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On the Existence of Metal Carbonyl Carbene Complexes.

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Compounds ( I ) can also be used for preparation of condensed heterocycles. For instance, 9 H-pyrimido[4,5-b]indole
(2) (m.p. 235-237 O C , yield 80 %) is formed when 2-chforoindole-3-carbaldehyde ( I c ) is heated for several hours in an
excess of formamide.
Received: October 14th, 1965
[Z 78/904IE]
German version: Angew. Chem. 77, 1141 (1565)
plexW We find that the compounds are isomorphous, with
the following unit cell dimensions:
a
b
C
[ I ] Z . Arnold and J. Zemlicka, Proc. chem. SOC.(London) 1958,
227; Coll. czechoslovak. chem. Commun. 24, 2385 (1959).
[2] W. Ziegenbein and H. Franke, Angew. Chem. 71, 573 (1959).
Thiophenes from 5 0 x 0 Derivatives of 1-Alkynes
By Prof. Dr. K. E. Schulte, Doz. Dr. J. Reisch, and
D. Bergenthal
Institut fur Pharmazeutische Chemie
der Universitst Miinster (Germany)
P-Dicarbonyl compounds in the 1-alkyne series can yield
furans by intramolecular ring closure [I]. Baumann and
Fromm 121 obtained thioketones by treating ketones with
H2S and HCI, and Mitra[3l found that f3-dicarbonyl compounds can be converted into monounsaturated thiols if
hydrogen sulfide is passed into their alcoholic solution previously saturated with hydrogen chloride. I n similar conditions thiophenes (2) are obtained from 5-0x0 derivatives
( I ) of 1-alkynes (for products see Table).
I I
R1
(la)
CHa
C6H5
(2bj
( 2 ~ ) CH3
C6Hs
(2d)
1
R2
C02CzHS
COzCzHs
GHs
H
B.p.['C/mm Hg]
108-109/8
129-130/2
109/1.5
(M.p. 49 "C)
I
nD (at "C)
1
1.5152(20)
1.5833 (21)
1.6044(19)
Z
Space'group
Received: October 14th, 1965
[Z 77/903IE)
German version: Angew. Chem. 77, 1141 (1965)
[I] K . E. Schulte, J. Reisch, and A . Mock, Arch. Pharmaz. 295,
627 (1962).
[2] E. Baumann and E. Fromm, Ber. dtsch. chem. Ges. 28, 598
(1895).
131 S. K . Mitra, J. Indian chem. SOC.10, 71, 491 (1933).
On the Existence of Metal Carbonyl Carbene
Complexes
By 0. S. Mills and Dr. A. D. RedhouserJJ
Department ofChemistry,University of Manchester, England
In a recent paper[zl, Fischer and Mnasbol have described
the preparation
of
complexes
of
stoichiometry
(C0)5W(RCOCH3) (J), where R=CH3 or C6H5. From a
study of infrared and proton magnetic resonance spectra the
possibility that (J), R=CH3, was methoxymethylcarbenepentacarbonyltungsten was considered.
We have analysed, by x-ray diffraction, single crystals of ( I ) ,
R=:Cf,H5, and also of the corresponding chromium com-
cc
cc
Cr-CO equat. 1.84- 1.92
1.12-1.15
C-C
ring 1.34-1.44
I%I
69
65
50
71
9.91 A
21.70 A
6.34 8,
96' 35'
4
The analysis of these complexes is complicated since the
symmetry of the heavy atoms alone corresponds to the
higher symmetry of space group C2/c with the metal atoms
in special positions on two-fold axes. The pseudo-symmetry
introduced into the resulting electron density calculation
corresponds to the superimposition of the molecule and its
two-fold rotation image.
Crystals of both complexes yielded relatively few diffraction
spots, consistent with large thermal vibrations. The structure
of the chromium complex was determined from 565 threedimensional data collected on precession photographs taken
with molybdenum Kcr radiation. The structure as given in
Yield
0.3 mole of H2S is passed at -2OoC, and then 1 mole of
HCI at between -20 and -10 "C, into a solution of 0.1 mole
of the unsaturated ketone in about 100 ml of ethanol. After
several hours at room temperature the solvent is removed
and the mixture is fractionated in a vacuum.
1082
P
10.00 8,
21.90 8,
6.45 8,
96" 12'
4
the figure clearly shows that the molecule does correspond
to a "carbene-metal complex". The structure shows the
following features:
(i) The phenyl group is roughly perpendicular to the
CH/
o
c
C
''
I
Cr
plane so that the Tc-electron system of the phenyl group
presumeably does not interact with the empty p orbital on
the carbene carbon atom. The carbene-phenyl distance
(1.49 = 0.03 A) corresponds to bonding between two sp2
hybridized carbon atoms.
(ii) The carbene - oxygen and methyl-oxygen distances
0.02 A and 1.43 5 0.03 A, respectively) are similar
(1.31
to those found in methyl esters of carboxylic acids.
(iii) The individual Cr-CO distances d o not differ from the
average (1.88 A) by more than one standard deviation (0.03A)
(iv) The Cr-carbene distance (2.05 k 0.03 A) is significantly
ionger than the Cr-CO distances.
(v) The normal to the "carbene plane", i.e. the direction of
the empty p-orbital, does not align parallel to a principal
axis of the Cr octahedron. Indeed, it lies at approximately
45 O to the x,y axes (with the carbene carbon on the z axis).
This arrangement could be caused by steric requirements.
*
Received: October 22nd, 1565
12 93/915IEI
German version: Angew. Chem. 77, 1142 (1965)
[I] Presented to the Second International Symposium on Organometallic Chemistry, Madison (U.S.A.), September 1st, 1965.
[2] E. 0.Fischer and A . Maasbol, Angew. Chem. 76, 645 (1964);
Angew. Chem. internat. Edit. 3, 580 (1964).
[3] We wish to thank Professor Fischer and Dr. Maasbol for the
preparation of the chromium complex at our request for this
analysis.
Angew. Chem. internat. Edit.
Vol. 4 (1965) No. I2
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