Titanium complexes of π-coordinated thiophene derivatives

Article abstract of DOI:10.1016/S0022-328X(03)00383-8

π-Coordinated tricarbonylchromium complexes of thiophene and benzothiophene are readily lithiated with butyllithium and reacted with titanocene dichloride to afford the binuclear complexes [Ti{(η¹,η⁵-thienyl)Cr (CO)₃}Cp₂Cl] (1) and [Ti{(η¹,η⁶-benzothienyl) Cr(CO)₃}Cp₂Cl] (5). These feature an activated chlorine ligand on the titanium moiety, which is easily substituted by a second π-coordinated arene precursor, thiols or water. Several novel bimetallic, trimetallic and tetrametallic complexes were synthesized exploiting this observation and are reported. Dilithiation of [Cr(η⁵-thienyl)(CO)₃] and subsequent reaction with two equivalents of titanocene dichloride yielded the unstable η¹,η¹, η⁶-thienylene-bridged trinuclear complex, [{μ-Cr(η⁵-thienyl)(CO)₃} {TiCp₂Cl}₂] (15), which was stabilized by replacing the chloro ligands by cyclohexylthiolato ligands. Crystals of the racemic mixture of [{(η¹, η⁵-thienyl)Cr(CO)₃}₂ TiCp₂] (4) was subjected to a single crystal X-ray diffraction study and the presence of both enantiomers causes a thiophene ring to be disordered.

Full text of DOI:10.1016/S0022-328X(03)00383-8

Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
www.elsevier.com/locate/jorganchem
Titanium complexes of p-coordinated thiophene derivatives
Marile´ Landman a,*, Thomas Waldbach b, Helmar Gorls c, Simon Lotz b,*
¨
a Department of Chemistry, University of South Africa, PO Box 392, Pretoria 0003, South Africa
b Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa
c Friedrich-Schiller-Universitat, Institut fur Anorganische und Analytische Chemie, Lessingstrasse 8, D-07743 Jena, Germany
¨
¨
Received 15 January 2003; received in revised form 30 April 2003; accepted 30 April 2003
Abstract
p-Coordinated tricarbonylchromium complexes of thiophene and benzothiophene are readily lithiated with butyllithium and
reacted with titanocene dichloride to afford the binuclear complexes [Ti{(h1,h5-thienyl)Cr(CO)3}Cp2Cl] (1) and [Ti{(h1,h6-
benzothienyl)Cr(CO)3}Cp2Cl] (5). These feature an activated chlorine ligand on the titanium moiety, which is easily substituted by a
second p-coordinated arene precursor, thiols or water. Several novel bimetallic, trimetallic and tetrametallic complexes were
synthesized exploiting this observation and are reported. Dilithiation of [Cr(h5-thienyl)(CO)3] and subsequent reaction with two
equivalents of titanocene dichloride yielded the unstable h1,h1,h6-thienylene-bridged trinuclear complex, [{m-Cr(h5-thie-
nyl)(CO)3}{TiCp2Cl}2] (15), which was stabilized by replacing the chloro ligands by cyclohexylthiolato ligands. Crystals of the
racemic mixture of [{(h1,h5-thienyl)Cr(CO)3}2TiCp2] (4) was subjected to a single crystal X-ray diffraction study and the presence of
both enantiomers causes a thiophene ring to be disordered.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Thiophene; Bimetallic complexes; Titanium; Chromium
1. Introduction
modes of thiophene coordination to a metal, which in
turn are determined by the electronic properties of the
metal and its ligands. Although several coordination
modes of thiophene (T) are known [7], one of the most
common is the h5 mode, i.e. coordination through the p-
system of the heteroaromatic ring usually to a d6 metal
fragment. Benzothiophenes (BT) coordinate to these
metal complexes [4c] through the six carbon atoms of
the benzene ring, since kinetic studies [8] showed a
higher affinity of metals for benzene over thiophene as
well as stronger bond formation. It also showed that
benzothiophenes bind more strongly to metals than
thiophenes.
The wide application of p-arene complexes of chro-
mium in stereoselective [9] and regioselective [10]
syntheses motivated the initial interest in synthesizing
heterobimetallic compounds by attaching the p-hetero-
arene ring to a second metal fragment. The coordination
of early, middle and late transition metals with benzene
The chemistry of thiophene and its derivatives is of
interest due to the presence of these compounds in fossil
fuels [1] as well as their potential application in material
chemistry [2]. The coordination chemistry of these
compounds has been studied owing to its relevance in
the metal-catalyzed hydrodesulfurization (HDS) of the
fossil fuels [3]. Several review articles dealing with model
HDS studies have been published [4], reporting a
number of other interesting reactions of thiophene
discovered during the course of the HDS studies. These
reactions opened a new area of thiophene chemistry
with application towards organic synthesis [5]. A recent
review article by Angelici [6] organized these reactions
and a clear idea of the reaction patterns of thiophene in
organometallic chemistry is perceived. It is concluded
that the specific types of reactivity are dependent on the
[11ꢀ13] or substituted benzene [12,14] as bridging ligand
/
has been investigated. It was found that a carbonyl-
inserted bridged benzoyl product was isolated when
lithiated [Cr(h6-benzene)(CO)3] was reacted with
* Corresponding authors. Tel.:
4298549.
E-mail address: landmm@unisa.ac.za (M. Landman).
ꢁ
/
27-12-4298229; fax:
ꢁ/27-12-
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00383-8

6
M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
[Mn(CO)5Br], while the s,p-phenyl-bridged product
could only be isolated when the large, more basic PPh3
ligand was introduced on the manganese [12]. When the
lithiated benzene precursor is substituted for lithiated
[Cr(h5-thiophene)(CO)3] [15] or [Cr(h6-benzothiophe-
ne)(CO)3] [16], the reaction with [Mn(CO)5Br] affords
both products but with the carbonyl-inserted product in
a lesser yield. The resulting [Mn{(h1,h5-thienyl)Cr-
(CO)3}(CO)5] product was observed to undergo an
unusual intramolecular metal exchange reaction [17],
in which the two metal centers irreversibly exchanged
s,p-coordination sites. Reactions between lithiated
[Cr(h5-thiophene)(CO)3] or [Cr(h6-benzothiophene)-
(CO)3] with late transition metals [18], in this case
[PtL2Cl2], resulted in the substitution of both chlorine
ligands by the p-coordinated heteroarene fragment. The
intermediate complex, which formed after replacing one
chloro with a p-coordinated heteroarene ligand, is
highly activated and the remaining chloro ligand
becomes the target of a second attack by the lithiated
precursor. In the case of the thiophene-bridged product,
the loss of one of the Cr(CO)3 moieties occurs sponta-
neously but in the benzothiophene product both stayed
intact. The remaining issue of interest is the reaction of
an early transition metal with lithiated [Cr(h5-thiophe-
ne)(CO)3] or [Cr(h6-benzothiophene)(CO)3]. In this
study, the properties and diverse reactivity of the
products isolated in these reactions are discussed.
