Matrix Isolation and Characterization of a Reactive Intermediate in Olefin Oxidation with Chromyl Chloride

Full text of DOI:10.1002/(SICI)1521-3773(19980302)37:4<496::AID-ANIE496>3.0.CO;2-V

COMMUNICATIONS
F(4a)
measured reflections, 1199 independent reflections, 996 reflections
used in the refinement, s limit 2.0, Lp and absorption correction (y
�
1
scans), m(MoKa) ˆ 5.035 mm , min./max. transmission 0.78/0.91, struc-
ture solution: Patterson, difference-Fourier synthesis, SHELXS-86,
SHELXL-93, PARST, PLATON, MISSYM, 114 free parameters;
hydrogen atoms were experimentally determined and refined from
H(21)
H(2)
O(2)
C(1)
F(6c)
1
21.2(6)°
DF, R ˆ 0.0485, wR ˆ 0.1194, R ˆ S j jF
o
2
j� j F
c
j j/S j F
o
j , refinement
H(22)
method: full-matrix least squares on F , min./max. residual electron
H(12)
�
3
C(2)
density ˆ 0.787/ � 0.980 eŠ . Further details on the crystal structure
investigation may be obtained from the Fachinformationszentrum
Karlsruhe, D-76344 Eggenstein-Leopoldshafen, Germany (fax:
O(1)
H(11)
F(5b)
(
‡49)7247-808-666 (Frau S. Höhler-Schlimm); e-mail: crysdata@fiz-
karlsruhe.de), on quoting the depository number CSD ± 407344.
[7] U. Blukis, P. H. Kasai, R. J. Meyers, J. Chem. Phys. 1963, 38, 2753 ±
F(4)
2
760.
Figure 2. Structure of the cation 3 in the crystal with contacts, atom labels,
and structural parameters for the central unit. Further distances [pm]:
F4a ´´´ H21 236(8), F5b ´´´ H22 217(8), F6c ´´´ H12 244(8), F4 ´´´ H11 240(9).
Symmetry operations: x � 1, ‡ y, ‡ z (a), � x ‡ 1, � y, � z ‡ 1 (b), x,
[
[
8] K. Takagi, T. Oka, J. Phys. Soc. Jpn. 1963, 18, 1174 ± 1175.
9] F. P. Lossing, J. Am. Chem. Soc. 1977, 99, 7526 ± 7530.
10] D. Farcasiu, J. A. Horsley, J. Am. Chem. Soc. 1980, 102, 4906 ± 4911.
11] R. J. Woods, C. W. Andrews, J. P. Bowen, J. Am. Chem. Soc. 1992, 114,
[
[
�
y � 0.5, ‡ z ‡ 0.5 (c).
8
50 ± 858.
[
12] I. F. Walker, J. Am. Chem. Soc. 1933, 55, 2821 ± 2826.
[
13] R. Minkwitz, A. Kornath, W. Sawodny, Angew. Chem. 1992, 104, 648 ±
Table 2. Selected bond lengths [pm] and angles [8] for 3-AsF
6
. Not all the
6
49; Angew. Chem. Int. Ed. Engl. 1992, 31, 643 ± 644.
atoms of the anion are shown in Figure 2.[
a]
As(1)�F(2)
As(1)�F(4)
As(1)�F(6)
O(1)�C(2)
O(1)�C(1)
O(2)�C(1)
171.8(4)
171.0(4)
170.2(5)
122.6(8)
147.0(8)
132.5(8)
C(2)-O(1)-C(1)
O(2)-C(1)-O(1)
F(1)-As(1)-F(4)
F(6)-As(1)-F(4)
F(1)-As(1)-F(2)
121.2(6)
108.8(5)
89.6(2)
90.4(3)
179.2(2)
Matrix Isolation and Characterization of a
Reactive Intermediate in Olefin Oxidation with
Chromyl Chloride**
[
a] The standard deviations refer to the last digit.
