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C4O2 (1 2 3-Butatriene-1 4-dione) the First Dioxide of Carbon with an Even Number of C Atoms.

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pseudotrigonal arrangement a total of three small and three
large cavities, of which the latter type is highlighted in Figure 1. The H atoms of the OHe ions probably project into
the small cavities. In agreement with the generally low proton-donor strength of the OHQion, they do not participarte
in hydrogen bonds.['' The large cavities enclose the Cs@ions
and may be considered as cuboctahedra consisting of nine
H,O molecules and the three OHe groups, compressed
along the pseudo-threefold axis (Fig. 2). The corresponding
ther details of the crystal structure determination can be obtained o n
request from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschdftlich-technische Information mbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-54521. the
names of the authors, and the journal citation.
[7] Even without definitely determined H-atom positions the assignment of
H,O and OHe as made for the subsequent description of the structure is
practically inevitable.
[8] M. OKeeffe, S. Anderson, Acta. Crystallogr. Sect. A 33 (1977) 914.
[9] Due to difficulties in the preparation of samples an IR spectrum of the
substance suitable for a check of this result could so far not be obtained.
However, apart from the O . - - Odistances already assigned as hydrogen
bonds (see text), there are no further distances with OH" ions smaller than
3.385(5) .& in the structure.
[lo] C. K . Johnson, ORTEP 11, Report ORNL-5138. Oak Ridge National
Laboratory, Oak Ridge, TN, 1976.
C 4 0 , (1,2,3-Butatriene-l,Cdione), the First Dioxide
of Carbon with an Even Number of C Atoms
By Giinther Maier,* Hans Peter Reisenauer, Heinz Balli,
Wilty Brandt, and Rudoy Janoschek
Fig. 2. Stereoscopic drawing of two cuboctahedra containing the Cs@ ions,
succeeding each other along the pseudo-threefold axis, and their connection by
hydrogen bonds; same way of representation as in Figure 1.
twelve Cs-0 distances of 3.287(3) to 3.981(3)A are the
shortest ones; the next shortest distance, however, is already
4.113(3) A.
In the higher hydrates of NaOH the OHQions are also not
coordinated to the small, hard Na@ ions.['] This generally
has to do with the lowered charge density of the OHe ions
due to multiple proton-acceptor function in hydrogen
bonds. Conversely, in the title compound the coordination
of two of the OHeions to the large, softer Cse ion is reflected in the shortest Cs-0 distances (3.287(3) and 3.296(3) A),
and also the third OHe ion, following after five H,O
molecules, i s still rather tightly bound at 3.542(3) A.
Received: September 28, 1989;
supplemented: April 9, 1990 [Z 3567 IE]
Publication delayed at authors' request
German version: Angew. Chem. 102 (1990) 949
CAS Registry number.
CsNa2(OH),.6H,0. 128112-95-8
P. A. Agron, W R. Busing, H. A. Levy, Winter Meet. f 9 7 2 Crystallogr.
Assoc.. Albuquerque, N M , Collect. Abstr., p. 52; 1. A. Wunderlich, Bull,
Soc. Fr. Mineral. Cristallogr. 81 (1958) 287; G. Beurskens, G. A. Jeffrey,
J Chem. Phys. 4 f (1964) 924; P. Hemily, C . R. Hebd. Seances Acad. Sci.
236 (1953) 1579.
R. Seidel. Dissertation, Universitat Dusseldorf 1988.
H. Jacobs, T. Tacke, J. Kockelkorn, 2. Anorg. Allg. Chem. 516 (1984) 67;
H. Jacobs, A. Schardey, zbid. 565 (1988) 34; H. Jacobs, B. Harbrecht, P.
Muller. W Bronger, ihid. 491 (1982) 154.
H. Jacobs, A. Schardey, 8. Harbrecht, Z . Anorg. A&. Chem. 555 (1987)
43.
L A . Sadokhina, V. V. Otdel'nov, G. V. Zimina, S. B. Stepina, R u n . J
Inorg. Chem. (Engl. Transl.) 25 (1980) 1266.
