Reactions of OsHCl(CO)(PiPr3)2 with Alkyn-1-ols: Synthesis of (Vinylcarbene)osmium(II) Complexes

The monohydride complex OsHCl(CO)(PiPr3)2 (1) reacts with 2-propyn-1-ol to give the vinyl compound Os(CH=CHCH2OH)Cl(CO)(PiPr3)2 (2a). The reaction of 1 with 1-phenyl-2-propyn-1-ol leads to a mixture of products, from which the complexes OsCl2(=CHCH=CHPh)(CO)(PiPr3)2 (3a) and Os(CHCHC(O)Ph)Cl(CO)(PiPr3)2 (4a) were separated. The molecular structures of complexes 3a and 4a were determined by X-ray crystallography. Crystals of 3a are monoclinic, space group P21/c, with unit cell dimensions a = 15.671(3) Å, b = 12.507(2) Å, c = 16.632(3) Å, and β = 108.95(1°). The structure was refined to the R and Rw values 0.0202 and 0.0239 on 5080 observed data. The coordination around the osmium atom can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying trans positions; the perpendicular plane is defined by the vinylcarbene and a carbonyl ligand, mutually cis disposed, and by two chloride atoms. Crystals of 4a are orthorhombic, space group P212121, with a = 8.797(1) Å, b = 15.268(2) Å and c = 22.275(3) Å. The structure was refined to the R and Rw values 0.0198 and 0.0223 on 5532 reflections. The osmium coordination environment can also be rationalized as a distorted octahedron with the two phosphine ligands disposed mutually irons. The remaining coordination sites of the octahedron are occupied by the carbonyl ligand, the chloride atom, and the chelate CHCHC(O)Ph ligand. The reaction of 1 with 1,1-diphenyl-2-propyn-1-ol also leads to a mixture of products, from which the complex OsCl2(=CHCH=CPh2)(CO)(PiPr3)2 (3b) was isolated and characterized.