Temperature dependence of carbon isotope effects in CO/CO complex exchange reactions

Abstract

The fractionation of carbon isotopes was investigated for two CO exchange systems; the CO/Cu^I–CO complex system in mixed NH₂CH₂CH₂OH + CH₃OH solvent, and the CO/Ag^I–CO complex system in FSO₃H + H₂SO₄ acid solvent, in the temperature range 226–351 K under a pressure of 9.5 × 10⁴ Pa. The Cu^I–CO complex system exhibits larger isotope separation coefficients ε (=α − 1) than those of the Ag^I–CO complex system. The experimentally observed εs for all systems were fitted by the equation ε = a/T² − b/T. In the low-temperature region below 233 K, sudden increases in ε for the CO/Ag^I–CO complex system were observed. These increases are thought to be due to the formation of a Ag^I(CO)₂ complex.