Phosphane ligands with enaminoketone scaffold and their palladium complexes

Article abstract of DOI:10.1002/zaac.201200070

The reaction of (Z)-4-aminopent-3-en-2-one with different chlorodiorganylphosphanes established three new ligands composed of a hard and soft coordination site. The soft phosphane site is easily coordinated to palladium(II) as a first step in the potential formation of heterodinuclear complexes. Surprisingly, the formed square-planar dichloridopalladium(II) complexes exhibit exclusively trans configuration. A cis configurated palladium(II) complex can be formed, when the linker between the phosphane and the enaminoketone unit is enlarged and allows more flexibility. The reaction between (Z)-4-(2'-hydroxyethylamino)pent-3-en-2-one and chlorodiorganylphosphanes revealed two new ligands that coordinate to palladium(II). With phenyl substituents at the phosphorus atom a cis palladium complex was obtained, whereas for isopropyl substituents a trans complex was formed. Molecular structures of all complexes were analyzed by single-crystal X-ray diffraction.

Full text of DOI:10.1002/zaac.201200070

ARTICLE
DOI: 10.1002/zaac.201200070
Phosphane Ligands with Enaminoketone Scaffold and their Palladium
Complexes
Michael Schmidt[a] and Jürgen Heck*[a]
Dedicated to Professor Ulrich Zenneck on the Occasion of His 65th Birthday
Keywords: Crystal structures; Palladium; Dichloridopalladium(II) complexes; Phosphorus; Phosphane ligands
Abstract. The reaction of (Z)-4-aminopent-3-en-2-one with different larged and allows more flexibility. The reaction between (Z)-4-(2Ј-
chlorodiorganylphosphanes established three new ligands composed of
a hard and soft coordination site. The soft phosphane site is easily revealed two new ligands that coordinate to palladium(II). With phenyl
coordinated to palladium(II) as a first step in the potential formation substituents at the phosphorus atom a cis palladium complex was ob-
of heterodinuclear complexes. Surprisingly, the formed square-planar tained, whereas for isopropyl substituents a trans complex was formed.
dichloridopalladium(II) complexes exhibit exclusively trans configura- Molecular structures of all complexes were analyzed by single-crystal
hydroxyethylamino)pent-3-en-2-one and chlorodiorganylphosphanes
tion. A cis configurated palladium(II) complex can be formed, when X-ray diffraction.
the linker between the phosphane and the enaminoketone unit is en-
nation of corresponding hard and soft metal atoms in one com-
Introduction
plex. As the soft metal atoms should be a group 10 element,
the coordination could be performed by soft phosphorus donor
atoms. The hard metal atom should be coordinated by a deriva-
tive of a hard acetylacetonato ligand. For complexes with only
one hard and one soft metal we needed a cis configuration,
while a trans configuration could only be used for a tri- or
oligonuclear species. We chose for a ligand combining a phos-
phane and a ketoiminato ligand via a direct bond between ni-
Metal complexes are necessary for a plethora of different
reactions. In special cases the application of only one metal is
not sufficient. Like, for example, in Wacker process, where
palladium is used as the catalyst metal in the formation of
acetaldehyde from ethylene, and copper(II) ions are needed for
the reoxidation of palladium(0) to palladium(II).[1] It has even
been demonstrated that some catalytic reactions can only be
carried out with two different metal atoms combined in a sin-
gle molecule.[2–5] Heterodinuclear complexes are also applied
as functional models in bioinorganic chemistry for the metal
reaction sites and therefore used as bio-mimics.[6,7] Heterodi-
nuclear complexes, bearing unpaired electrons, exhibit electron
exchange interactions between the two metal centers and can
display peculiar magnetic properties.[8–12] The electronic influ-
ence of a second metal has nicely been demonstrated in dif-
ferent electrochemical studies.[13–17] Finally, the complexation
of different metals is also an interesting topic in supramolec-
ular chemistry.[18]
trogen and phosphorus. The reaction of (Z)-4-aminopent-3-en-
[19]
2-one (1)
with chlorodiphenylphosphane or chlorodialkyl-
phosphane afforded the desired ligand (Scheme 1).
Scheme 1. Synthesis of (Z)-4-(diorganylphosphanylamino)pent-3-en-
2-one.
Results and Discussion
The synthesis of the ligands 2–4 revealed low to moderate
yields due to the formation of by-products, in particular for 2.
Some of them could be characterized by 31P NMR spec-
troscopy and were compared with literature data. The iden-
tified by-products are tetraphenyldiphosphane[20] and tet-
raphenyldiphosphane monoxide.[21] 1H NMR spectra of the de-
sired ligands are similar. Coupling of the phosphorus nucleus
with the proton bonded to the nitrogen atom could hardly be
observed because of a broadening of the signal. All ligands
Our approach to novel heterodinuclear complexes was to
design ligands with hard and soft binding sites for the coordi-
* Prof. Dr. J. Heck
Fax: +49 40-42838-6945
E-Mail: juergen.heck@chemie.uni-hamburg.de
[a] Department of Chemistry
Institute of Inorganic and Applied Chemistry
University of Hamburg
Martin-Luther-King-Platz 6
20146 Hamburg, Germany
Z. Anorg. Allg. Chem. 2012, 638, (7-8), 1151–1158
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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M. Schmidt, J. Heck
ARTICLE
demonstrate a coupling between phosphorus and the protons an increased broadening of the signal. However, in compound
in the enaminoketone scaffold except for the distal methyl
group next to the carbonyl function. In contrast to the starting
material 1 the methyl group next to the C–N bond was always
shifted more downfield than the methyl group next to the carb-
onyl function. A different influence of the substituents of the
phosphanyl groups can only be observed in the shift of the
proton bonded to the nitrogen atom. Whereas the signal of the
N–H proton for 2 is found above 11 ppm, the resonance signal
of the corresponding protons of the alkyl derivates 3 and 4
appear below this value. Chemical shifts in 31P NMR spec-
troscopy for compounds 2–4 fall in the range of 26.9 to 52.9
ppm and are shifted to higher field compared to amino phos-
phanes like 1,2-bis{(diphenylphosphino)amino}ethane (63.7
ppm) or 1,2-bis{(diphenylphosphino)amino}benzene (93.4
ppm).[22]
7 a 1:2:1 triplet pattern on each signal of a septet could be
observed for the methine protons of the isopropyl groups. 13C
NMR spectra of 6, 7 and 9 display a 1:2:1 pattern for the carbon
atom bonded to the phosphorus atom.
