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Norcaradiene Valence Tautomer of a 1 6-Methanol[10]annulene Tricyclo[4.4.1

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recently been reported by
We describe here preliminary results of ab initzo-SCF calculations of the deformation density distributions in the “low-spin” cobalt(I1)
porphyrin (COP) and the “intermediate-spin’’ iron(r1) porphyrin (FeP), which are considered as models for CoTPP
and FeTPP.
For COP, the calculations were carried out on the 2Al
configuration, which can be considered as the ground
state. In FeP, the assignment of the ground state is still under discussion: conflicting experimental results indicate
that the ground state might correspond either to a 3A2g
configuration ( ~ y ) ~ ( x z(yz)’
) ’ ( ~ ~ ) ~ or
[ ~ to
~ l a, 3 ~ configura,
tion (xY)~(xz)’
or to a spin-orbit coupling of
these two states[”I. We report here the deformation density
distribution for the 3A2gstate only. Comparison of the
computed distribution with that obtained from an X-ray
study, which will appear shortly, should give some indication about the nature of the ground state.
The calculated deformation density map computed for
COP in the plane containing the metal atom and one pyrrole ring is displayed in Figure 1 (right). The corresponding map obtained by Steoens from the observed X-ray
data, which is modeled using a multipole deformation refinementL4],is shown in Figure 1 (left). The difference between the two never exceeds 0.3 e A-3, except in the close
vicinity of the nuclei. Such an agreement can hardly be improved within the framework of a static theoretical investigation.
Fig. I. Right: Computed deformation density for COPplotted in the plane of
the pyrrole ring. Contour intervals 0.10 e k ’ . Negative contours dashed.Left: Observed deformation density (modeled) for CoTPP. Contours at 0.05
eA-’ with zero and negative contours dashed. Reproduced from [4] with permission of the author.
However, a map in the average molecular plane has little
interest for the nature of the ground state of FeP, since the
orbital populations in the xy-plane are similar for both the
3A2, and the 3Egconfigurations. Rather, one must consider
the population of the dzl orbital in FeP, which is 2 for the
3A2,state and 1 for the 3E, state. The deformation density
along the z-axis should therefore be quite different for
these two states. A section through the computed deformation density distribution by a plane containing the z axis
and bisecting two NFeN (or xOy) angles gave the following
for the ‘Azg state of FeP:
The computed distribution obtained shows four regions
of accumulation. Two of them are localized along the zaxis and the other two along the line perpendicular to Oz
bisecting the NFeN angles (in the xy-direction). These four
regions of accumulation are similar in height and shape,
and correspond to the filled d,, and dzl orbitals in the
(xy)’(xz)’ 5(yz)’’(z’)’ configuration. This result is imporAngew. Chem. In(. Ed. Engl. 21 (1982) No. 11
tant with regard to the nature of the SCF ground state of
FeP. One can reasonably infer that any mixing of the ’A2,
state with the ’E, state (xy)’(xz)’ ’(yz)’.’(z2)’ will reduce
the peak height along the z-axis, but not along the xy-direction. It can be therefore predicted that any significant
dissymmetry between these two directions-should it be
found experimentally- would represent a strong argument
in favor of a spin-orbit coupling between the 3A2, and 3E,
Received: March 22, 1982;
revised: September 6, 1982 [Z 196 IE]
German version: Angew. Chem. 92 (1982) 874
The complete version of this communication appears in:
Angew. Chem. Suppl. 1982. 1845-1852
CAS Registry numbers:
COP, 32662-36-5 ; FeP, 32647-22-6.
[I] The electron deformation density distribution @(r) is defined as the difference between a molecular electron density distribution and the superposition of spherically averaged distributions.
[4] E. D. Stevens, J. Am. Chem. Sac. 103 (1981) 5087.
[I31 H. Goff, G. N. La Mar, C. A. Reed, J. Am. Chem. Sac. 99 (1977) 3641.
114) T. Kitagawa, J. Teraoka, Chem. Phys. Letters 63 (1979) 443.