Large. colorless columns of the title compound were obtained by slow
evaporation of the solvent water; space group Pca2, (No. 29), a =
13.951(3). b = 6.089(1), e = 12.508(3) A, V = 1062.6 A3, 2 = 4, SiemensStoe AEDZ, Mo,. radiation, graphite monochromator, measuring range
3" < 20 < 70", 2430 measured symmetry-independent reflections, of
which 2202 with F > 4 4 6 , absorption correction with $-scan, R = 0.026,
R, = 0 040. Due to the strongly scattering Cs atoms the H atoms could not
be localized unambiguously; a neutron diffraction study is planned. FurAngen.. Chem. Int. Ed. EngI. 29 (1990) No. 8
0 VCH
Dedicated to Professor Wolfgang Kirmse on the occasion of
his 60th birthday
The long known dioxides of carbon, CO, 1 and C,O, 3, as
well as that recently prepared by us, C,O, 5:11 have an odd
number of carbon atoms. Analogues with an even number of
carbon atoms-C,O,
2 or C40, &have so far defied experimental detection.[', 31
Theoretically, the compounds 2 and 4 should-in contrast
to 1 , 3 and S h a v e a triplet ground
as also indicated
by simple MO considerations: the electronic situation compares with that in the 0, molecule. The .rc-molecular orbitals
of 1-5, with a linear geometry (D-,,), are pairwise degenerate
(x and y directions indistinguishable). This leads, with an
even number of C atoms, to two electrons being available for
the highest occupied pair of molecular orbitals instead of the
four electrons required for a closed shell. According to
Hund's rule this situation should lead to a triplet ground
state.
Motivated by the simple synthetic entry to 5 by photolytic
or thermal decomposition of trisdiazocyclohexanetrione [I1
we have prepared the structurally similar cyclic diazoketones
615'-8 by diazo-group transfer in the hope of finding an
entry to 2 or 4.
[*] Prof. Dr. G. Maier, Dr. H. P. Reisenauer
Institut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-6300 Giessen (FRG)
Prof. Dr. H. Balli, DipLChem. W. Brandt
Institut fur Farbenchemie der Universitat
St. Johannsvorstadt 10, CH-4056 Basel (Switzerland)
Prof. Dr. R. Janoschek
Institut fur Theoretische Chemie der Universitdt
Mozartgasse 14, A-8010 Graz (Austria)
Verlagsgesellschaft mbH. D-6940 Weinherm, 1990
0570-0833~90/0808-0905$3.50+ .25/0
905
'Ao
-
Table 1. Observed IR absorptions (argon matrix, 12 K) and calculated vibrations of
(3X8-,'A,) [cm-'I, relative IR intensities [%I in brackets.
4
hv, A
3
Calculation
Experiment
(PM3)
Z
',
N2
6
(0.0)
A, 2436
(0.0)
A, 2073
(00)
A, 740
B, 2303 (100.0)
(0.8)
B, 1374
(0.0)
A, 375
B,
312
(0.0)
(0.0) A, 317
(0.0)
(1.3) A, 616
(1.2)
B, 200
(2.2)
(0.0) A, 115
(0.0)
B, =O[c] (0.7)
C , 2515
(0.0)
Z, 2062
(0.0)
Zg 709
(0.0)
Z, 2319 (100.0)
Xu 1408
(1.1)
436
(0.0)
V,
II,
IT,
v8
n,
vg
326
408
107
'A, ( C d
(DmA
v,[a]
v2
v3
v4
v5
v6
n,
(MNDO)
'XF (Dad
(0.0) 2277[b]
2597
(0.0) 1816[b]
2144
(0.0) 642[b]
727
2481 (100.0) 2130.3 (100.0)
(0.2) 1276.9
(7.0)
1451
(0.0)
547
363
508
127
+ v4 (Z")
+ vs (X")
+ V& (Z")
+ v5 (X")
+ v4 (Z")
v3 (X,) + "3 (Z")
"5
I
1000
'
'
'
l
'
'
'
'
-
~
'
"
'
3000
l
'
'
2000
'
~
l
~
I ,
~
"
/
~
~
(0.0)
-
(2.0)
~
etries compare equally well with the experimental spectrum,
so that a decision between a linear and slightly bent structure
on the basis of the IR spectrum is not possible. The bands
observed at 2130 and 1277 cm-', however, can be assigned
to the two IR-active stretching vibrations C, or B, respectively, and the weak band at 467 cm-' to the higher of the
two IR-active bending vibrations IT, or A, respectively. The
positions of the three IR-inactive stretching vibrations Z,
and A, can be calculated indirectly from the six observable
combination bands (Cg+ C, or A, + BJ. They should be
observable at about 2277,1816 and 642 cm-' in the Raman
spectrum.
