Synthesis and structural characterization of molybdenum complexes with linked cycloheptatrienyl-phosphane ligands

Article abstract of DOI:10.1016/S0022-328X(03)00318-8

The synthesis of P-functionalized cycloheptatrienyl chelate complexes incorporating the linked cycloheptatrienyl-phosphane ligand [2-(diisopropylphosphanyl)phenyl]cycloheptatrienyl, o-ⁱPr₂P-C₆H₄-C₇ H₆, is described. The ligand precursor [2-(cyclohepta-2,4,6-trienyl)phenyl]diisopropylphosphane (2b) can be obtained by addition of lithiated 2-BrC₆H₄ PⁱPr₂ (1b) to the tropylium cation C₇H₇⁺. On reaction with Mo(CO)₆, the P-functionalized cycloheptatriene 2b acts as an eight-electron ligand to afford the cycloheptatriene-phosphane chelate complex [(o-ⁱPr₂P-C₆H₄ -η⁶-C₇H₇)Mo(CO)₂(P-Mo)] (3b) as a single, chiral regioisomer, which undergoes clean hydride abstraction on treatment with (Ph₃C)BF₄. The resulting cationic complex 4b reacts with sodium bromide to yield the 'chiral-at-metal' complex [(o-ⁱPr₂ P-C₆H₄-η⁷-C₇ H₆)Mo(CO)Br(P - Mo)] (5b). This 18-electron complex can be oxidized with 0.5 equivalent Br₂ to give paramagnetic [(o-ⁱPr₂P-C₆H₄ -η⁷-C₇H₆)MoBr₂ (P-Mo)] (6b). 6b is a versatile starting material for the preparation of various cycloheptatrienyl-molybdenum complexes, which is exemplified by the isolation of the dialkyl complex [(o-ⁱPr₂ P-C₆H₄-;η⁷-C₇ H₆)Mo(CH₂SiMe₃)₂(P-Mo)] (7b) upon reaction of 6b with Me₃SiCH₂MgCl. In addition, the X-ray crystal structures of 3b, 4b, 5b, 6b, and 7b are reported.

Full text of DOI:10.1016/S0022-328X(03)00318-8

Journal of Organometallic Chemistry 677 (2003) 1ꢀ9
/
www.elsevier.com/locate/jorganchem
Synthesis and structural characterization of molybdenum complexes
with linked cycloheptatrienylꢀphosphane ligands
/
Matthias Tamm a,*, Bernd Dreßel a, Kim Baum b, Thomas Lugger b, Tania Pape b
¨
a Anorganisch-Chemisches Institut, Lehrstuhl fur Anorganische Chemie, Technische Universitat Munchen, Lichtenbergstrasse 4, D-85747 Garching,
¨
¨
¨
Germany
b Institut fur Anorganische und Analytische Chemie, Westfalische Wilhelms-Universitat, Wilhelm-Klemm-Str. 8, D-48149 Munster, Germany
¨
¨
¨
Received 7 January 2003; received in revised form 11 March 2003; accepted 21 March 2003
Abstract
The synthesis of P-functionalized cycloheptatrienyl chelate complexes incorporating the linked cycloheptatrienylꢀ
/
phosphane
ligand [2-(diisopropylphosphanyl)phenyl]cycloheptatrienyl, o-iPr2PÃ
/
C6H4Ã
/
C7H6, is described. The ligand precursor [2-(cyclohepta-
2,4,6-trienyl)phenyl]diisopropylphosphane (2b) can be obtained by addition of lithiated 2-BrC6H4Pi Pr2 (1b) to the tropylium cation
C7H7ꢁ. On reaction with Mo(CO)6, the P-functionalized cycloheptatriene 2b acts as an eight-electron ligand to afford the
cycloheptatrieneꢀ
which undergoes clean hydride abstraction on treatment with (Ph3C)BF4. The resulting cationic complex 4b reacts with sodium
bromide to yield the ‘chiral-at-metal’ complex [(o-i Pr2PÃ h7-C7H6)Mo(CO)Br(P Ã
C6H4Ã Mo)] (5b). This 18-electron complex can be
oxidized with 0.5 equivalent Br2 to give paramagnetic [(o-i Pr2PÃ h7-C7H6)MoBr2(P Ã
C6H4Ã Mo)] (6b). 6b is a versatile starting
material for the preparation of various cycloheptatrienylꢀmolybdenum complexes, which is exemplified by the isolation of the
dialkyl complex [(o-iPr2PÃ h7-C7H6)Mo(CH2SiMe3)2(P Ã
C6H4Ã Mo)] (7b) upon reaction of 6b with Me3SiCH2MgCl. In addition,
/
phosphane chelate complex [(o-i Pr2PÃ
/
C6H4Ã
/
h6-C7H7)Mo(CO)2(P Ã
/Mo)] (3b) as a single, chiral regioisomer,
/
/
/
/
/
/
/
/
/
/
the X-ray crystal structures of 3b, 4b, 5b, 6b, and 7b are reported.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Cycloheptatrienyl complexes; Ligand functionalization; Molybdenum; Alkyl complexes
1. Introduction
cyclopentadienyl complexes are nowadays ubiquitous
and indispensable in research areas such as homoge-
neous catalysis [4], organic synthesis [5] and materials
science [6]. In contrast, h-cycloheptatrienyl transition
metal complexes, (h-C7R7)M, have been much less
thoroughly studied, and with a few exceptions, the use
of cycloheptatrienyl ligands had been confined to the
parent C7H7 system [7]. Only recently, we have been able
to report on the syntheses of the first complexes with the
heptamethylcycloheptatrienyl (CHT*) ligand [8] and of
complexes derived from sterically demanding cyclohep-
h-Cyclopentadienyl complexes, (h-C5R5)M, as well as
h-arene complexes, (h-C6R6)M, are among the most
important classes of compounds in organotransition
metal chemistry [1]. In particular, the widespread use of
cyclopentadienes as organometallic ligands is due to the
large number of ring-substituted derivatives, which have
been synthesized since the serendipitous synthesis and
discovery of ferrocene [2]. Successive replacement of
hydrogen atoms by alkyl or aryl substituents alters the
steric and electronic properties of the Cp ring and gives
rise to increased steric bulk, solubility and stability of
the resulting complexes [3]. Numerous routes to ring-
substituted Cp derivatives are known to date, and
* Corresponding author. Tel.: ꢁ
13473.
E-mail address: matthias.tamm@ch.tum.de (M. Tamm).
/
49-89-289-13080; fax: ꢁ49-89-289-
/
Fig. 1. Cycloheptatrienyl complexes bearing pendant P-, N-, S-, and
O-donors.
