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New Stable Cyclobutadienes.

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Compounds ( 2 a ) - ( 2 c ) and (3) have strong thioacylating
properties similarly to the corresponding thioketenes. but they
are thermally much more stable. However, ( 2 b ) , ( 2 c ) , and
( 3 ) can be handled only in solution; on attempting to isolate
them in substance they undergo decomposition. 3,3-Dimethylthiobutyryl chloride ( Z a ) , on the other hand, can be obtained
analytically pure in yields of >90",, by distillation. I t is an
orange-red. pungent oil, which can be stored indefinitely at
-40°C but slowly decomposes at room temperature. The
structure of ( 2 a ) follows from elemental analysis and from
its physical properties.
The 'H-NMR spectrum of ( 2 a ) (in CFCl,) shows two singlets
at 6 = 1.12 (9H)and 6=3.17 (2II). Thus, a possible tautomeric
form ( 4 ) can be ruled out. In the IR spectrum (2960, 1470,
chloride. Compound ( 9 ) is readily accessible by reaction of
(8) with potassium ethoxide in d i o ~ a n e [ ~ I .
3,3-Dimethylthiobutyryl chk)ritie ( 2 a )
A stream of dry hydrogen chloride is passed through a
vigorously stirred suspension ofwell-dried and finely powdered
( 9 ) (1.Og) in n-pentane (80ml) at -80°C. The temperature
of the mixture is allowed to increase to - 10°C over a period
of four hours; after decantation and subsequent removal of
solvent in vacuum, distillation of the residue at room temperature and
torr in a water-cooled condenser affords ( 2 a )
as an orange-red oil, n;,= 1.5130 (yield: 0.49gG49'x).
Received: June 23, 1975 [Z 278 I€]
German version: Angew. Chem. 87. 710 11975)
CAS Registry numbers:
( l a ) , 54191-76-3: i l h ) , 54191-77-4: ( 1 ~ ) .44158-23-8: 56008-74-3: f ? h ) .
56008-75-4; ( 2 c ), 56008-76-5; (3). 56008-77-6: ( 6 ) . 541 9 1-8 1-0; i7 ) . 13831 - 146; ( 8 ) . 40753-16-0; (9). 56008-78-7
1365, 1230, 1215, 940, 920, 850 cm-') the intense double
band at 1215/1230cm-' can beassigned to the CS stretching
vibration[3! The mass spectroscopic fragmentation of ( 2 a )
resembles that of a carbonyl chloride. No molecular ion is
observed even at an ionization energie of 20eV; the most
intense peak occurs at m/e= 115G M+-Cl. The UV spectrum
(in cyclohexane), h,,, (logs): 480 (1.08), 304 (2.24), 257 (3.74),
207(4.10),agreesremarkably well with that previously predicted
for thioacetyl ~hloride'~!The 3C-NMR spectrum contains
signals (in ppm rel. to TMS) for CS at 215.0, for CH, at
69.9, for C at 33.3, and for CH3 at 29.6[? It can therefore
be ruled out that ( 2 a ) is present as the symmetrical dithietane
(5) since the ring carbon atoms in dithietanes exhibit relatively
small chemical shifts (e.y. 74 ppm rel. to TMS in tetrachlorodithietaneE5]).
The chemical properties of ( 2 a ) are also in agreement
with the above structural assignment.
K . 7: Porra and C. Sapitlo in S. Putor. The Chemistry of Acylhalides.
Interscience. London 1972. p. i49
G. Sc,,rho/d. Tetrahedron Lett. 1974. 555: G . S r d d d and Ch. Hrihl.
Angew. Chem. X7, 171 (1975): Angew. Chem. internat. Edit. 14, 248
(1975).
R. M u r r r and S. Scheirliauo. J. Prakt. Chem. [4] 21, 214 (1963).
J . Fahiuri, H . Fioln, and R. Muyrr.. Tetrahedron 23. 4323 (1967).
We thank Dr. J . Fir./ for recording the I3C-NMR spectra.
The structure of the reaction products was confirmed by elemental
analysis and comparison with authentic samples.
