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Crystal Structure of 2 4 5 7 9 10-Hexaoxa-1 3 6 8-tetraphenyltricyclo[6.2.0

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formed separately and the Pe stabilized as a bisphosphane
complex[’0T.The complex with tris(dimethy1amino)phosphane, the 1,1,1,3,3,3-hexakis(dimethylamino)-l?~~,32.~-triphospha-2-enium tetraphenylborate 2, is particularly easy
to handle“’]. In order to accept Pe from 2, however, the
olefin must be particularly electron-rich. Thus, the biimidazolidinylidene 1 reacts with 2 in the way suggested to afford the phosphaallyl tetraphenylborates 4 (X = BPh,;
R = Me, Et), displacing two equivalents of tris(dimethy1amino)phosphane.
1151 T h e reaction of the fluorine compound corresponding to 5, i.e. of
bis(dimethylamino)difluoromethane, with 6 was recently described by
other workers. This leads to the 1 :1 product, (Me2N)2C=P-SiMe3, not
observed by us in the reaction of 5 with 6 : L. N. Markovskii, K. D. Romanenko, T. 1. Pidvarko, Zh. Obshch. Khim. 52 (1982) 1925.
Crystal Structure of 2,4,5,7,9,10-Hexaoxa-1,3,6,8tetraphenyltricyclo[ :
An Authentic Bisdioxetane**
By Waldemar Adam*, Ernst Schmidt, Eva-Maria Peters,
Karl Peters, and Hans Georg von Schnering
Dedicated to Professor Giuseppe Cilento on the occasion
of his 60th birthday
The stable product of the photooxygenation of tetraphenyl- 1,Cdioxin was assigned the bisdioxetane structure l”’,
since it thermally decomposed with formation of benzoic
anhydride and emission of light. Elemental analysis and
The reaction could commence by electrophilic attack of
2 and proceed via a phosphiranylphosphonium intermediate, which, however, has not yet been detected.
There is a second, more general and more effective route
to amino-substituted 2-phosphaallyl
for example, tetramethylchloroforamidinium chloride, 5 , reacts
with tris(trimethylsilyI)phosphane, 6, to form tetrakis(dimethylamino)phosphaallyl chloride, 7,X =C1[’sl.
+ (Me,Si)$P
- ~ M ~ , c I
In the same way the phosphaallyl chloride, 4, (X=C1,
R = Me) is formed from 2-chloro-1,3-dimethylimidazoIidinium chloride.
All of the products 4 and 7 are remarkably insensitive
towards oxidation and hydrolysis. In compounds with
X=Cl the chloride can be exchanged by other anions
without significant alteration of the chemical shifts in the
resulting NMR spectra. This result confirms their ionic
character. In 4, S(31P)is -93, but in 7, in contrast, -20,
which indicates that in the second case the positive charge
is less strongly transferred to the nitrogens. Irrespective of
the differences in degree, however, both cases should be of
the structural alternative A.
Received: February 28, 1983;
revised: March 28, 1983 [Z 294 IE]
German version: Angew. Chem. 95 (1983) 561
The complete version of this manuscript appears in:
Angew. Chem. Suppl. 1983, 710-717
[7] Cf. W. Kirmse: Carbene. Carbenoide und Carbenanaloge, Verlag Chemie, Weinheim 1969.
[lo1 A. Schmidpeter, S. Lochschmidt, W. S. Sheldrick, Angew. Chem. 94
(1982) 72: Angew. Chem. In!. Ed. Engl. 21 (1982) 63.
[I 11 A. Schmidpeter, S. Lochschmidt, unpublished results.
[I41 A third route to 2-phosphaallyl cations could be opened by alkylating
the tris(trirnethy1silyl)phosphane carbodiimide adducts (cf. K. Issleib. H.
Schmidt, C. Wirkner, Synfh. Reaa. fnorg. Met.-Org. Chem. 11 (1981)
279) in as far as this occurs at the nitrogen and not (as would be expected) at the phosphorus atom.
