Dinuclear Ce(IV) Aryloxides: Highly Active Catalysts for Anhydride/Epoxide Ring-Opening Copolymerization

Gray, Steven J; Brown, Karen; Lam, Francis Y. T.; Garden, Jennifer A.; Arnold, Polly L.

doi:10.1021/acs.organomet.1c00055

Cited by 11 publications

(11 citation statements)

References 75 publications

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“…36 Structurally authenticated Ce(IV) complexes bearing monovalent aryloxy ligands are rare, featuring homoleptic 50 The Ce(IV)Cl(OC 6 H 3 iPr 2 -2,6) moiety was recently reported in the dinuclear anionic complex [NEt 4 ] 2 [(TP)Ce 2 Cl 4 (OAr) 2 (THF) 2 ] supported by the TP tetraphenolato ligand. 51 The Ce−Cl distance of 2.638(5) Å in compound 6 appears to be slightly shorter than those in tris(cyclopentadienyl) complexes like Cp 3 CeCl [2.6666( 7) Å] and Cp Me 3 CeCl [2.658(1) Å]. 52,53 The remaining chlorido ligand may be useful for further salt-metathesis attempts, which will be investigated in future work.…”

Section: ■ Introductionmentioning

confidence: 98%

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry

Hirneise

Maichle‐Mößmer

2021

Inorg. Chem.

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Treatment of Cp*2CeCl2K(THF) with alkali-metal alkoxides and siloxides in the presence of hexachloroethane generates the monomeric bis(pentamethylcyclopentadienyl) cerium(IV) complexes Cp*2Ce(OR)2 (Cp* = C5Me5; R = Et, iPr, CH2 tBu, tBu, SiMe3, or SiPh3). Large substituents R trigger ligand scrambling to half-sandwich complexes Cp*Ce(OR)3, which could be isolated for R = tBu and SiPh3. Similar reactions with sodium aryloxide NaOAr (OAr = OC6H3 iPr2-2,6) led to Cp*2Ce(OAr)Cl. Treatment of tris(cyclopentadienyl) complexes CpR 3CeCl (CpH = Cp = C5H5; CpMe = C5H4Me) with NaOAr afforded CpMe 2Ce(OAr)2 and Cp3Ce(OAr). The cerium(IV) complexes display a pseudotetrahedral geometry in the solid state. Cyclic voltammetry revealed mostly chemically reversible as well as electrochemically quasi-reversible redox processes with potentials ranging from −0.84 to −1.61 V versus Fc/Fc+. Switching from sandwich to half-sandwich complexes decreased the electrochemical potentials drastically, showing better stabilization of the cerium(IV) center in the case of Cp*Ce(OR)3 than in the case of Cp*2Ce(OR)2. Enhanced stabilization of the cerium +IV oxidation state could be further demonstrated in the series alkoxy > siloxy > aryloxy as well as C5Me5 > C5HMe4.

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Section: ■ Introductionmentioning

confidence: 98%

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry

Hirneise

Maichle‐Mößmer

2021

Inorg. Chem.

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“…The simple, modular synthesis of the tetraphenol proligand has enabled us to make an analogue with a much longer terphenyl spacer between the two bis(phenol) groups . Reactions carried out in arene solvent, yield a range of unidentifiable products, but the base-free U(IV) complex [U( o - ter TP)] ( 2U ) may be formed cleanly from the reaction of UN″ 2 (N(SiMe 3 )SiMe 2 CH 2 ) with H 4 ( o - ter TP) in heptane (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…The modular synthesis of the tetraphenol proligands has enabled us to probe the importance of M–M cooperativity in the ring-opening copolymerization (ROCOP) for polyester formation catalyzed by new dinuclear Ce(IV) complexes, by varying the arene spacer between the pairs of phenolates that bind the two metal cations (Figure c) …”

