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New Results in the Chemistry of Complex Compounds of Metals in Lower Oxidation States.

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a further H atom to BeH requires no additional “promotion
energy”.
The calculated limits of error in our results arise mainly
because the “interpair correlation energy”, although small,
is not negligible and so far can only be estimated rather than
calculated.
1/2 H Z or
BeHz(gas) is exothermic with respect to BeH
6 kcal/mole) with
Be(gas) + Hz. but endothermic (by 38
respect to Be(so1id) + H2 o r (by 48 i 6 kcal/mole) with respect
to the known[3,41 solid BeHz which, however, apparently
does not consist of BeH2 molecules but is high-polymeric.
The BeHz molecule cannot be obtained by heating solid
BeHz since at the temperature at which this decomposes
into the elements f31 (about 400 OK) the BeH2 equilibrium
pressure amounts to only 10-18l3 atm. However, reaction of
metallic Be and Hz ( p >, 1 atm) at temperatures between 1000
and 1500’K should afford BeHz molecules in measurable
concentration.
[VB 110 IEI
Lecture at Gottingen (Germany) on December 14, 1967
*
+
German version: Ang-w. Chem. SO, 245 (1968)
New Developments in the Crystal Chemistry of
Multicomponent Oxides
By E. Kordes I *I
An astonishing tolerance for isomorphous replacement of
cations, even if of different valence, is often observed, not
only with complicated, but also with simple lattices. As long
ago as 1935 formation of a continuous series of mixed crystals
was established for MgO, LiFeOz, and LiZTi03[11 (all three
with NaCl structure). and more recently of MgO o r NiO and
LiFe02 (all with NaCl structure) with the rhombohedral
LiCrO2 (deformed NaCl structure with ordered cationic
distribution [ZJ), and also between MgO and LiVOz (isotypic
with LiCrOz). Cubic compounds Li3Nb04 and Li3Ta04,
isotypic with MgO, are also known. These two mixed oxides
give further continuous series of mixed crystals with MgO.
LizTi03, and LiFeOz; these are thus cases of coupled isomorphous replacement of (Li+)p(M5+)3 by (Mg2+)12 or
(Li+)s(Ti4+)4 o r (Li+)6(Fe3+)6.
Stable homogeneous mixed crystals with the composition
[“I Priv.-Doz. Dr. W. Kutzelnigg and Dipl.-Phys. R. Ahlrichs
Institut fur Physikalische Chemie,
Abteilung fur Theoretische Chemie der Universitat
34 Gottingen, Burgerstr. 50a (Germany)
[l] R. Ahlrichs and W . Kutzelnigg, J. chem. Physics, in press.
[2] W . W . Watson and R. F. Humphreys, Physic. Rev. 52, 318
(1937).
131 E. Wiberg and R . Bauer, Z.Naturforsch. 66, 171 (1951).
[4] G. D . Barbaras et a / . , J. Amer. chem. SOC.73, 4585 (1951).
Behavior of Molecules in High Electric Fields and
at Surfaces
By J. H. Block[*l
In extremely high electric fields (> lo7 V/cm) molecules are
so strongly polarized that an electron can tunnel out, whereby
a n ion arises. This process of field ionization is utilized in
studying the behavior of molecules in high electric fields by
means of mass spectrometry.
These high fields can be established only on surfaces, for
instance in the field ion microscope of E. W. Muller. Field-ion
mass spectrometry can thus be used for studying certain
surface reactions.
The energies induced in molecules at field strengths of 106 to
lo7 V/cm cause a perceptible change in the chemical behavior
of, particularly polar, substances. For instance, association
reactions of dipolar molecules become field-dependent. This
dependence can be demonstrated by field pulse methods.
For this purpose an electric field (< lo7 Vjcm) is first
created so as to produce a desired species, which is then
ionized by a pulse of short duration and analyzed directly
in the mass spectrometer. It can thus be shown that the
HCOOH molecule, whose polar monomer is associated to
the nonpolar dimeric form, becomes stabilized in the monomeric form in high electric fields.
Field pulse methods, coupled with direct mass spectrometric analysis of the resulting ions, also makes it possible
to study surface reactions kinetically. By varying the pulse
frequency from 1 sec to 10-5 sec, products of surface reactions
can be analyzed that have been formed within very short
times. This procedure provides a very direct method of
investigating heterogeneous catalysis, interpretation of the
results being made difficult only by field-induced processes.
The molecular ions produced by field ionization are of
particular interest. Owing to their very low excitation, they
show peculiar chemical behavior most impressively.
Lecture at Hannover (Germany) on November 9, 1967
[VB 112 IEI
German version: Angew. Chem. SO, 243 (1968)
[*I Priv.-Doz. Dr. J. H. Block
Fritz-Haber-Institut der Max-Planck-Gesellschaft
1 Berlin 33 (Dahlem), Faradayweg 4-6 (Germany)
Angew. Chem. internat. Edit.
Vol. 7 (1968) No. 3
LiloMgFerIITiIVMVM’VIO,,
(M=NbonTa;M’-WorMo)
and NaCl structure have also been prepared.
