Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)

Article abstract of DOI:10.1002/poc.721

The oxidation reactions of 2-methyl-2,4-pentanediol upon treatment with alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalysts are governed by two quasi-identical experimental rate equations, which show that both catalysts are equally effective for the oxidation of alcohols by Fe(CN)₆^3-. The reaction mechanism proposed involves the oxidation of 2-methyl-2,4-pentanediol by the catalyst, a process that occurs through the formation of a substrate-catalyst complex. The decomposition of this complex yields Ru(IV) and a protonated ketone (owing to a hydride transfer from the α-C - H bond of the alcohol to the oxoligand of ruthenium) in the case of Ru(VI), but a ketyl radical and Ru(II) (hydrogen transfer) for Ru(III). The role of the co-oxidant, Fe(CN)₆^3-, is to regenerate the catalyst. For both oxidation reactions, the rate constants of complex decomposition and catalyst regeneration have been determined. Copyright

Full text of DOI:10.1002/poc.721

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
J. Phys. Org. Chem. 2004; 17: 236–240
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/poc.721
Comparative study of the catalytic behaviour of Ru(III)
and Ru(VI) on the oxidation of alcohols by
hexacyanoferrate(III)
´
A. E. Mucientes,* R. E. Gabaldon, F. J. Poblete and S. Villarreal
´
´
´
´
Departamento de Quımica Fısica, Facultad de Ciencias Quımicas, Universidad de Castilla–La Mancha, Avda. Camilo Jose Cela 10, 13071
Ciudad Real, Spain
Received 17 March 2003; revised 18 June 2003; accepted 3 October 2003
ABSTRACT: The oxidation reactions of 2-methyl-2,4-pentanediol upon treatment with alkaline hexacyanoferra-
te(III) using Ru(III) or Ru(VI) as catalysts are governed by two quasi-identical experimental rate equations, which
show that both catalysts are equally effective for the oxidation of alcohols by Fe(CN)36ꢀ. The reaction mechanism
proposed involves the oxidation of 2-methyl-2,4-pentanediol by the catalyst, a process that occurs through the
formation of a substrate–catalyst complex. The decomposition of this complex yields Ru(IV) and a protonated ketone
(owing to a hydride transfer from the ꢀ-C—H bond of the alcohol to the oxoligand of ruthenium) in the case of
Ru(VI), but a ketyl radical and Ru(II) (hydrogen transfer) for Ru(III). The role of the co-oxidant, Fe(CN)36ꢀ, is to
regenerate the catalyst. For both oxidation reactions, the rate constants of complex decomposition and catalyst
regeneration have been determined. Copyright # 2004 John Wiley & Sons, Ltd.
KEYWORDS: oxidation; catalysis; hexacyanoferrate(III); ruthenium(III); ruthenium(VI); alcohols; 2-methyl-2,4-penta-
nediol
INTRODUCTION
EXPERIMENTAL
The metal-catalysed oxidation of organic substrates is a
topic of great interest, especially for reactions in which
the substrates are not easily oxidized by common oxi-
dants.1–3 One such example is the oxidation in alkaline
media of primary and secondary alcohols by hexacyano-
ferrate(III). The reaction rate is extremely slow, but the
presence of ruthenium compounds in catalytic concen-
trations allows the kinetics to be studied over a
reasonable time period.4 The most frequently used
ruthenium catalysts are Ru(III), Ru(VI) and Ru(VIII)
species. Numerous kinetic studies have been undertaken
using these catalysts,5–8 but the catalytic behaviour has
not been systematically compared in any study. The
