the polymerization of lactide, e-CL and CHO has been investigated in details.[a] Prof.

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Section: Introductionsupporting

confidence: 55%

Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

et al. 2016

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“…In the last decades, Mn‐based catalysts including carbonyl complex, halogenated compounds, alkene and cumulenylidene complexes were mainly used for radical polymerization of monomers like MMA, styrene, acrylonitrile, and olefins ,. Only a few reports depicted the application of Mn complexes in the lactones ROP process ,,,,. Mn II salts, like Mn halides and sulfates, acted as Lewis acids catalyzing the bulk polymerization of LA through the activated monomer mechanism were firstly reported ,.…”

Section: Introductionmentioning

confidence: 99%

Salen‐Manganese Complexes and their Application in the Ring‐Opening Polymerization of Lactide and ϵ‐Caprolactone

Zhang

Duan

et al. 2019

Asian J Org Chem

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Efficiency and sustainability are of vital concern to the polymer industry. Ring-opening polymerizations (ROP) of lactide (LA) and ɛ-caprolactone (ɛ-CL) producing biodegradable polymers polylactide (PLA) and polycaprolactone (PCL) were widely researched. Owing to their abundance and nontoxicity, manganese catalysts are a very good choice. A group of salen manganese (III) complexes were synthesized. Their catalytic activity in the ROP of LA and ɛ-CL in propylene oxide (PO) was. Under activation of PO, manganese complexes could efficiently mediate the ROP of LA and ɛ-CL. The molecular weight distributions could be controlled well. The influence of the bridging part and substitutions were fully discussed. Surprisingly, chlorine substituents showed a negative effect on catalytic activity. The analog computation results indicated that the metal center of 7 a did not become more electron-deficient. By switching the ligand backbone and substituents, the configuration of polylactide (PLA) turned from slight isotactic to slight heterotactic. a series of Salen-Mn chloride complexes (Scheme 1). [21a,b] PO as both solvent and in situ activator was introduced to enhance the ROP efficiency. The catalytic performance of the Salen-Mn complexes in LA and ɛ-CL polymerization was studied in this work. Results and DiscussionX-ray Studies of Complexes. X-ray diffraction of the single crystals (complexes 4 a and 5 a) were presented in Figure 1. According to the crystal analysis, both of complexes 4 a and 5 a belonged to the five-coordinated metal structure category. Complexes of this structure have two possible geometric configurations: trigonal bipyramidal (tbp) or square pyramidal 2 3 4 5 6 7 8

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“…Under a variety of conditions, use of the compounds 23 and 24 (Scheme 5) for the ROP of ε-caprolactone failed to afford any polymer product [14]. …”

Section: Manganese Complexesmentioning

confidence: 99%

“…As part of a programme aimed at exploring the use of earth abundant metal catalysts for ROP, [23][24][25] the manganese complexes 9 and 10 (Scheme 3) were screened for their ability to ROP ε-caprolactone in the presence of benzyl alcohol [14]. Results were compared against the acyclic salt compounds 11 and 12.…”

Section: Manganese Complexesmentioning

confidence: 99%

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Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

Redshaw

2017

Catalysts

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Schiff base macrocycles are emerging as useful scaffolds for binding two or more catalytic metals in close proximity. Such coordination chemistry allows for the evaluation of potentially beneficial catalytic cooperative effects. In the field of ring opening polymerization (ROP) of cyclic esters, only a handful of metal systems bound by Schiff base [2 + 2] type macrocycles have been studied. Nevertheless, results to date have, for certain metals, identified some interesting structure activity relationships, whilst for other systems results have revealed particular combinations of metals and macrocycles to be virtually inactive. This perspective review takes a look at two types of recently-reported Schiff base macrocycles that have been employed as pro-ligands in the metal-catalyzed ROP of cyclic esters, specifically ε-caprolactone and rac-lactide.

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Manganese coordination chemistry of bis(imino)phenoxide derived [2 + 2] Schiff-base macrocyclic ligands

Cited by 16 publications

References 30 publications

Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies

Salen‐Manganese Complexes and their Application in the Ring‐Opening Polymerization of Lactide and ϵ‐Caprolactone

Use of Metal Catalysts Bearing Schiff Base Macrocycles for the Ring Opening Polymerization (ROP) of Cyclic Esters

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