The first carbene-C,N chelate tetracarbonyl dihalogeno and carbene-C,O chelate tetracarbonyl benzochinone tungsten complexes

Article abstract of DOI:10.1016/S0022-328X(02)01255-X

The carbene-C,N chelate tetracarbonyl tungsten complex [(CO)₄ W=C(Ph)NHC₅H₄N-o] (4), obtained from [(CO)₅ W=C(Ph)OMe] (3) and o-aminopyridine, reacts with iodine by oxidative decarbonylation to give a single iso

Full text of DOI:10.1016/S0022-328X(02)01255-X

Journal of Organometallic Chemistry 651 (2002) 66ꢂ71
/
www.elsevier.com/locate/jorganchem
The first carbene-C,N chelate tetracarbonyl dihalogeno and carbene-
C,O chelate tetracarbonyl benzochinone tungsten complexes
Rudiger Stumpf, Nicolai Burzlaff, Bernhard Weibert, Helmut Fischer *
¨
Fachbereich Chemie, Universtat Konstanz, Universitaetsstr. 10, Fach M727, 78457 Konstanz, Germany
¨
Received 2 November 2001
Abstract
ꢀ
ꢁ
The carbene-C,N chelate tetracarbonyl tungsten complex [(CO)4/
WÄC(Ph)NHC5H4N
C(Ph)OMe] (3) and o-aminopyridine, reacts with iodine by oxidative decarbonylation to give a single isomer of the carbene-C,N
/
-o] (4), obtained from [(CO)5WÄ
/
ꢀ
ꢁ
chelate tricarbonyl dihalogeno tungsten(II) complex [(CO) I
ꢀ
/
3 2 WÄC(Ph)NHC5H4N
/
-o] (5). The analogous reaction of 4 with bromine
ꢁ
-o] (6). The oxidative decarbonylation of the carbene-C,O
affords two interconverting isomers of [(CO)3Br2/
WÄC(Ph)NHC5H4N
4 WÄC(OMe)C6H4O
/
ꢀ
ꢁ
chelate tetracarbonyl tungsten complex [(CO)
/
/
Me-o] (1) with tetrachloro-o-benzochinone yields the first
ꢁ
ꢀ
carbene-C,O chelate tricarbonyl-o-benzochinone tungsten(II) complex 8. The structures of 5 and of [(CO) I
/
4 2 WÄC(OMe)C6H4O
/
Me-o] (2c) were established by X-ray structural analyses. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Carbene complexes; Oxidative decarbonylation; Chelate complexes; Tungsten complexes
1. Introduction
ð1Þ
There are only few examples known of Fischer-type
molybdenum(II) and tungsten(II) carbene carbonyl
complexes not stabilized by aromatic p-ligands [1]. In
1977, Lappert and Pye reported the synthesis of some
Lappert-type W(II) complexes with cyclic bisaminocar-
bene ligands [2] by oxidation of the corresponding W(0)
carbene complexes. However, compared to Fischer-type
carbene ligands, the back-bonding properties of the N-
heterocyclic carbene ligands is almost negligible [3]. In
addition, a few compounds of the type [Cl2(CO)-
The reaction of non-chelated tetracarbonyl(phosphi-
ne)carbene complexes, [(CO)4(PR3)MÄC(OMe)C6H4-
OMe-o], with SnX4 or bromine was found to likewise
afford carbene-C,O chelate dihalogeno complexes [6,7].
In contrast, the reaction of the non-chelated pentacar-
/
bonylcarbene complex [(CO)5WÄ
/
C(OMe)Ph] (3) with
excess SnCl4 did not give a tungsten(II) carbene complex
but rather, among other products, a carbyne complex
[6]. From these observations and those by Lappert et al.,
it was concluded that an energetically high-lying HOMO
at the metal is required for the oxidative decarbonyla-
tion. To determine whether an aminocarbene ligand
sufficiently raises the electron density at the metal, the
reaction of aminocarbene pentacarbonyl complexes was
investigated.
(PMe3)2WÄ
/
C(R)H] (RꢀCMe3, Ph, C6H4Me-p) were
/
prepared by Schrock and coworkers [4] and Mayr et al.
[5].
