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Methyl Hydrogen Carbonate.

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Reversible N, Fixation by Dicarbonyl-rc-cyclopentadienyl(tetrahydrofuran)manganese(I) [11
When a CO/N, mixture is bubbled through a solution of
( 2 ) ,the complex (3) is the only product. Thus, as in most
N,-fixing systems, (2) is inactivated for uptake of N, by
absorption of CO.
By Dieter Sellmann"
Metal complexes that fix N, are of particular interest if, at
the site of N, fixation, other Iigands can also be introduced
reversibly. Such a ligand exchange is required for the mechanism of N, reduction in nitrogenase systems, where replacement of complex-bound H,O or NH, must occur :
It is, however, not possible from these facts to decide the
important question whether the preferential formation of
the CO complex is based on kinetic or thermodynamic
grounds. Nevertheless, a kinetic cause is favored by the
fact that spectroscopic data indicate N, to be a stronger
electron donor than CO in ( I ) ['I.
M-OH, + Nz + M-N,
M-NH, + N, + M-N,
M=central metal atom
Comparing eq. (1) and ( 5 ) Shows clearly the analogy to
nitrogenase systems. Alongside [Ru(NH,),H,O] t2[41 and
{C,H,~e[(CH3~,P(CHz),1'(~
1 I,),IOC(CH3)Z)BF4[51,(21
is the third system known in which N, is able to replace
an oxygen-donor ligand at atmospheric pressure.
+ H,O
+ NH,
Eq. (1) describes the beginning of the reaction chain if a
nitrogenase system interacts with N, for reduction,
while eq. (2) describes the liberation of the end product.
NH, is used for synthesis of amino acids, the N, complex
re-entering the reduction chain.
A study of the reactions of C,H,Mn(CO),N,
has
made it possible to simulate such replacement reactions.
First it was shown that ( I ) is unstable in tetrahydrofuran
(THF) at room temperature, being converted into the THF
complex C,H,Mn(CO),OC,H, (2) with evolution of N,:
The evolution of nitrogen stops after some time, although
small amounts of ( I ) are still detectable by IR spectroscopy in the T H F solution. The fact that the reaction leading to (2) does not procede to completion, in spite of the
large excess of THF, led to the assumption of an equilibrium
that is shifted largely to the side of (2) owing to the low N,
concentration. If such an equilibrium exists it should be
possible to synthesize ( I ) also by reaction of (2) with N,
in a reaction that is the reverse of eq. (3) :
+ N,
(2)
+
(I)
+ THF
(4)
This could in fact be done, either by reducing the concentration of THF relative to that of N, or by raising the N, concentration by pressure. In the first case N, was bubbled
through a freshly prepared solution of (2)[31until the THF
had volatilized completely in the gas stream. In the second
case N, was pressed at 150 atm into a solution of the same
kind for 24 h and the THF was then removed at room temperature in uacuo. At 20°C and z lo-' torr a mixture of ( I )
and C,H,Mn(CO), (3) sublimed from the residues of each
reaction. ( I ) can be easily identified in the mixture by
means of its characteristic IR bands. These findings prove
the assumed equilibrium and thus the competition between
N, and THF for the central metal in the complex fragment
CC,H,Mn(CO),} ( 4 ) :
[*] Dr. D. Sellmann
Anorganisch-chemisches Laboratorium der
Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
534
Received: January 24,1972 [Z 632 IE]
German version: Angew. Chern. 84,549 (1972)
[l] Reactions of Complexed Ligands, Part 6.-Part 5 : 0.Sellmann,
J. Organometal. Chern. 36, C 27 (1972).
[2] D. Sellmann, Angew. Chem. 83, 1017 (1971); Angew. Chem. internat. Edit. 10, 919 (1971).
[3] W Strohmeier, C. Barbeau, and D. von Hobe, Chem. Ber. 96, 3254
(1963).
