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Difference Electron Densities in a Spiropentene.

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tals of 4 are isolated from the resulting deep red solution at
product is air- and moisture-sensitive.
- 25°C.
Received: December 17, 1990 124329 IE]
German version: Angew. Chem. 103 (1991) 594
CAS Registry numbers :
2 (X= 3). 132645-88-6; 3, 74507-64-5; 4, 132645-87-5
Fig. 1. Left: Structure of 4 in the crystal (hydrogen atoms omitted.) Selected
distances [pm] and angles ["I (standard deviations in parentheses): (dm,,/dmi./d)
AI-AI (277.3 (4)/276.7 (5)/276.9), AI-CRiag(229.2 (13)/237.8 (11)/233.4), AlCp,,.,,, (203.2/199.7/201.5). AI-AI-A1 (60.1 (1)/59.9 (1)/60.0). Right: Spacefilling model of 4; AI atoms are black, C atoms hatched, and methy1-C and
hydrogen atoms white.
233.4pm and is thereby comparable with that in 3
(234.8 pm).[*'
The average AI-AI distance of 276.9 pm lies between that
of 1 (266.0 pm) and of metallic aluminum (286 pm). This
intermetallic distance distinguishes the aluminum compound
from other oligomeric and polymeric M'-q5-C,Me, compounds (M = I n , Tl). In the octahedral cluster [In(q5C5Me,)],,[91 the In-In distances are 394.2 and 396.3 pm and
therefore significantly longer than in In metal (394,336 pm).
Shorter metal atom distances are found in "dimeric" [In(q5C,(CH,Ph),}] (363.1 pm).['OI In the structurally analogous
thallium compound, [TI{q5-Cs(CH2Ph)5)],11 the distance
between thallium atoms is 363.2 pm, in metallic thallium
336 and 343 pm. [Tl(q5-C,Me,)][121forms a polymeric chain
of alternating thallium atoms and C,Me, rings. In this compound the distance between chains is so large (641 pm) that
a TI-TI interaction can be excluded. Thus, the interactions
between the aluminum atoms in 4 are significantly larger
than in the known cyclopentadienyl compounds of monovalent indium or thallium.
In the FT Raman spectrum of solid 4, a broad band is
which we assign to the breathing
observed at 377 cmvibration (A,) of the Al, tetrahedron. The AI-A1 frequency
of 1 lies at 373 ern-'.['' In spite of the weak bonding in the
Al, species relative to the AI-A1 bond in 1, the frequencies
agree. This can be explained by different vibration equations." '1
The 27AI NMR spectrum (70.4 MHz, external standard
[A1(H,0)J3@) of a solution of 4 in benzene exhibits a sharp
signal at 6 = - 80.8 ( C O ~=
, ~170 Hz). This is to our knowledge the highest known chemical shift for an aluminum
nucleus. The structure and reactions of 4 in solution are at
present under investigation.
The compound [{Al(q5-C,Me,)},] 4 presented here is the
first molecular aluminum(1) compound stable under normal
conditions, whose structure could be determined by diffraction methods and the third example (after In and TI) of a
M'(C,Me,) compound of the third main group elements. After the successful synthesis of 4 one expects that the
missing members [B(C,Me,)] and [Ga(C,Me,)] can be prepared along similar lines.
[l] W. Klemm, E. Voss, K. Geiersberger, 2.Anorg. Allg. Chem. 256 (1948) 15.
121 R. Nesper, J. Curda, Z . Naturforsch. B 42 (1987) 577.
[3] W. Uhl, 2. Naturforsch. B43(1988) 1113.
[4] a) H. Schnockel, Z . Naturforsch. B31(1976) 1291;b) H. Schnocke1,J. Mol.
Sfrucf.50 (1978) 275.
[S] a) H. Schnockel, M. Leimkiihler, R. Lotz, R. Mattes, Angew. Chem. 98
(1986) 929; Angew. Chem. Int. Ed. Engl. 25 (1986) 921 ;b) C. Dohmeier, R.
