Trichloropalladate(II) complexes with pyridine ligands - Molecular structure and conformational analysis of [K(18C6)][PdCl3(py)]

Article abstract of DOI:10.1002/zaac.200500009

[K(18C6)]₂[Pd₂Cl₆] (1) (18C6 = 18-crown-6) was found to react with pyridines in a strictly stoichiometric ratio 1:2 in methylene chloride or nitromethane to yield trichloropalladate(II) complexes [K(18C6)][PdCl₃(py*)] (py* = py, 2a; 4-Bnpy, 2b; 4-tBupy, 2c; Bn = benzyl; tBu = tert-butyl). The reaction of 1 with pyrimidine (pyrm) in a 1:1 ratio led to the formation of the pyrimidine-bridged bis(trichloropalladate) complex [K(18C6)]₂[(PdCl₃) ₂-(μ-pyrm)] (3). The identities of the complexes were confirmed by means of NMR spectroscopy (¹H, ¹³C) and microanalysis. The X-ray structure analysis of 2a reveals square-planar coordination of the Pd atom in the [PdCl₃(py)]^- anion. The pyridine plane forms with the complex plane an angle of 55.8(2)°. In the [K(18C6)]⁺ cation the K⁺ lies outside the mean plane of the crown ether (defined by the 6 O atoms) by 0.816(1) A. There are tight K...Cl contacts between the cation and the anion (K...Cl1 3.340(2) A, K...Cl2 3.166(2) A). To gain an insight into the conformation of the [PdCl ₃(py)]^- anion, DFT calculations were performed showing that the equilibrium structure (6eq) has an angle between the pyridine ligand and the complex plane of 35.3°. Rotation of the pyridine ligand around the Pd-N vector exhibited two transition states where the pyridine ligand lies either in the complex plane (6TS_pla, 0.87 kcal/mol above 6eq) or is perpendicular to it (6TS_per, 3.76 kcal/ mol above 6eq). Based on an energy decomposition analysis the conformation of the anion is discussed in terms of repulsive steric interactions and of stabilizing σ and π orbital interactions between the PdCl₃^- moiety and the pyridine ligand.

Full text of DOI:10.1002/zaac.200500009

Trichloropalladate(II) Complexes with Pyridine Ligands ؊ Molecular Structure
and Conformational Analysis of [K(18C6)][PdCl3(py)]
Marcin Konkol, Christoph Wagner, Sebastian Schwieger, Ronald Lindner, and Dirk Steinborn*
Halle, Institut für Anorganische Chemie der Martin-Luther-Universität
Received January 11th, 2005.
Dedicated to Professor Karl-Heinz Thiele on the Occasion of his 75th Birthday
˚
Abstract. [K(18C6)]2[Pd2Cl6] (1) (18C6 ϭ 18-crown-6) was found
to react with pyridines in a strictly stoichiometric ratio 1 : 2 in
methylene chloride or nitromethane to yield trichloropalladate(II)
complexes [K(18C6)][PdCl3(py*)] (py* ϭ py, 2a; 4-Bnpy, 2b; 4-
tBupy, 2c; Bn ϭ benzyl; tBu ϭ tert-butyl). The reaction of 1 with
pyrimidine (pyrm) in a 1 : 1 ratio led to the formation of the pyrim-
idine-bridged bis(trichloropalladate) complex [K(18C6)]2[(PdCl3)2-
(μ-pyrm)] (3). The identities of the complexes were confirmed by
means of NMR spectroscopy (1H, 13C) and microanalysis. The X-
ray structure analysis of 2a reveals square-planar coordination of
the Pd atom in the [PdCl3(py)]Ϫ anion. The pyridine plane forms
with the complex plane an angle of 55.8(2)°. In the [K(18C6)]ϩ
cation the Kϩ lies outside the mean plane of the crown ether (de-
3.166(2) A). To gain an insight into the conformation of the
[PdCl3(py)]Ϫ anion, DFT calculations were performed showing
that the equilibrium structure (6eq) has an angle between the pyri-
dine ligand and the complex plane of 35.3°. Rotation of the pyri-
dine ligand around the PdϪN vector exhibited two transition states
where the pyridine ligand lies either in the complex plane (6TSpla
,
0.87 kcal/mol above 6eq) or is perpendicular to it (6TSper, 3.76 kcal/
mol above 6eq). Based on an energy decomposition analysis the
conformation of the anion is discussed in terms of repulsive steric
interactions and of stabilizing σ and π orbital interactions between
Ϫ
the PdCl3 moiety and the pyridine ligand.
