Metal complexes of the tetradentate ligands rac- and meso-N,P,P,N: Synthesis, separation and structural characterization

Article abstract of DOI:10.1002/1099-0682(200210)2002:10<2625::AID-EJIC2625>3.0.CO;2-V

The N,P,P,N ligand 1,2-bis[(2-quinolinemethyl)(phenyl)phosphanyl]ethane (2) which contains two stereogenic phosphane units in the ligand backbone [rac-2 (R/R, S/S) and meso-2 (R/S)] and two pendant quinaldine moieties was synthesized. The diastereomeric forms were separated after conversion of the ligands to the corresponding palladium(II) diiodide complexes (rac-3, meso-3). The structure of both compounds was determined by X-ray structure analysis and revealed a bidentate coordination through phosphorus leading to the expected square-planar geometry. The free ligands were regenerated by treatment of the palladium(II) diiodides with potassium cyanide and the coordination behavior of rac-2 and meso-2 towards iron(II) and cobalt(II) dichloride (rac-5, meso-5, M = Fe; rac-6, meso-6, M = Co) was investigated by the means of IR and UV/Vis spectroscopy. The results indicate that in the case of Fe^II and Co^II the quinaldine moieties are not coordinated to the metal center and the ligands therefore act, as in the case of Pd^II, as bidentate systems. UV/Vis investigations suggest a tetrahedral coordination environment for the Co^II complexes. The Fe^II and Co^II derivatives were tested for ethene polymerization and the bis(acetonitrile)-palladium compounds (rac-4, meso-4) for ethene/CO copolymerization reactions. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

Full text of DOI:10.1002/1099-0682(200210)2002:10<2625::AID-EJIC2625>3.0.CO;2-V

FULL PAPER
Metal Complexes of the Tetradentate Ligands rac- and meso-N,P,P,N:
Synthesis, Separation and Structural Characterization
Gabi Müller,[a] Martti Klinga,[b] Markku Leskelä,[b] and Bernhard Rieger*[a]
Keywords: N ligands / P ligands / Iron / Palladium / Cobalt
The N,P,P,N ligand 1,2-bis[(2-quinolinemethyl)(phenyl)phos-
meso-5, M = Fe; rac-6, meso-6, M = Co) was investigated by
phanyl]ethane (2) which contains two stereogenic phosphane the means of IR and UV/Vis spectroscopy. The results indic-
units in the ligand backbone [rac-2 (R/R, S/S) and meso-2 ate that in the case of FeII and CoII the quinaldine moieties
(R/S)] and two pendant quinaldine moieties was synthesized.
The diastereomeric forms were separated after conversion of
are not coordinated to the metal center and the ligands there-
fore act, as in the case of PdII, as bidentate systems. UV/Vis
the ligands to the corresponding palladium(II) diiodide com- investigations suggest a tetrahedral coordination environ-
plexes (rac-3, meso-3). The structure of both compounds was
determined by X-ray structure analysis and revealed a bi-
ment for the CoII complexes. The FeII and CoII derivatives
were tested for ethene polymerization and the bis(acetonitrile)-
dentate coordination through phosphorus leading to the ex- palladium compounds (rac-4, meso-4) for ethene/CO copoly-
pected square-planar geometry. The free ligands were re- merization reactions.
generated by treatment of the palladium(II) diiodides with
potassium cyanide and the coordination behavior of rac-2
and meso-2 towards iron(II) and cobalt(II) dichloride (rac-5,
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
Introduction
towards iron and cobalt complexes with tetradentate li-
gands.
A variety of late-transition-metal polymerization cata-
lysts with different ligand (mono-, bi-, tri- or tetradentate)-
metal combinations are known in the literature.[1Ϫ3] Biden-
tate ligands are often used in nickel-catalyzed olefin homo-
polymerization and palladium-catalyzed olefin/CO copoly-
merization reactions. Highly active iron and cobalt com-
plexes with tridentate pyridyl-diimine systems were disco-
vered recently.[4,5] However less attention has been directed
Recently, our group reported the synthesis of a tetraden-
tate quinaldine-amine ligand 1 and on the application of
the corresponding palladium complexes for norbornene
polymerization.[6,7] When coordinated to iron() or cobalt()
dichloride, 1 exclusively forms an octahedral, C2-sym-
metric complex [(1)Fe/CoCl2, Figure 1].
