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Tetrakis(-cyclopentadienyl)tetranickel TrihydrideЧAn Unusual Tetranuclear Cluster.

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and mass spectra. The composition of the mixtures varied
between wide limits: the proportion of sulfate was I&
50 Yo and that of thiosulfate 5 6 - 9 0 % ; in addition, small
amounts of sulfite were also detectable in all cases.
The reaction of dimethyl sulfoxide with formamide takes
a completely different course. In the plasma, the reactants
yield dimethylamidosulfuric acid (0.4-4.0 torr, power consumption 100-150 W ; yield ca. 5 g/kWh; m.p. (dec. 161 to
163"C) alongside unidentified gaseous products. This product is not formed when one of the two reactants is added
behind the plasma zone, and must therefore arise from
the combination of reactive species of both components.
To our knowledge this is the first example of a plasma
synthesis in which a product is formed from fragments
of two different organic molecules.
Received: May 29, 1973 [Z 926b IE]
German version : Angew. Chem. 85, 1055 (1973)
Publication delayed at authors' request
[ I ] H. Suhr, Angew. Chem. X4, 876 (1972); Angew. Chem. internat.
Edit. I I , 781 (1972). and further literature cited therein.
[2] K . Gorrny and G. M a a h , Angew. Chem. 85, 1054 (1973); Angew.
Chem. internat. Edit. 12, 1004 (1973).
[3] K . Gollnick and H . U . Stracke, Tetrahedron Lett. 1971, 207.
[ 4 ] Eight Peaks Index of Mass Spectra. AWRE, Aldermaston. Reading
1970, Vol. I, p. 15.
Tetrakis(q -cyclopentadienyl)tetranickel
Trihydride-An Unusual Tetranuclear Cluster
By Jorn Miiller, Horst Dorner, Gottfried Huttner, and Hans
Reduction of dimeric cyclopentadienylnitrosylcobaltwith
LiAIH4/AIC13 produces diamagnetic tetrameric cyclopentadienylcobalt hydride"], [C,H,CoH], ( I ) , a tetranuclear
cluster with p3-hydrido bridges. In order to test whether
this kind of reaction is suitable as a general synthetic
route for the preparation of cyclopentadienylmetal clusters
we subjected dimeric cyclopentadienylnitrosyliron~'I,
[C5H5FeN0]2 (2), as well as cyclopentadienylnitro~ y l n i c k e l ~C,H,NiNO
( 3 ) , to the action of the above
reducing agent in tetrahydrofuran (THF) at 20 'C. Complex
(2) afforded exclusively ferrocene. Chromatography of the
product mixture obtained from the reaction of ( 3 ) afforded
nickelocene and a compound having the composition
C20H23Ni4 ( 4 ) .
The blackish violet crystals of ( 4 ) dissolve readily in benzene and THF, less readily in pentane, and d o not melt
below 320°C when heated under nitrogen. Its solutions
are air-sensitive.
In the mass spectrum of ( 4 ) the molecular ion appears
at m/e495 (based on ,*Ni) and exhibits an isotopic distribu-
tion characteristic of four Ni atoms. Apart from species
arising from loss of up to three H atoms, the 50-eV spectrum
contains the ions C I 5 H I 5 N i 2 ,CloH1,Ni:, CloHloNi+,
C5H5Ni+,and Ni+ as characteristic fragments. Prolonged
residence of the sample in the ion source results in gradual
decomposition with liberation of H2 and in partial degradation of the Ni4 unit; 12-eV spectra reveal that the complexes
and C20H20Ni4are also formed
as thermolysis products in addition to nickelocene.
The IR spectrum (KBr pellet) of ( 4 ) indicates the presence
of x-bonded symmetrical cyclopentadienyl ligands; the following bands appear (the corresponding absorptions of
nickelocene are given in paratheses for comparison): 3098
(3095), 1420(1425), 1332(1332), = 1270(1261), 1108(1111),
1050 (1046), 999 (1000), 800 (798), 770 (768), 342 (357)
.gm- '.The paramagnetic compound also gives a 'H-NMR
spectrum with a very broad signal at T = 157 (in THF)
which can also be assigned to cyclopentadienyl protons.
