Synthesis, structure, ligand dynamics, and catalytic activity of cationic [Pd(η3-allyl)(κ2(E,N)-EN-chelate)]+ (E = P, O, S, Se) complexes

Article abstract of DOI:10.1021/om200766y

A series of cationic palladium allyl complexes of the type [Pd(η3-allyl)(κ²(E,N)-EN-chelate)]+ containing several heterodifunctional EN (E = P, O, S, Se) ligands based on N-(2-pyridinyl) aminophosphines and oxo, thio, and seleno derivatives thereof are prepared. These complexes are studied by one- and two-dimensional NMR techniques together with X-ray and DFT calculations. Variable-temperature and phase-sensitive 1H,1HNOESYNMRmeasurements reveal both allyl and EN ligand dynamics. In the case of palladium, PN complexes' η3 to η1 isomerization takes place by opening the η3-allyl group selectively at the trans position with respect to the phosphorus center, while for EN (E = O, S, Se) complexes an "apparent" allyl rotation is observed proceeding with Pd-E and Pd-Nbond breaking. DFT calculations indicate that both isomerization processes are solvent assisted, in agreement with the NMR data. In addition, the use of the new palladium allyl complexes has been examined as catalysts for Suzuki-Miyaura coupling of various aryl bromides and arylboronic acids. [Pd(η3-CHPhCHCH2)(ON-Ph)]+, bearing an η3- cinnamyl ligand, is one of the most efficient catalysts, converting aryl bromides and arylboronic acids at 80 °C with a catalyst loading of 0.1 mol % quantitatively into the expected biaryl products.

Full text of DOI:10.1021/om200766y

ARTICLE
pubs.acs.org/Organometallics
Synthesis, Structure, Ligand Dynamics, and Catalytic Activity of Cationic
[Pd(η3-allyl)(j2(E,N)-EN-chelate)]+ (E = P, O, S, Se) Complexes
†
||
†
‡
§
€
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Bernhard Bichler, Luis F. Veiros, Ozg€ur Oztopcu, Michael Puchberger, Kurt Mereiter,
Kouki Matsubara,#,^ and Karl A. Kirchner*,†
†Institute of Applied Synthetic Chemistry, ‡Institute of Materials Chemistry, and §Institute of Chemical Technologies and Analytics,
Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
#Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Fukuoka 814-0180, Japan
Centro de Química Estrutural, Instituto Superior Tꢀecnico, Universidade Tꢀecnica de Lisboa, 1049-001 Lisboa, Portugal
S Supporting Information
b
ABSTRACT: A series of cationic palladium allyl complexes of
the type [Pd(η3-allyl)(k2(E,N)-EN-chelate)]+ containing sev-
eral heterodifunctional EN (E = P, O, S, Se) ligands based on
N-(2-pyridinyl)aminophosphines and oxo, thio, and seleno
derivatives thereof are prepared. These complexes are studied
by one- and two-dimensional NMR techniques together with
X-ray and DFT calculations. Variable-temperature and phase-sensitive 1H,1H NOESY NMR measurements reveal both allyl and EN
ligand dynamics. In the case of palladium, PN complexes' η3 to η1 isomerization takes place by opening the η3-allyl group selectively
at the trans position with respect to the phosphorus center, while for EN (E = O, S, Se) complexes an “apparent” allyl rotation is
observed proceeding with PdꢀE and PdꢀN bond breaking. DFT calculations indicate that both isomerization processes are solvent
assisted, in agreement with the NMR data. In addition, the use of the new palladium allyl complexes has been examined as catalysts
for SuzukiꢀMiyaura coupling of various aryl bromides and arylboronic acids. [Pd(η3-CHPhCHCH2)(ON-Ph)]+, bearing an η3-
cinnamyl ligand, is one of the most efficient catalysts, converting aryl bromides and arylboronic acids at 80 ꢀC with a catalyst loading
of 0.1 mol % quantitatively into the expected biaryl products.
Chart 1
’ INTRODUCTION
Heterodifunctional ligands are intensively studied and applied
in coordination and organometallic chemistry owing to the often
unique properties of their metal complexes and their ability to
generate hemilabile systems, which often display enhanced
reactivity.1 In particular soft/hard, e.g., P/N and P/O, assemblies
are able to coordinate reversibly to a metal center, providing or
protecting temporarily a vacant coordination site, a feature very
desirable for catalysts.
In this context, we have become interested in heterodifunctional
PN ligands based on 2-aminopyridine in which the pyridine moiety
is separated by an amino group.2,3 Due to the comparative ease of
phosphorusꢀnitrogen bond forming reactions compared to phos-
phorusꢀcarbon bonds, it is not surprising that many examples of
transition metal complexes featuring this type of PN ligands have
emerged over the last decades.4ꢀ13 The most prominent member of
these ligand family, with a few exceptions,14 is N-diphenylpho-
sphino-2-aminopyridine (PN-Ph). Another very useful and inter-
esting aspect of PN ligands is the fact that they can be readily
functionalized also at the phosphorus site by oxidation with H2O2,
sulfur, and gray selenium, respectively, to give chalcogen O, S, and Se
derivatives (EN ligands). Despite the fact that the synthesis of these
heterodifunctional EN ligands has been known for some time,10 it is
surprising that transition metal complexes containing these ligands
are relatively scarce.6,9,15,16
As part of our ongoing interest in transition metal com-
plexes containing heterodifunctional ligands,2,3 we herein
report on the synthesis, solution and solid-state structure,
and reactivity of palladium allyl complexes featuring bidentate
heterodifunctional EN (E = P, O, S, Se) ligands with R = Ph
and iPr as shown in Chart 1. The chemistry of palladium allyl
complexes is a topic of considerable contemporary interest
in view of the various fluxional processes observed in these
systems and also from the point of view of the potential
applications of these types of complexes in homogeneous
catalysis.17
Received: August 17, 2011
Published: October 14, 2011
r
2011 American Chemical Society
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Scheme 1
Scheme 2
Scheme 3
’ RESULTS AND DISCUSSION
Synthesis of Palladium Allyl Complexes. The cationic allyl
palladium complexes [Pd(η3-allyl)(k2(E,N)-EN-chelate)]+ (6ꢀ17)
were prepared in high yields from the reaction of the chloro-
bridged palladium allyl dimers [Pd(η3-allyl)(μ-Cl)]2 (5aꢀd)
with the corresponding EN ligands PN-Ph (1a), PN-iPr (1b),
ON-Ph (2a), ON-iPr (2b), SN-Ph(3a), SN-iPr (3b), SeN-Ph(4a),
and SeN-iPr (4b) in the presence of AgSbF6 (or AgCF3SO3) in
dichloromethane (Schemes 1 and 2). If the same reaction is
performed in the absence of a halide scavenger, only the strong
chelating PN, SN, and SeN ligands afforded the same complexes
(with chloride as counterion), whereas the weaker ON ligands
gave complexes where the ligand is coordinated in k1(N)-fashion.
This was exemplarily shown for the reaction of [Pd(η3-CH2-
CMeCH2)(μ-Cl)]2 (5b) with the ligand ON-Ph (2a), yielding
the neutral complex [Pd(η3-CH2CMeCH2)(k1(N)-ON-Ph)Cl]
(18), as shown in Scheme 3. There was no evidence for the for-
mation of complexes of the type [Pd(η1-allyl)(k2(E,N)-EN)Cl]
bearing an η1-coordinated allyl ligand as erroneously stated
recently.18
SN-iPr ligand was accomplished by reacting 14b with 1 equiv of
KOtBu in THF for 30 min, affording the neutral complex
[Pd(η3-CH2CHCH2)(SNH-iPr)] (19) in essentially quantita-
tive yield (Scheme 4).
All allyl complexes are thermally robust pale yellow solids that
are air stable both in the solid state and in solution for several
days. Characterization was accomplished by elemental analysis
and 1H, 13C{1H}, and 31P{1H} NMR spectroscopy. In addition,
the solid-state structures of representative compounds were
determined by X-ray diffraction.
As shown for several complexes bearing EN ligands,3 depro-
tonation of their acidic NH protons is typically achieved under
mild conditions, leading to complexes with anionic ENH ligands.
