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Hexameric Molybdenum Tetrachloride.

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Table 1. Preparation of a-trimethylsiloxythiols (2) and a,a'-bis(trimethylsiloxy) disulfides (3).
R
Comp.
I
Yield
[%] [a]
B.p.
pC/Torr]
'H-NMR (6,TMS, in CDC13)
5.03 (dt, J = 8 Hz; J = 5 Hz, 1 H), 2.06 (d,
J = 7 Hz, l H ) , 2.0-1.1 (m,4H), 0.92 (br.
t, 3H), 0.18 (s, 9H)
4.83 (dd, J = 8 Hz; J = 5 Hz, lH), 2.2-1.6
(m, 1 H), 1.90 (d, J = 8 Hz, 1 H)
0.98 (d, J = 6 Hz, 6H), 0.18 (s, 9H)
4.72 (d, J = 7 Hz, IH), 1.75 (d, J = 7 Hz,
1 H), 0.95 (s, 9H), 0.16 (s, 9H)
4.80(dd, J = 7 Hz; J = 5 Hz, IH), 1.90 (d,
J = 7 H z , IH),2.2-0.9(m,1IH),0.17(~,
9 H)
7.7-7.2 (m. SH), 6.14 (d, J = 7 Hz, IH),
2.50 (d, J = 7 Hz, I H), 0.20 (s, 9H)
Yield
[9/01PI
'H-NMR (6, TMS, in CDCl3)
Compd.
(3a)
84
(3b)
82
4.82, 4.76 (each t, J = 6 Hz, 2H), 2.051.15 (m. SH), 0.90 (t with fine structure,
6 H), 0.20 (s, 18 H)
4.74, 4.65 (each d, J = 5 Hz, 2H), 2.421.87 (m, 2H), 1.00 (dd, J = 7 Hz, 12H),
0.20 (s, 18H)
(3d)
80
4.70, 4.58 (each d, J = 5 Hz, 2H), 2.150.80 (m, 22H), 0.18 (s, 18H)
(3e)
75
7.65-7.10 (m, IOH), 5.78, 5.52 (each s,
2H), 0.15 (s, 18H)
~~
n-C3H7
(2a)
73
46/8
i-C,H,
(2b)
80
42/8
CC4H9
(2c)
75
61/15
C-C~HII
(2d)
83
6410.1
CsHs
f2e)
25, 48 [c]
63/0.25
CHFH-CH
(2fl
30[d]
50/7
(20)
+
CH~=CH-O-C~H,
hv
5.80-5.20(m,3H),2.20(d,J=7Hz,1H),
1.8-1.6 (m, 3H), 0.20 (s, 9H)
n-C,H,-qH-S-CH2-
CH2-0-C2H5
hv
+ i-C,H,-CH-S
I
(CH,),SiO
probably made up of linear chains of octahedra sharing
edges"], and P-MoCl,, which has been described as a layer
lattice in which three Mo atoms are assumed to statistically
occupy four positions with formation of cationic and an~ ]respectively[*].
~
ionic regions, [Mo2CI6]' and [ M o C ~-,
However, recent theoretical studies on the possible structures of tetra halide^'^] led to a more detailed determination
of the P-MoC14 structure.
Crystals of P-MoCI,, which were prepared under exactly
the same conditions as described earlier[*],exhibit an X-ray
diffraction pattern of sharp reflections, strong diffuse
lines, and weak diffuse lines which indicate the presence
of a one-dimensional disorder. If the intensity maxima on
the strong diffuse lines are treated as sharp reflections then
these, together with the actual sharp reflections indicate
the unit cell described earlier (trigonal, a = 605, c = 1172
pm)[']. In disordered crystals the actual structure can only
be determined if the intensities in the diffuse lines are fully
in~estigated~~];
the maxima on them cannot be simply
treated as sharp reflections. The sharp reflections alone are
inadequate for a structure determination, they afford only
a statistically averaged structural model[']. In the case of 0MoCI, even the weak diffuse lines must also be taken into
consideration; they require a doubling up of the lattice
constants a and b to a =b = 1209 pm.
+
(46). 85%
General Procedure
H2S is bubbled into a dry dichloromethane solution (150
mL) of (1) (0.07 mol), (CH,),SiCI (0.10 mol) and pyridine
(0.10 mol), and the solution vigorously stirred until no further gas is absorbed; the solution temperature is maintained below 15°C. The solution is then stirred for 2 h at
room temperature. After addition of dry pentane (150 mL),
the mixture is cooled to -78°C and the pyridinium chloride collected by filtration. The thiol (2) is distilled under
reduced pressure.