Recently, we reported the synthesis of the first
heptacoordinated dihalogeno carbene-C,O chelate tri-
carbonyl molybdenum(II) and tungsten(II) complexes
by oxidative decarbonylation of carbene-C,O chelate
tetracarbonyl complexes with SnX4 (Xꢀ/Cl, Br, I),
SbCl5, or TiCl4, e.g. Eq. (1) [6].
2. Results and discussion
* Corresponding author. Tel.: ꢁ
7531-883136.
E-mail address: helmut.fischer@uni-konstanz.de (H. Fischer).
/
49-7531-882783x052; fax: ꢁ49-
/
The aminocarbene complex [(CO)5WÄ
/
C(NMe2)Ph]
was prepared from [(CO)5WÄC(OMe)Ph] (3) and
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 2 5 5 - X

R. Stumpf et al. / Journal of Organometallic Chemistry 651 (2002) 66ꢂ
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67
HNMe2 as previously described [8]. When SnBr4 was
added to a solution of [(CO)5WÄC(NMe2)Ph] in CDCl3,
of these resonances are similar to those of 2c indicating a
similar structure. As expected, the carbene resonance in
/
the color of the solution changed from yellow to orange,
however, the spectra remained unchanged. When SnBr4
was replaced by bromine, the solution turned dark
brown. From the IR spectrum, it followed that several
complexes had been formed. The 1H-NMR spectrum
indicated dissociation of the carbene ligand from the
metal. A tungsten(II) carbene complex could not been
identified. Obviously, the electron-donating properties
of the aminocarbene ligand are insufficient for the
oxidative decarbonylation to occur.
In contrast, the reaction of the C,N-chelated amino-
carbene complex 4 with iodine afforded a tungsten(II)
carbene complex. Complex 4 was obtained analogously
to the homologous chromium complex [9] by aminolysis
of 3 [10] with 2-aminopyridine at low temperature and
subsequent decarbonylative chelation at ambient tem-
perature. When an equimolar amount of iodine was
slowly added to a solution of 4 in dichloromethane, the
evolution of a gas was observed. The solution turned red
and an orange precipitate 5 formed (Eq. (2)).
5 is at considerably higher field than that in 2c (dꢀ
/
258.5 ppm in 5 and 293.2 ppm in 2c).
The structure of 5 was additionally established by an
X-ray analysis (Fig. 1, Table 1). For comparison, an X-
ray structural analysis was also performed on 2c (Fig. 2,
Table 1). The synthesis of complex 2c (see Eq. (1)) has
already been described earlier [6].
Complex 5 crystallizes with two equivalents of THF
and complex 2c with 1/4 equivalent of CH2Cl2. The unit
cell of 2c contains two independent molecules. As
deduced from the IR and NMR spectra, the structures
of 2c and 5 are similar and are best described by a
distorted capped octahedron (Fig. 3).
One CO ligand occupies the capping position. The
chelating carbene ligand bridges the capped (CO, CO,
carbene carbon atom) and the uncapped face (I, I, N in 5
or OMe in 2c) of the octahedron. The carbene carbon
and one iodide, the heteroatom (O or N) and one CO
ligand as well as the second iodide and a CO ligand are
mutually ‘trans’. The chelate ring (W1, C4, C5, C10, O5
in 2c and W1, C4, N1, C21, N2 in 5) only slightly
ð2Þ
Complex 5 is readily soluble in tetrahydrofuran, but
poorly soluble in dichloromethane. Thus, small amounts
of CH2Cl2-soluble by-products are easily removed by
washing of the precipitate with CH2Cl2.
The IR spectrum of complex 5 in THF shows three
n(CO) absorption, indicating the lack of a mirror plane
in the complex. The spectrum is similar to that of the
carbene-C,O chelate diiodo complex 2c [6] but the
n(CO) absorptions are at slightly higher energies. In
contrast, the related Cs-symmetric dichloro complex 2a
[6] exhibits two n(CO) absorptions only.
