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ESR Measurements on Nitrogen-Fixing Titanium-Alkali Metal Systems.

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O = P ( C H ~ C I ) ,+ 3 KR'POR~
-
R,?
?
R'P
YHz
R1
CH3O
C2HSO
iso-CsH7O
n-GH90
2-Ethyl-hexyl-OC4H90
C6HS
"R'
PP=O
(1)
R
?,R
,P-cH,-P,-cH,-P
'Ri
+
RzC1
case of the titanium compound described here, and particularly after reduction with lithium naphthalide (LiNp),
NH3:Ti in molar ratios of 0.5, 0.7, and 0.96 being obtained
after 2, 4, and 16 hours respectively (at [CpzTiClr],, = 3x10-2
moleil; LiNp: Ti = 6 (mole/mole), and 1 atm of Nz).
M.p.
169- 171
168-170
85-87
109--III
oil
oil
223-234
5.7
76.7
85.0
61.8
82.0
83.7
97.5
-31.0
-34.0
-28.9
-29.7
-29.3
-29.0
-31.0
1 :3
1:3
1:3
1:3
1:3
1 :3
1:3
-22.8
-21.0
-18.6
-19.6
-21.0
-34.7
-24.4
[a] In CDCl, with 85 % H3PO4 as external standard.
Compounds (la)-(lei possess an extraordinarily high adsorption capacity. For example, a warm 2 % solution of ( I b )
in benzene solidifies completely on cooling so that no benzene
can be poured off.
The structure of compounds ( l a ) - ( l g ) was proved by 31Pand 1H-NMR spectroscopy. The 31P-NMR spectrum of
( I b ) contains signals for Pa at -34.0 and Pp at -21.0 ppm
(intensity ratio 1:3). The 1H-NMR spectrum also
agrees with the structure proposed: S 3 C H 2 at 6 = 1.30
(JHH= 7.0 Hz, 18 H), PCHzP at 8 = 2.93 ( J P ~ H
= 15.6 Hz,
J P ~=
H20.0 Hz, 6 H), and POCHz at 6 = 4.15 (JHH= 7 Hz,
JPH
= 7.9 HZ, 12.1 H).
Hydrolysis of ( I b ) by refluxing with conc. HCl as well as
thermal decomposition of (Ic) at 190 OC give tris(dihydroxyphosphonylmethy1)phosphine oxide O=Pa[CH2Pfi03H2]3 in
quantitative yield. The 31P-NMR spectrum of the acid
shows signals for Pa at -37.8 pprn and Pp at -15.3 ppm.
On titration, two breaks are recorded at p H = 4.4 (three
equivalents) and p H = 10.7 (three equivalents). The acid
forms a crystalline cyclohexyIamine salt (m.p. 190 "C) as well
as trisodium and hexasodium salts. It is an excellent chelating
agent.
Received: February 16, 1968
[Z 751c IE1
German version: Angew. Chem. 80, 401 (1968)
[*I Dr. Ludwig Maier
Monsanto Research SA
CH-8045 Zurich, Binzstrasse 39 (Switzerland)
[l] Part 34 of Organophosphorus Compounds. - Part 33: L.
Maier, Angew. Chem. 80, 401 (1968); Angew. Chem. internat.
Edit. 7, 385 (1968).
[2] A . Hoffman, J. Amer. chem. Soc. 52, 2995 (1930).
[3] M. Reuter and F. Jakob, German Pat. 1064511 (1960);
Chem. Abstr. 55,11302~(1961).
141 M. I . Kabachnik and E. M. Isvetkov, Proc. Acad. Sci. USSR,
Sect. Chem. (English Translation) 143, 211 (1962).
If the reduction is carried out under argon, the reaction
solution gives the ESR spectrum shown in Fig. la. At molar
ratios Li:Ti between 3 and 4 this is the only signal observed.
Its intensity has a maximum at Li/Ti = 3.5, and is nearly zero
at Li/Ti = 4.0. At higher ratios the signal of LiNp appears.
The ESR spectrum shown in Fig. l a disappears if the argon
is subsequently replaced by nitrogen. If the reduction is
carried out from the very beginning under nitrogen, conditions under which the system fixes Nz, the spectrum does
not appear at all.
