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Electrolytic Reduction of Higher Metal Halides in Methanol.

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tion is important for the possibility of ion-molecule
reactions. According to Freeman and Fayadh"] recombination occurs in 10- l o s.
'
The amounts of the main products of radiolysis of cyclohexane are increased by addition of small quantities of
organic compounds such as benzene, anthracene, and
pyrene; the amounts of all three products are maximal at
mole of aromatic compound per liter.
ca.
Complexes of VCl, can be divided into two groups: 1.
Compounds of type VC12.4L, which are blue or violet and
have temperature-independent magnetic moments of 3.8
BM. 2. Compounds of type VC1,.2L, which are green and
have magnetic moments lower than the spin-only values
and strongly temperature-dependent. X-ray and reflection
spectra of the hydrates show that group 1 compounds
contain isolated octahedra, whereas in compounds of
group 2 the octahedra are fourfold edge-connected
[VCl,,,L,]. Solution spectra show that VCl, is completely
dissociated in all solvents.
-
TiC1, can be reduced in methanol to the trivalent state. A
solvate TiC13.4CH,0H can be isolated from such solutions, and can also be made to exchange its methanol.
Thus blue TiCl,.3DMF and green TiC13.2DMF have
been isolated. TiCl, exists in solution as a 1 :1 electrolyte :
[TiCl,(DMF),] 'Cl-.
Aromatic compounds can scavenge electrons and species
having a positive charge; in such reactions, the mobility of
electrons may make attachment of electrons more effective
than charge transfer, and this increases the lifetime of cyclohexane radical cations. As a result, product formation by
ion-molecule reactions should have greater importance,
since the efficiency of product formation by ion-molecule
reactions is greater. Indications of this in the case of cyclohexane are provided by investigations with electron scavengers, for the probability of ion-electron recombination
is about 0.7 if that for ion-molecule reactions is set = 1.
Lecture at Garching (Germany) on January 25,1971 [VB 281 IE]
German version: Angew. Chem. 83, 41 t(1971)
[t] G . R . Freeman and J . M . Fayadh, J. Chem. Physics 43, 86 (1965).
Electrolytic Reduction of Higher Metal Halides in
Methanol
By H.-J. Seifert"]
VC1, can be reduced electrolytically in methanolic solution
exactly as in an aqueous medium. Green VC1,.2CH3OH
can be isolated on concentration of the violet solution of
V2+. Treatment with organic complexing reagents such
as pyridine, acetonitrile, tetrahydrofuran (THF), dimethylformamide (THF), etc., permits preparation of complexes
containing these ligands with removal of the methanol.
Similar results are obtained with VBr,. Methanolic solutions of VI, can be obtained by the precipitation reaction :
WC1, is reduced to the quadrivalent, or further to the
trivalent, state in dilute solution containing HCl. Chloro
complexes [N(CH,),],WCI,
and [N(CH,),],W,Cl,
can
be isolated from the reduced solutions. On reduction of
concentrated solutions a green, acid-insoluble precipitate
was formed, of composition W2Cl,(OCH,),(CH30H), ;
single-crystal photographs show a W-W distance of 2.47 A
and, at the present stage of the study, indicate union by
oxygen bridges. A compound [N(CH,),],W(OCH,)Cl,
can be isolated from the mother liquors. The monomeric
compounds of W" have magnetic moments of 1.6 BM,
but the dimeric ones are almost diamagnetic with 0.26 BM.
-
Lecture at Clausthal-Zellerfeld (Germany) on January 29,1971
[VB 282 IE]
German version: Angew. Chem. 83,412 (1971)
The Combustion of Elemental Boron in Air;
A Thermodynamic Study[']
By Eberhard Biichner and Ingo Husrnann"'
Boron is used as an additive for improving the performance
of rocket propellants; however, it does not suffice to
energize a propulsive unit having only one thrust chamber.
Satisfactory results have been obtained onh with an experimental set-up having two thrust chambers''] in which
the boron is heated in the first chamber and then burnt in
the second in the presence of air.
On combustion of boron in air a predominantly gaseous,
homogeneous or heterogeneous mixture is formed whose
composition can be determined by a newly derived method
of calculation. In the case of heterogeneous mixtures the
separation of boric anhydride as condensed phase is taken
into consideration. Elemental (unchanged) boron occurs
as condensed phase in mixtures containing little oxygen.
Further calculations were carried out for the case of boron
nitride being present as condensed phase.
Iodine compounds of quadrivalent vanadium can be
prepared in the same way, specifically those of types
[VOL,]I,, where L=DMF or DMSO, and VOI(OCH3).3
pyridine.
The above mentioned method of calculation takes into
consideration the possible formation of the following
species during combustion of boron in air: B, B,O,, B,O,,
BO,, BO, BN, N,, N, NO, 0,, and 0. If sufficient air is
supplied to the system, considerable amounts of BO, are
formed in addition to the main product of combustion
B203.
['I
[*I Doz. Dr. E. E. Biichner and DipLIng. I. Husmann
VCl,
+ 2KI = VI, + 2 KC1i
Prof. Dr. H.-J. Seifert
Institut fir Anorganische und Analytische Chemie der Universitat
630 Giessen, Ludwigstrasse 21 (Germany)
Angew. Chem. inrernai. Edit. / Vol. 10 (1971) j No. 6
Institut fur Flugantriebe der Technischen Universitat
8 Munchen 2, Arcisstrasse 21 (Germany)
42 1
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