Polyhedron 23 (2004) 611–616

www.elsevier.com/locate/poly

Novel ferrocenyl-oxazoline ligands: first preparationof non-symmetrical bis(oxazoline) q

Montserrat G�omez a,*, Eduardo Peris b,*, Helena Teruel c,*, Ingrid Arevalo c,Jos�e A. Mata b, Guillermo Muller a

a Departament de Qu�ımica Inorg�anica, Universitat de Barcelona, Mart�ı i Franqu�es, 1-11, E-08028 Barcelona, Spainb Departamento de Qu�ımica Inorg�anica y Org�anica, Universitat Jaume I, E-12080 Castell�on, Spain

c Universidad Sim�on Bol�ıvar, Baruta 6000, Caracas 1081, Venezuela

Received 22 September 2003; accepted 24 October 2003

Abstract

New ferrocenyl-arenylethenyl-oxazoline derivatives have been prepared (5–10) from the mono- and (1,10)-disubstituted (nitrile-

ethenylaryl)ferrocene compounds (1 and 2) and the appropriated b-aminoalcohol (3 and 4) in one step synthesis. The X-ray crystal

structure of one of the ferrocenyl-ethenylaryl-oxazoline (5) is described, revealing the unusual quasi-planarity of the oxazoline ring

with the phenyl and cyclopentadienyl cycles. Two compounds end-capped (9 and 10) with both, nitrile and oxazoline groups, are the

key intermediates to obtain the non-symmetrical bis(oxazoline) 11, containing two different substituted heterocycles.

� 2003 Elsevier Ltd. All rights reserved.

Keywords: Ferrocenes; Oxazolines; Non-symmetrical ligands; X-ray diffraction

1. Introduction

During the last three decades, much attention has

been devoted to the chemistry of ferrocenyl complexes

because ferrocene combines chemical versatility with

high thermal stability. These properties, together with

the exceptional electrochemical properties of ferrocene,

make ferrocene-based complexes good candidates forthe preparation of new materials with applications in

organic synthesis, catalysis and materials science [1,2].

In the search of new materials with electronic com-

munication between terminal subunits, we have focused

our interest on the preparation of new conjugated ferr-

ocenyl complexes with end capped nitro [3], pyridine [4]

and nitrile [5] groups. End-capping ferrocene with pyr-

idine and nitrile, allowed the ferrocenyl subunit to linkto different metallic fragments, affording interesting bi-

metallic complexes, in which the terminal metallic

qSupplementary data associated with this article can be found, in the

online version, at doi:10.1016/j.poly.2003.10.013*Corresponding author. Tel.: +34-934-021271; fax: +34-934-907725.

E-mail address: montserrat.gomez@qi.ub.es (M. G�omez).

0277-5387/$ - see front matter � 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/j.poly.2003.10.013

fragments are connected by a conjugated bridge. In all

cases, our compounds showed excellent coordination

capabilities which made them appropriate to obtain

highly stable heterometallic complexes [5c,6]. In the last

decade, an increasing eager effort to the introduction of

ferrocene fragments in the design of new homogeneous

catalysts has been done [1,7]. Since one of the most

useful tools in organic synthesis is asymmetric catalysis,a great effort has been devoted to the synthesis of chiral

ferrocenyl ligands, some of which show the planar chi-

rality in the ferrocenyl moiety [8], and some others also

in the ancillary ligands [9]. Among the latter ones, ox-

azoline-type ligands have shown excellent coordination

properties [10], which make them good candidates to the

synthesis of a large variety of chiral catalysts [11].

