Oxidation of magnesium with diphenylbismuth and diphenylantimony chlorides in polar solvents

Article abstract of DOI:10.1134/S1070363206010014

The intermediate and final products of the reactions of magnesium with diphenylantimony and diphenylbismuth chlorides were identified, and the formal kinetic relationships of the process were elucidated. The apparent equilibrium constants, enthalpies, and

Full text of DOI:10.1134/S1070363206010014

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 1, pp. 1 4.
Original Russian Text S.V. Maslennikov, S.V. Klement’eva, Ya.V. Losev, I.V. Spirina, V.P. Maslennikov, 2006, published in Zhurnal Obshchei Khimii,
006, Vol. 76, No. 1, pp. 3 6.
Pleiades Publishing, Inc., 2006.
2
Oxidation of Magnesium with Diphenylbismuth
and Diphenylantimony Chlorides in Polar Solvents
S. V. Maslennikov, S. V. Klement’eva, Ya. V. Losev,
I. V. Spirina, and V. P. Maslennikov
Research Institute of Chemistry, Lobachevsky Nizhni Novgorod State University,
pr. Gagarina 23, korp. 5, Nizhni Novgorod, 603950 Russia;
e-mail: spirina@ichem.unn.runnet.ru
Received February 17, 2005
Abstract The intermediate and final products of the reactions of magnesium with diphenylantimony and
diphenylbismuth chlorides were identified, and the formal kinetic relationships of the process were elucidated.
The apparent equilibrium constants, enthalpies, and entropies of adsorption of the reagents on the metal
surface, and also the rate constants and activation energies of the reactions in dimethylformamide p-xylene
mixture were determined. Probable schemes of magnesium oxidation with the organobismuth and organoanti-
mony chlorides were considered.
DOI: 10.1134/S1070363206010014
Organometallic halides are used as effective oxi-
acetic acid is accompanied by transfer of soluble Bi
compounds into solution. Analysis of this solution for
Bi ions [6] revealed the presence of 0.205 mol of Bi
dants in syntheses of heterometallic compounds [1].
Organoantimony and organobismuth halides oxidize
magnesium under relatively mild conditions in polar
solvents [2, 3]. Herbstman [2] suggested that oxida-
tion of magnesium turnings with (n-C H ) SbBr in
3
+
per mole of II. The metallic mirror did not dissolve
in acetic acid, and it was dissolved in 20% HNO ; the
3
3
+
resulting solution contained 0.237 mol of Bi per
mole of II. The liquid phase was evaporated, and the
residue (a mixture of a greenish oil and a white crys-
talline substance) was treated with 5 ml of toluene.
The crystals insoluble in toluene were identified by
4
9 2
THF involves formation of [(n-C H ) Sb] Mg. The
4
9 2
2
final reaction products are (n-C H ) Sb, (n-C H Sb) ,
4
9 3
4
9
n
Sb, originating from transformations of the unstable
intermediate [(n-C H ) Sb] , and also MgBr [4, 5].
4
9 2
2
2
According to [3], reduction of Ph SbBr with Mg ini-
chemical analysis as MgCl (yield 0.47 mol per mole
of II). The toluene solution was treated with warm
2
2
tially yields, as in [2], a Grignard-like reagent. Thus,
the scheme of the reaction of Mg with diphenylanti-
mony chloride I can be represented as follows:
(40 C) concentrated HCl; in so doing, Ph Bi, if pres-
3
ent in solution, should transform by the reaction [5]
Ph SbCl + Mg
Ph SbMgCl,
(1)
(2)
Ph Bi + 3HCl
3PhH + BiCl3.
(5)
2
2
3
2
Ph SbMgCl
(Ph Sb) Mg + MgCl ,
2
2
2
2
In the organic layer, we determined chromatograph-
ically benzene and diphenyl; their yields were, respec-
tively, 1.51 and 0.1 mol per mole of II. The content
Ph SbMgCl + Ph SbCl
Ph Sb SbPh + MgCl , (3)
2 2 2
2
2
Ph Sb SbPh
Ph Sb + (PhSb) + Sb.
(4)
3+
2
2
3
n
of the Bi ions in the aqueous phase was equivalent
As antimony and bismuth are elements of the same
subgroup, there are good grounds to anticipate that
oxidation of magnesium with diphenylbismuth chlo-
ride II will follow a similar pattern. To determine the
composition and yield of products formed in the reac-
tion of Mg with II, a 0.05 M solution of II in THF
was added at 293 K to a tenfold excess of Mg. In the
process, a black precipitate formed and a metallic
mirror deposited on the reactor walls. After separation
of the liquid phase and unchanged metal, the residue
was repeatedly washed with THF and dried at reduced
pressure. Treatment of the precipitate with 4 ml of
to 0.5 mol of BiCl per mole of II [6]. In a parallel ex-
3
periment, the organic layer after acid hydrolysis was
evaporated; the crystalline residue had mp 70.4 C,
which corresponded to diphenyl (mp 70.5 C [7]).
According to [4, 5], (Ph Bi) disproportionated to
2
2
form Ph Bi, (PhBi) , Bi, and Ph . Thus, the scheme
3
n
2
of the reaction of II with Mg can be represented as
follows:
Ph BiCl + Mg
Ph BiMgCl,
(6)
2
2
Ph BiMgCl + Ph BiCl
Ph Bi BiPh + MgCl , (7)
2
2
2
2
2
Ph Bi BiPh2
Ph Bi + (PhBi)n + Bi + Ph2. (8)
3
2
1

