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Rotaxane synthesis exploiting the M(i)/M(iii) redox couple
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Emerson-King, Jack, Knighton, Richard C., Gyton, Matthew R. and Chaplin, Adrian B. (2017) Rotaxane synthesis exploiting the M(i)/M(iii) redox couple. Dalton Transactions, 46 (35). pp. 11645-11655. doi:10.1039/c7dt02648j
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Official URL: https://doi.org/10.1039/c7dt02648j
Abstract
In the context of advancing the use of metal-based building blocks for the construction of mechanically interlocked molecules, we herein describe the preparation of late transition metal containing [2]rotaxanes (1). Capture and subsequent retention of the interlocked assemblies are achieved by the formation of robust and bulky complexes of rhodium(iii) and iridium(iii) through hydrogenation of readily accessible rhodium(i) and iridium(i) complexes [M(COD)(PPh3)2][BAr(F)4] (M = Rh, 2a; Ir, 2b) and reaction with a bipyridyl terminated [2]pseudorotaxane (3·db24c8). This work was underpinned by detailed mechanistic studies examining the hydrogenation of 1 : 1 mixtures of 2 and bipy in CH2Cl2, which proceeds with disparate rates to afford [M(bipy)H2(PPh3)2][BAr(F)4] (M = Rh, 4a[BAr(F)4], t = 18 h @ 50 °C; Ir, 4b[BAr(F)4], t < 5 min @ RT) in CH2Cl2 (1 atm H2). These rates are reconciled by (a) the inherently slower reaction of 2a with H2 compared to that of the third row congener 2b, and (b) the competing and irreversible reaction of 2a with bipy, leading to a very slow hydrogenation pathway, involving rate-limiting substitution of COD by PPh3. On the basis of this information, operationally convenient and mild conditions (CH2Cl2, RT, 1 atm H2, t ≤ 2 h) were developed for the preparation of 1, involving in the case of rhodium-based 1a pre-hydrogenation of 2a to form [Rh(PPh3)2]2[BAr(F)4]2 (8) before reaction with 3·db24c8. In addition to comprehensive spectroscopic characterisation of 1, the structure of iridium-based 1b was elucidated in the solid-state using X-ray diffraction.
| Item Type: | Journal Article | ||||||
|---|---|---|---|---|---|---|---|
| Subjects: | Q Science > QD Chemistry | ||||||
| Divisions: | Faculty of Science > Chemistry | ||||||
| SWORD Depositor: | Library Publications Router | ||||||
| Library of Congress Subject Headings (LCSH): | Rotaxanes -- Synthesis, Transition metals | ||||||
| Journal or Publication Title: | Dalton Transactions | ||||||
| Publisher: | Royal Society of Chemistry | ||||||
| ISSN: | 1477-9226 | ||||||
| Official Date: | 24 August 2017 | ||||||
| Dates: |
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| Volume: | 46 | ||||||
| Number: | 35 | ||||||
| Page Range: | pp. 11645-11655 | ||||||
| DOI: | 10.1039/c7dt02648j | ||||||
| Status: | Peer Reviewed | ||||||
| Publication Status: | Published | ||||||
| Publisher Statement: | ** From PubMed via Jisc Publications Router. | ||||||
| Access rights to Published version: | Open Access | ||||||
| Funder: | Engineering and Physical Sciences Research Council (EPSRC), Leverhulme Trust (LT), European Research Council (ERC), Royal Society (Great Britain), Advantage West Midlands (AWM), European Regional Development Fund (ERDF), Horizon 2020 (European Commission) (H2020) | ||||||
| Grant number: | RPG-2012-718 (LT), Grant agreement no. 637313 (H2020) |
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