Experimental Section
Christian Limberg,* Ralf Köppe, and
Hansgeorg Schnöckel
H
2
CO was obtained and purified according to ref. [12]. AsF
by allowing the elements to reaction and purified by fractional condensa-
tion. SbF was purified by fractional distillation, and HF was dried with
5
was obtained
Although the oxidation of organic substrates by CrVI
5
13]
fluorine.[
In a KEL-F reactor MF
The solution was frozen at � 1968C, and then H
onto the solution. The reaction mixture was allowed to warm slowly to
compounds has always been a useful tool in the hands of
chemists, the course of such reactions and the nature of the
intermediates have remained for the most part unknown. For
example, the mechanism of C�H activation in the Etard
5
(3 mmol; M ˆ As, Sb) was dissolved in HF ( ꢀ 5 g).
CO (3 mmol) condensed
2
�
408C. The excess reactant was removed either at � 788C or at � 408C
[1]
under a dynamic vacuum. Compound 3-MF
6
remained as a colorless solid.
reaction, known since 1877, was only revealed in detail in
1995.[ In the past, complex mechanisms were put forward for
2]
‡
Instruments: Raman: Jobin ± Yvon T64000, Ar laser (l ˆ 514.5 nm)
[3, 4]
Spectra Physics; IR: Bruker IFS133v; NMR: Bruker DPX300.
the oxidation of olefins with chromyl chloride CrO Cl
that
2
2
attempted to explain the great variety of products obtained on
the basis of widely differing intermediates such as chromaox-
etanes, chromium alkoxides, and epoxide complexes. None of
these intermediates has ever been proven. The occurrence of
carbonyl compounds among the products was explained by
Received: July 11, 1997 [Z10676IE]
German version: Angew. Chem. 1998, 110, 510 ± 512
Keywords: formaldehyde ´ IR spectroscopy ´ Raman spec-
troscopy ´ superacidic systems ´ oxonium ions
[3, 5]
rearrangements of certain products during work-up,
whereas more recent work highlights the relevance of
intermediate chromium complexes of these carbonyl com-
[
1] G. A. Olah, D. H. OꢁBrien, M. Calin, J. Am. Chem. Soc. 1967, 89,
582 ± 3586.
‡
pounds. For example, ethylene reacts with the CrO ion in the
3
2
[
[
2] G. A. Olah, G. D. Mateescu, J. Am. Chem. Soc. 1971, 93, 781 ± 782.
3] G. A. Olah, S. Yu, G. Liang, G. D. Mateescu, M. R. Bruce, D. J.
Donovan, M. Arvanaghi, J. Org. Chem. 1981, 46, 571 ± 577.
4] G. A. Olah, A. Burrichter, T. Mathew, Y. D. Vankar, G. Rasul, G. K. S.
Prakash, Angew. Chem. 1997, 109, 1958 ± 1961; Angew. Chem. Int. Ed.
Engl. 1997, 1875 ± 1877.
[*] Dr. C. Limberg
Anorganisch-Chemisches Institut der Universität
Im Neuenheimer Feld 270, D-69120 Heidelberg (Germany)
Fax: (‡49)6221-54-5707
[
E-mail: limberg@sun0.urz.uni-heidelberg.de
[
5] J. Weidlein, U. Müller, K. Dehnicke, Schwingungsspektroskopie,
Thieme, Stuttgart, 1982.
Dr. R. Köppe, Prof. H. Schnöckel
Institut für Anorganische Chemie der Universität Karlsruhe (Ger-
many)
[
6] Crystal structure analysis of 3-AsF
monoclinic, space group P2
6
: crystals grown from HF,
1
/c, a ˆ 632.0(4), b ˆ 1101.5(11), c ˆ
6 3
1
2
031.5(6) pm,
b ˆ 107.51(5)8,
Vˆ 684.8(9)  10 pm ,
1
calcd
ˆ
[**] C.L. is grateful to the Fonds der Chemischen Industrie and the
Deutsche Forschungsgemeinschaft for scholarships and equipment,
and to Professor G. Huttner for his generous support.
