Zwitterionic adducts from addition of imines to the α-carbon atom of pentacarbonyl(vinylidene)chromium and -tungsten complexes

Article abstract of DOI:10.1016/S0022-328X(00)00789-0

Imines, Im, such as MeN=C(Ph)H (5), 2-methyl 4,5-dihydrothiazole (8a), 2-methyl 4,5-dihydrooxazole (8b) and MeN=C(OMe)Me (13) add to the α-carbon atom of the vinylidene ligand in [(CO)₅Cr=C=CMe₂] (4) to give isolable zwitterionic adducts, [(CO)₅Cr^--C(=CMc₂)(Im^-)]. The reaction of [(CO)₅W=C=CPh₂] (12) with 13 also yields an adduct, [(CO)₅W^--C(=CPh₂){NMe=C(OMe)Me}⁺] (15), whereas from the corresponding reaction of 4 with xanthylideneimine, H-N=C(C₆H₄)₂O (16), a carbene complex, [(CO)₅Cr=C(i-Pr)-N=C(C₆H₄)₂O] (17), is obtained. Complex 17 presumably is formed by initial addition of 16 to 4 and subsequently rapid rearrangement. In solution, the adduct [(CO)₅Cr^--C(=CMe₂)(NMe=C(Ph)H)⁺] (6) slowly cyclizes to form the 2-azetidin-1-ylidene complex [(CO)₅Cr=C-NMe-C(Ph)H-CMe₂] (7). In contrast, when solution of those zwitterions are heated that are formed by addition of 4,5-dihydrothiazole or 4,5-dihydrooxazole to 4, no cyclization is observed but rather the formation of 4,5-dihydrothiazole and 4,5-dihydrooxazole complexes, respectively. The structures of two adducts, [(CO)₅Cr^--C(=CMe₂)(Im⁺)] (Im = MeN=C(Ph)H, 2-methyl 4,5-dihydrothiazole) and of the substitution product [(CO)₅W(2-methyl 4,5-dihydrothiazole)] have been established by X-ray structural analyses.

Full text of DOI:10.1016/S0022-328X(00)00789-0

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Journal of Organometallic Chemistry 620 (2001) 165–173
Zwitterionic adducts from addition of imines to the a-carbon atom
of pentacarbonyl(vinylidene)chromium and -tungsten complexes
Helmut Fischer *, Frank Kirchbauer, Angelika Fru¨h, Mokhles M. Abd-Elzaher 1,
Gerhard Roth, Christoph C. Karl, Markus Dede
Fachbereich Chemie, Uni6ersita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received 24 May 2000; received in revised form 15 September 2000; accepted 29 September 2000
Abstract
Imines, Im, such as MeNꢀC(Ph)H (5), 2-methyl 4,5-dihydrothiazole (8a), 2-methyl 4,5-dihydrooxazole (8b) and
MeNꢀC(OMe)Me (13) add to the a-carbon atom of the vinylidene ligand in [(CO)5CrꢀCꢀCMe2] (4) to give isolable zwitterionic
adducts, [(CO)5Cr−–C(ꢀCMe2)(Im+)]. The reaction of [(CO)5WꢀCꢀCPh2] (12) with 13 also yields an adduct, [(CO)5W−
–
C(ꢀCPh2){NMeꢀC(OMe)Me}+] (15), whereas from the corresponding reaction of 4 with xanthylideneimine, H–NꢀC(C6H4)2O
(16), a carbene complex, [(CO)5CrꢀC(i-Pr)–NꢀC(C6H4)2O] (17), is obtained. Complex 17 presumably is formed by initial addition
of 16 to 4 and subsequently rapid rearrangement. In solution, the adduct [(CO)5Cr−–C(ꢀCMe2)(NMeꢀC(Ph)H)+] (6) slowly
¸¹¹¹¹¹¹¹¹¹¹º
cyclizes to form the 2-azetidin-1-ylidene complex [(CO)5CrꢀC–NMe–C(Ph)H–CMe2] (7). In contrast, when solution of those
zwitterions are heated that are formed by addition of 4,5-dihydrothiazole or 4,5-dihydrooxazole to 4, no cyclization is observed
but rather the formation of 4,5-dihydrothiazole and 4,5-dihydrooxazole complexes, respectively. The structures of two adducts,
[(CO)5Cr−–C(ꢀCMe2)(Im+)] (Im=MeNꢀC(Ph)H, 2-methyl 4,5-dihydrothiazole) and of the substitution product [(CO)5W(2-
methyl 4,5-dihydrothiazole)] have been established by X-ray structural analyses. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Pentacarbonyl(vinylidene) complexes; Imines; Adduct formation; 4,5-Dihydrothiazole complexes; Carbene complexes
1. Introduction
tion proceeds in a stepwise fashion. Addition of the
imine via the lone electron pair at nitrogen to the
a-carbon atom of the vinylidene ligand to form a
zwitterion is followed by ring-closure of the intermedi-
ate to give the cyclic ligand. Such a mechanistic scheme
is corroborated by the observation of a zwitterionic
Vinylidene complexes react with imines by cycloaddi-
tion of the CꢀN bond of the imine to the CꢀC bond of
the vinylidene complex to give four-membered transi-
tion metal substituted N-heterocycles (Scheme 1) [1–8].
Subsequent oxidative cleavage of the MꢀC bond
affords b-lactams. Very likely, the cycloaddition reac-
cation
{Cp[P(OMe)3](CO)Fe–C(ꢀCMe2)NMeꢀCH-
Ph}+ (1) in the reaction of {Cp[P(OMe)3](CO)FeꢀCꢀ
CMe2}+ with MeNꢀC(H)Ph in 1,2-dichloroethane [1,2].
Complex 1 was characterized by IR and 1H-NMR
spectroscopy. On standing in solution, 1 underwent
cyclization to produce the corresponding 2-azetidin-1-
ylidene complex.
Scheme 1.
* Corresponding author. Tel.: +49-7531-882783; fax: +49-7531-
883136.
E-mail address: hfischer@dg6.chemie.uni-konstanz.de (H. Fischer).
1 Present address: Inorganic Chemistry Department, National Re-
search Centre, PO 12622 Dokki, Cairo, Egypt.
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00789-0

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H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
[(CO)5MꢀCꢀC(H)R] with N-aryl imines nor in that
with N-alkyl imines. To get more information on the
initial step of the reactions of pentacarbonyl vinylidene
complexes with imines we studied the reactions of
[(CO)5CrꢀCꢀCMe2] with various cyclic and acyclic
imines.
2. Results and discussion
Scheme 2.
