Palladium complexes with bidentate P,N ligands: Synthesis, characterization and application in ethene oligomerization

Article abstract of DOI:10.1515/znb-2002-0713

Palladium complexes of two different P,N ligands (a phosphane-pyridine and a phosphane-imine ligand) were synthesized and characterized. Single crystal X-ray structure analyses of the palladium diiodide compounds revealed a square-planar coordination geometry at the metal center with a longer Pd-I bond in trans-position to the phosphorus atom. The chloro-methyl palladium species of the phosphane-pyridine ligand was applied for the oligomerization of ethene using a borate salt as cocatalyst.

Full text of DOI:10.1515/znb-2002-0713

Palladium Complexes with Bidentate P,N Ligands: Synthesis, Characterization
and Application in Ethene Oligomerization
Gabi Müllera, Martti Klingab, Peter Osswalda, Markku Leskeläb,
and Bernhard Riegera
a
Department of Inorganic Chemistry II, Materials and Catalysis, University of Ulm,
D-89069 Ulm, Germany
b
Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014
University of Helsinki, Finland
Reprint request to Prof. Dr. B. Rieger.
Fax:+49-731-5023039. E-mail: bernhard.rieger@chemie.uni-ulm.de
Z. Naturforsch. 57b, 803Ð809 (2002); received March 11, 2002
P,N Ligands, Palladium Complexes, Ethene Oligomerization
Palladium complexes of two different P,N ligands (a phosphaneÐpyridine and a phos-
phaneÐimine ligand) were synthesized and characterized. Single crystal X-ray structure
analyses of the palladium diiodide compounds revealed a square-planar coordination geome-
try at the metal center with a longer PdÐI bond in trans-position to the phosphorus atom.
The chloro-methyl palladium species of the phosphaneÐpyridine ligand was applied for the
oligomerization of ethene using a borate salt as cocatalyst.
Introduction
ligands [15Ð18]. With respect to our recent investi-
gations with different N,N and P,P ligands, we pre-
pared the bidentate P,N ligands 1 and 2, consisting
of a pyridine and a bis(2-methyl-phenyl) substi-
tuted phosphane, or an imine and a diphenylphos-
phane unit, respectively [19]. To investigate their
catalytic properties several palladium complexes
of ligands 1 and 2 were synthesized (Fig. 1).
Complexes of the nickel group are well known
catalysts for late transition metal catalyzed poly-
merization reactions [1Ð7]. Bidentate chelating li-
gands are often used to fix the active coordination
sites of Pd(II) and Ni(II) complexes in a cis-ar-
rangement. P,O ligands which are used in the indu-
strial SHOP Process, P,P and N,N ligands are ap-
plied in catalytic olefin homo- and copolymeriza-
tion reactions [2Ð8, 11 and references cited
therein]. P,P palladium complexes are among the
most active and most stable catalysts for olefin/
CO copolymerizations [5Ð7]. Ligands with nitro-
Results and Discussion
Synthesis and characterization
The P,N ligands 1 and 2 as well as the corre-
gen functionalities are used in olefin/CO copoly- sponding palladium complexes were synthesized
merizations as well as in olefin homopolymeriza- as depicted in Fig. 1. Treatment of 2-(chloro-
tions [1, 5, 8Ð11]. In a series of publications the methyl)pyridine with one equivalent of bis(2-
influence of bulky imine substituents on the poly- methyl-phenyl)phosphane in the presence of po-
merization properties (activity of the catalyst as tassium tert-butanolate yielded ligand 1 which was
well as molecular weight of the isolated polymer) directly converted to the palladium diiodide com-
was described [1, 8, 12]. Molecular modeling re- plex 3. Purification of 3 was achieved by column
sults suggest that bulky substituents retard the rate chromatography. The free ligand 1 was regener-
of chain transfer reactions [1, 8, 13, 14] and recent ated by treating 3 with an excess of potassium cya-
investigations have shown that this concept can nide. Reaction of 1 with (COD)PdClMe afforded
also be applied to palladium complexes with the chloro-methyl palladium complex 4. In square-
bis(arylphosphane) ligands. Such complexes cata- planar (P,N)PdClMe complexes two isomers can
lyze the oligomerization/polymerization of ethene, be formed (Me cis or trans to P). In the case of 4
and the molecular weight of the products is in di- the formation of a single species was observed
rect relation with the substitution pattern of the [20]. In square-planar palladium complexes li-
0932Ð0776/2002/0700Ð0803 $06.00 ” 2002 Verlag der Zeitschrift für Naturforschung, Tübingen · www.znaturforsch.com
D
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804
G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
Fig. 1. Synthesis of the P,N ligands 1 and 2 and of the corresponding palladium complexes 3, 4, 5 and 6.