Figure 1. Octahedral C2-symmetric complexes containing ligand 1
[a]
Department of Materials and Catalysis, Inorganic Chemistry
II, University of Ulm,
89069 Ulm, Germany,
Fax: (internat.) ϩ49-(0)731/502-3039
E-mail: bernhard.rieger@chemie.uni-ulm.de
[b]
Laboratory of Inorganic Chemistry, Department of Chemistry,
P. O. Box 55, 00014 University of Helsinki, Finland
Figure 2. Synthesis of the N,P,P,N ligand 2 (rac-2 and meso-2)
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/1010Ϫ2625 $ 20.00ϩ.50/0
2625

G. Müller, M. Klinga, M. Leskelä, B. Rieger
FULL PAPER
After activation with MAO, (1)CoCl2 (R ϭ CH2Ph)
forms an active catalyst for the polymerization of ethene.[8]
The molecular weight of the product is relatively high
(Mw ഠ 1.5 ϫ 106 g/mol), however the activity (10 kg PE/
[Co]h) of this system is poor due to the low stability of the
Results and Discussion
Ligand and Complex Synthesis
The ligand 2 (rac-2 and meso-2) was prepared following
activated complex.[8] We report here on the synthesis of a the synthetic pathway depicted in Figure 2.[9]
tetradentate, mixed nitrogen/phosphorus-containing ligand
1,2-Bis(phenylphosphanyl)ethane was converted into 1,2-
2 which, instead of the donor-amine groups of ligand 1, bis(chlorophenylphosphanyl)ethane by treating the bis(Li
carries donor/acceptor phosphane functionalities in the li- phosphide) with ClSiMe3, followed by the addition of
gand backbone. The overall arrangement with the pendant hexachloroethane. Subsequent reaction of Li-quinaldine
quinaldine moieties was left unchanged to ensure the with 1,2-bis(chlorophenylphosphanyl)ethane afforded the
formation of the C2-symmetric, octahedral coordination tetradentate N,P,P,N ligand 2 which was isolated as a mix-
compound. PdII, FeII and CoII complexes bearing the new ture of two diastereoisomers due to the two stereogenic
N,P,P,N ligands were synthesized and tested in ethene and phosphorus atoms [rac-2 (R/R and S/S) and meso-2 (S/R)].
ethene/CO copolymerization reactions.
The ratio of rac-2/meso-2 was 1.7:1, indicating a preferred
Scheme 1
2626
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632

Metal Complexes of the Tetradentate Ligands rac- and meso-N,P,P,N
FULL PAPER
formation of the rac-form. Attempts to separate the two
ligands were unsuccessful.
The mixture of rac-2 and meso-2 was converted into the
corresponding, air-stable palladium() diiodide complexes
(Scheme 1, rac-3, meso-3) by treatment with [PdCl2(COD)]
in the presence of sodium iodide.[10] After purification of
the mixture by column chromatography, rac-3 could be sep-
arated by repeated crystallization from CH2Cl2/EtOAc. A
pure sample of meso-3 was isolated by crystallization from
hot acetone.
To investigate the catalytic properties of our diastereo-
meric PdII complexes for ethene/CO copolymerizations the
palladium diiodide compounds were converted into the bis-
(acetonitrile) complexes rac-4 and meso-4 by treating the
diiodides with silver tetrafluoroborate in acetonitrile.
The diastereomeric ligands rac-2 and meso-2 were iso-
lated in pure form after treatment of the corresponding
PdI2 species with aqueous KCN solution. The iron() and
cobalt() dichloride complexes of rac-2 and meso-2 were
synthesized by treatment of the free ligands with the appro-
priate metal() salt (rac-5, meso-5, M ϭ Fe; rac-6, meso-6,
M ϭ Co). Elemental analysis and FAB-MS indicated a 1:1
metal to ligand ratio.
Structural Characterization
Solid State Structures
Single crystals of the palladium() diiodide compounds
suitable for an X-ray structure determination were obtained
by crystallization from CH2Cl2/EtOAc (rac-3) or from acet-
one/toluene (meso-3) (Figure 3).