The dependence of the photolysis of 7 and 8 on the wavelength of the incident light is clearly demonstrated in Figure
2. C,O, absorbs at 1 = 340,334 and 212 nm; its absorption
at 250 nm, on the other hand, is negligible. Consequently,
the secondary cleavage into C,O and CO proceeds decisively
slower with light from a mercury low-pressure lamp
(1= 254 nm) than with light of longer wavelength. More-
2 0-
'
467.1
[a] Numbering referred to D,, symmetry. [b] Average value determined from combination bands. [c] The values for this vibration vary between 50 i and 50 cm- ' with
very small changes in geometry. The associated differences in energy are
<0.01 kcal mol-'. This suggests presence of a quasilinear molecule.
t
/
-
4403.0
3558.6
3943.4
3095.8
2771.3
1918.9
(Z,)
vi (Z,)
v2 (Z,)
vz (Z,)
v3
30Ext -
00
-
-
-~
V'
The three precursors were subjected both to a high-vacuum flash pyrolysis with subsequent isolation of the products
in an argon matrix, as well as to direct irradiation in the
matrix. In the thermolysis of 6 and its photolysis with a Hg
low-pressure lamp (254nm) only 3 could be detected IR
spectroscopically. In contrast, the gas-phase thermolysis of
the diazoketones 7 and 8 afforded the already known C,O
9,@1which could be identified by its characteristic bands in
the IR spectrum of the matrix-isolated products. More interesting is the photolysis of the matrix-isolated precursors 7
and 8, which crucially depends on the wavelength of the
irradiating light. With wavelengths > 300 nm (Hg high-pressure lamp/long pass filter or monochromator) 9 is smoothly
formed again in both cases. If, on the other hand, a Hg
low-pressure lamp (254 nm) is used as light source only a
small amount of 9 is formed initially. The main product is
now C,O, 4, the IR spectrum of which is shown in Figure 1 .
-
(0.0)
(1.5)
"
l
~
Ext
'
~
'
1l
1000
G icm-'~
Fig. 1. Photolysis of 7 in an argon matrix: difference spectrum (5 mm 254 nm 10 min 335 nm; the bands pointing downwards belong to C,O; numbering
referred to D,, symmetry). Ext. = absorbance.
This assignment is supported by the observation that 4
rapidly dissociates into CO and 9 upon continuation of the
photolysis with wavelengths > 300 nm.
To corroborate the analysis of the IR spectrum we have
calculated the geometry of C,O, (triplet and singlet state) by
semiempirical methods (PM3 and MNDO) [optimized geometries: linear (Dm,,)and bent (C,,J, resp.]. The calculated
vibrational spectra are listed together with the experimental
data in Table 1 . The band patterns obtained for both geom-
906
0 VCH VerlagsgesellschafrmbH. 0-6940 Weinheim. 1990
n
d
1
200
.--.
......-.
..-.
- - -250
300
350
inml
-
LOO
150
Fig. 2. Photolysis of 8 in an argon matrix: (-..) unirradiated, (-)
254 nm, (---) 10 min 335 f 10 nm.
OS70-0833J9OjO808-0906$3.50+.25/0
500
5 min
Angew. Chem. Int. Ed. Engl. 29 (1990) No. 8
over, C,O, must also weakly absorb above 400nm (not
recognizable in the spectrum), since it also dissociates into
C,O and CO on irradiation with monochromatic light of
wavelength 436 10 nm.
