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Molecular Sieve Properties of Polymeric Schiff Base-Metal Complexes.

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via the carbenes ( 4 ) (Table 1I4l). The pyrolysis temperatures
reported are those giving the highest yields while avoiding
the formation of tarry by-products. The acetylenes all tend
to polymerize, but are easily purified by distillation or sublimation in vacuo. A case in point is 2-ethynylpyrrole (5 a), which
rapidly polymerizes at room temperature, so that its preparation in solution by conventional methods would be highly
problematical. Indeed, previous attempts to isolate this compound failed[5].Nevertheless, (5 a ) is a thermodynamically
very stable compound, surviving gas-phase pyrolysis at temperatures up to 1000°C, and isolable in near-quantitative
yield on the pyrolysis of (3a) (Table I).
The preparation of 3-ethynylindole (Sf) in 20% yield by
classical methods was recently described['! The yield obtained
by the present method (79 %) is superior.
The feasibility of flash pyrolysis as a preparative method
depends, of course, on the volatility of the starting material.
The isoxazolones (3 a)-(3 h ) all sublime without difficulty
at 120-180°C. However, in other cases, e. g. the preparation
of p-nitrophenylacetylenefrom the corresponding isoxazolone
derivative, only low yields were obtained due to extensive
decomposition prior to volatilization of the starting material.
In such cases we have found that good yields can be obtained
by allowing the solid starting material to drop into a vertical
pyrolysis tube.
Experimental
Synthesis of (3a): A mixture of ( I ) (2.48g, 0.025mol) and
pyrrole-2-carbaldehyde ( 2 a ) (2.38 g, 0.025 mol) in CHCI3EtOH (1:3) (80ml) was stirred under N2 at 22°C for 16h.
After concentrating to half volume, the brown-yellow crystals
were filtered and recrystallized several times from CHC13-hexane, yielding 4.20g (95 %) of ( 3 a ) as yellow crystals of m.p.
187-188°C.
Synthesis of ( 3 h ) : To a solution of the morpholine salt[31
(0.93g, 0.005 mol) of ( I ) in EtOH (20 ml) was added azulene-lcarbaldehyde (2h)r9l (0.78 g, 0.005 mol) in EtOH (20 ml), and
the mixture was stirred at 22°C under N2 for 24 h. Work-up
as above and recrystallization from CHC13 (200 ml) furnished
( 3 h ) (0.83 g, 70%) as dark-red crystals of m.p. 218-219°C.
Synthesis of ( 5 a ) : A pyrolysis apparatus similar to that
previously describedr"' was used. At a pressure of ca.
torr and an oven temperature of 800"C, (3 a) (0.4 g, 2.27 mmol)
was sublimed from a flask maintained at 120°C in the course
of 5 h. The products were collected on a cold-finger at - 196°C.
Acetonitrile and COz were removed in vucuo by allowing
the temperature to rise to ca. 20°C. (5a) (0.20g; 97 %) was
isolated by vacuum transfer at 40°C (ca. lo-' torr) into a
receiver cooled in liq. N2. 'H-NMR (CCI,): 6=3.07 (s, 1 H),
6.07 (m, 1H), 6.41 (m, 1 H), 6.62 (m, 1H), 8.2 (br., NH).
Synthesis of ( 5 h ) : In a manner similar to ( j a ) , ( 5 h ) was
prepared in 93 % yield as blue crystals of m. p. 35°C by pyrolysis of ( 3 h ) at 700"C, followed by sublimation of the product
at 2O0C/1O- torr. 'H-NMR (CC14): 6=3.42 (s, C d - H ) ,
7.06-7.70 (m, 4H), 7.96 (d, H2, Jz3=4Hz), 8.26 (d, H',
J 7 8 = IOHz), 8.57 (d, H4, 545 = 10Hz).
Received: June 5, 1978 [Z 16 IE]
German version: Angew. Chem. YO, 643 (1918)
CAS Registry numbers:
(I), 1517-96-0; ( 2 a ) , 1003-29-8; ( 2 b ) , 1192-58-1; ( 2 c ) , 98-03-3; ( Z d ) ,
498-62-4; ( d e ) , 620-02-0; ( 2 f ) , 487-89-8; (Zg), 17422-74-1; ( 2 h ) , 7206-61-3;
.
