Ruthenium pentacarbonyl

Ruthenium pentacarbonyl is the ruthenium compound with the formula Ru₅. It is a colorless, light-sensitive liquid that readily decarbonylates upon standing at room temperature. It is of academic interest as an intermediate for the synthesis of metal carbonyl complexes.

Preparation

Ru₅ was originally prepared by carbonylation of ruthenium salts in the presence of a reducing agent. A more recent preparation involves photolysis of triruthenium dodecacarbonyl in the presence of carbon monoxide:
It is characterized by two intense ν_CO bands in the IR spectrum at 2038 and 2003 cm⁻¹.

Comparisons of M(CO)₅ (M = Fe, Ru, Os)

Whereas Fe₅ is completely robust at room temperature, samples of Ru₅ are typically reddish owing to contamination by Ru₃₁₂. The conversion is rapid in solution. Os(CO)₅ requires heating to 80 °C to effect conversion to triosmium dodecacarbonyl.