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Carboxime (Isofulminic Acid).

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171 R. S. Atkinson, M. J. P. Harger, J . Chem. SOC.Perkin Trans. 1 1974.
2619, and references cited therein.
[8] H. Sauter, H.-G. Horster, H. Prinzbach, Angew. Chem. 85 (1973) 1106;
Angew. Chem. Int. Ed Engl. 12 (1973) 991.
191 I. D. C. Rood, G. W. Klumpp, R e d . J. R. Nerh. Chem. SOC.103 (1984)
[lo] The elemental analysis (found C 50.16, H 2.12, N 41.37; (CN), calcd
C 46.14, N 53.86) merely reveals that the ratio C : N (1.4 : 1) roughly corresponds to the value expected; possibly, other substances are present.
The brown paracyanogen (CN), [ I l l formed from 1 at higher temperatures is also difficult to analyze [ I Ib]. It should be noted here that diisocyanomethane CH2(NC)>,like 3, polymerizes at -30°C [12].
[ I I] a) T. K. Brotherton, J. W. Lynn, Chem. Reu. 59 (1959) 841; b) L. L. Bircumshaw, F. M. Tayler, D. H. Whiffen, J. Chem. SOC.1954, 931.
1121 R. Neidlein, Angew. Chem. 76 (1964) 440: Angew. Chem. Int. Ed. Engl. 3
(1964) 382.
[I31 R. W. Stephany, M. J . A. de Bie, W. Drenth, Org. Magn. Res. 6 (1974)
[I41 8. E. Mann in R. K. Harris, B. E. Mann (Eds.): NMR and the Periodic
Table. Academic Press, London 1983, S. 96, and references cited therein.
[ 151. D. Herbison-Evans, R. E. Richards, Mol. Phys 8 (1964) 19.
[I61 NBS Library Compilorion. disk library number 55, Finnigan Corporation, San Jose, CA, USA 1984.
[ 171 a) See [I], p. 859; b) W. Reichen, C. Wentrup, Helm Chim.Actn 59 (1976)
2618; c) C . Wentrup, U. Stutz, H. J. Wollweber, Angew. Chem. 90 (1978)
731; Angew. Chem. Int. Ed. Engl. 17 (1978) 688, and references cited
1181 P. A. Kraakman, E. T. J. Nibbering, W. H. de Wolf, F. Bickelhaupt,
Tetrahedron 43 (1987) 5109, and references cited therein.
Upon acidification the fulminates furnish exclusively formonitrile oxide 1, whereas the cyanates give only isocyanic acid 3 (Raman@"]and IR[6b1spectrum). In agreement with these observations the structural data indicate
that resonance structure l e is the most important one in
the case of silver fulminate and that the canonical form 3
is the main contributor in the case of silver cyanate.
Only with the help of the matrix isolation technique has
it been possible to demonstrate the existence of cyanic acid
4 directly."' Herein, we report that the last and only missing isomer, namely the real carboxime 2 (isofulminic
acid)[*]-altogether there are four "chemically reasonable"
linear arrangements (cf. formulas 1-4) for a compound of
the formula CHNO-is detectable by the same technique.
Carboxime (Isofulminic Acid)**
By Giinther Maier, * Joaquim Henrique Teles,
B. Andes Hess, Jr., and Lawrence J. Schaad
When, after some controversy (1823-1 826),['] it became
clear that silver fulminate (Liebig) and silver cyanate
( Wohler) have the same composition but different chemical
properties, the theoretical interpretation followed inevitably: the phenomenon of isomerism had been observed
(Berzelius, 1830"l). The order of the C and N atoms in the
two salts is interchanged.[*]
The discussion concerning the free acids 1-4 related to
the fulminates (1'++2') and cyanates (3'++4') has continued until today: For fulminic acid only dimeric structures were considered initially.[31 NdT1 in 1894, was the
first to recognize the monomeric constitution and ascribed
to it the carboxime formula 2. Seventy more years were to
pass until fulminic acid was unequivocally characterized,
on the basis of its spectroscopic data (IR[5a.b1and microwave spectrumf5']), as formonitrile oxide 1 (instead of 2).
0 @
+ H-N=C=O
Irradiation of dibromoformoxime 519] in argon at 12 K
with a low-pressure mercury lamp leads to disappearance
of all IR bands of 5 within 20 minutes, and one obtains the
IR spectrum shown in Figure 1, which we assign to the
carboxime 2. Our arguments in support of this assignment
are: 1. The new species shows a spectrum different from
that of fulminic acid, and even more different from that of
isocyanic acid or cyanic acid. 2. The asymmetric stretching
vibration of the O N C unit in 2 appears at 2190 cm-'. This
CO. 2
- 3icm-']
Fig. I . IR spectrum of isofulminic acid in an Ar matrix at 12 K.