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00318-8

2
M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ9
/
tatrienyl ligands of the type (1,3,5-C7H4R3)BF4
(Rꢂt
Bu, SiMe3) [9].
sphanyl)phenyllithium to the tropylium cation C7H7ꢁ
[18] furnished 2b in large quantities. As shown for 2a,
/
Another concept, which has been extremely success-
ful, in particular in cyclopentadienyl chemistry, is ligand
functionalization, whereby an additional coordinating
site is linked to the periphery of the five-membered ring
via a suitable bridging moiety. This prospering area has
produced a large number of novel cyclopentadienyl
ligands bearing pendant N- [10,11], O- [12], P-, As-,
and S-donor groups [13]. If properly designed, these
ligands can coordinate to a transition metal center in a
chelating h5:h1-fashion, and several of these complexes
have played a key role in homogeneous catalysis as so-
called constraint-geometry catalyst systems [4]. In cyclo-
heptatrienyl transition metal chemistry on the other
hand, ligand functionalization is an almost unknown
concept, and we have recently started to apply this
concept to the preparation of cycloheptatrienyl com-
plexes bearing pendant phenolate [14], thioether, amine
[15] and phosphane donor groups (Fig. 1) [16,17].
the cycloheptatrieneꢀphosphane ligand 2b can be used
/
as a multi-dentate ligand, and the reaction of 2b with
Mo(CO)6 in refluxing methylcyclohexane leads to the
substitution of four carbonyl ligands and the formation
of cycloheptatrieneꢀ
/
phosphane complexes of the type
Mo)]. In com-
[(o-iPr2PC6H4Ãh6-C7H7)Mo(CO)2(P Ã
/
/
parison to the reaction of cycloheptatriene, C7H8, with
Mo(CO)6, the reaction described here proceeds much
faster, and no sublimation of hexacarbonyl out of the
flask into the reflux condenser was observed indicating
that the phosphane group adds rapidly to the molybde-
num center to form an involatile material followed by
coordination of the cycloheptatriene moiety. If the
reaction mixture is kept at 100 8C overnight, complex
3b crystallizes as the only detectable regioisomer from
the solution upon cooling with dry ice. The formation of
3b resulted from thermal rearrangement of the coordi-
nated cycloheptatriene ring involving in principle two
consecutive 1,5-hydrogen shifts [19]. In its 1H-NMR
spectrum 3b exhibits five resonances due to the vinylic
protons and two resonances due to the allylic exo and
endo protons (Fig. 2). The 31P-NMR resonance is
Molybdenum complexes with linked cyclo-
heptatrienylꢀphosphane ligands proved to be particu-
/
larly useful for applications in transition metal catalysis,
and we have reported on the syntheses and properties of
17- and 18-electron complexes containing ortho-phenyl-
shifted from ꢃ
/
7.7 ppm in uncoordinated 2b to 84.5
ene bridged ligands of the type (2-R2PC6H4Ã
/
C7H6)
Ph, Pr), which are capable to bind to the metal
center in a chelating h1:h7-fashion [16,17]. For Rꢂ
Ph,
we could demonstrate that the resulting paramagnetic
17-electron complexes of the type [(o-Ph2PC6H4Ã
h7-
C7H6)MoX2(P ÃMo)] (XꢂBr, CH2SiMe3) can be used
i
(Rꢂ
/
/
/
/
/
in the ring-opening metathesis polymerization of nor-
bornene [16]. In order to render the donor moiety more
sterically demanding and electron-rich, we aimed to-
wards the replacement of the phenyl substituents for
isopropyl groups, and the resulting complexes contain-
ing the cationic 14-electron complex fragment
[(o-iPr2PC6H4Ã
/
h7-C7H6)Mo(P Ã
/
Mo)]ꢁ were success-
alkyne coupling
fully employed in catalytic alkyneꢀ
/
reactions [17]. With this contribution, we would like to
supply a full account of the preparation and complexa-
tion of this new ligand system together with a detailed
structural investigation of the resulting 18- and 17-
electron molybdenum complexes, which had not been
described in our previous publication in this field [17b].
2. Results and discussion
The preparation of the cycloheptatriene 2a with a
diphenylphosphanyl donor group has already been
described [16]. In a similar manner, (2-bromophenyl)dii-
sopropylphosphane 1b was obtained in good yield by
careful monolithiation of ortho-dibromobenzene and
reaction with ClPiPr2. Subsequent treatment of 1b with
nBuLi and addition of the resulting 2-(diisopropylpho-
Scheme 1.

M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ
/
9
3
Fig. 3. ORTEP drawings of 3b (top) and of the cation in 4b (bottom)
with thermal ellipsoids drawn at 50% probability.
Fig. 2. Selected parts of the 1H-NMR spectra (600 MHz, CD2Cl2) of
3b (top) and 5b (bottom).
C7H8)Mo(CO)3] [20] and [(h6-C7H8)Mo(CRR?)(CO)2]
(Rꢂ
/
OEt, R?ꢂo-tolyl) [21], the bond lengths and
/
angles within the seven-membered ring fall in the
expected ranges (Table 1).
ppm revealing that the phosphorous atom is coordi-
nated to the metal center. As 3b is obtained as a racemic
mixture of two enantiomers, four CH3 and two CH
resonances are observed for the diastereotopic isopropyl
groups in the 13C-NMR spectrum. Accordingly, two
doublets are found for the 13CO carbonyl resonances at
In 3b the exo-hydrogen atom is easily accessible to the
trityl cation for hydride abstraction, and the cy-
cloheptatrienylꢀ
/
phosphane complex [(o-iPr2PÃ
/
C6H4Ã
/
h7-C7H6)Mo(CO)2(P Ã
/
Mo)]BF4 (4b) is formed almost
quantitatively upon treatment with (Ph3C)BF4 (Scheme
1). With removal of the hydrogen atom from the CH2
group, 4b becomes Cs symmetric and exhibits only three
227.6 (2JC,P
which almost perfectly coincides with the resonances
found for complex 3a at 227.2 (2JC,P
10 Hz) and 223.9
ppm (2JC,P
12 Hz).
ꢂ
/
10 Hz) and 224.4 ppm (2JC,P
ꢂ
/
12 Hz),
1
ꢂ
/
cycloheptatrienyl resonances in its H-NMR spectrum
ꢂ
/
at 5.90, 5.80 and 5.26 ppm in a 2:2:2 ratio. Accordingly,
the 13C-NMR spectrum displays four resonances for the
C7H6 carbon atoms. The 13CO resonance for the
magnetically equivalent carbonyl groups is observed as
In order to confirm the spectroscopic results, the
molecular structure of 3b was established by X-ray
diffraction analysis, and Fig. 3 (top) shows an ORTEP
diagram of one enantiomer. The 2-(diisopropylpho-
sphanyl)phenyl substituent is indeed attached to the
vinylic carbon atom C1, which is next to the CH2 (C7)
a doublet at 216.2 (2JP,C
ꢂ
14 Hz), and the 31P resonance
at 81.8 ppm is only slightly shifted to lower field in
/
comparison with 3b. To confirm the formation of a
group, and the cycloheptatrieneꢀphosphane ligand is
/
cycloheptatrienylꢀphosphane chelate complex, a single-
/
binding to the metal center in a chelating h6:h1-fashion.
