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Kinetically Stabilized [4]ParacyclophaneЧThe 1 4-Bis-(dicyanomethylene)-2-ene Derivative 1H NMR Measurement and Assessment of Its Diatropicity.

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Max.,min. residual peaks in the final difference map 1.936; - 0 . 3 6 4 e k ' .
Crystals of 3 and 4 were mounted in alr and in capillaries filled with drops of
mother liquid, respectively. The structures were solved by direct methods with
SHELXS-X6 and refined by full-matrix least-squares techniques on F Zby using
SHELXL-93. All non-hydrogen atom, (except those of the solvent molecules)
were refined anisotropically. All hydrogen atoms (except those of the methyl
groups of the acetate ligands and the OH- group in 3 and those of the
(py),COi- ligands in 4) were located by difference maps and their positions
refined isotropically. Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no. CCDC-179170. Copies of the data can be obtained free of charge on application to The
Director. CCDC. 12Union Road, Cambridge CB21E2, UK (Fax: Int.
code + (2223)336.033; e-mail. deposit@chemcrys.camac.uk).
[8] a) A. J. Blake, R. 0 Gould, C. M. Grant, P. E. Y. Milne, D. Reed, R. E. P.
Winpenny. An,qcw. Chrm 1994, 106.208; Angew. Chem. In!. Ed. Engl. 1994,33,
195: b) J. A. Real, G. De Munno, R. Chiappetta, M. Julve, F. Lloret,
Y Journaux. 1-C. Colin, G. Blondin, ihid. 1994, 106, 1223; 1994, 33, 1184.
191 S. S. Tandon, L. K Thompson, J. N. Bridson, C. Benelli, Inorg. Cltem. 1995.
34, 5507.
[lo] a) A. J. Blake. R. 0. Gould, P. E Y. Milne, R. E. Winpenny, J Chem. Soc.
Chern. Commun. 1991, 1453; b) X -M. Chen, S. M. J. Aubin, Y.-L. Wu. Y:S.
Ydng. T. C. W. Mak. D N. Hendrickson, J Am. Chem. Soc. 1995, 117,9600.
The preparation of 8, the precursor of 1, was carried out as
outlined in Scheme 1. The addition of singlet oxygen to 2[']
afforded endo-peroxide 3 as stable, colorless crystals. When
treated with Et,N, 3 was smoothly transformed into 4, and
subsequent selective hydrogenation of the enone moiety of 4
with Bu,SnH and [Pd(PPh,)4][61 followed by pyridinium
chlorochromate (PCC) oxidation provided dione 6. The p-ala-
2
4
3
d
;;*;
QX
P
P
83%
5
_ _
_ _
73%
6, X = O
e' 54%
8
7, X = C(CN),
Scheme 1. Preparation of 8. a) O,, hvltetraphenylporphyrin, CCI,; b) Et,N; c)
Bu,SnH, [Pd(PPh,),]; d) PCC; e) CH,(CN),, B-alanine; f) C,H,NH-Br,, C,H,N.
Kinetically Stabilized [4]ParacycIophaneThe 1,4-Bis-(dicyanomethylene)-2-ene Derivative :
'H NMR Measurement and Assessment
of Its Diatropicity""
Masahiro Okuyama and Takashi Tsuji*
[4]Paracyclophanes are the most strained of known paracyclophanes, but their extreme thermal instability has thwarted
the exploration of their physical and chemical properties." -41
They are persistent only under matrix isolation at low temperature and are rapidly consumed in fluid solution even below - 130 cC.[3,41Steric strain in [4]paracyclophanes is, however, mainly localized on the bridgehead carbon atoms, and
their extreme lability also arises from the high propensity for
undergoing addition at the bridgeheads. This tendency suggests
that the system may be kinetically stabilized, to some extent at
least, by introducing sterically demanding substituents that
specifically shield the bridgehead carbon atoms from access by
other reagents. We report here that the skeleton of [4]paracyclophane is kinetically stabilized successfully in 1 (Figure 1) to
permit the observation of 'H NMR spectrum and the evaluation of its diatropicity.
N
["I
dinium bromide perbromide.
The UV/Vis spectrum (Figure 2) of 8 in a glassy mixture of
isopentane-ether at 77 K exhibits a strong absorption band
with a fine structure in the region of 300-390 nm. Irradiation of
C
!.
1
250
350
300
....