2
MASLENNIKOV et al.
CDMF, M
CDMF, M
0
2
4
6
8
10 12 14
0
4
8
12
3
2
2
8
6
4
2
2
1
.6
4
1
1.2
4
2
0
3
1
0.8
.4
1
0
0
3
0
0.2
0.1
0.2
0.3
COx, M
0.05
0.1
COx, M
0.15
Fig. 1. Rate of magnesium oxidation with diphenyl-
Fig. 2. Rate of magnesium oxidation with diphenyl-
antimony chloride in DMF p-xylene as a function of the
bismuth chloride in DMF p-xylene as a function of the
0
0
concentration of the (1, 2) oxidant (C
13 M) and
concentration of the (1, 2) oxidant (C
13 M) and
DMF
DMF
0
0
(
(
3, 4) ligand (C
2, 4) 343.
0.1 M). T, K: (1, 3) 323 and
(3, 4) ligand (C
(2, 4) 303.
0.05 M). T, K: (1, 3) 283 and
Ox
Ox
It is interesting to compare the reaction products
unambiguous conclusion on the scheme of magnesium
oxidation in DMF p-xylene. However, examination of
the influence exerted by the oxidant concentration at
various ligand concentrations on the relative reaction
rate V/Vmax (V, reaction rate under given conditions;
Vmax, maximal reaction rate; Fig. 3) shows that in
this case, too, the reagent and ligand are adsorbed on
similar reaction centers. Thus, the reaction scheme can
be represented by Eqs. (9) (11):
formed in the systems Mg II and Mg [Cp(CO) Mo]2
3
BiCl [8, 9]. In the latter case, the reaction system does
not contain [Cp(CO) MoBi] and [Cp(CO) Mo] . It
3
n
3
2
5
should be noted that bis( -cyclopentadienyltricarbo-
nylmolybdenum) is relatively stable (decomposition
point 216 C [10]). According to [11], it reacts with
Mg, but the reaction occurs at a measurable rate at
temperatures higher than those in [8] by 60 70 C.
Hence, in organobismuth compounds in which the
central atom is bonded to metal-containing substitu-
ents, the pathway similar to the transformation of
tetraphenyldibismuthine into diphenyl and polymer
ads
Ox
K
Ox + S
L + S
Ox(S),
(9)
(10)
(11)
ads
KL
L(S),
(
PhBi) is not realized. Apparently, in this case the
n
k
Ox(S) + L(S)
Products,
intermediate dimer {[Cp(CO) Mo] Bi} decomposes
3
2
2
into [Cp(CO) Mo] Bi and unstable intermediate
3
3
[
Cp(CO) MoBi], which subsequently disproportion-
where K Oa dx s and K La ds are the equilibrium constants of
3
ates into [Cp(CO) Mo] Bi and Bi.
adsorption of the oxidant and ligand, respectively.
3
3
The dependence of the rate of magnesium oxida-
tion with I and II on the donor power of the solvent
passes through a maximum with dimethyl sulfoxide.
However, as previous experiments on oxidation of Mg
with other compounds were performed in dimethyl-
formamide [12], in this study we also used DMF as
polar solvent.
In this case, the reaction rate is described by
Eq. (12):
ads
ads
kKOx COxKL CL
V =
,
(12)
ads
ads
(
1 + KOx COx + KL C )
L
where COx is the oxidant concentration; C , ligand
L
2
0
concentration; k = k S (k , rate constant; S , number
0
The kinetic curves of magnesium oxidation with I
in DMF p-xylene (Fig. 1) show that the process can
be described by the Langmuir Hinshelwood scheme
with adsorption of the reagent and ligand (polar solv-
ent) on similar active centers of the metal surface [13].
With II, the reaction kinetics (Fig. 2) does not allow
of adsorption-active centers per unit surface area of
the metal).
Linearization of Eq. (12) in the coordinates
1
/2
1/2
(C /V) COx at CL = const and (C /V) CL at
Ox
L
COx = const and combined solution of the resulting
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 1 2006

