Study of nitrosation of hexaammineruthenium(II): Crystal structure of trans-[RuNO(NH3)4Cl]Cl2

Article abstract of DOI:10.1134/S0036023607010123

The nitrosation of [Ru(NH₃)₆]²⁺ in hydrochloric acid and alkaline ammonia media has been studied; the patterns of interconversion of ruthenium complexes in reaction solutions have been proposed. In both cases, nitrogen(II) oxide acts as the nitrosation agent. The procedure for the synthesis of [Ru(NO)(NH₃)₅]Cl₃ ? H₂O (yield 75-80%), the main nitrosation product of [Ru(NH ₃)₆]²⁺, has been optimized. Thermolysis of [Ru(NO)(NH₃)₅]Cl₃ ? H₂O in a helium atmosphere has been studied; the intermediates have been identified. One of these products is polyamidodichloronitrosoruthenium(II) whose subsequent decomposition gives an equimolar mixture of ruthenium metal and dioxide. The structure of trans-[RuNO(NH₃)₄Cl]Cl₂, formed in the second stage of thermolysis and as a by-product in the nitrosation of [Ru(NH₃)₆]Cl₂, has been determined by X-ray diffraction. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S0036023607010123

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 1, pp. 62–70. © Pleiades Publishing, Inc., 2007.
Original Russian Text © M.A. Il’in, V.A. Emel’yanov, I.A. Baidina, N.I. Alferova, I.V. Korol’kov, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 1,
pp. 67−75.
COORDINATION COMPOUNDS
Study of Nitrosation of Hexaammineruthenium(II): Crystal
Structure of trans-[RuNO(NH3)4Cl]Cl2
M. A. Il’in, V. A. Emel’yanov, I. A. Baidina, N. I. Alferova, and I. V. Korol’kov
Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
e–mail: maxilyin@ngs.ru
Received December 23, 2005
Abstract—The nitrosation of [Ru(NH3)6]2+ in hydrochloric acid and alkaline ammonia media has been stud-
ied; the patterns of interconversion of ruthenium complexes in reaction solutions have been proposed. In both
cases, nitrogen(II) oxide acts as the nitrosation agent. The procedure for the synthesis of [Ru(NO)(NH3)5]Cl3 · H2O
(yield 75–80%), the main nitrosation product of [Ru(NH3)6]2+, has been optimized. Thermolysis of
[Ru(NO)(NH3)5]Cl3 · H2O in a helium atmosphere has been studied; the intermediates have been identified.
One of these products is polyamidodichloronitrosoruthenium(II) whose subsequent decomposition gives an
equimolar mixture of ruthenium metal and dioxide. The structure of trans-[RuNO(NH3)4Cl]Cl2, formed in the
second stage of thermolysis and as a by-product in the nitrosation of [Ru(NH3)6]Cl2, has been determined by
X-ray diffraction.
DOI: 10.1134/S0036023607010123
The increased attention of researchers to nitroso directly from RuCl3, which is the most readily available
compounds of transition metals exhibited in recent
years is due to two discoveries made in the 1990s. The
first one is participation of nitrogen(II) oxide and com-
pounds containing it in physiological processes, and the
second one is the ability of nitroso complexes to
undergo a reversible photoinduced transition to a long-
lived metastable state. Of particular interest are ruthe-
nium ammine nitroso complexes as the most stable and
the least toxic. These compounds are successfully used
as biologically active agents [1, 2], to study photochem-
ical transformations [3–5], and in the synthesis of poly-
functional photomagnetic materials [6].
commercial chemical, has been described [14], but the
yield of the complex was only 47%. It has been stated
[11, 15, 16] that the required ruthenium nitroso pen-
taammine complex can be obtained by nitrosation of
ruthenium(II) hexaammine to reduce the number of
required operations; however, no detailed procedures or
product yields were reported.
The purpose of this work is to study nitrosation of
[Ru(NH3)6]Cl2 to optimize the method for the synthesis
of the ruthenium(II) pentaammine nitroso complex and
to investigate the physicochemical properties of the
products formed in this reaction.
The ruthenium nitroso pentaammine complex
[Ru(NO)(NH [RuNO(NH3)5]Cl3 · H2O is characterized
by one of the highest temperatures of thermal deacti-
vation of the photoinduced metastable state (260 K)
[3, 4]. The synthesis of this compound is faced with
certain difficulties. Not more than four ammonia mol-
ecules can be introduced into the inner sphere of
ruthenium in the reactions of ruthenium nitroso chlo-
rides with a solution of ammonia [7] or with liquid
ammonia [8]. The major product formed in these reac-
tions is trans-[Ru(NO)(NH3)4OH]Cl2. The methods for
the synthesis of pentaammine(nitroso)ruthenium
known to date are reduced to nitrosation of ruthe-
nium(III) pentaammines [9, 10] or hexaammine [11].