Mattes, H. Schnockel, J. Chem. SOC.Chem. Commun. 1990, 358.
[6] M. Tacke, H. Schnockel, Inorg. Chem. 28 (1989) 2895.
[7] X-ray analysis: C40H,oAI,, triclinic, space group Pi (No.2). a =
1095.3(2), b = 1101.2(3), c = 1828.8(4) pm, a = 83.83(2), 0 = 83.88(2),
y = 66.80(2)", V = 2010.6 x lo6 pm3, 2 = 2, ebe,= 1.07 g c r K 3 , F(OO0) =
704, p = 1.4 cm-' (Mo~.), 295 K, w-scan, O,,, = 25". scan speed 2.9314.65 deg min-', scan width 1.2", Siemans R3m/V diffractometer,
graphite monochromator, 7665 reflections of which 6966 are symmetry
independent, R,,, = 0.0240; 4891 reflections with IF1 > 3u(IFl) were considered observed. Calculations with SHELXTL-Plus, 374 parameters including an isotropic extinction parameters were refined, H atoms geometrically positioned, non-hydrogen atoms anisotropically refined with the
exception of C(21)c(30); R = 0.1227, R, = 0.0970, R, = 0.0801, w =
l/u2(F). Extremes of the final difference fourier synthesis + 1.1/
- 0.5 x 10-6pm-3. Further details of the crystal structure investigation
may be obtained from the Fachinformationszentrum Karlsruhe,
Gesellschaft fur wissenschaftlich-technische Information mbH, W-7514
Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number
CSD-55176, the names of the authors and the journal citation.
IS] R. A. Andersen, J. M. Boncella, C. J. Burns, R. Blom, A. Haaland, H. V.
Volden, J. Orgunomet. Chem. 312 (1986) C49.
IS] a) 0.T. Beachley, Jr., R. Blom, M . R. Churchill, K. Faegri. Jr., J. C.
Fettinger, J. C. Pazik, L. Victoriano, Organometallics8 (1989) 346; b) 0. T.
Beachley, Jr., M. R. Churchill, J. C. Fettinger, J. C. Pazik, L. Victoriano,
J. Am. Chem. SOC.108 (1986) 4666.
[lo] H. Schumann, C. Janiak, F. Gorlitz, J. Loebel, A. Dietrich, J. Orgunomet.
Chem. 363 (1989) 243.
[ l l ] H. Schumann, C. Janiak, J. Pickardt, U. Borner, Angew. Chem. 99 (1987)
788; Angew. Chem. Inf. Ed. Engl. 26 (1987) 789.
1121 H. Werner, H. Otto, H. J. Kraus, J. Orgunomel. Chem. 315 (1986) C57.
[13] FT Raman spectrum of4 (Bruker FRA 106 (Nd:YAG laser 1.06 p)) [cm- '
(rel. int.)]: 2910(10), 2859(4), 2721(2), 1486(2), 1431(5), 1179(1), 601(3),
559(2), 377(broad, 4). 124(5).
1141 The large half-height width possibly results from overlapping of bands.
[15] The G matrix element in an Al, tetrahedron is twice as large as that for an
AI-AI unit. The F matrix element contains besides the AI-AI force constant interaction force constants for the Al, unit; cf. E. 8. Wilson, J. C.
Decius, P. C. Cross, Molecular Vibrafions,McGraw-Hill, New York 1955.
1161 Note added in proof (March 14.1991): In the recently prepared dodecaaluminate K,[Al,,iBu,,] the AI-AI distance is 268 pm: W. Hiller, K. W.
Klinkhammer, W. Uhl, J. Wagner, Angew. Chem. 103 (1991) 182, Angew.
Chem. Int. Ed. Engl. 30 (1990) 179.