˚
fined by the 6 O atoms) by 0.816(1) A. There are tight K···Cl con-
Keywords: Palladium; Trichloropalladate complexes; N-donor li-
gands; Crystal structure; Quantum chemical calculations
˚
tacts between the cation and the anion (K···Cl1 3.340(2) A, K···Cl2
Introduction
asymmetric chlorohydrins [11]. We present here the molecu-
lar structure of [K(18C6)][PdCl3(py)] (18C6 ϭ crown ether
18-crown-6) and a DFT study on the conformation of the
[PdCl3(py)]Ϫ anion.
In contrast to a large number of neutral palladium(II) com-
plexes of the types [PdX2L2] (X ϭ halogen, L ϭ N-donor
ligand) and [PdX3LЈ] (LЈ ϭ zwitterionic ligand) [1, 2], only
some anionic trihalogenopalladate(II) complexes of the
type [PdX3L]Ϫ were reported [1, 3Ϫ7]. Few complexes of
the latter type have been structurally characterized so far,
Results and Discussion
The crown ether adduct of potassium hexachlorodipalla-
date(II) [K(18C6)]2[Pd2Cl6] (1) [12] was found to react in
methylene chloride or nitromethane with pyridines (py, 4-
Bnpy, 4-tBupy) in a strictly stoichiometric ratio 1 : 2 to
yield the novel crown ether adducts of potassium trichloro-
(pyridine)palladate(II) complexes [K(18C6)][PdCl3(py*)]
(2aϪc) as yellow-orange powders in yields between
53Ϫ69 %. The analogous reaction in a 1 : 1 ratio with a
bidentate N-donor such as pyrimidine led to the formation
of the pyrimidine-bridged bis(trichloropalladate) complex
[K(18C6)]2[(PdCl3)2(μ-pyrm)] (3) (Scheme 1). For compari-
son of NMR spectroscopic data, with excess of the ligands
neutral complexes of the common type [PdCl2L2] (4aϪd)
were obtained. In accordance with data given in literature
namely complexes with
a
benzamidine
ligand
(PPh4)[PdCl3{PhC(NH)(NH2)}] [8], with an N-substituted
sulfimide ligand (PPh4)[PdBr3(Ph2SNCH2CH2CN)] [9] and
those with bridging N2E2 ligands (PPh4)2[{PdX3}2(μ-N2E2-
κ2N,NЈ)] (E ϭ S, Se; X ϭ Cl, Br) [10]. However, mono N-
substituted anionic complexes with simple pyridine or py-
rimidine ligands have not been structurally characterized as
yet. They are also of interest with respect to their catalytic
potential. Thus, the trichloro(pyridine)palladate(II) com-
plex has received attention in view of its application in the
catalytic oxidation of ethylene to acetaldehyde in the
Wacker process and to 2-chloroethanol in syntheses of
[13], the IR spectrum of the complex 4a (νPdϪN
ϭ
* Prof. Dr. Dirk Steinborn
471 cmϪ1, m; νPdϪCl ϭ 356 cmϪ1, s) gave proof for its
trans configuration.
Institut für Anorganische Chemie
Martin-Luther-Universität Halle-Wittenberg
Kurt-Mothes-Straße 2
D-06120 Halle
E-mail: dirk.steinborn@chemie.uni-halle.de
The constitution of complexes 2 was confirmed by means
of microanalyses and NMR spectroscopy. Coordination of
the pyridines to palladium gave rise to a down-field shift of
the resonances for C2/C6 and H2/H6 by 3.0Ϫ3.8 ppm and
by 0.23Ϫ0.29 ppm, respectively. Although there are only
Supporting information for this article is available on the
WWW under http://www.wiley-vch.de/home/zaac or from the
author
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DOI: 10.1002/zaac.200500009
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Trichloropalladate(II) Complexes with Pyridine Ligands
Scheme 1
Figure 1 Molecular structure of [K(18C6)][PdCl3(py)] (2a), H atoms
are omitted for clarity, thermal ellipsoids are drawn with 30 %
probability.
small differences between the NMR spectroscopic data of
complexes 2 and the corresponding bis(pyridine)palladium
complexes [PdCl2(py*)2] (py* ϭpy, 4a; 4-Bnpy, 4b; 4-tBupy,
1
4c), a mixture of the complexes 2a and 4a exhibited in H
˚
Table 1 Selected interatomic distances (in A) and angles (in °) for
and 13C NMR spectra two sets of signals. Thus, by means
of NMR spectroscopy it can be clearly distinguished in a
reaction solution between [K(18C6)][PdCl3(py*)] (2) and a
mixture of [PdCl2(py*)2] (4) with [K(18C6)]Cl.
[K(18C6)][PdCl3(py)] (2a).
