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Direct Detection of Dicyanothioketene in the Gas Phase.

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NC-E-0-CN
NC
(4)
CN
Thus dicyanoketene (2), like di~yanothioketene~'],is stable
at low pressure in the gas phase.
Received: February 29. 1980 [Z 562a IE]
German version: Angew. Chem. YZ, 751 (1980)
CAS Registry numbers:
( I ) , 66563-24-4; (2). 4361-47-1; (3), 74408-85-8; (41, 74408-84-7
[ f ] R. C. De Selms, Tetrahedron Lett. 1969. 1179 H. W. Moore, W Weyler, H.
R . Shelden, rbid. 196Y, 3947; H. W. Moore, W Weyler, J. Am. Chem. SOC.92.
4132 (1970); W. Weyler, W. G Duncan, H. W. Moore, rbid. 97, 6187 (1975).
(21 R. Neidlein, E. Bernhard, Angew. Chem. 90. 395 (1978); Angew. Chem. Int.
Ed. Engl 17, 369 (1978).
[3j We are grateful to Dr. R. Gurtner for the preparation of 2,5-dichloro-3,6-dicyano-l,4-benzoquinone, from which ( I ) was obtained according to 121. The
premature deflagration of ( I ) in the experiments described could be suppressed by preparation of (I) in the presence of roughly twice the amount of
finely divided calcium carbonate ("solid state dilution"). The mixture of (/)
and CaCO, was thoroughly dried at 0 ° C and l o - * mbar prior to each experiment.
141 It could be demonstrated by mass spectrometry that carbon dioxide is formed
on thermal decomposition of the (di- or polymeric?) byproducts. This reaction becomes increasingly pronounced with rising temperature, hut plays
only a minor role below 100 "C. Increasing temperature considerably
strengthened the mass peak at m / e = 44 after that at m / e = 92 bad disappeared almost completely.
[5] D. Hall, J. P. Maier. P. Rosmus, Chem. Phys. 24, 373 (1977).
161 H. L. Hose, G. Lauer, K: W. Schulre, A. Schweig, Theor. Chim Acta 48, 47
(1978); the geometry was optimized by MNDO 171
171 M. J. S. Dewar, W. Thiel, J. Am. Chem. SOC.9Y. 4899 (1977).
181 J. Seiblr Massenspektrometrie Akademlsche Verlagsgesellschaft. Frankfurt
am Main 1974.
191 R. Schulz, A . Schweig. Angew. Chem. Y2, 752 (1980); Angew. Chem. Int. Ed.
Engl. IY, 740 (1980).
directly above the ionization region of a modified PS 18 photoelectron spectrometer and went to completion at 470 "C.
The PE spectrum of the starting material (1) (Fig. la ) shows
bands at @ 10.00 eV/'B,(n), @ 10.95-1 1.10 eV/2Az(T) and
'Bz(n), @ 12.80 eV/'B,(n), @ 13.08 eV/'B,(a) and 'Ai(a)
and @ 13.70 eV/2A,(n)151.The PE spectrum of the pyrolysis
products (Fig. Ib) contained not only the known bands of
carbon oxide sulfideI61but also the new bands at @ 9.94 eV/
'B,(n), @ 12.79 eV/'Bz(o), @ 13.00-13.8 eV/*B,(n),
'Bz(o), 'A,(o) and 2A2(~)15a1.
Band @ is split into vibrational
partial bands separated by 1500 cm - I and e xpe ~tedly[~]
cos
cos
Direct Detection of Dicyanothioketene in the Gas
Phase'"]
By Reinhard Schulz and Armin Schweig[*l
Dedicated to Professor Karl Dimroth on the occasion of
his 70th birthday
Dicyanothioketene (2) has been formulated as an intermediate on several occasions[l1; however, all attempts to isolate
this species or to detect it by spectroscopy have so far failed.
Not even monocyanothioketenes have yet been identified directly''].
We have now succeeded in directly detecting this apparently highly reactive molecule by variable temperature photoelectron spectroscopy (VTPES)r31o n gas phase pyrolysis of
2-(4-oxo-1,3-dithietan-2-ylidene)malonitrile( l ) ~ ' a l . A previous attempt to generate (2) in the gas phase by this reaction
and to isolate it in solution at low temperature afforded only
dimeric and polymeric material[41.