solvents such as THF or acetone. Since only a small
quantity of the initial portion of 1 in the reaction
mixture was eluted from the column, it was suggested
that 1 reacts with the hydroxy groups of the silica gel to
form an orange-colored complex. Thin layer chromato-
graphy of 1 supported this suggestion. The trimetallic
complexes 3 and 4 were found to be more stable than 1,
which is contradictory to observation that [TiCp2(R)Cl]
is more stable than the corresponding disubstituted
compound [TiCp2R2], with R being methyl groups [23]
or [(h6-R?C6H4)Cr(CO)3] [12]. By contrast, the mono-
substituted complex could not even be isolated in the
case of the reaction between [PtL2Cl2] (Lꢃ
/
PMe3, CO or
L2ꢃ
/
dppe) and [Cr(h1,h5-lithiothienyl)(CO)3] [18]. Both
chlorine ligands were immediately substituted by [Cr(h5-
thienyl)(CO)3] fragments. The novel complexes 3 and 4
exist as two diastereomers where 3 is the meso, achiral
isomer displaying a mirror plane while 4 represents an
enantiomeric pair of C2 symmetry. Using benzene as
eluent, these two diastereomers were separated on a
column. As expected, the meso compound 3 was less
polar than 4. The formation of 2 was unexpected and its
origin leads to some speculation. It was anticipated that
1 reacted with water on the column to substitute the
chlorine group for a hydroxy group, which could have
reacted with titanocene dichloride to yield the target
product. Another possibility was that the compound
[{TiCp2Cl}2(m-O)] was present as an impurity in titano-
cene dichloride [24] and, upon reaction with [Cr(h1,h5-
lithiothienyl)(CO)3], formed 2 (vide infra). Although
several test reactions were performed in order to imitate
the formation of 2, it was concluded that this was not
trivial to explain.
2. Results and discussion
The p-bonded heteroarene complexes, [Cr(h5-thio-
phene)(CO)3] and [Cr(h5-benzothiophene)(CO)3], were
prepared in a two-step synthetic process in variable
yields. [Cr(CO)6] was converted into [Cr(CO)3(NH3)3]
[19,20] and thereafter treated with an excess of thio-
phene and three equivalents of the Lewis acid BF3 in
diethyl ether. The complex [Cr(h6-benzothiophe-
ne)(CO)3] was also prepared by refluxing [Cr(CO)6]
and benzothiophene in dibutyl ether for several hours
[21], but isolation of the target product proved difficult
due to the formation of several by-products. Metallation
of these complexes is readily achieved with butyl lithium
The reaction of lithiated [Cr(h6-benzothienyl)(CO)3]
with titanocene dichloride (Scheme 2) afforded two
products initially, the green bimetallic complex 5 and
the trimetallic complex 6, even though the ratio of
reagents was 1:1. This is again an indication of the
enhanced reactivity of the chlorine ligand. The green
color of the compounds is seldom observed for areneꢀ
/
chromium complexes, although more often for titano-
cene derivatives. On purification of the green compound
5, the complex reacted with the hydroxy group of the
silica gel, substituting the remaining chloro ligand,
forming an orange compound that could not be eluated.
In order to record an NMR spectrum of 6, the complex
was dissolved in acetone. The color of the solution was
orange and not the expected green. In acetone, one of
the Cr(CO)3 moieties was decomplexed and only the
benzo[b]thiophene ligand remained bonded, affording
compound 7.
in THF at ꢂ78 8C [22], creating a strong nucleophilic
/
center on the metallated carbon. The lithiated precur-
sors were prepared using this same procedure.
Upon addition of [Cr(h1,h5-lithiothienyl)(CO)3] to
titanocene dichloride in THF at low temperatures
(Scheme 1), the red solution turned green. Chromato-
graphic separation of the mixture yielded four products:
the green complexes 1, 3 and 4 as well as the brown
complex 2. During column chromatography it was
observed that the column material turned orange upon
elution of the reaction mixture. This orange product
could not be eluted from the column, even with polar
Since the bimetallic complexes 1 and 5 are very
reactive because of the high lability of the TiÃ
/Cl bond,
it was decided to exchange the chlorine ligand for other
groups (Scheme 3). The substrates chosen for these
substitution reactions were the thiols, cyclohexylthiol

M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ
/
14
7
Scheme 1. Synthesis of 1, 2, 3 and 4.
and thiophenol. It was anticipated that this substitution
would increase the solubility of the complexes in
the mechanism of [MCp2X2] antitumor activity in
aqueous solution. While it was observed that the
coordination of a [Cr(h6-arene)(CO)3] moiety to titano-
cene dichloride enhanced the reactivity of the remaining
chlorine ligand, it was anticipated that this substitution
should proceed effortlessly. This was indeed the case, as
the red complexes 10 and 12 were formed, respectively,
after stirring 1 and 5 in water for some time. Stone and
coworkers [28] were the first to synthesize and char-
nonpolar solvents. It is also known that the TiÃ
bond in complexes of the type [TiCp2(SR)(SR?)] was
less reactive [25] than the TiÃO bond in [TiCp2-
/S
/
(OR)(OR?)] with regard to thermal conditions. The
conversion of 1 with cyclohexylthiol in dichloromethane
in the presence of excess TMEDA gave the target
complex 8. When the reaction was repeated with an
excess of cyclohexylthiol compared to the rest of the
reagents, the TiÃC s-bond was also broken and the blue
/
complex 9 was formed in a low yield (Fig. 1). Examples
of this type of complexes can be found in literature [26]
and was synthesized by reacting [TiCp2(SR)2] with
[(norbornadien)M(CO)4].
For the analogous reaction with 5 a different sulfur
compound was chosen, i.e. thiophenol. The reason for
this choice was to assign all the NMR signals in the
arene region unambiguously. In the same manner as
described for the synthesis of 8, the orange-red complex
11 was prepared.
The substitution kinetics of the chlorine ligands of
titanocene dichloride in aqueous solution was investi-
gated by Toney and Marks [27] in their studies to clarify
Scheme 3. Synthesis of 8, 10, 11 and 12.
Scheme 2. Synthesis of 5, 6 and 7.

8
M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
Fig. 1. Structure of 9.
acterize compounds of the type [TiCp2R(OH)]. This was
accomplished by adding a mixture of THF and water to
the compound [TiCp2(C6F5)Cl] in the presence of KOH.
When [{TiCp2Cl}2(m-O)] was reacted with two
equivalents of [Cr(h1,h5-lithiothienyl)(CO)3], two tetra-
metallic diastereomers, 13 and 14, were obtained
(Scheme 4). For these two complexes, both chlorine
ligands are substituted in each case, as expected, and the
monosubstituted complex 2 is not observed. The possi-
bility of [{TiCp2Cl}2(m-O)] being the precursor to 2 was
therefore not supported by these results. In this instance,
the diastereomers could not be separated using column
chromatography.
Dimetallation of thiophene in [Cr(h5-thiophe-
ne)(CO)3] is readily achieved [22] and reaction with
two equivalents of titanocene dichloride affords the
green, trimetallic complex 15 (Scheme 5). This complex
was found to be more reactive than 1 and all attempts to
purify the product with column chromatography were
unsuccessful. By converting 15 to 16 with cyclohex-
Scheme 5. Synthesis of 15 and 16.
ylthiol the stability and solubility of the complex were
increased and 16 could be purified on a column without
conversion.