The trans configuration is in agreement with the data re-
corded from far infrared spectroscopy. For all complexes 6, 7
and 9 only a single absorption band is observed for the palla-
dium-chlorine stretching vibration at about 360 cm–1.
Compound 6 could only be isolated with a small amount
(less than 3%) of a second palladium complex as byproduct.
The impurity appeared as an AB spin system in the 31P NMR
spectrum. It is probably an analogue palladium complex in
trans configuration with two different phosphorus containing
ligands. One signal center has the same shift as the signal cor-
responding to 6. Therefore, one ligand could be 2 while the
other is still unknown and further investigations were needed
to identify this compound.
First attempts to crystallize 6 afforded small amounts of
[{Pd(μ-Cl)(PPh2O)(PPh2OH)}2].[27] Formation of this com-
pound is explained by a hydrolysis of 6 with traces of water
in dichloromethane during crystallization. Therefore, all syn-
thesized palladium complexes should be taken as sensitive to
water.
The coordination of palladium(II) was carried out by reac-
tion of these ligands with suitable palladium precursors like
bis(benzonitrile)dichloridopalladium(II)
(5)[23]
or
dichlorido(η4-cyclooctadiene)palladium(II) (8)[24] (Scheme 2).
The reactions reveal square-planar, exclusively P-coordinated
palladium complexes in trans configuration.
A palladium complex with a cis configuration, which is nec-
essary for the coordination of a second metal atom next to the
first needed a different ligand design. To reduce the Tolman
cone angle a phosphonite ligand was considered, which con-
tains a longer spacer between the nitrogen function of the en-
aminoketone unit and the phosphorus atoms. With this type of
ligand it is also expected to improve the stability of the com-
plexes against hydrolysis. The synthesis of the new phos-
phonite ligands was achieved by an ethoxy bridge between
nitrogen and phosphorus of the previous ligand design. An ad-
ditional benefit would be an increased flexibility for a second
coordination. Compound 11 and 12 were obtained by reaction
of (Z)-4-(2Ј-hydroxyethylamino)pent-3-en-2-one (10)[28] with
chlorodiphenylphosphane and chlorodiisopropylphosphane,
respectively (Scheme 3).
Scheme 2. Synthesis of trans dichloridopalladium(II) complexes with
the ligands 2–4. *Not isolated in pure form.
1H NMR spectroscopic characterization of 11 and 12
showed only minor deviations of the proton shifts in the en-
aminoketone scaffold relative to 10. The proton signals of the
ethoxy bridge were slightly shifted downfield in both com-
pounds. The phenyl groups of 11 exhibit a stronger influence
than the isopropyl groups of 12.
A different purification method was used for these two li-
gands. While a chromatography on silica gel was successful
for 11, this method resulted in a complete decomposition of
12. Finally, 12 could only be obtained by vacuum distillation,
however, the product was still contaminated with a minimum
of a by-product (approx. 8%). Nevertheless, the product was
in sufficient quality for the coordination of palladium(II).
The formation of the palladium complex from 11 was car-
ried out under the same condition mentioned above. The reac-
tion afforded, on the contrary to 6, the expected palladium
The crystal system for all three crystalline palladium com-
plexes is monoclinic with the space group C2/c for compound
6 and 7 while 9 crystallizes in space group P21/c (Table 1).
The structure determination by means of single-crystal X-ray
diffraction verifies the trans configuration of the complexes
(Figure 1). Steric effects of the ligands like a large Tolman
cone angle[25] seem to be the reason for the formation of exclu-
sively trans palladium complexes.[26] Compounds 6 and 9 ex-
hibit dihedral angles between Cl–Pd–P–N of about 61° and
55°, respectively, whereas the bulky isopropyl groups in 7 re-
sult in a corresponding angle of 36°.
The square-planar trans configurated dichloridopalladium(II)
1
complexes 6, 7 and 9 are also characterized by H NMR spec-
troscopy. The coupling pattern for the proton of 6, which is
bonded to the nitrogen atom, resulted in a spin system of higher
order, which looked like a broadened 1:2:1 triplet. The coupling
pattern of this proton for 7 und 9 could not be verified due to complex 13 in cis configuration (Scheme 4).
1152 www.zaac.wiley-vch.de
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Z. Anorg. Allg. Chem. 2012, 1151–1158

Phosphane Ligands with Enaminoketone Scaffold and their Pd Complexes
Table 1. Crystal data of palladium complexes 6, 7 and 9.