NC
x ) o
NC
(1)
47O0C
NC,
c=c=s+ cos
NC'
(2)
The reaction (1)-+(2) was performed in a flash pyrolysis
reactor (stainless steel tube, 20 x 0.6 cm; ca. 5 x lo-' mbar)
"3 Prof. Dr. A. Schweig, DiplLChem. R. Schulz
Fachbereich Physikalische Chemie der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg 1 (Germany)
I"] Part 90 of Theory and Application of Photoelectron Spectroscopy. Tbls
work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen 1ndustrie.-Par1 89: [101.
I40
0 Verlag Chemie. CmbH, 6940 Wernheim, 1980
d)
I
I
1
10
12
11111 ,
1
I
I
16
IP/eV-
Fig. 1. He-I photoelectron spectrum of a ) the starting material ( I ) and b) its pyrolysis products at 470OC; c) experimental and d ) calculated (MNDO-PERTCI)
vertical ionization energies of dicyanothioketene (2).
shows the same fine structure as the energetically lowest-lying 'Bi(n) band in the PE spectrum of thioketenel*". The
identity of dicyanothioketene (2) follows not only from the
extremely clear-cut reaction but also from the good agreement between the experimental vertical ionization energies
and those predicted by MND0[9"1-PERTCI[9b1
calculations
(Fig. 1). The ionization energies are expectedly smaller than
for dicyanoketene"''. The energy difference between the
'Bi(n) states of dicyanoketene and dicyanothioketene (0.7
eV) is in excellent agreement with the corresponding difference in the case of the ketene/thioketene pair[*].
0570-0833/80/0909-0740
$02.50/0
Angew. Chem. Inr. Ed. Engl. 19 (1980) No. 9
Among the three isomers (Z), (3), and (41, MNDO calculations with optimized molecular geometries show dicyanothioketene (2) to have the lowest energy content (standard
enthalpies of formation: (2) 110 kcal/mol; (3) 134 kcal/mol;
and (4) 122 kcal/mol). These values suggest that it might
well be possible to generate thiirenedicarbonitrile (3) by photochemical methods.
Like dicyanoketeneclO1,
free dicyanothioketene (2) is stable
in the gas phase at low pressure. Unlike dicyanoketene, however, (2) can readily be generated continuously over a prolonged period in a flow system by gas phase pyrolysis.
In order to synthesize the hitherto unknown dibenzoylphosphane (l), R = C6H5, we treated monolithium phosphide. DMEf4]with benzoyl chloride in DME. However, instead of the expected monobenzoylphosphane, lithium dibenzoylphosphide. DME (2) was formed with slow evolution
of phosphane.
Received: February 29, 1980 [Z 562b I€]
German version: Angew. Chem 92, 752 (1980)
CAS Registry numbers:
(1). 13157-38-5; (0,54856-36-9; (3), 74808-29-0; (41, 74808-30-3
[ I ] a ) K. Dickore, R. Wegler, Angew. Chem. 78, 1023 (1966); Angew. Chem
Int. Ed. Engl. 5, 970 (1966); b) R. Nerdlein, H. G. Reuter, Arch. Pharm.
(Weinheim) 308, 189 (1975).
[2] E Schaumann, J. Ehlers, H. Mrotrek, Justus Liebigs Ann. Chem. 1979,
1734.
[3] A Schweig, H. Vermeer, U. Weidner, Chem. Phys. Lett. 26, 299 (1974); W.
Srhafer, A. Schweig, 2. Naturforsch. A 30, 1785 (1975); R. Schulz, A.
Schweig. Angew Chem. 92, 52 (1980); Angew. Chem. Int. Ed. Engl. 19, 69
(1980).
[4] G. Se.pbold, Ch. Heibl, Chem. Ber. 110, 1225 (1977).
[51 Assignment according lo MNDO [9a]-PERTCI (9b] calculations with optimized molecular geometries; b) assignment by comparison of He-I with
He-Il intensities; cf. P. Dechant, A. Schweig, W. Thief, Angew. Chem. 85.
358 (1973): Angew. Chem. Int. Ed. Engl 12, 308 (1973).
[61 D W. Turner, C. Baker, A . D. Baker, C. R. Brundle: Molecular Photoelectron Spectroscopy. Wiley-Interscience, London 1970.
