Flexible diphosphine ligands with overall charges of 0, +1, and +2: Critical role of the electrostatics in favoring trans over cis coordination

Article abstract of DOI:10.1021/ic201342z

The influence of the formal electrostatic interaction on the cis/trans coordination mode at a PdCl₂ center is investigated in a family of isostructural flexible diphosphine ligands Ph₂P-X-C₆H ₄-Y-PPh₂

Full text of DOI:10.1021/ic201342z

ARTICLE
pubs.acs.org/IC
Flexible Diphosphine Ligands with Overall Charges of 0, +1, and
+2: Critical Role of the Electrostatics in Favoring Trans over Cis
Coordination
Yves Canac,*,†,‡ Nathalie Debono,†,‡ Christine Lepetit,†,‡ Carine Duhayon,†,‡ and Remi Chauvin*,†,‡
†CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, F-31077 Toulouse, France
‡Universitꢀe de Toulouse, UPS, INP, LCC, F-31077 Toulouse, France
S Supporting Information
b
ABSTRACT:
The influence of the formal electrostatic interaction on the cis/trans coordination mode at a PdCl2 center is investigated in a family
of isostructural flexible diphosphine ligands Ph2PꢀXꢀC6H4ꢀYꢀPPh2, where X and Y stand for neutral or cationic N,C-
imidazolylene linkers. While the neutral and monocationic diphosphine spontaneously behave as classical cis-chelating ligands, only
the dicationic diphosphine, where the electrostatic repulsion between the formal positive charges specifically takes place, is observed
to behave as a trans-chelating ligand. The crucial role of electrostatics is analyzed on the basis of 31P NMR data in solution and X-ray
diffraction data in the crystal state. Comparative theoretical studies of the cis- and trans-chelated complexes, including EDA, static
31P NMR, MESP, and AIM analyses, have been undertaken on the basis of DFT calculations in the gas phase or in the acetonitrile
continuum. Whereas the cis-coordination mode is shown to be thermodynamically favored for the neutral ligand, the trans-
coordination mode is found to be preferred for the dicationic homologue. The stereochemical preference is thus shown to be parallel
to the expected effect of the formal electrostatic interaction. The results open perspectives for control of the cis- and trans-chelating
behavior of flexible bidentate ligands by more or less reversible charge transfer at the periphery of the coordination sphere of a
metallic center.
three classes of chelate ligands are thus distinguished: the strictly
cis-chelating ligands (PꢀMꢀP e 100°), the intermediate wide-
bite-angle ligands (100° < PꢀMꢀP e 160°), and the trans-
chelating ligands (PꢀMꢀP > 160°).2 Trans-chelating ligands
have been particularly exemplified by the TRANSphos,3 BISBI,4
and TRAP5 ligands for their applications in catalysis and asym-
metric catalysis (Scheme 1).6 Purely bidentate trans-chelating
diphosphines (without an auxiliary coordinating atom that could
drive enforced trans coordination of external P atoms, a situation
found in the tridentate pincer complexes) are today attracting a
renewed interest.7 Assuming a sequential coordination process,
after coordination of a first P atom, cis or trans coordination of
the second P atom is a priori enabled by two degrees of freedom:
(i) orientation of the P lone pair by rotation about the bridgeꢀP
bond and (ii) adaptation of the metallacycle conformation by
rotation about single bonds of the bridge. The bridge may also be
1. INTRODUCTION
The backbone of bidentate L∼L0 ligands plays a fundamental
role in the determination of specific properties of their transition
metal complexes, in particular in catalysis and asymmetric catal-
ysis. This has been widely illustrated in the design of spectator
chelating diphosphine ligands (L, L0 = P) of organometallic
catalysts.1 The length and flexibility of the L∼L0 bridge influence
first the ability of the ligand to achieve chelating or bridging co-
ordination modes. With sufficiently long bridges in appropriate
stoichiometry and dilution conditions, the mononuclear chelate
mode is favored, at least statistically and kinetically. In the case of
complexes with square-planar, bipyramid-trigonal, or octahedral
configuration, the same characteristics of the L∼L0 bridge also
influence the cis- vs trans-chelating mode preference. Whereas
most of the chelate ligands described in the literature have been
exclusively, and often implicitly, considered in their preferred cis-
coordination mode, the question of the cis- vs trans-coordination
preference has been explicitly addressed by the definition of the
PꢀMꢀP bite angle.2 In the C2-symmetric diphosphine series,
Received: June 24, 2011
Published: October 07, 2011
r
2011 American Chemical Society
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Scheme 1. Selected Trans-Chelating Ligands with a C2-Symmetric Core Either Quasi-Exclusive (Rigid Trans-Spanning Ligands,
Left)10 or Adaptative (with Two Internal Degrees of Freedom of the Bridge Indicated by Curved Arrows, Right)
more rigid like in the SPANphos8 and TRANSDIP9 ligands,
which mainly adopt the trans-coordination mode (trans-
spanning ligands: Scheme 1).10 In most cases, however, residual
flexibility of the ligand makes the alternative cis-coordination
mode more accessible. If kinetically allowed, the transꢀcis iso-
merization might then proceed either directly (without any
PꢀM bond breaking through a tetrahedral intermediate) or via
decoordination of one of the P atoms and possibly through a
reservoir of bimetallic species where two L∼L moieties act as
bridging ligands between two metallic centers. Nevertheless,
known ligands with marked cis- or trans-coordination preference
possess backbones with quite different steric demand. Control
of the cis- vs trans-coordination mode by minimal alteration of
the ligand backbone remains desirable. A controlled switch of
the configuration (e.g., by reversible proton, electron, or photon
transfer) is an ultimate challenge.
The bis(imidazolylphosphine) 1 based on the o-phenylene
bridge (Scheme 1) possesses the required characteristics of a
trans-chelating ligand while a priori preserving the possibility
of acting in a cis-chelating manner through optimized rotation
about the ArꢀN single bonds. This neutral ligand is sterically
very similar (quasi-isosteric) to its N-methylated cationic homo-
logue 2 and its N,N0-dimethylated dicationic derivative 3. It has
been shown that the dication 3 indeed behaves as a versatile cis-
or trans-coordinating ligand depending on the environment
(especially the formal charge) of a given type of metallic center
(Rh(I)):trans-chelatingataneutralRhCl(CO) center(PꢀRhꢀP=
163.8°), cis-chelating at a cationic [Rh(MeCN)2]+ center (Pꢀ
Rh+ꢀP = 96.8°).11 This configurational change was interpreted
by a subtle interplay between electrostatic and orbital effects.
