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Dimanganese Heptoxide for the Selective Oxidation of Organic Substrates.

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Table I. Melting points and 'H- and "C-NMR data [a] for the compounds I ,
6, and 9- 12 [S].
M.p. [ "C] 324-325 324
"c-N M R
- [b]
1.89, 1.61
175.76 (s)
2.84, 2.17 2.56, 2.45
2.49, 2.40 2.55
173.87 (s)
124.16 (d)
122.21 (s)
51.77 (4)
51.81 (4)
C atoms
48.15 (s)
34.89 ( s )
31.93 (d)
30.89 (t)
26.83 (t)
51.70 (s)
3.46, 3.29
172.67 ( s )
136.45 ( s )
127.25 (d)
126.54 (d)
51.73 (q)
35.47 (t)
34.75 ( s ) 33.98 (t)
30.84 (d) 30.71 (t)
28.56 (t)
[a] 'H-NMR: 250 MHz, CDCI,; "C-NMR: 250 MHz, CDC13. [b] Not isolated.
pure, double tetraasterane 9 in only about 21% yield as
colorless needles (m.p. = 230-235 "C, methanol). Whereas 1
melts at very high temperature (Table 1) and is thermally
stable at temperatures over 300°C, heating of 9 in the injection part of a gas chromatograph at 270°C results in the
formation of two isomers; however, the structures of the
isomers have not yet been determined.
Received: February 2, 1987;
revised: March 6, 1987 [Z 2082 IE]
Publication delayed at authors' request
German version: Angew. Chem. 99 (1987) 1036
(I] S. Housmans, P. H. Honnef, Nachr. Chem. Tech. Lab. 32 (1984) 379.
121 H. G. Fritz, H.-M. Hutmacher, H. Musso, G. Ahlgren, B. Akermark, R.
Karlson, Chem. Ber. 109 (1976) 3781.
[3] G. Kaiser, H. Musso, Chem. Ber. 118 (1985) 2266.
[4] V. T. Hoffmann, Dissertation. Universitat Karlsruhe 1987.
77 (1955) 73; R. Askani,
151 W. J. Bailey, J. Rosenberg, J . Am. Chem. SOC.
Giessen, private communication.
161 X-ray structure analysis (Mo,,, A = 71.073 pm, graphite monochromator):
6 (M. Schmidt, Diplomarbeit. Universitat Karlsruhe 1985): C28H3ZOX
(496.56): p= 1.43 g cm-',
PI, Z = 2 ; a=719.7(4), b = 1115.2(6),
c = 1534.0(8) pm, n=98.8(4), /l=89.95, y = 107.9(4)", V= 1.15689 x 10'
pm': R=0.088 (R,%=0.074). 10 [4]: C28H,208-2CH30H (560.65);
p=1.32, C2/r, Z = 4 (-86°C); a=2058.9, b=1109.5, c=1834.6 pm,
p= 137.9", Y=2.8118 x lo9 pm', 5705 reflections, R = R , . =0.067.-Further details of the crystal structure investigation may be obtained from
the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D75 14 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository
number CSD-52466, the names of the authors, and the journal citation.
171 K. B Beder, M. Geisel, C . A. Grob, F. Kuhnen, Synfhesis 1973, 493.
[8] The spectra and elemental analyses of all other new compounds (41are in
accord with the structures given.
Dimanganese Heptoxide for the Selective Oxidation
of Organic Substrates
By Martin Tromel* and Manuel Russ
2 KMn0,
M n z 0 7 + 2 KHSO,
+ 2 H,SO,
+ H20
The stability of the solutions is probably due to the fact
that oxidizable impurities and traces of water, which cause
decomposition of Mn207, are removed during its formation. The deep red solutions contain approximately 100 mg
of Mn20, per mL, are practically completely stable at
room temperature, and, in contrast to undiluted Mn,O,,
can be handled safely. Our investigations so far have
shown that selective oxidation reactions are possible which
can be carried out simply with efficient thermal control.