Accordingly, as a representative example, deprotonation of the
X-ray Diffraction Studies. The solid-state structures of the
palladium allyl complexes 7b, 8b, 9, 10, 14b, 15a, 15b, 17b, 18
(as the solvate 18 1/2CH2Cl2), and 19 were determined by
3
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Scheme 4
Figure 3. Molecular structure of [Pd(η3-CHPhCHCHPh)(PN-iPr)]SbF6
(9) showing 50% displacement ellipsoids (SbF6ꢀ anion omitted for
clarity).
Figure 1. Molecular structure of [Pd(η3-CH2CMeCH2)(PN-iPr)]SbF6
(7b) showing 50% displacement ellipsoids (SbF6ꢀ anion omitted for
clarity).
Figure 4. Molecular structure of [Pd(η3-CH2CHCH2)(ON-iPr)]SbF6
ꢀ
(10) showing 50% displacement ellipsoids (SbF6 anion omitted for
clarity). The allyl group is orientation disordered with CBtC13 alter-
natively in one of two positions, of which only the major position
is shown.
carbon atoms CA (cis to N1) and CC (cis to E) as the ligands. As
can be seen from Table S1, the bond lengths PdꢀN1, mean value
2.127 Å, and PdꢀCC (trans to N1), mean value 2.116 Å, are
relatively uniform throughout the 10 compounds. In contrast, the
bond length PdꢀE varies from 2.12 to 2.48 Å and PdꢀCA varies
from 2.10 to 2.28 Å.
The three pyridyl aminophosphine complexes 7b, 8b, and 9
contain ligands that form a largely planar five-membered chelate ring
with N1ꢀPd1ꢀP1 bond angles near 83ꢀ. The coordination figure
about Pd, defined by the four ligand atoms N1, P1, CA, and CC is
essentially coplanar, with the pyridine ring showing interplanar
angles of only about 10ꢀ. The bond distances PdꢀN, PdꢀP, PdꢀCA,
and PdꢀCC are each quite uniform and average 2.121, 2.259, 2.255,
and 2.118 Å. This means that the PdꢀCA bonds trans to PdꢀP are
all significantly elongated compared with the PdꢀCC bonds trans to
PdꢀN. This feature is either due to bonding properties of the
phosphorus ligand atoms and/or due to the low NꢀPdꢀCA bond
angles, but it is practically independent of the substitution pattern of
the allyl ligands (2-methyl, 1-phenyl, and 1,3-diphenyl).
Figure 2. Molecular structure of [Pd(η3-CHPhCHCH2)(PN-iPr)]SbF6
(8b) showing 50% displacement ellipsoids (SbF6ꢀ anion omitted for
clarity).
single-crystal X-ray diffraction. The molecular structures of these
compounds are shown in Figures 1ꢀ10. Selected bond lengths
and angles and crystallographic data are provided in the Support-
ing Information (Tables S1 and S2). Disregarding the central
allyl carbon atom CB, the palladium coordination of all com-
plexes can be described as square planar with the pyridine
nitrogen N1, the donor atom E (P, O, S, Se, or Cl), and the allyl
The complexes 10, 14b, 15a, 15b, 17b, and 19 contain six-
membered chelate rings that are distinctly bent, depending on
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Figure 5. Molecular structure of [Pd(η3-CH2CHCH2)(SN-iPr)]CF3-
SO3 (14b) showing 50% displacement ellipsoids. Hydrogen bond
N2ꢀH O1 has N2 O1 = 2.920 Å. The allyl group is orientation
Figure 7. Molecular structure of [Pd(η3-CH2CMeCH2)(SN-iPr)]SbF6
(15b) showing 50% displacement ellipsoids (SbF6 anion omitted
for clarity).
ꢀ
3 3 3
3 3 3
disordered with CBtC13 alternatively in one of two positions, of which
only the major position is shown.
Figure 8. Molecular structure of [Pd(η3-CH2CHCH2)(SeN-iPr)]CF3-
SO3 (17b) showing 50% displacement ellipsoids. Hydrogen bond
N2ꢀH O1 has N2 O1 = 2.917 Å. The allyl group is orientation
Figure 6. Molecular structure of [Pd(η3-CH2CMeCH2)(SN-Ph)]SbF6
(15a) showing 50% displacement ellipsoids (SbF6 anion omitted
for clarity).
ꢀ
3 3 3
3 3 3
disordered with CBtC13 alternatively in one of two positions, of which
only the major position is shown.
not affect the positions of the CA and CC atoms. In contrast, the
remaining six complexes with substituted allyl groups (2-methyl,
1-phenyl, and 1,3-diphenyl) show only a single allyl orientation
in the solid state.
the size of the additional heteroatom O, S, or Se. Hence, the angle
between the pyridine ring and the plane of the four Pd ligand
atoms increases from 27.7ꢀ in 10 (E = O) to 47.5ꢀ in 14b (E = S)
and finally to 49.0ꢀ in 17b (E = Se). In compounds 15a and 19
this interplanar angle is notably smaller, most likely because of
the space requirement of the two P-bonded phenyl rings in 15a
and a different hybridization of the chelate ring in 19 due to the
deprotonated nitrogen atom N2 (Figure 10).
The complexes 10, 14b, 17b, and 19, with unsubstituted
allyl groups, show the usual static orientation disorder/order of
this group whereby the allyl carbon CB points out from the
N1ꢀEꢀCAꢀCC coordination plane to both sides in different
proportions, which vary from 0.82/0.18 for 10 to 0.57/0.43 in 19.
In the four complexes this orientation disorder practically does
The NꢀH groups of the EN ligands are distinctly acidic and
form therefore hydrogen bonds with available acceptor atoms. In
the SbF6 salts these are relatively straight NꢀH F bonds with
3 3 3
N
F distances between 2.84 and 3.03 Å (8b is an exception
3 3 3
because of a bifurcated bond), and in the two triflate salts the
NꢀH O bonds have N O = 2.92 Å. In the two indepen-
3 3 3
3 3 3
dent complexes [Pd(η3-CH2CMeCH2)(k1(N)-ON-Ph)Cl] of 18
intramolecular NꢀH Cl bonds (N Cl = 3.19 and 3.21 Å)
3 3 3
3 3 3
are formed instead. This propensity of the NH group for H-bond
formation was also observed for the bare ligands EN with E = S
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Figure 9. Molecular structure of [Pd(η3-CH2CMeCH2)(k1(N)-ON-
Ph)Cl] 1/2CH2Cl2 (18 1/2CH2Cl2) showing 50% displacement
3
3
ellipsoids and only one of the two independent Pd complexes.
Figure 11. 300 MHz 1H NMR variable-temperature spectra of [Pd(η3-
CH2CHCH2)(k2(P,N)-PN-iPr)]SbF6 (6b) in CD2Cl2 from ꢀ40 to
25 ꢀC.
3ꢀ6 Hz, which is typical for a two-bond cis coupling of
phosphorus and carbon nuclei. The central allyl carbon atoms
give rise to doublets in the range 121 to 138 ppm, as expected for
k2(P,N)-coordination. In the case of palladium EN (E = O, S, Se)
complexes 10ꢀ19 all allyl carbon atoms give rise to singlet
resonances at 61ꢀ90, 56ꢀ74, and 119ꢀ135 ppm, assignable to
the two terminal and the central allyl carbon atoms, respectively.
In the 31P{1H} NMR spectra, the palladium PN and ON
complexes 6ꢀ13 exhibit singlets that show the expected low-
field shifts of the k2(P,N)-coordinated PN ligands relative to the
free uncoordinated ligands. This trend is reversed in the case of
the palladium SN and SeN complexes 14ꢀ17. In the case of the
SeN complexes 17a and 17b, the phosphorus signals exhibit a
77
pair of Se satellites with 31Pꢀ Se coupling constants of 651 and
Figure 10. Molecular structure of [Pd(η3-CH2CHCH2)(SNH-iPr)]
(19) with 50% displacement ellipsoids. The allyl group is orientation
disordered with CBtC13 alternatively in one of two positions, of which
only the major position is shown.