After having investigated the change of charge at the metal atom
for the given ligand 3, the change of charge at the ligand back-
bone for a given neutral metallic center is anticipated to bring out
the electrostatic effect only: this is hereafter investigated through
the series of homologous quasi-isosteric ligands 1ꢀ3 at the
neutral homoleptic PdCl2 center.
(SO3ꢀ, PO32ꢀ) or two positive (R4N+, R4P+) formal charges has
also been reported to dictate the trans preference of pairs of
anionic or cationic monophosphines, respectively.14 In the latter
cases, however, the electrostatic effect is assisted by the steric
effect, also repulsive in nature and thus favoring trans arrange-
ments. Even if steric and electrostatic effects remain globally
stronger than the antisymbiotic electronic effect (HSAB cis
preference or trans influence for class b soft metallic centers),15
the contribution of the electrostatic component is generally quite
weak as the interacting formal charges are located at the peri-
phery of the ligand and thus remote from the metallic center.
In the ligand 3 the charges are located as closely as possible to
the metal center and even formally at the coordinating P atoms
themselves: since imidazoliophosphines have been demon-
strated to be true NHC-phosphenium adducts,16 the formal posi-
tive charge can be considered to be more concentrated at the P
atoms than at the adjacent C and N atoms (at least as soon as the
semipolar form N2C+ꢀP of the dative N2Cꢀ>P+ bond is not
invoked).
Moreover, the bidentate and flexible nature of 3 is anticipated
to lower the purely steric effect on the trans to cis preference
ratio. If the quasi-isosteric ligands 1 and 2 (where formal electro-
static repulsion is absent) exhibited a cis-chelating behavior, a
second example of the trans-chelating behavior of 3 (at a PdCl2
center instead of a Rh(CO)Cl center) would provide further
support to an interpretation based on electrostatic effects in the
corresponding complexes.11
2. RESULTS AND DISCUSSION
2.1. Experimental Results. Following a recently described
procedure (Scheme 2),11 the neutral and dicationic diphosphines
1 and 3 were prepared from the readily available 1,2-bis(imidazol-
N-yl)benzene and characterized by X-ray diffraction analysis of
corresponding single crystals (Figure 1 and Table 1).17 Addition
of a single equivalent of MeOTf to the neutral diphosphine 1 in
CH2Cl2 afforded the monocationic diphosphine 2 in 70% yield
(Scheme 2). The ionic nature of 2 is indicated by its low solubility
in nonpolar solvents, and its dissymmetric structure is confirmed
by two coupled inequivalent 31P NMR signals at δ = ꢀ22.9
(d, N2C+P) and ꢀ31.8 (d, N2CP) ppm (JPP = 28.3 Hz) and by
Structural effects of the attractive interaction between formal
point charges of opposite signs in the coordination sphere of
transition metals have been explicitly addressed on examples
of either metalꢀligand12 or ligandꢀligand electrostatic interac-
tions.13 Likewise, the repulsive interaction between two negative
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Scheme 2. Selective N-Methylation of the Neutral Diphosphine 1 to the Mono- and Dicationic Diphosphines 2 and 3
Figure 1. ORTEP views of the X-ray crystal structures of ligands 1 (left) and 3 (right) (Scheme 2) with thermal ellipsoids drawn at the 30% probability
level (for clarity, H atoms were omitted). See Table 1 for details.
Table 1. Selected Bond Lengths [Å] and Angles [deg] from
X-ray Diffraction Analyses of Ligands 1 and 3 and Their
Respective Complexes 4, 5, and 6
Scheme 3. Preparation of PdCl2 Complexes 4ꢀ6 of the
Neutral and Cationic Diphosphines 1ꢀ3
1a
3b
4
5
6
C1ꢀP1
1.820(2) 1.845(4) 1.809(4)
1.824(2) 1.831(5) 1.801(4)
1.317(3) 1.358(6) 1.306(5)
1.371(3) 1.347(6) 1.371(5)
1.371(3) 1.362(6) 1.373(5)
1.317(3) 1.314(6) 1.312(5)
2.2349(9)
1.836(4)
1.818(5)
1.356(6)
1.356(6)
1.381(6)
1.322(6)
2.2973(11)
2.2983(12)
1.839(4)
1.836(3)
1.338(4)
1.361(4)
1.347(4)
1.338(4)
2.2880(9)
2.2918(9)
2.3138(9)
2.2723(9)
165.72(3)
178.38(4)
C10ꢀP2
C1ꢀN1
C1ꢀN2
C10ꢀN3
C10ꢀN4
P1ꢀPd
P2ꢀPd
2.2676(9)
PdꢀCl1
PdꢀCl2
P1ꢀPd-P2
Cl1ꢀPd-Cl2
2.3475(10) 2.3306(13)
2.3194(9)
93.22(3)
91.69(4)
2.3245(11)
97.17(4)
88.47(4)
a The neutral molecule 1 is quasi-C2 symmetric with the two neutral
imidazolylphosphine moieties in the anti position with respect to the
1,2-phenylene bridge. b The dication 3 is quasi-Cs symmetric with the
two imidazoliophosphine moieties maintained in the syn position with
respect to the 1,2-phenylene bridge by an intercalated triflate anion
(electrostatic pincer, see Scheme 4). In MeCN solution, 3 appears as a
mixture of two atropisomers, possibly corresponding to the quasi-C2 and
quasi-Cs conformers.
afforded the corresponding PdCl2 complexes 4, 5, and 6 in 94%,
91%, and 92% yield, respectively (Scheme 3).18 The 31P{1H}
NMR spectrum of 4 and 6 displays a singlet at 8.8 and 9.2 ppm,
respectively, while that of the dissymmetric complex 5 exhibits
two singlets at 4.1 and 10.6 ppm, in the typical range for Pdꢀ
diphosphine complexes.19 The absence or very weak value of the
JPP coupling constant is indicative of a cis arrangement of ligand 2
in 5 (see calculated spectra, section 2.2.2). All complexes were
thus formed as single isomers at the NMR time scales at room
the 3-H integral of the NꢀCH3 1H NMR signal at δ =
+3.22 ppm.
Treatment of the diphosphines 1, 2, and 3 with a stoichio-
metric amount of (PhCN)2PdCl2 in THF at room temperature
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Figure 2. ORTEP views of the X-ray crystal structures of the palladium complexes 4 (left), 5 (middle), and 6 (right) (Scheme 3) with thermal ellipsoids
drawn at the 30% probability level (for clarity, triflate anions and H atoms were omitted, except for 6). See Table 1 for details.