171 The PE band of the lowest-energy 'B,(P) state of dicyanoketene has the
same fine structure as the corresponding band of ketene [lo].
[XI P. Romus. B. So!ouki, H. Bock. Chem. Phys. 22. 453 (1977).
191 a) M J. S. Dewar, W. Thiel, J. Am. Chem. SOC.99,4899 (1977); M. J. S. Dewar. M. L. MrKee, H. S. Rzepa, ibid. 100, 3607 (1978); b) H.-L. Hase, G.
Lauer. K.- W. Schulte, A . Schweig, Theor. Chim. Acta 48. 47 (1978).
1101 A Horrel, R. Neidlein. R. Schulz, A. Schweig, Angew. Chern. 92, 751 (1980);
Angew. Chem. In1 Ed. Engl. 19, 739 (1980).
The reaction course can be rationalized by assuming formation of the monosubstituted compound, subsequent lithium/hydrogen exchange, and renewed reaction with an excess of benzoyl chloride. The resulting dibenzoylphosphane
reacts with lithium phosphide to form (2).
Compound (2) was characterized by elemental analysis
and by its NMR and IR data. The 3'P- and I3C-NMR signals
of the C-P-C
group show a downfield shiftf5]as has been
observed in similar c o m p o ~ n d s [ l ~Since
. ~ ~ .the poor solubility
in apolar solvents containing no DME precluded determination of the molecular size and constitution, we investigated
(2) by an X-ray structure analysis (see Fig. 1).
-
Lithium Dibenzoylphosphide 1,2-Dimethoxyethane
-A New 2-Phospha-1,3-dionate"*'
By Gerd Becker, Matthias Birkhahn, Werner Massa, and
Werner Uhl'']
Dedicated to Professor Karl Dimroth on the occasion of
his 70th birthday
The diacylphosphanes ( l ) ,R = CH3, (CH3)& synthesized
so far show a remarkable keto-enol tautomerism and resemble 1,3-diketones in their properties[''. According to X-ray
structure
analyses
of
nickel
bis(dipivaloy1phosphide). DMEr21(DME = 1,2-dimethoxyethane) and of aluminum tris(diben~oy1phosphide)~~~l
this similarity is also
shown by 2-phospha-1,3-dionates; the metal ions are not
coordinated to the phosphorus atoms but in chelate rings to
the oxygen atoms of the anions.
['I Prof. Dr. G. Becker, M. Birkhahn, Dr. W. Massa, DipLChem. W. Uhl
Fachbereich Chemie der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg (Germany)
[**I Part 14 of Acyl- and Alkylidenephosphanes. This work was supported by
the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie
13. Mitteilung: C. Becker. W. Uhl, Z . Anorg. Allg. Chem.. in press.
Angew. Chem. Inr. Ed. Engl. I9 (1980) No. 9
Fig. I . ORTEP plot of the molecular structure of dimeric lithium dibenzoylphosphide - 1.2-dimethoxyethane. The vibrational ellipsoids correspond to 50%probability. (2). space group P2,/c, with a = 1907.1(7), b=762.6(7), c=1259(2) pm.
p = 104.5(1)"; 4 formula units. 1907 independent, observed ( F > v ) reflections recorded on an automatic four-circle diffractometer CAD4 (Enraf-Nonius) al
- 80°C (MoKItradiation, 4"<20<48") and corrected In the conventional way:
R, = 0.034.
(2) exists as 2-phospha-1,3-dionate; the lithium ion is
bonded to all oxygen atoms of the ligands. No monomer is
present in the solid state; by the inversion as a
crystallographic symmetry operation the molecules are
linked pairwise to form dimers (Fig. 1). The coordination
number of lithium is raised to 5 by bonding to a further oxygen atom 012' belonging to the inverse dibenzoylphosphide
ion; the two lithium atoms of the dimer are located 45 pm
above the basal planes of two edge-linked, somewhat distorted square pyramids of 0 atoms. Although the Li-Li distance (283 pm) is shorter than in the element (304 pm)@+I,
metal-metal interaction can be ruled out at a covalent radius
of 134 pm[6b'.Similar association is observed in other 1,3dionatesI6"l.
Q Verlag Chemie. GmbH, 6940 Weinheim, 1980
0570-0833/80/0909-074I
$ 0 2 50/0
741
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