Preparation, coordination properties and catalytic use of 1′-(diphenylphosphanyl)-1-ferrocenecarboxamides bearing 2-hydroxyethyl pendant groups

Article abstract of DOI:10.1016/j.jorganchem.2009.04.007

Polar amido-phosphane ligands, viz 1-(diphenylphosphanyl)-1′-[N-(2-hydroxyethyl)carbamoyl]ferrocene (1) and 1-(diphenylphosphanyl)-1′-[N,N-bis(2-hydroxyethyl)carbamoyl]ferrocene (2) were synthesised from 1′-(diphenylphosphanyl)-1-ferrocenecarboxylic acid

Full text of DOI:10.1016/j.jorganchem.2009.04.007

Journal of Organometallic Chemistry 694 (2009) 2519–2530
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Preparation, coordination properties and catalytic use of
10-(diphenylphosphanyl)-1-ferrocenecarboxamides bearing
2-hydroxyethyl pendant groups
*
ˇ
ˇ
ˇ
ˇ
Jirí Schulz, Ivana Císarová, Petr Štepnicka
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 12840 Prague, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Polar amido-phosphane ligands, viz 1-(diphenylphosphanyl)-10-[N-(2-hydroxyethyl)carbamoyl]ferrocene
(1) and 1-(diphenylphosphanyl)-10-[N,N-bis(2-hydroxyethyl)carbamoyl]ferrocene (2) were synthesised
from 10-(diphenylphosphanyl)-1-ferrocenecarboxylic acid (Hdpf) by direct amide coupling or via Hdpf-
Article history:
Received 14 February 2009
Received in revised form 30 March 2009
Accepted 8 April 2009
pentafluorophenyl ester 3. Subsequent reactions of 1 and 2 with [PdCl2(cod)] (cod = g2 2-cyclocta-
:g
Available online 17 April 2009
1,5-diene) gave the respective bis(phosphane) complexes trans-[PdCl2L2] (4, L = 1; 5, L = 2). Depending
on the solvent used in their subsequent crystallisation (ethanol or chloroform), these complexes were
isolated in several defined solvated forms. The structure determination for free ligands and their solvated
complexes (4ꢀ2EtOH, 4ꢀ6CHCl3, 5ꢀ2EtOH, and 5ꢀ4CHCl3) revealed the dominating role of hydrogen bond-
ing in their crystal assemblies, the nature and complexity of the formed hydrogen-bonded arrays strongly
varying with the ligand structure (one vs. two 2-hydroxethyl chains), their number in the discrete species
(free ligands vs. the complexes), and also with the solvate. Catalytic tests performed with 4 and 5 in
Suzuki–Miyaura cross-coupling reaction showed that both complexes form active catalysts for the cou-
pling of aryl bromides with phenylboronic acid in common polar organic solvents, in water and in tolu-
ene–water biphasic mixture. Yet, complex 4 gave rise to hydrolytically more stable catalyst, which could
be used five times without any detectable loss of activity in the toluene/water system. Complex 4 was
also successfully applied to the synthesis of biaryl anti-inflammatory drugs and their analogues in pure
water and in the toluene–water mixture.
Keywords:
Ferrocene
Phosphanyl-carboxamides
Palladium
Suzuki–Miyaura reaction
Water-soluble ligands
Structure elucidation
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
water-solubility of (diphenylphosphanyl)ferrocene moiety, partic-
ularly when the group is dissociated [8]. In order to prepare ferro-
Ferrocene ligands have found manifold use as catalyst compo-
nents for various transition metal-mediated reactions [1,2]. De-
spite their vast number, there is continuing demand for new
ferrocene donors, particularly those tailored for a specific reaction
type, substrate and reaction solvent. The ligand design thus reflects
the surge for the development of ‘‘green” synthetic processes based
on alternative feedstock and environmentally benign solvents
including water and homogeneous or biphasic water–organic sol-
vent mixtures [3,4]. The application of ferrocene phosphanes, that
are the most abundant and successful class among the ferrocene
donors [1,2], is unfortunately hindered in aqueous media by their
hydrophobic nature. Attempts to prepare water-soluble ferrocene
phosphanes for catalytic use remain still very scarce and can be
demonstrated by the synthesis of a chiral ferrocene diphosphane
modified with a hydrophilic urea tag [5].
cene ligands with a higher affinity to water and aqueous media in
their native (non-dissociated) form, we decided to make use of the
synthetic potential of the carboxyl group rather than its inherent
polarity. Among carboxylic derivatives, we chose amides that are
resistant towards hydrolysis (particularly ferrocene ones) and can
be structurally varied through changing the substituents at the
amide nitrogen.
Recently, we reported about the preparation of phosphanyl–fer-
rocene–carboxamides from 10-(diphenylphosphanyl)ferrocene-1-
carboxylic acid (Hdpf; Scheme 1) [8a] and their utilisation as syn-
thetic precursors to chiral ferrocene oxazolines [9] and P-chelated
carbenes [10], and as ligands for transition metals and metal-cata-
lysed reactions (Scheme 1, I: n = 1, X/Y = N/CH, CH/N; n = 2, X/
Y = N/CH [11]; II and PAMAM-analogues [12]). Furthermore, we
designed several types of chiral phosphanylferrocene-carboxam-
ides, that proved to be efficient ligands for palladium-catalysed
asymmetric allylic alkylation [7b,13]. This contribution extends
our previous studies on phosphanyl-ferrocene carboxamides, deal-
ing with the synthesis of novel Hdpf-based amides bearing the
2-hydroxyethyl groups at the amide nitrogen. Preparation of
While studying phosphanyl-ferrocenecarboxylic acids [6,7], we
found that introduction of a single CO2H group already improves
* Corresponding author. Fax: +420 221 951 253.
ˇ
ˇ
E-mail address: stepnic@natur.cuni.cz (P. Štepnicka).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.04.007

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J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
sets of signals due to the phosphanoferrocenyl and the amide moi-
eties. The spectra of secondary amide 1 reveal no unexpected fea-
tures at room temperature (in CDCl3) whilst those of 2 show
markedly broadened resonances of the amide pendants. Such sig-
nal broadening apparently reflects a limited mobility of the polar
chains, resulting from their hydrogen bonding interactions. Vari-
able-temperature (VT) NMR spectra support this explanation
(Fig. 1). The 1H NMR spectrum of 2 recorded at 50 °C displays the
signals due to the ethan-1,2-diyl groups as a pair of triplets as ex-
pected for the equivalent 2-hydroxyethyl chains that are void of
mobility constraints and rapidly exchange the acidic hydrogens.
Upon cooling, the exchange processes become slower, which is re-
flected first by broadening of the signals and then by separation of
four distinct resonances. Further cooling to ꢁ25 °C causes a col-
lapse of two neighbouring signals into a broad singlet. The
31P{1H} NMR signals of 1 and 2 are found at positions similar to
that of free Hdpf [8a].
Scheme 1.
The molecular structures of 1 and 2 are shown in Figs. 2 and 3
together with selected geometric data. In both compounds, the
geometry of ferrocene moieties are quite regular with similar Fe-
ring centroid (Cg) distances and tilts below 5°. As evidenced by
the torsion angles C1–Cg1–Cg2–C6 = 93° for 1 and 83° for 2 (see
Fig. 2 for definitions), the ferrocene substituents are mutually ro-
tated, adopting intermediate conformations between synclinal-
eclipsed and anticlinal-staggered. The amide moieties are planar
[cf. the torsion angles O1–C1–N–C24 = 8.5(3)° for 1, and O1–C1–
N–C24/O1–C1–N–C26 = 175.1(1)/2.8(2)° for 2] but deviate from
the planes of their parent rings Cp1 [cf. the dihedral angles of the
{C11O1 N} and Cp1 planes: 18.5(2)° in 1 and 18.3(3)° in 2].