For both complexes a water molecule was located in the
unit cell which forms intermolecular hydrogen bonds to
neighboring quinaldine moieties. Both compounds crystal-
lize in the monoclinic form. The two iodides (I1 and I2)
and the two phosphorus units (P1 and P2) form the ex-
pected square-planar coordination sphere around the palla-
dium center. Small deviations might result from crystal
packing (Table 1). Bond lengths and angles are within the
range expected for this type of complex (Table 2).[11Ϫ13] In
rac-3 one of the quinaldine moieties is located above, and
the second below, the PdϪP1ϪP2ϪI1ϪI2 coordination
plane, while in meso-3 both units lie on the same side of
the plane. Considering this geometrical arrangement it is
obvious that only the rac-form of the ligand is able to co-
ordinate as a tetradentate ligand in a manner identical to
the N,N,N,N ligand 1 (see Figure 1), with the quinaldine
fragments occupying both axial positions.[6] Attempts to
obtain single crystals of rac-5,6 or meso-5,6 suitable for an
X-ray structure analysis were unsuccessful.
Figure 3. The structure of rac-3 (upper) and meso-3 (lower)
IR Analysis
For structure elucidation IR analysis was performed on The IR spectra of the octahedral FeII and CoII complexes
the free ligands 1, rac-2 and meso-2 as well as on the corres- of ligand 1 [(1)FeCl2 and (1)CoCl2] were used as references,
ponding FeII and CoII complexes. Coordination of an N- since in this case the coordination of the quinaldine moiet-
heteroaromatic unit to a metal center is indicated by a fre- ies has been confirmed by an X-ray structure determina-
quency shift of the heteroaromatic ring vibrations.[14Ϫ16] tion.[6,8]
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632
2627

G. Müller, M. Klinga, M. Leskelä, B. Rieger
meso-3·0.5(C7H8)·H2O
FULL PAPER
Table 1. Crystallographic data for rac-3 and meso-3
rac-3·H2O
Chemical formula
Molecular weight [g/mol]
Crystal color and form
Crystal system
C34H32I2N2OP2Pd
906.76
yellow plate
monoclinic
P21/n
12.518(5)
11.243(5)
23.584(5)
100.63(3)
3262(2)
C37.5H36I2N2OP2Pd
952.82
yellow prism
monoclinic
C2/c
35.069(7)
10.734(2)
22.419(4)
120.44(3)
7276(2)
Space group
˚
a [A]
˚
b [A]
˚
c [A]
β [°]
3
˚
Volume [A ]
Z
4
8
Dcalcd. [mg/m3]
1.846
2.590
1760
1.740
2.327
3720
Absorption coefficient [mmϪ1
F(000)
]
Crystal size [mm]
θmax [°]
Number of observed reflections [I Ͼ 2σ(I)]
Number of collected reflections
Number of unique reflections
Number of parameters
0.44 ϫ 0.38 ϫ 0.16
25.01
4923
5714
5461
0.48 ϫ 0.45 ϫ 0.43
25.03
5508
6173
6070
409
418
Index range
0 Յ h Յ 14
0 Յ k Յ 13
Ϫ28 Յ l Յ 27
1.039
R1 ϭ 0.0368
wR2 ϭ 0.0881
R1 ϭ 0.0427
wR2 ϭ 0.0912
1.310 and Ϫ0.836
0 Յ h Յ 41
0 Յ k Յ 12
Ϫ26 Յ l Յ 22
1.021
R1 ϭ 0.0620
wR2 ϭ 0.1579
R1 ϭ 0.0665
wR2 ϭ 0.1626
2.438 and Ϫ2.046
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)][a][b]
R indices (all data)[a,b]
3
˚
Largest differential peak and hole [e/ A ]
[a]
[b]
2
2 2
4
R1 ϭ Σ||F0| Ϫ |Fc||/Σ|F0|. wR2 ϭ {Σ[w(F0 Ϫ Fc ) ]/Σ[wFo ]}1/2
.
vibration of the free ligands at 1614 cmϪ1 and 1595 cmϪ1
(1), 1617 cmϪ1 and 1597 cmϪ1 (rac-2), 1614 cmϪ1 and 1595
cmϪ1 (meso-2) were attributed to the quinaldine moiety.[17]
Table 2. Selected bond lengths and angles for rac-3 and meso-3
˚
Bond lengths [A]
rac-3·H2O
meso-3·0.5(C7H8)·H2O
The spectra of the FeII and CoII complexes of ligand 1
show a high frequency band at 1647 and 1648 cmϪ1, re-
spectively, which is not present in the spectrum of the free
ligand. Also, a distinct shift of the bands in the 1400Ϫ1570
cmϪ1 region is detectable upon coordination of the quinald-
ine moiety. No differences of band positions and intensities
in the spectra of the FeII and CoII complexes were observed.
