1,1′-Bis(oxazolin-2-yl)ferrocenes: An investigation of their complexation behavior toward [Pd(η3-allyl)Cl]2

Article abstract of DOI:10.1002/ejic.200400737

The coordination behavior of several aryl- and alkyl-bis(oxazolinyl) ferrocenes, which were prepared in high yields from ferrocene-1,1′- dicarbonyl dichloride and enantiomerically pure or racemic amino alcohols via the corresponding bis(β-hydroxyamide)s and dimesylates or ditosylates as intermediates, toward [Pd(η³-allyl)Cl]₂ was investigated by ESI mass spectrometry. The synthesized compounds were characterized by NMR spectroscopy and elemental analysis and the molecular structures of 1,1′-bis[(R)-4-isopropyloxazolin-2-yl]-ferrocene (6b), 1,1′-bis[(S)-4-isopropyloxazolin-2-yl]ferrocene (7b), 1,1′-bis[(S)- 4-sec-butyloxazolin-2-yl]ferrocene (11b), 1,1′-bis[(S)-4-tert- butyloxazolin-2-yl]ferrocene (12b), 1,1′-bis[(R)-4-phenyloxazolin-2-yl] ferrocene (13b), and 1,1′-bis[(S)-4-phenyloxazolin-2-yl]ferrocene (14b) were determined by single-crystal X-ray diffraction analysis. The coordination behavior studies by ESI-MS show a strong preference for monodentate complex formation. This result is supported by theoretical studies carried out at the B3LYP level of theory. It was found that the latter coordination type of 1,1′-bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b) to an allylpalladium moiety is kinetically favored over the bidentate one.

Full text of DOI:10.1002/ejic.200400737

FULL PAPER
1,1Ј-Bis(oxazolin-2-yl)ferrocenes: An Investigation of Their Complexation
Behavior toward [Pd(η3-allyl)Cl]2
Christian G. Hartinger,*[a] Alexey A. Nazarov,*[a] Vladimir B. Arion,[a] Gerald Giester,[b]
Maxim L. Kuznetsov,[c] Markus Galanski,[a] and Bernhard K. Keppler*[a]
Keywords: Asymmetric catalysis / Density functional calculations / Mass spectrometry / Metallocenes / Palladium
The coordination behavior of several aryl- and alkyl-bis(ox- 1,1Ј-bis[(R)-4-phenyloxazolin-2-yl]ferrocene (13b), and 1,1Ј-
azolinyl)ferrocenes, which were prepared in high yields from
ferrocene-1,1Ј-dicarbonyl dichloride and enantiomerically
pure or racemic amino alcohols via the corresponding bis(β-
hydroxyamide)s and dimesylates or ditosylates as intermedi-
ates, toward [Pd(η3-allyl)Cl]2 was investigated by ESI mass
spectrometry. The synthesized compounds were charac-
terized by NMR spectroscopy and elemental analysis and the
molecular structures of 1,1Ј-bis[(R)-4-isopropyloxazolin-2-yl]-
bis[(S)-4-phenyloxazolin-2-yl]ferrocene (14b) were deter-
mined by single-crystal X-ray diffraction analysis. The coor-
dination behavior studies by ESI-MS show a strong prefer-
ence for monodentate complex formation. This result is sup-
ported by theoretical studies carried out at the B3LYP level
of theory. It was found that the latter coordination type of
1,1Ј-bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b) to an allyl-
palladium moiety is kinetically favored over the bidentate
ferrocene (6b), 1,1Ј-bis[(S)-4-isopropyloxazolin-2-yl]ferro- one.
cene (7b), 1,1Ј-bis[(S)-4-sec-butyloxazolin-2-yl]ferrocene
(11b), 1,1Ј-bis[(S)-4-tert-butyloxazolin-2-yl]ferrocene (12b),
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
or 4,5-dihydrooxazole moiety in the laboratory (for reviews
see refs.[6,7,11]): the dehydration and ring formation of some
carboxamides, for example hydroxy amides, the reaction be-
tween halo carboxamides and strong bases, as well as the
addition of oxiranes to nitriles and of amino alcohols to
carboxylic acids or imino esters offer a synthetic pathway
to build up the required five-membered heterocycle. Lately,
coordination-chemistry-driven approaches have moved into
the focus of synthetic chemists’ interest,[25,26] and the ad-
dition of haloalcohol/base or oxirane/chloride systems to
PtII-bound nitrile,[27,28] and reactions between nitriles and
amino alcohols catalyzed or mediated by a variety of metal
ions, for example ZnII, CdII, NiII, AlIII, CoII, CuII, show
high potential for the assembly of the oxazoline sys-
tem.[29–32]
An impressive number of reports and essays show the
applicability but also the popularity of ferrocene and its
derivatives in many fields of organic, materials, synthetic,
and also medicinal chemistry,[33–37] and the use of substi-
tuted ferrocenes in metal-catalyzed enantioselective synthe-
sis has been a very important application for more than
twenty years. Herein chiral ferrocene derivatives are in-
volved which either bear the center of chirality on a substit-
uent or contain an element of planar chirality.[38]
Introduction
Oxazolines are an intensively studied class of com-
pounds. These five-membered heterocycles are found in nat-
ural metal chelators,[1–3] show interesting biological proper-
ties,[4,5] and also play an important role in synthesis[6–10] as
well as have a remarkable range of applicability. Their uses
vary widely from organic[6–8] and coordination chemis-
try,[9,10] via polymer chemistry,[11–13] to antiacaricide as well
as antiinsecticidic purposes.[14] Oxazolines are used in a
manifold variety of catalytic processes, for example hydro-
silylation,[15] transfer hydrogenation,[16] allylic substitu-
tion,[17] allylic oxidation,[18] aziridination of olefins,[19]
aziridination of imines,[20] cyclopropanation,[21–23] and the
Diels–Alder reaction.[24] Furthermore, it should be noted
that there is a great interest in oxazolines as they possess
interesting properties in asymmetric synthesis when coordi-
nated to transition metals.
Beside the natural occurrence of oxazolines, there are se-
veral methods that are useful for constructing the oxazoline
[a] Institute of Inorganic Chemistry, University of Vienna,
Waehringer Str. 42, 1090 Vienna, Austria
Fax: +43-1-4277-52680
E-mail: bernhard.keppler@univie.ac.at,
christian.hartinger@univie.ac.at
alex.nazarov@univie.ac.at
The combination of the coordinating oxazoline structure,
which is easily obtainable (also in an enantiomerically pure
form) from reactions involving nonracemic starting materi-
als, such as α-amino alcohols, and ferrocene (with the pos-
sibility to introduce planar chirality) has led to the develop-
[b] Institute of Mineralogy and Crystallography, University of Vi-
enna,
Althanstr. 14, 1090 Vienna, Austria
[c] Department of Chemistry, Moscow Pedagogical State Univer-
sity,
Nesvigskiy per. 3, 119021 Moscow, Russian Federation
Eur. J. Inorg. Chem. 2005, 1589–1600
DOI: 10.1002/ejic.200400737
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C. G. Hartinger, A. A. Nazarov, B. K. Keppler et al.
FULL PAPER
ment of compounds containing both moieties, i.e., ferrocene were isolated by flash column chromatography on silica gel
and an oxazolinyl moiety.[39–43] This method offers a using a mixture of ethyl acetate and n-hexane as eluent.
straightforward way to synthesize chiral ferrocene deriva-
tives which are, due to their distinct structural features, ap-
plicable in asymmetric synthesis. Surprisingly, Ahn et al.
have reported a lack of catalytic activity for 1,1Ј-bis[(S)-
4-tert-butyloxazolin-2-yl]ferrocene (12b) in the palladium-
catalyzed allylic alkylation, while there are many examples
of non-metallocene complexes with bisoxazoline ligands
that give high enantiomeric excesses and turnover
rates.[17,44–48]
Electrospray ionization mass spectrometry (ESI-MS) is
the softest desorption/ionization method, and its suitability
to determine the coordination behavior of transition metal
cations toward ligands has been studied extensively (for ex-
amples see refs.[49–52] and for a review see ref.[53]). The desol-
vation process mainly leads to the presence of ions in the
gas phase that are also found in solution.[54] ESI-MS has a
number of advantages over other techniques; in particular,
it provides information on the characteristic isotopic pat-
terns of compounds (especially metal compounds) and al-
Scheme 1. General scheme for the synthesis of the 1,1Ј-bis-
lows low sample consumption and use of many compatible
(oxazolin-2-yl)ferrocenes.
solvents.[49]
In order to clarify the influence of the nature of the sub-
stituents on the catalytic potential of 1,1Ј-bis(oxazolin-2-
yl)ferrocenes, several derivatives of the parent compound
Table 1. List of the synthesized 1,1Ј-bis(oxazolin-2-yl)ferrocenes.
Substituents
Tosyl/mesyl chloride
1,1Ј-bis[(S)-4-tert-butyloxazolin-2-yl]ferrocene (12b) were
synthesized and tested with respect to their catalytic poten-
tial in asymmetric allylic substitution, where the catalytic
activity depends strongly on the formation of chelate struc-
tures between multidentate ligands and transition met-
als.[55,56] The coordination behavior of new 1,1Ј-bis(oxazo-
lin-2-yl)ferrocenes bearing alkyl (1b, 7b, and 12b) or aryl
substituents (14b) in the 4-position of the oxazoline ring
toward [Pd(η3-C3H5)Cl]2 was studied in detail by ESI-MS.
In order to elucidate the energetic preference for the coordi-
nation of 1,1Ј-bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b)
to an allylpalladium moiety, DFT calculations at the
B3LYP level of theory were also carried out.