If compared to the molecular structures of 3a, or related
crystal of 4b was subjected to X-ray diffraction analysis.
The molecular structure of the cation in 4b is depicted in
Fig. 3 (bottom). It reveals that the ligand does indeed act
cycloheptatrieneꢀ
molybdenum complexes, e.g. [(h6-
/

4
M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ9
/
Table 1
˚
Selected bond distances (A) and angles (8) for 3b, 4b, 5b, 6b and 7b
3b
4b
5b
6b
7b
C1Ã
C2Ã
C3Ã
C4Ã
C5Ã
C6Ã
C1Ã
C1Ã
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
MoÃ
/
C2
C3
C4
C5
C6
C7
C7
C8
1.392(3)
1.423(3)
1.417(3)
1.424(3)
1.382(3)
1.505(3)
1.523(3)
1.491(3)
2.369(2)
2.315(2)
2.287(2)
2.306(2)
2.338(2)
2.454(2)
1.404(6)
1.398(6)
1.400(7)
1.377(7)
1.407(6)
1.420(6)
1.394(5)
1.509(5)
2.253(3)
2.313(4)
2.292(4)
2.295(4)
2.292(4)
2.315(4)
2.314(4)
2.003(5)
2.003(5)
1.429(3)
1.395(3)
1.423(3)
1.390(3)
1.420(3)
1.410(3)
1.413(3)
1.509(3)
2.237(2)
2.329(2)
2.306(2)
2.291(2)
2.320(2)
2.286(2)
2.280(2)
2.020(3)
1.421(4)
1.404(4)
1.419(4)
1.396(4)
1.407(4)
1.396(4)
1.425(4)
1.495(4)
2.244(2)
2.278(3)
2.260(3)
2.295(3)
2.316(3)
2.287(3)
2.282(3)
1.416(3)
1.409(3)
1.415(3)
1.394(4)
1.403(3)
1.403(3)
1.430(3)
1.498(3)
2.268(3)
2.339(2)
2.323(2)
2.311(2)
2.282(2)
2.305(2)
2.337(2)
2.236(2)
2.231(2)
2.5753(7)
/
/
/
/
/
/
/
/
C1
/
C2
/
C3
/
C4
/
C5
/
C6
/
C7
/
C14/C20
C15/C24
P
1.987(2)
1.952(2)
/
/
2.4618(5) 2.4915(11)
2.4861(5)
2.6465(3)
2.5658(8)
2.5861(5)
2.5884(5)
/
Br1
Br2
/
Mean/max deviation a
0.033/ꢃ
/
0.061 (at C1)
0.062/ꢃ
/
0.059 (at C1)
0.033/ꢃ
/
0.024 (at C1)
0.055/ꢃ0.043 (at C7)
/
PÃ
PÃ
PÃ
PÃ
(C1Ã
/
MoÃ
MoÃ
MoÃ
MoÃ
/
C14/C20
C15/C24
Br1
99.45(6)
91.63(6)
91.74(16)
90.08(13)
89.36(6)
88.22(2)
106.4
94.29(6)
82.75(6)
/
/
/
/
93.65(2)
86.11(2)
107.2
/
/Br2
/
C7)ꢀ
/
(C8Ã
/
C13) b
102.0
96.5
a
Minimum and maximum deviation from the least-squares plane containing C1ÃC7.
/
b
Interplanar angles.
as a chelate ligand in a h7:h1-fashion with a slightly
distorted perpendicular orientation of the six- and
seven-membered rings (interplanar angle of 78.08). The
molybdenum atom is symmetrically bound to the seven
ring-carbon atoms with the shortest bond to C1
tative of so-called ‘chiral-at-metal’, half-sandwich com-
pounds [22,23] is configurationally stable, the
diastereotopic cycloheptatrienyl hydrogen atoms give
1
rise to six different H-NMR resonances. This portion
of the 600 MHz spectrum is shown in Fig. 2 (bottom).
Accordingly, seven 13C-NMR resonances are observed
for the C7H6 carbon atoms together with six resonances
each for the phenylene-bridge as well as for the for the
˚
[2.253(3) A] and the longest bond to C6 [2.315(4) A]
˚
(Table 1). These distances fall in the range observed for
˚
the cation in 4a (MoÃ
/
C1ꢂ
/
2.262(3) A; MoÃ
/
C6ꢂ
/
1
isopropyl groups. The assignment of all H- and 13C-
˚
2.323(4) A). Additionally, no significant deviation
from planarity can be observed for the seven-membered
ring in 4b, and the mean and maximum deviations from
NMR resonances in 5b is supported by two-dimensional
NMR spectroscopy (COSY and NOE experiments). The
13CO carbonyl resonance in 5b is observed as a doublet
˚
the least-squares plane (C1Ã
(for C1).
For the preparation of catalytically active cy-
cloheptatrienylꢀmolybdenum complexes containing the
[(o-iPr2PC6H4Ãh7-C7H6)Mo(P Ã
Mo)] moiety [16,17],
/
C7) are 0.033 and ꢃ
/
0.061 A
at 237.0 ppm (2JC,P
ꢂ
17 Hz), and one single 31P-NMR
/
resonance is found at 65.5 ppm. As expected, the IR
spectrum of 5b exhibits one CO absorption at 1941
cmꢃ1, which is in good agreement with the stretching
frequencies observed for 5a at 1946 cmꢃ1 and for the
/
/
/
we sought for the removal of the two CO ligands in
4b. As described for 4a, this can be achieved stepwise by
subsequent substitution and oxidation reactions. The
first CO is easily substituted upon treatment of 4b with
an excess of NaBr in acetone at elevated temperature
closely
related,
unbridged
analogue
[(h-
C7H7)Mo(CO)Br(PPh3)] at 1944 cmꢃ1 [24].