I1ϪPd
I2ϪPd
PdϪP2
PdϪP1
P1ϪC1
P1ϪC20
P2ϪC3
P2ϪC2
2.6514(9)
2.6468(8)
2.2429(15)
2.2526(14)
1.830(5)
1.850(5)
1.832(5)
2.6528(8)
2.6499(12)
2.2527(17)
2.2554(17)
1.828(6)
1.832(6)
1.826(6)
1.833(5)
1.834(6)
In the case of the FeII and CoII complexes of the N,P,P,N
ligands rac-2 and meso-2 no band at higher frequencies is
detectable, which would indicate a coordination of the quin-
aldine moiety. The slight variation in the 1400Ϫ1570 cmϪ1
region might be due to the coordination of the phosphane
units to the metal center. These investigations imply that,
in contrast to 1, which coordinates as a tetradentate ligand,
rac-2 and meso-2 form FeII and CoII complexes where the
heteroaromatic unit is not coordinated to the metal center
and the ligands therefore act as bidentate systems.
Bond angles [°]
rac-3·H2O
meso-3·0.5(C7H8)·H2O
P2ϪPdϪP1
P2ϪPdϪI2
P1ϪPdϪI2
P2ϪPdϪI1
P1ϪPdϪI1
I2ϪPdϪI1
PdϪP2ϪC3
PdϪP1ϪC20
87.10(5)
87.73(4)
170.50(4)
171.48(4)
90.15(4)
96.06(3)
115.81(19)
117.22(18)
84.78(6)
87.23(4)
170.55(4)
177.22(4)
92.44(4)
95.55(2)
114.0(2)
124.1(2)
The high frequency region (1700Ϫ1400 cmϪ1) of the ring
deformations of the aromatic and heteroaromatic units is
depicted in Figure 4.[17,18] The IR diagrams 1 (ligand 1 and
UV/Vis Spectroscopy
To support this hypothesis, UV/Vis measurements were
complexes), 2 (rac-2 and complexes) and 3 (meso-2 and performed on the CoII complexes rac-6 and meso-6 in solu-
complexes) show the spectra of the free ligand (top), and tion (Figure 5). The spectra of both isomers show a similar
the iron (middle) and cobalt (bottom) complexes. The ring structure of band positions and intensities, suggesting the
2628
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632

Metal Complexes of the Tetradentate Ligands rac- and meso-N,P,P,N
FULL PAPER
same overall coordination geometry for both complexes
(Table 3).
Table 3. Positions of the band maxima and molar extinction coeffi-
cient of the UV/Vis spectra of a solution of rac-6 and meso-6 in
CH2Cl2
λmax [nm] (εmax [L·molϪ1·cmϪ1])
rac-6
meso-6
368 (852)
377 (985)
599 (329)
597 (316)
663 (375)
661 (390)
683 (381)
690 (414)
UV/Vis investigations on other tetrahedral CoCl2L2 com-
plexes (L ϭ P donor) have shown that the absorption in the
500Ϫ800 nm region can be attributed to the spin-allowed
4
4
transition A2 Ǟ T1.[19Ϫ25] The observed absorption spec-
tra for rac-6 and meso-6 resemble the reported spectra for
the tetrahedral complex [CoCl2(PPh3)2], indicating a bi-
dentate coordination of rac-2 and meso-2 (through the P
units) to give the corresponding tetrahedral CoCl2 com-
Figure 6. Coordination behavior of 1 and proposed coordination
behavior of rac-2 and meso-2 in their FeII and CoIICl2 complexes
plexes (Figure 6).[20,24] We assume a similar coordination
behavior for the FeII complexes.
Figure 4. IR spectra of the free ligands (top), the FeII (middle) and
the CoII (bottom) complexes of the ligands 1 (diagram 1), rac-2
(diagram 2) and meso-2 (diagram 3)
Analysis of the bond lengths and angles found for the
strained, octahedral complex (1)FeCl2 revealed an
FeϪN(R)ϪCH2 angle of 107°.[6] This angle, together with
the N(R)ϪFe bond length determines the distance of the
quinaldine moiety from the axial coordination site in the
complexes. The strained structure of (1)FeCl2 indicates that
an angle of 107° together with an NϪFe bond length of
˚
2.25 A is necessary to allow coordination of the quinaldine
moieties.[6] In the square-planar PdII complexes rac-3 and
meso-3, where the quinaldine moieties are not coordinated
to the metal center, a PdϪPϪCH2 angle of 116° was ob-
served. It is likely that bidentate coordination of the
N,P,P,N ligands stabilizes the tetrahedral CoCl2P2 com-
plexes (PϪCo ഠ 2.2 A [26]) sufficiently so that there is no
˚
need to diminish this angle considerably, forming a highly
constrained ring systems.
