American Chemical Society
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Preparation, Spectroscopic Characterization, X-ray Structure, and Theoretical Investigation of Hydride−, Dihydrogen−, and Acetone−OsTp Complexes:  A Hydridotris(pyrazolyl)borate−Cyclopentadienyl Comparison

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journal contribution
posted on 2020-04-02, 15:50 authored by Ruth Castro-Rodrigo, Miguel A. Esteruelas, Ana M. López, Montserrat Oliván, Enrique Oñate
Complex OsH3Cl(PiPr3)2 (1) reacts with KTp (Tp = hydridotris(pyrazolyl)borate) in tetrahydrofuran at room temperature to give OsH32-Tp)(PiPr3)2 (2). In toluene at 80 °C, the κ2-Tp complex 2 is transformed to the κ3-Tp derivative OsH3Tp(PiPr3) (3) in quantitative yield after 7 h. Protonation of 3 with HBF4 affords the bis(dihydrogen) compound [OsTp(η2-H2)2(PiPr3)]BF4 (4). In acetone complex 4 releases the coordinated hydrogen molecules in a sequential manner. At room temperature, the dihydrogen-solvate complex [OsTp(η2-H2)(κ1-OCMe2)(PiPr3)]BF4 (5) is formed, while at 56 °C the loss of both hydrogen molecules gives rise to the bis-solvento derivative [OsTp(κ1-OCMe2)2(PiPr3)]BF4 (6). Complexes 26 have been characterized by X-ray diffraction analysis, and DFT calculations support their formulation. The structures of 35 have been compared with those of their Cp counterparts OsH3Cp(PiPr3), [OsH2Cp(η2-H2)(PiPr3)]BF4, and [OsH2Cp(κ1-OCMe2)(PiPr3)]BF4. The results show that the Tp ligand avoids piano stool geometries, while it enforces dispositions allowing N−Os−N angles close to 90° such as octahedron and pentagonal bipyramid.