In the solid state, the molecules of 1 and 2 associate expectedly
by means of hydrogen-bond interactions generated by their polar
amide pendants. The molecules of 1 assemble into inversion-re-
lated pairs via hydrogen bonds between the terminal hydroxyl
and the amide carbonyl groups, O2–H92ꢀꢀꢀO1 (Fig. 4 and Table 1).
These pairs are further connected by N–H91ꢀꢀꢀO2 hydrogen bonds
to four adjacent molecules so that each dimer unit acts as a twofold
hydrogen bond donor and a twofold acceptor. When combined,
such interactions result in the formation of infinite layers oriented
parallel to the crystallographic ac plane (at y = 0, ½, and 1 in the
unit cell). The bulky non-polar phosphanoferrocenyl moieties are
palladium(II) complexes from these ligands and their use in palla-
dium-catalysed Suzuki–Miyaura cross-coupling in homogeneous
and biphasic polar reaction media are also reported.
2. Results and discussion
2.1. Preparation and crystal structures of the ligands
1-(Diphenylphosphanyl)-10-[N-(2-hydroxyethyl)carbamoyl]fer-
rocene (1) and 1-(diphenylphosphanyl)-10-[N,N-bis(2-hydroxy-
ethyl)carbamoyl]ferrocene (2) were both prepared from Hdpf
(Scheme 2). Whereas the former compound resulted directly by
reaction of Hdpf with 2-aminoethanol in the presence of peptide
coupling agents [14], a similar reaction with diethanolamine affor-
ded only unreacted Hdpf-benzotriazolyl ester [12a]. Hence, the de-
sired tertiary amide 2 was synthesised alternatively via active
Hdpf-pentafluorophenyl ester (3) [15]. The amides were isolated
by column chromatography and further purified by crystallisation
from ethyl acetate–hexane to afford analytically pure 1 and 2 as
air-stable orange crystalline solids in 82% and 70% yield,
respectively.
In IR spectra, compounds 1 and 2 display diagnostic mC@O
(amide I) bands at 1633 and 1594 cmꢁ1, respectively. For 1, an
additional dN–H band (amide II) is seen at 1552 cmꢁ1 1H and 13C
.
NMR spectra support the formulations by showing characteristic
Scheme 2. Preparation of 1 and 2 (EDC, N-[3-dimethylamino)propyl]-N0-ethylcar-
bodiimide; HOBt, 1-hydroxybenzotriazole; DMF, N,N-dimethylformamide; DMAP,
4-(dimethylamino)pyridine).
Fig. 1. VT 1H NMR spectra of amide 2 in the region of ferrocene (CH) and aliphatic
(CH2) protons. The asterisk indicates the signal due to hydrogen-bonded protons
whose position changes with the temperature.

J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
2521
Fig. 2. View of the molecular structure of 1 showing displacement ellipsoids at the
30% probability level. Selected distances and angles (Å and °): Fe–Cg1 1.6510(9), Fe–
Cg2 1.644(1), C1–C11 1.476(2), C11–O1 1.240(2), C11–N 1.340(2), N–C24 1.448(2),
C25–O2 1.418(2), P–C6 1.810(2), P–C12 1.838(2), P–C18 1.839(2); <Cp1,Cp2 4.5(1),
O1–C11–N 122.2(2), C11–N–C24 123.1(2), C24–C25–O2 114.3(2). The ring planes
are defined as follows: Cp1 = C(1–5), Cp2 = C(6–10), Ph1 = C(12–17), Ph2 = C(18–
23); Cg1 and Cg2 stand for the centroids of the rings Cp1 and Cp2, respectively.
Fig. 4. A projection of a hydrogen-bonded layer in solid 1 onto the ac plane (at
b = 0). Because of the crystallographic symmetry, the layer located at b/2 is shifted
by c/2. Hydrogen bonds are shown as dashed lines and the 10-(diphenylphospha-
nyl)ferrocen-1-yl moieties were replaced with black circles.
Table 1
Summary of hydrogen bond parameters.a
D–Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA (Å)
Angle at H (°)
Compound 1
O2–H92ꢀ ꢀ ꢀO1i
N–H92ꢀ ꢀ ꢀO2ii
2.666(2)
2.955(2)
167
153
Compound 2
O2–H92ꢀ ꢀ ꢀO1iii
2.691(2)
2.833(2)
170
165
O3–H93ꢀ ꢀ ꢀO2iv
Compound 4ꢀ2EtOH
N–H91ꢀ ꢀ ꢀO2v
2.934(3)
2.714(4)
2.674(5)
163
173
168
O2–H92ꢀ ꢀ ꢀO3
O3–H93ꢀ ꢀ ꢀO1vi
Compound 4ꢀ6CHCl3
N–H91ꢀ ꢀ ꢀO1vii
3.311(4)
2.697(4)
3.089(5)
3.602(4)
154
166
173
144
O2–H92ꢀ ꢀ ꢀO1vii
C70–H70ꢀ ꢀ ꢀO2viii
C80–H80ꢀ ꢀ ꢀCl
Compound 5ꢀ2EtOH
O2–H91ꢀ ꢀ ꢀO3
2.740(2)
2.641(3)
2.617(3)
161
168
173
O3–H92ꢀ ꢀ ꢀO4ix
O4–H93ꢀ ꢀ ꢀO1
Compound 5ꢀ4CHCl3
O2–H91ꢀ ꢀ ꢀO3x
2.666(4)
2.660(4)
3.569(4)
164
166
144
O3–H92ꢀ ꢀ ꢀO1xi
C80–H80ꢀ ꢀ ꢀClxii
a
D, donor; A, acceptor. Symmetry codes: i. ꢁx, ꢁy, 1 ꢁ z; ii. ½ ꢁ x, y, ꢁ½ + z; iii.
. 1 + x, y, z;
1 ꢁ x, 2 ꢁ y, ꢁz; i
v
v. 2 ꢁ x, 2 ꢁ y, 1 ꢁ z; vi. 1 + x, y, z; vii. 3/2 ꢁ x, ½ + y,
Fig. 3. Thermal ellipsoid plot of 2, drawn at the 30% probability level. Selected
distances and angles (Å and °): Fe–Cg1 1.6558(8), Fe–Cg2 1.6467(9), C1–C11
1.494(2), C11–O1 1.244(2), C11–N 1.351(2), N–C24 1.468(2), N–C26 1.479(2), C25–
O2 1.423(2), C26–O3 1.426(2), P–C(6) 1.819(2), P–C12 1.844(2), P–C18 1.837(2);
<Cp1,Cp2 0.7(1), O1–C11–N 119.5(2), C11–N–C24 127.4(2), C11–N–C26 116.6(1),
C24–C25–O2 113.3(1), C26–C27–O3 109.8(1). The ring planes are defined as for 1.
½ꢁz, viii. 2 ꢁ x, 1 ꢁ y, 1 ꢁ z, ix. 1 ꢁ x, 1 ꢁ y, 1 ꢁ z; x. 2 ꢁ x, ꢁy, 1 ꢁ z; xi. 1 ꢁ x, ꢁy, ꢁz;
xii. 1 + x, y, z. The solvent molecules are labelled as follows: C31–C30–O3–H93 for
4ꢀ2EtOH, C31–C30–O4–H93 for 5ꢀ2EtOH, C70–H70–Cl(71,72,73)/C80–H80–
Cl(81,82,83)/C90–H-90–Cl(91,92,93) for 4ꢀ6CHCl3, and C80–H80–Cl(81,82,83)/C90–
H-90–Cl(91,92,93) for 5ꢀ4CHCl3.
packed essentially at the distances defined by their van der Waals
envelope and thus separate the polar hydrogen-boded sheets.
