New arene ruthenium complexes with planar chirality

Article abstract of DOI:10.1016/S0020-1693(03)00425-0

1,2,4-Trimethyl-cyclohexadiene reacts with RuCl₃·nH ₂O in refluxing ethanol to afford quantitatively [RuCl ₂(1,2,4-C₆H₃Me₃)]₂ (1), the coordination of 1,2,4-trimethylbenzene to the ruthenium atom introducing planar chirality at the η⁶-arene ligand. The dinuclear complex 1 reacts with two equivalents of triphenylphosphine (PPh₃) to give quantitatively, as a racemic mixture of enantiomers, [RuCl₂(1,2,4- C₆H₃Me₃)(PPh₃)] (2), the structure of which has been determined by a single-crystal X-ray structure analysis of (rac)-2. Similarly, 1 reacts with two equivalents of the enantiopure phosphine (1S,2S,5R)-(+)-neomenthyldiphenylphosphine (nmdpp) to afford in good yield [RuCl₂(1,2,4-C₆H₃Me₃)(nmdpp)] (3) as a mixture of diastereoisomers, from which the isomer 3a was isolated by crystallisation. A single-crystal X-ray structure analysis of 3a allowed the determination of the absolute configuration at the planar chiral η ⁶-arene moiety. Finally, complex 1 reacts with one equivalent of the diphosphine ligand 1,1′-bis(diphenylphosphino)ferrocene (dppfc) to give the heteronuclear complex [RuCl₂(1,2,4-C₆H ₃Me₃) (dppfc)RuCl₂(1,2,4-C₆H ₃Me₃)] (4). All complexes were fully characterised by elemental analysis, mass spectrometry, NMR and IR spectroscopies.

Full text of DOI:10.1016/S0020-1693(03)00425-0

Inorganica Chimica Acta 357 (2004) 219–224
www.elsevier.com/locate/ica
New arene ruthenium complexes with planar chirality
*
€
Bruno Therrien , Georg Suss-Fink
Institut de Chimie, Universiteꢀde Neucha^tel, Case postale 2, CH-2007 Neucha^tel, Switzerland
Received 18 June 2003; accepted 20 June 2003
Abstract
1,2,4-Trimethyl-cyclohexadiene reacts with RuCl3 ꢀ nH2O in refluxing ethanol to afford quantitatively [RuCl2(1,2,4-C6H3Me3)]2
(1), the coordination of 1,2,4-trimethylbenzene to the ruthenium atom introducing planar chirality at the g6-arene ligand. The
dinuclear complex 1 reacts with two equivalents of triphenylphosphine (PPh3) to give quantitatively, as a racemic mixture of
enantiomers, [RuCl2(1,2,4-C6H3Me3)(PPh3)] (2), the structure of which has been determined by a single-crystal X-ray structure
analysis of (rac)-2. Similarly, 1 reacts with two equivalents of the enantiopure phosphine (1S,2S,5R)-(+)-neomenthyldiphenyl-
phosphine (nmdpp) to afford in good yield [RuCl2(1,2,4-C6H3Me3)(nmdpp)] (3) as a mixture of diastereoisomers, from which the
isomer 3a was isolated by crystallisation. A single-crystal X-ray structure analysis of 3a allowed the determination of the absolute
configuration at the planar chiral g6-arene moiety. Finally, complex 1 reacts with one equivalent of the diphosphine ligand 1,10-
bis(diphenylphosphino)ferrocene (dppfc) to give the heteronuclear complex [RuCl2(1,2,4-C6H3Me3) (dppfc)RuCl2(1,2,4-C6H3Me3)]
(4). All complexes were fully characterised by elemental analysis, mass spectrometry, NMR and IR spectroscopies.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Ferrocene; Phosphine ligand; Planar chirality; Ruthenium
1. Introduction
or 1,10-bis(diphenylphosphino)ferrocene gives rise to the
formation of the corresponding phosphine complexes
which exist as mixtures of enantiomers or diastereomers,
respectively.
It is known that an arene ligand bearing two non-
equivalent substituents in 1,2 or 1,3 positions relative to
each other, coordinated in an g6-fashion to a transition
metal, generates planar chirality at the metal with re-
spect to the face of the coordinated arene [1]. Arene–
ruthenium complexes with planar chirality have been
studied first by Bennett and co-workers [2]. They are of
great interest because of their potential as chiral cata-
lysts for asymmetric synthesis [3–5].