R1
R2
tosyl
mesyl
1
2
(S)-methyl
H
(R)-ethyl
(S)-ethyl
n-propyl
(R)-isopropyl
(S)-isopropyl
n-butyl
(R)-isobutyl
(S)-isobutyl
(S)-sec-butyl
(S)-tert-butyl
(R)-phenyl
(S)-phenyl
H
H
X
X
(S)-methyl
3
H
H
H
H
H
H
H
H
H
H
H
H
phenyl
H
X
X
X
X
X
X
X
X
X
X
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
X
X
X
X
X
X
(R)-benzyl
(S)-benzyl
(S)-phenyl
H
Results and Discussion
(R)-phenyl
Synthesis
NMR spectroscopy was found to be a useful tool to fol-
The oxazolines bearing alkyl and aryl substituents at the low the ring-closing process, i.e., the transformation from
4- and/or 5-position of the oxazoline residue (see Scheme 1 hydroxy amides to oxazolines. This process is marked in the
and Table 1) were synthesized by a condensation reaction 1H NMR spectrum by the disappearance of the protons of
of 1,1Ј-ferrocenedicarbonyl dichloride with the correspond- the hydroxy and amide groups and in the 13C NMR spec-
ing α-amino alcohols at room temperature, followed by a trum by a characteristic high-field shift from about δ = 170
ring-closing procedure with either methanesulfonyl chloride to 166 ppm of the CO group, as well as by low-field shifts
and triethylamine or p-toluenesulfonyl chloride, triethyl- of the primary (for 2, 15, and 18) or secondary amino
amine and a catalytic amount of 4-(dimethylamino)pyridine alcohol carbon atoms from about δ = 64 ppm to about δ =
at 0 °C.[41,57–62] The yield for the syntheses of the methyl- 73 ppm [with the exception of 8 (from ca. δ = 52 to 73 ppm)
and aryl-substituted compounds was higher when using p- and 18 (from ca. δ = 75 to 79 ppm] as well as of the amino
toluenesulfonyl chloride, and the methyl and diphenyl alcohol carbon atoms next to the nitrogen from about δ =
amides that precipitated during the synthesis were obtained 50 to about 69 ppm (with the exception of 18: from approxi-
in high purity by filtration. All oxazolines and other amides mately δ = 60 to 89 ppm).
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1,1Ј-Bis(oxazolin-2-yl)ferrocenes
FULL PAPER
Figure 1. The molecular structure and labeling scheme of 1,1Ј-bis[(R)-4-isopropyloxazolin-2-yl]ferrocene (6b; top) and 1,1Ј-bis[(S)-4-
isopropyloxazolin-2-yl]ferrocene (7b; bottom) with displacement ellipsoids drawn at the 50% probability level.
The syntheses of hydroxy amides as well as of the corre- Table 2. Selected bond lengths [Å] and angles [°] in 6b, 7b, 11b, and
sponding oxazolines with (S)-isopropyl, (S)-tert-butyl,[41]
12b.
and (S)-phenyl moieties[39] in the 4-position of the oxazo-
6b
7b
11b
12b
line moiety have been reported earlier, but no crystal struc-
ture data were published. The synthesis of the 1,1Ј-ferro-
C1–C6
C6–N7
1.4685(18) 1.468(2)
1.2643(18) 1.264(2)
1.3641(17) 1.364(2)
1.4854(17) 1.487(2)
1.5397(19) 1.538(2)
1.479(8)
1.259(8)
1.345(8)
1.481(8)
1.520(9)
1.458(4)
1.265(3)
1.361(3)
1.474(4)
1.534(4)
1.461(3)
1.543(3)
1.511(4)
1.517(5)
104.1(2)
111.8(2)
115.5(2)
cenedicarboxamide 6a has been reported, but no analytical C6–O10
data were presented.[42]
N7–C8
C8–C9
C9–O10
C8–C11
C11–C12
C11–C13
1.4586(16) 1.4586(19) 1.455(8)
1.530(2)
1.525(2)
1.510(8)
1.466(14)
1.586(12)
1.5314(19) 1.534(2)
1.5312(17) 1.533(2)
103.97(11) 103.95(13) 104.8(5)
110.08(11) 110.03(13) 110.8(6)
116.23(12) 116.36(15) 116.8(6)
Crystal Structure Analysis
N7–C8–C9
Crystal structure analysis has been performed to eluci-
N7–C8–C11
date the influence of different substituents, viz., isopropyl,
phenyl, sec- and tert-butyl, at oxazoline rings on the tor-
sional twist angle of the Cp rings around the iron atom.
The results of the X-ray diffraction study of 6b and 7b,
which crystallized as pure enantiomers in the noncentro-
C9–C8–C11
Like 6b and 7b, complex 11b crystallizes as the (S)-en-
symmetric C2 space group, are summarized in Figure 1. The antiomer in the noncentrosymmetric C2221 space group
asymmetric unit consists of one half of the molecule in 6b (see Figure 2 top) and the asymmetric unit consists of half
and 7b. The C8 atom in 6b and 7b possesses an (R) and (S) the molecule. The Cp rings in 11b adopt an antiperiplanar
absolute configuration, respectively. The Cp rings in 6b and (staggered) arrangement with a torsional twist angle
7b approach an anticlinal eclipsed arrangement with a tor- Cp···Fe···Cp of 176.5°. The Cp rings are almost parallel to
sional twist angle Cp···Fe···Cp of 140.0° and 138.3°, respec- each other, with a dihedral angle of 1.6°. The oxazoline ring
tively. The Cp rings are almost parallel to each other, the is almost parallel to the Cp ring. The torsion angle C2–C1–
dihedral angles being 2.2° (6b) and 2.3° (7b). The orienta- C6–O10 is 3.2°. Like 11b, complex 12b crystallizes as the
tion of the oxazoline ring with respect to the Cp ring can (S)-enantiomer in the noncentrosymmetric C2221 space
be characterized by the torsion angle C2–C1–C6–O10, group (see Figure 2 bottom) and the asymmetric unit con-
which is 28.1° and –28.0° in 6b and 7b, respectively. The sists of half the molecule. The Cp rings in 12b adopt an
distribution of the electron density in the 4-isopropyl- antiperiplanar (staggered) arrangement with a torsional
oxazoline fragments in both 6b and 7b is very similar (see twist angle Cp···Fe···Cp of 174.9°. The Cp rings are almost
Table 2). The bond lengths and angles in the ferrocene moi- parallel to each other, with a dihedral angle of 0.4°. The
ety in both complexes are normal.[39]
oxazoline ring is almost parallel to the Cp ring. The torsion
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C. G. Hartinger, A. A. Nazarov, B. K. Keppler et al.
FULL PAPER
Figure 2. The molecular structure and labeling scheme of 1,1Ј-bis[(S)-4-sec-butyloxazolin-2-yl]ferrocene (11b; top) and 1,1Ј-bis[(S)-4-tert-
butyloxazolin-2-yl]ferrocene (12b; bottom) with displacement ellipsoids drawn at the 50% probability level.
angle C2–C1–C6–O10 is 8.1°. Selected bond lengths and
angles of 11b and 12b are given in Table 2.
Figure 3 shows one of the two independent molecules in
the crystal structures of 13b (R) and 14b (S). Like in all
previous compounds, the ferrocene moiety shows the ex-
pected geometry, with no unusual bond lengths or angles.
The two Cp rings are almost parallel to each other, with
dihedral angles of 4.5° and 2.0° in the two independent
molecules of 13b and 4.4° and 2.0° in 14b. The Cp···Fe···Cp
torsional twist angle is 54.2° and 52.9° for the independent
molecules in 13b, and –54.2° and –53.0° in 14b, thus indicat-
ing a conformation between synclinal staggered (ideal twist
angle of 36°) and synclinal eclipsed (ideal twist angle of
72°). As in 12b, the oxazoline rings are almost parallel to
the Cp rings, the torsional angles C2–C1–C6–O10, C18–
C17–C22–O26 and C34–C33–C38–O42, C50–C49–C54–
O58 being 6.1°, –11.5° and 4.7°, –3.6° in 13b and –6.6°,
11.4°, –4.2°, 3.3° in 14b (see Table 3 for selected bond
lengths and angles).
Investigation of the Coordination Properties
The application of bisoxazoline-based ligands in palla-
Figure 3. The molecular structure and labeling scheme of 1,1Ј-
dium-catalyzed allylic alkylation and in many other metal-
bis[(R)-4-phenyloxazolin-2-yl]ferrocene (13b; top) and 1,1Ј-bis[(S)-
catalyzed enantioselective reactions is well known.[9,17,44–48]
4-phenyloxazolin-2-yl]ferrocene (14b; bottom) with displacement
ellipsoids drawn at the 50% probability level.
Therefore the results of a study done by Ahn and co-
workers, who found no catalytic activity for 1,1Ј-bis[(S)-4-
tert-butyloxazolin-2-yl]ferrocene (12b), is rather surprising, [Pd(η3-C3H5)Cl]2 under standard conditions, i.e., (E)-1,3-
although the ligand does bear a bulky tert-butyl group.
diphenylprop-2-enyl acetate as substrate and dimethyl ma-
The catalytic potential of the ligands applied depends on lonate as nucleophile with the N,O-bis(trimethylsilyl)acet-
several structural features, especially the bite angle and the amide base system (BSA-KOAc; see Scheme 2).[63] In agree-
bulkiness of the substituents. In order to study the influence ment with the results of Ahn and co-workers, we did not
of the substituents nature and of their bulkiness, a series of observe any catalytic activity for any of the synthesized
analogues was synthesized and their catalytic potential in compounds. The variation of the ligand/Pd ratio from 1:1
the asymmetric allylic substitution investigated. The experi- to a large excess of the Pd compound (up to 10 times excess)
ments were carried out with palladium complexes generated did not affect the catalytic activity, and all efforts to isolate
in situ by stirring the corresponding chiral ligand and a defined Pd complex were unsuccessful.
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1,1Ј-Bis(oxazolin-2-yl)ferrocenes
FULL PAPER
Table 3. Selected bond lengths [Å] and angles [°] in 13b and 14b.
Table 5. Operational MS parameters chosen for investigations on
the complexation behavior of 1b, 7b, 12b, and 14b.
