Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions
<p>A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated.</p><p>The use of potentially hemilabile l...
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| Format: | Thesis |
| Language: | English |
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2011
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| _version_ | 1826295830310551552 |
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| author | Dallanegra, R |
| author2 | Weller, A |
| author_facet | Weller, A Dallanegra, R |
| author_sort | Dallanegra, R |
| collection | OXFORD |
| description | <p>A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated.</p><p>The use of potentially hemilabile ligands DPEphos and XANTphos in the intramolecular dehydrogenation chemistry of tricyclopentylphosphine is reported. The comparison in reactivity of these isolated diphosphine phosphine-alkene complexes towards hydrogenation and with acetonitrile is discussed along with their ability to dehydrocouple secondary silane, Ph₂SiH₂, and amine-borane H₃B·NMe₂H. The acceptorless dehydrogenation of a tethered cyclopentane with cationic Rh(I) diphosphine complexes has also been extended to include thioethers.</p><p>Isolated cationic Rh(I) phosphine-alkene complexes with labile fluorobenzene ligands are found to act as a source of the reactive 12-electron [Rh{PR₂(ƞ²-C₅H₇)}]+ (R = cyclopentyl (Cyp)/ iPr) fragment in solution and can coordinate two amine-borane ligands (either H₃B·NMe₃, H₃B·NMe₂H or H₃B·NMeH₂) in a novel and unique bis-σ-binding mode. The catalytic activity of some of these isolated complexes in the dehydrocoupling of H₃B·NMe₂H and H₃B·NMeH₂ has been determined. With a view to further understanding the mechanism of catalytic transition metal assisted amine-borane dehydrogenation and dehydrocoupling, known B-N intermediates H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ were also coordinated to the [Rh{PCyp₂(ƞ²-C₅H₇)}]+ fragment and investigated with regard to their role in the catalytic cycle.</p><p>Structure activity relationships determined from stoichiometric reactions of cationic Rh(I) diphosphine fluorobenzene complexes with amine-boranes enabled the design of a highly efficient homogeneous catalyst capable of dehydrogenating H₃B·NMe₂H to [H₂BNMe₂]₂ at 0.2 mol% loading in 30 minutes at 298 K. Rapid dehydrogenation and dehydrocoupling of H₃B·NMeH₂ to form high molecular weight poly(N-methylaminoborane) with a low PDI has also been achieved. Investigations using model aminoborane H₂B=NiPr₂ and intermediate B-N species H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ has helped establish an overall mechanistic rationale for this process.</p> |
| first_indexed | 2024-03-07T04:07:02Z |
| format | Thesis |
| id | oxford-uuid:c6841db3-aadf-428f-bd4e-a16e9eaa3511 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:07:02Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | oxford-uuid:c6841db3-aadf-428f-bd4e-a16e9eaa35112022-03-27T06:38:39ZCationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactionsThesishttp://purl.org/coar/resource_type/c_db06uuid:c6841db3-aadf-428f-bd4e-a16e9eaa3511CatalysisOrganometallic ChemistryInorganic chemistryEnglishOxford University Research Archive - Valet2011Dallanegra, RWeller, A<p>A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated.</p><p>The use of potentially hemilabile ligands DPEphos and XANTphos in the intramolecular dehydrogenation chemistry of tricyclopentylphosphine is reported. The comparison in reactivity of these isolated diphosphine phosphine-alkene complexes towards hydrogenation and with acetonitrile is discussed along with their ability to dehydrocouple secondary silane, Ph₂SiH₂, and amine-borane H₃B·NMe₂H. The acceptorless dehydrogenation of a tethered cyclopentane with cationic Rh(I) diphosphine complexes has also been extended to include thioethers.</p><p>Isolated cationic Rh(I) phosphine-alkene complexes with labile fluorobenzene ligands are found to act as a source of the reactive 12-electron [Rh{PR₂(ƞ²-C₅H₇)}]+ (R = cyclopentyl (Cyp)/ iPr) fragment in solution and can coordinate two amine-borane ligands (either H₃B·NMe₃, H₃B·NMe₂H or H₃B·NMeH₂) in a novel and unique bis-σ-binding mode. The catalytic activity of some of these isolated complexes in the dehydrocoupling of H₃B·NMe₂H and H₃B·NMeH₂ has been determined. With a view to further understanding the mechanism of catalytic transition metal assisted amine-borane dehydrogenation and dehydrocoupling, known B-N intermediates H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ were also coordinated to the [Rh{PCyp₂(ƞ²-C₅H₇)}]+ fragment and investigated with regard to their role in the catalytic cycle.</p><p>Structure activity relationships determined from stoichiometric reactions of cationic Rh(I) diphosphine fluorobenzene complexes with amine-boranes enabled the design of a highly efficient homogeneous catalyst capable of dehydrogenating H₃B·NMe₂H to [H₂BNMe₂]₂ at 0.2 mol% loading in 30 minutes at 298 K. Rapid dehydrogenation and dehydrocoupling of H₃B·NMeH₂ to form high molecular weight poly(N-methylaminoborane) with a low PDI has also been achieved. Investigations using model aminoborane H₂B=NiPr₂ and intermediate B-N species H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ has helped establish an overall mechanistic rationale for this process.</p> |
| spellingShingle | Catalysis Organometallic Chemistry Inorganic chemistry Dallanegra, R Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title | Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title_full | Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title_fullStr | Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title_full_unstemmed | Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title_short | Cationic rhodium complexes with chelating phosphine and phosphine alkene ligands. Application in dehydrogenation and dehydrocoupling reactions |
| title_sort | cationic rhodium complexes with chelating phosphine and phosphine alkene ligands application in dehydrogenation and dehydrocoupling reactions |
| topic | Catalysis Organometallic Chemistry Inorganic chemistry |
| work_keys_str_mv | AT dallanegrar cationicrhodiumcomplexeswithchelatingphosphineandphosphinealkeneligandsapplicationindehydrogenationanddehydrocouplingreactions |