400
I
-LO
430
;3./nm-
Figure 2. UV/Vis absorption spectra measured in ether-isopentane (1 : 1) at 77 K.
a) 8 (;.,,,(log&) = 346 nm (5.15)); b) difference spectrum obtained by subtracting
the above spectrum from that recorded after irradiation with light of wavelength
365 nm; c) difference spectrum between the spectra before and after further irradiation ( >400 nm)
N
Figure I . Structural formula of 1 and its ball-and-stick model (front view) calculated by MNDO-PM3 method.
['I
nine-catalyzed condensation of mal~nonitrile['~
to 6 furnished
7,which was readily converted into 8 upon treatment with pyri-
Prof. Dr. T Tsuji, M. Okuyama
Division of Chemistry, Graduate School of Science
Hokkaido University, Sapporo 060 (Japan)
Fax: Int. code +(11)746-2557
e-mail: tsujiOi science.hokudai.ac.jp
This research was supported by a Grant-in-Aid for Scientlfic Research
(06453031) from the Ministry of Education, Science, and Culture of Japan.
T. T. thanks the Computer Center of the Institute for Molecular Science for the
use of the NEC HSP computer.
A n g w . Chem. Int. Ed. Engl. 1997. 36, No. 10
the mixture (2 = 365 nm) led to the development of a broad
absorption band between 270 and 420 nm at the expense of the
above characteristic band. The process was reversed by irradiating the resulting mixture with light of wavelength >400 nm,
with which only the newly generated species was excited, and 8
was almost quantitatively regenerated as demonstrated by the
accompanying spectral change. Ready photoisomerization to a
Dewar benzene derivative is a feature common to
[4]para~yclophanes,[~.
41 and the above observation strongly
suggested that the species generated from 8 was 1.
The generated intermediate was, however, remarkably stable
for [4]paracyclophane and remained intact for more than 1 h in
isopentane-ether at - 50 "C, thus permitting the measurement
of an 'H NMR spectrum (Figure 3 ) . The 'H NMR spectrum of
<! VCH Verlagsgesellschaft mbH, D-69451 Weinheim, 1997
057(l-0833jY7i3610-1085$ 17.50+ .SOfJ
1085
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8.0
7.0
6.0
5.0
-6
Figure 3. Changes in the 'H N M R spectrum (400 MHz)observed upon irradiation
of 8 in CD,CI, at -90 "C. Top: Before irradiation. Signals at 6 = 6.93 and 7.20 are
due to Hb and Ha of 8, respectively, and an intense peak at 6 = 5.40 is due t o residual
protons in the deuterated solvent. Middle: Spectrum after irradiation a t 365 nm.
Bottom: After further irradiation at 2 4 0 0 nm.
instructive. Thus, Ha is predicted to be upfield shifted by
A6 = 1.34 and Hb downfield shifted by A6 = 1.58 upon the isomerization of 9 to 10, in good agreement with the experimental
observation. The corresponding prismane derivative is apparently incompatible with the observed signals. Because it is expected that the effects of the cyano groups on the chemical shifts
are largely compensated in those chemical shift changes, the
calculation results provide a strong support for the structure 1,
and suggest that relatively strong diatropicity is sustained in the
aromatic ring moiety of 1 despite its extreme bending.'". 1 2 ]
Schleyer and his co-workers recently proposed two probes as
effective aromaticity/antiaromaticity criteria: the diamagnetic
susceptibility exaltation (A)['31 and the nucleus-independent
chemical shift (NICS).['41 According to those definitions, significantly exalted (negative) A and large negative NICS denote
aromaticity, whereas positive A and NICS indicate antiaromaticity. NICS calculated at the center['51 of the C, ring moiety
of 10 (GIA0/6-31 + G*//B3LYP/6-31G*) is -9.0 as compared
with -9.7 for planar benzene, and A computed for a bent benzene whose geometry was constrained to that present in 10
is 11.6 ppmcgs (CSGT''61/6-311 +G**) as compared with
- 15.1 ppmcgs reported for planar benzene." ','*I The relatively large negative A and NICS values, coupled with the calculated
small degree of bond alteration in the C, ring in 10 (0.022 and
0.018 8, at the MP2/6-31G* and B3LYP/6-31G* levels, respectively), suggest that 10 and, accordingly, 1 retain relatively good
electron delocalization in their bent benzene
~
8 (in CD,Cl,) exhibits a pair of singlets at 6 = 6.93 and 7.20 in
a ratio of 2: 1. Irradiation of 8 with 365 nm light at - 90 "C led
to the development of a pair of weak singlet signals with an
intensity ratio of about 1:2 at 6 = 5.85 and 7.97, respectively;[*]
the signal of Ha has thus been shifted upfield by A6 = 1.35 and
that of Hb downfield by A6 = 1.04 upon the transformation of
8 into the product. When the resulting mixture was irradiated
with light of wavelength longer than 400 nm, the latter pair of
signals disappeared to restore the original two line spectrum ;
these shifts correspond closely with the changes in the UV/Vis
spectra. If the species generated from 8 is indeed 1, the observed
chemical shift changes imply the induction of a substantial aromatic ring current in its bent benzene ring moiety. The extremely
simple 'H NMR spectrum with such low signal intensity, however, suggested the possibility that the observed signals were due
to an unknown side product. Therefore, recourse to computational analysis was made to confirm the structural assignment.