The starting ammine complexes are prepared in several
stages from industrial ruthenium trichloride; as a rule,
the first stage yields hexaammineruthenium(II) dichlo-
ride [10, 12, 13]. The synthesis of [Ru(NH3)5Cl]Cl2
EXPERIMENTAL
A solution of RuCl3 in HCl prepared from high-
purity grade RuCl3 (46.51% Ru) as described previ-
ously [17] was used. Hexaammineruthenium(II) dichlo-
ride [Ru(NH3)6]Cl2 was obtained in 70—80% yield by a
procedure described previously [15]. The other reagents
were commercial chemicals, of at least chemically pure
grade (Russian state standard).
The IR spectra of polycrystalline samples as mineral
and fluorinated oil mulls or KBr pellets were recorded
on Specord IR-75 and Scimitar FTS 2000 spectropho-
tometers in the range 3800–400 cm–1.
Thermogravimetric analysis was carried out on a
Q-1000 instrument in a helium atmosphere. A ~150-mg
sample of the compound was placed in a quartz cruci-
ble; the heating rate was 8 K/min.
62

STUDY OF NITROSATION OF HEXAAMMINERUTHENIUM(II)
63
Table 1. Effect of sodium nitrite concentration and hydrochlo-
X-ray diffraction analysis of ground crystals was car-
ried out on a DRON UM1 diffractometer (R = 192 mm,
CuKα radiation, Ni filter, scintillation detector with
amplitude discrimination). The samples were applied
as thin layers on the smooth side of a standard quartz
cell.
The unit cell parameters and the experimental inten-
sities for solution of the crystal structure of
trans-[RuNO(NH3)4Cl]Cl2 were measured at room tem-
perature on a CAD4 four-circle automated diffractome-
ter (MoKα radiation, graphite monochromator). The
structure was solved by the standard heavy-atom
method and refined in the anisotropic–isotropic (for H)
approximation; hydrogen atoms were specified geo-
metrically. All calculations were carried out by the
SHELX97 program package [18].
Nitrosation in acidic medium. The nitrosation proce-
dure was as follows. A calculated amount of sodium nitrite
(Table 1) was added to [Ru(NH3)6]Cl2 (~0.6 g, ~2 × 10–3 mol),
and the resulting mixture was dissolved in distilled
water. Then the required volume of 1 M HCl was added
dropwise to the magnetically stirred solution. The over-
all volume of the reaction mixture was 15–17 mL.
Within 5–10 min after the addition of HCl, the reaction
mixture was concentrated on a water bath to the begin-
ning of crystallization (2–3 mL) and cooled. The product
was collected on a glass filter and washed with a water–
ethanol mixture (~1 : 1) and acetone.
The resulting product was dissolved in a minimum
amount of 1 M HCl (~10 mL). The insoluble fraction
(fraction 1, [Ru(NH3)5Cl]Cl2 + [Ru(NO)(NH3)4Cl]Cl2)
was collected on a glass filter, washed with ethanol and
acetone, dried in air, and weighed.
ric acid on the ruthenium recovery to the solid phase (c
=
Ru
–3
–3
1.7 × 10 to 2.1 × 10 mol/l)
Yield, %
2nd
The molar ratio
Entry
1st
Ru : NaNO2 : HCl
total
fraction fraction
1
2
1.0 : 1.0 : 3.0
1.0 : 1.0 : 4.0
1.0 : 1.0 : 5.0
1.0 : 1.3 : 3.9
1.0 : 1.3 : 5.2
1.0 : 1.3 : 6.5
1.0 : 1.3 : 9.75
1.0 : 1.5 : 4.5
1.0 : 1.5 : 6.0
1.0 : 1.5 : 7.5
1.0 : 1.5 : 4.5
1.0 : 3.0 : 4.5
13.4
14.1
22.2
6.6
77.3
74.0
74.6
73.6
78.4
80.6
79.5
77.0
79.5
81.9
68.9
39.8
90.7
88.1
96.8
80.2
84.8
86.7
87.6
83.1
85.5
87.6
86.8
84.4
3
4
5
6.4
6
6.1
7
8.1
8
6.1
9
6.0
10
11*
12*
5.7
17.9
44.6
* The experiments were carried out at elevated temperature
(~95°C).
by adding conc. HCl (~10 mL) followed by heating for
2–3 h. The yellow-orange precipitate was filtered off
and washed with a water–ethanol mixture (~1 : 1) and
acetone. The yield of [Ru(NO)(NH3)4Cl]Cl2 was up to
~20%.