The FeII and CoII complexes were tested for the poly-
merization of ethene. However, in contrast to the octahedral
(1)CoCl2, the tetrahedral complexes rac-5,6 and meso-5,6 of
the present study decomposed upon addition of MAO to
Figure 5. UV/Vis spectra of a solution of rac-6 and meso-6 in
CH2Cl2
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632
2629

G. Müller, M. Klinga, M. Leskelä, B. Rieger
FULL PAPER
44 mmol) in THF (300 mL) cooled to Ϫ78 °C. The reaction mix-
ture was warmed to 0 °C and chlorotrimethylsilane (11.4 mL,
90 mmol) was added slowly with a syringe. The solvent was re-
moved under reduced pressure and CH2Cl2 (300 mL) was added.
The reaction mixture was cooled to 0 °C and hexachloroethane
(20.9 g, 88 mmol) was added in small portions. The reaction mix-
ture was stirred at room temperature for 72 hours. The solvent was
removed under reduced pressure and the solid was suspended in
THF (250 mL). In a separate flask BuLi (55.2 mL, 88 mmol) was
added slowly to a solution of quinaldine (12 mL, 88 mmol) in
200 mL of THF cooled to Ϫ78 °C. The dark red solution of the
quinaldine anion was allowed to reach room temperature and was
then added to the suspension of the chlorophosphane at Ϫ78 °C
until the red color of the quinaldine anion remained. A further
10 mL of quinaldine solution was added to ensure the complete
transformation of the chlorophosphane. The reaction mixture was
allowed to reach room temperature and was stirred overnight.
Water (10 mL) was added and the solvent was removed under re-
duced pressure. The remaining solid was dissolved in water
(300 mL) and CH2Cl2 (500 mL). The organic layer was separated
and the water layer was extracted with two 200 mL portions of
CH2Cl2. The organic layers were dried over sodium sulfate. Evap-
oration of the solvent left a red oil which contained a 1:1.7 meso:rac
mixture of the ligand. The crude product was used without further
purification. Yield: 80% (18.6 g).
give a suspension of the complexes in toluene (black precip-
itate, most likely Fe0 or Co0). Initial experiments showed
that the diastereomeric bis(acetonitrile)palladium com-
plexes rac-4 and meso-4 are suitable catalyst precursors for
the copolymerization of ethene and CO using methanol as
cocatalyst. Further investigations on the behavior of the
diastereomeric complexes towards the polymerization of
1-olefins and CO are in progress.
Conclusion
Exchanging the backbone nitrogen functionalities in the
tetradentate N,N,N,N ligand 1 for phosphorus leads to the
formation of two stable diastereoisomers rac-2 and meso-2.
At the same time a distinct variation in the coordination
behavior of the new N,P,P,N ligands is induced. While the
N,N,N,N ligand 1 forms octahedral FeII and CoII com-
plexes, a tetrahedral environment is suggested for the FeII
and CoII complexes of rac-2 and meso-2. Whereas (1)CoCl2
shows some activity for ethene polymerization, the tetra-
hedral rac-5,6 and meso-5,6 complexes undergo fast decom-
position upon treatment with MAO. However, the PdII ana-
logues rac-4 and meso-4 show some activity in the ethene/
CO copolymerization reaction; this will be investigated fur-
ther.
Synthesis of rac-3, meso-3: [PdCl2(COD)] (10.5 g, 36.7 mmol) was
added to a solution of the ligand (36.7 mmol) in CH2Cl2 (300 mL).
NaI (22 g, 1.47 mol) was added after 10 minutes and the reaction
mixture was stirred for 12 hours. CH2Cl2 (500 mL) was added and
the solution was stirred for a further 24 hours. The reaction mixture
was filtered and the solvent was removed under reduced pressure.
The product was purified by column chromatography on silica us-
ing a 10:1 (v:v) mixture of CH2Cl2 and ethyl acetate as eluent.
