High-pressure Raman study on the decomposition of crystalline Cr(CO)6

High-pressure Raman spectra (300-2200 cm−1) of crystalline Cr(CO)6 at room temperature for pressures up to 29.5 GPa have been recorded. A probable second-order phase transition is assigned at ∼4.1 GPa. Recorded Raman spectra started to vanish at 20.8 GPa and upon further increase in pressures resulted in complete vanishing at 29.5 GPa. The dν/dp values suggest the breakdown of Dewar-Chatt-Duncanson model for the first time in homoleptic mono carbonyls which has been discussed. Decomposition of Cr(CO)6 leads to the formation of polymeric CO with characteristic sp2 carbon and (OCO) units for the first time.

Recorded Raman spectrum of the decomposed crystalline Cr(CO)6 at ambient conditions in diamond anvil cell. Presence of δ(OCO) and ν(CC) vibrations is an evidence for the polymeric CO phase.