The starting vinylidene complex [(CO)5CrꢀCꢀCMe2]
(4) [9] was generated by the reaction sequence shown in
Scheme 3. Reduction of [Cr(CO)6] with potassium-
graphite (C9K2) laminate in THF at 0°C gave
K2[Cr(CO)5] [10]. Subsequent reaction with isobutyryl
chloride afforded potassium pentacarbonyl(isobu-
tyryl)chromate which was then transformed into 4 by
reaction with trifluoroacetic acid anhydride in CH2Cl2
at −78°C [11]. Complex 4 is unstable and rapidly
decomposes in solution at room temperature. There-
fore, 4 was not isolated but only characterized by its
w(CO) spectrum. The solutions of 4 were then immedi-
ately employed for the reactions with imines.
Scheme 3.
When one equivalent of N-methyl benzylideneamine
(5) was added to a solution of 4 in pentane–CH2Cl2
(ca. 1:1) at −45°C the initially green solution immedi-
ately turned red. Addition of a tenfold excess of pen-
tane led to precipitation of the complex 6 in the form of
red crystals (Scheme 4). The zwitterionic iron complex
{Cp[P(OMe)3](CO)Fe
–
C(ꢀCMe2)NMeꢀCHPh}+-
[CF3SO3]− could be isolated by chromatography [1]. In
contrast, attempted chromatography of 6 only led to
decomposition of the complex. Therefore, 6 had to be
purified by recrystallization from diethyl ether.
Complex 6 is only poorly soluble in unpolar solvents
but readily soluble in polar solvents such as CH2Cl2. In
the solid state, 6 is stable at room temperature.
The mass spectrum of 6 established its composition
as a 1:1 complex of 4 and 5. The proposal of a
zwitterionic constitution of 6 as shown in Scheme 4
rather than of an 2-azetidin-1-ylidene complex structure
(7 in Scheme 4) is based on several spectroscopic
observations:
1. The w(CO) absorptions are at rather low wave num-
bers indicative of a considerable electron transfer
from the ligand to the (CO)5Cr fragment. The
w(CO) absorptions of a 2-azetidin-1-ylidene complex
like 7 are expected at higher wave numbers (vide
infra).
Scheme 4.
We recently observed that in the reaction of
[(CO)5MꢀCꢀC(H)R] (M=Cr, W; R=aryl) generated
by tautomerization of the alkyne complexes
[(CO)5M(HCꢁCR)] with N-aryl benzylideneamines two
types of complexes are formed: 2-azetidin-1-ylidene
complexes (2) and alkenyl(amino)carbene complexes (3)
(Scheme 2).
Mechanistic experiments established that the alkenyl-
(amino)carbene complexes 3 are not derived from the
2-azetidin-1-ylidene complexes 2 [8]. In contrast to N-
aryl imines, alkenyl(amino)carbene complexes were not
found among the products of the reaction of N-alkyl
imines with [(CO)5MꢀCꢀC(H)R] [7]. Zwitterionic inter-
mediates were not detected, neither in the reactions of
2. The UV–vis spectrum of 6 exhibits a pronounced
negative solvatochromic effect when nonpolar pen-
tane is replaced by polar DMF in accord with a
dipolar constitution. The UV–vis absorption at
lowest energy in pentane is at 568 nm, however, at
452 nm in DMF [Dw(pentane–DMF)=4520 cm−1].

H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
167
1
3. The H-NMR spectrum shows in addition to three
dichloromethane. The most prominent feature of the
structure of 6 is the almost perpendicular arrangement
of the vinylidene plane formed by the atoms Cr(1),
C(6), C(7), C(8), and C(9) and the imine plane [N(1),
C(6), C(10), C(11), C(12)]. The torsion angle C(7)–
C(6)–N(1)–C(10) is 87.6(3)°. Thus, the formation of an
extended p-system involving the planar coordinated
atoms C(6), C(7), and N(1) [sum of angles 360.0° at
C(6), 359.8° at C(7) and 360° at N(1)] is prevented. As
singlets for the inequivalent methyl groups and the
multiplet for the phenyl hydrogens a singlet at low
field (l 7.82) for the benzylidene hydrogen atom.
From the observation of only one set of methyl
resonances it follows that predominantly one isomer
with respect to the NꢀC bond is formed (ratio of
isomers \9:1).
4. The resonance of the chromium-bound carbon atom
of the cyclic ligand in 2-azetidin-1-ylidene(pentacar-
bonyl)chromium complexes is usually observed in
between l=285 and 300 ppm [7,8]. A peak in this
range in the 13C-NMR spectrum of 6 is absent. The
signals at lowest field are those of the CO ligands at
l=223.29 (trans) and 219.34 (cis).
The zwitterionic constitution of 6 was additionally
confirmed by the results of an X-ray structural analysis
(Fig. 1, Table 1). Suitable crystals for an X-ray analysis
,
a consequence, the N(1)–C(11) bond [1.286(3) A] is
short and corresponds to a typical NꢀC(sp2) double
bond [12]. Both N–C single bonds, N(1)–C(6)(sp2) and
N(1)–C(10)(sp3), are equal in length indicating that the
N(1)–C(6) bond is rather weak. The Cr(1)–C(6) dis-
,
tance [2.191(2) A] is longer than that usually observed
for chromium alkoxycarbene or aminocarbene com-
plexes
[13]
indicating
that
the
C(ꢀCMe2)–
NMeꢀC(Ph)H ligand exhibits only poor p-acceptor
properties. In accord with such a conclusion, a pro-
nounced trans influence is observed: the Cr–CO(trans)
were obtained by recrystallization of
6
from
,
bond [1.840(2) A] is significantly shorter than the aver-
,
age of the Cr–CO(cis) bonds [1.892 A]. To avoid
unfavorable steric interactions the C(ꢀCMe2)N plane
bisects the adjacent OC–Cr–CO angle [torsion angle
C(2)–Cr(1)–C(6)–C(7) 54.5(3)°].
In 1.1.2-trichloroethane complex 6 slowly formed the
2-azetidin-1-ylidene complex 7 (Scheme 4). At room
temperature the reaction was complete after about 1
week. The cyclization rate increased with increasing
polarity of the solvent and with increasing temperature.
Thus, in methanol or ethanol the reaction was already
complete within about 1 day and in butyl vinyl ether at
60°C after ca. 5 h. Chromatographic workup afforded
complex 7 in ca. 45% yield.
