Carbonylchlorohydrotris(triphenylphosphine)osmium is a coordination complex with the formula . It contains four different ligands: hydride, carbon monoxide, chloride, and triphenylphosphine. As confirmed by X-ray crystallography, the complex has with meridional geometry (three phosphine ligands are coplanar) and the CO and Cl are mutually trans.
Properties It forms white crystalline prisms. It is insoluble in water, alcohols, and non-aromatic hydrocarbons, but moderately soluble in benzene, chloroform, dichloromethane, and acetone. When heated to its melting point in air, it reacts with oxygen and decomposes. In a sealed container of nitrogen it melts at 290°C with decomposition. The infrared spectrum shows a strong band at 2099 cm−1.
Synthesis It is prepared by heating ammonium hexachloroosmate(IV) with triphenylphosphine in boiling 2-(2-methoxyethoxy)ethanol. As described by the following equation, the high boiling alcohol serves as a source of CO:
A similar but milder method (refluxing 2-methoxyethanol) employs formalin as a source of carbon monoxide. Again this complicated reaction is described by an idealized equation:
It can also be prepared by reducing with formaldehyde.
Reactions It reacts with N-methyl-N-nitrosotoluene sulfonamide to yield the nitrosyl complex , which in turn can react with oxygen and triphenylphosphine to produce .
When treated with sodium hydroxide in a boiling solution of 2-methoxyethanol, it converts to the dihydride :
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