635 Hz, respectively. The deprotonated complex 19 also displays
a sharp single 31P{1H} NMR resonance at 64.2 ppm, which is
significantly shifted to higher field than the starting material 14b
(cf. 100.0 ppm). The 1H spectrum of 19 is very similar to that of
14b except that the NH resonance is now absent.
and Se, where the phenyl-substituted phosphines showed
The room-temperature 1H NMR spectra of the PN complexes
6ꢀ9 in CD2Cl2 exhibit sharp signals for all protons except for the
NꢀH Npyridine and the ispopropyl-substituted phosphines
3 3 3
showed NꢀH E hydrogen bonds.38 In the solid-state struc-
3 3 3
0
0
tures of the bare ligands 2a and 2b, EN with E = O, both phenyl-
syn and anti protons Hs and Ha . These are in pseudo-trans
position to the pyridine moiety and show slightly broadened
resonances. Figure 11 shows a variable-temperature NMR study
for 6b. Lowering the temperature causes the two broad lines
observed at ambient temperature to sharpen. Moreover, this
exchange process is facilitated in more strongly coordinating solvents
such as CD3CN, indicating a selective dynamic η3 to η1 isomeriza-
tion process induced by solvent coordination (vide infra).
and ispopropyl-substituted phosphines show NꢀH O bonds
3 3 3
with N O = 2.77ꢀ2.82 Å, whereas the pyridine nitrogen is
3 3 3
inactive as an acceptor (see Supporting Information).
NMR Studies. An analysis of the 13C{1H} NMR spectra of
allyl carbons of the palladium PN complexes 6ꢀ9 clearly shows
P,N-coordination. A doublet is observed for each of the two
terminal allyl carbon nuclei. The resonances of the terminal allyl
carbon atoms trans to the coordinated phosphorus center appear
in the range about 79 to 100 ppm with a coupling constant
2JPꢀC of 24ꢀ33 Hz, which lies in a region usually observed for
The 1H NMR spectra of the palladium EN complexes 10ꢀ17
give rise to sharp signals at room temperature but are strongly
solvent (and counterion) dependent. In Figure 12, the ꢀ1H NMR
spectra of 14b (with the poorly coordinating SbF6 anion)
recorded in CD2Cl2 and CD3CN are depicted. While in the poorly
coordinating solvent CD2Cl2 the expected five allyl resonances
13
trans 31Pꢀ C coupling. The signal for the terminal allyl carbon
nucleus trans to nitrogen resonates in a more shielded region
(ca. 44ꢀ68 ppm) with a coupling constant 2JPꢀC on the order of
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Figure 12. Section of the 300 MHz 1H NMR spectra of [Pd(η3-
CH2CHCH2)(k2(S,N)-SN-iPr)]SbF6ꢀ (14b) in CD2Cl2 (lower spectrum),
in CD3CN (middle spectrum), and in the presence of NEt4Cl (2 equiv)
in CD2Cl2 (upper spectrum) at 25 ꢀC.
Scheme 5
Figure 13. Section of a phase-sensitive 300 MHz 1H,1H NOESY
spectrum of [Pd(η3-CH2CHCH2)(k2(P,N)-PN-iPr)]SbF6 (6b) in
CD2Cl2 at 25 ꢀC. The exchange cross-peaks between syn/anti protons
are shown as black circles, whereas the NOE contacts between the
corresponding syn/anti and central allyl protons are indicated in red.
Scheme 6
are observed, in the coordinating solvent CD3CN the spectrum
simplifies, and only three allyl resonances are observed. This
observation points to a (solvent-induced) dynamic process
involving the EN ligand; that is, the EN ligand is hemilabile,
exhibiting rapid and reversible PdꢀE bond cleavage and solvent
coordination as indicated in Scheme 5 (vide infra). Noteworthy, a
similar 1H NMR spectrum is observed for 14b with chloride as
counterion dissolved in CD2Cl2 or when NEt4Cl was added to
14b (as SbF6ꢀ salt). In these cases, the chloride anion reversibly
coordinates to the palladium center, competing with E-donor
coordination (Scheme 5).
that the η3ꢀη1ꢀη3 isomerization follows a mechanism in which
the PdꢀCA bond opens, forming an η1 intermediate wherein
Allyl Dynamics. Palladium allyl complexes are well known19ꢀ27
to exhibit various dynamic processes including η3 to η1 isomeri-
zation and “apparent” allyl rotation. According to the literature,
these allyl isomerization processes may occur via different mecha-
nisms and may be under either electronic or steric control. In
addition, these dynamics may be associated with Pdꢀligand bond
breaking and may be solvent or counterion assisted. In order to
determine the solution structure of our palladium PN and EN
complexes as well as to establish the nature of their dynamic
behavior, complexes 6b and 14b were studied by two-dimensional
NMR and DFT calculations.
the CBꢀCC bond rotates 180ꢀ, completed by re-formation of the
3
0
0
η -allyl with an interchange of Hs and Ha (Scheme 6). Importantly,
the selective opening of the η3-allyl occurs trans to the phos-
phine. The η3ꢀη1-allyl isomerization can be either under
electronic control (the strongest donor labilizes the terminal
allyl carbon in pseudo-trans position) or under steric control (the
largest ligand induces opening of the cis-positioned terminal
allyl carbon).26,28 In the present case the isomerization is electro-
nically controlled due to the much stronger trans influence of the
phosphine moiety. The increased PdꢀCA bond length is also
apparent in the crystal structures of 7b, 8b, and 9 (Table 1). It was
found in several palladium complexes containing either bidentate
PP and NN ligands with different phosphorus and nitrogen donor
atoms,29,30 heterodifunctional ligands,31,32 or two different mono-
dentate ligands33,34 that this isomerization is selective, involving
opening of only one PdꢀC bond of the allyl fragment.
a. Selective Allyl η3ꢀη1ꢀη3 Isomerization. Figure 13 shows a
1
phase-sensitive 300 MHz H,1H NOESY for 6b in CD2Cl2 at
25 ꢀC. The spectrum shows exchange peaks (black) for the syn/
0
0
anti protons Hs and Ha at the terminal allyl carbon atom CC (cis
to the PR2 moiety) and selective NOE contacts (red) between
the syn/anti and central allyl protons. There is no exchange of syn
and anti protons at CA. The selective syn/anti exchange indicates
b. Allyl Pseudorotation. The ligand dynamics in the palladium
allyl EN (E = O, S, Se) complexes is clearly different from the
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Table 1. Precatalyst Performance in the SuzukiꢀMiyaura
type of selective syn/syn0 and anti/anti0 exchange in Pd-allyl
chemistry.22b,27 The fluxional process observed in these mol-
ecules, called exo/endo isomerization, effectively results in rota-
tion of the allyl ligand in its own plane about the Pdꢀη3-allyl axis.
The complex process may involve (a) dissociative (one must
consider that the heterodifunctional EN ligand is hemilabile,
resulting in the reversible decoordination of the E or N atoms)
and/or (b) associative pathways (coordination of solvent or
counterions present in solution). The latter pathway is usually
called “apparent” allyl rotation. Both processes have the effect of
switching the allylic termini with respect to their position relative
to the EN donor set. In the present case, this process is solvent
dependent and strongly facilitated in the presence of a coordinat-
ing solvent such as CH3CN. We thus favor pathway (b) involving
both reversible PdꢀE and PdꢀN bond cleavage with concomi-
tant solvent coordination, as shown in Scheme 7 (see DFT
calculations below).
c. DFT Studies. The mechanism of the dynamic processes
described above for the allyl complexes 6b and 14b was
investigated by means of DFT calculations.35 For each complex,
η3ꢀη1ꢀη3 allyl isomerization and “apparent” allyl rotation (or
η3-allyl pseudorotation) were compared in order to corroborate
the experimental results. The energy profile calculated for the
η3ꢀη1ꢀη3 allyl isomerization process in [Pd(η3-CH2CHCH2)-
(k2(P,N)-PN-iPr)]+ (6b+) is represented in Figure 15.