gands with a strong trans influence prefer a cis- chromatography. Complex 6 proofed to be unsta-
arrangement [21]. We assume therefore, that 4 is ble in solution (halogenated solvents) as could be
the isomer where the methyl and the phosphane seen by the appearance of several new signals in
groups are oriented in cis-position. Such arrange- the 31P NMR spectrum with time. Attempts to
ments were also found for other (P,N)PdClMe prepare the chloro-methyl palladium complex of
complexes [22,26].
2, either by treatment of 6 with SnMe4 or by re-
The bis(acetonitrile) complex 5 was synthesized generation of the free ligand 2 with KCN and sub-
by treating 3 with two equivalents of silver tetra- sequent reaction with (COD)PdClMe were unsuc-
fluoroborate in acetonitrile. Complex 3, 4 and 5 cessful.
which are stable in solution were characterized by
1
Solid state structures
FAB-MS, elemental analysis, IR- as well as H-
and 31P NMR analysis.
Single crystals of 3 and 6, suitable for an X-ray
The condensation of acetophenone and 2,6-di- structure determination were obtained by crystal-
isopropyl-aniline afforded the imine (Schiff-base), lization from EtAc/CH2Cl2. ORTEP-plots of both
which was deprotonated with lithium diisopropy- structures are depicted in Fig. 2. Characteristic
lamide [19]. Subsequent addition of chlorodiphe- bond lengths and angles are listed in Table 1.
nylphosphane yielded 2 in about 65% yield [23].
In both complexes the P,N units together with
The ligand was converted directly to the palladium the iodine atoms form a distorted square-planar
diiodide complex 6 which was purified by column coordination sphere around the metal center.
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G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
805
Fig. 2. Molecular structure of 3 (left) and 6 (right).
Table 1. Selected bond lengths and angles of complex 3
and 6.
Polymerization reactions
Different P,N ligands were applied in olefin po-
lymerization as well as in olefin/CO copolymeriza-
tion reactions [2, 19, 24Ð27]. Complex 4 was tested
for ethene polymerization in CH2Cl2 after activa-
tion of the complex with sodium tetrakis[3,5-
bis(trifluoromethyl)phenyl]borate (NaBAF) in di-
ethyl ether. Runs were performed at 10 and 60 bar.
