Synthesis of a trinuclear cation [H3Ru3(Fc-arene) (C6Me6)2(O)]+ containing a ferrocenyl group tethered to an arene ligand

Article abstract of DOI:10.1016/S0020-1693(03)00273-1

Ferrocene carboxylic acid 2-cyclohexa-1,4-dienyl-ethyl ester (1) is prepared from ferrocene carboxylic acid and 2-cyclohexa-1,4-dienyl-ethanol. This diene reacts with RuCl₃·nH₂O in refluxing ethanol to afford quantitatively [Ru(Fc-arene)Cl₂]₂ (2) (Fc-arene=ferrocene carboxylic acid phenethyl ester). The dinuclear complex 2 reacts with triphenylphosphine to give the mononuclear complex [Ru(Fc-arene)(PPh₃)Cl₂] (3). The trinuclear arene-ruthenium cluster cation [H₃Ru₃(Fc-arene)(C ₆Me₆)₂(O)]⁺ (4) is synthesised from the dinuclear precursor [H₃Ru₂(C₆Me ₆)₂]⁺ and the mononuclear complex [Ru(Fc-arene)(H₂O)₃]²⁺, accessible from 2 in aqueous solution. The water-soluble trinuclear cluster cation 4 catalyses the hydrogenation of benzene to give cyclohexane under biphasic conditions.

Full text of DOI:10.1016/S0020-1693(03)00273-1

Inorganica Chimica Acta 355 (2003) 335Á339
/
www.elsevier.com/locate/ica
Synthesis of a trinuclear cation [H3Ru3(Fc-arene)(C6Me6)2(O)]ꢀ
containing a ferrocenyl group tethered to an arene ligand
Ludovic Vieille-Petit, Sabine Unternahrer, Bruno Therrien, Georg Suss-Fink *
¨
¨
Institut de Chimie, Universite´ de Neuchaˆtel, Case postale 2, CH-2007 Neuchatel, Switzerland
Received 14 April 2003; accepted 25 April 2003
Abstract
Ferrocene carboxylic acid 2-cyclohexa-1,4-dienyl-ethyl ester (1) is prepared from ferrocene carboxylic acid and 2-cyclohexa-1,4-
dienyl-ethanol. This diene reacts with RuCl3×nH2O in refluxing ethanol to afford quantitatively [Ru(Fc-arene)Cl2]2
(2) (Fc-areneꢁferrocene carboxylic acid phenethyl ester). The dinuclear complex 2 reacts with triphenylphosphine to give the
mononuclear complex [Ru(Fc-arene)(PPh3)Cl2] (3). The trinuclear arene-ruthenium cluster cation [H3Ru3(Fc-arene)(C6Me6)2(O)]ꢀ
(4) is synthesised from the dinuclear precursor [H3Ru2(C6Me6)2]ꢀ and the mononuclear complex [Ru(Fc-arene)(H2O)3]2ꢀ
/
/
,
accessible from 2 in aqueous solution. The water-soluble trinuclear cluster cation 4 catalyses the hydrogenation of benzene to give
cyclohexane under biphasic conditions.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Arene ligands; Biphasic catalysis; Cluster compounds; Ferrocene; Hydrogenation; Phosphine ligands; Ruthenium complexes
1. Introduction
phobic pocket and the catalytic activity of the water-
soluble trinuclear ruthenium cluster.
Recently we have shown that the water-soluble cluster
cation [H3Ru3(C6H6)(C6Me6)2(O)]ꢀ to be catalytically
active in the hydrogenation of benzene to cyclohexane
under biphasic conditions [1]. Experimental as well as
modelling studies suggest that the substrate molecule is
incorporated in the hydrophobic pocket spanned by the
three arene ligands, suggesting the catalytic reaction to
occur within this host-guest complex [2,3]. On the other
hand, it is well known that rhodium and iridium
complexes with chiral Josiphos ligands (phosphine
ligands containing a ferrocenyl group) are highly active
and selective catalysts for the enantioselective hydro-
genation of enamides, itaconic acid derivatives and
acetoacetates [4]. Therefore, we decided to incorporate
a ferrocenyl group tethered to the benzene ligand in
[H3Ru3(C6H6)(C6Me6)2(O)]ꢀ, in order to study the
effect of a ferrocenyl moiety on the size of the hydro-
2. Experimental
2.1. General
All manipulations were carried out by routine under
nitrogen atmosphere. De-ionised water and organic
solvents were degassed and saturated with nitrogen
prior to use. NMR spectra were recorded on a Varian
200 MHz spectrometer. IR spectra were recorded on a
PerkinÁ
/
Elmer 1720X FT-IR spectrometer (4000Á400
/
cmꢂ1). Microanalyses were performed by the Labora-
tory of Pharmaceutical Chemistry, University of Geneva
(Switzerland). Electro-spray mass spectra were obtained
in positive-ion mode with an LCQ Finnigan mass
spectrometer. Organic products were analysed by gas
chromatography (GC) on a DANI 86.10 HT gas
chromatograph using a CHROMPACK Carbowax
WCOT fused silica column. The starting dinuclear
dichloro
complexes
[Ru(C6Me6)Cl2]2
[5]
and
* Corresponding author. Tel.: ꢀ
2511.