The cyclization is accompanied by a shift of the
w(CO) absorptions toward higher frequencies. Indica-
tive for the formation of the carbene (2-azetidin-1-yli-
dene) complex 7 is the resonance of the carbene carbon
1
atom at l=295.42 ppm. In general, the H- and 13C-
Fig. 1. Molecular structure of complex 6 in the crystal (hydrogen
atoms are omitted for clarity). Selected torsion angles (°) are: C(2)–
Cr(1)–C(6)–C(7) 54.5(3), N(1)–C(6)–C(7)–C(8) 2.1(4), C(7)–C(6)–
N(1)–C(10) 87.6(3), C(6)–N(1)–C(11)–C(12) 1.5(3).
NMR resonances of 7 are comparable to those of the
2-azetidin-1-ylidene chromium complexes reported ear-
lier [7,8].
Analogously to 5, the addition of 2-methyl 4,5-dihy-
drothiazole (8a) to a solution of 4 led to an immediate
color change from green to yellow. However, contrary
to the reaction of 4 with 5, the workup of the reaction
mixture afforded two complexes, the adduct 9a and the
substitution product 10a (Scheme 5). The adduct 9a
constituted the major product.
The w(CO) absorptions of 9a are shifted to smaller
wave numbers relative to those of 6 by ca. 2–5 cm−1
indicating slightly increased donor properties of 8a as
compared with those of 5. The 13C-NMR resonances of
structurally comparable atoms in 6 and 9a are observed
at similar positions. The ring hydrogen atoms are
diastereotopic giving rise to two well-separated groups
Scheme 5.

168
H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
N(1)–C(10) in 9a is 93.6(5)° as compared with 87.6(3)°
in 6. Within error limits the distances and angles within
the (CO)5Cr–C(ꢀCMe2)N fragment are equal in 6 and
9a (Table 1). The 4,5-dihydrothiazole ring adopts an
slight envelope conformation, the torsion angle S(1)–
C(13)–C(10)–N(1) is 7.7(7)°.
1
Complex 10a was characterized by IR and H-NMR
spectroscopy only. The spectroscopic data are com-
parable to those of the corresponding tungsten complex
(11) formed in the reaction of 8a with
[(CO)5WꢀCꢀC(Ph)H] (Scheme 6) which in solution is in
equilibrium with its alkyne tautomer [(CO)5W(Ph–
CꢁC–H)] [14].
Complex 11 was characterized fully including by an
X-ray structural analysis (Fig. 3). As expected, the
w(CO) absorptions of 10a and 11 are similar, however,
are at significantly higher wave numbers than those of
the adduct 9a (Dw=15–28 cm−1). From these shifts it
follows that the C(ꢀCMe2)(4,5-dihydrothiazole) ligand
transfers considerably more electron density to the
(CO)5M fragment than 4,5-dihydrothiazole which is in
accord with the zwitterionic structure of 9a.
Fig. 2. Molecular structure of complex 9a in the crystal (hydrogen
atoms are omitted for clarity). Selected torsion angles (°) are: C(2)–
Cr(1)–C(6)–C(7) 51.4(4), N(1)–C(6)–C(7)–C(8) 3.2(5), C(7)–C(6)–
N(1)–C(10)
93.6(5),
C(11)–N(1)–C(10)–C(13)
−7.5(8),
S(1)–C(13)–C(10)–N(1) 7.7(7).
Table 1
,
Selected bond lengths (A) and bond angles (°) for 6 and 9a
6
9a
In contrast to the 4,5-dihydrothiazole ring in 9a that
in 11 is nearly planar. All torsion angles of the ring are
smaller than 2°. The torsion angle S(1)–C(7)–C(6)–
N(1) is −1.6(13)° as compared with 7.7(7)° for the
corresponding angle in 9a. As expected from steric
considerations the plane of the ring bisects the adjacent
OC–W–CO angle [torsion angle C(4)–W(1)–N(1)–
C(8) 49.7(7)°]. Due to the large standard deviations in
11 a detailed discussion and comparison of the dis-
tances and angles in the 4,5-dihydrothiazole ring in 9a
and 11 is not feasible.
Bond lengths
Cr(1)–C(1)
Cr(1)–C(2)
Cr(1)–C(3)
Cr(1)–C(4)
Cr(1)–C(5)
Cr(1)–C(6)
C(6)–C(7)
C(6)–N(1)
C(7)–C(8)
C(7)–C(9)
N(1)–C(10)
N(1)–C(11)
1.905(2)
1.909(3)
1.878(2)
1.873(3)
1.840(2)
2.191(2)
1.335(3)
1.475(3)
1.513(3)
1.511(4)
1.478(4)
1.286(3)
1.878(4)
1.894(4)
1.887(4)
1.869(5)
1.847(5)
2.170(5)
1.349(6)
1.469(6)
1.488(8)
1.522(8)
1.460(6)
1.286(5)
Bond angles
Cr(1)–C(6)–C(7)
Cr(1)–C(6)–N(1)
N(1)–C(6)–C(7)
C(6)–C(7)–C(8)
C(6)–C(7)–C(9)
C(6)–N(1)–C(10)
C(6)–N(1)–C(11)
C(10)–N(1)–C(11)
N(1)–C(11)–C(12)
N(1)–C(11)–S(1)
134.8(2)
112.8(1)
112.4(2)
125.4(2)
122.3(2)
115.4(2)
126.0(2)
118.7(2)
130.0(2)
134.2(4)
113.3(3)
112.5(4)
122.6(5)
124.5(5)
119.4(3)
126.8(3)
113.8(4)
123.3(4)
115.6(3)
Fig. 3. Molecular structure of complex 11 in the crystal (hydrogen
,
atoms are omitted for clarity). Selected bond lengths (A) and bond
angles (°) in 11 are: W(1)–C(1) 2.056(10), W(1)–C(5) 1.992(8), W(1)–
N(1) 2.287(6), N(1)–C(6) 1.506(10), N(1)–C(8) 1.275(10), C(6)–C(7)
148.0(13) C(7)–S(1) 1.793(12), C(8)–S(1) 1.768(7), C(8)–C(9)
1.504(11); W(1)–N(1)–C(6) 116.7(5), W(1)–N(1)–C(8) 130.9(5),
C(6)–N(1)–C(8) 112.4(6), N(1)–C(6)–C(67) 111.2(8), C(6)–C(7)–
S(1) 108.5(7), C(7)–S(1)–C(8) 90.7(4), N(1)–C(8)–C(9) 125.8(7),
N(1)–C(8)–S(1) 117.2(6), C(9)–C(8)–S(1) 117.1(6); C(1)–W(1)–
N(1)–C(8) 137.9(7).
