Synthesis, coordination and catalytic use of 1-(diphenylphosphino)- 1′-carbamoylferrocenes with pyridyl-containing N-substituents

Article abstract of DOI:10.1039/b701012e

Ferrocene phosphinocarboxamides, 1-(diphenylphosphino)-1′-{N-[(2- pyridyl)methyl]carbamoyl}ferrocene (1) and 1-(diphenylphosphino)-1′-{N-[2- (2-pyridyl)ethyl]carbamoyl}ferrocene (2) were prepared from 1- (diphenylphosphino)-1′-ferrocenecarboxylic acid and studied as ligands for palladium. Starting with [PdCl₂(cod)], the reactions at a 2: 1 ligand-to-metal ratio gave uniformly the bis-phosphine complexes [PdCl ₂(L-κP)₂] (3, L = 1; 4, L = 2) whereas those performed at a 1: 1 ratio yielded distinct products: [PdCl₂(1- κ²P,N)] (5) with 1 coordinating as a trans-spanning P,N-donor, and the symmetric, P,N-bridged dimer [(-2-N,P)₂{PdCl ₂}₂] (6), respectively. The crystal structures of 1, 2, 4·4CHCl₃, 5·AcOH, and 6·8CHCl₃ as determined by X-ray diffraction showed the compounds to form well defined solid-state assemblies through hydrogen bonds. Testing of the phosphinocarboxamides in the palladium-catalysed Suzuki cross-coupling reaction revealed 1 and 2, combined with Pd(OAc)₂ to form efficient catalysts for the reactions of aryl bromides while aryl chlorides coupled only when activated with electron-withdrawing groups. The Royal Society of Chemistry 2007.

Full text of DOI:10.1039/b701012e

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www.rsc.org/dalton | Dalton Transactions
Synthesis, coordination and catalytic use of 1-(diphenylphosphino)-
1ꢀ-carbamoylferrocenes with pyridyl-containing N-substituents
b
a
Janett Ku¨hnert,a,b Michal Dusˇek,c Jan Demel,a,d Heinrich Lang and Petr Steˇpnicˇka*
ˇ
Received 22nd January 2007, Accepted 17th April 2007
First published as an Advance Article on the web 4th May 2007
DOI: 10.1039/b701012e
Ferrocene phosphinocarboxamides, 1-(diphenylphosphino)-1ꢀ-{N-[(2-pyridyl)methyl]-
carbamoyl}ferrocene (1) and 1-(diphenylphosphino)-1ꢀ-{N-[2-(2-pyridyl)ethyl]carbamoyl}ferrocene (2)
were prepared from 1-(diphenylphosphino)-1ꢀ-ferrocenecarboxylic acid and studied as ligands for
palladium. Starting with [PdCl2(cod)], the reactions at a 2 : 1 ligand-to-metal ratio gave uniformly the
bis-phosphine complexes [PdCl2(L-jP)2] (3, L = 1; 4, L = 2) whereas those performed at a 1 : 1 ratio
yielded distinct products: [PdCl2(1-j2P,N)] (5) with 1 coordinating as a trans-spanning P,N-donor, and
the symmetric, P,N-bridged dimer [(l-2-N,P)2{PdCl2}2] (6), respectively. The crystal structures of 1, 2,
4·4CHCl3, 5·AcOH, and 6·8CHCl3 as determined by X-ray diffraction showed the compounds to form
well defined solid-state assemblies through hydrogen bonds. Testing of the phosphinocarboxamides in
the palladium-catalysed Suzuki cross-coupling reaction revealed 1 and 2, combined with Pd(OAc)2 to
form efficient catalysts for the reactions of aryl bromides while aryl chlorides coupled only when
activated with electron-withdrawing groups.
In view of the variability of functionalised ferrocene–
carboxamides and their broad application field we designed
1-(diphenylphosphino)-1ꢀ-ferrocenecarboxamides substituted by
pyridyl-containing groups at the amide nitrogen as novel ferrocene
donors. In their synthesis we made use of 1-(diphenylphosphino)-
1ꢀ-ferrocenecarboxylic acid (Hdpf).9 This compound has been
studied in detail as a ligand and catalyst component.10 Besides,
it was demonstrated that it can be readily converted to functional
derivatives of which amides hold particular synthetic potential.
So far, the amides have been used in the preparation of Fischer-
type, P-chelated phosphino-ferrocenyl aminocarbenes11 and chiral
phosphino-ferrocene oxazolines.12 In this contribution, we report
the preparation of two homologous pyridyl-substituted Hdpf-
amides, their coordination behaviour towards palladium(II) and
use in palladium-catalysed Suzuki cross-coupling reactions.14
Introduction
N-Pyridyl substituted ferrocenecarboxamides and ferrocene-1,1ꢀ-
dicarboxamides are well established as versatile metallo-ligands
and redox- and NMR-responsive receptors to anions and polar
organic molecules.1–4 By contrast, their unsymmetric analogues
that combine the pyridyl-amide moiety with another donor
functionality have been studied much less even though they
retain the specific properties of their symmetric counterparts. For
example, 1-[N-(6-methylpyrid-2-yl)carbamoyl]-1ꢀ-carboxyferro-
cene, isolated as a by-product from the reaction of 1,1ꢀ-bis-
(chlorocarbonyl)ferrocene with 2-amino-6-methylpyridine, has
been shown to form hydrogen-bonded aggregates in both solid
state and solution,5 whilst the unsymmetric diamide 1-[N-(6-
methylpyrid-2-yl)carbamoyl]-1ꢀ-[N-(2,5,8,11,14,17-hexaoxacyclo-
octadec-1-yl)carbamoyl]ferrocene has been studied as an
electrochemical sensor to carboxylic acids and L-phenylalanine.6
In 1999, Beer et al. reported the preparation of 1,1ꢀ-bis{N-
[3-(diphenylphosphino)propyl]carbamoyl}ferrocene and P,Pꢀ-
chelated complexes thereof, and tested the amide and its complexes
as redox- and NMR-responsive receptors to inorganic anions.7
Later, two isomeric N,Nꢀ-bis[6-(benzoylamino)pyrid-2-yl]-1,1ꢀ-
ferrocendicarboxamides substituted with diphenylphosphino moi-
eties at the terminal benzoyl groups were synthesised and studied
as ligands for Pd(0) and in Heck reactions, as well as macrocyclic
hosts to barbital.8
Results and discussion
1-(Diphenylphosphino)-1ꢀ -{N-[(2-pyridyl)methyl]carbamoyl}-
ferrocene (1) and 1-(diphenylphosphino)-1ꢀ-{N-[2-(2-pyridyl)-
ethyl]carbamoyl}ferrocene (2) were prepared by amidation of
Hdpf with appropriate (aminoalkyl)pyridines in the presence of
peptide coupling agents13 (Scheme 1) and isolated by chromatog-
raphy as air-stable, crystalline solids in good yields.
Phosphinocarboxamides 1 and 2 were characterised by spectral
methods and elemental analysis, and their crystal structures have
been determined by single-crystal X-ray diffraction. In H and
13C NMR spectra, they show characteristic signals due to 1ꢀ-
aCharles University, Faculty of Natural Sciences, Department of Inorganic
Chemistry, Hlavova 2030, 128 40, Prague, Czech Republic. E-mail: stepnic@
natur.cuni.cz; Fax: +420 221 951 253
1
bChemnitz University of Technology, Institute of Chemistry, Department of
Inorganic Chemistry, 09111, Chemnitz, Germany
=
(diphenylphosphino)ferrocenyl and pyridyl groups. The C O
resonances in the 13C NMR spectra (dc 169.92 and 169.63 for
1 and 2, respectively) are shifted upfield vs. the parent acid (Hdpf,
dC 177.2) while the position of the 31P NMR signals remains
practically unchanged (cf. dP −17.0 for 1 and 2, and dP −17.6
cInstitute of Physics, Academy of Sciences of the Czech Republic, 182 21,
Prague, Czech Republic
dJ. Heyrovsky´ Institute of Physical Chemistry, Academy of Sciences of the
Czech Republic, 182 23, Prague, Czech Republic
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Scheme 1 Preparation of the ligands (EDC = N-[3-(dimethylamino)-
propyl]-Nꢀ-ethylcarbodiimide, HOBt = 1-hydroxybenzotriazole).
for Hdpf).9 The IR spectra of 1 and 2 display strong mC= (amide
O
I) bands at 1645 cm−1.
Solid-state structures
Fig. 2 PLATON plot of ligand 2. Displacement ellipsoids are represented
The molecular structures of 1 and 2 are shown in Fig. 1 and 2,
respectively, together with the relevant geometric parameters. The
structures are quite similar; the ferrocene units exert balanced Fe–
Cg distances and only negligible tilts of their cyclopentadienyl
rings (∠Cp1,Cp2: 1, 4.5(1)◦; 2, 5.6(1)◦; see Fig. 1 for definitions).