3. Spectroscopic properties
The replacement of a proton by a titanium moiety in
[Cr(p-arene)(CO)3] (areneꢃ/thiophene, benzothiophene)
complexes has a definite effect on the electronic
structure of the complex. This can be deduced from
the difference in the wavenumbers (Table 1) of the bands
in the IR spectra of the monometallic substrate and the
bimetallic products. The decrease in wavenumber with
the addition of the titanium fragment, compared to the
wavenumbers of the complexes [Cr(p-arene)(CO)3] (are-
Scheme 4. Synthesis of 13 and 14.

M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ
/
14
9
Table 1
Spectroscopic data of complexes 1-16
a
Complex IR (n (cmꢂ1) in 1H-NMR (d (ppm) in CDCl3)
CH2Cl2)
13C-NMR (d (ppm) in CDCl3)
1
2
3
4
5
1945 (s), 1848,
1866 (vs)
6.73 (s, 5H, Cp), 6.53 (s, 5H, Cp), 6.21 (dd, 1H, H5,
236.0 (CrCO3), 143.2 (C2), 106.1 (C3), 97.4 (C5), 96.1
3.23), (C4), 119.9, 119.7 (Cp)
3JHH
5.58 (dd, 1H, H3, JHH
ꢃ/
3.44, 4JHH
ꢃ
/
0.58), 5.84 (t, 1H, H4, 3JHH
ꢃ/
3
4
3.12, JHH
ꢃ/
ꢃ/0.57)
1943 (s), 1855 (vs), 6.44 (s, 5H, Cp), 6.42 (s, 5H, Cp), 6.21 (s, 10H, Cp), 6.27 236.0 (CrCO3), 137.0 (C2), 107.4 (C3), 99.3 (C5), 97.1
3
(d, 1H, H5, JHH
3
3.38), 6.18 (d, 1H, H3, JHH
720 (TiÃ
/
OÃ
/
Ti)
ꢃ
/
ꢃ2.97), (C4), 115.0, 115.6, 117.1 (Cp)
/
3
6.07 (t, 1H, H4, JHH 3.23)
ꢃ/
3
1938 (s), 1866 (vs) 6.76 (s, 10H, Cp), 6.21 (dd, 2H, H5 and H5?, JHH
ꢃ
/
236.3 (CrCO3), 144.4 (C2), 106.3 (C3), 97.9 (C5), 97.2
3.53), 6.19 (d, 2H, H3 and H3?, 3JHH
ꢃ/
3.11), 5.80 (t, 2H, (C4), 116.5 (Cp)
3
H4 and H4?, JHH
1938 (s), 1859 (vs) 6.76 (s, 5H, Cp), 6.73 (s, 5H, Cp), 6.23 (d, 2H, H5 and 236.3 (CrCO3), 144.4 (C2), 106.3 (C3), 97.9 (C5), 97.2
ꢃ/3.34)
3
3
H5?, JHH
ꢃ/
3.44), 6.13 (d, 2H, H3 and H3?, JHH
ꢃ/
(C4), 116.1, 117.3 (Cp)
3
3.13), 5.83 (t, 2H, H4 and H4?, JHH
ꢃ/
3.40)
1.0), 6.16 (d, 234.0 (CrCO3), 123.5 (C3), 90.4 (C7), 89.0 (C6), 86.8 (C5),
6.7), 6.08 (dd, 1H, H5, JHH 6.2, 85.5 (C8), 116.7, 116.9 (Cp)
6.7, JHH 6.3),
6.3)
1954 (s), 1875 (vs) 6.40 (s, 5H, Cp), 6.39 (s, 5H, Cp), 6.33 (s, 2H, H3 and 234.5 (CrCO3), 150.2 (C2, C2?), 126.6 (C3, C3?), 103.1
1953 (s), 1872 (vs) 6.45 (m, 10H, Cp), 6.40 (d, 1H, H3, 4JHH
ꢃ
/
3
3
1H, H8, JHH
4JHH
1.0), 5.32 (dd, 1H, H7, JHH
5.21 (dd, 1H, H6, JHH
ꢃ
/
ꢃ/
3
3
ꢃ/
ꢃ
ꢃ/
/
ꢃ/
3
3
ꢃ/
6.2, JHH
6
7
8
H3?), 6.20 (d, 2H, H8 and H8?, 3JHH
ꢃ/
6.5), 5.99 (dd, 2H, (C9, C9?), 98.8 (C4, C4?), 90.3 (C7, C7?), 89.1 (C6, C6?),
3
4
6.1, JHH
H5 and H5?, JHH
ꢃ
/
ꢃ
/
1.3), 5.22 (dd, 2H, H7 87.5 (C5, C5?), 87.3 (C8, C8?), 116.0, 116.3 (Cp)
3
3
5.9, JHH
and H7?, JHH
ꢃ/
ꢃ5.9), 5.21 (dd, 2H, H6 and
/
3
3
5.9, JHH
H6?, JHH
ꢃ/
ꢃ/5.9)
1953 (s), 1873 (vs) 6.60 b (s, 5H, Cp), 6.51 (s, 5H, Cp), 7.19 (m, 4H, H5?,
236.0 b (CrCO3), 150.9 (C2), 173.7 (C2?), 138.3 (C3),
H6?, H7?, H8?), 6.65 (d, 1H, H8, 3JHH
ꢃ
/
6.0), 6.55 (s, 1H, 168.4 (C3?), 105.3 (C9), 132.5 (C4?), 92.5 (C7), 129.6
4
H3?), 6.49 (d, 1H, H3, JHH
ꢃ
/
1.68), 6.33 (d, 1H, H5,
(C7?), 90.9 (C6), 128.9 (C6?), 89.7 (C5), 127.6 (C5?), 89.3
3JHH
5.53 (dd, 1H, H6, JHH
1939 (s), 1845 (vs) 6.42 (s, 5H, Cp), 6.24 (s, 5H, Cp), 6.03 (d, 1H, H5,
ꢃ
/
6.0), 5.54 (dd, 1H, H7, JHH
ꢃ
/4.3, JHH
ꢃ/6.1), (C8), 126.0 (C8?), 119.1, 119.3 (Cp)
3
3
3
3
ꢃ/4.3, JHH
ꢃ
/
6.1)
237.0 (CrCO3), 140.4 (C2), 107.3 (C3), 98.1 (C5), 97.2
3
3JHH
ꢃ
/
3.39), 5.73 (t, 1H, H4, JHH
H3, JHH 2.89), 4.17 (m, 1H, H1), 1.1ꢀ
C6H11 S-group)
2069 (w), 1988 (s), 5.69 (s, 10H, Cp), 2.71 (m, 2H, H1), 1.2ꢀ
1941 (m), 1897 (vs) C6H11 S-group)
1940 (s), 1847 (vs) 12.44 (s, 1H, OÃ
ꢃ/
3.24), 5.47 (d, 1H, (C4), 113.1, 114.3 (Cp), 57.1, 36.4, 27.0, 25.8 (C6 H11S-
3
ꢃ/
/1.9 (m, 10H, group)
9
/2.0 (m, 20H, 221 (CrCO4), 108.9 (Cp), 68.7, 38.4, 28.2, 25.8 (C6 H11S-
group)
10
/
H), 6.41 (s, 5H, Cp), 6.19 (s, 5H, Cp), 237.2 (CrCO3), 139.3 (C2), 107.1 (C3), 97.5 (C5), 97.1
3
3
6.14 (d, 1H, H5, JHH
3
3.18), 5.72 (d, 1H, H3, JHH
ꢃ/3.01), 5.83 (t, 1H, H4, JHH
ꢃ/
(C4), 115.7, 115.9 (Cp)
ꢃ/2.94)
11
12
1952 (s), 1870 (vs) 7.27ꢀ7.30 (m, C6H5 S group), 6.09 (s, 5H, Cp), 6.10 (s, 234.8 (CrCO3), 128.4 (C3), 90.5 (C7), 89.4 (C6), 87.7 (C5),