˚
Fig. 1. Molecular structure of 2c. Selected bond distances (A) and
angles (8): molecule 1: W(1)Ã
C(1) 2.037(14), W(1)ÃC(2) 1.982(13), W(1)Ã
2.130(12), W(1)ÃO(5) 2.256(7), C(4)ÃC(5) 1.472(16), C(5)Ã
1.375(16), C(10)ÃO(5) 1.387(14), I(1)ÃW(1)ÃI(2) 85.70(4), C(1)Ã
W(1)ÃC(2) 106.2(6), C(1)ÃW(1)ÃC(3) 72.6(5), I(1)ÃW(1)ÃC(4)
153.3(3), I(2)ÃW(1)ÃC(4) 70.8(3), I(1)ÃW(1)ÃO(5) 91.9(2), I(2)Ã
W(1)ÃO(5) 85.8(2), C(4)ÃW(1)ÃO(5) 74.2(4), W(1)ÃC(4)ÃC(5)
115.7(9), C(5)ÃC(10)ÃO(5) 114.7(10), W(1)ÃO(5)ÃC(10) 116.7(6);
molecule 2: W(1A)ÃI(1A) 2.891(1), W(1A)Ã
C(1A) 2.005(15), W(1A)ÃC(2A) 1.939(16), W(1A)Ã
W(1A)ÃC(4A) 2.129(13), W(1A)ÃO(5A) 2.264(9), C(4A)Ã
1.463(17), C(5A)ÃC(10A) 1.371(19), C(10A)Ã
I(1A)ÃW(1A)ÃI(2A) 87.11(4), C(1A)ÃW(1A)Ã
C(1A)ÃW(1A)ÃC(3A) 72.6(6), I(1A)ÃW(1A)Ã
I(2A)ÃW(1A)ÃC(4A) 74.3(3), I(1A)ÃW(1A)ÃO(5A) 93.0(2), I(2A)Ã
W(1A)ÃO(5A) 86.3(2), C(4A)ÃW(1A)ÃO(5A) 73.7(4), W(1A)Ã
C(4A)ÃC(5A) 116.9(9), C(5A)ÃC(10A)ÃO(5A) 114.4(11), W(1A)Ã
O(5A)ÃC(10A) 116.6(8).
/
I(1) 2.867(1), W(1)Ã
C(3) 1.930(15), W(1)Ã
C(10)
/
I(2) 2.830(1), W(1)Ã
/
/
/
/
C(4)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
I(2A) 2.829(1), W(1A)Ã
/
On oxidative decarbonylation, the resonance of the
ortho proton of the pyridyl group in the 1H-NMR
/
/
C(3A) 1.938(14),
/
/
/C(5A)
spectrum shifts to lower field (dꢀ/9.38 ppm) compared
/
/
O(5A) 1.399(14),
C(2A) 103.8(6),
C(4A) 157.5(4),
/
/
/
/
to that of 4 (dꢀ8.97 ppm) as expected from the change
/
/
/
/
/
in the oxidation number from 0 to 2. In accord with the
conclusions drawn from the n(CO) spectrum the 13C-
/
/
/
/
/
/
/
/
/
NMR spectrum of 5 exhibits three CO resonances (dꢀ
/
/
/
/
/
213.0, 214.5, and 238.0 ppm). The number and position
/

68
R. Stumpf et al. / Journal of Organometallic Chemistry 651 (2002) 66ꢂ71
/
Table 1
Crystallographic data for and 2c×1/4CH2Cl2 and 5×2THF
2c×1/4CH2Cl2
5×2THF
Empirical formula
C
12H10I2O5W×1/
C15H10I2-
N2O3W×2THF
848.1
4CH2Cl2
682.2
Mr (g molꢃ1) (including
solvent)
Temperature (K)
Crystal system
Space group
240(2)
Monoclinic
C2/c
245(2)
Monoclinic
P21/c
˚
a (A)
16.550(4)
15.630(5)
28.029(5)
102.62(2)
7075(2)
8
11.857(1)
12.842(1)
18.429(2)
90.50(1)
2806.1(4)
4
˚
b (A)
˚
c (A)
b (8)
Cell volume (A )
3
˚
Z
Dcalc (g cmꢃ3
)
2.603
10.110
5000
2.008
6.350
1592
m(Moꢂ
F(000)
Crystal size (mm)
Scan rate (8 minꢃ1 in v)
Scan range Dv (8)
Observed reflections
/
Ka) (mmꢃ1
)
0.25ꢄ0.20ꢄ0.15 0.4ꢄ0.3ꢄ0.2
2ꢂ29.3 4ꢂ30
1.4 1.5
4598 [F ꢀ4.0s(F)] 5148
[F ꢀ4.0s(F)]
6134
/
/
˚
Fig. 2. Molecular structure of 5. Selected bond distances (A) and
angles (8): W(1)Ã
1.986(9), W(1)ÃC(2) 2.008(10), W(1)Ã
2.135(8), W(1)ÃN(2) 2.225(7), C(4)ÃN(1) 1.326(10), N(1)Ã
1.391(12), C(21)ÃN(2) 1.326(11); I(1)ÃW(1)ÃI(2) 86.78(2), C(1)Ã
