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Fluorinated Inorganic Radicals.

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[*I Prof. Dr. H. J. Bestmann and Dipl.-Chem. R. W. Saalfrank
Institut fur Organische Chemie der Universitat
Erlangen-Numberg
852 Erlangen, Henkestrasse 42 (Germany)
Prof. Dr. J. P. Snyder
Belfer Graduate School of Science, Yeshiva University,
2469 Amsterdam Ave.
New York, N.Y. 10033 (USA)
[l] H. J . Bestman and H . Schulz, Chem. Ber. 95, 2921 (1962);
H. J . Bestniann, F. Seng, and H. Schulz, ibid. 96, 465 (1963).
[2] H. J . Bestmann, G. Joachim, I . Lengyel, J . F. M . Oth, R.
Merenyi, and H. Weitkamp, Tetrahedron Letters 1966, 3355;
H. J . Bestmann and J . P. Snyder, J. Amer. chem. SOC.89, 3936
(1967).
the temperature is lowered and completely disappears at
-40°C. The ratio of the intensities of the remaining signals
(d) is about 1:4. On increasing the temperature the middle
signal reappears. At the starting temperature the original
signals are once again obtained; the ratio of the three intensities, however, changes somewhat (1 :0.37:4). The process is
reversible. These findings can be best explained by assuming
an equilibrium to be present between the two different structures ( I ) and (2) of the primary titanium-aluminum complex.
Temperature Dependence of the NMR Spectrum
of a Soluble Ziegler-Natta Catalyst
By K . H . Reichert and M . Mallmann[*]
Biscyclopentadienylmethyltitanium(rv) chloride and trimethylaluminum react extremely rapidly with each other t o
form a titanium-aluminum complex. Formation of the complex is followed by very slow loss of methane111. The N M R
signals of the methyl protons of (CsH5)2TiCICH3 (a) and of
AI(CH3)3 (b) are shown in Figure 1.
+I
0
0
-1
0
-1
+1
0
Cp
Immediately after the mixing of the above components, three
resonance signals (c) appear in the ratio 1:0.47:3.8. The two
outer signals appear at almost the same position as d o those
of the starting compounds. The intensity of the middle signal
is very much dependent o n temperature. It decreases when
Cyclopentadienyl
At low temperatures, the titanium-aluminum complexes
ought t o have a tetrahedral structure (2) in agreement with
the proton resonance signals occurring in the ratio 1 :4. (excess
of alkylaluminum). With increasing temperature the equilibrium is displaced in favor of the octahedral complex ( I ) ; an
additional signal, that of the bridge methyl group, is then to
be observed. The very slow decomposition taking place after
complex formation and during the time of measurement can
be disregarded a t the concentration ratios given. Only after
several hours is a slight change o f the original spectrum t o be
observed.
If the interpretation of this finding is valid then the respective
structural parts of the complex formed are also to be considered when the question of these catalytic systems is discussed from the standpoint of polymerization active species.
A n octahedral structure[21 is generally assigned to the active
species. Our results[31 suggest that the complex (3) should
initiate polymerization.
R = Alkyl
-1
Fig. 1 . 'H-NMR spectrum a) of a 0.5 M solution of CpzTiCICH, in
benzene at 33 "C; b) of a 0.5 M solution of AI(CH,), in benzene at 33 "C;
c) immediately after mixing solutions of both compounds in toluene at
33 "C, [CpzTiCICH,] = 0.38 mole/l, [AI(CH,),] = 0.5 mole/]; d) after
cooling the reaction solution to -6OOC. TMS was used as external
standard.
=
Received: November 28, 1968; revised: January 30, 1969 [Z 941 IE]
German version: Angew. Chem. 81, 228 (1969)
[*] Dr. K. H. Reichert and Dipl.-Chem. M. Mallmann
Institut fur Technische Chemie der Technischen Hochschule
8 Munchen, Arcisstrasse 21 (Germany)
[l] H . Sinn, H. Hinck, F. Bandermann, and H. F. Grutzmacher,
Angew. Chem. 80, 190 (1968); Angew. Chem. internat. Edit. 7,
212 (1968).