goal of the work described here was to perform a
comparative study of the efficiency of Ru(III) and
Ru(VI) as catalysts in the oxidation of 2-methyl-2,4-
pentanediol with alkaline hexacyanoferrate(III). With
this aim in mind, the results found in this work, using
Ru(VI) as a catalyst, are compared with those obtained
previously for Ru(III).9
Reactants. The reagents used, i.e. hexacyanoferrate(III),
sodium hydroxide, 2-methyl-2,4-pentanediol and sodium
perchlorate, were all of analytical-reagent grade and were
purchased from Merck. The solutions were prepared
using water obtained from an OSMO BL-6 deionizer
from SETA. Sodium ruthenate solution was prepared
following the literature procedure.6 The purity of stock
solutions was assessed by taking into account that the
ratio between the absorbance at 465 and 386 nm should
equal 2.07 for pure ruthenate.10
General. The oxidation kinetics of 2-methyl-2,4-penta-
nediol were followed by measuring the optical absor-
bance of hexacyanoferrate(III), A, at 420 nm on a
Perkin-Elmer Lambda 3B spectrophotometer. The initial
rates method was used for kinetic analysis. The initial
rates of disappearance of hexacyanoferrate(III) were
obtained as described previously,9 using the expression
v0 ¼ ꢀ1="ðdA=dtÞ, where " ¼ 1000 l molꢀ1 cmꢀ1 at
420 nm. The ionic strength was kept constant at 0.5 M
by the addition of sodium perchlorate. The only organic
reaction product of the oxidation of 2-methyl-2,4-penta-
nediol was 4-hydroxy-4-methyl-2-pentanone, which was
identified using a Hewlett-Packard 5890 Series II gas
chromatograph equipped with a BP-21 polyethylene
´
*Correspondence to: A. E. Mucientes, Departamento de Quımica
Fısica, Facultad de Ciencias Quımicas, Universidad de Castilla—La
´
´
´
Mancha, Avda. Camilo Jose Cela 10, 13071 Ciudad Real, Spain.
E-mail: antonio.mucientes@uclm.es
´
Contract/grant sponsor: Consejerıa de Educacion y Cultura de la Junta
de Comunidades de Castilla La Mancha.
´
Copyright # 2004 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2004; 17: 236–240

Ru(III) AND Ru(VI) CATALYSIS OF ALCOHOLS OXIDATION BY Fe(CN)63ꢀ
237
glycol column (50 m ꢁ 0.22 mm i.d., 25 mm film thick-
ness). The stoichiometry of the reaction was deduced
using an excess concentration of hexacyanoferrate(III) in
relation to diol. The residual oxidant concentration was
measured spectrophotometrically and this showed that
1 mol of diol consumed 2 mol of hexacyanoferrate(III).
RESULTS
The values of v0 for five series of kinetic runs at different
[Fe(CN)63ꢀ]0 are shown in Fig. 1. In each series the value
[diol]0 was varied while the concentrations of ruthenate
and hydroxide ions were kept constant. The dependence
of v0 on both [Fe(CN)63ꢀ]0 and [diol]0 was ascertained
using a previously described procedure.11 This study led
to the following expression:
Figure 2. Effect of [catalyst]0 on the initial rate. [2-Methyl-
2,4-pentanediol]0 ¼ 0.08 M,
[Fe(CN)63ꢀ]0 ¼ 1.2 ꢁ 10ꢀ3 M,
[OHꢀ] ¼ 0.1 M, T ¼ 30 ꢄC, I ¼ 0.5 M. ~, Ru(VI); *, Ru(III)
Â
3ꢀÃ
FeðCNÞ6 ½diolꢂ0
0
The v0–[catalyst]0 data were fitted to a linear regression,
which gave the following expression:
v0 ¼
Â
3ꢀÃ
Â
3ꢀÃ
k0½diolꢂ0 þ k00 FeðCNÞ6
þ k000½diolꢂ0 FeðCNÞ6
0
0
ð1Þ
v0 ¼ vunc þ kc½catalystꢂ0
ð2Þ
where k0 ¼ 3.5 ꢃ 0.1 min, k00 ¼ (1.3 ꢃ 0.1) ꢁ 103 min and
k000 ¼ (1.1 ꢃ 0.2) ꢁ 103 l molꢀ1 min. This equation indi-
cates a change of order from one to zero for both
hexacyanoferrate(III) and diol species upon increasing
their concentrations.