6
7
9
Empirical formula
Formula weight
M /g·mol–1
Temperature T /K
Crystal system
Space group
C34H36Cl2N2O2P2Pd
743.89
C22H44Cl2N2O2P2Pd
607.83
C18H36Cl2N2O2P2Pd
551.73
153(2)
monoclinic
C2/c
100(2)
monoclinic
C2/c
100(2)
monoclinic
P21/c
a /pm
b /pm
1976.66(6)
851.26(3)
2036.13(6)
104.755(1)
3.31312(18)
4
1903.98(11)
1067.50(6)
1582.41(9)
114.324(1)
2.9307(3)
4
750.49(1)
1499.63(3)
2238.17(4)
97.819(1)
2.49554(7)
4
c /pm
β /°
Volume V /nm3
Z
Density (calculated)
1.491
1.378
1.468
ρ /g·cm–3
Absorption coefficient
μ /mm–1
0.852
0.945
1.101
θ range for data
collection /°
2.62–31.99
2.24–32.50
2.28–32.50
Reflections collected
Independent reflections
Data / restraints /
parameters
23226
5600 [R(int) = 0.0310]
5600 / 0 / 198
38291
5268 [R(int) = 0.0240]
5268 / 0 / 148
64803
9017 [R(int) = 0.0292]
9017 / 0 /252
Goodness-of-fit on F2
R1, wR2 (IϾ2σ(I))
R1, wR2 (all data)
CCDC ref.
1.058
1.046
1.261
0.0264, 0.0727
0.0283, 0.0738
819804
0.0213, 0.0507
0.0296, 0.0546
819792
0.0283, 0.0636
0.0310, 0.0646
819796
Crystals were measured using a Bruker SMART CCD with Mo-Kα radiation (λ = 71.073 pm). Full-matrix least-squares were used as method
of refinement. Programs: SAINT and SADABS (Bruker AXS) as well as SHELXS-97 and SHELXL-97 (Sheldrick). Hydrogen atoms were re-
fined by the rider model.
Scheme 3. Synthesis of (Z)-4-(2Ј-((diorganylphosphanyl)oxy)ethyl-
amino)pent-3-en-2-one. *Not isolated in pure form.
Figure 1. ORTEP drawing of the molecular structure of (SP-4–1)-
dichloridobis((Z)-4-((diphenylphosphanyl)amino)pent-3-en-2-one-κP)
palladium(II) (6). Hydrogen atoms were omitted for clarity except the
hydrogen bonded to nitrogen. Displacement ellipsoids were drawn at
the 50% probability level.
A first indication for the cis configuration of 13 was ob-
tained by 13C NMR spectroscopy. The coupling pattern for the
carbon atom bonded to the phosphorus atom was not a 1:2:1
triplet like in previous palladium complexes. This result was
attested by far infrared spectroscopy. Two absorption bands
were observed, one for the symmetrical and one for the asym- the ligand 11.
Scheme 4. Synthesis of the cis dichloridopalladium(II) complexes with
Z. Anorg. Allg. Chem. 2012, 1151–1158
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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1153

M. Schmidt, J. Heck
ARTICLE
metrical palladium-chlorine stretching vibration mode of 13 palladium–phosphorus bond (d = 223.50(3) pm) in the cis con-
(309 cm–1 (νs Pd–Cl), 284 cm–1 (νas Pd–Cl)).
figuration for complex 13 compared to the palladium–phos-
The formation of a palladium complex with ligand 12 phorus bond length (d = 231.04(4) pm) in the trans complex
gained a different result. In the 13C NMR spectra again a 1:2:1 14. This result is in agreement with the trans influence, which
triplet signal for the carbon atom bonded to phosphorus atom predicts a stronger phosphorus-metal bond, when the phos-
was observed and with the far infrared spectroscopy only one phonite as a σ-donor-π-acceptor ligand is in trans position to a
absorption band at 362 cm–1 was measured. Thus, complex 14 chlorido ligand with σ- and π-donating properties. In all crystal
exclusively forms a trans configuration (Scheme 5).
structures we observe an intramolecular hydrogen bonding be-
tween the proton bonded to the nitrogen and the oxygen atom
of the enaminoketone. Distances between the proton and the
oxygen atom are in the range of 1.89 to 2.03 Å. No indication
could be found for an interligand or an intermolecular hydro-
gen bond.
Scheme 5. Synthesis of the trans dichloridopalladium(II) complexes
with the ligand 12.
The different configuration of the complexes 13 and 14
could also be derived from their 1H NMR spectra. The methyl-
ene protons bonded to oxygen in the ethoxy bridge of both
ligands showed a diverse behavior. Compared to their corre-
sponding free ligand the signals of the methylene protons are
shifted downfield in palladium complex 14 while the reso-
nance signals of the related protons in 13 get a slight shift to
a higher field. In addition both complexes illustrate a different
coupling pattern (Figure 2).
Figure 3. ORTEP drawing of the molecular structure of (SP-4–2)-
dichloridobis((Z)-4-(2Ј-((diphenylphosphanyl)oxy)ethylamino)pent-3-
en-2-one-κP)palladium(II) (13). Hydrogen atoms were omitted for
clarity except the hydrogen atom bonded to the nitrogen atom. Dis-
placement ellipsoids were drawn at the 50% probability level.