Scheme 4. Representation of the Pincer PC+ Oꢀ +CP
Attractive Electrostatic Interaction Inducing the Syn Con-
formation of 3 in the Crystal State (See Figure 3)
example of the previously reported trans-chelating behavior of 3
3 3 3
3 3 3
at neutral late transition metal centers, namely, PdCl2 and RhCl-
(CO) centers.11
The chelation mode is naturally correlated with the range of
distances between the atoms where the positive charges are formally
located upon of N-methylation of imidazolyl rings of 4, namely, the
N, C, and P atoms of the facing N2CꢀP moieties (MeN2C:ꢀ>
P+ T MeN2C+ꢀP T MeN+dC(N)ꢀP). For a first-level compara-
tive purpose, the average location of the formal charge is assumed to
be the centroid of these four atoms, namely, the C atom.16
The P P and C C distances are thus, respectively, close
3 3 3
3 3 3
to 3.36 and 3.98 Å ((0.1 Å) in complexes 4 and 5 and are much
greater at 4.54 and 4.61 Å in complex 6 (Table 1). The formal
electrostatic repulsion occurring in 6 can be reasonably assumed
to be the driving force of the change in chelation mode of the
flexible ligand by passing from complexes 4 and 5 (without
formal electrostatic strain) to complex 6.
1
temperature. The 31P and H NMR spectra of the complexes
showed neither decoalescence nor peak broadening in CD3CO-
CD3 at low temperature (down to ꢀ50 °C), suggesting that the
dynamicsofthecomplexesislimitedtolow-energy conformational
changes without cis/trans interconversion at room temperature.
All complexes, including the electrostatically strained dicationic
complex 6, proved to be thermally stable in air both in solution
and in the solid state. Their exact structure was determined by
X-ray diffraction analysis of single crystals deposited at room
temperature from CHCl3 for 4, CH2Cl2 for 5, and CH3CN/
Et2O for 6 (Figure 2, Table 1).17
Whereas the square-planar-type configuration is almost per-
fect in complex 4 (five atoms in the quasi-coplanar P2PdCl2
motif), it is distorted in both complexes 5 (four atoms in quasi-
coplanar PPdCl2 or P2PdCl motifs, from which the remaining
PdꢀP or PdꢀCl bond is tilted by ca. 17.6°) and 6 (four atoms of
the PPdCl2 motifs, including a quasi-linear PdCl2 unit, from
which the second PdꢀP bond is tilted by ca. 14.3°). In all com-
plexes, however, the palladium atom occupies a position such
that the sum of the four successive bond angles at Pd is close to
that of the planar geometry (∑° = 360 ( 1.8°), far from the
tetrahedral geometry (for which, ideally, ∑° = 438°). The Pꢀ
PdꢀP bite angles (and corresponding ClꢀPdꢀCl angles) are
equal to 93.2° (91.7°), 97.2° (88.5°), and 165.7° (180°) for 4, 5,
and 6, respectively. Clearly, the diphosphine ligands act in a cis-
chelating manner in 4 and 5 and in a trans-chelating manner in 6.
The trans-chelating behavior at the neutral PdCl2 center is there-
fore specific of the sole ligand 3, where electrostatic repulsion
between positive formal charges occurs. This result is a second
It is however noteworthy that in the crystal state the free lig-
ands 1 and 3 seem to freely adopt conformations where the
C
P
C distances are identical (4.24 ( 0.04 Å) and where the
P distance is even shorter in free 3 (4.21 Å) than in the
3 3 3
3 3 3
chelate complex 6 (4.54 Å) (Table 1). At first sight, this suggests
that the zeroth-order analysis of the formal electrostatic repulsion
effect might not apply to the free ligands. Nevertheless, inspec-
tion of the X-ray crystal structures indicates that the dicationic
diphosphine adopts the same conformation in the free state 3 and
in the trans-chelated state 6, where the two imidazoliophosphine
moieties reside in the syn position with respect to the 1,2-pheny-
lene bridge (Figures 1 and 2, and Scheme 4). This syn arrange-
ment is imposed by the PꢀPdꢀP chelation in complex 6 and by
a PC+ Oꢀ +CP electrostatic pincer at a negatively charged
3 3 3
3 3 3
oxygen atom of an intercalated triflate anion (C+ Oꢀ = 3.38 (
3 3 3
0.06 Å) in the free ligand 3 (for steric reasons, no triflate anion is
intercalated in 6 and the two neutral imidazolylphosphine moie-
ties of the free ligand 1 reside in the anti position with respect to
the 1,2-phenylene bridge).
The paradox is therefore explained by an electrostatic attrac-
tive interaction between the triflate anion and the two cationic
moieties of ligand 3. The triflate anion thus screens the facing
positive charges, compensates for their repulsion, and induces a
specific electrostatic packing in the crystal state.
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Table 2. Relative Energies of the Cis and Trans Isomers of Complexes 4-6 Calculated at Various Levels Using the 6-31G**/
LANL2DZ*(Pd) Basis Seta
PBE
B3PW91
M05-2X
COSMO-PBE
PCM-PBE
PCM-B3PW91
ZPEb
cis-4
0.0
0.0
0.66
11.39
0.0
0.0
4.22
9.61
0.0
0.0
0.0
0.0
0.0
trans-4
cis-5
2.91
4.96
0.0
6.76
0.0
4.81
1.64
0.0
4.29
2.32
0.0
trans-5
cis-6
0.77
6.63
0.0
0.53
4.76
0.0
19.19
0.0
17.81
0.0
7.35
0.0
7.38
0.0
trans-6
a Energies are given in kcal/mol. PCM and COSMO methods were used to take into account the acetonitrile solvent (ε = 35.688). b Zero-point-
corrected energies from PCM-B3PW91 calculations.
Table 3. Calculated (PCM-B3PW91) and Experimental Data
for Selected Geometrical Parameters of Pd Complexes 4ꢀ6
(Bond Lengths in Å, Bond Angles in deg)a
In such a polar solvent, the anionꢀcation interactions are a priori
weakened and the presence of the triflate anions of 6 can indeed
be neglected. The latter methods thus suggest an energy differ-
ence of ca. 6 ( 1 kcal/mol between the cis and the trans isomers
of 4 and 6. Gas-phase calculations, including M05-2X calcula-
tions expected to account for weak intramolecular interactions,
deviate strongly from this value.
The calculated structures are in good agreement with the avai-
lable X-ray crystal data (Tables 1 and 3). As previously reported
for calculations using the same LANL2DZ* pseudopotential for
the Pd atom, PdꢀP and PdꢀCl bonds and to a lesser extent PꢀC
bonds are calculated to be longer (up to 0.1 Å) than in the
experimental structures.20 As M05-2X does not perform better
than B3PW91 for both cis-4 and trans-6 (see Supporting Infor-
mation, Tables S1 and S2), the PCM-B3PW91 level was selected
as an optimal compromise for further studies.
