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Distortion of the Trigonal-Bipyramidal Ligand Arrangement in BicyclophosphoranesЧStructure of 2 3 8 8- Tetraphenyl[1 3 25]oxazaphospholino[2 3-b]benzo[d]-[1 3 25]oxazaphospholine.

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After removal of solvent, compounds ( 5 ) are vacuum-distilled
or recrystallized.
c) R = X = O C H 3 : Compound ( I ) or ( 4 ) is heated with
an excess of P(OCH& in the absence of a solvent to 100°C
and the methanol formed distilled off. On completion of reaction, the remaining P(OCH3)3 is also distilled off; compound
( 3 ) or (5) is obtained as residue.
The new compounds are readily soluble in benzene, CHCI3,
and CH 2C12 ; acetonitrile proves suitable for recrystallization.
The yields range between 50 and 90%.
The structure ofa phosphorane bridgehead of fused five- and
six-membered and fused five- and four-membered rings has
been established for the examples ( I ) [ 3 1 and (3)"- 'I, respectively. We now report the structure of a phosphorane bridgehead
of two fused five-membered rings for the example of the title
compound (2).
Received: March I I , 1975 [Z 218a IE]
German version: Angew. Chem. 87. 517 (1975)
CAS Registry numbers:
(3a). 55590-36-8; ( 3 h ) . 55590-37-9: ( 3 ~ 1 55590-38-0;
.
( 3 d ) . 55590-39-1 : ( S a ) . 55590-40-4; / S h ) . 55590-41-5:
1 5 ~ 1 55590-42-6;
.
(sf/).5559n-43-7; /sl,i. w ~ n - 4 4 - x :
( 5 1 1. 55590-45-9: (5~11.55590-46-0; /5/7). 55590-47-1 :
( 5 ; ) . 55590-48-2; i 5 j ) . 55590-49-3; (CH,),PCI. 811-62-1 :
(C,H5)>PCI. 1079-66-9; [N(CH j)z]2PCI, 3348-44-5:
(CH30)zPCI, 3743-07-5; P(OCH,),. 121-45-9: P[N(CH3)Jj. 1608-26-0
i l l (R=CH,). 55590-51-7: (41 IR = C H 2 P h ) . 55590-524;
( 4 1 , (K= Phl. 55590-53-9: benzil-mono-o-hydroxyanil. 555Y0-50-6
[ I ] Four- and Five-Membered Phosphorus Heterocycles. Part 10. This work
was supported by the Fonds der Chemischen 1ndustrie.-Part 9: A .
J. Liihrr. Chem. Ber. / O K . 820 (1975).
123 So far three phosphordnes having a hetero-bicyclo[3.3.0]octane skeleton
have been prepared by other routes: a ) D. B. DmnrI.. D. Z . Drnnr!.
C. D. Hull. and K. L. Morsi. J. Amer. Chem. SOC. Y4. 245 (1972): b)
D. Houo//u. J . F . Bruzirr. M . Suirche:. and R. W d f : Tetrahedron Lett.
1972, 2969; c) D. H r l l i r i t i k ~ land W Krupp. Angew. Chem. 86. 524
( I 974): Angew. Chem. internat. Edit. /3. 542 ( I 974).
[3] F . Raniire;. Acc. Chem. Res. 1 , 168 11968): Bull. SOC.Chim. Fr. 1970.
3491: D. B r r n d and R. Bimyclu. C. R. Acad. Sci. 172. 2077 (1971).
Sc./imidprtrr and
( 2 ) forms monoclinic crystals, C2/c, with a = 24.556(5),
b= 8.816(5),
C = 23.220(4)A ;
p =97.22(2)";
Z = 8;
d,,,,= 1.29gcm-3.The structure was solved by direct methods
and refined to R=0.065, RG=0.075 for 2402 independent
reflections (four-circle diffractometer, F a 2.5a(F)).The positions of the hydrogen atoms could be localized in a Fourier
difference synthesis and were then included in the final cycles
of refinement with one common temperature factor each per
benzene ring. All the other atoms were assigned anisotropic
temperature factors.
Distortion of the Trigonal-Bipyramidal Ligand Arrangement in Bicyclophosphoranes4tructure of 2,3,8,8Tetraphenyl[l,3,2 ls]oxazaphospholino[2,3- b] benzo[d][I ,3,2 15]oxazaphospholine [ ' I
By William S. Sheldrick, Aljired Schmidpeter, and Josef Helmut
Weinmaier['I
In recent years the number of known phosphoranes (compounds containing pentacovalent phosphorus) has increased
considerably. Their stability is usually attributable to the incorporation of the phosphorus into one or two small rings, which
inevitably leads, however, to some degree of distortion of
the trigonal-bipyramidal arrangement of ligands coordinated
to the phosphorus. Although thecoplanarity of the phosphorus
and the three equatorial ligands is always retained, this does
not apply to their regular trigonal arrangement or to the
linearity of the axis.