[*] Prof. Dr. G. Maier, DipLChem. J. H. Teles
Institut fur Organische Chemie der Universitat
Heinrich-Buff-Ring 58, D-6300 Giessen (FRG)
Prof. Dr. B. A. Hess, Jr., Prof. Dr. L. J. Schaad
Department of Chemistry, Vanderbilt University
Nashville, T N 37235 (USA)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen 1ndustrie.-B. A . H . and L. J. S. thank the
National Science Foundation (Grant CHE 8605951) for financial support.
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position almost coincides with the position of the corresponding band of fulminic acid 1 (2193 cm-'), but is located at much lower wavelength than the corresponding
absorption of isocyanic acid 3 (2260 cm -') o r cyanic acid
4 (2286 cm-'). Calculations also predict that carboxime 2
should show the smallest wave number for this vibration.
3. The difference of 96 cm-' between the wavelengths at
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Angew. Chem. Int. Ed. Engl. 27 (1988) No. 7
a) J. Goubeau, Chem. Ber. 68 (1935) 912; b) G. Herzberg, C. Reid, Discuss. Faraday Soc. 9 (1950) 92. In many textbooks the free acid is, as
previously, given the wrong structure 4 .
a) M. E. Jacox, D.E. Milligan, J . Cbem. Phys. 40 (1964) 2457; b) V. E.
Bondybey, J. H. English, C. W. Mathews, R. J. Contolini, J . Mol. Spectrosc. 92 (1982) 431.
This molecule is not only of interest in a "local" sense-Liebig carried
out his investigations on fulminic acid here in Giessen-but also because this species, in analogy to 3, could occur in intersteller space: G.
Winnewisser, E. Herbst, Top. Curr. Chem. 139 (1987) 119; M. Winnewisser, Chem. Unserer Zeit 18 (1984) 1, 55.
G. Maier, J . H. Teles, Angew. Chem. 99 (1987) 152; Angew. Chem. Inr.
Ed. Engl 26 (1987) 155.
C. Wentrup, B. Gerecht, D.Laqua, H. Briehl, H.-W. Winter, H. P. Reisenauer, M. Winnewisser, J . Org. Chem. 46 (1981) 1046.
Within the context of the naming of the free acids (1: fulminic acid,
formonitrile oxide; 2 : isofulminic acid, carboxime; 3 : isocyanid acid,
cyanic acid) and salts ( l * - Z e : fulminates, 3 e + + 4 e : cyanates) it would
of fulminic acid fulminates
be logical to name the esters R-C-N"-Oe
or nitrile oxides and the esters of isofulminic acid isofulminates (and not
fulminates [lo]) or 0-alkylcarboximes.
G. Maier, H. P. Reisenauer, W. Schwab, P. Carsky, B. A. Hess, Jr., L. J.
Schaad, J. Am. Chem. SOC. 109 (1987) 5183.
a) G. Maier, H. P. Reisenauer, Angew. Chem. 98 (1986) 829; Angew.
Chem. Inr. Ed. Engl. 9 (1986) 819. The UV spectra of 2a and 2c depicted therein (in Fig. 2) must be interchanged; b) G. Maier, H. P. Reisenauer, unpublished.
a) MP2/6-31G** calculations (B. A. H.,L. J. S.);sequence of the stabilities: 3 > 4 > 1 > 2 ; b) cf. also: D. Poppinger, L. Radoc, J. A. Pople, J .
Am. Cbem. SOC. 99 (1977) 7806 ( 3 > 4 > 1 > 2 ) ; c) A. D. McLean, C. H.
Loew, D.S. Berkowitz, J. Mol. Spectrosc. 64 (1977) 184 ( 3 > 4 > 1 = 2).
which these absorptions of 4 and 2 appear has also been
observed in the spectra of the corresponding esters; the 0alkyl derivatives of 2 prepared by Wentmp et al.["] absorb
at 2108-2160 cm-', the cyanates at about 2250 cm-'. 4.
The experimental and calculated IR spectra of 2 and its
isotopomer [D]2 (Table I ) are in satisfactory agreement,
even though the difference is greater than in other cases.[121
5. On prolonged irradiation (254 nm), the photoproduct of
5 is converted into isocyanic acid.