The rac form was separated by crystallization of the diastereomeric
mixture from CH2Cl2 and ethyl acetate. A pure sample of the meso-
isomer was obtained by crystallization of a meso-enriched fraction
from hot acetone. Overall yields: 37% (12.1 g) rac-3, 25% (8.1 g)
meso-3.
Experimental Section
General Remarks: All manipulations except the handling of the pal-
ladium diiodide complexes were carried out in dry solvents under
an inert atmosphere of argon using standard Schlenk techniques.
THF, diethyl ether and toluene were distilled from LiAlH4, and
CH2Cl2 and petroleum ether were distilled from CaH2. All solvents
were stored over molecular sieves. Commercially available anhyd-
rous acetonitrile and ethanol, BuLi (1.6  in hexane), hexachloroe-
thane, KCN, anhydrous FeCl2 and CoCl2 were used without further
purification. Quinaldine and chlorotrimethylsilane were purified by
distillation. (cis,cis-Cycloocta-1,5-diene)dichloropalladium,[27] 1,2-
bis(phenylphosphanyl)ethane,[28] ligand 1, as well as the corres-
ponding iron and cobalt complexes,[6] were prepared according to
literature procedures.
1
rac-3: H NMR (CDCl3): δ ϭ 2.13 (m, 1 H), 2.22 (m, 1 H), 2.50
(m, 2 H), 4.14 (dd, J1 ϭ 15.9, J2 ϭ 13.1 Hz, 2 H), 4.80 (dd, J1 ϭ
12.9, J2 ϭ 10.1 Hz, 2 H), 6.80 (m, 4 H), 7.12 (dd, 2 H), 7.24 (m, 4
H), 7.53Ϫ7.61 (m, 4 H), 7.65 (d, J ϭ 8.1 Hz, 2 H), 7.83 (d, J ϭ
8.1 Hz, 2 H), 8.08 (d, J ϭ 8.4 Hz, 2 H), 8.15 (d, J ϭ 8.7 Hz, 2
H) ppm. 31P NMR (CDCl3): δ ϭ 69.48 ppm. FAB-MS (matrix: 2-
NPOE): m/z (%) ϭ 889 (22) [MHϩ], 761 (100) [Mϩ Ϫ I].
C34H30I2N2P2Pd·H2O (906.8): calcd. C 45.03, H 3.56, N 3.09;
found C 44.65, H 3.45, N 2.95.
Polymerization experiments were performed in a 100 mL steel auto-
clave (Roth) with a glass inlet and mechanical stirring. Ethene
(BASF, 2.7) and CO (BASF, 2.0) were used without further puri-
fication. MAO (10% in toluene) was purchased from Witko.
meso-3: 1H NMR (CDCl3): δ ϭ 1.78Ϫ1.96 (m, 2 H), 2.02Ϫ2.19
(m, 2 H), 4.27 (dd, J1 ϭ 14.9, J2 ϭ 13.6 Hz, 2 H), 4.65 (dd, J1 ϭ
13.5, J2 ϭ 10.5 Hz, 2 H), 7.34 (m, 4 H), 7.41Ϫ7.50 (m, 4 H), 7.55
(d, J ϭ 8.3 Hz, 2 H), 7.59Ϫ7.64 (m, 4 H), 7.74Ϫ7.82 (m, 8 H) ppm.
31P NMR (CDCl3): δ ϭ 67.33 ppm. FAB-MS (matrix: 2-NPOE):
m/z (%) ϭ 889 (25) [MHϩ], 761 (100) [Mϩ Ϫ I]. C34H30I2N2P2Pd
(888.8): calcd. C 45.95, H 3.40, N 3.15; found C 45.54, H 3.71,
N 2.96.[29]
NMR measurements were conducted on a Bruker DRX 400 spec-
trometer at 400 MHz (1H) and 162 MHz (31P). Chemical shifts are
reported in ppm. Tetramethylsilane and 85% phosphoric acid were
used as references. IR spectra were measured on a Bruker IFS 113v
spectrometer, FAB-MS spectra on a Finnigan MAT TSQ 7000
spectrometer using meta-nitrobenzyl alcohol (m-NBA), 2,3,4-trime-
thoxyacetophenone (TMAP) or 2-nitrophenyloctyl ether (2-NPOE)
as matrices. Elemental analysis were measured on an Vario EL ele-
mentar. UV/Vis absorption spectra were conducted on a J & M
spectrometer using 2 mm solutions in CH2Cl2.