Difference Electron Densities in a Spiropentene**
By Hermann Irngartinger,* and Stefan Gries
Dedicated to Professor Heinz A . Staab
on the occasion of his 65th birthday
Spiropentene ranks among the most strained organic molecules known. The calculated strain energy lies between 82.l
and 92.3 kcal mol- .I1, To prove that the bonds are bent,
Experimental Procedure
To a solution of 3.3 mmol 2 in 13 mL toluene at -78 "C is added dropwise a
solution of 1.5 mmol3 in 10 mL toluene. 214 mg(44%) yellow octahedral crysAngew. Chem. Int. Ed. Engl. 30 (1991) No. 5
Prof. Dr. H. Irngartinger
Organisch-chemisches Institut
der Universitat
Im Neuenheimer Feld 270, W-6900 Heidelberg (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0 VCH Verlagsgesellschafi mbH, W-6940 Weinheim. 1991
0570-0833/91/0505-0S65$3.50+ .25/0
we determined the difference electron density of the crystalline spiropentene derivative, dimethyl 4,5-diphenyl-4spiropentene-(4-1 ,Zdicarboxylate 1, by low temperature
X-ray diffraction measurements (105 K) according to the
The spiropentene 1 was synthesized by carbenoid-addition
technique^.'^] As in spiropentanes,[61 the central bonds in
spiropentene 1 are shorter than the peripheral C-C single
bonds (Fig. 1). Because of the large strain and the conjugation with both phenyl rings, the C-C double bond in l (C4C5: 1.311 A) is longer than in cyclopropene (from microwave spectroscopy: l .296 A[']). The conditions for conjugation with both phenyl rings are favorable, because the
dihedral angles are only 6.0" and 11.3'.
positions, respectively. Therefore, on comparison with spiropentaner6]no significant differences in these bond lengths
can be observed. The interatomic distances at low temperature are longer than at room temperature, because the shortening effects due to libration and to the influence of the
bonding electrons are minimal (Fig. 1).
All the single bonds of the spiropentene 1 are strongly
bent, which is easily recognized in the shifts of the electron
density maxima relative to the bond axes (Fig. 2). The bending of the bonds in spiropentanes is of the same order of
magnitude.I6I Significantly more pronounced bending in the
saturated three-membered ring of 1 relative to the less strained
c y c l ~ p r o p a n e and
[ ~ ~ its derivatives['. "1 could not be observed within experimental error.
The C4-C5 bond has a very high degree of bending compared with other strained double bonds. The density maximum is shifted significantly from the bond axis (0.18 A, angle between bond axis and the line connecting the atom and
the electron density maximum: 15"). The bending is more
pronounced than in the double bonds of the four-membered
ring system of cyclobutadiene (0.08 A and 8" respectively'"'). In benzocyclopropenes the bending is greater as a
result of the reduced bond
Strong deformations of
the bonds in spiropentane and spiropentene are also predicted by quantum mechanical calculations.'2* 3l
Received: January 11, 1990 [Z 4380 IE]
German version: Angew. Chem. 103 (1991) 595
CAS Registry number:
1, 132856-63-2.
Fig. 1. Bond lengths (A) of the spiropentene 1: a) at room temperature (293 K),
b) at 105 K.
The peripheral bond C1 -C2 in 1 is longer than in spiropentane.161As in the cyclopropane derivatives''] this bond is
lengthened by the electron-withdrawing properties of the
ester groups (Fig. 1). The two ester groups deviate by only
0.3" and 5.3" from a bisecting orientation, which allows an
optimal interaction between the orbitals of the substituents
and the Walsh orbitals of the three-membered ring. The electronic effects on the central bonds C1 -C3 and C2-C3 weaken each other, since these bonds are in geminal and distal
[I] J. Kao, L. Radom. J. Am. Chem. SOC.100 (1978) 760.
[2] Z. B. MaksiC, K. KovaEeviC, A. Magus, J. Mol. Sfrucr. 85 (1981) 9.
