close

Вход

Забыли?

вход по аккаунту

?

On the Existence of a Tungsten Carbonyl Carbene Complex.

код для вставкиСкачать
activation energy for B1 --f X I as 14 kcal/mole [73]. The
activation energy for the dark reverse reaction of salicylidene-m-toluidine was found to be 25 kcal/mole [73],
and that for the phototrspic cis-tram rearrangement of
the methinecyanines was 8 kcal/mole [74].
V. Closing Remarks
In 1899, in the first publication dealing with phototropy,
Marckxald concluded that “the action of light described
here is a purely physical phenomenon; my reason for
describing it is to encourage, physicists to investigate
the matter further”. In 1929, Chalkley [17] declined to
differentiate between purely physical or chemical
explanations for phototropy.
Today it is clear that phototropy mostly represents
transformations into thermodynamically unstable, chem[73] G. Lindemnnn, 2. wiss. Photogr., Photophysik Photochem.
50, 347 (1955).
1741 G. Scheibe, E . Giinther, and F. Diirr, S.-B. bayer. Akad. Wiss.
Jan. 15th, 1954; G. Scheibe, E. Giinther, and F. Baiiingariner, Z.
Elektrochem., Ber. Bunsenges. physik. Chem. 60, 570 (1956);
G. Dohmeier, Ph. D. Thesis, Technische Hochschule Munchen,
19.57.
ically still partly unknown states of molecules. Owing
to the revolution i n physico-chemical techniques, the
study of phototropy has recently received great impetus
and may substantially help to clarify the reaction
mechanisms of photochemical processes. Its general
laws are today fairly well understood; what is still
lacking is a larger amount of evidence to help to
explain the dependence of the mechanism on chemical
constitution. Just as the list of stable atomic nuclei has
been complemented by unstable nuclei, photochemistry
will enrich the number of thermodynamically stable
compounds with thermodynainically unstable species.
In 1964, it is therefore reasonable to alter Marclcwald’s
words as follows: “My reason for describing this
phenomenon is to encourage c h e m i s t s to investigate
the matter further”.
The authors wish to express their thanks to their colleagues, particularly Mr. W. Ditter, .for assistance with
the measurements and their evaluation, to Dr. Beck (Ludwigshafen), who carried out the polarographir measurements. and to Dr. Schlag (Lttdwigshqfen) for the electron
spin resonance stitdies.
Received, February 2lst. 1964
[A 377/173 IE]
German version: Angew. Chem. 76, 463 (1964)
Translated by Express Translation Service, London
C 0M M U N I C AT10 N S
O n the Existence of a Tungsten Carbonyl
Carbene Complex
By Prof. Dr. E. 0. Fischer and Dipl.-Chem. A. Maasb6l
Institut fur Anorganische Chemie der Universitat
Munchen (Germany)
When W(CO)6 is treated with LiC6Hj in ether under nitrogen,
nucleophilic addition takes place without elimination of
CO t o yield an orange-yellow, water-soluble, diamagnetic
anion, which can be precipitated as its tetramethylammoninm salt. This orange, finely crystalline derivative has the
composition [N(CH3)4][W(C0)5COCsHs] and melts at
102.5 “C (decomp.). The anion can be protonated bg acids.
On attempting to isolate the free “hydride” resulting from
acidification by extraction with ether, only w ( c o j 6 and benzaldehyde were found after removal of solvent from the extract. In dilute solution, the protonated product can be methylated in good yields using diazornethane. After chromatography and sublimation in vacua at 45-50 “C, orange-red,
diamagnetic crystals, m.p. 59OC, which are very soluble in
organic media, can be isolated. Analysis and molecularweight determinations indicate that their composition is
W(C~)~(COC~HS)(CH~).
Yellow diamagnetic crystals of [N(CH3)4][W(C0)5COCH3]
m.p. 143”C, can be obtained in an analogous manner by
addition of LiCH3 to W(CO)6 in ether and precipitation of
the salt from aqueous solution. On protonation and subsequent methylation with CHzN2, the anion gives yellow,
diamagnetic, volatile W(CO)5(COCH3)(CH3) ( I ) , m. p. 52 “C.
The nature of the bonding of the methyl group introduced
into the complex (I) by CHzNz could not be settled by infrared spectroscopy. The spectrum of W(CO)s(COCH3)(CH,),
the compound which has so far been more thoroughly investigated, shows two strong, somewhat broadened bands at
1252 and 1167 cm-1 (Nujol/Hostaflon). While the band at
580
1252 cm-1 can be attributed quite plausibly to a C-0 single
bond, that at 1167 cni-1 may be due t o either a C - 0 bond or
a CH3-W group, as a comparison with the spectrum of
CsH5W(C0)3CH3 [I] shows, in which t h e S(CH3-W) vibration appears at 1179 cm-1 [ 2 ] .