The complex [Ru(NO)(NH3)5](SO4)(S2O8)0.5 was
treated with conc. HCl (~10 mL) with heating on a
water bath for 20–30 min. The reaction mixture was
cooled to ~5°ë and the resulting precipitate of
[Ru(NO)(NH3)5]Cl3 · H2O was collected on a filter and
washed with a water–ethanol mixture (~1 : 1) and acetone.
The complex [Ru(NO)(NH3)5]Cl3 · H2O was puri-
fied by reprecipitation from a saturated aqueous
solution by conc. HCl. The yield of purified
[Ru(NO)(NH3)5]Cl3 · H2O was ~75% based on RuCl3.
A double volume of ethanol was added to the
mother liquor and the reprecipitated apricot-colored
complex (fraction 2) was separated on a glass filter. The
precipitate was washed with ethanol and acetone, dried
in air, and weighed.
Nitrosation in an alkaline ammonia medium. A
solution of [Ru(NH3)6]Cl2 in ammonia was prepared
by a known procedure [15] by the reaction of RuCl3
(~4 × 10–3 mol) with aqueous NH3 and Zn metal in the
presence of NH4Cl. The solution was filtered, conc.
NH3 (~20 mL) was added (to pH 10.5–11), and ammo-
nium peroxodisulfate (~4.6 g, 2 × 10−2 mol) was added
in small portions under magnetic stirring. During the
addition, the solution warmed up and changed color
from greenish-yellow to red-orange. At the end of
the reaction, acrid odor of nitrogen oxides was
clearly perceived together with the strong smell of
ammonia. The resulting orange precipitate of
[Ru(NO)(NH3)5](SO4)(S2O8)0.5 was collected on a filter and
washed with 1–2 mL of conc. NH3 and 1–2 mL of H2O.
RESULTS AND DISCUSSION
Nitrosation in acidic medium. The introduction of
a nitroso group by means of NaNO2 in HCl is widely
used to prepare ruthenium nitroso chloro complexes in
high yields. The key mechanistic features of this pro-
cess were described in detail [17]. The results of
hexaammineruthenium(II) nitrosation experiments,
which we carried out at different reactant ratios, are
summarized in Table 1. During nitrosation, some
ruthenium separates as a poorly soluble yellow pre-
cipitate that remains on the filter after reprecipitation
(fraction 1). According to IR spectroscopy and powder
The minor amount of ruthenium left in the mother liquor
can be isolated as the trans-tetrammine(chloro)nitrosoru-
thenium dichloride [Ru(NO)(NH3)4Cl]Cl2. This was done
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 1 2007

64
IL’IN et al.
[Ru(NO)(NH3) ]3+ + HNO2
X-ray diffraction, fraction 1 is either a mixture of
[Ru(NH3)5Cl]Cl2 (major component) and trans-
[Ru(NO)(NH3)4Cl]Cl2 (when nitrosation is carried
out at room temperature) or only trans-
[Ru(NO)(NH3)4Cl]Cl2 (when nitrosation is carried out
at elevated temperature).
5
trans-[Ru(NO)(NH3) ]3+
(11)
5
+ N2↑ + H2O,
trans-[Ru(NO)(NH3) (H2O)]3+ + Cl–
4
The data of Table 1 demonstrate that, even at a
[Ru(NH3)6]Cl2 : NaNO2 : HCl ratio of 1 : 1 : 3 (entry 1),
the yield of pure pentaammine(nitroso)ruthenium
(fraction 2) is more than 75%. An increase in the
NaNO2 or HCl concentration hardly affects the yield of
fraction 2 and slightly increases the proportion of trans-
[Ru(NO)(NH3)4Cl]Cl2 in fraction 1. A temperature rise
results in almost quantitative nitrosation of ruthenium
but markedly decreases the yield of the target complex
(entries 11, 12). Our experiments substantiate the con-
clusion that the formation of the pentaammine nitroso
complex under these conditions can basically be
described by the following equation:
(12)
(13)
trans-[Ru(NO)(NH3) Cl]2+ + H2O,
4
trans-[Ru(NO)(NH3) Cl]2+ + 2Cl–
4
trans-[Ru(NO)(NH3)4Cl]Cl2↓.
In acidic medium, nitrous acid formed from the nitrite
ion (reaction 1) acts as an oxidant (HNO2 + H+ + e
NO + H2O, E0 = 0.99 Ç, [21]); redox reaction (2) is sin-
gle-electron; therefore, no kinetic hindrance occurs in
this reaction. The standard electrode potential for
[Ru(NH3)6]3+ + e
25°C [22].