[2] G. Henrici-Olive and S . OlivP, Angew. Chem. 79, 764 (1967);
Angew. Chem. internat. Edit. 6, 790 (1967).
[3] K . H . Reichert and E. Schrrbert, Makromolekulare Chem.,
in press.
C O N F E R E N C E REPORTS
Fluorinated Inorganic Radicals
By H . J. Emele'us 1*I
In recent years the chemistry of fluorine-containing radicals
such as BF, CF3, SiF2. NF2, N(CF3)z. S 0 3 F , and (CF3)zNO
has been widely studied and substantial advances in preparative inorganic chemistry have resulted.
The radicals BF and SiFz are typical of those formed in high
temperature reactions at a low pressure between the element
and its fluoride (BF3 or SiF4). Under these conditions
Angew. Chem. internat. Edit.
1 VoI. 8
(1969) 1 No. 3
Margrave and his co-workers have shown that the SiFz
radical reacts, for example, with ethylene to form the cyclic
compounds (CH2)2(SiF2)2 and (CHz)&iFz)z. Higher boron
and silicon fluorides such as B3F5 and SidFIO have also
been described, as well as mixed boron-silicon fluorides
(SiF3SiFzBFz and SiF3(SiF&BFz).
The NF2 radical, which Colburn showed t o be formed in the
reversible dissociation of N2F4, combines with other free
radicals. With N O it forms NFzNO and with SF5. formed
inter alia by the thermal dissociation of SzF10. it yields
SFsNFz. It may also be added to olefins and will abstract
217
hydrogen from compounds such as thiols to give NF2H.
The bistrifluoromethylamino radical, though less reactive,
has yielded many new derivatives, though not directly.
These include H ~ [ N ( C F ~ ) Z It(CF3)zN12Sj
Z,
[(CF~)ZNIZS~,
[(CF3)2N]zSe, and (CF&NSeCI. Addition of (CF3)zNCI to
PF3 or PF2Cl gives phosphorus(v) derivatives and with
P(CF3)3 and (CF&NCl it is possible, by stepwise elimination
of CF,CI, t o form P[N(CF3)2]3.
The radical FS020, formed in the reversible thermal disso,
ciation of bis(fluorosulfonyl)peroxide, F S O ~ O O S O ~ Fhas
been shown, largely by Cudy and his co-workers, to undergo
a number of typical addition reactions. Thus with CzF4 it
forms F S O ~ O ( C F 2 ) ~ O S O
and,
~ F with SF4, F S O Z O S F ~ O S O ~ F .
I t also reacts directly with halogens t o give fluorosulfonates
(e.g. ClSO3F, I(S03F)3).
The bistrifluoromethyl nitroxide radical, first isolated by
Bfuckley and Reinhurd, forms a violet gas with much the same
stability as nitric oxide. It is formed by the oxidation of
(CF3)zNOH and has now been shown t o react at room temperature with mercury t o form crystalline Hg[ON(CF3)2]2,
from which the radical may be recovered quantitatively at
85 “C. The radical reacts with PF3 t o give PF3[ON(CF,)&.
The mercurial is also a useful reagent for the transfer of the
(CF3)zNO group, POCl3 and PSC13 forming PO[ON(CF3)2]3
and PS[ON(CF3)&,
respectively, while BC13 gives
B[ON(CF3)z13.
Lecture at Gottingen on July 4, 1968 [VB 179 IE]
German version: Angew. Chem. 8 / , 190 (1969)
[ * ] Prof. H.. J. Emeleus, F. R. S .
