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Crystal Structure of [-Nitrobenzyllithium ╖ Ethanol]n; A Lithium Nitronate-Ethanol Interaction.

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[4] J. Evers, G. Oehlinger, G. Sextl, A. Weiss, Angew. Chern. 96 (1984) 5 12;
Angew. Chem. Int. Ed. Engl. 23 (1984) 528.
[5] J. Evers, G. Oehlinger, G. Sextl, A. Weiss, Angew. Chem. 9 7 (1985) 499;
Angew. Chern. Int. Ed. Engl. 24 (1985) 500.
16) H. G. von Schnering, Nova Acta Leopold. 264. Bd. 59 (1985), S. 165.
[7] R. A. Young (School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA): Program for Rierueld-Analysis of %Ray a n d Neutron Powder Diffraction Patterns by D. B. Wrles. 1982.
[S] Program inplemented on a Cyber 875 by Dr. H . - 0 . Becker, Munich
[9] Change of the PL factor for Guinier geometry by G. Sextl, Munich
[lo] W. Miiller, H. Schafer, 2. Naturjorsch. 8 2 8 (1973) 246.
(111 A Zalkin, W. J. Ramsey, J. Phys. Chem. 61 (1957) 1413.
Crystal Structure of
[a-Nitrobenzyllithium .Ethanol], ;
A Lithium Nitronate-Ethanol Interaction**
By Gerhard Klebe, Karl Heinz Bohn, Michael Marsch,
and Gernot Boche*
Ninety-three years ago, Holleman””] described the conversion of phenylnitromethane 1 into the sodium salt (“nitronate”) 2-Na. Shortly thereafter, Hantzsch et al.[’blfound
that protonation of 2-Na leads to an isomer of 1, the phenylmethanenitronic acid 3, which is slowly transformed
into 1 in solution (see also ref. [Ic]).
d C,H,-CH=N
Numerous applications have been reported for nitronates in synthesis.[21Nitronates are of particular interest in
substitution reactions that proceed through electron transfer.13] Here we report on the crystal structure of a lithium
nitronate, the title compound [2-Li. C2H50H], (see
Fig. la).[41
2-Li, which is prepared from 1 with lithium ethoxide in
crystallizes with ethanol in a molar ratio of 1 :1
as a polymeric aggregate. Two 2-Li.C2H50H species are
present in the asymmetric unit of the unit cell. Each lithium atom is bound to three oxygen atoms of three different
nitronate ions and to an oxygen atom of an ethanol molecule, resulting in the formation of Li-0-N-0-Li-0 sixmembered rings. These “annelated” rings are connected
through Li and 0 atoms forming an infinite, ribbonlike
structure, which is further stabilized by internal hydrogen
bonds. As a part of this framework, three six-membered
rings are shown in Figure lb. The conformation of these
rings is close to a boat form. With respect to a “best” plane
through the four basal atoms (Lil, N8, 0 9 , 0 2 9 ) of this
boat, the planes through the atoms of two neighboring
phenyl rings (Fig. la) are oriented nearly parallel whereas
those through the atoms of the two remaining phenyl rings
are arranged nearly perpendicular. In the C6H5CHN02
moiety, the “best” plane through C7, N8, 0 9 , 0 1 0 is
twisted by 15.2” with respect to a plane through C1 to C6.
This twisting and the significant expansion of the bond
angles to values larger than 120” indicate a reduction
of the van der Waals repulsion between H1 and 0 1 0
(distance 236 pm). Related bond angles were found for
2-Si(t-Bu)Me2.16] The C7-N8 bond (129 pm) is signifi-
Fig. I . a) Crystal structure of [Z-Li.C2H,0H].. The H atoms on the phenyl ring and the ethyl moiety have been omitted; the C atoms are only labeled by numbers
A Li-0-N-0-Li-0
six-membered ring is shown which has been extracfed from the infinite, ribbonlike framework of “annelated” six-membered rings. The
additional rings are connected through the oxygen atoms of the NO2 groups (cf. Fig. Ib). As indicated by the numbering scheme, the part shown in Fig. la is built
up from two Li atoms, two ethanol molecules, and four C6HSCHN02moieties, of which two are related by a symmetry operation.-Space group PnaZ,, selected by
means of intensity statistics; a=732.4(1), b = 1703.6(3), c = 1640.8(4) pm, Z = 8 (2 formula units per asymmetric unit). Data collection at ca. 230 K with monochromated CuKo radiation, profile analysis, structure solution by direct methods; refinement with 1351 reflections with F > 4 a ( F ) leads to R =0.054, SHELXTL
program [12]. The alkyl moiety of one of the ethanol molecules is disordered over two positions (C32, C32‘. C33, C33‘); only one arrangement is shown in the
figure. The positions of the H atoms on the anions and the ordered atoms of ethanol were determined by difference Fourier synthesis. Important distances [pm]
and angles [“I (average values or ranges): Lib0 191.9(10)-197.9(10); C-C(pheny1) 136.3(9)-141.5(8); C7-N8 129.3(7); N8-09 133.2(6); N8-010 130.1(5); 0-Lib0
99.7(4)- 122.3(4); CI-C6-C7 126.8(5); C6-C7-N8 126.5(5); C7-N8-010 124.7(5).-b) Three “annelated” Li-0-N-0-Li-0 six-membered rings of the infinite structure of [Z-Li .C2H50H],. For clarity, except for the C atoms of ethanol, all atoms that are not directly involved in the ring structure have been omitted: O H . . .O
hydrogen bonds of ethanol to the nitro group: 0 1 1 . . ,010 272.6(10) pm; 0 3 1 . . . 0 2 9 281.6(10) pm; 0 - H . . . O (averaged) 158”.-Further details of the crystal
structure investigation may be obtained from the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-75 14 Eggenstein-Leopoldshafen2 (FRO), on
quoting the depository number CSD-52057, the names of the authors, and the journal citation.