Despite the number of ferrocene-oxazoline com-pounds reported so far is large, most of the examples

that we can find in the literature are phosphine based

[12]. In this work, we report the synthesis and charac-

terization of new phosphine-free ferrocenyl-oxazoline

ligands from our previously reported ferrocenyl-

ethenylaryl-nitrile ligands [5a,5b]. The introduction of

the ethenylaryl bridge between the ferrocene and the

612 M. G�omez et al. / Polyhedron 23 (2004) 611–616

terminal oxazoline unit introduces a new dimension to

this new type of complexes, since all of the ferrocene-

oxazoline compounds reported so far have the oxazolinefragment directly bound to ferrocene, because of the

ortho directing behaviour of this functional group which

leads to the synthesis of planar chiral ferrocenes [7,13].

In this exploratory work, racemic amino alcohols have

been used. Preliminary attempts to coordinate these

compounds to Pd and Au failed.

2. Experimental

2.1. General data

All compounds were prepared under a purified nitro-

gen atmosphere using standard Schlenk and vacuum-line

techniques. The solvents were purified by standard pro-

cedures [14] and distilled under nitrogen. Ethenyl-ferro-cene derivatives 1 and 2 were prepared as previously

described [5a,5b]. 2-aminobutanol (Fluka) and leucinol

(Aldrich) were used without previous purification. NMR

spectra were recorded on JEOLEclipse 400, BrukerDRX

500 (1H, standard SiMe4) andVarianGemini 200 (13C, 50

MHz, standard SiMe4) in CDCl3. Chemical shifts were

reported downfield from standards. IR spectra were re-

corded on aNicolet 520 FT-IR and FTIRNicolet Impact400 spectrometers. FAB mass chromatograms were ob-

tained on a Fisons V6-Quattro instrument. Optical rota-

tions were measured on a Perkin Elmer 241MC

spectropolarimeter. Elemental analyses were carried out

by the Serveis Cient�ıfico-T�ecnics de la Universitat de

Barcelona in an Eager 1108 microanalyzer.

2.2. 1-Ethenyl-(4-(40-ethyl-30,40-dihydrooxazol-20-yl)ph-

enyl)ferrocene, 5

0.100 g (0.227 mmol) of 1-(ethenyl-4-cianophenyl)fer-

rocene, 0.155 g (1.74 mmol) of 2-aminobutanol and a

catalytic amount of zinc chloride were dissolved in 10 cm3

of toluene at room temperature. Themixture was refluxed

for 8 days (monitored by TLC). The mixture was filtered

off and the solvent was removed under reduced pressure,affording an oil, which was chromatographied over SiO2

using ethyl acetate/hexane (1/1) as eluent. After removing

the solvent, 5 was obtained as a red solid. Yield: 0.045 g

(52%). 1HNMR (400MHz,CDCl3) d 1.01 (t, 7.0Hz, 3H),

1.72 (m, 2H), 4.05 (m, 2H), 4.28 (m, 1H), 4.32 (2, 5H), 4.46

(m, 4H), 6.65 (d, 16.0 Hz, 1H), 6.76 (d, 16.0 Hz, 1H), 7.69

(d, 8.0 Hz, 2H), 7.81 (d, 8.0 Hz, 2H) ppm. 13C NMR (50

MHz, CDCl3) d 12.00, 22.00, 25.20, 44.35, 64.00, 65.40,68.00, 68.10, 71.50, 82.00, 123.90, 124.30, 127.40, 127.70,

164.00 ppm. IR (KBr) 1650 (C@N) cm�1. Anal. Calc. for

C23H23NOFe: C, 71.70; H, 6.02; N, 3.64. Found C, 70.50;

H, 6.00; N, 3.50%. MS (FAB positive) m=z 385 ([M]þ).

2.3. 1-Ethenyl-(4-(40-isobutyl-30,40-dihydrooxazol-20-yl)-

phenyl)ferrocene, 6

Compound prepared following the methodology de-

scribed for 5. Starting materials: 0.100 g (0.227 mmol) of1-(ethenyl-4-cianophenyl)ferrocene, 0.204 g (1.74 mmol)

of leucinol and a catalytic amount of zinc chloride.