�
3
3
.425 gcm , crystal dimensions 0.20 Â 0.19 Â 0.12 mm , MoKa radia-
tion (l ˆ 71.073 pm), 2q/w scans, 2qmax ˆ 50.08, Tˆ 171 K, 2910
4
96
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3704-0496 $ 17.50+.50/0
Angew. Chem. Int. Ed. 1998, 37, No. 4

COMMUNICATIONS
‡
[6]
[9]
mass spectrometer to yield OˆCr ´´´ OˆCHCH . The aim of
noble gas matrices is commonly observed ). In addition,
3
the matrix studies presented here was to isolate intermediates
in olefin oxidation with CrO Cl in order to gain reliable
since investigations into the concentration dependence
showed that only one equivalent of ethylene is involved in
the reaction, the organic product must consist of a carbonyl
compound with a C unit (OˆCH can be excluded as the
2
2
information concerning the reaction mechanism. The inves-
tigations began with ethylene, the simplest olefin, and the first
step was to identify the products formed on treatment with
CrO Cl under thermal conditions. The reaction of ethylene
2
2
product[ ). Only acetaldehyde meets these requirements,
10]
and the connectivity 1 shown in reaction (1) can be assigned to
2
2
with CrO Cl at � 808C in dichloromethane yields primarily 2-
2
2
chloroethanol after isolation of the resulting Etard complex
and work-up with wet acetonitrile. Therefore CrOCH CH Cl
Cl
Cl
O
O
10 K, Ar, 411 nm
Cl
Cl
O
Cr
+
Cr
(1)
2
2
O
fragments should be present in the Etard complex, and,
consequently, A can be postulated as a possible inter-
mediate.
1
Cl(Oˆ)Cr�O�CH
�CH
�Cl
A
the product of the matrix experiment. Further proof was
2
2
obtained by using [D ]ethylene to synthesize the deuterated
4
In the next step, CrO Cl was co-condensed with a mixture
version of 1, whose IR spectrumÐwhen compared with that of
the hydrogenated compoundÐshowed all the changes ex-
pected in terms of the above interpretation: All bands
2
2
of ethylene and argon, the resulting matrix irradiated at
11 nm (activation of the Cl !Cr charge-transfer (CT)
4
[
7]
[8]
transition), and the reaction followed by IR spectroscopy.
assigned to the OˆCrCl fragment exactly maintained their
2
The spectra (Figure 1) show that a product has formed in good
previous positions, indicating that this fragment oscillates
yield (approximately 40%) which produces an intense new
independently. The carbonyl band shows a slight shift (D nÄ ˆ
�
1
� 1
band in the CrˆO region at 1009 cm ; this indicates the
presence of only one CrˆO bond. In the Cr�Cl region, two
18 cm ) due to weak coupling to C�H modes (such as
d(CH)). All other bands show strong shifts due to the large
�
1
18
[11]
new bands at 452 and 385 cm appear suggesting that the
contributions from C�H vibrations. When O CrCl
was
2
2
used with the aim of synthesizing the 18O isotopomer of 1,
CrCl fragment is preserved during the reaction. This excludes
2
A as the product. These findings tend to point to the fragment
significant shifts were only observed for three bands: the
OˆCrCl as the inorganic part of the reaction product, and,
n(CˆO) band (D nÄ ˆ 29 cm ), the n(CrˆO) band (43 cm ),
�
1
� 1
2
�
1
� 1
consequently, CrO Cl must have transferred one oxygen
and a further band at 852 cm (26 cm ), which can be
assigned as having principally d(CCO) character. The re-
maining signals shift only marginally. Reaction of the mixed
2
2
atom to the organic substrate ethylene. A new band at
�
1
1
669 cm helps to clarify the composition of the resulting
isotopomer 18O OCrCl does not lead to new bands, which
16
organic product. This must belong to a carbonyl compound
2
whose n(CˆO) band is shifted to lower wavenumber due to
further proves the presence of only one CrˆO bond in 1.
