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Preparation of homotropylium transition metal carbonyl complexes by hydride extraction
Tetrahedron Letters
No. 12, pp. 9Oj-906,
PREPARATION
1970.
OF HOMOTROI’YLIUM
PergamonPress.
TRANSITION
Printed in Great Britain.
METAL
CARBONYL
COMPLEXES BY HYDRIDE EXTRACTION1 R. Aumann’ and S. Winstein Contribution No. 2440 from the Department of Chemistry University of California, Los Angeles, California 90024 (Received in USA20 October 1969; received in UK for publication 5 February 1970) The homoaromatic
homotropylium molybdenum tricarbonyl
cation3 II(M=Mo) was formerly
generated in sulfuric acid solvent by protonation of the cyclooctatetraeie molybdenum tricarbonyl 3a complex I(M=Mo) prepared specifically for this purpose. The tungsten analog of the homotropylium molybdenum tricarbonyl
complex,
fashion by protonation of the corresponding
namely II(M=W),3cp 4 could also be prepared in this cyclooctatetraene
complex I(M=W).3c’ 4 These two
homotropylium
species were also generated by protonation and loss of CO from the corresponding cyclooctatetraene molybdenum5 of tungsten 3c,4 tetracarbonyl complexes. On the other hand,
attempts to generate the homotropylium chromium tricarbonyl the cyclooctatetraene
chromium tricarbonyl
cation II(M=Cr)
by protonation of
complex6 I(M=Cr) were unsuccessfuL4
H+ 5
I M(C0)3 I
11
We now report a convenient synthesis tungsten tricarbonyl
6
I WW3
tetrafluoraborates
CBhomotropylium
chromium,
molyWenum
and
which permits easy isolation of the solid crystalline
The latter in liquid sulfur dioxide give better resolved nmr spectra than formerly
salts.
obtained in
H2S04 solution; thus, complete analyses of the nmr spectra are possible. The present synthesis involves hydride abstraction by the trltyl cation from the 1,3,5cyclooctatriene
transition metal tricarbonyl
complexes
(III)7.
veniently prepared in the present work in yields of ca.70-9% (CH3CN)3Cr(C0)3,8a
diglyme Mo(CO)3,8b or (NH3)3i(CO)3,8c
The latter complexes were confrom the cyclooctatriene respectively,
and
in dioxane or THF.
To a 600 mg. (2.48 mmole) quantity of C8Hlo Cr(CO)3 dissolved in 5 ml. of CH2C12 was
903
904
No.12
added a solution
of 800 mg.
microcrystalline washed
material
with 5 x 2 ml.
(2.42
mmole)
began
of (C6Hj)3C?BFyin
to precipitate.
of CH2C12
and dried
After in vacua
sensitive
in 72% and 62% yields,
and hygroscopic,
definite
melting
points,
All three
in the presence
but decomposed
gradually
Anal.
Calcd.
for CllH9Cr03BF4:
Anal.
Calcd.
for C11H9Mo03BF4:
Anal.
Calcd.
for C11H9W03BF4:
A dark were
red
collected,
(73%) of C8H9Ct(CO)3
9 BF4.0
c,~~w(cof&~
of
homotropylium
of moisture.
complexes
These
salts
are
showed
air
no
on heating.
C, 40.28; H, 2.77.
Found: C, 39.63; H, 3.20.
C, 35.51; H, 2. 44. C,
of CH2C12.
the crystals
brown crystals
respectively.
decomposing
minutes
to give 605 mg.
Similarly. .maroon crystals of C8H9Mo(CO)~8F~and were obtained
5 ml.
20
28.73;
H, 1.98.
@
(C6H5)3C
Found:
C,
35. 33; H, 2.51.
Found:
C,
28.83;
H, 2.21.