Yield: 0.068 g (73%). 1H NMR (400 MHz, CDCl3) d0.95 (m, 3H), 0.97 (m, 3H), 1.40 (m, 1H), 1.80 (m, 2H),

3.98 (t, 8.0 Hz, 1H), 4.13 (s, 5H), 4.29 (m, 2H), 4.47 (m,

2H), 6.69 (d, 16.0 Hz, 1H), 6.94 (d, 16.0 Hz, 1H), 7.42

(d, 8.0 Hz, 2H), 7.88 (d, 8.0 Hz, 2H) ppm. 13C NMR (50

MHz, CDCl3) d 21.62, 21.93, 24.46, 44.54, 64.06, 65.97,68.17, 68.24, 71.93, 81.69, 124.13, 124.35, 127.43,

127.86, 163.0 ppm. IR (KBr) 1640 (C@N) cm�1. Anal.

Calc. for C25H27NOFe: C, 72.65; H, 6.58; N, 3.39.

Found C, 71.90; H, 6.80; N, 3.10%. MS (FAB positive)

m=z 413 ([M]þ).

2.4. 1,10-Bis(ethenyl-(4-(40-ethyl-30,40-dihydrooxazol-20-

yl)phenyl))ferrocene, 7

0.200 g (0.454 mmol) of 1,10-bis(ethenyl-4-cianophe-nyl)ferrocene, 0.624 g (7.0 mmol) of 2-aminobutanol

and a catalytic amount of zinc chloride. The mixture

was filtered off and the solvent was removed under re-

duced pressure, affording an oil, which was chroma-

tographied over SiO2 using dichloromethane/hexane (1/

1) as eluent. The product corresponded to the fractionswith Rf ¼ 0:4 on the TLC sheet. After removing the

solvent, 7 was obtained as a red solid. Yield (based on

2): 0.053 g (20%). 1H NMR (400 MHz, CDCl3) d 0.98 (t,

7.5 Hz, 6H), 1.63 (m, 2H), 1.77 (m, 2H), 4.05 (t, 8.0 Hz,

2H), 4.28 (m, 2H), 4.29 (m, 4H), 4.42 (m, 4H), 4.44 (dd,

11.8 Hz, 8.0 Hz, 2H), 6.61 (d, 16.5 Hz, 2H), 6.85 (d, 16.5

Hz, 2H), 7.31 (d, 8.4 Hz, 4H), 7.81 (d, 8.4 Hz, 4H) ppm.

IR (KBr) 1645 (C@N) cm�1. Anal. Calc. forC36H36N2O2Fe: C, 73.97; H, 6.21; N, 4.79. Found C,

74.30; H, 6.40; N, 4.55%. MS (FAB positive) m=z 585

([M]þ).

2.5. 1,10-Bis(ethenyl-(4-(40-isobutyl-30,40-dihydrooxazol-

20-yl)phenyl))ferrocene, 8

0.200 g (0.454 mmol) of 1,10-bis(ethenyl-4-cianophe-nyl)ferrocene, 0.820 g (7.0 mmol) of leucinol and a

catalytic amount of zinc chloride. The mixture was fil-

tered off and the solvent was removed under reduced

pressure, affording an oil, which was chromatographied

over SiO2 using dichloromethane/hexane (1/1) as eluent.

The product corresponded to the fractions with Rf ¼ 0:4on the TLC sheet. After removing the solvent, 8 was

obtained as a red solid. Yield (based on 2): 0.047 g(16%). 1H NMR (400 MHz, CDCl3) d 0.98 (m, 12H),

1.39 (m, 2H), 1.73 (m, 2H), 1.76 (m, 2H), 3.98 (t, 8.0 Hz,

2H), 4.14 (m, 8H), 4.29 (m, 4H), 4.46 (m, 4H), 6.52 (dd,

Table 1

Crystal data and structure refinement for compound 5

Empirical formula C23H23FeNO

Formula weight 385.27

Temperature (K) 293(2)

