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New Free-Radical Reactions with Phosphorins.

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pounds ( I ) [2,31. The C-C bond lengths in the phosphorin
ring 0) agree, within experimental error, both mutually and
with the C-C bond lengths in benzene. The CsP ring deviates
slightly but significantly from planarity (deviations from t h e
C2PC4 plane: CI, -0.11; C3, 0.07; C5, --0.02 A).
The three bonds to the phenyl rings project out a little from
the C2PC4 plane ( 0 , -0.33; C14, 0.17; C20, -0.20 A). The
bond angle, like that in the phosphorins ( I ) f2.31, is
relatively small, having a value of 107 O ; the symmetrical
variation of the remaining inner angles of the central ring is
worthy of note.
The O'PO2 plane is perpendicular t o the ClPCs plane; the
OlPO* angle of 93 is surprisingly small. The P-OCH3 bond
lengths (1.57 and 1.59 A) are comparable with the P--OR
distances found in phosphoric esters.
The observed P-C bond distances suggest participation of
the d orbitals of phosphorus in these bonds. The aromaticity
of the central ring I can be deduced from its near planarity
and from the bond lengths. The three bonds between the rings
have a length corresponding to that of a C(sp2)-C(sp2) single
bond. The phenyl rings are twisted with respect to the plane
of the central ring; the configuration is not propeller-like.
The C-C distances in rings I1 and I11 are, within the limits of
error, the same as those of normal aromatic bond lengths.
In ring IV, on the other hand, unrealistic distances (1.28 t o
1.45 /i) - due t o extensive thermal motion of this ring are observed.
Received: July 25, 1969
12 68a IE]
German version: Angew. Chern. 81, 783 (1969)
[*] Dr. U. Thewalt
Mineralogisches Institut der Universitat
355 Marburg/Lahn, Deutschhausstr. 10 (Germany)
[l] K . Dimroth and W. Stude, Angew. Chem. 80, 966 (1968);
Angew. Chem. internat. Edit. 7, 881 (1968).
[2] J. C. J. Bart and J . J . Daly, Angew. Chern. 80, 843 (1968);
Angew. Chern. internat. Edit. 7, 811 (1968).
[3] W . Fischer, E. Hellner, A . Chatzidukis, and K . Dimroth,
Tetrahedron Letters 1968, 6227.
[41 Thanks are due to Dr. Stude for growing the crystals.
[5] J . Karle and I. L. Karle, Acta crystallogr. 21, 849 (1966).
161 J . C . J . Bart, Angew. Chem. 80, 697 (1968); Angew. Chern.
internat. Edit. 7, 730 (1968); J . C . J . Bart, J. chem. SOC.(London)
B 1969,350.
New Free-Radical Reactions with Phosphorins
By K. Dimroth, A . Hettche, W. Stade, and F. W. Steuberf*I
Oxidation of 2,4,6-trisubstituted phosphorins ( I ) with
mercury(I1) acetate in the presence of alcohols or phenols
leads to the formation of compounds containing tetravalent
phosphorus, i.e. to 1,l-dialkoxy- or 1,l-diaryloxyphosphorins
(21 respectively[lJ. In o u r opinion, this reaction proceeds in
the first step via the phosphorin radical cation[2,31.
We have now been able to prepare 1,l-diaryloxyphosphorins
using 2,4,64riphenyIphenoxyl as oxidizing agent and the
phenoxide from this reaction as reaction partner; thus, reaction of 2,4,6-triphenylphosphorinwith 2,4,6-triphenylphen-
oxyl in the molar ratio 1 : 2 leads t o formation of 1,l-bis(2,4,6-triphenylphenoxy)-2,4,6-triphenylphosphorin.
A further reaction of this type is that of phosphorins with
tetraphenylhydrazine. When 2,4,6-triphenylphosphorinwas
allowed to react with the diphenylaminyl radical formed on
heating the hydrazine the first representative of a new class
of compounds ( 3 ) was formed, namely 1,I-bis(dipheny1amino)-2,4,6-triphenylphosphorin(yellow fluorescing crystals, m.p. 179°C; 31P-NMR: 8 -29.5 ppm (8H3P04 = 0),
JpH3,S = 36 Hz in pyridine as solvent; UV:,,,A
(E): 439
(8.45 x 103) 330 nm (1.9 x 104) in cyclohexane as solvent).