W(1)ÃC(2) 106.8(4), C(1)ÃW(1)ÃC(3) 74.4(4), I(1)ÃW(1)ÃC(4)
155.3(2), I(2)ÃW(1)ÃC(4) 73.4(2), I(1)ÃW(1)ÃN(2) 91.7(2), I(2)Ã
W(1)ÃN(2) 85.9(2), C(4)ÃW(1)ÃN(2) 72.7(3), W(1)ÃC(4)ÃN(1)
116.4(6), C(4)ÃN(1)ÃC(21) 120.4(7), N(1)ÃC(21)ÃN(2) 113.2(8),
W(1)ÃN(2)ÃC(21) 117.0(6).
/
I(1) 2.8846(8), W(1)Ã
/
I(2) 2.8438(7), W(1)Ã
/
C(1)
/
/
C(3) 1.972(10), W(1)Ã
/C(4)
/
/
/C(21)
Independent reflections
Min/max transmission
Parameters refined
R1 (%)
7702
/
/
/
/
0.2690/0.5872
375
5.29
0.0396/0.0797
298
4.97
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
wR2 (%)
Res. electron density (e A
10.00
12.38
/
/
/
/
ꢃ3
˚
) 1.578 and ꢃ1.446 0.983 and ꢃ0.967
/
/
deviates from planarity. The iodo ligands are cis and
occupy positions on the same side of the chelate plane.
In contrast, the dichloro complex 2a is Cs-symmetric
and the mirror plane (formed by the chelate ring and
one CO ligand) bisects the ClÃ
OCÃWÃCO angle [6]. The IÃWÃ
CO and the OCÃWÃC (carbene) angles in both com-
plexes, 2c and 5, are similar. The phenyl ring in 5 is tilted
against the chelate plane by 33.98. In 2c, the methyl
group lies within the chelate plane and is oriented
/
WÃ
/
Cl angle and one
Fig. 3. Structure of 2c and 5 shown in two different perspectives: (A)
side view; and (B) view along the capping OCÃW axis.
/
/
/
/
I angle, the OCÃ
/
WÃ
/
/
/
/
broad signals at ambient temperature. Based on the
observation of two resonances for the carbene carbon
atom, five CO signals, and 18 peaks in the aromatic
region of the 13C-NMR spectrum at ꢃ
/
80 8C and on the
IR spectrum, the two isomers 6a and 6b were assigned
structures corresponding to 2cꢂ5 and 2a. At ꢃ80 8C
the ratio 6aꢂ6b is 1:3. The formation of a mixture of
towards the metalꢂligand fragment (Z conformation).
/
This conformation is usually observed also with non-
chelated alkoxycarbene complexes [11].
The reaction of 4 with bromine proceeded analo-
gously to that with iodine. However, two interconvert-
ing isomers (6a and 6b, Eq. (3)) were formed.
/
/
/
isomers in the oxidative decarbonylation of carbene
chelate tetracarbonyl complexes has not been observed
before. Oxidation of carbene C,O-chelate tetracarbonyl
complexes gave either Cs-symmetric complexes such as
2a and 2b or C1-symmetric complexes like the more
electron-rich compounds 2c and 5. Obviously, increas-
ing electron-donating power of the ligands in these
metal(II) complexes increasingly disfavors the Cs-sym-
metric structure (2a and 6b) and favors the C1-sym-
ð3Þ
The 1H-NMR spectrum of 6a/6b is temperature-
metric structure as in 2c,
5 and 6a. For the
dependent. At ꢃ80 8C, two sharp resonances are
observed for the ortho proton of the pyridyl group.