As indicated by the torsion angles C1–Cg1–Cg2–C6 (s) of 156◦
for 1 and 160◦ for 2, the ferrocene cyclopentadienyls adopt an in-
termediate conformation between anti-eclipsed and anti-staggered
that brings the centres of gravity of the bulky substituents to the
most distant positions.10
at 30% probability. Selected geometric data (in A and ◦): Fe–Cg1
˚
1.636(1), Fe–Cg2 1.644(1), ∠Cp1,Cp2 5.6(1); C1–P 1.811(2), C–P–C angles
101.82(9)–102.50(9); C6–C11 1.487(3), C11–O 1.228(2), C11–N1 1.342(3),
N1–C24 1.451(2), C24–C25 1.520(3), C25–C26 1.499(3), O–C11–N1
123.9(2), C11–N1–C24 122.4(2), N1–C24–C25 112.1(2), C24–C25–C26
115.2(2). Cpn and Cgn (n = 1, 2) are defined as for 1 (see Fig. 1).
only by 5.5(2)◦ but simultaneously tilted above the Cp2 plane,
the perpendicular distances from the Cp2 plane ranging from
˚
˚
0.126(2) A for C11 to 0.205(1) A for O. The ethylene bridge in 2
adopts a gauche conformation, characterised by the torsion angle
N1–C24–C25–C26 (w) of 61.6(2)◦.
Notably, the length of the pyridyl-linking groups seems to have
only a minor influence on the overall molecular conformation,
the pyridine rings in both amides showing similar orientations
with respect to the ferrocene moiety (cf. the dihedral angles of
the pyridyl and Cp2 planes of 80.46(9)◦ and 82.6(1)◦ for 1 and 2,
respectively). The analogy in disposition of the functional groups
in compounds 1 and 2 is reflected in the similarity of their crystal
packing patterns. Both compounds form centrosymmetric dimers
via pairs of N1–H1N · · · N2 hydrogen bonds. The dimers are in-
terconnected via relatively weaker C–H(pyridyl) · · · O interactions
into one-dimensional arrays running along the crystallographic b
axis (Table 1).
Palladium(II) complexes
As the phosphinoamides combine several donor sites, we first
decided to study their coordination behaviour towards palla-
dium(II), which is known to be readily coordinated by both
phosphorus and nitrogen donors.15 Quite expectedly, the reactions
Fig. 1 PLATON plot of ligand 1. Displacement ellipsoids are represented
at 30% probability. Selected geometric data (in A and ◦): Fe–Cg1
˚
1.639(1), Fe–Cg2 1.645(1), ∠Cp1,Cp2 4.5(1); C1–P 1.810(2), C–P–C angles
101.96(9)–102.87(9); C6–C11 1.480(2), C11–O 1.232(2), C11–N1 1.345(2),
N1–C24 1.454(2), C24–C25 1.507(3), O–C11–N1 122.2(2), C11–N1–C24
120.7(2), N1–C24–C25 111.4(2). Cp1 [Cp2] denote cyclopentadienyl rings
C(1–5) [C(6–10)]; Cg1 and Cg2 are their centroids.
2
2
with [PdCl2(cod)] (cod = g :g -1,5-cyclooctadiene) at a 1 : 2
metal-to-ligand ratio afforded the square-planar bis(phosphine)
complexes, trans-[PdCl2(L-jP)2] (3, L = 1; and 4, L = 2; Scheme 2).
P-Monodentate coordination of the ligands in 3 and 4 is clearly
manifested in their NMR and IR spectra. Upon coordination, the
31P NMR signals shift to lower fields, the 31P NMR coordination
shifts, DP = dP(complex) − dP(ligand), being 32.5 ppm for both 3
and 4 (cf. DP = 35.1 ppm for [PdCl2(Hdpf-jP)2]17). In addition, all
13C NMR resonances due to carbon atoms of the phosphorus-
substituted cyclopentadienyl and phenyl rings are observed as
virtually coupled triplets as is typical for ABX spin systems 12C–
31P(A)–metal–31P(B)–13C(X) with relatively large JAB values.16,17
The geometry of the amide groups in 1 and 2 is similar, too.
The {C11(O)N1C24} moieties are planar and syn-arranged, the
torsion angles C24–N1–C11–O (u) being 3.9(3)◦ for 1 and 2.6(3)◦
for 2. In both cases the amide planes {C11ON1} deviate slightly
from the least-squares planes of their parent cyclopentadienyl
rings Cp2. Whereas the amide moiety in 2 is symmetrically
rotated around the C6–C11 axis by 14.2(2)◦, that in 1 is rotated
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Table 1 Summary of hydrogen bond parametersa
Angle at H/◦
˚
D–H · · · A
D · · · A/A
Compound 1
N1–H1N · · · N2i
3.011(3)
3.258(3)
162(1)
164
C26–H26 · · · Oii
Compound 2
N1–H1N · · · N2iii
3.076(3)
3.219(3)
161
147
C27–H27 · · · Oiv
Compound 4·4CHCl3
N1–H1N · · · N2v
Compound 5·AcOH
N1–H1N · · · Cl1viii
O31–H1O · · · O (S)
Compound 6·8CHCl3
N1–H1N · · · Cl2
C60–H60 · · · Ovi (S)
C70–H70 · · · Ovi (S)
C80–H80 · · · Cl1vii (S)
3.024(3)
161
3.350(2)
2.699(3)
137
159
3.533(4)
3.036(7)
3.095(7)
3.350(7)
157
160
153
151
a D = donor, A = acceptor. Symmetry codes: i. −x, −y, 2 − z; ii. x − 1,
y, z; iii. −x, 1 − y, 1 − z; iv. 1 + x, y, z; v. 2 − x, 1 − y, 1 − z; vi. x −
1, y, z; vii. 1 − x, y − 1/2, 1/2 − z. (S) is used to distinguish interactions
involving solvate molecules.
Scheme 3 Synthesis of 5 and 6.
Unfortunately, the spectral data do not provide firm evidence as
to whether the dimeric structure of 6 is retained in solution or if it is
just part of an equilibrium involving other species (e.g., monomer
[PdCl2(2)]). For instance, the variable temperature NMR data of 6
are indicative of some structural dynamics. The spectra recorded
at +25 ◦C show markedly broad resonances due to the ferrocene
and 2-(2-pyridyl)ethyl groups, which broaden even further upon
cooling and sharpen on heating to 50 ◦C. On the other hand,
there is practically no difference between the spectra of a sample
obtained by dissolving crystalline 6 and that prepared in situ
by reacting [PdCl2(cod)] with 2 (in CDCl3), which supports the
formulation as a dimer (concentration independent). The ESI mass
spectra are hardly informative here, showing ions due to [LPdCln]+
and [LPdCl + Na]+ (n = 0, 1; L = 1 and 2) as the major fragments
for both 5 and 6. The bis-phosphine complexes 3 and 4 measured
for comparison also gave rise to ions due to [LPdCln]+ (n = 0, 1;
in addition, the ions [(2)2PdCln]+ and [2 + H]+ were observed only
for 4).
It should be pointed out that complexes related to 5 in
which bidentate donors span trans positions of a coordina-
tion polyhedron have been obtained predominantly with bis-
phosphines whose rigid, usually hydrocarbon backbone pre-
arranges the donor groups into positions suitable for trans
chelation. The analogous donor-unsymmetric ligands (such
as 1) are still much less common.18 In ferrocene chemistry,
nonetheless, coordination behaviour similar to 1 has been
reported already for 1-(diphenylphosphino)-1ꢀ-(2,2ꢀ-bipyridyl-6-
yl)ferrocene.19,20 Even so, the variable coordination behaviour
of 1 and 2 has precedents among the related organic donors.
For instance, triphenylphosphine-based ligands bearing x-(2-
pyridyl)alkyl pendant groups, 2-Ph2PC6H4CH2O(CH2)n(C5H4N-
2) (Lꢀ), were all shown to form [PdCl2(Lꢀ-j2P,N)] complexes the
configuration of which changed with the length of the spacer
group: cis for n = 1, trans for n = 2 and 3.21
Scheme 2 Synthesis of 3 and 4.
On the other hand, the positions of the NMR signals due to
the pyridylamide moieties as well as the amide bands in the IR
spectra remain largely unaffected, thus excluding coordination
of the pyridylamide pendants. The crystal structure of 4·4CHCl3
clearly confirmed the coordination mode (see below).
Complexation reactions performed at a 1 : 1 metal-to-ligand
ratio proved more interesting (Scheme 3). Thus, the reaction
involving 1 gave trans-[PdCl2(1-j2P,N)] (5) where the phosphi-
noamide coordinates simultaneously via the phosphorus and
pyridine nitrogen atoms as a trans-chelating P,N-donor. By
contrast, a similar reaction between 2 and [PdCl2(cod)] furnished
complex 6, the dimeric structure of which was established by X-ray
diffraction analysis.