When Ru(III) was used as catalyst, under the same
experimental conditions, except that [Ru(III)]0 was 2.4 ꢁ
10ꢀ6 M, an equation identical with Eqn (1) was obtained
with the parameters now being k0 ¼ 1.3 ꢃ 0.1 min,
k00 ¼ (1.3 ꢃ 0.4) ꢁ 103 min and k000 ¼ (1.4 ꢃ 0.2) ꢁ 103 l
molꢀ1 min.
where the respective values of vunc and kc are (3.0 ꢃ
0.1) ꢁ 10ꢀ7 mol lꢀ1 minꢀ1 and 29.53 ꢃ 0.04 minꢀ1 for
Ru(VI) and (2.2 ꢃ 0.2) ꢁ 10ꢀ6 mol lꢀ1 minꢀ1 and 28.16
ꢃ 0.03 minꢀ1 for Ru(III). These results indicate that the
kinetics are first order with respect to catalyst and that the
rate of the uncatalysed reaction, vunc, is negligible com-
pared with that of the catalysed reaction.
For both catalysts the initial rate passes through a
maximum as [OHꢀ] is varied, as shown in Fig. 3. In
the case of Ru(VI), v0 does not tend to zero at very low
[OHꢀ], whereas it does for Ru(III). The variation of v0
with the basicity of the medium is complicated and obeys
the following equation:
The variation of v0 with [catalyst]0 is shown in Fig. 2
for the oxidation of 2-methyl-2,4-pentanediol by hexa-
cyanoferrate(III) using Ru(VI) and Ru(III) as catalysts.
Figure 1. Plot of v0 vs [2-methyl-2,4-pentanediol]0.
[RuO42ꢀ]0 ¼ 2.0 ꢁ 10ꢀ6 M, [NaOH] ¼ 0.1 M, I ¼ 0.5 M and
T ¼ 30 ꢄC; [Fe(CN)63ꢀ]0 ¼ (a) 1.0 ꢁ 10ꢀ4; (b) 2.0 ꢁ 10ꢀ4; (c)
Figure 3. Variation of v0 with respect to [NaOH].
[Fe(CN)63ꢀ]0 ¼ 1.2 ꢁ 10ꢀ3 M, I ¼ 0.5 M and T ¼ 30 ꢄC. [2-
Methyl-2,4-pentanediol]0 ¼ 0.08 M. (a) [Ru(III)]0 ¼ 2.4 ꢁ
4.0 ꢁ 10ꢀ4; (d) 8.0 ꢁ 10ꢀ4; (e) 1.2 ꢁ 10ꢀ3
Copyright # 2004 John Wiley & Sons, Ltd.
M
10ꢀ6 M; (b) [Ru(VI)]0 ¼ 2.0 ꢁ 10ꢀ6
M
J. Phys. Org. Chem. 2004; 17: 236–240

238
A. E. MUCIENTES ET AL.
2
A0 þ A1½OHꢀꢂ þ A2½OHꢀꢂ
which then decomposes slowly to produce a reduced
form of catalyst, RuO3ðOHÞ3ꢀ, and a protonated ketone
v0 ¼
ð3Þ
2
1 þ B1½OHꢀꢂ þ B2½OHꢀꢂ
as follows:
The v0–[OHꢀ] data were fitted to Eqn (3) by means of a
non-linear regression program. The best average error
was obtained for Ru(VI) when A2 ¼ 0 and for Ru(III)
when A0 ¼ 0.
---- þ
k2
3ꢀ
0
C21ꢀꢀ! RR C---- OH þ RuO3ðOHÞ
ð5Þ
Such an intermediate would have the following structure:
The possible formation of free radicals as intermedi-
ates was investigated by adding radical scavengers to the
reaction mixture. The addition of either 0.01 M acryloni-
trile or 1.6 ꢁ 10ꢀ4 M 2,4,6-tri-tert-butylphenol (a stronger
radical scavenger) did not have any effect on the reaction
rate when Ru(VI) was used as catalyst. For Ru(III),
however, the presence of 0.01 M acrylonitrile reduced v0
by 15% and the addition of 1.6 ꢁ 10ꢀ4 M 2,4,6-tri-tert-
butylphenol decreased v0 by 40%. Moreover, when 0.7 M
acrylonitrile was added to the reaction mixture, poly-
meric species were observed after a few minutes.