Herein we report the synthesis of a dinuclear arene
ruthenium complex with planar chirality, [RuCl2(1,2,4-
C6H3Me3)]2, in which the presence of three methyl
groups in positions 1,2 and 4 of the g6-arene rings is
responsible for the planar chirality. The reaction of this
dimer with phosphine ligands, such as triphenylphos-
phine, (1S,2S,5R)-(+)-neomenthyldiphenylphosphine,
2. Experimental
2.1. General remarks
Ethanol and methanol were dried and distilled under
nitrogen prior to use. Except for RuCl3 ꢀ nH2O (Johnson
Matthey), all reagents were purchased either from Al-
drich or Fluka and used as received. Nuclear magnetic
resonance spectra were recorded using a Varian Gemini
200 BB or a Bruker 400 MHz spectrometer and refer-
enced to the signals of the residual protons in the deu-
terated solvents. Electro-spray mass spectra were
obtained in positive-ion mode with an LCQ Finnigan
mass spectrometer. IR spectra were recorded with a
Perkin–Elmer Spectrum One FTIR spectrometer. Mi-
croanalyses were carried out by the Laboratory of
Pharmaceutical Chemistry, University of Geneva,
* Corresponding author. Tel.: +41-32-718-2499; fax: +41-32-718-
2511.
E-mail addresses: bruno.therrien@unine.ch (B. Therrien), georg.
€
suess-fink@unine.ch (G. Suss-Fink).
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00425-0

220
B. Therrien, G. S€uss-Fink / Inorganica Chimica Acta 357 (2004) 219–224
Switzerland. 1,2,4-Trimethyl-cyclohexadiene was pre-
pared according to published method [6].
3.53 (m, 4H), 2.95 (m, 2H), 2.27 (m, 2H), 2.05 (m, 2H),
1.97 (s, 3H), 1.92 (s, 6H), 1.76 (m, 2H), 1.71 (s, 3H), 1.50
(s, 3H), 1.39 (s, 3H), 1.25 (s, 3H), 1.06 (m, 2H), 0.95 (m,
2H), 0.83 (s, 3H), 0.55 (s, 3H), 0.04 (s, 3H), 0.01 ppm (s,
3H); 31P{1H} NMR (81 MHz, CDCl3); d ¼ 24:6 and
24.7 ppm; IR (KBr): 2954 s, 1632 w, 1438 s, 1374 m,
1094 m, 1032 m, 883 w, 748 s, 698 s, 519 s cmꢁ1; ESI-
MS: m=z: 581 [M ) Clꢁ]; elemental Anal. Calc. For
C31H41Cl2PRu (616.6), C, 60.4; H, 6.7. Found: C, 60.6;
H, 6.7%. The less soluble diastereomer 3a crystallised in
a pure form from a methanol solution of 3 at room
temperature.
2.2. Preparation of [RuCl2(1,2,4-C6H3Me3)]2 (1)
A solution of RuCl3 ꢀ nH2O (3.2 g, 12.0 mmol) and 10
equivalents of 1,2,4-trimethyl-cyclohexadiene (14.7 g,
0.12 mol) in ethanol (40 ml) was refluxed for 12 h. The
volume was then reduced to 5 ml, and the solid pre-
cipitated with ether. The red, air-stable, microcrystalline
material was isolated by filtration, giving 1 (550 mg, 0.81
mmol) in 50% yield. 1H NMR (400 MHz, CDCl3):
d ¼ 5:34 (d, 1H; CHar), 5.33 (d, 1H; CHar), 5.27 (d, 1H;
CHar), 5.25 (d, 1H; CHar), 5.00 (s, 1H; CHar), 4.99 (s,
1H; CHar), 2.17 (s, 3H, CH3), 2.16 (s, 3H, CH3), 2.11 (s,
3H, CH3), 2.10 (s, 6H, CH3), 2.09 ppm (s, 3H, CH3);
13C{1H} NMR (100 MHz, CDCl3): d ¼ 96:97, 96.93,
95.75, 95.67, 90.81, 90.78, 84.57, 84.52, 80.90, 80.86,
79.63, 79.53, 19.17, 17.74, 17.21 ppm; IR (KBr): 3043 m,
2918 m, 1621 w, 1531 w, 1448 s, 1376 s, 1122 w, 1031 s,
889 w, 734 w, 631 w cmꢁ1; ESI-MS: m=z: 606 [M + Naþ];
elemental Anal. Calc. For C18H24Cl4Ru2 (584.21), C,
37.0; H, 4.1. Found: C, 36.8; H, 4.2%.