The equilibrium structure of C,O, in the triplet state was
calculated both at the ab-initio UHF/3-21G(d) level as well
as by the semiempirical UHF-PM3 method (Scheme 1, left).
results. The orbital
In both cases a linear structure (Dmh)
situation also requires, despite Hund's rule, the investigation
of the lowest singlet state in order to determine the nature of
the ground state of 4, for the singlet state could, other than
in the case of the 0, molecule, be stabilized by bending and
thus compete energetically with the triplet state. Both ab-initio SCF as well as P M 3 calculations indicate a non-linear
singlet structure with C,, symmetry (Scheme 1, right).
1275 169"
(1.306)(160"1C+
1.268
(I .288)
0=c=c=c=c=0
1268
1.150
c=p-
0 + ~ ,.270
4 176"
0
1.147 (1.268) (166")
(1.174)
(1.266) (1.178)
Scheme 1. Left: equilibrium structure o f 4 in the lowest triplet state, calculated
at the ab initio UHF/3-21G(d) level (UHF-PM3 values in brackets). The bond
lengths are given in A. Right: equilibrium structure of 4 in the lowest singlet
state, calculated at the ab initio SCF/3-21G (d) level (PM3 values in brackets).
Four different sets of calculations consistently indicate a
triplet ground state. The small term splittings (Table 2), howTable 2. Calculated relativeenergy [kcal mol-'] of the lowest singlet and triplet
states of 4 ['A,(C,,) correlates with 'Ag (Dmh)].
PM3-C1[7]
'A, (CZJ
8.8
0.0
3xL ( R J
MCSCF[a]
3-21 + G
UMP2[9]
3-21G(d)
6-31G(d)
8.5
0.0
4.8
0.0
4.0
0.0
[a] 2-Electron-4-orbital-(rr,, rr,)-MCSCF[8]
ever, do not permit unequivocal conclusions to be drawn
about the ground state.
The electronically excited states and vertical excitation energies of C,O, were calculated by the MCSCF method.[*]
The results are listed in Table 3. There are symmetry allowed
Table 3. Calculated (2-configuration-MCSCF)vertical electronic transitions 2.
[nm] from Z
' , ( D e b )and 'Ag (C2J.*:symmetry allowed transitions.
~
~
32*-
h
3A"
433
42 1
400
299
295
32:
*32-
'A""
32:
*32
-
above 400 nm. For the photolysis product C,O we have calculated 317 and 288 nm respectively for the symmetry allowed transitions 'C+ + 'II and 'C+ + ' C + . These values
are in good agreement with measured values 295 and
280 nm.
The photolysis of C,O, at wavelengths of over 400 nm can
be correlated with the calculated transition 'A, + 'B, at
412 nm (Fig. 3). If the photolysis starting from the C,, sym-
176
~
1
'A,
* 'A,
* 'B,
*'BU
*'A,
* 'A,
*lB"
510
435
412
339
324
186
excitations at ca. 180 and 400 nm in both the triplet as well
as the singlet term scheme, whereas transitions, at 330 nm
are only possible from the 'A, state. The data for the observed absorptions of C,O, (Fig. 2) are, in good agreement
with the calculated singlet transitions, at 212, 334, 340 and
Angew. Chem.I n t . Ed. Engl. 29 (1990) No. 8
0 VCH
"4
'4'2
c30+co
Fig. 3. State correlation diagram for the mechanism of photolysis of C,O,.
metry terminates in the C, symmetry, 'A, (C,O, with eight
n electrons) correlates with the doubly excited state 'C+
(C,O with six n electrons) f IC+ (CO with two n electrons).
'B, (C,O, with six z electrons) correlates with the ground
state 'C+ C,O with four R electrons) + 'Z'(C0). As a result
of the avoided crossing C,O, ('BJ can dissociate non-adiabatically to C,O + CO in the ground states. The height of
the barrier to kinetic stabilization of C,O, ('AJ must, according to Figure 3, lie below the point of intersection of the
correlation lines, 1.e. below 60 kcal mol- '.Literature values
of 200 kcal molare based on unsuitable methods of
calculation (SCF), which cannot describe an avoided crossing.