13b
14b
Parameters
Values
C1–C6
C6–N7
C6–O10
N7–C8
C8–C9
C9–O10
C8–C11
C11–C12
C11–C16
N7–C8–C9
N7–C8–C11
C9–C8–C11
1.462(3)
1.269(2)
1.370(2)
1.485(2)
1.542(3)
1.456(2)
1.515(3)
1.396(3)
1.386(3)
103.72(14)
108.53(14)
115.39(16)
1.465(3)
1.269(3)
1.367(2)
1.489(3)
1.541(3)
1.455(3)
1.506(3)
1.398(3)
1.394(3)
103.36(17)
108.55(17)
115.73(18)
HV capillary [V]
Dry gas flow [Lmin–1]
Dry gas temperature [°C]
Nebulizer gas [psi]
Skimmer 1 [V]
Capillary exit offset [V]
Octopole [V]
4000
5
80
10
35.7
73.6
2.50
2.40
30.6
6
Octopole Δ [V]
Trap drive
Injection rate [μLmin–1]
Polarity
positive
50–1200
Scan range, m/z
[C18H20FeN2O2 + Pd2(η3-C3H5)2Cl]+.
Increasing
the
amount of palladium (molar ratio 1:2) in the incubation
mixture resulted only in a minor increase of the peak at
m/z = 683; the signal assigned to [C18H20FeN2O2 + Pd(η3-
C3H5)]+ remained the most intense.
Scheme 2. General scheme for the palladium-catalyzed allylic alky-
lation.
Similar investigations were performed for 1,1Ј-bis[(S)-4-
isopropyloxazolin-2-yl]ferrocene (7b): at a molar ratio of
1:1 the most intense peak was again the ligand coordinated
to one PdII center, which in this case also bears an allyl
ligand. At the lower ligand/transition metal molar ratio
(1:1) a remarkable amount of [C22H28FeN2O2 + Pd2(η3-
C3H5)2Cl]+ is already detectable in this case. Addition of
[Pd(η3-C3H5)Cl]2 to obtain molar ratios of 1:2 and 1:10 in-
fluenced the mass spectra by increasing the signal with m/z
= 739, and at a molar ratio of 1:10 there are already peaks
with equal relative intensities for the mono-palladium (m/z
= 555) and the bis-palladium conjugates (m/z = 739; see
Figure 4). Additionally, MS/MS experiments of both ad-
ducts were done and it was found that the fragmentation of
m/z = 739 leads to a peak for the mono adduct (m/z = 555).
In order to investigate the reasons for this lack of cata-
lytic activity, the coordination of [Pd(η3-C3H5)Cl]2 toward
several 1,1Ј-bis(oxazolin-2-yl)ferrocenes was studied by
ESI-MS in the positive-ion mode (for calculated m/z ratios
of the parent compound and the expected adducts see
Table 4). The incubation solution of the Pd complex and
the oxazoline ligand was injected directly into the mass
spectrometer and the MS measurement parameters were
optimized in order to maximize signals corresponding to
the mass-to-charge ratio of the ligands (see Table 5).
Table 4. List of the calculated m/z ratios for the ligands and for the
complexes formed with [Pd(η3-C3H5)Cl]2 (measured in positive-ion
mode).
Formula
m/z ratio
1b
[C18H20FeN2O2 + H]+
353
499
495
683
409
555
551
739
437
583
577
767
761
477
623
617
807
1b + [Pd(η3-C3H5)Cl]2
1b + [Pd(η3-C3H5)Cl]2
1b + [Pd(η3-C3H5)Cl]2
7b
[C18H20FeN2O2 + Pd(η3-C3H5)]+
[C18H20FeN2O2 + PdCl]+
[C18H20FeN2O2 + Pd2(η3-C3H5)2Cl]+
[C22H28FeN2O2 + H]+
7b + [Pd(η3-C3H5)Cl]2
7b + [Pd(η3-C3H5)Cl]2
7b + [Pd(η3-C3H5)Cl]2
12b
[C22H28FeN2O2 + Pd(η3-C3H5)]+
[C22H28FeN2O2 + PdCl]+
[C22H28FeN2O2 + Pd2(η3-C3H5)2Cl]+
[C24H32FeN2O2 + H]+
12b + [Pd(η3-C3H5)Cl]2 [C24H32FeN2O2 + Pd(η3-C3H5)]+
12b + [Pd(η3-C3H5)Cl]2 [C24H32FeN2O2 + PdCl]+
12b + [Pd(η3-C3H5)Cl]2 [C24H32FeN2O2 + Pd2(η3-C3H5)2Cl]+
12b + [Pd(η3-C3H5)Cl]2 [C24H32FeN2O2 + Pd2(η3-C3H5)Cl2]+
14b
[C28H24FeN2O2 + H]+
14b + [Pd(η3-C3H5)Cl]2 [C28H24FeN2O2 + Pd(η3-C3H5)]+
14b + [Pd(η3-C3H5)Cl]2 [C28H24FeN2O2 + PdCl]+
14b + [Pd(η3-C3H5)Cl]2 [C28H24FeN2O2 + Pd2(η3-C3H5)Cl2]+
For 1,1Ј-bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b), a
signal at m/z = 353 was observed as the most intense peak
[C18H20FeN2O2 + H]+. Addition of [Pd(η3-C3H5)Cl]2 in 1:1
ligand/Pd molar ratio resulted in the formation of a peak
at m/z = 499 assignable to the mono-palladium complex
[C18H20FeN2O2 + Pd(η3-C3H5)]+ and a relatively much less
Figure 4. Mass spectrometric investigation of the coordination be-
havior of 1,1Ј-bis[(S)-4-isopropyloxazolin-2-yl]ferrocene (7b) to-
ward [Pd(allyl)Cl]2 at molar ratios of 1:1, 1:2, and 1:10 (ligand/
palladium), with peaks found at m/z = 555 and 739 assignable to
abundant one at m/z = 683 for the bis-palladium one the mono- and bis-palladium complexes, respectively.
Eur. J. Inorg. Chem. 2005, 1589–1600
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C. G. Hartinger, A. A. Nazarov, B. K. Keppler et al.
FULL PAPER
Further MS3 experiments did not result in any assignable
signals.
In the case of (S)-tert-butyloxazoline (12b) a major ad-
duct with m/z = 767 is formed which was assigned to
[C24H32FeN2O2 + Pd2(η3-C3H5)2Cl]+. Additionally, a coor-
dination compound was detected which contains one allyl
and two chloro ligands instead of two allyl and one chloro
ligand. Note that due to the broad isotope distribution of
palladium and chloro ligands an overlapping of the signals
with m/z = 761 and 767 can not be avoided.
The (S)-phenyloxazoline 14b was chosen as representa-
tive for the aryloxazolines for the MS experiments. At a
molar ratio of 1:1 the monoadduct with [Pd(η3-C3H5)Cl]2
is the most intense peak, while at a 1:2 ratio the dinuclear
Pd species is formed. Extension of the reaction times for all
the MS experiments did not influence the appearance of the
mass spectra. The increase of the peak with two Pd atoms
coordinated to the 1,1Ј-bis(oxazolin-2-yl)ferrocene ligands
reveals that there is no stable chelate formed between the
two oxazoline rings and the PdII cation. These results are
in good agreement with a report published by Imai et al.,
who showed by NMR spectroscopy that 1,1Ј-bis[(S)-4-iso-
propyloxazolin-2-yl]ferrocene (7b) functions, independently
of the Pd/oxazoline ratio, as a monodentate ligand.[64]
In order to study the experimentally found monodentate
coordination of the ferrocene ligand to the allylpalladium
moiety instead of the expected chelate formation, quantum-
chemical calculations of equilibrium structures of the par-
ent methyl-substituted ligand 1,1Ј-bis[(S)-4-methyloxazolin-
2-yl]ferrocene (1b) and possible complexes with mono- and
bidentate coordination of 1b to PdII (1c and 1d, respec-
tively) were carried out at the B3LYP level of theory. The
calculated structural parameters of 1b are in perfect agree-
ment with those found experimentally for 12b, with a maxi-
mum deviation of 0.021 Å for the C8–C9 bond. For the
other bonds, the difference between the calculated and ex-
perimental bond lengths often appears within the 3σ inter-
val of the X-ray data.
Figure 5. Equilibrium structures of complexes 1c (top) and 1d (bot-
tom).
A possible explanation for the preferred monodenticity
of the ligands might be the hindrance of rotation of the
oxazoline moiety around the C–C axis. Taking into account
the crystal structure analyses, the nitrogen atoms are not
orientated toward each other and therefore the nitrogen
lone-pairs in the solid state point in opposite directions.
The minima corresponding to both 1c and 1d were lo-
cated (see Figure 5). A comparison of the total energies of
these structures shows that the chelate complex 1d is
19.07 kcalmol–1 more stable than complex 1c. In terms of
Gibbs free energy, when the entropic factor is taken into
account, the stability of 1d relative to 1c decreases slightly
Conclusions
Bisoxazolines are known to be excellent ligands in many
but is still significant (ΔG = G1d – G1c = –15.83 kcalmol–1). enantioselective syntheses. A central factor in enantioselec-
Consideration of the solvent effects at the CPCM level (for tive synthesis is the formation of chelate structures by coor-
CH2Cl2 as a solvent) results in a further, but only moderate, dination of multidentate ligands to transition metals. The
lowering of the energy difference between 1d and 1c (by chelation process therefore has a great influence on the suc-
3.16 kcalmol–1). Thus, the chelate complex displays a signif- cess of metal complexes in many catalytic processes.
icantly higher stability than the monodentate structure de-
We have described the synthesis and characterization of
spite the possible steric hindrances in the former; the exclus- a wide variety of differently substituted 1,1Ј-bis(oxazolin-2-
ive formation of the monodentate-type complexes must yl)ferrocenes with substituents located in either the 4- or 5-
therefore be determined by kinetic factors rather than by position of the oxazoline rings and being either alkyl or aryl
thermodynamic ones. Indeed, the formation of chelates is groups. The synthesized compounds were characterized by
accompanied by the mutual rotation of two Cp cycles and standard analytical methods (NMR, elemental analysis).
by significant conformational changes in the ligand that Additionally, for compounds 6b, 7b, 11b, 12b, 13b, and 14b
should increase the activation energy compared to the for- the absolute configuration was determined by single-crystal
mation of 1c and similar structures.
X-ray diffraction analysis.
1594
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1,1Ј-Bis(oxazolin-2-yl)ferrocenes
FULL PAPER
tert-butyloxazolin-2-yl]ferrocene (12b), and 1,1Ј-bis[(S)-4-phenyl-
oxazolin-2-yl]ferrocene (14b) were prepared following a literature
procedure.[39] The synthesized amides were stable for more than
one year at room temperature while the oxazolines degraded over
time. Therefore they should be stored under argon and in the refrig-
erator.