Wavelength (�A) 0.71073

Crystal system monoclinic

Space group P2ð1Þ=nUnit cell dimensions

a (�A) 7.9462(18)

b (�A) 22.897(5)

c (�A) 10.922(3)

a (�) 90

b (�) 106.222(5)

c (�) 90

Volume (�A3) 1908.0(8)

Z 4

Density (calculated) (Mg/m3) 1.341

Absorption coefficient (mm�1) 0.801

F (0 0 0) 808

Crystal size (mm) 0.19� 0.15� 0.14

h range for data collection 1.78–20.81�Index ranges �76 h6 7,

�226 k6 22,

�86 l6 10

Reflections collected 7111

Independent reflections 1992 [Rint ¼ 0:0340]

Completeness to h ¼ 20:81� 100.0%

Absorption correction Bruker SADABS

Maximum and minimum

transmission

1.955654 and 1.409375

Refinement method Full-matrix least-

squares on F 2

Data/restraints/parameters 1992/0/253

Goodness-of-fit on F 2 1.164

Final R indices [I > 2rðIÞ] R1 ¼ 0:0492,

wR2 ¼ 0:1152

R indices (all data) R1 ¼ 0:0626,

wR2 ¼ 0:1203

Largest diffraction peak and hole

(e�A�3)

0.319 and )0.329

M. G�omez et al. / Polyhedron 23 (2004) 611–616 613

11.8 Hz, 8.0 Hz, 2H), 6.69 (d, 16.0 Hz, 2H), 6.96 (d, 16.0

Hz, 4H), 7.43 (d, 8.0 Hz, 4H), 7.88 (d, 8.0 Hz, 4H) ppm.

Anal. Calc. for C40H44N2O2Fe: C, 74.95; H, 6.92; N,4.37. Found C, 74.40; H, 7.05; N, 4.40%. MS (FAB

positive) m=z 641 ([M]þ).

2.6. 1-Ethenyl-(4-(40-ethyl-30,40-dihydrooxazol-20-yl)phen-

yl)-10-ethenyl-(4-cianophenyl)ferrocene, 9

Co-product obtained with 7 (see preparation of 7) by

condensation of 2 with 3. The compound 9 corre-sponded to the eluted fractions with Rf ¼ 0:6 on the

TLC sheet, on the column chromatography over SiO2

using dichloromethane/hexane (1/1) as eluent. Yield

(based on 2): 0.082 g (41%). 1H NMR (400 MHz,

CDCl3) d 1.01 (t, 7.2 Hz, 3H), 1.65 (m, 1H), 1.80 (m,

1H), 4.09 (t, 8.1 Hz, 1H), 4.20 (m, 1H), 4.29 (m, 2H),

4.32 (m, 2H), 4.45 (m, 4H), 4.55 (dd, 8.0 Hz, 9.5 Hz,

2H), 6.45 (d, 16.1 Hz, 1H), 6.52 (d, 16.5 Hz, 1H), 6.65(d, 16.1 Hz, 1H), 6.67 (d, 16.5 Hz, 1H), 7.14 (d, 8.5 Hz,

2H), 7.16 (d, 8.5 Hz, 2H), 7.33 (d, 8.5 Hz, 2H), 7.69 (d,

8.5 Hz, 2H) ppm. Anal. Calc. for C32H28N2OFe: C,

75.01; H, 5.51; N, 5.47. Found C, 75.30; H, 5.60; N,

5.30%. MS (FAB positive) m=z 512 ([M]þ).

