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Computer-Controlled Precipitation of Metal Hydroxides and Hydrous OxidesЧPreparation of Manganese Dioxide Having Uniform Particle Sizes.

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1 shows two multiplets, 6= -272 (bridgehead P atoms)
and 6 = - 130, while the 'H(3'P)-NMR spectrum contains
two singlets at 6= 1.27 (4-tBu) and 1.74 (2,6-tBu) as well as
a multiplet at 6=7.0. These findings are consistent with
the results of an X-ray structure analysis (Fig. l).I5'
Eggenstein-Leopoldshafen2, on quoting the depository number CSD51 578, the names of the authors, and the full citation of the journal.
161 E. Niecke, R. Ruger, B. Krebs, Angew. Chem. 94 (1982) 553; Angew.
Chem. I n t . Ed. Engl. 21 (1982) 544.
[7] D. E. Pearson, M. G. Frazer, V. S. Frazer, L. C. Washburn, Synfhesis~
19 76, 621.
Computer-Controlled Precipitation of Metal
Hydroxides and Hydrous Oxides-Preparation of
Manganese Dioxide Having Uniform Particle
Sizes**
By Dieter H . Buss, Gottjiried Schaurnberg, and
Oskar Glemser*
Fig. I . ORTEP plot of the crystal structure of 1 (vibration ellipsoids at the
50% probability level). Bond lengths [pm] and bond angles ["I: PI-F2
222.3(4), PILP4 223.5(7), P2-P3 222.2(3), P2-P4 216.6(2), P3-P4 223.6(9), PI-C
189.2(8), p3-C 188.5(1); P2PlP4 58.1(1), PlP2P4 61.2(1), PlP2P3 80.9(1),
P3P2P4 61.3(1), P2P3P4 SS.I(l), P3P4P2 60.6(1), P3P4Pl 80.4(1), P2P4Pl
60.7(1), CPlP2 98.2(1), CPIP4 97.3(1), CP3P4 99.2(1), CP3P2 97.8(1). The
numbering of the P atoms is arbitrary.
The two 2,4,6-tri-tert-butylphenyl moieties in 1 are cis
oriented. The folding angle of the P4 bicycle, 95.5", is just
about the same as that in bis(trimethylsily1amino)bicyclotetraphosphane (95.2 which has been synthesized from
diphosphanes.[6' The P-P bonds in both compounds are
(with exception of the central bond) about the same length
as normal P-P single bonds (in 1 222.2-223.6 pm); only
the central P-P bond in 1 is slightly longer (216.6 pm) than
in the bis(trimethylsily1amino) derivative (213 pm).
O),
Experimen tal
All operations were carried out under argon. A solution of l-bromo-2,4,6tri-ferf-butylbenzene [7] (61.55 g, 189.3 mmol in ether (500 mL) was treated at
room temperature with 85 mL (212.6 mmol) of a 2.5 molar solution of nbutyllithium in n-hexane. The mixture was stirred for 3 h and then treated
with 12.4 g (100 mmol) of white phosphorus. After 10 min, the resulting red
solution began to boil and was then heated at the boiling point for a further
60 min. After 24 h, the mixture was hydrolyzed. A reddish-brown oil was obtained (72 g). from which an air-stable orange-red solid crystallized which
was collected on a frit and washed with acetone. After recrystallization from
benzene, 3 g of a coarsely crystalline mixture of 1 and 2 (ca. 3 : 1) was isolated. The crystals of 1 obtained by a second recrystallization were selected
for the X-ray structure analysis.
Received: July 16, 1985;
supplemented: Sectember 10, 1985 [Z 1391 IE]
German version: Angew. Chem. 97 (1985) 1050
[I] M. Baudler, Z. Chem. 24 (1984) 352.
[2] M. Baudler, Angew. Chem. 94 (1982) 520; Angew. Chem. Inr. Ed. Engl. 21
(1982) 492.
[3] P. Jutzi, T. Wippermann, J. Organomer. Chem. 287 (1985) CS.
[4] M. Yoshifuji, 1. Shima, N. Inamoto, K. Kirotsu, T. Higuchi, J. Am. Chem.
SOC.I03 (1981) 4587.
[S] 1 crystallizes monoclinically; space group P2,/n, II = 1677.2(4),
h= 1079.7(3), c=2071.5(3) pm,b=96.01(2)"; Z=4,pcal,= 1.09 glcm'). All
atoms occupy the general positions of the space group. The structure was
derived from 5516 independent reflections (4409 observed) via direct
methods and Fourier syntheses and refined to R=0.051. Further details
of the crystal structure investigation are available on request from the
Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-75 14
Angew. Chem. I n l . Ed. Engl. 24 (1985) No. I2
It is difficult to precipitate metal hydroxides and hydrous oxides"] that always have the same properties from
aqueous solution. Recently, we were able to obtain cobalt,
nickel, and manganese hydroxides, as well as their double
hydroxides with a l u m i n ~ m , [ ~by
- ~ ] computer-controlled
precipitation at a constant pH value. Their compositions,
structures, and discharge capacities could be well reproduced. We report here on the application of this technique
to the Guyard reaction,[51 the formation of manganese
dioxide from manganese([]) salts and potassium permanganate in acidic solution.
