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 wi th pyrazole in the presence of KOH to afford the six-coordinate hydrido-vin ylidene OsH(pz)(=C=CHPh)(Hpz)((PPr3)-Pr-i)(2) (2). The structure of 2 in th e solid state has been determined by an X-ray diffraction study. The geomet ry around the metal center could be described as a distorted octahedron wit h the two phosphorus atoms of the phosphines occupying apical positions. Th e equatorial plane is defined by the hydride, the vinylidene, the pyrazole, and the pyrazolato ligands. The N-H hydrogen atom of the pyrazole lies bet ween this azole group and the pyrazolate, forming an intramolecular N ... H ... N hydrogen bond. Reaction of 2 with HBF4 leads to the fluoro-carbyne d erivative [OsHF(=CCH2Ph)(Hpz)((PPr3)-Pr-i)(2)]BF4 (3), whose structure has been determined by an X-ray diffraction study. The geometry around the meta l center could be also described as a distorted octahedron with the two pho sphorus atoms of the phosphines occupying apical positions. The equatorial plane is defined by the hydride, the carbyne, the pyrazole group, and the f luoride ligand. The X-ray structure analysis of 3 shows that the N-H hydrog en 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(=C CH2Ph)(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 a re involved in hydrogen bonding.