P-Stereogenic ligands with the tert-butylmethylphosphine fragment. Coordination chemistry and catalysis of their organometallic complexes
[eng] The Thesis deals with the preparation, coordination chemistry and use in asymmetric homogeneous catalysis of several optically pure P-stereogenic ligands containing a tert-butylmethylphosphino fragment. In the first part a highly stereoselective synthesis of the Secondary Phosphine Oxide (SPO)...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/131193 |
| Acceso en línea: | https://hdl.handle.net/2445/131193 http://hdl.handle.net/10803/666577 |
| Access Level: | acceso abierto |
| Palabra clave: | Síntesi orgànica Compostos de coordinació Catàlisi asimètrica Complexos metàl·lics Fosfina Organic synthesis Coordination compounds Enantioselective catalysis Metal complexes Phosphine |
| Sumario: | [eng] The Thesis deals with the preparation, coordination chemistry and use in asymmetric homogeneous catalysis of several optically pure P-stereogenic ligands containing a tert-butylmethylphosphino fragment. In the first part a highly stereoselective synthesis of the Secondary Phosphine Oxide (SPO) tert-butylmethylphosphine oxide is presented. Despite its simplicity, the stereoselective synthesis of this SPO had not been described in the literature. It is known that SPOs present a tautomeric equilibrium between the air-stable pentavalent form (phosphine oxide) and the trivalent form (phosphinous acid), usually completely shifted towards the pentavalent form but that can be displaced towards the phosphinous acid form by metal complexation. In the Thesis the complexation of the mentioned oxide towards Ru, Rh, Ir, Ni, Pd and Au has been explored, yielding a variety of coordination and organometallic compounds, with several coordination modes of the ligand. Some asymmetric catalytic applications of these species have also been studied, giving good conversions but low enantioselectivities. In the second part of the Thesis, the C1-symmetric P-stereogenic ligand MaxPhos has been coordinated to [MCp*Cl] (M = Rh and Ir) and [Ru(p-cymene)Cl] fragments, yielding cationic M-stereogenic organometallic compounds as tetrafluoroborate or hexafluorophosphate salts. Interestingly, in all cases a single stereoisomer has been formed, as confirmed by NMR and X-ray crystallography. This has been rationalised by steric grounds. For Ir, the abstraction of the remaining chloride ligand by silver salts produced a diastereoselective C–H activation of a tert-butyl group of the ligand. The complexes have been used in transfer hydrogenation giving good activities but no enantioselectivities. Finally the third part of the Thesis is devoted to the cyclometallation of [Ir(MaxPHOX)COD]BArF complexes (MaxPHOX stands for a type of P,N phosphinooxazoline ligand recently described by our group having three stereogenic centres) by several ligands under hydrogen atmosphere. It has been found that cyclometallated Ir(III)-hydrido complexes are formed, which are very stable and have been characterised thoroughly. They have been used in asymmetric hydrogenation of N-alkylimines, giving in general complete conversions and very high enantioselectivities (up to 96% ee) for these substrates, which rank among the best described to date. The mechanism of the reaction has been studied and the stereochemical outcome rationalised by means of DFT-based computational methods. |
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