The energy calculation results are thus parallel to the experi-
mental observations but do not give any hint about the possible
electrostatic origin of the difference in the stereochemical pre-
ference of 4 and 5. Indeed, the steric hindrance provided by the
assumed quasi-isosteric ligands 1ꢀ3 is indeed not strictly equi-
valent because of the presence or absence of N-methyl substit-
uents. In spite of the smallness and peripheral position of the
methyl groups, steric effects cannot be ruled out a priori for
explaining the trans preference of the dicationic complex 6.
Dispersive interactions between the methyl groups and phenyl
substituents of the adjacent PPh2 fragments might indeed be
ultimately responsible for a steric relaxation from cis-6 to trans-6,
but the difference has been checked to be nonsignificant (the
shortest distance between carbon atoms of two such fragments is
calculated at 3.17 Å in trans-6 vs 3.12 Å in cis-6).21
Between the extreme cases of the neutral and dicationic com-
plexes 4 and 6, the intermediate case of the monocationic com-
plex 5 deserved particular attention. The calculated structure of
cis-5 optimized at PCM-B3PW91 (in acetonitrile) was found to
be in good agreement with the X-ray diffraction analysis data
(Table 3). The relative energy calculation results for cis-5 and
trans-5 are however less conclusive. Indeed, whereas gas-phase
calculations are in favor of a cis-coordination mode, PCM and
COSMO calculations in acetonitrile solvent suggest that the cis
and trans isomers of 5 are almost isoenergetic (Table 2). The
trans-5 isomer is predicted to be more stable than cis-5 at the
B3PW91 level, while the reverse is predicted at the PBE level, in
agreement with the observation in the crystal state. The lower
energy difference between the isomers of 5 (as compared to the
corresponding isomers of 4) cannot be explained by a formal
electrostatic repulsion: in contrast to 3 and 6, indeed, a single
Pd complex
PdꢀP PdꢀCl PꢀCN2 PꢀPdꢀP ClꢀPdꢀCl
cis-4
exp. XRD 2.235 2.319
2.268 2.348
1.809
1.801
1.821
1.823
1.836
1.819
1.862
1.818
1.839
1.836
1.860
1.861
93.2
91.7
calcd
2.310 2.392
2.326 2.410
94.6
89.3
cis-5
exp. XRD 2.297 2.331
2.298 2.325
97.17
98.4
88.47
88.5
calcd
2.284 2.339
2.289 2.322
trans-6
exp. XRD 2.288 2.314
2.292 2.272
165.7
164.5
178.4
177.5
calcd
2.354 2.333
2.358 2.387
a All calculations were performed with the 6-31G**/LANL2DZ*(Pd)
basis set.
Though possibly trans chelating, as observed in complex 6,
the dicationic ligand 3 is not trans spanning and might also be
able to behave in a cis-chelating manner. Whatever is the origin of
the stereochemical preference (electrostatic vs orbital vs steric),
one main question is whether the observed trans chelation of the
dicationic ligand 3 in 6 results from thermodynamic or kinetic
control. This point and others are addressed below by resorting
to computational methods.
2.2. Computational Analysis. 2.2.1. Optimized Structures
and Energies. The relative stability of the cis and trans isomers
of complex 4 and complex ions 5 and 6 (in the absence of triflate
anion) was investigated at various DFT levels (Table 2) either in
the gas phase or taking into account the acetonitrile solvent via a
continuum dielectric medium as implemented in the PCM or
COSMO methods. The trans-4 and trans-6 complexes were cal-
culated to be Cs symmetric, whereas all other complexes were
found to exhibit a C1 symmetry.
In the absence of anion, the same stereochemical stability
order is found for the neutral and dicationic complexes 4 and 6
whatever the calculation level: cis-4 is more stable than trans-4,
and trans-6 is more stable than cis-6. The calculated thermody-
namic data are thus in qualitative agreement with the stereo-
chemical preferences observed in the crystal state (see preceding
section). The relative energy values of the isomers are sensitive to
the calculation level (Table 2), but PCM or COSMO calculations
in the acetonitrile continuum are expected to be more reliable.
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formal positive charge occurs in 2 and 5. This illustrates the fact
that electrostatics is just a competing contribution in the general
case. Nevertheless, the trans isomer remains much less stabilized
in the monocation 5 than in the dication 6.
The quasi-degeneracy of the cis-5 and trans-5 cations suggests
kinetic control in the stereoselective formation of the cis isomer.
However, although the scenario of a very fast cis-5 a trans-5
interconversion at the NMR time scales accompanied with a shift
toward the cis isomer upon crystallization could be ruled out on
the basis of the general knowledge on Pd(II) complexes,22 confir-
mation was required. This point is addressed in the next section
by comparing the calculated NMR spectra of cis-5 and trans-5
cations.
2.2.2. Static NMR Spectrum of Complex 5. Although variable-
temperature NMR analyses of complex 5 did not allow us to
reveal any equilibrium between interconverting species, the cis
and trans isomers of the cation were calculated to be close in
energy (see Table 2). Nevertheless, the vanishing value of the JPP
coupling constant strongly suggests the occurrence of the sole
cis-coordinated complex (vide supra). In order to confirm this
point, the 31P NMR chemical shifts and corresponding JPP coup-
ling constants in the equilibrium structures of cis-5 and trans-5
were calculated at 0 K and compared with results on a series of
related Pd complexes described in ref 15a and 17 (Table 4 and
Supporting Information, Table S3). In accordance with pre-
viously reported NMR data for trans-diphosphine Pd complexes,
a large value is calculated for trans-5 (JPP = 416.4 Hz) whereas a
much lower value is calculated for cis-5 (JPP = ꢀ15.6 Hz).
The latter value and its difference with the former are therefore
in agreement with the occurrence of the cis-5 isomer as the major
species in solution, as it could be expected.
origin of the stereochemical inversion observed for complexes 4
and 6, electrostatics provides only a contribution to the global
interaction. From a quantitative viewpoint, EDA allows for parti-
tioning the interaction energy (Eint) between two fragments into
three components resulting from three types of interactions,
namely, (i) the Pauli repulsion (EPauli), (ii) the electrostatic inter-
actions (Eelstat), and (iii) the orbital overlaps (Eorb). The latter
accounts for the charge transfer induced by the interaction be-
tween occupied and empty orbitals not belonging to the same
fragment and for polarization effects corresponding to the mixing
of orbitals within each fragment.