[Ru(NH3)6]2+ is ~ –0.05 V at
[Ru(NH3)6]Cl2 + NaNO2 + 3HCl
[RuNO(NH3)5]Cl3 · H2O + NaCl + NH4Cl,
In addition, at elevated temperature (heating in a
water bath) HNO2 disproportionates (reaction (3)) to
give an additional amount of NO. Nitrous acid is also
consumed in comproportionation with the ammonium
ion present in the solution (reaction(4)).
however, it is complicated by a number of side reac-
tions that decrease the yield of this complex.
On the basis of analysis of the data on nitrosation of
ruthenium chloro complexes [17] resorting to the published
data [11, 19, 20] and relying on our results (Table 1), one
can propose the following set of processes taking place
in HCl solutions containing the [Ru(NH3)6]2+ complex
cation and the nitrite ion:
In acidified aqueous solutions, preactivation of the
[Ru(NH3)6]2+ cation (reaction (5)) (k298 = (1.24 0.03)
× 10−3 L mol–1 s–1 [22]) followed by oxidation by
nitrous acid ([Ru(NH3)5(H2O)]3+
+
e
[Ru(NH3)5(H2O)]2+, E0 ~ –0.07 V [22]) may occur.
H+ + NO–2
HNO2,
[Ru(NH3) ]3+
(1)
The mechanism of nitrosation of the [Ru(NH3)6]3+
ion with nitrogen(II) oxide in an acidified aqueous solu-
tion has been studied [11]. It was found that the reaction
is bimolecular, does not require preactivation of the
ammine complex, and gives the pentaam-
mine(nitroso)ruthenium cation [Ru(NO)(NH3)5]3+
(reaction(7)). The same complex may form upon the
displacement of coordinated water molecules in the
aqua complex [Ru(NH3)5(H2O)]3+ by nitrogen(II) oxide
(reaction (8)), as in the case of Ru(III) aqua chloro com-
plexes [17].
[Ru(NH3) ]2+ + HNO2 + H+
6
6
(2)
+ NO + H2O,
~90°C
3HNO2
HNO3 + 2NO + H2O,
(3)
(4)
NH+4 + HNO2
N2↑ + 2H2O + H+,
~90°C
[Ru(NH3) ]2+ + H2O + H+
6
(5)
(6)
(7)
[Ru(NH3) (H2O)]2+ + NH4+,
5
The formation of fraction 1 components is due to
the following reactions. In hydrochloric acid solutions
containing [Ru(NH3)5(H2O)]3+, the coordinated water
molecules are replaced by chloride ions (reaction 9, K ~
70−240 L/mol [22, 23]), the resulting [Ru(NH3)5Cl]2+ cat-
ion being precipitated as poorly soluble [Ru(NH3)5Cl]Cl2
(10). The trans-tetraammine(chloro)nitrosoruthenium cat-
ion is formed upon oxidation of the coordinated ammonia
molecules present in the [Ru(NO)(NH3)5]3+ cation by
nitrous acid (reaction 11) with subsequent displacement of
the coordinated water molecules by chloride ions (reac-
tion 12, K ~ 170 L/mol) [24]. Its chloride salt is also
poorly soluble [19], which ensures a shift of equilib-
[Ru(NH3) (H2O)]2+ + HNO2 + H+
5
[Ru(NH3) (H2O)]3+ + NO + H2O,
5
[Ru(NH3) ]3+ + NO + H+
6
[Ru(NO)(NH3) ]3+ + NH4+,
5
[Ru(NH3)5(H2O)]3+ +NO
[Ru(NH3)5(H2O)]3+ + Cl–
[Ru(NH3)5Cl]2+ + 2Cl–
[Ru(NO)(NH3)5]3+ +H2O, (8)
[Ru(NH3)5Cl]2+ + H2O, (9)
[Ru(NH3)5Cl]Cl2↓, (10)
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STUDY OF NITROSATION OF HEXAAMMINERUTHENIUM(II)
65
rium (12) and almost quantitative precipitation of direct oxidation of coordinated ammonia molecules to
trans-[Ru(NO)(NH3)4Cl]Cl2 (13).
give nitroso complexes.
The NO molecules formed react with hexaam-
mineruthenium(III) cation
A temperature rise entails a decrease in the yield of
the target [Ru(NO)(NH3)5]Cl3 · H2O (Table 1, entry
11), and only trans-[Ru(NO)(NH3)4Cl]Cl2 is formed as
the by-product, its yield increasing to ~45% upon an
increase in the nitrite ion concentration (Table 1, entry
12). Thus, at room temperature fraction 1 is formed via
processes (9), (10) (mainly), and (11)–(13), while tem-
perature rise results in quantitative nitrosation and in a
noticeable relative increase in the rates of processes
(11) and (12).