The phosphorin radical cation can be detected by ESR
spectroscopy in this reaction too.
The compounds of type ( 2 ) and ( 3 ) must - as crystal structure analysis showsf41- contain an aromatic system with spd
hybridization at the tetravalent phosphorus.
Also in agreement with this assumption is the fact that compounds (2) and (3) can be readily oxidized both electrolytically and by lead(1v) benzoate to give a new class of stable
radical cations. The ESR spectrum of the 1,l-dimethoxy2,4,6-triphenylphosphorinradical cation (/up\= 18.4 gauss)
is shown in Figure 1. The radical cation of 1,l-bisttrideuteriomethoxy)-2,4,6-triphenylphosphoringives exactly the
same spectrum.
This indicates that the delocalization of the unpaired electrons
is mainly limited to the aromatic system.
I , l-Bis(2,4,6-triphenyIphenoxy)
A solution of 2,4,6-triphenylphenoxyl (2.2 g, 6.8 mmoles) in
benzene (20 ml) is added dropwise at room temperature t o a
solution of 2,4,6-triphenylphosphorin(1.1 g, 3.4 mmoles) in
benzene (20 ml). The mixture is stirred for 2 hours. Yield
1.6 g (48 %) of yellow crystals having m.p. 249--251 "C; UV:
Amax(&): 425 (1.32 x lO4), 323 ( 1 . 7 0 ~lO4), 251 n m (9.20 x 104)
in cyclohexane.
I , I-Bis(dipheny1amino)-2,4,6-triphenylphosphorin
A mixture of 2,4,64riphenylphosphorin (324 mg. 1 mmole)
and tetraphenylhydrazine (390 mg, 1.16 mmole) in 30 ml dry
benzene is heated for 2 hours. The benzene is then evaporated
and the dark green fluorescing, viscous residue is taken up in
a little benzenein-hexane and chromatographed on a n Si02
column. The product thus obtained can be recrystallized
from ethanol/acetone; m.p. 179 "C (decomp); yield: 340 mg
Received: July 28, 1969
[Z 68b IEI
German version: Angew. Chern. 81, 784 (1969)
Prof. Dr. K. Dimroth, A . Hettche, Dr. W. Stade, and
Dr. F. W. Steuber
Institut fur Organische Chemie der Universitat
355 Marburg/Lahn, Bahnhofstr. 7 (Germany)
Angew. Chem. internat. Edit. / Vol. 8 (1969)/ No. I0
[l] K. Dimroth and W. Stiide, Angew. Chem. 80, 966 (1968);
Angew. Chem. internat. Edit. 7, 881 (1968).
[2] K. Dimroth, N . Gr&& H . Perst, and F. W. Steuber, Angew.
Chem. 79, 58 (1967); Angew. Chem. internat. Edit. 6, 85 (1967).
[3] K. Dimroth, N . Greif, W. Stade, and F. W. Steuber, Angew.
Chem. 79, 725 (1967); Angew. Chem. internat. Edit. 6,711 (1967).
[4] (1. Thewalt, Angew. Chem. 81, 783 (1969); Angew. Chem.
internat. Edit. 8, 770 (1969).
Electron Transfer from an Excited Electron Donor
in the Triplet State to an Acceptor Molecule
By G . Briegleb and H. Scliuster[*]
We have investigated the influence of electron donor-acceptor
(EDA) complex formation on the triplet-triplet (TT) absorppossibilities of electron transition (energy level scheme, see
tion spectrum of the electron donors (D) naphthalene (f)
Figure). Comparison of the observed and estimated Gm*
and phenanthrene (2) in complexes with the electron accepvalues shows that G C T ~ does not correspond to the measured
tors (A) tetrachlorophthalic anhydride (3) and pyromellitic
CT*-absorption bands. No distinction can be made between
dianhydride ( 4 ) .The TT absorption spectra were recorded in
GCT; and GCT:
within the limits of accuracy of estimation.
n-propyl ether,glass at T = 96 to 118°K by flash spectroA superposition of both transitions is conceivable, thus
photometryrll. The triplet state of ( 1 ) and ( 2 ) in the cornproviding a possible explanation inter aliu for a diffuse
plex IDA/ with (3) or ( 4 ) was excited by irradiation within
broadening of the CT* band in the case of the phenanthrene
the frequency of the charge transfer (CT) absorption bands
complex ( 2 1 4 3 ) .