In the hope of obtaining direct evidence for the triplet
character of C,O, we have investigated the irradiated
(2 = 254 nm) samples of 7 and 8 (argon matrix) ESR spectroscopically. However, up to the maximum magnetic field
strength of 7000 Gauss (measuring frequency: 9.38 GHz) of
the spectrometer available, no triplet signal could be recorded. On the assumption that C,O, does in fact have a triplet
ground state, the zero-field splitting parameter D must be
greater than 1.0 cm-'.rlO1Such a value is not unreasonable,
since very high D values have been measured for structurally
similar, linear cumulenes (ground state ,C)such as C,O (n
even),["] C, (n > 2, even),[lZ1 CNN,[131 SiC0,"41 and
SiNN.L'41
Hence, the negative ESR results do not in any way
rule out a triplet ground state for C,O,.
Summarizing: C,O, is a stable molecule under matrix conditions. It can be readily split photochemically into C,O and
CO. The question whether the molecule has a singlet or
triplet ground state is open.
Experimenlal
7: A mixture of 1,2,4-cyclopentanetrione[IS] (0.50 g, 4.5 mmol) and 2-azido-3ethyibenzothiazolium tetrafluoroborate [16] (5.00 g, 17.1 mmol) in water
Verlagsgeseiischaff mbH, 0-6940 Weinheim,1990
057#-0833/90/0808-0907 $3.50+ .25/0
907
(200 mL) was acidified with 3 drops of 32% HCI and stirred for 15 min at 50°C
(exclusion of light). After extraction with CH,CI,, the organic phase was dried
(Na,SO,) and purified on silica gel (20 8). After removal of the solvent there
remained 0.53 g (72%) of a crystalline product. For further purification the
substance was recrystallized from CH,CI,/Et,O; yield 0.42 g (57 %), colorless
platelets. M.p. 135- 137 "C (decomp.), noticeable decomposition above 120 "C.
(Igs)
,,*
=,
256 nm (4.37), 288 (4.011, 311 (3.51), 340 (3.55). IR
UV (CH,CI,): ,I,
(KBr): 3 = 2160cm-', 2135, 1755, 1685, 1355, 1355, 1310, 712. MS (70eV):
m / z (%) = 164 (9,Me), 136(7), 80(86), 68(69), 52(100). Correct elemental
analysis.
8: A mixture of dihydropyran-2,4,6-trione
[17] (0.60 g, 4.7 mmol) and 2-az1do3-ethylbenzothiazolium tetrafluoroborate [16] (3.00 g, 10.3 mmol) in 150 mL of
100 % glacial acetic acid was stirred for 2 h at 60 "C. The crude desired product
was precipitated by addition of 180 mL of Et,O. After filtration the crystalline
residue almost completely dissolved in CH,CI,/CH,CN (4: 1) and was purified
chromatographically on silica gel with CH,CI, as eluent. Evaporation of the
liquid phase to dryness furnished a crystalline residue, which was dissolved in
60 mL of CH,CI, and 20 mL of CH,CN. Subsequent dropwise addition of
250mL of Et,O and filtration afforded 0.31 g (36%) of colorless platelets.
Noticeable decomposition above 150°C. UV (CH,CI,): A,, (Ig E ) = 244 nm
(4.23, 258 (4.281, 268 (4.27), 280 (4.24). IR (KBr): V = 2170cm-', 2100, 1750,
1740, 1715,1640,1355,740,735. MS(70eV).m/z(%) = 180(30,M@),80(10),
68(39), 52(100). Correct elemental analysis.
Received: March 5,1990 [Z 3830 IE]
German version: Angew. Chem. 102 (1990) 920
[l] G. Maier, H. P. Reisenauer, U. Schafer, H. Balli, Angew. Chem. 100(1988)
590; Angew. Chem. Inf. Ed. Engl. 27 (1988) 566; see also: F. Holland, M.
Winnewisser, G. Maier, H. P. Reisenauer, A. Ulrich, J. Mol. Spectrosc. 130
(1988) 470.
