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Nitrogen Fixation on New Transition Metal Complexes.

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We obtained mixtures of 4-alkylthiepan-3-ones (2) and
3-alkylthiepan-4-ones (3) on ring expansion [31 of thian-3one ( I ) by diazo-methane, -ethane, or -isobutane. These
products were separated by distillation through a spinningband column. Reduction with LiAlHl led to the alcohols (4)
and ( 5 ) . When R = CH3 or CH(CH& the reduction gave
mixtures of cis-truns-alcohols from which the pure cisisomers were isolated by chromatography on silica gel with
benzenejethyl acetate.
The IR spectra of compounds (4a) and (5a) in CC14 (<10-2
mole/l) each contained two VO-H bands - (4.) at 3623 and
3489 cm-1, (Sa) at 3623 and 3496 cm-1, which shows that in
both cases an equilibrium must be set up between a transannular-associated (lower frequency) and a non-associated
conformation (higher frequency).
In cis-(4b), cis-(Sb), cis-(4c), and cis-(Sc) the proportion of
transannular-associated conformation is greater than in (4.)
and (5a). Thus the pseudoaxial position of the O H groups,
which according t o considerations of a model is necessary
for transannular association, is f a v o x d by the alkyl group in
the cis-position to the neighboring hydroxyl group.
Received: July 13th, 1967
IZ 571 IE]
German version: Angew. Chem. 79. S63 (1967)
[ * ] Dr. R. Borsdorf, Dip1.-Chem. H. Kasper, and
Dipl.-Chem. H.-D. Repp
Institut fur Organische Chemie der Universitat
Liebigstr. 18
DDR 701 Leipzig (Germany)
[l] Part VI of Seven- and Eight-membered Rink Compounds. Part V: R. Borsdorf and B. Olesch, J. piakr. Chem., in the press.
[2] A . Liittringhaus, S. Kabuss, H . Prinzbach, and F. Langenbucher, Liebigs Ann. Chem. 653, 195 (1962).
[3] Conditions: in situ method.
In the complexes ( I ) , transition metals behave as highly
reactive metal(0) species, as in the metal carbonyls. The reaction of the nickel complex with tetramethylcyclobutene dibromide (TCD) to give tetramethylcyclobutadienenickel(rr)
(TCNi) clearly demonstrates this similarity. Criegee et a/. prepared the chlorider31 and bromider41 of (TCNi)zi from
Ni(C0)l; prolonged heating of the reactants was required.
With the complex ( I ) , however, the reaction took a few
minutes at room temperature, giving TCNi in quantitative yield (referred to reacted nickel).
A solution of NiBr2 in T H F (concentration 1.2 x 10-2 mole/l)
is added t o a solution of LiNp in T H F (concentration 7 x 10-2
moleil, 5 % excess over the amount necessary for the reduction Ni(I1) + Ni(0)). An excess of TCD is then added under
argon. Within 10-15 minutes at room temperature, the color
changes from brown-black t o dark violet. Elimination of the
solvent from the filtered solution and extraction of the
residue with water lead to the isolation of the complex salt
TCNiBr2.
Visible and IR spectra141 as well as precipitation of the
complex cation with sodium dicyanoethylenedithiolate 131
established the identity of the compound. Recrystallization
from chloroform-butanol (1:1) gave solvent-free fine needles [51. X-ray analysis on single crystals afforded the following
crystallographic data: a = 16.2 A, b = 8.5 A, c = 17.5 A,
(3 = 108 O ; volume of the unit cell -= 2292 A3; space group
P21/n(Czh, No. 14); 8 molecules in the unit cell[**]. Thus the
dibromide appears isomorphous with the dichloride as
reported by Bunitz et al. [51.
Another reaction in which the reported complexes behave in
a similar manner to the carbonyls is the initiation of radical
polymerization to].
Compared with the carbonyls, the Me(0) complexes have the
advantage that they are easier and safer t o handle as well as
more reactive.
Received: July 17th, 1967
[Z 572a IE]
German version: Angew. Chem. 79, 897 (1967).
Synthesis of Tetramethykyclobutadienenickel(1i)
Bromide with a New Nickel(0) Complex
By G. Heiirici-Olive and S. Olivd[*l
Transition metal salts such as VC13, CrC13, NiBr2, and PtC14
can be reduced in tetrahydrofuran (THF) with lithium naphthalide (LiNp). On slow addition of the metal salt solution t o
the naphthaliderl.21, very stable, dark solutions of the
corresponding reduced metals are obtained.