E-mail address: georg.suess-fink@unine.ch (G. Suss-Fink).
/
41-32-718-2405; fax: ꢀ41-32-718-
/
[H3Ru2(C6Me6)2]ꢀ [6] were prepared according to
published methods.
¨
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00273-1

336
L. Vieille-Petit et al. / Inorganica Chimica Acta 355 (2003) 335Á339
/
2.2. Syntheses
(10:2) to give 3 as an orangeÁbrown powder. Orange
/
crystals suitable for X-ray analysis were obtained by
crystallisation from CHCl3/n-hexane. Yield: 153 mg
(50%).
2.2.1. Ferrocene carboxylic acid 2-cyclohexa-1,4-dienyl-
ethyl ester (1)
A solution of ferrocene carboxylic acid (2.41 g, 10.48
mmol), N,N-dicyclohexylcarbodiimide (3.30 g, 15.99
mmol), 4-(dimethylamino)pyridine (1 g, 8.18 mmol), 4-
pyrrolidinopyridine (1.20 g, 8.10 mmol), and 2,5-dihy-
drophenethylalcohol (1 g, 8.06 mmol) in CH2Cl2 (80 ml)
was stirred under nitrogen at room temperature during 3
days. The resulting solution was filtered through Celite
to remove N,N-dicyclohexylurea, and the filtrate con-
centrated under reduce pressure. A chromatogram of
the residue was recorded on a silica gel column, eluting
with hexane/acetone (10:1). The pure product was
isolated from the first fraction, giving 1 as red oil.
Yield: 2.54 g (94%).
Spectroscopic data: IR (KBr, cmꢂ1): nꢁ
/
1698 (CÄ
/
O
1
ester). H NMR (200 MHz, CDCl3): dꢁ
PÃC6H5), 7.43 (m, 9H, PÃC6H5), 5.41Á
RuÃ
(m, 2H, Ã
OCH2CH2Ã
/
7.78 (m, 6H,
/
/
/
5.27 (m, 5H,
/
C6H5), 4.78 (m, 2H, CpH), 4.55 (m, 2H, CpH), 4.43
OCH2CH2Ã), 4.15 (s, 5H,CpH), 3.07 (t, 2H, Ã
). 13C NMR (50 MHz, CDCl3): dꢁ
171.71,
/
/
/
/
/
134.52, 134.33, 130.85, 130.81, 128.58, 128.38, 108.02,
89.93, 88.53, 82.57, 71.77, 70.81, 70.35, 70.04, 62.86,
32.88. 31P NMR (81 MHz, CDCl3): dꢁ
/28.63 (s). MS
(EI mode, CHCl3): m/zꢁ
/
733 [MÃ
/
Cl]ꢀ. Anal. Calc. for
C37H33Cl2Fe1O2P1Ru1: C, 57.83; H, 4.33. Found: C,
58.07; H, 4.38%.