The oxidation of cyclobutanol was carried out because
the nature of its oxidation products depends on the
reaction mechanism. One-electron oxidation produces
acyclic four-carbon compounds, which appear to be
derived from the primary free radical .CH2CH2CH2CHO,
whereas two-electron oxidation produces cyclobutanone
directly.12,13 The following kinetic conditions were em-
ployed in this experiment: [OHꢀ] ¼ 0.1 M, I ¼ 0.5 M and
T ¼ 30 ꢄC. Under these conditions the oxidation of 0.08 M
cyclobutanol by 2.0 ꢁ 10ꢀ3 M hexacyanoferrate(III) using
2.5 ꢁ 10ꢀ6 M catalyst produced butanal as the major
product in the case of Ru(III) and cyclobutanone in the
case of Ru(VI).
----
Step 5 involves a hydride transfer from the ꢀ-C H
bond of the alcohol to the oxo ligand of ruthenium, a
process that is favoured by the prior coordination of the
organic substrate to the metal through the oxygen of the
hydroxy group.15 The occurrence of this hydride transfer
is supported by the following experimental results: (a) a
moderate kinetic isotope effect, which indicates cleavage
----
of a C H bond, and the absence of free radicals in the
reaction mixture, (b) oxidation of cyclobutanol produces
cyclobutanone as the sole product and (c) the negative
value of the Hammett reaction constant found for the
oxidation of benzyl alcohol.16
The following rapid reaction would yield the corre-
sponding ketone:
---- þ
RR C---- OH þ OH ꢀ! R CO R þ H2O
0
ꢀ
0
---- ----
ð6Þ
Although the organic substrate is a diol, only the 2-
hydroxy group will be oxidized, as observed experimen-
tally, because tertiary alcohols (0.1 M tert-butanol) were
found not to react under kinetic conditions.11 The pre-
sence of a hydrogen on the ꢀ-carbon of the alcohol is
therefore necessary for the reaction to progress.14
The dependence of v0 on ½FeðCNÞ3ꢀꢂ0 can be explained
6
if it is accepted that the oxidation of the reduced form of
catalyst occurs. In this way, the role of the co-oxidant,
FeðCNÞ36ꢀ, is solely the regeneration of the catalyst
through steps (7) and (8):