University Chemical Laboratory
Lensfield Road
Cambridge (England)
R
Ri
x
N
GH
H
V
O
HC-12‘
H3C
,NH
I
0 HN,I
C6H5
C6H5
O&
(6)
( 7 u ) , R = R2 = H,R1 = C6H5
( 7 h ) , R = H, R’ = C&, R2 = CH,
( 8 ) , -R-R’-= -(CH2)5-. R2 = H
A competing reaction that is also observed with ( I ) and (2)
preponderates when 5-phenyl-l,3-~yclohexanedioneand
spiro[4.5]decane-7,9-dioneare oxidized in aqueous-alcoholic
solution: the starting ketone condenses with the aldehydes
formed from the methanol (or ethanol), giving (7u) [or (7b/]
or (81. It is thus proved that under these conditions alcohols
are dehydrogenated t o aldehydes. In the case of 2-methyl1,3-cyclohexanedione the ring is cleaved; this occurs also
with 1,2-cyclohexanedione, which is converted into adipic
acid (J. Hohn).
I n acid solution benzhydrazide affords N2 and benzoic acid,
but in alkaline solution gives benzaldehyde and benzoylbenzyiidenehydrazine (G. Kiihler).
Lectures at Kiel (Germany) on November 21, 1968,
and at Stuttgart (Germany) on December 5, 1968
German version: Angew. Chem. 8 1 , 190 (1969) [VB 180IEl
[*I Prof. Dr. H.-J. Teuber
Institut fur Organische Chemie der Universitat
6 Frankfurt/M., Robert-Mayer-Strasse 7 - 9 (Germany)
Potassium Nitrosobissulfate as Specific Oxidizing
Agent in Organic Chemistry
By H . J . TeuberI*l
Enols, like phenols, are oxidized by potassium nitrosobissulfate (Fremy’s salt), ON(SO3K)z. Dihydroresorcinol
and dimedone are converted into the tertiary alcohols (1)
and (21, respectively; the former product can also be synthesized from its components, 1,2,3-cyclohexanetrione and
dihydroresorcinol. ( I ) and (2) are cleaved by phenylhydrazine to the tris(pheny1hydrazones) (3) and ( 4 ) and are
(I). R
(2). R
=
H
= CH3
(J), I t = H
( 4 ) , R = Cli,
cyclized t o furan derivatives by acids or by catalytically
excited hydrogen. Oxindole is analogously oxidized t o the
compound ( S ) , which affords isoindigo by dehydration. I n
the case of 4.6-dimethyl-l,3-cyclohexanedione
the formation
of a dimer (aldol reaction) does not occur, but the oxidation
product formed (as in the reaction with selenium dioxide)
can be isolated as bisphenylhydrazone ( 6 ) .
218
Trimethylenemethane, a Theoretically and
Synthetically Valuable Allylic Structure
By F. Weiss[*]
Trimethylenemethane, in the form of the diradicai 2-methylene-l,3-propanediyl ( I ) , is an interesting allylic species
containing the skeleton of cr,a’-disubstituted isobutenes ( 2 ) .
The theoretically predicted triplet ground state of ( I ) has
recently been confirmed by EPR studies of the diradical
produced by low-temperature photolysis of 4-methylene-l1-pyrazoline and of 3-methylenecyclobutanone. This reactive 1,3-diradical can, like the cyclobutadienes, be isolated as
its stable tricarbonyliron complex.
The properties of the 1,3-diradical as intermediate can be
explained on the basis of its triplet structure. For instance, it
affords practically no methylenecyclopropane, but instead
1,4-dimethylenecycIohexane,i.e., a coupling product, when
a,%’-dihaloisobutenes react with potassium vapor, when 6methylene-l,4-dioxepane-2,3-dione is pyrolyzed, when the
above-mentioned photolysis reactions are carried out, and
when trimethylenemethane-tricarbonyliron is photolyzed in
pentane. If other triplet radicals are also formed in the first
step, then ( I ) can react partly with them, e.g., with triplet
methylene produced from diiodomethane. Cycloaddition of
( I ) t o olefins such as butadiene, cyclopentene, and cyclopentadiene has been achieved only in the photochemical reactions mentioned above.
Trimethylenemethane intermediates produced under nonradical conditions also behave unusually. Reaction of a,a’Angew. Chem. internal. Edit.
Vol. 8 (1969) / No. 3
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