Geometrical optimization and calculations of proton chemical shifts were carried out for truncated systems 9-11, since
computations for 1 and 8 to reasonable accuracy were impractical.['] The results are summarized in Table 1. Calculated chemical shifts (GIAO['I/6-31 +G*//B3LYP/6 - 31G*) are not in
particularly good agreement with the experimental values owing
to the omission of the substituents, but the results are quite
Table 1. Calculated ' H chemical shifts for 9-11 [a]
Compound
&Ha)
Ab(H") [b]
9
10
11
6.30
4.82
6.51
- 1.48
-
0.21
Wb)
6.82
8.38
2.72
Ad(Hb) [b]
-
1.56
-4.10
[a] CIAO [10]/6-31 +G*//B3LYP/6-31G* [b] Shifts of the ' H N M R signals relative t o those of 9; positive values denote downfield shifts.
1086
f> VCH Verlugsgesellschaft m h H , 0-69451 Wernheim. 1997
Received. December 9, 1996 [Z98641E]
German version: Angew Chem. 1997. f09, 1157 - 1158
Keywords: aromaticity
substituent effects
-
cyclophanes
-
strained molecules
-
[l] Review on small cyclophanes: V. V. Kane, W. H. De Wolf, F. Bickelhaupt,
Tetruhedron 1994. SO, 4575.
[2] B. G. M. Kostermans, M. Bobeldijk, W. €3. De Wolf. F.Bickelhaupt, J Am.
Chem. Soc. 1987, 109, 2411
[3] T. Tsuji, S . Nishida, J. Chum. Soc. Chem. Commun. 1987, 1189; J Am. Chem.
Soc. 1988, 110, 2157.
[4] a) T. Tsuji, S. Nishida. J. Am. Chem Soc. 1989,111,368; b) T. Tsuji, S. Nishida,
M. Okuyama, E. Osawa, ibrd. 1995, 117, 9804.
[5] a) T. Tsuji, 2.Komiya, S.Nishida, Terrahedron Lett. 1980,21,3583; b) T Tsuji,
S. Nishida, ibid. 1983, 24, 3361.
[6] E. Keinan. P. A. Gleize, Telruhedron Letr. 1982, 23, 477.
[7] R. J. Crawford, J. Org. Chem. 1983, 48, 1366.
[S] The ratio of the product t o 8 was about 6:94. Further irradiation did not bring
about an appreciable increase in the proportion owing to the high photochemical reactivity of the product to revert to 8.
[9] All calculations were performed with the Gaussian 94 program. Gaussian 94
(RevisionC.3). M. J. Frisch. G. W. Trucks. H. B. Schlegel, P. M W Gill. B G
Johnson, M. A. Robb, J. R. Cheeseman, T. Keith. G A. Petersson, J. A. Montgomery. K. Rachavachan. M. A. Al-Laham, V. G. Zackrewski, 1. V. Ortiz, J. B.
Foresman. J. Cioslowski. B. B. Stefanov, A. Nanayakkara, M. Challacombe,
C. Y Peng, P. Y. Ayala, W. Chen, M. W Wong, J. L. Andres, E. S. Replogle,
R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P.
Steward, M. Head-Gordon. C. Gonzales, J. A. Pople, Gaussian Inc., Pittsburgh PA, 1995.