2.7. 1-Ethenyl-(4-(40-isobutyl-30,40-dihydrooxazol-20-yl)-

phenyl)-10-ethenyl-(4-cianophenyl)ferrocene, 10

Co-product obtained with 8 (see preparation of 8) by

condensation of 2 with 4. The compound 10 corre-

sponded to the eluted fractions with Rf ¼ 0:6 on the

TLC sheet, on the column chromatography over SiO2

using dichloromethane/hexane (1/1) as eluent. Yield

(based on 2): 0.076 g (31%). 1H NMR (500 MHz,

CDCl3) d 0.98 (m, 6H), 1.42 (m, 2H), 1.75 (m, 2H), 1.82(m, 2H), 4.02 (t, 8.0 Hz, 2H), 4.28 (m, 2H), 4.31 (m, 2H),

4.35 (m, 2H), 4.44 (m, 4H), 4.55 (dd, 8.0 Hz, 9.5 Hz,

2H), 6.45 (d, 16.0 Hz, 1H), 6.51 (d, 16.0 Hz, 1H), 6.66

(pt, 16.8 Hz, 2H), 7.13 (d, 7.0 Hz, 2H), 7.15 (d, 8.5 Hz,

2H), 7.32 (d, 8.5 Hz, 2H), 7.68 (d, 8.5 Hz, 2H) ppm. 13C

NMR (50 MHz, CDCl3) d 22.68, 22.99, 25.57, 45.59,

65.26, 68.10, 68.14, 68.30, 70.21, 70.48, 73.11, 77.20,

83.21, 84.07, 109.28, 119.22, 124.81, 125.19, 125.68,126.11, 127.34, 128.47, 130.01, 132.27, 140.18, 141.86,

163.03 ppm. Anal. Calc. for C34H32N2OFe: C, 75.56; H,

5.97; N, 5.18. Found C, 75.00; H, 6.05; N, 5.25%. MS

(FAB positive) m=z 540 ([M]þ).

2.8. 1-Ethenyl-(4-(40-isobutyl-30,40-dihydrooxazol-20-yl)-

phenyl)-10-ethenyl-(4-(40-ethyl-30,40-dihydrooxazol-20-yl)-

phenyl)ferrocene, 11

0.100 g (0.220 mmol) of 9, 0.400 ml (2.386 mmol) of

leucinol and a catalytic amount of zinc chloride. The

mixture was filtered off and the solvent was removed

under reduced pressure, affording an oil, which was

chromatographied over SiO2 using dichloromethane/

hexane (1/1) as eluent. After removing the solvent, 11

was obtained as a red solid. Yield: 0.015 g (11%). 1HNMR (400 MHz, CDCl3) d 0.91 (t, 3H), 0.99 (7, 6H),

1.30 (m, 2H), 1.41 (m, 2H), 1.82 (m, 1H), 4.17 (t, 8.0 Hz,

1H), 4.22 (m, 1H), 4.29(m, 1H), 4.32 (m, 2H), 4.45 (m,

2H), 4.48 (m, 1H), 6.43 (d, 16.3 Hz, 1H), 6.53 (d, 16.0

Hz, 1H), 6.63 (d, 16.0 Hz, 1H), 6.68 (d, 16.3Hz, 1H),

7.05–7.15 (m, 4H), 7.15 (d, 8.5 Hz, 2H), 7.32 (d, 8.5 Hz,

2H), 7.68 (d, 8.5 Hz, 2H) ppm. Anal. Calc. for

C38H40N2O2Fe: C, 74.50; H, 6.58; N, 4.57. Found C,75.00; H, 6.40; N, 4.55%.

2.9. Crystallography

Single crystals were grown by slow diffusion of

hexane into concentrated CH2Cl2 solution of 5 and

mounted on a glass fiber in a random orientation. Data

collection was performed at room temperature on aSiemens Smart CCD diffractometer using graphite

614 M. G�omez et al. / Polyhedron 23 (2004) 611–616

monochromated Mo Ka radiation (k ¼ 0:71073 �A)

with a nominal crystal to detector distance of 4.0 cm.