( 3 d ) , 67231-46-1;
(3a), 61237-43-8; (3b), 67237-44-9; ( 3 ~ ) 67237-45-0;
( 3 e ) , 67231-47-2; (3f), 61237-48-3; (39), 61237-49-4; (3h), 67231-50-7;
(Sa), 67237-51-8; (Sb), 61231-52-9; ( S C ) , 4298-52-6; ( S d ) , 67237-53-0;
(Se), 67231-54-1 ; ( 5 f ) . 62365-78-0; ( S q ) , 67271-48-1; ( S h ) , 67237-55-2
[l] Reviews: C . Wentrup, Chimia 31,258 (1977); G . Seybold, Angew. Chem.
89, 377 (1977); Angew. Chem. Int. Ed. Engl. 16, 365 (1977).
610
[2] C . Wentrup, W Reichen, Helv. Chim. Acta 59, 2615 (1976).
[3] A . R. Katritzky, S. Bksne, A . J . Boulron, Tetrahedron 18, 177 (1962).
[4] All new compounds were completely characterized by spectral and
microanalytical data.
[5] W D. Crow, A. R. Lea, M . N . Paddon-Row, Tetrahedron Lett. 1972,
2235.
[6] L. Brandsma: Preparative Acetylenic Chemistry. Elsevier, Amsterdam
1971, p. 117.
[7] C. Troyanowsky, Bull. SOC.Chim. Fr. 1955, 424.
[S] N . N . Suvornv, A . B . Kamenskii, Yu. I . Smushkevich, A . I . Livshits,
Zh. Org. Khim. 13, 197 (1977).
[9] K . Hafner, C. Bernhard, Angew. Chem. 69, 533 (1957).
[lo] N . M . Lrin, C. Wentrup, Helv. Chim. Acta 59, 2068 (1976).
Molecular Sieve Properties of Polymeric Schiff BaseMetal Complexes
By Manfred Riederer and Wolfgang Sawodny"]
Materials exhibiting specific absorption features due to pore
openings of molecular dimensions, and thus capable of physically separating molecules or atoms according to their size
and shape, are called molecular sieves. Examples of such materials already well documented include the zeolites, activated
charcoals, porous polymers, and porous glasses.
We recently reported the synthesis of novel polymeric Schiffbase complexes and their ability to form addition compounds
with neutral molecules[']. In the meantime we have also been
able to demonstrate their selective adsorption capacity as a
function of the critical diameter of the guest component.
Data for the most effective of the compounds known so far,
i. e. (I), are listed in Table 1.
Table 1. Comparison of the adsorption capacities of compound (I),
zeolite and active charcoal molecular sieves in wt.-% (20"C, ca. 760 torr).
Adsorbate
Critical
diameter
[A]
(I)
Benzene
CH,OH
CH2C12
Cumene
Cyclohexane
n-Pentane
H20
5.24
6.88
5.24
3.00
4.48
5.34
5.37
4.89
2.60
65.75
56.72
50.64
34.03
32.01
29.92
26.92
17.38
10.75
1,3,5-Triethylbenzene
9.00
0.00
Pyridine
cc14
Zeolite
Cal
Adsorban t
Active
charcoal [a]
18.80
10.90
37.13
19.60
12.40
33.00
21.00
28.00
~
[a] Highest value from the literature
With exception of the results for water, ( 1 ) shows a greater
adsorption capacity than molecular sieves of the zeolite or
active-charcoal type.
We have also investigated the behavior of the polymeric
compound ( 1 ) when used as stationary phase in molecular
[*I Prof. Dr. W. Sawodny, Dr. M. Riederer
Abteilung fur Anorganische Chemie der Universitat
Oberer Eselsberg, Postfach 4066, D-7900 Ulm (Germany)
Angew. Chem. Int. Ed. Engl. 17 (1978) No. 8
sieve gas chromatography[’]. As an example of the efficiency
of ( I ) as a molecular sieve, the complete separation of a
mixture of noble gases (He, Ne, Ar, K, and Xe) except for He
and Ne at room temperature is reproduced in Figure 1. Many
other gases, such as Ar and 02,can also be separated
from each other in a similar way at room temperature.
0
2
4
6
t [minl-
a
10
12
Fig. 1. GC separation of a noble gas mixture on ( 1 ) at 28°C (column
200 x 0.2 cm, flow rate 30 ml/min, NZ).
Both the selective adsorption capacity of the polymeric
Schiff-base complex ( I ) as well as its efficiency at separating
gases in gas-chromatography are similar to that observed for
zeolites of the type 13 X having pore diameters of 8&3J. This
lends support to the following molecular model (Fig. 2),
based on the bond lengths and angles observed in the structure
of Cu(~alen)‘~].
Fig. 2. Cavity in a possible helix structure of compound ( 1 ) (schematic).
Only the metal ion displaced from the ligand plane and
the tetrahedral methylene carbon of the ligand bridge were
considered, and were arranged assuming a helical structure.