EDA of the interaction between the neutral PdCl2 fragment
and the neutral or cationic ligand 1, 2, or 3 frozen in the geometry
adopted in the corresponding complex was performed for com-
plexes 4ꢀ6. Following the MorokumaꢀZiegler scheme imple-
mented in the ADF program package,23 the EDA results are listed
in Table 5. This EDA study allows us to investigate the role of
electrostatics in the metalꢀligand interaction and provides only
indirect insight into the origin of the cis/trans stereochemical
preference of ligands 1ꢀ3.24
In the three complexes, the total interaction energy Eint is close
to ꢀ4.0 kcal/mol, a rather small value as compared to other
reported Pdꢀphosphine complexes.25 In all cases, the electro-
static term dominates the orbital term in the total attractive inter-
action energy Eattr = Eorb + Eelstat, with a Eelstat/Eattr ratio
remaining very close to 60% (Table 5). Although the electrostatic
term intervenes for ca. 1/3 in the sum of the three absolute
interaction terms of the EDA ouput, it is equal to ca. 2/3 of the
sum of the absolute electrostatic and quantum terms (Table 5,
columns 9 and 8). These values are thus approximately the same
for all complexes and illustrate the importance of the electrostatic
interaction in chemical bonding.26 It is also noteworthy that
whatever is the criterion used, the contribution of the electro-
static term is systematically higher for the most stable isomer of
each pair of isomers of 4, 5, and 6.
2.2.3. Energy Decomposition Analysis (EDA). In spite of the
above proposed qualitative arguments on a possible electrostatic
Table 4. Calculated 31P Chemical Shifts and JPP Coupling
Constants for cis-5, trans-5, and trans-6a
2.2.4. AIM Topological Analysis. Topological analysis of the
electron density provides a partition of the molecular space into
atomic basins and allows for estimation of the corresponding
δ
31P (ppm)
JPP (Hz)
calcd
exp.
calcd
exp.
cis-5
44.6
19.7
27.4
43.9
37.5
37.5
10.6
4.1
na
ꢀ15.6
0
trans-5
trans-6
416.4
432.5
na
na
Figure 3. Atom labeling for the AIM analysis of the diphosphine ligands
in complexes 4ꢀ6 (see Table 6). The E2 and E4 substituents at the N2
and N4 atoms, respectively, denote either lone pairs (LP) or methylium
9.2
equiv. P
+
a B3PW91/6-31+G**/LANL2DZ*(Pd) level of calculation.
groups (CH3 ).
Table 5. Energy Decomposition Analysis of Complexes 4ꢀ6 (Optimized at the PCM-B3PW91/6-31G**/LANL2DZ*(Pd) Level)a
b
EPauli
Eelstat
Eorb
Eint
Eint/Eelstat
Eelstat/Eattr
|Eelstat|/[|Eelstat| | + |Equant|]c
|Eelstat|/(|Eelstat| + |EPauli| + |Eorb|)d
trans-4
cis-4
15.448
11.030
10.910
10.747
10.987
11.414
ꢀ11.974
ꢀ9.501
ꢀ9.553
ꢀ8.858
ꢀ9.417
ꢀ9.095
ꢀ9.362
ꢀ6.153
ꢀ5.984
ꢀ5.879
ꢀ5.988
ꢀ6.144
ꢀ4.889
ꢀ4.625
ꢀ4.628
ꢀ3.990
ꢀ4.418
ꢀ3.824
0.446
0.487
0.484
0.450
0.469
0.421
0.540
0.607
0.615
0.601
0.611
0.597
0.643
0.661
0.660
0.645
0.653
0.633
0.307
0.356
0.361
0.348
0.357
0.341
trans-5
cis-5
trans-6
cis-6
a Energies are given in kcal/mol. b Ratio of the electrostatic interaction term to the total energy of attractive interactions (Eattr = Eelstat + Eorb). c Ratio of
the absolute electrostatic term to the sum of the absolute electrostatic and quantum terms (Equant = EPauli + Eorb). d Ratio of the absolute electrostatic
term to the sum of the three absolute terms of EDA. Values for the most stable isomer are given in bold.
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Table 6. AIM Atomic Charges of the Cis and Trans Isomers of Complexes 4ꢀ6a
Pd
P1
P2
C1
C2
N1
N2
N3
N4
CH3
Cl
4
cis
0.30
0.32
1.82
1.80
1.79
1.80
0.47
0.49
0.48
0.49
ꢀ1.30
ꢀ1.30
ꢀ1.20
ꢀ1.20
ꢀ1.30
ꢀ1.30
ꢀ1.20
ꢀ1.20
ꢀ0.54
ꢀ0.54
E2 = LP
E4 = LP
5
E2 = LP
E4 = Me+
6
trans
cis
0.31
0.33
1.74
1.73
1.78
1.84
0.58
0.59
0.47
0.49
ꢀ1.30
ꢀ1.30
ꢀ1.20
ꢀ1.20
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
0.26
0.26
ꢀ0.50
ꢀ0.50
trans
cis
0.31
0.34
1.75
1.75
1.70
1.75
0.58
0.6
0.58
0.6
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
ꢀ1.30
0.25
0.25
ꢀ0.50
ꢀ0.50
E2 = Me+
E4 = Me+
trans
a Atom labeling in Figure 3. B3PW91/6-31G**/DGDZVP(Pd)//PCM-B3PW91/6-31G**/LANL2DZ*(Pd) level of calculation.
Figure 4. Isodensity surface (0.02 au) color coded with the MESP of complexes 4ꢀ6 (optimized at the PCM-B3PW91/6-31G**/LANL2DZ*(Pd)
level). Color scale: red MESP < 0.05; yellow MESP = 0.1; green MESP = 0.20; light-blue MESP = 0.30; dark-blue MESP > 0.45.
atomic AIM (atoms in molecules) charges.27 AIM analysis of
complexes 4ꢀ6 was performed using either the available experi-
mental XRD geometry or the calculated structure in the acet-
onitrile continuum (Figure 3, Table 6).
compensated by a decrease of the positive charge at the adjacent
P atoms.
2.2.5. Molecular Electrostatic Potential (MESP). The molec-
ular electrostatic potential (MESP) is the potential generated by
the molecular charge distribution as experienced by a positive
point charge28
In each pair of isomers, the AIM charges of all the atoms in the
coordination sphere are very similar. The negative AIM charges
are located at the N and Cl atoms and do not depend on neither
the remote environment (beyond the Ei substituents for the N
atoms) nor on the stereochemistry (Table 6). The same trend
applies to the positively charged atoms in the whole series: the Pd
atoms (qPd = +0.32 ( 0.02 e), the neutral phosphine P atoms
(qP = +1.81 ( 0.03 e), the phosphenium P atoms (qP = +1.73 (
0.02 e), the P-bonded imidazolyl C atoms (qC = +0.48 ( 0.01 e),
and the P-bonded imidazolium C atoms (qC = +0.59 ( 0.01 e).