Removal of the remaining CO group in 5b requires an
oxidative decarbonylation, and the addition of 0.5
equivalent of bromine to a solution of 5b in THF results
leading to the high-yield formation of [(o-iPr2PC6H4Ã
/
h7-C7H6)Mo(CO)Br(Mo Ã
/P)] (5b). In 5b, the pseudote-
in a rapid color change from green to redꢀ
simultaneous gas evolution. After stirring for 1 h at
ambient temperature, paramagnetic [(o-iPr2PÃ
C6H4Ã
h7-C7H6)MoBr2(Mo Ã
P)] (6b) can be isolated as an
/brown and
trahedrally coordinated molybdenum center has four
different ligands, and the complex is thus obtained as a
racemic mixture of two enantiomers. As this represen-
/
/
/

M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ
/
9
5
air-stable, microcrystalline brown solid after precipita-
tion with hexane (Scheme 1). The formation of 6b can be
explained by oxidation of 5b with (1/2) eq. Br2 to give
the labile odd-electron intermediate [(o-iPr2PÃ
/
C6H4Ã
/
h7-C7H6)Mo(CO)Br(Mo Ã
/
P)]Br, which rapidly under-
goes carbonyl substitution by bromide to afford the
dibromo complex 6b in high-yield. Due to the unpaired
electron in 6b, the compound was only characterized by
mass spectrometry, and the purity was additionally
checked by elemental analysis.
Single crystals of both 5b and 6b could be obtained by
recrystallization from dichloromethane/hexane allowing
to establish their molecular structures by X-ray crystal
structure determinations (Fig. 4). The MoÃ
/
C(ring)
distances (Table 1) in both complexes do not differ
˚
significantly and range from 2.2237(2) to 2.320(2) A
˚
(mean 2.29 A) in 5b and from 2.244(2) to 2.316(3) A
˚
˚
(mean 2.28 A) in 6b. In contrast, the MoÃ
/
P bond length
of 2.5658(8) A in 6b is significantly longer than that in
˚
˚
5b [2.4861(5) A], whereas the reverse trend is observed
for the MoÃBr distances (Table 1). It should be noted
/
that the positions of all hydrogen atoms could be refined
for 5b and 6b. Therefore, it is possible to establish in
each case the angles between the centroid of the
cycloheptatrienyl ring, the C7 carbon atoms and the
adjacent hydrogen atoms revealing a significant out-of-
plane displacement for the C7 hydrogen atoms. The
average bending is about 9ꢀ108 toward the molybde-
/
num center, and such a deviation has been attributed to
a reorientation of the large seven-membered ring for a
better metal overlap [7,25].
We had previously shown that the dibromide 6a
forms mono- and dialkyl complexes on reaction with
an etheral solution of Me3SiCH2MgCl [16]. Similarly,
treatment of 6b with a large excess of the Grignard
Fig. 4. ORTEP drawings of 5b (top) and 6b (bottom) with thermal
ellipsoids drawn at 50% probability.
reagent furnished the dialkyl complex [(o-iPr2PÃ
/
C6H4Ã
/
h7-C7H6)Mo(CH2SiMe3)2(Mo Ã
/P)] (7b). Extraction
with hexane, transfer of the mother liquor to a
chromatography column (SiO2) and elution with diethyl
ether/petroleum ether (1:1) led to the collection of an
orange fraction, from which air-stable 7b could be
isolated in quantitative yield. The purity of the para-
magnetic complex was only checked by mass spectro-
metry and by elemental analysis. The molecular
structure of 7b could additionally be established by
means of X-ray diffraction analysis, and Fig. 5 shows an
ORTEP presentation of 7b. The substitution of the two
bromine atoms in 6b by the sterically more demanding
Me3SiCH2 group does not seem to have great conse-
quences on the structural parameters of the cy-
Fig. 5. ORTEP drawing of 7b with thermal ellipsoids drawn at 50%
probability.
identical. The cycloheptatrienyl ring in 7b remains
planar, and the mean and maximum deviations from
cloheptatrienylꢀ
MoÃC distances range from 2.281(2) to 2.339(2) A
(mean 2.31 A), and they are only slightly enlongated in
/
phosphane scaffold in 7b. Thus, the
˚
/
˚
the least-squares plane (C1Ã
dihedral angle between the best planes containing C1Ã
C7 and C8ÃC13 are summarized in Table 1. The metal-
to-alkyl carbon distances observed for 7b [2.231(2),
/
C7) together with the
˚
2.316(3) A (mean
P bond lengths of
/
comparison to those in 6b [2.244(2)ꢀ
/
˚
2.280 A)] (Table 1), and the MoÃ
/
/
˚
2.5658(8) A (6b) and 2.5753(7) A (7b) are almost
˚

6
M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ9
/
1
˚
2.236(2) A] are rather large but still comparable to those
Vector 22 instrument. The assignment of all H- and
13C-NMR resonances has been supported by two-
dimensional NMR spectroscopy (COSY and NOE
experiments). For the atomic numbering schemes used
found in other molybdenum alkyl complexes, which lie
˚
in the range 2.08ꢀ
/
2.20 A [26]. The bond angles MoÃ
/
CÃ
/
Si of 124.34(12) and 130.52(11)8 in 7b are significantly
larger than expected for sp3-hybridized carbon atoms,
although similar bond angles have also been found in
molybdenum(VI) and tungsten(VI) neosilyl complexes
[16,26].
in Section 4, see Figs. 2ꢀ5.
