Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl) (PMe 3) 3

Khalimon, A.Y.; Shirobokov, O.G.; Peterson, E.; Simionescu, R.; Kuzmina, L.G.; Howard, J.A.; Nikonov, G.I.

Авторы: Khalimon A.Y., Shirobokov O.G., Peterson E., Simionescu R., Kuzmina L.G., Howard J.A.K, Nikonov G.I.
Журнал: Inorganic Chemistry
Том: 51
Номер: 7
Год издания: 2012
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 4300
Последняя страница: 4313
DOI: 10.1021/ic300010c
Аннотация: The reaction of (ArN=)MoCl 2(PMe 3) 3 (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe 3) 3 (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH 3; however, a slow H/D exchange and formation of (ArN=)Mo(D)(Cl)(PMe 3) 3 (2 D) was observed upon addition of PhSiD 3. Reactivity of 2 toward organic substrates was studied. Stoichiometric reactions of 2 with benzaldehyde and cyclohexanone start with dissociation of the trans-to-hydride PMe 3 ligand followed by coordination and insertion of carbonyls into the Mo-H bond to form alkoxy derivatives (ArN=)Mo(Cl)(OR)(PMe 2)L 2 (3: R = OCH 2Ph, L 2 = 2 PMe 3; 5: R = OCH 2Ph, L 2 = ν 2-PhC(O)H; 6: R = OCy, L 2 = 2 PMe 3). The latter species reacts with PhSiH 3 to furnish the corresponding silyl ethers and to recover the hydride 2. An analogous mechanism was suggested for the dehydrogenative ethanolysis with PhSiH 3, with the key intermediate being the ethoxy complex (ArN=)Mo(Cl)(OEt)(PMe 3) 3 (7). In the case of hydrosilylation of acetophenone, a D-labeling experiment, i.e., a reaction of 2 with acetophenone and PhSiD 3 in the 1:1:1 ratio, suggests an alternative mechanism that does not involve the intermediacy of an alkoxy complex. In this particular case, the reaction presumably proceeds via Lewis acid catalysis. Similar to the case of benzaldehyde, treatment of 2 with styrene gives trans-(ArN=)Mo(H) (ν 2-CH 2=CHPh)(PMe 3) 2 (8). Complex 8 slowly decomposes via the release of ethylbenzene, indicating only a slow insertion of styrene ligand into the Mo-H bond of 8. © 2012 American Chemical Society.
Добавил в систему: Халимон Андрей Юрьевич

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Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl) (PMe 3) 3статья Исследовательская статья