The predominant hyperfine splitting (HFS) in the spectrum
of Fig. l a has the intensity distribution 1:2:1, indicating the
interaction of the unpaired electron($ of the titanium with
two equivalent hydrogen nuclei within the complex. The
relatively high coupling constant (see Table 1) points to Ti-H
bonds. Each of the three lines is further split into four
equidistant lines of equal intensity. In the present system
this can be due only t o interaction with one Li nucleus
(nuclear spin I = 3 / 2 ) .
Furthermore, a relatively weak interaction with aromatic
hydrogen atoms is to be observed which splits each of the
twelve lines mentioned into an odd number of very narrow
lines, although well resolved only at T < 0 'C. These protons
are situated o n the Cp-rings, which are not eliminated
during the reduction with LiNp. The spectrum also shows
pronounced line width effects in the hydrogen as well as in
the lithium HFS that are probably due to anisotropy of the
g-value and the hyperfine tensors. However. these effects
have not yet been quantitatively interpreted.
A very similar spectrum is obtained if the reduction is
carried out with NaNp (Fig. l b ; only the high field part of
the spectrum is shown). Whereas the 1:2:1 hydrogen splitting
is identical for both complexes, the 1:1:1:1 sodium splitting
( 1 = ~3/2)~ is considerably greater than that of the lithium
ESR Measurements on Nitrogen-Fixing
Titanium-Alkali Metal Systems111
By G . Henrici-Olivd and S. Olive"*1
I
I
2 Gauss
u
In recent communications [*, 31 we suggested that negatively
charged transition metal complexes with alkali metal counterions are formed during the reduction of transition metal salts
with alkali naphthalide in tetrahydrofuran. We now present
convincing ESR evidence for the existence of such transition
metal-alkali metal interaction, in the particular case of dicyclopentadienyltitanium dichloride (CpzTiCIZ), after reduction with alkali naphthalide.
Several of the reduced transition metal complexes are able to
fix and to reduce nitrogen under mild conditions 141. A timedependent nitrogen fixation has also been observed in the
386
Fig. I . ESR spectra of the reaction solutions (a) CplTiClz -t LiNp and
(b) CpzTiCIz
NaNp at -4OOC in tetrahydrofuran under argon.
Arrows indicate center of spectra.
+
Angew. Chern. internat. Edit. / VoI. 7 (1968) J No. 5
(Table 1); as a consequence, the three quadruplets, which are
clearly separated in the upper spectrum, become superimposed in the lower one, the last line of the first and the
first line of the last quadruplet coinciding in the center of
spectrum 1b.
Table 1. ESR parameters of the complexes formed from CpzTiClz and
alkali naphthalides.
Alkali
naphthalide
g-value
I
LiNp
NaNp
1.9938
1.9938
20
0
-40
-80
20
-40
9.5
9.8
9.6
9.5
9.5
9.8
-
0.27
0.27
0.25
0.23
0.23
2.5
2.4
2.3
2.1
6.3
6.7
Second derivative representation of one of the line groups
(Fig. 2) shows that the aromatic H F S consists of an odd
number of lines. Nine lines can be detected, the intensity
distribution of which makes it probable that ten hydrogen
atoms, i.e. two Cp-rings, are the cause of this HFS. (The
extreme lines, the intensities of which are only 0.4/100 of that
of the center line, cannot be seen [I]).
Fig. 2. Second derivative representation of the last high field group of
lines of the spectrum of Fig. l b .
It should be noted that the reaction solution is only weakly
paramagnetic at molar ratios 3 < Li:Ti < 4, and a rough
double integration [51 of the ESR spectra intensities accounts
only for 10-20 % of the Ti possessing one unpaired electron.
The ESR data suggest either of the two structures:
where x is the number of negative charges, as in the complexes
described previously [*,31. Presumably several complexes,
with varying x , are in equilibrium, but only one is ESR
active.
A complex Cp2Ti(m)HZTi(Iu)Cp2 (i.e. a species analogous
to ( 2 ) . but with x = 0) has been suggested by Brintzinger for
the reaction product of CpzTiClZ and ethylmagnesium
chloride in tetrahydrofuran [61; however, this suggestion was
recently rejected in favor of a complex analogous t o ( 1 ) “ 1 .