/
3
5H, Cp), 6.44 (s, 1H, H3), 6.21 (d, 1H, H8, JHH
ꢃ
/
6.0), 87.6 (C8), 113.4 (Cp)
3
6.00 (d, 1H, H5, JHH
3
6.4), 5.22 (dd, 1H, H6, JHH
ꢃ
/
ꢃ
/
3
7.7, JHH
3
6.4), 5.22 (dd, 1H, H7, JHH
3
7.6, JHH
ꢃ/
ꢃ/
ꢃ/
6.0)
1952 (s), 1870 (vs) 8.06 (s, 1H, OÃ
/
H), 6.40 (s, 5H, Cp), 6.39 (s, 5H, Cp), 6.43 NR
3
3
(s, 1H, H3), 5.23 (dd, 1H, H7, JHH
ꢃ
/
6.2, JHH
5.9)
1942 (s), 1853 (vs), 6.33 (s, 5H, Cp), 6.25 (s, 5H, Cp), 6.23 (s, 5H, Cp), 6.14 236.6, 236.5 (CrCO3), 136.4, 136.0 (C2, C2?), 107.4 (C3,
ꢃ/6.0),
3
3
5.22 (dd, 1H, H6, JHH
ꢃ/6.3, JHH
ꢃ/
13 and
14
723 (TiÃ
/
OÃ
/
Ti)
(s, 5H, Cp), 6.29 (d), 6.19 (m), 6.11 (t)
C3?), 99.7, 99.4 (C5, C5?), 97.9, 97.5 (C4, C4?), 115.6,
115.1 (Cp)
15
16
1925 (s), 1833,
1850 (vs)
6.68 (s, 10H, Cp), 6.56 (s, 10H, Cp), 5.63 (s, 2H, H3 and 108 (C3 and C4), 119.2, 119.1 (Cp)
H4)
1918 (s), 1821 (vs) 6.39 (s, 10H, Cp), 6.23 (s, 10H, Cp), 5.46 (s, 2H, H3 and 239.4 (CrCO3), 148.9 (C2 and C5), 108.8 (C3 and C4),
H4), 4.10 (m, 2H, H1), 1.0ꢀ1.8 (m, 20H, C6H11 S-group) 113.6, 113.4 (Cp), 57.1, 32.2, 27.3, 26.0 (C6 H11S-group)
/
NR, not recorded.
a
Carbonyl region.
Recorded in deuterated acetone.
b
neꢃ
/
thiophene 1967(s) cmꢂ1, 1877(vs) cmꢂ1; ben-
ascribed to a large polarization effect of the TiÃ
bond, with dꢁ at the titanium and dꢂ at the ring. This
effect is enhanced for complexes 15 and 16, resulting in
even lower wavenumbers, signifying high electron den-
/
C(arene)
zothiophene 1964(s) cmꢂ1, 1885(vs) cmꢂ1) [29], sug-
gests that the electron density is higher on the
substituted arene ring relative to the [Cr(p-arene)(CO)3]
/
/
(areneꢃ
/thiophene, benzothiophene) substrate. It is
sity on the arene ring, two highly polarized TiÃ
/
C(arene)

10
M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
bonds and consequently the instability of 15. The
electronic influence of the different substituents on the
titanium moiety is apparently negligible, since the
vibrational frequencies for the different types of com-
plexes are approximately the same.
Table 2
˚
Selected bond distances (A) and angles (8) of 4
Bond distance
Cr1Ã
Cr1Ã
Cr1Ã
Cr1Ã
Cr2Ã
Cr2Ã
Cr2Ã
Cr2Ã
Cr1Ã
Cr2Ã
S1Ã
C11Ã
C12Ã
C13Ã
C14Ã
S2Ã
C15Ã
C16Ã
C17Ã
C18Ã
/
C11
C12
C13
C14
C15
C16
C17
C18
S1
2.281(3)
2.222(3)
2.227(3)
2.197(3)
2.229(3)
2.183(16)
2.200(3)
2.202(4)
2.371(1)
2.425(3)
1.768(3)
1.445(5)
1.442(4)
1.385(5)
1.723(4)
1.733(5)
1.469(15)
1.476(16)
1.378(5)
1.660(5)
/
/
Two singlets were observed for the two Cp-ring
protons on the NMR spectra of the compounds
belonging to the class Cp2TiXY (1, 2, 5, 7, 8, 10, 11
and 12), which indicate the absence of a mirror plane in
the molecule and hence the two Cp-rings are not
equivalent but diastereotopic. On the spectrum of 5,
instead of two singlet resonances for the two Cp-rings, a
broad, unresolved multiplet was observed. For com-
plexes belonging to the class Cp2TiX2 two cases should
be considered. In the case where the Cp-rings are
equivalent, a mirror plane should be present in the
molecule, for example complexes 3 and 9. On the spectra
of these complexes the Cp-rings resonate as a singlet.
Complexes 4 and 6 both exist as enantiomeric pairs and
thus display two Cp signals each. The same is true for
the oxygen-bridged dimers 13 and 14, which show four
different environments for the Cp-rings. The Cp signals
of 15 and 16 are similar to those of the Cp2TiXY class,
although a symmetry plane exists in these complexes,
resulting in a doubling of the number of protons. The
1H- and 13C-NMR chemical shifts of the Cp-rings were
shifted more upfield for 8 and 11 compared to those of
1, 5, 10 and 12. In 8 and 11, a sulfur atom, a stronger
donor ligand compared to Clꢂ and OHꢂ, is bonded to
the titanium atom. Thus, electron density is shifted to
the titanium and causes greater shielding of the Cp-
protons. This may also simply be a result of the
difference in electronegativity of the donor atoms.
Assignments of chemical shift values for the thienyl
protons are based on studies by Gronowitz [30].
