title: mer, fac, and Bidentate Coordination of an Alkyl-POP Ligand in the Chemistry of Nonclassical Osmium Hydrides.
abstract: Nonclassical and classical osmium polyhydrides containing the diphosphine 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(PiPr2)2), coordinated in κ3-mer, κ3-fac, and κ2-P,P fashions, have been isolated during the cyclic formation of H2by means of the sequential addition of H+and H-or H-and H+to the classical trihydride OsH3Cl{xant(PiPr2)2} (1). This complex adds H+to form the compressed dihydride dihydrogen complex [OsCl(H···H)(η2-H2){xant(PiPr2)2}]+(2). Under argon, cation 2 loses H2and the resulting unsaturated fragment dimerizes to give [(Os(H···H){xant(PiPr2)2})2(μ-Cl)2]2+(3). During the transformation the phosphine changes its coordination mode from mer to fac. The benzofuran counterpart of 1, OsH3Cl{dbf(PiPr2)2} (4; dbf(PiPr2)2= 4,6-bis(diisopropylphosphino)dibenzofuran), also adds H+to afford the benzofuran counterpart of 2, [OsCl(H···H)(η2-H2){xant(PiPr2)2}]+(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(η2-H2)(CH3CN){xant(PiPr2)2}]+(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 H2. Complex 1 reacts with a second hydride ion to give OsH4{xant(PiPr2)2} (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 [OsH5{xant(PiPr2)2}]-(8), containing a κ2-P,P-diphosphine. Complex 8 is easily protonated to afford OsH6{xant(PiPr2)2} (9), which releases H2to regenerate 7, closing a second cycle for the formation of molecular hydrogen.
authors.affiliation: Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza-CSIC , 50009 Zaragoza, Spain.
authors.forename: Miguel A
authors.identifier: http://orcid.org/0000-0002-4829-7590
authors.initials: MA
authors.lastname: Esteruelas
authors.affiliation: Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza-CSIC , 50009 Zaragoza, Spain.
authors.forename: Cristina
authors.identifier: http://orcid.org/0000-0002-5545-5112
authors.initials: C
authors.lastname: García-Yebra
authors.affiliation: Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza-CSIC , 50009 Zaragoza, Spain.
authors.forename: Jaime
authors.identifier: http://orcid.org/0000-0003-0909-3509
authors.initials: J
authors.lastname: Martín
authors.affiliation: Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza-CSIC , 50009 Zaragoza, Spain.
authors.forename: Enrique
authors.identifier: http://orcid.org/0000-0003-2094-719X
authors.initials: E
authors.lastname: Oñate