The C and P atoms of the N2CꢀP unit exhibit opposite charge
sensitivities upon N-methylation (Ei: LP f Me, ΔQ = +1 e):
a natural sensitivity for the C atom (ΔqC ≈ +0.1 e) and an
unnatural one for the P atom (ΔqP ≈ ꢀ 0.08 e). The excess
positive charge is spread over the N-methylated imidazole ring,
and the increase of positive charge at the C1 and C2 atoms is
Z
ZA
Fðr0Þ
VðrÞ ¼
ꢀ
d3r0
∑
jr ꢀ RAj
jr ꢀ r0j
A
where ZA denotes the nuclear charges, RA the position of the
nuclei, and F(r) the electron density. The MESP minima indicate
the sites of concentration of the electron density and the most
favorable sites for electrophilic attack.29 Exploration of positive
MESP regions are visualized by MESP-textured isodensity sur-
faces, as shown in Figure 4 for complexes 4ꢀ6.
Regions of increasing positive MESP are clearly building up by
shifting from the neutral complex 4 to the dication 6, through the
intermediate monocation 5. For the dication 6, large positive
MESP values (dark blue) appear to be more equally distributed
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Inorganic Chemistry
ARTICLE
in the most stable trans-6 isomer than in the cis-6 isomer. This
illustrates that electrostatic repulsion is globally reduced by trans
coordination of the dicationic diphosphine 3 by comparison with
cis coordination of the same ligand. This also tends to confirm
that the driving force of the observed trans-coordination pre-
ference of 3 in 6 is at least partly of electrostatic nature.
Diphosphines 1 and 3 were prepared according to a recently reported
procedure.11
Synthesis of Diphosphine 2. To a solution of 1 (0.62 g,
1.07 mmol) in CH2Cl2 (20 mL) cooled at ꢀ78 °C was added MeOTf
(0.11 mL, 0.96 mmol). The mixture was stirred at room temperature for
2 h. After concentration under vacuum, the residue was washed with
Et2O (40 mL) to afford a white solid (yield 0.56 g, 70%).
1H NMR (CD3CN, 25 °C): 7.79 (br s, 1H, Har), 7.64ꢀ7.60 (m, 4H,
Har), 7.57ꢀ7.54 (m, 4H, Har), 7.50ꢀ7.45 (m, 3H, Har), 7.43ꢀ7.30 (m,
12H, Har), 7.25ꢀ7.21 (m, 2H, Har), 7.11 (d, JHH = 9.2 Hz, 1H, Har), 6.95
(br s, 1H, Har), 3.22 (s, 3H, CH3). 13C NMR (CD3CN, 25 °C): 145.5 (d,
JCP = 57.4 Hz, C), 134.1ꢀ133.5 (m, 5 CH), 132.3 (d, JCP = 18.9 Hz,
CH), 132.2 (CH), 131.8 (CH), 131.4 (CH), 130.9 (m, C), 130.6 (d,
JCP = 5.8 Hz, CH), 130.4 (d, JCP = 4.1 Hz, CH), 130.0 (d, JCP = 8.3 Hz,
CH), 129.8 (d, JCP = 3.0 Hz, CH), 129.7 (d, JCP = 6.1 Hz, CH), 129.5
(CH), 129.4 (CH), 129.2 (CH), 128.4 (CH), 127.5 (d, JCP = 7.1 Hz, C),
127.3 (d, JCP = 7.2 Hz, C), 121.2 (q, JCF = 322.0 Hz, CF3SO3ꢀ), 38.1
(CH3). 31P NMR (CD3CN, 25 °C): ꢀ22.9 (d, JPP = 28.3 Hz), ꢀ31.8 (d,
JPP = 28.3 Hz). MS (ESI+): m/z = 593 [M]+. HRMS (ESI+): calcd for
C37H31N4P2 593.2024; found 593.1993.
Synthesis of Complex 4. A mixture of complex PdCl2(PhCN)2
(0.066 g, 0.17 mmol) and 1 (0.10 g, 0.17 mmol) was dissolved in THF
(5 mL) at ꢀ30 °C and then stirred at room temperature for 3 h. After
concentration under vacuum, the residue was washed with Et2O (5 mL),
affording an orange solid (yield 0.12 g, 94%). Recrystallization at room
temperature from CHCl3 afforded yellow crystals (mp 245ꢀ250 °C).
1H NMR (CDCl3, 25 °C): 7.86ꢀ7.90 (m, 4H, Har), 7.62ꢀ7.65 (m,
2H, Har), 7.51 (d, JHH = 0.9 Hz, 2H, Har), 7.32ꢀ7.41 (m, 10H, Har),
7.10ꢀ7.14 (m, 2H, Har), 6.84ꢀ6.91 (m, 8H, Har). 13C NMR (CDCl3,
25 °C): 140.2 (d, JCP = 89.8 Hz, C), 134.3 (d, JCP = 11.3 Hz, CH), 132.9
(d, JCP = 12.2 Hz, CH), 132.1 (d, JCP = 10.4 Hz, CH), 131.8 (CH), 131.3
(d, JCP = 65.4 Hz, C), 131.0 (CH), 130.8 (CH), 130.5 (CH), 130.3 (dd,
JCP = 3.8 Hz, JCP = 57.9 Hz, C), 127.8 (d, JCP = 12.8 Hz, CH), 127.8 (d,
JCP = 12.1 Hz, CH), 126.6 (CH). 31P NMR (CDCl3, 25 °C): 8.76. MS
(ESI+): m/z = 719 [M ꢀ Cl]+. HRMS (ES+): calcd for C36H28N4P2-
PdCl 719.0522; found 719.0503.
’ CONCLUSION
The trans-chelating character of the flexible generic dipho-
sphines 1ꢀ3 has been shown to be governed by the formal
electrostatic interaction, the two positive charges of the dicatio-
nic ligand specifically repelling the coordinating P atoms in trans
positions at a PdCl2 center. The combined effects of the electron-
poor and trans-chelating characters of this dicationic ligand in
homogeneous catalysis deserve now to be investigated. From a
still more speculative viewpoint, the results start to pave the way
to a reversible control of the cis- and trans-chelating behavior of
flexible (non-trans-spanning) bidentate ligands by proton trans-
fer (instead of the irreversible methylation process investigated
here) outside the coordination sphere of the metal atom.