PdϪN
PdϪCl2
K···Cl1
2.020(4)
2.310(1)
3.340(2)
PdϪCl1
PdϪCl3
K···Cl2
2.312(1)
2.298(2)
3.166(2)
The symmetric coordination of pyrimidine to two PdCl3
moieties in the complex 3 is clearly established by only three
resonances in 13C and 1H NMR spectra due to the chemical
equivalence of H4/H6 and C4/C6. On the other hand, the
monodentate coordination of pyrimidine in the complex 4d
PdϪNϪC13
KϪPdϪCl2
Cl1ϪPdϪCl3
Cl3ϪPdϪN
Cl1ϪPdϪN
122.3(4)
55.32(4)
176.17(5)
88.4(1)
PdϪNϪC17
KϪPdϪCl1
Cl2ϪPdϪN
Cl1ϪPdϪCl2
Cl2ϪPdϪCl3
119.6(3)
59.63(4)
176.4(1)
89.43(5)
92.34(5)
90.1(1)
1
gives rise to four resonances in 13C and H NMR spectra.
The coordination induced shifts of H2/H6 and C2/C6
atoms are greater in 3 (Δδ(C2/C6) ϭ 3.8Ϫ4.3, Δδ(H2/H6) ϭ
0.45Ϫ0.74) than in 4d (Δδ(C2/C6) ϭ 2.2Ϫ2.9, Δδ(H2/
H6) ϭ 0.34Ϫ0.36) and also than in the case of complexes
2a-c.
CϪOϪCϪC and 61Ϫ66° for the OϪCϪCϪO units. The
conformation of the macrocycle is characterized by an
alternating sequence of the partial conformation of the
OϪCϪCϪO subunits (ap, ϩsc, ap) and (ap, Ϫsc, ap). An
analogous one has been found in the alkene and alkyne
complexes of Zeise’s salt type [K(18C6)][PtCl3(cis-RHCϭ
CHRЈ)] (R/RЈ ϭ Me/Me, Et/Me) [14] and [K(18C6)]-
[PtCl3(RCϵCRЈ)] (R/RЈ ϭ Me/Me, Et/Et, Ph/D) [15] as
well as in the starting complex [K(18C6)]2[Pd2Cl6] [12]. In
contrast, the unhydrated solid 18-crown-6 has three confor-
mationally different OϪCϪCϪO subunits [(ap, ap, ap), (ap,
ϩsc, ap), (ap, Ϫsc, ϩsc)] [16]. The potassium cation is lo-
From the methylene chloride solution of [K(18C6)]-
[PdCl3(py)] (2a) well-shaped dark yellow crystals precipi-
tated that proved to be suitable for single-crystal X-ray dif-
fraction analysis. Complex 2a crystallizes in the non-centro-
symmetric monoclinic space group P21. Crystals of 2a are
composed of discrete molecules without any unusual inter-
molecular interactions; the shortest distance between non-
˚
hydrogen atoms is 3.338(5) A (Pd···C14Ј). The molecular
˚
structure of complex 2a is shown in Figure 1; selected struc-
tural parameters are given in Table 1.
cated 0.816(1) A outside the mean plane of the crown ether
(defined by the six O atoms). It is in a close contact with
The Pd atom is square-planar coordinated by three
chloro atoms and the nitrogen atom of the pyridine ligand.
Deviations from the square-planar coordination are small;
the sum of angles around Pd is 360.0° and all angles be-
tween neighbored atoms are close to 90° (88.4(1)Ϫ
92.34(5)°). The angle between the complex plane and the
pyridine plane amounts to 55.8(2)°. The PdϪN bond length
two chloro ligands of the [PdCl3(py)]Ϫ anion. The K···Cl
˚
˚
distances (K···Cl2 3.166(2) A; K···Cl1 3.340(2) A) are only
˚
slightly longer than those in the solid KCl (3.146 A) [17].
The mean plane of the crown ether and the complex plane
are nearly parallel to each other, with the interplanar angle
being only 15.04(9)°. Likely, these cationϪanion contacts
give rise to a slight elongation of the PdϪCl1 bond as re-
vealed by the comparison with the PdϪCl3 bond length
˚
is 2.020(4) A. It is only slightly shorter than the median
˚
value reported for square-planar palladium complexes with
pyridine ligands (median: 2.044, lower/higher quartile:
2.027/2.072, n ϭ 81, n Ϫ number of observations). The
crown ether 18-crown-6 in the [K(18C6)]ϩ cation has tor-
sion angles (absolute values) in the ranges 170Ϫ179° for the
(2.312(1) versus 2.298(2) A).
To gain further insight into the molecular structure of
2a, quantum chemical calculations on the DFT level of the
theory were performed. The calculated equilibrium struc-
ture of the complex (2acalc) is shown in Figure 2 with selec-
Z. Anorg. Allg. Chem. 2005, 631, 1456Ϫ1462
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M. Konkol, Ch. Wagner, S. Schwieger, R. Lindner, D. Steinborn
Figure 2 Calculated structure of [K(18C6)][PdCl3(py)] (2acalc).