On warming, these resonances broaden to give two
/
interconversion of 6a and 6b, several different mechan-
isms are conceivable. The most likely one involves a
series of rearrangements via a capped trigonal prism.

R. Stumpf et al. / Journal of Organometallic Chemistry 651 (2002) 66ꢂ
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69
The difference in energy between the different structures
for heptacoordinated complexes is small. Complexes
with a structure intermediate between a capped octahe-
dron and a -trigonal prism are known, for example
[(CO)3Br(Br3Ge)W(bipy)] [12] or [(CO)2Cl2Mo(P-
Me2Ph)3] [13]. Compound in which the coordinating
heteroatom of the chelating ligand determines whether
the complex adopts a capped octahedral or a -trigonal
prismatic structure have also been reported [14]. The
oxidizing agents whose reduced form also can function
as ligands were investigated next and o-benzochinone
was chosen for that.
When a solution of tetrachloro-o-benzochinone in
dichloromethane was added to a solution of 3 in CH2Cl2
at ꢃ
Chromatography of the reaction mixture with
pentaneꢂdichloromethane at 50 8C yielded the
/
10 8C, the evolution of a gas was observed.
/
ꢃ
/
dark-green complex 8 as the major product (isolated
yield: 62%) and a red compound. The red compound
turned out to be a decomposition product of 8 since it
was also formed when solutions of 8 were kept for
prolonged periods of time at ambient temperature. The
compound was not further characterized.
structure of [(CO)2Cl2Mo(h2-Ph2XÃ
Ph2XÃCH2ÃXPh2)] is that of a capped octahedron for
Xꢀ
Xꢀ
/
CH2Ã
XPh2)(h1-
/
/
/
/As and that of a distorted capped trigonal prism for
/P. In the crystal [(CO)3I2W(NCPh)2] is a capped
octahedron, one of the three CO ligand assuming the
capping position. In solution all carbonyl ligands are
equivalent in the 13C-NMR spectrum even at ꢃ
70 8C
/
[15].
Next the reaction of bromine with the C,C Ä
chelating complex 7 [16] was investigated.
ð4Þ
/
C-
Two signals for OMe groups in the 1H-NMR
spectrum of 8 indicated that the carbene ligand was still
coordinated to the metal. From the observation of two
n(CO) absorptions in the IR spectrum and of two
carbonyl resonances (ratio ca. 1:2) in the 13C-NMR
spectrum a Cs-symmetric structure as shown in Eq. (4)
and similar to that of 2a was assigned. Compared with
the chloro and bromo complexes 2a and 2b, the
resonances for the carbene carbon atom and the
carbonyl ligands are at lower field.
The electron-donating properties of chelating ‘C(Ph)Ã
/
NHÃ
/
CH2ÃCHÄCH2’ are less than those of carbene-
/
/
C,O or -C,N chelating ligands but intermediate between
a carbene-C,O chelate ligand and the combination of an
aminocarbene ligand and CO as in [(CO)5WÄ
C(Ph)NMe2]. Complex 7 reacted in acetonitrile with
bromine even at ꢃ30 8C. The similarity of the IR
/
/
Complex 8 is less stable than its dihalogeno analogues
spectrum of the reaction solution with that of 5 or 6a
indicated the formation of a new complex with a
structure similar to that of 5 and 6a. However, it was
not possible to isolate and completely characterize the
2aꢂ
slowly, but can be stored under nitrogen at ꢃ
prolonged periods of time.
/
c. At ambient temperature in solution, 8 decomposes
/
30 8C for
In contrast to the reaction of 3 with tetrachloro-o-
benzochinone that with 3,5-di-tert-butyl-o-benzochi-
none proceeded only slowly at room temperature.
When one equivalent of the chinone was added, the
two new n(CO) absorptions in the IR spectrum indi-
cated the formation of a new complex, however, the
reaction was still incomplete. When benzochinone was
added in excess until all absorptions of 3 had disap-
peared, no chelate carbene tungsten(II) complex could
be isolated from the reaction mixture. Presumably a
tungsten(II) complex related to 8 had been formed in the
reaction of 3 with 3,5-di-tert-butyl-o-benzochinone
albeit slowly but quickly decomposed again either by
reaction with the chinone or by another pathway.