Conclusions
We successfully developed the synthesis of compounds con-
taining a combination of a soft phosphorus and a hard enami-
noketone ligand. (Z)-4-((diorganylphosphanyl)amino)pent-3-
en-2-one was synthesized with different substituents like ethyl,
isopropyl and phenyl at the phosphorus atom. These com-
pounds form square-planar dichlorido palladium(II) complexes
Figure 2. Details of the methylene protons in the 1H NMR spectra
from complexes 13 (right) und 14 (left).
The configuration of both palladium complexes are con- in a trans configuration, which could be verified by NMR and
firmed by X-ray structure analysis. In the case of the phenyl far infrared spectroscopy. Furthermore, the molecular struc-
derivative 13 the reduced steric requirement results in a tures of these compounds were solved by the determination of
dichloridopalladium(II) complex with cis configuration (Figure X-ray diffraction. A complex in a cis configuration could not
3). This could be explained by the flexibility of the ethoxy be obtained probably due to the steric requirements of the en-
bridge and, therefore, a smaller Tolman cone angle (round aminoketone part of the ligands. The strategy for the synthesis
about 133° estimated from PPh2OEt[25,26]). Due to the bulky of cis configurated complexes was based on the development
isopropyl groups complex 14 can only be obtained in trans of a new ligand with an increased flexibility. Introduction of
configuration. Compound 13 crystallized in a monoclinic sys- an ethoxy linker in our previous desired ligand design led to
tem whereas for 14 a triclinic crystal system was determined the
compounds
(Z)-4-(2Ј-((diphenylphosphanyl)oxy)eth-
(Table 2). The X-ray structure determination reveals a shorter ylamino)pent-3-en-2-one (11) and (Z)-4-(2Ј-((diisoproylphos-
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Z. Anorg. Allg. Chem. 2012, 1151–1158

Phosphane Ligands with Enaminoketone Scaffold and their Pd Complexes
1H (400 MHz) NMR spectra were measured with a Bruker AVANCE
Table 2. Crystal data of palladium complexes 13 and 14.
400 spectrometer at room temperature with residual protons of the
solvent as reference. 13C{1H} (100 MHz) NMR spectra were measured
proton decoupled using solvent signals as reference. Multiplicities of
high order signals were described as first order and marked with the
prefix ‘m~’. 31P{1H} (162 MHz) NMR spectra were measured proton
decoupled without external standard.
13
14
Empirical
formula
C38H44Cl2N2O4P2Pd
C26H52Cl2N2O4P2Pd
Formula weight 831.99
695.94
100(2)
triclinic
M /g·mol–1
Temperature
T /K
100(2)
Far infrared spectra were recorded with a Bruker Vertex 70 FT-IR
spectrometer. Mass spectra were recorded with a Finnigan MAT 311
A (EI, 70 eV) or with a VG Analytical 70–250 S (FAB, xenon, m-
nitrobenzyl alcohol) spectrometer. Elemental analyses were performed
with Carlo Erba EA 1108 CHNS-O and with Elementar Vario EL III
analyzers for air-sensitive compounds by Zentrale Elementanalytik,
Fachbereich Chemie, Universität Hamburg.
Crystal system
Space group
a /pm
b /pm
c /pm
monoclinic
C2/c
1290.44(5)
1436.25(6)
2073.00(9)
90
¯
P1
828.79(5)
1076.67(7)
1101.45(7)
60.935(1)
74.021(1)
78.057(1)
0.82276(9)
1
α /°
β /°
γ /°
94.004(1)
90
Volume V /nm3 3.8327(3)
Z
4
Synthesis of (Z)-4-((diphenylphosphanyl)amino)pent-3-en-2-
one (2)
Density
1.442
1.405
(calculated)
ρ /g·cm–3
Absorption
coefficient
μ /mm–1
Compound 1 (5.239 g, 52.85 mmol) was dissolved in diethyl ether (50
mL) and triethylamine was added (5.348 g, 52.85 mmol). A solution
of chlorodiphenylphosphane (11.736 g, 53.191 mmol) in diethyl ether
(100 mL) was added dropwise. The reaction mixture was stirred at
room temperature for 21 h. Afterwards, the suspension was filtered.
The solvent was removed in vacuum and the residue was chromato-
graphed on silica gel with diethyl ether as eluent. After removing the
solvent a second chromatography with toluene as eluent was per-
formed. The solvent was removed and the product was isolated after
distillation in vacuum. Compound 2 was obtained as pale yellow oil.
Yield: 5.822 g (20.55 mmol); 39%. Elemental analysis: C17H18NOP
(283.30): C 72.09 (calc. 72.07), H 6.44 (6.40), N 4.93 (4.94)%.
0.748
0.855
θ range for data 2.12–27.50
2.16–27.49
collection /°
Reflections
collected
12002
9148
Independent
reflections
Data / re-
straints /
4285 [R(int) = 0.0105]
4285 / 0 / 224
3669 [R(int) = 0.0201]
3669 / 0 /175
parameters
Goodness-of-fit 1.069
1.039
on F2
R1, wR2
(IϾ2σ(I))
R1, wR2
(all data)
CCDC ref.