Accordingly, compound ( 4 ) is to be regarded as tetrakis(qcyclopentadieny1)tetranickel trihydride [C5H5NiI4H3. In
contrast to ( 1 ) , no v N ~ H absorption can be recognized
ip the IR spectrum, which, however, cannot be construed
as contraindicating the presence of metal hydride groups'41.
The structure of ( 4 ) was proved by X-ray analysis[5].
Crystal data: space group C2/c; u=2832+2, 6=923* I,
c = 1 5 0 3 f l pm; p=102.77f0.08"; V=3831flOx lo6
pm3; dcalc.=1.726k0.005, dexp.= 1.78kO.05g cm-' ; 2 = 8 ;
R 1 =0.064 for 1227 independent nonzero structure factors.
The molecule consists of a slightly distorted Ni tetrahedron
having a x-bonded cyclopentadienyl ring at each corner
(average distances :Ni-Ni 246, Ni-ring cen ter 177.7, N i x
210, and C-Cring 138 pm). The hydride hydrogen atoms
could not be directly located in the electron density diagram
of a difference Fourier synthesis; however, their positions
could be deduced from the deviations of the molecute
from strictly tetrahedral symmetry. The rings (C2 1 ... C25),
(C31 ... C35), and (C41 ... C45) form angles with the basal
face Ni2-Ni3-Ni4
that are significantly smaller than
the corresponding angles formed by all the rings with
the other tetrahedral faces, i.e. an average of 63.4'. compared with 73.0". The prevailing steric conditions can be
interpreted by assuming that the three H atoms act as
Fig. I. Schematic representation of the molecule [C,H5Ni],H,
projection perpendicular to the Ni2-Ni3-Ni4
(4) ;
Doz. Dr. J. Miiller, DipLChem. H. Dorner, Doz. Dr. G. Huttner,
and DipL-Chem. H. Lorenz
Anorganisch-chemisches Laboratorium der Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
Reactions of Nitrosyl Complexes, Part 3. This work was supported
by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen
Industrie. Part 2: [I].
Anyew. Chem. internat.
Edit. / Vol. 12 (1973) 1 N o . 12
p3 bridges across three tetrahedral faces. This is in accord
with the elongation of the Ni-Ni distances by ca. 10 pm
compared to Ni-Ni single
The dipole moment of 2.0k0.1 D measured in benzene
is also in accord with the deviation of the structure of
( 4 ) from an ideal tetrahedron.
In contrast to ( I ) , compound ( 4 ) exceeds the noble gas
rule. Tetrahedral [CSH5NiJ4would be isoelectronic with
( 1) and thereforediamagnetic. The three hydride hydrogen
atoms in [C5H5Ni14H3supply three additional electrons.
It is, however, remarkable that no spin pairing takes place
in the complex; instead, magnetic measurements both by
the Gouy method (77°K: xg=44.35x
cm3 g g t ,
p,,,=3.72*0.08 pB; 295°K: xg=13.84x
cm3 g-',
per, = 4.10i 0.08 p~ ; xg independent of field) and by the
'H-NMRshiftmethod (peff=4.10*0.1 p,)indicate thepresence of three unpaired electrons. No explanation of the
observed paramagnetism and its temperature independence has yet been forthcoming; accidental orbit degeneracy may be present.
( 1 ) and ( 4 ) are the first organometallic tetranuclear
clusters containing only hydrogen and cyclopentadienyl
as ligands. All other known cyclopentadienyl-metal clusters
having four and more directly linked metal atoms are
stabilized by carbonyl or hetero ligands in addition to
CsHs ligands. Attempts to prepare the hydride-free
complex [C5H5NiI4 which appears at least momentarily
under thermolytic conditions in the mass spectrometer,
have so far been unsuccessful. For instance, mild oxidation
of ( 4 ) with a substoichiometric quantity of iodine in pyridine yielded merely nickelocene and Ni12 (as pyridine
adduct) as well as pyridinium iodide. This finding suggests
that the stability of the nickel cluster is largely due to
the hydride bridges.
5-Substituted Ethyl ZThiazoIine-4-carboxylates
By Ulrich Schollkopf and Dieter Hoppt."]
Ethyl 2-thiazoline-4-~arboxylates[~.