˚
Selected parameters (distances in A, angles in °):
PdϪCl1 2.421, PdϪCl2 2.385, PdϪCl3 2.404, PdϪN 2.053, K···Cl1 3.731,
K···Cl2 3.214; NϪPdϪCl1 89.5, NϪPdϪCl2 176.8, NϪPdϪCl3 88.3,
Cl1ϪPdϪCl3 173.1.
Figure 3 Calculated structures of [PdCl3(py)]Ϫ. a) Equilibrium
structure 6eq (atoms defining the dihedral angle for conformational
analysis are marked with asterisks). b) Transition state 6TSpla. c)
Transition state 6TSper
.
ted parameters in the figure caption. All characteristic fea-
tures of the experimental structure were also found in the
calculated one. The pyridine ligand forms an angle of 49.7°
(exp.: 55.8(2)°) with the complex plane. The conformation
of the [K(18C6)]ϩ cation in 2acalc is the same as that in 2a.
Table 2 Calculated structural parameters for [PdCl3(py)]Ϫ: a) Equi-
librium structure 6eq. b) Transition state with pyridine in the com-
plex plane 6TSpla. c) Transition state with pyridine perpendicular
to the complex plane 6TSper. For comparison the values of the
equilibrium structure of [PdCl3]Ϫ are given.
˚
˚
The potassium cation is located 0.558 A (exp.: 0.816(1) A)
outside the mean plane of the six crown ether oxygen atoms
and is in a close contact with two chloro ligands of the
6eq
6TSpla
6TSper
[PdCl3]Ϫ
[PdCl3(py)]Ϫ anion (K···Cl: 3.214/3.731 A; exp.: 3.166(2)/
˚
PdϪN
PdϪCltrans
PdϪClcis
NϪPdϪCltrans
ClcisϪPdϪClcis
ClcisϪPdϪCltrans
2.079
2.319
2.372
179.9
178.9
90.6
2.116
2.315
2.376/2.377
179.8
176.5
2.045
2.318
2.370
180.0
175.1
92.5
˚
3.340(2) A). The angle between the complex plane and the
2.280
2.311/2.312
a)
mean plane of the crown ether is 17.4° (exp.: 15.04(9)°).
After calculating the equilibrium structures of the cation
[K(18C6)]ϩ (5) and the anion [PdCl3(py)]Ϫ (6) on the same
level of theory, the interaction energy (corrected for the
basis set superposition error, BSSE) for the reaction
165.5
97.1/97.4
a)
88.3
a) Identical values for the two cis-chloro ligands are given only once.
[K(18C6)]ϩ ϩ [PdCl3(py)]Ϫ Ǟ [K(18C6)][PdCl3(py)]
(6TSpla, interplanar angle py/PdCl3N: 0.4°) or is perpen-
dicular to it (6TSper, interplanar angle py/PdCl3N: 90.0°).
The former one (6TSpla) is 0.86 kcal/mol above the equilib-
rium structure and the latter one (6TSper) 3.71 kcal/mol.
These two structures are shown in the Figures 3b and 3c;
selected structural parameters are given in Table 2. There
was found a pronounced elongation of the PdϪN bond go-
ing from the structure with the pyridine ligand perpendicu-
5
6
2acalc
was shown to be Ϫ68.8 kcal/mol and Ϫ69.1 kcal/mol if the
zero-point vibrational energies were taken into account.
The equilibrium structure of the anion [PdCl3(py)]Ϫ (6eq)
is shown in Figure 3a, selected structural parameters are
given in Table 2. Similarly to 2a/2acalc, the plane of the pyri-
dine ligand is also declined to the complex plane; the in-
terplanar angle was calculated to be 35.3°. This angle pro-
ved to be strongly dependent on the method used in the
calculations; an angle of 40.7° was calculated in 6. Differ-
˚
lar to the complex plane 6TSper (2.045 A) via the equilib-
˚
rium structure 6eq (2.079 A) to the planar structure 6TSpla
˚
(2.116 A). This indicates the presence of increasing (repul-
sive) steric interactions between the pyridine and the
Ϫ
ences of these angles between 6eq/6 (35.3/40.7°) and 2acalc
/
PdCl3 moiety in the order 6TSper < 6eq < 6TSpla.
2a (49.7/55.8(2)°) may be caused by the cation-anion inter-
actions.