As in previous cases, coordination via phosphorus can be
inferred from low-field shifts in the 31P NMR spectra, which are,
however, larger than for 3 and 4 (DP(5) = 41.5 ppm, DP(6) =
38.8 ppm). In the 13C NMR spectra, the Cipso(CpP) signals appear
1
shifted to lower fields while the value of the associated JPC
coupling constant increases by one order of magnitude (cf. 1JPC
7
and 63 Hz for 1 and 5, respectively). Coordination of the pyridine
Solid-state structures
moiety is reflected by a shift of its 1H and 13C NMR resonances to
=
lower fields; the response of the amide C O remains practically
X-Ray diffraction analysis revealed that complex 4 crystallises as
the solvate 4·4CHCl3. A view of the complex molecule is shown
unchanged in both 13C NMR and IR spectra.
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◦
a
˚
above and below the coordination plane, the dihedral angles vs.
the coordination plane {PdClClꢀPPꢀ} being 74.6(1)◦ and 50.8(1)◦
for the pyridyl and Cp1 planes, respectively.
It is interesting to note that the coordinated ligand retains
the key feature of the hydrogen bonding patterns of its free
form, associating via centrosymmetric, double N1–H1N · · · N2
hydrogen bridges (Table 1). However, since the interaction involves
ligand moieties from adjacent complex molecules, the hydrogen
bonding itself results in the formation of infinite chains along the
b axis (Fig. 4).
Table 2 Selected bond lengths and angles for 4·4CHCl3 (in A and
)
Pd–Cl
Pd–P
C1–P
2.296(1)
2.325(1)
1.795(3)
1.639(1)
1.648(1)
1.475(4)
1.235(3)
1.338(3)
1.461(3)
1.522(4)
1.496(4)
Cl–Pd–P
Cl–Pd–Pv
C–P–C angles
∠Cp1,Cp2
sb
86.22(3)
93.78(3)
101.4(1)–106.1(1)
6.0(2)
Fe–Cg1
Fe–Cg2
C6–C11
C11–O
C11–N1
N1–C24
C24–C25
C25–C26
151
O–C11–N1
C11–N1–C24
N1–C24–C25
C24–C25–C26
uc
122.5(2)
122.8(2)
111.4(2)
115.9(3)
0.4(4)
wd
65.9(3)
a Cp(1,2) and Cg(1,2) are defined as for 1 (see Fig. 1), v. 2 − x, 1 − y,
1 − z. b Torsion angle C1–Cg1–Cg2–C6. c Torsion angle O–C11–N1–C24.
d Torsion angle N1–C24–C25–C26.
in Fig. 3 and the relevant structural data are listed in Table 2.
Not surprisingly, the complex possesses imposed crystallographic
symmetry, which renders only half of the molecule symmetrically
independent. As a result, the coordination environment of the
palladium atom is perfectly planar, showing no significant angular
deformation. The Pd–donor distances do not depart from those
reported for the related complexes trans-[PdCl2(Ph2PfcX-jP)2],
where fc = ferrocene-1,1ꢀ-diyl and X = CO2H (i.e. Hdpf),17
PO3Et2,22 P(O)PPh2,23 SMe,24 and oxazolinyl.12a When viewed
along the P · · · Pꢀ direction, the ‘PC3’ units in 4 appear mutually
staggered, which apparently minimises steric interactions of the
bulky phosphorus substituents. This also seems to be a feature
common to complexes of this type.
Fig. 4 Section of the hydrogen-bonded array in the structure of 4·4CHCl3.
The arrows indicate propagation of the linear assembly. For clarity, only
the H1N hydrogen atom and the pivotal phenyl carbons are shown.
The structure of 5·AcOH corroborates the trans-chelate coordi-
nation of 1 (Fig. 5 and Table 3). The palladium atom is coordinated
symmetrically with the donor atoms coplanar ◦within less than
˚
0.1 A (the sum of the inter-donor angles is 360.1 ).
Fig. 3 PLATON plot of the complex molecule in the structure of
4·4CHCl3 showing 30% displacement ellipsoids. The prime-labelled atoms
are generated by the (2 − x, −y, 1 − z) symmetry operation.
The structure of the P-coordinated ligand differs only
marginally from the free form both in interatomic distances and
angles and in overall conformation. The most notable but still
rather minor change can be seen in a slight reorientation of the
pyridyl ring versus the ferrocene unit. The dihedral angle of the
pyridyl and Cp2 planes in 4·4CHCl3 is 76.1(2)◦, while the w angle
increases by about 4◦. In addition, the ferrocene substituents are
anti-eclipsed with s = 151◦ (the ideal value is 144◦). Finally, the
amide plane is rotated from Cp2 by 12.9(3)◦, and the pyridylamide
groups that are not involved in bonding to palladium(II) extend
Fig. 5 PLATON plot of the complex molecule in the structure of
5·AcOH. Displacement ellipsoids correspond to 30% probability.
As for the ligand moiety, the coordination has again only a
little influence on the bond lengths and angles when compared
with free 1. However, the overall conformation is changed so as
to allow for an efficient chelation. The ferrocene substitutents
are rotated closer to each other as evidenced by s of 63◦, which
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◦
◦
a
a
˚
˚
Table 3 Selected bond lengths and angles for 5·AcOH (in A and
)
Table 4 Selected bond lengths and angles for 6·8CHCl3 (in A and
)
Pd–Cl1
Pd–Cl2
Pd–P
Pd–N2
C1–P
Fe–Cg1
Fe–Cg2
C6–C11
C11–O
C11–N1
N1–C24
2.296(1)
2.302(1)
2.243(1)
2.124(2)
1.799(2)
1.646(1)
1.652(1)
1.471(3)
1.233(3)
1.342(3)
1.443(3)
Cl1–Pd–P
Cl1–Pd–N2
Cl2–Pd–P
Cl2–Pd–N2
C–P–C angles
∠Cp1,Cp2
sb
O–C11–N1
C11–N1–C24
N1–C24–C25
uc
92.78(3)
88.85(6)
89.95(3)
88.55(6)
103.1(1)–105.9(1)
5.4(1)
Pd–Cl1
Pd–Cl2
Pd–Pi
Pd–N2
C1–P
Fe–Cg1
Fe–Cg2
C6–C11
C11–O
C11–N1
N1–C24
C24–C25
C25–C26
2.300(1)
2.298(1)
2.243(1)
2.107(4)
1.794(5)
1.646(2)
1.647(2)
1.501(7)
1.226(6)
1.348(6)
1.463(7)
1.520(7)
1.485(6)
Cl1–Pd–Pi
Cl1–Pd–N2
Cl2–Pd–Pi
Cl2–Pd–N2
C–P–C angles
∠Cp1,Cp2
sb
95.57(5)
85.8(1)
88.77(5)
90.0(1)
99.8(2)–107.2(2)
4.0(3)
63
143
122.2(2)
119.4(2)
114.8(2)
2.0(3)
O–C11–N1
C11–N1–C24
N1–C24–C25
C24–C25–C26
uc
123.0(5)
120.2(4)
110.4(4)
114.2(4)
0.3(7)
a See Fig. 1 for definitions. Geometric data for the solvating acetic acid
molecule: C30–O31 1.199(4), C30–O32 1.313(4), C30–C31 1.489(4), O31–
C30–O32 122.8(3). b Torsion angle C1–Cg1–Cg2–C6. c Torsion angle C24–
N1–C11–O.
wd
52.8(6)
a See Fig. 1 for definitions; i. 1 − x, −y, −z. b Torsion angle C1–Cg1–Cg2–
C6. c Torsion angle C24–N1–C11–O. d Torsion angle N1–C24–C25–C26.
corresponds to a conformation near to syn-eclipsed (ideal value
72◦) while the N-pyridyl amide part reorients via rotations along
the N1–C24 and C24–C25 bonds (cf. the following torsion angles
in 1/5: C11–N1–C24–C25 76.2(2)/152.0(2)◦ and N1–C24–C25–
N2 85.6(2)/40.3(3)◦) and of the pyridyl plane (cf. the dihedral
angle of the pyridyl and Cp2 planes of 47.5(1)◦). Consequently,
the pyridyl plane appears to be bisecting the C12–P–C18 angle
when viewed along the N2 · · · P direction. The amide moiety is
planar (u = 2.0(3)◦) but rotated from the Cp2 plane along the
pivotal C6–C11 bond by 15.1(3)◦.
In the crystal, molecules of 5 aggregate into dimers by means of
N1–H1N · · · Cl1 hydrogen bonds (Fig. 6, Table 1) while the amide
=
carbonyl groups bind the solvating acetic acid via C O · · · H–O
hydrogen bonds. The assembly of the thus formed {52(AcOH)2}
repeating units is further supported by intra- and intermolecular
C–H · · · Cl2/O hydrogen bonds and by offset p–p stacking interac-
tions between aromatic rings (pyridyl, phenyl C(18–23) and Cp2)
and their parallel, inversion-related counterparts located in three
proximal complex molecules (see ref. 25 for details).