The course of the reaction can be observed owing to the
intense color of the Mn,O, solution themselves. The reagent is especially suitable for use in aprotic medium.
Aliphatic and alicyclic C-C bonds, C-F and C-CI
bonds, and primary C-H bonds are not usually attacked at
room temperature; the same holds true for trimethylsilyl
Primary and secondary alcohols, such as 1 and 2-6 (Table I), respectively, are smoothly oxidized to carboxylic
acids and ketones, respectively. The reactions proceed in
aprotic medium at temperatures as low as - 7 0 T , thereby
making it possible to react thermally unstable and acidsensitive compounds such as 2 and 5 , respectively.
+ 2 Mn20,
, A
- 4 Mn02
- 3 HZ0
- 2 MnOt
3 O
- 3 H20
Table 1 Oxidation of selected secondary alcohols with Mn2O7.
Yield [%I [a]
cyclohexyl methyl ketone
[a] Yields of isolated product.
Mn,O, has been described as a dark red, volatile, unstable oil,['1which, apart from its strong oxidative ability, can
explode unexpectedly (for example, on contact with or[*] Prof. Dr. M. Tromel, DipLChem. M Russ
lnstitut fur Anorganische Chemie der Universitat
Niederurseler Hang, D-6000Frankfurt am Main 50 (FRG)
Angew. Chem lnt. Ed. Engl. 26 (1987) No. 10
ganic compounds or with dust from the air). There are apparently no reports on controlled oxidation reactions, although the compound has been known for over 125 years.
The Mn-0 bond lengthsJ2] which have been determined
indicate that Mn,O, should be a stronger
oxidizing agent than permanganate.
According to the most detailed investigation carried out
so far,[41solvents such as glacial acetic acid or CCl, undergo oxidation by Mnz07 even at low temperature. In
contrast, we have been able, by means of a special procedure, to obtain stable solutions of Mn,O, in CCl, or 1,1,2trifluoro-l,2,2-trichloroethane (Freon 113). Mn207, prepared by reaction of KMnO, with concentrated sulfuric
acid in the presence of the solvent according to the following reaction, is immediately taken up by the organic
Owing to the low temperature, the oxidation of primary
alcohols such as 1 can be carried out without accompanying acetalization. Ketones formed from secondary alcohols
can be easily separated by filtration from the Mn02 precipitate. In addition, the MnO, binds the water formed dur-
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ing the reaction. Oxidative C-C bond cleavage does not
occur at all, and tertiary C-H bonds such as those in 4 and
2 are not attacked. Phenyl and cyclopropyl groups such as
those in 5 and 2 , respectively, are stable under the reaction conditions, so that the reactions occur chemoselectively and afford high yields of products.
C C double bonds, such as those in 7-13 (Table 2), undergo oxidative cleavage already at - 80°C with formation
of the same products, albeit in high yield, as those formed
by ozonolysis followed by oxidative workup. These oxidations can also be carried out selectively in the presence of
aromatic systems.
employing extraction procedures. The resulting manganese
oxide, which is easily filtered off, binds water formed during the reaction, so that the organic product can be simply
isolated by evaporation of the solvent. In all reactions
leading to carboxylic acids, the products are bound to the
MnO, precipitate. They can be separated by reduction
with sulfite followed by extraction (see Experimental Procedure). The extraction is unnecessary if the M n 0 2 is immediately reduced in the reaction mixture by reaction with
a defined mixture of solid Na2S0,. 7 H 2 0 and Na2SZ05or,
more elegantly, with glyoxylic acid 17.
MnOz + (H0)2CH-COOH
+ 4 Mn207
The carboxylic acid is thereby released and taken u p by
the solvent. Glyoxylic acid and the manganese oxalate
formed are insoluble in the reaction medium, so that the
carboxylic acid may be obtained by filtration and evaporation of the solvent. At temperatures up to approximately
15"C, solvents such as acetone, methyl and ethyl acetate,
CCI4, Freon 113, and mixtures thereof, are suitable for the
oxidations with Mn207.
