Coordination and rupture of methyl C(sp3)-H bonds in osmium-polyhydride complexes with δ agostic interaction

Miguel Baya, Beatriz Eguillor, Miguel A. Esteruelas, Agustí Lledós, Montserrat Olivan, Enrique Oñate

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Abstract

The hexahydride complex OsH6(PiPr3) 2 (1) reacts with 8-methylquinoline and 2-(dimethylamino)pyridine to give OsH3(CH2C9H6N)(P iPr3)2 (2) and OsH3{CH 2(CH3)-o-C5H4N}(PiPr 3)2 (3), respectively, as a result of the release of two hydrogen molecules of 1 and the C(sp3)-H bond activation of a methyl group of the organic substrates. In solution the hydride ligands and the hydrogen atoms of the methylene group of 2 exchange their positions. The activation parameters for the process are ΔH‡ = 18.9 ± 0.1 kcal·mol-1 and ΔS‡ = 3 ± 2 eu. Treatment of 2 with HBF4 affords the hydride-elongated dihydrogen derivative [OsH(η2-H2)(CH 3C9H6N)(PiPr3) 2]BF4 (6), with the methyl group of the quinoline ligand coordinated in a η3-H2C fashion. The X-ray structure of 6 and the DFT optimization of the structure of the model cation [OsH(η2-H2)(CH4)(NH3)(PMe 3)2]+ prove that the methyl coordination in the δ agostic complex is similar to the methane coordination in the model compound. The reaction of 3 with HBF4 leads to the cyclic carbene derivative [OsH3{=CHN(CH3)-o-C5H 4N}(PiPr3)2]BF4 (7), as a result of the release of a hydrogen molecule and a C(sp3)-H bond activation on the methylene group of 3. The formation of 2, 3, 6, and 7 has been analyzed by DFT calculations. © 2007 American Chemical Society.
Original languageEnglish
Pages (from-to)5140-5152
JournalOrganometallics
Volume26
Issue number21
DOIs
Publication statusPublished - 8 Oct 2007

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