By varying the acidity, the nitrite ion concentration,
and nitrosation temperature, we selected conditions for
the preparation of the pentammine nitroso complex
[Ru(NO)(NH3)5]Cl3 · H2O (fraction 2) in the highest
yield (82%, Table 1, entry 10). Nitrosation of
[Ru(NH3)6]Cl2 by sodium nitrite in acidic medium
should be carried out at room temperature and at the
molar ratio Ru : NaNO2 : HCl = 1.0 : 1.5 : 7.5.
[Ru(NH3)6]3+ + NO
[Ru(NO)(NH3)5]3+ + NH3.
The resulting [Ru(NO)(NH3)5]3+ is eliminated from
the reaction solution as a poorly soluble double salt [9]:
[Ru(NO)(NH3)5]3+ + 1/2 S2O82– + SO24–
[Ru(NO)(NH3)5](SO4)(S2O8)0.5↓.
On treatment with concentrated hydrochloric acid,
the peroxodisulfate ion is reduced
[Ru(NO)(NH3)5](SO4)(S2O8)0.5 + 4HCl + H2O
[Ru(NO)(NH3)5]Cl3 · H2O + 1/2Cl2↑ + 2H2SO4.
According to IR spectroscopy, the precipitate
obtained after treatment with HCl contains, together
with pentaamminenitrosoruthenium, a minor amount of
sulfate ions and trans-[Ru(NO)(NH3)4Cl]Cl2.
Nitrosation in an alkaline ammonia medium.
When [Ru(NH3)6]Cl2 is prepared by the reported proce-
dure [15], up to 30% of ruthenium added as the trichlo-
ride remains in the reaction solution due to the solubil-
ity of the hexaammine complex. In order to increase the
yield of the target complex [Ru(NO)(NH3)5]Cl3 · H2O
based on commercial ruthenium trichloride, we
decided to perform the nitrosation of ruthenium
ammine complexes in alkaline ammonia medium with-
out intermediate isolation of solid hexaammine.
It was found experimentally that nitrosation of ammo-
nium peroxodisulfate takes place within pH 10.5–11 in
the presence of aqueous ammonia. The reaction carried
out at pH 8–10 or above 11 yields black colloid solu-
tions, while the yield of the target complex decreases
appreciably, in some cases, down to 0%.
Complexes of the nitrosotetraammine series
result from the following side processes. In alkaline
medium, the coordinated NH3 molecules in the
[Ru(NO)(NH3)5]3+ cation are replaced by hydroxo
groups [9, 22]:
[Ru(NO)(NH3) ]3+ + OH–
5
(14)
[Ru(NO)(NH3) OH]2+ + NH3.
4
On heating of [Ru(NO)(NH3)4OH]2+ with concen-
trated HCl, the coordinated hydroxy group is proto-
nated (K ~ 103 L/mol [25]):
[Ru(NO)(NH3)4OH]2+ + H+
[Ru(NO)(NH3)4(H2O)]3+,
the coordinated water molecule in the aqua complex
The results of nitrosation of [Ru(NH3)6]2+ with [Ru(NO)(NH3)4(H2O)]3+ is replaced by the chloride
ammonium peroxodisulfate in the absence of free ion, and poorly soluble [Ru(NO)(NH3)4Cl]Cl2 precipi-
ammonia (pH was brought to 10.5–11 by adding aque-
ous NaOH) were also unsatisfactory.
The experimental data and the presence of nitrogen
oxides in ammonia solutions detected by smell suggest
the following process scheme.
tates (reactions (12) and (13)).
The main nitrosation product was purified by repre-
cipitation by concentrated HCl. The complex obtained
in 75% yield was pure [Ru(NO)(NH3)5]Cl3 · H2O.
Physicochemical studies of [Ru(NO)(NH3)5]Cl3 ·
H2O. IR spectra of the isolated [Ru(NO)(NH3)5]Cl3 · H2O
samples coincided in band positions and intensities
with the spectrum reported in the literature [26]; the
X-ray diffraction patterns were completely indexed based
on the reported data from a single crystal study [27].
The peroxodisulfate ion oxidizes the hexaam-
mineruthenium(II) cation:
2[Ru(NH3)6]2+ + S2O82–
2[Ru(NH3)6]3+ + 2SO42– .
