J. Lilie et al., STUDY OF THE REACTIONS OF PALLADIUM(II) MACROCYCLIC TETRAAMINE COMPLEXES WITH HYDROXYL AND METHYL RADICALS, Inorganica Chimica Acta, 246(1-2), 1996, pp. 59-64
The technique of pulse radiolysis has been used to study in aqueous me
dia the reactions of hydroxyl radical with 1,4,8,11-tetraazacyclotetra
decanepalladium(II) [Pd(cyclam)](2+) and hyl-1,4,8,11-tetraazacyclotet
radecanepalladium(II) [Pd(tmc)](2+) and of methyl radical with the for
mer complex. While methyl radical appears to be unreactive on short-ti
me scales, hydroxyl radical reacts rapidly with the palladium(II) comp
lexes to form transitory products absorbing in the near UV-visible reg
ion. The second-order rate constants for the OH-reactions are (5.0 +/-
0.7) x 10(9) M(-1) s(-1) for [Pd(cyclam)](2+) and (2.8 +/- 0.7) x 10(
9) M(-1) s(-1) for [Pd(tmc)](2+). The intermediates are reactive towar
ds dioxygen with rate constants of (1.3 +/- 0.4) x 10(8) M(-1) s(-1) f
or the cyclam case and of (2.4 +/- 0.8) x 10(7) M(-1) s(-1) for the tm
c-system. This high reactivity towards O-2 along with other features i
ndicates that the reaction-mode of hydroxyl radical with the palladium
(II) complexes involves predominately ligand-attack.