In carrying out these reactions, it is important that undiluted M n 2 0 pnot be allowed to collect (e.g., by evaporation of
the solvent), since, in the presence of flammable vapors, it
can explode. The reactions should therefore be carried out in
a stream of inert gas. Moreover, the spout of the dropping
funnel should be drawn out to a point and, during prolonged
addition, this should be washed with Freon 113 or CCl,. The
ground glass must not be greased.
+ Mn20:,
10 MnO,
3 H20. - 3 CO,
Table 2. Oxidation of selected alkenes with M n 2 0 7
Yield [Yo] [a]
adipic acid
pimelic acid
heptanoic acid
perfluorononoic acid
Experimental Procedure
[a] Yields of isolated product.
a-Methylene groups in ethers such as 14-16 react at
-45°C to form lactones or esters. Aromatic systems, for
example that of benzene, on the other hand, are attacked
at temperatures around - 20°C.
+ 2 Mn20,
- 4 Mn02
- 3 H
- 3
3 H,O
Oxidations with dimanganese heptoxide are, without exception, complete within a short period of time (seconds or
minutes) and are characterized by simple operational procedures and a smooth course of reaction. The reaction
mixtures can be worked up easily without the necessity of
- 8 Mn02
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Preparation of a Mn2O7 solufion: Powdered KMnO, (16.3 g) was added in
portions to a stirred mixture of concentrated H,SO, (24 mL) and dry CCI,
(100 mL) in a 250-mL flask kept at 20-25°C. The resulting reaction mixture
was stirred for several hours and the deep red organic phase was then decanted from the lower layer. The solution was stored in the refrigerator at
approximately 4°C.-The procedure can also be carried out using correspondingly larger amounts of reactants (up to approximately 5 0 g of
Determination of the confent: 0.3 m L of the solution was added to approximately 30 m L of water and the resulting mixture was stirred. After addition
of KI (1.5 g) and glacial acetic acid (p.a., 4 mL), the solution was titrated.
1 mL of 0.1 N thiosulfate solution corresponds to 2.2 mg of Mn20,.
Oxidations: The reactant (7.8 mmol) in a 1 : 1 mixture of CCI, and acetone
(both dry) or of methyl or ethyl acetate and Freon 113 was placed in a 100m L three-necked flask equipped with a thermometer, a stirrer, a dropping
funnel, and a n inlet for inert gas. 3 to 4 mL of the solvent was required per
100 mg of the stoichiometrically required Mn20, amount to ensure easy stirring. After cooling to the reaction temperature (alcohols,, -70°C; alkenes,
- 80°C; ethers, -45"C), M n 2 0 7in CCI, solution was added with stirring in
il moderate stream of nitrogen or argon at such a rate that the temperature
did not increase by more than 5°C. M n 2 0 , was thereby used in a small excess. The reaction mixture was then stirred for 5 min at the same temperature. Excess MnZ07can be removed by addition of several m L of isopropyl
Workup ofesiers and ketones: After warming to room temperature, the precipitate was filtered off under suction, the filtrate was concentrated, and the
crude product was purified by recrystallization or by distillation.
Workup of carboxylic acids (extractiue): The M n 0 2 precipitate obtained by
liltration or evaporation of the solvent was combined with 20-30 mL of water and the resulting slurry was treated with Na2S205(0.95 g per 1 g of
reacted Mn20,). 50% aqueous H2S04was then added to the stirred mixture
until full dissolution had occurred and the reaction mixture was strongly
acidic. The carboxylic acid was extracted and purified according to the
standard procedures.