Received: November 18, 1980 [Z 803 IE]
German version: Angew. Chem. 93,706 (1981)
[I] T.Aida. D. N . Harpp. T. H. Chan, Tetrahedron Lett. 1980. 3247. T. H.
Chan, B. S. Ong, ibid. 1976. 319.
121 A solution of CHzCll (2.0 ml), (2) (0.5 mol) and olefin (1.0 mol) was
sealed under dry nitrogen into a Pyrex tube. After 12 h irradiation at 5 "C
(General Electric Co., Model SHK-2,275 W), (4) was isolated by column
chromatography (silica gel, hexane) or preparative GC. The yield was determined by G C using an internal standard. 'H-NMR (CDCI,): ( 4 ~ ) :
g-4.90(t,J-6Hz,lH),3.50(qwithfinestructure,J-6Hz,4H),2.75(t,
5 - 6 Hz, 2H), 2.0-0.8 (m,7H), 1.22 (t. J=1 Hz, 3H), 0.18 ( s , 9H); (46):
6-4,70 (d, J - 6 Hz, 1 H), 3.45-2.9 (m,1 H, 2.3-1.0 (m, 9H), 1.00 (d, J = 7
Hz, 6H), 0.17 (s, 9H).
[3] For alternative routes to a-trimethylsiloxy sulfides, see D.J . Ager, R . C.
Cookson, Tetrahedron Lett. 1980, 1677; P. J . Kocienski, ibid. 1980, 1559.
Hexameric Molybdenum Tetrachloride
By Ulrich Miiller~*J
Dedicated to Professor Josef Goubeau on the occasion
of his 80th birthday
Two modifications of molybdenum tetrachloride have
so far been described in the literature: a-MOC14, which is
['I Prof. Dr. U. Miiller
Fachbereich Chemie der Universitrt
Hans-Meerwein-Strasse, D-3550 Marburg (Germany)
692
0 Verlag Chemie GmbH, 6940 Weinheim. 1981
Fig. I. (MoCl& molecule in &MoCl4: ellipsoids of thermal vibration for 68%
probability at 21 "C.
057~0833/81/0808-0692 $02.50/0
Angew. Chem. Inf. Ed. EngI. 20 (1981) No. 8
A comparison of these lattice constants with the values
expected for the theoretically predicted structural possibilitied3’suggests the likelihood of a structure type containing
cyclic ( M o C I ~molecules.
)~
An analysis of the intensities on
the diffuse lines according to a recently described method”] confirms this (refinement to R=7.2% for 226 measured points on diffuse lines and R =2.8% for 155 sharp reflections).
Our structural model shows that P-MoC1, is made up of
hexameric cyclic molecules (MOC& (Fig. 1). The bond
lengths are: Mo-CI,,,,,,,,
220, Mo-CI,,,,,,
243 and 251
pm. The molecules are arranged in layers (parallel to the
plane of the picture in Figure 1. The stacking of the layers
is disordered, but in such a way that the C1 atoms assume
an hexagonal closest-packed arrangement. The pairwise
closing up of metal atoms between adjacent octahedra,
which is often observed in compounds of metals with electron configuration d ’ and d2, is not apparent here, the
Mo- . . M o distances of 367 pm are too large for any notable interactions between the metal atoms ; this is consistent
with the known magnetic properties”], which indicate a
virtually undistorted d’-configuration.
Although molybdenum tetrachloride has already been
known for some time and has been the subject of repeated
investigations, nothing has previously been mentioned
about its ability to form hexameric molecules. There is as
yet no other such example of a structure of this kind.
Received: January 29, 1981 [ Z 822 IE]
German version: Angew. Chem. 93, 697 (1981)
CAS Registry number:
(MoCI&, 78456-38-9.
acid esters and separation of the acetylated derivativesf4].
In a similar procedure the preparation of diastereomeric
derivatives was achieved by glycosidation with (-)-2-butano1 and separation of the trimethylsilylated derivatives on
glass capillary columns151.In addition to the difficulties involved with the derivatization, the quantitative determination of enantiomers via formation of diastereomeric derivatives suffers from a systematic error arising from the incomplete purity of the chiral reagents.