0 BF4
CH2 Cl2
I MWV3
I M(W3
111
11
For the Mo(C0)3 constants are
are
very
obtainable
similar,
successive
approximation the spectrum
are
summarized
For
directly
comparison
using
of the nmr
of cyclocctatetraene
complexes
SO2 solution
is in accord
for the free chemical According free
to the present
C8H9$but
C8Hp> simply
difference
also
is also
cation
However,
b values
out on these
on the A values.
are
in Table
inside
complexes
sensitive
of their
shifts
spin system
(r1_7)
and coupling
con-
and outside
nmr
evaluate
in SO2
of equimolar
spectrum
species
as the free
spectra
referred
One of these
in Table
The observed This
of the aromatic
to molecular
The nmr
of this
salt
geometry,
II,
are
to previously
so until x-ray effect
not only for the
of Avalues
of Avalues
ring current
the quantitative
is the
respectively.
large
sequence
sequence
ion and in its
features
H8b and HSa protons,
summarized as well.
ligand
by reaction
1.
complex.3
C8H9 W(CO)3?
we can’t
material
of the C8HF
features
of the magnitudes
species,
for a seven
chemical
SO2 at -60”.
and its MOM
C8H9Mo(CO)Fa
quite
T 395 and r2,6 obtained by
with that of the free
crystalline
description
the L! values,
taken as the sequence
is carried
summarized
(A) between data,
and coupling
complex, 3 constants were
program9
of the complexes
in liquid
with two general
for the three
C8H9Cr(CO)y>
LAOCN3
shifts
the Cr(C0)
and coupling
All the derived
as a yellow
electronic
homotropylium
shift
spectra
and FS03H
The tropylium-like
For
chemical
I.
was obtained
amounts
dilute
shifts
the Bothner-By
in Table
C8H9@ FSOF
the various
the spectra.
chemical
in the H2_6 region.
solvent,
in more
complexes
from
so the pertinent
to simulate stants
and W(CO),
1s most
in the four structure
of molecular
is
species. analysis geometry
No.12
905
Table 1. Summary of NMR Spectraa of Homotropylium Fluorosulfonate and Homotropylium M(CO)3 Tetrafluoroborate
ce$
Corn lexes C8H93CC), @ BF4O MO w-
%r
1. 4
3. 3gb
3.38
3.43
1. 4
3. 47b
3.87
4.02
r4
1. 4
4. 32b
4.06
4.20
r1,7
3. 30
5.63
5.58
5.71
‘8a
4.74
6.60
6.53
6.21
r8b
10.55
11.05
10.15
9.72
10. ob
IO. 0
10.0
C
7. sb
7.5
7.5
_C
f3.0b
8.0
8-9
7.0
8.5
8.5
8.5
10.0
10.0
9.0
9.0
7.0
11.5
12.5
r3,5 r2,6
C
134,5l=jJ3,4 135,6(=1J2,d \16,71= 1’1,2\
i’l,8$
p7,8b\
IJ8a, 84
11.5
a In -ca.lO% liquid SO2 solution; internal TMS; b the spectr$m was well simulated by means of the Bothner-By LAOCN3 program using these parameters:the spectrum was not analyzed completely because of second order coupling between protons 2,3,4,5 and 6. Table II. Some Features of the NMR Spectra of C8H9@and C8H9M(CO)y
Species
r1-7 Ave. Species ‘gH9
A
0
0 C8H9Cr(CC)3
C8H9M4W3 C8H,WW3
0 8
‘2-6
in C7H7@ IO species
5.85
1.4
0.72
4.45
3.60
3.42
3.62
3.71
3.82
3.51
3. 82
3.83
906
No.12
The other feature electronic
structure
tropylium
species
of the nmr spectra
is the close
species
of the C8H9
comparison
between average
indicating
a homotropylium
T values for H2_6 in the homo-
3b for the corresponding parent tropylium species. 0 . As shown in Table 11, the average ~2-6 for the free C8H9 aglees with ‘l-7 for C7H7@within 8 The agreement is even better between ~2-6 for the C8H9 0.7 ppm in liquid SO2 solvent. @ completis and ~l_~ in the corresponding C7H7 complexes lo in liquid SO2. Thus, for the three complexes,
and the ~1-7 value observed
~2-6 for the C8Hpspecies
on the average.
It is quite remarkable
the homotropylium
species
0 with T~_~ for the C7H7 complexes
agree
simulates
how closely
the electronic
state of carbon atoms C2_6 in
in the parent tropylium
that for CI_7
to within 0. 1 ppm
analogs.
