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New Initiators for Low-Temperature Polymerization.

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Reaction of Tungsten Hexacarbonyl with Azide
By Priv.-Doz. Dr. W. Beck and Dipl.-Chem. H. S. Smedal
The crystalline distilbation residue was bis-(1,3-dioxolan-2-yl)
peroxide (3) (white leaflets, m.p. 73.5-74.5 "C from
peroxide bands-atl810 and
alcohol, peroxide content 97.8
870 cm-1).
Anorganisch-Chemisches Laboratorium
der Technischen Hochschule Munchen (Germany)
Tungsten hexacarbonyl reacts with alkali or tetraalkylammonium halides or pseudohalides MIX (X = halogen or
NCS) with elimination of one CO ligand, giving compounds
of the type MI[W(CO),X] 121. However, tetraethylammonium
azide [31 and W(CO)6 (molar ratio 1 : 15) in diethylene glycol
dimethyl ether (diglyme) at 80 "C afford yellow, diamagnetic
tetraethylammoniuin isocyaiiatopentacarbonyltungstate(O),
[N(C2H5)jl[W(CO).jNCO]. The anion [W(CO)5NCO]- is
also directly accessible from W(CO)6 and potassium cyanate
in diglyme at 100 "C and can be precipitated by tetraphenylarsonium chloride in ethano1,'water as a lemon-yellow,
crystalline salt, [As(CgH5)4] [W(CO),NCO], m.p. 157 O C (decamp.), soluble in ethanol, acetone, and tetrahydrofuran.
This complex corresponds in analysis and infrared spectrum
to the product obtainable from W(CO)6, azide, and
and molecular-weight deterA s ( C ~ H ~ ;) ~conductivity
minations indicate the salt to be extensively dissociated
(Mexp. = 377). In accord with
symmetry, the infrared
spectrum of the anion [W(CO)5NCO]- (in acetone) contains
three CO bands, at 2067(w), 1927(st), and 1868(m) cm-1, and
pseudoasymmetric and symmetric NCO stretching vibrations
at 2236(m) and 1323(m) cm-.1 141. The positions of the vaSNCO
and 'J,NCO vibrations prove the anion [W(CO)jNCO]- to
be an isocyanate complex containing a W-NCO bond.
Reaction of W(CO)6 with azide probably occurs by nucleophilic attack of azide on a CO ligand, loss of nitrogen, and
rearrangement to the stable isocyanate, analogously to the
Curtius azide degradation. Several reactions of metal
carbonyls involving nucleophilic attack o n carbon monoxide
bound in a complex have been discovered recentlyr5l. The
first such reaction of W(CO)6 observed was that with carbanions [61.
Received: December 15th, 1965 [Z 124/955 IE]
German version: Angew. Cheni. 78, 267 (1966)
[ I ] Part 13 o f Pseudohalogcn-Metal Compounds. - Part 12:
W. Beck, E. Schuierer, and K. Feldl, Angew. Chem. 78, 267
(1966); Angew. Chem. internat. Edit. 5, 249 (1966).
[2] E. 0. Fischer and K. ofere, Chem. Ber. 93, 1156 (1960);
E. W. Ahel, I. S. Butler. and J. G. Reid, J. chem. SOC.(London)
1963, 2068; A. Wujcicki and M . F. Furunu, J. inorg. nuclear
Chem. 26, 2289 (1964).
[3] Prepared according to V. Gutmanii, G. Hampel, and 0. Leitmann, Mh. Chem. 95, 1034 (1964).
[4] vjNCO from the infrared spectrum of solid [As(CsH&]
[W(CO),NCO] (in KBr).
[ 5 ] Th. Krirck and M . Noack, Chem. Bcr. 97, 1693 (1964).
[6] E. 0. Fischer and A. Mansbol, Angew. Chem. 76, 645 ( I 964) ;
Angew. Chem. internat. Edit. 3, 580 (1964).
Hydrogenation of the hydroperoxide ( 2 ) (PdO in ether,
20 "C) gave 2-hydroxyethyl formate (4) quantitatively.
After hydrolysis (1 N H2SO4, 20"C, 2 h) of (2), 98 "/, of
H202 was found.
The cyclic acetals of acetaldehyde, propionaldehyde, and isobutyraldehyde behave similarly. The derived hydroperoxides
were isolated in 90 to 95 :d purity. Hydrogenation afforded
the corresponding glycol monoesters, and peroxides of type
(3) were either detected or isolated [*I.