The precipitations were carried out at the potential that
is established at an electrographite electrode (measured as
U,,, versus a Ag/AgC1//3 M KCl reference electrode), for
a given pH value of the solution, after the manganese dioxide begins to precipitate and while a small excess of MnO?
is still visible. The excess or deficiency of MnO? ions is
controlled with this potential, which remains relatively stable (k 5 mv) during the course of the precipitation (hours).
The upper control limit is U,,,,,,
the lower, the approximately 20 mV more negative potential. Between these limits, nearly stoichiometric amounts of KMn04 and
Mn(N03)2 solutions are added simultaneously during the
precipitation. When the lower limit of the potential is exceeded, KMn04 solution is added; when the upper limit is
exceeded, Mn(N03)2 solution is
Using this procedure, it has been possible, for the first
time, to prepare manganese dioxide having nearly uniform
Fig. I. Scanning electron micrograph of manganese dioxide that was precipitated with computer control at pH 0 and I (left and middle, respectively) or
without computer control at about pH 1 (right). Left: Enlargement 110 times;
potential limits 1407/1432 mV; 87.1 wt.-Yo active M n 0 2 ; particle size 70 pm:
bulk density 0.72 g/cm3; BET surface: 169 m2/g; discharge capacity
q,,,=73.9 mA h/g.-Middle:
Enlargement: 119 times; potential limits
1347/1357 mV; 80.1 wt.-% active M n 0 2 ; particle size 45 pm; bulk density
1.53 g/cm3; BET surface: 0.4 m2/g; discharge capacity q,.,=81.3
mA h/g.
-Right: Enlargement: 122 times: without control of potential: 85.7 wt.-%
active M n 0 2 ; bulk density 0.41 g/cm'; BET surface: 108 mZ/g; discharge
capacity qmrx= 11 mA h/g.
['I Prof. Dr. 0. Glemser, Dr. D. H. Buss, Dipl.-Chem. G. Schaumberg
Institut fur Anorganische Chemie der Universitat
Tammannstrasse 4, D-3400 Gottingen (FRG)
[**I This work was supported by the Akademie der Wissenschaften in Gottingen, the Fonds der Chemischen Industrie, and the Herbert-QuandtStiftung.
0 VCH Verlagsgesellschaft mbH, 0-6940 Weinheim, 1985
0570-0833/85/1212-1057~02.50/0
1057
particle sizes at pH 0, 1, and 2 ; the precipitates settle
quickly and are easy to wash. Particle size, surface characteristics,['] bulk density, and electrochemical properties['"'
of the product depend strongly on the p H value during the
precipitation (Fig. 1, left and middle). The properties of
the samples obtained at p H 2 and p H 1 are nearly identical. At the same p H values, uncontrolled precipitation affords precipitates that are difficult to filter and wash and
that, after drying, are present as nonuniform agglomerates
(Fig. 1, right). The preparations obtained by controlled
precipitation belong structurally to the 6-Mn02 group:L81
those prepared by uncontrolled precipitation are primarily
amorphous.
Particularly noteworthy is the possibility of obtaining
uniform particles with very large surface areas (169 m2/g)
and also with much smaller surface areas (0.4 m'/g) by
controlled precipitation of manganese dioxide at p H 0 and
at pH 1 and 2, respectively. The latter are somewhat similar in appearance to the manganese nodules found in the
ocean.
Received: July 22, 1985;
supplemented: August 19, 1985 [Z 1397 IE]
German version: Angew. Chem. 97 (1985) 1050
[ I ] 0. Glemser, Angew. Chem. 73 (1961) 785.
[Z] D. H. Buss, W. Diembeck, 0. Glemser, J. Chem. SOC.Chem. Commun.
1985, 81.
131 J. Bauer, D. H. Buss, 0. Glemser, Ber. Bunsenges. Phys. Chem. 89 (1985)
1070.
[4] J. Bauer, D. H. Buss, 0. Glemser, J. Electrochem. Soc., in press.
[5] A. Guyard, Chem. News 8 (1863) 292.
[6] Detailed description: G. Schaumberg, Diplomarbeit, Gottingen 1984.
[7] Precipitation of the samples from aqueous nitric acid in a 4-L roundbottom flask: pH measurement with lngold pH single-rod measuring
chain HA-605. Potential measurement on electrographite (Sigri), reference Ag/AgCI via Luggin capillaries. Computer-controlled addition of
solutions using a C F G metering pump: computer: Rockwell AIM 65.
Solutions employed (p.A. chemicals): 0.6 M Mn(N03)z solution, 0 . 4 ~
KMnO, solution, 1 M KOH, 1 M HNO,. Work-up of the product by repeated suspension in distilled water and subsequent drying at 50°C and
I5 torr.