/
4.1. [2-(Cyclohepta-2,4,6-
trienyl)phenyl]diisopropylphosphane (2b)
A solution of 1b (9.62 g, 28.20 mmol) in THF (140 ml)
was treated with n-butyllithium (12.2 ml of a 2.5 M
solution in hexane, 30.5 mmol). After stirring for 45
min, solid (C7H7)BF4 (5.01 g, 28.16 mmol) was added at
3. Conclusion
With this contribution, we have presented a full
account of the preparation of 18- and 17-electron
molybdenum complexes containing a chelating [2-(dii-
sopropylphosphanyl)phenyl]cycloheptatrienyl ligand to-
gether with a comparative structural investigation of
ꢃ78 8C, and the resulting reaction mixture was slowly
/
warmed to room temperature (3 h). Extraction with
hexane (100 ml) and evaporation of the solvent afforded
2b as a colorless, viscous liquid. Yield: 5.12 g (64 %). 1H-
complexes
C7H6)Mo(P Ã
3bꢀ
containing
Mo)] moieties (Rꢂ
the
[(o-R2PC6H4Ã
/
h7-
Pr,
NMR (CDCl3, 200 MHz): d 7.42 (m, 1H, C6H4), 7.32ꢀ
/
/
/
Ph, 3aꢀ
/
7a; Rꢂi
/
7.16 (m, 2H, C6H4), 7.10 (td, 1H, C6H4), 6.57 (t, 2H, C7
ring: CH), 6.07 (m, 2H, C7 ring: CH), 5.13 (dd, 2H, C7
ring: CH), 3.87 (m, 1H, C7 ring: tert-CH), 1.88 (sep.,
2H, iPr: CH), 0.86 (dd, 6H, iPr: CH3), 0.71 (m, 6H, iPr:
/7b). It can be concluded that rendering the phos-
phane donor group more sterically demanding and
electron-rich by replacing the phenyl substituents for
isopropyl groups does generally lead to an increased
stability and solubility of the resulting complexes, which
will be useful for further exploration and exploitation of
the applicability of these systems in homogeneous
transition metal catalysis. Both dibromides 6a and 6b
have already proven to be versatile starting materials for
the generation of catalytically active molybdenum com-
plexes [16,17], which indicates that cycloheptatrienyl
complexes can indeed be potentially useful for applica-
tions in homogeneous transition metal catalysis. This
work is part of our general goal to extend the chemistry
of cycloheptatrienyl complexes and to raise their level of
significance in comparison with that of cyclopentadienyl
and benzene complexes.
CH3). 31P-NMR (CDCl3, 81 MHz): d ꢃ
m/z (%) 284 (78) [Mꢁ], 269 (8) [MꢃCH3]ꢁ, 241 (56)
[MꢃiPr]ꢁ. Anal. Calc. for C19H25P (284.38): C, 80.25;
H, 8.86. Found: C, 80.23; H, 8.59%.
/7.7. MS (EI):
/
/
4.2. [(o-iPr2PÃ
(3b)
/
C6H4Ã
/
h6-C7H7)Mo(CO)2(P Ã
/
Mo)]
The phosphane 2b (9.72 g, 28.58 mmol) and Mo(CO)6
(7.65 g, 28.98 mmol) were dissolved in methylcyclohex-
ane (250 ml) and slowly heated to 120 8C within 2 h.
Heating was continued at this temperature with stirring
for 10 h. The solvent and unreacted Mo(CO)6 were
removed in vacuo, and the residue was recrystallized
from dichloromethane/hexane at ꢃ78 8C. After 12 h, 3b
/
was isolated as a red, crystalline solid by filtration.
1
Yield: 8.84 g (64 %) H-NMR (CDCl3, 600 MHz): d
4. Experimental
7.48ꢀ
1H, 3-H), 5.44 (t, 1H, 4-H), 5.24 (t, 1H, 5-H), 4.61 (d,
1H, 2-H), 2.98ꢀ Pr: CH), 2.65 (dd,
2.90 (m, 2H, 6-Hꢁi
1H, 7-endo-CH2), 2.32 (dd, 1H, 7-exo-CH2), 2.18 (sep.,
1H, iPr: CH), 1.42 (dd, 3H, iPr: CH3), 1.38 (dd, 3H, iPr:
/
7.45 (m, 1H, C6H4), 7.29 (m, 3H, C6H4), 5.73 (t,
All operations were performed in an atmosphere of
dry argon by using Schlenk and vacuum techniques.
Solvents were dried by standard methods and distilled
prior to use. Tropylium tetrafluoroborate [27] and
triphenylcarbenium tetrafluoroborate [28], were pre-
pared according to published procedures. Elemental
analyses (C, H, N) were performed on a Heraeus
CHNO-Rapid elemental analyzer. EI and ESI mass
spectra were recorded on a Varian MAT 212 or on a
Micromass Quattro LCZ mass spectrometer, respec-
tively. 1H and 13C-NMR spectra were measured on
Bruker AC 200, Bruker AMX 400 or Varian U 600
spectrometers using the solvent as internal standard,
whereas 31P-NMR measurements were run on a Bruker
AC 200 spectrometer using aqueous H3PO4 (85%) as an
external reference. IR spectra were recorded on a Bruker
/
/
i
i
CH3), 1.25 (dd, 3H, Pr: CH3), 0.99 (dd, 3H, Pr: CH3).
13C-NMR (CDCl3, 150.7 MHz): d 227.6 (d, J(C,P)ꢂ
9.8 Hz, CO), 224.4 (d, 2J(C,P)ꢂ
12.2 Hz, CO), 152.7 (d,
2J(C,P)ꢂ25.1 Hz, C-8), 149.7 (d, 1J(C,P)ꢂ
32.7 Hz, C-
9), 131.4 (s, C6H4), 129.4 (d, J(C,P)ꢂ2.2 Hz, C6H4),
127.1 (d, J(C,P)ꢂ11.1 Hz, C6H4), 126.5 (d, J(C,P)ꢂ
5.2 Hz, C6H4), 103.7 (d, J(C,P)ꢂ
C-2), 88.0 (d, 2J(C,P)ꢂ2.0 Hz, C-3), 85.8 (d, 2J(C,P)ꢂ
2.5 Hz, C-4), 85.1 (s, C-1), 44.9 (d, J(C,P)ꢂ
6), 36.1 (d, 1J(C,P)ꢂ18.7 Hz, iPr: CH), 34.0 (d,
2J(C,P)ꢂ
1.3 Hz, C-7), 27.6 (d, J(C,P)ꢂ
CH), 21.4 (d, 2J(C,P)ꢂ6.3 Hz, iPr: CH3), 19.9 (d,
/
2
/
/
/
/
/
/
2
/
1.2 Hz, C-5), 97.3 (s,
/
/
2
/
4.7 Hz, C-
/
1
i
/
/
22.6 Hz, Pr:
/

M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ
/
9
7
i
2
i
CH3), 1.02 (dd, 3H, Pr: CH3), 0.82 (dd, 3H, Pr: CH3).