All these results already confirm 1 unequivocally as the
product of the matrix experiments, but additional calcula-
complexation with a Lewis acidic center (the formation of
complexes, often only weakly bound, after photoreaction in
in an ethylene/argon matrix (4/96) at 10 K in the region of 1800 ± 330 cm 1; upper trace: absolute spectrum (a) after
�
Figure 1. IR spectra of CrO
2
Cl
2
deposition of the starting materials for 15 min; lower trace: difference spectrum (b) after irradiation at l ˆ 411 nm for 10 min. and the absolute spectrum (a)
�
1
for the region below 400 cm to give an impression of the conversion in the reaction. When the bands of the initial spectrum overlap with newly formed
bands, the intensity ratios can be slightly perturbed upon spectrum subtraction.
Angew. Chem. Int. Ed. 1998, 37, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3704-0497 $ 17.50+.50/0
497

COMMUNICATIONS
tionsÐwith respect to the structure of 1 on the one hand and
in order to obtain information on the theoretically expected
frequencies on the otherÐwere of interest. Since DFT
The oxo chromium dichloride molecule in 1, with chromium
in the rare oxidation state of ‡iv, is particularly significant.
This species was often mentioned as an important intermediate
[
12]
[3, 4, 17]
calculations (B3LYP, LanL2DZ, G94) yielded good results
for the structure of CrO Cl (the maximum deviations in bond
in oxidations with CrO Cl .
The experiments presented
2
2
here describe for the first time the isolation and character-
ization of this fragment as complexed with acetaldehyde.
The fact that a primary product must exist between the
substrate and 1, which rearranges to 1 by a hydrogen shift,
raises the question of the mechanism for the formation of 1. In
principle, the primary product could be a chromaoxetane B,
which could then be the source of a photochemically
2
2
lengths and angles from those of the gas-phase structure[
13]
amounted to 0.03 Š and 28, respectively), this method was
employed for calculating the structure of 1. The most stable
�
1
syn conformation is energetically only 5.1 kJmol less stable
than the most stable anti conformation. It is therefore the
most likely structure of the product originating from a
[
4]
.
.
chromaoxetane potentially generated in the primary step.
However, because the latter intermediate step has never been
proved and because conformers are photochemically inter-
convertable in matrices, a decision in favor of one structure or
another cannot be made. Both show the features expected
from the experimental IR spectra: the CrˆO bond is shorter
generated diradical OCH CH for which experimental data
2
2
and MO calculations favor isomerization to acetaldehyde.[
18]
However, a more likely alternative is the intermediate
formation of the oxirane adduct C in Scheme 1, either directly
than in CrO Cl , and the bond to the acetaldehyde oxygen Cl
O
O
Cl
Cl
O
Cl
Cl
O
2
2
Cr
+
Cr
Cr
atom is very strong (almost in the region of a Cr�O single
Cl
O
O
[
14]
bond ). This explains the significant shift of n(CˆO) to lower
C
1
�
1
wavenumbers (observed: D nÄ ˆ 52 cm in comparison to free
[
15]
acetaldehyde ). The enthalpy of reaction (1) was calculated
�
1
as � 157.5 kJmol , whereas reaction (2) already proceeds
O
�
1
exothermically with � 144.4 kJmol . Therefore, product for-
mation is also accounted for on energetic grounds.
O
Cl
Cr
Cl
B
O
Scheme 1. Possible mechanism for the formation of 1.
Cl
Cl
O
+
O
Cr
(2)
Cr
O
Cl
Cl
from the starting materials or via B. The adduct C was
1
[4]
mentioned previously as a possible intermediate and could
isomerize to form 1. Such rearrangements of oxiranes to
Calculations of the vibrational frequencies showed that the
carbonyl compounds catalyzed by Lewis acids are widely
known in synthetic chemistry, and it is possible that in the
IR spectra of the two conformers differ only slightly[ with
respect to the error present in the calculations, thus prevent-
ing the assignment of one conformer to the experimental
spectrum. However, as can be seen for the example of the
most stable syn conformer in Table 1, the band pattern
obtained experimentally could be reproduced qualitatively.