Scheme 6.
of signals for the NCH2 protons (Dl=0.59 ppm). The
SCH2 protons appear as a triplet only. Analogously to
6, the imine plane and the vinylidene plane are almost
perpendicular (Fig. 2). The torsion angle C(7)–C(6)–

H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
169
that of other alkylideneaminocarbene complexes. The
1H-NMR spectrum exhibits a doublet and a heptet
(intensity ratio 6:1) in addition to aromatic resonances
for eight protons. In accord with an alkylide-
neaminocarbene complex constitution a low-field reso-
nance at l=225.45 ppm for the carbene carbon atom
is observed in the 13C-NMR spectrum [15].
Our results demonstrate that imines rapidly add to
pentacarbonyl(vinylidene)metal complexes. However,
the addition is reversible as has already been shown
earlier [4]. Therefore, whether addition is succeeded by
formation of a 2-azetidin-1-ylidene complex or not
depends on the relative rates of cyclization and dis-
soziation of the imine (followed by decomposition of
the resulting vinylidene complex). Cyclization and dis-
soziation may be regarded as competing reaction path-
ways. The dissociation is facilitated by a weak C(a)–N
bond. Strongly electrophilic vinylidene complexes and
strongly nucleophilic imines give rise to the formation
of adducts stable with respect to dissociation. Then,
cyclization clearly dominates as is observed with com-
plex 6. The same is true for those imines employed in
the reactions with pentacarbonyl(vinylidene) complexes
reported earlier [7,8].
Cyclization requires among others rotation around
the C(a)–C(b) bond of the former vinylidene ligand,
the C(a)–N and the NꢀC bond. Therefore, steric fac-
tors in determining the rate of ring formation cannot
be discarded. However, the failure of 9a and 9b to
form 2-azetidin-1-ylidene complexes is very likely not
due to steric reasons since cationic {Cp[P(OMe)3](CO)-
FeꢀCꢀCMe2}+ has been reported to react with 2-
methyl 4,5-dihydrothiazole by cycloaddition to give
the corresponding 2-azetidin-1-ylidene complex [2]. In
contrast, the bonding of 8a to the vinylidene ligand in
neutral pentacarbonyl(vinylidene) complexes such as 4
is expected to be weaker than in {Cp[P(OMe)3](CO)-
FeꢀCꢀCMe2}+. Presumably, at room temperature or
at elevated temperatures dissociation of the imine from
the zwitterions 9a,b, 14, and 15 is faster than cycliza-
tion. The resulting vinylidene complex is labile and
quickly decomposes by elimination of the vinylidene
ligand and addition of the imine to form pentacar-
bonyl(imine)metal complexes.
Scheme 7.
Scheme 8.
Similarly to 8a, the reaction of 2-methyl 4,5-dihy-
drooxazole (8b) with 4 afforded a mixture of predomi-
nantly the adduct (9b) and small amounts of the
substitution product (10b) (Scheme 5). The IR and
NMR spectra of 9b and 10b are similar to those of 9a
and 10a, respectively, indicating similar structures.
In contrast to
6
and {Cp[P(OMe)3](CO)Fe–
C(ꢀCMe2)NMeꢀCHPh}+ (1) [1,2], when solution of
the adducts 9a and 9b were kept at room temperature
for days or were heated under reflux, no cyclization to
give 2-azetidin-1-ylidene complexes but rather substitu-
tion and formation of the 4,5-dihydrothiazole and 4,5-
dihydrooxazole complexes 10a and 10b were observed.
Adducts (14, 15) were also formed rapidly when
N-methyl 1-methoxyethylideneamine (13) was added
to solutions of 4 or of [(CO)5WꢀCꢀCPh2] (12) [4]
(Scheme 7).
The NMR spectra of 14 and 15 exhibit one set of
resonances for the methyl groups of the former imine
indicating that only one isomer (with respect to the
NꢀC bond) is formed. Again, the cyclization of the
ligand in 14 and 15 to give 2-azetidin-1-ylidene com-
plexes could not be induced.
In contrast, the products of the reactions of N–H
imines with vinylidene complexes deviate from those
of N-alkyl or N-aryl imines although the first reaction
step is presumably analogous. When xanthyli-
deneimine (16) was added to a solution of vinylidene
complex 4 neither an adduct nor an 2-azetidin-1-yli-
dene complex was obtained. Instead, the isopropyl(x-
anthylideneamino)carbene complex 17 was isolated as
the major product from the reaction mixture (Scheme
8).
The reactions of N-unsubstituted imines with pen-
tacarbonyl(vinylidene) complexes take
a
different
course although the initial step in the reaction of 4
with xanthylideneimine presumably also involves addi-
tion of imine to the a-carbon atom of the vinylidene
ligand. The adduct then rapidly rearranges to form 17
either by migration of hydrogen from nitrogen to the
b-carbon atom of the former vinylidene ligand or,
more likely, by a deprotonation/reprotonation se-
quence.
The structure of 17 was deduced from the IR and
NMR spectra. The w(CO) spectrum of 17 is similar to

170
H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
3. Experimental
3.1. General
3.3. Pentacarbonyl{2-methyl-1-[N-methyl-N-
benzylideneaminium]-1-propenyl}chromate (6)
At −45°C, 0.65 ml (5 mmol) of N-methyl benzylide-
neamine (5) is added to a solution of [(CO)5CrꢀCꢀ
CMe2] (4) freshly prepared as described above from 2.1
g (9.5 mmol) of [Cr(CO)6], 3.54 g (19 mmol) of C9K2
and 1 ml of isobutyryl chloride (9.5 mmol) and concen-
trated to a volume of ca. 20 ml. The solution immedi-
ately turns red. After stirring the solution for 15 min, it
is allowed to warm to room temperature. Stirring is
continued for 1 h, the volume of the solution reduced in
vacuo to 10 and 100 ml of pentane is added. A red
precipitate forms. The suspension is kept at −20°C for
24 h and then fritted at room temperature (r.t.) through
a 2-cm layer of neutral alumina. The red solid on top of
the Al2O3 layer is washed with 100 ml of pentane and
subsequently dissolved in 150 ml of CH2Cl2. The sol-
vent is removed in vacuo and the residue dissolved in
20 ml of diethyl ether. The solution is kept at −20°C
for 24 h and then filtered at −18°C over a 6-cm layer
of sand–glass wool–sand. The layer is eluted with 20
ml of precooled diethyl ether. The solvent is removed in
vacuo to yield 6 as a red solid. Yield: 790 mg (23%
relative to [Cr(CO)6]). M.p. 73°C. IR (CH2C12) w(CO)
All operations were performed under an inert atmo-
sphere (nitrogen or argon) by using standard Schlenk
techniques. Solvents were dried by refluxing over CaH2
(CH2Cl2, pentane) or sodium–benzophenone ketyl
(Et2O) and were freshly distilled under argon prior to
use. The silica gel used for chromatography (Baker,
silica gel for flash chromatography) was nitrogen satu-
rated. The yields refer to analytically pure compounds
1
and were not optimized. Instrumentation: H- and 13C-
NMR spectra were recorded with a Bruker AC 250 or
1
a Bruker WM 250 spectrometer. H-NMR resonances
are reported relative to Me4Si, 13C-NMR resonances
relative to the residual solvent peaks of acetone-d6.
