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Isomerizations of N-Silylated Cyclosilazanes.

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The readily accessible tert-butyl acetate that is formed not
only very easily decomposes into its components, isobutylene
and acetic acid, but also reacts like isobutylene and thus can
be trapped and used as "masked" isobutylene. tert-Butyl
acetate is, in fact, superior to isobutylene as regards manipulation and yields.
The complexes (3), like (2) [I], react as selective hydrogenation catalysts. The complexes (3c) and (3d) have ahydrogenation activity comparable with that of (2), whereas the
salt-like compounds (3a) and (3b) exhibit only weak activity.
Compound (7) does not catalyze hydrogenation.
Bis (cyclopentadienyl) vanadium-tricarbonylcycyclopentadienylchromium (3c)
A solution of (2) (1.07 g) in benzene (140 ml) is treated dropwise with a solution of ( l c ) (1.03 g) in benzene (15 ml). The
mixture is stirred during the addition and the color changes
from green to dark-brown, it is concentrated to about 40 ml
under vacuum, filtered free of decomposition products, and
treated with 200ml of pentane. The almost black crystals
which separate are filtered off and washed with pentane. On
cooling, (3c) crystallizes as black-brown needles, m.p. 147 to
149 "C [yield 1.07 g (51 731. The analogous reaction of ( I d )
with (2) leads to the formation of (3d) in 5 6 % yield (dark
brown crystals that decompose a t temperatures above 160 "C).
Both complexes are extremely sensitive to air and undergo
spontaneous combustion.
Table 1. Examples of the tert-butylation of aromatic compounds and
conversion of nitriles into N-fert-butylcarboxamides(Ritter reaction).
mole/mole
of TBA
Starting
material
T
( "C
,
2
I00
45
Toluene
2
100
60
Phenol
0.7
67
20
1.1
20
125
Hydroquinone 0.5
20
50
Anisole
20
Received: May 3, 1969
[ Z 998 1E1
German version: Angew. Chem. 81,498 (1969)
2
[*] Dr. A. Miyake, Dip1.-Chem. H. Kondo, and
Dip1.-Chem. M. Aoyama
Basic Research Laboratories, Toyo Rayon Co., Ltd.
Kamakura (Japan)
[I] A. Miyake and H. Kondo, Angew. Chem. 81, 663 (1968);
Angew. Chem. internat. Edit. 7, 631 (1968).
[2] Cf. e.g. L. Lucos, Ber. dtsch. chem. Ges. 21, 2510 (1888).
[3] The following examples of oxidations carried out with iodine
are known:
t41
[51
161
[41 E. 0. Fischer and H. P. Kogler, Angew. Chem. 68,462 (1956);
E. 0. Fischer and K . Ulnr, Chem. Ber. 95, 692 (1962).
151 H. J. de Liefde Meijer, M . J. Janssen, and G. J. M. van der
Kerk, Recueil Trav. chim. Pays-Bas 80, 831 (1961).
[6] G. Wilke, B. Bogdanovid, P. Hardt, P. Heimbach, W. Keim,
M . Kroner, W. Oberkirch, K. Tanaka, E. Steinrucke, D . Walter,
and H. Zimmermann, Angew. Chem. 78, 157 (1966); Angew.
Chem. internat. Edit. 5, 151 (1966).
171 E. 0. Fischer and W. Hafnei, Z. Naturforsch. 106,140 (1955);
E. 0. Fischer, W . Hafner, and H. 0. Stahl, 2. anorg. allg. Chem.
282, 47 (1955).
[81 Cf. E. W. Abel, Quart. Rev. 17, 1 3 3 (1963).
191 K . N . Anisimov, N. E. Kolovoba, and M . Ya. Zakharora,
Doklady Akad. Nauk SSSR 156,612 (1964); H. R . H . Patel, and
W. A. G. Graham, Inorg. Chem. 5, 1401 (1966).
Reaction
products
Yield
ferf-Butylbenzene i1,4-ditert-butylbenzene
1-terr-Butyl4-methylbenzene
p-tcrf-Butylphenol -!
