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Chemical Reactions of Dimethyl Sulfoxide in a Plasma Discharge.

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Chemical Reactions of Morpholine in a Plasma
Discharge
By Klaus Gorzny and Giinther Maahs[*]
Dedicated to Professor Heinrich Hellmann on the occasion
of his 60th birthday .
If morpholine is passed through the plasma of a high-frequency glow discharge (27 MHz), reaction proceeds at high
conversion rates to yield two main products: dimorpholinomethane and morpholinoacetonitrile. This unexpected
reaction course can be explained on the basis of the massspectrometric fragmentation pattern of morpholine-a
strategy already employed in the interpretation of other
plasma reactions". 'I.
The mass spectrum of morpholine contains the following
main
The experiments were carried out in quartz glass apparatus
with capacitative coupling to a highfrequency generator". 41. The reaction mixture was collected in low-temperature traps and analyzed by gas chromatography. The output was vacuum fractionated to isolate and identify the
main products. ( 4 ) : b. p. 1 15-120°C/3 torr, nio= 1.4802;
( 5 ) : m.p. 59-60 C (from methanol). The structures of
( 4 ) and ( 5 ) were established by IR, NMR, and mass
spectrometry.
Received: May 29. 1973 [Z 926a IE]
German version: Angew. Chem. 85, 1054 (1973)
Publication delayed at authors' request
[ I ] Cf., e.9.. H. Suhr and R. I . Weiss, 2. Naturforsch. 25b, 41 (1970).
[2] H. Suhr, Angew. Chem. 84, 876 (1972): Angew. Chem. internat.
Edit. I / , 781 (1972).
[3] We are grateful to Dr. P. J . Frenzrl for recording the mass spectrum.
[4] R. Wursbeck, Chem. Ing. Tech. 43, 721 (1971).
29
100
mk
Yo
28
74
57
73
30
41
87
36
56
24
27
20
42
15
43
4
Hence it may be seen that the degradation preferentially
generates C H 2 0 and CHzNH, and to a lesser extent,
CHz-CHz-NH
fragments. In view of these cleavage
products, reaction mechanism ( I ) would appear reasonable.
Chemical Reactions of Dimethyl Sulfoxide in a
Plasma Discharge
By Klaus Gorzny and Gunther Maahs"]
Dedicated to Professor Heinrich Hellmann on the occasion
of his 60th birthday
A
The intermediates ( I ) to (3) are probably in a highly
excited state. ( I ) and (2) can then undergo further reaction
with unreacted morpholine.
A
+o
NII
In contrast, (3) is dehydrogenated to morpholinoacetonitrile ( 5 ) , since this stabilization appears to be more favorable than the analogous 1,2-dimorpholinoethane formation.
Dehydrodimerizations, cyclizations, and eliminations are
the preferred reactions under the conditions of a low-pressure high-frequency glow discharge"? Only a few examples
are known ofreactions in which a reactive species generated
in the plasma is scavenged by another molecule to give
a main
Morpholine is a particularly suitable scavenger for plasmagenerated reactive intermediated2]. For instance, if morpholine is passed with dimethyl sulfoxide through the
plasma of a glow discharge, a mixture of morpholinium
sulfate and thiosulfate is formed in yields of up to 163
g/kWh, alongside gaseous products which were not further
investigated. The same products are also obtained when
the morpholine is added behind the plasma zone, thus confirming the scavenger action of morpholine.
By variation of the reaction parameters pressure and power
consumption the reaction course can be controlled at will
to produce ( 4 ) or ( 5 ) as main product. Thus 95.4%
conversion takes place at 0.5-1 torr and 15&-200W
to give 138g/kWh of ( 4 ) and 14g/kWh of ( 5 ) , whereas
at 2 torr and 15&300W conversion is about 80% to
give 15g/kWh of ( 4 ) and 125.5ghWh of ( 5 ) . A small
amount (up to 8 g/kWh) of j3-morpholinopropionitrile
could be detected as minor product.