Unless mentioned specifically IR and NMR spectra are
taken at room temperature (r.t.). IR: Biorad FTS 60
spectrophotometer; MS: Finnigan MAT 312 (EI, 70
eV). Elemental analyses: Heraeus CHN-O-RAPID. The
complex 12 [4] and the imine 13 [16] were prepared
according to literature procedures. All other imines
were commercially available and were used without
further purification.
1
(cm−l): 2044 m, 1960 m, 1917 vs, 1910 vs. H-NMR
3.2. Generation of
pentacarbonyl[dimethyl6inylidene]chromium (4)
(CDC13): l 1.48 (s, 3H, CCH3), 2.02 (s, 3H, CCH3),
3.85 (s, 3H, NCH3), 7.5–7.7 (m, 3H, Ph), 7.82 (s, 1H,
NꢀCH), 8.01–8.04 (pseudo-d, J=7.5 Hz, 2H, Ph).
13C-NMR (CDC13, for the numbering scheme see Fig.
1): l 19.09 [C(8)], 24.14 [C(9)], 50.68 [C(10)], 126.54,
128.70, 129.04, 129.14, 132.62, 133.07 [Ph], 135.13,
153.90 [C(6), C(7)], 169.97 [C(11)], 219.34 [cis-CO],
223.29 [trans-CO]. UV–vis (nm) [solvent] umax (log m):
[pentane] 568 (2.996), [DMF] 452 (3.045). MS m/z (%):
365 (5) [M+], 309 (2) [M+−2CO], 281 (4) [M+−
3CO], 253 (10) [M+−4CO], 246 (3) [M+−N-methyl
benzylideneamine], 225 (44) [M+−5CO]. Anal. Found:
C, 56.38; H, 4.27; N, 4.03. C17H15CrNO5 (365.17).
Calc.: C, 55.89; H, 4.14; N, 3.83%.
A suspension of 2.54 g (13.6 mmol) of C9K2 in 50 ml
of THF is charged at −78°C with 1.5 g (6.8 mmol) of
chromium hexacarbonyl and stirred for 15 min. The
suspension is warmed to 0°C. Within ca. 10 min the
color changes from bronze to green and the evolution
of a gas is detectable. After a total of ca. 90 min the
formation of pentacarbonylchromate is complete. The
green suspension is cooled to −78°C and 0.72 ml (6.8
mmol) of isobutyryl chloride is added. The color imme-
diately changes to olive-green [IR (THF): w(CO)
(cm−l): 2031 s, 1892 vs]. After 5 min the temperature of
the suspension is allowed to rise to 0°C. The solvent is
removed in vacuo at 0°C and the black–green residue is
treated with 75 ml of CH2Cl2. The suspension is cooled
to −78°C and, after addition of 0.54 ml (3.4 mmol) of
trifluoroacetic acid, stirred for 1 h. 75 ml of pentane
precooled to −78°C is added. The reaction mixture is
fritted over a 6-cm layer of Al2O3 at −45°C. The
stationary phase is eluted with cold pentane–CH2Cl2
(1:2) until the dark-green band is eluted completely. At
−45°C, the solvent of the combined eluates [4: IR
(CH2Cl2): w(CO) (cm−l): 2082 s, 2025 sh, 1998 vs, 1971
vs] is reduced in vacuo to a volume of ca. 20 ml. These
solutions are employed for the subsequent reactions
with imines. The yields of [(CO)5CrꢀCꢀCMe2] (4) are
between 60 and 65% (determined by trapping experi-
ments with bis-N,N-diethylaminopropyne).
3.4. Pentacarbonyl[(N-methyl-3-phenyl-4,4-
dimethylazetidin-2-ylidene]chromium (7)
A solution of 240 mg (6.6 mmol) of 6 in 12 ml of
butyl vinyl ether is heated at 50°C for 3 h. The solvent
is removed in vacuo and the brown residue is chro-
matographed at −20°C on flash silica with pentane–
CH2Cl2 mixtures (ratio decreasing from 1:0 to 9:1). The
first yellow band is collected. Removal of the solvent in
vacuo affords complex 7 as a yellow solid. Yield: 110
mg (45% relative to 6). M.p. 33°C. IR (pentane) w(CO)
(cm−l): 2056 m, 1969 w, 1942 vs, 1925 s. 1H-NMR
(CD3COCD3): l 0.84 and 1.46 (2 s, 3 H each, CCH3),
3.52 (s, 3H, NCH3), 3.53 (s, 1H, CCH), 7.19–7.50 (m,
5H, Ph). 13C-NMR (CDC13): l 19.44, 24.16 [CCH3],

H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
171
36.62 [NCH3], 58.9 [CMe2], 84.38 [C(H)Ph], 126.56,
3.6. Pentacarbonyl[4,5-dihydro-2-methylthiazole-
N]tungsten (11)
128.72, 129.05, 133.49 [Ph], 217.93 [cis-CO], 222.61
[trans-CO], 295.42 [C(carbene)]. MS m/z (%): 365 (12)
[M+], 309 (7) [M+−2CO], 281 (8) [M+−3CO], 253
(21) [M+−4CO], 225 (100) [M+−5CO].
At −30°C 0.36 ml (0.23 mmol) of 2-methyl 4,5-dihy-
drothiazole (8a) is added to the highly concentrated
solution of the alkyne complex [(CO)5W(H–CꢁC–Ph)].