References 1.
(a) Research
supported
(b) acknowledgement by the American 2.
Fulbright
3.
(a) S. Winstein,
in part by the U. S. Army
is made to the donors
Chemical
Scholar,
Society,
1967-1969.
F)
S. Winstein,
4.
A. Maasbol,
5.
H. D. Kaesz,
6.
C. G. Kreiter,
The Chemical
unpublished
requests
Special
Fund, administered
should be sent.
and E. C. Friedrich,
C. G. Kreiter, Society
Research
support of this research.
C. G. Kreiter,
87, 3267 (1965); (b) S. Winstein,
Office(Durham);
c# the Petroleum
for partial
To whom reprint
H. D. Kaesz,
Research
Chem. -- SOL, 88 2047 (1966); =,
J. Am.
and J. I. Brauman, jb&, Rblications,
2& 5 (1967).
work.
S. Winstein
and C. G. Kreiter,
A. Maasbol,
F. A. L. Anet,
J. Am.
Chem.
H. D. Kaesz
SE.,
88, 1319 (1966).
and S. Winstzn
) i,ibid
E,
3444
(1966). 7.
(a) E. O.Fischer,
C. Palm and H. P. Fritz,
(b) R. B. King, 8.
inorg.
Chem.,
5
W. R. Knipple and J. M. Augl,
Werner
H. Coffield,
prepared Z. anorg.
analogous allg.
9.
A. A.
Bothner-By
IO.
G. F.
Emerson,
3589 (1964).
Chem.
Inorg.
Ind. (London),
to (NH3)3 Cr(C0)3;
Chem.,
Ber.,
92 -’
807 (1963).
(a) D. P. Tate, and T.
Chem.
W. Hieber,
Chem.,
2645 (1959);
L, 433 (1962); (b) R. P. M.
936 (1960); (c) (NH3)3 W(CO)3
was
W. Abeck and H. K. Platzer,
28J 252 (1955).
and S. Castellano, J. E. Mahler,
J. Chem.
Physics,
R. Pettit and R. Collins,
2,
3863 (1964).
J. Am.
Chem, Sot.,
86 =’
No. 12, pp. 9Oj-906,
PREPARATION
1970.
OF HOMOTROI’YLIUM
PergamonPress.
TRANSITION
Printed in Great Britain.
METAL
CARBONYL
COMPLEXES BY HYDRIDE EXTRACTION1 R. Aumann’ and S. Winstein Contribution No. 2440 from the Department of Chemistry University of California, Los Angeles, California 90024 (Received in USA20 October 1969; received in UK for publication 5 February 1970) The homoaromatic
homotropylium molybdenum tricarbonyl
cation3 II(M=Mo) was formerly
generated in sulfuric acid solvent by protonation of the cyclooctatetraeie molybdenum tricarbonyl 3a complex I(M=Mo) prepared specifically for this purpose. The tungsten analog of the homotropylium molybdenum tricarbonyl
complex,
fashion by protonation of the corresponding
namely II(M=W),3cp 4 could also be prepared in this cyclooctatetraene
complex I(M=W).3c’ 4 These two
homotropylium
species were also generated by protonation and loss of CO from the corresponding cyclooctatetraene molybdenum5 of tungsten 3c,4 tetracarbonyl complexes. On the other hand,
attempts to generate the homotropylium chromium tricarbonyl the cyclooctatetraene
chromium tricarbonyl
cation II(M=Cr)
by protonation of
complex6 I(M=Cr) were unsuccessfuL4
H+ 5
I M(C0)3 I
11
We now report a convenient synthesis tungsten tricarbonyl
6
I WW3
tetrafluoraborates
CBhomotropylium
chromium,
molyWenum
and
which permits easy isolation of the solid crystalline
The latter in liquid sulfur dioxide give better resolved nmr spectra than formerly
salts.
obtained in
H2S04 solution; thus, complete analyses of the nmr spectra are possible. The present synthesis involves hydride abstraction by the trltyl cation from the 1,3,5cyclooctatriene
transition metal tricarbonyl
complexes
(III)7.
veniently prepared in the present work in yields of ca.70-9% (CH3CN)3Cr(C0)3,8a
diglyme Mo(CO)3,8b or (NH3)3i(CO)3,8c
The latter complexes were confrom the cyclooctatriene respectively,
and
in dioxane or THF.