Section: Introductionmentioning

confidence: 99%

A Combined Experimental and Theoretical Investigation of Arene-Supported Actinide and Ytterbium Tetraphenolate Complexes

et al. 2022

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Modular tetraphenolate ligands tethered with a protective arene platform (para-phenyl or para-terphenyl) are used to support mononuclear An(IV) (An = Th, U) complexes with an exceptionally large and open axial coordination site at the metal. The base-free complexes and a series of neutral donor adducts were synthesized and characterized by spectroscopies and single-crystal Xray diffraction. Anionic Th(IV) -ate complexes with an additional axial aryloxide ligand were also synthesized and characterized. The para-phenyl-tethered mononuclear complexes exhibit rare An(IV)−arene interactions, and the An(IV)−arene distance broadly increases with axial donor strength. The para-terphenyl-tethered complexes have almost no interaction with the arene base, isolating the central metal cation. Computational analysis of the mononuclear complexes and their reduced analogues, and Yb(III) congeners, as well as the effect of additional donor ligand binding, seek to elucidate the electronic structure of the metal−arene interactions and establish whether they, or their reduced or oxidized counterparts, could function as molecular qubits.

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“…Organometallics are one kind of potential catalytic system for ROCOP, because their catalytic performance can be easily modulated by tuning the Lewis acidity of the metal center and modifying the electronic or steric effects of ligand backbone. − The pioneering work in UPES synthesis via ROCOP was carried out by Coates and co-workers, who reported ROCOP of MAH with trans -( R )-limonene oxide mediated by a (β-diiminate)ZnOAc complex . Their seminal work inspired the development of additional metal-based complexes for the synthesis of UPES via ROCOP of MAH/epoxide, in spite of the relatively low catalytic activity and undesired polyether linkages.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Unsaturated (Co)polyesters from Ring-Opening Copolymerization by Aluminum Bipyridine Bisphenolate Complexes with Improved Protonic Impurities Tolerance

et al. 2022

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Synthesis of unsaturated polyesters (UPES) via ring-opening copolymerization (ROCOP) of maleic anhydride (MAH) and epoxides still remains a great challenge, because the reported catalytic systems generally showed low catalytic activity or complete deactivation at low catalyst concentration and exhibit poor tolerance to protonic impurities. In this work, we synthesized a series of bipyridine bisphenolate aluminum (BpyBph-Al) complexes and used these complexes to catalyze the MAH/ epoxide copolymerization for synthesis of UPES. UPES with perfectly alternating structure could be synthesized using BpyBph-Al complexes without onium salt as cocatalyst, and the catalytic activities seem to be dependent on the steric and electronic effects of the ligands as well as the leaving ability of the axial group. The catalytic activities were further increased in the binary catalysts consisting of a BpyBph-Al as Lewis acid and an onium salt as a Lewis base. Compared with salen-Al/onium salt and typical Lewis pairs, the BpyBph-Al/onium salt binary system exhibited a completely maintained catalytic activity even when the [epoxide]/ [MAH]/[catalyst pair] feed ratio was high up to 25 000:5000:1 ([catalyst pair] = 0.004 mol %). In addition, BpyBph-Al/onium salt exhibited better tolerance to protonic impurity than salen-Al/onium salt and Lewis pairs. The catalytic activity was slightly decreased (about 15%) in the presence of 100 equiv (relative to catalyst) of external-added maleic acid, while a substantial decrease in activity or complete deactivation was observed in the ROCOPs catalyzed by salen-Al/onium salt and Lewis pairs. These features of BpyBph-Al/onium salt further allowed UPES synthesis by using commercial MAH without any purification as a comonomer. The maleic acid residuals in the commercial MAH could serve as a chain transfer agent (CTA), and UPES polyols with uniform −OH chain ends were obtained via reversible-deactivation chain transfer reaction. Chain extension could be initiated by the active alkoxide end when adding the second cyclic anhydride after the full conversion of MAH, finally producing ABA-type triblock copolymers.

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Dinuclear Ce(IV) Aryloxides: Highly Active Catalysts for Anhydride/Epoxide Ring-Opening Copolymerization

Cited by 11 publications

References 75 publications

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry

A Combined Experimental and Theoretical Investigation of Arene-Supported Actinide and Ytterbium Tetraphenolate Complexes

Synthesis of Unsaturated (Co)polyesters from Ring-Opening Copolymerization by Aluminum Bipyridine Bisphenolate Complexes with Improved Protonic Impurities Tolerance

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