The solution is stirred and gradually warmed to r.t. The
reaction is followed by IR spectroscopy. When the
w(CO) absorptions due to the alkyne complexes had
disappeared the solvent is removed in vacuo and the
reaction products are chromatographed at −30°C on
silica gel. First, [Cr(CO)6] and imine are eluted with
pentane. Next, with pentane–CH2Cl2 (10/3) a yellow
band containing the 2,4-dihydrothiazole complex is
eluted. Removal of the solvent in vacuo and recrystal-
lization from pentane–CH2Cl2 give yellow 11. Alterna-
tively, complex 11 is also obtained from the reaction of
[(CO)5W(THF)] with 8a. Yield 0.59 g (30% relative to
[Cr(CO)6]), M.p. 116°C. IR (pentane): w(CO) (cm−l):
3.5. Pentacarbonyl[1-(4,5-dihydro-2-methylthiazolium)-
2-methyl-1-propenyl]chromate (9a) and pentacarbonyl-
[4,5-dihydro-2-methylthiazole-N]chromium (10a)
When a green solution of [(CO)5CrꢀCꢀCMe2] (see
Section 3.2) is charged at −45°C with 0.36 ml (0.23
mmol) of 2-methyl 4,5-dihydrothiazole (8a) the color
immediately turns yellow. After stirring the solution for
15 min, it is allowed to warm to r.t. Stirring is contin-
ued for 1 h, the volume of the solution reduced in
vacuo to 5 and 50 ml of pentane is added. A yellow
precipitate forms. The suspension is kept at −20°C for
24 h and then fritted at r.t. through a 2-cm layer of
neutral alumina. The Al2O3 layer is eluted with 50 ml of
pentane. The volume of the combined pentane fractions
is reduced to ca. 7 ml. The solution is then chro-
matographed at −20°C on flash silica with pentane–
CH2Cl2 mixtures (ratio decreasing from 1:0 to 5:2). The
first yellow band contains [Cr(CO)6], the second one
complex 9a. Removal of the solvent of the second
fraction affords 80 mg (7.5% relative to [Cr(CO)6]) of
10a. The residue on top of the Al2O3 layer is dissolved
in 80 ml of CH2Cl2. The solvent is removed in vacuo
and the residue dissolved in 8 ml of diethyl ether. The
solution is kept at −20°C for 24 h and then filtered at
−18°C over a 6-cm layer of sand/glass wool/sand. The
layer is eluted with 8 ml of precooled diethyl ether. The
solvent is removed in vacuo to yield 0.56 g (11%
relative to [Cr(CO)6]) of 9a as a yellow solid. M.p.
108°C. IR (CH2C12): w(CO) (cm−l): 2042 m, 1958 w,
1
2070 w, 1932 vs, 1921 m. H-NMR (CDCl3): l 2.45 (s,
3
3H, CH3), 3.44 (t, J=8.6 Hz, 2H, SCH2), 4.42 (dt,
J=8.6 and 1.4 Hz, 2H, NCH2). 13C-NMR
(CD3COCD3): l 23.97 [CH3], 32.97, 76.01, 181.67
[NꢀC], 198.89 [JWC=130.5 Hz, cis-CO], 202.67 [trans-
CO]. MS: m/z (%). Anal. Found: C, 25.75; H, 1.80; N,
2.78. C9H7NO5SW (425.1) Calc.: C, 25.43; H, 1.66; N,
3.30%.
3.7. Pentacarbonyl[1-(4,5-dihydro-2-methyloxazolium)-
2-methyl-1-propenyl]chromate (9b) and pentacarbonyl-
[4,5-dihydro-2-methyloxazole-N]chromium (10b)
The synthesis from 2.80 g (12.8 mmol) of [Cr(CO)6],
4.76 g (25.5 mmol) of C9K2, 1.3 ml of isobutyryl
chloride (12.8 mmol), and 0.54 ml (6.38 mmol) of
2-methyl 4,5-dihydrooxazole (8b) and the purification
of the products are carried out analogously to 3.2 and
3.6.
1
1911 vs, 1904 vs. H-NMR (CD3COCD3): l 1.54 and
1.92 (2 s, 3 H each, CꢀCCH3), 2.43 (s, 3H, NꢀCCH3),
3.81 (t, 3J=8.8 Hz, 2H, SCH2), 4.35 (dt, 2J=12.8,
2
3
3J=8.8 Hz, 1H, NCH2), 4.94 (dt, J=12.8, J=8.8
Hz, 1H, NCH2). 13C-NMR (CD3COCD3, for the num-
bering scheme see Fig. 2): l 17.62, 20.17 [C(8), C(9)],
25.87 [C(13)], 28.73 [C(11)], 61.85 [C(12)], 139.14,
161.23 [C(6), C(7)], 173.85 [C(10)], 221.35 [cis-CO],
224.44 [trans-CO]. MS m/z (%): 347 (4) [M+], 319 (1)
[M+−2CO], 291 (1) [M+−2CO], 263 (1) [M+−
3CO], 246 (6) [M+−2-methyl 4,5-dihydrothiazole], 235
(49) [M+−4CO], 218 (7) [M+−2-methyl 4,5-dihy-
drothiazole–CO], 207 (30) [M+−5CO]. Anal. Found:
C, 44.49; H, 3.81; N, 4.33. C13H13CrNO5S (347.30).
Calc.: C, 44.96; H, 3.77; N, 4.03%.
9b: Yellow solid. Yield: 880mg (21% relative to
[Cr(CO)6]). M.p. 108°C. IR (CH2C12) w(CO) (cm−l):
2044 w, 1959 w, 1911 vs, 1900 vs. 1H-NMR
(CD3COCD3): l 1.59 and 1.91 (2 s, 3 H each,
CꢀCCH3), 2.31 (s, 3H, NꢀCCH3), 4.07 (dt, 2J=3J=8.7
2
Hz, 1H, NCH2), 4.71 (dt, J=3J=8.7 Hz, 1H, NCH2),
5.05 (t, 3J=8.7 Hz, 2H, OCH2). 13C-NMR
(CD3COCD3, for the numbering scheme see Fig. 2): l
12.61, 19.99 [C(8), C(9)], 26.13 [C(13)], 52.25 [C(12)],
70.28 [C(11)], 141.57, 154.53 [C(6), C(7)], 167.54
[C(10)], 221.81[cis-CO], 224.54 [trans-CO]. MS m/z (%):
331 (4) [M+], 303 (1) [M+−CO], 275 (1) [M+−2CO],
246 (8) [M+−2-methyl 4,5-dihydrooxazole], 218 (9)
[M+−2-methyl 4,5-dihydrooxazole–CO], 191 (25)
[M+−5CO]. Anal. Found: C, 47.20; H, 4.09; N, 4.43.
C13H13CrNO6 (331.21). Calc.: C, 47.14; H, 3.96; N,
4.23%.
10a: Yield: 200 mg (7.5% relative to [Cr(CO)6]). M.p.
67°C. IR (pentane): w(CO) (cm−l): 2067 w, 1934 vs,
1
1919 s. H-NMR (CD3COCD3): l 2.46 (s, 3H, CH3),
3
3
3.41 (t, J=6.9 Hz, 2H, SCH2), 4.37 (t, J=5.7 Hz,
2H, NCH2).