0 Verlag Chemie GmbH. 6940 Weinheim,1983
iodometric peroxide titration were consistent with the emWhile chemiluminescence is inpirical formula CZ8HZ0O6.
dicative but not necessarily definitive for 1,2-dioxetane~[~’,
the cited evidence is in principle also consistent with the
alternative structures 2 and 3 for this unusual “benzoic
anhydride dimer’’I3I. ’H-NMR is uninformative in this
structural problem and I3C-NMR (S= 107.80 ppm for the
dioxetane carbon) cannot differentiate between the possible alternatives. Since 1 is the first bisdi~xetane’~~
to be reported, it was essential that an X-ray structure analysis be
carried out. Aside from confirming the bisdioxetane
structure 1, we expected information about the stereochemical arrangement of the two dioxetane rings, i. e.
whether they are oriented syn or anti with respect to each
Fig. 1. Stereodiagram of the structure of 1. Space group F’2Jn; a = 1417.3,
b=766.6, c=1036.7 pm, fl=90.0o0, Z = 2 , p,rc=1.304’, 1653
F > 3 o ( F ) , R=0.062.
The CZ8HZoO6
product was prepared as described[”, and
well defined crystals were grown by low-temperature re[*] Prof. Dr. W. Adam, E. Schmidt
Institut fur Organische Chemie der Universitlt
Am Hubland, D-8700 Wiirzburg (Germany)
Dr. E.-M. Peters, Dr. K. Peters, Prof. Dr. H. G. von Schnering
Max-Planck-Institut fur Fesrkorperforschung
Heisenbergstrasse 1, D-7000 Stuttgart 80 (Germany)
Generous financial support from the Deutsche Forschungsgesellschaft,
the Fonds der Chemischen Industrie, and Volkswagenstiftung is gratefully acknowledged.
0570-0833/83/0707-0546 $02.50/0
Angew. Chem. Int. Ed. Engl. 22 (1983) No. 7
crystallization from petroleum ether/dichloromethane
(m. p. 111 "C, pale yellow prisms). X-ray structure analysisr5]confirmed beyond any doubt (Fig. 1) that this product
is the "benzoic anhydride dimer" 1,the first authentic bisdioxetane. As expected, the dioxetane rings are arranged
anti to each other. Surprisingly, however, they are appreciably puckered (dihedral angle ca. 16.3"). The dioxane ring
is almost planar; it has a markedly flattened chair conformation (all atoms deviate about 8 pm from the equalizing
plane). Presumably, in an almost planar dioxane ring the
non-bonding repulsive forces between the dioxetane oxygen atoms and the syn-oriented phenyl groups are minimal (inspection of Dreiding models indeed suggest this to
be the case).
On the other hand, the related dioxetane 4 (m.p. 1131 16"C, pale yellow prisms from n-pentane), prepared by
singlet oxygenation of diphenylbenzodioxid6](Fig. 2) has
Fig. 2. Stereodiagram of the structure of 4. Space group P2,/a; a=1923.2,
b=1239.3, c=1320.6 pm, 8=93.44", Z = 8 , p,.=1.346', 2332
F > 3 ~ ( k ) R=0.084.
an almost planar dioxetane ring (dihedral angle ca. 0.8")
and a puckered dihydro-1,4-dioxin ring. In 1 and 4 the
oxygen-oxygen bond lengths are 150.0 and 155 pm, respectively, the dioxetane carbon-carbon bond lengths 155.5
and 161 pm, respectively.
Received: March 21, 1983 [Z 317 IE]
German version: Angew. Chem. 95 (1983) 566
W. Adam, C.-C. Cheng, 0. Cueto, I. Erden, K. Zinner, J . Am. Chem. SOC.
I01 (1979) 473s.
[2] W. Adam, G. Cilento: Chemical and Biological Generation of Electroniculiy Excited Stares, Academic Press, New York 1982.
[ 3 ] The compound is not polymeric, since it is crystalline and has a well detined melting point.
[4] Since this type of "high energy" molecule contains two dioxetane rings,
higher excited states could be formed on thermal decomposition.
[ S ] Details of the crystal structure investigation can be obtained on request
from the Fachinformationszentrum Energie Physik Mathematik, D-75 14
Eggenstein-Leopoldshafen, by quoting the depository number CSD
50458, the names of the authors, and full citation of the journal.
[6] W. Adam, 0 . Cueto, E. Schmidt, K. Takayama, Angew. Chem. 93 (1981)
1100; Angew. Chem. Inr. Ed. Engl. 20 (1981) 1031.