[2] a) J. J. Bloomfield, I. R. S. Irelan, A. P. Marchand, Tetrahedron Lett. 1968,
5647. The bridged 1,2-diones described in this work have already been
irradiated by us in an argon matrix in a previous study (unpublished
experiments, 1979), and only CO was found. b) H.-D. Scharf, R. Klar,
Tetrahedron Lett. 1971, 517; c) J. Strating, B. Zwanenburg, A. Wagenaar,
A. C. Udding, ibid. 1969,125; d) D. Bryce-Smith, A. Gilhert,J. Chem. Soc.
Chem. Commun. 1968,1319; e) D. L. Dean, H. Hart, J Am. Chem. Sac. 94
(1972) 687; 9 M. B. Rubin, M. Weiner, H.-D. Scharf, ibid. 98(1976) 5699.
[3] The existence of the analogous carbon sulfides C,S, and C,S, has been
confirmed mass spectroscopically: D. Sulzle, H. Schwarz, Angew. Chem.
fOO(1988) 1384; Angew. Chem. Int. Ed. Engl. 27(1988) 1591; Chem. Ber.
122 (1989) 1803. Nole added i n proof: In the meantime we have generated
C,S, via an independent route, and isolated it in an argon matrix. Conversely, H. Schwarz and D.Siilzle have detected C,O, by neutralizationreionization mass spectrometry (private communication, April 30, 1990).
(41 a) G. P. Raine, H. F. Schaefer 111, R. C. Haddon, J Am. Chem. Sac. 105
(1983) 194, b) R. C. Haddon, D. Poppmger, L. Radom, &id. 97 (1975)
1645; c) R. C. Haddon, Tetrahedron Lett. 1972, 3897; d) J. Fleischhauer,
M. Beckers, H.-D. Scharf, ibid. 1973, 4275; e) P. Lindner, Y Ohm, J. B.
Sabin, I n ! . J. Quanrum Ckem. Symp. 7(1973) 261 ; 9 R. D. Brown, E. H. N.
Rice, J Am. Chem. Sac. 106 (1984) 6475.
[S] F. Henle, Justus Liebigs Ann. Chem. 350 (1906) 344.
[6] a) R. L. DeKock, W. Weltner, Jr., J. Am. Chem. Sac. 93 (1971) 7106;
b) R. D. Brown, F. Eastwood, P. S. Elmer, P. D. Godfrey, thid. 105 (1983)
6496; c) R. D. Brown, P. D. Godfrey, P. S. Elmer, M. Rodler, L. M. Tack,
ibid. 107 (1985) 4112; d)R. D. Brown, D. E. Pullin, E. H. N. Rice, M.
Rodler, ibid. 107 (1985) 7877.
171 J. J. P. Stewart, J. Comput. Chem. 10 (1989) 209, 221.
[8] H. J. Werner, W Meyer, J. Chem. Pkys. 74(1981) 5794; H. J. Werner, E. A.
Reinsch, ibid. 76 (1982) 3144.
[9] J. S. Binkley, M. J. Frisch, D. J. DeFrees, R. Krishnan, R. A. Whiteside,
H. B. Schlegel, E M. Fluder, J. A. Pople: GAUSSIAN 82, CarnegieMellon University, Pittsburgh 1982.
[lo] E. Wasserman, L. C. Snyder, W. A. Yager, J. Chem. Phys. 41 (1964) 1763.
[ l l ] a) R. J. Van Zee, G. R. Smith, W. Weltner, Jr., J. Am. Chem. Sac. 110 (1988)
609; b) D. W. Ewing, ibid. 111 (1989) 8809.
[12] R. J. Van Zee, R. F. Ferrante, K. J. Zeringue, W. Weltner, Jr., D. E. Ewing,
J. Chem. Phys. 88 (1988) 3465
[I31 a) E. Wasserman, L. Barash, W. A. Yager, J. Am. Chem. Sac. 87 (1965)
2075; b) G. R. Smlth, W. Weltner, Jr., J Chem. Phys. 62 (1975) 4592.