2.5. Preparation of [RuCl2(1,2,4-C6H3Me3) (dppfc)
RuCl2(1,2,4-C6H3Me3)] (4)
A solution of 1 (58 mg, 0.1 mmol) and 1,10-
bis(diphenylphosphino)ferrocene (55 mg, 0.1 mmol) in
methanol (10 ml) was heated at 60 °C for 4 h. The
solvent was reduced to 2 ml, and the product purified
on silica gel plates (CH2Cl2/acetone, 15:1) to afford
[RuCl2(1,2,4-C6H3Me3)(dppfc)RuCl2(1,2,4-C6H3Me3)]
4 as an orange solid (35 mg, 0.03 mmol). Yield: 31%.
1H NMR (200 MHz, CDCl3): d ¼ 7:67 (m, 8H, PPh2),
7.36 (m, 12H, PPh2), 5.37 (s, 2H, CHar), 4.14 (m, 2H,
CHar), 4.11 (m, 2H, CHar), 4.03 (m, 4H, CHFc), 3.50 (s,
4H, CHFc), 2.15 (s, 6H, CH3), 1.86 (s, 6H, CH3), 1.61
ppm (s, 6H, CH3); 31P{1H} NMR (81 MHz, CDCl3);
d ¼ 20:7 ppm; IR (KBr): 1630 w, 1434 s, 1161 m, 1095
m, 1026 m, 752 s, 698 s, 545 m cmꢁ1; ESI-MS: m=z:
1161 [M + Naþ]; elemental Anal. Calc. For
C52H52Cl4FeP2 Ru2(1138.74), C, 54.8; H, 4.6. Found:
C, 55.0; H, 4.7%.
2.3. Preparation of [RuCl2(1,2,4-C6H3Me3)(PPh3)]
(2)
A solution of 1 (290 mg, 0.5 mmol) and triphenyl-
phosphine (270 mg, 1.0 mmol) in methanol (20 ml) was
heated at 60 °C for 3 h. Then the solvent was evaporated
to dryness to afford quantitatively [RuCl2(1,2,4-
1
C6H3Me3)(PPh3)] (2) as an orange solid. H NMR (200
MHz, CDCl3): d ¼ 7:80 (m, 6H; PPh3), 7.40 (m, 9H;
PPh3), 5.40 (s, 1H, CHar), 4.29 (m, 1H, CHar), 4.18 (m,
1H, CHar), 2.22 (s, 3H, CH3), 2.01 (s, 3H, CH3), 1.86
ppm (s, 3H, CH3); 13C{1H} NMR (50 MHz,
CDCl3): ¼ 134.65, 134.55, 134.36, 130.48, 128.32,
128.14, 107.57, 97.65, 96.30, 94.67, 86.11, 83.78, 17.93,
16.84, 16.20 ppm; 31P{1H} NMR (81 MHz, CDCl3);
d ¼ 28:5 ppm; IR (KBr): 1630 m, 1479 w, 1436 s, 1375
w, 1089 m, 1023 m, 753 s, 698 s, 528 s cmꢁ1; ESI-MS:
m=z: 519 [M ) Clꢁ]; elemental Anal. Calc. For
C27H27Cl2P1Ru2 (554.46), C, 58.5; H, 4.9. Found: C,
58.6; H, 4.8%.
2.6. X-ray crystallographic study
Crystals of (rac)-2 and 3a were mounted on a Stoe
Image Plate Diffraction system equipped with a /
circle goniometer, using Mo Ka graphite monochro-
ꢁ
mated radiation (k ¼ 0:71073 A) with / range 0°–
100°, increment of 0.9° and 0.7°, respectively, 2h range
ꢁ
from 2.0° to 26°, Dmax–Dmin ¼ 12:45–0:81 A. The
structures were solved by direct methods using the
programme SHELXS-97 [7]. The refinement and all
further calculations were carried out using SHELXL-
97 [8]. The H-atoms were included in calculated po-
sitions and treated as riding atoms using the SHELXL
default parameters. The non-H atoms were refined
anisotropically, using weighted full-matrix least-
square on F 2. Crystallographic details are summarised
in Table 1. Figures were drawn with the ORTEP
program [9].
2.4. Preparation of [RuCl2(1,2,4-C6H3Me3)(nmdpp)]
(3)
A solution of (1S,2S,5R)-(+)- neomenthyldiphenyl-
phosphine (110 mg, 0.34 mmol) and 1 (100 mg, 0.17
mmol) in ethanol (20 ml) was refluxed for 2 h. The so-
lution was evaporated under vacuum to give
[RuCl2(1,2,4-C6H3Me3)(nmdpp)] (182 mg, 0.29 mmol).