The reaction products were characterized by GC-
MS which was calibrated using commercially
available 1-olefins (1-octene, 1-decene and 1-do-
decene) as standards. Oligomers with molecular
weights between 112g/mol (C 8) and 448 g/mol
(C32) were detected. Signals of lower molecular
weight compounds were overlapped by the
solvent-signal. Olefins with a chain length Cn > 32
were only present in minor quantities (< 1%). As
3
Bond lengths
Bond angles
˚
˚
[A]
[A]
I1ÐPd1
I2ÐPd1
2.573(1)
N1ÐPd1ÐP1
P1ÐPd1ÐI1
83.2(2)
2.6608(8)
90.22(5)
Pd1ÐN1 2.100(5)
N1ÐPd1ÐI294.6(1)
Pd1ÐP1
2.230(2)
I1ÐPd1ÐI293.11(3)
6
Bond lengths
Bond angles
˚
˚
[A]
[A]
I1ÐPd1
I2ÐPd1
2.653(1)
2.574(1)
N1ÐPd1ÐP1
P1ÐPd1Ð.I1289(28)
N1ÐPd1ÐI1
I2ÐPd1ÐI1
81.9(3)
Pd1ÐN1 2.131(9)
94.7(2)
92.14(4)
Pd1ÐP1
2.223(3)
The PdÐI bonds trans to the phosphorus atoms expected, only signals for olefins with an even
(Pd1ÐI2in 3 and Pd1ÐI1 in 6) are longer (0.08 number of carbon atoms were observed. In the
˚
and 0.09 A) than the PdÐI bonds trans to the ni- GC-MS spectra for each Cn-fraction (C8ÐC32) one
trogen atoms which might be attributed to the intense as well as several less intense signals were
larger trans influence of the phosphorus atoms as detected. We attribute the main signal to the linear
compared to nitrogen atoms (imine and pyridine) 1-olefin (in accordance with our linear standards
[21].
used for calibration). An influence of the polymer-
In the solid state one of the ortho-aryl substitu- ization pressure on the isomer distribution was not
ents (methyl in the case of 3 and isopropyl in the observed. At 10 and 60 bar the content of 1-octene
case of 6) is oriented above/below the coordina- within the C8-fraction was between 94 and 98%
tion planes, occupying the space along the z-axis. [28].
A connection between shielding of the metal cen-
The catalyst system 4/NaBAF, as well as the cor-
ter and chain transfer reactions was found for sev- responding palladium systems containing the P,P
eral N,N complexes [1, 8, 12, 13, 14].
ligand 1,3-bis[bis(2-methyl-phenyl)phosphino]pro-
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806
G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
Table 2. Crystallographic data for 3 and 6.
3
6
Molecular formula
Formula weight [g/mol]
Crystal color and form
Crystal system
C20H20I2NPPd
665.54
red prism
monoclinic
P21/n
C32H34I2NPPd
823.77
red plate
orthorhombic
Pna21
Space group
˚
a [A]
9.657(4)
16.288(3)
14.258(4)
108.50(3)
2126.8(11)
4
21.936(4)
13.793(5)
10.128(5)
90
˚
b [A]
˚
c [A]
ꢀ [∞]
3
˚
Volume [A ]
3064(2)
4
Z
Dcalcd. [mg/m3]
Absorption coefficient [mmÐ1
F(000)
2.079
1.786
]
3.854
2.694
1256
1600
Crystal size [mm]
θmax [∞]
25.25
0.24 ¥ 0.22 ¥ 0.15
0.40 ¥ 0.24 ¥ 0.08
25.24
Number of collected reflections
Number of observed reflections [I > 2σ(I)]
Number of unique reflections
Number of parameters
4054
4041
3220
3496
3815
3825
226
334
Index range
0 Յ h Յ 11
0 Յ k Յ 19
Ð17 Յ l Յ 16
1.065
Ð21 Յ h Յ 26
Ð13 Յ k Յ 16
Ð12 Յ l Յ 5
1.074
Goodness-of-fit on F2
R Indices (all data)a,b
R1 = 0.0551
wR2= 0.1059
1.298 and Ð1.001
R1 = 0.0531
wR2= 0.1189
1.452and Ð0.991
3
˚
Largest differential peak and hole [e/A ]
a R1 = Σ||Fo | Ð |Fc ||/Σ|Fo |; b wR2 = [Σ[w(Fo2 Ð F2c)2]/Σ[wF4o]]1/2
.
pane (2-Me)2P,P(2-Me)2 or the (py)N,N(im) ligand Conclusion
N-(1-methyl-1-pyridylmethylidene)-2,6-diisopro-
We synthesized the P,N ligands 1 and 2 as well
as several of their palladium complexes. The X-ray
structure analysis of the PdI2 complexes revealed
a distorted square-planar coordination sphere for
the metal atoms. In both compounds the PdÐI
bond trans to the phosphorus atom was longer
than the one trans to nitrogen. The chloro-methyl
palladium complex of 1 was used for the oligomer-
ization of ethene after activation with a borate
salt. This system produces a mixture of isomers
with a high content of linear 1-olefins. No activity
for the copolymerization of ethene and CO was
observed at room temperature.
