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Inorganic Syntheses. Volume 33 - Coucouvanis D.

Coucouvanis D. Inorganic Syntheses. Volume 33 - University of Michigan, 2002. - 299 p.
Download (direct link): inorganiksintesis2002.djvu
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520(sh) (390), 428 (657)
a Per double cubane. ^Per single cubane.
A. MOLYBDENUM-IRON CLUSTER AQUA ION, [Mo3FeS4(H2O)10]4 + (Mo3Fe), IN
SOLUTION AND [Mo3FeS4(H2O)i0]
(6480)4 7H20 (Mo3Fepts)
I. Decaaquotrimolybdenum-iron-tetrasulfide, [84(20)]4+ (Mo3Fe), in
solution
[Mo3S4(H20)9]4+ + Fe + H20 - [Mo3FeS4(H2O)10]4+
23. Sulfur-Bridged Cubane Type Mixed-Metal Clusters
153
N2 gas
Figure 2. Apparatus for column chromatography under a dinitrogen
atmosphere.
Procedure2,3a
Iron wire (3.0 g, 54 mmol) is introduced into a conical flask containing
the aqua ion Mo3 (0.05 M per trimer in HC1 (2 M), 25 mL).7a During
stirring, the color of the solution changes from green to red-purple in a
few hours. After the remaining iron is removed, the solution is filtered
and diluted to 10 times its original volume with water, and the resultant
solution is absorbed on a Dowex 50W-X2 cation exchanger (diameter 2.2 cm,
length 80 cm). [Fe(H20)6]2+ is eluted with HC1 (0.5 M) and a red-purple
fraction containing Mo3Fe is obtained by elution with HC1 (1 M): yield
78% (based on Mo3). A green band of the unreacted starting material Mo3
(~10%) follows the red-purple band.
154
Solid-State Materials and Clusters
II. Decaaquotrimolybdemim-iron-tetrasuffide-tetrakis-/j-toluenesulfonate-
heptahydrate, | M 031; eS4 (112()) 101 (II3C ()114 S ( >3)47112
(Mo3Fepts)
Procedure
Method 1. In order to obtain crystals of Mo3Fepts, the solution of Mo3Fe
in HC1 (1 M) is absorbed on a short cation exchanger, Dowex 50W-X2
(diameter 2.2 cm, length 5 cm). The resin is washed with Hpts (0.1 M) to
remove chloride ion, and a red-purple solution is obtained by slow
elution with Hpts (4 M). The eluate from the column is stored in a
refrigerator (ca. - 5C). After one week black plate-shaped crystals
deposit, which are collected by filtration, washed with ethyl acetate,
and air-dried: yield 0.92 g (65% based on Mo3Fe in HC1 (1 M).
Anal. Calcd. for Mo3FeS8029C28H62 (MW = 1462.98): Mo, 19.67; Fe, 3.82;
C, 22.99; H, 4.27. Found: Mo, 19.56; Fe, 3.90; C, 22.92; H, 3.66.
Method 2. Iron powder (0.40 g, 7.2 mmol) is introduced into a conical
flask containing the aqua ion Mo3 (0.025 M per trimer in Hpts (4 M), 25
mL). The mixture is heated at above 90C for 1 h with stirring in a water
bath, and then brought to room temperature and filtered to remove the
remaining iron (~0.2 g) and white precipitates (mainly Fe(pts)2 n H20).
Hpts-H20 (3.0 g, 16 mmol) is added to the filtrate and kept in a
refrigerator (ca. - 10C) for 4 days. The black crystals obtained are
collected by filtreation, washed with ethyl acetate, and air-dried: yield
0.40 g (44% based on Mo3).
Properties3a
Solutions of Mo3Fe in acid are air-sensitive. Exposure to air gives back
the Mo3 cluster together with [Fe(H20)6]2+ after several hours [Eq. (1)]
Solid Mo3Fepts is more stable toward air oxidation and can be handled in
air for brief periods of time (i.e., weighing a sample).
[Mo3FeS4(H2O)10]4+ 'o, 211 4H20 -
[Mo3S4(H20)9]4+ + [Fe(H20)6]2+
(1)
The advantage of method 2 is that no column chromatography separation
is required. However, using this procedure Mo3Fepts is contaminated by a
few percent of the white iron salt of Fe(pts)2-"H20.
23. Sulfur-Bridged Cubane Type Mixed-Metal Clusters
155
B. MOLYBDENUM-COBALT CLUSTER AQUA ION,
[(H20)9Mo3S4CoCoS4Mo3(H20)9]s+ (-D), IN SOLUTION AND
[(H20)9M03S4CoCoS4Mo3(H20)9(CH3C6H4S03)s 18H20 (Mo3Co-Dpts)
I. Bisnonaaquotrimolybdenum-cobaU-tetrasulfide,
[(H20)9Mo3S4CoCoS4Mo3(H20)9]s+ (Mo3Co-D), in solution
2[Mo3S4(H20)9]4+ +2Co -" [(H20)9Mo3S4CoCoS4Mo3(H20)9]8+
Procedure10
Cobalt powder (0.20 g, 3.4 mmol) is introduced into a conical flask
containing the aqua ion Mo3 (0.05 M per trimer HC1 (2 M), 25 mL).7a The
color of the solution turns from green to brown within a couple of days.
After a week the solution is filtered and chromatographed through a Dowex
charged column (diameter 2.2 cm, length 80 cm). [(20)]2+ is eluted
with HC1 (0.5 M), the green aqua ion Mo3 (with HC1 (1 M), and the dark
brown -D [with HC1 (2 M); yield 45%].
Anal. Mo/Co = 3.06.
II. Bisnonaaquotrimolybdenum-cobalt-tetrasulfide-octakis-/?-
toluenesulfonate-octadecahydrate, [(H20)9Mo3S4CoCoS4Mo3(H20)9]
(CH3C6H4S03)s 18H20 (Mo3Co-Dpt)
Procedure
In order to obtain crystals of -Dpts the dark brown solution -D
is absorbed on a short cation exchanger, Dowex 50W-X2 (diameter 2.2 cm,
length
5 cm), and eluted with Hpts (4 M) The eluate from the column is kept in
a refrigerator (ca. - 5C). After one week black-brown crystals deposit,
which are collected by filtration, washed with ethyl acetate, and air-
dried: yield 0.13 g (15% based on -D in HC1 (1 M).
Anal. Calcd. for Mo6Co2S16O60C56H128 (MW = 2968.16): Mo, 19.39; Co, 3.97;
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