Similarly to 1, the molecules of 2 form centrosymmetric dimers
via pairs of hydrogen bonds between the hydroxyl and carbonyl
groups, O2–H92ꢀꢀꢀO1 (Fig. 5 and Table 1). However, in contrast to
1, the dimers in the crystals of 2 further associate in only one
dimension forming infinite ribbons via hydrogen bonds between
the hydroxyl group of the ‘other’ hydroxyethyl chain and the OH
oxygen in an adjacent dimer unit.
2.2. Preparation and crystal structures of palladium(II) complexes
Replacement of the diene ligand in [PdCl2(cod)] (cod = g2 g2
: -
cycloocta-1,5-diene) with the stoichiometric amounts of 1 and 2
expectedly gave the respective bis(phosphane) complexes 4 and
5 (Scheme 3). The complexes possess a strong tendency to retain
reaction solvents but, fortunately, separate as defined stoichiome-
tric solvates upon crystallisation. Depending on the solvent used
(ethanol or CHCl3), the following crystalline solvates were isolated

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J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
Fig. 6. View of the complex molecule in the structure of 4ꢀ2EtOH. Displacement
ellipsoids enclose the 30% probability level. The half of the molecule is generated by
the inversion operation.
Fig. 5. Section of the ladder-like hydrogen-bonded array in the crystal of 2. The
hydrogen bonds are indicated with dashed lines and the phosphanoferrocenyl
moieties were replaced with black circles.
Fig. 7. View of the complex molecule in the structure of 5ꢀ2EtOH showing
displacement ellipsoids at the 30% probability level. The half of the molecule is
generated by the inversion operation.
Table 2
Selected distances and angles for 4ꢀ2EtOH, 4ꢀ6CHCl3, 5ꢀ2EtOH and 5ꢀ4CHCl3 (Å, °).a
Parameter
4ꢀ2EtOH
4ꢀ6CHCl3
5ꢀ2EtOH
5ꢀ4CHCl3
Pd–Cl
Pd–P
2.297(1)
2.3398(8)
94.84(3)
1.650(2)
1.645(2)
2.7(2)
2.3059(8)
2.3445(8)
88.10(3)
1.650(2)
1.647(2)
4.4(2)
2.3074(5)
2.3568(5)
95.48(2)
1.6478(8)
1.6396(9)
4.9(1)
2.2924(8)
2.3320(7)
90.33(3)
1.647(1)
1.650(1)
1.8(2)
Cl–Pd–Pb
Fe–Cg1
Fe–Cg2
<Cp1,Cp2
sc
Scheme 3. Preparation of complexes 4 and 5 (cod = cycloocta-1,5-diene).
139
142
140
142
and structurally characterised: 4ꢀ2EtOH, 5ꢀ2EtOH, 4ꢀ6CHCl3, and
5ꢀ4CHCl3.
C11–O1
C11–N
O1–C11–N
ud
N–C24–C25–O2
1.238(4)
1.339(5)
121.5(3)
22.9(4)
ꢁ63.7(4)
1.235(4)
1.330(5)
121.6(3)
12.9(4)
60.4(4)
1.237(2)
1.349(2)
119.8(2)
21.4(2)
1.241(4)
1.349(4)
120.0(3)
20.2(4)
Spectroscopic data for 4 and 5 suggest P-monodentate coordi-
nation of the ferrocene ligands. The amide bands in IR spectra
are observed at positions similar to the free ligands while the
31P{1H} NMR signals appear shifted to lower fields, to a position
53.3(2)e
60.8(4)f
a
Definition of the ring planes: Cp1 = C(1–5), Cp2 = C(6–10); Cg1 (Cg2) are the
centroids of the cyclopentadienyl rings Cp1 (Cp2). The primed atoms are generated
by the crystallographic inversion operations.
similar to trans-[PdCl2(Hdpf-j
P)2] (dP +16.8) [16]. The VT 1H NMR
spectra of the complexes do not show any unexpected features.
The solid-state structures of 4ꢀ2EtOH, 4ꢀ6CHCl3, 5ꢀ2EtOH and
5ꢀ4CHCl3 have been established by single-crystal X-ray diffraction.
Structures of the ethanol solvates are depicted in Figs. 6 and 7 (the
structures of the complex moieties in the crystals of the CHCl3 sol-
vates are very similar). Selected geometric data for all solv-
atomorphs are presented in Table 2.
b
The sum of the Cl–Pd–P and Cl–Pd–P0 is 180° due to the imposed symmetry.
Torsion angle C1–Cg1–Cg2–C6.
Dihedral angle subtended by the Cp1 and {C11O1N} planes.
N–C26–C27–O3 = 47.1(2)°.
c
d
e
f
N–C26–C27–O3 = 178.5(3)°.
The structures confirm the expected trans-square planar geom-
etry in all cases. The coordination environments around the palla-
dium atoms show minor angular deformations—though without
any pronounced tetrahedral distortion because of the imposed
symmetry (the Pd atoms reside on the crystallographic inversion
centres). The deviation of the interligand angles from 90° (by ca.
5°) likely helps in minimising steric interaction of the ligands.
The individual geometric parameters as well as the overall molec-
ular conformation compare favourably with those reported for
complexes with other 10-functionalised (diphenylphosphanyl)fer-
rocenes, trans-[PdCl2(Ph2PfcX-j
P)2] (fc = ferrocene-1,10-yl; X =
CO2H [16], C(O)NHCH2CH2(C5H4N-2) [11a], PO3Et2 [17], CH@CH2
[18], a chiral oxazolinyl group [9], P(O)Ph2, [19] and SMe [20]).
The bond distances and angles in the coordinated ferrocene ligands

J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
2523
Fig. 8. (a) Section of the infinite hydrogen bonded array in the structure of 4ꢀ2EtOH. (b) Projection of the crystal assembly onto the crystallographic ac plane. Domains
accommodating the hydrogen-bonded layers are indicated with gray boxes. The hydrogen bonds are indicated with dashed lines (only hydrogen bonded H-atoms are shown).
For clarity, the PdCl2 moieties are omitted in part (a), and only pivotal carbon atoms from the phenyl rings and one position of the disordered CH2 group in the solvent
molecule are shown (parts a and b).
do not depart much from those in free ones. Some differences can
be found in the conformation of the ferrocene framework. The fer-
rocene substituents in 4 and 5 are mutually rotated to attain more
tion noticeably differ in both compounds. Because of the imposed
symmetry, the polar groups capable of hydrogen bonding in
5ꢀ2EtOH are anti-arranged and, hence, appropriately set up for lin-
ear propagation of the molecular array. The key feature of the crys-
tal packing of 5ꢀ2EtOH is a centrosymmetric cyclic assembly
distant positions (cf.
s in Table 2) such that avoid their spatial con-
tacts and facilitate hydrogen bond formation.
As with the free ligands, the crystal packing of the complexes is
dominated by hydrogen bonds between the amide moieties. Com-
plexity of the formed assemblies roughly parallels that of the
respective ligands but it is further increased owing to the presence
of two ligands per the complex molecule and the presence of the
solvents of crystallisation. In the crystals of 4ꢀ2EtOH, the hydrogen
bonding interactions (Fig. 8) give rise to polar layers oriented per-
pendicular to the crystallographic ac plane. Since the two trans-dis-
posed ligand moieties are the parts of different layers, the PdCl2
unit interconnects two adjacent polar domains that are separated
by the non-polar phosphano-ferrocenyl units. The basic hydro-
gen-bonded unit it the structure of 4ꢀ2EtOH comprises two inver-
sion-related ligand units from two different complex molecules
that are linked by N–Hꢀ ꢀ ꢀOH hydrogen bonds (Fig. 8a, Table 1).
