The selective conversion of variously substituted epoxides into the corresponding cyclic carbonates (COCs) under mild reaction conditions was achieved with mononuclear Fe(III) complexes bearing bis-thioether-di-phenolate [OSSO]-type ligands, in combination with tetrabutylammonium bromide (TBAB). For example, propylene carbonate was obtained in 6 h at 35 °C with a conversion of 65% (TOF = 108 h-1), from propylene oxide and 1 bar of CO2 pressure, using 0.1 mol% of the Fe(III) complex and 0.5 mol% of TBAB. Product divergence is observed only for cyclohexene oxide toward the exclusive formation of the aliphatic polycarbonate (APC) (TOF = 165 h-1 at 80 °C and 1 bar of CO2 pressure, using 0.1 mol% of the Fe(III) complex and 0.1 mol% of TBAC). Kinetic investigations indicated reaction orders of two and one, with respect to the Fe(III) complex, for the production of propylene carbonate and the poly(cyclohexene carbonate), respectively. The enthalpy and entropy of activation were determined using the Eyring equation (for propylene carbonate: ΔH‡ = 8.4 ± 0.7 kcal/mol and ΔS‡ = -33 ± 3 cal/(mol · K); for poly(cyclohexene carbonate): ΔH‡ = 11.9 ± 0.3 kal/mol and ΔS‡ = -36 ± 2.2 cal/(mol · K)). Supported by density functional theory based investigations, we propose a mechanistic scenario in which the rate limiting step is the bimetallic ring opening of the epoxide, in the case of propylene carbonate, and the monometallic insertion of the epoxide in the growing polymer chain, in the case of poly(cyclohexene carbonate).

[OSSO]-Type Iron(III) Complexes for the Low-Pressure Reaction of Carbon Dioxide with Epoxides: Catalytic Activity, Reaction Kinetics and Computational Study

Della Monica, Francesco;Buonerba, Antonio;De Nisi, Assunta;Grassi, Alfonso;Cavallo, Luigi
;
Capacchione, Carmine
2018

Abstract

The selective conversion of variously substituted epoxides into the corresponding cyclic carbonates (COCs) under mild reaction conditions was achieved with mononuclear Fe(III) complexes bearing bis-thioether-di-phenolate [OSSO]-type ligands, in combination with tetrabutylammonium bromide (TBAB). For example, propylene carbonate was obtained in 6 h at 35 °C with a conversion of 65% (TOF = 108 h-1), from propylene oxide and 1 bar of CO2 pressure, using 0.1 mol% of the Fe(III) complex and 0.5 mol% of TBAB. Product divergence is observed only for cyclohexene oxide toward the exclusive formation of the aliphatic polycarbonate (APC) (TOF = 165 h-1 at 80 °C and 1 bar of CO2 pressure, using 0.1 mol% of the Fe(III) complex and 0.1 mol% of TBAC). Kinetic investigations indicated reaction orders of two and one, with respect to the Fe(III) complex, for the production of propylene carbonate and the poly(cyclohexene carbonate), respectively. The enthalpy and entropy of activation were determined using the Eyring equation (for propylene carbonate: ΔH‡ = 8.4 ± 0.7 kcal/mol and ΔS‡ = -33 ± 3 cal/(mol · K); for poly(cyclohexene carbonate): ΔH‡ = 11.9 ± 0.3 kal/mol and ΔS‡ = -36 ± 2.2 cal/(mol · K)). Supported by density functional theory based investigations, we propose a mechanistic scenario in which the rate limiting step is the bimetallic ring opening of the epoxide, in the case of propylene carbonate, and the monometallic insertion of the epoxide in the growing polymer chain, in the case of poly(cyclohexene carbonate).
File in questo prodotto:
File Dimensione Formato  
ACSCat2018_watermark.pdf

accesso aperto

Descrizione: Articolo principale
Tipologia: Documento in Pre-print (manoscritto inviato all'editore, precedente alla peer review)
Licenza: DRM non definito
Dimensione 2 MB
Formato Adobe PDF
2 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/4714219
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 76
  • ???jsp.display-item.citation.isi??? 69
social impact