pyl-aniline oligomerize ethene to a mixture of iso-
meric olefins [10, 15]. The contents of linear ole-
fins is significantly higher for 4/NaBAF (98%)
than for the system containing (2-Me)2P,P(2-Me)2
(1-olefins < 5%) under similar reaction conditions
[15, 29]. Also the maximum chain length obtained
with 4 (C32) is significantly higher than with the
(2-Me)2P,P(2-Me)2 complex (C16). In polymeriza-
tion experiments with (py)N,N(im) several iso-
mers for one Cn fraction were also obtained (e.g.
nine isomers for the C10-fraction) [10].
The catalyst system 4/NaBAF was tested for
ethene/CO copolymerization reactions. However,
only traces of 1-olefins could be isolated which
were probably formed during the initiation of the
reaction, before CO was added to the autoclave.
The bis(aceonitrile) complex 5 also showed no ac-
tivity for the copolymerization of ethene and CO
at room temperature (using methanol as cocata-
lyst).
Experimental Section
All manipulations except the handling of the
palladium diiodide complexes were carried out in
dry solvents under an argon atmosphere using
standard Schlenk techniques. THF and diethyl
ether were distilled from LiAlH4; CH2Cl2 was dis-
tilled from CaH2. All solvents were stored over
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G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
807
molecular sieves. Commercially available acetoni- 123.6 (d, J = 6.0 Hz), 126.0, 128.5, 129.8 (d, J =
trile (water contents < 30 ppm), 2-(chlormethyl)- 4.53), 131.4, 135.9, 136.5 (d, J = 15.5 Hz), 142.3 (d,
pyridine hydrochloride, acetophenone, lithium dii- J = 25.7 Hz), 149.3, 158.3 (d, J = 8.3 Hz). Ð 31P
sopropylamide (THF-complex, 1.5 molar solution NMR (CDCl3): Ð30.44.
in cyclohexane), potassium tert-butanolate (95%),
chlorodiphenylphosphane (95%), KCN, NaI and Diiodo-{2-[bis(2-methyl-phenyl)phosphino-
AgBF4 were used without further purification. 2,6- methyl]pyridine}palladium(II) (3)
Diisopropylaniline (techn.) was purified by distil-
(COD)PdCl2 (7.16 g, 25 mmol) was added to a
lation. (Cis,cis-cycloocta-1,5-diene)dichloropalla-
solution of 1 (7.63 g, 25 mmol) in 100 ml of
dium (COD)PdCl2 [30], (cis,cis-cycloocta-1,5-di-
CH2Cl2. After the solution had been stirred for
5 min NaI (15.04 g, 100 mmol) was added and the
ene)chloromethylpalladium (COD)PdClMe [31],
sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]-
reaction mixture was stirred at RT for 48 h. After
borate (NaBAF) [32] and bis(2-methyl-phenyl)-
filtration the solvent was removed under reduced
phosphane [33] were prepared according to litera-
pressure and the product was purified by column
ture procedures. NMR measurements were con-
chromatography on silica using CH2Cl2/petroleum
ducted on a Bruker DRX 400 spectrometer.