----
----
The observed oxidation rate of CD3 CDOD CD3
----
----
k3
was compared with that of CH3 CHOH CH3 in order
to verify the existence of a kinetic isotope effect. A
substantial primary kinetic isotope effect was indeed
observed [(v0,H=v0,D) ¼ 5.9] for both catalysts under the
following kinetic conditions: [catalysts] ¼ 2.0 ꢁ 10ꢀ6 M,
2ꢀ
RuO3 ðOHÞ3ꢀ þ FeðCNÞ63ꢀ ꢀ! RuO3 ðOHÞ
4ꢀ
þ FeðCNÞ6 ð7Þ
3ꢀ
½FeðCNÞ6 ꢂ ¼ 1:2 ꢁ 10ꢀ3 M, [diol] ¼ 0.5 M, [OHꢀ] ¼
RuO3 ðOHÞ2ꢀ þ FeðCNÞ6 ꢀ! RuO3 ðOHÞꢀ
3ꢀ
0.2 M, I ¼ 0.5 M and T ¼ 30 ꢄC.
4ꢀ
þ FeðCNÞ6
ð8Þ
ð9Þ
DISCUSSION
RuO3 ðOHÞꢀ þ OHꢀ ꢀ! RuO42ꢀ þ H2O
For Ru(VI) the dependence of the initial rate on
0
----
----
[R CHOH R ]0 [where R ¼ (CH3)2COHCH2 and
R0 ¼ CH3] suggests the formation of an intermediate
complex, C21ꢀ, between RuO24ꢀ and the organic substrate:
Step (7) is supported by the previously discovered fact
that the oxidation of alcohols by catalytic quantities of
ruthenate proceeds at a similar rate to the reoxidation of
3ꢀ
the reduced form of the catalyst by FeðCNÞ6 .11 Step (7)
k1
0
----
2ꢀ
R CHOH R þ RuO4 Ð C21ꢀ
ð4Þ
is fast relative to oxidation of the substrate at high
----
½FeðCNÞ36ꢀꢂ0 and, under these circumstances, v0 does
J. Phys. Org. Chem. 2004; 17: 236–240
k
ꢀ1
Copyright # 2004 John Wiley & Sons, Ltd.

Ru(III) AND Ru(VI) CATALYSIS OF ALCOHOLS OXIDATION BY Fe(CN)63ꢀ
239
not depend on ½FeðCNÞ36ꢀꢂ0. At low ½FeðCNÞ63ꢀꢂ0,
however, both reactions have a comparable rate and v0
is dependent on ½FeðCNÞ36ꢀꢂ0.
In the absence of scavengers, the rate of disappearance
of hexacyanoferrate(III) is determined by steps (11) and
(14) as follows:
For Ru(III),9 we obtained the same variation of v0
Â
3ꢀÃ
with [R CHOH R ]0 and ½FeðCNÞ3ꢀꢂ0 as in the case
0
----
----
Â
Ã
Â
3ꢀÃ
d FeðCNÞ6
dt
6
ꢀ
¼ k2 Cþ1 þ k3 FeðCNÞ6
of Ru(VI). For this reason we propose an analogous
scheme to that outlined in steps (4)–(9) (a slightly
different scheme was reported in our previous paper).
Given that theþactive catalytic species of Ru(III) is
RuðH2OÞ4ðOHÞ2 ,9 the following equations can be pro-
posed:
Â
Ã
ꢁ RuðH2OÞ ðOHÞþ
5
If the added scavengers compete with hexacyanofer-
rate for the ketyl radical, the disappearance rate of
hexacyanoferrate(III) would be expected to decrease, as
observed experimentally.
k1
þ
0
----
þ
The dependence of v0 on [OHꢀ] in the case of ruthe-
----
R CHOH R þ RuðH2OÞ4ðOHÞ2 Ð C1
ð10Þ
k
ꢀ1
nate may be explained by assuming the existence of two
,
3ꢀ
active species of catalyst, RuO24ꢀ and RuO4ðOHÞ
which are in equilibrium as follows:16
---- ꢅ
k2
þ
0
þ
C1 ꢀ! RR C---- OH þ RuðH2OÞ5OH
ð11Þ
K1
3ꢀ
ꢀ
The intermediate Cþ1 would have the following structure:
RuO24ꢀ þ OH + RuO4ðOHÞ
(
ð16Þ
K2
(
3ꢀ
4ꢀ
ꢀ
RuO4ðOHÞ þ OH + RuO4ðOHÞ2
ð17Þ
The existence of these hydroxy-oxy complexes of
ruthenium was suggested by Luoma and Brubaker, who
studied the reaction between perruthenate and manganate
ions in aqueous alkaline media.17
The decomposition of C1þ yields a ketyl radical and
Ru(II). Step (11) involves a hydrogen atom transfer from
----
the ꢀ-C H bond of the alcohol to the oxygen of the
Application of the steady-state conditions with respect
3ꢀ
to RuO3ðOHÞ and C21ꢀ, and on the assumption that the
hydroxo ligand of ruthenium. Evidence for this transfer is
provided by the presence of free radicals in the reaction
mixture and by the fact that the oxidation of cyclobutanol
yields butanal as the major product.