An hemisphere of data was collected based on three x-scans runs (starting x ¼ �28�) at values / ¼ 0�, 90�and 180� with the detector at 2h ¼ 28�. At each of

these runs, frames (606, 435 and 230, respectively) were

collected at 0.3� intervals and 40 s per frame. Space

group assignments are based on systematic absences, Estatistics and successful refinement of the structures.

Structure was solved by direct methods with the aid of

successive difference Fourier maps and were refinedusing the SHELXTLSHELXTL 5.1 software package [15]. All non-

hydrogen were refined anisotropically. Hydrogen atoms

were assigned to ideal positions and refined using a

riding model. Details of the data collection and cell

dimensions are given in Table 1 and structure refine-

ment. The diffraction frames were integrated using the

SAINTSAINT package and corrected for absorption with

SADABSSADABS [16].

3. Synthesis and characterization

Ferrocenyl-ethenylphenyl-oxazoline compounds 5–10

have been obtained (Scheme 1), by zinc-catalyzed reac-

tion of the corresponding nitrile derivative (1 or 2)

[5b,5c] with the appropriate b-aminoalcohol (rac-3 orrac-4), as described in the literature for related com-

pounds [17]. The products were obtained in moderate to

good yields (up to ca. 70% on the pure product) and

fully characterized by usual techniques (IR and NMR

spectroscopies, FAB-mass spectra, elemental analysis

and X-ray diffraction).

Monoxazolines 5 and 6 were obtained in one-step

synthesis from 1 and the aminoalcohol 3 and 4, re-spectively (see Scheme 1). Suitable monocrystals for 5

Scheme 1. Synthesis of

were obtained by slow evaporation from dichlorome-

thane/hexane solution.

Reaction of the ferrocenyl-dinitrile 2 with the amin-oalcohols 3 or 4 gave a mixture of the bis(oxazoline) (7

or 8) and nitrile-oxazoline (9 or 10) compounds (Scheme

1), after one week in refluxing toluene. The nitrile-

oxazoline compounds (8 and 10) were the major products

obtained, with a bis(oxazoline):nitrile-oxazoline molar

ratio of ca. 1:2. Further silica column chromatography

(dichloromethane/hexane (1/1) used as eluent) of crude

led to the separation of both compounds: nitrile-oxazo-line ligands (9 and 10) and bis(oxazoline) compounds

(7 and 8), as described in the experimental section.

Starting material 2, was also recovered (ca. 50–60%).

One of the main goals of our work is that the syn-

thesis of pure 9 and 10 allowed the synthesis of non-

symmetrical bis(oxazoline) compounds, containing

different substituents in the oxazoline ring. Therefore, 11

was obtained by reaction of 9 with the aminoalcohol 4in low yield (11%), following the same methodology

described above.

3.1. Molecular structure of 5

Slow diffussion of a CH2Cl2 solution of a racemic

mixture of 5 in hexane afforded orange crystals suitable

for X-ray diffraction. Compound 5 crystallizes in thecentrosymmetric space group P2ð1Þ=n. The unit cell

contains four molecules, two corresponding to each of

the enantiomeric forms because racemic mixture of

aminoalcohol was used in the synthesis of the product.

As seen in Fig. 1, the molecule displays a quasiplanar

arrangement between the ferrocenyl, the phenyl and

the oxazoline groups, which facilitates conjugation. The

distances from iron to cyclopentadienyl rings, and theC–C distances within the rings lie in the expected range.

compounds 5–11.

Fig. 1. Molecular structure and atomic labelling scheme for 5. All hy-

drogens and double bond disorder have been omitted for clarity. An-

isotropicdisplacement ellipsoids at 50%.Selectedbonddistances (�A)and

angles (�). Fe-Cp(centr.)¼ 1.65; Fe–C (Cp)¼ 2.04; C(18)–

C(19)¼ 1.480(8); C(19)–N(1)¼ 1.237(7); C(19)–O(1)¼ 1.342(6); O(1)–

C(21)¼ 1.457(7); N(1)–C(20)¼ 1.493(9); C(20)–C(21)¼ 1.429(10);

N(1)– C(19)–O(1)¼118.7(5); C(19)–O(1)–O(21)¼104.4(4); C(19)–N(1)–

C(20)¼ 105.7(6); N(1)–C(20)–C(21)¼ 105.2(6). Planes: Cpsubs–Cp¼1.03(0.43); Cpsubs–Ph¼ 8.31(0.40); Ph–Oxazoline ring¼ 2.82(0.49).