ether (30:1) as eluent. Yield: 64%. M.p. 273 ∞C
Chemical shifts are reported in ppm. Tetramethyl-
1
(decomp.) Ð H NMR (CDCl3): 2.65 (s, 6H, Me),
silane and 85% phosphoric acid were used as ref-
4.36 (d, 2H, J = 12.6 Hz, CH2P), 7.24Ð7.31 (m, 5H,
erences. FAB-MS spectra were measured on a
Ar), 7.42Ð7.46 (m, 3H, Ar), 7.79 (m, 1H, Ar), 7.90
Finnigan MAT TSQ 7000 spectrometer using
(m, 2H, Ar), 10.09 (dd, 1H, J1 = 5.9 Hz, J2 = 1.0
2-nitrophenyloctylether (2-NPOE) as matrix. GC-
Hz, Ar). Ð 31P NMR (CDCl3): 40.95. Ð FAB-MS
MS measurements were performed on a Varian
(matrix: 2-NPOE): m/z 665 (M+, 10%), 638
Saturn GC/MS 2000 spectrometer. Melting points
(M+ÐI, 60%). Ð Elemental analysis (C20H20I2NPPd):
were determined on a Büchi B-540 (2 ∞C/min).
calcd. C 36.09, H 3.03, N 2.10; found C 36.10,
Elemental analysis were measured on a Vario EL
H 3.10, N 2.12.
elementar.
{[Bis(2-methylphenyl)phosphinomethyl]pyridine}-
chloromethylpalladium(II) (4)
2-[Bis(2-methyl-phenyl)phosphinomethyl]-
pyridine (1)
3 (1 g, 1.5 mmol) and KCN (65 mg, 30 mmol)
were dissolved in 10 ml of CH2Cl2 and 15 ml of
water. After 5 min the organic phase had decolo-
rized, but the reaction mixture was stirred over
night. The aqueous phase was separated and the
organic phase extracted with water (4 ¥ 20 ml).
The organic phase was dried over MgSO4 and the
solvent was removed under reduced pressure to
leave the product as a colorless solid which was
dried under vacuum. (COD)PdClMe (1 eq.) was
added to a solution of the ligand in 20 ml of
CH2Cl2 and the reaction mixture was stirred over
night. The solvent was reduced to 5 ml and 80 ml
of Et2O was added. The colorless precipitate was
separated, washed with 2 ¥ 15 ml of Et2O and
dried under vacuum. Yield: 82%. Ð 1H NMR
(CDCl3): 0.67 (d, 3H, J = 2.8 Hz, PdMe), 2.53 (s,
6H, Me), 4.14 (d, 2H, J = 11.1 Hz, CH2P), 7.19 (m,
2H, Ar), 7.24Ð7.30 (m, 3H, Ar), 7.40 (m, 2H, Ar),
7.45 (d, 1H, J = 7.8 Hz, Ar), 7.59 (m, 2H, Ar), 7.74
(m, 1H, Ar), 9.43 (dd, 1H, J1 = 5.4 Hz, J2 = 1 Hz,
Ar). Ð 31P NMR (CDCl3): 36.6. Ð FAB-MS (mat-
rix: 2-NPOE, CH2Cl2): m/z 462(M +ÐH, 12%), 426
(M+ÐCl, 80%), 410 (M+ÐHClÐCH3, 100%). Ð El-
emental analysis (C21H23ClNPPd): calcd. C 54.56,
H 5.02, N 3.03; found C 54.58, H 5.07, N 3.00.
2-(Chloromethyl)pyridine (3.20 g, 25 mmol),
generated from the hydrochloride using an aque-
ous solution of NaHCO3, was dissolved in 50 ml
of THF and the solution added to bis(2-methyl-
phenyl)phosphane (5.37 g, 25 mmol) in 50 ml of
THF. Potassium tert-butanolate (5.61 g, 50 mmol)
was added and the reaction mixture was stirred at
RT for 48 h. The solvent was removed under re-
duced pressure and the solid residue was dissolved
in 100 ml of CH2Cl2 and 100 ml of water. The or-
ganic phase was separated and the aqueous phase
extracted with 100 ml of CH2Cl2. The combined
organic layers were dried over sodium sulfate and
the solvent was removed under reduced pressure.