i
2J(C,P)ꢂ
iPr: CH3), 19.4 (m, 2C, iPr: CH3). 31P-NMR (CDCl3, 81
MHz): d 84.5. MS (EI): m/z (%)ꢂ
436 (52) [Mꢁ], 408
2CO]ꢁ. IR (CH2Cl2): n˜
/
8.8 Hz, Pr: CH3), 19.5 (d, J(C,P)ꢂ
/
2.5 Hz,
2
13C-NMR (CD2Cl2, 150.7 MHz): d 237.0 (d, J(C,P)ꢂ
/
2
/
16.5 Hz, CO), 151.2 (d, J(C,P)ꢂ
/
25.0 Hz, C-8), 138.5
34.4 Hz, C-9), 130.2 (d, J(C,P)ꢂ2.3 Hz,
C6H4), 130.0 (s, C-12), 128.2 (d, J(C,P)ꢂ4.5 Hz, C6H4),
127.2 (d, J(C,P)ꢂ8.3 Hz, C6H4), 109.2 (s, C-1), 100.9 (s,
C-3), 95.9 (d, 2J(C,P)ꢂ1.3 Hz, C-2), 95.5 (d, 2J(C,P)ꢂ
5.1 Hz, C-4), 94.4 (d, 2J(C,P)ꢂ
4.5 Hz, C-5), 87.5 (s, C-
1
(8) [Mꢃ
/
CO]ꢁ, 380 (100) [Mꢃ
/
/
(d, J(C,P)ꢂ
/
/
(CO) 1908, 1826 cmꢃ1. Anal. Calc. for C27H21MoO2P
(436.22): C, 57.94; H, 5.56. Found: C, 57.32; H, 5.58%.
/
/
/
/
/
1
i
4.3. [(o-iPr2PÃ
P)]BF4 (4b)
/
C6H4Ã
/
h7-C7H6)Mo(CO)2(Mo Ã
/
7), 79.1 (s, C-6), 24.6 (d, J(C,P)ꢂ
/
18.4 Hz, Pr: CH),
4.3
3.3 Hz, Pr: CH3), 17.0
5.2 Hz,
24.5 (d, 1J(C,P)ꢂ
/
14.1 Hz, iPr: CH), 19.1 (2J(C,P)ꢂ
/
Hz, Pr: CH3), 17.8 (2J(C,P)ꢂ
/
i
i
i
A solution of 3b (8.84 g, 17.53 mmol) in dichloro-
methane (200 ml) was treated with (Ph3C)BF4 (5.20 g,
15.75 mmol) at 0 8C, and the resulting mixture was
subsequently heated to reflux for 30 min. The solution
was reduced in volume to about 50 ml and added
dropwise to rapidly stirred diethyl ether at 0 8C to
precipitate 4b, which was isolated as an orange, crystal-
line solid by filtration, washing with diethyl ether and
drying in vacuo. Yield: 8.34 g (90 %). 1H-NMR
(2J(C,P)ꢂ
/
4.4 Hz, Pr: CH3), 16.8 (2J(C,P)ꢂ
/
iPr: CH3). 31P-NMR (CD2Cl2, 81 MHz): d 66.5. MS
(EI): m/z (%)ꢂ459 (100) [Mꢃ COÃ
CO]ꢁ, 379 (8) [Mꢃ
Br],ꢁ 336 (10) [Mꢃ C3H7]ꢁ. IR (CH2Cl2) n˜
COÃBrÃ
(CO)ꢂ
1941 cmꢃ1. Anal. Calc. for C20H24BrMoOP
(487.22): C, 49.30; H, 4.96. Found: C, 49.83; H, 4.95%.
/
/
/
/
/
/
/
/
/
4.5. [(o-iPr2PÃ
/
C6H4Ã
/
h7-C7H6)MoBr2(Mo Ã
/
P)] (6b)
(CD3CN, 400 MHz): d 7.64 (dt, 1H, C6H4), 7.60ꢀ7.48
/
(m, 2H, C6H4), 7.57 (dd, 1H, C6H4), 5.90 (m, 2H, 3, 6-
H), 5.80 (dd, 2H, 4,5-H), 5.26 (dd, 2H, 2,7-H), 2.47
(sep., 1H, Pr: CH), 2.45 (sep., 1H, Pr: CH), 0.96 (d,
3H, iPr: CH3), 0.91 (dd, 6H, iPr: CH3), 0.86 (d, 3H, iPr:
CH3). 13C-NMR (CD3CN, 100.6 MHz): d 216.2 (d,
A solution of 5b (4.92 g, 8.86 mmol) in tetrahydro-
furane (120 ml) was treated with a solution of bromine
(0.24 ml, 4.68 mmol) in tetrahydrofurane (10 ml) at
0 8C, and the resulting mixture was subsequently stirred
for 12 h at ambient temperature. The solution was
reduced in volume to about 50 ml and added dropwise
to rapidly stirred hexane to precipitate 6b, which was
isolated as a crystalline solid by filtration, washing with
hexane and drying in vacuo. Purification was possible
by recrystallization from dichloromethane to afford
brown crystals of 6b. Yield: 5.30 g (86 %). MS (EI):
i
i
2J(C,P)ꢂ
8), 139.3 (d, 1J(C,P)ꢂ
2.5 Hz, C6H4), 132.2 (s, C6H4), 130.7 (d, J(C,P)ꢂ
/
14.4 Hz, CO), 148.4 (d, 2J(C,P)ꢂ
37.3 Hz, C-9), 133.0 (d; J(C,P)ꢂ
5.5
3.1 Hz, C-1), 127.8 (d,
10.4 Hz, C6H4), 97.8 (s, C-2,7), 97.1 (s, C-3,6),
94.6 (d, 2J(C,P)ꢂ4.0 Hz, C-4,5), 27.6 (d, 1J(C,P)ꢂ
24.3
4.1 Hz, Pr: CH3), 18.3
(s, iPr: CH3). 31P-NMR (CD3CN, 81 MHz): d 81.8. MS
(ESI): m/z (%)ꢂ435 (100) [Mꢃ
BF4]ꢁ. IR (CH2Cl2) n˜
(CO)ꢂ2024, 1983 Anal. Calc. for
cmꢃ1
/
20.9 Hz, C-
/
/
/
3
Hz, C6H4), 128.6 (d, J(C,P)ꢂ
/
J(C,P)ꢂ
/
/
/
i
2
i
Hz, Pr: CH), 18.4 (d, J(C,P)ꢂ
/
m/z (%)ꢂ
/
539 (51) [Mꢁ], 459 (68) [Mꢃ
/
Br]ꢁ, 379 (1)
[Mꢃ
/
2Br],ꢁ 293 (9) [Mꢃ
/
2BrÃ
/
2iPr]ꢁ. Anal. Calc. for
/
/
/
C19H24Br2MoP (539.12): C, 42.33; H, 4.48. Found: C,
41.73; H, 4.48%.
/
.
C21H24BF4MoO2P (522.13): C, 48.31; H, 4.63. Found:
C, 48.07; H, 4.52%.
