Inquiry into the Formation of Cyclic Carbonates during the (Salen)CrX Catalyzed CO<sub>2</sub>/Cyclohexene Oxide Copolymerization Process in the Presence of Ionic Initiators

Darensbourg, Donald J.; Bottarelli, Paolo; Andreatta, Jeremy R.

doi:10.1021/ma071206o

Cited by 88 publications

(61 citation statements)

References 22 publications

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“…[21][22][23][24][25]27] Therefore, to investigate whether mononuclear complexes could catalyse the synthesis of cyclic carbonates under much milder conditions than previously reported, and to provide a benchmark against which to judge subsequent work, mononuclear metalA C H T U N G T R E N N U N G (salen) complexes 1-5 were prepared following literature procedures. [23b, 31] Although the chirality associated with the salen ligand in complexes 1-5 was superfluous for this project, the cyclohexanediamine unit and the tert-butyl groups on the aromatic rings were retained to enhance the solubility of the salen complexes.…”

Section: Resultsmentioning

confidence: 99%

“…[28] Previous work from our group [29] has demonstrated that bimetallic salen complexes display much higher catalytic activity in the asymmetric synthesis of cyanohydrins than their monometallic counterparts, as the two metal ions can each activate one of the two components of the reaction. Polycarbonate and cyclic carbonate synthesis catalysed by chromiumA C H T U N G T R E N N U N G (salen) complexes are known to be bimolecular; [25] therefore, we reasoned that a suitable bimetallic salen complex might display significantly improved catalytic activity in the reaction between carbon dioxide and epoxides. In this paper we give full details of our work in this area, [30] which was aimed at developing a catalyst, which would be sufficiently active to allow the synthesis of cyclic carbonates from waste carbon dioxide without requiring energy input.…”

Section: Introductionmentioning

confidence: 99%

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Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

Clegg¹,

Harrington²,

North³

et al. 2010

Chemistry A European J

367

174

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The development of bimetallic aluminium-salen complexes [{Al(salen)}(2)O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

Clegg¹,

Harrington²,

North³

et al. 2010

Chemistry A European J

367

174

View full text Add to dashboard Cite

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“…[5][6][7] Furthermore, the formation of cis-CHC is unusual: the trans-isomer is more commonly formed, usually by back-biting reactions under thermodynamic control (Scheme 3). 7,25 However, the low pressure and moderate temperature used here are insufficient to yield significant competing copolymerisation. Increasing the pressure of CO 2 to 10 atm, keeping all other conditions the same, led to an increase in production of PCHC (with 99% carbonate linkages), with low amounts of the trans-CHC also being observed (entry 9).…”

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confidence: 98%

“…A copolymerisation mechanism is proposed (Scheme 3) where the Fe-Cl bond(s) initiate the ring-opening of CHO to generate an Fe-OR species, which undergo CO 2 insertion to 25 produce an iron-carbonate intermediate. Propagation and copolymerisation occurs by sequential repetition of the ringopening and insertion reactions.…”

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confidence: 99%

A bimetallic iron(iii) catalyst for CO₂/epoxide coupling

et al. 2011

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“…The presence of electron-donating or electron-withdrawing groups on the backbone of the metal-salen complex can be used to favor the preferred formation of the cyclic or polycarbonate product [43][44][45][46].…”

Section: Introductionmentioning

confidence: 99%

Metal Complexes Catalyzed Cyclization with CO2

Rintjema

Carrodeguas

Laserna

et al. 2015

Topics in Organometallic Chemistry

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This chapter describes in general terms the catalytic methodology that has been made available for the use of carbon dioxide (CO 2 ) in cyclization reactions that incorporate an intact CO 2 fragment without changing the formal oxidation state of the carbon center. The major focus of this chapter will be on the most successful organometallic/inorganic complexes that have been used as catalyst systems throughout the last decade and the preferred ligand frameworks leading to elevated reactivity and/or selectivity behavior in CO 2 coupling reactions. Attention will be especially given to homogeneous catalyst systems as they have proven to be more versatile in CO 2 conversion catalysis and often have modular characteristics that allow for optimization of structure-activity relationships. The most important reactions that have been studied in the current context are designated CO 2 "addition" reactions to small molecule heterocycles such as epoxides and aziridines, though more recently other coupling partners such as diamines, dialcohols, and amino nitriles have further advanced the use of CO 2 in organic synthesis providing access to a wider range of structures. This chapter will serve to demonstrate the utility of CO 2 as a carbon reagent in the catalytic formation of the most prominent organic structures using cyclization strategies specifically.

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Inquiry into the Formation of Cyclic Carbonates during the (Salen)CrX Catalyzed CO₂/Cyclohexene Oxide Copolymerization Process in the Presence of Ionic Initiators

Cited by 88 publications

References 22 publications

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

A bimetallic iron(iii) catalyst for CO₂/epoxide coupling

Metal Complexes Catalyzed Cyclization with CO2

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Inquiry into the Formation of Cyclic Carbonates during the (Salen)CrX Catalyzed CO2/Cyclohexene Oxide Copolymerization Process in the Presence of Ionic Initiators

Cited by 88 publications

References 22 publications

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

A bimetallic iron(iii) catalyst for CO2/epoxide coupling

Metal Complexes Catalyzed Cyclization with CO2

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Inquiry into the Formation of Cyclic Carbonates during the (Salen)CrX Catalyzed CO₂/Cyclohexene Oxide Copolymerization Process in the Presence of Ionic Initiators

A bimetallic iron(iii) catalyst for CO₂/epoxide coupling