Kinetics and mechanism of the photolytic CO-substitutions of cyclopentadienyl(dicarbonyl)iron thiocarboxylate complexes, Cp′Fe(CO)2SCOR (Cp′ = C5H5, ButC5H4,1,3-Bu2tC5H3; R = alkyl, aryl)

Abstract

The kinetics of the photolytic CO-substitution of Cp′Fe(CO)2SCOR [Cp′ = C5H5, Bu t C5H4, 1,3-Bu2 t C5H3; R = Me, Bu t , Ph, 2-(O2N)C6H4, 3-(O2N)C6H4, 4-(O2N)C6H4, 3,5-(O2N)2C6H3] with PPh3 were studied in CH2Cl2 at 0 °C by i.r. spectroscopy. The reactions yielded exclusively the mono-CO-substituted derivatives, Cp′Fe-(CO)(PPh3) SCOR, and were found to follow second order kinetics with first order dependence on the concentration of each reactant. The differences in rates are discussed in terms of current knowledge pertaining to such reactions. An associative mechanism is proposed to account for the kinetic data of the reactions described.