Received: December 20th, 1965 [Z 1201952 IE]
German version: Angew. Chem. 78, 269 (1966)
[1] A . Rieche, E. Sclimitz, and E. Beyer, Chem. Ber. 91, 1935
[21 R. Criegee and M. Lederer have described di-(2-methyl-1,3dioxolan-2-yl) peroxide; Houben-Weyl: Methoden der organischen Chemie. 4th Edit., Thieme-Verlag, Stuttgart 1952, Vol.
V111/3, p. 23 ; M. Lederer, Diploma 'Thesis, Technischc Hochschule Karlsruhe, 1950.
New Initiators for Low-TemperaturePolymerization
By Priv.-Doz. Dr. Ch. Ruchardt, Dipl.-Chem. H. Bock, and
Dip1.-Chem. I. Ruthardt
Institut fur Organische Chemie
der Universitat Munchen (Germany)
t-Butyl peroxycarboxytates ( I ) containing in a-position to
the carboxy group a n aryloxy or alkoxy group or a corresponding sulfur function have been obtained in good yields
Half-lives of peresters ( I ) in ethylbenzene.
R = H ; 70.5"C
H (38; 17)
1,4,S-Trichloro-C6H~-O~ - N O Z - - C ~ H ~ - - (O
3 1-; 13)
2,4-Dichloro-C6H3-O~-CZHSO-CO-C~H~-O4-B~C6H4-04-Cl-C6H4-0C6Hg-SC6Hj-0- (27; 4)
~-CHI-C~H~-O4-CH30-CeH4-0(25; -1)
By Prof. Dr. A. Rieche, Dr. H.-E. Seyfarth, and
Dipl.-Chem. A. Hesse
Institut fur Technische Chemie der Universitiit Jena (Germany)
Angew. CIietn. internnt. Edit.
Vul. 5 (1966) 1 No. 2
t y2 (min)
1,3-Dioxolan-2-y1 Hydroperoxide
1,3-Dioxolane (ethylene glycol formal) ( I ) is a n excellent
solvent but, because of its marked tendency to peroxide
formation in air, it cannot always be used[ll.
We have isolated 1,3-dioxolan-2-y1 hydroperoxide after
peroxidation of the formal (1). After peroxidation to 15 :(
conversion (I 8 " C , 0 2 , UV-irradiation) enrichment was
effected by distillation at 20°C (bath temperature) and
10 mm. The colorless oily residue contained 9 0 % of the
peroxide (2) (determined iodometrically), which gave
hydroperoxy-OH bands at 3350 cm--l. H202 and a little of
the peroxide distilled at 80 'C (bath temperature) and 0.2 mm.
15; 40.0 "C
(24; -2,s)
(24; 2)
(25 ; 4)
(25; 3,5)
(24; 2)
ca. 45 000
z= CH3; 40.0"C
[a1 Values in parentheses are A l l *
(kcal/mole) a n d 1:
(cal deg
from acid chlorides and t-butyl hydroperoxide by the
Schotten-Raumann procedure or with pyridine in pentane,
ether, methylene chloride, or benzene at -20 "C. They have
been characterized by their spectra and elemcntal analyses.
They undergo thermolysis up to 50000 times faster
than t-butyl peracetate or other simple peresters and thus
have significance as low-temperature initiators. Product
analyses, dependence of the reaction rate on solvent
and concentration, activation parameters, and polymerization
experimentswith styrene and acrylonitrile indicate a homolytic
fragmentation 111 as the rate-determining step.
Since dccomposition of thc compounds with oxygencontaining substituents is faster than that of those with thc
corresponding sulfur-containing substituents, and that of
alkoxy compounds is faster than that of aryloxy compounds,
it is concluded that a polar effect [ I ] is responsible for the
therniolability of these substances. Acyloxy groups have a
similar but weaker effecl. The compounds should bc prepared
only with special precautions and in small quantities (grams),
since some of them deflagrate at room temperature. Explosions have not yet occurred [?].
Received: December 14th, 1965
[ Z 125/956 IE]
German version: Angew. Chern. 78, 268 (1966)
[I] Review and references: Ch. Riichordr, Fortschr. chem.
Forsch., in the press.
[2] The compounds listed in the Table under 70.5"C can be
prepared and handled in 50- 100 g lots if the temperature is
maintaincd at or below 0°C by efficient cooling. Larger amounts
have so far not been prepared. The more labile a-peroxyacetates
should be prepared and stored only in dilute solution at -20OC
exccpt in dealing w i t h small amounts.
Eighth European Congress on Molecular Spectroscopy
The Eighth European Congress on Molecular Spectroscopy
was held in Copenhagen from August 14th to 20th, 1965.
Four hundred lectures were delivered to about 800 participants in up to ten simultaneous sessions.