The oxidic spinel lattice shows a similar tolerance for cation
replacement. The alkali spinel LiA1508 can be derived from
the very similar spinel MgpAl4Oe by the replacement 2 Mgz’
+ Li+Al3+; a corresponding derivation applies to the
analogous spinel LiFezOs. Surprisingly, LiFesOs gives a
continuous series of mixed crystals with the rhombohedral
LiCrOz or Li4Cr408 (deformed NaCl structure) that is not
isotypic with it: an excess of cations is accommodated in the
spinel lattice of the LiFesOs.
Cur ions can also be accommodated in spinels. LiFesO8 and
CuFe508, for instance, give a continuous series of mixed
crystals. 20 mole- % of Li+ in LiInIIICrIrI40s can be replaced
by Cu+.
CuzO also forms compounds with the oxides of the lighter
trivalent rare-earth metals; for instance, new mixed oxides
CuLaOZ. CuPrOz, CuNdOz, CuSmOz, and CuEuOz have
been obtained that are isotypic with one another and crystallize with the rhomobedral NaHF2 lattice.
[VB 113 IE]
Lecture at Bonn (Germany) on November 7, 1967
German version: Angew. Chem. SO, 243 (1968)
[*] Prof. Dr. E. Kordes
Chemisches Institut der Universitat
53 Bonn, Meckenheimer Allee 168 (Germany)
[I] E. Kordes, Z. Kristallogr. Mineralog. Petrogr., Part A, 92,
139 (1935).
[2] W. Riidorff, Z. Naturforsch. 9b, 614 (1954).
New Results in the Chemistry of Complex
Compounds of Metals in Lower Oxidation States
By H. Behrens f *I
Oxidation by iodine of Naz[Crz(CO)lo], which is isoelectronic
with Mnz(CO)lo, leads stepwise to [Cr(CO),I]-, Crz(CO)loI,
and Cr(C0)sI [l’zl. The binuclear anionic complex
[crz(CO)l~I]-,which is not accessible by this route, is formed
when the binuclear neutral complex is reduced with sodium
amalgam in T H F [31. The IR spectra of (OC)5Cr-I-Cr(C0)5
and [(OC)5Cr-I-Cr(CO)&
indicate a double octahedral
arrangement of the ligands with I as common apex and
linear Cr-I-Cr
linkage [41. The ionic CrI complex
[Cr(C0)2(NH3)4]1, in which the C O groups are trans to one
another, can be obtained from Cr(C0)sI and liquid NH3.
Cr(C0)5I generally reacts with other uni- o r bidentate N
or P ligands by oxidation to elemental iodine and reduction
to penta- or tetra-carbonylchromium(0) compounds 151.
23 1
In the series Cr(C0)5X, [Cr(CO)5X]-, Cr2(CO)loX, and
[Crz(CO)loX]- (X = CN, SCN, or OCN)[3,6,71 the pseudohalogen of the binuclear complexes is in the bridge position,
as is iodine in the iodine derivatives. Like [Cr(CO)sNCS]-,
Cr(C0)5NCS is a n isothiocyanate compound with a Cr-N
bond [41.
MO compounds can be synthesized from cyanometalates(0) 181
as well as from pure dicyclopentadienylcomplexes(x-C~H~)~M
(M = V, Cr, Fe, Co, or Ni) and mixed cyclopentadienylmetalcarbon monoxide complexes [9,101. Particular mention may
be made of the preparation of the trigonal-bipyramidal
Fe(C0)Ztripy from [(rr-C5H5)Fe(C0)2]2 and 2.2‘: 6‘,2”terpyridyl (tripy) [11J.
Whereas Co2(CO)8 disproportionates with Lewis bases to
CorI and Car-, the compounds
[CoI(bipy)3l [Co-I(CO)d] and [CoI(phen)3] [Co-I(CO)4]
C121
are formed o n treatment of (C~H&COZ(CO)~
(C6Hg = 1,3cyclohexadiene) with 2,2’-bipyridyl (bipy) or 1,lO-phenanthroline @hen). respectively.
However, the norbornadiene in (nor-C7H8)2C02(C0)4 can be
replaced according to the equation:
1. differences in hybridization,
2. differences in electronegativity of the components,
3. multiple bonding (dn-pn), and
4. polar valence contributions.
The force constants increase markedly with increasing
s-contribution to the a-bonds, in phosphorus chemistry as
in other combinations of elements. Force constants of certain
phosphorus compounds become larger with increase in
electronegativity of the other components when other
bonding conditions are unchanged (hydrogen bonds are
understandably a n exception). I n both these cases the maximum change in the force constants is of the order of 30-40%.
The greatest changes are due to contributions from multiple
bonds: as an example, the PS force constants in tetraligated
SPXYZ were discussed; the bond order varies between 2.0
and 1.3 according to the electronegativity of the ligands. The
influence of polar contributions to the bonding, which
weaken the force constants, was explained for the cases of
some fluorine, chlorine, and cyanide derivatives of phosphorus; with these examples the effect of variation in force
constant o n the reactivity of the compounds could be
demonstrated.