3
CCDC-212744 (rac)-2 and 212743 3a contain the
supplementary crystallographic data for this paper. These
data can be obtained free of charge at www.ccdc.cam.
ac.uk/conts/retrieving.html [or from the Cambridge
1
Yield: 87%. H NMR (200 MHz, CDCl3): d ¼ 7:90 (m,
8H, PPh2), 7.55 (m, 4H, PPh2), 7.25 (m, 8H, PPh2), 5.16
(s, 1H, CHar), 5.06 (s, 1H, CHar), 4.34 (m, 2H, CHar),

B. Therrien, G. S€uss-Fink / Inorganica Chimica Acta 357 (2004) 219–224
221
Table 1
Crystallographic and selected experimental data of (rac)-2 and 3a
(rac)-2 ꢀ 2CHCl3
29H29Cl8PRu
793.16
3a
Chemical formula
Formula weight
Crystal system
C
C31H41Cl2PRu
616.58
orthorhombic
P bca
orthorhombic
P 212121
Space group
Crystal colour and shape
Crystal size
orange plate
0.30 ꢂ 0.20 ꢂ 0.05
18.885 (2)
13.7506(6)
25.1922(12)
6541.8(7)
8
orange block
0.40 ꢂ 0.30 ꢂ 0.15
9.2724(5)
9.6036(4)
32.447(2)
2889.3(3)
4
ꢁ
a (A)
ꢁ
b (A)
ꢁ
c (A)
3
ꢁ
V (A )
Z
T (K)
153(2)
1.611
1.202
153(2)
1.417
0.801
Dc (g cmꢁ1
)
l (mmꢁ1
)
Scan range (°)
3:88 < 2h < 51:92
6355
3001
4:42 < 2h < 51:76
4884
4023
Unique reflections
Reflections used [I > 2rðIÞ]
Rint
0.0861
0.0534
Final R indices [I > 2rðIÞ]
R indices (all data)
Goodness-of-fit
0.0484, wR2 0.1012
0.1193, wR2 0.1160
0.814
0.0425, wR2 0.1028
0.0538, wR2 0.1060
0.981
ꢁ3
ꢁ
Max., Min. Dq=e (A
)
0.920, )0.806
1.059, )0.668
Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: (internat.) +44-1223/336-033;
e-mail: deposit@ccdc.cam.ac.uk].
refluxing ethanol to afford quantitatively [RuCl2(1,2,4-
C6H3Me3)]2 (1). Coordination of 1,2,4-trimethylbenzene
to the ruthenium atom introduces a planar chirality at
the g6-arene ligand. The dinuclear complex 1 is present
as a mixture of three species, as shown in Scheme 1, in
which 1a and 1b are enantiomers and 1c the meso form.
The 13C{1H} NMR spectrum of 1 shows in the arene–
ruthenium carbons region two sets of signals due to the
two diastereoisomers that are present in equal amounts.
Complex 1 reacts with two equivalents of triphenyl-
phosphine (PPh3) to give quantitatively the mononu-
clear complex [RuCl2(1,2,4-C6H3Me3)(PPh3)] (2), as a
racemic mixture of enantiomers 2a and 2b, see Scheme 2.
The 31P{1H} NMR of 2 shows a singlet at 28.5 ppm, the
chemical shift being comparable to those observed for
the analogous g6-arene ruthenium complexes [RuCl2
(C6Et6)(PPh3)] [11], and [RuCl2(C6H5fc)(PPh3)] [12]
which show signals at 24.0 and 28.6 ppm, respectively.
As expected for enantiomers, only one set of signals is
observed in the 1H and 13C{1H} NMR spectra. All
3. Results and discussion
1,2,4-Trimethyl-cyclohexadiene, accessible by stan-
dard Birch reduction [10], reacts with RuCl3 ꢀ nH2O in
Scheme 1.
Scheme 2.

222
B. Therrien, G. S€uss-Fink / Inorganica Chimica Acta 357 (2004) 219–224
attempts to separate the enantiomers 2a and 2b were
unsucessful.
Crystals of the racemate have been obtained by slow
evaporation of a chloroform solution containing 2. A
single-crystal X-ray analysis of a (rac)-2 was performed.
The molecular structure is presented in Fig. 1, and re-
lated bond lengths and angles are listed in Table 2.
