A stand-alone cobalt bis(dicarbollide) photoredox catalyst epoxidates alkenes in water at extremely low catalyst load
dc.contributor.author
dc.date.accessioned
2021-11-30T14:43:33Z
dc.date.available
2021-11-30T14:43:33Z
dc.date.issued
2021-11-12
dc.identifier.issn
1463-9262
dc.identifier.uri
dc.description.abstract
The cobalt bis(dicarbollide) complex, Na[3,3′-Co(η5-1,2-C2B9H11) (Na[1]), is an effective photoredox catalyst for the oxidation of alkenes to epoxides in water. Advantageous features of Na[1] include its lack of photoluminescence, high solubility and surfactant behavior in aqueous media, as well as the donor ability of the carborane ligand and high oxidizing power of the Co4+/3+ couple. These features differentiate it from the well-known and widely used photosensitizer tris (2,2′-bipyridine) ruthenium(II) ([Ru(bpy)3]2+), which also participates in electron transfer through an outer sphere mechanism. A comparison of the catalytic performance of [Ru(bpy)3]2+ with Na[1] for alkene photo-oxidation is fully in favor of Na[1], as the former shows very low or null efficiency. With a catalyst loading of 0.1 mol% conversions between 65–97% have been obtained in short reaction times, 15 minutes, with moderate selectivity for the corresponding epoxide, due to the formation of side products as diols. But when the catalyst loading is reduced to 0.01 mol%, the selectivity for the corresponding epoxide increased considerably, being the only compound formed after 15 minutes of reaction (selectivity >99%). High TON values have been obtained (TON = 8500) for the epoxidation of aromatic and aliphatic alkenes in water. We have verified that Na[3,3′-Co(η5-1,2-C2B9H11)2] acts as a photocatalyst in both the epoxidation of alkenes and in their hydroxylation in aqueous medium with a higher rate for epoxidation than for hydroxylation. Preliminary photooxidation tests using methyl oleate as the substrate led to the selective epoxidation of the double bond. These results represent a promising starting point for the development of practical methods for the processing of unsaturated fatty acids, such as the valorisation of animal fat waste using this sustainable photoredox catalyst
dc.description.sponsorship
This research has been financed by MINECO (PID2019-106832RB-I00 and CTQ2015-66143-P) and Generalitat de Catalunya (2017 SGR 1720). “Severo Ochoa” Program for Centers of Excellence in R&D 234 (SEV-2015-0496) is appreciated. Dedicated to Prof. M.F. Hawthorne that passed away on July 8, 2021 for his great vision and development of boron hydrides, particularly boron clusters and metallacarboranes and their applications, especially in catalysis
dc.format.mimetype
application/pdf
dc.language.iso
eng
dc.publisher
Royal Society of Chemistry (RSC)
dc.relation
CTQ2015-66143-P
dc.relation.isformatof
Versió postprint del document publicat a: https://doi.org/10.1039/D1GC03119H
dc.relation.ispartof
© Green Chemistry, 2021, Advance Article
dc.relation.ispartofseries
Articles publicats (D-Q)
dc.rights
Tots els drets reservats
dc.subject
dc.title
A stand-alone cobalt bis(dicarbollide) photoredox catalyst epoxidates alkenes in water at extremely low catalyst load
dc.type
info:eu-repo/semantics/article
dc.rights.accessRights
info:eu-repo/semantics/openAccess
dc.date.embargoEndDate
info:eu-repo/date/embargoEnd/2022-11-12
dc.relation.projectID
info:eu-repo/grantAgreement/MINECO//CTQ2015-66143-P/ES/COMPLEJOS FUNCIONALES PARA PROCESOS CATALITICOS SOSTENIBLES Y RESPETUOSOS CON EL MEDIO AMBIENTE/
dc.type.version
info:eu-repo/semantics/acceptedVersion
dc.identifier.doi
dc.identifier.idgrec
034042
dc.contributor.funder
dc.type.peerreviewed
peer-reviewed
dc.relation.FundingProgramme
dc.relation.ProjectAcronym
dc.identifier.eissn
1463-9270