[S] The Debye-Scherrer diagrams of the samples are identical with those of
W. Buser, P. Graf, W. Feitknecht (Helu. Chim. Acru 37 (1954) 2322) who
obtained samples by precipitation from K M n 0 4 solutions with acetic
acid MnCI, solutions.
[9] We thank VARTA AG (Forschungs- und Entwicklungszentrum), Kelkheim, for the BET measurements.
[ 101 Determination of the electrocbernical charge capacity: A paste prepared
from 3 g of the sample being tested, 1.5 g of graphite, 3.5 g of Ni powder, and 1 mL of water was pressed into a 1 I-cm tube made of nickel
wire mesh. This test electrode was galvanostatically cyclized in cylindrical plexiglass cells with a Cd sintered sheet as counter electrode using
30% KOH solutions as electrolyte. Discharge procedure: charging of the
cell with 25 mA current, subsequent discharge with 25 mA countercurrent to a cell voltage of 0.8 V (vs. Cd/Cd(OH)* in 30% KOH solution).
4-~ri(n-butyl)phosphonio]-2,5-diselenoxo-l,3diselenacyclopentanide* *
By Heinz P. Fritz,* Gerhard Miiller, Gabriele Reber, and
Michael Weis
The search for electronically or ionically conducting
nonmetallic compounds has focused on charge-transfer
salts, highly conjugated polymers, and graphite intercala[*I
[**I
tion compounds.['-41 A chainlike structure [-Se-C(Se)-1,
has been postulated for p ~ l y - C S e ~ ,which
[ ~ I should be electronically c ~ n d u c t i n g ' ~and
. ~ ' which is obtained from CSe,
by polymerization under normal conditions or, better still,
under high pressure. We have been able to characterize the
two previously d e ~ c r i b e d ' ~(CSe,),
.~'
modifications as different polymers ; the electrically conducting polymer is
(CZSe3),."] The composition and structure of the amorphous polymerizate are unknown. Accordingly, it appeared to us worthwhile to seek possible routes for the uniform polymerization of CSe,.
Trialkylphosphanes react with CSe2 to form zwitterionic, partly oligomeric adducts of the type R,P(CSe,),,[']
which may be used as building blocks for a selective reaction to give a linear polymer. The reaction of nBu3P with
CSez affords dark red, flat prisms,[91which are readily soluble in the conventional organic solvents and which are
not very sensitive to air and moisture. Elemental analysis
and mass spectroscopy gave the unexpected formula
nBu3PC3Se4. IR absorptions at 1465, 968, 902, and 750
cm-' indicate the presence of C=C, two different C=Se,
and P-C bonds. The 3'P-NMR signal at 6 = +20.78 (relative to H3P04) suggests a phosphorus ylide type structure;
nBu3P=Se and nBu3P=0 exhibit 3'P-NMR signals at
6= +37 and 43.2, respectively.
Se 2
Fig. 1. Structure of one of the two crystallographically independent molecules of 1 (PLUTO). Important bond lengths [A] for both molecules. PI-CI I
I.77(1)/l.78(1), C l l - C I 2 1.42(2)/1.38(2), C12-Se3 l.9l(l)/l.88(l), C13-Se3
l.86( l)/l.87(2), C 13-Sel I.SS( I)/l.88(1), C1I-Se I l,89(l)/l.9l(l), C12-Se4
1.82(1)/1.87( I), C13-Se2 1.79(l)/l.77( 1).
The X-ray structure analysis['01 shows the presence of
planar C3Se2 five-membered rings in both crystallographically independent molecules in the crystal (Fig. 1). The
ylide-like character is supported by the length of the PCrrng
bond ( 1.78( 1) A). The lengths .Of the exo- and endocyclic C-Se bonds (1.77(1)-1.91(1) A) indicate a bond order between that of a formal double bond and that of a
formal single bond." 'I The nearly identical C-Se distances
and the slightly shorter (compared to single bonds) C-C
bond in the ring suggest partial delocalization of the electron pairs at the ylidic carbon and the Se atoms. This is
further supported by the ylidic P-C bond which is significantly longer than that in simple alkylidenephosphoranes.
The compound is best described, therefore, by formula 1 .
Apart from the known, spontaneous oligomerization of
CSe,, the chalcogen abstraction and adduct formation of
Prof. Dr. H. P. Fritz, Dr. G. Miiller, cand. chem. G. Reber, Dipl.-Chem.
M. Weis
Anorganisch-chemisches Institut der Technischen Universitat
Miinchen
Lichtenbergstrasse 4, D-8046 Garching (FRG)
This work was supported by the Stiftung Volkswagenwerk and by the
Fonds der Chemischen Industrie.
1058
0 VCH Verlugsgesellschufr mbH. 0-6940 Weinheim. 1985
0570-0833/85/1212-1058 $ 02.50/0
se
Angew. Chem. Int. Ed. Engl. 24 (19851 No. 12
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