By Klaus Porschke*, Giinther Wilke, and Carl Kriiger
Reaction of (cdt)NiCO 1[']with organolithium compounds or lithium amides in ether/pmdta as solvent leads
to formation of the thermolabile lithiumacyl- or lithiumcarbamoyLnickel(0) complexes ((pmdta)LiO(R)C)Ni(cdt)
(R=CH3 (2), C6H5 (3), NMez (4))"], which may be regarded as precursors of carbonyl-free and olejin-containing
carbene complexes. We have now been able to replace the
I*] Dr. K. Porschke, Prof. Dr. G. Wilke, Prof. Dr.C. Kriiger [**I
Max-Planck-Institut fiir Kohlenforschung
Kaiser-Wilhelm-Platz 1, D-4330 Miilheim a. d. Ruhr 1 (Germany)
[**I X-ray structure analysis.
Angew. Chem. Inr. Ed Engl. 22 (1983) No. 7
triene ligand cdt in 4 by ethene and to isolate the 16e-complex 5 in crystalline form.
- 40'C
NMe, 4
4 + 2 C,H, ~ ( p m d t a ) L i O C N i ( C , H , ) , + c d t
= cyclooctatetraene
= pentamethyldiethylenetriamine
= tetramethylethylenediamine
The yellow-brown crystals of the pmdta-stabilized lithiumcarbamoyl-bis(ethene)nickel(o) 5, which are stable at
room temperature, are readily soluble in polar organic solvents such as ether, tetrahydrofuran (THF) and acetonitrile, moderately soluble in toluene, and only sparingly soluble in pentane. As shown by the NMR spectra, the pmdta
ligand is released on dissolution of 5 in THF; the slight
electrical conductivity of such a solution (A =0.014
c m - ' / ! 2 ~ ; 0.1 M, 0°C) infers a very weak dissociation into
Methanolysis of 5 in presence of cod yields dimethylamine, which was detected gas-chromatographically, and
the expected amounts of ethene, as well as CO, Ni(CO),
and Ni(cod)'. Apparently, the nitrogen atom in 5 is protonated by weak acids, with dissociation of the carbamoyl
group. The bonded ethene in 5 is quantitatively liberated
by cot. An exchange between bonded and excess ethene
cannot be detected by NMR spectroscopy at room temperature. 5 reacts with CO at -78 "C, the CO replacing the
ethene to give the 18e-complex 6 , which can also be prepared from Ni(CO), or qrzl.
5 + 3 CO
- 780C+O~C
2 C,H,
The 400-MHz 'H- and 75.5-MHz I3C-NMR spectra of a
solution of 5 in [D&THF are temperature-dependent between + 20°C and - S O T , and show a remarkable complexity at -80°C. At 20°C they are consistent with a trigonal-planar coordination of the nickel atom by the two
ethene ligands and the carbamoyl ligand, whereby-referred to the NMR time scale-all ligands freely rotate about
the axis of coordination, while rotation of the NMez group
about the bond to the carbamoyl C-atom is appreciably restricted. The strong shielding of the ethene C-atoms and
H-atoms in 5, which compares with that in
7I3] in [D,]-THF, points to a
high negative charge on the bis(ethene)nickel moiety of the
complex through the lithiumcarbamoyl ligand. Lowering
of the temperature leads to freezing-in of the ethene rotation (< - 20°C) and to the appearance at - 80°C of two
detectable isomers, A and B (ca. 1 :IS), which presumably
differ in the bonding of the lithium atom to the carbamoyl
ligand (Li-0- and Li-N contacts).
5 is present in only one form in the crystalline state. As
shown by X-ray structure analysis (Fig. I), the planar
bis(ethene)nickel moiety, whose structural data are already
k n o ~ n ~ ~is. ~linked
to the likewise planar carbamoyl
moiety via a short Ni-C bond. The plane of the carbamoyl
system is nearly perpendicular (84") to the trigonal coordination plane of the transition metal. The geometry of the
carbamoyl ligand deviates only slightly from that of formamide and its complexed derivatives. The lithium atom,
which is surrounded by a highly distorted tetrahedral array
0 Verlag Chemie GmbH. 6940 Weinheim. 1983
0570-0833/83/0707-0547 $02.50/0
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crystals, structure, tetraphenyltricyclo, hexaoxa
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