To a 600 mg. (2.48 mmole) quantity of C8Hlo Cr(CO)3 dissolved in 5 ml. of CH2C12 was
903
904
No.12
added a solution
of 800 mg.
microcrystalline washed
material
with 5 x 2 ml.
(2.42
mmole)
began
of (C6Hj)3C?BFyin
to precipitate.
of CH2C12
and dried
After in vacua
sensitive
in 72% and 62% yields,
and hygroscopic,
definite
melting
points,
All three
in the presence
but decomposed
gradually
Anal.
Calcd.
for CllH9Cr03BF4:
Anal.
Calcd.
for C11H9Mo03BF4:
Anal.
Calcd.
for C11H9W03BF4:
A dark were
red
collected,
(73%) of C8H9Ct(CO)3
9 BF4.0
c,~~w(cof&~
of
homotropylium
of moisture.
complexes
These
salts
are
showed
air
no
on heating.
C, 40.28; H, 2.77.
Found: C, 39.63; H, 3.20.
C, 35.51; H, 2. 44. C,
of CH2C12.
the crystals
brown crystals
respectively.
decomposing
minutes
to give 605 mg.
Similarly. .maroon crystals of C8H9Mo(CO)~8F~and were obtained
5 ml.
20
28.73;
H, 1.98.
@
(C6H5)3C
Found:
C,
35. 33; H, 2.51.
Found:
C,
28.83;
H, 2.21.
0 BF4
CH2 Cl2
I MWV3
I M(W3
111
11
For the Mo(C0)3 constants are
are
very
obtainable
similar,
successive
approximation the spectrum
are
summarized
For
directly
comparison
using
of the nmr
of cyclocctatetraene
complexes
SO2 solution
is in accord
for the free chemical According free
to the present
C8H9$but
C8Hp> simply
difference
also
is also
cation
However,
b values
out on these
on the A values.
are
in Table
inside
complexes
sensitive
of their
shifts
spin system
(r1_7)
and coupling
con-
and outside
nmr
evaluate
in SO2
of equimolar
spectrum
species
as the free
spectra
referred
One of these
in Table
The observed This
of the aromatic
to molecular
The nmr
of this
salt
geometry,
II,
are
to previously
so until x-ray effect
not only for the
of Avalues
of Avalues
ring current
the quantitative
is the
respectively.
large
sequence
sequence
ion and in its
features
H8b and HSa protons,
summarized as well.
ligand
by reaction
1.
complex.3
C8H9 W(CO)3?
we can’t
material
of the C8HF
features
of the magnitudes
species,
for a seven
chemical
SO2 at -60”.
and its MOM
C8H9Mo(CO)Fa
quite
T 395 and r2,6 obtained by
with that of the free
crystalline
description
the L! values,
taken as the sequence
is carried
summarized
(A) between data,
and coupling
complex, 3 constants were
program9
of the complexes
in liquid
with two general
for the three
C8H9Cr(CO)y>
LAOCN3
shifts
the Cr(C0)
and coupling
All the derived
as a yellow
electronic
homotropylium
shift
spectra
and FS03H
The tropylium-like
For
chemical
I.
was obtained
amounts
dilute
shifts
the Bothner-By
in Table
C8H9@ FSOF
the various
the spectra.
chemical
in the H2_6 region.