4.6. [(o-iPr2PÃ
/
C6H4Ã
/
h7-
4.4. [(o-iPr2PÃ
(5b)
/
C6H4Ã
/
h7-C7H6)Mo(CO)Br(Mo Ã
/
P)]
C7H6)Mo(CH2SiMe3)2(Mo Ã
/
P)] (7b)
A solution of 6b (500 mg, 0.93 mmol) in THF (20 ml)
was treated with a large excess of Me3SiCH2MgCl (9.3
ml of a 1.0 M solution in diethyl ether, 7.2 mmol) at
A solution of 4b (2.40 g, 4.07 mmol) in acetone (160
ml) was treated with NaBr (3.04 g, 29.55 mmol), and the
resulting mixture was subsequently heated to reflux for
14 h. After evaporation of the solvent, the residue was
transferred to a silica-chromatography column. Elution
with dichloromethane produced a green band that was
collected to give 5b as a green, crystalline solid. Yield:
0.72 g (35 %). 1H-NMR (CD2Cl2, 600 MHz): d 7.68 (dt,
ꢃ78 8C, and the resulting mixture was allowed to warm
/
to room temperature and was subsequently stirred for
12 h at ambient temperature. The solvent was evapo-
rated, and the residue was extracted with hexane (20 ml).
Purification was possible by column chromatography on
silica using diethyl ether/petroleum ether (1:1) as eluent
to isolate 7b as an orange, crystalline solid. Yield: 445
1H, C6H4), 7.55 (t, 1H, C6H4), 7.53ꢀ7.47 (m, 2H, C6H4),
/
7.20 (dd, 2H, o-C6H5), 5.80 (t, 1H, H-5), 5.35 (d, 1H, H-
2), 5.28 (t, 1H, H-4), 5.23 (t, 1H, H-3), 4.87 (t, 1H, H-6),
mg (90%). MS (EI): m/z (%)ꢂ
/
554 (B
/
1) [Mꢁ], 467 (1)
[Mꢃ
/
CH2SiMe3]ꢁ, 379 (2) [Mꢃ
/
2CH2SiMe3]ꢁ. Anal.
i
4.12 (d, 1H, H-7), 2.57 (sep., 1H, Pr: CH), 2.56 (sep.,
Calc. for C27H46MoPSi2 (553.74): C, 58.56; H, 8.37.
Found: C, 59.30; H, 8.99%.
1H, iPr: CH), 1.31 (dd, 3H, iPr: CH3), 1.07 (dd, 3H, iPr:

8
M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ9
/
Table 2
Crystallographic data for 3b, 4b, 5b, 6b, and 7b
3b
4b
5b
6b
7b
Formula
C
436.32
21H25MoO2P
C21H24BF4MoO2P
522.13
C20H24BrMoOP
487.21
monoclinic
C19H24Br2MoP
539.11
triclinic
C27H46MoPSi2
553.73
Formula weight (amu)
Crystal system
Space group
Unit cell
tetragonal
I41/a (no. 88)
monoclinic
C2 (no. 5)
orthorhombic
P212121 (no. 19)
¯
P1 (no. 2)
P21/n (no. 11)
/
˚
a (A)
29.8475(11)
29.8475(11)
8.7098(5)
90
14.1728(18)
10.1940(13)
15.613(2)
90
7.3399(3)
17.3379(7)
15.2786(6)
90
7.4390(12)
8.4097(13)
16.236(3)
77.982(3)
80.976(3)
75.498(3)
955.9(3)
1.873
10.0229(14)
13.3649(19)
21.519(3)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
90
90
104.198(2)
90
98.674(1)
90
90
90
g (8)
3
V (A )
˚
7759.3(6)
1.494
16
2186.8(5)
1.580
1922.1(1)
1.684
2882.5(7)
1.276
4
Dcalc (g cmꢃ1
)
Z
4
0.721
5003
4
2.848
4418
2
4.947
5474
m (mmꢃ1
Unique data
)
0.770
3407
0.606
6950
Observed data {I ꢀ/2s(I)}
3138
4273
4017
4915
6631
R1 (observed data) (%)
R2 (all data) (%)
Goodness-of-fit
2.22, wR1ꢂ
/
5.30
3.74, wR1ꢂ
/
7.24
2.28, wR1ꢂ
/
5.26
3.29, wR1ꢂ
/
7.66
2.81, wR1ꢂ
/
6.11
6.17
2.50, wR2ꢂ
/
5.42
4.71, wR2ꢂ
/
7.54
2.63, wR2ꢂ
/
5.39
3.79, wR2ꢂ
/
7.88
3.02, wR2ꢂ
/
1.075
326
0.958
312
1.046
319
1.053
304
1.057
280
No. of variables
˚
Res. electr. dens. (e A
ꢃ3
)
0.37/ꢃ
/
0.20
0.67/ꢃ
/
0.33
0.65/ꢃ
/
0.34
1.22/ꢃ
/
1.08
0.87/ꢃ0.35
/
4.7. X-ray crystallography
Acknowledgements
All data sets were collected at ꢃ
/
120 8C with a Bruker
This work was financially supported by the Deutsche
Forschungsgemeinschaft, the Fonds der Chemischen
Industrie and the government of North Rhine-West-
phalia (Bennigsen-Foerder-Preis 2000 to M.T.). M.T. is
grateful to Prof. W.A. Herrmann (Munich) for the
appointment to temporarily represent the Chair of
AXS APEX diffractometer equipped with a rotating
˚
Ka radiation (lꢂ0.71073 A). Empiri-
anode using Moꢀ
/
/
cal absorption correction with SADABS [29] (for 4b, 6b
and 7b) was applied to the raw data. Structure solution
in all cases with SHELXS [30] and refinement with
SHELXL [31] with anisotropic thermal parameters
for all atoms. Hydrogen atoms were added to the
structure models on calculated positions are unrefined.
Hydrogen atoms for 3b, 5b and 6b were located in the
difference Fourier map and were refined with isotropic
thermal parameters. ORTEP [32] was used for all draw-
ings. Additional crystallographic data are listed in Table
2.
Inorganic Chemistry at the Technische Universitat
Munchen.
¨
¨
References
[1] (a) G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.), Comprehen-
sive Organometallic Chemistry, Pergamon Press, Oxford, 1982;
(b) E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehen-
sive Organometallic Chemistry II, Chapman and Hall, Oxford,
1995;
(c) A. Togni, R.L. Halterman (Eds.), Metallocenes, Wiley-VCH,
Weinheim, 1998.
[2] R.D. Adams (Ed.), Special Issue: 50th Anniversary of the
5. Supplementary material
Discovery of Ferrocene, J. Organomet. Chem., 637ꢀ639 (2001) 1.