Dimethyl sulfoxide decomposes, both in the presence of
light[31and in the mass ~pectrometer[~],
to give methyl
and methylsulfinyl radicals. An analogous fragmentation
may also be expected in a plasma''.21. However, no products arising form these intermediate fragments, e.g. 4-Methylsulfinylmorpholine, could be detected in the reaction
mixture. It may therefore be concluded that the SO-CH3
fragment is unstable under plasma conditions and decomposes further to SO and CH3 fragments, the SO fragment
undergoing stabilization to sulfate and thiosulfate ion.
The reaction of dimethyl sulfoxide and aniline proceeds
analogously but in poorer yield (up to 54.5 g/kWh).
Optimum results (for apparatus see ref.''') were obtained
at pressures of 0 . 6 1 torr and power consumptions
between 50 and 15OW. The products were characterized
by elemental analysis and on the basis of their IR, NMR,
[*] Dr. K. Gorzny and Dr. G. Maahs
p] Dr. K. Gorzny and Dr. G. Maahs
(3)
-
n
Cj-CHz-CN
5)
Forschungslaboratorien der Chemische Werke Hiils AG
437 Marl, Postfach 1180 (Germany)
1004
Forschungslaboratorien der Chemische Werke Hiils AG
437 Marl, Postfach 1180 (Germany)
Angew. Chem. internut. Edit.
/ Vol. I 2 (1973) / No. 12
and mass spectra. The composition of the mixtures varied
between wide limits: the proportion of sulfate was I&
50 Yo and that of thiosulfate 5 6 - 9 0 % ; in addition, small
amounts of sulfite were also detectable in all cases.
The reaction of dimethyl sulfoxide with formamide takes
a completely different course. In the plasma, the reactants
yield dimethylamidosulfuric acid (0.4-4.0 torr, power consumption 100-150 W ; yield ca. 5 g/kWh; m.p. (dec. 161 to
163"C) alongside unidentified gaseous products. This product is not formed when one of the two reactants is added
behind the plasma zone, and must therefore arise from
the combination of reactive species of both components.
To our knowledge this is the first example of a plasma
synthesis in which a product is formed from fragments
of two different organic molecules.
Received: May 29, 1973 [Z 926b IE]
German version : Angew. Chem. 85, 1055 (1973)
Publication delayed at authors' request
[ I ] H. Suhr, Angew. Chem. X4, 876 (1972); Angew. Chem. internat.
Edit. I I , 781 (1972). and further literature cited therein.
[2] K . Gorrny and G. M a a h , Angew. Chem. 85, 1054 (1973); Angew.
Chem. internat. Edit. 12, 1004 (1973).
[3] K . Gollnick and H . U . Stracke, Tetrahedron Lett. 1971, 207.
[ 4 ] Eight Peaks Index of Mass Spectra. AWRE, Aldermaston. Reading
1970, Vol. I, p. 15.
Tetrakis(q -cyclopentadienyl)tetranickel
Trihydride-An Unusual Tetranuclear Cluster
By Jorn Miiller, Horst Dorner, Gottfried Huttner, and Hans
LorenzC']
Reduction of dimeric cyclopentadienylnitrosylcobaltwith
LiAIH4/AIC13 produces diamagnetic tetrameric cyclopentadienylcobalt hydride"], [C,H,CoH], ( I ) , a tetranuclear
cluster with p3-hydrido bridges. In order to test whether
this kind of reaction is suitable as a general synthetic
route for the preparation of cyclopentadienylmetal clusters
we subjected dimeric cyclopentadienylnitrosyliron~'I,
[C5H5FeN0]2 (2), as well as cyclopentadienylnitro~ y l n i c k e l ~C,H,NiNO
~],
( 3 ) , to the action of the above
reducing agent in tetrahydrofuran (THF) at 20 'C. Complex
(2) afforded exclusively ferrocene. Chromatography of the
product mixture obtained from the reaction of ( 3 ) afforded
nickelocene and a compound having the composition
C20H23Ni4 ( 4 ) .