’ COMPUTATIONAL DETAILS
Geometries were fully optimized at the B3PW91/6-31G**/LANL2DZ*-
(Pd) level of calculation using Gaussian09.30 LANL2DZ*(Pd) means
that f-polarization functions derived by Ehlers et al.31 for Pd have
been added to the LANL2DZ(Pd) basis set. Vibrational analysis was
performed at the same level as the geometry optimization. Solvent
effects were included using the polarizable continuum model (PCM)
implemented in Gaussian0930 or the conductor-like screening model
(COSMO)32 implemented in ADF 2008.01.
The magnetic shielding tensor and nuclear spin coupling constants
were calculated at B3PW91/6-31+G**/LANL2DZ*(Pd) using the
GIAO (gauge-independent atomic orbital) method implemented in
Gaussian09.30 The 31P NMR chemical shifts were estimated with respect
to the usual H3PO4 reference.
The gas-phase molecular electrostatic potential (MESP) was com-
puted at the same B3PW91/6-31G**/LANL2DZ*(Pd) level as above
using Gaussian09.30 The MESP has been shown to be weakly sensitive
to the level of calculation.33 Visualization of the isodensity surfaces
color coded with the MESP were performed using Molden.34 AIM27
analysis was performed with the TopMoD package.35 Energy decom-
position analyses for optimized structures (PCM-B3PW91/6-31G**/
LANL2DZ*(Pd) level) were performed with the ADF 2008.01 pro-
gram,36 following the implemented MorokumaꢀRaukꢀZiegler parti-
tion scheme37 and using the PBEPBE functional in combination with
STO-type all-electron basis sets of TZP quality.38 Scalar relativistic
effects were taken into account in all EDA calculations using the ZORA
Hamiltonian. Molecular orbitals were plotted using the GABEDIT
program.39
Synthesis of Complex 5. A mixture of complex PdCl2(PhCN)2
(0.46 g, 1.21 mmol) and 2 (0.90 g, 1.21 mmol) was dissolved in THF
(30 mL) at ꢀ30 °C and then stirred at room temperature for 3 h. After
concentration under vacuum, the residue was washed with Et2O (40 mL),
affording an orange solid (yield 1.01 g, 91%). Recrystallization at room
temperature from CH2Cl2 afforded orange crystals (mp 188ꢀ190 °C).
1H NMR (CD3CN, 25 °C): 8.33 (dd, JHP = 13.4 Hz, JHH = 1.2 Hz,
1H, Har), 8.31 (dd, JHP = 13.3 Hz, JHH = 1.2 Hz, 1H, Har), 8.26 (t, JHP
=
JHH = 2.3 Hz, 1H, Har), 8.01 (d, JHH = 1.8 Hz, 1H, Har), 7.81ꢀ7.88 (m,
2H, Har), 7.61ꢀ7.78 (m, 8H, Har), 7.41ꢀ7.50 (m, 3H, Har), 7.33ꢀ7.38
(m, 4H, Har), 7.21ꢀ7.24 (m, 1H, Har), 7.10ꢀ7.14 (m, 2H, Har), 6.86
(pseudo td, JHH = 7.6 Hz, JHP = 3.3 Hz, 2H, Har), 5.75 (br.s, 2H, Har),
3.05 (s, 3H, CH3). 13C NMR (CD3CN, 25 °C): 139.5 (dd, JCP = 4.0 and
88.7 Hz, C), 135.9 (d, JCP = 43.7 Hz, C), 133.3 (d, JCP = 9.7 Hz, CH),
133.2 (d, JCP = 6.6 Hz, CH), 133.1 (d, JCP = 11.6 Hz, CH), 132.9 (d,
JCP = 11.1 Hz, CH), 132.8 (d, JCP = 11.2 Hz, CH), 132.4 (CH), 132.3
(CH), 132.1 (d, JCP = 2.9 Hz, CH), 132.0 (d, JCP = 3.5 Hz, CH), 132.0
(C), 131.7 (d, JCP = 3.1 Hz, CH), 131.1 (C), 131.1 (CH), 130.9 (CH),
’ EXPERIMENTAL SECTION
130.8 (CH), 130.7 (d, JCP = 10.0 Hz, CH), 130.5 (CH), 130.4 (d, JCP
=
66.7 Hz, C), 129.5 (d, JCP = 10.6 Hz, CH), 129.4 (d, JCP = 12.6 Hz, CH),
128.9 (d, JCP = 12.9 Hz, CH), 128.2 (dd, JCP = 2.7 and 63.0 Hz, C), 128.2
(d, JCP = 1.8 Hz, CH), 128.0 (d, JCP = 12.5 Hz, CH), 126.2 (d, JCP = 64.2
Hz, C), 122.3 (dd, JCP = 6.0 and 47.0 Hz, C), 121.2 (q, JCF = 320.8 Hz,
CF3SO3ꢀ), 40.2 (CH3). 31P NMR (CD3CN, 25 °C): 10.64 (s); 4.10 (s).
MS (ESI+): m/z = 771 [M]+. HRMS (ESI+) calcd for C37H31N4P2-
(104)PdCl2 767.0441; found 767.0497.
General Remarks. THF and diethyl ether were dried and distilled
over sodium/benzophenone, pentane, dichloromethane, and acetoni-
trile over P2O5. All other reagents were used as commercially available.
All reactions were carried out under an argon atmosphere using Schlenk
and vacuum-line techniques. The following analytical instruments were
used. 1H, 13C, and 31P NMR: Bruker ARX 250, DPX 300, and Avance
500. NMR chemical shifts δ are in ppm, with positive values to high
frequency relative to the tetramethylsilane reference for 1H and 13C and
to the H3PO4 reference for 31P; coupling constants J are in Hertz.
Synthesis of Complex 6. A mixture of complex PdCl2(PhCN)2
(0.084 g, 0.22 mmol) and 3 (0.20 g, 0.22 mmol) was dissolved in THF
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Inorganic Chemistry
ARTICLE
(10 mL) at ꢀ30 °C and then stirred at room temperature for 3 h. After
concentration under vacuum, the residue was washed with Et2O (10 mL),
affording an orange solid (yield 0.22 g, 92%). Recrystallization at room
temperature from CH3CN/Et2O afforded orange crystals (mp 198ꢀ
200 °C).
’ ACKNOWLEDGMENT
Beyond the Ministꢁere de l’Enseignement Supꢀerieur de la
Recherche et de la Technologie and the Universitꢀe Paul Sabatier,
the authors thank the Centre National de la Recherche Scienti-
fique for the postdoctoral fellowship of N.D. and french public
funding for research (ANR-08-JCJC-0137-01). Theoretical stud-
ies were performed using HPC resources from CALMIP (Grant
2009 and 2010 [0851]]) and from GENCI-[CINES/IDRIS]
(Grant 2009 and 2010 [085008]).