0.0196, 0.0501
0.0234, 0.0526
0.0282, 0.0549
819799
0.0209, 0.0510
819803
1H NMR (CDCl3) δ /ppm = 11.29 (d br, 1 H, J = 8.4 Hz, N–H), 7.37–
7.31 (m, 4 H, Ph–H), 7.25–7.16 (m, 6 H, Ph–H), 5.15 (d, 1 H, J =
3.5 Hz, 3–H), 2.04 (d, 3 H, J = 2.3 Hz, 5–H), 1.94 (s, 3H, 1–H);
13C{1H} NMR (CDCl3) δ /ppm = 197.6 (C2), 164.1 (d, J = 19.6 Hz,
C4), 139.0 (d, J = 10.6 Hz, C1‘), 131.1 (d, J = 21.6 Hz, C2‘), 129.4
(C4‘), 128.7 (d, J = 7.2 Hz, C3‘), 100.5 (d, J = 2.4 Hz, C3), 29.5 (C1),
21.3 (d, J = 22.4Hz, C5); 31P{1H} NMR (CDCl3) δ /ppm = 26.9 MS-
EI m/z = 283 (100%, [M+]), 268 (50%, [M+–CH3]), 206 (30%, [M+–
C6H5]), 201 (19%), 183 (52%), 82 (32%).
phanyl)oxy)ethylamino)pent-3-en-2-one (12). The dichlorido-
palladium(II) complexes with these ligands differ in their con-
figurational isomerism. While the square-planar complex with
the ligand 11 exhibits a cis configuration, the complex obtained
from 12 can only be isolated in the trans configuration due to
the bulky isopropyl groups. These results are confirmed by
NMR and far infrared spectroscopy, and their molecular struc-
ture was elucidated by X-ray structure determination. The co-
ordination of a second metal to the enaminoketone unit is sub-
ject of current investigations.
Synthesis of (Z)-4-((diisopropylphosphanyl)amino)pent-3-
en-2-one (3)
To a solution of 1 (1.065 g, 10.74 mmol) in diethyl ether (15 mL) was
added triethylamine (1.070 g, 10.57 mmol). A solution of chlorodiiso-
propylphosphane (1.630 g, 10.68 mmol) in diethyl ether (20 mL) was
added dropwise. The reaction mixture was stirred at room temperature
Experimental Section
The synthesis of the phosphane ligands and their palladium complexes
were carried out under standard Schlenk technique using nitrogen as for 24 h. The suspension was filtered and washed with diethyl ether
inert gas and distilled solvents. Solvents and chemicals were dried with
different desiccants: Diethyl ether (sodium potassium alloy), triethyl-
amine (potassium), chloroform and dichloromethane (calcium chlor-
(5 mL) twice. The solvent of the combined solutions was removed in
vacuum and the crude product was purified by chromatography on
silica gel with diethyl ether as eluent. Compound 3 was obtained as
ide). (Z)-4-Aminopent-3-en-2-one (1),[19] [PdCl2(C6H5CN)2Cl2] colorless oil. Yield: 1.576 g (7.321 mmol); 69%. Elemental analysis:
(5),[23] [PdCl2(COD)Cl2] (8),[24] and (Z)-4-(2Ј-hydroxyethyl)ami-
nopent-3en-2-one (10)[28] were synthesized according to the literature. (6.51)%.
C11H22NOP (215.27): C 61.37 (calc. 61.37), H 10.21 (10.30), N 6.37
Z. Anorg. Allg. Chem. 2012, 1151–1158
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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1155

M. Schmidt, J. Heck
ARTICLE
1H NMR (CDCl3) δ /ppm = 10.61 (br, 1H, N–H), 5.11 (d, 1H, J =
The reaction mixture was stirred for 48 h. The yellow precipitate was
3.0 Hz, 3–H), 2.02 (d, 3H, J = 2.0 Hz, 5–H), 1.99 (s, 3H, 1–H), 1.76 filtered and washed twice with diethyl ether (5 mL). The solvent was
(d sept, 2H, J = 2.4 Hz, J = 7.0 Hz, (CH(CH3)(CH3))2), 1.03 (dd, 6H, removed from the combined solutions in vacuum. The residue was
J = 10.9 Hz, J = 7.0 Hz, (CH(CH3)(CH3))2), 0.98 (dd, 6H, J = 16.4 Hz, washed twice with hot n-hexane (10 mL). The combined solids were
J = 7.0 Hz, (CH(CH3)(CH3))2); 13C{1H} NMR (CDCl3) δ /ppm = dried in vacuum and purified by crystallization of a dichloromethane
196.9 (C2), 166.9 (d, J = 16.4 Hz, C4), 99.5 (d, J = 1.4 Hz, C3), 29.4
(C1), 26.1 (d, J = 11.4 Hz, (CH(CH3)(CH3))2), 21.8 (d, J = 20.4 Hz,
C5), 18.5 (d, J = 19.6 Hz, (CH(CH3)(CH3))2), 17.2 (d, J = 7.3 Hz,
(CH(CH3)(CH3))2); 31P{1H} NMR (CDCl3, 162 MHz) δ /ppm = 52.9;
MS-EI m/z = 215 (32%, [M+]), 172 (100%, [M+–C3H7]), 130 (25%),
112 (17%), 84 (32%), 49 (50%).
solution layered by diethyl ether. Compound 7 was obtained as yellow
crystals. Yield: 270 mg (0.444 mmol); 76%. Elemental analysis:
C22H44Cl2N2O2P2Pd (607.87): C 43.43 (calc. 43.47), H 7.22 (7.30), N
4.51 (4.61)%.
