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N-Methyl-3 4 5-tricyanopyridinium Perchlorate a Pyridinium Salt of Extremely High Electron Affinity.

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Preparation of Heavy Metal Halides
in Anhydrous Acetic Acid
39 "C, or 2-diphenylphosphino-2-phenyl-1
-triphenylstannylethane (3), m.p. 59 OC, respectively.
By Prof. Dr. H. D. Hardt and Dipl.-Chem. R. Bollig
Institut fur Anorganische Chemie der Universitit
Saarbrucken (Germany)
If pure acetyl chloride is added slowly (about 0.2 ml per min)
to 100 ml of a 0.1 M solution of lead acetate in anhydrous
acetic acid, minima in the specific conductivity of the solution are observed at Pb: CI molar ratios of 1: 1 and 1 :2 corresponding to the formation of lead acetate chloride and lead
dichloride, respectively.
+ CH3COCl + (CH3COO)PbCI+ (CH3CO)zO
(CH3COO)PbCIf CH3COCl + PbC12 + (CH3CO)zO
(CH3COO)zPb
Pure lead acetate chloride can be prepared by interrupting
the reaction at the first conductivity minimum. The colorless
precipitate is filtered off,washed with anhydrous acetic acid,
and dried over solid sodium hydroxide in a vacuum desiccator.
In this way, lead acetate chloride monoacetic acid-solvate
(CH3COO)PbCICH3COOH is obtained in over YO % yield.
This product releases its acetic acid of crystallization at
120 "C to give lead acetate chloride (CH3COO)PbCl, which
decomposes at about 270 "C to basic lead chloride Pb20Clz.
Lead acetate bromide can be obtained similarly at 60 OC and
decomposes at about 300 OC to lead oxide bromide. Solvated
lead acetate bromide is not formed under these conditions.
Lead acetate iodide cannot be made in this way.
The iodides PbI2, AgI, HgI2, Aga(HgId), CuI, and CdI2 are all
highly insoluble in anhydrous acetic acid and can be obtained in quantitative yields by adding a stoichiometric
amount of acetone plus the calculated amount of iodine in
acetic acid dropwise to solutions of the acetates of these
metals in anhydrous acetic acid at 70-80 "C. Silver iodide is
precipitated even without addition of acetone.
n CH3COCH3 t n I p
+ (CH3COO)nM +
MIn + nCH3COCH21+ nCH3COOH
The precipitation of lead iodide is very slow at room temperature (30 % conversion after 40 h), but the rate can be almost
doubled by passing an alternating current (220 volts between
Pt or Ag electrodes) through the solution containing acetic
acid, acetone, iodine, and lead(I1) acetate. The current
density increases to a maximum of 3.3 amp/dm2 during the
first 3 h and then falls to about 1.6 amp/dm2 during the
next 30 h.
Thermochromic Agz(HgI4) is obtained at 70-80°C from a
2:1.3 mixture of silver and mercury acetates. The yellow
modification of HgIz is formed from mercury(I1) acetate alone
in anhydrous acetic acid at 118.1 "C. Crystals about 0.5 mm
long are obtained which can be kept for a few days (metastable) if quenched rapidly to room temperature.
This new method is especially suitable for the preparation of
cadmium iodide. A solution of iodine in acetic acid is added
dropwise to a hot solution of CdzQ in acetic acidlacetone
until the color of the iodine persists. The yield is quantitative
and the product is very pure.
Received: July 5th. 1965
[Z 34/859 IE]
German version: Angew. Chem. 77. 860 (1965)
Addition of Diphenyl(triphenylstanny1)phosphine
to Multiple Bonds
By Dr. H. Schumann, Dr. P. Jutzi,
and Prof. Dr. Max Schmidt
Institut fur Anorganische Chemie
der Universitat Marburg (Germany)
Diphenyltriphenylstannylphosphine ( I ) [l] reacts with ally1
chloride or styrene in boiling benzene to afford 3-chloro-2diphenylphosphino-1-triphenylstannylpropane (2).
m.p.
Angew. Chem. internat. Edit. / VoI. 4 (1965) / No. I0
Reaction of phenylacetylene with even a great excess of ( I )
stops at the stage 2-diphenylphosphino-2-phenyl-1-triphenylstannylethylene (4), m.p. 45 "C.
