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N. B. Morozova et al.
Experimental
the help of PIT-3 PID controller that allowed stabilizing
temperature at accuracy of 0.1 K for a long time. To carry
out calibration of the mass spectrometer, a published pro-
cedure involving evaporation of a known amount of the
substance was used [19]. The limiting error of pressure
measurement was 10%.
Synthesis and identification of Ru compounds
All beta-diketonate derivatives of ruthenium(III) were
synthesized according to original procedure developed by
us [18], starting from hexafluorocomplexes of ruthe-
nium(V) with following reduction up to Ru3? and inter-
action of aqua-complexes of Ru3? with beta-diketones at
heating and neutralization with KOH up to pH 5–6. 2,2,6,6-
Tetramethyl-4-fluoro-3,5-heptanedione has been kindly
given by Dr. J. Norman, Air Products Inc., USA. The
purification of Ru compounds was made by the method of
vacuum zone sublimation at p = 6 Pa and temperature
range 323–473 K depending on nature of ligand. Ru(ptac)3
was purified by the method of column chromatography on
SiO2, solvent was the mixture of benzol-hexane. The
substances were identified by the methods of mass spec-
trometry. The yield of compounds varied from 50 to 90%
(exclusion is Ru(tfhd)3, the yield of which was some per-
cents). Almost all compounds are red crystalline sub-
stances, Ru(ptac)3 is a red liquid.
The partial pressure of the vapor in Knudsen chamber
was calculated on the basis of the amount of evaporating
substance using equation [19]:
17:14WIiTi
Pi ¼
;
R
P
Seff M1=2
0t IiTi1=2dt
i
here W is the mass of the substance evaporated during the
whole experiments, Ii, Ti is measured intensity under the
established temperature mode, Seff = Ka is the product of
Klausing coefficient and the area of the effusion orifice, Ii
and Ti are the current intensity and temperature during the
establishment of isothermal regime. Experimental data are
presented as the equation lg (p, Torr) = A - B/(T, K),
where A ¼ DSoTꢀ=4:575 þ 2:88 b B = DHT*/4.575, T* is
mean temperature in the examined interval. For vapor
pressure researches the Ru compounds after two times of
sublimation in the vacuum were used.
The mass spectra of the gas-phase ruthenium(III) com-
plexes were recorded with a MI-1201 mass spectrometer
with the energy of ionizing electrons 35 eV. The source
temperature was 373 K for Ru(acac)3, 333 K for Ru(tfac)3,
381 K for Ru(thd)3, 388 K for Ru(tfhd)3, and 363 K for
Ru(ptac)3. The limiting resolution of MI-1201 mass spec-
trometer within the mass number range 1200 a.m.u was not
less than 1000 at a level of 10% of the peak height.
Results and discussion
Synthesis and identification of Ru compounds
The synthesis procedure developed by us for obtaining
beta-diketonate derivatives of ruthenium(III) and described
in detail in [18] gives the yield of compounds after puri-
fication within the range 65–90%.
Vapor pressure
The temperature dependencies of saturated vapor pressure
of the ruthenium(III) complexes were investigated by
means of Knudsen’s effusion method with mass spectro-
metric registration of gas phase composition using the
equipment described in detail in [19, 20]. Experiments
were performed using MI-1201 mass spectrometer men-
tioned above to analyze the composition of the gas phase.
Vapor source was placed directly before the entrance slit of
the ionizer—ion source of the mass spectrometer. A
cylindrical effusion chamber was made of molybdenum;
the dimensions of the internal cavity were: d = 7 mm,
h = 8 mm. Effusive hole was 0.3 mm in diameter; the
channel length was 0.2 mm. Weighed portions of 2–3 mg
of the compound were vaporized at different temperatures
within the required temperature range till complete disap-
pearance of the ion peaks corresponding to the molecular
forms of compound vapors. The temperature of effusion
chamber was changed stepwise at an arbitrary step. At each
established temperature, full mass spectrum was recorded.
The temperature of effusion chamber was maintained with
ꢀ
ꢁ
HL;KOH
Acid medium
½RuF6ꢂꢃꢃꢃꢃꢃꢃꢃꢃ! RuðH2OÞ 3ꢃꢃꢃꢃꢃꢃ! RuL3
ð1Þ
n
reducer
pH control
The data on identification of the compounds by means of
IR, NMR spectroscopy, and melting point determination,
were reported therein, too. When we use reaction (1) to
obtain a liquid complex Ru(ptac)3 and apply column
chromatography on SiO2 for subsequent purification, the
yield of the product decreases to 50%, which is likely to be
connected with partial decomposition of the compound on
the column during chromatography process. The Ru(tfhd)3
complex can be obtained according to reaction (1) only
with a small yield (several per cent). For clearing up the
reason of such low yield additional 1H NMR study of Htfhd
water–ethanol solutions in different mediums was carried
out. The research has shown that Htfhd destruction occurs
in acid medium. It was confirmed by appearance of addi-
tional shifts in 1H NMR spectra. However, practically
100% enol form of Htfhd solution is observed in alkaline
123
Morozova
