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Tetraalkylidene-1 4-diboracyclohexanes from 3 4-Dilithio-2 5-dimethyl-2 4-hexadiene; the First УHetero[6]radialeneФ with Chair Conformation.

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Tetraalkylidene-l,4-diboracyclohexanesfrom
3,4-Dilithio-2,5-dimethyl-2,4-hexadiene;the First
“Hetero[6]radialene” with Chair Conformation**
By Adalbert Maercker *, Walter Brieden, Thomas Schmidt,
and Heinz Dieter Lutz
We recently reported the synthesis and structure of the
first “dimetalla[6]radialene” 2 a.“] In the crystalline state it
has a twist conformation. Besides 2a, only one further “hetero[6]radialene” has so far been reported in the literature, the
corresponding sulfur compound 2 b, which was obtained-likewise with twist conformation-in a multistep synthesis.[’] In the meantime we have been able to prepare 2b quite
easily, and analogously to 2 a, from 3,4-dilithio-2,5dimethyl-2,4-hexadiene 1,13] whereby it is advantageous to
convert the sulfur dichloride into diimidazolyl sulfide prior
to the reaction.14]
Fig. I . Structure of 4 in the crystal. ORTEP plot of the centrosymmetric molecule. Important bond lengths [pm] and angles [“I: Na-Cl 265.8 (4), Na-Cl’
268.2(6). Na-NI 264.6(3),Na-N2271.2(3). Na-N3 260.9(3), Na-Na’323.7(3),
C-C (phenyl) 138.6 (mean value, min. 134.4, max. 141.0); N-C 145.3 (mean
value, min. 142.9, max. 148.7); Na-C1-Na‘ 74.6, C1-Na-C1‘ 105.4. Nl-Na-N2
67.6, N2-Na-N3 67.7. Nl-Na-N3 119.1 (1). CI-Na-N1 102.5(1), Cl-Na-N3
99.7(1). C2-C1-C6 111.7(3), Cl-C2-C3 124.3(4), C2-C3-C4 120.8(4), C3-C4C5 119.3(5). C4-C5-C6 119.0(4), C5-C6-C1 124.9(4).
Experimental
All operations were carried out under an inert gas and with carefully dried
solvents. For the synthesis of phenylsodium according to equation (a) [2], it is
advisable to recrystallize the NaOrBu before use; sublimation leads to considerable losses and less pure products. A suspension of 0.25 g (2.5 mmol) of NaPh
(containing ca. 0.6 weight-% Li, corresponding to 7.3 mol-% LiPh) in 30 mL
of hexane was brought into solution by addition of 1.2 mL (5.8 mmol) of anhydrous pmdta. Upon completion of the addition, a part of the phenylsodium
already in solution re-precipitated as a white powder. The supernatant, intensely red solution was pipetted off and yielded, after cooling to -30”C, 1.17 g
(17%) of 4 in the form of coarsely crystalline light-brown, pyrophoric platelets
(correct analysis for Na, C, H, N). Single crystals suitable for an X-ray structure
analysis were obtained from the mother liquor.
Received: November 7, 1988 [Z 3040 IE]
German version: Angew. Chem. f0f (1989) 481
CAS Registry number:
4, 119503-02-5.
[l] F. S . Acree, Ber. Dtsch. Chem. Ges. 37 (1904) 2753; W. Schlenk, J. Holtz,
ibid.50 ( I 917) 262.
121 G. Thirase, E. Weiss, J. Organomel. Chem. 81 (1974) C1.
[3] H. Hope, P. P. Power, J. Am. Chem. Soc. I05 (1983) 5320.
[4] D. Thonnes, E. Weiss, Chem. Ber. 11f (1978) 3157.
151 a) U Schiimann, J. Kopf, E. Weiss, Angew. Chem. 97 (1985) 222; Angew.
Chem. In!. Ed. Engl. 24 (1985) 215; b) W. Bauer, W. R. Winchester, P. von
R. Schleyer, Orgunometallics 6 (1987) 2371.
[6] U. Schiimann, E. Weiss, H. Dietrich. W Mahdi, J. Orgunomet. Chem. 322
(1987) 299.
