SYNTHESIS OF NITROGEN-CONTAINING METAL DITHIOPHOSPHATES
259
A calculated amount of Mannich bases (4 mol for
compound 1 and 2 mol for 2) was charged into the
reactor, to which the solvent (toluene) was also delivered.
The mixture was heated to 70–80°C and finely ground
P2S5 (or its suspension in toluene) was added in portions
under agitation. After the addition of P2S5 was complete,
the mixture was heated to the boiling point of the
solvent and the reaction continued until H2S evolution
ceased. The reaction was performed under a somewhat
reduced pressure (650–670 mm Hg); after the reaction
was complete, nitrogen was passed through the reaction
mass during 20–30 min. H2S released in the reaction
was passed through an aqueous solution of CdCl2 and
the amount of the CdS precipitate was used to determine
the amount of released H2S, with the reaction course
thus monitored. The analytical and physicochemical
characteristics of O,O1-dialkyl dithiophosphoric acids
are listed in Table 1.
Metal dithiophosphates. Taking into account
that O,O1-dialkyl dithiophosphoric acids are obtained
in nearly theoretical yield, we subjected the acid to
neutralization with a 10% NaOH solution directly in the
toluene solution. Because the neutralization reaction is
strongly exothermic, it is necessary to intensively cool
the reaction mass. The alkali was delivered at such a rate
that the reaction mass temperature did not rise to above
20–25°C; at higher temperatures, the acid is hydrolyzed.
The neutralization was performed to pH 6–7 or weakly
acid reaction, with the acidity of the medium determined
at regular intervals of time.
After the reaction was complete and the reaction
mixture was allowed to settle for 1.5–2.0 h, the organic
layer was separated and the aqueous layer containing
the sodium salt of an acid was delivered to the exchange
reaction.
The neutralization equivalent was also used to
determine the purity of O,O1-dialkyl dithiophosphoric
acids. It was found that the acids are characterized by
a rather high purity (99.0–99.5%).
The IR spectra of compounds 1 and 2 show at 3680–
3620 cm–1 a strong broad absorption band characteristic
of vibrations of OH groups; stretching vibrations
of the NH group appear at 3400–3380 cm–1, and its
deformation vibrations, at 1650–1600 cm–1. At 1225–
1250 cm–1, there are absorption bands corresponding to
skeletal vibrations of the tert-butyl group. The spectra
contain absorption bands characteristic of pendular
vibrations of the –CH2– group bonded in an aliphatic
chain to a nitrogen atom (–CH2–N*) at 735–730 cm–1,
and deformation vibrations of this group bonded to
a benzene ring at 1470–1460 cm–1.
1H NMR spectra of compounds 1 and 2 (CCl4, δ,
ppm): 6.95–6.98 (1H for shielded OH), 5.15 (1H for
alcoholic OH of compound 1) and 5.17 (2H for alcoholic
OH of compound 2), 3.2–3.4 (1H for NH group of
compound 1), 7.12–7.15 (3H for aromatic nucleus), and
1.70–1.72 (9H for tert-butyl group).
Metal salts and complexes of O,O1-dialkylsubstituted
dithiophosphoric acids were produced by the
exchange reaction of a sodium salt of a disubstituted
dithiophosphoric acid obtained in the preceding stage
with a 70–75% aqueous solution of the corresponding
metal chloride (at a 2 : 1 ratio). The reaction was
performed at room temperature under agitation. As
the metal chloride was supplied, salts and complexes
of disubstituted dithiophosphates precipitated from
solution. The precipitate was filtered off, washed with
water, and dried at 60–70°C in a vacuum.
When cobalt complexes are to be obtained, it is
preferable to perform the process in an alcoholic–
aqueous medium at a (10–15) : 1 alcohol : water volume
ratio.
The IR spectra of compounds 3 and 4 contain, in
addition to the bands observed for compounds 1 and
2, a band of stretching vibrations of the S–H group at
2550–2500 cm–1. In addition, there appear vibrations
characteristic of the following groups (cm–1): P–S (560–
530), P=S (679–650), and P–O–C aryl (1190–1160).
1H NMR spectra of compounds 3 and 4 (CCl4, δ,
ppm): 6.71–6.76 (2H for shielded OH), 3.05 (1H SH for
compound 3] and 3.10 [1H for compound (4)], 7.30–
7.35 (6H for aromatic nucleus), 1.60–1.63 (18H for
tert-butyl group), and 3.18–3.21 [2H for NH group of
compound (3)].
Analytical and physicochemical characteristics of
metal dithiophosphates are listed in Table 2.
An analysis of the IR spectra demonstrated that there
are no bands associated with vibrations characteristic of
the S–H group. Instead, the long-wavelength part of the
spectra contains absorption bands typical of vibrations
of the S–metal group. Stretching vibrations of S–Ni, S–
Co, and S–Cu appear as a rather strong absorption band
at 355–350, 325–320, and 330–325 cm–1, respectively.
Metal dithiophosphates as antioxidants for motor
oil. The compounds 3–Ni, 3–Co, 4–Ni, and 4–Zn
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 85 No. 2 2012
Markova