1H NMR (CD2Cl2) δ /ppm = 11.49–11.44 (m, 2H, N–H), 5.36–5.34
(m, 2H, 3–H), 2.64 (m~ t sept, 4H, (CH(CH3)(CH3))2), 2.49 (s, 6H,
5–H), 2.04 (s, 6H, 1–H), 1.38–1.32 (m, 12H, (CH(CH3)(CH3))2), 1.32–
1.25 (m, 12H, (CH(CH3)(CH3))2); 13C{1H} NMR (CD2Cl2) δ /ppm =
198.4 (C2), 164.0 (C4), 102.0 (m~ t, C3), 29.5 (C1), 27.2 (m~ t,
(CH(CH3)(CH3))2), 24.1 (m~ t, C5), 18.9 (m~ t, (CH(CH3)(CH3))2),
17.6 (CH(CH3)(CH3))2); 31P{1H} NMR (CD2Cl2, 162 MHz) δ /ppm =
73.2; MS-FAB m/z = 609 (2%, [M+H+]), 573 (1%, [M+–Cl]), 535
(2%, [M+–2Cl–H]), 216 (100%), 215 (53%), 214 (77%); IR (PE) ν /
cm–1 = 349 (νas Pd–Cl).
Synthesis of (Z)-4-((diethylphosphanyl)amino)pent-3-en-2-
one (4)
To a solution of compound 1 (1.915 g, 19.32 mmol) in diethyl ether
(30 mL) was added triethylamine (1.849 g, 18.27 mmol). A solution
of chlorodiethylphosphane (2.334 g, 18.74 mmol) in diethyl ether (40
mL) was added dropwise. The reaction mixture was stirred at room
temperature for 5 d. The suspension was filtered and washed with
diethyl ether (5 mL) twice. The solvent of the combined solutions was
removed in vacuum and the crude product was purified by vacuum
distillation with a vigreux column. Compound 4 was isolated as color-
less oil. Yield: 1.484 g (7.927 mmol); 42%. Elemental analysis:
C9H18NOP (187.22): C 57.46 (calc. 57.74), H 9.51 (9.69), N 7.34
(7.48)%.
Synthesis of (SP-4–1)-dichloridobis((Z)-4-
((diethylphosphanyl)amino)pent-3-en-2-one-κP)
palladium(II) (9)
1H NMR (CDCl3) δ /ppm = 10.55 (br, 1H, N–H), 5.14 (d, 1H, J =
3.0 Hz, 3–H), 2.08 (d, 3H, J = 2.2 Hz, 5–H), 2.03 (s, 3H, 1–H), 1.65–
1.49 (m, 4H, (CH2CH3)2), 1.07 (dt, 6H, J = 15.2 Hz, J = 7.6 Hz,
(CH2CH3)2) 13C{1H} NMR (CDCl3) δ /ppm = 197.0 (C2), 166.1 (d,
J = 16.6 Hz, C4), 99.4 (d, J = 1.6 Hz, C3), 29.4 (C1), 23.5 (d, J =
11.0 Hz, (CH2CH3)2), 21.8 (d, J = 21.7 Hz, C5), 8.4 (d, J = 12.2 Hz,
(CH2CH3)2); 31P{1H} NMR (CDCl3) δ /ppm = 37.7; MS-EI m/z =
187 (45%, [M+]), 172 (3%, [M+–CH3]), 158 (100%, [M+–CH2CH3]),
140 (6%), 130 (4%), 82 (13%).
To a suspension of 8 (217 mg, 0.760 mmol) in diethyl ether (10 mL)
was added a solution of 4 (299 mg, 1.60 mmol) in diethyl ether (20
mL). The reaction mixture was stirred for 20 h. The yellow precipitate
was filtered and washed three times with diethyl ether (5 mL). The
crude product was dried in vacuum and dissolved in dichloromethane
layered by diethyl ether. Compound 9 was obtained as yellow crystals.
Yield: 280 mg (0.689 mmol); 91%. Elemental analysis:
C18H36Cl2N2O2P2Pd (551.76): C 38.76 (calc. 39.19), H 6.44 (6.58), N
4.89 (5.08)%.
Synthesis of (SP-4–1)-dichloridobis((Z)-4-
((diphenylphosphanyl)amino)pent-3-en-2-one-κP)
palladium(II) (6)
1H NMR (CDCl3) δ /ppm = 11.25–11.20 (m, 2H, N–H), 5.35–5.32
(m, 2H, 3–H), 2.47 (s, 6H, 5–H), 2.23–2.13 (m, 8H, (CH2CH3)2), 2.06
(s, 6H, 1–H), 1.26–1.16 (m, 12H, (CH2CH3)2); 13C{1H} NMR
(CDCl3) δ /ppm = 198.5 (C2), 161.5 (C4), 102.2 (m~ t, C3), 29.6 (C1),
23.3 (m~ t, C5), 19.2 (m~ t, (CH2CH3)2), 7.1 ((CH2CH3)2); 31P{1H}
NMR (CDCl3, 162 MHz) δ /ppm = 58.3; MS-FAB m/z = 553 (6%,
[M+H+], 515 (3%, [M+–Cl), 479 (3%, M+–2Cl–H), 188 (83%), 187
(71%), 186 (78%); IR (PE) ν /cm–1 = 367 (νas Pd–Cl).
To a suspension of 5 (1.277 g, 3.329 mmol) in diethyl ether (40 mL)
was added a solution of 2 (2.159 g, 7.621 mmol) in diethyl ether (25
mL). The reaction mixture was stirred for 22 h. The yellow precipitate
was filtered and dried in vacuum. For purification a solution of the
crude product in dichloromethane was layered with diethyl ether. Com-
pound 6 was obtained as yellow crystals. Yield: 2.097 g (2.819 mmol);
approx. 85%. Elemental analysis: C34H36Cl2N2O2P2Pd (743.94): C
54.82 (calc. 54.89), H 4.96 (4.88), N 3.65 (3.77)%.
