Pressure as the key parameter to distinguish between associative charge-transfer and dissociative ligand-field photochemistry. CO substitution in W(CO)4(1,10-phenanthroline)

Abstract

The pressure dependence of the quantum yield for photosubstitution of CO in W(CO)₄(1,10-phenanthroline) was studied at different excitation wavelengths: volumes of activation of –12 cm³ mol^–1 for the reaction following irradiation into the charge-transfer band and +8 cm³ mol^–1 for the reaction following short wavelenght excitation are clear evidence for an associative reaction of the charge-transfer excited state and a dissociative reaction of the energetically higher ligand-field excited state, respectively.