Coupling of a Simple Substratea
entry
[Pd]
yield (%)b
1
2
3
4
5
6
7
8
9
[Pd(η3-CH2CHCH2)(PN-Ph)]SbF6 (6a)
[Pd(η3-CH2CHCH2)(ON-iPr)]SbF6 (10)
[Pd(η3-CH2CHCH2)(SN-Ph)]SbF6 (14a)
[Pd(η3-CHPhCHCH2)(PN-Ph)]SbF6 (8a)
[Pd(η3-CHPhCHCH2)(PN-iPr)]SbF6 (8b)
[Pd(η3-CHPhCHCH2)(ON-Ph)]SbF6 (12a)
[Pd(η3-CHPhCHCH2)(ON-iPr)]SbF6 (12b)
[Pd(η3-CHPhCHCH2)(SN-Ph)]SbF6 (16a)
[Pd(η3-CHPhCHCH2)(SN-iPr)]SbF6 (16b)
77
96
traces
95
86
96
96
35
traces
a Reaction conditions: aryl bromide (1.0 mmol), boronic acid (1.5 mmol),
KOtBu (2.0 mmol), and catalyst (1 mol %). The reaction was stirred for 12 h.
b Isolated yields, average of two runs.
The entire path calculated for the process of syn/anti exchange
in 6b+ involves three steps. First there is coordination of one
molecule of solvent (CH3CN in the calculations), going from A
to B, and, at the same time, the allyl ligand slips from η3- to η1-
coordination. In A the acetonitrile molecule is away from the
metal center with a PdꢀNMeCN separation of 4.42 Å, but once
the transition state TSAB is reached, that distance shortens to
2.34 Å, indicating an incipient bond, as shown by a Wiberg index
(WI)36 of 0.13. In B, formation of the PdꢀNMeCN bond is
accomplished (dPdꢀN = 2.13 Å, WI = 0.21) and the allyl ligand
has slipped to a η1-coordination, resulting from the breaking of
the PdꢀC bond involving the C atom trans to phosphorus
(dPdꢀC = 3.88 Å). This cleavage of the PdꢀCallyl bond is already
well advanced in TSAB, as shown by a long distance (3.00 Å) and
a Wiberg index indicative of a weak interaction (WI = 0.11).
The second step in the mechanism of syn/anti exchange in 6b+
corresponds to rotation around the CꢀC bond in the η1-allyl
ligand, from B to C. In the transition state (TSBC) CꢀC rotation
is halfway through, and the allyl ligand is in an upright position,
with a PdꢀCꢀCꢀC dihedral angle of 172ꢀ.
Finally, in the last step (from C to D) η3-allyl coordination is
re-established with formation of the third PdꢀCallyl bond and
loss of acetonitrile. In the transition state, TSCD, formation of the
new PdꢀC bond is only incipient (dPdꢀC = 2.99 Å, WI = 0.12),
while coordination of the solvent molecule is still significant
(dPdꢀN(MeCN) = 2.31 Å, WI = 0.13). The overall result of the
path, from A to D, is the exchange of the relative position of the
allyl CꢀH bonds: the CH2 cis to the phosphine retains its
conformation along the path, while the central CꢀH bond and
the CH2 trans to the P atom exchange from one side of the
coordination plane in A to the other, in D. Naturally, A and D are
isoenergetic, for practical purposes.
In the mechanism discussed above, coordination of a solvent
molecule provides the fourth ligand necessary to maintain the
coordination number and the square-planar geometry character-
istic of Pd(II) complexes in the η1-allyl intermediates, B and C,
giving rise to a smooth process with a maximum energy barrier of
Figure 14. Section of a phase-sensitive 300 MHz 1H,1H NOESY
spectrum of [Pd(η3-CH2CHCH2)(k2(S,N)-SN-iPr)]SbF6 (14b) in
CD2Cl2 at 25 ꢀC. The exchange cross-peaks between syn/syn and
anti/anti protons are shown as black circles, whereas the NOE contacts
between the corresponding syn/anti and central allyl protons are
indicated in red.
1
analogous PN compounds. A phase-sensitive 300 MHz H,1H
NOESY spectrum of 14b in CD2Cl2 at 25 ꢀC is shown in
Figure 14. In contrast to palladium allyl PN complexes, no
η3ꢀη1ꢀη3 isomerization takes place, as evident from the
absence of any syn/anti exchange. Instead, an analysis of the
2D NMR data reveals selective syn/syn0 and anti/anti0 allyl
proton exchange in this case. There are several reports of this
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Scheme 7
Scheme 8
11.6 kcal molꢀ1, in good accordance with the fluxional process
observed in the NMR (see above).
The mechanism of “apparent” allyl rotation was also explored
for complex 6b+, and the corresponding energy profile is
presented as Supporting Information (Figure S13). That me-
chanism is equivalent, in its general features, to the one obtained
for complex 14b+, discussed below. Interestingly, the energy barrier
calculated for complex 6b+ (19.3 kcal molꢀ1, see Figure S13)
indicates that η3ꢀη1ꢀη3 allyl isomerization is clearly the most
favorable mechanism for that species, in agreement with the
experimental data.
Figure 15. Energy profile (in kcal/mol) for the solvent -assisted
(CH3CN) η3ꢀη1ꢀη3 allyl isomerization in [Pd(η3-CH2CHCH2)-
(k2(P,N)-PN-iPr)]+ (6b+). The allyl ligand is darkened to highlight
the fluxional process, and the numbers in italics indicate energy
barriers.
The energy profile calculated for the mechanism of η3-allyl
pseudorotationincomplex[Pd(η3-CH2CHCH2)(k2(S,N)-SN-iPr)]+
(14b+) is represented in Figure 16.
The mechanism obtained for η3-allyl pseudorotation in 14b+
comprises three steps. First, there is coordination of one molecule of
solvent with simultaneous breakage of the PdꢀS bond, from E to F.
In the corresponding transition state (TSEF) cleavage of the PdꢀS
bond is already apparent with a distance (2.58 Å) longer than the
one presented in the reactant, E (2.41 Å), indicating the weakening
of the corresponding interaction, WI = 0.27 (E) and 0.15 (TSEF).
On the other hand, coordination of the acetonitrile molecule is also
evident in TSEF with a PdꢀNMeCN distance of 2.43 Å, indicative of
incipient bond formation (WI = 0.11).
The second step in the mechanism corresponds to exchange
between N- and S-coordination of the SN-iPr ligand, from F to
G, respectively. The PdꢀN interaction goes from a clear bond in
F (dPdꢀN(py) = 2.20 Å, WI = 0.17) to a negligible interaction in G
(dPdꢀN(py) = 3.12 Å, WI = 0.02), while the opposite happens with
the PdꢀS bond: nonexisting in F (dPdꢀS = 2.84 Å, WI = 0.06)
and full coordination in G (dPdꢀS = 2.43 Å, WI = 0.28). The
corresponding transition state, TSFG, presents an intermedi-
ate situation with the PdꢀN bond considerably weakened
Figure 16. Energy profile (in kcal/mol) calculated for the solvent-
assisted (CH3CN) η3-allyl pseudorotation in [Pd(η3-CH2CHCH2)-
(k2(S,N)-SN-iPr)]+ (14b+). The allyl ligand is darkened to highlight
the fluxional process, and the numbers in italics indicate energy
barriers.
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Figure 17. Relevant coordination distances (Å) and Wiberg indices (in italics) for complexes [Pd(η3-CH2CHCH2)(k2(P,N)-PN-iPr)]+ (6b+) and
[Pd(η3-CH2CHCH2)(k2(S,N)-SN-iPr)]+ (14b+).
(dPdꢀN(py) = 2.47 Å, WI = 0.08) and formation of the new
PdꢀS bond (dPdꢀS = 2.62 Å, WI = 0.15) already evident.