Complex 2 crystallises in the centrosymmetric space
group P bca.
The ruthenium atom in 2 possesses a pseudo-octa-
hedral geometry, and the metrical parameters around
the metallic core compare well with those of simi-
lar three-legged piano-stool [RuCl2(g6-arene)(PPh3)]
complexes [11–17], the P–Ru–Cl angles being P(1)–
Ru(1)–Cl(1) 85.82(5)° and P(1)–Ru(1)–Cl(2) 91.46(5)°,
respectively. A distortion at the arene ligand is present,
the Ru–C bond distances trans to the phosphorous
ꢁ
atom, Ru(1)–C(2) 2.255(6) and Ru(1)–C(3) 2.248(7) A,
are elongated as compared to the other Ru–C bonds
ꢁ
[ranging between 2.203(6) and 2.234(7) A]. Similar
observations have been made for the complexes [RuCl2
(C10H14)(PMePh2)], [RuCl2(C6H6)(PMePh2)] [13] and
[RuCl2(C16H16)(PPh3)] [14], where the distortion was
attributed to the trans lengthening bond effect of
tertiary phosphine ligands. No meaningful interactions
Fig. 1. ORTEP drawing of (rac)-2 showing the numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level. Hy-
drogen atoms and chloroform molecules are omitted for clarity.
Table 2
ꢁ
Selected bond lengths (A) and angles (°) for (rac)-2 and 3a
(rac)-2
3a
Interatomic distances
Ru(1)–C(1)
Ru(1)–C(2)
Ru(1)–C(3)
Ru(1)–C(4)
Ru(1)–C(5)
Ru(1)–C(6)
Ru(1)–P(1)
2.234(7)
2.255(6)
2.248(7)
2.230(6)
2.203(6)
2.208(7)
2.3533(14)
2.4008(18)
2.4299(15)
2.207(5)
2.249(6)
2.226(7)
2.221(6)
2.223(6)
2.199(7)
2.3740(14)
2.3961(14)
2.4141(14)
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Angles
Cl(1)–Ru(1)–P(1)
Cl(1)–Ru(1)–Cl(2)
P(1)–Ru(1)–Cl(2)
85.82(5)
86.40(6)
91.46(5)
86.16(5)
87.52(5)
92.66(5)
Fig. 2. ORTEP drawing of 3a showing the numbering scheme. The
hydrogen atoms are omitted for clarity. Displacement ellipsoids are
drawn at the 50% probability level.
Scheme 3.

B. Therrien, G. S€uss-Fink / Inorganica Chimica Acta 357 (2004) 219–224
223
Scheme 4.
between complex 2 and the chloroform solvent mole-
cules were observed.
diphenylphosphine ferrocene ligand generates a trinu-
clear compound possessing two planar chiral g6-arene
ruthenium units per ferrocene centre. Thus, as for
complex 1, the synthesis of 4 should give rise to the
formation of three different species, two enantiomers (4a
and 4b) and a meso form (4c).
By contrast, the 31P{1H} NMR spectrum of 4 shows
only one singlet at 20.7 ppm, the chemical shift being
identical to that observed for the analoguous achiral
complex [RuCl2(1,2,3,4-C6H2Me4)(dppfc)RuCl2(1,2,3,
4-C6H2Me4)] [18]. Accordingly, the 1H and 13C{1H}
NMR spectra of 4 show only one set of signals. This
means that either only one of the diasteromers (meso or
rac) is formed or that, despite the presence of both dia-
stereomers (meso and rac), the two chiral elements are too
far away from each other to differentiate between the di-
astereoisomers. All attempts to resolve 4 into isomers
were unsuccessful.
As the resolution of the enantiomers of 2 was un-
successful, we reasoned that the coordination of an
enantiopure phosphine ligand to the ruthenium atom,
thus giving rise to the formation of diastereoisomers,
would facilitate the separation.
Thus, complex 1 reacts with two equivalents of
the commercially available enantiopure (1S,2S,5R)-(+)-
neomenthyldiphenylphosphine (nmdpp) to afford in
good yield the complex [RuCl2(1,2,4-C6H3Me3)
(nmdpp)] (3), as a mixture of diastereomers 3a and 3b,
see Scheme 3. The 31P{1H} NMR spectrum of the
crude product shows two singlets at 24.6 and 24.7
ppm, respectively. Crystals of the less soluble diaste-
reoisomer 3a were obtained from a methanol solution
containing 3.