3ꢀ
reactivities of RuO42ꢀ and RuO4ðOHÞ are equal (for
simplicity), gives the following theoretical rate equation
for the disappearance of hexacyanoferrate(III):
Â
3ꢀÃ
Â
3ꢀÃ
d FeðCNÞ6
dt
2k1k2k3kA FeðCNÞ6 ½diolꢂ½RuðVIÞꢂT
ꢀ
¼
ð18Þ
Â
3ꢀÃ
Â
3ꢀÃ
k1k2kA½diolꢂ þ k3 ðkꢀ1 þ k2ÞkB FeðCNÞ6 þ k1k3kA FeðCNÞ6 ½diolꢂ
Regeneration of the catalyst occurs through steps (12)
and (13), whereas the fast step (14) and a step as (6)
would yield 4-hydroxy-4-methyl-2-pentanone:
where [Ru(VI)]T is the sum of the concentrations of
Ru(VI) and Ru(IV); the concentration of Ru(V) would
negligible at any time because such species are involved
in fast steps. Moreover, kA ¼ 1 þ K1[OHꢀ] and kB ¼
1 þ K1[OHꢀ] þ K1K2[OHꢀ]2. Equation (18) explains the
k3
Â
3ꢀÃ
2þ
RuðH2OÞ ðOHÞþ þ FeðCNÞ3ꢀꢀ! RuðH2OÞ ðOHÞ
dependence of v0 on [OHꢀ], FeðCNÞ6 , [diol] and
5
6
5
4ꢀ
[catalyst].
þ FeðCNÞ6
ð12Þ
In the case of Ru(III), the dependence of v0 on [OHꢀ]
can be justified, as reported previously,5 by accepting that
the catalytic reactive species are RuðH2OÞ ðOHÞþ and
2þ
RuðH2OÞ5ðOHÞ þ OHꢀꢀ! RuðH2OÞ4ðOHÞ2þ þ H2O
4
2
RuðH2OÞ3ðOHꢀÞ3, which are involved in the following
ð13Þ
equilibria:
K1
þ
ꢀ
RuðH2OÞ5OH2þ þ OH +RuðH2OÞ4ðOHÞ2 þ H2O ð19Þ
(
K2
---- ꢅ
3ꢀ
4ꢀ
0
0
---- þ
RR C---- OH þ FeðCNÞ6 ꢀ! RR C---- OH þ FeðCNÞ
ð614Þ
þ
ꢀ
(
RuðH2OÞ4ðOHÞ2 þ OH +RuðH2OÞ3ðOHÞ3 þ H2O ð20Þ
J. Phys. Org. Chem. 2004; 17: 236–240
Copyright # 2004 John Wiley & Sons, Ltd.

240
A. E. MUCIENTES ET AL.
Application of the steady-state conditions with respect
to RuðH2OÞ5ðOHÞþ and C12ꢀ, and on the assumption that
decomposition involves a hydride transfer from the ꢀ-
C—H bond of the alcohol to the oxo ligand of ruthenium
in the case of Ru(VI), but a hydrogen transfer for Ru(VI).
Reduced catalyst species are later oxidized by Fe(CN)6
to regenerate the catalyst. For both oxidations the rate
the reactivities of RuðH2OÞ ðOHÞþ and RuðH2OÞ ðOHÞ
4
2
3
3
3ꢀ
are equal (for the sake of simplicity), provides the
following equation:
Â
3ꢀÃ
Â
3ꢀÃ
d FeðCNÞ6
dt
2k1k2k3kA FeðCNÞ6 ½diolꢂ½RuðIIIÞꢂT
ꢀ
¼
ð21Þ
Â
3ꢀÃ
Â
3ꢀÃ
k1k2kA½diolꢂ þ k3ðkꢀ1 þ k2ÞkB FeðCNÞ6 þ k1k3kA FeðCNÞ6 ½diolꢂ
In this case [Ru(III)]T is the sum of the concentrations of
constants of complex decomposition and catalyst regen-
eration have been obtained.