Fig. 7 PLATON plot of the complex molecule in the structure of
6·8CHCl3. Prime-labelled atoms are generated by the (1 − x, −y,
−z) symmetry operation. Displacement ellipsoids correspond to 30%
probability.
centre (i.e., away from the ferrocene unit). The Pꢀ–Pd–N and Cl1–
Pd–Cl2 angles are 178.2(1) and 171.19(5)◦, respectively, while the
dihedral angles towards the {PdPCl1Cl2N2} plane are 52.3(2)◦
for Cp1 and 87.2(2)◦ for the pyridyl ring.
Similar to 5·AcOH, the formation of 6 leads mainly to
conformational changes within the ligand molecule. The most
notable changes occur at the N1–C24 and C25–C26 bonds and
in the orientation of the pyridyl plane (cf. the dihedral angle of
the Cp2 and pyridyl planes of 70.4(3)◦). The substituents at the
ferrocene unit are anti-eclipsed (s = 143◦) and the amide group is
rotated from the Cp2 plane by 13.2(5)◦.
The structure of the dimer is stabilised by intramolecular N1–
H1N · · · Cl2 hydrogen bonds while the solvating molecules take
part in C–H · · · X hydrogen interactions (one to Cl1 and two
to O, Table 1). Hence, the overall crystal packing of 6·8CHCl3
is essentially molecular with the solvated complex molecules
functioning as the repeat units.
Fig.
6 View of hydrogen-bonded dimers in the structure of
5·AcOH. Prime-labelled atoms are generated by the (−x, 1 − y, 1 − z)
Catalytic tests
symmetry operation. Only amide and carboxyl hydrogen atoms are shown.
Having probed the ability of 1 and 2 to ligate palladium,
we tested the phosphinocarboxamides in palladium-catalysed
Suzuki reactions.26 Catalytic systems were prepared by mixing
palladium(II) acetate (1 mol%) with 1.2 molar equivalent of the
appropriate ligand (see Experimental section for an in situ study).
Solvate 6·8CHCl3 crystallises as a centrosymmetric dimer
(Fig. 7, Table 4). Whereas the Pd–donor distances compare
favourably to those in 5·AcOH, the coordination plane is markedly
twisted due to bending of the chloride ligands away from the dimer
2806 | Dalton Trans., 2007, 2802–2811
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Table 5 Results for the palladium-catalysed Suzuki reactions with
tectons in organometallic crystal engineering, particularly in
the preparation of defined supramolecular metal–organic and
coordination assemblies.34
phenylboronic acida
Experimental
Aryl halide
G
X = Cl
L = 1
X = Br
L = 1
General comments
L = 2
L = 2
Quant.b
Quant.b
Quant.b
Quant.b
Quant.b
Quant.b
Quant.b
Quant.b
The syntheses were performed under an argon atmosphere and
with an exclusion of direct daylight. Dichloromethane and chloro-
form were dried over anhydrous potassium carbonate. Hdpf9 was
prepared as previously reported. Other chemicals and solvents for
crystallisations and chromatography were used as received (Fluka,
Aldrich; solvents from Lach-Ner).
CH3
No reaction
No reaction
24%
No reaction
No reaction
17%
OCH3
C(O)CH3
NO2
27%
56%
a Conditions: aryl halide (1.0 mmol), PhB(OH)2 (1.5 mmol), Pd(OAc)2
(10 lmol, 1 mol%), ligand (12 lmol) and K2CO3 (2.0 mmol); dioxane, 16 h
at 100 ◦C (in bath). The yields were determined NMR-spectroscopically
and are an average of two independent runs. See Experimental section for
the detailed procedure. b Complete conversion. Isolated yields ranged from
93–99%.
Melting points were determined on a Kofler apparatus. NMR
spectra were measured on a Varian UNITY Inova 400 spectrome-
ter (1H, 399.95; 13C, 100.58; 31P, 161.90 MHz) at 298 K. Chemical
shifts (d/ppm) are given relative to internal tetramethylsilane
(1H and 13C) and external 85% aqueous H3PO4 (31P). Standard
notation of the signal multiplicity is used. In addition, vt and
vq are used to distinguish virtual multiplets due to magnetically
non-equivalent AAꢀBBꢀ and AAꢀBBꢀX spin systems of the amide-
and phosphorus-substituted cyclopentadienyl rings CpC and CpP,
respectively (Note: fc = ferrocen-1,1ꢀ-diyl). Multiplets arising
in the second-order 13C NMR spectra of trans-bis(phosphine)
complexes do not obey binomial intensity distribution and, hence,
are labelled as pseudotriplets (pt). IR spectra were recorded on an
FT IR Nicolet Magna 760 instrument in the range 400–4000 cm−1.
Electrospray (ESI) mass spectra were recorded on a Bruker
Esquire 3000 spectrometer. The samples for ESI measurements
were first dissolved in chloroform and then diluted with methanol
in large excess.
The reactions were performed with various aryl halides using
1.5 molar excess of phenylboronic acid and potassium carbonate
as the base in dioxane solvent at 100 ◦C for 16 h. The results are
summarised in Table 5. In a separate series of experiments, we
also tested complexes 3–6 as catalyst precursors under otherwise
identical conditions.
The Pd(OAc)2-based systems proved highly efficient for cou-
pling of both activated and deactivated aryl bromides, showing
complete conversions and practically quantitative isolated yields
of the respective biphenyls. With less reactive chlorides,27 the
biphenyls were obtained only from the activated substrates (4-
C(O)CH3 and 4-NO2 chlorobenzenes) in modest yields whilst aryl
chlorides with electron-donating groups (4-CH3 and 4-OCH3) did
not react at all.
The observed activity of catalysts based on 1 or 2 and
palladium(II) acetate is similar to or higher than that reported
for similar systems based on Hdpf,28 Ph2PfcEMe (E = O and
S)29 and on tris(2-methylferrocenyl)phosphine30 but lower than
the activity achieved with 1ꢀ-(phosphino)ferrocenyl acetals31 and
imines32 bearing electron-rich dialkylphosphino groups. The use of
defined complexes as (pre)catalysts had no beneficiary effect. For
instance, the conversions achieved in the coupling reaction with
4-bromotoluene catalysed with complexes 3–6 were only 80–93%.
Preparation of phosphinocarboxamides 1 and 2
1-(Diphenylphosphino)-1ꢀ -{N -[(2-pyridyl)methyl]carbamoyl}-
ferrocene (1). N-(3-Dimethylaminopropyl)-Nꢀ-ethylcarbodiimide
(EDC; 0.931 g, 6.0 mmol) was added with stirring to an ice-cooled
mixture of Hpdf (2.070 g, 5.00 mmol), 1-hydroxybenzotriazole
(HOBt; 0.811 g, 6.00 mmol), and dry dichloromethane (50 mL;
the solid triazole dissolved during the addition). The mixture
was stirred for 30 min at 0 ◦C and treated with neat 2-
(aminomethyl)pyridine (0.62 mL, 6.00 mmol). The cooling was
removed and stirring continued at room temperature overnight.
Then, the reaction solution was washed sequentially with 1%
aqueous citric acid, saturated aqueous NaHCO3, and brine, dried
over MgSO4 and evaporated under vacuum. The solid residue
was purified by column chromatography on silica gel using first
dichloromethane to remove some unreacted benzotriazolyl ester
and then dichloromethane–methanol (50 : 1 v/v) to elute the
phosphinoamide. Solvent removal followed by crystallisation from
hot ethyl acetate (overlayed with hexane after cooling) gave pure
1 as◦an orange crystalline solid. Yield: 1.862 g (74%); mp 172–
175 C. 1H NMR (CDCl3): d 4.11 (vq, J = 1.8 Hz, 2 H, CpP), 4.22
(vt, J = 2.0 Hz, 2 H, CpC), 4.38 (vt, J = 1.7 Hz, 2 H, CpP), 4.63
Conclusions
Phosphinocarboxamides 1 and 2 reported in this paper represent a
new type of hybrid32 ferrocene donor. The particular combination
of the ligating sites and their spatial arrangement make the
amidophosphines coordinationally highly variable, which has been
exemplified by several distinct types of isolated palladium(II)
complexes. Clearly, the coordination properties of ferrocene
phosphinocarboxamides can be widely varied by means of rather
independent modifications at the phosphorus atom and within
the amide N-substituents. The high structural versatility, relative
stability as well as easy synthetic access make these donors
interesting ligands and catalyst components.33
3
It should be pointed out that the ligands under study form well-
defined supramolecular hydrogen-bonded assemblies in the solid
state (see the results of the structure determinations presented
above). The compounds therefore have potential prospects as
(d, JHH = 5.2 Hz, 2 H, CH2), 4.64 (vt, J = 2.0 Hz, 2 H, CpC),
3
3
6.90 (t, JHH = 5.2 Hz, 1 H, NH), 7.17 (dddt, JHH = 7.4 (H4),
4JHH = 4.9 (H5), 5JHH = 1.2 (H6), 4JHH = 0.6 (CH2) Hz, 1 H, H3 of
C5H4N), 7.28–7.38 (m, 11 H, PPh2 and H5 of C5H4N), 7.64 (ddd,
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3
1
3JHH ≈ JHH = 7.7 (H3 and H5), 4JHH = 1.8 (H6) Hz, 1 H, H4 of
structures). The content of the solvent was verified by H NMR
spectra recorded in dmso-d6 solutions.