In the final step of the mechanism there is coordination of the
N atom belonging to the pyridine ring of the SN-iPr ligand, with
concomitant loss of the solvent molecule, from G to H. This
process is only incipient in the corresponding transition state,
TSGH, with a very weak PdꢀNpy interaction (dPdꢀN(py) = 2.56 Å,
WI = 0.07) and the acetonitrile molecule still moderately bound
to the metal (dPdꢀN(MeCN) = 2.35 Å, WI = 0.13).
equivalent mechanism with the SN ligand. On the other hand, a
P-donor atom has a much stronger trans influence than an
S-donor atom, and thus, the weakening of the corresponding
trans PdꢀCallyl bond is considerably more effective in the case of
the PN ligand. As a consequence, the difference between the two
PdꢀC bonds involving the terminal allyl C atoms is enhanced in
the case of 6b+, resulting in an asymmetry on the allyl coordina-
tion that facilitates the η3ꢀη1 isomerization process in this
species, compared with the SN complex.
SuzukiꢀMiyaura Cross-Coupling Reactions. Palladium
complexes containing allyl ligands were shown to be excellent
catalysts for the SuzukiꢀMiyaura cross coupling.34,37 On the
basis of these findings we were interested in whether our
palladium complexes containing EN ligands exhibit similar
reactivities in CꢀC bond coupling reactions. Accordingly, we
investigated the activity of several new palladium allyl com-
plexes as catalysts for the coupling of aryl bromides with aryl
boronic acids.
In general, the coupling reaction is more efficient if complexes
10, 8a, 12a, and 12b, with PN-Ph and ON-Ph ligands, are used
(Table 1, entries 2, 4, 6, and 7) instead of complexes with SN
ligands, possibly due to metal poisoning through the sulfide
group. While it is difficult to establish any clear trends in the
catalytic activity of these particular complexes on these preli-
minary data, complexes 8a, 12a, and 12b, featuring cinnamyl
ligands, show higher activity than the other complexes, on
average. This reactivity trend suggests that substitution at the
terminal position of the allyl moiety increases the dissymmetry of
the allyl scaffold bound to the palladium and renders the catalyst
more active. Similar effects have been observed by others.37 For
substrate screening we thus focused on the cinnamyl complex
12b as precatalyst. The results of this study are summarized in
Table 2. Under classical conditions, complex 12b was shown
to be promising, although it does not surpass the activities of
other related cataysts.37a,38 At 80 ꢀC, a catalyst loading of
0.1 mol % was sufficient to observe quantitative conversion of
the starting materials into the expected biaryl products
(entries 1ꢀ10). On the other hand, with 4-chloroacetophe-
none and phenylboronic acid, even with a catalyst loading of
1 mol %, the yield of 4-acetylbiphenyl was rather low (entry 11).
Though these results do not compare with those obtained by
the group of Nolan37 using palladium allyl complexes with
N-heterocyclic carbenes as coligands, these catalysts do prove
to be very efficient.
The mechanism obtained for η3-allyl pseudorotation in 14b+
is represented in Scheme 8 in a simplified way, highlighting
solvent assistance. The overall result of that fluxional process is a
180ꢀ rotation of the allyl ligand in its own plane, that is, a syn/syn0
and anti/anti0 exchange, from E to H, two conformers practically
isoenergetic with cation 14b+ (within 0.2 kcal molꢀ1). Solvent
plays a crucial role in the fluxional process, providing the fourth
ligand necessary to maintain the coordination number and the
square-planar geometry around the metal in the intermediates, F
and G, avoiding, thus, the existence of pseudotetrahedral inter-
mediates or transition states, unfavorable in a d8 metal center
such as Pd(II). The maximum barrier calculated for the allyl
pseudorotation is rather small (7.9 kcal molꢀ1), in good agree-
ment with the NMR results (see above).
The mechanism of η3ꢀη1ꢀη3 allyl isomerization was also
investigated for complex 14b+, and the corresponding energy
profile is presented as Supporting Information (Figure S14). The
energy barrier calculated for that process (14.8 kcal molꢀ1) is
higher than the one obtained for the alternative path, i.e., η3-allyl
rotation, indicating the latter as the most favorable process in the
case of complex 14b+, in agreement with the experimental data.
The mechanism obtained for η3ꢀη1ꢀη3 allyl isomerization in
14b+ is equivalent, in its general features, to the one calculated for
complex 6b+, discussed above (Figure 15).
The reason for the different paths observed for the fluxional
processes of the PN complexes, compared to the EN analogues
(E = O, S, Se), can be traced to the nature of the PdꢀP/E bond
and to the trans influence of this donor atom.
Comparing cations 6b+ and 14b+ (see Figure 17), the differ-
ences in the coordination environment around the metal are
evident. On one hand, the PdꢀP bond in 6b+ is considerably
stronger than the PdꢀS bond in 14b+, as shown by the
corresponding Wiberg indices in Figure 17. Naturally, this makes
any path involving decoordination of the PN ligand, such as the
one obtained for η3-allyl pseudorotation, less favorable than an
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Table 2. SuzukiꢀMiyaura Cross-Coupling of Aryl Halides
with Arylboronic Acids Catalyzed by [Pd(η3-CHPhCHCH2)-
(j2(O,N)-ON-Ph)]SbF6 (12a)a,b,c,d
place by opening of the η3-allyl group selectively at the trans
position with respect to the phosphorus center, while for EN
(E = O, S, Se) complexes an “apparent” allyl rotation is observed
proceeding with PdꢀE and PdꢀN bond breaking. Thus, the
PdꢀP and PdꢀN bonds are stronger and the PdꢀE and PdꢀN
bonds are weaker than the allylic PdꢀC bonds, respectively.
DFT calculations indicate that both isomerization processes are
solvent assisted, corroborating the NMR experiments. The palla-
dium allyl complexes proved to be active as catalysts for Suzukiꢀ
Miyaura coupling reactions, representing an interesting alterna-
tive to existing catalytic palladium allyl systems due to the simplicity
and modularity as their synthesis is concerned.
’ EXPERIMENTAL SECTION
General Procedures. All manipulations were performed under
an inert atmosphere of argon by using Schlenk techniques. The sol-
vents were purified according to standard procedures.39 The ligands
N-diphenylphosphino-2-aminopyridine (PN-Ph) (1a),40 N-diisopropyl-
phosphino-2-aminopyridine (PN-iPr) (1b), N-(2-pyridinyl)aminodiphenyl-
phosphine sulfide (SN-Ph) (3a), N-(2-pyridinyl)aminodiisopropylphos-
phine sulfide (SN-iPr) (3b), N-(2-pyridinyl)aminodiphenylphosphine
selenide (SeN-Ph) (4a),41 and N-(2-pyridinyl)aminodiisopropylphosphine
selenide (SN-iPr) (4b) and the [Pd(η3-allyl)(μ-Cl)]2 dimers (5aꢀd)42
were prepared according to the literature. The deuterated solvents were
dried over 4 Å molecular sieves. 1H, 13C{1H}, and 31P{1H} NMR
spectra were recorded on Bruker AVANCE-250 and AVANCE-300
DPX spectrometers and were referenced to SiMe4 and H3PO4 (85%),
respectively. 1H and 13C{1H} NMR signal assignments were confirmed
13
by 1H-COSY, 135-DEPT, and HMQC(1Hꢀ C) experiments. For the
1H,1H NOESY experiments a mixing time of 1 s was used.
N-(2-Pyridinyl)aminodiphenylphosphine Oxide (ON-Ph)
(2a). A solution of N-(2-pyridinyl)aminodiphenylphosphine (PN-Ph)
(1a) (3.01 g, 10.8 mmol) in THF was cooled to 5 ꢀC, and aqueous H2O2
(30 w/w, 2.18 mL, 32.5 mmol) was slowly added. After the solution
reached room temperature the reaction mixture was stirred for 30 min.
The solvent was then evaporated, and the crude solid product was
purified with column chromatography using THF and silica gel. Yield:
2.81 g (88%). Anal. Calcd for C17H15N2OP: C, 69.38; H, 5.14; N, 9.52.