In the presence of ruthenium ammine complexes,
ammonia molecules are oxidized in the reaction solu-
tion at pH 10.5–11 to nitrogen(II) oxide [9]:
The thermolysis of [Ru(NO)(NH3)5]Cl3 · H2O was
studied in a helium atmosphere. The thermogram (Fig. 1)
is generally in good agreement with that reported pre-
viously [28] for thermolysis of this compound in air.
The first two endotherms are observed in a helium
atmosphere at somewhat lower temperatures than in air
(by 20°ë and 15°ë, respectively) and also correspond
[Ru(NH3) ]
12NH3 + 2H2O + 5S2O82–
2NO
x
+ 10SO24– + 10NH+4 .
The unsuccessful nitrosation experiments without
addition of aqueous ammonia confirm the absence of to the removal of a water molecule of crystallization
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 1 2007

66
IL’IN et al.
m, %
TG
100
94.8%
89.7%
80
60
40
20
DTG
DTA
34.4%
226°ë
111°ë
401°ë
367°ë
330°ë
0
100
200
300
400
500
T, °C
Fig. 1. Thermoanalytical curves of [Ru(NO)(NH ) ]Cl · H O.
3 5
3
2
and one ammonia molecule (calculated, 5.3 + 5.0%; spectrum of product 3 mainly correspond to those
found from the weight loss curve, 5.2 + 5.1%). We stud- reported previously [30] for mer-[Ru(NO)(NH3)2Cl3]
ied the intermediates obtained by heating of the initial
compound to 130 (1) and 270°ë (2) and subsequent cool-
ing to room temperature under helium. The removal of the
water molecule is reversible; on storage in air, the anhy-
drous product is again converted gradually into the crystal
hydrate. This is confirmed by X-ray diffraction and IR
spectroscopy; the stretching (3420 cm–1) and bending
(1625 cm–1) bands for the water molecule of crystalliza-
tion, which are absent from the IR spectrum of compound
1, appear again when the compound is stored in air.
obtained upon thermolysis of (NH4)2[RuNOCl5]. The loss
of mass with respect to the initial [Ru(NO)(NH3)5]Cl3 ·
H2O was 20.5% (calculated for [Ru(NO)(NH3)2Cl3],
20.3%).
The next stage is assumed, most reasonably, to
involve elimination of two more ammonia molecules to
give a rather stable ruthenium nitroso trichloride.
According to published data [8], this is formed from the
monohydrate at 360°ë and decomposes at 440°ë. How-
ever, apart from the bands for the coordinated nitroso
group (ν(NO) = 1889 cm–1, ν(Ru–NO) = 610 cm–1), the
IR spectrum of product 4 clearly contains bands that are
usually assigned to coordinated ammonia molecules
(ν(NH3) = 3287 and 3178 cm–1; δ(NH3) = 1613 and
The positions and the intensities of the IR bands of
product 2 fully coincide with reported data [26] for
trans-[Ru(NO)(NH3)4Cl]Cl2. The X-ray diffraction pat-
tern of the sample recrystallized from 0.1 M HCl coin-
cides with that of trans-[Ru(NO)(NH3)4Cl]Cl2 we
obtained in nitrosation experiments.
1292 cm–1, ρ(NH3) = 795 cm−1) and strong bands at
3233, 1508, 1068, and 670 cm–1. The theoretical weight
of the residue calculated for RuNOCl3 is 69.7% of the
initial complex; however, the weight of product 4 was
only 63.1%. This means that the fragment eliminated at
~370°ë is heavier than this was suggested. The calcula-
tion taking into account the retention of the ruthenium
charge shows that this fragment is NH4Cl (the calcu-
lated weight of the residue is 64%). Thus, the composi-
tion of product 4 is best described by the molecular for-
mula [Ru(NO)(NH2)Cl2]. Due to the requirement of
Further destruction of the complex occurs as three
poorly resolved stages with endothermic peaks at 330,
367, and 401°ë (in air, these temperatures are 310, 365,
and 425°ë [28, 29]). The first one, according to pub-
lished data [29], corresponds to the loss of two ammo-
nia molecules, while the last one was reported [28] to
reflect complete destruction of the complex (the
destruction products were not identified in the study
cited). We studied the products obtained by heating of
the complex to 325.5 (3), 369.5 (4), and 500°ë (5) fol- retaining the coordination number of six, which is most
lowed by slow cooling to room temperature in a helium typical of ruthenium nitroso complexes, polymeric
atmosphere. The X-ray diffraction pattern and the IR structure with two bridging ligands can be suggested
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 1 2007

STUDY OF NITROSATION OF HEXAAMMINERUTHENIUM(II)
67
Table 2. Crystal data and X-ray experiment details for
trans-[Ru(NO)(NH3)4Cl]Cl2
for this compound. According to published data [31], the
bridging amido group in the polymeric mercury amido
chloride is responsible of bands at 3200, 3175 cm–1
(ν(NH2)), 1530 cm–1 (δ(NH2)), and 1022, 688 cm–1
(ρ(NH2)), which is in satisfactory agreement with the IR
spectrum of complex 4. The following structure appears to
be the most likely: [Ru(NO)Cl(µ-NH2)(µ-Cl)]n.
