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Detection of the Forbidden Transition in Dimeric Carbocyanines at Low Temperatures.

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Organogallogermoxanes, Compounds Containing
the Structural Unit Ga-0-Ge
By Priv.-Doz. Dr. H. Schmidbaur and
cand. chem. Brunhilde Armer
the dimerization is accompanied by approximately symmetrical splitting of the principal absorption maximum, although the longer-wavelength transition is forbidden [41. Prerequisite is that the dimer has symmetry Ci (or Cz),
Institut fur Anorganische Chemie der Universitat
Wiirzburg (Germany)
For preparation of the basic member (R CH3) of the homowe conlogous series of gallogermoxanes RjGe-O-GaRz
verted trimethylgallium etherate with ethereal HCl into dimethylgallium chloride: (CH&GaCI, m.p. 48-50 OC, b.p.164
to 165"C, IH-NMR: S(CH)3 = -16.0 cps[ll. Treatment of
(CH&GaCl with lithium trimethylgemanolate in diethyl
ether, removal of the separated LiCI, and sublimation afforded high yields of pentamethylgallogermoxane ( I ) :
C2H5
:
[(CH&GaCI]z
(la): R = CH3; X = S; fIc): R = CH3; X = Se;
( l b ) : R = C2HS; X = S ; (Id): R = C2H5; X = Se.
+ 2 LiOGe(CHd3 +
2 LiCl + [ ( C H ~ ) Z G ~ - O ~ G ~ ( C H (1)
~~~]Z
Compound ( I ) has m.p. 42-44'C,
b.p. 84-85"C/l mm,
and, according to molecular-weight determinations in benzene, is dimeric. Its 1H-NMR spectrum contains the expected
singlet signals of S(CH3Ga) = +25.0 and S(CH3Ge) =
-20.2 cps (ratio of areas 2: 3). Infrared-spectroscopic analogies
to pentamethylalumosiloxane (2) permit structure ( 3 ) containing a four-membered ring to be assumed, and this was
confirmed by X-ray analysis [21; compound (2) is accordingly
isomorphous with compound (3) and there are only slight
differences in the dimensions of the unit cells. From this it is
concluded that compounds (2) and (3) are isostructural,
having a planar inorganic skeleton [31.
H3C p
3
&a
( C H3)3Ge ;O - G e( CH3)3
Ga
H3C' \CH3
H3C, F H 3
A1
( CH3) Si- 0: O
: - Si(CH3)3
A1
H3C' \CH3
<
(2) Monoclinic, Pzl/n
a = 7.008 8 , b = 12.220 8
c sin p = 10.655 8
( 3 ) Monoclinic, P2l/n
a = 7.010 8 , b = 13.299 8
c sin p = 10.697 A
We have found another synthesis of compounds of the type
RzGa-O-GeR3 in the reaction of compounds R3GeOH with
GaR3 :
2 (C6H5)3GepOH-1 2 Ga(CH3)3 -+
2 CH4 [ ( C ~ H S ) ~ G ~ O G ~ ( C H ~ )(Z
4 )] Z
+
Ge-Triphenyl-Ga-dimethylgallogermoxane (4), like
compound (2), forms colorless crystals, m.p. 175-177 "C, sensitive to moisture. It is dimeric in benzene (by cryoscopy).
[(C6H5)3GeOGa(C6H5)2]2: m.p. 219-293 "c.
[ Z 127/959 IE]
Received: December 22nd. 1965
German version: Angew. Chem. 78, 305 (1966)
[I] We were unable to confirm the different data of G . E. Coates
et al. [J. chem. SOC.(London) 1963, 243)]. All NMR data in this
paper are for C C 4 solutions at 30°C and 60 Mc/s with tetra-
methylsilane as internal standard.
[2] We thank Dr. P . J . Wheatley for these investigations.
[3] H . Schmidbaur, J. organomet. Chemistry I , 28 (1963).
Detection of the Forbidden Transition in Dimeric
Carbocyanines at Low Temperatures
50
4E
-
0
m
4c
1
i
I
3;
Fig. 1 . Absorption spectra of meso-methylthiacarbocyanine iodide ( l a )
in ethanol at --18O"C. Concentrations (mole/l): 3.25x 10-6 (-);
1.33X10-5 (---);
8.17XlO-5 (.......):5.53XlO-4
).