The crude product (87% pure according to 31P
NMR analysis) was used without further purifica-
tion. Analytical data were determined from a pure
sample which was generated form the diiodide
1
complex. Ð H NMR (CDCl3): 2.11 (s, 6H, Me),
3.44 (s, 2H, CH2P), 6.75 (dd, 1H, J1 = 7.8 Hz, J2 =
0.9 Hz, Ar), 6.91 (m, 1H, Ar), 6.98 (m, 2H, Ar),
7.04Ð7.12(m, 4H, Ar), 7.32 Ð7.26 (m, 2H, Ar),
7.29 (m, 1H, Ar), 8.39 (dd, 1H, J1 = 4.9 Hz, J2 =
0.9 Hz, Ar). Ð 13C NMR (CDCl3): 20.9 (d, J = 21.5
Hz), 37.9 (d, J = 16.2Hz), 120.8 (d, J = 2.3 Hz),
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G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
Bis(acetonitrile-[2-bis(2-methyl-phenyl)phosphino- (4 equiv.) was added and the reaction mixture was
methylpyridine]palladium bistetrafluoroborate (5)
stirred over night and filtered, and the solvent was
removed under reduced pressure. The product was
purified by column chromatography on silica using
CH2Cl2/EtAc (100:1) as eluent. The complex
proved to be unstable in solution (halogenated
AgBF4 (607 mg, 3.12mmol) was added to a sus-
pension of 3 (1.04 g, 1.56 mmol) in 50 ml of aceto-
nitrile. The reaction mixture was stirred at RT
over night and filtered, and the solvent was re-
moved under reduced pressure. The solid residue
was extracted with CH2Cl2 (2 ¥ 20 ml). Removal
of the solvent left the product as a pale yellow,
microcrystalline solid. Yield: 98%. Ð IR (KI-pel-
lets): 2334, 2307 (NϵCÐCH3, m), 1075 (BF4,
bs). Ð 1H NMR (CDCl3): 2.17 (s, 3H, NCMe), 2.39
(s, 3H, NCMe), 2.62 (s, 6H, Me), 4.66 (d, 2H, J =
14.0 Hz, CH2P), 7.40Ð7.48 (m, 4H, Ar), 7.57 (dd,
1H, Ar), 7.67 (m, 2H, Ar), 7.80Ð7.90 (m, 3H, Ar),
8.05 (m, 1H, Ar), 8.67 (d, 1H, J = 6.0 Hz, Ar). Ð
31P NMR (CDCl3): 51.54. Ð FAB-MS (matrix:
2-NPOE): m/z 411 (M2+Ð2CH3CNÐ2BF4, 100%).
1
solvents). Ð H NMR (CD2Cl2): 0.28 (d, 6H, J =
6.7 Hz, CHMe), 1.29 (d, 6H, J = 6.7 Hz, CHMe),
2.77 (sep, 2H, J = 6.7 Hz, CHMe), 4.38 (d, 2H, J =
13.4 Hz, CHMe), 6.94 (m, 4H, Ar), 7.11 (m, 3H,
Ar), 7.28 (t, 1H, J = 7.4 Hz, Ar), 7.45Ð7.57 (m,
6H, Ar), 7.76 (m, 4H, Ar). Ð 31P NMR (CD2Cl2):
41.66. Ð FAB-MS (matrix: 2-NPOE, DMF) m/z
823 (M+, 5%), 696 (M+ÐI, 100%) elemental analy-
sis (C32H34I2NPPd): calcd. C 46.65, H 4.16, N 1.70;
found: C 45.94, H 4.09, N 1.72.
Polymerizations
Polymerization experiments were performed in
an 100 ml steel autoclave (Roth) with a glass inlet
and mechanical stirring. Ethene (BASF, 2.7) was
used without further purification. The autoclave
was purged with argon prior to use. Under an inert
atmosphere 4 (50 µmol) and NaBAF (50 µmol)
were stirred in 10 ml of diethyl ether for 10 min.
The solid residue was removed by filtration and
the solution was transferred to the autoclave
which had been charged with 30 ml of CH2Cl2.