This argumentation is further confirmed by an energy
decomposition analysis according to Morokuma [18] and
Ziegler [19], see Ref. [20] for an explanation of the funda-
mental steps. The results shown in Table 3 suggest that the
values of both ΔEPauli (repulsive) and ΔEelstat (attractive)
are in the order 6TSpla < 6eq < 6TSper. Although the orbital
contribution ΔEorb remains to be approximately constant,
the breakdown into energy contributions from σ (A sym-
metry) and π (B symmetry) interactions makes the follow-
To gain an insight into this aspect of the structure, the
conformational energy of the anion [PdCl3(py)]Ϫ (6eq) in
dependence on the C2ϪNϪPdϪClcis coordinate (being a
measure of the interplanar angle py/PdCl3N, see Figure 3a)
has been calculated. Rotation of the pyridine ligand around
the PdϪN vector resulted in two different transition states
where the pyridine ligand lies either in the complex plane
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Trichloropalladate(II) Complexes with Pyridine Ligands
Table 3 Energies and energy decomposition analyses of equilibrium
structure and transition states of [PdCl3(py)]Ϫ. All energies are
given in kcal/mol
6TSpla
6eq
6TSper
Ϫ
Angle (in °) py/PdCl3 0.4
35.3
0
90.0
3.71
Energy (rel.)
0.86
Ϫ
ΔEprep (PdCl3
ΔEprep (py)
ΔEint
ΔEPauli
ΔEelstat
)
4.63
0.54
Ϫ26.77
108.17
Ϫ90.01
Ϫ44.93
2.92
0.51
Ϫ26.03
115.29
Ϫ95.40
Ϫ45.92
1.92
0.35
Ϫ21.07
120.51
Ϫ97.45
Ϫ44.13
Figure 4 Localized orbitals for 6TSpla (left) and 6TSper (right) show-
ing π-type back-donation into virtual pyridine fragment orbital.
ΔEorb (ΔEσ/ΔEπ)a)
(Ϫ32.43/Ϫ12.52) (Ϫ34.42/Ϫ11.50) (Ϫ34.98/Ϫ9.14)
Ϫ21.60 Ϫ22.60 Ϫ18.80
ΔEb)
and 65°. Only four complexes were found to have the pyri-
dine ligands perpendicular to the complex plane (in-
terplanar angle > 80°). In general, we have to take into
consideration that the conformation of the complexes in the
crystals may be strongly influenced by packing effects and
also by specific intermolecular interactions. Such specific
intermolecular interactions can be Ϫ depending on the co-
ordination pattern of the pyridine ligands Ϫ hydrogen
bonds or πϪπ stacking between aromatic rings and in
charged complexes also the cation-anion interactions.
Concluding, novel trichloropalladate(II) and bis(tri-
chloropalladate) complexes with simple mono- and biden-
tate heterocyclic N-donor ligands have been presented. The
complex with the pyridine, [K(18C6)][PdCl3(py)] (2a), is the
first structurally characterized representative of that type.
The quantum chemical analysis of the anion [PdCl3(py)]Ϫ
(6eq, 6TSpla, 6TSper) reveals the factors upon which the
conformation of the pyridine ligand with respect to the
complex plane is dependent. Most likely, this can be gen-
eralized, because similar conformations as in 2a/6eq were
found in most of the other square-planar chloro complexes
of transition metals with pyridine ligands.
a) Energy contributions from σ (A symmetry) and π interactions (B sym-
metry), respectively.
b) Total bond energy (PdϪN).
ing clear: i) The σ contributions amount to 72Ϫ79 %. ii) As
expected, the shorter the PdϪN distances are, the stronger
are the energy contributions from σ interactions (6TSpla
<
6eq < 6TSper). iii) The reverse order was found for the π
contributions, likely, due to stronger participation of the Pd
dxy orbital into π-type interaction with the chloro ligands
than the dxz orbital (Figure 4). Thus, the overall stabilizing
contribution ΔEint is greater for 6TSpla (Ϫ26.77 kcal/mol)
and 6eq (Ϫ26.03 kcal/mol) than for 6TSper (Ϫ21.07 kcal/
mol). On the other hand, the energies to promote the equi-
librium structures of the fragments to the geometries and
electronic states which they have in the compound
[PdCl3(py)]Ϫ (ΔEprep) show the opposite dependence:
6TSper (2.27 kcal/mol) < 6eq (3.43 kcal/mol) < 6TSpla
(5.17 kcal/mol). The major contribution comes from the
Ϫ
distortion of the PdCl3 fragment. Overall, the twist be-
tween the pyridine ligand and the complex plane in the
equilibrium structure seems to be an energetic compromise
between repulsive steric interactions (lowest in 6TSper) and
attractive π interactions (greatest in 6TSpla). It remains to
be speculative, whether weak CϪH···Cl hydrogen bonds
[21] between the 2/6-CϪH groups („ortho“) and the cis-
chloro ligands play a significant role in stabilizing the equi-
Experimental
Syntheses of complexes were carried out under argon using stand-
ard Schlenk techniques whereas the work-up procedures were per-
formed on air. Methylene chloride, nitromethane and diethyl ether
were dried (CH2Cl2 over CaH2, CH3NO2 over molecular sieve A4,
Et2O over NaϪbenzophenone) and distilled prior to use.
