A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium.
A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η(2)-H3B·NMe3)][BAr(F)4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; Ar(F) = 3,5-(CF3)2C6H3) is reported. The processes...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
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Royal Society of Chemistry
2014
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| _version_ | 1797086124080889856 |
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| author | Algarra, A Sewell, L Johnson, H Macgregor, SA Weller, A |
| author_facet | Algarra, A Sewell, L Johnson, H Macgregor, SA Weller, A |
| author_sort | Algarra, A |
| collection | OXFORD |
| description | A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η(2)-H3B·NMe3)][BAr(F)4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; Ar(F) = 3,5-(CF3)2C6H3) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D2 leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D2/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy3)2(H)2(η(2)-H3B·NMe3)][BAr(F)4]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H2 exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. |
| first_indexed | 2024-03-07T02:17:34Z |
| format | Journal article |
| id | oxford-uuid:a2ca4a3c-590e-4456-a487-6246c59cc4c5 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T02:17:34Z |
| publishDate | 2014 |
| publisher | Royal Society of Chemistry |
| record_format | dspace |
| spelling | oxford-uuid:a2ca4a3c-590e-4456-a487-6246c59cc4c52022-03-27T02:22:23ZA combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:a2ca4a3c-590e-4456-a487-6246c59cc4c5EnglishSymplectic Elements at OxfordRoyal Society of Chemistry2014Algarra, ASewell, LJohnson, HMacgregor, SAWeller, AA combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η(2)-H3B·NMe3)][BAr(F)4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; Ar(F) = 3,5-(CF3)2C6H3) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D2 leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D2/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy3)2(H)2(η(2)-H3B·NMe3)][BAr(F)4]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H2 exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. |
| spellingShingle | Algarra, A Sewell, L Johnson, H Macgregor, SA Weller, A A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title | A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title_full | A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title_fullStr | A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title_full_unstemmed | A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title_short | A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium. |
| title_sort | combined experimental and computational study of fluxional processes in sigma amine borane complexes of rhodium and iridium |
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