Weller, Andrew orcid.org/0000-0003-1646-8081, Gyton, Matthew Robert orcid.org/0000-0002-7565-5154, Johnson, Chloe-Louise et al. (2 more authors) (2025) An Operationally Unsaturated Iridium-Pincer Complex That C-H Activates Methane and Ethane in the Crystalline Solid-State. Journal of the American Chemical Society. ISSN 1520-5126
Abstract
The known complex [Ir( t Bu-PONOP)MeH][BAr F 4], 1[BAr F 4 ] [ t Bu-PONOP = κ 3-2,6-( t Bu 2PO) 2C 5H 3N); Ar F = 3,5-(CF 3) 2(C 6H 3); J. Am. Chem. Soc. 2009, 131, 8603], is a robust precursor for in crystallo single-crystal to single-crystal (SC-SC) C-H activation of methane and ethane at 80 °C. This contrasts with the reported solution (CD 2Cl 2) behavior, where 1[BAr F 4 ] decomposes by methane loss. Crystalline 1[BAr F 4 ] is accessed as a single polymorph on a gram scale. A single-crystal neutron diffraction study locates the hydride. 13C{ 1H} SSNMR experiments on 1[BAr F 4 ], and its isotopologue [Ir( t Bu-PONOP)(CD 3)D][BAr F 4], d 4 -1[BAr F 4 ], suggest a rapid and reversible endergonic reductive bond formation is occurring in crystallo to access an Ir(I) σ-methane complex. Heating 1[BAr F 4 ] to 80 °C under high vacuum results in loss of methane and intramolecular C-H activation to form cyclometalated [Ir(cyclo- t Bu-PONOP')H][BAr F 4], 2[BAr F 4 ], in a SC-SC reaction. This is reversible, and the addition of CH 4 or CD 4 to 2[BAr F 4 ] at 80 °C results in an equilibrium with 1[BAr F 4 ] or d 4 -1[BAr F 4 ], respectively. Complex 2[BAr F 4 ] is thus an operationally unsaturated source of 14-electron [Ir( tBu-PONOP)][BAr F 4], III, that undergoes C-H activation with methane. Periodic DFT studies, alongside isotope labeling experiments, link 1[BAr F 4 ] and 2[BAr F 4 ]/CH 4 via a reductive elimination/oxidative addition pathway. Heating 2[BAr F 4 ] to 80 °C under N 2 forms [Ir( t Bu-PONOP)(κ 1-N 2)][BAr F 4], in a SC-SC transformation. Reaction with CO forms [Ir( t Bu-PONOP)(CO)][BAr F 4] at room temperature. Calculations suggest reaction with N 2 occurs via an associative process or competitively through III, while with CO only an associative process operates. Heating 2[BAr F 4 ] to 80 °C under an ethane atmosphere results in alkane dehydrogenation, via a SC-SC reaction, forming a ∼1:1 mixture of [Ir( t Bu-PONOP)(η 2-H 2C═CH 2)][BAr F 4], and [Ir( t Bu-PONOP)H 2][BAr F 4].
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2025 The Authors |
Dates: |
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Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Chemistry (York) |
Funding Information: | Funder Grant number EPSRC EP/W015552/1 |
Depositing User: | Pure (York) |
Date Deposited: | 06 Feb 2025 15:50 |
Last Modified: | 19 Mar 2025 00:13 |
Published Version: | https://doi.org/10.1021/jacs.4c18122 |
Status: | Published online |
Refereed: | Yes |
Identification Number: | 10.1021/jacs.4c18122 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:223001 |
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Description: An Operationally Unsaturated Iridium-Pincer Complex That C−HActivates Methane and Ethane in the Crystalline Solid-State
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