1H NMR (CD2Cl2) δ /ppm = 11.82 (m~ t, 2H, N–H), 7.88–7.82 (m,
8H, Ph–H), 7.57–7.45 (m, 12H, Ph–H), 5.41–5.38 (m, 2H, 3–H), 2.07
(s, 6H, 1–H), 2.04 (s, 6H, 5–H); 13C{1H} NMR (CD2Cl2) δ /ppm =
198.9 (C2), 161.2 (C4), 133.3 (m~ t, C2‘), 131.9 (C4‘), 131.7 (m~ t,
C1‘), 128.9 (m~ t, C3‘), 103.4 (m~ t, C3), 29.8 (C1), 23.5 (m~ t, C5);
31P{1H} NMR (CD2Cl2, 162 MHz) δ /ppm = 49.3; MS-FAB m/z =
745 (2%, [M+H+]), 707 (2%, [M+–Cl]), 671 (7%, [M+–2Cl–H]), 284
(36%), 283 (47%), 282 (100%); IR (PE) ν /cm–1 = 367 (νas Pd–Cl).
Synthesis of (Z)-4-(2Ј-((diphenylphosphanyl)oxy)
ethylamino)pent-3-en-2-one (11)
To a suspension of 10 (1.996 g, 13.94 mmol) in diethyl ether (150
mL) was added triethylamine (1.455 g, 14.38 mmol). A solution of
chlorodiphenylphosphane (3.032 g, 13.74 mmol) in diethyl ether (30
mL) was slowly added dropwise. The suspension was stirred for 24 h.
The precipitate was filtered and washed twice with diethyl ether (10
mL). The solvent was removed from the combined solutions in vac-
uum. The crude product was purified by chromatography on silica gel
with diethyl ether as eluent. The solvent was removed and compound
11 was isolated as pale yellow oil. Yield: 2.844 g (8.688 mmol); 63%.
Elemental analysis: C19H22NO2P (327.36): C 69.54 (calc. 69.71), H
Synthesis of (SP-4–1)-dichloridobis((Z)-4-
((diisopropylphosphanyl)amino)pent-3-en-2-one-κP)
palladium(II) (7)
A solution of 3 (253 mg, 1.18 mmol) in diethyl ether (5 mL) was added
to a suspension of 5 (225 mg, 0.587 mmol) in diethyl ether (25 mL). 6.80 (6.77), N 4.09 (4.28)%.
1156 www.zaac.wiley-vch.de
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Z. Anorg. Allg. Chem. 2012, 1151–1158

Phosphane Ligands with Enaminoketone Scaffold and their Pd Complexes
C38H44Cl2N2O4P2Pd (832.04): C 54.43 (calc. 54.85), H 5.46 (5.33), N
3.23 (3.77)%.
1H NMR (CDCl3) δ /ppm = 10.60 (t br, 2H, J = 5.9 Hz, N–H), 7.80–
7.73 (m, 8H, Ph–H), 7.53–7.47 (m, 4H, Ph–H), 7.44–7.37 (m, 8H, Ph–
H), 4.90 (s, 2H, 3–H), 3.71–3.62 (m, 4H, 2‘–H), 3.07–3.00 (m, 4H,
1‘–H), 1.95 (s, 6H, 1–H), 1.66 (s, 6H, 5–H); 13C{1H} NMR (CDCl3)
δ /ppm = 195.4 (C2), 162.5 (C4), 132.7 (m~ t, C2‘‘), 132.3 (C4‘‘),
132.2–131.4 (m, C1‘‘), 128.6 (m~ t, C3‘‘), 96.2 (C3), 67.7 (m~ t, C2‘),
42.4 (m~ t, C1‘), 29.0 (C1), 18.8 (C5); 31P{1H} NMR (CDCl3) δ /
ppm = 111.7; MS-FAB m/z = 795 (14%, [M+–Cl]), 759 (100%, [M+–
2Cl–H]), 634 (22%), 470 (26%), 432 (91%), 326 (20%), 284 (37%),
244 (21%), 222 (28%), 201 (67%); IR (PE) ν /cm–1 = 309 (νs Pd–
Cl), 284 (νas Pd–Cl).
1H NMR (CDCl3) δ /ppm = 10.94 (br, 1H, N–H), 7.52–7.46 (m, 4H,
Ph–H), 7.38–7.31 (m, 6H, Ph–H), 4.97 (s, 1H, 3–H), 3.90 (dt, 2H, J
= 8.5 Hz, J = 5.7 Hz, 2‘–H), 3.46 (dt, 2H, J = 5.8 Hz, J = 6.0 Hz, 1‘–
H), 2.03 (s, 3H, 1–H), 1.84 (s, 3H, 5–H); 13C{1H} NMR (CDCl3) δ /
ppm = 195.0 (C2), 162.8 (C4), 141.3 (d, J = 17.9 Hz, C1‘‘), 130.4 (d,
J = 22.3 Hz, C2‘‘), 129.5 (C4‘‘), 128.4 (d, J = 6.9 Hz, C3‘‘), 95.9 (C3),
68.6 (d, J = 18.1 Hz, C2‘), 44.0 (d, J = 8.3 Hz, C1‘), 28.9 (C1), 18.9
(C5); 31P{1H} NMR (CDCl3, 162 MHz) δ /ppm = 115.5; MS-EI m/z
= 327 (19%, [M+]), 284 (47%, [M+–COCH3]), 203 (62%), 201
(56%), 143 (52%), 112 (60%), 109 (100%).