1H NMR (CD3CN, 25 °C): 8.19 (d, JHP = 2.0 Hz, 2H, Har), 8.08 (br.
d, JHH = 5.5 Hz, 4H, Har), 7.85ꢀ7.92 (m, 4H, Har), 7.80 (t, JHH = 7.5 Hz,
2H, Har), 7.64ꢀ7.73 (m, 12H, Har), 7.21ꢀ7.24 (m, 2H, Har), 7.14ꢀ7.17
(m, 2H, Har), 3.44 (s, 6H, CH3). 13C NMR (CD3CN, 25 °C): 144.5 (t,
JCP = 17.8 Hz, C), 138.3 (t, JCP = 8.3 Hz, CH), 135.3 (t, JCP = 6.1 Hz,
CH), 135.0 (CH), 133.7 (CH), 133.2 (CH), 132.8 (CH), 130.4 (C),
130.2 (t, JCP = 6.0 Hz, CH), 130.0 (CH), 129.7 (t, JCP = 5.9 Hz, CH),
127.6 (CH), 124.1 (t, JCP = 28.8 Hz, C), 121.3 (q, JCF = 320.9 Hz,
CF3SO3ꢀ), 120.9 (t, JCP = 23.1 Hz, C), 39.5 (CH3). 31P NMR (CD3CN,
25 °C): 9.21. MS (ESI+): m/z = 935 [M2+ ꢀ CF3SO3ꢀ]+. HRMS (ESI+)
calcd for C39H34N4P2PdClF3SO3 900.0506; found 900.0505.
’ ASSOCIATED CONTENT
S
Supporting Information. Calculation details. This mate-
b
rialisavailablefreeofchargevia theInternet at http://pubs.acs.org.
Crystal Structure Determination of Ligands 1 and 3 and
Complexes 4ꢀ6. Intensity data were collected at 180 K on Apex2
Bruker or a Xcalibur Oxford Diffraction diffractometer using a graphite-
monochromated Mo Kα radiation source and equipped with an Oxford
Cryosystems Cryostream Cooler Device. The structures were solved
by direct methods and refined by full-matrix least-squares procedures on
F using the programs of the PC version of CRYSTALS. Atomic scat-
tering factors were taken from the International Tables for X-ray
Crystallography. All non-hydrogen atoms (excepted water molecules
for 5) were refined anisotropically. Hydrogen atoms were located in a
difference map (those attached to carbon atoms were repositioned geo-
metrically) and then refined using a riding model. Absorption correc-
tions were introduced using the program MULTISCAN.
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Crystal Data of 1. C36H28N4P2, M = 578.59 g molꢀ1, monoclinic, a =
1991, 2, 593.
3
(6) (a) Schuecker, R.; Mereiter, K.; Spindler, F.; Weissensteiner, W.
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(10) SPANphos is a trans-spanning diphosphine that has also been
reported to act as a cis-chelating ligand. See: Jimꢀenez-Rodríguez, C.;
Roca, F. X.; Bo, C.; Benet-Buchholz, J.; Escudero-Adꢀan, E. C.; Freixa, Z.;
van Leeuwen, P. W. N. M. Dalton Trans. 2006, 268.
49.677(3) Å, b = 8.5858(5) Å, c = 14.3598(9) Å, β = 94.008(3)°, V =
6109.8(6)Å3, space group C2/c, Z = 8, μ(Mo Kα) = 0.174 mmꢀ1, 75237
reflections measured, 5014 unique (Rint =0.055), 379 parameters, 3828 re-
flections used in the calculations [I > 0.7σ(I)], R1 = 0.0487, wR2 = 0.0578.
Crystal Data of 3. C40H34F6N4O6P2S2, M = 906.77 g molꢀ1
,
3
monoclinic, a = 30.774(3) Å, b = 12.2594(14) Å, c = 28.281(3) Å,
β = 105.148(4)°, V = 10299(2) Å3, spacegroupC2/c, Z= 8, μ(MoKα) =
0.229 mmꢀ1, 75 266 reflections measured, 8001 unique (Rint = 0.079),
544 parameters, refinement on F2, [I > 2σ(I)], R1 = 0.0810, wR2 =
0.2048.
Crystal Data of 4. C38H30Cl8N4P2Pd, M = 994.65 g molꢀ1, mono-
3
clinic, a = 12.7655(4) Å, b = 16.8290(5) Å, c = 18.7918(6) Å, β =
94.954(3)°, V = 4022.0(2) Å3, space group P21/n, Z = 4, μ(Mo Kα) =
1.108 mmꢀ1, 38 029 reflections measured, 10 770 unique (Rint = 0.068),
478 parameters, 4855 reflections used in the calculations [I > 1.9σ(I)],
R1 = 0.0298, wR2 = 0.0347.
(11) Canac, Y.; Debono, N.; Vendier, L.; Chauvin, R. Inorg. Chem.
2009, 48, 5562.
Crystal Data of 5. C38H37Cl2F3N4O6P2PdS, M = 974.05 g molꢀ1
,
3
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(14) (a) Snelders, D. J. M.; Siegler, M. A.; von Chrzanowski, L. S.;
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monoclinic, a = 9.3420(4) Å, b = 26.2671(8) Å, c = 17.4220(5) Å, β =
93.916(5)°, V = 4265.1(3) Å3, space group P21/c, Z = 4, μ(Mo Kα) =
0.746 mmꢀ1, 46 239 reflections measured, 10 316 unique (Rint = 0.081),
511 parameters, 6247 reflections used in the calculations [I > 3σ(I)],
R1 = 0.0518, wR2 = 0.0551.
Crystal Data of 6. C44H40Cl2F6N6O6P2PdS2, M = 1166.21 g molꢀ1
,
3
monoclinic, a = 16.8049(4) Å, b = 16.7864(4) Å, c = 17.5998(5) Å, β =
103.697(3)°, V = 4823.6(2) Å3, space group P21/n, Z = 4, μ(Mo Kα) =
0.726 mmꢀ1, 45 594 reflections measured, 12 882 unique (Rint = 0.060),
622 parameters, 6390 reflections used in the calculations [I > 1.6σ(I)],
R1 = 0.0299, wR2 = 0.0330.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: yves.canac@lcc-toulouse.fr (Y.C.); chauvin@lcc-toulouse.
fr (R.C.). Fax: (+33)5 61 55 30 03.
10818
dx.doi.org/10.1021/ic201342z |Inorg. Chem. 2011, 50, 10810–10819

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