Synthesis of rac-4, meso-4: Silver tetrafluoroborate (223 mg,
1.13 mmol) was added to a suspension of the palladium diiodide
(0.5 g, 0.56 mmol) in acetonitrile (50 mL). The reaction mixture
was stirred overnight and the solution was filtered through celite.
The solvent was removed under reduced pressure and the re-
maining solid was extracted twice with 20 mL portions of CH2Cl2.
Evaporation of the solvent left a yellow, microcrystalline solid.
Yield: 90Ϫ95% (0.45Ϫ0.47 g).
Synthesis of rac-2, meso-2: BuLi (55.2 mL, 88 mmol) was added
slowly to a solution of 1,2-bis(phenylphosphanyl)ethane (10.9 g,
2630
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632

Metal Complexes of the Tetradentate Ligands rac- and meso-N,P,P,N
FULL PAPER
1
rac-4: H NMR (CD3CN): δ ϭ 2.26 (s, CH3CN), 2.96Ϫ3.20 (m, 4 solvent (50 mL of CH2Cl2) and methanol (Cat.:Cocat. ϭ 1:200)
H), 4.34 (m, 2 H), 4.65 (m, 2 H), 7.25 (m, 4 H), 7.47 (m, 2 H), 7.60
were added and the autoclave was pressurized with the ethene (20
(m, 4 H), 7.67Ϫ7.71 (m, 4 H), 7.86 (m, 2 H), 8.00 (d, J ϭ 8.1 Hz, bar) and CO (60 bar). After stirring for 1 h at room temp. the gases
2 H), 8.09 (d, J ϭ 8.6 Hz, 2 H), 8.44 (d, J ϭ 8.5 Hz, 2 H) ppm. were vented off and the polymer was isolated by filtration. Yields:
31P NMR (CD3CN): δ ϭ 86.09 ppm. FAB-MS (matrix: TMAP):
50 mg (meso-4), 65 mg (rac-4). IR: ECO (meso-4): 2912.3 cmϪ1 (ν
CH2), 1693.6 (ν CϵO); ECO (rac-4): 2912.3 cmϪ1 (ν CH2), 1693.9
m/z (%) ϭ 721 (10) [Mϩ Ϫ 2CH3CN Ϫ BF4], 653 (92) [Mϩ
Ϫ
2CH3CN Ϫ BF4 Ϫ BF3], 633 (100) [Mϩ Ϫ 2CH3CN Ϫ BF4 Ϫ BF3 (ν CϵO)
Ϫ HF]. IR (KI): ν˜ ϭ 2320 cmϪ1, 2292 (NϵCϪCH3, m), 1057 (ν
X-ray Crystallographic Study: Crystal data of the compounds rac-
BF4, bs).
3 and meso-3 were collected with a Rikagu AFC7S single-crystal
diffractometer at 193(2) K using Mo-Kα radiation (graphite mon-
1
meso-4: H NMR (CD3CN): δ ϭ 2.25 (s, CH3CN), 2.80Ϫ3.18 (m,
4 H), 4.30Ϫ4.70 (m, 4 H), 7.25 (m, 2 H), 7.45Ϫ7.71 (m, 10 H),
7.84 (m, 4 H), 7.98Ϫ8.10 (m, 4 H), 8.43Ϫ8.48 (m, 2 H) ppm. 31P
NMR (CD3CN): δ ϭ 86.40 ppm. FAB-MS (matrix: m-NBA): m/z
(%) ϭ 721 (2) [Mϩ Ϫ 2CH3CN Ϫ BF4], 653 (52) [Mϩ Ϫ 2CH3CN
Ϫ BF4 Ϫ BF3], 633 (100) [Mϩ Ϫ 2CH3CN Ϫ BF4 Ϫ BF3 Ϫ HF].
IR (KI): ν˜ ϭ 2321 cmϪ1, 2293 (NϵCϪCH3, m), 1060 (ν BF4, bs).
˚
ochromator, λ ϭ 0.71073 A; omega scans). Intensities were cor-
rected for Lorentz and polarization effects.[30] A psi-scan absorp-
tion correction was performed, 0.592 Ͻ T Ͻ 1.000 (rac-3), 0.920
Ͻ T Ͻ 1.000 (meso-3).[31] Solution and refinement: SHELX97
(Sheldrick, 1997).[32,33] The structure was solved by direct methods.
