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

摘要

Complex OsH_3Cl(P~iPr_3)2 (1) reacts with KTp (Tp = hydridotris(pyrazolyl)borate) in tetrahydrofuran at room temperature to give OsH_3(kappa~2-Tp)(P~iPr_3)_2 (2). In toluene at 80 °C, the kappa~2-Tp complex 2 is transformed to the kappa~3-Tp derivative OsH_3Tp(P~iPr_3) (3) in quantitative yield after 7 h. Protonation of 3 with HBF_4 affords the bis(dihydrogen) compound [OsTp(eta~2-H_2)_2(P~iPr_3)]BF_4 (4). In acetone complex 4 releases the coordinated hydrogen molecules in a sequential manner. At room temperature, the dihydrogen-solvate complex [OsTp(eta~2-H_2)(kappa~1-OCMe_2)(P~iPr_3)]BF_4 (5) is formed, while at 56 °C the loss of both hydrogen molecules gives rise to the bis-solvento derivative [OsTp(kappa~1-OCMe_2)_2(P~iPr_3)]BF_4 (6). Complexes 2-6 have been characterized by X-ray diffraction analysis, and DFT calculations support their formulation. The structures of 3-5 have been compared with thdse of their Cp counterparts OsH_3Cp(P~iPr_3), [OsH_2-Cp(eta~2-H_2)(P~iPr_3)]BF_4, and [OsH_2Cp(kappa~1-OCMe_2)(P~iPr_3)]BF_4. 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.