The catalytic activity of these compounds was tested in
the palladium-catalyzed allylic alkylation. These experi-
ments showed that this type of ligand possesses no activity
in the test reaction and that a change of the substituent on
the oxazoline ring does not influence this. We suppose that
the lack of catalytic activity results from the insufficient co-
ordination properties of the studied 1,1Ј-bis(oxazolin-2-yl)-
ferrocenes, i.e., chelate formation with the palladium center,
a fact that was enlightened in mass spectrometric studies:
the bisoxazolines are not capable of functioning as biden-
tate ligands. This feature was found to be independent of
the type of substituents as well as their positions on the
oxazoline ring. Comparing the presented results with the
outcome of an NMR study reported by Imai and co-
workers it can be assumed that the effect is also indepen-
dent of the type of palladium complex.
N,NЈ-Bis[(1S)-(2-hydroxy-1-methylethyl)]ferrocene-1,1Ј-dicarbox-
amide (1a): A solution of 1,1Ј-ferrocenyldicarbonyl dichloride
(0.78 g, 2.50 mmol) in CH2Cl2 (30 mL) was added slowly at 0 °C to
a solution of (R)-(–)-2-amino-1-propanol (0.37 g, 5.00 mmol) and
triethylamine (0.7 mL, 5.05 mmol) in CH2Cl2 (20 mL). The reac-
tion mixture was stirred for 4 h, the formed precipitate was filtered
off and washed five times with CH2Cl2 (30 mL). This procedure
yielded 0.69 g (71%) of pure product after drying in vacuo. [α]2D0
=
+18 (c = 0.25, DMSO); m.p. 200–201 °C decomp. 1H NMR
3
([D6]DMSO): δ = 7.52 (d, J = 7.6 Hz, 2 H, NH), 4.75 (br. s, 4 H,
Fc-H), 4.29 (br. s, 4 H, Fc-H), 3.97 (m, 2 H, NHCH), 3.45 (m, 2
H, HOCH2), 3.38 (m, 2 H, HOCH2), 1.12 (d, 3J = 6.5 Hz, 6 H,
CH3) ppm. 13C{1H} NMR: δ = 169.24 (CO), 78.83 (Fc-C), 72.46
(Fc-C), 70.95 (Fc-C), 70.65 (Fc-C), 65.34 (HOCH2), 47.78
(NHCH), 18.19 (CH3) ppm. C18H24FeN2O4 (388.2): calcd. C 55.69,
H 6.23, N 7.22; found C 55.50, H 6.08, N 6.96.
In contrast, DFT calculations for this type of com-
pounds revealed, as expected, that chelating structures are
energetically more stable than the equivalent monodentate
complexes. Therefore it is suggested that the chelate forma-
tion of the ferrocene ligands with an allylpalladium moiety
instead of the bidentate one is kinetically controlled.
N,NЈ-Bis[(1S)-(1-hydroxy-1-methylethyl)]ferrocene-1,1Ј-dicarbox-
amide (2a): Following the same procedure as described for 1a
yielded 0.95 g (98%) of 2a. [α]2D0 = +4 (c = 0.25, DMSO); m.p. 122–
123 °C decomp. 1H NMR ([D6]DMSO): δ = 7.92 (br. s, 2 H, NH),
4.87 (br. s, 2 H, OH), 4.77 (br. s, 2 H, Fc-H), 4.74 (br. s, 4 H, Fc-
H), 3.81 (m, 2 H, HOCH), 3.15 (m, 2 H, NHCH2), 3.14 (m, 2 H,
Experimental Section
General Remarks: All reactions were carried out in dry solvents
under argon. The NMR spectra were recorded on a Bruker Avance
DPX 400 instrument (UltrashieldTM Magnet) at 400.13 MHz (1H)
and 100.63 MHz (13C) at 298 K in [D6]DMSO or CDCl3. Optical
rotations were measured with a Perkin–Elmer 341 polarimeter
using a 10 cm cell. Melting points were determined with a Büchi
B-540 apparatus and are uncorrected. Electrospray ionization mass
spectra were recorded on a Bruker esquire3000 spectrometer in posi-
tive-ion mode (see Table 5 for measurement parameters). The ele-
mental analyses were done by the Laboratory for Elemental Analy-
sis of the Institute of Physical Chemistry, University of Vienna,
with a Perkin–Elmer 2400 CHN Elemental Analyzer. Silica gel
(Fluka-60 70–230 mesh) was used for column chromatography and
silica gel (Polygram® SIL G/UV254) for thin layer chromatography.
3
NHCH2), 1.10 (d, J = 6.5 Hz, 6 H, CH3) ppm. 13C{1H} NMR: δ
= 169.66 (CO), 78.83 (Fc-C), 72.33 (Fc-C), 70.74 (Fc-C), 70.45 (Fc-
C), 66.16 (HOCH), 47.78 (NHCH), 18.19 (CH3 ) ppm.
C18H24FeN2O4 (388.2): calcd. C 55.69, H 6.23, N 7.22; found C
55.41, H 6.44, N 7.15.
N,NЈ-Bis[(1R)-(1-(hydroxymethyl)propyl]ferrocene-1,1Ј-dicarbox-
amide (3a): A solution of 1,1Ј-ferrocenyldicarbonyl dichloride
(0.78 g, 2.50 mmol) in CH2Cl2 (20 mL) was added slowly at 0 °C
to a solution of (R)-(–)-2-amino-1-butanol (0.45 g, 5.00 mmol) and
triethylamine (0.70 mL, 5.05 mmol) in CH2Cl2 (20 mL). The reac-
tion mixture was stirred for 4 h and washed with a saturated solu-
tion of NaHCO3 and then with brine. The organic phase was dried
with Na2SO4 and the solvent was removed in vacuo. This procedure
yielded 0.68 g (65%) of the title compound 3a after purification by
column chromatography. [α]2D0 = –17 (c = 0.25, DMSO); m.p. 181–
The full geometry optimization of all structures was carried out in
Cartesian coordinates with the Gaussian 98[69] program package at
the DFT level of theory. The calculations were performed using
Becke’s three-parameter hybrid exchange functional[70] in combina-
tion with the gradient-corrected correlation functional of Lee et
al.[71] (B3LYP). A quasi-relativistic Stuttgart pseudopotential was
used for the 28 core-electrons, the appropriate contracted basis set
(8s7p6d)/[6s5p3d][72] for the palladium atom, and the 6-31G* basis
set[73–76] for other atoms. For the Fe atom, the relativistic Stuttgart
pseudopotential describing 10 core-electrons and the appropriate
contracted basis set (8s7p6d1f)/[6s5p3d1f][77] was also used in some
calculations. Symmetry operations were not applied for all struc-
tures. The Hessian matrix was calculated analytically for all equilib-
rium structures to prove the location of correct minima (no imagi-
nary frequencies were found) and to estimate the thermodynamic
functions calculated at 25 °C. Solvent effects were taken into ac-
count at the single-point calculations based on the gas-phase equi-
librium geometries by using the polarizable continuum model[78] in
the CPCM version[79] with CH2Cl2 as a solvent.
1
3
182 °C decomp. H NMR (CDCl3): δ = 6.73 (d, J = 6.0 Hz, 2 H,
NH), 4.70 (br. s, 2 H, Fc-H), 4.45 (br. s, 4 H, Fc-H), 4.30 (br. s, 2
H, Fc-H), 4.26 (br. s, 2 H, OH), 3.91 (br. s, 2 H, NHCH), 3.83 (br.
s, 2 H, HOCH2), 3.78 (br. s, 2 H, HOCH2), 1.97 (m, 4 H, CH2CH3),
3
1.01 (dd, J = 7.0, 8.5 Hz, 6 H, CH2CH3) ppm. 13C{1H} NMR: δ
= 170.91 (CO), 78.28 (Fc-C), 72.60 (Fc-C), 71.81 (Fc-C), 71.34 (Fc-
C), 69.37 (Fc-C), 63.25 (HOCH2), 57.51 (NHCH), 29.75
(CH2CH3), 20.04 (CH2CH3) ppm. C20H28FeN2O4 (416.3): calcd. C
57.70, H 6.78, N 6.73; found C 57.59, H 6.66, N 6.51.
Ferrocene-1,1Ј-dicarboxamide 4a: Following the same procedure as
described for 3a yielded 0.89 g (86%) of 4a. [α]2D0 = +20 (c = 0.25,
DMSO); m.p. 181–182 °C decomp. 1H NMR (CDCl3): δ = 6.70 (d,
3J = 8.5 Hz, 2 H, NH), 4.71 (br. s, 2 H, Fc-H), 4.49 (br. s, 2 H, Fc-
H), 4.44 (br. s, 2 H, Fc-H), 4.35 (br. s, 2 H, OH), 4.33 (br. s, 2 H,
Fc-H), 4.05 (m, 2 H, NHCH), 3.87 (dd, 3J = 3.0, 11.5 Hz, 2 H,
HOCH2), 3.67 (dd, 3J = 6.0, 11.5 Hz, 2 H, HOCH2), 1.65 (m, 4 H,
CH2CH3), 1.00 (dd, J = 6.0, 11.5 Hz, 6 H, CH2CH3) ppm. 13C{1H}
NMR: δ = 170.88 (CO), 78.28 (Fc-C), 71.77 (Fc-C), 71.46 (Fc-C),
69.87 (Fc-C), 64.77 (HOCH2), 53.77 (NHCH), 24.79 (CH2CH3),
The N-substituted 1,1Ј-ferrocenedicarboxamides 7a, 12a, and 14a,
1,1Ј-bis[(S)-4-isopropyloxazolin-2-yl]ferrocene (7b), 1,1Ј-bis[(S)-4-
Eur. J. Inorg. Chem. 2005, 1589–1600
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C. G. Hartinger, A. A. Nazarov, B. K. Keppler et al.
FULL PAPER
11.19 (CH2CH3) ppm. C20H28FeN2O4 (416.3): calcd. C 57.70, H
6.78, N 6.73; found C 57.63, H 6.83, N 6.68.