Lecture at Braunschweig (Germany) on November 13, 1967 [VB 115 IE]
German version: Angew. Chem. 80, 246 (1968)
[*I Prof. Dr. J. Goubeau
Laboratorium fur anorganische Chemie
der Technischen Hochschule
7 Stuttgart N, Schellingstr. 256 (Germany)
these being the first cobalt carbonyl derivatives to be obtained
in which four CO groups are replaced by N or P ligands [12J ;
they have the same structure as Co2(CO)8.
The compounds Co2(CO)4L2 are oxidized by I2 to the covalent
pentacoordinated ICo(CO)2L, but are reduced by sodium
to the salt-like tetracoordinated Na[Co(C0)2L] [12J.
Lecture at Erlangen (Germany) on November 17, 1967, and at
Tubingen (Germany) on December 7, 1967
[VB 114 IE]
German version: Angew. Chem. 80, 244 (1968)
[*] Prof. Dr.-Ing. H. Behrens
Institut fur Anorganische Chemie der Universitat
852 Erlangen, Fahrstr. 17 (Germany)
[l] H.Behrens and H.ZizIsperger, Z.Naturforsch.I6b, 349 (1961).
[2] H. Behrens and R. Schwab, Z. Naturforsch. 19b, 768 (1964).
[3] H. Behrens and D. Herrmann, Z. Naturforsch.2Ib, 1234 (1966).
[4] E. Lindner and H. Behrens, Spectrochim. Acta 23 A, 3025
(1967).
[5] H. Behrens and D. Herrmann, Z. anorg. allg. Chem. 351, 225
(1967).
[6] H. Behrens, R. Schwab, and D. Herrmann, Z . Naturforsch.
216, 590 (1966).
[7] H. Behrens and D.Herrnann, Z.Naturforsch.Zlb,l236 (1966).
[8] H.Behrens and A.MiiZler, Z.anorg.allg.Chem. 341, 124 (1965).
[9] H. Behrens and K . Meyer, Z. Naturforsch. ZIb, 489 (1966).
[lo] H. Behrens, H. Brandl, and K . Lufz, Z. Naturforsch. 226, 99
(1967).
[ l l ] H . Behrens and W . Aquila, Z. Naturforsch. 22b, 454 (1967).
[12] H. Behrens and W . Aquiiu, Z. anorg. allg. Chem. 356, 8
(1967).
Valence Force Constants of Various Phosphorus
Compounds
By J . Goubeau [ *I
The author’s method of calculating “force constants”
was described. By examining systematically selected examples from various transition series of the type
PX3-PX2Y-PXY2-PY3
and similar series with quadri- and
quinque-valent phosphorus the important bases for changes
of force constants (differences of up to nearly 200 %) were
established as:
232
Mechanism of Eliminations over Solid Catalysts
By H . Noller[*J
Static and dynamic studies have been carried out, particularly
by the microcatalytic method, with Cz to C4 alkanes between
100 and 400 OC. The catalysts were salts and oxides; metals
are ineffective. Alkaline-earth salts have much greater
activity than alkali salts, doubtless because of their higher
cationic charge. The activity of cations with the same charge
increases with decreasing radius. The activity of the anions
approximately parallels their basicity.
Reactivity decreases in the substituent series C1, Br, OH,
NH2, C6H5. Methyl and, in particular, phenyl substitution
on C, increases the reactivity appreciably. Methyl substitution on Cg is without influence, but this does not apply to
phenyl substitution. Deuterium introduced on C, remains
in the molecule (indicating @-elimination), although not
always on C,. The secondary kinetic isotope effect, if present
at all, is < 5 %.
Reactions are always of the first order. It is impossible to
decide kinetically between El and E2 mechanisms, but this
can be done by considering the distribution of primary
products. On alkaline-earth salts the primary products from
1-halogenobutanes (X = C1 or Br) are the same as from 2halogenobutanes; 2-butenes always largely preponderate
(Saytzeff rule), and among these in the lower temperature
region often the (thermodynamically less stable) cis-2butene. This indicates an El mechanism that operates
through the same 2-butyl cation. Lithium salts are highly
selective; with 2-halogenobutanes they give primarily cis-2butene, and with 1-halogenobutanes they yield primarily
I-butene.
The stereoselectivity of the catalysts follows from the cisjtrans
proportions of the 2-halogeno-2-butenes that are formed from
the meso- and DL-forms of 2,3-dihalogenobutanes. The series
of catalysts with decreasing selectivity KB02, KzCO3, K3P04.
K2SO4. BaC03, Ca(BO&, Ba3(P04)2, CaClz covers the
whole range of almost complete stereoselectivity (KB02:
cisltrans from meso = 97:3, from DL 9:91, at 25OoC), i.e.,
trans-elimination, to vanishing stereoselectivity (CaCb:
cisltrans from meso = cis/truns from DL = 17:83, at 200 “C),
Angew. Chem. internat. Edit.
/ VoI. 7 (1968) J No. 3
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