Workup of carboxylic acids (wirhouf extraction): After completion of the reaction and warming of the reaction mixture to 0°C. 0.97 g of Na2S0,.7 H20,
0.76 g of Na2S20s(both powdered), and 1.25 mL of HCOOH (p.a.) per 1 g of
Mn2O7employed were added to the mixture, which was stirred at room temperature. After complete disappearance of the color (ca. 1 hj, the salts were
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Angew. Chem. In!. Ed. Engl. 26 (1987) No. I0
filtered o f f under suction, the filtrate was concentrated, and the residue was
purified by distillation or by crystallization.-Alternatively, after completion
of the reaction, 0.94 g of powdered glyoxylic acid monohydrate and 1.25 m L
of HCOOH (p.a.) were added per I g of reacted Mn207at 0°C. The reaction
mixture was then worked up as described above.
Received: March 30, 1987;
supplemented: July 10, 1987 [Z 2170/2171]
German version: Angew. Chem. 99 (1987) 1037
[I] H. Aschoff, Ann. Phys. Chem. 1 1 1 (1860) 217; J . Prakr. Chem. 81 (1860)
[2] M. Tromel, A d a CryslaNogr. Sect. 8 3 9 (1983) 664.
[3] A. Simon, R. Dronskowski, B. Krebs, B. Hettich, Angew. Chem. 99 (1987)
160: Angew. Chem. Inr. Ed. Engl. 26 (1987) 139.
[4] 0. Glemser, H. Schroder, Z . Anorg. ANg. Chem. 271 (1953) 293.
the First Telluride-Tellurolate Complex**
By Wolfgang Simon, AIfons Wilk. Bernt Krebs, and
Gerald Henkel*
Complexes having cubane-like M4X4 frameworks and
tetrahedral MX4 centers are of considerable interest, in
particular because of their widespread occurrence in ironsulfur proteins (see, e.g., Ref. 111). In addition to roughly 40
differently substituted sulfide-thiolate clusters of the type
[Fe4(p3-S)4(SR)4]2Q'3e(see, e.g., Ref. [2]), the ion [Fe4(p3Se)4(SePh)4]2Q,13.41the
first example of a species having a
selenide-selenolate ligand sphere has been reported. Tellurium-coordinated soluble cubane clusters, however, were
previously unknown.
In our attempts to prepare the first members of this new
class of compounds, we initially prepared the precursor 1,
which was reacted with NaHTe in acetonitrile to give the
complex salt 2, containing the cubane-like anion 3.I5]
MeCN 2
The X-ray crystal structure analysis@]revealed that crystals of 2 consist of E 4 N @cations, MeCN molecules, and
isolated anions 3. The arrangement of the cations and
MeCN molecules precludes unusually short intermolecular contacts between the anions of 2. The center of 3 (Fig.
1) contains the characteristic Fe,Te, cage with the cubanelike structure well known from iron-sulfide-thiolate chemistry. This cage consists of two interpenetrating distorted
tetrahedra of different size, the smaller one being defined
by Fe atoms and the larger one by Te atoms. They are arranged in such a way that the Te atoms are located above
the centers of the faces of the iron tetrahedron.
The Fe atoms complete their coordination by each
binding aotellurophenolateligand with a n average distance
of 2.598 A, thereby increasing their coordination number
to 4. This results in an Fe4Tes framework consisting of four
FeTe, tetrahedra sharing common edges in such a way that
three vertices always coincide. Very similarly constructed
Fe4Te8 units are present in the ternary solid-state compound Cs7Fe4Tes reported by Bronger et
The analo[*I Priv.-Doz. Dr. G. Henkel, DipLChem. W. Simon, A. Wilk,
Prof. Dr. B. Krebs
Anorganisch-chemisches Institut der Universitat
Wilhelm-Klemm-Strasse 8, D-4400 Miinster (FRG)
This work was supported by the Bundesminister fur Forschung und
Technologie under grant number 05339GAB/3, by the Minister fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen, and by the
Fonds der Chemischen Industrie.
Angew. Chem.