A single-crystal X-ray structure analysis of 3a allows
us to determine the absolute configuration at the planar
chiral g6-arene moiety. The molecular structure of 3a is
presented in Fig. 2, and selected bond lengths and angles
are given in Table 2.
Acknowledgements
The X-ray analysis shows that the absolute configu-
ration of the planar chiral g6-arene is S. As in the case of
2, also in 3a the ruthenium atom is in a slightly distorted
octahedral geometry with angles closed to 90° [Cl(1)–
Ru(1)–Cl(2) 87.52(5)°, P(1)–Ru(1)–Cl(1) 92.66(5)° and
P(1)–Ru(1)–Cl(2) 86.16(5)°]. A similar distortion of the
arene ligand is observed, the longest Ru–C distances
being trans to the phosphorous atom, Ru(1)–C(2)
This work was supported by the Swiss National Sci-
ence Foundation (Grant No. 20-61227-00). We thank
Professor H. Stoeckli-Evans for free access to X-ray
facilities and the Johnson Matthey Technology Centre
for a generous loan of ruthenium chloride.
References
ꢁ
2.249(6) A. The fact that the Ru–P bond is slightly
ꢁ
longer [2.3740(14) A] than that observed in 2 [2.3533(14)
ꢁ
A] is probably due to the greater bulk of nmdpp relative
[1] H. Brunner, Adv. Organomet. Chem. 18 (1980) 151.
[2] P. Pertici, P. Salvadori, A. Biasci, G. Vitulli, M.A. Bennett, L.A.P.
Kane-Maguire, J. Chem. Soc. Dalton Trans. (1988) 315.
[3] P. Salvadori, P. Pertici, F. Marchetti, R. Lazzaroni, G.
Vitulli, M.A. Bennett, J. Organomet. Chem. 370 (1989)
155.
to PPh3. The bond distances and angles in the neo-
menthyl fragment of 3a are similar to those found in
[RuCl2(g6-o-MeC6H4CO2Me)(nmdpp)] [3] and [RuCl2
t
(g6-C6H5CHMeR)(nmdpp)] (R ¼ Et, Bu) [4].
[4] P. Pertici, E. Pitzalis, F. Marchetti, C. Rosini, P. Salvadori, M.A.
Bennett, J. Organomet. Chem. 466 (1994) 221.
Finally, complex
1
reacts with 1,10-bis(diph-
[5] G. Bodes, F.W. Heinemann, G. Jobi, J. Klodwig, S. Neumann, U.
Zenneck, Eur. J. Inorg. Chem. (2003) 281.
enylphosphino)ferrocene (dppfc) to give the heteronu-
clear complex [RuCl2(1,2,4-C6H3Me3)(dppfc)RuCl2
(1,2,4-C6H3Me3)] 4, see Scheme 4. The symmetrical bis-
[6] L.A. Paquette, J.H. Barrett, J. Malmin, R. Breslow, Org. Synth. 5
(1973) 467.

224
B. Therrien, G. S€uss-Fink / Inorganica Chimica Acta 357 (2004) 219–224
[7] G.M. Sheldrick, Acta Cryst. A 46 (1990) 467.
€ €
[8] G.M. Sheldrick, SHELXL-97, University of Gottingen, Gottingen,
[13] M.A. Bennett, G.B. Robertson, A.K. Smith, J. Organomet. Chem.
43 (1972) C41.
[14] M.R.J. Elsegood, D.A. Tocher, Polyhedron 14 (1995) 3147.
Germany, 1999.
[9] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[10] A.J. Birch, J. Chem. Soc. (1950) 1951.
€
[15] A. Hafner, A. Muhlebach, P.A. van der Schaaf, Angew. Chem.
109 (1997) 2213.
[16] A. Hafner, A. Muhlebach, P.A. van der Schaaf, Angew. Chem.
€
Int. Ed. Engl. 36 (1997) 2121.
[11] R. Baldwin, M.A. Bennett, D.C.R. Hockless, P. Pertici, A.
Verrazzani, G.U. Barretta, F. Marchetti, P. Salvadori, J. Chem.
Soc. Dalton Trans. (2002) 4488.
[17] H.D. Hansen, J.H. Nelson, Organometallics 19 (2000) 4740.
[18] J.-F. Mai, Y. Yamamoto, J. Organomet. Chem. 560 (1998)
223.
€
€
[12] L. Vieille-Petit, S. Unternahrer, B. Therrien, G. Suss-Fink, Inorg.
Chim. Acta 2003, in press.