C5H4N), 8.51 (ddd, 3JHH = 4.9 (H5), 4JHH = 1.8 (H4), 5JHH = 1.0
(H3) Hz, 1 H, H6 of C5H4N). 13C{ H} NMR (CDCl3): d 44.52
1
Complex 3. Following the above procedure, 1 (50 mg,
0.10 mmol) and [PdCl2(cod)] (14 mg, 0.05 mmol) gave 3. Yield:
72 mg (88%); mp 136 ◦C (decomp.). 1H NMR (CDCl3): d 4.41 (vt,
J = 1.9 Hz, 2 H, fc), 4.61–4.64 (m, 4 H, fc and CH2), 4.72 (vt, J =
2.0 Hz, 2 H, fc), 4.88 (vt, J = 2.0 Hz, 2 H, fc), 7.07 (t, 3JHH = 5.3 Hz,
1 H, NH), 7.17 (m, 1 H, C5H4N), 7.12–7.68 (m, 12 H, PPh2 and
(CH2), 69.37, 71.71 (d, J = 2 Hz) (2 × CH of CpC); 72.95 (d, JPC
=
4 Hz), 74.24 (d, JPC = 14 Hz) (2 × CH of CpP); 76.75 (Cipso of
CpC), 77.41 (d, 1JPC = 7 Hz, Cipso of CpP), 122.20 (C5 of C5H4N),
122.31 (C3 of C5H4N), 128.21 (d, JPC = 7 Hz), 128.65, 133.44 (d,
JPC = 20 Hz) (3 × CH of PPh2); 136.72 (C4 of C5H4N), 138.57 (d,
1JPC = 10 Hz, Cipso of PPh2), 149.05 (C6 of C5H4N), 156.96 (Cipso
C5H4N), 8.52 (m, 1 H, C5H4N). 31P{ H} NMR (CDCl3): d +15.6.
1
of C5H4N), 169.92 (C O). 31P{ H} NMR (CDCl3): d −17.0. IR
1
=
−1
=
IR (Nujol, cm ): 3233m (N–H), 1629vs (C O), 1589m, 1570s,
−1
=
(Nujol, cm ): 1644vs (C O), 1595w, 1570w, 1533s, 1326w, 1298s,
1558s, 1436s, 1417m, 1365m, 1317m, 1307m, 1171m, 1096m,
1035m, 995m, 840m, 745s, 708m, 696s, 689s, 517s, 505m, 498m,
479m, 454m. Anal. calc. for C58H50Cl2Fe2N4O2PdP2·0.2CHCl3
(1209.8): C 57.78, H 4.18, N 4.63. Found: C 57.85, H 4.04, N
4.40%.
1180m, 1161m, 1094w, 1069w, 1056w, 1021m, 1002w, 833m, 776m,
744vs, 697s, 635m, 619m, 503s, 451m, 435w, 409w. Anal. calc. for
C29H25FeN2OP (504.3): C 69.06, H 5.00, N 5.55. Found C 68.90,
H 5.10, N 5.26%.
1-(Diphenylphosphino)-1ꢀ -{N-[2-(2-pyridyl)ethyl]-carbamoyl}-
ferrocene (2). Amide 2 was synthesised similarly starting with
Hpdf (2.070 g, 5.00 mmol), HOBt (0.811 g, 6.00 mmol), EDC
(0.931 g, 6.0 mmol), and 2-(2-aminoethyl)pyridine (0.72 mL,
6.00 mmol) in 50 mL of dry dichloromethane. Column chromatog-
raphy was carried out on silica gel using first dichloromethane
and then a dichloromethane–methanol mixture (20 : 1 v/v).
Evaporation under vacuum of the major fraction◦ gave 2 as an
Complex 4. This compound was obtained similarly from 2
(52 mg, 0.10 mmol) and [PdCl2(cod)] (14 mg, 0.05 mmol). Yield:
44 mg (72%); mp 140 ◦C (decomp.). 1H NMR (DMSO): d 2.97 (t,
3JHH = 7.1 Hz, 2 H), 3.55 (q, J = 6.7 Hz, 2 H, 2 × CH2), 4.35
(vt, J = 1.9 Hz, 2 H, fc), 4.45 (vt, J = 1.7 Hz, 2 H, fc), 4.66 (vt,
J = 1.9 Hz, 2 H, fc), 4.95 (vt, J = 1.9 Hz, 2 H, fc), 7.19 (ddd,
3
4
3JHH = 7.5 (H4), JHH = 4.8 (H6), JHH = 1.1 (H3) Hz, 1 H, H5
3
4
5
of C5H4N), 7.27 (ddd, JHH = 7.8 (H4), JHH = 1.1 (H5), JHH
=
1
orange solid. Yield: 2.163 g (84%); mp 121–122 C. H NMR
1.0 (H6) Hz, 1 H, H3 of C5H4N), 7.46–7.57 (m, 10 H, PPh2), 7.67
3
(CDCl3): d 3.06 (t, JHH = 6.3 Hz, 2 H, CH2C5H4N), 3.75 (q,
(ddd, 3JHH ≈ JHH = 7.8 (H3 and H5), 4JHH = 1.8 (H6) Hz, 1 H,
3
JHH = 6.1 Hz, 2 H, CH2NH), 4.02 (vq, J = 1.9 Hz, 2 H, CpP), 4.17
(vt, J = 2.0 Hz, 2 H, CpC), 4.30 (vt, J = 1.8 Hz, 2 H, CpP), 4.54 (vt,
J = 2.0 Hz, 2 H, CpC), 6.80 (t, 3JHH = 5.4 Hz, 1 H, NH), 7.12 (ddd,
H4 of C5H4N), 7.96 (t, 3JHH = 5.7 Hz, 1 H, NH), 8.49 (ddd, 3JHH
=
4.8 (H5), 4JHH = 1.8 (H4), 5JHH = 1.0 (H3) Hz, 1 H, H6 of C5H4N)
(tentative assignment for C5H4N given). 13C{ H} NMR (DMSO):
1
3
4
3JHH = 7.6 (H4), JHH = 4.9 (H6), JHH = 1.2 (H3) Hz, 1 H, H5
d 37.32, 38.63 (CH2CH2); 69.62 (CH of CpC), 71.23 (pt, J = 27 Hz,
Cipso of CpP), 72.70 (CH of CpC), 73.87 (m), 75.44 (pt, J = 6 Hz)
(2 × CH of CpP); 78.10 (Cipso of CpC), 121.38, 123.04 (2 × CH
of C5H4N); 127.87 (pt, J = 5 Hz), 130.39 (2 × CH of PPh2);
130.48 (pt, J = 25 Hz, Cipso of PPh2), 133.47 (pt, J = 6 Hz, PPh2),
3
4
5
of C5H4N), 7.19 (ddd, JHH = 7.8 (H4), JHH = 1.0 (H5), JHH
=
1.0 (H6) Hz, 1 H, H3 of C5H4N), 7.29–7.36 (m, 10 H, PPh2), 7.59
(ddd, 3JHH ≈ JHH = 7.7 (H3 and H5), 4JHH = 1.8 (H6) Hz, 1 H, H4
3
3
4
5
of C5H4N), 8.55 (ddd, JHH = 4.9 (H5), JHH = 1.8 (H4), JHH
=
1.0 (H3) Hz, 1 H, H6 of C5H4N). 13C{ H} NMR (CDCl3): d 36.97
(CH2C5H4N), 38.65 (CH2NH), 69.15, 71.57 (d, J = 1 Hz) (2 ×
CH of CpC); 72.91 (d, JPC = 4 Hz), 74.11 (d, JPC = 14 Hz) (2 ×
1
31
1
=
136.31, 148.95, 159.13 (3 × CH of C5H4N); 167.76 (C O). P{ H}
NMR (DMSO): d +16.8. IR (Nujol, cm−1): 3283m (N–H), 1653vs
=
(C O), 1591m, 1566m, 1545vs, 1435vs, 1298s, 1289s, 1198m,
CH of CpP); 77.16 (d, JPC = 6 Hz, Cipso of CpP), 77.22 (Cipso of
1
1183m, 1169m, 1099m, 1055m, 1028m, 997m, 840m, 827m, 759s,
747s, 691s, 621m, 517vs, 502s, 494s, 479m, 469m. Anal. calc. for
C60H54Cl2Fe2N4O2PdP2·0.3CHCl3 (1247.5): C 57.95, H 4.38, N
4.48. Found C 57.93, H 4.30, N 4.48%.
CpC), 121.59 (C5 of C5H4N), 123.57 (C3 of C5H4N), 128.20 (d,
JPC = 7 Hz), 128.63, 133.43 (d, JPC = 20 Hz), (3 × CH of PPh2);
1
136.62 (C4 of C5H4N), 138.57 (d, JPC = 10 Hz, Cipso of PPh2),
=
149.19 (C6 of C5H4N), 159.83 (Cipso of C5H4N), 169.63 (C O).