2.4.6-tri-tertbutylphenol
76
( %)
-
Benzene
Phenol
~
125
-
19
96
5
86
p-fen-Butylphenol
2,5-Di-ferfbutylhydroquinone
p-ferf-Butylanisole
96
87
86
Acetonitrile
1
100
40
acetarnide
N-terf-Butyl-
91
Acrylnitrile
1
100
40
88
Benzonitrile
1
I08
40
3-Nitrohenzonitrile
1
I08
40
LOO
40
N-tert-Butylacrylamide
N-ferf-Butylbenzarnide
3-Nitro-Nferf-Butylbenzamide
N,N-Di-ferfbutylmalonodiamide
I
dinitrile
Ma'ono-
o.5
94
95
92
The alkylation of aromatic compounds is best carried out by
adding the amount of tert-butyl acetate shown in Table 1,
with stirring, to a mixture of aromatic compound and conc.
sulfuric acid over a period of 2 h and then stirring the reaction
mixture for a further 2-3 h before separating and purifying
the reaction product. To carry out the Ritter reaction the
nitrile is mixed with tert-butyl acetate, and concentrated
sulfuric acid is added dropwise to the stirred and cooled mixture, the temperature of the reaction mixture not being allowed to exceed the temperature given in Table 1.
The reaction mixture is finally stirred for a further 1-2 h and
then poured into ice-water. The precipitated amide is isolated
and purified.
Received: May 6, 1969
I 2 994 IE]
German version: Angew. Chem. 81, 496 (1969)
~
fert-Butyl Acetate as Alkylating Agent
By H . Fernholz and H. J . Schmidt[*]
Dedicated to Professor 0. Horn on the occasion
of his 65th birthday
tert-Alkyl esters of carboxylic acids are readily accessible by
addition of tertiary olefins to a carboxylic acid in the presence
of polyphosphoric acid as catalyst [IT. The action of the polyphosphoric acid in such additions is extraordinarily selective
and limited exclusively to addition of tertiary olefins. This
fact is made use of, for example, in a process for the separation of isobutylene from olefin fractions o n a technical scale the olefin fraction is passed through a polyphosphoric acidacetic acid mixture [21.
Angew. Chem. infernat. Edit. J VoI. 8 (1969) 1 No. 7
[*I Prof. Dr. H. Fernholz and Dr. H. J. Schmidt
Farbwerke Hoechst AG, vorm. Meister Lucius & Bruning
6230 Frankfurt/Main - 80 (Germany)
I11 a) H. Fernholz and E. Mundlos, DBP 1128428 (August 8,
1959), Farbwerke Hoechst AG; b) H. Fernholz and H. J . Schmidt,
DBP 1196190 (September 5, 1962), Farbwerke Hoechst AG.
PI H. Fernholz and H. J. Schmidt, Erdol u. Kohle 18, 523 (1965).
Isomerizations of N-Silylated Cyclosilazanesrll
By W. Fink[*]
After metalation, the hydrogen atoms attached t o nitrogen in
hexamethylcyclosilazane can be replaced by silyl groups [2,31.
In the case of trimethylsilyl-substituted compounds, intact
521
cyclosilazane structures are assumed. We have now observed
on the side of ( 3 ) . Thus, 78 % of the isomer ( 5 ) and only 11%
that partial isomerizations takeplace in thesereactions which
of compound ( 6 ) are obtained by metalation, at -6OoC, and
depend strongly o n the reaction conditions.
subsequent silylation of ( 4 ) .
The monosilylation of hexamethylcyclotrisilazane with butylReceived: May 7, 1969
[Z 999 IE]
lithium/trimethylchlorosilane in diglyme at temperatures beGerman version: Angew. Chem. 81, 499 (1969)
tween -60 and 1 6 0 "C affords 2,2,4,4,6,6-hexamethyl-l-tri- methylsilylcyclotrisilazane( I ) . Formation of (2). the isomer
[*I Dr. W. Fink
Monsanto Research S.A.
of ( I ) , which melts at 36 "C and which can be prepared by
CH-8050 Zurich, Eggbuhlstrasse 36 (Switzerland)
ammonolysis of 2,2,4,4-tetramethyl-l-dimethylchlorosilyl-3trimethylsilylcyclodisilazane,was not observed. Whereas the
[l] Part 20 in the series "Contributions to the Chemistry of the
Si-N Bond". - Part 18 and 19: Helv. chim. Acta, in press.
doubly silylated hexamethylcyclotrisilazane (3) is obtained
when hexamethylcyclotrisilazane is silylated in diglyme at
[2] W. Fink, Helv. chim. Acta 45, 1081 (1962).