[7] X-ray structure analysis of 4: space group P 2 , / n (monoclinic),
a = 1001.6(4), b = 1219.2(5), c = 1476.7(6) pm, f l = 92.93(3)”, 293 K,
@.a,cd = 1.01 gcm-3, Z = 2, Mo,, radiation, structure determination by
direct methods (SHELXS 84 [lo]), refinement to R = 0.052 (unweighted),
1611 symmetry independent and significant reflections in the range
4 < 2 8 < 50’ (IF1 > 5 o ( f l ) . Anisotropic temperature factors for Na, C,
N, H atoms at calculated positions with common isotropic temperature
factors. Number of refined parameters 173. Further details of the crystal
structure investigation are available on request from the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-7514 EggensteinLeopoldshafen 2 (FRG), on quoting the depository number CSD-53692,
the names of the authors, and the journal citation.
[8] U. Schiimann. Dissertution, UniversitPt Hamburg 1987.
[9] R. Zerger. W. Rhine, G. D. Stucky, J. Am. Chem. SOC.96 (1974) 5441.
(101 G. Sheldrick, SHELXS-84, Programs for Crystal Structure Solution,
Gottingen 1984.
A n g r u . Chmi. In, Ed. En$
28 (1989) N o 4
2
1
a:
X = MesSn
b: x = s
C :
X = tBuB
d:
X = Ph,NR
Since boraheterocycles are currently the subject of intensive studies-both theoretically and preparatively I5]--we
have also tried to synthesize 1,4-dibora[6]radialenes by our
method, particularly as these compounds can be expected to
exhibit interesting properties with regard to their stereochemistry, NMR spectroscopy, and reactivity towards
dienophiles.
Reaction of 1 [ 6 , with tert-butyldichloroborane in diethyl
ether at - 50 “C leads to formation of a colorless, crystalline
substance that is surprisingly stable towards air and hydrolysis, and which, according to the spectroscopic data!’]
is 1,4-di(tert-butyl)-2,3,5,6-tetra-2-propylidene-l,4-diboracyclohexane 2c (yield 34%, not optimized, remainder presumably polymers). However, before any comments could
be made about the conformation, an X-ray structure analysis[’] had to be carried out. It was established that 2c is in
fact the first “hetero[6]radialene” with chair conformation
(Fig. 1).
Remarkable features of the structure of 2c are, on the one
hand, the large dihedral angles in the two butadiene units
(with 74” and 73” they are only 10” smaller than in the
analogous ditin compound 2a, which has a twist conformation) and, on the other, that the central bonds of the butadiene units, which exhibit practically no double bond character, are, with lengths of 1.511 (4) and 1.517(4) A, identical
with the corresponding distances in 2 a, i.e. there is no detectable influence of the heteroatoms on these bonds.
[*] Prof. Dr. A. Maercker, DipLChem. W. Brieden
Institut fur Organische Chemie der Universitat
Adolf-Reichwein-Strasse. D-5900 Siegen (FRG)
DipLChem. T. Schmidt[+], Prof. Dr. H. D. Lutz[+]
Institut fur Anorganische Chemie der Universitat
AdolGReichwein-Strasse, D-5900 Siegen (FRG)
[‘I X-ray structure analysis.
[**I Polylithium Organic Compounds, Part 10. This work was supported by
the Stiftung Volkswagenwerk and the Fonds der Chemischen 1ndustrie.Part 9: A. Maercker, K.-D. Klein, Angew. Chem. 101 (1989) 63; Angew.
Chem. h i . Ed. Engt. 28 (1989) 83.
c> VCH ~ ~ r l a ~ s g ~ ~ s e l mbH,
l . ~ ~ hD-6Y40
afi
Weinheim, 1989
0570-0S33/89j0404-0477$02.50/0
477
small amount of methanol. 2c crystallized (3.0 g, 34%) [XI; m.p. 241 -243 C
(from ethanol). correct elemental analysis (C, H, B).
2d: A 1.0 M solution of 1 (50 mL. 0.05 mol) 16.71 in diethyl ether (diluted with
150 mL of diethyl ether) was added dropwise within 2 h to a stirred solution of
dichloro(N,N-dipheny1amino)borane1151 (12.5 g, 0.05 mol) in diethyl ether
(200mL) at -6O'C; work-up as in the case of 2c. 2d was obtained (5.4g,
38 %) [l I ] ; m.p. 265-266°C (from dichloromethane). correct elemental analysis (C. H, B).