(-.-.-
If an alkyl group is introduced at the mesu-position of certain
thia- or selena-carbocyanines ( I ) , dimerization occurs in
solution in 95 % aqueous ethanol at about -100°C. The
figure shows the spectra for various concentrations of mesumethylthiacarbocyanine iodide ( I a) at -180 "C. With increasing concentration the monomer band decreases in intensity, and the short-wavelength, shifted, dimer band increases, but a n additional, very weak, long-wavelength band
also appears. The concentration dependence of the lastmentioned band, its small extinction coefficient, and its occurence at about the same distance from the monomer
band as the short-wavelength dimer band (see table), lead
to the conclusion that we have here the forbidden, longwavelength dimer transition of the Forster model. That
it can be observed is probably due to the low temperature
and the fact that the meso-alkyl group somewhat distorts
the Ci (or C2) symmetry of the dimer by steric hindrance
and thus partly allows the transition.
Earlier attempts, by Forster 151 and Levinson [6,71, to find this
band were apparently unsuccessful.
Wave numbers (cm-1) of the absorption maxima of monomeric and
dimeric thia- and selena-carbocyanines.
By Prof. Dr. G. Scheibe and Dipl.-Chem. 0. Worz
Arbeitsgemeinschaft fur Strukturchemie und PhysikalischChemisches Institut der Technischen Hochschule
Munchen (Germany)
The absorption of a dimeric dye cation of carbocyanine type
is shifted towards short wavelengths relative to that of the
monomer [1-31. According t o a model proposed by Forster,
Angew. Chem. internat. Edit.
/ Vol. 5 (1966) 1 No. 3
aH5
Dye
1 1
Forbidden
dimer
transition
Monomer
all-trans-form
Permitted
dimer
transition
19700
19450
19200
I9 100
313
Splitting of the monomer bands was also observed; it is attributed to cis-trans-isomerism; the band of shorter wavelength is assigned to the all-trans-form, that of longer wavelength to a mono-cis-isomer that arises by rotation around
the C-2/C-8 bond
Received: December 22nd, 1965
[Z 134/964 IE]
German version: Angew. Chem. 78, 304 (1966)
~~
[ I ] G. Scheibe, Z. Elektrochem. angew. physik. Chem. 47, 73
(1941).
[2] H. 0. Dickinson, J. photogr. Sci. 2, 50 (1954).
(31 G. Scheibe, Angew. Chem. 52, 631 (1939).
[4] Th. Forster, Naturwissenschaften 33, 166 (1946).
[j] Th. Forster and E. Xonig, 2. Elektrochem., Ber. Bunsenges.
physik. Chem. 61, 344 (1957).
[6] G . S. Levinson, W. T. Simpson, and W. Curtis, J. Amer. chem.
SOC.79, 4314 (1957).
[7] W. West and S . Pearce, J. physic. Chem. 69, 1894 (1965).
Preparation of Fluoromethane in Molten Fluorides
By Dip].-Chem. W. Verbeek and Dr. W. Sundermeyer
Institut fur Anorganische Chemie der UniversitLt
Gottingen (Germany)
Fluoromethane is usually prepared from methyl derivatives
such as esters or alcohols that are cleaved by anhydrous H F or
KF. Treatment of methane with fluorine leads to a difficultly
separable mixture of fluorocarbons, containing mainly more
highly fluorinated products. A fluorocarbon mixture is also
obtained on electrofluorination of methane. Direct halogen
exchange has hitherto been obtained only in the reaction of
CH31 with HgF2 or AgF.
We have led chloromethane, with vigorous strirring, into a
LiF-NaF-KF melt at 500 "C, using a n apparatus described
previously [ I ] but with a nickel reaction vessel, inlet tube,
stirrer, and thermoelement supports. CH3F resulted in 85 %
yield with 42 % conversion, and was easily freed from traces
of C 0 2 and unchanged CH3Cl. A yield of 96 % and conversion of 32 % can be attained if CH3C1 is led into a K F - H F
melt at 350°C. The CH3F, which has thus become easily
accessible, can be brominated to afford bromofluoromethanes, and these can be pyrolysed by a known method to
yield hexafluorobenzene.
Reaction of CH2Cl2 with the KF-HF melt leads to CH2F2
with 82 % yield and 34 % conversion, whereas CHC13 gives,
in the main, a mixture of partially substituted products.