A. Skufier and I. Lairxwi. J. Heterocycl. Chem. 1 0 , I 1 [ 1973).
[I]
[2]
[3]
[4]
[5]
[6]
[7]
New Stable Cyclobutadienes
By Rudolf Gompper, Siegj?icd Merisch, and Giirither SeyholtlL*J
The unusual properties of the cyclobutadiene derivative
(l)['](dimerization only above 12O"C, almost square
induced us to look for other combinations of substituents
that would lead to stabilization of the antiaromatic four-membered ring and might give information about the nature of
the stabilizing effect.
Even at - 80°C it reacts spontaneously and quantitatively
with dimethylamine to give the thioamide (6). On reaction
with ethanethiol at room temperature it affords the dithioester
( 7 ) in 73% yield[6]. ( 2 b ) , (2c), and ( 3 ) behave similarly.
On prolonged standing at room temperature ( 2 a ) - ( 2 c ) and
( 3 ) polymerize with concomitant elimination of hydrogen
chloride to give undefined resinous products.
The synthesis of ( 2 0 ) can also be accomplished, albeit
in lower yields, under conditions in which ( I a ) occurs only
as intermediate: when the thiadiazole ( 8 ) is pyrolyzed at
500 T / 4 0 torr in a stream of hydrogen chloride/nitrogen, ( 2 a )
is obtained in yields of 40-50'x. A simple apparatus can
be used for the pyrolysis, as is usually employed for carrying
out ester pyrolyses.
The preparatively most simple route to ( 2 a ) is the reaction
of potassium 3,3-dimethyl-l -butynethiolate ( 9 ) with hydrogen
704
PIIS-c-
c-zI:t,
IlF,
I'hO11
( 2J
PIlS
NEt,
I3 F4C
We were able to synthesize the cyclobutadiene derivative
N , N , N ' , N ' - tet raeth yl- 2,4- bis (phenylthio)cyclobutadiene - 1,3diamine (2) [orange crystals; IR (CCl.,): 1635, 1580, 1475,
[*] Prof. Dr. R. Gompper, Dr. S. Mensch, and Dr. G . Seybold
lnstitut fur Organische Chemie der Universitat
8 Munchen 2, Karlstrasse 23 (Germany)
Estimated from the 65 t o 75 'x, yield of recrystallized product of reaction
of 1 6 ) with methyl iodide.
[**I
1438, 1375, 1278 cm- I ; UV (THF): 370,301 nni].This remains
unchanged for more than 48h in the solid state at room
temperature. At 60°C it decomposes with darkening, but
dimerization, as for ( I ), could not be observed. The reactions
of (2) with HX, methyl iodide, bromine or acetylenedicarboxylic esters correspond to those of ( 1 ) " " .
CAS Registry numbers:
~2~,56008-79-8:/3),5600~-80-1:(4).56008-8l-2:
/S)(X=CIO,), 56008-82-3;
(5) (X=CI). 56008.83-4: ( 5 ) (X=BF,I, 15005-77-3: (6). 56008-84-5: ( 7 0 ) .
56008-85-6; ( 7 b ) . 56008-86-7; (8 i , 56008-87-8: ( 9 1 IR = S O Z C , H,-CH
-p).
56008-88-9: ( 9 ) (R = C,H,-NO,-p).
56008-89-0
a ) K. Gompprr and G. Srybold in E. D. Bergmrrrln and B. Pullnzanrr.
Aromaticity, Pseudo-Aromatlcity, Anti-Aromaticity. Israel Academy of
Sciences and Humanities, Jerusalem 1971. p. 2 1 5 : b) R. ( ; r ~ ~ n p / ~Jr .~ ' .
Kroner. G. Seybold, and H.-U. Wagner. Tetrahedron. in the press.
[2] a ) J . Ficini and C. Borboru, Tetrahedron Lett. 1966. 6425: b) L. Ghose:,
8. Huorcriu. and H. G. Viehe, Angew. Chem. 81. 468 (1969): Angew.
Chem. internat. Edit. 8,454 ( I 969).
[3] Cf. C. W! Rrrc. 3. F . Goir. and K. C. Srorr. Chem. Commun. 1971.
1545: C. W Rees, S . F . Gair, M . J . Roiiw. and R . C. Srorr. J. C . S .
Chem. Comm. 1972. 688. We thank Prof. R w \ for valuable advice.