Also in the present case a dimeric structure containing two
Ti(I1r) species is highly improbable, since n o evidence could
be detected for the existence of a triplet state (no “half field
line”[sl, no dipole-dipole interaction in rigid media at low
temperatures [g]). The observation, o n the other hand, that
under nitrogen a molar ratio of NH3: Ti = 1 (i.e. Nz: Ti = 0.5)
could not be exceeded, points strongly t o a complex containing two Ti atoms. Thus, most probably, structure ( 2 ) has t o
be considered, the ESR active species being that with x = 1,
i.e. with only one unpaired electron per complex unit.
Angew. Chern. internat. Edit. 1 Vof. 7 (1968) 1 No. 5
The extraordinarily high coupling constants of the alkali
metals (Table l), which indicate about 2.4% and 2.0% of
unpaired spin density at the Li and N a nucleus respectively,
show that these metals must be relatively tightly bound to the
Ti, presumably within the inner coordination sphere. This is
consistent with the observed low temperature-dependence of
the alkali metal splitting, suggesting little or no ionic dissociation.
Concerning the fixation of nitrogen it is assumed at the
present stage of the investigation that a similar mechanism is
at work as that suggested recently for other reduced metal
complexes [41: the negative charges of the complexes are used
up for the reduction of the nitrogen molecule.
Received: February 14, 1968
[Z 755 IEI
German version: Angew. Chem. 80, 398 (1968)
[ * ] Dr. G. Henrici-Olive and Dr. S. OlivC
Monsanto Research S.A.
CH-8045 Zurich, Binzstr. 39 (Switzerland)
[I] Part 2 of ESR Investigations on Transition Metal Complexes.
- Part 1: G. Hersrici-Olive and S . Olive, Z. physik. Chem. N.F.
56, 223 (1967).
[2] G. Henrici-Olive and S . Olive, J. organometallic Chem. 9, 325
(1967).
[3] G. Henrici-Olive and S . Olivk, Angew. Chem. 79, 897 (1967);
Angew. Chem. internat. Edit. 6, 873 (1967).
[41 G . Henrici-OlivP and S. Olive, Angew. Chem. 79, 898 (1967);
Angew. Chem. internat. Edit. 6, 873 (1967).
[5I W . A.Tolkatschev and A. J . Michailov, Pribory y technika
eksper. 6, 95 (1964).
[6] H . Brintzinger, J. Amer. chem. SOC.88, 4305, 4307 (1966).
[71 H. Brintzinger, J. Amer. chem. SOC.89, 6871 (1967).
[ 8 ] A. Carrington and A. D . McLachlan: Introduction to
Magnetic Resonance. Harper and Row, New York, 1967.
[9] N . Hirotu, J. Amer. chem. SOC.89, 32 (1967).
A Productive Method for the Preparation of
Geminal Chloronitroso Compounds
By H. Diekmann and W. Liittke[*l
Several methods are known for the preparation of geminal
chloronitroso compounds RlRZC(N0)Cl L1-71, all except
one[2] being based o n the reaction of oximes with chlorinating agents containing positively polarized chlorine. W e
have found that treatment of the oximes with alkyl hypochlorites in trichlorofluoromethane represents a method
possessing considerable advantages over previous processes:
In all cases investigated the yields are almost quantitative;
the products are obtained in a high state of purity; and the
mild reaction conditions even permit smooth preparation of
the very unstable chloronitroso compounds that are derived
from aldoximes.
The alkyl hypochlorites used as chlorinating agents are either
isolated as such or are prepared in solution [81 by shaking the
corresponding alcohol in trichlorofluoromethane with
aqueous hypochlorous acid. The solution, whose hypochlorite content can be checked iodometrically, can be used
directly for the reaction with the oxime. With most oximes
the reaction proceeds smoothly and is complete within a few
minutes, even at temperatures as low as -70°C. I t is only
in the case of highly substituted reactants, such as tert-butyl
methyl ketoxime and tert-butyl hypochlorite, that the reaction
mixture has t o stand a t room temperature for about half an
hour. As a rule, the pre-cooled hypochlorite solution was
added dropwise and rapidly t o a solution of the oxime kept
at -40 O C in a cryostat, the operation being carried out in a
darkened room. The reaction mixture was gradually warmed
t o room temperature while being stirred. If the oxime is
insufficiently soluble in trichlorofluoromethane, chloroform
is added to the mixture. Product recovery can be executed
mildly and simply by virtue of the low boiling point of tri-
387
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measurements, titanium, esr, fixing, metali, nitrogen, alkali, system
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