Intermetallic Cooperation in C−H Activation Involving Transient Titanium-Alkylidene Species: A Synthetic and Mechanistic Study
RRemote carbon-hydrogen activation on titanium dinuclear complexes [{Ti(eta(5)-C5Me5)R-2}(2)(mu-O)] [R = CH2SiMe3 2, CH2CMe3 3, and CH2Ph 5) have been examined both synthetically and theoretically. While the thermal treatment of the oxoderivative [{Ti(eta(5)-C5Me5)(CH2SiMe3)(2)}(2)(mu-O)] (2) led to...
| Autores: | , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2017 |
| País: | España |
| Institución: | Universidad de Alcalá (UAH) |
| Repositorio: | e_Buah Biblioteca Digital Universidad de Alcalá |
| Idioma: | inglés |
| OAI Identifier: | oai:ebuah.uah.es:10017/63041 |
| Acceso en línea: | http://hdl.handle.net/10017/63041 https://dx.doi.org/10.1021/acs.organomet.7b00416 |
| Access Level: | acceso abierto |
| Palabra clave: | Química Chemistry |
| Sumario: | RRemote carbon-hydrogen activation on titanium dinuclear complexes [{Ti(eta(5)-C5Me5)R-2}(2)(mu-O)] [R = CH2SiMe3 2, CH2CMe3 3, and CH2Ph 5) have been examined both synthetically and theoretically. While the thermal treatment of the oxoderivative [{Ti(eta(5)-C5Me5)(CH2SiMe3)(2)}(2)(mu-O)] (2) led to a series of metallacycle complexes (2a-c) by sequential carbon-hydrogen activation processes, [{Ti(eta(5)-C5Me5)(CH2CMe3)(2)}(2)(mu-O)] (3) gave rise to the formation of the metallacycle tuck-over species [Ti-2(eta(5)-C5Me5)(mu-eta(5)-C5Me4CH2-kappa C)(CH2CMe3)(mu-CH2CMe2CH2)(mu-O)] (4), as result of hydrogen abstraction from a eta(5)-C5Me5 ligand. However, the thermolysis of the tetrabenzyl complex [{Ti(eta(5)-C5Me5)(CH2Ph)(2)}(2)(mu-O)] (5) yielded the derivative [Ti-2(eta(5)-C5Me5)(mu-eta(5)-C5Me4CH2-kappa C)(CH2Ph)(3)(mu-O)] (6) that only exhibits tuck-over eta(5)-C5Me5 metalation. DFT calculations show that the mechanism involves a first alpha-hydrogen abstraction to generate a transient titanium alkylidene, which enables it to activate beta- and gamma-C(sp(3))-H bonds on the adjacent titanium center. The calculations also establish a reactivity order for the different type of gamma-H abstractions, trimethylsilyl > neopentyl congruent to benzyl, allowing us to explain the observed selectivity. |
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