[*] Prof. Dr. G. Boche, M. Marsch
Fachbereich Chemie der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg (FRG)
Dr. G. Klebe, K. H. Bohn
BASF AG, D-6700 Ludwigshdfen (FRG)
This work was supported by the Fonds der Chemischen lndustrie and
the Deutsche Forschungsgemeinschaft.
0 VCH Verlagsgesellschafr mhH, 0-6940 Weinheirn. 1987
cantly shorter and the N8-09 and N8-010 bonds (133
and 130 pm, respectively) are significantly longer compared
with similar bonds in uncharged nitro compound^."^
Ethanol, which is used as solvent and which is formed as
reaction product from lithium ethoxide, is incorporated
into the crystal.[81In spite of the fact that for one of the
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Angew. Chem. In[. Ed. Engl. 26 (1987) No. 1
ethanol molecules a disordered arrangement of the carbon
atoms on two positions is found, the difference Fourier
synthesis reveals two peaks in the neighborhood of 0 1 1
and 0 3 1 which can be assigned to two protons o n the ethanolic oxygens. Furthermore, these maxima are suitably
oriented for a hydrogen-bond formation to the oxygen
atoms of the vicinal nitro groups. The geometry of these
hydrogen bonds matches that normally found for such
bonds (Fig. lb).i91
The presence of an O H . . .O hydrogen bond in the crystal structure of [2-Li.C2H50H], is in agreement with the
findings for nitronates taken from acidity measurements
on nitro compounds in protic
For example, in
alcohol or water nitromethane is appreciably more acidic
( p K , ( H 2 0 )= 10.2 1)1"1 than in aprotic dimethyl sulfoxide
(pK, = 17.2).1'01In the protic solvent the nitronate form is
stabilized by the formation of O H . . - 0hydrogen bonds.
As mentioned earlier, the nitronate 2-Na is protonated
to form the nitronic acid 3 and not the nitro compound 1.
Accordingly, it might be tempting to use the structure correlation principle to assign the geometry of the fragment
formed by the phenylmethylnitronate and the ethanol to
an incipient step of such a protonation reaction. However,
it has to be kept in mind, that any conclusion taken from
structure correlations gain their significance and reliability
from the statistical evaluation of a large data set containing the fragment under consideration embedded in various
environments. Thus, to support the outlined assumption,
the results for [2-Li.C2H50H], have to be completed by
further examples.
Received: August 1, 1986;
supplemented: September 4, 1986 [Z 1885 IE]
German version: Angew. Chem. 99 (1987) 62
[ I ] a) A. F. Holleman, Reel. Trau. Cfiim. Pays-Bas 13 (1894) 403; b) A.
Hantzsch, 0. W. Schultze, Ber. Dtsck. Chem. Ges. 29 (1896) 699; c) A. T.
Nielsen in H. Feuer (Ed.): The Chemistry of the Nitro and Nitroso Group,
Part I . Wiley, New York 1969, p. 349.
[2] a) D. Seebach, E. W. Colvin, F. Lehr, T. Weller, Ckimra 33 (1979) I ; b)
M. Eyer, D. Seebach, J. Am. Chem. SOC.107(1985) 3601; c) M. Braun,
Nachr. Chem. Tech. Lab. 33 (1985) 598.
131 a) N. Kornblum, R. E. Michel, R. C. Kerber, J . Am. Chem. SOC.88
(1966) 5660,5662; b) G. A. Russell, W. C. Danen, ibid. 88 (1966) 5663; c)
N. Kornblum, Angew. Cfiem. 87 (1975) 797; Angew. Chem. Int. Ed. Engl.
14 (1975) 734.
[4] Crystal structures of nitronates that contain several acceptor substituents are known; see, e.g., a) 2K"[02CCHN02]", D. J. Sutor, F. J.
Llewellyn, H. S. Maslen, Acta Crystallogr. 7 (1954) 145; b)
NHf(K@)[(H2NC0),CNO2]', 0. Simonsen, ibid. 8 3 7 (1981) 344; c)
2 Rb"[(0,N)2C-C(N02)2]2G, B. Klewe, Acra Chem. Scand. 26 (1972)
1049; d ) K'(R~",CS@)[(O,N)~CH]', N. V. Grigor'eva, N. V. Margolis, I.