ria the singlet excited state lD-'A-\: of the complex with
Received: July 28, 1969
[Z 72 IEl
German version: Angew. Chem. 81, 790 (1969)
subsequent "intersystem crossing" energy transfer
+ ID+A[. This excitation mechanism was possible since the
[*I Prof. Dr. G. Briegleb and Dr. H. Schuster
condition Epj+A-jz > FD;AI. or in the case of complexes
Institut f u r Physikalische Chemie der Universitat
with donor-triplet excimers ED..jD+d.-Ix > ~ D D ~ A I ,
87 Wurzburg, Markusstrasse 9-11 (Germany)
was fulfilled. The triplet state had to be excited via the C T
[ l ] H . T. Witt, R . Moraw, and A. Miiller, 2. physik. Chem. N . F.
singlet state in order to prevent a triplet excitation of the free
20,193 (1959); G. Porter, Angew. Chem. 73,7 (1961); in A . Weissdonor molecules not bonded in the complex.
berger: Technique of Organic Chemistry. Interscience, New York
The TT absorption spectra of complexed ( 1 ) and (2) in the
1963, Vol. VI11/2, p. 1055; J . S. Brinen, J. chem. Physics 49, 586
frequency range 20 t o 25 Y lo3 crn-1 exhibit characteristic
changes compared t o the TT absorption spectra of the free
[ 2 ] G. Briegleb and H . Schuster, Chem. Physics Letters 4 , 51
donors ( I ) and (2) 121. The triplet lifetime is also reduced by
complex formation, i.e. the probability of the T + So transiI31 hVcTf "_ hvcT - ED(S0 TI) ;JWX; 2 hvcTj f E A ( S 1 7 S 2 ) ;
tion is increased. The TT spectrum of complexed triplet exhvCT5 2 hvCTT f ED+ + D+*; for further details see: G. Brregleb
cimers of (f) and (2) was measured at slightly higher
and H . Schuster, Z. Naturforsch. a, to be published.
temperatures (106-113 OK) and/or in the presence of an excess of donor. It was also possible to detect the excimers in
the phosphorescence spectrum by irradiation within the
frequency of the CT band at T = 100 t o 120'K and in the
N-Halogenoimidosulfur Difluorides
presence of an excess of the donor [21.
and N,N'-Dihalogenosulfur Diimides
The ionization energy of the triplet excited donor bonded in
the complex lD+AI is reduced by the energy required for
T1 + SO excitation. Hence CT* absorption bands corresponding to transition of an electron f r o m the rriplet excited donor
to an unoccupied energy level of the acceptor in frequency
ranges of relatively long wavelength could be expected. We
first found CT* bands of this kind in complexes IDFA[ of
triplet excited ( I ) and (2) with ( 3 ) and ( 4 ) after the population of IDFA1 had been increased by flash excitation in the
frequency range of the C T bands of the complexes IDA1 in
the ground state in solutions in n-propyl ether glass at 96 to
By K . Seppelt and W. Sundermeyer[*I
N-Halogenoimidosulfur difluorides (2) have previously been
prepared by reaction of halogens with N-fluoroformylimidosulfur difluoriderll, FC(O)NSFz, in the presence of cesium
fluoride or by reaction of halogens with bis(difluorosu1fur(1v)imido)mercury 121, Hg(NSF&.
We have recently investigated the cleavage of N-halogenobis(trimethylsily1)amines( I ) with non-metallic halides 131 and have
found a further route to compounds (2) by reaction of ( I )
(X = CI, Br) with sulfur tetrafluoride.
The experimentally determined C T * frequencies of the CT*
band maxima are given in the Table, as are the CT* freGcT;,
and G C T ~ for a transition of the DT
quencies GcT!,
electron 1 or 2 of theT1-excited donor to various energy
levels of the acceptor calculated (31 assuming the various
Angew. Chem. internat. Edit.
GCT; [a]
C C T [a]
1 Vol. 8 (1969) 1 No. 10
X-N[Si(CH3)312 iSF4
(lb), X
+ 2 (CH3)jSiF
GCT; [a]
77 1
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phosphorite, reaction, free, radical, new
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