Parameter
Temperature
Value
293(2) K
0.71073 Å
Wavelength
Space group
P2(1)
Complete destruction of the complex with removal
of the nitroso group starts at 375°ë (the peak is at
401°ë). According to X-ray diffraction, product 5 is a
mixture of ruthenium metal and dioxide. The weight of
the residue is 34.4%, which exactly coincides with the
value calculated for the equimolar mixture RuO2 + Ru
(34.4%). Note that ruthenium nitroso trichloride
decomposes under inert atmosphere at 440°ë to ruthe-
nium dioxide and trichloride [8]. Decomposition of
ruthenium trichloride into elements, i.e. the reduction
of Ru(III) with the chloride ion, occurs in the tempera-
ture range of 655–840°ë [32]. In all probability, under
our experimental conditions (T ~ 400°ë), chlorine is
removed as hydrogen chloride, and the last stage of
thermolysis can be described by the equation
Unit cell parameters
a = 6.7270(13) Å α = 90°
b = 10.444(2) Å β =100.49(3)°
c = 6.7394(13) Å γ = 90°
465.59(16) Å3
2
volume
Z
Density (calcd)
Absorption coefficient
F(000)
2.180 g/cm3
2.497 mm–1
300
θ range
3.08°–24.98°
Range of h, k, l
-6 ≤ h ≤ 7,
–12 ≤ k ≤ 12,
–6 ≤ l ≤ 7
2[Ru(NO)Cl(µ-NH2)(µ-Cl)]n
+ 2nN2 + 4nHCl.
nRu + nRuO2
The number of measured
reflections
1732
1624 [R(int) = 0.0821]
99.9 %
The chemistry of this stage is elimination of HCl
from polyamidodichloronitrosoruthenium(II) and
redox disproportionation of Ru2+ to Ru and Ru4+ and
comproportionation of N3+ and N3– to give N2.
The number of independent
reflections
The data collection com-
pleteness for θ = 24.98°
Crystal structure of trans-[Ru(NO)(NH3)4Cl]Cl2.
The structure of the tetraammine complex formed in
the second stage of thermolysis [Ru(NO)(NH3)5]Cl3 ·
H2O and as the main impurity during nitrosation of
[Ru(NH3)6]Cl2 was determined by X-ray diffraction.
The crystal data and X-ray diffraction experiment
details are summarized in Table 2, and selected inter-
atomic distances and bond angles in the complex cat-
ion trans-[Ru(NO)(NH3)4Cl]2+ are in Table 3. The struc-
ture of the complex cation with atom numbering and
ellipsoids of thermal vibrations is shown in Fig. 2.
Refinement method
full-matrix least-squares on F2
1624/1/95
S on F2
0.981
R [I > 2σ(I)]
R (all data)
R1 = 0.0569, wR2 = 0.1430
R1 = 0.0747, wR2 = 0.1565
–0.1(2)
Absolute structure parame-
ter
Max. and min. of the resid-
ual electron density
1.402 and –0.708 e/Å3
The central Ru atom has a somewhat distorted octa-
hedral environment formed by the chlorine atom and
Table 3. Interatomic distances and angles in trans-[Ru(NO)(NH3)4Cl]Cl2
Distance
Ru–N
d, Å
Angle
NRuN(1)
NRuN(2)
NRuN(3)
NRuN(4)
N(1)RuN(2)
N(1)RuN(3)
N(1)RuN(4)
N(2)RuN(3)
ω, deg
95.7(17)
91.1(5)
92.3(5)
88.8(18)
92.9(9)
91.1(10)
175.5(4)
174.5(9)
Angle
ω, deg
1.799(12)
2.15(2)
N(2)RuN(4)
N(3)RuN(4)
NRuCl(1)
N(1)RuCl(1)
N(2)RuCl(1)
N(3)RuCl(1)
N(4)RuCl(1)
ONRu
86.6(10)
89.2(10)
177.9(15)
86.4(6)
88.6(3)
87.9(3)
Ru–N(1)
Ru–N(2)
Ru–N(3)
Ru–N(4)
Ru–Cl(1)
N–O
2.112(9)
2.093(9)
2.039(16)
2.376(3)
1.026(12)
89.1(8)
176(6)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 1 2007

68
IL’IN et al.