[lo] K. Wolinski. J. F. Hinton, P Pulay, J. Am. Chem. Soc. 1990. 112, 8251.
[ l l ] According to the theoretical calculations (B3LYP/6-31G*), 10 is C,, symmetric, and the deformation angles 1 and /$. which give a measure of the degree to
which the benzene ring is bent, are 28.6- and 43.0', respectively.
[12] The UV/Vis absorption spectrum of 1 is similar in shape to that of
[4]paracyclophane-l,3-dienefor which a similar degree of deformation in the
benzene ring has been predicted by tbeory[4]. N o particular absorption suggesting electronic interactions between theelectron-deficient side chain and the
bent benzene ring in 1 was detected. The kinetic stabilization of I seems to be
rationalized on the steric grounds. though thecontribution of electronic effects
exerted by the cyano groups is not rigorously ruled out.
[13] a) P. von R. Schleyer, H. Jiao. Pure Appl. Chem. 1996.68.209. b) This criterion
was first proposed by Dauben et al.: H. J. Dauben, Jr ,J D. Wilson, 1. L. Laity,
J Am. Chem Soc. 1968, 90. 811; ihid. 1969, 91, 1991
OS70-0833/U7/36/O-l086 S 17.50+ SOjO
Angew. Chem. Int Ed. Engl. 1997, 36, N o . 10
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[I41 P. von R. Schleyer, C. Maerker. A. Dransfeld. H. Jiao. N . J R. van
Eikcrna Honinies, .I A i l 7 Chciir S o c 1996. 118. 6317 .
[ I S ] Mcaii of the carbon coordinates. The C, ring in 10 is not planar. and [he NlCS
changes depending on the point iit which the value is computed The NlCS
value at the midpoint between the bridgehead cai bon atoms i\ - 11 8 and that
a t the center oi'rectanglc formed by tlie other four aromatic cai-bons is -7 8 .
[I61 T. A. Keith. R . F W. Bader, Clieni. P/ij..s.Lett. 1992. 194. 1 : rhid. 1993.110. 223
[17] D. V. Siinion, T. S Sorensen, J. Ail?. C'ho??. Soi. 1996, 118, 7345.
[ I X ] Thc A valiie wiis calciilatcd following the protocol used in U. Fleischer.
W. Kutrelnigg. P. La~7eretti.V. Muhlenkanip. .I ,4171. Clioii. Soc. lYY4. 116,
529X; see also ref. [I71
[lO] A detailed theoretical study on the siructui-e. strain energy, and magnetic
susceptibility of [4]paracyclophane recently appcarcd. B. Ma. H M . Sulrhacli.
R. B. Reiniiigton, H F. Scliaefcr Ill.J .4i!r. C / i m So(. 1995. 117. 8392.
One-Dimensional Semiconducting Chains of the
Quaternary Zintl Anion in
(Et,N),IAu(Ag, - xA~,),Sn*Te,l**
Sandeep S. Dhingra, Dong-Kyun Seo,
Glen R. Kowach, Reinhard K. Kremer,
Julie L. Shreeve-Keyer, Robert C. Haushalter.* and
Myung-Hwan Whangbo*
One particularly desirable type of 1-D conducting solid,
which is analogous to a macroscopic copper wire surrounded by
an organic polymer insulator, would be composed of chains of
covalently bonded metals surrounded by insulating organic regions that hinder electronic coupling between the moleculgr
wires. We report here the preparation of ii semiconductive 8 Awide, 1-D chain composed of four different elements surrounded by insulating organic material. The synthesis, crystal stl-ucture, physical properties, and electronic structure of the first
quaternary Zintl-anion material (Et,N),[Au(Ag, -xAux)2Sn,Te,] (.Y = 0.32), which exhibits a delocalized 1-D band structure, are discussed.
The title compound is prepared by ethylenediamine (en) extraction of a pentanary alloy of composition K,AuAg,Sn,Te, .
Other compositions were attempted, including K,AuAg,Sn,Te,, but they gave either no products or significantly lower
yields. After the alloy is extracted, and Et,N ' cations are added
to the filtrate, it generally takes several months for the first
crystals to appear. This is followed by a period of more rapid
crystal growth. The crystal quality, and to a lesser extent the
yield, vary from reaction to reaction, but no other products are
detected and all crystals examined contain Au, Ag, Sn, and Te.