[31 L. W. Breed and R . L. ENiott, Inorg. Chern. 2, 1069 (1963).
RZ
Rz
~
,Si,
c R3Si-N,
N-SIRZ-NHZ
Sl'
Rz
(1 )
I
R.7
R9
f 2)
R?
I .
I
H
StR3
(5)
SiR3
f6)
R = CH3; Bu = n-C4H,
-60"C, only the cyclodisilazane derivative ( 4 ) , which is isomeric with (3). can be isolated when the silylation is carried
out at +6OoC in the same solvent or at 16OoC in hexane
(under pressure). Similarly, the triple silylation of hexamethylcyclotrisilazane in diglyme at -60 OC affords hexamethyl
tris(trimethy1silyl)cyclotrisilazane ( 5 ) in yields of over 62 %.
A mixture of (5) and the isomer ( 6 ) is obtained when the
silylation is carried out at +60°C (or at 160°C in benzene).
(The physical properties of a few cyclosilazanes are given in
Table 1.)
IH-NMR measurements between -60 and 100 "C show that
neither hexamethylcyclotrisilazane itself nor the pure compounds ( I ) to ( 6 ) isomerize. The rearrangements are basecatalyzed and occur during the metalation step. Thus (21, in
diglyme or hexane, is already converted to a great extent at
20 OC into ( I ) as a result of a rapid but spectroscopically observable reaction that is catalyzed by small amounts of butyllithium. Likewise, in the presence of equivalent amounts of
butyllithium. compounds (3) and ( 4 ) isomerize until equilibrium is established, which, at low temperatures, lies wholly
Table 1.
Physical properties of a few cyclosilazanes
Synthesis of Metal Complexes Having FluorineContaining Phosphine LigandsIll
By Th. Kruck, M . Hoyer, H . Jung, and H. BIume[*J
As previously reportedf2.31 for the case of strong bases of
high or low concentration, the nucleophilic replacement of
fluorine atoms by ROO and HOG ions affords a general synthetic route for the preparation of trialkoxy-, difluoroalkoxy-,
and difluorohydroxyphosphine complexes, which are either
inaccessible or difficultly accessible by conventional methods.
We have now extended the use of these solvolyses to systems
involving reaction of PF3 ligands in complexes with amines
(as prototype of relatively weak bases). Since tetrakis (trifluorophosphine)nickel(@) ( I ) is readily obtainable we have
now directed our attention to all model reactions which
are required for a formulation of the reaction; the applicability of the method to the PF, complexes of other metals
has meanwhile been established.
To avoid polymerization [41, onlysecondaryamines were reacted with ( I ) (molar ratio 12:l) in the preliminary experiments.
Ni(PF&
+2nRzNH
-----+ Ni(PF3)4-n(PF2NR2)n(n=4,3,2)
--n[RzNH21F
B.p.
( 'C/torr)
1.4613
108/12
10711.1
82/2
12610.4
l08/0.3
54-57
69-70
3.96 (6H), 8.68 (9H),
Il.30(12H)
0.34 (6 H), 1.20 (9 H),
15.24 (12 H)
I .4725 10.20 (18H). 11.71 (lZH),
21.00(6H)
1.4422 0.80 (9H), 2.12 (6H).
3.76 (9H), 15.36 (12H)
12.20(27H), 21.50(18H)
1.08 (9H). 12.40 (6H),
13.29 (18H), 17.00(12H)
[a] Chemical shift (at lower field strengths) at 60 MHz; tetramethylsilane as internal standard.
522
We have found that these reactions proceed rapidly and
almost quantitatively with separation of ammonium fluoride
according to the above equation - even at temperatures between 0 and 25 'C. Such aminolyses, which have also been investigated for the case of primary amines and sodamide,
yield monomeric homogeneous reaction products, i.e. n is
constant for a particular amine. A few of the difluoroaminophosphine complexes of nickel that have previously been
prepared by this method are given in the following Table.
Compounds (2) render possible for the first time the synthesis
of, inter alia. definite complexes of chlorodifluorophosphine,
whose attempted preparation by substitution reactions of
PCIFz with tetracarbonylnickel leads instead to the formation
Angew. Chem. internat. Edit. / Vol. 8 (1969) 1 No. 7
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