We have now for the first time prepared a temperaturestable chiral stationary phase which allows the separation
of volatile derivatives of carbohydrate enantiomers. This
involves the saponification of methyl(cyanoethy1)silicone
XE-60I6] with alkali and coupling the carboxylic groups
formed to L-valine-(S)-a-phenylethylamide by conventional methods. Glass capillaries were coated with this
modified polymer and trifluoroacetylated sugars[71or their
methyl glycosides separated. Columns prepared according
to this procedure did not exhibit a reduction in their separation efficiency after continuous operation at temperatures up to 180 ’C over several weeks.
Trifluoroacetylation of sugars (TFA = trifluoracetyl) resulted in an isomeric mixture of a-and j3-furanosides and
a- and 0-pyranosides, which were identified by G U M S in~estigation~~’.
The TFA-methyl glycosides (prepared by
reaction of the sugars with methanolic 1 . 5 HCl
~
at 100°C
and subsequent trifluroacetylation) formed isomeric mixtures corresponding in composition to literature data“’ and
were identified by measurement of their peak areas. The
results are presented in Table 1 and in some examples in
Figure 1. The TFA-groups appear to be essential for the
separation, since trimethylsilyl derivatives of the sugars
with comparable volatility are not separated.
[ I 1 D. L Kepert. R . Mandyczewsky. Inorg. Chem. 7. 2091 (1968).
12) H. Schafer. H. G . von Schnering, J. Tillack, F. Kuhnen, H. Wohrle. H.
Baumann. Z. Anorg. Allg. Chem. 353, 281 (1967).
131 U. Miiller, Acta Crystallogr. 837, 532 (1981).
141 H . Jogodzinski, Acta Crystallogr. 2, 201, 209 (1949).
151 U . Miiller. Acta Crystallogr. A35, 957 (1979).
Gas Chromatographic Separation
of Carbohydrate Enantiomers
on a New Chiral Stationary Phase
Table I. Gas chromatographic enantiomer separation of carbohydrates on a
glass capillary column coated with XE-60-L-valine-(S)-a-phenylethylamide
(TFA = trifluoroacetyl, P = pyranoside, F = furanoside). For conditions see
Figure 1.
Sugar
Separation Factor a/Column Temperature [“C)
TFA-Derivative
TFA-Methyl Glycoside
Glucose
a-(P)
By WiIfried A . Konig, Ingrid Benecke, and
Hagen Bretting[’I
Mannose
Micromethods for the configurational analysis of low
molecular weight chiral compounds are essential for the
structural elucidation of natural products[’.’].
While the problem of the gas chromatographic determination of the configuration of the constituents of peptides
and proteins seems to be solved[*’,this is not the case with
the constituents of polysaccharides. Since in nature sugars
occur rather more frequently than amino acids in both
configuration^'^^, a simple gas chromatographic procedure
would be of interest for their analysis.
As early as 1968 Poiiock and Jermany suggested a
method involving oxidation of aldoses to aldonic acids, esterification with a chiral alcohol to diastereomeric aldonic
Galactose
[*I
Prof. Dr.W. A. Konig, DipLChem. I. Benecke
Institut fur Organische Chemie und Biochemie der Universitat
Martin-Luther-King-Platz 6, D-2000Hamburg 13 (Germany)
Dr.H. Bretting
Zoologisches Institut und Zoologisches Museum der Universitat
Martin-Luther-King-Platz 3, D-2000Hamburg 13 (Germany)
Angeus. Chem. I ~ Ed.
I . Engl. 20 (1981) No. 8
1.071/140
1.044/140
(F)
(F)
1.031/140
B-(P)
a-(P)
(F)
B-(P)
a-(P)
(F)
B-(P)
(F)
Xylose
Arabinose
B-(P)
[a]
[a]
[a]
[a]
Fucose
I .032/120
1 . 0 3 120
~
1.140/140
1.036/140
1.045/140
1.247/140
1.019/140
1.019/140
1.045/140
1.029/140
1.030/100
1.028/100
1.017/100
1.048/100
1.026/100
1.053/120
1.0841120
1.010/120
1.044/120
1.049/120
1.089/I20
-
1.019/100
1.023/100
I .046/100
-
-
-
-
[a] 1.035/100
1.014/100
1.046/100
[a] Designation uncertain.
The order of elution of enantiomers is not identical in all
the examples investigated. In the case of TFA-derivatives
of glucose and mannose and in that of the TFA-methyl
glycosides, the L-enantiomers eluted before the D-enantiomers: the same order was observed for the first three
isomeric pairs of TFA-arabinose, however, for the pair
0 Verlag Chemie GmbH, 6940 Weinheim. 1981
OS70-0833/81/0808-0693 $02.50/0
693
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