The calculated shifts of the bands resulting from replacement
16]
[19]
present case the required activation energy is supplied
photochemically and not thermally.[ To compare the role
of 1 in the reaction under inert conditions and irradiation with
that under thermal conditions, a transfer of the results of the
matrix experiments to preparative chemistry was attempted.
As already mentioned, the reaction of ethylene with CrO Cl
20]
2
2
1
6
18
of O by O agree very well with the experimental spectrum;
any errors made previously cancel each other. In only one
at � 508C in the dark followed by decomplexation of the
Etard complex yields mainly chloroethanol. However, ace-
taldehyde (5%) was also present among the products, which
�
1
case (852 cm ) was the calculated shift too low.
�
1
16
18
2 2 2 2
Table 1. Experimental frequencies nÄ in cm measured after photolysis of an ethylene/argon (4/96) matrix doped with Cr O Cl or Cr O Cl , and
16
18
frequencies calculated with a combination of B3LYP/LanL2DZ for the most stable syn conformer of 1 ( O and O isotopomer, respectively) (the values in
parentheses refer to relative intensities I; no scaling). The last column gives a qualitative assignment based on the calculations and the isotopic shifts.
1
6
18
D nÄ ( O � 18O)
16
16
calcd D nÄ ( O � 18O)
16
Cr O
2
Cl
2
Cr O
2
Cl
2
calcd 1( O)(I)
Assignment
1
1
1
1
1
1
1
669
453
413
349
271
141
009
1640
1453
1408
1349
1266
1141
966
29
0
5
0
5
0
43
26
1651(0.58)
1492(0.15)
1483(0.26)
1434(0.37)
1418(0.09)
1166(0.18)
1104(1.00)
932(0.12)
26
0
4
1
7
1
47
6
n(CˆO)/n(CC)/d(CH)
d
d
d
d
as(CH
as(CH
3
)
)
3
s
(CH
(CH
3
)/d(CH)
)/d(CH)
s
3
n(CC)/d(CCO)
n(CrˆO)
8
52
826
d(CCO)
8
5
09(0.08)
35(0.12)
0
11
0
t
r
(CH
3
),d(CH)
d(CrOC)
n
4
3
52
85
451
379
1
6
425(0.85)
362(0.15)
as(CrCl
2
)
7
n
s
(CrCl )
2
4
98
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3704-0498 $ 17.50+.50/0
Angew. Chem. Int. Ed. 1998, 37, No. 4

COMMUNICATIONS
could, in principle, originate in 1 incorporated in the Etard
complex. When the matrix conditions are simulated by
dissolving the two reactants in a Freon mixture at � 808C
and quenching the resulting solution at 77 K to form a glass,
the amount of acetaldehyde among the oxidation products
increases to 35% after subsequent photolysis at 77 K and
usual work-up; this is then comparable to the yield in the
[14] P. Stavropoulos, N. Bryson, M.-T. Youinou, J. A. Osborn, Inorg. Chem.
1
990, 29, 1807 ± 1811.
[
15] C. O. Della V e dova, O. Sala, J. Raman Spectrosc. 1991, 22, 505 ± 507.
[
16] The fact that some of the calculated bands deviate by approximately
� 1
1
00 cm from the experimental values is not unusual for such
calculations and presumably has its origin in slight deviations of the
calculated structure from the real one. The structure of CrO Cl
calculated with the B-P functional and SV(P) basis sets (Turbomol
R. Ahlrichs, M. Baer, M. Haeser, H. Horn, C. Kölmel, Chem. Phys.
2
2
[
[
21]
matrix experiment. Therefore, 1 should also occur inter-
Lett. 1989, 162, 165 ± 169]) represents the real structure almost ideally
(Dr< 0.01 Š, D(angle) < 18), and therefore shows that this combina-
tion of functional and basis sets has to be considered
more suitable for structure determination (the calculation of the
frequencies is not possible) than the combination of B3LYP/
LanL2DZ. The more reliable B-P/SV(P) structure of 1 differs slightly
mediately in the thermal reaction of ethylene with CrO Cl .