Spectroscopic data: IR (solution in CHCl3, cmꢂ1):
2.2.4. [H3Ru3(Fc-arene)(C6Me6)2(O)]ꢀ (4)
To a solution of [H3Ru2(C6Me6)2][BF4] (120 mg, 0.19
mmol) in acetone (40 ml) and H2O (5 ml) was added 2
(150 mg, 0.15 mmol). The mixture was heated to 60 8C
for 45 h in a closed pressure Schlenk tube. The resulting
red solution was filtered on Celite and evaporated to
dryness; the residue was dissolved in CH2Cl2 (10 ml) and
purified on silica-gel plates (eluent: CH2Cl2/Acetone 2:1)
to give pure [4][BF4] as red crystalline powder. Red
crystals suitable for X-ray analysis were obtained by
crystallisation from acetone/n-hexane. Yield: 80 mg
(39%).
nꢁ
5.76 (m, 2H, ethylenic H), 5.61 (m, 1H, ethylenic H),
4.82 (m, 2H, CpH), 4.41 (m, 2H, CpH), 4.34 (t, 2H, Ã
OCH2CH2Ã 6.84 Hz), 4.21 (s, 5H, CpH), 2.75 (m,
, 3Jꢁ
4H, ÃCHCH2CHÃ
6.84 Hz). 13C NMR (50 MHz, CDCl3): dꢁ
/
1705 (CÄ
/
O ester). 1H NMR (200 MHz, CDCl3): dꢁ
/
/
/
/
3
/
/
), 2.42 (t, 2H, Ã
/
OCH2CH2Ã
/
, Jꢁ
/
/
172.02,
131.69, 124.43, 124.33, 121.08, 71.54, 70.40, 70.21,
70.04, 62.77, 36.93, 29.40, 27.06. MS (EI mode,
CHCl3): m/zꢁ
336 [M]ꢀ. Anal. Calc. for C19H20FeO2:
C, 67.88; H, 6.00. Found: C, 67.85; H, 5.98%.
/
2.2.2. [Ru(Fc-arene)Cl2]2 (2)
Spectroscopic data: IR (KBr, cmꢂ1): nꢁ
/
1709 (CÄ
ester). H NMR (200 MHz, acetone-d6): dꢁ6.01 (m,
2H, RuÃC6H5), 5.62 (m, 3H, RuÃC6H5), 4.81 (t, 2H,
/
/
O
1
To a solution of ruthenium trichloride hydrate (350
mg, 1.34 mmol) in ethanol (40 ml) was added 1 (1.80 g,
5.36 mmol), and the mixture was refluxed overnight.
The yellow-brown precipitate was filtered, washed with
ether and acetone, and dried under vacuum to give
[Ru{C6H5(CH2)2O2CC5H4FeC5H5}Cl2]2. Yield: 590 mg
(87%).
/
/
/
3
3
CpÃ
6.83 Hz), 4.50 (t, 2H, CpÃ
CpÃH), 2.93 (t, 2H, ÃOCH2CH2Ã
(s, 36H, RuÃC6(CH3)6), ꢂ19.16 (d, 2H, Ru hydride,
2Jꢁ 19.85 (t, 1H, Ru hydride, 2Jꢁ
3.42 Hz), ꢂ 3.42
Hz). 13C NMR (50 MHz, acetone-d6): dꢁ
172.84,
/
H, Jꢁ
/
1.96 Hz), 4.66 (t, 2H, Ã
/
OCH2CH2Ã
/
, Jꢁ
/
H, 3Jꢁ
/
1.96 Hz), 4.20 (s, 5H,
3
/
/
/
, Jꢁ6.83 Hz), 2.35
/
/
/
/
/
/
Spectroscopic data: IR (KBr, cmꢂ1): nꢁ
ester). 1H NMR (200 MHz, dmso-d6): dꢁ
6.11Á
1.83 Hz), 4.47
1.83 Hz), 4.43 (t, 2H, 2H, Ã
5.86 Hz), 4.12 (s, 5H, CpH), 2.86 (t,
/
1707 (CÄ
/
O
/
/
/
5.79 (m,
102.61, 94.92, 85.55, 80.26, 78.50, 71.64, 70.17, 70.02,
3
5H, (RuÃ
/
C6H5), 4.75 (t, 2H, CpH, Jꢁ
/
69.90, 63.71, 34.06, 17.47. MS (ESI, positive mode,
(t, 2H, CpH, 3Jꢁ
/
/
acetone) : m/zꢁ
/
982 [Mꢀ
2H]ꢀ. Anal. Calc. for
C43H57B1F4Fe1O3Ru3: C, 48.37; H, 5.38. Found: C,
48.12; H, 5.36%.
/
3
OCH2CH2Ã
2H, ÃOCH2CH2Ã
dmso-d6): dꢁ171.18, 104.00, 89.26, 87.03, 84.88, 72.21,
71.04, 70.48, 70.28, 63.53, 32.91. MS (EI mode, dmso):
m/zꢁ976.5 Anal. Calc. for
Cl]ꢀ.