1
31P{ H} NMR (CDCl3): d −17.0. IR (Nujol, cm−1): 3259m (N–
Complex 5. Reacting 1 (50 mg, 0.10 mmol) and [PdCl2(cod)]
(29 mg, 0.10 mmol) as indicated above gave complex 5. Yield:
55 mg (79%); mp 115–116 ◦C (decomp.). 1H NMR (CDCl3): d 4.61
(vt, J = 1.9 Hz, 2 H, CpC), 4.71 (br m, 2 H, CpP), 4.75 (m, 2 H, CpP),
5.02 (d, 3JHH = 3.9 Hz, 2 H, CH2), 5.65 (vt, J = 1.9 Hz, 2 H, CpC),
7.34–7.68 (m, 12 H, PPh2 and C5H4N), 7.70 (t, 1 H, 3JHH = 3.9 Hz,
=
H), 1645vs (C O), 1594m, 1569m, 1549vs, 1433vs, 1303vs, 1291vs,
1200m, 1193m, 1182m, 1161m, 1094m, 1042m, 1032m, 1025m,
998m, 956w, 889m, 870m, 837s, 829m, 796m, 761s, 750vs, 746vs,
701vs, 629m, 574w, 520m, 510s, 503vs, 491s, 471m, 446m. Anal.
calc. for C30H27FeN2OP·0.04CH2Cl2 (521.7): C 69.15, H 5.23, N
5.37. Found C 69.04, H 5.29, N 5.31%.
3
NH), 7.78 (ddd, 1 H, 3JHH ≈ JHH = 7.8 (H3 and H5), 4JHH = 1.6
(H6) Hz, H4 of C5H4N), 9.04 (dddd, 1 H, J = 5.5, 2.9, 1.7, 0.6
1
(H3, H4, H5, and P) Hz, H6 of C5H4N). 13C{ H} NMR (CDCl3):
Preparation of palladium(II) complexes 3–6
d 46.23 (CH2), 70.04 (d, 1JPC = 63 Hz, Cipso of CpP), 71.99, 72.10
(2 × CH of CpC); 73.04 (d, JPC = 9 Hz), 77.11 (d, JPC = 11 Hz) (2 ×
CH of CpP); 77.22 (Cipso of CpC), 124.02 (d, JPC = 2 Hz, C5 or C3
of C5H4N), 126.52 (d, JPC = 4 Hz, C3 or C5 of C5H4N), 127.73 (d,
JPC = 12 Hz, CH of PPh2), 129.61 (d, 1JPC = 60 Hz, CH of PPh2),
130.94 (d, JPC = 3 Hz), 133.81 (d, JPC = 10 Hz) (2 × CH of PPh2);
General procedure. Stoichiometric amounts of [PdCl2(cod)]
and the appropriate amide were dissolved in chloroform (6 mL).
The thus formed red-orange solutions were stirred for 3 h and
precipitated with hexane. The precipitates were filtered off, washed
with diethyl ether and pentane and, finally, dried under reduced
pressure to afford the complexes as fine orange solids showing
a strong tendency to hold the reaction solvents (cf. the crystal
138.67 (C4 of C5H4N), 151.97 (d, JPC = 3 Hz, C6 of C5H4N), 156.49
1
(Cipso of C5H4N), 169.23 (C O). 31P{ H} NMR (CDCl3): d +24.5.
=
2808 | Dalton Trans., 2007, 2802–2811
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−1
=
IR (Nujol, cm ): 3535m, 3479m, 3391m (N–H); 1645vs (C O),
1602m, 1514vs, 1435s, 1310m, 1275m, 1181m, 1173m, 1036m,
1026m, 862m, 824m, 762s, 741s, 710m, 690m, 528m, 512m,
496m, 478s, 434m. Anal. calc. for C29H25Cl2FeN2OPdP·0.3CHCl3
(717.4): C 49.05, H 3.55, N 3.90. Found C 49.13, H 3.60, N 3.66%.
added a mixture of aryl halide (1.0 mmol), phenylboronic acid
(1.5 mmol), K2CO3 (2.0 mmol), and diethylene glycol dimethyl
ether (0.5 mmol; internal standard). The reaction mixture was
◦
heated for 16 h (100 C, temperature of the bath). After cooling
to room temperature, the conversions were determined from
1
integration of the H NMR spectra. The results listed in Table 5
Complex 6. This compound was obtained similarly starting
with 2 (52 mg, 0.10 mmol) and [PdCl2(cod)] (29 mg, 0.10 mmol).
are an average of two independent runs. Reactions with defined
complexes 3–6 were performed similarly.
◦
1
Yield: 58 mg (83%); mp 138 C (decomp.). H NMR (CDCl3): d
3.73–3.84 (m, 4 H, 2 × CH2), 4.51 (vt, J = 1.9 Hz, 2 H, CpC),
4.74 (bs, 2 H, CpP), 4.78 (m, 2 H, CpP), 5.47 (vt, J = 1.8 Hz,
For reactions showing complete conversions, the coupling
products were isolated as follows. The reaction mixture was
filtered, evaporated, and the residue extracted with CHCl3. The
extract was washed with water, dried (MgSO4), and passed through
a short silical gel column (CHCl3). Evaporation of the eluate under
vacuum gave the biphenyls as colourless solids (light yellow for the
4-nitro derivative).
2 H, CpC), 7.26–7.78 (m, 12 H, PPh2 and C5H4N), 7.93 (t, 3JHH
=
6.0 Hz, 1 H, NH), 9.01 (dddd, J = 5.6, 3.5, 1.7, 0.9 (H3, H4,
H5, and P) Hz, 1 H, H6 of C5H4N) (tentative assignment given
for C5H4N). 13C{ H} NMR (CDCl3): d 39.64, 40.87 (2 × CH2);
1
70.03 (d, JPC = 62 Hz, Cipso of CpP), 71.10, 71.76 (2 × CH of CpC);
72.94 (d, JPC = 8 Hz, CH of CpP), 76.85 (CH of CpP, the signal
is partly obscured by the solvent resonance), 78.17 (Cipso of CpC),
122.50 (d, JPC = 2 Hz, C5 of C5H4N), 126.55 (d, JPC = 5 Hz,
C3 of C5H4N), 127.72 (d, JPC = 11 Hz, CH of PPh2), 130.51 (d,
1JPC = 60 Hz, Cipso of PPh2), 130.70 (d, JPC = 3 Hz), 133.63 (d,
JPC = 10 Hz) (2 × CH of PPh2); 138.74 (C4 of C5H4N), 151.51 (d,
In situ NMR study of the ligand–Pd(OAc)2 systems. Palla-
dium(II) acetate (25 lmol) and the appropriate ligand (30 lmol)
were dissolved in CDCl3 (1 mL). The resulting orange solutions
were stirred for 30 min at room temperature and analysed by
1
31P{ H} NMR and ESI MS spectra.
In both cases, the NMR spectra showed the presence of two new
species with similar chemical shifts (dP 15.3 and 16.8 with 1, and
dP 18.3 and 19.2 with 2) but no free ligands. ESI spectra displayed
mainly ions due to [Pd(L) − H]+ (L = 1, 2).
=
JPC = 3 Hz, C6 of C5H4N), 163.67 (Cipso of C5H4N), 169.74 (C O).
31P{ H} NMR (CDCl3): d +21.8. IR (Nujol, cm−1): 3393m (N–H),
1
=
1652vs (C O), 1603m, 1539s, 1483s, 1354m, 1297s, 1194m, 1175m,
1166m, 1100m, 1034m, 993w, 838m, 810m, 770s, 752s, 741m,
708m, 694s, 624m, 550m, 520s, 505s, 490m, 478s, 453m, 440m,
428m. Anal. calc. for C30H27Cl2FeN2OPdP·0.6CHCl3 (767.4): C,
47.89; H, 3.62; N, 3.65; found C 47.79, H 3.70, N, 3.36%.
The obtained data suggest that the ligands coordinate as P-
donors. However, they provide no clue about the nature of the true
catalytically active species. Attempts to isolate defined products
failed even at exact ligand-to-metal stoichiometry.