21 oftype ( 4 ) , unsubstituted at position 2, are of interest for synthesis of penicillin
derivativesc2]. We have found that they are obtained in
good yield and relatively pure if a solution of an ethyl
and ca. 10 mol-% of a weak base
(such as triethylamine or pyridine) in chloroform is saturated with hydrogen sulfide at 2 M " C and the mixture
is then distilled.
Table 1. Ethyl 2-thiazoline-4-carboxylates( 4 ) synthesized from ethyl
2-isocyanoacrylates (I).
141 R '
All operations must be carried out under nitrogen.
A solution of ( 3 ) (2m1, 20mmol) and A1Cl3 (2.7g) in
TWF (80ml) is slowly added dropwise to one of LiAlH4
(0.76g, 20mmol) and AlC13 (2.7g) in T H F (1 IOml), the
color changing from dark red to blackish green. After
2 hours' stirring, the reaction mixture is hydrolyzed with
water (200ml) with ice-cooling and extracted with ether.
The ether phase is washed with NaHCO, solution, dried
over Na2S04,and the ether is drawn off. The black residue
is dissolved in benzene and A1203 (Woelm, 10% H2O)
is added until the solution has been completely absorbed,
the benzene then being drawn off. The dark green solid
mixture is placed in the head of a chromatography column
(2cm diam., 80cm length) packed with A1203 (Woelm,
6 % H 2 0 ) in pentane. Nickelocene and unreacted (3)
are first eluted with pentane, and then ( 4 ) as a dark
green zone with benzene. Removal of the benzene and
recrystallization from ether/pentane (1 :3) at low temperature affords 150mg of (6) in analytically pure form.
Received: August 13, 1973 [Z 928 IE]
German version: Angew. Chem. 85,1117 (1973)
[l] J. Muller and H . Dorner, Angew. Chem. 85, 867 (1973); Angew.
Chem. internat. Edit. 12, 843 (1973).
[2] H . Brunner, J. Orgaeometal. Chem. 14, 173 (1968).
[3] E . 0. Fischer, 0 . Beckert, W: Hafner, and H . 0. Stahf, 2. Naturforsch.
lob, 598 (1955).
[4] H . D. Kavsz and R . B. Saillant, Chem. Rev. 72, 231 (1972).
[5] G . Huttner and H. Lorenz, Chem. Ber., in press.
161 H . Vahrenknmp, V. A. Uchfman, and L. F . Dahl, J. Amer. Chem.
SOC. 90, 3273 (1968).
[ C/torr] cis [a] (CCI,) [I]
SCrXl/O.l -
8.3 and 8.65 (CH,),
2 05 id, 2-H),
5.55 (d. 4-H1
5.50 (d, 4-H)
fraiis: 1.95 Id. ?-H),
5.28 (q.4-H),5.97
(d, 5-H);
cis: 2.13 (d,2-H),
5.12 (9, 4-H)
100[b] not
3:l[d] trans: 2.03(d.2-H),
5.82 and 8.75
(9 and t, resp,C,H,),
4.98 (9. 4-H), 4.75
(4 5-HI;
cis: 1.90 (d. 2-H),
6.30 and 9.20
(q and t, resp.,C,H,)
trans: 2.02(d, 2-H),
4.80 (4. 4-H), 4.60
(4 5-H);
cis: 1.85 (d, 2-H)
[a] Isomer ratio determined by NMR spectroscopy.
[b] Crude product.
[c] 72% of the thioformamide ( 3f),m. p. 154°C was isolated (see text).
[d] The ratio can be increased to ca. 9 : l on subsequent equilibration by
10 mol-% of sodium ethoxide in ethanol (1 h, 20°C).
The reaction probably proceeds mainly by route A, i.e.
by base-catalyzed addition of hydrogen sulfide to the activated double bond of (1 ),yielding P-mercapto isocyanides
(2) which cyclize to ( 4 ) . In an experiment with ( I d )
the intermediate ( 2 d ) was detected by IR spectroscopy
[*] Prof. Dr. U. Schollkopf and Dr. D. Hoppe
Organisch-Chemisches Institut der Universitat
34 Gottingen, Wtndausweg 2 (Germany)
Angew. Chem. internat.
Edit. Vol. 12 (1973) 1 No. 12
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clusters, tetranuclear, unusual, cyclopentadienyl, trihydrideчan, tetrakis, tetranickel
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