Further oxidation of the tungsten(II) complex seems
possible since [Mo(CO)6] was found to react with
tetrachloro-o-benzochinone or 3,5-di-tert-butyl-o-ben-
zochinone to give molybdenum(VI) complexes [17].
Nevertheless, these observations demonstrate that
anionic ligands other than halides can be introduced
into chelate carbene tungsten(II) complex.
complex since already above ꢃ
via subsequent reactions.
/
30 8C it ‘decomposed’
Until now, only chlorine, bromine or metal halides
were used as the oxidizing agent in the oxidative
decarbonylation. All attempts to subsequently replace
the halide ligands in the resulting heptacoordinated
dihalogeno carbene chelate tricarbonyl metal(II) com-
plexes by other simple nucleophiles such as [OR]ꢃ or
[SR]ꢃ failed. The reactions of 2b or 2c with NaOEt or
LiO-t-Bu led to dissociation of the carbene ligand.
Likewise, no substitution product could be isolated
from the reactions of 2b with Na[SC6H4Me-p] and
sodium
hydridotris(3,5-dimethylpyrazolyl)borate
(NaTp), respectively, although in all of these experi-
ments an alkali metal halide was formed. Similarly, the
reaction of 2b with AgOTf or TlBF4 in the presence of
oxalate did not give an isolable substitution product but
only led to decomposition of the complex.
These observations seemed to indicate that anionic
ligands other than halides have to be introduced in close
connection with the oxidation reaction. Therefore,

70
R. Stumpf et al. / Journal of Organometallic Chemistry 651 (2002) 66ꢂ71
/
3. Experimental
(m, br, 7H, Ph and pyridyl), 9.58 (d, JHH
pyridyl-o-H of 6b), 9.83 (s, br, pyridyl-o-H of
6a). * 80 8C): 6a: d 112.7,
13C-NMR (C3H6O-d6, ꢃ
ꢀ
/
4.5 Hz,
3.1. General
/
/
113.4, 116.8, 121.9, 132.8, 140.6, 143.4, 150.0, 153.2
(aryl), 214.5, 216.0, 243.4 (CO), 256.2 (carbene-C); 6b: d
115.6, 120.0, 128.4, 128.6, 129.2, 133.9, 143.6, 151.6,
156.1 (aryl), 210.0, 216.7 (CO), 240.1 (carbene-C).
All operations were carried out under nitrogen by
using conventional Schlenk techniques. Solvents were
dried by refluxing over Naꢂbenzophenone ketyl or
/
CaH2 and were freshly distilled prior to use. The yields
refer to analytically pure compounds and were not
optimized. The complexes 1 [18], 2c [6], 3 [10], 7 [12]
were prepared according to literature procedures. IR:
3.4. Tricarbonyl[methoxy(o-methoxyphenyl)carbene-
k2C,O](tetrachloro-o-chinolato-k2C1,2)tungsten(II)
(8)
FTIR spectrophotometer, Bio.-Rad. *
1H-NMR and
/
13C-NMR: Bruker WM 250, Bruker AC 250, JEOL
JNX 400. Unless specifically mentioned, spectra were
recorded at room temperature. Chemical shifts are
reported relative to Me4Si (1H-NMR spectra) or to the
At ꢃ10 8C, a solution of 0.77 g (3.13 mmol) of
/
tetrachloro-o-benzochinone in 50 ml of CH2Cl2 was
added within 30 min to a solution of 1.47 g (3.3 mmol)
of 1 in 50 ml of CH2Cl2. The solvent was removed in
residual solvent peaks (13C-NMR spectra: CDCl3 dꢀ
77.0 ppm, CD2Cl2 dꢀ53.8 ppm, C3H6O-d6ꢀ206.6
ppm).