Received: November 15, 1988 [Z 3054 IE]
German version: Angen. Chem. 101 (1989) 477
~
Fig. 1. Molecular structure of 2c (thermal ellipsoids at the 50% probability
level). Important bond lengths [A]and angles I"]: Bl-C2 1.566(4), C2-C3
1.511(4), C3-B4 1.572(5), B4-CS 1.568(4), C5-C6 1.517(4), C6-Bl 1.567(4),
B1-Cll 1.590(5), B4-C41 1.586(5),C2-C21 1.338(4),C3-C31 1.344(4). C5-C51
1.343(4), C6-C61 1.341 (4); C2-BI-C6 ll3.0(3), C2-Bl-Cl1 122.5(3), C6-BlC11 122.6(3), Bl-C2-C3 110.2(2), Bl-C2-C21 125.8(3), C3-C2-C21 123.20).
C2-C3-B4 110.0(2), C2-C3-C31 123.0(3). B4-C3-C31 126.2(3), C3-B4-C5
112.8(3). C3-B4-C41 122.6(3). C5-B4-C41 122.6(3), B4-C5-C6 109.5(2), B4C5-C51 126.6(3), C6-C5-C51 123.3(3), Bl-C6-C5 110.3(2). Bl-C6-C61
126.2(3), C5-C6-C61 122.7(3); dihedral angles C2l-CZ-C3-C31 74.0(2). C61C6-CS-C51 73.4 (2).
In contrast to the disulfur compound 2brZ1-but in
analogy to 2 a"l-2 c does not react with 4-phenyl-I ,2,4triazole-3,s-dione in a [4 2]-cycloaddition. Probably the
coplanar attitude of the isopropylidene groups is additionally thwarted by the tert-butyl groups on the boron atoms.
A further 1,4-dibora[6]radialene, 2d, could be prepared
analogously in 38% yield by reaction of 1 with dichloro(N,N-dipheny1amino)borane. 2d is likewise a colorless, crystalline air-stable compound, whose structure was
confirmed NMR spectroscopically and mass spectroscopically.'"]
+
Whether 2d, like 2c, has a chair conformation is not
known. The relationship of 2 d with the isocyclic [6]radialene
3, which is strikingly evident in the mesomeric resonance
structure with B=N double bonds, leads us to presume,
however, that 2d, in analogy to 3,'12' has a chair conformation. The importance of the ionic resonance structure in describing the bonding of 2d manifests itself in the ''B NMR
spectrum: as expected1131the resonance of 2d (6 zz 43)
absorbs at very much higher field than that of 2c (6 % 77).
Even knowing that 2c, other than 2a, b, assumes a chair
conformation, it was not possible to discover any indications
of this difference in the 'H or 13C NMR spectra. Furthermore, the spectra of the crude products also did not show
any evidence of the presence of di-2-propylideneboracyclopropanes, which are conceivable as intermediates of the reaction of 1 with dihaloboranes.
Experimental
2c: A solution of rerl-butyldichloroborane(7.0 g, 0.05 mol) 1141 in diethyl ether
(100 mL) was added dropwise within 2 h to a stirred 1.O M solution of 1 (50 mL,
0.05mol) 16, 71 in diethyl ether (diluted with 150mL of diethyl ether) at
- 50°C. After warming t o room temperature and aqueous work-up the reaction mixture was evaporated down in a rotary evaporator and treated with a
478
$2 VCH
I/v-iug~geseNscliafimhH, 0-6940 Weinheim, 1989
[I] A. Maercker, F. Brauers, W. Brieden, M. Jung. H. D. Lutz, Angew. Chem.
100 (1988) 413; Angew. Chem. I n f . Ed. Engl. 27 (1988) 404.
[2] W. Ando. Y. Hanyu, T. Takata, K. Ueno. 7huhedron Lett. 26 (1985) 3019.
[ 3 ] A. Maercker, W. Brieden, A. Groos, unpublished.
141 A. Banerji, G. P. Kalena, Terruhedron Lerr. 21 (1980) 3003.
IS] Review: W. Siebert. Purr Appl. Chem. 59 (1987) 947.
[6] A. Maercker, R. Dujardin, Angew. Chem. 97 (1985) 612; Angrn. Chem.
I n f . Ed. EngI. 24 (1985) 571.
[7] A. Maercker. R. Dujardin, F. Brauers, Orgunomer. Synfh. 4 (1988) 362.
[XI 2 ~ 'H-NMR
:
(80 MHz, CDCI,): 6 = 0.98 (s, 18 H: 2 x C(CH,),). 1.57 (s,
1 2 H ; 4 x C H , ) , 1.65 (s. 1 2 H ; 4xCH,).-I3C-NMR
(100.6MHz,
CDCI,): d = 21.3 (CH,), 26.2 (CH,), 28.7 (CH,), 31.7 (CMe,), 125.9
(CMe,), 147.2 (BC).-"B-NMR (128.4 MHz, CDCI,): 6 = 76.9 ( v , z
700 Hz). -UV (n-hexane): i.,,,
= 337 nm (c = 12400).-MS (70 eV): mi:
352 ( M e . 33%) 295 (Me-CMe,, 17%), 239(30%), 41 (100%).