The blackish violet crystals of ( 4 ) dissolve readily in benzene and THF, less readily in pentane, and d o not melt
below 320°C when heated under nitrogen. Its solutions
are air-sensitive.
In the mass spectrum of ( 4 ) the molecular ion appears
at m/e495 (based on ,*Ni) and exhibits an isotopic distribu-
tion characteristic of four Ni atoms. Apart from species
arising from loss of up to three H atoms, the 50-eV spectrum
contains the ions C I 5 H I 5 N i 2 ,CloH1,Ni:, CloHloNi+,
C5H5Ni+,and Ni+ as characteristic fragments. Prolonged
residence of the sample in the ion source results in gradual
decomposition with liberation of H2 and in partial degradation of the Ni4 unit; 12-eV spectra reveal that the complexes
CZOH22Ni4,
CZOHZ1Ni4,
and C20H20Ni4are also formed
as thermolysis products in addition to nickelocene.
The IR spectrum (KBr pellet) of ( 4 ) indicates the presence
of x-bonded symmetrical cyclopentadienyl ligands; the following bands appear (the corresponding absorptions of
nickelocene are given in paratheses for comparison): 3098
(3095), 1420(1425), 1332(1332), = 1270(1261), 1108(1111),
1050 (1046), 999 (1000), 800 (798), 770 (768), 342 (357)
.gm- '.The paramagnetic compound also gives a 'H-NMR
spectrum with a very broad signal at T = 157 (in THF)
which can also be assigned to cyclopentadienyl protons.
Accordingly, compound ( 4 ) is to be regarded as tetrakis(qcyclopentadieny1)tetranickel trihydride [C5H5NiI4H3. In
contrast to ( 1 ) , no v N ~ H absorption can be recognized
ip the IR spectrum, which, however, cannot be construed
as contraindicating the presence of metal hydride groups'41.
The structure of ( 4 ) was proved by X-ray analysis[5].
Crystal data: space group C2/c; u=2832+2, 6=923* I,
c = 1 5 0 3 f l pm; p=102.77f0.08"; V=3831flOx lo6
pm3; dcalc.=1.726k0.005, dexp.= 1.78kO.05g cm-' ; 2 = 8 ;
R 1 =0.064 for 1227 independent nonzero structure factors.
The molecule consists of a slightly distorted Ni tetrahedron
having a x-bonded cyclopentadienyl ring at each corner
(average distances :Ni-Ni 246, Ni-ring cen ter 177.7, N i x
210, and C-Cring 138 pm). The hydride hydrogen atoms
could not be directly located in the electron density diagram
of a difference Fourier synthesis; however, their positions
could be deduced from the deviations of the molecute
from strictly tetrahedral symmetry. The rings (C2 1 ... C25),
(C31 ... C35), and (C41 ... C45) form angles with the basal
face Ni2-Ni3-Ni4
that are significantly smaller than
the corresponding angles formed by all the rings with
the other tetrahedral faces, i.e. an average of 63.4'. compared with 73.0". The prevailing steric conditions can be
interpreted by assuming that the three H atoms act as
C32
Fig. I. Schematic representation of the molecule [C,H5Ni],H,
projection perpendicular to the Ni2-Ni3-Ni4
plane.
(4) ;
[*I
Doz. Dr. J. Miiller, DipLChem. H. Dorner, Doz. Dr. G. Huttner,
and DipL-Chem. H. Lorenz
Anorganisch-chemisches Laboratorium der Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
Reactions of Nitrosyl Complexes, Part 3. This work was supported
by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen
Industrie. Part 2: [I].
[**I
Anyew. Chem. internat.
Edit. / Vol. 12 (1973) 1 N o . 12
p3 bridges across three tetrahedral faces. This is in accord
with the elongation of the Ni-Ni distances by ca. 10 pm
compared to Ni-Ni single
1005
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