2
2
Since other olefins are quantitatively oxidized to carbonyl
[
3]
compounds by CrO Cl in thermal reactions, intermediates
2
2
analogous to 1 could play a more important role in these cases,
although, of course, other mechanisms for the formation of
(
Dr< 0.05 Š,D(angle) < 48)from the B3LYP/LanL2DZ structure
[
5]
carbonyl compounds are imaginable.
which forms the basis for the calculation of the spectrum. These
differences can have drastic effects on the calculation. Accordingly,
the deviations of the experimental IR spectrum calculated for chromyl
chloride with the combination of B3LYP/LanL2DZ from the exper-
imental spectrum were of the same magnitude. For DFT structure and
frequency calculations for CrO Cl , see M. Torrent, P.Gili, M. Duran,
The isolation of an intermediate in an olefin oxidation by
CrO Cl was achieved for the first time. The presence of this
2
2
intermediate could explain the occurrence of carbonyl com-
pounds in the product spectrum of such reactions.
2
2
M. Sol aÁ J. Chem. Phys. 1996, 104, 9499 ± 9510. Differences in
Received: August 8, 1997 [Z10808IE]
German version: Angew. Chem. 1998, 110, 512 ± 515
frequencies of the two most stable syn and anti conformations:
�
1
n
s
(CrCl
2 2
): 10, nas(CrCl ): 6, d(CCO): 18, n(Cr
ˆ
O): 20, n(CˆO): 1 cm
.
The maximum deviation was obtained for a band that should be at
5
�
1
� 1
35 cm for syn-1 and at 576 cm for anti-1, but which does not
Keywords: chromium ´ ethylene ´ matrix isolation ´ inter-
mediates ´ oxygenations
appear in the experimental spectrum due to low intensity; the
calculated intensity ratios do not differ significantly.
17] A. K. Rapp e , W. A. Goddard III, J. Am. Chem. Soc. 1982, 104, 3287 ±
3294.
[18] A. Lifshitz, H. Ben-Hamon, J. Phys. Chem. 1983, 87, 1782 ± 1787; J. G.
Serafin, C. M. Friend, J. Am. Chem. Soc. 1989, 111, 6019 ± 6026; F. W.
McLafferty, Science (Washington DC) 1990, 247, 925 ± 929.
[
[
[
1] A. L. Etard, C. R. Hebd. Seances Acad. Sci. 1877, 84, 127 ± 129.
2] G. K. Cook, J. M. Mayer, J. Am. Chem. Soc. 1994, 116, 1855 ± 1868;
ibid. 1995, 117, 7139 ± 7156.
[
3] M. A. Etard, H. M. Moissan, C. R. Hebd. Seances Acad. Sci. 1893, 116,
434 ± 437; S. J. Cristol, K. R. Eilar, J. Am. Chem. Soc. 1950, 72, 4353 ±
4356; R. A. Stairs, D. G. M. Diaper, A. L. Gatzke, Can. J. Chem. 1963,
41, 1059 ± 1064; F. Freeman, P. J. Cameran, R. H. Dubois, J. Org.
[19] R. O. C. Norman, J. M. Coxon, Principles of Organic Synthesis, 3rd
ed., Chapman and Hall, London, 1993, p. 590.
[20] C. Schmidt, Dissertation, Universität Giessen, Germany, 1995.