191 2 c : crystal dimensions 0.16 mm x 0.26 mm x 0.35 mm, space group
P7, u = 16.385(3), h = 14.106(3), c = 9.672(3) A. x = 98.34(2), 0 =
119.69(2), 7 = 100.53(2)". V = 1835.1 A
'. Z = 3, eealcd= 0.956gcm-'.
gcrp= 0.94gcm-'. p(MoK.) = 0.5cm-', fl,,, = 25'. 3068 independent
reflections with I > 20 (I)were measured a t 293 K on a four-circle diffractometer (CAD 4. Enraf-Nonius, Mo,, radiation, graphite monochromator); structure solution by direct methods, protons located by difference
Fourier analyses. Refinement by the full matrix method (B, C anisotropic.
H isotropic) converged in the last cycle for 352 parameters a t R = 0,050.
R, = 0.035 (11 = l / u 2 ( F , ) ) . All calculations were carried out with the
system NRCVAX [lo]. Further details of the crystal structure investigation
are available on request from the Fachinformationszentrum Energie,
Physik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG).
on quoting the depository number CSD-53427, the names of theauthors,
and the journal citation.
1101 The NRCVAX Crystal Structure System: E. J. Gabe, F. L. Lee. Y. Le Page.
Crysrallogr. Compur. Data Collerr. Srrucr. Deferm. Proteins Dalabases
Pup. I n / . Summer Sch. 9th 1984 (1985) 167-174.
1111 2d: 'H-NMR (80 MHz. CDCI,): 6 = 1.03(~,
12H;4 x CH,), 1 . 7 2 ( ~12H:
,
4 x CH,). 7.10-7.20 (m, 20H: 4 x C,H,).--"C-NMR
(100.6 MHz,
CDCI,): 6 = 22.0 (CH,), 26.1 (CH,). 125.0 G0-C). 127.3 (CMe,). 128.1
(m-C), 128.4 (OK),142.1 (BC), 149.7 (NC).-"B-NMR
(128.4 MHz,
6 = 42.5 ( Y ~ ,%, 950 Hz).-UV
(n-hexane): imSx
= 228 sh
C,D,):
(c = 32800), 276nm (19100).-MS
(70eV); mi: 574 (,We, 100%).
234(40%), 194(90%), 165 (40%).
1121 G. Wilke, Angew. Chem. 100 (1988) 189; Angeu. Chem. Int. Ed. EngI. 27
(1988) 185.
1131 Cf. B. Wrackmeyer, R. Koster in R. Koster (Ed.): Houhen-Wed-Miiller,
Methoden der Organischen Chemie. XIiI13c. Thieme, Stuttgart 1984,
p. 377-61 1; H. Noth, B. Wrackmeyer, N M R Basrc Prinr. Prog. 14, (1978)
29-61.
1141 P. A. McCusker, E. C. Ashby. H. S. Makowski, J. Am. Chem. Soc. 79
(1957) 5179. 5182.
1151 H. J. Becher. Z. Anorg. Allg. Chem. 2x9 (1957) 262.
The Influence of Packing Effects on the Solid-state
Fluorescence of Diketopyrrolopyrroles**
By Heinz Langhals,* Thomas Potrawa, Heinrich Noth, and
Gerald Linti
Very little is known about the influence of the crystal structure of a compound on its fluorescence quantum yield."'
~~~
[*] Prof. Dr. H. Langhals. Dip1.-Chem. T. Potrawa
Institut fur OrganiSChe Chemie der Universitit
Karlstrasse 23. D-8000 Munchen 2 (FRG)
Prof. Dr. H. Noth 1'1, Dip1.-Chem. G. Linti ['I
Institut fur Aiiorgdnische Chemie der Universitat
Karlstrasse 23. D-8000 Munchen 2 (FRG)
[ '1 X-ray structure analyses.
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0570-0833:89/0404-047L($02.5010
A n g w . Chem. I n t . Ed. Engl. 28 (19x9) No. 4
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conformational, tetraalkylidene, уhetero, diboracyclohexanes, first, hexadien, radialene, dilithio, dimethyl, chaire
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