Synthesis and Reactivity of the Unusual Five-Coordinate Hydrido−Hydroxo Complex OsH(OH)(CO)(PiPr3)2

Abstract

The five-coordinate complex OsHCl(CO)(PiPr3)2 (1) reacts with KOH in methanol to give the hydroxo derivative OsH(OH)(CO)(PiPr3)2 (2). Treatment of 2 with 1 equiv of dimethyl acetylenedicarboxylate which is the result of the trans addition of the OH bond of 2 to the carbon−carbon triple bond of the alkyne. The structure of 3 was determined by an X-ray investigation. The geometry of the complex can be rationalized as a distorted octahedron with the two phosphorus atoms of the triisopropylphosphine ligands occupying apical positions. The equatorial plane is formed by the hydride, the carbonyl group, and the κ2-O-donor ligand, which has a bite angle of 84.17(7)°. Complex 2 also reacts with methyl acrylate, methyl vinyl ketone, and allyl alcohol. Reaction with methyl acrylate leads to OsH(OH)(CO)(η2-CH2CHCO2CH3)(PiPr3)2 (4). The structure of 4 was also determined by an X-ray investigation. The coordination geometry around the osmium atom can be rationalized as derived from a highly distorted octahedron with th...