Chem. 1968, 33, 3970 ± 3972; F. Freeman, R. H. Dubois, N. J. Yama-
chika, Tetrahedron 1969, 25, 3441 ± 3446; F. Freeman in Organic
Syntheses by Oxidation with Metal Compounds (Eds.: W. J. Mijs,
C. R. H. I. de Jonge), Plenum, New York, 1986, chapter 2, pp. 41 ±
[21] Whereas residual amounts of CrO
2 2
Cl do not react in the matrix
experiment, free CrO Cl reacts further thermally when the Freon
2
2
mixture is warmed to temperatures that allow volatile components to
be pumped off. The compounds produced by this route are also among
the products.
1
18.
4] K. B. Sharpless, A. Y. Teranishi, J.-E. Bäckvall, J. Am. Chem. Soc.
977, 99, 3120 ± 3128.
[
1
[
[
5] K. B. Sharpless, A. Y. Teranishi, J. Org. Chem. 1973, 38, 185 ± 186.
6] A. Fiedler, I. Kretzschmar, D. Schröder, H. Schwarz, J. Am. Chem.
Soc. 1996, 118, 9941 ± 9952.
Si , Si , and Si Rings in Iodide Silicides of
6
14
22
[
7] J. P. Jasinski, S. L. Holt, J. H. Wood, L. B. Asprey, J. Chem. Phys. 1975,
Rare Earth Metals**
63, 757 ± 771.
[
8] The photolyses were performed with a 200-W Hg high-pressure arc
lamp in combination with interference filters. The IR spectra were
recorded on a Bruker-IFS-113 VFTIR spectrometer in the region of
Hansjürgen Mattausch and Arndt Simon*
�
1
� 1
Numerous metal-rich halides MX A (n ꢁ 2) of rare earth
4
000 ± 400 and 1000 ± 200 cm with a resolution of 1 cm
.
n
[
9] R. N. Perutz, Chem. Rev. 1985, 85, 77 ± 127.
metals M with interstitial atoms A ˆ H,C,N,O have been
[
[
10] M. J. Almond, A. J. Downs, J. Chem. Soc. Dalton Trans. 1988, 809 ± 817;
H. Khoshkhoo, E. R. Nixon, Spectrochim. Acta A 1973, 29, 603 ± 612.
11] 18
[1±3]
prepared.
Recently we reported on boride and boride
carbide halides.[ Owing to the electropositive character of
4±6]
O
2
CrCl
2
was synthesized by the reaction of anhydrous CrCl
Na OH, oxidation by Cl , and treatment of the resulting chromate
with an excess of anhydrous HCl. The level of enrichment was
3
with
18
the rare earth metals, the interstitial atoms are present as
2
6
�
4�
anions, and in the case of carbon C and C2 units are found
2
1
8
18 16
4�
[1]
approximately 70 ± 80%. IR data for Cr O
992) [nas(CrO )], 943 (951) [n (CrO )], 502 [nas(CrCl
(CrCl )].
2
Cl
2
(Cr O OCl
2
): nÄ ˆ 960
besides discrete C ions. In M X B the boron atoms form
4 5 4
rhomboids which are linked into chains. Several factors
influence the nature of the interstitial species: the number of
�
1
(
2
s
2
2
)], 461 cm
[6]
[
n
s
2
[
12] M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson,
M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A.
Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski,
J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y. Ayala, W. Chen, M. W.
Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J.
Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-
Gordon, C. Gonzalez, J. A. Pople, Gaussian, Inc., Pittsburgh, PA,
[
*] Prof. Dr. A. Simon, Dr. H. Mattausch
Max-Planck-Institut für Festkörperforschung
Heisenbergstrasse 1, D-70569 Stuttgart (Germany)
Fax: (‡49)711-689-1642
E-mail: hansm@vaxff2.mpi-stuttgart.mpg.de
1
995.
13] C. J. Marsden, L. Hedberg, K. Hedberg, Inorg. Chem. 1982, 21, 1115 ±
118.
[**] We are grateful to C. Kamella for preparing the structural drawings, to
R. Eger for help with the preparations, and to H. Gärttling for the
diffractometer data.
[
1
Angew. Chem. Int. Ed. 1998, 37, No. 4
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1433-7851/98/3704-0499 $ 17.50+.50/0
499