In these phosphoranes the small rings are always in an
axial-equatorial arrangement; for the bicyclophosphoranes
there exist two
( A ) and ( B ) , capable of
interconversion by pseudorotation about the bond marked
with an asterisk as a pivot:
['I
490
Dr. W. S. Sheldrick
Gesellschaft fur Molekularbiologische Forschung mbH
3 3 Braunschweig-Stockheim. Mascheroder Weg 1 (Germany)
Priv.-Doz. Dr. A. Schmidpeter and J. H. Weinmaier
lnslitut f u r Anorganische Chemie der Universitat
8 Miinchen 2, Meiserstrasse I (Germany)
Fig. I . Molecular structure of ( 2 ) . A selection of bond lengths
standard deviations:
P-0'
P-C'
P-N
=
1.763(5)
= 1.818(5)
= 1.703(6)
P-0'
P-C'
=
=
[A]
with
1.7005)
1.81 l(6)
As for ( I ) and ( 3 ) , the structural alternative ( A ) with
equatorial annelation is again approximately fulfilled in the
case of (2). Expectedly, the planarity of the equator is retained
(deviation from the plane <0.001 A); however, a striking and
unexpected feature is the large difference in the two equatorial
NPC angles (Table 1). The 0 P O . a x i s is distinctly bent as
a result of the small internal angle of the ring. Regarding
its deviation from axial linearity, (2) assumes a position intermediate between the five/six- and the five/four-membered ring
phosphoranes: ( I ) 3.1"<(2) 8.4"<(3) 15.6". The overall distortion of the trigonal-bipyramidal ligand arrangement thus
remains fairly small for ( I ) . while it is considerable for (2)
and ( 3 ) ;however, their structures differ fundamentally regarding the direction of bending of the axis.
In (3) the axis is bent in the direction of the equatorial
bridge, i.e. the equatorial N atom lies in the OPN plane
formed perpendicular to the equatorial plane by bending of
the axis. The CZhsymmetry of ( 3 ) possible by virtue of the
molecular skeleton is retained in this "eclipsed" arrangement.
In (2). however, the two axial 0 atoms are "staggered",
i.e. the axis is bent towards one of the two equatorial NPC
angles. Hence this angle (N-P-C4)
becomes larger and the
other ( N - P X ' ) smaller than 120". Furthermore, the two
equatorial phenyl groups are no longer equivalent and ( 2 )
no longer possesses any symmetry. The non-equivalence of
the two exocyclic phosphorane bonds is characteristic of the
structural alternative ( B ) , and the angles found for (2) can
indeed be interpreted to a good approximation as an incipient
transition ( A ) + ( B ) (Table 1). The pivot for this pseudorotaTable I. Bond angles ["I at phosphorus in ( 2 ) according to the models
( A ) and ( B ) . for a 15 ";, transformation f A ) -+ ( B ) . and the experimental
values with standard deviations.
Transition
Experimen1:ll
I20
90
90
I20
I20
171
90
90
94.5
94.5
90
90
90
180
90
90
90
129
115.5
115.5
171.6(3)
89.7(4)
89.4(4)
93.3(4)
94.7(4)
87.q3)
86.60)
130.614)
I16.5(4)
I12.8(5)
(A)
f
I80
90
90
90
90
90
90
120
1 20
I20
0 ' - P~ 0'
O'-P-C'1
0'-P-c'1
0 I -p-c'
02-p-cs
0'-P-N
0'-P-N
N-P-CJ
N-P-C'
ca-p-cs
B)
tional transition is C5, which lies almost exactly in the OPO
plane formed perpendicular to the equatorial plane by bending
of the axis. Agreement between model and experimental values
is at its weakest for the two OPN and the CPC angles. This
is due to a certain degree of approach to the "eclipsed" arrangement: because of the small OPN angle arising from the ring
the O P O plane does not exactly bisect the N-P-C4
angle
but lies closer to the PN bond. Thus the C4-P-C5
angle
is "relieved" and decreases further. With regard to this angle
too, compound (2) assumed a position between ( I ) and
( 3 ) : ( 1 ) 116.8">(2) 112.8">(3) 111.3".
Whereas P as one of the bridgeheads of the bicyclic is
located far outside the plane of the surrounding ring members,
the other bridgehead N is in a planar environment. This
is possible because, while the benzooxazaphospholine ring
P-Ol-C'-C6-N
forms a good plane which also approximately contains C3. the other five-membered ring is in the
envelope configuration with the phosphorus lying 0.19 A outside the plane 02-C2-C3-N.
Among the bond lengths, a remarkable difference is observed
between the phenolic PO' and enolic PO2 bond. The relatively
long PN bond length is significant for the structural discussion.