M. G�omez et al. / Polyhedron 23 (2004) 611–616 615

The molecular structure presents a disorder in a 1:1 ratio

with regard to the orientation of the trans olefinic moi-

eties. This kind of disorder has been observed in similar

molecules [4,18].

3.2. NMR studies

1H NMR spectra of bis(oxazoline) products (7, 8, 11)

do not exhibit the evidence of isomers in solution (1H

NMR spectra were recorded in the temperature range

223–323 K), in spite of the formation of diastereomers

due to the racemic aminoalcohols employed in their

syntheses. We can establish that average structures

are observed, because polarimetry results (for 7 and 8)

indicate that no optically enriched compounds areobtained.

Preliminary coordination tests of these ligands

towards gold, [AuCl(PPh3)], and palladium, [PdCl2-

(PhCN)2], precursors led to decomposition products,

using several solvents (chloroform, dichloromethane,

toluene) at different temperatures (253–298 K).

In conclusion, we have prepared new oxazoline

compounds from ferrocene ethenylaryl conjugatedbridge derivatives, describing for the first time a non-

symmetrical bis(oxazoline). Unfortunately, these ligands

are not good candidates to stabilize coordination com-

pounds with transition metals.

4. Supplementary material

1H NMR spectra of compounds 8, 9 and 11.

The crystal structure of 5 has been deposited at the

Cambridge Crystallographic Data Centre and allocated

the deposition number CCDC 215315. Copies of the in-

formation may be obtained free of charge from The Di-

rector, 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).

Acknowledgements

The authors thank the Ministerio de Ciencia y Tec-

nolog�ıa (BQU 2001-3358), the Generalitat de Catalunya,

DGESIC (MAT2002-04421-C02-01) and the Decanato

de Investigaci�on y Desarrollo de la Universidad Sim�onBol�ıvar (S1-CB-005) for financial support. The authors

thanks Miss G. Noguera and Miss Y. Gorr�ın for their

help in the preparation of the ferrocenyl precursors.

References

[1] (a) A. Togni, T. Hayshi (Eds.), Ferrocenes: Homogenous Catal-

ysis. Organic Synthesis. Materials Science, VCH, Weinheim,

Germany, 1995;

(b) O.B. Sutcliffe, M.R. Bryce, Tetrahedron: Asymmetry 14

(2003) 2297.

[2] N.J. Long, Metallocenes, 1st ed., Blackwell Science, London,

1997.

[3] J.A. Mata, E. Peris, I. Asselberghs, R. Van Boxel, A. Persoons,

New. J. Chem. 25 (2001) 299.

[4] J.A. Mata, S. Uriel, R. Llusar, E. Peris, Organometallics 19 (2000)

3797.

[5] (a) J.A. Mata, E. Peris, R. Llusar, S. Uriel, M.P. Cifuentes, M.G.

Humphrey, M. Samoc, B. Luther-Davies, Eur. J. Inorg. Chem.

(2001) 2113;

(b) J.A. Mata, E. Falomir, R. Llusar, E. Peris, J. Organomet.

Chem. 616 (2000) 80;

(c) J. Mata, S. Uriel, E. Peris, R. Llusar, S. Houbrechts, A.

Persoons, J. Organomet. Chem. 562 (1998) 197.

[6] J.A. Mata, E. Peris, S. Uriel, R. Llusar, I. Asselberghs, A.

Persoons, Polyhedron 20 (2001) 2083.

