MECHANISM OF CATALYTIC CIS-TRANS ISOMERIZATION OF PLANAR DIACIDODIAMINOPALLADIUM(2) COMPLEXES

The kinetics of the second stage of the reactions of the complexes [Pd(S-S)X2] (S-S = C6H5 -S-CH2CH2-S-C6H5; X = N3, Br, I, CNS) with a variety of amines (am) have been studied in 1,2-dimethoxyethane at 25°. The results indicate that the process is the isomerization of the species [Pd(am)2X2] from the cis to the trans form, catalyzed by the presence of excess amine. The rate shows a first-order dependence on both the concentration of complex and free amine, and the rate-determining step is the displacement of one of the anionic ligands, X, followed by the fast reentering of X- into the intermediate complex, [Pd(am)3X]+. The effects on the kinetics of systematically changing the nature of X and am confirm this mechanism and also allow a discussion of the details of the mechanism. © 1969, American Chemical Society. All rights reserved.