Crystals of (Et,N),[Au(Ag, -,Au,),Sn,Te,] contain unprecedented, linear, 1-D chains of cornposition Au(Ag, -xAu,)2Sn,Te:- (Figure 1) separated by Et,N+ cations.[51The closest
Dedicated to Hans Georg V O I ZSclinerir7g
on tlic. occasion of his 65th birthday
Several chemical approaches have been
developed over the last two decades for
preparing one-dimensional conducting materials such as platinum chain compounds,
the salts of organic donor molecules, and
transition metal chalcogenides.['I We recently initiated a study designed to determine the possibility of introducing unpaired
electrons into closed-shell, low-dimensional
Figure 1. Structure of the I-D Au(Ag,. ,Au,),Sn,Tct- chaiii drawn with tlicriniil ellipsoids at the 50%
Zintl-phase materials, by suitable structural
probability level. I n t h i s iiiitiiil model Tc2 was relined as il single. fully occupied position, and the Agl and
modifications or elemental substitutions,
Ag? positions were refined with Ag occupancy only. Selcctcd bond lengths [A]: Aul -Te2 2 970(6),Te?-TeS
hence increasing their electrical conductivi3.187(6). and angle[ ] Te2-TeS-Te2 1S4.7(4)
ty. In several cases the structures achieve a
closed-shell electronic configuration by uninterchain Te ' . Te contact is 7.0 A. The Au atom has distorted
dergoing site specific elemental substitutions (for example
square-planar coordination, whereas the Sn and mixed Ag/Au
K,GeIn,Sb,,)r21 or forming exceedingly complex structures (for
site show tetrahedral and trigonal-planar coordination, respecexample K,In,Ge,As,, or K,In,Ge5A~,,).[31Likewise, several
tively. Structure refinement (by fixing the thermal parameter of
binary and ternary I-D Zintl anions such as InGeTe,,
the site and allowing the Au:Ag ratio to refine) gives 3 2 %
HgSnTe:-,
Hg2Te:-, Hg3Te;-. Hg2Tei-, As,Te:-,
and
substitution of Au onto the Agl and Ag2 sites; a small stoichioInTe,
possess structures consistent with closed-shell electronic configurations
metric range is apparent from refinements of other crystals.
Substitution is possible since Au-Te and Ag-Te bond distances in trigonal-planar coordination are very similar.r61From
[*I Dr. R C . Haushaltcr. Dr. S. S Dhingra. G R. Kowach,
an initial refinement with a single Te2 position (see below), each
Dr. J. L. S h r e w - K e y c r
Te
atom is twofold coordinated if only bonds shorter than 3
NEC Keseoirh I nst i t LI te
4 lndcpeiidrnce Way
are considered. The prominent structural feature of the polyPrinceton. N J 08540 (USA)
anion is the {-Au-Te-Te-Te-) strand composed of Au atoms
Far: lnt code +(609)951-?4X?
and
approximately linear Te2-TeS-Te2 units (4:Te-Te-Te =
e-inail haush,ilr.u i-cscarcli uj.n
154.7").
The two symmetry-equivalent Te2-Te5 distances are
Prof. M -H Whaiigho. D:K. Seo
3.187(6) A, which is longer than a typical Te-Te single bond
(2.75 A) but much shorter than the vim der Waals Te . . . Te
contact (4.0 A). This suggests a bonding interaction of the type
observed in tellurides such as Te:;.
HgTef ~, Cu,SbTe:;,
Dr R K. Kreiiicr
and
Au,Tet;
,['I as well its some othtr solid-state tellurides.[''
Max-Planck-ln\littit Kii- Fcjihijrpeil'oi scliung. Stuttgai-1 (Gerniany)
The Au-Te2 distance of 2.970(6) A is much longer than
[**I The work at North Carolina State I ei-sit! n.a\ supportcd by the U. S
Au-Te
contacts (about 2.65 A) found for Au,Te:;.
iices. Di\i\ion of Materials Scieiiccs
Dep;irtincnt of Eiicrgy. Oflice o f 13;i~ic
KAu,Te$-, K,Au,Te: ~, and Au2Te:-.r41 However, the Te2
(grant 110. DE-FG05-XhFRJ5259)
'
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measurements, paracyclophaneчthe, stabilizer, nmr, dicyanomethylene, diatropicity, ene, bis, assessment, kinetically, derivatives
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