The autoclave was pressurized with ethene for
5 min. The reaction was quenched by the addition
of water after 1 h. The reaction mixture was ana-
lyzed by GC-MS.
N-(1-phenylethylidene)-2,6-diisopropyl-aniline
A solution of acetophenone (24.7 ml, 0.2 mol),
2,6-diisopropyl-aniline (40 ml, 0.21 mol), formic
acid (10 ml) and 200 ml of methanol was stirred at
RT for 48 h. Upon reduction of the volume of the
solvent the crude product precipitated and was
further purified by column chromatography on sil-
ica using CH2Cl2/petroleum ether (6:1) as eluent.
1
Yield: 25%. Ð H NMR (CDCl3): 1.13 (d, 6H, J =
5.3 Hz, CHMe), 1.15 (d, 6H, J = 5.0 Hz, CHMe),
2.09 (s, 3H, Me), 2.75 (sep, 2H, CHMe), 7.07 (m,
1H, Ar), 7.13 (s, 1H, Ar), 7.15 (s, 1H, Ar), 7.48 (m,
3H, Ar), 8.03(m, 2H, Ar). Ð 13C NMR (CDCl3):
17.9, 22.8, 23.1, 28.1, 122.8, 123.1, 127.0, 128.2,
130.2, 135.9, 139.0, 146.6, 164.6; EI-MS m/z 279
(M+, 30%), 264 (M+ÐCH3, 100%).
Crystallography
Crystal data of the compounds 3 and 6 were col-
lected with a Rikagu AFC7S single-crystal diffrac-
tometer at 193(2) K using MoÐKα radiation
N-[2-(Diphenylphosphino)-1-phenylethylidene]-
2,6-diisopropyl-aniline (2)
˚
(graphite monochromator), λ = 0.71073 A (ω/2-ꢁ-
scans). Intensities were corrected for Lorentz and
polarization effects [34]. A ψ-scan absorption
correction was performed, 0.75 < T < 1.00 (3),
0.573 < T < 1.000 (6) [35]. Solution and refine-
ment: SHELX-97 (Sheldrick, 1997); figures with
the labelling scheme: ORTEP3 (Farrugia, 1997)
[36]. The structure was solved by direct methods.
All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were refined on calculated
positions. The displacement factor of the H-atoms
was 1.2¥ (or 1.5¥ for methyl hydrogens) that of
the host atom.
Lithium diisopropylamide (6.6 mmol) was ad-
ded slowly to a solution of N-(1-phenylethyl-
idene)-2,6-diisopropyl-aniline (1.6 g, 5.7 mmol) in
100 ml of diethyl ether at Ð78 ∞C. After chloro-
diphenylphosphane (1.1 ml, 5.7 mmol) had been
added the reaction mixture was allowed to reach
RT and was stirred for additional 2h. Evaporation
of the solvent left the crude product in about 65%
1
yield (according to 31P- and H NMR analysis).
The product was used without further purification.
Diiodo-{N-[(Z)-2-(diphenylphosphine]-1-phenyl-
ethylidene)-2,6-diisopropyl-aniline}palladium(II) (6)
(COD)PdCl2 (1 equiv.) was added to a solution
of the ligand in 200 ml of CH2Cl2. After 5 min NaI
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G. Müller et al. · Palladium Complexes with Bidentate P,N Ligands
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bridge, CB21EZ UK, Fax: +44-132-336033;
E-mail: deposit@ccdc.cam.ac.uk or
Crystallographic data for the structural analysis www: http://www.ccdc.cam.ac.uk.
have been deposited with the Cambridge Crystal-
Acknowledgements
lographic Data Center, CCDC 179852for com-
pound 3, CCDC 179853 for compound 6. Copies
The Fonds der Chemischen Industrie and the
of this information may be obtained free of charge DAAD are gratefully acknowledged for their fi-
from The Director, CCDC, 12Union Road, Cam- nancial support.
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[20] One single signal was detected in the 31P NMR as
1
well as one signal for the PdÐMe group in the H
NMR spectrum.
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