Synthesis of hydrido-vinylidene and hydrido-carbyne osmium complexes containing pyrazole:: New examples of N-H-Y (Y = N, F, Cl) hydrogen bonds

The hydride - carbyne complex OsHCl2(=CCH2Ph)((PPr3)-Pr-i)(2) (1) reacts with pyrazole in the presence of KOH to afford the six-coordinate hydrido-vinylidene OsH(pz)(=C=CHPh)(Hpz)((PPr3)-Pr-i)(2) (2). The structure of 2 in the solid state has been determined by an X-ray diffraction study. The geometry around the metal center could be described as a distorted octahedron with the two phosphorus atoms of the phosphines occupying apical positions. The equatorial plane is defined by the hydride, the vinylidene, the pyrazole, and the pyrazolato ligands. The N-H hydrogen atom of the pyrazole lies between this azole group and the pyrazolate, forming an intramolecular N ... H ... N hydrogen bond. Reaction of 2 with HBF4 leads to the fluoro-carbyne derivative [OsHF(=CCH2Ph)(Hpz)((PPr3)-Pr-i)(2)]BF4 (3), whose structure has been determined by an X-ray diffraction study. The geometry around the metal center could be also described as a distorted octahedron with the two phosphorus atoms of the phosphines occupying apical positions. The equatorial plane is defined by the hydride, the carbyne, the pyrazole group, and the fluoride ligand. The X-ray structure analysis of 3 shows that the N-H hydrogen atom of the pyrazole and the fluoride ligand are involved in intra- and intermolecular F ... H-pz hydrogen bonding. Reaction of [OsHCl(=CCH2Ph)(Hpz)((PPr3)-Pr-i)(2)]BF4 (4) with pyrazole and acetonitrile leads to [OsHCl(=CCH2Ph)(Hpz)((PPr3)-Pr-i)(2)]BF4 (5) and [OsHCl(=CCH2Ph)(CH3CN)((PPr3)-Pr-i)(2)]BF4 (6), respectively. Similarly to the fluoro - carbyne complex, the N-H hydrogen atom of the pyrazole group and the chloro ligand of complex 5 are involved in hydrogen bonding.