/
/
/
/
/
/
/S2
/
C11
/
C12
C13
C14
S1
/
/
/
/
C15
/
C16
C17
C18
S2
/
/
/
Bond angle
C11Ã
S1ÃC11Ã
C11Ã
C12Ã
C13Ã
C15Ã
S2ÃC15Ã
C15Ã
C16Ã
C17Ã
C11Ã
TiÃC11Ã
TiÃC11Ã
TiÃC15Ã
TiÃC15Ã
/
S1Ã
/
C14
95.2(1)
106.2(2)
114.7(3)
112.5(3)
111.1(3)
93.9(2)
/
/C12
/
C12Ã
C13Ã
C14Ã
/
C13
C14
S1
/
/
/
/
/
S2Ã
/C18
/
/C16
106.4(6)
115.0(7)
106.1(5)
118.1(3)
85.2(1)
/
C16Ã
C17Ã
C18Ã
/
C17
C18
S2
/
/
/
/
/
TiÃ
/C15
/
/S1
124.2(1)
128.5(2)
123.0(1)
129.4(6)
/
/C12
/
/S2
/
/C16
which correspond well with structural data reported
S dis-
tances in 4 are slightly longer. The tripod formed by the
for [Cr(h5-C4H3S)(CO)3] [31], although the CrÃ
/
4. Crystal structure
three carbonyl ligands on the chromium metal is
Single crystal X-ray diffraction studies confirmed the
molecular structure of 4. The compound crystallized in
both enantiomeric forms in such a way that the
thiophene ring S2, C15, C16, C17, C18 appears as a
disordered ring. S2 and C16 alternatively occupied the
same position. The green crystals were afforded from a
characteristic of areneꢀ
tripods are arranged with one carbonyl ligand trans to
C15 distances
/
chromium complexes [32]. These
the sulfur atom [31]. The TiÃ
/
C11 and TiÃ
/
˚
are equal within experimental error and are 2.204(3) A
on average. This value does not differ significantly from
values for TiÃ
/
C(arene) bonds of similar titanium com-
dichloromethaneꢀhexane (1:1) solution. Selected bond
/
plexes reported in literature [12,33ꢀ
/
35]. By contrast, TiÃ
/
distances and angles are given in Table 2. Fig. 2
represents ball-and-stick plots of the enantiomeric
pair, form A and form B.
C distances with perceivable p-interaction distributions
between titanium and a carbon atom are significantly
˚
shorter and ranges from 2.00 to 2.10 A [36].
The torsion angle S1Ã
/
C11Ã
/
C15Ã
/
S2 for form A is
On comparing the bond lengths of the thienyl ring in
complex 4 with the bond lengths of uncoordinated
thiophene [37], all of the bonds are longer in the
complex. Usually, the bond lengths of the h5-coordi-
126.18 and for form B is ꢂ
/
1.08. Both thiophene units,
coordinated to Cr(CO)3 moieties, are planar. The
thiophene ring carbons are equidistant from the Cr
atoms, signifying h5-coordination. The CrÃ
/
C(ring) dis-
˚
nated thienyl ring follow the trend of short C11Ã
/C12
tances range from 2.183(16) to 2.281(3) A and the CrÃ
/S
˚
distances are 2.371(1) and 2.425(3) A, respectively,
and C13ÃC14 bonds and a long C12ÃC13 bond
/
/

M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ
/
14
11
Fig. 2. Molecular structures of the enantiomeric forms of 4.
[15,17,38]. In this case, however, the C11Ã
C16) and C12ÃC13 (C16ÃC17) bonds are the longer
bonds and C13ÃC14 (C17ÃC18) is the short bond,
/
C12 (C15Ã
/
5.1.1. Syntheses: general preparation of [Cr(h5-
/
/
thiophene)(CO)3] and [Cr(h6-benzothiophene)(CO)3]
[Cr(NH3)3(CO)3] (2.00 g, 10.7 mmol) was dissolved in
/
/
displaying allylic character. This sequence is character-
istic of thiophene rings bonded in a h1-fashion to a
metal fragment with significant p-delocalization from
the ring to the metal [17,38]. The longer bond lengths
compare with the characteristic bond distances of a
diethyl ether (ꢀ
95 cm3). Freshly distilled Et3OBF4 (3.95
/
cm3, 33 mmol) was added to the solution, followed by 21
mmol of thiophene substrate. The reaction mixture was
stirred for 12 h. Diethyl ether (100 cm3) was added and
the solution was cooled to 0 8C after which 100 cm3 of
air-free water was added. The mixture was repeatedly
extracted with diethyl ether until the extracts were
virtually colorless. The ether extracts were combined
and dried over anhydrous sodium sulfate. The solvent
was removed under reduced pressure. The product was
purified with column chromatography that afforded the
starting compound and the orange product. The crude
2
C(sp2)Ã
/
C(sp ) single bond (1.46 A), while the short
bond distance resemble a C(sp2)Ã
(1.32 A) [39].
˚
/
C(sp2) double bond
˚
5. Experimental
product was recrystallized from a dichloromethaneꢀ
/
5.1. Materials and method
hexane mixture. The orange crystals were washed with
cold hexane and dried. Yields were higher than 70%
based on the mass of [Cr(NH3)3(CO)3].
All reactions and manipulations were performed
under an inert atmosphere using standard Schlenk
tube techniques [40]. Solvents were dried by the usual
procedures [41] and distilled under nitrogen prior to use.
The starting materials thiophene, benzo[b]thiophene
and n-BuLi were used as obtained from Aldrich and
thiophene was purified as described in literature [42].
The precursors [Cr(NH3)3(CO)3] [43], [Cr(h5-thiophe-
ne)(CO)3] [20] and [{TiCp2Cl}2{m-O}] [44] were synthe-
sized according to known literature methods. Column
5.1.2. [Ti{(h1,h5-thienyl)Cr(CO)3}Cp2Cl] (1)
1.2 g (5.46 mmol) of [Cr(h5-thiophene)(CO)3] was
dissolved in 30 cm3 of THF and cooled to ꢂ
90 8C when
/
3.6 cm3 (5.76 mmol) n-BuLi (1.6 M solution in hexane)
was added. The color of the reaction mixture changed
from orange to yellow. The mixture was stirred at ꢂ
/
chromatography was performed on silica gel (0.063ꢀ
0.200 mm) on columns that were cooled by circulating
cold isopropanol (ꢂ20 8C) through column jackets. The
solvents used for column chromatography were
dichloromethaneꢀpetroleum ether mixtures in varying
/
70 8C for 10 min and then cooled to ꢂ90 8C again. A
/
solution of 1.36 g (5.46 mmol) of [TiCp2Cl2] in THF was
added. The solution was allowed to warm to room
temperature (r.t.) while the color changed from red to
green. The solvent was removed in vacuo. Column
chromatography of the residue yielded three fractions.
The first red band isolated was unreacted starting
compound, [Cr(h5-thiophene)(CO)3], while the second
green band contained a mixture of products, meso-
[Ti{(h1,h5-thienyl)Cr(CO)3}2Cp2] (3) and [Ti{(h1,h5-
thienyl)Cr(CO)3}2Cp2] (4), in a 1:1 ratio. These two
compounds were separated on a second column using
toluene as eluent. The main product, 1, was isolated as a
green fraction. After isolation of this compound, the
polarity of the eluent was increased to dichloro-
/
/
ratios, unless stated otherwise. NMR spectra were
recorded in CDCl3 as solvent on a Bruker AC-300
spectrometer with reference to the deuterium signal
1
CDCl3. H- and 13C-NMR spectra were measured at
300.133 and 75.469 MHz, respectively. Infrared spectra
were recorded as CH2Cl2 solutions on a BOMEM
Michelson-100 FT spectrophotometer. Mass spectra
were recorded on a PerkinꢀElmer RMU-6H instrument
/
operating at 70 eV. Melting points were recorded in
capillaries on a Gallenkamp hot-stage apparatus and are
uncorrected.
methaneꢀether (1:1) and a brown product [(TiCp2Cl)-
/

12
M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
(Ti{(h1,h5-thienyl)Cr(CO)3}Cp2){m-O}] (2) as well as
the yellow compound [{TiCp2Cl}2{m-O}] were isolated.