Found: C, 69.30; H, 5.20; N, 9.62. 1H NMR (δ, CDCl3, 20 ꢀC):
7.91ꢀ7.83 (m, 4H, Ph2,6), 7.65 (d, J = 4.5 Hz, py6), 7.54ꢀ7.30 (m, 8H,
Ph3,4,5, py5, NH), 6.98 (d, 8.3 Hz, py3), 6.63 (m, py4). 13C{1H} NMR
(δ, CDCl3, 20 ꢀC): 154.1 (s, py2), 147.9 (s, py6), 137.9 (s, py4), 132.3
(s, Ph4), 131.9 (d, J = 10.1 Hz, Ph2,6), 131.7 (d, J = 129.2 Hz, Ph1),
128.7 (d, J = 13.2 Hz, Ph3,5), 117.0 (s, py5), 112.0 (s, py3). 31P{1H}
NMR (δ, CD2Cl2, 20 ꢀC): 31.9.
N-(2-Pyridinyl)aminodiisopropylphosphine Oxide (ON-
iPr) (2b). This ligand was prepared analogously to 2a with 1b (5.15 g,
24.5 mmol) and aqueous H2O2 (30 w/w, 4.95 mL, 73.5 mmol) as the
starting materials. Yield: 5.09 g (92%). Anal. Calcd for C11H19N2OP: C,
58.39; H, 8.46; N, 12.38. Found: C, 58.42; H, 8.21; N, 12.30. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 8.06 (d, J = 4.5 Hz, py6), 7.88 (s, NH), 7.49 (t, J =
7.2 Hz, py4), 7.09 (d, J = 8.3 Hz, py3), 6.74 (dd, J = 6.6 Hz, J = 5.6 Hz,
py5), 2.69ꢀ2.42 (dh, J = 2.0 Hz, J = 7.2 Hz, 2H, CH(CH3)2), 1.32ꢀ1.10
(m, 12H, CH(CH3)2). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 156.2 (s,
py2), 147.3 (s, py6), 137.5 (s, py4), 115.3 (s, py5), 111.4 (d, J = 5.5 Hz,
py3), 26.7 (d, J = 79.8 Hz, CH(CH3)2), 15.8 (d, J = 3.4 Hz, CH(CH3)2),
15.5 (s, CH(CH3)2). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 70.9.
[Pd(η3-CH2CHCH2)(PN-Ph)]SbF6 (6a). A solution of 5a (92 mg,
0.25 mmol) and 1a (140 mg, 0.50 mmol) in 10 mL of CH2Cl2 was
treated with AgSbF6 (172 mg, 0.50 mmol) and stirred for 30 min. Solid
materials (AgCl) were then removed by filtration over Celite, and the
solvent was removed under reduced pressure to give a pale yellow solid,
which was washed twice with diethyl ether (10 mL) and dried under
a Reaction conditions: aryl halide (1.0 mmol), boronic acid (1.5 mmol),
KOtBu (2.0 mmol), and catalyst (0.1 mol %). The reaction was stirred
for 12 h. b Isolated yields, average of two runs. c Catalyst loading 0.01 mol
%. d Catalyst loading 1 mol %
’ CONCLUSION
In summary, we have shown that cationic palladium allyl
complexes of the type [Pd(η3-allyl)(k2(E,N)-EN-chelate)]+ are
obtained in high yields from the reaction of the chloro-bridged
palladium allyl dimers [Pd(η3-allyl)(μ-Cl)]2 with several hetero-
difunctional EN (E = P, O, S, Se) ligands in the presence of
AgSbF6 or AgCF3SO3. These complexes were studied by one-
and two-dimensional NMR techniques together with X-ray struc-
ture determinations and DFT calculations. Variable-temperature
and phase-sensitive 1H,1H NOESY NMR measurements reveal
that both allyl and EN ligands exhibit fluxional behavior. In the
case of palladium PN complexes η3 to η1 isomerization takes
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vacuum. Yield: 322 mg (97%). Anal. Calcd for C20H20F6N2PPdSb: C,
36.31; H, 3.05; N, 4.23. Found: C, 36.42; H, 3.21; N, 3.00. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 8.46 (d, J = 5.6 Hz, 1H, py6), 7.81 (t, J = 7.9 Hz, 1H,
py4), 7.75ꢀ7.44 (m, 10H, Ph), 7.28 (d, J = 8.5 Hz, 1H, py3), 7.02ꢀ6.89
(m, 2H, NH, py5), 6.24ꢀ5.62 (m, 1Hc, CH), 4.91 (t, J = 5.8 Hz, 1Hs,
CH), 4.21 (dd, J = 10.0 Hz, 14.0 Hz, 1Ha, CH), 4.12 (d, J = 6.5 Hz, 1Hs,
CH), 2.96 (d, J = 12.2 Hz, 1Ha, CH). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 160.0 (d, JCP = 13.4 Hz, py2), 153.4 (d, JCP = 2.1 Hz, py6), 141.6
(s, py4), 132.5 (s, Ph), 131.9 (d, JCP = 16.1 Hz, Ph), 131.7 (d, J = 15.6 Hz,
(δ, CD2Cl2, 20 ꢀC): 7.80ꢀ7.36 (m, 17H, py, Ph), 7.27 (d, J = 8.4 Hz,
1H, py3), 6.90 (d, J = 5.3 Hz, 1H, NH), 6.53 (t, J = 6.5 Hz, 1H, py5), 6.36
(m, 1H, CH), 5.49 (dd, J = 13.3, 10.3 Hz, 1H, CH), 3.70ꢀ3.50 (m, 2H,
CH2). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 160.5 (d, JCP = 14.0 Hz, py2),
146.8 (s, py6), 141.2 (s, py4), 134.8 (d, JCP = 6.1 Hz, Ph), 132.4 (d, JCP
=
2.6 Hz, Ph), 132.0 (s, Ph), 131.7 (s, Ph), 129.9 (d, JCP = 2.2 Hz, Ph),
129.5 (s, Ph), 129.3 (s, Ph), 128.0 (d, JCP = 3.7 Hz, Ph), 116.6 (s, py5),
115.0 (d, JCP = 6.6 Hz, CH), 112.5 (d, JCP = 7.1 Hz, py3), 100.5 (d, JCP
=
28.8 Hz, CHPh), 50.6 (d, JCP = 3.9 Hz, CH2). 31P{1H} NMR (δ, CD2Cl2,
20 ꢀC): 90.6.
Ph), 129.5 (d, J = 3.7 Hz, Ph), 129.4 (d, J = 3.8 Hz, Ph), 123.2 (d, JCP
=
=
6.0 Hz, CH), 117.4 (s, py5), 112.7 (d, JCP = 7.2 Hz, py3), 82.2 (d, JCP
[Pd(η3-CHPhCHCH2)(PN-iPr)]SbF6 (8b). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol),
1b (110 mg, 0.52 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 328 mg (98%). Anal. Calcd for C20H28F6N2PPdSb: C,
35.88; H, 4.21; N, 4.18. Found: C, 35.92; H, 4.11; N, 4.30. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 7.69ꢀ7.41 (m, 6H, py, Ph), 7.17 (d, J = 8.4 Hz, 1H,
Ph), 6.84 (d, J = 5.4 Hz, 1H, py), 6.48 (t, J = 6.5 Hz, 1H, py), 6.37 (s, 1H,
NH), 6.18 (dd, J = 13.4, 9.6 Hz, 1H, CH), 5.39ꢀ5.29 (m, 1H, CH),
4.13ꢀ2.87 (m, 2H, CH2), 2.49 (dd, J = 13.6, 6.8 Hz, 2H, CH),
1.34ꢀ1.11 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC):
162.0 (d, J = 10.5 Hz, py2), 146.8 (s, py6), 140.93 (s, py4), 135.0 (d,
JCP = 5.6 Hz, Ph), 129.8 (d, JCP = 2.0 Hz, Ph), 129.3 (d, JCP = 2.6 Hz,
Ph), 127.7 (d, JCP = 3.4 Hz, Ph), 116.0 (s, py5), 113.9 (d, JCP = 6.1 Hz,
CH), 112.0 (d, JCP = 5.8 Hz, py3), 100.8 (d, JCP = 27.2 Hz, CHPh), 44.9
(d, JCP = 2.8 Hz, CH2), 27.5 (s, CH), 19.2ꢀ16.4 (m, CH3). 31P{1H}
NMR (δ, CD2Cl2, 20 ꢀC): 129.1.