All non-hydrogen atoms were refined anisotropically and hydrogen
atoms were refined isotropically with their displacement factors
1.2-times that of the host atom. The hydrogen atoms of the lattice
water were picked up from the final electron density map and were
not further refined. The solid-state structures are stabilized by hy-
drogen bonds. The water molecule in both compounds is H-bonded
to N5 and N22, the nitrogen acceptor atoms being situated in dif-
ferent complex molecules. In meso-3 a toluene molecule is present
in the unit cell which lies on a twofold rotation axis and is slightly
disordered. All the final electron densities greater than one lie
within one angsterom unit from palladium or iodine atoms.
CCDC-175209 (rac-3) and -175208 (meso-3) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.)
ϩ44Ϫ1223/336Ϫ033; E-mail: deposit@ccdc.cam.ac.uk].
Synthesis rac-2: rac-3 (1 g, 1.125 mmol) and KCN (1.4 g,
22.5 mmol) were added to a mixture of water (20 mL) and toluene
(25 mL). The two-phase system was stirred overnight. The water
phase was separated and the organic phase was washed four times
with 20 mL portions of water. The organic phase was dried over
MgSO4 and the solvent was removed under reduced pressure to
1
leave the ligand as a colorless solid. Yield: 84% (0.50 g). H NMR
(CDCl3): δ ϭ 1.77Ϫ1.88 (m, 4 H), 3.38 (dd, J1 ϭ 14.8, J2
ϭ
13.1 Hz, 4 H), 6.99 (d, J ϭ 8.4 Hz, 2 H), 7.19Ϫ7.29 (m, 6 H), 7.34
(m, 4 H), 7.45 (m, 2 H), 7.63 (m, 2 H), 7.70 (d, J ϭ 8.1 Hz, 2 H),
7.87 (d, J ϭ 8.4 Hz, 2 H), 7.94 (d, J ϭ 8.5 Hz, 2 H) ppm. 31P NMR
(CDCl3): δ ϭ Ϫ14.82 ppm.
Synthesis of meso-2: meso-3 (500 mg, 0.56 mmol) and KCN
(730 mg, 11.25 mmol) were added to a mixture of water (20 mL)
and CH2Cl2 (15 mL). The two-phase system was stirred for 2 h.
The water phase was separated and the organic phase was washed
four times with 20 mL portions of water. The organic phase was
dried over MgSO4 and the solvent was removed under reduced
pressure to leave the ligand as a colorless solid. Yield: 80% (0.24 g).
1H NMR (CDCl3): δ ϭ 1.79Ϫ1.92 (m, 4 H), 3.39 (s, 4 H), 6.96 (d,
J ϭ 8.5 Hz, 2 H), 7.21Ϫ7.30 (m, 6 H), 7.37 (m, 4 H), 7.44 (m, 2
H), 7.63 (m, 2 H), 7.70 (d, J ϭ 8.2 Hz, 2 H), 7.86 (d, J ϭ 8.4 Hz,
2 H), 7.92 (d, J ϭ 8.5 Hz, 2 H) ppm. 31P NMR (CDCl3): δ ϭ
Ϫ14.23 ppm.
Acknowledgments
The Fonds der Chemischen Industrie and the DAAD are gratefully
acknowledged for their financial support.
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C34H30Cl2FeN2P2·H2O (673.3): calcd. C 60.65, H 4.79, N 4.16;
found C 60.23, H 4.71, N 3.99.
[5]
S. J. McTavish, G. A. Solan, A. J. P. White, D. J. Williams,
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[7]
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[8]
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60.37, H 4.77, N 4.14; found C 59.92, H 4.60, N 4.08.
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with bromoquinaldine were unsuccessful due to metal-halogen
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meso-6: FAB-MS (matrix: 2-NPOE): m/z (%) ϭ 622 (100) [Mϩ
Ϫ
Cl], 587 (35) [Mϩ Ϫ 2Cl]. C34H30Cl2CoN2P2·H2O (676.4): calcd. C
60.37, H 4.77, N 4.14; found C 59.86, H 4.85, N 4.05.[30]
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Eur. J. Inorg. Chem. 2002, 2625Ϫ2632
2631

G. Müller, M. Klinga, M. Leskelä, B. Rieger
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2632
Eur. J. Inorg. Chem. 2002, 2625Ϫ2632