From t h e lectures:
M . Zawder (Castrop-Rauxel, Germany) discussed the continued interest in the systematic changes in absorption, fluorescence, and phosphorescence bands, brought about by systematic variation of the basic structure of a molecnie. In
single or multiple ortho-fusion to carbazole, for example,
fusion in the 2,3-position and the 6,7-position leads to an appreciable bathochromic shift, whereas the latter is small when
fusion takes place in the 3,4-position and the 5,6-position.
J . H. Eggers et a/. (Aarhus, Denmark) used the dichroism of
molecules oriented in stretched films to determine the transition moment directions of individual bands.
This parameter is increasingly used in the classification of
spectra and electronic excitation states. F. Durr and G. Hohlnrichrr (Munich, Germany) determined the relative transition
moment directions of biphenylene derivatives from the emission anisotropy, and compared the results with thosc of model
calculations. Until recently only the energies of excited molecular states were known, and only now have attempts been
made to determine other physical parameters of these states.
Thus D. E. Freeman and W. A . Klernperer (Cambridge, Mass.,
USA) have determined the dipole moment of formaldehyde
in the ~ A state
(excited at 339 mp) from the Stark shift of
single rotational lines and obtained a value of 1.57 D (the
dipole moment in the ground state is 2.34 I)). There is a lack
of detailed data o n the intramolecular transitions between the
energy levels, and this problem requires thorough quantitative investigations of the type carried out by H . Lablznrt
(Zurich, Switzerland) to determine the probability of singlettriplet transitions occurring when optically excited molecules
return to the ground state. This new technique can also be
applied to the measurement of triplet-triplet absorption
spectra. M. A . El-Snjwd (Los Angeles, USA) discussed a
further means of studying the singlet-triplet transition probabilities by the perturbation of phosphorescence through incorporation o f a heavy atom, or by resonance effects in the
host lattice. R. M. Hocltstrasser (University of Pennsylvania,
USA) investigated the line splitting, often caused by lattice
defects, in the singlet-triplet transitions taking place in crystalline derivatives of benzene and naphthalene. H . H. Jtrffi
(Cincinnati, USA) used the Parker-Parr-Pople method to
interpret the electronic spectra of trans-stilbene and trnnsazobenzene.
The results of the Pariser-Parr-Pople calculations and similar
approximations are known to depxid on the choice of the
parameters (one-electron one-center and two-center integrals
and two-electron one-center integrals), and I. Fisclzer-Hjrrlmars (Stockholm, Sweden) attempted to deduce from theoretical considerations parameters applicable to as many compounds as possible, particularly to sr-electron systems containing heteroatoms. By contrast, M . Klcssiizger (Gottingcn.
Germany) estimated the parameters from experimental data
(transition energies, oscillator strengths, dipole moments) for
simple molecules such as aniline, so as to improbe the agreement between experimental values and the resulis of the
Pariser-Parr-Pople treatment. These calculations were used
to interpret the electronic spectra of merocyanines and indigoids. F. F. Seelig (Marburg, Germany) reported on the use
of digital computers in further developments of the theory of
r-electron systems on the basis of the Kuhn model of a twodimensional electron gas. J. Liwderbrrg and Y. Ohrn (Uppsala, Sweden) investigated a new model for the spectra of xelectron systems, particularly alternant aromatic hydrocarbons, the model being based on Green's Functions.
The model used in most theoretical treatments is still based
on the assumption that the nuclear configuration does not
change in the course of electronic transitions. The fact is,
however, that excitation rnay be accompanied by a change in
the nuclear configuration and even in the syinnietry of the
molecule. Non-vertical transitions are then determined by
Franck-Condon factors. W. L. Smith and P . A . Worsop
(Dundee, U. K.) calculated these factors for HCN, and compared the results with those obtained from the analysis of
molecular rotations. The theoretical investigations of L.Ilro.iielle (Balto, Md., USA) confirmed that, in the lowest triplet
state, the CH2 groups in ethylene are staggered and tilted
with respect to each other.
As can be seen from the last example, the applicability of the
Pariser-Parr-Pople method is not restricted to the interpretation of electronic spectra. Thus J. Hinze (Stuttgart, Germany)
developed a theory for the excimers of alternant hydrocarbons. H. Dreesknmp (Stuttgart) calculated the indirect,
heteronuclear spin-spin coupling, and compared his results
with experimental values. M. J. S. Dewor et crl. (University of
Texas, USA) calculated the x-electron densities in nionofluorinated aromatic hydrocarbons and correlated the results
with the fluorine-NMR spectroscopic data. E. A . C. Lztckeii
Aiigew. Clzeni. iiitermt. Edit. / Vol. 5 (1966)
/ No. 2
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initiator, low, temperature, new, polymerization
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