More reliable information on the structure of ( I ) was obtained from comparison of the proton magnetic resonance
spectra [3] of W(CO),(COCH3)(CH3), CsHjW(CO)3CH3, and
[41.
CSHSW(CO)~COCH
~
Compound
Chemical shift 7
referred t o CsH6 (relative t o
T M S at 7 = 2.88)
[ I = relative intensities
Concn.: 1 mmoIe/nd CsH6
5.23[51
5.45[51
6.17[3] 7.69[31
7.50[31
9.55[31
We assign the peak at T = 7.69 for ( I ) to the methyl group
introduced by LiCH3 addition. If it is assumed that this is
present as a W-COCH3 grouping, the value agrees well with
that of the peak for the acetyl group bound to tungsten in (2)
[T = 7.501. The fact that the other CH3 proton peak for compound ( I ) occurs at T = 6.17 and that of a CH3 group bound
directly to tungsten only appears at much higher fields, e . g .
T = 9.55 for (3), leads to the conclusion that no CH3-W
grouping is present in ( I ) .
We believe therefore that a structure such as
may be assumed for W(CO),(COCH3)(CH3). This corresponds to a “methoxymethylcarbene” bound to W(C0)s and
Angew. Chem. internut. Edit./ Vol. 3 (1964)
/ No. 8
would thus represent t h e first transition-metal complex of a
carbene. X-ray investigations currently in progress a r e expected to show that t h e alternative structure
does not occur. We a r e of this opinion because of t h e evidence
already cited a n d also beause o f the absence o f a n y characteristic :C=O vibrations in t h e infrared spectrum between
I500 a n d 1800 cm-1.
__
Received, April 6th, 1964
[Z 745/577 IEI
German version: Angew. Chem. 76, 645 (1964)
[ I ] E. 0 . Fischer, W . Hufner, and H. 0. Stahl, Z . anorg. allg.
Chern. 282, 47 (1955); 7 . S . Piper and G. W i k i n s o n , J. inorg.
nucl. Chem. 3, 104 (1956).
[2] We wish to thank Doz. H . P . Fritz for numerous discussions.
[3] We wish to thank Dipl.-Chem. C.G. Kreiter for measurement
of the N M R spectra and for many discussions.
[4] K. Fichtel, Ph. D. Thesis, Universitdt Miinchen, 1961.
___
n-CpHrCOOH
C6H5COOH
n-C1oHzloH
I
96
98
97 (95)
93
c,H,-c=c-N(cH,),
+
CH,CI,, -80 to 0°C/15 min-
n-CloHzlC1
yield 85%
yield 81%
-
C 6 H s E N(CH,),,
C ~ H ~ - C H ~ - C H ~+ OHHF
Ether
C6Hcj-CH2-CH2F
addition at - 8 O T
pyrolysis at 30W'C in vacuo
yield 60-9070
3 . Addition of Amines
a) Amidine Formation
Addition Reactions of Alkynylamines [lI
By Dr. H. G. Viehe, D r . R. Fuks, a n d M. Reinstein [ l a ]
( C H ~ ) Z N - C - C - N ( C H ~+ ) ~
CsHS-NHZ
Union Carbide European Research Associates,
Brussels (Belgium)
M a n y compounds react with alkynylamines [2] by addition
t o their nitrogen-polarized triple bond, mostly under very
mild conditions. Examples a r e given i n the following equations. T h e tendency of alkynylamines (which can be considered a s intramolecular anhydrides of carboxamides) to
combine with water is so strong t h a t they promise t o become
dehydrating agents of general importance. F o r example, the
formation of anhydrides from cdrboxyhc acids occurs m o r e
rapidly with alkynylamines t h a n with dicyclohexylcarbodih i d e or ethoxyacetylene.
b.p. ca. 110°C/0,02 m m
yield 8 0 %
b) Amidoxime Formation
( CHs)3C - C C - N( CH3)2
f
+ H2N- OH
'OH
1. Cycloadditions
C, ZH5
c~H5-c-c-N
+ 2 CH300C-C-C-COOCH3
'C?Hs
_ .
zsC
" ,
Z O T2, h
Ether
___)
m.p. 114°C
yield 7 3 %
c) Amide Hydrazone Formation
zH5
H
3 c o o c ~ C IO O2' H5C H 3
H,COOC
COOCH,
m . p . 140°C, yleld c a . 8 0 %
N
II
C&,-CH~-C-N(CH~)Z
n1.p. 147-148'C
yield 50%
4. Addition of Alcohols
'.
m.p. 228"C, yield 91%I41
n
--.+
HCI
2. Dehydration Reactions
p
C6H5-CHz-C:
OC ZH5
Received, May 1 lth, 1964
IZ 746/580 IE]
Publication deferred until now at the authors' request
German version: Angew. Chem. 76, 571 (1964)
~~
a) Amide Formation [ 3 ]
b) Carboxylic Anhydride Formation
T h e table gives yields [%I after 5 min a t 10°C i n benzene.
T h e d a t a were obtained by titration of t h e residual free acid,
the figure in brackets is yield of isolated anhydride.
A n g e w . Chem. internat. E d i t . J V d . 3 (1964)
/ No. 8
~
[ I ] Heterosubstituted Acetylenes, Part 8. .- Part 7 : H . G. Viehe,
S. I. Miller, and J. 1. Dickstein, Angew. Chem. 76, 537 (1964);
Angew. Chem. internat. Edit. 3, 582 (1964).
[ I a] Responsible for experimental work.
[2] H . G. Viehe and M . Reinstein, Angew. Chem. 76, 537 (1964);
Angew. Chem. internat. Edit. 3, 506 (19641.
[3] R . Euijle and H . G. Viehe, Angew. Chem. 76, 572 (1964);
Angew. Chem. internat. Edit. 3, 582 (1964).
[4] We are indebted to Dr. F. Eloj. for carrying o u t this experiment.
58 1
Документ
Категория
Без категории
Просмотров
0
Размер файла
200 Кб
Теги
complex, carbonyl, carbene, existencia, tungsten
1/--страниц
Пожаловаться на содержимое документа