The high stability of these solutions can be interpreted on the
assumption of complex formation of the reduced metal with
naphthalene, and hydrogen transfer from the hydrocarbon
to the metalr2l. Such complexes can carry up to 6 negative
charges. Results of deuterolysis and EPR evidence suggest
n 4 2; S = solvent; f n = number of
structure ( I ) r21. (0
solvent molecules required as ligands by the corresponding
symmetry of the metal complex. x 4 6 = number of negative
charges. The greater the excess of naphthalide the higher the
value of x . )
<
[ * ] Dr. G. Henrici-Olive and Dr. S. Olive
Monsanto Research S.A.
Rinzstr. 39
CH-8045 Zurich (Switzerland)
[**I Our thanks are due to Dr. P. J . Wheattey and Dr. J . J . Daly
for the crystallographic determinations.
[I] G. Henrici-Olive!and S. Olive, Chimia 19, 46 (1965).
[2] G. Henrici-Olive and S. Olivd, J. organometallic Chem.
9, 325 (1967).
[2a] G. Henrici-Olive! and S . Olivd, unpublished.
[3] G. Srhroder and R. Criegee, Liebigs Ann. Chem. 623, 1
(1959).
[4] J. F. Pfrommer., Dissertation, Technische Hochschule
Karlsruhe, 1961.
151 J . D. Dunitz, H. C. Mez, 0. S. Mills, and H. M . M . Shearer,
Helv. chim. Acra 45, 647 (1962).
[6] G. Hewici-Olive! and S. OlivP, Chimia 19,47 (1965); Makromolekulare Chem. 88, 117 (1965).
Nitrogen Fixation on New Transition
Metal Complexes
By G. Henrici-Olive' and S. Olive'[*] [**I
Although the stable solutions d o not contain the metal in
colloidal form, minor amounts of colloidal metal are
formed as a by-product, particularly during the reduction of
transition metals with high population of the d orbitalsrzl.
Several species ( I ) having different values of x may be present in equilibrium. If the excess of LiNp is small, the bisarene complex ( n = x = 0) takes part in the equilibrium, as
EPR measurements with vanadium 121 and chromium 12al
have shown.
Angew. Cliem. internat. Edit.
1 Vul. 6 (1967) / N u . 10
A number of the complexes that are obtained on reduction
of a transition metal salt with lithium naphthalide (LiNp) in
tetrahydrofuran (THF) c1-31 are capable of fixing and reducing molecular nitrogen. The ability t o do this increases with
the number of electrons carried by the complex (i.e. with
increasing excess of LiNp) and, in favorable cases, results in
the fixation of one N2 molecule per molecule of metal complex. Since the number of electrons stored within the complex reaches a maximum of 6 per metal atom [2,31, it can be
assumed that the nitrogen is present as N3- in the complex:
Nz+ 6e + 2 N7-
(1)
873
The results of some fixation experiments are shown in Table 1
(2OoC, duration of reaction of N Z with the complex in
T H F = 30 min).
Table 1 . Nitrogen fixation on reduced transition
metal salts in solution.
LiNp/
metal
Salt
CrCl3
Tic14 [a]
ences cited therein.
[ 5 ] M . P . Volpin, V . B. Shur, and M . A . Ilntovskaya, Izvest.
.4kad. Nauk SSSR, Ser. Chim. 19, 1728 (1964).
metal
3
5
7
10
VCIA
120
120
120
0.9
1
0.9
10
10
1
0.4
10
15
120
120
1.3
1.7
1.2
2.0
Preparation of Maleic Thioanhydride [**I
By H.-D. Scharf and M . Verbeek [*I
Attempts to prepare maleic thioanhydride (3) have hitherto
failed 111. We have now succeeded in findine a method for
preparing this substance and for studying its properties [21.
[a] In toluene
The solution of the metal salt was added to that of LiNp
under Nz. After half an hour the reaction mixture was
hydrolysed and analysed for ammonia according to reference 141. At higher pressures, a n ampoule containing the
salt solution was broken (by the stirrer) in a solution of
LiNp in an autoclave at the desired N2 pressure No NH3
was found in LiNp solution alone (120 atm, 24 h).
The mechanism of fixation and reduction indicated in eq. (1)
finds support in the results of hydrolysis experiments. The
electrons stored in the complex are consumed in decomposing water when the complex is hydrolysed. Thus the volume
of hydrogen produced on hydrolysis gives a n indication of
the number of electrons available[zl. If the complexes are
prepared under nitrogen the number of hydrogen atoms
evolved on hydrolysis will be reduced by a quantity equal to
the number of electrons that have been consumed in reducing
the molecular nitrogen. This behavior is shown in Table 2.