It lies between the ranges commonly encountered for an equatorial and an axial PN bond of a phosphorane (1.62-1.68A
and 1.73-1.78 A respectively) and thus also corresponds to
a transition from ( A ) with an equatorial and ( B ) with an
axial PN bond.
With modified and in particular different occupations of
its two exocyclic phosphorane positions, the structural type
presented in this communication opens a new approach for
determining fine differences in ligand apicophilic character
on the basis of the ( A ) + ( E ) transition.
Photo-Diels-Alder Reactions of AnthraceneL"]
By Grrd Kaupp, Rainrr Dyllick-Brmzinger, and Inge Zimmermann"]
Preparative importance attaches to photochemical DielsAlder reactions"! Since these appear to be "forbidden" by
orbital-symmetry considerationsI2. 31, antarafacial concerted
mechanisms have been postulated[21.For the geometrically
more likely suprafacial course it has been predicted that shortshould
wave or charge-transfer excitation (to exciplexe~)'~]
"allow" the reactions14! Finally, one-stage stereospecific formation of cyclohexenes was expected from M O correlations
between polar excited reaction complexes and products in
the electronic ground stateL5'.Irrespective of these theoretical
positions, the experimental findings accord with non-concerted
mechanisms via short-lived intermediates". 61. We now report
on [4 + 21-photoadditions with dienophiles of various polarities which are open to choose formally "allowed" [ 4 + 4 ] processes or (and) radical chain polymerizations as well.
Selective irradiation ( I > 330 nm) of anthracene ( / )
(0.75 x
mol/'l) in the presence of the muconic ester ( 2 a )
(5.8 x 10- mol/l) in benzene leads to the trans-[4 + 21-adduct
(3a) (61%). along with sensitized isomerizations of ( 2 a ) .
dimerization of ( I ) (13%) and copolymerization of ( I ) and
(2a). The adduct can be catalytically hydrogenated to give
( 6 a ) . Formation of (4a) or (Sa) is not detectable by NMR
spectroscopy. The photoreaction occurs with fluorescence
quenching [55% quenching with 2.0 x lo-' mol/l of (Za)], i.4.
it follows a singlet mechanism. Long-wave exciplex fluorescence occurs simultaneously (h:: = 525 nm ; +I, = 0.01 ). The
surprisingly slow disappearance of anthracene (+= 0.0031) is
explained, at least in part, by non-productive exciplex formation. Thus the spectroscopic detection of exciplexes does not
suffice to prove their intermediate role in photochemical reactions. The following experiments also fail to substantiate this
postulate. The sorbic ester (2b) reacts with ( I ) (@=0.015)
without detectable exciplex fluorescence and distinctly faster.
although the fluorescence quenching is weaker (13 7 , ) than for
( 2 a ) . Even with a ten-fold increase in concentration of (2b)
R2
( a ) : R' = R~ = COOCH,
( b ) : R' = CH,, R2 = COOCH,
(c): R' = CO(>CH,, Ra = CH,
I
(1)
Received: March 1 I . 1975:
revised: March 18. 1975 [Z 218b IE]
German version: Angew. Chem. 87. 419 (1975)
CAS Registry numbers:
i 2 / . 55590-37-9
[I]
[2]
[3]
[4]
[5]
Four- and Five-Membered Phosphorus Heterocycles. Part I I.-Part
10: ref. [Z]
A . Schmidpvto. and J. H . Wrinmuirr. Angew. Chem. 87. 517 (1975);
Anpew. Chem. internal. Edit. 14.489 ( I9751.
D. D. S ~ r r r n k .C . N . Cuughlin. F . Rumirrz. and J . F. Pifor. J . Amer. Chem.
SOC.Y3.5236 ( 1 971 1.
A . Schmidprrrr and J . Luhrr. Phosphorus 5. 45 (1974).
M. 1. Kuhochiiil. V A. Gifyuroc, N. A. Tiklioninu. A . E . Kulinin. V
G. Andrionor. Yr. 7: Strurhkor. and G. 1. Tiiiio/rera. Phosphorus 5, 65
(1974).
A n g r w . Chrin. inreriiut. Edir. i
&I/.
1 4 I 197.5) I No. 7
[*I
Doz. Dr. G. Kaupp and 1. Zimmermann
Chemisches Laboratorium der Universitat
78 Freiburg, Albertstrasse 2 I (Germany)
DipLChem. R. Dyllick-Brenzinger
Orpanisch-chemisches Laboratorium der Eidgenossischen Technischen
Hochschule
CH-8006 Zurich, Universitatsstrasse 6 (Switzerland)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
491
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tetraphenyl, benz, oxazaphospholine, oxazaphospholino, distortion, bicyclophosphoranesчstructure, bipyramidal, arrangement, trigonal, ligand
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