Table 4. Atomic coordinates and isotropic displacement parameters (Å2) for trans-[Ru(NO)(NH3)4Cl]Cl2
Atom
Ru
x
y
z
Ueq
Atom
O
x
y
z
Ueq
0.26585(12) 0.2203
0.76603(12) 0.0315(3)
–0.0616(13) 0.223(4)
0.4378(14) 0.051(2)
Cl(1) 0.5417(4)
0.2205(15) 1.0421(4)
0.0470(7) N(1) 0.280(3)
0.015(2)
N(2) 0.4763(15) 0.229(3)
N(3) 0.0724(14) 0.226(3)
0.784(2)
0.035(5)
Cl(2) –0.2224(17) 0.4603(7) –0.2731(14) 0.051(3)
0.5691(15) 0.044(3)
0.9765(15) 0.045(3)
0.4155(15) 0.766(3) 0.051(7)
Cl(3) 0.2264(15) 0.4605(7)
0.2794(14) 0.047(2)
0.5564(18) 0.044(4)
N
0.0579(18) 0.226(5)
N(4) 0.273(4)
five nitrogen atoms belonging to four ammonia mole- toward the nitroso group. These values are quite consis-
cules and the nitroso group. The geometric characteris- tent with published data for the known ruthenium
ammine nitroso complexes [2, 27, 35–39]. The atom
coordinates and isotropic parameters of atom displace-
ments are given in Table 4.
tics of the Cl–Ru–NO fragment are usual for ruthenium
complexes containing a coordinated chloride ion in the
trans position to the nitroso group [33, 34]. The bond
angles at the Ru atom deviate by 5.7° from 90°. The
Ru–N(NH3) distances are in the range of 2.04–2.15 Å
(average 2.098 Å), the ruthenium atom deviates from
the root-mean-square equatorial plane N4 by 0.075 Å
The structure projected along z direction is shown in
Fig. 3. The unit cell contains two crystallographically
independent chloride anions, which are connected to
the [Ru(NO)(NH3)4Cl]2+ complex cations by N–H···Cl
type hydrogen bonds (N–Cl, 3.21–3.49 Å). The shortest
distances between the central Ru atom and the chloride
anion vary from 4.10 to 4.42 Å. The shortest Ru···Ru
distance in the structure is 6.597 Å. The scheme of
hydrogen bonds involving ammine groups of the com-
plex is shown in Fig. 3 by dashed lines.
O
N
Thus, the complex [Ru(NO)(NH3)5]Cl3 · H2O can be
prepared in high yield by nitrosation of hexaammineru-
thenium(II) by both sodium nitrite in hydrochloric acid
and ammonium peroxodisulfate in alkaline ammonia
medium. In the former case, the highest yield is ~80%
based on ruthenium(II) hexaammine, while in the latter
case, this is ~75% based on the initial commercial
ruthenium trichloride. Thus, the latter method should
be preferred for large-scale preparation of the pentam-
mine nitroso complex. Both processes are complicated
by a number of side reactions that decrease the yield of
the target product and result in its contamination by
trans-tetrammine(chloro)nitrosoruthenium chloride,
whose structure was determined by X-ray diffraction.
N(4)
N(3)
Ru
N(2)
N(1)
Cl(1)
The thermal decomposition of [Ru(NO)(NH3)5]Cl3 ·
H2O goes through the formation of [Ru(NO)(NH3)5]Cl3,
trans-[Ru(NO)(NH3)4Cl]Cl2, mer-[Ru(NO)(NH3)2Cl3],
Fig. 2. Structure of the complex cation in
[Ru(NO)(NH ) Cl]Cl .
3 4
2
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STUDY OF NITROSATION OF HEXAAMMINERUTHENIUM(II)
69
y
0
z
x
Fig. 3. Packing of the structure and hydrogen bonds for trans-[Ru(NO)(NH ) Cl]Cl .
3 4
2
5. D. Schaniel, T. Woike, B. Delley, et al., Phys. Chem.
and [Ru(NO)Cl(µ-NH2)(µ-Cl)]n, and results in an
equimolar mixture of ruthenium metal and dioxide.
Chem. Phys. 7 (6), 1164 (2005).
6. L. A. Kusch, L. S. Plotnikova, Yu. N. Shvachko, et al.,
J. Phys. IV France 114, 459 (2004).
7. N. M. Sinitsyn, G. G. Novitskii, I. A. Khartonik, et al.,
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