After the solvent has been distilled off, compounds (2),(3),
and (4) crystallize readily (by scratching) from pentane and
can be recrystallized from benzene/pentane. Before this
crystallization, unchanged ( I ) is oxidized by prolonged
stirring in air to the insoluble triphenyltin diphenylphosphinate which is filtered off.
(C&5)3? ?(C6H5)2
HC=C-CsHs
(4)
We assume a free-radical reaction mechanism, by analogy
with hydrostannylation [2].This is in line with the considerable
increases in yield that result on addition of small amounts of
azobisisobutyronitrile :
(2):26% + 6 5 % ; ( 3 ) : 16% +68%;and(4):21% +78%.
Mixtures of isomers were not found in these reactions, even
on use of chromatography. The structures given follow from
the consideration that the bulky triphenylstannyl group will
add preferentially at the terminal-carbon end of the double
bond. NMR spectroscopy gave no structural indication. The
extraordinarily high solubility of (2), (3), and (4) in benzene,
pyridine, and carbon disulfide nevertheless did not suffice to
permit detection of the Sn- and P-linked protons on aliphatic
carbon atoms in 1H-NMR spectra alongside the 25 or 30
protons of the phenyl nuclei. Moreover, the Sn- and P-NMR
spectra were extremely complicated by numerous couplings
and could not be interpreted.
Received: July 12th, 1965
[Z50/876 IE]
German version: Angew. Chem. 77, 912 (1965)
[l] H . Schumann, H. KOpL and M . Schmidt, J. organornet. Chem.
2, 159 (1964).
[2] W. P. Neumann, Angew. Chem. 76, 849 (1964).
N-Methyl-3,4,5-tricyanopyri&nium Perchlorate, a
Pyridinium Salt of Extremely High Electron
Affinity [l]
By Prof. Dr. K. Wallenfels and Dipl.-Chem. W. Hanstein
Chemisches Laboratorium
der Universitat Freiburg (Germany)
The anion affinity of pyridinium salts is greatly increased
by the introduction of electron-attracting substituents [2].
The phenomenon is most readily examined by measuring
the equilibrium constants of the reaction
b
Py
+ CNe +
PyCN
for the various pyridinium derivatives. The redox potentials
of the pyridinium saltldihydropyridine system are directly
proportional to the logarithms of the cyanide ion affinities.
We have synthesized a pyridinium salt (4) of extremely high
869
anion and electron affinity by the following route. 3,5-Dicyanopyridine is fused and methylated with methyl p toluenesulfonate for 4 h at 110 "C. The N-methylpyridinium
I
CN
on reduction or (4) with zinc in acetonitrile. The formation
of free radicals of this type during the reduction of pyridinium
cations containing substituents-capable of mesomerism has
already been observed [4].
1. N20,
2. HzO
CN
118-120
p-toluenesulfonate (90 % yield) is treated with KCN to give
the 2-cyanide adduct ( I ) in 80 % yield, which when heated
in the melt at 125 "C or in dimethylformamide at 15O-16O0C,
is converted in 95 % yield into the 4-isomer (2). The latter is
suspended in carbon tetrachloride and oxidized for 12 h at
25 "C (90 % yield) with excess N2O4. The solvent and reagent
are removed in vacuum, the residue is stirred with water,
and the (3) formed filtered off. Compound (3) is then
dissolved in acetonitrile, and HClO4 and ether are added.
The perchlorate (4) crystallizes in the form of long thin
needles in 70 % yield.
The N-methyl-3,4,5-tricyanopyridiniumcation (4) is a strong
x-acid. It forms intensely colored charge-transfer complexes
with anisole (red, Amax = 475 mp), hexamethylbenzene (red,
505 mp), and pyrene (green, 620 mp). The salt (4) reacts as a
Lewis acid with 2 moles of 9-fluorenol in acetonitrile within
12 h at 25 "C to yield di-9-fluorenyl ether (9%) and the
adduct (3).
Anisole is acetylated in acetonitrile in the presence of the
salt (4) to give 34 % p-methoxyacetophenone, which was
isolated as the 2,4-dinitrophenylhydrazone.
The cation (4) combines with hydroxide and cyanide ions
to form the adducts (3), PKa = -14.5 [31, and (5), pK. =
-14.9 [3], respectively, which are both extremely resistant
to acids.