The ratio NH3/metal in the last column was calculated according to equation (2), which follows from eq. (1):
NH3imetal = 2 (a-b)/3
(2)
Table 2. Hydrolysis of solutions of transition metals reduced under
argon and under nitrogen.
LiNplmetal = 10; T
Metal
1
Hzlmetal
[I] C. Henrici-Olive and S . Olive, Chimia 19, 46 (1965).
[ 2 ] C . Henrici-Olive and S . Olivi, J. organometallic Chem.
9, 325 (1967).
[3] G. Henrici-Olivd and S . Olive, Angew. Chem. 79, 897 (1967);
Angew. Chem. internat. Edit. 6, 873 (1967).
[4] M. E. Volpin and V. B. Shur, Doklady Akad. Nauk SSSR
156, 1102 (1964); Nature (London) 209, 1236 (1966) and refer-
=
20 "C; Nz-pressure = 1 atm.
1
1.9
2.8
2.0
It is worthy of note that Ni solutions, which under the given
conditions did not fix any nitrogen, evolved the same amount
of hydrogen when reduced under nitrogen as when reduced
under argon.
Fixation of nitrogen under mild conditions by non-enzymatic
systems which are based on transition metal salts and reducing agents such as Al-alkyls, Grignard compounds, or
LiAlH4 has been extensively investigated by Volppin et al. r4.51.
The highest yield was reported for the system bis(cyc1opentadieny1)titanium dichloride/ethylmagnesium bromide, where
0.47 molecules of nitrogen per Ti atom were detectedrsl after
31 hours at 150 atm nitrogen pressure.
Starting from the readily accessible 1,2,3,6-tetrahydrophthalic anhydride ( I ) , we prepared the hitherto unknown
thio derivative (2) as follows: The anhydride and NazSx.9Hz0
were triturated in a mortar and then poured into 10 hydrochloric acid; the thioanhydride (2) was extracted with ether
and isolated by vacuum distillation in 40 to 50 % yield with
b.p. 81-83 "Cj0.l mm[31. It solidified to colorless crystals
which melt a t 29 "C [31. It is sparingly soluble in toluene, from
which it recrystallizes at room temperature. On treatment
with an aqueous suspension of mercury(r1) oxide it is converted into the known cis-l,2,3,6-tetrahydrophthalicacid.
In the I R spectrum of (2) (in CHC13), the carbonyl vibration
is at 1710 cm-1, being shifted by 70 cm-1 towards lower wavenumbers in comparison with ( I ) .
Thermal retro-diene fission of (2) in an electrically heated
quartz tube (2.5 cmx30 cm) at 430 to 4 5 0 ° C with nitrogen
as carrier gas (between 6.0 and 6.2 liter/h) leads to maleic
thioanhydride(3) with cn. 50 % conversionandmore than90 %
selectivity. The mixed product contains small amounts of
decomposition products with, mainly, the thioanhydrides
(2) and (3), which are separated by distillation. The compound (2) recovered is used for further cleavage experiments.
The thioanhydride (3) boils at 72--74'C/10
mm[3l; it
solidifies to pale yellow, translucent crystals of m.p. 28 "C [31.
It becomes deep brownish-yellow in air and is sensitive to
moisture. UV absorption (in n-hexane): 318 nm (E = 620)
and 230 nm (E = 9300). N M R spectrum (CDC13, tetramethylsilane as internal standard): the signal of the two protons
is at T = 2.8 (maleic anhydride, T = 2.85). I R spectrum
(CHCI3): (3) shows typical anhydride splitting (Ay = 40 cm-1)
of the carbonyl vibration at 1690 cm-1 (high intensity) and
1730 cm-1 (low intensity); these bands are both shifted by
ca. 100 cm-1 to lower wavenumbers in comparison with
maleic anhydride (Ay = 70 cm-1) at 1780 cm-1 (high intensity) and 1850 cm-1 (low intensity) [41.
Received: July 17th, 1967
[Z 572b IE]
German version: Angew. Chem. 79, 898 (1967).
[*] Dr. G . Henrici-Olive and Dr. S. Olive
Monsanto Research S.A.
Binzstrasse 39
CH-8045 Zurich (Switzerland)
[**I We thank Mr. F. Bangerter for able and conscientious experimental work.
874
(4)
According to Mirone and Chiorbo/i[S]the fairly large splitting
of the IR carbonyl bands of maleic anhydride is due to
participation of polar limiting structures (cf. (4)). In (3)
Angew. Chem. internat. Edit. 1 Vol. 6 (1967)
No. 10
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