mer, fac, and Bidentate Coordination of an Alkyl-POP Ligand in the Chemistry of Nonclassical Osmium Hydrides

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• 作者：Miguel A. EsteruelasCristina García-Yebra ; Jaime MartínEnrique Oñate
• 刊名：Inorganic Chemistry
• 出版年：2017
• 出版时间：January 3, 2017
• 年：2017
• 卷：56
• 期：1
• 页码：676-683
• 全文大小：494K
• ISSN：1520-510X

文摘

Nonclassical and classical osmium polyhydrides containing the diphosphine 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>), coordinated in κ<sup>3sup>-mer, κ<sup>3sup>-fac, and κ<sup>2sup>-P,P fashions, have been isolated during the cyclic formation of H<sub>2sub> by means of the sequential addition of H<sup>+sup> and H<sup>–sup> or H<sup>–sup> and H<sup>+sup> to the classical trihydride OsH<sub>3sub>Cl{xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>} (1). This complex adds H<sup>+sup> to form the compressed dihydride dihydrogen complex [OsCl(H···H)(η<sup>2sup>-H<sub>2sub>){xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>}]<sup>+sup> (2). Under argon, cation 2 loses H<sub>2sub> and the resulting unsaturated fragment dimerizes to give [(Os(H···H){xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>})<sub>2sub>(μ-Cl)<sub>2sub>]<sup>2+sup> (3). During the transformation the phosphine changes its coordination mode from mer to fac. The benzofuran counterpart of 1, OsH<sub>3sub>Cl{dbf(P<sup>isup>Pr<sub>2sub>)<sub>2sub>} (4; dbf(P<sup>isup>Pr<sub>2sub>)<sub>2sub> = 4,6-bis(diisopropylphosphino)dibenzofuran), also adds H<sup>+sup> to afford the benzofuran counterpart of 2, [OsCl(H···H)(η<sup>2sup>-H<sub>2sub>){xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>}]<sup>+sup> (5), which in contrast to the latter is stable and does not dimerize. Acetonitrile breaks the chloride bridge of 3 to form the dihydrogen [OsCl(η<sup>2sup>-H<sub>2sub>)(CH<sub>3sub>CN){xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>}]<sup>+sup> (6), regenerating the mer coordination of the diphosphine. The hydride ion also breaks the chloride bridge of 3. The addition of KH to 3 leads to 1, closing a cycle for the formation of H<sub>2sub>. Complex 1 reacts with a second hydride ion to give OsH<sub>4sub>{xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>} (7) as consequence of the displacement of the chloride. Similarly to the latter, the oxygen atom of the mer-coordinated diphosphine of 7 has a tendency to be displaced by the hydride ion. Thus, the addition of KH to 7 yields [OsH<sub>5sub>{xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>}]<sup>−sup> (8), containing a κ<sup>2sup>-P,P-diphosphine. Complex 8 is easily protonated to afford OsH<sub>6sub>{xant(P<sup>isup>Pr<sub>2sub>)<sub>2sub>} (9), which releases H<sub>2sub> to regenerate 7, closing a second cycle for the formation of molecular hydrogen.