Synthesis of (SP-4–1)-dichloridobis((Z)-4-(2Ј-
((diisopropylphosphanyl)oxy)ethylamino)pent-3-en-2-one-
κP)palladium(II) (14)
Synthesis of (Z)-4-(2Ј-((diisopropylphosphanyl)oxy)
ethylamino)pent-3-en-2-one (12)
To a suspension of 8 (176 mg, 0.616 mmol) in diethyl ether (10 mL)
was added a solution of 12 (329 mg, 1.27 mmol) in diethyl ether (10
mL). The reaction mixture was stirred for 24 h. The pale yellow pre-
cipitate was filtered and washed three times with diethyl ether (5 mL).
The crude product was dried in vacuum and solved in dichloromethane
layered by diethyl ether. Compound 14 was obtained as pale yellow
crystals. Yield: 336 mg (0.483 mmol); 78%. Elemental analysis:
C26H52Cl2N2O4P2Pd (695.98): C 44.79 (calc. 44.87), H 7.47 (7.53), N
3.89 (4.01)%.
To a suspension of 10 (2.133 g, 14.90 mmol) in diethyl ether was
added triethylamine (1.512 g, 14.94 mmol). A solution of chlorodiiso-
propylphosphane (2.289 g, 15.00 mmol) in diethyl ether was slowly
added dropwise. The suspension was stirred for 70 h. The precipitate
was filtered and washed twice with diethyl ether (10 mL). The com-
bined solutions were reduced in vacuum to about 25 mL. Overnight
a precipitate was formed. After filtration the solvent was completely
removed from the solution. n-Hexane was added to the residue and
after filtration the solvent was removed again. The crude product was
purified by vacuum distillation. Compound 12 was isolated as pale
yellow oil. Yield: 2.419 g (9.328 mmol); approx.. 63%. Elemental
analysis: C13H26NO2P (259.32): C 58.30* (calc. 60.21), H 9.66
(10.11), N 5.28 (5.40)% (* Insufficient value, due to the easy forma-
tion of by-product).
1H NMR (CDCl3) δ /ppm = 10.83 (m~ t, 2H, N–H), 4.95 (s, 2H, 3–
H), 4.20–4.13 (m, 4H, 2‘–H), 3.57–3.51 (m, 4H, 1‘–H), 2.55–2.43 (m,
4H, (CH(CH3)(CH3))2), 1.98 (s, 6H, 1–H), 1.93 (s, 6H, 5–H), 1.42–
1.33 (m, 12H, (CH(CH3)(CH3))2), 1.32–1.24 (m, 12H, (CH(CH3)
(CH3))2); 13C{1H} NMR (CDCl3) δ /ppm = 195.2 (C2), 163.2 (C4),
95.9 (C3), 69.2 (C2‘), 44.2 (m~ t, C1‘), 29.0 (C1), 28.3 (m~ t,
(CH(CH3)(CH3))2), 19.2 (C5), 18.6 (m~ t, (CH(CH3)(CH3))2), 16.9
(CH(CH3)(CH3))2); 31P{1H} NMR (CDCl3, 162 MHz) δ /ppm =
145.2; MS-FAB m/z = 697 (28%, [M+H+]), 659 (4%, [M+–Cl]), 623
(6%, [M+–2Cl–H]), 402 (35%), 364 (100%), 260 (88%), 252 (43%),
216 (56%), 188 (25%); IR (PE) ν /cm–1 = 362 ( νas Pd–Cl).
1H NMR (CDCl3) δ /ppm = 10.80 (br, 1H, N–H), 4.95 (s, 1H, 3–H),
3.77 (dt, 2H, J = 7.4 Hz, J = 5.8 Hz, 2‘–H), 3.39 (dt, 2H, J = 5.9 Hz,
J = 5.8 Hz, 1‘–H), 1.97 (s, 3H, 1–H), 1.92 (s, 3H, 5–H), 1.70 (d sept,
2H, J = 1.3 Hz, J = 7.0 Hz, (CH(CH3)(CH3))2), 1.06 (dd, 6H, J =
10.6 Hz, J = 7.0 Hz, (CH(CH3)(CH3))2), 1.00 (dd, 6H, J = 15.7 Hz, J
= 7.0 Hz, (CH(CH3)(CH3))2); 13C{1H} NMR (CDCl3) δ /ppm = 194.7
(C2), 162.6 (C4), 95.5 (C3), 71.0 (d, J = 19.7 Hz, C2‘), 43.9 (d, J =
8.0 Hz, C1‘), 28.7 (C1), 27.8 (d, J = 16.2 Hz, (CH(CH3)(CH3))2), 18.9
(C5), 17.6 (d, J = 20.0 Hz, (CH(CH3)(CH3))2), 16.7 (d, J = 8.3 Hz,
(CH(CH3)(CH3))2); 31P{1H} NMR (CDCl3) δ /ppm = 154.8; MS-EI
m/z = 259 (7%, [M+]), 216 (27%, [M+–C3H7] or [M+–CH3CO]), 188
(7%), 172 (10%), 135 (41%), 125 (42%), 109 (34%), 82 (32%), 43
Acknowledgment
This work was supported by the Graduate School 611 (Design and
Characterization of Functional Materials).
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Received: February 17, 2012
Published Online: May 31, 2012
1158
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1151–1158