[K(18C6)]2[Pd2Cl6] (1) was obtained according to the literature [12].
Microanalyses (C, H, N, Cl) were performed by the microanalytical
laboratory of the University of Halle using CHNS-932 (LECO)
and Vario EL (elementar Analysensysteme) elemental analyzers. 1H
and 13C NMR spectra were recorded on Varian Gemini 200, VXR
400 and Unity 500 NMR spectrometers. Chemical shifts are rela-
tive to CHCl3 (δ 7.24), CHDCl2 (δ 5.32) and CDCl3 (δ 77.0),
CD2Cl2 (δ 53.8) as internal references. IR spectra were recorded on
a Galaxy FT-IR spectrometer Mattson 5000 using CsBr pellets.
librium structure 6eq and the planar transition state 6TSpla
.
Upon inspection of the Cambridge structural database
(CSD) it was revealed that other structurally characterized
square-planar transition metal complexes of the types
[MCl3(py*)]z (8) and [MCl2(py*)2]z (9) (py* ϭ pyridine de-
rivative) show in most cases an analogous ligand position,
except that the pyridine ligands are 2- or 2/6-substituted.
Such pyridine ligands tend to be approximately perpendicu-
lar to the complex plane, most likely, owing to steric hin-
drance caused by the substitution in 2- or 2/6-positions.
ϩ
Thus, in three type 8 complexes, Q[PtCl3(py)] (Q ϭ NEt4
,
Preparation of [K(18C6)][PdCl3(py*)] (2aϪc). To a suspension
of the crown ether adduct of potassium hexachlorodipalladate
[K(18C6)]2[Pd2Cl6] (1) (103 mg, 0.1 mmol) in methylene chloride
(6 ml) or to a solution of 1 in nitromethane (3 ml) the correspond-
ing pyridine (0.2 mmol) was added. Within a minute a light orange
solution was formed. The solution was concentrated (50 % of the
PPh3Bnϩ) [22] and [AuCl3(py)] [23], interplanar angles
(pyridine/complex plane) between 44 and 58° were ob-
served. About 80 % of all complexes (total 38 entries) of
the type [MCl2(py*)2]z (9, M ϭ PdII, PtII, CuII, CdII, z ϭ
0; AuIII, z ϭ 1ϩ) exhibited interplanar angles between 40
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M. Konkol, Ch. Wagner, S. Schwieger, R. Lindner, D. Steinborn
volume) by evaporation of the solvent in vacuo. Diethyl ether
(10 ml) was added resulting in the formation of a yellow-orange
precipitate that was filtered off, washed with diethyl ether (15 ml)
and dried.
Table 4 Crystal data and structure refinement for 2a.
Empirical formula
Formula weight
C17H29Cl3NO6KPd
595.26
Crystal system/space group
monoclinic/P21
11.530(5)
8.453(1)
˚
a/A
py* ϭ py (2a). Yield: 69 mg (58 %). Anal. Found: C, 34.18; H, 4.81;
N, 2.05; Cl, 18.06 %. C17H29Cl3NO6KPd (595.30). Calc.: C, 34.30;
H, 4.91; N, 2.35; Cl, 17.87 %.
1H NMR (CDCl3, 400 MHz): δ 3.67 (s, 24H1), 18C6), 7.18Ϫ7.22 (m, 2H,
H3/H5), 7.61Ϫ7.66 (m, 1H, H4), 8.86Ϫ8.88 (m, 2H, H2/H6). 13C NMR
(CDCl3, 50 MHz): δ 70.1 (18C6), 124.4 (C3/C5), 137.5 (C4), 153.5 (C2/C6).
˚
b/A
˚
c/A
12.705(3)
β/°
101.26(4)
1214.4(6)
3
˚
V/A
Z
2
ρ/g cmϪ3
1.628
1.296
604
μ(Mo-Kα)/mmϪ1
F(000)
py* ϭ 4-Bnpy (2b). Yield: 75 mg (55 %). Anal. Found: C, 41.34; H,
5.41; N, 1.75; Cl, 15.88 %. C24H35Cl3NO6KPd (685.42). Calc.: C,
42.06; H, 5.15; N, 2.04; Cl, 15.52 %.