[14] R. R. Lemhke, R. F. Ferrante, W. Weltner, Jr., J. Am. Chem. Sac. 99(1977)
416
1151 J. H. Boothe, R G. Wilkinson, S. Kushner. J. H. Williams, J. Am. Chem.
Soc. 75 (1953) 1732.
[16] H. Balli, F. Kersting, Justus Liebigs Ann. Chem. 647 (1961) 1.
[17] R. Kaushal, J. Ind. Chem. Sac. f7(1940) 138.
908
c) VCH Verla~sgesell.scliaflmhH, 0-6940 Weinheim, 1990
Identification of Butatrienedione, Its Radical Anion,
and Its Radical Cation in the Gas Phase**
By Detlev Siilzle and Helmut Schwarz*
Dedicated to Professor Wolfgang Kirmse on the occasion
of his 60th birthday
There are several reasons for the exceptional interest"] in
linear and quasi-linear cumulenes of the general structure
XC,Y (X,Y = lone pair, H,, 0, S; n 2 2). The compounds,
some of which have been postulated as key intermediates in
the formation of interstellar species, possess unusual spectroscopic properties, and their reactivity/stability, as well as
their electronic ground state (singlet versus triplet), is governed by an "even/odd alternation". Although many combinations of XC,Y have long been known for n = 3, 5, the
even-numbered analogues (n = 2, 4, 6) have often eluded
unambiguous experimental identification. However, this situation is not due-as originally assumed 12]-to an intrinsic
instability of these curnulenes, but rather must be the result
of fast bimolecular reactions. For example, the dithiocumuand also the mixed S/O cumulenes SC,S (n = 2,4, 6)r1.3,41
lenes SC,0[51 and SC,0161 have been identified in the gas
phase by neutralization-reionization mass spectrometry
(NRMS)."]
On the other hand, all attempts so far to prepare and
characterize even-numbered cumulenediones OC,O (n = 2,
4, 6) have been unsuccessful. Although ethylenedione,
OC,O, for example, is expected to be a kinetically extremely
stable triplet on the basis of ab initio calculations,[*]from the
earlier attempts of S t a ~ d i n g e r [to
~ ] this day no group has
succeeded in generating and identifying this
Here we report the generation of the radical anion, radical
cation, and neutral molecule of butatrienedione, OC,O, in
the gas phase. These experiments complement the recent matrix studies of Maier et a1.I' l l
to 1[13] affords an
Dissociative electron
intense signal at m / z 80, which corresponds to a compound
having the elemental formula C,O?@. Mass selection of
C,Of@ via B(1)E and subsequent collisional activation of
the 8-keV ion beam (collision gas 0,; 80% transmission 7 )
afford the collisional activation (CA) spectrum shown in
Figure 1 a. All anionic decomposition products in Figure 1 a
can be explained by direct bond cleavage in 20e. The assignment of the connectivity OCCCCOoe to C,O?@ is supported by the fact that the tendency to undergo skeletal rearrangements is appreciably less for radical anions than for
radical
Accordingly, we conclude that loo eliminates CO, and (CH,),CO and is transformed into 20°
(Scheme 1). We further maintain that, except for COO'
(whose electron affinity (EA) is negative), all other species
(C,O,, C,O, C,O, C,O, C,, C,, and C,) must have positive
EA values.
Subjection of 20° in a further collision experiment to a
vertical charge reversal (CR)['4b, 16] results in the spectrum given in Figure 1 b. This spectrum contains an intense
"recovery signal" for C,Oye and establishes that not only
C,Ofe but also C,0Ye exists in a potential minimum.
Again remarkable is that, typical for a cumulene structure
20°, decomposition occurs via cleavage of individual bonds.
''3
[*] Prof. Dr. H. Schwarz, DipLChem. D. Sulzle
[**I
Institut fur Organische Chemie der Technischen Universitat
Strasse des 17. Juni 135, D-1000 Berlin 12
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and the Graduiertenkolleg Chemie
Berlin.
0S70-0833190/0808-0908$3.50+ ,2510
Angew. Chem. Int. Ed. Engl. 29 (1990) N o . 8
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