2
Ru(III) and Ru(II); kA ¼ K1½OHꢀꢂ þ K1K2½OHꢀꢂ and
kB ¼ 1 þ K1[OHꢀ] þ K1K2 [OHꢀ]2. This equation is con-
sistent with all of the results obtained.
Acknowledgement
Equations (18) and (21) are very similar because they
contain the same dependence of v0 on the concentration
of catalyst, substrate and hexacyanoferrate(III). However,
the dependence of v0 on [OHꢀ] is slightly different in the
two equations. Comparison of these equations with the
experimental equation that combines Eqns (1) and (2)
provides the rate constants for intermediate complex
decomposition, k2, and catalyst regeneration, k3. The
respective values of k2 and k3 were found to be (2.7 ꢃ
0.5) ꢁ 102 minꢀ1 and (8.2 ꢃ 0.5) ꢁ 104 l molꢀ1 minꢀ1 for
Ru(VI) and (1.9 ꢃ 0.3) ꢁ 102 minꢀ1 and (2.0 ꢃ 0.2) ꢁ
105 l molꢀ1 minꢀ1 for Ru(III).
The authors acknowledge the financial support of the
´
Consejerıa de Educacion y Cultura de la Junta de Comu-
nidades de Castilla La Mancha.
´
REFERENCES
1. Hiremath GA, Timmanagoudar PL, Nandibewoor ST. J. Phys.
Org. Chem. 1998; 11: 31.
2. Panari RG, Chougale RB, Nandibewoor ST. J. Phys. Org. Chem.
1998; 11: 448.
3. Griffith WP, Suriaatmaja M. Can. J. Chem. 2001; 79: 598.
4. Kelson EP, Phengsy PP. Int. J. Chem. Kinet. 2000; 32: 760–770.
´
5. Mucientes AE, Poblete FJ, Santiago F, Rodrıguez MA. J. Chim.
Phys. 1997; 94: 1642.
6. Lalitha TV, Sethuram B. Transition Met. Chem. 1992; 17: 29.
7. Dwivedi RK, Verma M, Kumar P, Behari K. Tetrahedron 1983;
39: 815.
CONCLUSION
8. Singh HS, Singh RK, Singh SM, Sisodia AK. J. Phys. Chem.
1977; 81: 1044.
The kinetics for the oxidation of 2-methyl-2,4-pentane-
3ꢀ
´
´
9. Mucientes AE, Poblete FJ, Gabaldon RE, Rodrıguez MA,
Santiago F. J. Chem. Res. (S) 1998; 6: 286.
10. Larsen RP, Ross LE. Anal. Chem. 1959; 31: 176.
diol by FeðCNÞ6 , using Ru(VI) or Ru(III) as catalysts,
are governed by very similar experimental rate equations.
These equations show a change of order from one to
zero for both hexacyanoferrate(III) and diol species
upon increasing their concentrations and are first order
with respect to the catalyst. The reaction mechanism
proposed involves oxidation of 2-methyl-2,4-pentanediol
by Ru(VI) or Ru(III) through the formation of a sub-
strate–catalyst complex, which subsequently decomposes
to give Ru(IV) or Ru(II). Intermediate complex
´
11. Mucientes AE, Poblete FJ, Rodrıguez MA, Santiago F. J. Phys.
Org. Chem. 1999; 13: 901.
12. Rocek J, Radkowsky AE. J. Am. Chem. Soc. 1973; 95: 7123.
13. Meyer K, Rocek J. J. Am. Chem. Soc. 1972; 94: 1209.
14. Marmion ME, Takeuchi KJ. J. Chem. Soc., Dalton Trans. 1988;
2385–2391.
15. Cundary TR, Drago RS. Inorg. Chem. 1990; 29: 3904.
16. Mucientes AE, Santiago F, Almena MC, Poblete FJ, Rodriguez-
Cervantes AM. Int. J. Chem. Kinet. 2002; 34: 421.
17. Luoma EV, Brubaker CH. Inorg. Chem. 1966; 5: 1637.
Copyright # 2004 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2004; 17: 236–240