1H NMR (CDCl3, 400 MHz): δ 3.65 (s, 24H, 18C6), 3.90 (s, 2H, CH2),
6.98Ϫ6.99 (m, 2H, H3/H5 of py), 7.07Ϫ7.09 (m, 2H, o-H of Bn), 7.22Ϫ7.30
(m, 1H, p-H of Bn, 2H, m-H of Bn), 8.69Ϫ8.71 (m, 2H, H2/H6 of py). 13C
NMR (CDCl3, 50 MHz): δ 40.9 (CH2), 70.1 (18C6), 124.8 (C3/C5 of py),
127.0 (p-C of Bn), 128.9/129.1 (o/m-C of Bn), 137.6 (i-C of Bn), 152.3 (C4
of py), 153.0 (C2/C6 of py).
Scan range/°
2.18 < θ < 25.85
Ϫ14 Ǟ 14, Ϫ9 Ǟ 10, Ϫ15 Ǟ 15
9433
4413 (Rint ϭ 0.0570)
4413/1/262
1.000
0.0324, 0.0691
0.0414, 0.0749
0.476 and Ϫ0.833
Reciprocal lattice segments h, k, l
Reflections collected
Reflections independent
Data/restraints/parameters
Goodness-of-fit on F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Ϫ3
˚
Largest diff. peak and hole/e A
py* ϭ 4-tBupy (2c). Yield: 90 mg (69 %). Anal. Found: C, 38.53;
H, 5.72; N, 2.14; Cl, 16.03 %. C21H37Cl3NO6KPd (651.40). Calc.:
C, 38.72; H, 5.73; N, 2.15; Cl, 16.33 %.
1H NMR (CDCl3, 400 MHz): δ 1.23 (s, 9H, CH3), 3.66 (s, 24H, 18C6),
7.15Ϫ7.17 (m, 2H, H3/H5), 8.69Ϫ8.71 (m, 2H, H2/H6). 13C NMR (CDCl3,
100 MHz): δ 30.2 (CH3), 34.9 (C(CH3)3), 70.1 (18C6), 121.7 (C3/C5), 152.8
(C2/C6), 162.0 (C4).
8.63Ϫ8.65 (m, 4H, H2/H6 of py). 13C NMR (CDCl3, 100 MHz): δ 41.0
(CH2), 125.2 (C3/C5 of py), 127.2 (p-C of Bn), 129.0/129.1 (o/m-C of Bn),
137.2 (i-C of Bn), 152.8 (C4 of py), 153.6 (C2/C6 of py).
py* ϭ 4-tBupy (4c). Yield: 64 mg (72 %). 1H NMR (CDCl3,
400 MHz): δ 1.28 (s, 18H, CH3), 7.27Ϫ7.29 (m, 4H, H3/H5),
8.65Ϫ8.67 (m, 4H, H2/H6). 13C NMR (CDCl3, 100 MHz): δ 30.2
(CH3), 35.1 (C(CH3)3), 122.2 (C3/C5), 152.6 (C2/C6), 163.4 (C4).
Preparation of [K(18C6)]2[(PdCl3)2(μ-pyrm)] (3). [K(18C6)]2-
[Pd2Cl6] (1) (103 mg, 0.1 mmol) was suspended in methylene chlo-
ride (3 ml). Then pyrimidine (8.0 mg, 0.1 mmol) was added. Within
a few minutes of stirring the brown suspension turned to a dark
orange solution. After adding diethyl ether (4 ml) the solution was
stored at Ϫ40 °C for one day. After that time a yellow-orange mi-
crocrystalline precipitate was formed that was filtered off, washed
with diethyl ether (15 ml) and dried. Yield: 80 mg (72 %).
Anal. Found: C, 29.96; H, 4.63; N, 2.60; Cl, 18.80 %.
C28H52N2O12Cl6K2Pd2 (1112.48). Calc.: C, 30.23; H, 4.71; N, 2.52;
Cl, 19.12 %.
py* ϭ pyrm (4d). Yield: 61 mg (88 %).
1H NMR (CD2Cl2, 400 MHz): δ 7.32Ϫ7.35 (m, 2H, H5), 8.69Ϫ8.71 (m, 2H,
H4), 9.05Ϫ9.07 (m, 2H, H6), 9.51 (s, 2H, H2). 13C NMR (CD2Cl2,
100 MHz): δ 121.7 (C5), 158.0 (C4), 160.1 (C6), 161.5 (C2).
X-ray structure determination
1H NMR (CD2Cl2, 400 MHz): δ 3.70 (s, 48H, 18C6), 7.30 (dt, 1H, 3J(H5,H4/
6) ϭ 5.7 Hz, 5J(H2,H5) ϭ 1.1 Hz, H5), 9.15 (dd, 2H, 3J(H5,H4/6) ϭ 5.6 Hz,
Single-crystal X-ray diffraction analysis of 2a was per-
formed at 220(2) K on a STOE-IPDS diffractometer for a
single crystal of 2a with dimensions 0.42 ϫ 0.09 ϫ
4J(H2,H4/6)
ϭ ϭ 1.1 Hz,
0.6 Hz, H4/H6), 9.91 (dd, 1H, 5J(H2,H5)
4J(H2,H4/6) ϭ 0.5 Hz, H2). 13C NMR (CD2Cl2, 100 MHz): δ 70.6 (18C6),
121.2 (C5), 161.0 (C4/C6), 163.6 (C2).
