8
FEDOSEEV, GORDEEV
samples average weight loss upon thermolysis is
16.62%.
Concentrated HCl dissolves PdCOCl to yield
anionic carbonyl chloride:
2HCl = 2PdCOCl
H2[Pd2(CO)2Cl4].
We isolated the anionic form of palladium(I) carbonyl
chloride as the salt Cs2[Pd2(CO)2Cl4] when water–alco-
hol and water–acetone solutions of PdCl2 in concen-
trated HCl were treated with carbon monoxide under
vigorous stirring at room temperature. For the systems
R–H2O–HCl–H2[PdCl4], where R is ethanol, propanol-1,
butanol-2, acetone, or ethyl methyl ketone, the color
rapidly changes from orange, which is characteristic of
the chloropalladium(I) complex, through yellow to
muddy green and palladium black segregates. In order
for palladium black to segregate, a certain minimal
amount of water should be present in the solution and
the acidity should be low.
2000
1900
1800
The change of solution color is associated with the
change of both the ligand surrounding of the palladium
atom and the degree of its oxidation.
–1
ν, cm
Fig. 2. IR spectrum of a PdCOCl sample.
Using 95% ethanol and concentrated HCl in the vol-
ume ratio 4 : 1 with the palladium(II) content 83 g/L
and passing CO for 25 min, we obtained a yellow solu-
tion. When a solution of CsCl in concentrated HCl was
added to this solution, a straw-colored precipitate
appeared immediately. The product was separated by
filtration using a glass filter, washed with ethanol and
acetone, and air-dried at 130°C.
T, °C
1
Elemental analysis showed that the product corre-
300
sponds to the formula Cs2[Pd2(CO)2Cl4]. Bands ν(CO) =
1916 cm–1(s) and ν(CO) = 1873 cm–1 (w) appeared in
its IR spectrum (Fig. 4).
By increasing the water content and the duration of
CO treatment, we isolated cesium salts of other compo-
sitions with differing IR spectra, for example, the prod-
uct of gross formula Cs6[Pd5(CO)4Cl12], whose spec-
trum involved bands ν(CO) = 1966 cm–1 (s), ν(CO) =
1916 cm–1 (s), and ν(CO) = 1871 cm–1 (m). No detailed
investigation of these products was carried out. How-
ever, we may assume that a mixed (Pd(I) + Pd(II)) car-
bonylchloride anion is formed in this case.
After carbonylation of alcohol solutions, cesium
chloride quantitatively precipitated palladium. The
residual concentration of palladium was less than
0.03 mg/L.
∆m, mg
3
2
200
100
0
5
10
15
Time
Reduction Pd(II)
Pd(I) in the system
acetone−HCI–H2[PdCl4]–CO proceeds rather rapidly,
which manifests itself in the change in color and a
decrease in the oxidation–reduction potential. As the
potential attains 180–170 mV with respect to the sil-
ver/silver chloride electrode, pouring of a solution of
CsCl in concentrated HCl causes immediate formation of
Fig. 3. Thermogravimetry pattern of the PdCOCl sample in
helium. (1) T, °C; (2) ∆m, mg; and (3) DTA curve.
In the IR spectrum of the thermolysis products, no
absorption in the region of CO groups is observed,
while the band of the PdCl2 compound is present.
a
straw-colored precipitate of the composition
Cs2[Pd2(CO)2Cl4], whose IR spectrum involves the
sis of PdCOCl should be 16.48%. For three PdCOCl bands ν(CO) = 1916 cm–1 (s) and ν(CO) = 1873 cm–1 (w).
According to Eq. (4), weight loss during thermoly-
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 1 2007
Fedoseev
