Russian Chemical Bulletin, International Edition, Vol. 51, No. 1, pp. 41—45, January, 2002
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Powder Xꢀray diffraction study of the double complexes
[
M(NH ) Cl][M´Cl ] as precursors of metal powders
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(
M = Ir, Rh, Co; M´ = Pt, Pd)
Yu. V. Shubin,a S. V. Korenev, K. V. Yusenko, T. M. Korda, and A. B. Venediktov
a
b
a
a
aInstitute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences,
3
prosp. Akad. Lavrent´eva, 630055 Novosibirsk, Russian Federation.
Fax: +7 (383 2) 39 1144. Еꢀmail: shubin@che.nsk.su
b
Novosibirsk State University,
2
ul. Pirogova, 630090 Novosibirsk, Russian Federation
According to the results of powder Xꢀray diffraction study of the complex salts of composiꢀ
tion [M(NH ) Cl][M´Cl ] (M = Ir, Rh, or Co and M´ = Pt or Pd), the anhydrous salts
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crystallize in the orthorhombic system (space group Pnma) and are isostructural to the
Ir(NH ) Cl][PtCl ] complex studied previously. The unit cell parameters of the resulting salts
[
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were refined. The metal powders, which were obtained by thermal decomposition of these salts
under an atmosphere of hydrogen, were studied by powder Xꢀray analysis.
Key salts: iridium, rhodium, cobalt, platinum, palladium, chloropentammines, chloro
complexes, powder Xꢀray diffraction analysis.
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The present work was undertaken as part of our conꢀ
tinuing studies on the double complex compounds, which
are promising precursors of biꢀ and polymetallic powders.
Compounds of the [M(NH ) Cl][M´Cl ] series have been
dure described by us previously. A known procedure for the
synthesis of [Ir(NH ) Cl]Cl required prolonged heating in an
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autoclave, involved many steps, and was very laborious. In this
procedure, numerous separation operations must be performed
for obtaining pure samples. In addition, iridium chloride, which
is characterized by a polynuclear structure8 and is difficultly
accessible, served as the starting compound. We developed a
more convenient procedure for the synthesis of [Ir(NH ) Cl]Cl .
A small amount of water was added to a weighed sample of
ammonium hexachloroiridate(IV) and the reaction mixture was
treated with hydroxylamine hydrochloride with heating and stirꢀ
ring using a magnetic stirrer until the precipitate was completely
dissolved and a darkꢀgreen solution was obtained. The reaction
was accompanied by copious nitrogen liberation and was comꢀ
pleted in several minutes. The resulting solution was cooled to
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studied in sufficient detail. The crystal structure and seꢀ
lected properties of [Ir(NH ) Cl][PtCl ] have been invesꢀ
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tigated.1 Reduction of the latter complex afforded a metal
powder, which was proposed to use for the preparation of
a catalyst. The [Co(NH ) Cl][PdCl ] complex was also
,2
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synthesized and studied. Previously, we have prepared
and characterized the complexes [Rh(NH ) Cl][PtCl ]
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and [Rh(NH ) Cl][PdCl ]•H O. It was demonstrated
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that thermal decomposition of the latter compounds unꢀ
der an inert or reductive atmosphere gave rise to finely
dispersed powders of solid solutions of two metals. Howꢀ
ever, the question of whether these salts are isostructural
to each other remained open. If these salts are isoꢀ
structural, one would expect the preparation of metal
phases containing three or more components, the content
of each component being strictly specified by the starting
composition of the solid solution of the complex salts.
In the present study, we carried out powder Xꢀray
diffraction analysis of complexes of the aboveꢀmentioned
series and the products of their reduction with hydrogen.
∼
20 °C and then solid NH Cl and NH HCO and a concenꢀ
4 4 3
trated solution of NH OH were added successively (24—27 moles
4
of each reagent per mole of the iridium salt). The reaction mixꢀ
ture (pH ∼ 9) was placed in a beaker, which was covered with a
watch glass, and refluxed with weak heating for 6—10 h. As pH
decreased, a 2—3 M solution of NH4HCO3 in NH4OH (pH ∼ 10)
was added from two to three times. After the formation of a
paleꢀyellow precipitate, the watch glass was removed and the
mixture was heated until pH reached ∼ 6. Then the solution was
cooled and treated with hydrochloric acid until a ∼ 10% HCl
solution was obtained. The precipitate that formed was filtered
off and successively washed with a ∼ 1 M HCl solution, ethanol,
and ether. To purify the compound, the precipitate was disꢀ
Experimental
solved in a minimum amount of boiling H O, the hot solution
2
was filtered through a paper filter, and an equal volume of conꢀ
centrated HCl was added to the filtrate. Small pale crystals that
rapidly precipitated were filtered off and washed as described
above and then dried. The yield of pure [Ir(NH ) Cl]Cl
The starting complexes [Co(NH ) Cl]Cl , K PtCl , and
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6
,7
K PdCl were synthesized according to standard procedures.
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The salt [Rh(NH ) Cl]Cl was prepared according to a proceꢀ
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 39—43, January, 2002.
066ꢀ5285/02/5101ꢀ41 $27.00 © 2002 Plenum Publishing Corporation
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