31.4 Hz, CH2), 52.1 (d, JCP = 3.9 Hz, CH2). 31P{1H} NMR (δ, CD2Cl2,
20 ꢀC): 76.1.
[Pd(η3-CH2CHCH2)(PN-iPr)]SbF6 (6b). This complex was pre-
pared analogously to complex 6a using 5a (184 mg, 0.50 mmol), 1b
(220 mg, 1.05 mmol), and AgSbF6 (343 mg, 1 mmol) as starting materials.
Yield: 585 mg (98%). Anal. Calcd for C14H24F6N2PPdSb: C, 28.33; H,
4.08; N, 4.72. Found: C, 28.20; H, 4.11; N, 4.65. 1H NMR (δ, CD2Cl2,
ꢀ40 ꢀC): 8.38 (d, J = 5.6 Hz, 1H, py6), 7.76 (t, J = 7.8 Hz, 1H, py3), 7.23
(d, J = 8.5 Hz, 1H, py4), 6.86 (t, J = 7.0 Hz, 1H, py5), 6.34 (s, 1H, NH),
6.03ꢀ5.51 (m, 1Hc, CH), 4.81 (dd, J = 7.8, 5.3 Hz, 1Hs, CH), 4.05 (dd,
J = 14.1, 9.4 Hz, 1Ha, CH), 3.92 (d, J = 9.4 Hz, 1Hs, CH), 2.76 (d, J =
7.8 Hz, 1Ha, CH), 2.60ꢀ2.29 (m, 2H, CH), 1.19 (dd, J = 17.6, 8.8 Hz,
12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 161.7 (d, JCP = 10.0 Hz,
py2), 153.4 (s, py6), 141.2 (s, py4), 121.9 (d, JCP = 5.5 Hz, CH), 116.6
(s, py5), 112.2 (d, JCP = 6.1 Hz, py3), 82.7 (d, JCP = 29.6 Hz, CH2), 46.4
(d, JCP = 3.1 Hz, CH2), 27.3 (d, JCP = 25.7 Hz, CH), 17.9 (d, JCP = 7.9 Hz,
CH3), 16.8 (s, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 127.1.
[Pd(η3-CH2CMeCH2)(PN-Ph)]SbF6 (7a). This complex was pre-
pared analogously to complex 6a using 5b (100 mg, 0.25 mmol), 1a
(140 mg, 0.50 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 326 mg (95%). Anal. Calcd for C21H22F6N2PPdSb: C,
37.34; H, 3.28; N, 4.15. Found: C, 37.45; H, 3.21; N, 4.45. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 8.48 (d, J = 4.7 Hz, 1H, py6), 7.88ꢀ7.5 (m, 10H, py,
Ph), 7.28 (d, J = 10.7 Hz, 2H), 7.07 (s, 1H, NH), 6.99ꢀ6.89 (m, 1H,
py5), 4.66 (s, 1Hs, CH), 4.00 (d, J = 10.1 Hz, 1Hs, CH), 3.89 (s, 1Ha,
CH), 2.86 (s, 1Ha, CH), 2.13 (s, 3H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 160.1 (d, JCP = 13.6 Hz, py2), 153.2 (d, JCP = 2.3 Hz, py6), 141.5
(s, py4), 138.9 (d, JCP = 5.8, CCH3), 132.5 (d, JCP = 2.4 Hz, Ph), 132.4
(d, JCP = 2.4 Hz, Ph), 131.9 (d, JCP = 16.4 Hz, Ph), 131.6 (d, JCP = 15.7 Hz,
Ph), 131.0 (d, JCP = 11.3, Ph), 129.4 (d, JCP = 11.7 Hz, Ph), 128.5.0 (d, J =
13.4, Ph), 117.3 (s, py5), 112.7 (d, JCP =7.1 Hz, py3), 79.9 (d, JCP = 33.1 Hz,
CH2), 52.6 (s, CH2), 23.9 (s, CH3). 31P{1H} NMR (δ, CD2Cl2,
20 ꢀC): 89.3.
[Pd(η3-CHPhCHCHPh)(PN-iPr)]SbF6 (9). This complex was
prepared analogously to complex 6a using 5e (167 mg, 0.25 mmol),
1b (110 mg, 0.50 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 325 mg (87%). Anal. Calcd for C26H32F6N2PPdSb: C,
41.88; H, 4.33; N, 3.76. Found: C, 41.92; H, 4.27; N, 3.50. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 7.87ꢀ7.20 (m, 12H, py6,3, Ph), 7.09 (d, J = 8.6 Hz, 1H,
py4), 6.94ꢀ6.59 (m, 1H, CH), 6.44 (t, J = 3.0 Hz, 1H, py5), 6.00 (s, 1H,
NH), 5.51 (d, J = 13.4 Hz, 1H, CH), 4.93 (d, J = 11.4 Hz, CH),
2.48ꢀ2.24 (m, 2H, CH), 1.52ꢀ0.60 (m, 12H, CH3). 13C{1H} NMR
(δ, CD2Cl2, 20 ꢀC): 161.7 (d, JCP = 10.4 Hz, py2), 146.7 (s, py6), 140.9
(s, py4), 139.0 (d, JCP = 2.1 Hz, Ph), 135.0 (d, JCP = 5.9 Hz, Ph), 130.0
(d, JCP = 2.0 Hz, Ph), 129.6 (d, JCP = 2.6 Hz, Ph), 129.4 (d, JCP = 1.4 Hz,
Ph), 128.5 ꢀ 128.0 (Ph), 127.1 (d, JCP = 3.0 Hz, Ph), 115.8 (s, py5),
112.5 (d, JCP = 6.0 Hz, CH), 112.0 (d, JCP = 5.2 Hz, py3), 97.1 (d, JCP
=
24.9 Hz, CHPh), 68.8 (d, JCP = 5.5 Hz, CH), 27.3 (d, JCP = 22.6 Hz, CH),
25.0 (d, JCP = 22.5 Hz, CH), 17.4 (d, JCP = 4.9 Hz, CH3), 15.3 (d, JCP
=
4.2 Hz, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 118.6.
[Pd(η3-CH2CHCH2)(ON-iPr)]SbF6 (10). This complex was pre-
pared analogously to complex 6a using 5a (184 mg, 0.50 mmol), 2b
(237 mg, 1.05 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 540 mg (89%). Anal. Calcd for C14H24F6N2OPPdSb: C,
[Pd(η3-CH2CMeCH2)(PN-iPr)]SbF6 (7b). This complex was pre-
pared analogously to complex 6a using 5b (196 mg, 0.50 mmol), 1b
(220 mg, 1.05 mmol), and AgSbF6 (343 mg, 1 mmol) as starting
materials. Yield: 600 mg (98%). Anal. Calcd for C15H26F6N2PPdSb: C,
29.66; H, 4.31; N, 4.61. Found: C, 29.68; H, 4.21; N, 4.70. 1H NMR (δ,
acetone-d6, 20 ꢀC): 8.62 (d, J = 5.8 Hz, 1H, py6), 7.89 (t, J = 7.4 Hz, 2H,
NH, py3), 7.24 (d, J = 8.5 Hz, 1H, py4), 6.95 (t, J = 6.5 Hz, 1H, py5), 4.83
(d, J = 3.0 Hz, 1Hs, CH), 4.07 (d, J = 9.5 Hz, 1Hs, CH), 3.94 (s, 1Ha,
CH), 2.87 (s, 1Ha, CH), 2.72ꢀ2.45 (m, 1H, CH), 2.09 (s, 2H, CH3),
1.37ꢀ1.13 (m, CH3). 13C{1H} NMR (δ, acetone-d6, 20 ꢀC): 162.4 (s,
py2), 153.8 (d, JCP = 1.9 Hz, py6), 141.3 (s, py4), 137.3 (d, JCP = 5.3 Hz,
CCH3), 116.5 (s, py5), 111.8 (d, JCP = 6.1 Hz, py3), 80.9 (d, JCP = 30.9
Hz, CH2), 47.6 (d, JCP = 2.6 Hz, CH2), 26.8 (d, JCP = 25.2 Hz, CH), 23.1
(s, CH3), 17.5 (dd, JCP = 22.6, 8.0 Hz, CH3), 16.5 (d, JCP = 12.6 Hz,
CH3). 31P{1H} NMR (δ, acetone-d6, 20 ꢀC): 126.5.
