138583-13-8Relevant articles and documents
Kinetic study of the interaction of aquated palladium (II) complexes with purine 5′-nucleoside monophosphates and ribose 5′-monophosphate in aqueous solution. Effects of steric hindrance and phosphate-induced reactivity
Hohmann, Heribert,Hellquist, Bj?rn,Van Eldik, Rudi
, p. 1090 - 1095 (2008/10/08)
The complex formation reactions of a series of complexes of the type Pd(R4en)(H2O)22+ (R4en = N-substituted ethylenediamine, R = H, Me, Et) with ribose, adenosine, inosine, and guanosine 5′-monophosphate were investigated as a function of monophosphate concentration and temperature in the pH range 4-5. In all cases the complex formation with 5′-XMP (X = R, A, I, G) occurs in two consecutive steps for which the pseudo-first-order rate constants fit the equation kobs = ka + kb[XMP]. The experiments with ribose monophosphate revealed complex formation rate constants significantly smaller than those reported before for inosine, but larger than those found for adenosine. This trend is also observed for the nucleoside monophosphates for which the rate constants follow the sequence AMP a significant transition state stabilization effect by the monophosphate group during the complex formation reactions. The systematic variation of the substituents on the en ligand decreases the formation rate constant by as much as 3 orders of magnitude in going from the unsubstituted (R = H) to the most sterically hindered species (R = Et). The complex formation reactions all proceed according to an associative substitution mechanism and are accompanied by significantly negative ΔS? values. The results are discussed in reference to data available for the corresponding nucleosides and structural information on the final reaction products reported in the literature.