[C6H11SH] and 10 cm3 dichloromethane. The mix-
ture was stirred for 1 h at r.t. and the color of the
solution changed from green to violet. The solvent
was removed under reduced pressure. Column
chromatography yielded the blue complex [(TiCp2)-
(Cr(CO)4){m-C6H11S}] (9), the orange compound
[Cr(h5-thiophene)(CO)3] and the violet compound
[TiCp2(C6H11S)2] (76.4 mg, 81%).
1*
Calc.: C, 47.19; H, 3.03. Found: C, 46.88; H, 2.85%.
2*Yield: 0.12 g (6%). C27H23ClO4SCrTi2 (626.8)*
Calc.: C, 51.74; H, 3.70. Found: C, 51.92; H, 3.93%.
3 and 4*Yield: 1.03 g (36%). C24H16O6S2Cr2Ti
(616.4)*Calc.: C, 46.77; H, 2.62. Found: C, 46.48; H,
2.34%.
/
Yield: 0.74 g (36%). C17H13ClO3SCrTi (432.7)*
/
/
/
/
/
9*
/
Yield: 6.0 mg (6%). C26H32O4S2CrTi
(572.6)*
54.68; H, 5.75%.
/
Calc.: C, 54.54; H, 5.63. Found: C,
5.1.3. [Ti{(h1,h6-benzothienyl)Cr(CO)3}Cp2Cl] (5)
[Cr(h6-benzothienyl)(CO)3] (0.55 g, 2.04 mmol) was
dissolved in THF (ꢀ
/
15 cm3). The solution was cooled
5.1.5. Reaction of 1 with water
A solution of 114 mg (0.26 mmol) of 1 in 40 cm3 of
distilled water was stirred at r.t. for 20 min. The color of
the solution changed from green to red. The solution
was concentrated until a red precipitate appeared, while
the solution was only lightly colored. Dichloromethane
(80 cm3) was added to this suspension and the red
organic layer was separated from the water phase. The
organic phase was dried over anhydrous sodium sulfate
and the residue was recrystallized from a dichloro-
to ꢂ
/
40 8C and 1.4 cm3 (2.24 mmol) of n-BuLi was
added to the stirred solution. Stirring was maintained
for 1 h at this temperature during which time the color
of the solution changed from orange-yellow to dark
brown. 0.50 g (2.04 mmol) of [TiCp2Cl2] was gradually
added to the cooled reaction mixture, after which
stirring was maintained for a further 30 min. The
mixture was heated to r.t. and stirred for 30 min. The
mixture was filtered through silica gel, using dichlor-
omethane as eluent. The solvent was removed under
reduced pressure. Two bands were separated by means
methaneꢀpetroleum ether (1:1) mixture. Red-brown
/
needle-like crystals of [Ti{(h1,h5-thienyl)Cr(CO)3}C-
p2(OH)] (10) were formed.
of column chromatography (eluent: petroleum etherꢀ
/
10*
/
Yield: 86 mg (79%). C17H14O4SCrTi (414.3)*
/
dichloromethane (1:2)). The first band removed from
the column was characterized as unreacted orange
starting compound. The second green band was identi-
fied as [Ti{(h1,h6-benzothienyl)Cr(CO)3}Cp2Cl] (5)
while a third green product was characterized as
[Ti{(h1,h6-benzothienyl)Cr(CO)3}2Cp2] (6).
Calc.: C, 49.29; H, 3.41. Found: C, 48.82; H, 3.29%.
5.1.6. Reaction of 5 with thiophenol
Thiophenol (0.92 cm3, 7.46 mmol) was added to 0.40
g (0.82 mmol) of 5. Dichloromethane (10 cm3) and 0.62
cm3 (4.10 mmol) of TMEDA were added and the
mixture was stirred for 1 h at r.t. The color changed
from green to orange-red. The solvent was removed
under reduced pressure. Three bands were separated
5*
Calc.: C, 52.25; H, 3.13. Found: C, 52.41; H, 3.25%.
MS (EI); m/z: 482 [Mꢁ], 398 [Mꢁꢂ3CO], 346 [Mꢁꢂ
3COꢂ
Cr], 213 [TiCp2Clꢁ], 148 [TiCpClꢁ].
6*Yield: 0.54 g (37%). C32H20O6S2Cr2Ti (716.5)*
Calc.: C, 53.64; H, 2.81. Found: C, 53.90; H, 2.97%.
7*C29H20O3S2Cr2Ti (664.5)*Calc.: C, 52.42; H,
3.03. Found: C, 52.66; H, 3.16%.
/
Yield: 0.54 g (55%). C21H15ClO3SCrTi (482)*
/
/
/
/
with column chromatography (eluent: petroleum etherꢀ
/
/
/
dichloromethane (1:2)). The first yellow band was
identified as the starting compound [Cr(h6-benzothio-
phene)(CO)3]. The second orange-red band was char-
acterized as [Ti{(h1,h6-benzothienyl)Cr(CO)3}Cp2-
(SC6H5)] (11). The third purple band was characterized
as TiCp2(SPh)2. Yield: 0.13 g (41%).
/
/
5.1.4. Reaction of 1 with [C6H11SH]
a) 100 mg (0.23 mmol) of 1 was dissolved in 5 cm3
(33.3 mmol) of TMEDA, 4 cm3 (32.6 mmol) of
[C6H11SH] and 10 cm3 dichloromethane. The mix-
ture was stirred for 1 h at r.t. and the color of the
solution changed from green to brown-green. The
solvent was removed under reduced pressure. Col-
umn chromatography yielded the orange compound
[Cr(h5-thiophene)(CO)3] and the complex [Ti-
{(h1,h5-thienyl)Cr(CO)3}(SC6H11)Cp2] (8).
11*
Calc.: C, 58.28; H, 3.62. Found: C, 58.42; H, 3.73. MS
(EI); m/z: 500 [Mꢁꢂ2CO], 472 [Mꢁꢂ
3CO], 420
[Mꢁꢂ Cr], 287 [TiCp2SPhꢁ], 178 [TiCp2ꢁ].
3COꢂ
/
Yield: 0.11 g (24%). C27H20O3S2CrTi (556.5)*
/
/
/
/
/
5.1.7. Reaction of 5 with water
5 (0.48 g, 1.00 mmol) was dissolved in dichloro-
methane (ꢀ
/
50 cm3). Distilled water (ꢀ20 cm3) was
/
added and the mixture was stirred for 12 h, during which
time the color of the solution changed from green to
orange. The organic and water layers were separated
and the organic layer was dried over anhydrous sodium
sulfate. The solvent was removed under reduced pres-
sure. The orange-brown product [Ti{(h1,h6-benzothie-
8*
/Yield: 98.3 mg (83%). C23H24O3S2CrTi
(512.5)*
/
Calc.: C, 53.91; H, 4.72. Found: C,
53.69; H, 4.94%.
b) 100 mg (0.23 mmol) of 1 was dissolved in 4 cm3
(26.6 mmol) of TMEDA, 8 cm3 (65.2 mmol) of

M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ
/
14
13
nyl)Cr(CO)3}Cp2(OH)] (12) was washed with hexane
and dried in vacuo. Yield: 0.28 g (65%).
