Abstract
The kinetics of oxidation of [Fe
II
(phen)
2
(H
2
O)
2
]
2+
(phen = 1,10-phenanthroline) by periodate were investigated in aqueous acidic medium at different [H
+
] over a temperature range of 20–40 °C. The reaction was studied under pseudo-first-order conditions by taking [IO
4
−
] > tenfold over [Fe
II
(phen)
2
(H
2
O)
2
2+
]. The reaction rate increases with increasing [H
+
], and the kinetics of oxidation obeyed the following rate law:
Rate
=
Fe
II
(
phen
)
2
(
H
2
O
)
2
2
+
IO
4
-
k
4
K
2
+
k
5
K
1
K
3
[
H
+
]
The surfactant sodium dodecyl sulfate was found to enhance the rate, whereas cetyltrimethylammonium bromide had little effect. Activation parameters associated with
k
2
and
k
3
were calculated. An electron transfer from Fe(II) to I(VII) is identified as the rate-determining step. The I(VI) species thus generated reacts in a fast step with another Fe(II) complex.