DOUBLE COMPLEX SALTS [M(NH3)5Cl][M'Br4]
203
specified operations. The product was dissolved in
Table 1. Results of chemical analysis for DCSs
water and treated portionwise with aqueous bromine by
stirring and with the potential being adjusted to about
650 mV relative to the Ag/AgCl electrode. The result-
ing dark brown solution was transferred to an Erlenm-
eyer flask 250 ml in capacity, an equal volume of hydro-
chloric acid was added, and the mixture was refluxed
for 2 h. A light yellow solution and a brown precipitate
formed as a result; the precipitate was separated. The
crude yield was at least 90%. The precipitate was puri-
fied as follows: it was dissolved in a minimal amount of
boiling water with HCl (~3.8 g HCl per 100 ml water);
the insoluble brown substance was separated on a hot-
filter funnel. To the transparent yellow filtrate, an equal
volume of concentrated HCl was added. The precipitate
was collected on a filter; then, it was washed with dilute
HCl, ethanol, and acetone and air-dried. If the resulting
[Ru(NH3)5Cl]Cl2 did not have a pure yellow color, the
purification was repeated. The yield was at least 80%.
The product as analyzed contained 34.5% Ru (for
[Ru(NH3)5Cl]Cl2, calcd.: 34.56%). The electronic
absorption spectra of the solution exactly coincided
with the spectrum reported in [17].
Total metals, %
Compound
found
calcd.
[Ir(NH3)5Cl][PtBr4]
[Rh(NH3)5Cl][PtBr4]
[Ru(NH3)5Cl][PtBr4]
[Co(NH3)5Cl][PtBr4]
[Cr(NH3)5Cl][PtBr4]
[Ru(NH3)5Cl][PdBr4]
[Cr(NH3)5Cl][PdBr4]
45.1 0.1
38.9 0.1
38.3 0.1
35.5 0.1
36.2 0.1
32.0 0.1
27.2 0.1
46.80
40.37
40.22
36.59
35.94
32.03
26.47
The solubilities of all the DCSs with the [PtBr4]2–
anion were similar and fell in the range from 10–4 to
10−3 mol/l, which proved a weak effect of the nature of
the central cation on the solubility.
IR spectra were recorded on a Scimitar FTS 2000
Fourier-transform spectrometer in the wavenumber
region of 400–4000 cm–1 as KBr discs or mineral oil
mulls (Table 2).
The X-ray powder diffraction experiment was car-
ried out on a DRON-Seifert RM4 diffractometer (CuKα
radiation, graphite monochromator, scintillation detec-
tor with amplitude discrimination). The test samples
were prepared by spreading an ethanol suspension over
the polished side of a standard quartz cell. The external
reference used was a polycrystalline silicon sample
(a = 5.4309 Å) prepared in the same manner. The X-ray
diffraction patterns were recorded in the frame mode in
the 2θ range 5°–55° for the complex salts and 20°–135°
for the thermolysis products. The refinement of the unit
cell parameters (Table 3) and the quantitative phase
analysis were carried out over the entire data set using
the PowderCell 2.4 program [18]. The mean coherent
scattering domain (CSD) size for the metal powders
was derived from the analysis of diffraction peak
broadening using the WinFit 1.2 program [19].
The DCSs with the [PdBr4]2– anions were prepared
by converting the chloropentaammine chlorides to the
bromides as follows. The [M(NH3)5Cl]Cl2 (M = Cr, Ru)
complexes were dissolved in a minimal amount of boil-
ing water, and concentrated HBr was added. Precipi-
tates appeared immediately. The reaction mixtures
were cooled in ice water; the precipitates were filtered
and washed with ice water, methanol (until the test for
Br– in the washes was negative), and diethyl ether. The
[M(NH3)5Cl]Br2 yield was at least 85%. The complexes
were analyzed for bromide ions (as AgBr). The results
of the analysis coincided with the calculated bromine
concentration in [M(NH3)5Cl]Br2.
The [M(NH3)5Cl][PdBr4] DCSs were synthesized as
follows. The precursor complexes [M(NH3)5Cl]Br2
were dissolved in a minimal amount of water under
heating to ~50°ë. The concentration of each complex
was 0.01 mol/l. To the resulting solution, a 0.01 M
K2[PdBr4] solution in 0.1 M KBr was added. Crystals
precipitated immediately after the solutions were com-
bined. The reaction mixtures were cooled to ~0°C; the
precipitates were filtered and washed with ice water,
acetone, and ethanol. The yield was 70% (for M = Cr)
and 90% (for M = Ru). The [M(NH3)5Cl][PtBr4] DCSs
were synthesized in the same manner but starting from
chloropentaamminemetal(III) chlorides. The yields
were 70% (for M = Ir, Co), 80% (M = Cr, Rh), and 99%
(M = Ru).
The thermogravimetric (TG) experiments were on
a Q-1000 instrument modified to operate in various
gases with digitizing of the analog signal.
RESULTS AND DISCUSSION
The need to convert the chloropentaammines into
bromides in the synthesis of the DCSs with the
[PdBr4]2– anion was dictated by the fact that the outer-
sphere chloride ions from [M(NH3)5Cl]Cl2 can partially
substitute for the bromide ions in labile [PdBr4]2– due to
The compounds were analyzed for the total metals the higher thermodynamic stability of the chloropalla-
by calcination in flowing hydrogen at temperatures to dium(II) complexes [20]. This fact was discovered in
[8]. In the case where tetrabromoplatinate(II) was the
anion, the conversion was not carried out: the afore-
500°C and subsequent calcination in flowing helium at
~600°ë; the results of the analysis are listed in Table 1.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 2 2006
Shubin