172
H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
10b: Yellow solid. Yield: 120 mg (3.4% relative to
148.79 [Ph], 143.57, 163.67 [WC, CPh2], 165.63 [NꢀC],
200.86 [cis-CO], 206.53 [trans-CO]. MS m/z (%): 589
(24) [M+], 561 (19) [M+−CO], 533 (33) [M+−2CO],
505 (100) [M+−3CO], 418 (23) [M+−3CO–methyl
methoxyethylideneamine], 266 (92) [M+−W(CO)5],
193 (16.34) [M+−5CO]. Anal. Found: C, 46.38; H,
3.49; N, 2.09. C23H19NO6W (589.25) Calc.: C, 46.92; H,
3.25; N, 2.37%.
[Cr(CO)6]). M.p. 62°C. IR (CH2C12): w(CO) (cm−l):
1
2062 w, 1935 vs, 1917 s. H-NMR (CDC13): l 2.15 (s,
3H, CH3), 3.79 (t, 3J=7.9 Hz, 2H, NCH2), 4.24 (t,
3J=8.1 Hz, 2H, OCH2). MS m/z (%): 277 (68) [M+],
249 (3) [M+−CO], 221 (1) [M+−2CO], 193 (2) [M+
−3CO], 165 (22) [M+−4CO], 137 (100) [M+−5CO].
3.8. Pentacarbonyl{2-methyl-1-[N-methyl-N-
(1-methoxy)ethylideneaminium]-1-propenyl}chromate
(14)
3.10. Pentacarbonyl[(isopropyl(N-xanthylideneamino)-
carbene]chromium (17)
The reaction of 3.20 g (14.6 mmol) of [Cr(CO)6], 5.44
g (29.2 mmol) of C9K2, and 1.5 ml of isobutyryl
chloride (14.6 mmol) with 0.67 ml (7.3 mmol) of N-
methyl 1-methoxyethylideneamine (13) and the purifica-
tion of the products are carried out analogously to 3.2
and 3.6. Complex 14 is obtained in form of a yellow
solid. Yield: 0.67 g (14% relative to [Cr(CO)6]). M.p.:
88°C. IR (CH2C12): w(CO) (cm−l): 2039 w, 1954 w,
The reaction of 1.65 g (7.5 mmol) of [Cr(CO)6], 2.8 g
(15 mmol) of C9K2, and 0.8 ml of isobutyryl chloride
(7.5 mmol) with 0.74 ml (4.9 mmol) of xanthylide-
neamine (16) is carried out analogously to 3.2. The
color of the suspension immediately changes from dark
green to red. After stirring for 15 min, the solvent is
removed in vacuo. The oily residue is chromatographed
at −20°C on flash silica with pentane–CH2Cl2 mix-
tures (ratio decreasing from 1:0 to 7:1). First, a green
fraction is eluted. The second fraction (orange) is col-
lected containing 17. Removal of the solvent in vacuo
at r.t. affords complex 17 as an orange solid. Yield: 560
mg (17% relative to [Cr(CO)6]). M.p.: 113°C. IR
(CH2C12): w(CO) (cm−l): 2051 m, 1967 w, 1925 vs.
1
1909 vs, 1892 vs. H-NMR (CD3COCD3): l 1.43 and
1.83 (2 s, 3 H each, CꢀC–CH3), 2.67 (s, 3H,
C(OCH3)CH3), 3.47 (s, 3H, NCH3), 4.17 (s, 3H,
OCH3). 13C-NMR (CD3COCD3):
l 13.62, 19.71
[C(CH3)2], 28.83 [C(OCH3)CH3], 41.00 [NCH3], 59.36
[OCH3], 134.26, 163.96 [CrC, CMe2], 165.36 [NꢀC],
222.32 [cis-CO], 225.27 [trans-CO]. MS m/z (%): 333
(3.3) [M+], 305 (0.3) [M+−CO], 2.77 (0.3) [M+−
2CO], 246 (8.54) [M+−methyl methoxyethylide-
neamine], 221 (2.44) [M+−4CO], 193 (16.34)
[M+−5CO]. Anal. Found: C, 44.75; H, 4.43; N, 4.16.
C13H15CrNO6 (333.26) Calc.: C, 46.85; H, 4.54; N,
4.20%.
3
1H-NMR (CDC13): l 1.24 (d, J=6.7 Hz, 6H, CH3),
3
3.46 (hept, J=6.7 Hz, 1H, CHMe2), 7.3–7.4 (m, 8H,
Ph). 13C-NMR (CDC13):
l
20.96 [CH3], 49.36
[CMe2H], 111.58, 117.92, 125.00, 125.60, 133.29 [Ph],
152.92 [NꢀC], 219.34 [cis-CO], 223.29 [trans-CO],
225.45 [C(carbene)]. MS m/z (%): 441 (6) [M+], 413
(2.5) [M+−CO], 385 (1) [M+−2CO], 357 (2) [M+−
3CO], 329 (13) [M+−4CO], 301 (49) [M+−5CO].
Anal. Found: C, 59.53; H, 3.52; N, 3.59. C22H14CrNO6
(440.02). Calc.: C, 60.00; H, 3.21; N, 3.18%.
3.9. Pentacarbonyl{1-[N-methyl-N-(1-methoxy)-
ethylideneaminium]-2,2-diphenylethenyl}tungsten (15)
A green solution of 0.25 g (0.5 mmol) of complex 12
in 4 ml of CH2Cl2 is charged at −20°C with 0.043 g
(0.5 mmol) of N-methyl 1-methoxyethylideneamine (13)
in 2 ml of CH2Cl2. The solution is stirred and allowed
to warm to r.t. The progress of the reaction is followed
by IR spectroscopy. After ca. 4–5 h the reaction is
complete. Then, 150 ml of precooled pentane is added
and a yellow precipitate formed. The suspension is
fritted over Na2SO4 and the solid washed 3× with 50
ml of pentane each. The adduct on top of the Na2SO4
layer is dissolved in CH2Cl2. The solvent is removed in
vacuo to give 15 as a slightly yellow powder. Yield: 0.18
g (61% relative to 12). M.p. (dec.) 28°C. IR (CH2C12):
w(CO) (cm−l): 2053 m, 1961 w, 1910 vs, 1900 sh, 1875
sh. 1H-NMR (CD3COCD3, −50°C): l 2.46 (s, 3H,
CCH3), 3.28 (s, 3H, NCH3), 4.36 (s, 3H, OCH3), 7.1–
7.33 (m, 10H, Ph). 13C-NMR (CD3COCD3, −50°C): l
13.22 [CCH3], 41.17 [NCH3], 59.50 [OCH3], 126.78,
126.84, 127.79, 128.53, 128.74, 130.13 [Ph], 147.26,
3.11. X-ray structural analyses of 6, 9a and 11
6: C17H15CrNO5, molecular mass (365.3), crystal size
0.35×0.35×0.35 mm3 (obtained by recrystallization
from diethyl ether); crystal system triclinic, space group
(
,
P1, a=8.622(3), b=9.319(3), c=12.225(4) A, h=
3
,
89.49(2), i=88.39(3), k=62.76(2)°; V=872.6(5) A ,
Z=2, Dcalc=1.390 g cm−3, u(Mo–Ka)=0.71073 A,
,
F(000) 376; Wyckoff scan, 2[ range 4.0–54.0°, scan
rate variabel 4.0–30.0° min−1 in ꢀ; 4035 independent
reflections, 3282 reflection with F\4|(F); 217 refined
parameters; R=0.0377, wR=0.0443. Largest differ-
−3
,
ence peak (hole): +0.33 e A
(−0.30 e A−3).