Ferrocene-1,1Ј-dicarboxamide 10a: Following the same procedure
as described for 3a yielded 1.14 g (96%) of 10a. [α]2D0 = +18 (c =
3
0.25, DMSO); m.p. 53–54 °C. 1H NMR (CDCl3): δ = 6.70 (d, J =
Ferrocene-1,1Ј-dicarboxamide 5a: Following the same procedure as
described for 3a yielded 0.88 g (79%) of 5a. M.p. 47–48 °C. 1H
9.0 Hz, 2 H, NH,), 4.69 (br. s, 2 H, Fc-H), 4.45 (br. s, 2 H, Fc-H),
3
4.26 (m, 2 H, NHCH), 3.87 (dd, J = 3.0, 11.0 Hz, 2 H, HOCH2),
3
3
NMR (CDCl3): δ = 6.77 (d, J = 8.5 Hz, 1 H, NH), 6.69 (d, J =
9.0 Hz, 1 H, NH), 4.73 (br. s, 2 H, Fc-H), 4.55 (br. s, 1 H, Fc-H),
4.50 (br. s, 1 H, Fc-H), 4.45 (br. s, 1 H, Fc-H), 4.41 (br. s, 2 H, Fc-
3.61 (dd, 3J = 5.5, 11.0 Hz, 2 H, HOCH2), 1.70 [m, 2 H,
CH2CH(CH3)2], 1.57 [m, 2 H, CH2CH(CH3)2], 1.38 [m, 2 H,
CH2CH(CH3)2], 0.98 (d, 3J = 6.0 Hz, 12 H, CH3) ppm. 13C{1H}
NMR δ = 170.83 (CO), 78.16 (Fc-C), 72.48 (Fc-C), 71.81 (Fc-C),
71.42 (Fc-C), 69.60 (Fc-C), 65.77 (HOCH2), 50.35 (NHCH), 40.82
[CH2CH(CH3)2], 25.46 [CH2CH(CH3)2], 23.58 (CH3), 22.66 (CH3)
ppm. C24H36FeN2O4 (472.4): calcd. C 61.02, H 7.68, N 5.93; found
C 60.80, H 7.83, N 5.82.
3
H), 4.34 (br. s, 1 H, Fc-H), 4.15 (m, 2 H, NHCH), 3.87 (dd, J =
3.0, 11.0 Hz, 2 H, HOCH2), 3.65 (dd, 3J = 5.0, 11.0 Hz, 2 H,
HOCH2), 1.61–1.52 (m, 4 H, CH2CH2CH3), 1.47–1.36 (m, 4 H,
3
3
CH2CH2CH3), 0.97 (t, J = 8.0 Hz, 3 H, CH2CH2CH3), 0.94 (t, J
= 7.0, 3 H, CH2CH2CH3) ppm. 13C{1H} NMR: δ = 170.89 (CO),
170.86 (CO), 78.26 (Fc-C), 77.87 (Fc-C), 72.43 (Fc-C),72.21 (Fc-
C), 71.81 (Fc-C), 71.57 (Fc-C), 71.44 (Fc-C), 70.11 (Fc-C), 69.83 Ferrocene-1,1Ј-dicarboxamide 11a: Following the same procedure
(Fc-C), 65.64 (HOCH2), 65.23 (HOCH2), 52.00 (NHCH), 51.95
as described for 3a yielded 1.08 g (91%) of 11a. [α]2D0 = +23 (c =
3
(NHCH), 33.88 (CH2CH2CH3) 33.58 (CH2CH2CH3), 19.82 0.25, DMSO); m.p. 60–61 °C. 1H NMR (CDCl3): δ = 6.66 (d, J =
(CH2CH2CH3), 14.43 (CH2CH2CH3), 14.39 (CH2CH2CH3) ppm.
C22H32FeN2O4 (444.3): calcd. C 59.47, H 7.26, N 6.30; found C
59.28, H 7.30, N 6.21.
8.5 Hz, 2 H, NH), 4.72 (br. s, 2 H, Fc-H), 4.46 (br. s, 4 H, Fc-H),
3
4.32 (br. s, 2 H, Fc-H), 3.99 (m, 2 H, NHCH), 3.85 (dd, J = 3.0,
11.5 Hz, 2 H, HOCH2), 3.77 (dd, 3J = 6.0, 11.5 Hz, 2 H, HOCH2),
1.78 [m, 2 H, CH(CH3)CH2CH3], 1.58 [m, 2 H, CH(CH3)
Ferrocene-1,1Ј-dicarboxamide 6a:[42] Yield: 0.97 g (87%). [α]2D0
=
3
CH2CH3], 1.24 [m, 2 H, CH(CH3)CH2CH3], 1.00 (d, J = 6.5 Hz,
1
–53 (c = 0.25, DMSO); m.p. 108–109 °C. H NMR (CDCl3): δ =
3
6 H, CH3), 0.95 (t, J = 7.0 Hz, 6 H, CH3) ppm. 13C{1H} NMR:
3
6.65 (d, J = 9.0 Hz, 2 H, NH), 4.72 (br. s, 2 H, Fc-H), 4.46 (br. s,
δ = 170.73 (CO), 78.27 (Fc-C), 72.49 (Fc-C), 71.79 (Fc-C), 71.36
(Fc-C), 69.36 (Fc-C), 63.03 (HOCH2), 56.05 (NHCH), 36.12
[CH(CH3)CH2CH3], 26.21 [CH(CH3)CH2CH3], 15.96 (CH3), 11.63
(CH3) ppm. C24H36FeN2O4 (472.4): calcd. C 61.02, H 7.68, N 5.93;
found C 61.12, H 7.70, N 5.83.
4 H, Fc-H), 4.32 (br. s, 2 H, Fc-H), 4.16 (br. s, 2 H, OH), 3.92 (m,
3
2 H, NHCH), 3.85 (dd, J = 3.0, 11.5 Hz, 2 H, HOCH2) 3.76 (dd,
3J = 6.0, 11.5 Hz, 2 H, HOCH2), 1.97 (m, 3J = 7.0 Hz, 2 H,
3
3
CH(CH3)2], 1.03 (d, J = 7.0 Hz, 6 H, CH3), 1.00 (d, J = 7.0 Hz,
6 H, CH3) ppm. 13C{1H} NMR: δ = 170.84 (CO), 78.32 (Fc-C),
72.45 (Fc-C), 71.79 (Fc-C), 71.37 (Fc-C), 69.43 (Fc-C), 63.30 Ferrocene-1,1Ј-dicarboxamide 13a: Following the same procedure
(HOCH2), 57.50 (NHCH), 29.80 [CH(CH3)2], 20.02 (CH3), 19.70
(CH3) ppm. C22H32FeN2O4 (444.3): calcd. C 59.47, H 7.26, N 6.30;
found C 59.35, H 7.09, N 6.35.
as described for 3a yielded 1.30 g (83%) of 13a. [α]2D0 = –88 (c =
0.25, DMSO); m.p. 207–208 °C decomp. H NMR ([D6]DMSO): δ
1
= 8.22 (d, 3J = 7.5 Hz, 2 H, NH,), 7.41–7.26 (m, 10 H, Ph-H), 5.04
(m, 4 H, NHCH, OH), 4.91 (br. s, 2 H, Fc-H), 4.60 (br. s, 2 H, Fc-
H), 4.31 (br. s, 2 H, Fc-H), 4.26 (br. s, 2 H, Fc-H), 3.70.(m, 4 H,
HOCH2) ppm. 13C{1H} NMR: δ = 169.53 (CO), 142.36 (Ph-C),
128.97 (Ph-C), 127.90 (Ph-C), 127.73 (Ph-C), 78.48 (Fc-C), 72.46
(Fc-C), 72.25 (Fc-C), 71.90 (Fc-C), 69.67 (Fc-C), 65.23 (HOCH2),
56.49 (NHCH) ppm. C28H28FeN2O4 (512.4): calcd. C 65.64, H
5.51, N 5.47; found C 65.52, H 5.41, N 5.25.
Ferrocene-1,1Ј-dicarboxamide 8a: Following the same procedure as
described for 3a yielded 0.73 g (62%) of 8a. M.p. 39–40 °C. 1H NMR
(CDCl3): δ = 6.68 (d, 3J = 8.0 Hz, 1 H, NH), 6.59 (d, 3J = 8.5 Hz, 1
H, NH), 4.75 (br. s, 2 H, Fc-H), 4.55 (br. s, 1 H, Fc-H), 4.51 (br. s, 1
H, Fc-H), 4.46 (br. s, 1 H, Fc-H), 4.43 (br. s, 2 H, Fc-H), 4.36 (br. s,
1 H, Fc-H), 4.14 (m, 2 H, NHCH), 3.89 (dd, 3J = 3.0, 12.0 Hz, 2 H,
HOCH2), 3.65 (dd, 3J = 5.5, 11.0 Hz, 2 H, HOCH2), 1.59 [m, 4 H,
CH2(CH2)2CH3], 1.36 [m, 8 H, CH2(CH2)2CH3], 0.92 [m, 6 H, Ferrocene-1,1Ј-dicarboxamide 15a: Following the same procedure
CH2(CH2)2CH3]. 13C{1H} NMR: δ = 170.82 (CO), 170.78 (CO), as described for 3a yielded 1.37 g (87%) of 15a. M.p. 207–208 °C
78.30 (Fc-C), 77.88 (Fc-C), 72.51 (Fc-C), 72.18 (Fc-C), 71.80 (Fc-C),
decomp. 1H NMR ([D6]DMSO): δ = 7.96 (m, 2 H, NH), 7.42–7.27
71.53 (Fc-C), 71.46 (Fc-C), 70.03 (Fc-C), 69.82 (Fc-C), 65.74 (m, 10 H, Ph-H), 5.61 (dd, 3J = 4.5, 9.0 Hz, 2 H, HOCH), 4.82 (br.