[7] C.J. Richards, A.J. Locke, Tetrahedron: Asymmetry 9 (1998)

2377.

[8] (a)

See, for example: J. Chiffre, Y. Coppel, G.G.A. Balavoine, J.C.

Daran, E. Manoury, Organometallics 21 (2002) 4552;

(b) C. Bolm, K. Muniz-Fernandez, A. Seger, G. Raabe, K.

Gunther, J. Org. Chem. 63 (1998) 7860;

(c) T. Tu, Y.G. Zhou, X.L. Hou, L.X. Dai, X.C. Dong, Y.H. Yu,

J. Sun, Organometallics 22 (2003) 1255;

(d) S. Shirakami, T. Itoh, Tetrahedron: Asymmetry 11 (2000)

2823.

[9] (a) C.O. Turrin, J. Chiffre, D. de Montauzon, G. Balavoine, E.

Manoury, A.M. Caminade, J.P. Majoral, Organometallics 21

(2002) 1891;

(b) M. Catasus, A. Bueno, A. Moyano, M.A. Maestro, J. Mahia,

J. Organomet. Chem. 642 (2002) 212;

(c) A. Hess, J. Sehnert, T. Weyhermuller, N. Metzler-Nolte,

Inorg. Chem. 39 (2000) 5437;

(d) M. Takeuchi, T. Mizuno, S. Shinkai, S. Shirakami, T. Itoh,

Tetrahedron: Asymmetry 11 (2000) 3311;

(e) M. Widhalm, U. Nettekoven, K. Mereiter, Tetrahedron:

Asymmetry 10 (1999) 4369;

(f) A. Togni, T. Hayashi (Eds.), Ferrocenes: Homogenous

Catalysis. Organic Synthesis. Materials Science, VCH, Weinheim,

Germany, 1995, pp. 279–316.

[10] M. G�omez, G. Muller, M. Rocamora, Coord. Chem. Rev. 193–

195 (1999) 769.

[11] (a) A.K. Ghosh, P. Mathivanan, J. Cappiello, Tetrahedron:

Asymmetry 9 (1998) 1;

(b) G. Helmchen, A. Pfaltz, Acc. Chem. Res. 33 (2000) 336.

[12] A. Togni, Angew. Chem., Int. Ed. Engl. 35 (1996) 1475.

616 M. G�omez et al. / Polyhedron 23 (2004) 611–616

[13] (a) First works published simultaneously by: C.J. Richards, T.

Damalidis, D.E. Hibbs, M.B. Hursthouse, Synlett (1995) 74;

(b) T. Sammakia, H.A. Latham, D.R. Schaad, J. Org. Chem. 60

(1995) 10;

(c) Y. Nishibayashi, S. Uemura, Synlett (1995) 79.

[14] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of Lab-

oratory Chemicals, third ed., Pergamon Press, Oxford, UK, 1988.

[15] SAINT version 5.0 Bruker Analytical X-ray Systems, Madison,

WI.

[16] G.M. Sheldrick, SADABS empirical absorption program, Uni-

versity of G€ottingen, 1996.

[17] (a) C. Bolm, K. Weickhardt, M. Zehnder, T. Ranff, Chem. Ber.

124 (1991) 1173;

(b) A. El Hatimi, M. G�omez, S. Jansat, G. Muller, M. Font-

Bard�ıa, X. Solans, J. Chem. Soc., Dalton Trans. (1998) 4229, and

references therein.

[18] (a) S. Sakanishi, D.A. Bardwell, S. Couchman, J.C. Jeffrey, J.A.

McCleverty, M.D. Ward, J. Organomet. Chem. 528 (1997)

35;

(b) A. Hradsky, B. Bildstein, N. Schuler, H. Schottenberger, P.

Jaitner, K.-H. Ongania, K. Wurst, J.-P. Launay, Organometallics

16 (1997) 392.