/
, Jꢁ
/
3
/
/
, Jꢁ
5.86 Hz). 13C NMR (50 MHz,
/
/
2.3. Catalytic runs
/
[MÃ
/
C38H36Cl4Fe2O4Ru2: C, 45.08; H, 3.58. Found: C,
44.89; H, 3.56%.
A solution of [4][BF4] (10 mg) in 10 ml of degassed
water was placed in a 100 ml stainless steel autoclave,
and the substrate benzene was added with a 1/1000 ratio
catalyst/substrate. After purging four times with hydro-
gen, the autoclave was pressurised with hydrogen (60
bar) and heated to 110 8C in an oil bath under vigorous
stirring. After 4 h, the autoclave was placed in an ice-
bath and the pressure released. The two-phase system
was separated by decanting. The aqueous phase contain-
ing the catalyst was evaporated to dryness under
2.2.3. [Ru(Fc-arene)(PPh3)Cl2] (3)
To a suspension of 2 (200 mg, 0.20 mmol) in 25 ml of
CH2Cl2 was added triphenylphosphine (114 mg, 0.43
mmol). The mixture was stirred at room temperature
during 24 h and filtered through Celite to eliminate
insoluble degradation materials. The product was pur-
ified on a silica gel column, eluting CH2Cl2/acetone

L. Vieille-Petit et al. / Inorganica Chimica Acta 355 (2003) 335Á
/339
337
Table 2
Selected bond lengths (A) and angles (8) for [3], and [4][BF4]
vacuum, and the residue was analysed by NMR and
mass spectroscopy. The organic phase containing cyclo-
hexane and benzene was analysed by NMR spectro-
scopy and GC.
˚
[3]
[4][BF4]
Interatomic distances
O(1)Ã
O(2)Ã
O(1)Ã
Ru(1)Ã
Ru(1)Ã
Ru(1)Ã
/
C(8)
C(9)
C(9)
1.460(9) O(1)Ã
1.192(10) O(2)Ã
1.336(9) O(1)Ã
2.337(2) Ru(1)Ã
2.407(2) Ru(2)Ã
2.409(2) Ru(1)Ã
/
C(8)
C(9)
C(9)
1.449(5)
/
/
1.207(5)
1.357(5)
2.7422(6)
2.7845(5)
2.7468(5)
2.4. X-ray crystallography
/
/
/P(1)
/
Ru(2)
Ru(3)
Ru(3)
Crystals of [3], and [4][BF4] were mounted on a Stoe
Image Plate Diffraction system equipped with a f circle
/Cl(1)
/
/Cl(2)
/
goniometer, using Mo Ka graphite monochromated
Angles
Cl(1)Ã
Cl(1)Ã
P(1)ÃRu(1)Ã
˚
/
Ru(1)Ã
/
P(1)
Cl(2)
Cl(2)
87.76(7) Ru(1)Ã
88.55(8) Ru(1)Ã
89.02(7) Ru(2)Ã
Ru(1)Ã
Ru(1)Ã
Ru(2)Ã
/
Ru(2)Ã
Ru(3)Ã
Ru(1)Ã
/
Ru(3) 59.599(15)
Ru(2) 59.435(15)
Ru(3) 60.965(14)
radiation (lꢁ
/
0.71073 A) with f range 0Á
/
2008, incre-
˚
/
Ru(1)Ã
/
/
/
ment of 1.3 and 1.58, Dmax
ꢂ/Dmin
ꢁ
/
12.45ꢂ0.81 A. The
/
/
/
/
/
structures were solved by direct methods using the
program SHELXS-97 [7]. The refinement and all further
calculations were carried out using SHELXL-97 [8]. In [3]
and [4][BF4] the hydrogen atoms have been included in
calculated positions and treated as riding atoms using
the SHELXL default parameters. All non-H atoms were
refined anisotropically, using weighted full-matrix least-
square on F2. Crystallographic details are summarised in
Table 1. Figures were drawn with ORTEP [9].
Full tables of atomic parameters, bond lengths and
angles are deposited at the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK, Deposition numbers: [3] 208397, [4][BF4] 208398.