[3] Crystallographic data at room temperature and 105 K: a) Room temperature: colorless prisms from ethanol/ether, a = 11.637(2), b = 17.548(3),
c = 17.692(3) A; orthorhombic space group Pbca; 2 = 8, pcrlCd=
1.23 Mg m-3, crystal size 0S3 mm3; Mo,. radiation, Enraf-Nonius
CAD4 diffractometer, graphite monochromator sin8/1 < 0.66 k l , 3868
independent reflections, of which 1719 observed (I> 2.5a(I)). Refinement: C, 0 anisotropically, H isotropically, R = 0.04. b) Low temperature
(105 K): a = 11.427(2). b = 17.476(2), c = 17.617(3)A, eCmlrd
1.27 Mg m-3, crystal size 0.453 mm3; three (2" 5 8 I28") and four
(28" 5 8 I 55") independent sets of data with a total of 18 269 reflections
were measured. In the high order region only strong reflections
(IF(hkl)l > 3) were collected. After averaging (Ria, = 0.029) 7173 independent reflections remained, of which 6074 reflections were treated as observed (I > 2.5a(I)) in the range to sin8/>.= 1.15 A-'. Refinement (C,O
anisotropically) with 3003 high order reflections (sinB/A^= 0.661.15 A w l ) , R = 0.052. Parameters of the H atoms from the refinement
Hirshfeld test [4]: average
with low order reflections (sin8/1 < 0.66 k').
difference of the anisotropic displacement parameters along the bonds
0.0008 A'. Further details of the crystal structure investigation may be
obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur
wissenschaftlich-technische Information mbH, W-7514 Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number CSD-55258, the
names of the authors and the journal citation.
[4] F. L. Hirshfeld, Acta Crysfallogr.Sect. A 32 (1976) 239.
[5] M. W.Jones, M. E. Stowe, E. E. Wells, Jr., E. W.Lester, J. Am. Chem. SOC.
90 (1968) 1849.
[6] R. Boese, D. Blaser, K. Gomann, U. H. Brinker, J. Am. Chem. SOC.111
(1989) 1501; G. Dallinga, R. K. van der Draai, L. H. Toneman, R e d . Trav.
Chim. Pays-Bas 87 (1968) 897.
[7] W.M. Stigliani, V. W.Laurie, J. C. Li, J. Chem. Phys. 62 (1975) 1890.
[8] F. H. Allen, Acfa Crysfallogr. Secf. B 3 6 (1980) 81.
191 D. Nyveldt, A. Vos, Acra Crysfallogr. Sect. 8 4 4 (1988) 289, 296.
[lo] A. Hartmann, F. L. Hirshfeld, Acfa Crysfallogr. 20 (1966) 80.
I l l ] H. Irngartinger, M. Nixdorf, Chem. Ber. 121 (1988) 679.
(12) D. Blaser, R. Boese, W A. Brett, P. Rademacher, H. Schwager, A. Stanger,
K. P. C. Vollhardt, Angew. Chem. 101 (1989) 209; Angew. Chem. I n f . Ed.
Engl. 28 (1989) 206.
[13] K. B. Wiberg, R. E W.Bader, C. D. H. Lau, J. Am. Chem. SOC.109(1987)
985; Z. B. Maksic, K. KovafeviC, J. Org. Chem. 39 (1974) 539.
Fig. 2. Difference electron density map of the planes containing the cyclopropene (C3, C4, C5) and cyclopropane (Cl, C2, C3) rings of spiropentene 1.
Contour interval 0.05 e/A-3. Standard deviation of the difference density outside the atomic positions 0.03-0.04 e/A-3. Zero density line dotted, negative
electron densities dashed.
Verlagsgesellschafl mbH. W-6940 Weinheim, 1991
0570-0833/91/0505-0566 S 3.50+ ,2510
Angew. Chem. Inf. Ed. Engl. 30 (1991) No. 5
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