˚
0.02 mm, using MoϪKα radiation (λ ϭ 0.71073 A, graphite
Preparation of [PdCl2(py*)2] (4aϪd). To a suspension of 1
(103 mg, 0.1 mmol) in methylene chloride (3 ml) or to a solution of
1 in nitromethane (4 ml) the corresponding pyridine or pyrimidine
(0.4 mmol) was added. Within a few minutes of stirring a yellow
solution was formed and a yellow precipitate was observed. Diethyl
ether (5 ml) was added to accomplish the precipitation and the yel-
low product was filtered off, washed with diethyl ether (15 ml)
and dried.
monochromator). A summary of the crystallographic data,
the data collection parameters, and the refinement param-
eters is given in Table 4. Absorption correction was applied
numerically (Tmin/Tmax 0.86/0.98). The structure was solved
by direct methods with SHELXS-97 [24]. The structure re-
finement was carried out by full-matrix least-squares pro-
cedures on F2 (SHELXL-97 [24]) for all reflections. All
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were added to the model
in their calculated positions (riding model) and refined iso-
tropically. Crystallographic data (excluding structure fac-
tors) for the structure reported in this paper have been de-
posited at the Cambridge Crystallographic Data Center
(CCDC) as Supplementary Publication No. CCDC-261953
(2a). Copies of the data can be obtained free of charge on
application to the CCDC, 12 Union Road, Cambridge, CB2
1EZ, U.K. (fax, (internat.) ϩ44-1223-336033; e-mail, de-
posit@ccdc.cam.ac.uk.
py* ϭ py (4a). Yield: 53 mg (79 %).
1H NMR (CDCl3, 400 MHz): δ 7.30Ϫ7.34 (m, 4H, H3/H5), 7.74Ϫ7.79 (m,
2H, H4), 8.81Ϫ8.83 (m, 4H, H2/H6). 13C NMR (CDCl3, 100 MHz): δ 124.9
(C3/C5), 138.5 (C4), 153.3 (C2/C6). IR (CsBr): ν(PdϪCl) 357, ν(PdϪN)
471 cmϪ1
.
py* ϭ 4-Bnpy (4b). Yield: 72 mg (70 %).
1H NMR (CDCl3, 400 MHz): δ 3.97 (s, 4H, CH2), 7.08Ϫ7.12 (m, 4H, H3/
H5 of py, 4H, o-H of Bn), 7.23Ϫ7.33 (m, 2H, p-H of Bn, 4H, m-H of Bn),
1) The number of protons for 18C6 was found to be slightly higher
in all cases.
1460
© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2005, 631, 1456Ϫ1462

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Computational Details
DFT calculations of the compounds 2acalc, 5 and 6 were carried
out by the Gaussian98 program package [25] using the hybrid func-
tional B3LYP [26] and the basis sets SDD as implemented in the
Gaussian program. All systems have been fully optimized without
any symmetry restrictions. The resulting geometries were charac-
terized as equilibrium structures by the analysis of the force con-
stants of normal vibrations [27]. The interaction energy was cor-
rected for basis set superposition errors (BSSE) that were estimated
with counterpoise type calculations [28]. The conformational
analysis of the [PdCl3(py)]Ϫ anion was performed by means of the
Amsterdam Density Functional package ADF (Release 2004.01)
[29] using a generalized gradient approximation (GGA; mPWx ϩ
PW91c) in addition to the local density approximation (LDA) [30,
31]. Use was made of the frozen core approximation (coretyp ϭ
small) and triple-zeta basis sets extended with a polarization func-
tion. Relativistic effects have been considered by the zero order
approximation (ZORA) as implemented in the ADF program
package. These optimizations were also performed without any
symmetry restrictions. The resulting geometries were characterized
as equilibrium structure (6eq) and transition states (6TSpla, 6TSper),
respectively, by the analysis of the force constants of normal vi-
brations. The energy decomposition analysis was performed as im-
plemented in the ADF program package. The breakdown of the
ΔEorb into energy contributions from σ symmetry (A symmetry,
neglecting a small contribution from δ symmetry) and π (B) sym-
metry was done in the symmetry group C2. Orbitals were localized
as implemented in the ADF package according to the Boys-Foster-
Method [32]. The canonical orbitals of different irreducible rep-
resentations were localized seperately (symmetry group C2v).
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