(NHCH), 65.29 (NHCH), 52.27 (HOCH2), 52.19 (HOCH2), s, 2 H, OH), 4.71 (br. s, 4 H, Fc-H), 4.29 (br. s, 4 H, Fc-H), 3.46
31.52 (CH2CH2CH2CH3), 31.18 (CH2CH2CH2CH3), 28.79 (m, 2 H, NHCH2), 3.26 (m, 2 H, NHCH2) ppm. 13C{1H} NMR:
(CH2CH2CH2CH3), 23.02 (CH2CH2CH2CH3), 22.97 (CH2CH2- δ = 169.60 (CO), 144.69 (Ph-C), 128.94 (Ph-C), 127.94 (Ph-C),
CH2CH3), 14.45 (CH2CH2CH2CH3), 14.41 (CH2CH2CH2CH3) 126.93 (Ph-C), 78.52 (Fc-C), 72.43 (Fc-C), 72.19 (Fc-C),70.65 (Fc-
ppm. C24H36FeN2O4 (472.4): calcd. C 61.02, H 7.68, N 5.93; found
C 61.15, N 5.93.
C), 70.53 (Fc-C), 70.43 (HOCH), 48.15 (NHCH2) ppm.
C28H28FeN2O4 (512.4): calcd. C 65.64, H 5.51, N 5.47; found C
65.34, H 5.69, N 5.31.
Ferrocene-1,1Ј-dicarboxamide 9a: Following the same procedure as
described for 3a yielded 0.81 g (68%) of 9a. [α]2D0 = –19 (c = 0.25,
DMSO); m.p. 59–60 °C. 1H NMR (CDCl3): δ = 6.78 (d, 3J =
8.5 Hz, 2 H, NH,), 4.69 (br. s, 2 H, Fc-H), 4.45 (br. s, 2 H, Fc-H),
4.43 (br. s, 2 H, Fc-H), 4.30 (br. s, 2 H, Fc-H), 4.25 (m, 2 H,
NHCH), 3.85 (dd, 3J = 3.0, 11.0 Hz, 2 H, HOCH2), 3.61 (dd, 3J =
5.5, 11.5 Hz, 2 H, HOCH2), 1.69 [m, 2 H, CH2CH(CH3)2], 1.57
Ferrocene-1,1Ј-dicarboxamide 16a: Following the same procedure
as described for 3a yielded 1.31 g (79%) of 16a. [α]2D0 = +41 (c =
1
0.25, DMSO); m.p. 173–174 °C decomp. H NMR ([D6]DMSO): δ
3
= 7.67 (d, J = 8.5, 2 H, NH), 7.31 (m, 8 H, Ph-H), 7.18 (m, 2 H,
3
Ph-H), 4.91 (t, J = 5.5 Hz, 2 H, NHCH,), 4.66 (br. s, 2 H, Fc-H),
4.32 (br. s, 2 H, Fc-H), 4.16 (br. s, 2 H, OH), 4.08 (br. s, 2 H, Fc-
[m, 2 H, CH2CH(CH3)2], 1.38 [m, 2 H, CH2CH(CH3)2], 0.98 (d, 3J H), 4.05 (br. s, 2 H, Fc-H), 3.51 (m, 2 H, HOCH2), 3.43 (m, 2 H,
= 6.6 Hz, 12 H, CH3) ppm. 13C{1H} NMR: δ = 170.88 (CO), 78.14 HOCH2), 2.99 (m, 2 H, CH2Ph), 2.76 (m, 2 H, CH2Ph) ppm.
(Fc-C), 72.50 (Fc-C), 71.84 (Fc-C), 71.42 (Fc-C), 69.63 (Fc-C), 13C{1H} NMR: δ = 169.33 (CO), 140.53 (Ph-C), 129.94 (Ph-C),
65.73 (HOCH2), 50.34 (NHCH), 40.80 [CH2CH(CH3)2], 25.46
128.99 (Ph-C), 126.77 (Ph-C), 78.62 (Fc-C), 72.37 (Fc-C), 72.20
[CH2CH(CH3)2], 23.59 (CH3), 22.67 (CH3) ppm. C24H36FeN2O4 (Fc-C), 71.94 (Fc-C), 69.12 (Fc-C), 64.21 (HOCH2), 53.65
(472.4): calcd. C 61.02, H 7.68, N 5.93; found C 60.81, H 7.52, N
5.75.
(NHCH), 37.39 (CH2Ph) ppm. C30H32FeN2O4 (540.4): calcd. C
66.67, H 5.97, N 5.18; found C 66.33, H 5.96, N 5.04.
1596
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1589–1600

1,1Ј-Bis(oxazolin-2-yl)ferrocenes
FULL PAPER
Ferrocene-1,1Ј-dicarboxamide 17a: Following the same procedure
as described for 3a yielded 1.19 g (72%) of 17a. [α]2D0 = –37 (c =
70.82 (Fc-C), 68.27 (NCH), 28.87 (CH2), 10.37(CH3) ppm.
C20H24FeN2O2 (380.3): calcd. C 63.17, H 6.36, N 7.37; found C
63.28, H 6.36, N 7.45.
1
0.25, DMSO); m.p. 175–176 °C decomp. H NMR ([D6]DMSO): δ
3
= 7.68 (d, J = 8.5 Hz, 2 H, NH), 7.31 (m, 8 H, Ph-H), 7.18 (m, 2
1,1Ј-Bis[(S)-4-ethyloxazolin-2-yl]ferrocene (4b): Following the same
3
H, Ph-H), 4.92 (t, J = 5.0 Hz, 2 H, NHCH), 4.66 (br. s, 2 H, Fc-
procedure as described for 3b yielded 0.30 g (79%) of 4b. [α]2D0
=
H), 4.32 (br. s, 2 H, Fc-H), 4.16 (br. s, 2 H, OH), 4.07 (br. s, 2 H,
Fc-H), 4.04 (br. s, 2 H, Fc-H), 3.51(m, 2 H, HOCH2), 3.42 (m, 2
H, HOCH2), 2.99 (m, 2 H, CH2Ph), 2.75 (m, 2 H, CH2Ph) ppm.
13C{1H} NMR: δ = 169.34 (CO), 140.53 (Ph-C), 129.94 (Ph-C),
128.99 (Ph-C), 126.77 (Ph-C), 78.62 (Fc-C), 72.37 (Fc-C), 72.20
(Fc-C), 71.94 (Fc-C), 69.12 (Fc-C), 64.21 (HOCH2), 53.65
(NHCH), 37.39 (CH2Ph) ppm. C30H32FeN2O4 (540.4): calcd. C
66.67, H 5.97, N 5.18; found C 66.57, H 5.90, N 4.99.
+52 (c = 0.25, CH2Cl2); m.p. 72–73 °C. 1H NMR (CDCl3): δ =
3
4.75 (br. s, 4 H, Fc-H), 4.39 (t, J = 8.0 Hz, 2 H, OCH2,), 4.36 (br.
s, 4 H, Fc-H), 4.10 (m, 2 H, NCH), 3.98 (t, 3J = 8.0 Hz, 2 H,
OCH2), 1.76 (m, 2 H, CH2CH3), 1.59 (m, 2 H, CH2CH3), 1.00 (t,
3J = 7.5 Hz, 6 H, CH3) ppm. 13C{1H} NMR: δ = 165.39 (CO),
72.37 (Fc-C), 72.32 (Fc-C), 72.13 (Fc–C, OCH2), 71.01 (Fc-C),
70.82 (Fc-C), 68.30 (NCH), 28.88 (CH2), 10.38 (CH3) ppm.
C20H24FeN2O2 (380.3): calcd. C 63.17, H 6.36, N 7.37; found C
63.40, H 6.24, N 7.34.
Ferrocene-1,1Ј-dicarboxamide 18a: Following the same procedure
as described for 1a yielded 1.61 g (79%) of 18a. [α]2D0 = +76 (c =
1,1Ј-Bis(4-propyloxazolin-2-yl)ferrocene (5b): Following the same
procedure as described for 3b yielded 0.18 g (44%) of 5b as an oil.
1H NMR (CDCl3): δ = 4.74 (br. s, 4 H, Fc-H), 4.39 (dd, 3,2J = 2.5,
9.0 Hz, 2 H, OCH2), 4.35 (br. s, 4 H, Fc-H), 4.15 (m, 2 H, NCH),
3.96 (dd, 3,2J = 3.0, 7.5 Hz, 2 H, OCH2), 1.72 [m, 2 H, (CH2)2CH3],
1.47 [m, 6 H, (CH2)2CH3], 0.99 (t, 3J = 7.0 Hz, 6 H, CH3) ppm.
13C{1H} NMR: δ = 165.30 (CO), 72.60 (OCH2), 72.38 (Fc-C),
72.34 (Fc-C), 72.32 (Fc-C), 72.15 (Fc-C), 72.12 (Fc-C), 71.01 (Fc-
C), 70.97 (Fc-C), 70.90 (Fc-C), 70.84 (Fc-C), 66.86 (NCH), 38.49
(CH2), 19.51 (CH2), 14.55 (CH3) ppm. C22H28FeN2O2 (408.3):
calcd. C 64.71, H 6.91, N 6.86; found C 64.54, H 6.83, N 6.83.
1
0.25, DMSO); m.p. 277–278 °C decomp. H NMR ([D6]DMSO): δ
3
= 8.25 (d, J = 9.0 Hz, 2 H, NH), 7.59–7.48 (m, 8 H, Ph-H), 7.44–
3
7.02 (m, 12 H, Ph-H), 5.44 (br. s, 2 H, OH), 5.04 (t, J = 9.0 Hz,
3
2 H, NHCH,), 4.91 (dd, J = 5.5, 8.5 Hz, 2 H, CHOH,), 4.35 (br.
s, 2 H, Fc-H), 4.18 (br. s, 2 H, Fc-H), 3.82 (br. s, 2 H, Fc-H), 3.78
(br. s, 2 H, Fc-H) ppm. 13C{1H} NMR: δ = 168.54 (CO), 145.00
(Ph-C), 143.07 (Ph-C), 129.15 (Ph-C), 128.70 (Ph-C), 128.55 (Ph-
C), 128.10 (Ph-C), 127.94 (Ph-C), 127.57 (Ph-C), 78.44 (Fc-C),
75.39 (CHOH), 72.23 (Fc-C), 71.81 (Fc-C), 71.07 (Fc-C), 69.17
(Fc-C), 59.77 (NHCH) ppm. C40H36FeN2O4 (664.6): calcd. C
72.29, H 5.46, N 4.22; found C 72.46, H 5.45, N 4.14.