OXIDATION OF MAGNESIUM WITH DIPHENYLBISMUTH
3
Apparent equilibrium constants, enthalpies, and entropies
of adsorption; rate constants and activation energies of
compared to the Sb Cl bond. Similar relationships
were observed previously, in particular, with organic
magnesium oxidation with diphenylantimony and diphenyl- halides used as oxidants [14].
a
bismuth chlorides in DMF p-xylene
EXPERIMENTAL
3
K 10 ,
ads
ads
102
T, K
K
L
Ox
L
g cm 2 min 1
Magnesium wire [GOST (State Standard) 804 56,
9.92%) 0.5 mm in diameter and magnesium turnings
9
Ph SbCl
were used without additional treatment. Organic solv-
ents, if necessary, were purified and dried by standard
procedures [15]. The content of Mg, Sb, Bi, and Cl in
the starting substances and reaction products was
determined according to [6]. Liquid mixtures were
degassed by repeated freeze pump thaw cycles. Di-
phenylantimony and diphenylbismuth chlorides were
synthesized by procedures suggested in [5]. According
2
323
333
343
26.4
23.0
20.8
32
28
23
2.0
2.9
3.9
Ph BiCl
2
2
2
3
83
93
03
5.1
5.0
4.9
0.46
0.30
0.18
85
206
499
to the content of Cl and Sb [6], the Ph SbCl sample
contained 99.6% main substance, mp 68.7 C (pub-
2
a
ads
H
1
ads
Ph SbCl:
11.0 0.8
ads
kJ mol
,
S
Ox
7.0
57.0
1.4
33.4
63.2
2
Ox
1
1
1
ads
1
0
0
2
1
.2 J mol
.7 Jmol
.1 kJ mol
.4 kJ mol
.4 kJ mol
K
1
,
H
15.2 1.9 kJ mol
1
,
S
lished data: mp 68 69 C [5]). Ph BiCl used in the
L
L
2
1
ads
K
1
, E 30.0 1.0 kJ mol ; Ph BiCl:
H
experiments was 99.6% pure according to the analysis
for Cl and Bi [6]; mp 184.8 C (published data: mp
184 185 C [5]).
2
L
ads
1
1
ads
,
S
S
8.5 1.0 J mol
K
,
K
H
Ox
ads
L
1
1
1
,
62.5 1.0 J mol
,
E
L
1
.
Diphenyl and benzene were determined chromato-
graphically with a Tsvet-105 device. Analysis condi-
tions: 2.5 3000-mm glass column, 10% Reoplex-
400 on Cellite 545; thermal conductivity detector, I
180 mA; carrier gas He, flow rate 60 ml min ; tem-
perature of the injector, detector, and oven 180 C;
retention time: benzene 35 s and diphenyl 7 min 15 s.
equations allow calculation of the apparent equilibri-
um constants of adsorption of the reagent and ligand
and of the reaction rate constant. From the tempera-
ture dependences of these quantities, we calculated the
apparent enthalpies and entropies of adsorption of the
oxidant and ligand and the activation energy of the
corresponding reactions (see table).
1
The reaction kinetics was monitored by the resisto-
metric method [16] modified for experiments with
readily hydrolyzable and oxidizable substances.
It should be noted that the enthalpy of adsorption
of II on the Mg surface is lower by almost an order
of magnitude than that of I. This may be due to a
larger energy required to deform of the Bi Cl bond
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