Catalytic experiments
X-Ray crystallography
Under an argon atmosphere, the catalyst was prepared in situ
by mixing Pd(OAc)2 (10 lmol, 1 mol%) with the respective
phosphinoamide (12 lmol) in dioxane (2 mL) to which was
Single-crystals suitable for X-ray diffraction analyses were
grown by liquid-phase diffusion of hexane into ethyl acetate
(1: orange plate, 0.03 × 0.17 × 0.35 mm; 2: orange plate,
a
Table 6 Crystallographic data and structure refinement parameters for 1, 2, 4·4CHCl3, 5·AcOH, and 6·8CHCl3
Compound
1
2
4·4CHCl3
5·AcOH
6·8CHCl3
Formula
2M
C29H25FeN2OP
504.33
C30H27FeN2OP
518.36
C64H56Cl14Fe2N4O2P2Pdf
1689.47
C31H29Cl2FeN2O3PPd
741.68
C68H62Cl28Fe2N4O2P2Pd2
2346.26
Monoclinic
P21/c (no.14)
12.541(1)
17.300(3)
21.570(4)
Crystal system
Space group
Triclinic
Triclinic
Triclinic
Triclinic
¯
¯
¯
¯
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
˚
a/A
8.217(4)
11.453(2)
13.079(4)
81.11(2)
73.58(4)
80.57(3)
1157.1(7)
2
8.709(4)
11.067(2)
13.459(7)
87.88(2)
75.51(4)
77.53(2)
1226.1(9)
2
11.069(2)
12.650(3)
13.042(4)
93.48(2)
102.39(2)
91.18(2)
1779.3(8)
1
1.577
1.260
0.706–0.773
24109
7356/5406
2.62
9.343(2)
10.403(3)
15.822(5)
100.40(2)
99.44(2)
93.87(2)
1484.6(7)
2
1.659
1.364
0.759–0.959
20227
6157/4185
3.55
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
101.99(1)
3
˚
U/A
4578(1)
2
1.702
1.593
0.636–0.725
60436
9544/5832
4.89
4.35
7.95, 13.08
1.75, −1.28
Z
Dc/g mL−1
1.448
1.404
l(Mo Ka)/mm−1
Tb
0.747
0.707
e
e
—
—
Diffractions collected
15853
16668
5081/3273
4.18
3.08
5.49, 6.46
Independent/obsdc diffrns 4825/3607
d
Rint (%)
4.28
2.91
4.24, 7.24
0.43, −0.27
Rd observed diffrns (%)
3.29
4.46, 9.82
0.63, −0.30
2.53
4.62, 4.90
0.78, −0.36
R, wRd all data (%)
−3
˚
Dq/e A
0.37, −0.22
ꢀ
ꢀ
a Common details: T = 150(2) K. b Transmission factor range. c I > 2r(I). d Definitions: Rint
=
|Fo − Fo2(mean)|/ Fo2, where Fo2(mean) is the
2
ꢀ
ꢀ
ꢀ
ꢀ
average intensity of symmetry-equivalent diffractions. R = ꢁFo| − |Fcꢁ/ |Fo|, wR = [ {w(Fo − Fc2)2}/ w(Fo2)2]1/2
.
e Not corrected. f Solvent
2
contribution removed by SQUEEZE routine (see Experimental section).
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0.05 × 0.14 × 0.27 mm) or into chloroform solutions (4·4CHCl3:
red prism, 0.10 × 0.15 × 0.25 mm, 6·8CHCl3: orange prism, 0.10 ×
0.16 × 0.20 mm) and by recrystallisation from hot acetic acid
(5·AcOH: red plate, 0.02 × 0.10 × 0.25 mm).
3 (4-Pyridyl)-substituted ferrocenecarboxamides: (a) Y.-M. Tsou and
F. C. Anson, J. Phys. Chem., 1985, 89, 3818; (b) G. Li, Y. Song, H.
Hou, L. Li, Y. Fan, Y. Zhu, X. Meng and L. Mi, Inorg. Chem., 2003,
42, 913.
4 The related ferrocenecarboxamides substituted with a (2,2ꢀ-bipyridyl-
6-yl)methyl group have also been prepared and utilised as ligands and
electrochemical anion receptors: (a) M. Buda, A. Ion, J.-C. Moutet,
E. Saint-Aman and R. Ziessel, J. Electroanal. Chem., 1999, 469,
132; (b) A. Ion, J.-C. Moutet, E. Saint-Aman, G. Royal, S. Tingry,
J. Pecaut, S. Menage and R. Ziessel, Inorg. Chem., 2001, 40, 3632;
(c) A. Ion, M. Buda, J.-C. Moutet, E. Saint-Aman, G. Royal, I.
Gautier-Luneau, M. Bonin and R. Ziessel, Eur. J. Inorg. Chem., 2002,
1357.
Full-set diffraction data ( h
k
l, 2h ≤ 53◦) were collected
on an Oxford Diffraction XCalibur 2 diffractometer with a CCD
detector Sapphire 2 equipped with an Oxford Instruments Cryojet
HT Cooler using graphite-monochromatised Mo-Ka radiation
˚
(k = 0.71073 A) throughout. If appropriate, analytical absorption
corrections based on indexation of the crystal faces were applied
to the data sets. Details of the data collection, structure solution
and refinement are given in Table 6.
5 H. Miyaji, M. Dudic, G. Gasser, S. J. Green, N. Moran, I. Prokesˇ,
G. Labat, H. Stoeckli-Evans, S. M. Strawbridge and J. H. R. Tucker,
Dalton Trans., 2004, 2831.
6 H. Miyaji, G. Gasser, S. J. Green, Y. Molard, S. M. Strawbridge and
J. H. R. Tucker, Chem. Commun., 2005, 5355.
7 J. E. Kingston, L. Ashford, P. D. Beer and M. G. B. Drew, J. Chem.
Soc., Dalton Trans., 1999, 251.
The structures were solved by direct methods (SIR-9735) and
refined by full-matrix least-squares on F2 (SHELXL9736). Non-
hydrogen atoms were refined with anisotropic displacement pa-
rameters. Amide and carboxyl (OH) hydrogen atoms were located
on the difference electron density maps and refined freely (only
for 1) or as riding atoms. All other hydrogen atoms were fixed in
theoretical positions and treated as riding atoms with Uiso(H) set
to a multiple (1.2 or 1.5) of Ueq of the riding atom. The refinement
was routine with the exception of complex 4, which crystallises
as the unstable solvate 4·4CHCl3. The solvate molecules located
in structural voids were severely disordered in structural voids
and, hence, their contribution to the scattering was removed by
8 H. S. Sørensen, J. Larsen, B. S. Rasmussen, B. Laursen, S. G. Hansen,
T. Skrydstrup, C. Amatore and A. Jutand, Organometallics, 2002, 21,
5243.
ˇ
9 J. Podlaha, P. Steˇpnicˇka, I. C´ısarˇova´ and J. Ludv´ık, Organometallics,
1996, 15, 543.
ˇ
10 P. Steˇpnicˇka, Eur. J. Inorg. Chem., 2005, 3787.
11 L. Meca, D. Dvorˇa´k, J. Ludv´ık, I. C´ısarˇova´ and P. Steˇpnicˇka,
ˇ
Organometallics, 2004, 23, 2541.
ˇ
12 (a) D. Drahonˇovsky´, I. C´ısarˇova´, P. Steˇpnicˇka, H. Dvorˇa´kova´, P. Malonˇ
and D. Dvorˇa´k, Collect. Czech. Chem. Commun., 2001, 66, 588. See
also: (b) W. Zhang, Y. Yoneda, T. Kida, Y. Nakatsuji and I. Ikeda,
Tetrahedron: Asymmetry, 1998, 9, 3371.
SQUEEZE routine37 as incorporated in the PLATON program38
3
˚
(void volume 609.8 A with 54.5 electrons).
13 (a) H.-B. Kraatz, J. Inorg. Organomet. Polym., 2005, 15, 83; (b) see also
ref. 11.
Final geometric calculations were perfomred with a recent ver-
sion of the PLATON program. All numerical values are rounded
with respect to their estimated standard deviations (e.s.d.s) given
with one decimal; parameters involving fixed hydrogen atoms are
given without esds.
14 The related, symmetric diamides [Fe{C5H4C(O)NH(CH2)n(C5H4N-
2)}2] (n = 1 and 2) have been synthesised and studied as ligands for
palladium: (a) T. Moriuchi, I. Ikeda and T. Hirao, Inorg. Chim. Acta,
1996, 248, 129; (b) T. Moriuchi, I. Ikeda and T. Hirao, J. Organomet.
Chem., 1996, 514, 153.
15 (a) F. R. Hartley, The Chemistry of platinum and palladium, Ap-
plied Science, London, 1973; (b) C. F. J. Barnard and M. J. H.
Russell, Palladium, in Comphrehensive Coordination Chemistry, ed.
G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon Press,
Oxford, 1987, vol. 5, ch. 51pp. 1099–1130; (c) A. T. Hutton and C. P.
Morley, Palladium(II): Phosphorus Donor Complexes, Comphrehen-
sive Coordination Chemistry, ed. G. Wilkinson, R. D. Gillard and
J. A. McCleverty, Pergamon Press, Oxford, 1987, vol. 5, ch. 51.9, pp.
1157–1188.
CCDC reference numbers 633466–633470.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b701012e
Acknowledgements
This work was supported by the Ministry of Education, Youth and
Sports of the Czech Republic as a part of the long-term research
projects no. LC06070 and MSM0021620857, the Mobility Fund of
Charles University (J.K.), and by the Grant Agency of the Czech
Republic (project no. 202/05/0421).