Table 1. Comparison of the experimental (Ar matrices, 12 K ; relative intev- and 6-absorpgrated intensities) and calculated IR spectra of 2 and [D]2:
tions in cm -I
628 (0.03)
379 (0.05) [a]
361 (0.03)[al
e N C
2 x HOW DO^)
3803(1.00) 2545(1.00)
2139(0.03) 2190(0.13)
1416(0.69) 903(0.22)
1001(0.37) 623(0.04)
319(0.02) 274(0.06) 362(0.09) [a]
1794(0.03) [b]
998 (0.52)
267 (0.10)
[a] Assignment may have to be changed. [b] Assignment based on the matrix
A conceivable alternative is that 5 loses only one halogen atom upon irradiation, resulting in formation of the
isomer 6. This type of reaction has recently been described
by us for iodine-containing dihal~methanes.['~"~
Dibromomethane 7 could analogously be isomerized to 8."3bJ
This photoisomer shows a strong characteristic UV band at
360nm. In contrast, no absorption is observed between
250 and 800 nm in the photolysis of 5 . In other words: irradiation of 5 does not lead to 6 but to carboxime 2.
It is no wonder that compound 2 has hitherto evaded
direct detection, since it has the highest energy of the four
isomers 1-4.
Received: March 7, 1988 [Z 2652 IE]
German version: Angew. Chem. 100 (1988) 1014
[ I ] R. Winderlich in G. Bugge (Ed.): Das Buch der grossen Chemiker, Vol. 2,
Verlag Chemie, Weinheim 1955, p. 6.
121 X-ray stmcture analyses of silver fulminate and silver cyanate: a) D.
Britton, J. D. Dunitz, Acta Crystallogr. 19 (1965) 662; b) ibid. 18 (1965)
[3] Summary: C. Grundmann, P. Griinanger: The Nitrile Oxrdes, Springer,
New York 1971, p. 3ff.
[41 J. U. Nef, Jusfus Liebigs Ann. Chern. 280 (1894) 291.
[5] a) W. Beck, K. Feldl, Angew. Chem. 78 (1966) 746; Angew. Chem. Int.
Ed. Engl. 5 (1966) 722: W. Beck, P. Swoboda, K. Feldl, R. S. Tobias,
Cbem. Ber. 104 (1971) 533; b) B. P. Winnewisser, M. Winnewisser, F.
Winther, J . Mol. Specrrosc. 51 (1974) 65; c) M. Winnewisser, H. Bodenseh, 2. Naturforsch. A 2 2 (1967) 1724; ibid. A24 (1969) 1966, 1973.
Angew. Chem Inr. Ed. Engl. 27 (1988) No. 7
Stepwise Synthesis and Crystal Structure of
Tricarbonyl[pentakis(methylthio)cyclopentadienyl]manganese I(C5(SMe)5)Mn(CO)31**
By Karlheinz Siinkel* and Doris Motz
Complexes containing cyclopentadienyl ligands substituted with functional groups are an interesting class of
compounds.[*] Owing to both their electronic effect and
their ability to coordinate further metal fragments, the
functional groups can be of great importance for the reactivity, in particular the catalytic activity, of the c ~ m p l e x . [ ~ , ~ ~
Whereas a large number of metal complexes containing
one functional group on the cyclopentadienyl ring are
known, relatively few examples containing five such substituents R ( R = CI,I5] BrJ6I C02Me[']) have been reported.
Although the anions [C5(CN)5]Q'81
and [C5(SMe),lQr91
been known for some time, it has not been possible so far
to incorporate them into n complexes. In view of the increased interest in mono- and dichalcogen-substituted ferrocenes,['*I we have developed a stepwise synthesis of the
complexes 5 starting from 1, which is obtainable from
By successive halogen-metal exchange and reactions
with dimethyldisulfane, it is possible to prepare each member of the series [(T~'-C~C&
px(SMe),]Mn(C0)3]with x = 1-5.
The reaction of 1 with BuLi/Me2S2 can afford in principle two stereoisomers of 2. An X-ray crystal structure
analysis showed that the 1,3-disubstituted isomer was
[*] Dr. K. Sunkel, D. Motz
lnstitut fur anorganische Chemie der Universitat
Meiserstrasse I, D-8000Miinchen 2 (FRG)
Complexation Chemistry of Perhalogenated Cyclopentadienes and Alkynes, Part 2. We thank Prof. Dr. W . Beck for his interest in and support
of this work.-Part 1: [I].
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acid, isofulminic, carboxime
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