/
vacuo. The residue was chromatographed at ꢃ
with C5H12ꢂCH2Cl2 (ratio slowly changing from 10:1 to
1:20) on silica gel. Four fractions were eluted. The first
orange fraction contained
[(CO)5WÄ
C(OMe)C6H4OMe-o], the second yellowꢂbrown un-
/
50 8C
/
/
/
/
3.2. Tricarbonyldiiodo[phenyl(2-pyridylamino)carbene-
k2C,N]tungsten(II) (5)
/
reacted 1, and the third red one a decomposition
product of 8. Finally, a green band containing the
product 8 was eluted. Removal of the solvent in vacuo
gave 8 as fine, dark-green almost black, metallic shiny
crystals. Yield: 1.28 g (62% relative to tetrachloro-o-
Iodine (0.51 g, 2.0 mmol) was added in small portions
to a solution of 0.96 g (2.0 mmol) of complex 2 in 50 ml
of CH2Cl2. The solution was stirred for 20 min. With
evolution of a gas, the color of the solution turned red
and an orange precipitate formed. The precipitate was
decanted and twice washed with 50 ml of C5H12 each.
Recrystallization of the residue from THF afforded red
crystals, which decomposed in vacuo to give an orange
benzochinone). *
(CH2Cl2, cmꢃ1): n(CO) 2043 s, 1958 vs. *
(C3H6O-d6): d 4.03 (s, 3H, carbene-OMe), 4.70 (s, 3H,
aryl-OMe), 7.42 (t, Jꢀ7.5 Hz, 1H, aryl), 7.64 (d, Jꢀ8.6
Hz, 1H, aryl), 7.84 (d, Jꢀ7.9 Hz, 1H, aryl), 7.87 (t, Jꢀ
7.3 Hz, 1H, aryl). *
1H-NMR (CDCl3): d 3.95 (s, 3H,
carbene-OMe), 4.52 (s, 3H, aryl-OMe), 7.20ꢂ7.35 (m,
2H, aryl), 7.67ꢂ7.72 (m, 2H, aryl). *
13C-NMR
(CD2Cl2, ꢃ80 8C): d 59.4 (s, carbene-OMe), 67.3 (s,
aryl-OMe) 111.8, 117.1, 118.0, 122.5, 123.4, 132.4, 138.1,
153.8, 163.9 (9s, aryl), 216.7 (CO), 221.5 (JWC 115 Hz,
/
M.p.
169 8C
(dec.). *
/
IR
/
1H-NMR
/
/
/
/
powder. Yield: 1.26
(dec.). *
IR (THF, cmꢃ1): n(CO) 2033 s, 1964 vs,
1921 m. * 7.14 (m,
1H-NMR (C3H6O-d6): d 6.99ꢂ
4H, Ph), 7.38ꢂ7.42 (m, 2H, pyridyl), 7.58ꢂ7.62 (m, 1H,
pyridyl), 7.71ꢂ7.77 (m, 1H), 9.38 (d, JHH
pyridyl-o-H). *
13C-NMR (C3H6O-d6):
g
(89%). *
/
M.p. 235 8C
/
/
/
/
/
/
/
/
/
/
/
ꢀ/5.3 Hz,
/
d
117.8,
ꢀ
/
122.6, 129.5 130.2, 133.9, 142.3, 146.0, 154.5, 158.2
(aryl), 213.0 (CO), 214.5 (CO), 238.0, 258.5 (carbene-
2CO), 287.5 (carbene-C). Anal. Found: C, 32.17; H,
1.86. Calc. for C18H10Cl4O7W (663.9): C, 32.56; H,
1.52%.
C). * Anal. Found: C, 25.41; H, 1.67; N, 4.16. Calc.
/
for C15H10I2N2O3W (703.9): C, 25.59; H, 1.43; N,
3.98%.
3.5. X-ray structural analyses of 2c and 5
3.3. Dibromotricarbonyl[phenyl(2-
pyridylamino)carbene-k2C,N]tungsten(II) (6)
Single crystals of 2c suitable for an X-ray structural
analysis were obtained by slow diffusion of C5H12 into a
solution of 2c in CH2Cl2 at ꢃ
/
30 8C and from THF (5),
Bromine (0.404 g, 2.5 mmol) was added dropwise to a
solution of 1.25 g (2.5 mmol) of complex 2 in 50 ml of
CH2Cl2. The solution was stirred for 20 min. With
evolution of a gas, the color of the solution turned red
respectively.