Ncp$N
CN
(5)
CN
c H3
The salt (4) also acts as an oxidizing agent. In the reaction
fluorenone can be
with 9-fluorenol described above, 8
isolated in the form of its 2,4-dinitrophenylhydrazoneafter
6 days at 25 ' C . This is therefore the first model system for
the enzymatic dehydrogenation of an alcohol by a pyridinium
salt.
When solutions of (4) and p-bisdimethylaminobenzene in
acetonitrile are mixed, a deep blue solution is formed in
which Wurster's blue can be detected.
So far the primary reduction product formed from the
pyridinium salt has not been isolated from any oxidation;
it appears to be readily oxidized by oxygen. The product
obtained is N-methyl-3,4,5-tricyano-2-pyridone
(6), which
can also be made by oxidation of (5) with nitric oxide. The
sensitivity of the primary reduction product towards air
suggests that it is a pyridyl radical or the dihydropyridine
derivative (7). Compound (7), which can be made by
reduction of (4) in acidic solution, is also converted to the
pyridone (6) when its solution in acetonitrile is left standing
in air. A free pyridyl radical is formed as an intermediate in
this oxidation; the hyperfine structure of its characteristic
electron-spin resonance spectrum is being investigated. A
free radical with a very similar ESR spectrum is produced
870
168-169.5
130-13 1.5
190-191
144-150
206-207.5
decomp. above 170 "C
350
246
359
384
261
313
418
263
372
~
3.95 (CHJOH)
3.92
3.87 (CHIOH)
3.93 (HzO)
3.76
3.71 (H?O/HC104)
3.84 (CH3CN)
3.60
3.90 (CH3OH)
-
[Z 37/863 IEI
Received: July 16th. 1965
German version: Angew. Chem. 77, 861 (1965)
[ 11 The MechanismofHydrogenTransfer by Pyridine Nucleotides,
Part 27. Part 26: K. Wallenfels and 8. Muller-Hill, Biochem. Z .
339, 352 (1964).
[2] K,WaIIenfets and H, Diekmann, Liebigs Ann. Chem. 621, 166
(1959).
131 The pK values were determined from the pH-dependent
intensity of the bands at 384 mp for ( 3 ) and 418 mp for (5).
141 K. WalIenfelsand M. Gellrich, Liebigs Ann. Chem. 621, 198
(1959); E. M. Kosower and E. J. Poziomek, J. Amer. chem. SOC.
86, 5515 (1964).
Synthesis of Tetrakistrifluorophosphinoiridium
Hydride and the Proton Magnetic Resonance
Spectra of the Hydrides HM(PF&
(M = CO,Rh, Ir) [l]
By Priv.-Doz. Dr. Th. Kruck and Dip1.-Chem. W. Lang
Anorganisch-Chemisches Laboratorium der Technischen
Hochschule Miinchen (Germany)
Tetrakistrifluorophosphinoiridium hydride, HIr(PF3)4, has
now been made in 86 % yield analogously to the corresponding derivatives of cobalt [2] and rhodium [3], but using a
temperature of 260°C and a PF3 pressure of 1000 atm.
The new compound is a colorless, mobile, extremely volafile
liquid with a choking odor and boils at 95 OC/725 mm; the
solid melts at -39OC. It is surprisingly stable towards heat
and starts to decompose only above 245 OC; it is unaffected
by air. It dissolves to a small extent in water; its solution is
acidic.
HIr(PF3)4 reacts with potassium amalgam in ether to form
potassium tetrakistrifluorophosphinoiridate(-I), K[Ir(PF3)4],
which crystallizes readily to a colorless solid. This salt can
be kept for weeks in dry air and decomposes under nitrogen only above 240 "C. It is readily soluble in ether, acetone,
tetrahydrofuran, and water; its aqueous solution is slightly
alkaline.
The infrared spectrum of HIr(PF3)4 vapor 141 contains P-F
stretching vibrations at 965 (w-m), 925 (vs), 910 (s, shoulder),
and 877 (vs) cm-1. In the spectrum of the tetrakistrifluorophosphinoiridate(-I) these bands are shifted to much longer
wavelengths on account of the greater x-bond character of
the metal-phosphorus bond, which reduces the doubleAngew. Chem. internat. Edit. 1 Vol. 4 (1965) [ No. 10
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