1151 J. Mispelter, M. Momenteau, J. M. Lhoste, J. Chem. Phys. 72 (1980)
Norcaradiene Valence Tautomer of a
By Emanuel Vogel*, Thomas Scholl, Johann Lex, and
Georg Hohlneicher
In memoriam, Otto Bayer
According to the ab initio calculations of Cremer and
Dick1’],the Huckel aromatic 1,6-methano[lO]annulene and
its unknown norcaradiene valence tautomer (tricycl0[’~~]undeca-2,4,7,9-tetraene)are separated by a
free energy difference (AG= 4.5 kcal/mol), which is practically equal to that between cycloheptatriene and norcaradiene. It is, therefore, to be expected that under the influence of n. acceptor substituents on the methylene carbon
atom[51the postulated equilibrium 1,6-methano[101annulene-tricycl0[4.4.1.O’~~]undeca-2,4,7,9-tetraene~~~
should experience similar displacements to the side of the norcaradiene component as those observed for the cycloheptatriene-norcaradiene equilibrium.
The reaction of 5 with butyllithium and phenyl cyanate
affords a transient dicyanide which, as evidenced by ‘HNMR findings, must be 3 and/or 4. Attempts at the isolation and full characterization of this species have until now
been futile due to its pronounced tendency to undergo the
Berson-Willcott rearrangement with formation of the
known cycloheptatriene derivative 6 . We have now found
[*] Prof. Dr. E. Vogel, T. Scholl, Dr. J. Lex
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (Germany)
Prof. Dr. G. Hohlneicher
Lehrstuhl fur Theoretische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (Germany)
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
OS70-0833/82/1111-0869 $ 0 2 . 5 0 / 0
that the dicyanide can be isolated if the reaction product is
worked-up below - 10 “C and recrystallized at low temperature from dichloromethane; yield 27%. The compound, which occurs as colorless parallelepipeds, readily
isomerizes in solution in chloroform [tlIz(20“C)= 28 min]
to give 6; in the crystal it is transformed into 6 only at
65-68 “C.
Received: August 5, 1982 [Z 126 IE]
German version: Angew. Chem. 94 (1982) 875
The complete version of this manuscript appears in:
Angew. Chem. Suppl. 1982, 1882-1890
The temperature independent ’H-NMR ‘spectrum (in
CD2CI2) of the dicyanide exhibits an AA‘BB‘ system at
6=6.27 and 6.43 (J1,’=9.64 and JZ,,=6.20 Hz), whose center is shifted by approximately 0.8 ppm to higher field relative to that of the AA’BB’-system of the vinylic protons in
1,6-methano[lO]annulene. In the I3C-NMR spectrum the
C-l/C-6 signal of the dicyanide (6=54.5) is shifted to high
field by no less than 59 ppm relative to that of 1,6-methano[ lO]annulene (6= 113.7) and, hence, approaches the signal of C-1/C-6 in tricycl0[4.4.1.O’~~]undeca-3,8-diene11,ll-dicarbonitrile (6 = 37.3).
The NMR spectra of the dicyanide are consistent with
the norcaradiene structure 4, but leave open the possibility
that the concentration of 3 at equilibrium is up to 10%.
A more precise statement on the maximum concentration of 3 is provided by the electronic spectrum. Whereas
1,6-methano[lO]annulene displays the characteristic three
band spectrum of a [4+2]annulene [with an intense
( ~ = 6 8 0 0 0 )band at 256 nm] the dicyanide exhibits a spectrum consisting of two bands [L=243 nm (~=6450),283
(2400) (in 2-methyltetrahydrofuran)] which in its appearance resembles that of tricycl0[4.4.2.O’~~]dodeca-2,4,7,9-tetraene. A weak shoulder in the region of the long wavelength band of the dicyanide probably arises from 3
( IW O ) .
Fig. 2. Molecular structure of 4 in the crystal: bond lengths
The X-ray structural analysis (Fig. 2) of the dicyanide
indicates that this also exists as 4 in the crystal. In contrast
to the 11,ll-dimethyl and 11-cyano-11-methyl derivatives
of 1,6-methano[ lO]ann~lenel’~~,
whose structuraf parameters lie between the values expected for the [lOIannulene
and onorcaradiene structures (C-1 -C-6 distance of 1.6
1.8 A), the dicyanide exhibits a C-1-C-6 distance (1.54244)
corresponding to the length of a cyclopropane bond, and
in consequence possesses 1,3-diene-type molecular segments C-2 to C-5 and C-7 to C-10.