The remaining OH groups of the ligand form additional hydrogen
bonds towards oxygen atoms in the solvent of crystallisation (O–
Hꢀ ꢀ ꢀO(EtOH)). The solvate molecules further interact with the
proximal dimer units via (EtOH)O–Hꢀ ꢀ ꢀO@C hydrogen bonds and
thus interconnect the dimer units located above and below into
the wall-like molecular architecture mentioned above.
In comparison with the ethanol solvate, the crystal packing of
4ꢀ6CHCl3 is relatively simple. The amide pendants in 4ꢀ6CHCl3
associate in only one dimension, forming infinite chains (Fig. 9).
However, since these chains involve molecules from two complex
molecules related by the 21 screw axes, the intermolecular interac-
tions result in the formation of layers in the ac plane. Similarly to
the ethanol solvate, the phosphano-ferrocenyl units in 4ꢀ6CHCl3
are located between the hydrogen-bonded sheets, leaving enough
space for the solvent molecules that occupy cylindrical voids ori-
ented parallel to the crystallographic b axis.
Fig. 9. Hydrogen bonding interactions in 4ꢀ6CHCl3. For clarity, only the pivotal
phenyl carbons and hydrogen-bonded H-atoms are shown and the solvent
molecules are omitted.
Likewise free 2, the solvate 5ꢀ2EtOH aggregates into infinite
chains in the crystal (Fig. 10). Nonetheless, the modes of aggrega-

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J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
cules forms hydrogen bonds to the Pd-bound chloride ligand
(Table 1).
2.3. Catalytic tests
For catalytic testing of the complexes 4 and 5, we chose Suzuki–
Miyaura cross-coupling [21], which is an obvious candidate among
the cross-coupling reactions for performing it in polar and aqueous
solvents because of hydrolytic stability of boron reagents [4,22].
Initially, we probed complexes 4 and 5 as defined pre-catalysts
in the model coupling of phenylboronic acid and 4-bromoaceto-
phenone (6a) to give biphenyl 8a (Scheme 4). The reactions were
carried out in various solvents in the presence of potassium car-
bonate as the base and catalyst amount corresponding to 1 mol.%
Pd at 60 °C for 24 h. The results given in Table 3 indicate that both
complexes efficiently promote the coupling reaction, compound 4
showing slightly better conversions. The higher catalytic activity of
complex 4 (or catalyst formed thereof) presumably reflects a high-
er stability of this complex under the reaction conditions which, in
turn, parallels the higher hydrolytic stability of ligand 1. When li-
gands 1 and 2 were heated with 5 mole equivalents of K2CO3 in
ethanol (80 °C/2 h) to mimic the conditions of the catalysed reac-
tion, the former compound was isolated virtually unchanged (con-
taminated with <2 mol% of the corresponding phosphane oxide)
whilst for the tertiary amide, a mixture of unchanged 2 (73%), its
P-oxide (ca. 1%) and two unidentified hydrolytic products (11
and 15%; not the parent Hdpf or its P-oxide) was obtained. Finally,
the reactions performed in dioxane and acetonitrile gave lower
yields than those carried out in ethanol, water and, surprisingly,
even in the respective aqueous solvents.
Fig. 10. Hydrogen bonding interactions in solid 5ꢀ2EtOH. Only the pivotal phenyl
carbons and H-bonded hydrogen atoms are shown for clarity.
(Fig. 10, Table 1) formed via four O–Hꢀ ꢀ ꢀO hydrogen bonds be-
tween two ligand moieties (located in two proximal complex mol-
ecules) and two molecules of the solvent. The ethanol solvate acts
as a molecular ‘clamp’, serving both as a hydrogen bond donor for
the C@O group in one ligand and as an acceptor for the OH group in
the other. The other terminal OH group of the ligand does not par-
ticipate in intermolecular aggregation, being involved in an
intramolecular O–Hꢀ ꢀ ꢀO interaction.
The crystal assembly of 5ꢀ4CHCl3 (Fig. 11) differs from that of
the corresponding ethanol solvate in that each ligand moiety forms
a cyclic dimer with its inversion-related counterpart through pairs
of O3–H92ꢀ ꢀ ꢀO1 hydrogen bonds (Table 1). These dimers further
aggregate into infinite ladder-like array by means of O2–
H91ꢀ ꢀ ꢀO3 hydrogen bonds generated by the second hydroxyethyl
chain (translation in the a-direction). Since each complex molecule
possesses two ligand units, the ladder arrays are cross-linked by
the PdCl2 units into infinite layers. In contrast to the ethanol sol-
vate, the solvent molecules in 5ꢀ4CHCl3 are only spectators in the
crystal assembly, filling vacancies between the bulky complex mol-
ecules. Only one of the two structurally independent CHCl3 mole-
Since the kinetic tests revealed that the model reaction pro-
ceeds rapidly, affording quantitative isolated yields of 8a within
1 h in both water and ethanol under mild conditions (60 °C), we
extended our study towards reactions in water-toluene biphasic
mixture and also lowered the catalyst loading to 0.1 mol%. The
more stable pre-catalyst 4 was tested in the coupling of PhB(OH)2
with aryl bromides possessing activating and deactivating groups
(6a–d, Scheme 4). The coupling reactions performed in biphasic
mixture (Table 4) proceed satisfactorily only with the activated
substrates 6a and 6b. Nevertheless, the results achieved with 4
[Pd]
Y
X + PhB(OH)
Y
2
base
X = Br: 6a-d
X = Cl, Y = C(O)Me 7a
8a-d
Scheme 4. Suzuki–Miyaura reaction of aryl bromides with PhB(OH)2 [Y = C(O)Me
(a), NO2 (b), Me (c), OMe (d)].
Table 3
Survey of the reaction Solvents for the model coupling reaction.a
Solvent
Conversion to 8a (%)b
Catalyst 4
Catalyst 5
Dioxane
85
94
Dioxane–water (1/1)
Ethanol
Ethanol–water (1/1)
MeCN
Quant. (96)
Quant. (99)
Quant. (98)
84
Quant. (96)
Quant. (97)
Quant. (97)
75
MeCN–water (1/1)
Water
Quant. (99)
Quant. (95)
Quant. (94)
Quant. (94)
a
Reaction of 6a (1 mmol), PhB(OH)2 (1.2 mmol), and K2CO3 (2 mmol) with
1 mol% Pd-catalyst in 5 ml of the solvent at 60 °C for 24 h.
Fig. 11. View of the hydrogen-bonded layer in the structure of 5ꢀ4CHCl3 as
projected onto the crystallographic ac-plane. For clarity, only pivotal phenyl
carbons and hydrogen-bonded H-atoms are shown and the solvent molecules are
omitted.
b
The cases where no aryl halide was detectable by NMR, the conversions were
considered to be quantitative (quant.; ꢂ99%). Isolated yields in parentheses. All
values are an average of two independent runs.

J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
2525
Table 4
Summary of the catalytic results for the reactions performed in toluene–water
biphasic mixture.a
Substrate
Product
Conversion with catalyst 4 (%)
4-YC6H4Br
1 mol%
0.1 mol%
Y = C(O)Me
NO2
Me
8a
8b
8c
8d
Quant.
64
28
86
47
27
16
OMe
18
a
Conditions: water–toluene (1/1), 1 mol% of 4, 1.2 equiv. PhB(OH)2, 2 equiv.
K2CO3, 60 °C/1 h.
were better than those attained with the related complex
[PdCl2(Hdpf-jP)2] [16], which gave 8a with 85% conversion under
otherwise identical conditions. Replacing 6a for the less reactive
[4,22,23] 4-chloroacetophenone (7a) ensued in a considerably low-
er yield of the coupling product 8a (conversions with 1 mol% of 4:
ca. 4% after 1 h, and 11% after 24 h at 60 °C).
Fig. 13. Recyclation tests with pre-catalyst 5 (conversions in black, isolated yields
in grey).