1,1Ј-Bis[(R)-4-isopropyloxazolin-2-yl]ferrocene (6b):[42] Yield: 0.37 g
(90%). [α]2D0 = –83 (c = 0.25, CH2Cl2); m.p. 64–65 °C. 1H NMR
(CDCl3): δ = 4.77 (br. s, 2 H, Fc-H), 4.75 (br. s, 2 H, Fc-H), 4.36
(br. s, 4 H, Fc-H), 4.31 (t, 2 H, OCH2, J = 9.0), 4.07 (t, 3J = 9.0 Hz,
2 H, OCH2), 4.00 (m, 2 H, NCH), 1.87 [m, 2 H, CH(CH3)2], 1.03
1,1Ј-Bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b): A solution of p-
toluenesulfonyl chloride (0.42 g, 2.20 mmol) in CH2Cl2 (20 mL)
was added dropwise at 0 °C to a solution of 1a (0.39 g, 1.00 mmol),
triethylamine (0.70 mL, 5.00 mmol), and a catalytic amount of 4-
(dimethylamino)pyridine in CH2Cl2 (50 mL). The reaction mixture
was stirred at room temperature for 10 h and then washed with a
saturated solution of NaHCO3 and with brine. The water layer was
extracted with CH2Cl2 and the combined organic phases were dried
with Na2SO4. Purification by column chromatography gave 0.31 g
(88%) of 1b. [α]2D0 = +77 (c = 0.25, CH2Cl2); m.p. 85–86 °C. 1H
3
3
(d, J = 7.0 Hz, 6 H, CH3,), 0.95 (d, J = 6.5 Hz, 6 H, CH3) ppm.
13C{1H} NMR: δ = 165.26 (CO), 72.84 (NCH), 72.32 (Fc-C), 72.27
(Fc-C), 70.01 (Fc-C), 70.69 (Fc-C), 69.91 (OCH2), 32.78 (CH),
19.40 (CH3), 18.32 (CH3) ppm. C22H28FeN2O2 (408.3): calcd. C
64.71, H 6.91, N 6.86; found C 64.62, H 6.95, N 6.67.
3
1,1Ј-Bis(4-butyloxazolin-2-yl)ferrocene (8b): Following the same
procedure as described for 3b yielded 0.34 g (78%) of 8b as an oil.
1H NMR (CDCl3): δ = 4.76 (br. s, 4 H, Fc-H), 4.40 (m, 2 H,
OCH2), 4.36 (br. s, 4 H, Fc-H), 4.14 (m, 2 H, OCH2), 3.96 (m, 2
H, NCH), 1.76 [m, 2 H, (CH2)3CH3], 1.54 [m, 2 H, (CH2)2CH3],
1.40 [m, 8 H, (CH2)2CH3], 0.95 (t, 3J = 7.0 Hz, 6 H, CH3) ppm.
13C{1H} NMR: δ = 165.31 (CO), 72.60 (OCH2), 72.40 (Fc-C),
72.37 (Fc-C), 72.33 (Fc-C), 72.15 (Fc-C), 70.98 (Fc-C), 70.96 (Fc-
C), 70.90 (Fc-C), 70.84 (Fc-C), 67.07 (NCH), 36.00 (CH2), 28.41
(CH2), 23.16 (CH2), 14.44 (CH3) ppm. C24H32FeN2O2 (436.4):
calcd. C 66.06, H 7.39, N 6.42; found C 66.00, H 7.27, N 6.36.
NMR (CDCl3): δ = 4.72 (br. s, 4 H, Fc-H), 4.41 (t, J = 8.5, 2 H,
3
OCH2), 4.34 (br. s, 4 H, Fc-H), 4.20 (m, 2 H, NCH), 3.84 (t, J =
8.0 Hz, 2 H, OCH2), 1.30 (d, 3J = 6.6 Hz, 6 H, CH3) ppm. 13C{1H}
NMR: δ = 165.39 (CO), 74.15 (OCH2), 72.38 (Fc-C), 72.26 (Fc-C),
72.01 (Fc-C), 71.02 (Fc-C), 70.94 (Fc-C), 62.26 (NCH), 21.91(CH3)
ppm. C18H20FeN2O2 (352.2): calcd. C 61.38, H 5.72, N 7.95; found
C 61.36, H 5.80, N 7.76.
1,1Ј-Bis[(S)-5-methyloxazolin-2-yl]ferrocene (2b): Following the
same procedure as described for 1b yielded 0.28 g (79%) of 2b.
[α]2D0 = +22 (c = 0.25, CH2Cl2); m.p. 101–102 °C. 1H NMR
(CDCl3): δ = 4.73 (m, 6 H, Fc–H, OCH), 4.35 (br. s, 2 H, Fc-H),
4.32 (br. s, 2 H, Fc-H), 3.97 (dd, 3,2J = 9.5, 14.0 Hz, 2 H, NCH2),
1,1Ј-Bis[(R)-4-isobutyloxazolin-2-yl]ferrocene (9b): Following the
same procedure as described for 3b yielded 0.32 g (73%) of 9b as
an oil. [α]2D0 = –83 (c = 0.25, CH2Cl2). 1H NMR (CDCl3): δ = 4.75
3
3.44 (dd, 3,2J = 7.0, 14.0 Hz, 2 H, NCH2), 1.40 (d, J = 6.5 Hz, 6
H, CH3) ppm. 13C{1H} NMR: δ = 165.64 (CO), 76.20 (OCH),
72.42 (Fc-C), 72.32 (Fc-C), 72.15 (Fc-C), 70.78 (Fc-C), 70.59 (Fc-
C), 62.00 (NCH2), 21.62(CH3) ppm. C18H20FeN2O2 (352.2): calcd.
C 61.38, H 5.72, N 7.95; found C 61.50, H 5.52, N 7.93.
3
(br. s, 4 H, Fc-H), 4.43 (t, J = 8.5 Hz, 2 H, OCH2), 4.36 (br. s, 4
3
H, Fc-H), 4.19 (m, 2 H, NCH), 3.92 (t, J = 7.5 Hz, 2 H, OCH2),
1.77 (m, 2 H, CH2CH), 1.71 (m, 2 H, CH2CH), 1.37 (m, 2 H,
3
CH2CH), 0.98 (t, J = 6.5 Hz, 12 H, CH3) ppm. 13C{1H} NMR: δ
1,1Ј-Bis[(R)-4-ethyloxazolin-2-yl]ferrocene (3b): Following a similar
procedure as described for 1b, but changing p-toluenesulfonyl chlo-
ride for methanesulfonyl chloride, yielded 0.29 g (77%) of 3b.
= 165.28 (CO), 73.21 (OCH2), 72.44 (Fc-C), 72.33 (Fc-C), 72.08
(Fc-C), 71.04 (Fc-C), 70.92 (Fc-C), 65.41 (NCH), 46.04 (CH2),
25.87 (CH), 23.49 (CH3), 23.01 (CH3) ppm. C24H32FeN2O2 (436.4):
calcd. C 66.06, H 7.39, N 6.42; found C 66.02, H 7.45, N 6.34.
1
[α]2D0 = –63 (c = 0.25, CH2Cl2); m.p. 75–76 °C. H NMR (CDCl3):
3
δ = 4.75 (br. s, 4 H, Fc-H), 4.38 (t, J = 9.0 Hz, 2 H, OCH2,), 4.35
3
(br. s, 4 H, Fc-H), 4.10 (m, 2 H, NCH), 3.97 (t, J = 8.0 Hz, 2 H, 1,1Ј-Bis[(S)-4-isobutyloxazolin-2-yl]ferrocene (10b): Following the
OCH2), 1.75 (m, 2 H, CH2CH3), 1.48 (m, 2 H, CH2CH3), 0.99 (t, same procedure as described for 3b yielded 0.36 g (82%) of 10b as
3J = 7.5 Hz, 6 H, CH3) ppm. 13C{1H} NMR: δ = 165.39 (CO),
an oil. [α]2D0 = –83 (c = 0.25, CH2Cl2). 1H NMR (CDCl3): δ = 4.73
3
72.37 (Fc-C), 72.32 (Fc-C), 72.13 (Fc–C, OCH2), 71.01 (Fc-C), (br. s, 4 H, Fc-H), 4.40 (t, J = 8.5 Hz, 2 H, OCH2), 4.43 (br. s, 4
Eur. J. Inorg. Chem. 2005, 1589–1600
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1597

C. G. Hartinger, A. A. Nazarov, B. K. Keppler et al.
H, Fc-H), 4.16 (m, 2 H, NCH), 3.90 (t, J = 7.5 Hz, 2 H, OCH2), (m, 4 H, Ph-H), 7.27 (m, 6 H, Ph-H), 4.78 (br. s, 2 H, Fc-H), 4.75
FULL PAPER
3
1.77 (m, 2 H, CH2CH), 1.69 (m, 2 H, CH2CH), 1.35 (m, 2 H,
(br. s, 2 H, Fc-H), 4.45 (m, 2 H, NCH), 4.36 (br. s, 2 H, Fc-H),
3
3
CH2CH), 0.97 (t, J = 6.0 Hz, 12 H, CH3) ppm. 13C{1H} NMR: δ
4.34 (br. s, 2 H, Fc-H), 4.27(t, 3J = 8.0 Hz, 2 H, OCH2), 4.07 (t, J
= 165.10 (CO), 73.15 (OCH2), 72.35 (Fc-C), 72.26 (Fc-C), 72.17 = 8.0 Hz, 2 H, OCH2), 3.23 (dd, 3,2J = 5.0, 13.5 Hz, 2 H, CH2Ph),
(Fc-C), 70.98 (Fc-C), 70.86 (Fc-C), 65.50 (NCH), 46.06 (CH2), 2.72 (dd, 3,2J = 9.0, 13.5 Hz, 2 H, CH2Ph) ppm. 13C{1H} NMR: δ
25.86 (CH), 23.50 (CH3), 23.00 (CH3) ppm. C24H32FeN2O2 (436.4):
calcd. C 66.06, H 7.39, N 6.42; found C 66.12, H 7.42, N 6.47.