The measurements were performed with a crystal
mounted in a glass capillary on a Siemens R3m/V (2c)
and P4 diffractometer (5) (graphite monochromator,
˚
0.71073 A). For the data collec-
and a redꢂ
/
brown precipitate formed. The precipitate
Moꢂ
/
Ka radiation, lꢀ
/
was decanted and twice washed with 50 ml of C5H12
each. Recrystallization of the residue from THF af-
tion, the Wykoff technique was used (4.0B
/
2u B54.08).
/
With both complexes a semiempirical absorption cor-
rection (C scan with 10 reflections) was performed. The
structures were solved by Patterson methods using the
SHELXTL PLUS (VMS) program package. The positions
forded a brown powder. Yield: 1.10 g (72%). *
(THF, cmꢃ1): n(CO) 2037 m, 1967 vs, 1945 m, 1917
w. * 80 8C): d 6.90ꢂ8.31
1H-NMR (C3H6O-d6, ꢃ
/
IR
/
/
/

R. Stumpf et al. / Journal of Organometallic Chemistry 651 (2002) 66ꢂ
/71
71
(1985) 1744;
of the hydrogen atoms were calculated by assuming
ideal geometry, and their coordinates were refined
together with those of the attached carbon atoms as
‘riding model’. The positions of all other atoms were
refined anisotropically by the full-matrix least-square
methods. The crystal of 2c consisted of two independent
molecules.
(e) B. Lungwitz, A.C. Filippou, NATO ASI Ser. Ser. C 392 (1993)
249;
(f) A.C. Filippou, D. Wossner, B. Lungwitz, G. Kociok-Kohn,
¨ ¨
Angew. Chem. 108 (1996) 981; Angew. Chem. Int. Ed. Engl. 35
(1996) 876.
[2] (a) M.F. Lappert, P.L. Pye, Chem. Soc. Dalton Trans. (1977)
1283;
(b) M.F. Lappert, P.L. Pye, J. Chem. Soc. Dalton Trans. (1977)
2172.
[3] For a recent review on complexes with cyclic bisaminocarbene
4. Supplementary material
ligands see: W.A. Herrmann, C. Kocher, Angew. Chem. 109
¨
(1997) 2256; Angew. Chem. Int. Ed. Engl. 36 (1997) 2162.
[4] J.H. Wengrovius, R.R. Schrock, M.R. Churchill, H.J. Wasser-
man, J. Am. Chem. Soc. 104 (1982) 1739.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos.173231, 173232 for compounds
2c and 5. Copies of the data may be obtained free of
charge on application to The Director, CCDC, 12
[5] A. Mayr, M.F. Asaro, M.A. Kjelsberg, K.S. Lee, D. Van Engen,
Organometallics 6 (1987) 432.
[6] M. Jaeger, R. Stumpf, C. Troll, H. Fischer, Chem. Commun.
(2000) 931.
Union Road, Cambridge CB2 1EZ, UK (Fax: ꢁ44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk. or www:
http://www.ccdc.cam.ac.uk).
/
[7] R. Stumpf, M. Jaeger, H. Fischer, Organometallics 20 (2001)
4040.
[8] E.O. Fischer, K.R. Schmid, W. Kalbfus, C.G. Kreiter, Chem. Ber.
106 (1973) 3893.
[9] K.H. Dotz, A. Rau, K. Harms, Chem. Ber. 125 (1992) 2137.
¨
[10] (a) E.O. Fischer, A. Maasbol, Angew. Chem. 76 (1964) 645;
¨
Acknowledgements
(b) E.O. Fischer, A. Maasbol, Angew. Chem. Int. Ed. Engl. 3
¨
(1964) 580.
[11] U. Schubert, in: K.H. Dotz, H. Fischer, P. Hofmann, F.R.
¨
Support of these investigations by the Fonds der
Chemischen Industrie is gratefully acknowledged.
Kreissl, U. Schubert, K. Weiss (Eds.), Transition Metal Carbene
Complexes, Verlag Chemie, Weinheim, 1983, p. 73 ff.
[12] E.M. Cradwick, D. Hall, J. Organomet. Chem. 25 (1970) 91.
[13] A.J. Mawby, G.E. Pringle, J. Inorg. Nucl. Chem. 34 (1972) 917.
[14] M.G.B. Drew, A.P. Wolters, I.B. Tomkins, J. Chem. Soc. Dalton
Trans. (1977) 974.
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