[I]
New observations are the formation of ( 3 ) from (2) and
carbon disulfide as well as the production of the pyrrole ( 4 )
from (2) and p-nitrophenyl azide. Apparently (2), unlike ( 1 )
can also react in accord with a 1,3-dipolar cycloaddition.
C6H,P[Mn(C0)2CSHs]2 : A Phosphinidene Complex
with Trigonal Planar Coordinated Phosphorus(l)[**]
By Gottfried Huttner, Hans-Dieter Miller, Albin Frank, and
Hans Lorend*]
Although (2) can be fitted at least formally into the donoracceptor scheme"], this interpretation is inapplicable to (6).
Deprotonation of the cyanine salt (5)[,1 can be effected by
NaH in dioxane or THF, by NaNH, in THF, by KH in
THF or by Li diisopropylamide/tetramethylethylenediamine
in THF. By the last method (6) can be isolated as a light
brown crystalline substance containing as impurity maximally
30 [**I of the complex of Li perchlorate and tetramethylethylenediamine [the other methods afford solutions of (6)]. (6)
is stable for at least 1 h in the solid state at room temperature.
'x
Et
Ph'
%Eta
Ph'
x"
'NEt,
We recently reported on the synthesis and structure of
the arsinidene complex C,H,As[Cr(CO),], ( I ) [ I 1 , in which
phenylarsanediyl, C,H,As, is stabilized as a bridging ligand
with trigonal planar coordinated arsenic([).
While the occurrence of phenylarsinidenes was first established by the detection of ( 1 ), the occurrence of phosphinidene
intermediates was demonstrated-especially by U . Schrnidt'sl2I
work--by means of trapping reactions. We have now found
that phenylphosphinidene, C,H ,P, can, like phenylarsinidene,
also be stabilized as a ligand in transition metal complexes.
The phosphinidene complex ( 4 ) is formed in the thermolysis
of tris(cyclopentadienyldicarbonylmanganese)triphenylcyclotriphosphane ( 3 ) , which is obtained by delithiation of
cyclopen tadienyldicarbonylmanganesedilithiophenylphosphane (2)13].
C s HK O ) , M n P ( C , H s)Li2
161
(5)
(2)
X = C1, J3b'4, C10,
The reactions of (6) with methyl iodide, acetylenedicarboxylic esters, propiolic esters and water correspond to those of
( 1 ) and (2). Zwitterionic products ( 7 ) are formed from (6)
and isothiocyanates; when heated, (7a) is transformed into
Ph/
YKEt,
Ph
(81
the thiopyridone ( 8 ) .The action of p-nitrophenyl or p-toluenesulfonyl azide on (6) affords 1 : 1 adducts which are probably
the pyridazine-N-imides ( 9 ) rather than the triazepinesc3I.
Ph
19)
C,H, ,NCI,
[C,H dCOJ,Mn] A ( C , H
5)3
(31
On warming ( 3 ) to 110°C at
torr ( 4 ) collects at
a cool finger (12°C) as a violet finely-crystalline solid. It can
also be obtained by boiling (3) in toluene for 20 minutes.
( 4 ) melts at 125°C with decomposition; it dissolves readily
in CH,CI, or toluene, but sparingly in n-pentane, to give
reddish violet solutions.
Its 'H-NMR spectrum shows two signals in the intensity
ratio 1 : 2, which are assigned to the phenyl- and the cyclopentadienylprotons [6(C,H5)=6.9. 6(C,Hs)=4.1 5 ppm, internal
TMS].
In the IR spectrum of ( 4 ) six bands are observed for the
C O stretching vibrations [1992 (s), 1972 (s), 1938 (vs), 1912
(vs), 1883 (s) cm-' in toluene]. From the number of bands
it can be concluded that rotameric forms are present; the
band positions would indicate that the phosphinidene ligand
has good electron-acceptor properties.
[*] Doz. Dr. G. Huttner. DipLChem. H.-D. Muller. Dipl.-Chem. A. Frank.
and Dr. H. Lorenr
Anorganisch-chrmisches 1-aboratorium der Technischen Universitit
8 Miinchen 2. Arcisstr. 21 (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft,
the Fonds der Chernischen Industrie. and the Leibniz Rechenzentrum der
Baverischen Akademie der Wissenschaften.
[**I
Received: June 30, 1975 [Z 281 IE]
German version: Angeh. Chem. 87. 71 1 (1975)
705
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