Any direct comparison of 4- and 5-based catalysts with other
systems is rather difficult due to varying reaction conditions (sub-
strate, solvent, temperature, and catalyst loading). Notwithstand-
ing, the conversions achieved with 4- and 5-based catalysts in
homogenous reaction media compare favourably to those reported
for catalysts based on sulphonated [24], R3N+-substituted [25] or
dendrimeric [26] phosphanes while being inferior to catalysts
based on (biphenyl-2-yl)phosphanes [27]. Similar applies also to
pure water and water-toluene biphasic system [25b,28] except
that our catalysts do not require the presence of phase-transfer re-
agents for the coupling reaction to proceed efficiently.
Since the reactions performed under biphasic conditions are
particularly attractive due to simple reaction setup, easy product
separation and facile recovery of the catalyst ‘phase’ [4,22,28],
we studied next the possibility of catalyst recyclation. The reac-
tions were performed in toluene–water mixture with complexes
4 and 5 at 1 mol% Pd loading. After heating to 60 °C for 1 h organic
layers were separated and replaced with those containing fresh re-
agents. The results are presented graphically in Figs. 12 and 13. At
first sight, the results reflect the higher stability of the catalytic
system based on 4 (vide supra), which retained its original high
activity unchanged (complete conversions, isolated yields ꢂ94%)
during five consecutive runs. By contrast, the catalyst resulting
from 5 showed a lower initial conversion and a steady decline in
the activity with a sharp drop after the fourth run.
CO R
2
CO R
2
PhB(OH)
1 mol.-% [Pd]
2
OH
OH
o
K CO /60 C
2
3
Br
Br
Ph
10a (R = H)
10b (R = Me)
9a (R = H)
9b (R = Me)
CO R
CO R
2
2
PhB(OH)
2
1 mol.-% [Pd]
o
K CO /60 C
2
3
Ph
11a (R = H)
11b (R = Me)
12a (R = H)
12b (R = Me)
Scheme 5.
These results encouraged us to study biaryl couplings with sub-
strates that can either react with bases (esters) or possess dissocia-
ble polar groups (carboxylic acids). For testing we chose the
preparation of non-steroidal anti-inflammatory drugs and their
model compounds: 5-phenylsalicylic acid (10a) as a model for 5-
(2,4-difluorophen-yl)-2-hydroxybenzoic acid (DiflunisalTM), and
(biphenyl-4-yl)acetic acid (12a; FelbinacTM) [22c,29,30]. The syn-
theses were carried out with free acids (10a, 12a) and their respec-
Table 5
Application of complex 4 to the synthesis of 10a,b and 12a,b.a
Substrate
Solvent
Time (h)
Product
Yield (%)b
9a
9a
9a
11a
11a
11a
9b
9b
11b
11b
W
W
B
W
W
B
B
B
B
B
1
10a
10a
10a
12a
12a
12a
10b
10b
12b
12b
53
83
84
63
94
Quant.
86
Quant.
74
Quant.
24
24
1
24
24
1
24
1
24
a
Conditions: 1 mol% of 4, 1.2 equiv. PhB(OH)2, 2 equiv. K2CO3, 60 °C. B, biphasic
mixture toluene–water (1/1), W, water. See Section 3 for details.
Fig. 12. Recyclation tests with pre-catalyst 4 (conversions in black, isolated yields
in grey).
b
Isolated yields.

2526
J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
tive methyl esters (10b, 12b; Scheme 5) in the biphasic system and
in the presence of complex 4 (1 mol% Pd).
3.8 mmol) was added, causing an immediate (partial) precipita-
tion. The cooling bath was removed and stirring was continued
at room temperature for 16 h. Then, the reaction mixture was
washed with 3 M HCl, the organic layer was separated, and the
aqueous phase was back-extracted with dichloromethane
(2 ꢃ 10 mL). The combined organic layers were washed with satu-
rated aqueous NaHCO3 and brine, dried over MgSO4, and evapo-
rated under vacuum. The orange residue was purified by column
chromatography (silica gel, CH2Cl2–methanol 10:1 v/v). The first,
minor band was discarded and the following, major orange band
was collected and evaporated to afford an orange glassy residue.
This crude product was immediately dissolved in hot ethyl acetate
(30 mL), the solution was mixed with hexane (30 mL) and allowed
to crystallise at room temperature and then at 4 °C. The separated
solid was filtered off, washed with hexane and dried under vac-
uum. Yield: 1.120 g (82%), orange crystalline solid.
The results (Table 5) confirm that even free acids can be effi-
ciently coupled in water and in toluene–water biphasic mixture
with catalyst 4, affording the respective carboxyl-substituted
biphenyls in excellent isolated yields. Esters 9b and 11b also re-
acted smoothly in the toluene–water mixture to give good yields
of the respective coupling products even after 1 h.
3. Conclusions
Introduction of amide moieties equipped with hydrophilic sub-
stituents offers an alternative approach towards the design of no-
vel phosphinoferrocene ligands suitable for polar reaction media
including water-containing ones. Even the relatively simple
hydroxyethyl-substituted amide moieties present in the molecules
of 1 and 2 improve water-solubility of such donors and their com-
plexes. Complexes 4 and 5 can thus serve as defined pre-catalysts
for Suzuki–Miyaura cross-coupling of aryl bromides with boronic
acids in polar organic solvents, water and in toluene–water bipha-
sic mixtures. Yet, compound 4 appears to be practically more use-
ful, affording a faster reacting and more robust (hydrolytically
stable) catalyst, which can be conveniently re-used in toluene–
water mixture. Ligand 1 thus constitutes an alternative to the com-
monly used non-polar ferrocene ligands [1,2,31]. Furthermore,
amido-phosphanes 1 and 2 hold considerable potential for the de-
sign of self-assembled organometallic supramolecular arrays [32].
This was demonstrated by the crystal structures of free ligands
and their solvated complexes, which are dominated by hydrogen
bonding interactions of the amide groups and polar solvent mole-
cules (where present), and distinctively change along with the
structure of the ligand (its amide pendant) and the type and
amount of the solvent molecules.
M.p. 135–137 °C. 1H NMR (CDCl3): d 3.39 (br s, 1H, OH), 3.49 (br
3
dt, JHH,1 ꢄ JHH,2 ꢄ 4.3 Hz, 2H, NCH2), 3.75 (br t, JHH = 4.6 Hz, 2H,
OCH2), 4.09 (apparent q, J0 = 1.9 Hz, 2H), 4.22 (apparent t,
J0 = 1.9 Hz, 2H), 4.44 (apparent t, J0 = 1.8 Hz, 2H), 4.60 (apparent t,
3
J0 = 2.0 Hz, 2H) (CH of fc); 6.34 (br t, JHH ꢄ 5.6 Hz, 1H, NH), 7.27–
7.41 (m, 10H, PPh2). 13C{1H} NMR (CDCl3): d 42.7 (NCH2), 62.6
(OCH2), 69.6 (d, JPC ꢄ 1 Hz), 71.6, 72.8 (d, JPC = 4 Hz), 74.5 (d,
1
JPC = 14 Hz) (CH of fc); 76.3 (C–CO of fc), 77.1 (d, JPC = 6 Hz, C–P
of fc), 128.3 (d, JPC = 7 Hz), 128.8, 133.4 (d, JPC = 19 Hz) (CH of
1
PPh2); 138.1 (d, JPC = 8 Hz, Cipso of PPh2), 171.3 (C@O). 31P{1H}
NMR (CDCl3): d ꢁ17.1 (s). IR (Nujol):
m
/cmꢁ1 3293 (br s), 1633
(s), 1583 (w), 1552 (s), 1295 (s), 1193 (s), 1159 (s), 1055 (m),
1027 (s), 1008 (m), 916 (m), 889 (m), 833 (m), 822 (m), 749 (s),
741 (s), 696 (s), 636 (m), 569 (m), 550 (m), 516 (s), 505 (s), 489
(s), 453 (s), 421 (m). Anal. Calc. for C25H24FeNO2P (457.3): C,
65.66; H, 5.29; N, 3.06. Found: C, 65.39; H, 5.14; N, 2.83%.