16 P. S. Pregosin and R. W. Kunz, in 31P and 13C NMR of Transition
Metal Phosphane Complexes, NMR Basic Principles and Progress, ed.
P. Diehl, E. Fluck and R. Kosfeld, Springer Verlag, Berlin, 1979, vol.
16, ch. E, p. 65 ff and references therein.
ˇ
17 P. Steˇpnicˇka, J. Podlaha, R. Gyepes and M. Pola´sˇek, J. Organomet.
Chem., 1998, 552, 293.
18 (a) C. A. Bessel, P. Aggarwal, A. C. Marschilok and K. J. Takeuchi,
Chem. Rev., 2001, 101, 1031 (a review). For recent examples of trans-
coordinating bis-phosphines, see: (b) Z. Freixa, M. S. Beentjes, G. D.
Batema, C. B. Dieleman, G. P. F. van Strijdonck, J. N. H. Reek,
P. C. J. Kamer, J. Fraanje, K. Goubitz and P. W. N. M. van Leeuwen,
Angew. Chem., Int. Ed., 2003, 42, 1284; (c) Z. Freixa, P. C. J. Kamer,
M. Lutz, A. L. Spek and P. W. N. M. van Leeuwen, Angew. Chem.,
Int. Ed., 2005, 44, 4385; (d) S. Burger, B. Therrien and G. Su¨ss-
Fink, Eur. J. Inorg. Chem., 2003, 3099; (e) S. Burger, B. Therrien and
G. Su¨ss-Fink, Helv. Chim. Acta, 2005, 88, 478; (f) R. C. Smith and
J. D. Protasiewicz, Organometallics, 2004, 23, 4215; (g) O. Grossman,
C. Azerraf and D. Gelman, Organometallics, 2006, 25, 375. For
trans-spanning diphosphines generated in the coordination sphere by
metathesis of P-coordinated alkenylphosphines, see: (h) E. B. Bauer, J.
Ruwwe, J. M. Mart´ın-Alvarez, T. B. Peters, J. C. Bohling, F. A. Hampel,
S. Szafert, T. Lis and J. A. Gladysz, Chem. Commun., 2000, 2261; (i) J.
Ruwwe, J. M. Mart´ın-Alvarez, C. R. Horn, E. B. Bauer, S. Szafert, T.
Lis, F. Hampel, P. C. Cagle and J. A. Gladysz, Chem.–Eur. J., 2001, 7,
3931; (j) T. Shima, E. B. Bauer, F. Hampel and J. A. Gladysz, Dalton
Trans., 2004, 1012.
References
1 N-(6-Methyl-2-pyridyl) and N-(2-picolyl) substituted ferrocene-
carboxamides: (a) J. D. Carr, L. Lambert, D. E. Hibbs, M. B.
Hursthouse, K. M. A. Malik and J. H. R. Tucker, Chem. Commun.,
1997, 1649; (b) P. D. Beer, A. R. Graydon, A. O. M. Johnson and D. K.
Smith, Inorg. Chem., 1997, 36, 2112; (c) J. D. C a r r, S. J. C o l e s, W. W.
Hassan, M. B. Hursthouse, K. M. A. Malik and J. H. R. Tucker,
J. Chem. Soc., Dalton Trans., 1999, 57; (d) J. D. Carr, S. J. Coles,
M. B. Hursthouse, M. E. Light, J. H. R. Tucker and J. Westwood,
Angew. Chem., Int. Ed., 2000, 39, 3296; (e) J. D. Carr, S. J. Coles, M. B.
Hursthouse and J. H. R. Tucker, J. Organomet. Chem., 2001, 637–639,
304; (f) J. Westwood, S. J. Coles, S. R. Collinson, G. Gasser, S. J. Green,
M. B. Hursthouse, M. E. Light and J. H. R. Tucker, Organometallics,
2004, 23, 946.
2 N,Nꢀ-Bis[2-(2-pyridyl)ethyl]- and N,Nꢀ-bis(2-picolyl)-1,1ꢀ-ferrocene-
dicarboxamide: (a) T. Moriuchi, I. Ikeda and T. Hirao, Inorg. Chim.
Acta, 1996, 248, 129; (b) N-[2-(m-pyridyl)ethyl]ferrocenecarbox-amides
(m = 2 and 4): T. Moriuchi, I. Ikeda and T. Hirao, J. Organomet. Chem.,
1996, 514, 153.
19 I. R. Butler, Organometallics, 1992, 11, 74.
2810 | Dalton Trans., 2007, 2802–2811
This journal is
The Royal Society of Chemistry 2007
©

View Article Online
20 I. R. Butler, M. Kalaji, L. Nehrlich, M. Hursthouse, A. I.
Karaulov and K. M. A. Malik, J. Chem. Soc., Chem. Commun., 1995,
459.
32 (a) A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108, 27; (b) C. S.
Slone, D. A. Weinberger and C. A. Mirkin, Prog. Inorg. Chem., 1999,
48, 233; (c) P. Braunstein and F. Naud, Angew. Chem., Int. Ed., 2001,
40, 680.
33 (a) Ferrocenes-Homogeneous Catalysis, Organic Synthesis, Materials
Science, ed. A. Togni and T. Hayashi, VCH, Weinheim, 1995; (b) A.
Togni, New Chiral Ferrocenyl Ligands for Asymmetric Catalysis in
Metallocenes-Synthesis, Reactivity, Applications, ed. A. Togni and
R. L. Halterman, Wiley-VCH, Weinheim, 1998, vol. 2, ch. 11, pp.
685–721; (c) T. J. Colacot, Chem. Rev., 2003, 103, 3101; (d) R. C. J.
Atkinson, V. C. Gibson and N. J. Long, Chem. Soc. Rev., 2004, 33, 313;
(e) R. G. Arraya´s, J. Adrio and J. C. Carretero, Angew. Chem., Int. Ed.,
2006, 45, 7674.
34 (a) D. Braga, Chem. Commun., 2003, 2751; (b) D. Braga, L. Maini, M.
Polito, E. Tagliavini and F. Grepioni, Coord. Chem. Rev., 2003, 246, 53;
(c) D. Braga and F. Grepioni, Chem. Commun., 1996, 571; (d) D. Braga,
F. Grepioni and G. R. Desiraju, Chem. Rev., 1998, 98, 1375.
35 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano,
C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori and
R. Spagna, J. Appl. Crystallogr., 1999, 32, 115.
36 G. M. Sheldrick, SHELXL97. Program for Crystal Structure Refine-
ment from Diffraction Data, University of Go¨ttingen, Germany, 1997.
37 P. von der Sluis and A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46,
194.
21 K. Tani, M. Yabuta, S. Nakamura and Y. Yamagata, J. Chem. Soc.,
Dalton Trans., 1993, 2781.
ˇ
22 P. Steˇpnicˇka, I. C´ısarˇova´ and R. Gyepes, Eur. J. Inorg. Chem., 2006,
926.
23 R. J. Coyle, Y. L. Slovokhotov, M. Y. Antipitin and V. V. Grushin,
Polyhedron, 1998, 17, 3059.
24 V. C. Gibson, N. J. Long, A. J. P. White and C. K. Williams, J. Chem.
Soc., Dalton Trans., 2002, 3280.
25 The p-stacking interactions operate between pyridyl (centroid–centroid
˚
˚
distance/slippage: 4.326(2)/2.64 A), Cp2 (4.420(2)/2.73 A) and phenyl
˚
C(18–23) (4.470(2)/2.75 A) rings.
26 Metal-Catalyzed Cross-Coupling Reactions, ed. A. de Meijere and
F. Diederich, F., Wiley-VCH Weinheim, Germany, 2nd edn, 2004.
27 A. F. Littke and G. C. Fu, Angew. Chem., Int. Ed., 2002, 41, 4176.
ˇ
28 P. Steˇpnicˇka, M. Lamacˇ and I. C´ısarˇova´, Polyhedron, 2004, 23, 921.
29 (a) R. C. J. Atkinson, V. C. Gibson, N. J. Long, A. J. P. White and
D. J. Williams, Organometallics, 2004, 23, 2744; (b) V. C. Gibson, N. J.
Long, A. J. P. White, C. K. Williams, D. J. Williams, M. Fontani and P.
Zanello, J. Chem. Soc., Dalton Trans., 2002, 3280.
30 T. E. Pickett, F. X. Roca and C. J. Richards, J. Org. Chem., 2003, 68,
2592.
31 (a) S. Teo, Z. Weng and T. S. A. Hor, Organometallics, 2006, 25, 1199;
(b) Z. Weng, S. Teo, L. L. Koh and T. S. A. Hor, Organometallics, 2004,
23, 4342.
38 A. L. Spek, PLATON, a multipurpose crystallographic tool, Utrecht
University, Utrecht, The Netherlands, 2003 and updates. Distributed
via the Internet at http://www.cryst.chem.uu.nl/platon/.
This journal is
The Royal Society of Chemistry 2007
Dalton Trans., 2007, 2802–2811 | 2811
©