S-cornpound
N-2-Naphthylthiohenzamide
Benzyl N-phenyldithiocarbamate
Methyl henzylidenedithiocarbazinate
Benzimidazole-2-thio1
4,s-Diphenylimidazole2-thiol
5-Methyl- 1,2,4-triazoline-2-thione
5-Phenyl- 1,3,4-oxadiazoline-2-thione
6-Phenyl-3[4H]-thioxo1,2,4-triazin-S[2H]-one
4-Benzylideneamino-6methyl-3[4H]thioxo1,2,4-triazin-5[2H]-one
3-Phenyl-2[4HI-thioxoquinazolin-4[2Hl-one
( "C)
Benzene
80
5
100
Benzene
80
8
85 b l
Toluene
Benzene
110.8
80
10
10
80 Icl
95
NMP
I00
12
90
NMP
100
I2
80
Toluene
110.8
10
85
NMP
100
12
80
NMP
100
12
78
NMP
100
12
90
W . Sundermeyer, Z. anorg. allg. Chem. 313, 290 (1962).
Desulfuration with Hydroximoyl Chlorides
By the late Prof. Dr. A. Dornow and Dipl.-Chem. H. U. Voigt
314
Reaction
time (h)
The potential mercapto form of the thiocarbamoyl group is a
prerequisite for the reaction; this group may comprise part
of a ring (the sulfur being exocyclic), or it may be part of an
open chain. The hydroximoyl chloride reacts with the thiol
group that is in tautomeric equilibrium with the thioxo group,
HC1 being evolved, and the oxime group adds intramolecularly to the C=S double bond. The 1,4,2-oxathiazoles formed
as intermediates in this way decompose to isothiocyanate and
the 0-analogue of the starting material [21. Ready decomposition of 1,4,2-oxathiazoles was observed previously by R.
Huisgen when he added nitrile oxides to N,N-disubstituted
thioamides and obtained the 0-products directly 131.
We have used this desulfuration repeatedly as a criterion for
exocyclic sulfur, e.g., with isomer pairs of 5-methyltriazoleand the like.
2-thione, 5-methylthiadiazole-2-amine,
Received: January 3rd. 1966
[Z 1351965 IE]
German version: Angew. Chem. 78, 308 (1966)
[ I ] G. S. Skinner, J. Amer. chem. SOC.46, 731 (1924).
[2] A . Dornow and K . Fischer, Chem. Ber., in press.
[3] R. Huisgen, Chem. Ber. 73, 656 (1961).
Acyl- and Sulfonyl-carbamoyl Azides
By Doz. Dr. R. Neidlein
Pharmazeutisch-Chemisches Institut der Universitat
Marburg (Germany)
Acylcarbamoyl azides (2) (as far as we know not previously
reported) were obtained by addition of equimolar amounts
of hydrazoic acid to acyl isocyanates ( I ) [I] with stirring in
cooled benzene solution.
HN
Institut fur Organische Chemie der Technischen Hochschule
Hannover (Germany)
An exchange of sulfur for oxygen in good yield was observed
on treatment of hydroximoyl chlorides with compounds containing a thiocarbamoyl group. The preferred hydroximoyl
chloride was chlorohydroxyiminoacetic ester because of its
stability and accessibility [I]. The reaction was carried out in
anhydrous benzene or toluene; 1-methylpyrrolidone proved
a n excellent solvent for reactions of thioxo compounds, but
experiments with dimethylformamide, dioxane, and nitromethane failed.
Equimolar amounts of the components were allowed to react
for 5 to 12 hours at 80 to 100 "C, the solutions were concentrated, and the products were precipitated by light petroleum
or water. Some examples are given in the Table.
Temp.
[a] N M P = I-methylpyrrolidone. - [b] Product: S-benzyl thiocarbanilate.
[c] Product: S-methyl benzylidenethiocarbazinate.
[Z 130/958 IE]
Received: December 23rd, 1965
German version: Angew. Chem. 78, 307 (1966)
[I]
Yield (%) of
0-compound
Solvent
Ial
R - C - N = C = O4 R-C-N-C-N,
&A&
b
R
1 1
$:
Yield
(decomp.)
111-112
141-142
112-113
115-116
109-110
94
88
89
93
94
p-Toluenesulfonylcarbamoyl azide (4)is formed analogously
from p-toluenesulfonyl isocyanate ( 3 ) [21 and hydrazoic acid.
Angew. Chem. internat. Edit. / Vol. 5 (1966)
/ No.
3
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