solvent,
in more
complexes
from
so the pertinent
to simulate stants
and W(CO),
1s most
in the four structure
of molecular
is
species. analysis geometry
No.12
905
Table 1. Summary of NMR Spectraa of Homotropylium Fluorosulfonate and Homotropylium M(CO)3 Tetrafluoroborate
ce$
Corn lexes C8H93CC), @ BF4O MO w-
%r
1. 4
3. 3gb
3.38
3.43
1. 4
3. 47b
3.87
4.02
r4
1. 4
4. 32b
4.06
4.20
r1,7
3. 30
5.63
5.58
5.71
‘8a
4.74
6.60
6.53
6.21
r8b
10.55
11.05
10.15
9.72
10. ob
IO. 0
10.0
C
7. sb
7.5
7.5
_C
f3.0b
8.0
8-9
7.0
8.5
8.5
8.5
10.0
10.0
9.0
9.0
7.0
11.5
12.5
r3,5 r2,6
C
134,5l=jJ3,4 135,6(=1J2,d \16,71= 1’1,2\
i’l,8$
p7,8b\
IJ8a, 84
11.5
a In -ca.lO% liquid SO2 solution; internal TMS; b the spectr$m was well simulated by means of the Bothner-By LAOCN3 program using these parameters:the spectrum was not analyzed completely because of second order coupling between protons 2,3,4,5 and 6. Table II. Some Features of the NMR Spectra of C8H9@and C8H9M(CO)y
Species
r1-7 Ave. Species ‘gH9
A
0
0 C8H9Cr(CC)3
C8H9M4W3 C8H,WW3
0 8
‘2-6
in C7H7@ IO species
5.85
1.4
0.72
4.45
3.60
3.42
3.62
3.71
3.82
3.51
3. 82
3.83
906
No.12
The other feature electronic
structure
tropylium
species
of the nmr spectra
is the close
species
of the C8H9
comparison
between average
indicating
a homotropylium
T values for H2_6 in the homo-
3b for the corresponding parent tropylium species. 0 . As shown in Table 11, the average ~2-6 for the free C8H9 aglees with ‘l-7 for C7H7@within 8 The agreement is even better between ~2-6 for the C8H9 0.7 ppm in liquid SO2 solvent. @ completis and ~l_~ in the corresponding C7H7 complexes lo in liquid SO2. Thus, for the three complexes,
and the ~1-7 value observed
~2-6 for the C8Hpspecies
on the average.
It is quite remarkable
the homotropylium
species
0 with T~_~ for the C7H7 complexes
agree
simulates
how closely
the electronic
state of carbon atoms C2_6 in
in the parent tropylium
that for CI_7
to within 0. 1 ppm
analogs.
References 1.
(a) Research
supported
(b) acknowledgement by the American 2.
Fulbright
3.
(a) S. Winstein,
in part by the U. S. Army
is made to the donors
Chemical
Scholar,
Society,
1967-1969.
F)
S. Winstein,
4.
A. Maasbol,
5.
H. D. Kaesz,
6.
C. G. Kreiter,
The Chemical
unpublished
requests
Special
Fund, administered
should be sent.
and E. C. Friedrich,
C. G. Kreiter, Society
Research
support of this research.
C. G. Kreiter,
87, 3267 (1965); (b) S. Winstein,
Office(Durham);
c# the Petroleum
for partial
To whom reprint
H. D. Kaesz,
Research
Chem. -- SOL, 88 2047 (1966); =,
J. Am.
and J. I. Brauman, jb&, Rblications,
2& 5 (1967).
work.
S. Winstein
and C. G. Kreiter,
A. Maasbol,
F. A. L. Anet,
J. Am.
Chem.
H. D. Kaesz
SE.,
88, 1319 (1966).
and S. Winstzn
) i,ibid
E,
3444
(1966). 7.
(a) E. O.Fischer,
C. Palm and H. P. Fritz,
(b) R. B. King, 8.
inorg.
Chem.,
5
W. R. Knipple and J. M. Augl,
Werner
H. Coffield,
prepared Z. anorg.
analogous allg.
9.
A. A.
Bothner-By
IO.
G. F.
Emerson,
3589 (1964).
Chem.
Inorg.
Ind. (London),
to (NH3)3 Cr(C0)3;
Chem.,
Ber.,
92 -’
807 (1963).
(a) D. P. Tate, and T.
Chem.
W. Hieber,
Chem.,
2645 (1959);
L, 433 (1962); (b) R. P. M.
936 (1960); (c) (NH3)3 W(CO)3
was
W. Abeck and H. K. Platzer,
28J 252 (1955).
and S. Castellano, J. E. Mahler,
J. Chem.
Physics,
R. Pettit and R. Collins,
2,
3863 (1964).
J. Am.
Chem, Sot.,
86 =’