N. Shokhor, I. V. Tselinski, V. V. Mel'nikov, Zh. Strukt. Khim. 9 (1968)
475 (engl. translation); e) K0(Rb@,Cse)[(O2N),C]', N. V. Grigor'eva, N.
V. Margolis, I . N. Shokor, V. V. Mel'nikov, 1. V. Tselinski, ibid. 7 (1966)
272 (engl. translation).
[S] Preparation of [2-Li.C2H50HIn:1 (100 mg, 0.73 mmol) in 2 mL of ethanol was treated at 20°C with 0.87 mmol of lithium ethoxide. After 2 h,
the solution was concentrated in vacuum to ca. I mL. After 12 h, it was
possible to free the colorless. needle-shaped crystals from the solvent
using a syringe; yield 0.1 1 g (78%).
[6] E. W. Colvin, A. K. Beck, B. Bastani, D. Seebach, Y . Kai, J. D. Dunitz,
Helo. Chim. Acta 63 (1980) 697.
171 Examples: a) 2.3-dimethyI-2.3-dinitrobutane: C-N 154.7, N - 0 122.1
and 122.7 pm; Y. Kai, P. Knochel, S. Kwiatkowski, J. D. Dunitz, J. F.
M. Oth, D. Seebach, Helu. Chim. Acta 65 (1982) 137; b) 1.2-diphenyl3-nitrocyclopropene: C-N 151.8, N - 0 121.4 and 121.7 pm; M. Marsch,
W. Massa, G. Boche, unpublished results.
[8] T. Laube, J. D. Dunitz, D. Seebach, Helu. Chim. Acta 68 (1985) 1373,
reported on the interaction between lithium enolates and secondary amines in the crystal (and in solution).
[9] Similar distances and bond angles have been found for other 0 - H . . . O
hydrogen bonds; see, e.g., a) I. Olovsson, P.-G. Jonsson in P. Schuster,
Angew Chem. Int. Ed. Engl. 26 (1987) No. I
G. Zundel, C. Sandorfy (Eds.): The Hydrogen Bond, Vol. 2. North Holland, Amsterdam 1976, S. 393: b) F. A. Allen, 0. Kennard, R. Taylor,
Ace. Chem. Res. 16 (1983) 146; c ) H. B. Biirgi, J. D. Dunitz. ibid. 16
(1982) 153; d) R. Taylor, 0. Kennard, rbrd. 17 (1984) 320.
[lo1 F. G. Bordwell, J. C. Branca, D. L. Hughes, W. N. Olmstead, J . Org.
Chem. 45 (1980) 3305, and references cited therein.
[ I l l See [Ic], p. 373.
[I21 G. M. Sheldrick, SHELXTL Program Package, Universitat Gottingen
Synthesis of Nitriles via the Ylide Anion of
Sodium Cyanotriphenylphosphoranylidenemethanide
By Hans Jurgen Bestmann* and Martin Schmidt
In phosphonium ylides, the phosphorus atom is capable
of stabilizing quasi two negative charges."] For this reason,
anionic compounds of type 2 may be generated from
ylides 1 that have an H atom in the a position to phosphorus.~2-~]
We have now been able to deprotonate cyanomethylenetriphenylphosphorane 3 with a benzene solution of sodium bis(trimethylsilyl)amide 4 to give the salt 5 having
an ylide anion.
Compound 5 is isolated, upon evaporation of the solvent, as a yellow, air- and moisture-sensitive powder, thus
allowing the first spectroscopic investigation of such a species. In the IR spectrum of 5 , the nitrile band appears at
6=2000 c m - ' ; in comparison, 6=2130 c m - ' in the case
of 3.I6l Whereas the "P-NMR signal of 3 appears at
6=23.2 (H3POa as external standard), that of 5 occurs at
6 ~ 2 . 5 a, value that is similar to that found for the N-substituted triphenylphosphoranylidene ketenimines (6= 2.35.0)."' We conclude from this that the resonance structure
5b strongly contributes to the electron distribution in 5 .
The l3C-NMR signal of the ylidic C atom appears at
6=6.60; Jpc=94.6 Hz. The coupling constant shows that
the anion 5 has a smaller P-C,,-C,, angle than open-chain
phosphacumulene y l i d e ~ . ~ ' . ~ ]
Compound 5 reacts with halogen compounds 6 to give
the cyanomethylenetriphenylphosphoranes 7, which are
thereby accessible more readily in greater variety than previously. Examples are listed in Table I.[91
@ I
- XH
@ I
e e
e O
A Na@ Ph3P-C-CN
- HN(SiMe3)Z
e 'I.
- NaX
[*] Prof. Dr. H. J. Bestmann, Dip].-Chem. M. Schmidt
Institut fur Organische Chemie der Universitat Erlangen-Nurnberg
Henkestrasse 42, D-8520 Erlangen (FRG)
0 VCH Verlagsgeseflscha/r mbH, 0-6940 Weinheim. 1987
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crystals, structure, ethanol, interactiv, nitrobenzyllithium, nitronate, lithium
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