/
[3] (a) C. Janiak, H. Schumann, Adv. Organomet. Chem. 33 (1991)
331;
Crystallographic data (excluding structure factors) for
the structures 3bꢀ7b reported in this paper have been
/
(b) J. Okuda, Top. Curr. Chem. 160 (1991) 99;
(c) N.J. Coville, K.E. du Plooy, W. Pickl, Coord. Chem. Rev. 116
(1992) 1;
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication nos. CCDC
(d) R.L. Halterman, Chem. Rev. 92 (1992) 965;
(e) M.L. Hays, T.P. Hanusa, Adv. Organomet. Chem. 40 (1996)
117.
194077ꢀ
free of charge on application to 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).
/
194081. Copies of the data can be obtained
/
[4] (a) B. Cornils, W.A. Herrmann (Eds.), Applied Homogenous
Catalysis with Organometallic Compounds, Wiley-VCH, Wein-
heim, 1996;

M. Tamm et al. / Journal of Organometallic Chemistry 677 (2003) 1ꢀ
/
9
9
(b) W.A. Herrmann, B. Cornils, Angew. Chem. 109 (1997) 1074;
(c) W.A. Herrmann, B. Cornils, Angew. Chem. Int. Ed. Engl. 36
(1997) 1048;
[17] (a) M. Tamm, B. Dreßel, V. Urban, T. Lugger, Inorg. Chem.
¨
Commun. 5 (2002) 837;
(b) M. Tamm, B. Dreßel, T. Lugger, R. Frohlich, S. Grimme, Eur.
¨
¨
J. Inorg. Chem. (2003) 1088.
(d) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. 111
(1999) 448;
[18] C. Jutz, F. Voithenleitner, Chem. Ber. 97 (1964) 29.
[19] (a) A. Roberts, M.W. Whiteley, J. Organomet. Chem. 458 (1993)
131;
(e) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int.
Ed. Engl. 38 (1999) 428;
(b) H. Wadepohl, W. Galm, H. Pritzkow, Organometallics 15
(1996) 570 (and references cited therein).
(f) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Chem. Rev. 100
(2000) 4, Special Volume, Frontiers in Metal-Catalyzed Polymer-
isation.
[20] J.D. Dunitz, P. Pauling, Helv. Chim. Acta 43 (1960) 2188.
[21] C. Jiabi, Y. Jiengo, L. Guixin, X. Weihua, S. Meicheng, Z.
Zeying, T. Youqi, J. Organomet. Chem. 329 (1987) 69.
[22] (a) H. Brunner, Eur. J. Inorg. Chem. (2001) 905;
(b) H. Brunner, Angew. Chem. 111 (1999) 1248;
(c) H. Brunner, Angew. Chem. Int. Ed. Engl. 38 (1999) 1194.
[23] (a) H. Brunner, J. Klankermayer, M. Zabel, Eur. J. Inorg. Chem.
(2002) 2494;
[5] (a) L.S. Hegedus, Transition Metals in the Synthesis of Complex
Organic Molecules, University Science, California, 1994;
(b) M. Beller, C. Bolm (Eds.), Transition Metals for Organic
Synthesis, Wiley-VCH, Weinheim, 1998.
[6] D.W. Bruce, D. O’Hare (Eds.), Inorganic Materials, Wiley,
Chichester, 1992.
[7] M.L.H. Green, D.K.P. Ng, Chem. Rev. 95 (1995) 439.
(b) H. Brunner, J. Klankermayer, M. Zabel, Organometallics 21
(2002) 5746;
[8] (a) M. Tamm, B. Dreßel, R. Frohlich, K. Bergander, Chem.
¨
Commun. (2000) 1731;
(c) H. Brunner, J. Klankermayer, M. Zabel, Z. Anorg. Allg.
Chem. 628 (2002) 2264;
(b) M. Tamm, B. Dreßel, R. Frohlich, J. Org. Chem. 65 (2000)
¨
6795.
[9] M. Tamm, T. Bannenberg, B. Dreßel, R. Frohlich, D. Kunz,
¨
(d) H. Brunner, M. Muschiol, I. Bernal, G.M. Reisner, J.
Organomet. Chem. 198 (1980) 169.
Organometallics 20 (2001) 900.
[24] R.W. Grime, M.W. Whiteley, J. Chem. Soc. Dalton Trans. 23
(1994) 1671.
[10] (a) J. Okuda, T. Eberle, in: A. Togni, R.L. Halterman (Eds.),
Metallocenes, vol. 1, Wiley-VCH, Weinheim, 1998, p. 415;
(b) J. Okuda, Comments Inorg. Chem. 16 (1994) 185.
[11] P. Jutzi, T. Redeker, Eur. J. Inorg. Chem. (1998) 663.
[12] U. Siemeling, Chem. Rev. 100 (2000) 1495.
[25] M. Elian, M.M.L. Chen, D.M.P. Mingos, R. Hoffmann, Inorg.
Chem. 15 (1976) 1148.
[26] J.A.M. Brandts, J. Boersma, A.L. Spek, G. van Koten, Eur. J.
Inorg. Chem. (1999) 1727 (and references cited therein).
[27] T. Asao, M. Oda, M. in: H. Kropf (Ed.), Methoden der
Organischen Chemie (Houben-Weyl), vol. V/2c, Georg Thieme
Verlag, Stuttgart, 1985, p. 49.
[13] H. Butenschon, Chem. Rev. 100 (2000) 1527.
¨
[14] M. Tamm, T. Bannenberg, B. Dreßel, R. Frohlich, C. Holst,
¨
Inorg. Chem. 41 (2002) 47.
[15] (a) K. Baum, Dissertation, Westfalische Wilhelms-Universitat
¨
¨
[28] H.J. Dauben, L.R. Lewis, R. Honnen, K.M. Harmon, J. Org.
Chem. 25 (1960) 1442.
[29] SMART, Bruker AXS, 2000.
Munster, 2001.;
¨
(b) S. Dehn, Diploma Thesis, Westfalische Wilhelms-Universitat
¨ ¨
Munster, 2002.
¨
[16] M. Tamm, K. Baum, T. Lugger, R. Frohlich, K. Bergander, Eur.
[30] SHELXS-97, G.M. Sheldrick, Acta Cryst. Sect. A 46 (1990) 467.
[31] SHELXL-97, G.M. Sheldrick, Universitat Gottingen, 1997.
¨ ¨
¨
¨
J. Inorg. Chem. (2002) 918.
[32] ORTEP-3, L.J. Farrugia, University of Glasgow, 1999.