4.3. Preparation of pentafluorophenyl 1-
4. Experimental
(diphenylphosphanyl)ferrocene-1-carboxylate (3)
4.1. Materials and methods
Hdpf (2.075 g, 5.0 mmol), pentafluorophenol (1.104 g,
6.0 mmol),
N-ethyl-N0-[3-(dimethylamino)propyl]carbodiimide
The syntheses were performed under an argon atmosphere.
Dichloromethane was dried over anhydrous K2CO3 or CaH2 and
distilled. Dioxane and acetonitrile were dried over sodium metal
and K2CO3, respectively, and distilled. 2-Aminoethanol was dis-
tilled under reduced pressure. Hdpf [8a], [PdCl2(cod)] [33], and
9b [34] were prepared by the literature methods. Ester 11b [35]
was obtained by esterification of 11a with diazomethane. Other
chemicals and solvents were used without any purification.
NMR spectra were measured on a Varian Unity Inova 400 spec-
trometer (1H, 399.95; 13C, 100.58; 31P, 161.90; 19F, 376.29 MHz) at
25 °C unless indicated otherwise. Chemical shifts (d/ppm) are given
relative to internal SiMe4 (13C and 1H), external 85% aqueous H3PO4
hydrochloride (1.160 g, 6.0 mmol) and 4-(dimethylamino)pyridine
(0.122 g, 1.0 mmol) were dissolved in CH2Cl2 (50 mL) and the
resulting solution was stirred at room temperature for 20 h. The
reaction mixture was washed with brine (2 ꢃ 20 mL), dried over
MgSO4 and evaporated. The residue was purified by column chro-
matography (silica gel, hexane–diethyl ether 1:1 v/v) to yield, after
evaporation, pure ester 3 as an orange solid. Yield: 2.419 g (83%).
1H NMR (CDCl3): d 4.25 (apparent q, J0 = 1.9 Hz, 2H), 4.44 (appar-
ent t, J0 = 2.0 Hz, 2H), 4.55 (apparent t, J0 = 1.8 Hz, 2H), 4.87 (apparent
t, J0 = 2.0 Hz, 2H) (fc); 7.29–7.39 (m, 10H, PPh2). 13C{1H} NMR
(CDCl3): d 67.6 (C–CO), 71.8, 73.6 (d, JPC = 4 Hz), 74.3 (d, JPC = 2 Hz),
74.7 (d, JPC = 14 Hz) (CH of fc); 79.1 (d, JPC = 10 Hz, C–P of fc), 128.3
31P) or neat CFCl3 19F). IR spectra were recorded with an FTIR
(
3
2
(
(d, JPC = 7 Hz), 128.8, 133.4 (d, JPC = 20 Hz) (CH of PPh2); 137.9
1
Nicolet Magna 650 spectrometer. Positive-ion electron impact
(EI+) mass spectra including the high resolution (HR) data were ob-
tained with a ZAB EQ spectrometer (VG Analytical). Electrospray
(ESI ) mass spectra were recorded with a Bruker Esquire 3000
spectrometer on dichloromethane/methanol solutions. Melting
points were determined on a Kofler hot stage.
(dm, JFC = 255 Hz, Cmeta of C6F5), 138.2 (d, JPC = 10 Hz, Cipso of
1
PPh2), 139.3 (dm, JFC = 253 Hz, Cpara of C6F5), 141.3 (dm,
1JFC = 250 Hz, Cortho of C6F5); 167.6 (C@O). The resonance due to Cip-
so(C6F5) was not found. 19F{1H} NMR (CDCl3): d ꢁ162.8 (m, Fmeta),
ꢁ158.7 (t, 3JFF = 22 Hz, Fpara), ꢁ152.9 (m, Fortho) (C6F5). 31P{1H} NMR
(CDCl3): d ꢁ17.8 (s). MS (EI+): m/z (relative abundance) 580 (M+Å),
488 (11), 413 (4, [MꢁC6F5]+), 397 (26, [MꢁOC6F5]+), 370 (19), 305
(35), 183 (18), 171 (19), 149 (40). HR MS (EI+) calcd. for
C29H18O2F5P56Fe 580.0314, found 580.0297.
4.2. Preparation of 1-(diphenylphosphanyl)-10-[N-(2-hydroxyethyl)-
carbamoyl]ferrocene (1)
Hdpf (1.244 g, 3.0 mmol) and 1-hydroxybenzotriazole (0.476 g,
3.5 mmol) were dissolved in dichloromethane (45 mL). The solu-
tion was cooled in an ice bath and treated with N-ethyl-N0-[3-
(dimethylamino)propyl]carbodiimide (0.62 mL, 3.5 mmol). After
stirring for 30 min at 0 °C, neat 2-aminoethanol (0.23 mL,
4.4. Preparation of 1-(diphenylphosphanyl)-1-[N,N-bis(2-
hydroxyethyl)-carbamoyl]ferrocene (2)
Ester 3 (1.161 g, 2.0 mmol), diethanolamine (0.421 g, 4 mmol)
and 4-(dimethylamino)pyridine (61 mg, 0.5 mmol) were dissolved

J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
2527
in dry DMF (15 mL) under argon. The reaction mixture was stirred
at room temperature for 20 h, evaporated under vacuum, and the
residue was purified by column chromatography (silica gel, dichlo-
romethane–methanol 10:1 v/v). The first orange band was col-
lected and evaporated to give 2 as orange-brown viscous oil that
slowly solidified. The product was further crystallised by dissolving
in a hot mixture of ethyl acetate and hexane (1:2 v/v) and slow
cooling to ꢁ18 °C. The separated material was filtered off, washed
with hexane and diethyl ether, and dried under vacuum. Yield of 2:
0.695 g (70%), orange crystalline solid.
(w). Anal. Calc. for C54H56Fe2N2O6P2Cl2PdꢀCH2Cl2 (1264.02): C,
52.22; H, 4.62; N, 2.22. Found: C, 51.84; H, 4.47; N, 2.15%.
4.7. Catalytic tests
Reaction vessel (20 mL) was charged with phenylboronic acid
(146 mg, 1.2 mmol), K2CO3 (276.5 mg, 2.0 mmol), aryl halide
(1.0 mmol) and the catalyst (1 or 0.1 mol% of 4 or 5). After flushing
with argon, solvent (5 mL) was introduced and the reaction flask
was sealed and transferred to an oil bath maintained at 60 °C.
The reaction mixture was heated and stirred for 1 or 24 h and then
quenched by adding water (5 mL) and stirring for 15 min. The
resulting mixture was extracted with diethyl ether (3ꢃ 5 mL),
the organic layers were combined, dried over MgSO4, and evapo-
rated. Subsequent purification by column chromatography (silica
gel and diethyl ether) afforded the coupling products (in the case
of incomplete conversion contaminated with the starting halide).
The identity and purity (conversion) of the products was estab-
lished by 1H NMR spectra.