The existence of 4, as well as the recent synthesis of tricycl0[4.4.l.O~~~]undeca-2,4,7,9-tetraene transition-metal
corroborate the statements,
complexes by Wilke et a1.[161
chiefly based on theoretical calculations, that the stability
relationships in the “arene-olefin equilibrium” 1,6-methano[ lO]annulene-tricyclo[’,6]undeca-2,4,7,9-tetraene
and in the cycloheptatriene-norcaradiene equilibrium correspond to each other to a remarkable degree.
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
[I] D. Cremer, B. Dick, Angew. Chem. 94 (1982) 877; Angew. Chem. Inr. Ed.
Engl. 21 (1982) 865.
[4] E. Vogel, Pure Appl. Chem. 20 (1969) 237.
[S] R. Hoffmann, Terrahedron Lerr. 1970, 2907; H . Giinther, ibid. 1970.
[I41 M. Simonetta, Pure Appl. Chem. 52 (1980) 1597; R. Bianchi, T. Pilati, M.
Simonetta, J . Am. Chem. SOC.103 (1981) 6426; a structural analysis of 4
at low temperatures is presently being undertaken by M. Simonetta.
(161 P. Mues, R. Benn, C. Kriiger, Y.-H. Tsay, E. Vogel, G. Wilke, Angew.
Chem. 94 (1982) 879; Angew. Chem. h:.Ed. Engl. 21 (1982) 868.
[Ta4F1206]4-: A Tetranuclear Fluorooxotantalate(v)
with Adamantane Skeleton
By Jean Sala-Pala, Jacques-E. Guerchais*, and
Anthony J. Edwards
As mentioned by Van Wazer et al.[’]about twenty years
ago, “an outstanding challenge in chemistry is the preparation and characterization of families of compounds (ranging from the smallest molecule of the series-the neso molecule-to the infinitely large macro molecules) based on
atoms other than carbon in the spine of the molecule”. If
we consider group V in this light, most work has been carried out since this date on compounds of the main group,
mainly those of phosphorus[’]. With tantalum, and particularly fluorotantalate species, only few studies have been
published[31,and in order to fill this gap we recently studied the hydrolysis of Et4N[TaF6]. The I9F-NMR
obtained are rather complicated and suggest formation of
several anions made up from the following structural
units: [TaF6]- (“neso molecule”), [TaF,O,,,]- (end group),
[TaF4(01/2)21- (middle group) and [TaF3-x(Ol,~)3+xl(x = 0.. .3 ; branch groups).
We report here on the complex (Et4N)4[Ta4F12061,1,
whose anion is made up of f o ~ r f a c - [ T a F ~ ( O ~ / branch
~)~]groups; the complex (Et4N)Z[Ta2F100],
2, built up from
two end groups, has been described previously[41.
Complex, 1, which was obtained by hydrolysis of 2, is
hygroscopic and its IR spectrum is not significantly different from that of 2 [880 cm-’, vs, v(Ta0Ta); 500 cm-’, s,
v(TaF)]. In the I9F-NMR spectrum only a sharp singlet is
observed even at low temperature [(CDCI,), standard :
CF3C02H):6- 50.0?0.5] suggesting that all the fluorine
atoms are equivalent. The results of an X-ray diffraction
analysis of 2 are illustrated in Figure la[’]. [Ta4FlZO6l4has an adamantane skeleton consisting of four Ta and six
[*] Prof. Dr. J. E. Guerchais, Dr. J. Sala-Pala
Laboratoire de Chimie Inorganique Moltculaire
associe au C.N.R.S. No 322,
Facult6 des Sciences et Techniques
F-29283 Brest-Cedex (France)
Dr. A. J. Edwards
Department of Chemistry, The University of Birmingham
PO Box 363, Birmingham B15 2TT (England)
0570-0833/82/1I11-0870 $ 02.50/0
Angew. Chem. inr. Ed. Engl. 21 (1982) No. 11
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valence, tautomeric, annulene, tricyclo, norcaradiene, methanol
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