Such a polymeric molecule contains an internal cavity (diameter = 7 81, which is consistent with its selective adsorption
capacity. Thus tetrachloromethane, with a diameter 6.88 8,
is quite readily adsorbed, whereas 1,3,5-triethylbenzene, with
a diameter of 9 A is not.
Received: May 31, 1978 [Z 17 IE]
German version: Angew. Chem. 90, 642 (1978)
CAS Registry number:
( / ), 64440-58-0
[I]
W Sawodny, M. Riederer, Angew. Chem. 89, 897 (1977); Angew. Chem.
Int. Ed. Engl. 16, 859 (1977); M. Riederer, E. Urban, W Sawodny, ibid.
89, 898 (1977) and 16, 860 (1977), respectively; W Sawodny, M . Riederer,
E. Urban, Inorg. Chim. Acta 29, 63 (1978).
[2] E. Leibnitr, H . G . Struppe: Handbuch der Gas-Chromatographie, 2nd
Edit. Verlag Chemie, Weinheim 1970.
[ 3 ] 0.Grubner, P . Jira, M. Ralek: Molekularsiebe. VEB Deutscher Verlag
der Wissenschaften, Berlin 1968.
[4] D.Hull, 7: N . Waters, J. Chem. SOC.1960, 2644.
Angew. Chem. In[. Ed. Engl. 17 ( 1 9 7 8 ) N o . 8
Ring Contraction by Peracid Oxidation: Preparation
of cyclo-Heptasulfur Dioxide, S 7 0 2 ,from S,[
By Ralj”Steudel and Torsten Sandow[*]
Sulfur rings S, (n=6-8) are oxidized by trifluoroperacetic
acid to the monoxides S.0, which are isolable in pure formiz1.
Only on reaction of the sulfanes R,S, (R=organyl, n =
3, 4) with an excess of peroxy acid have disulfoxides been
obtained. However, they very readily decompose to sulfones,
particularly if the sulfoxide groups are separated by only
one sulfur atomL31.
In an attempt to oxidize s 8 with excess peroxy acid to
S 8 0 2 ,we found that S 7 0 2was formed and could be isolated
in pure form in 5-10 % yield:
Even on extensive variation of the molecular ratio of the
reactants there was no indication of a higher oxide of s8;
on the other hand, the reaction product sometimes contained
traces of S 7 0 , which could be identified along with S 7 0 2
by Raman spectroscopy. S 7 0 2 could also be obtained from
SsO, S7, and S 7 0 , but the yields were lower o r at best the
same.
The formation of S 7 0 2 from SB most likely proceeds via
the following steps:
We assume that the hypothetical S80? is oxidized very much
more rapidly than S80, so fast that it cannot be isolated,
and that S s 0 3 immediately decomposes into S 7 0 and SO,,
since it must contain two SO groups which at most can
be separated by only one sulfur atom. Decomposition of S 8 0 z
into SO2 and S7 can be ruled out since S7 has never been
observed as an intermediate.
S 7 0 2forms dark-orange crystals, which are more intensely
colored and much less stable than S,O. At 6 M 2 ” C spontaneous decomposition occurs with vigorous evolution of SO2
and formation of polymeric sulfur. At 25°C decomposition
begins within a few minutes and is complete after 2 h in
the dark. Heating in a vacuum (50--60°C) leads to the characteristic decomposition product of polysulfur oxides, namely
SzO, which is also observed in the mass spectrumi4] besides
SO+ and S,‘ (n= 1-8). The composition of S 7 0 2was determined by elemental analysis and osmometric determination
of the relative molecular mass in CS2.
S 7 0 2 is far less soluble in CSz (ca. Ig/l CS, at 0°C) than
s70; the solution decomposes within 1 h to s g , s7, s8, and
SOz. The IR spectrum of a freshly prepared solution shows
two strong absorptions at 1138 and 1127cm-’, which can
be assigned to the two SO stretching vibrations.
The Raman spectrum[4] shows the typical lines of the S7
ring in the region 150-280 cm- ,as well as the SO- stretching and SSO deformation vibrations characteristic for the
-S-SO-Sgroups (Table 1). Assignment of the signals
is based on a comparison with the spectra of S7[’l and S70[61.
There is a distinct connection between the wave numbers
of theSS stretching vibrations of sulfur rings and the lengths
of the corresponding bondsL71 from which the values for the
‘
[*] Prof. Dr. R. Steudel, Dipl.-Chem. T. Sandow
Institut fur Anorganische und Analytische Chemie der Technischen Universitat
Strasse des 17. Juni 135, D-1000 Berlin 12 (Germiny)
61 1
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