Ak. Ghosh et al., KINETICS AND MECHANISM OF ANATION OF HYDROXOPENTAAQUARHODIUM(III) IONBY DL-METHIONINE, Indian journal of chemistry. Sect. A: Inorganic, physical, theoretical & analytical, 35(4), 1996, pp. 342-345
The kinetics of anation of [Rh(OH2)(5)(OH)](2+) by DL-methionine has b
een studied spectrophotometrically by monitoring the characteristic ab
sorption peak of the product complex (lambda(max) = 262 nm) as a funct
ion of substrate and ligand concentrations in the 50-65 degrees C temp
erature range and in the pH range 2.5-4.3. The rate law involving the
outersphere complex formation has been established at pH 4.3 as d[Rh(O
H2)(2)(OH)(L)(+)]/dt = k(a)K(E)[Rh(OH2)(5)(OH)(2+)](T)[LH]/1 + K-E[LH]
The activation parameters have been calculated and compared with thos
e for water exchange reaction and other substitution reactions. A mech
anism involving the prior formation of an outersphere complex followed
by associative interchange (I-a) is suggested where both bond making
and bond breaking are equally important in the transition state.