Slattery, John Martin orcid.org/0000-0001-6491-8302, Leeb, Nina Maria, Drover, Marcus et al. (2 more authors) (2018) Phosphoramidate-assisted alkyne activation: Probing the mechanism of proton shuttling in a N,O-chelated Cp*Ir(III) complex. Organometallics. ISSN 0276-7333
Abstract
Ligand lability offers a unique opportunity for access to metal-ligand cooperativity (MLC), helping to direct new organometallic and catalytic reactions. In recent years, ligand-assisted C-H bond activation, and more generally, proton migration, have been of particular interest. This contribution describes a detailed computational study into the mechanism, regio-, and stereoselectivity observed in a recently reported transformation where MLC in a 16-electron iridium(III) phosphoramidate complex plays a critical role in directing the activation of terminal alkynes toward the generation of novel five-membered (E)-vinyloxyirida(III)cycles. Five possible pathways for the formation of such products were investigated. Based on our findings, it is proposed that the reaction proceeds via a ligand-assisted proton shuttle (LAPS) mechanism, where the phosphoramidate phosphoryl (P=O) group assists in both alkyne C-H bond activation and C-H bond formation to form a vinylidene intermediate. Next, C-O bond formation occurs via nucleophilic attack at the -carbon of the vinylidene giving the observed product. Although C-N (and not C-O) bond formation is thermodynamically favored in this model system, this trend is not observed experimentally and the computational study suggests that the observed regioisomer is simply the kinetic reaction product. In terms of stereoselectivity, formation of the (E)-irida(III)cycle is explained by its thermodynamic stability, when compared to the (Z)-isomer, and the relatively low barrier to interconversion between them.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details. |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) |
Depositing User: | Pure (York) |
Date Deposited: | 16 Nov 2018 12:00 |
Last Modified: | 04 Jan 2025 00:15 |
Published Version: | https://doi.org/10.1021/acs.organomet.8b00656 |
Status: | Published online |
Refereed: | Yes |
Identification Number: | 10.1021/acs.organomet.8b00656 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:138748 |
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