556
A. Srivastava et al. · Diarylthiourea Derivatives of Tungsten Carbonyl
Table 3. CO stretching frequencies of mixed ligand deriva-
tives.
Complex
ture was refluxed up to 4 h when a considerable amount
of crystals settled at the bottom of the flask. The solution
was cooled to r.t. and filtered. The crystalline solid was
v (CO) (cm−1
)
◦
[(dptu)(Ph3P)W(CO)4]
[(dottu)(Ph3P)W(CO)4]
[(dpttu)(Ph3P)W(CO) 4]
[(doatu)(Ph3P)W(CO)4]
1957 w, 1905 s, 1817 s, 1790 m
1962 w, 1910 s, 1830 s, 1793 m
1965 w, 1910 s, 1830 s, 1793 m
1963 w, 1907 s, 1822 s, 1800 m
washed with petroleum ether (40 – 60 C) and 2 – 3 times
with benzene to remove unreacted reactants. It was dried in
vacuo. [(PhNHCSNHPh)(C10H8N2)W(CO)3] (yield 1.03 g,
78.3%). C26H20N4O3SW (652 g mol−1): calcd. C 47.8;
H 3.0; N 8.5; S 4.9; found C 48.0; H 3.0; N 8.6; S 4.7.
[(dαntu)(Ph3P)W(CO)4]
[(dptu)(Ph3As)W(CO)4]
[(dottu)(Ph3As)W(CO)4]
[(dpttu)(Ph3As)W(CO)4]
1961 w, 1905 s, 1830 s, 1800 m
1955 w, 1902 s, 1815 s, 1788 m
1958 w, 1905 s, 1822 s, 1785 m
1958 w, 1900 s, 1818 s, 1785 m
Preparation of tetracarbonyl(sym-diphenylthiourea)-
(triphenylphosphine)tungsten(0)
[(doatu)(Ph3As)W(CO)4]
[(dαntu)(Ph3As)W(CO)4]
[(dptu)(2,2I -bipy)W(CO)3]
1960 w, 1902 s, 1820 s, 1792 m
1957 w, 1901 s, 1820 s, 1788 m
1890 s, 1781 s, 1746 s
Pentacarbonyl(triphenylphosphine)tungsten(0) (1.17 g,
2 mmol) and sym-diphenylthiourea (0.45 g; 2 mmol) were
refluxed in xylene (25 cm3) for 5 h. The solution was
[(dottu)(2,2I -bipy)W(CO)3] 1886 s, 1775 s, 1746 s
cooled to r.t. and a yellow-brown solid was recovered by [(dpttu)(2,2I -bipy)W(CO)3] 1892 s, 1790 s, 1743 s
evaporating the solvent under vacuo. The unreacted reac- [(doatu)(2,2I -bipy)W(CO)3] 1885 s, 1778 s, 1740 m
[(dαntu)(2,2I -bipy)W(CO)3] 1900 s, 1775 s, 1750 s
tants were removed by washing the residue 4 – 5 times with
petroleum ether (40 – 60 ◦C). The solid was dried in vacuo.
[(PhNHCSNHPh)(Ph3P)W(CO)4] (yield: 1.13 g, 72.0%).
C35H27N2O4PSW (786 g mol−1): calcd. C 53.4; H 3.4;
N 3.5; S 3.9; found C 53.1; H 3.3; N 3.6; S 3.8.
[(dptu)(o-phen)W(CO)3]
[(doatu)(o-phen)W(CO)3 ]
[(dpttu)(o-phen)W(CO)3 ]
[(doatu)(o-phen)W(CO)3 ]
[(dαntu)(o-phen)W(CO)3]
1897 s, 1785 s, 1742 s
1894 s, 1792 s, 1740 s
1893 s, 1800 s, 1755 s
1890 s, 1796 s, 1753 s
1900 s, 1796 s, 1753 m
Preparation of tetracarbonyl(sym-diphenyl-
thiourea)diiodotungsten(II)
The IR spectra of the complexes indicated that the
sym-diarylthiourea molecules are attached to the tung-
sten via the sulphur atom. A strong absorption of
the parent diarylthioureas at ∼ 1075 cm−1 is very
much weaker or even disappears on complex forma-
tion. This observation can be explained by the consid-
erable change in the nature of the N-C bond, as well
as C=S bond, on coordination of sym-diarylthioureas
through the sulphur atom. A lowering of ∼ 30 cm−1
observed for the band near ∼ 730 cm−1 may be at-
tributed to the reduced double bond character of the
C=S bond.
A hexane solution of iodine (0.10 g in 30 cm3) was added
dropwise to a solution of pentacarbonyl(sym-diphenylthio-
urea)tungsten(0) (0.22 g in 10 cm3 benzene) at r.t. with con-
stant stirring. The colour of the iodine solution disappeared
during the addition and an orange precipitate settled at the
bottom of the reaction flask. The supernatant liquid was de-
canted and the precipitate was washed repeatedly with hex-
ane to remove unreacted iodine. The solid was again dis-
solved in the minimum amount of benzene (5 cm3) and re-
precipitated by adding hexane (40 cm3). The precipitate was
dried in vacuo. [(PhNHCSNHPh)W(CO)4I2] (yield: 0.21 g,
68.0%). C17H12N2O4SI2W (778 g mol−1): calcd. C 26.2;
H 1.5; N 3.6; S 4.1; I 32.4; found C 26.3; H 1.6; N 3.6; S 4.2;
I 32.8.
Complexes of type [(L)W(CO)5] must have local
C4v symmetry due to which there should be three
IR active C-O stretching bands assigned to 2A1 + E
modes, but the IR spectra of the complexes exhib-
ited four C-O stretching bands in the ranges 2060–
Results and Discussion
Five sym-diarylthioureas (L) were found to react 2070, 1970– 1975, 1918– 1925, 1893– 1898 cm −1
with tungsten hexacarbonyl to give the correspond- (Table 2). Bands in the range 2060– 2070 cm−1 arise
ing pentacarbonyl derivatives, [(L)W(CO)5] (yield : from the A1 mode of the trans pair of carbonyl groups
78.6– 84.2%). Repeated attempts to achieve a second and bands in the range 1918– 1925 cm−1 may be
substitution by prolonged refluxing or ultra-violet ir- due to E mode whereas bands of the range 1893–
radiation were unsuccessful and not more than one 1898 cm−1 can be assigned to the A1 mode of cis-
CO group could be replaced. These derivatives were carbonyls. Bands due to B1 mode (1970– 1975 cm−1
)
yellowish-brown solids, insoluble in petroleum ether which are Raman active are also visible in the IR spec-
(all fractions) or hexane and dissolved in benzene, tra of all the complexes because the structure of the
dichloromethane, chloroform, acetone, tetrahydrofu- sym-diarylthiourea ligands interferes with the perfect
ran and dimethylformamide.
C4v symmetry. Assignments of all these bands have
Brought to you by | Tulane University
Authenticated
Download Date | 2/2/19 10:26 PM