M.p. 128–130 °C. 1H NMR (CDCl3): d 3.40 (br s, 2H, OH), 3.69
and 3.87 (2ꢃ br s, 4H, NCH2CH2OH); 4.11 (apparent q, J0 = 1.9 Hz,
2H), 4.20 (apparent t, J0 = 2.0 Hz, 2H), 4.47 (apparent t, J0 = 1.8 Hz,
2H), 4.68 (apparent t, J0 = 2.0 Hz, 2H) (CH of fc); 7.29–7.38 (m, 10
H, PPh2). 13C{1H} NMR (CDCl3): 50.7, 52.9 (2ꢃ br s, NCH2); 61.2
(br, OCH2), 71.2, 72.0, 73.2, 74.5 (br d, JPC = 14 Hz) (CH of fc);
78.4 (C–CO of fc), 128.3 (br d), 128.7, 133.5 (br d, JPC = 20 Hz) (CH
of PPh2); 138.4 (br, Cipso of PPh2), 172.6 (br) (C@O). The signal of
C(fc)–P was not observed, probably due to overlaps. 31P{1H} NMR
(CDCl3): d ꢁ17.1 (s). IR (Nujol):
m
/cmꢁ1 3449 (s), 3282 (s), 1594
(s), 1366 (w), 1350 (w), 1330 (w), 1271 (m), 1192 (m), 1162 (m),
1093 (m), 1070 (s), 1043 (m), 919 (w), 885 (m), 836 (w), 821
(w), 747 (s), 697 (s), 676 (m), 522 (m), 495 (s), 447 (m), 422 (m).
Anal. Calc. for C27H28FeNO3P (501.3): C 64.68, H 5.63, N 2.79.
Found: C 63.58, H 5.65, N 2.67%.
4.8. Catalyst recyclation tests
The initial reaction mixture was prepared as described above by
mixing PhB(OH)2 (146 mg, 1.2 mmol), K2CO3 (276.5 mg, 2.0 mmol),
4-bromoacetophenone (199 mg, 1.0 mmol), the catalyst (1 mol% of
4 or 5), and toluene and water (3 mL each). The mixture was
heated to 60 °C while stirring for 1 h and then cooled in ice. The
cold reaction mixture was washed with hexane (2 ꢃ 5 mL) and
the organic layers were decanted to collect the coupling product.
The organic solutions were washed with saturated aqueous
K2CO3 (2 ꢃ 5 mL), dried (MgSO4), and the product was isolated as
described above.
To the aqueous layer were immediately added PhB(OH)2
(122 mg, 1.0 mmol), 4-bromoacetophenone (199 mg, 1.0 mmol),
K2CO3 (138 mg, 1.0 mmol) and toluene (3 mL). The resulting bipha-
sic mixture was used in the next catalytic run (60 °C/1 h) and trea-
ted as described above. For each pre-catalyst, such recyclation was
repeated four times.
4.5. Preparation of complex [PdCl2(1-P)2] (4)
[PdCl2(cod)] (28.5 mg, 0.1 mmol) and 1 (91.4 mg, 0.2 mmol)
were dissolved in dichloromethane (5 mL) and the resulting red
solution was stirred for 30 min. The solution was filtered (PTFE syr-
inge filter, 0.45 lm pore size) and the filtrate evaporated under
vacuum. The crude product was crystallised from hot ethanol
(10 mL). The separated crystalline product was isolated by suction,
washed with diethyl ether and dried under vacuum. Yield of
4ꢀ2EtOH: 103 mg (91%), red crystalline solid. Solvate 4ꢀ6CHCl3 re-
sulted by crystallisation from CHCl3.
1H NMR (CDCl3, 50 °C): d 2.83 (t, 3JHH = 4.6 Hz, 1H, OH), 3.38 (q,
JHH = 5.2 Hz, 2H) and 3.68 (q, JHH = 5.0, 2H) (CH2CH2); 4.51 (appar-
ent t, J0 = 1.9 Hz, 2H), 4.56 (apparent t, J0 = 2.0 Hz, 2H), 4.57 (br
apparent t, J0 ꢄ 1.9 Hz, 2H), 4.90 (apparent t, J0 = 2.0 Hz, 2H) (fc);
4.9. Catalytic synthesis of 10a and 12a
A Schlenk tube was charged with PhB(OH)2 (146 mg, 1.2 mmol),
K2CO3 (276 mg, 2.0 mmol), aryl bromide (9a or 11a, 1.0 mmol), and
the catalyst (1 mol% of 4). Water (5 mL) or water and toluene (3 mL
each) were added, and the reaction flask was flushed with argon,
sealed with septum and transferred to an oil bath kept at 60 °C.
After stirring for the reaction time (1 or 24 h), the mixture was
cooled, quenched by adding 3 M HCl (10 mL) and extracted with
diethyl ether (4 ꢃ 5 mL). Combined organic layers were washed
with brine, dried (MgSO4) and purified by flash chromatography
(silica gel and diethyl ether). The products were isolated as white
solids following solvent removal.
3
6.45 (t, JHH = 5.5 Hz, 1H, NH), 7.36–7.68 (m, 10H, PPh2). 31P{1H}
NMR (CDCl3, 50 °C): d +16.2 (s). IR (Nujol):
m
/cmꢁ1 3242 (bs),
2725 (w), 2360 (m), 1629 (m), 1541 (m), 1541 (m), 1297 (m),
1165 (m), 1073 (m), 694 (m), 536 (m), 504 (m). Anal. Calc. for
C50H60Fe2N2O6P2Cl2Pd (4ꢀ2EtOH; 1135.94): C, 52.86; H, 5.32; N,
2.47. Found: C, 52.98; H, 4.97; N 2.20%.
4.6. Preparation of complex [PdCl2(2-P)2] (5)
[PdCl2(cod)] (28.5 mg, 0.1 mmol) and ligand
2 (100 mg,
Analytical data for 10a. 1H NMR (DMSO): d 7.07 (d, JHH = 8.5 Hz,
1H), 7.32–7.63 (m, 6 H), 7.83 (dd, JHH = 8.7, 2.6 Hz, 1H), 8.04 (d,
JHH = 2.5 Hz, 1H) (aromatics). 13C{1H} NMR (DMSO): d 113.3,
117.7, 126.1, 127.0, 127.9, 127.9, 131.2, 133.8, 139.0, 160.5 (aro-
matics); 171.79 (C@O) [30c,i]. ESI-MS: m/z 213 ([MꢁH]ꢁ).
Analytical data for 12a. 1H NMR (CDCl3): d 3.69 (s, 2H, CH2),
7.13–7.61 (m, 9H, aromatics). 13C{1H} NMR (CDCl3): d 40.6 (CH2);
127.1, 127.3, 127.4, 128.8, 129.8, 132.3, 140.4, 140.7 (aromatics);
177.2 (C@O) [30b,f,i,36]. ESI+MS: m/z 235 ([M+Na]+).
0.2 mmol) were dissolved in dichloromethane (5 mL). The result-
ing solution was stirred for 30 min whereupon the product sepa-
rated. The precipitate was filtered off, washed with diethyl ether
and pentane, and dried under vacuum. Another crop was obtained
by precipitation of the mother liquor with pentane. Combined
yield of 5: 90 mg (76%), orange solid. The precipitated product
tends to hold solvents; defined solvates resulted upon crystallisa-
tion from EtOH or CHCl3.
1H NMR (CDCl3): d 3.64 and 3.83 (2ꢃ br s, 4H, CH2CH2); 4.55 (br
m, 2H), 4.58 (apparent t, J0 = 1.8 Hz, 2H), 4.66 (br m, 2H), 4.84
(apparent t, J0 = 1.9 Hz, 2H) (fc); 7.36–7.65 (m, 10H, PPh2).
