The Co + CO Reaction: Infrared Matrix Isolation Study and Density Functional Calculations

The Co + CO reaction argon has been reinvestigated using deposition of ground-state reagents in solid argon. The Co + CO reaction products observed without activation energy are Co 2 CO, a van der Waals Co···CO complex, and the higher carbonyl species Co(CO) x . Infrared radiation at approximately 3000 cm -1, to promote Co into the first excited-state b 4 F (3d 8 4s 1 configuration), converts the van der Waals complex to the chemically bound, most stable carbonyl form CoCO. A second irradiation with an approximately 580 nm wavelength (17000 cm -1 ) reconverts the chemically bound CoCO ( 2 Δ) state into the Co···CO van der Waals ( 4 Φ) state. The photoprocess is fully reversible. Isotopic data on ν 1, ν 2, ν 3, 2ν 1, ν 1 + ν 2, and ν 1 + ν 3 have been measured in the near- and far-infrared regions for the carbonyl form. This enables a complete harmonic force-field calculation based on a linear geometry, in agreement with all theoretical predictions. DFT calculations of the geometrical and electronic properties of CoCO complexes from the Co + CO reaction are also presented and compared to the experimental values. Reaction mechanisms are proposed and comparisons with bond force constants of NiCO and CuCO are also presented.