5.2. Crystal structure determination
12*
/
Yield: 0.28 g (65%). C21H16CrO4STi (464.3)*
/
The intensity data for the compound were collected
on a Nonius CAD4 diffractometer, using graphite-
Calc.: C, 54.33; H, 3.47. Found: C, 54.52; H, 3.58%.
monochromated MoꢀKa radiation. Data were corrected
/
for Lorentz polarization and absorption effects [45]. The
structures were solved by direct methods (SHELXS) [46]
and refined by full-matrix least-squares techniques
against Fo2 (SHELXL-97) [47]. The thienyl ring S2, C15,
C16, C17, C18 is disordered in such a way that S2 and
C16 alternatively occupied the same positions. This
disorder could be solved. The hydrogen atoms of the
structure were included at calculated positions with
fixed thermal parameters. All non-hydrogen atoms
were refined anisotropically. XP (SIEMENS Analytical
X-ray Instruments, Inc.) was used for structure repre-
sentations (Table 3).
5.1.8. meso-[Ti{(h1,h5-thienyl)Cr(CO)3}Cp2Cl]2{m-
O} (13) and [Ti{(h1,h5-thienyl)Cr(CO)3}Cp2Cl]2{m-
O} (14)
0.6 g (2.71 mmol) of [Cr(h5-thiophene)(CO)3] was
dissolved in 30 cm3 of THF and cooled to ꢂ
90 8C when
/
1.8 cm3 (2.88 mmol) n-BuLi was added. The color of the
reaction mixture changed from orange to yellow. The
mixture was stirred at ꢂ
/
70 8C for 10 min and then
cooled to ꢂ
/
90 8C again. A cooled solution of 0.6 g (1.35
mmol) of [{TiCp2Cl}2(m-O)] in 80 cm3 of THF was
added. The solution was allowed to warm to r.t. while
the color changed from yellow-red to dark red. The
solvent was removed in vacuo. Column chromatography
(dichloromethaneꢀpetroleum ether) of the residue
/
yielded the starting material and the red-brown isomers
13 and 14.
13 and 14*
(810.5)*Calc.: C, 50.39; H, 3.23. Found: C, 50.01; H,
3.08%.
/
Yield: 0.85 g (77%). C34H26O7S2Cr2Ti2
/
Table 3
Crystal data and structure refinement of 4
Empirical formula
Formula weight (g molꢂ1
Temperature (K)
C24H16O6S2Cr2Ti
616.39
5.1.9. [TiCp2Cl]2{m-Cr(h5-thienyl)(CO)3} (15)
0.6 g (2.73 mmol) of [Cr(h5-thiophene)(CO)3] was
)
183(2)
0.71073
Triclinic
dissolved in 30 cm3 of THF and cooled to ꢂ
/
90 8C. 5.1
cm3 (8.18 mmol) of n-BuLi was added and the mixture
was stirred for 10 min at ꢂ50 8C. The color of the
reaction mixture changed from orange to yellow. The
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
¯
P1
/
/
˚
a (A)
7.942(1)
10.290(1)
14.679(1)
80.84(1)
79.71(1)
85.90(1)
1164.1(2)
2
˚
b (A)
solution was again cooled to ꢂ90 8C and a solution of
/
1.36 g (5.46 mmol) of [TiCp2Cl2] in 100 cm3 of THF was
added. The temperature of the solution was allowed to
˚
c (A)
a (8)
b (8)
g (8)
Volume (A )
Z
warm to ꢂ20 8C after which the solvent was evapo-
/
rated. The green residue was dissolved in 80 cm3 of
dichloromethane and filtered. The green solid 15 was
recrystallized from acetone and the crystals washed with
3
˚
Density (calculated) (mg mꢂ3
)
1.758
1.471
620
Absorption coefficient (mmꢂ1
F(0 0 0)
)
an etherꢀ
15*Yield: 0.50
(645.2)*Calc.: C, 50.26; H, 3.44. Found: C, 50.45; H,
3.22%.
/
petroleum ether (1:1) mixture and dried.
/
g
(34%). C27H22Cl2O3SCrTi2
Crystal size (mm3)
0.40ꢄ
2.28ꢀ27.44
105h 5
135k 5
195l 518
5549
5266 [Rint
/
0.38ꢄ
/
0.36
/
Theta range for data collection (8)
Index ranges
/
ꢂ
/
/
/
9,
0,
ꢂ
/
/
/
ꢂ/
/
/
Reflections collected
Independent reflections
Absorption correction
Max./min. transmission
Refinement method
5.1.10. Reaction of 15 with C6H11SH
0.50 g (0.78 mmol) of 15 was reacted with 12 cm3 (79.9
mmol) of TMEDA, 9 cm3 (73.4 mmol) of C6H6SH and
20 cm3 of dichloromethane. The solution was stirred for
1 h at r.t. The color of the solution changed from green
to black-green. The solvent was removed in vacuo and
column chromatography of the residue yielded an olive-
green complex [TiCp2(C6H11S)]2{m-Cr(h5-thienyl)-
(CO)3} (16).
ꢃ/0.0315]
PSI-SCAN
0.364/0.325
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit on F2
3516/0/322
0.962
Final R indices [I ꢁ
R indices (all data)
Largest difference peak and hole
/
2s(I)]
R1ꢃ
R1ꢃ
0.557 and ꢂ
/
0.041, wR2ꢃ
0.100, wR2ꢃ
0.720
/
0.099
/
/0.108
/
ꢂ3
˚
(e A
)
16*
/
Yield: 0.47 g (76%). C39H44CrO3S3Ti2 (804.8)*
/
Calc.: C, 58.21; H, 5.51. Found: C, 57.95; H, 5.32%.

14
M. Landman et al. / Journal of Organometallic Chemistry 678 (2003) 5ꢀ14
/
(b) G. Richter-Addo, A.D. Hunter, N. Wichrowska, Can. J.
Chem. 68 (1990) 41.
6. Supplementary material
[14] R. Meyer, P.L. Wessels, P.H. van Rooyen, S. Lotz, Inorg. Chim.
Acta 284 (1999) 127.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 180975 (FO429). Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
[15] T.A. Waldbach, P.H. van Rooyen, S. Lotz, Angew. Chem. Int.
Ed. Engl. 32 (1993) 710.
[16] M. Landman, T. Isenburg, S. Lotz, Unpublished results.
[17] T.A. Waldbach, R. van Eldik, P.H. van Rooyen, S. Lotz,
Organometallics 16 (1997) 4056.
1EZ, UK (Fax: ꢁ44-1223-336033; e-mail: deposit@
/
[18] A. du Toit, M. Landman, S. Lotz, J. Chem. Soc. Dalton Trans.
(1997) 2955.
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
[19] M.D. Rausch, G.A. Moser, E.J. Zaiko, A.L. Lipman, Jr., J.