[4] D. F. Harrison, E. Weissberger, and H . Taube, Science 159, 320
(1968).
[S] W E. Siloerthorn, Chem. Commun. 1971, 1310.
Methyl Hydrogen Carbonate"]
By Gerhard Gattow and Werner Behrendt"'
Continuing our studies of carbonic acid[" we have now
concerned ourselves with the half esters, which have not
previously been prepared.
Methyl hydrogen carbonate ( I ) is formed on treatment
of a suspension of Na[CH,OCO,] (obtained by reaction
of NaOCH, dissolved in methanol with CO,) in dimethyl
ether with a solution of HCl(g) in dimethyl ether at - 50°C.
After filtration from the NaCl formed and removal of the dimethyl ether by distillation at -80"C, the half ester remains as a solid.
CH,OCO(OH) is a colorless material that melts at
- 36 "C ; decomposition (+CO, +CH,OH) at temperatures above the melting point. The half ester is only moderately soluble in dimethyl or diethyl ether; it decomposes immediately in water. The dissociation constant,
determined by way of the hydrolysis constant of
Na[CH,OCO,], at 25°C in H,O is: K,=2.44.10-6. By
measurement of the CO, pressure of the solid (-70 to
-36"C), the heat of formation of ( I ) was found to be:
AH,= - 155.5k 1 kcal/mol.
The IR spectrum of a solution of ( I ) in (C,H,),O at
- 70°C contains, besides the ether bands, the following
absorption bands that can be unambiguously assigned to
the half ester: 3484 [s; v(OH)], 1779 [m; vaS(CO)],1730
Is; v,,(CO)], 1277 [s; 6,(CH3)], 1255 [s, 6,(CH3)1, 823 [s,
x(OCO,)], 665 [m; ?], 652 [m; ?], 567 [w; S,(OCO,)]
cm-'.
[*I
Prof. Dr. G. Gattow and Dip1.-Chem. W. Behrendt
Institut fur Anorganische Chemie und Kernchemie der Universitat
65 Mainz, Johann-Joachim-Becher-Weg 24 (Germany)
Angew. Chem. internat. Edit. 1 Vol. I 1 (1972) 1 No. 6
The substance with a melting range of -57 to -60°C
described by Hempel and Seidelc3Jas methyl hydrogen
carbonate probably consisted of a mixture of solid carbon
dioxide and methanol (m.p. - 56.6 "C at 5.28 atm.).
Received: February 11,1972 [Z 633 IE]
German version: Angew. Chem. 84,549 (1972)
[l] Part 60 of Chalogenolates.
-
Part 59: M . Drager and G . Gattow,
rn
2.Anorg. Allg. Chem., in the press.
[2] G . Gattow and U . Gerwarth, Angew. Chem. 77,132 (1965); Angew.
Chem. internat. Edit. 4,149 (1965); Z. Anorg. Allg. Chem. 357,78 (1968).
131 W Hempel and J . Seidei, Ber. Dtsch. Chem. Ges. 31, 2997 (1898).
2,3:3,4:4,2-Tri-p-carbonyl-2,2,3,3,4,4-hexacarbonyl-1-aluminotricobalt: Preparation and
Spectroscopic Findings[**I
C
0
Fig. 1. Structure proposed for AICo,(CO),.
Metal clusters with the compositions (C,H,),TiCo,(CO),
and (C,H,),Zr,Co,(CO),
have also been obtained
analogously to the reaction mentioned above.
Received: March 3,1972 [Z 636 IE]
German version: Angew. Chem. 84, 587 (1972)
By Karl E . Schwarzhans and Hans Steiger"]
AlCo,(CO),, a metal cluster containing aluminum-cobalt
bonds, has been obtained by reaction of sublimed aluminum
trichloride with an excess of sodium tetracarbonylcobaltate(-I) in dry benzene under an inert gas (NJ.