4.10. Catalytic Preparation of 10b and 12b
31P{1H} NMR (CDCl3): d +16.6 (s). IR (Nujol):
m
/cmꢁ1 3299 (s),
1588 (vs), 1304 (m), 1271 (w), 1164 (m), 1048 (m), 938 (w), 898
(w), 841 (w), 746 (w), 692 (m), 627 (w), 514 (w), 500 (m), 473
Reaction flask was charged with PhB(OH)2 (146 mg,
1.2 mmol), K2CO3 (276 mg, 2.0 mmol), aryl bromide (9b or 11b,

2528
J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
Table 6
Crystallographic data, data collection and structure refinement parameters for 1, 2, 4ꢀ2EtOH, 4ꢀ6CHCl3, 5ꢀ2EtOH, and 5ꢀ4CHCl3.a
Compound
1
2
4ꢀ2EtOH
C54H60Cl2Fe2N2O6P2Pdf
1183.98
4ꢀ6CHCl3
C56H54Cl20Fe2N2O4P2Pdh
1808.05
5ꢀ2EtOH
C58H68Cl2Fe2N2O8P2Pdj
1272.08
5ꢀ4CHCl3
C58H60Cl14Fe2N2O6P2Pdk
1657.42
Formula
C25H24FeNO2P
425.27
C27H28FeNO3P
501.32
M (g molꢁ1
)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Orthorhombic
Pccn (No. 56)
14.3332(1)
36.4044(5)
8.0570(1)
Triclinic
P1 (No. 2)
Triclinic
P1 (No. 2)
Monoclinic
P21/n (no. 14)
18.2832(5)
10.3326(2)
19.0708(5)
Triclinic
P1 (No. 2)
Triclinic
P1 (No. 2)
ꢀ
ꢀ
ꢀ
ꢀ
8.3328(2)
8.9101(3)
16.9636(6)
89.839(2)
87.331(2)
66.776(2)
1156.00(6)
2
1.440
0.752
15 918
7.7
8.8555(3)
11.6714(5)
13.4224(6)
98.978(2)
103.252(3)
106.257(3)
1259.8(1)
1
1.561
1.144
19 085
5.1
10.1226(2)
12.4024(3)
12.4331(3)
74.060(1)
72.918(1)
72.918(1)
1368.81(6)
1
1.543
1.061
26 812
4.2
9.5303(1)
11.0754(2)
16.1583(2)
90.7960(8)
94.2906(9)
99.4265(9)
1677.20(4)
1
a
(°)
b (°)
97.969(1)
c
(°)
V (Å3)
4204.08(8)
8
3567.9(2)
2
Z
Dcalc (g cmꢁ3
)
1.445
1.683
1.641
l
(Mo K
a
) (mmꢁ1
)
0.816e
44 656
4.83
1.489i
42 124
6.4
1.340l
Diffractions total
34 739
7.1
Rint (%)b
Unique diffrns
Observedc diffrns
R (obsd) (%)d,c
R, wR (all) (%)d
4827
4022
3.30
4.55, 7.73
0.30, ꢁ0.30
5195
4638
3.11
3.65, 7.93
0.38, ꢁ0.42
5517
4341
3.95
7801
6417
4.33
6257
5689
2.64
3.06, 6.57
0.46, ꢁ0.60
7750
6691
4.27
5.88, 9.34
5.74, 11.4
5.14, 10.6
D
q
(e Åꢁ3
)
0.94, ꢁ0.78g
1.05, ꢁ1.30g
1.67, ꢁ1.19g
a
b
c
d
e
f
Common details: T = 150(2) K.
P
P
Rint
¼
P
j Fo2 ꢁ Fo2ðmeanÞ j = F2o, where F2o(mean) is the average intensity for symmetry-equivalent diffractions.
Diffractions with Io > 2
r(Io).
P
P
P
1=2
R ¼ kFo j ꢁ j Fck= j Fo j, wR ¼ ½ wðF2o ꢁ Fc2Þ2= wðFo2Þ2ꢆ
.
Corrected for absorption; the range of transmission coefficients = 0.778–0.945.
C50H48Cl2Fe2N2O4P2Pdꢀ2C2H6O.
g
h
i
Residual electron density in the space accommodating the solvent.
C50H48Cl2Fe2N2O4P2Pdꢀ6CHCl3.
Corrected for absorption; the range of transmission coefficients = 0.589–0.874.
C54H56Cl2Fe2N2O6P2Pdꢀ2C2H6O.
j
k
l
C54H56Cl2Fe2N2O6P2Pdꢀ4CHCl3.
Corrected for absorption; the range of transmission coefficients = 0.505–0.910.
1.0 mmol), and the catalyst (1 mol% of 4). Water and toluene
were added (3 mL each), and the reaction flask was flushed with
argon, sealed with septum and transferred to an oil bath main-
tained at 60 °C. After stirring for the reaction time (1 or 24 h),
the mixture was cooled, diluted with water and extracted with
diethyl ether. The organic extracts were washed with saturated
aqueous K2CO3 solution, dried (MgSO4) and passed through a
short silica gel column, eluting with diethyl ether. Subsequent
evaporation afforded the products as a white solid (10b) or a col-
ourless oil (12b).
and from chloroform (4ꢀ6CHCl3: red plate, 0.10 ꢃ 0.35 ꢃ
0.55 mm3; 5ꢀ4CHCl3: red plate, 0.10 ꢃ 0.30 ꢃ 0.65 mm3).
The diffraction data ( h k l, 2h ꢅ 54–55°, data completeness
>97%) were collected with a Nonius KappaCCD diffractometer
equipped with a Cryostream Cooler (Oxford Cryosystems) using
graphite monochromatised Mo Ka radiation (k = 0.71073 Å) and
were analysed with the HKL program package [39]. The structures
were solved by direct methods (SIR97, Ref. [40]) and refined by
full-matrix least-squares procedure based on F2
(SHELXL97, ref.
[41]). Non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Amide and hydroxyl hydrogens were identified
on the difference electron density maps and refined as riding
atoms. Other hydrogen atoms were included in their ideal posi-
tions and treated as riding atoms. The solvent molecule in 4ꢀ2EtOH
is disordered and was modelled over two positions (50:50) with
the CH3 and OH groups as the pivots.
Relevant crystallographic data are given in Table 6. Geometric
parameters and structural drawings were obtained with a recent
version of PLATON program [42]. All numerical values are rounded
with respect to their estimated standard deviations (esd’s) given
with one decimal; parameters involving fixed hydrogen atoms
are given without esd’s.
Analytical data for 10b. 1H NMR (DMSO): d 3.93 (s, 3H), 7.10 (d,
1H, JHH = 8.7 Hz), 7.32–7.37 (m, 1H), 7.44–7.47 (m, 2H), 7.61–7.63
(m, 2H), 7.84 (m, 1H), 8.01 (d, 1H, JHH = 2.4 Hz), 10.53 (br s, 1 H).
13C{1H} NMR (DMSO): d 52.4 (CH3); 113.6, 118.0, 126.1, 127.1,
127.6, 128.9, 131.4, 133.7, 138.8, 159.2 (aromatics); 168.9
(C@O).[37] ESI+ MS: m/z 251 ([M+Na]+); ESI– MS: m/z 227
([MꢁH]ꢁ).
Analytical data for 12b. 1H NMR (CDCl3): d 3.67 (s, 2H, CH2), 3.71
(s, 3H, CH3), 7.34–7.59 (m, 9H, aromatics). 13C{1H} NMR (CDCl3): d
40.8 (CH2), 52.1 (CH3); 127.1, 127.3, 127.4, 129.7, 133.0, 140.1,
140.8 (aromatics); 172.1 (C@O) [30a,38]. ESI+ MS: m/z 249
([M+Na]+).
4.11. X-ray crystallography
5. Supplementary material
Single crystals suitable for diffraction analysis were grown by
crystallisation from ethyl acetate–hexane (1: orange plate,
0.06 ꢃ 0.25 ꢃ 0.30 mm3; 2: orange prism, 0.27 ꢃ 0.30 ꢃ 0.40
mm3), ethanol–diethyl ether (4ꢀ2EtOH: red plate, 0.05 ꢃ
0.10 ꢃ 0.30 mm3; 5ꢀ2EtOH: red prism, 0.15 ꢃ 0.18 ꢃ 0.25 mm3),
CCDC 711639, 711640, 711641, 711642, 711643 and 711644
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.

J. Schulz et al. / Journal of Organometallic Chemistry 694 (2009) 2519–2530
2529
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