Organomet. Chem. 23 (1970) 185.
[20] M. Novi, G. Guanti, C. Dell’Erba, J. Heterocycl. Chem. 12 (1975)
1055.
Acknowledgements
[21] C.A.L. Mahaffy, P.L. Pauson, Inorg. Synth. 38 (1990) 136.
[22] M.N. Nefedova, V.N. Setikina, D.N. Kursanov, J. Organomet.
Chem. 244 (1983) C21.
We wish to thank Mr. E. Palmer for the NMR
measurements and the University of Pretoria and the
Foundation for Research and Development, Pretoria,
for financial assistance.
[23] M. Bottrill, P.D. Gavens, J.W. Kelland, J. McMeeking, Compre-
hensive Organometallic Chemistry, Part 22, vol. 405, Pergamon
Press, Oxford, 1982.
[24] A.N. Nesmeyanov, E.I. Fedin, O.V. Nogina, N.S. Kochetkova,
V.A. Dubovitsky, P.V. Petrovsky, Tetrahedron Suppl. 8 (1966)
389.
References
[25] H. Kopf, B. Block, M. Schmidt, Chem. Ber. 101 (1968) 272.
¨
[26] (a) P.S. Braterman, V.A. Wilson, K.K. Joshi, J. Chem. Soc. A
(1971) 191.;
[1] W.L. Orr, C.M. White (Eds.), Geochemistry of Sulfur in Fossil
Fuels, American Chemical Society, Washington, DC, 1990.
[2] (a) G.M. Tsivgoulis, J.-M. Lehn, Angew. Chem. Int. Ed. Engl. 34
(1995) 1119;
(b) C.J. Ruffing, T.B. Rauchfuss, Organometallics 4 (1985) 524.
[27] J.H. Toney, T.J. Marks, J. Am. Chem. Soc. 107 (1985) 947.
[28] M.A. Chaudhari, P.M. Treichel, F.G.A. Stone, J. Organomet.
Chem. 2 (1964) 206.
(b) S. Le Stang, F. Paul, C. Lapinte, Organometallics 19 (2000)
1035;
[29] M.J. Sanger, R.J. Angelici, Organometallics 13 (1994) 1821.
[30] S. Gronowitz, Adv. Heterocycl. Chem. 1 (1963) 1.
[31] M.F. Bailey, L.F. Dahl, Inorg. Chem. 4 (1965) 1306.
[32] E.L. Muetterties, J.R. Bleeke, E.J. Wuckerer, T.A. Albricht,
Chem. Rev. 82 (1982) 499.
(c) M. Hmyene, A. Yassar, M. Escorne, A. Percheron-Guegan, F.
Garnier, Adv. Mater. 6 (1994) 564.
[3] B.C. Gates, J.R. Katzer, G.C.A. Schuit, Chemistry of Catalytic
Processes, McGraw-Hill, New York, 1979.
[4] (a) R.J. Angelici, Acc. Chem. Res. 21 (1988) 387;
(b) R.J. Angelici, Coord. Chem. Rev. 105 (1990) 61;
(c) R.J. Angelici, Bull. Soc. Chim. Belg. 104 (1995) 265;
(d) C. Bianchini, A. Meli, J. Chem. Soc. Dalton Trans. (1996)
801.;
[33] R. Meyer, M. Schindehutte, P.H. van Rooyen, S. Lotz, Inorg.
Chem. 33 (1994) 3605.
[34] J.D. Zeinstra, J.H. Teuben, F. Jellinek, J. Organomet. Chem. 170
(1979) 39.
[35] J.L. Attwood, W.E. Hunter, D.C. Hrncir, E. Samuel, H. Alt,
Inorg. Chem. 14 (1975) 1757.
(e) C. Bianchini, A. Meli, Acc. Chem. Res. 31 (1998) 109.
[5] (a) C. Bianchini, A. Meli, Synlett 6 (1997) 643;
(b) W.D. Harman, Chem. Rev. 97 (1997) 1953.
[6] R.J. Angelici, Organometallics 20 (2001) 1259.
[7] (a) T.B. Rauchfuss, Prog. Inorg. Chem. 21 (1991) 259;
[36] A.K. Rappe, Organometallics 6 (1987) 354.
[37] W.R. Harshbarger, S.H. Bauer, Acta Crystallogr. B 26 (1970)
1010.
[38] (a) T.A. Waldbach, P.H. van Rooyen, S. Lotz, Organometallics
12 (1993) 4250;
(b) J. Chen, R.J. Angelici, Coord. Chem. Rev. 206ꢀ207 (2000) 63.
/
[8] (a) J.W. Hachgenei, R.J. Angelici, Organometallics 8 (1989) 14;
(b) S. Zhang, J.K. Shen, F. Basolo, T.D. Ju, R.F. Lang, G. Kiss,
C.D. Hoff, Organometallics 13 (1994) 3692;
(b) S. Lotz, P.H. van Rooyen, R. Meyer, Adv. Organomet. Chem.
37 (1995) 219.
[39] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen,
R. Taylor, J. Chem. Soc. Perkin Trans. II (1987) S1.
[40] D.F. Shriver, M.A. Drezdzon, The Manipulation of Air-sensitive
Compounds, 2nd ed., Wiley, New York, 1980.
[41] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, 2nd ed., Pergamon Press, New York,
1980.
(c) J.A.S. Howell, P.C. Yates, N.F. Ashford, D.T. Dixon, R.
Warren, J. Chem. Soc. Dalton Trans. (1996) 3959.
[9] (a) J. Besancon, J. Tiroflet, A. Card, Y. Dusausoy, J. Organomet.
Chem. 59 (1973) 267;
(b) F. Rose-Munch, O. Bellot, M. Laurent, A. Semra, F. Robert,
Y. Jeannin, J. Organomet. Chem. 402 (1991) 1.
[10] (a) M.F. Semmelhack, J. Bisaha, M. Czarney, J. Am. Chem. Soc.
101 (1979) 768;
[42] G.H. Spies, R.J. Angelici, Organometallics 6 (1987) 1897.
[43] M.D. Rausch, G.A. Moser, E.J. Zaiko, A.L. Lipman, Jr., J.
Organomet. Chem. 23 (1970) 185.
(b) M. Ghavshou, D.A. Widdowson, J. Chem. Soc. Perkin Trans.
1 (1983) 3065.
[44] D. Nath, R.K. Sharma, A.N. Bhat, Inorg. Chim. Acta 20 (1976)
109.
[11] S. Lotz, M. Schindehutte, P.H. van Rooyen, Organometallics 11
(1992) 629.
[45] MOLEN, An Interactive Structure Solution Procedure, Enraf-
Nonius, Delft, The Netherlands, 1990.
[46] G.M. Sheldrick, Acta Crystallogr. A 46 (1990) 467.
[12] P.H. van Rooyen, M. Schindehutte, S. Lotz, Organometallics 11
(1992) 1104.
[13] (a) J.A. Heppert, M.A. Morgenstern, D.M. Scherubel, F.
Takusagawa, M.R. Shaker, Organometallics 7 (1988) 1715;
[47] G.M. Sheldrick, SHELXL-97 (Release 97-2), University of Gottin-
¨
gen, Germany, 1997.