3Na[Co(CO),]
[(18 mmol)
+ AICI,
-+
+ (2 mmol)
AICo,(CO),
250rn' 'bH<,
3 0 T , 3d
[1]
[2]
[3]
[4]
G . Bor, Spectrochim. Acta 19, 1209 (1963).
P. Corradini, J. Chem. Phys. 31, 1676 (1959).
L. F . Dahl and C. H . Wei, J. Amer. Chem. SOC.88,1821 (1966).
C.H . Wei, Inorg. Chem. 8,2384 (1969).
[ 5 ] D. L. Smith, J. Phys. Chem. 42,1460 (1965).
+ 3NaC1 + 3 C 0
1
This crystalline compound (yield 25-30% calc. on AlCl,)
is deep red, sensitive to moisture, and not very stable
thermally, but can be sublimed at room temperature and
0.1 mm. Its composition is proved by elemental analysis
and by IR and mass spectra.
In the mass spectrum (50eV) the molecular ion (Ire,=5.4) is
accompanied by the following characteristic fragments :
AlCo,(CO); (16.3), AICo,(CO): (5.2), AlCo,(CO): (3.6),
AlCo,(CO)l (18.2),AlCo,(CO)z (34.6),AlCo,(CO): (18.3),
AlCo,(CO): (18.2), AlCo,(CO)+ (14.5), AlCo: (31.1),
Co,(CO): (20), Co(C0); (14.4), CoCO+ (3.7), Cot (100).
The relatively high intensity of the AlCol fragment is
striking.
The vco region of the IR spectrum is to a large extent comparable with that of dodecacarbonyltetracobalt"' in respect of the positions, number, and intensities of the bands :
Cyclophanes Possessing Cavities"] [**I
By Fritz Viigtle and Rainer G . Lichtenthalev"'
We wish to report the planned synthesis of a new heterocyclic system in which approximately parallel benzene
rings joined by three bridges enclose a cavity.
Using a method that had been optimized for the metacyclophane seriesc2]and applying the dilution principle we treated 1,3,5-tris(bromoacetyl)benzenewith 1,3,5-tris(mercaptomethy1)benzene and with sodium sulfide ( x 9H,O) in terrbutanol as solvent. We obtained the crystalline C4.4.41(1,3,5)cyclophane( 1 ) [m.p. > 360"C, dec. ;from (CH,),SO]
and the [5.5.5](1,3,5)cyclophane (2)13] [m. p. > 360"C,
dark coloration ; from (CH,),SO], respectively, in reproducible yields of 10 and 0.16%.
AlCo,(CO),, vco in benzene: 2100 (w), 2066 (m), 2053 (s),
2032 (m), 1893 (w), 1858 (m-s) cm-' ;-Co,(CO),,,
vco in
n-hexane: 2104 (w), 2063 (m-s), 2054 (s), 2037 (w), 2027 (w),
1898 (w), 1867 (m) cm-'.
The IR spectra show that the structure of the metal skeleton
is similar in the two clusters. A structure is therefore proposed for AlCo,(CO), that differs from that of Co,(CO),,
(for which several X-ray investigations are available"
in that the apical Co(CO), group of Co,(CO),, is replaced
by the aluminum ion, as shown in Figure 1. The agreement
of the IR spectra further indicates that Co,(CO),, has this
structure also in solution, contrary to a previous structural
R spectroscopic findings.
proposal[51that was based on I
The molecular weights of the two cyclophanes and the
presence of three sulfur atoms were initially confirmed by
mass spectrometry. Compound ( I ) , which was obtained
["I
Doz. Dr. K. E. Schwarzhans and H. Steiger
Anorganisch-chemisches Laboratorium der
Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
[**I
Angew. Chem. internat. Edit.
Vol. I 1 f1972)
1 No. 6
[*] Prof. Dr. F. Vogtle and Dip1:Chem. R. G. Lichtenthaler
Institut fur Organische Chemie der Universitat
87 Wiirzburg, Landwehr (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
535
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