/
O(3)Ã
O(3)Ã
O(3)Ã
/
Ru(2)
Ru(3)
Ru(3)
86.36(9)
86.58(9)
88.32(9)
/
/
/
/
3. Results and discussion
The hydroxi function of 2-cyclohexa-1,4-dienyl-etha-
nol, accessible by standard Birch reduction [10], is
available for esterification by classical methods [11]. 2-
Cyclohexa-1,4-dienyl-ethanol reacts with ferrocenyl car-
boxylic acid in dichloromethane, in the presence of
condensation agents (N,N-dicyclohexylcarbodiimine, 4-
(dimethylamino)pyridine, 4-pyrrolidinopyridine) to give
the corresponding ester-ferrocenyl derivative (1).
Table 1
Crystallographic and selected experimental data of [3], and [4][BF4]
[3]
[4][BF4]×(CH3)2CO
/
Chemical formula
Formula weight
Crystal system
Space group
C37H33Cl2FeO2PRu
768.42
C46H63BF4FeO4Ru3
1125.83
triclinic
monoclinic
P21/n
orange rod
¯
P1
/
The infrared spectrum of 1 exhibits the characteristic
nCO absorption at 1705 cmꢂ1 of the ester function and
the n bands at 1459, 1280 and 1142 cmꢂ1 due to the
presence of a ferrocene moiety.
Crystal colour and
shape
orange plate
Crystal size
˚
0.28ꢃ
/
0.08ꢃ
/
0.08
0.50ꢃ0.40ꢃ0.12
/
/
a (A)
˚
13.361(4)
13.944(3)
17.651(5)
90
11.771(1)
14.671(1)
14.696(1)
117.90(1)
90.53(1)
94.47(1)
2232.9(4)
2
b (A)
˚
c (A)
The dienyl function of 1 reacts with RuCl3×
refluxing ethanol to afford quantitatively [Ru(Fc-are-
ne)Cl2]2 (2) (Fc-areneꢁferrocene carboxylic acid phe-
/nH2O, in
a (8)
b (8)
g (8)
V (A )
Z
T (K)
Dcalc (g cmꢂ3
m (mmꢂ1
105.00(3)
90
/
nethyl ester). The dinuclear complex is only sparingly
soluble in CH2Cl2, and decomposes slowly in DMSO to
form the well known species [RuCl2(DMSO)4] [12].
3
˚
3176.6(15)
4
153(2)
1.607
1.185
153(2)
1.674
1.372
)
)
Scan range (8)
Unique reflections
4.30B
/
2u B
/
52.02
4.40B
/
2u B51.80
/
6065
3046
8132
6483
Reflections used
[I ꢀ
Rint
Final R indices [I ꢀ
2s(I)]
R indices (all data) R1ꢁ
/
2s(I)]
0.1268
0.0383
/
R1ꢁ
0.1233
0.1270, wR2
/
0.0584, wR2
R1ꢁ
0.0799
R1ꢁ0.0428, wR2
/
0.0319, wR2
/
/
0.1403
0.845
0.0833
0.994
To gain further insight in the possible structural
effects on the presence of a ferrocenyl group tethered
to an arene ligand, the mononuclear triphenylphosphine
Goodness-of-fit
Max, Min Dr/
1.326, ꢂ
/1.242
1.205, ꢂ0.666
/
ꢂ3
˚
e (A
)

338
L. Vieille-Petit et al. / Inorganica Chimica Acta 355 (2003) 335Á339
/
compound [Ru(Fc-arene)(PPh3)Cl2] (3) has been synthe-
sised. The dinuclear complex 2 reacts with 2 equivalents
of triphenylphosphine in CH2Cl2 to afford in moderate
yield complex 3. The formation of 3 is conveniently
monitored by 31P NMR spectroscopy. The 31P NMR
signal is shifted downfield by 32.9 ppm (as compared to
uncoordinated triphenylphosphine).
The
trinuclear
cation
[H3Ru3(Fc-arene)-
(C6Me6)2(O)]ꢀ (4) is synthesised in a water/acetone
solution from the dinuclear precursor [H3Ru2-
(C6Me6)2]ꢀ [19] and [Ru(Fc-arene)(H2O)3]2ꢀ
mononuclear analogue of the known cation
[(C6H6)Ru(H2O)3]2ꢀ [20], accessible from 2 in aqueous
solution.