= 166.08 (CO), 139.55 (Ph-C), 129.71 (Ph-C), 128.99 (Ph-C),
126.93 (Ph-C), 72.50 (Fc-C), 72.45 (Fc-C), 71.89 (OCH2), 71.08
(Fc-C), 70.95 (Fc-C), 68.85 (Fc-C), 68.27 (NCH), 42.17 (CH2Ph)
ppm. C30H28FeN2O2 (504.4): calcd. C 71.44, H 5.60, N 5.55; found
C 71.31, H 5.89, N 5.74.
1,1Ј-Bis[(S)-4-sec-butyloxazolin-2-yl]ferrocene (11b): Following the
same procedure as described for 3b yielded 0.35 g (80%) of 11b.
1
[α]2D0 = –83 (c = 0.25, CH2Cl2); m.p. 78–79 °C. H NMR (CDCl3):
δ = 4.77 (br. s, 2 H, Fc-H), 4.75 (br. s, 2 H, Fc-H), 4.36 (br. s, 4 H,
Fc-H), 4.29 (t, 3J = 7.5 Hz, 2 H, OCH2), 4.11 (m, 2 H, NCH), 4.08
(m, 2 H, OCH2), 1.73 (m, 2 H, CH), 1.57 (m, 2 H, CH2), 1.24 (m,
2 H, CH2), 0.97 (t, 3J = 7.0 Hz, 6 H, CH2CH3), 0.90 (d, 3J =
6.5 Hz, 6 H, CHCH3) ppm. 13C{1H} NMR: δ = 165.14 (CO), 72.32
(Fc-C), 71.36 (NCH), 70.83 (Fc-C), 70.65 (Fc-C), 69.29 (OCH2),
39.10 (CH), 26.65 (CH2), 14.55 (CH3), 12.17 (CH3) ppm.
C24H32FeN2O2 (436.4): calcd. C 66.06, H 7.39, N 6.42; found C
65.95, H 7.26, N 6.29.
1,1Ј-Bis[(S)-4-benzyloxazolin-2-yl]ferrocene (17b): Following the
same procedure as described for 1b yielded 0.40 g (79%) of 17b as
an oil. [α]2D0 = +3 (c = 0.25, CH2Cl2). H NMR (CDCl3): δ = 7.34
1
(m, 4 H, Ph-H), 7.27 (m, 6 H, Ph-H), 4.78 (br. s, 2 H, Fc-H), 4.76
(br. s, 2 H, Fc-H), 4.45 (m, 2 H, NCH), 4.36 (br. s, 2 H, Fc-H),
3
4.34 (br. s, 2 H, Fc-H), 4.27 (t, J = 9.0 Hz, 2 H, OCH2), 4.07 (t,
3J = 9.0 Hz, 2 H, OCH2), 3.24 (dd, 3,2J = 4.5, 13.5 Hz, 2 H,
CH2Ph), 2.73 (dd, 3,2J = 9.0, 13.5 Hz, 2 H, CH2Ph) ppm. 13C{1H}
NMR: δ = 166.11 (CO), 138.43 (Ph-C), 129.71 (Ph-C), 128.99 (Ph-
C), 126.93 (Ph-C), 72.51 (Fc-C), 72.45 (Fc-C), 71.90 (OCH2), 71.08
(Fc-C), 70.97 (Fc-C), 69.84 (Fc-C), 68.25 (NCH), 42.16 (CH2Ph)
ppm. C30H28FeN2O2 (504.4): calcd. C 71.44, H 5.60, N 5.55; found
C 71.24, H 5.52, N 5.65.
1,1Ј-Bis[(R)-4-phenyloxazolin-2-yl]ferrocene (13b): Following the
same procedure as described for 1b yielded 0.43 g (91%) of 13b.
[α]2D0 = +190 (c = 0.25, CH2Cl2); m.p. 92–93 °C. 1H NMR (CDCl3):
δ = 7.41–7.28 (m, 10 H, Ph-H), 5.26 (dd, 3,2J = 8.5, 10.0 Hz, 2 H,
NCH), 4.91 (br. s, 2 H, Fc-H), 4.89 (br. s, 2 H, Fc-H), 4.73 (dd,
1,1Ј-Bis[(4R,5S)-4,5-diphenyloxazolin-2-yl]ferrocene (18b): Follow-
ing the same procedure as described for 1b yielded 0.13 g (21%) of
3
3,2J = 8.5, 10.0 Hz, 2 H, OCH2), 4.47 (m, 4 H, Fc-H), 4.22 (t, J =
8.5 Hz, 2 H, OCH2) ppm. 13C{1H} NMR: δ = 166.92 (CO), 142.79
(Ph-C), 129.18 (Ph-C), 128.03 (Ph-C), 127.22 (Ph-C), 75.08
(OCH2), 72.61(Fc-C), 72.46 (Fc-C), 71.81 (Fc-C), 71.28 (Fc-C),
70.50 (NCH) ppm. C28H24FeN2O2 (476.3): calcd. C 70.60, H 5.08,
N 5.88; found C 70.45,Ͻztabr6" pos="x22Ͼ H 5.30, N 5.88.
1
18b as an oil. H NMR (CDCl3): δ = 7.43–7.28 (m, 20 H, Ph-H),
3
3
5.36 (d, J = 8.0 Hz, 2 H, NCH), 5.12 (d, J = 7.5 Hz, 2 H, OCH),
5.07 (m, 2 H, Fc-H), 5.02 (m, 2 H, Fc-H), 4.60 (m, 2 H, Fc-H),
4.51 (m, 2 H, Fc-H) ppm. 13C{1H} NMR: δ = 166.22 (CO), 142.36
(Ph-C), 140.71 (Ph-C), 129.30 (Ph-C), 129.26 (Ph-C), 128.87 (Ph-
C), 128.14 (Ph-C), 127.23 (Ph-C), 126.33 (Ph-C), 89.24 (NCH),
79.37 (OCH), 73.02 (Fc-C), 72.62 (Fc-C), 71.93 (Fc-C), 71.75 (Fc-
C), 70.80 (Fc-C) ppm. C40H32FeN2O2 (628.5): calcd. C 76.44, H
5.13, N 4.46; found C 76.28, H 5.13, N 4.20.
1,1Ј-Bis(5-phenyloxazolin-2-yl)ferrocene (15b): Following the same
procedure as described for 1b yielded 0.36 g (76%) of 15b as an oil.
1H NMR (CDCl3): δ = 7.43–7.32 (m, 10 H, Ph-H), 5.58 (m, 2 H,
OCH), 4.88 (br. s, 2 H, Fc-H), 4.86 (br. s, 2 H, Fc-H), 4.44 (br. s,
4 H, Fc-H), 4.34 (m, 2 H,NCH2), 3.86 (m, 2 H, NCH2) ppm.
13C{1H} NMR: δ = 161.21 (CO), 141.31 (Ph-C), 129.21 (Ph-C),
128.71 (Ph-C), 126.38 (Ph-C),126.30 (Ph-C), 81.28 (OCH),
72.59(Fc-C), 72.49 (Fc-C), 72.45 (Fc-C), 72.32 (Fc-C), 72.15 (Fc-
C), 71.91 (Fc-C), 71.33 (Fc-C), 70.93 (Fc-C), 70.86 (Fc-C), 70.59
(Fc-C), 63.53 (NCH2) ppm. C28H24FeN2O2 (476.3): calcd. C 70.60,
H 5.08, N 5.88; found C 70.71, H 5.12, N 5.91.
X-ray diffraction measurements were performed on a Nonius
Kappa CCD diffractometer. Single crystals were positioned at
40 mm from the detector and 567 and 495 frames were measured,
each for 60 and 40 s over a 1.5° scan for 13b and 14b, respectively.
The data were processed using the Denzo-SMN software package.
Crystal data, data collection parameters, and structure refinement
details for 6b, 7b, 11b–14b are given in Table 6. The structures were
solved by direct methods and refined by full-matrix least-squares
techniques. Non-hydrogen atoms were refined with anisotropic dis-
placement parameters. H-atoms were located on difference Fourier
1,1Ј-Bis[(R)-4-benzyloxazolin-2-yl]ferrocene (16b): Following the
same procedure as described for 1b yielded 0.47 g (93%) of 16b as
an oil. [α]2D0 = +34 (c = 0.25, CH2Cl2). 1H NMR (CDCl3): δ = 7.34
Table 6. Crystallographic data for 6b, 7b, 11b–14b.
Compound
6b
7b
11b
12b
13b
14b
Chemical formula C22H28FeN2O2
C22H28FeN2O2
408.31
110
C24H32FeN2O2
436.37
110
C24H32FeN2O2
436.37
120
C112H96Fe4N8O8.4 C112H96Fe4N8O8.60
Formula mass
T [K]
408.31
110
1911.77
120
1914.97
120
Space group
a [Å]
b [Å]
C2
C2
C2221
C2221
C2
C2
20.099(3)
6.388(1)
7.833(2)
108.20(1)
960.26(4)
2
8.05
0.008(10)
0.019
20.092(7)
6.387(2)
7.872(2)
108.18(2)
959.78(5)
2
8.05
–0.002(12)
0.023
6.786(6)
10.068(1)
32.13(4)
6.839(4)
10.316(6)
30.799(2)
13.637(3)
15.431(3)
21.698(4)
102.03(3)
4465.7(15)
2
13.640(2)
15.427(3)
21.733(3)
102.03(2)
4471.85(13)
2
c [Å]
β [°]
V [Å3]
2195.4(7)
4
7.09
0.07(6)
0.065
0.1829
2172.9(2)
4
7.16
0.03(3)
0.033
0.0765
Z
μcalcd. [cm–1]
Flack parameter
7.05
7.04
–0.011(7)
0.0322
0.0643
0.001(8)
0.0463
0.0746
[a]
R1
[b]
wR2
0.0468
0.0552
[a] R1 = ∑||Fo| – |Fc|/∑||Fo|. [b] wR2 = [∑w|Fo2| – |Fc |)2/∑w|Fo2|2]½.
2
1598
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 1589–1600

1,1Ј-Bis(oxazolin-2-yl)ferrocenes
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Received: September 01, 2004
1600
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Eur. J. Inorg. Chem. 2005, 1589–1600