,
9a: C13H13CrNO5S, molecular mass (347.3), crystal
size 0.25×0.25×0.25 mm3 (obtained by recrystalliza-
tion from diethyl ether); crystal system triclinic, space
(
,
group P1, a=8.936(3), b=9.470(3), c=9.888(3) A,
h=89.82(2), i=71.76(2), k=75.32(1)°; V=767.3(4)
3
A , Z=2, Dcalc=1.503 g cm−3, u(Mo–Ka)=0.71073
,

H. Fischer et al. / Journal of Organometallic Chemistry 620 (2001) 165–173
173
,
A, F(000) 356; Wyckoff scan, 2[ range 4.0–54.0°,
scan rate variabel 4.0–30.0° min−1 in ꢀ; 3352 inde-
pendent reflections, 2527 reflection with F\4|(F);
Acknowledgements
Support of these investigations by the Deutscher
Akademischer Austauschdienst (grant for M.M. Abd-
Elzaher), the Volkswagen-Stiftung and the Fonds der
Chemischen Industrie is gratefully acknowledged.
190 refined parameters; R=0.0561, wR=0.0611.
−3
,
Largest difference peak (hole): +0.87 e A
(−0.53
e A−3).
,
11: C9H7NO5SW, molecular mass (425.1), crystal
size 0.28×0.28×0.28 mm3 (obtained by recrystalliza-
tion from pentane); crystal system monoclinic, space
group P21/c, a=9.648(7), b=11.436(8), c=12.155(12)
References
3
,
,
A, i=106.53(9); V=1285.6(17) A , Z=4, Dcalc
=
2.196 g cm−3, F(000) 792; adaptive ꢀ scan, [ range
2.2–26.99°, scan rate variabel 4.0–30.0° min−1; 3352
independent reflections, 2084 reflection with |\2|(I);
[1] A.G.M. Barrett, J. Mortier, M. Sabat, M.A. Sturgess,
Organometallics 7 (1988) 2553.
[2] (a) A.G.M. Barrett, M.A. Sturgess, Tetrahedron Lett. 27 (1986)
3811. (b) A.G.M. Barrett, M.A. Sturgess, J. Org. Chem. 52 (1987)
3940.
[3] M.R. Terry, L.A. Mercando, C. Kelley, G.L. Geoffroy, P.
Nombel, N. Lugan, R. Mathieu, R.L. Ostrander, B.E. Owens-
Waltermire, A.L. Rheingold, Organometallics 13 (1994) 843.
[4] H. Fischer, A. Schlageter, W. Bidell, A. Fru¨h, Organometallics 10
(1991) 389.
[5] K. Weiss, E.O. Fischer, J. Mu¨ller, J. Chem. Ber. 107 (1974) 3548.
[6] A.G.M. Barrett, C.P. Brock, M.A. Sturgess, Organometallics 4
(1985) 1903.
[7] M.M. Abd-Elzaher, H. Fischer, J. Organomet. Chem. 588 (1999)
235.
[8] M.M. Abd-Elzaher, T. Froneck, G. Roth, V. Gvozdev, H. Fischer,
J. Organomet. Chem. 599 (2000) 288.
[9] H. Fischer, F. Leroux, G. Roth, R. Stumpf, Organometallics 15
(1996) 3723.
[10] M.A. Schwindt, T. Lejon, L.S. Hegedus, Organometallics 9 (1990)
2814.
[11] H. Fischer, C.C. Karl, G. Roth, Chem. Ber. 129 (1996) 615.
[12] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen,
R. Taylor, J. Chem. Soc. Perkin Trans. II (1987) S1.
[13] U. Schubert, in: K.H. Do¨tz, H. Fischer, P. Hofmann, F.R. Kreissl,
U. Schubert, K. Weiss (Eds.), Transition Metal Carbene Com-
plexes, Verlag Chemie, Weinheim, 1983, p. 73.
[14] H. Fischer, H.-P. Volkland, A. Fru¨h, R. Stumpf, J. Organomet.
Chem. 491 (1995) 267.
[15] For the IR and NMR spectra of other alkylideneaminocarbene
complexes of chromium and tungsten see: (a) H. Fischer, S.
Zeuner, K. Ackermann, U. Schubert, J. Organomet. Chem. 263
(1984) 201. (b) H. Fischer, R. Ma¨rkl, Chem. Ber. 118 (1985) 3683.
(c) F. Seitz, H. Fischer, J. Riede, J. Organomet. Chem. 287 (1985)
87. (d) C.K. Murray, B.P. Warner, V. Dragisich, W.D. Wulff,
Organometallics 9 (1990) 3142.
154 refined parameters; R=0.0344, wR2=0.0782.
−3
,
Largest difference peak (hole): +0.998 e A
(−
1.245 e A−3).
,
The measurements were performed at −44°C (6),
−34°C (9a), −35°C (11) with a crystal mounted in a
glass capillary on
a Siemens P4 diffractometer
(graphite monochromator, Mo–Ka radiation, u=
,
0.71073 A).
The structures were solved by Patterson methods (6,
9a) or by direct methods (11) using the SHELXTL PLUS
(VMS) program package. The positions of the hydro-
gen atoms were calculated by assuming ideal geometry
,
(dC–H=0.96 A), and their coordinates were refined
together with those of the attached C atoms as ‘riding
model’. The positions of all other atoms were refined
anisotropically by the full-matrix least-squares method.
4. Supplementary material
Crystallographic data for the structural analysis
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC no. 144590 for com-
pound 6, CCDC no. 144591 for compound 9a and
CCDC no. 144589 for compound 11. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 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).
[16] H. Bredereck, F. Effenberger, E. Hensllit, Chem. Ber. 98 (1965)
2734.
.