Ed. Engl. 26 (1987) No. I0
Fig. 1. Molecular structure of the anion 3 in crystals of 2 (hydrogen atoms
omitted). Large empty circles, tellurium; large solid circles, iron; - 120°C.
Important distances [A]: Fe,Tee, framework: Fel . . .Fe4 2.640(1), Fez.. . Fe3
2.624(2), Fel . . .Fe2 2.799(2), Fel . . . Fe3 2.781(2), Fe2. . . Fe4 2.825(2),
Fe3.. .Fe4 2.810(1); Fel-Te4 2.588(1), Fe2-Te3 2.564(1), Fe3-Te2 2.56%I),
Fe4-Tel 2.571(1); Fel-TeZ 2.646(1), Fel-Te3 2.627(1), Fe2-TeI 2.620(I), Fe2Te4 2.604( I), Fe3-Tel 2.631( I), Fe3-Te4 2.640( I), Fe4-Te2 2.598( I), Fe4-Te3
2.61111); Fe-Te,,;, : Fel-TeS 2.601(1), Fe2-Te6 2.594(2), Fe3-Te7 2.589(1),
Fe4-Te8 2.606(1); Angles I"]: Fe,Tea framework: Fe-Te-Fe 60.0( 1) to 60.5(1)
(average 60.2, 4 x ) and 64.3(1) to 66.2(1) (average 65.3, 8 x ) ; Te-Fe-Te
105.7(1) to 108.9(1) (average 106.8, S x ) and 116.7(1) to 119.1(1) (average
118.0, 4 x); Te,.,,-Fe-Te,,,
94.3(1) to 100.0(1) (average 96.5, 4 x ) and
108.0(1) to 118.1(1) (average 114.4, S x ) .
gies between soluble clusters and discrete structural units
in typical solids extend beyond mere topological relationships. They are also revealed in the oxidation state of iron,
which, in both the salt 2 and Cs7Fe4Te8,has an average
value of 2.25.
The magnetic properties of 2 in solution indicate the existence of antiferromagnetic coupling of the iron atoms.
Based o n the results of NMR spectroscopy,[51similar magnetic properties are expected as for the corresponding sulfur-containing trianions.''' The magnetic properties of crystalline 2 are still under investigation. Values for Cs7Fe4Te8
are not available.
The Fe4Te4 framework in 3 is significantly distorted
from the Td symmetry of a regular &B, cubane system towards a n idealized DZdsymmetry; in addition to four short
Fe-Te bonds, which correspond to a set of parallel edges
of a n undistorted cube and which are 2.512 A long on the
average, the cluster contains eight significantly longer distances with an average value of 2.622 A. With respect to
the 5 axis, which passes through the center of the edges
Fel-Fe4 and Fe2-Fe3, the Fe, tetrahedron is clearly
stretched (average edge lengths: 2 x 2.632, 4 x 2.804 A),
whereas the Te, tetrahedron is just as cleadly compressed
(average edge lengths: 4 x 4.169, 2 x 4.496 A). Both effects
are reflected in the observed compression of the overall
Fe,Te4 cubane unit, the distances Fel-Fe4 and Fe2-Fe3
average) being unusually short for mixed cubane
clusters and approaching the iron-ligand distances.
At first sight, these findings appear to violate an empirical rule formulated by Holm et a1.T) which-based on a
number of sulfide-thiolate complexes-establishes a relationship between the distortion of the cubane unit and the
average oxidation state of the iron atoms. In accordance
with this rule, the cubane unit should be stretched along
the 5 axis for an average oxidation state of +2.25. The
compression observed here, which is also present- albeit
to a smaller extent-in Cs7Fe,Te8, might be due to electronic factors caused by the specific influence of the tellurium ligands. However, in analyzing electronically induced
distortions in solids, one should note that these effects
overlap with the effects due to packing. Thus, it is also
possible that the molecular 5 axis of the thermodynami-
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oxidation, heptoxide, organiz, selective, dimanganese, substrate
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