, the
The orange air-stable compound is crystallised from a
slow diffusion of hexane into a chloroform solution
containing 3. A single-crystal X-ray analysis was per-
formed, confirming the molecular structure of 3, see Fig.
1. Selected bond distances and angles are given in Table
2.
The molecular structure of 4 is shown in Fig. 2. The
metal core consists of three ruthenium atoms, the three
RuÃ
/
Ru distances being in accordance with a metalÁ
/
metal single bond. The three ruthenium atoms are
capped by a m3-oxo ligand which is almost symmetrically
coordinated. The three hydrido ligands bridging the
The ruthenium atom possesses a pseudo-octahedral
geometry, and the metrical parameters around the
metallic core compare well with those of similar three-
legged piano-stool [Ru(h6-arene)(PPh3)Cl2] complexes
three rutheniumÁruthenium bonds could be localised
/
and fixed. Selected bond lengths and angles are listed
in Table 2. The triruthenium framework is compar-
able with [H3Ru3(C6H2Me4)3(O)]ꢀ [5], [H3Ru3(C6H6)
(C6Me6)2(O)]ꢀ [1], [H3Ru3{C6H5(CH2)2OH}(C6Me6)2
(O)]ꢀ and [H3Ru3{C6H5(CH2)3OH}(C6Me6)2(O)]ꢀ [3],
showing similar geometric parameters, differences ap-
pear only at the periphery. In the crystal structure, the
ferrocene moiety shows no interaction with the triruthe-
nium framework. The ferrocene moiety which is in the
eclipsed conformation, is surrounded by acetone solvent
molecules, and tetrafluoroborate ions. The torsion angle
[13Á15]. The ferrocene moiety is in the eclipsed con-
/
formation. The phenethyl substituent is rotated out of
the ester plane by 75.5(9)8, allowing no p-interaction
between the Cp ring and the h6-arene ligand. A similar
behaviour has been observed for benzoylferrocene [16]
and for methylenebenzotriazolylferrocene derivatives
˚
O(1) distance [1.336(9) A] is shorter
than that of ferrocenecarboxylic acid benzotriazole ester
[17]. The C(9)Ã
/
˚
[1.427(2) A], which is known to have a weak and reactive
formed by C(1)Ã
/
C(7)Ã
/
C(8)ÃO(1) [71.0(5)8] is identical
/
ester bond [18]. These observations are in agreement
with the stability of the ester bond observed for 3. The
stability of the ester function allows us to synthesise the
trinuclear cation [H3Ru3(Fc-arene)(C6Me6)2(O)]ꢀ (4) in
good yield.
to the one observed in 3 [70.3(10)8].
Compound [4][BF4] is indeed catalytically active for
the hydrogenation of benzene under biphasic condi-
tions, it shows a catalytic activity of 157 hꢂ1 (TOF) for
a catalyst/substrate ratio 1:1000, at 110 8C under 60 bar
H2 during
4
h, as compared to 190 hꢂ1 for
Fig. 2. Molecular structure of [4]BF4; tetrafluoroborate ion, acetone
molecule, and H atoms omitted for clarity; displacement ellipsoids are
drawn at the 35% probability level.
Fig. 1. Molecular structure of 3 at 50% probability level, H atoms
omitted for clarity.

L. Vieille-Petit et al. / Inorganica Chimica Acta 355 (2003) 335Á
/339
339
[3] L. Vieille-Petit, B. Therrien, G. Suss-Fink, T.R. Ward, J.
¨
Organomet. Chem., in press.
[H3Ru3(C6H6)(C6Me6)2(O)][BF4] under the same condi-
tions. Unfortunately, it appears that, after a catalytic
run, 4 is partially decomposed into mono- and di-
nuclear species, among which, we identified by NMR
spectroscopy [H3Ru2(C6Me6)2]ꢀ. The fate of the
[4] A. Togni, C. Breutel, A. Schnyder, F. Spindler, H. Landert, A.
Tijani, J. Am. Chem. Soc. 116 (1994) 4062.
[5] M.A. Bennett, T.-N. Huang, T.W. Matheson, A.K. Smith, Inorg.
Synth. 21 (1982) 74.
[6] M.A. Bennett, J.P. Ennett, Inorg. Chim. Acta 198Á200 (1992)
/
ferrocenylÁ
/
areneÁruthenium moiety is unclear, no de-
/
583.
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