1
27.59; H, 3.97; N, 4.60. Found: C, 27.55; H, 4.07; N, 4.50. H NMR
(δ, CD2Cl2, 20 ꢀC): 8.23 (d, J = 4.2 Hz, 1H, py6), 7.86 (t, J = 7.31 Hz, 1H,
py3), 7.31 (d, J = 7.8 Hz, 1H, py4), 7.09 (t, J = 5.81 Hz, 1H, py5), 6.32
(d, J = 11.1 Hz, 1H, NH), 5.88ꢀ5.70 (m, 1H, CH), 4.18 (bs, 1Hs, CH),
3.90 (bs, 1Hs, CH), 3.62 (bs, 1Ha, CH), 3.22 (bs, 1Ha, CH), 2.37 (d, J =
6.8 Hz, 2H, CH), 1.38ꢀ1.08 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 155.4 (s, py2), 152.1 (s, py6), 141.4 (s, py4), 119.5 (s, CH), 118.7
(s, py3), 116.0 (s, py5), 62.8 (s, CH2), 58.9 (s, CH2), 16.4 (d, JCP = 82.9 Hz,
CH), 15.1 (d, JCP = 3.2 Hz, CH3), 14.7 (s, CH3). 31P{1H} NMR (δ,
CD2Cl2, 20 ꢀC): 81.5.
[Pd(η3-CH2CMeCH2)(ON-iPr)]SbF6 (11). This complex was
prepared analogously to complex 6a using 5b (196 mg, 0.50 mmol),
2a (237 mg, 1.05 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 556 mg (89%). Anal. Calcd for C15H26F6N2OPPdSb:
C, 28.90; H, 4.20; N, 4.49. Found: C, 28.95; H, 4.29; N, 4.59. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 8.24 (d, J = 5.3 Hz, 1H, py6), 7.86 (t, J = 7.5 Hz, 1H,
py3), 7.30 (d, J = 8.3 Hz, 1H, py4), 7.08 (t, J = 6.4 Hz, 1H, py5), 6.26
[Pd(η3-CHPhCHCH2)(PN-Ph)]SbF6 (8a). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol),
1a (140 mg, 0.50 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 369 mg (100%). Anal. Calcd for C26H24F6N2PPdSb: C,
1
42.34; H, 3.28; N, 3.80. Found: C, 42.42; H, 3.18; N, 3.70. H NMR
5938
dx.doi.org/10.1021/om200766y |Organometallics 2011, 30, 5928–5942

Organometallics
ARTICLE
(d, J = 12.0 Hz, 1H, NH), 3.97 (s, 1Hs, CH), 3.63 (s, 1Hs, CH), 3.13
(s, 1Ha, CH), 2.92 (s, 1Ha, CH), 2.37 (s, J = 6.3 Hz, 2H, CH), 2.23 (s,
3H, CH3), 1.4ꢀ1.02 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 155.6 (s, py2), 152.1 (s, py6), 141.2 (s, py4), 132.8 (s, CCH3),
(500 mg, 2.06 mmol), and AgSbF6 (686 mg, 2.00 mmol) as starting
materials. Yield: 1.1 g (88%). Anal. Calcd for C14H24F6N2SPPdSb: C,
26.88; H, 3.87; N, 4.48. Found: C, 26.75; H, 3.97; N, 4.50. H NMR
1
(δ, CD2Cl2, 20 ꢀC): 8.37 (dd, J = 5.7, 1.7 Hz, 1H, py6), 7.86 (dd, J = 8.3,
1.8, 1H, py3), 7.37 (d, J = 8.4 Hz, 1H, py4), 7.11 (t, J = 6.5 Hz, 1H, py5),
6.38 (dd, J = 7.0, 0.7 Hz, 1H, NH), 5.86ꢀ5.60 (m, 1Hc, CH), 4.42 (d, J =
5.2 Hz, 1Hs, CH), 4.07 (d, J = 6.8 Hz, 1Hs, CH), 3.54 (d, J = 12.6 Hz,
1Ha, CH), 3.07 (d, J = 12.3 Hz, 1Ha, CH), 2.77ꢀ2.49 (m, 2H, CH),
1.48ꢀ1.12 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 154.1
(d, J = 5.7 Hz, py2), 152.1 (s, py6), 141.1 (s, py4), 119.9 (s, CH), 119.8 (s,
py3), 117.1 (s, py5), 73.4 (s, CH2), 58.1 (s, CH2), 30.3 (d, JCP = 54.9 Hz,
CH), 6.0 (d, JCP = 3.5 Hz, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC):
100.0. The same complex with CF3SO3ꢀ as counterion was obtained by
using AgCF3SO3 as halide scavenger.
119.4 (s, py3), 118.6 (s, py5), 61.5 (s, CH2), 57.9 (s, CH2), 26.4 (d, JCP
=
89.6 Hz, CH), 22.8 (s, CH3), 15.1 (d, JCP = 3.4 Hz, CH3), 14.7 (s, CH3).
31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 81.3.
[Pd(η3-CHPhCHCH2)(ON-Ph)]SbF6 (12a). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol), 2a
(158 mg, 0.54 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 372 mg (98%). Anal. Calcd for C26H24F6N2OPPdSb:
C, 41.44; H, 3.21; N, 3.72. Found: C, 41.52; H, 3.16; N, 3.60. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 8.14 (d, J = 6.1 Hz, 1H, py6), 7.94 (t, J = 7.8 Hz, 1H,
py3), 7.86ꢀ7.42 (m, 15H, Ph, py), 7.34 (dd, J = 16.0, 7.9 Hz, 2H, NH,
Ph), 7.22 (t, J = 6.7 Hz, 1H, py4), 6.25ꢀ6.0 (m, 1Hc), 4.77 (d, J = 11.1
Hz, 1Ha), 4.17 (d, J = 5.6 Hz, 1Hs), 3.22 (d, J = 11.8 Hz, 1Ha). 13C{1H}
NMR (δ, CD2Cl2, 20 ꢀC): 152.4 (s, py2), 148.6 (s, py6), 143.3 (s, py4),
135.6 (s, Ph), 132.0 (d, JCP = 11.6 Hz, Ph), 129.8 (d, JCP = 14.1 Hz, Ph),
128.2 (s, Ph), 124. Eight (s, Ph), 122.7 (s, Ph), 120.9 (s, CH), 118.5
(s, py3), 108.0 (s, py5), 80.7 (s, CH2), 67.5 (s, CH2). 31P{1H} NMR
(δ, CD2Cl2, 20 ꢀC): 58.3.
[Pd(η3-CH2CMeCH2)(SN-Ph)]SbF6 (15a). This complex was
prepared analogously to complex 6a using 5b (196 mg, 0.50 mmol),
3a (330 mg, 1.06 mmol), and AgSbF6 (343 mg, 1 mmol) as starting
materials. Yield: 630 mg (89%). Anal. Calcd for C21H22F6N2SPPdSb: C,
35.65; H, 3.13; N, 3.96. Found: C, 35.59; H, 3.17; N, 4.01. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 9.06 (s, 1H, NH), 8.59 (d, J = 4.7 Hz, 1H, py6),
8.33ꢀ7.50 (m, 11H, py3, Ph), 7.42 (d, J = 8.7 Hz, 1H, py4), 7.16 (t, J =
5.8 Hz, 1H, py5), 4.31 (s, 1Hs, CH), 3.82 (s, 1Hs, CH), 3.44 (s, 1Ha,
CH), 2.85 (s, 1Ha, CH), 1.65 (s, 3H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 153.7 (d, J = 3.0 Hz, py2), 152.5 (s, py6), 141.0 (s, py4), 134.7
(s, CCH3), 133.9 (s, Ph), 131.1 (d, JCP = 12.0 Hz, Ph), 129.6 (s, Ph),
119.0 (s, py3), 117.7 (d, JCP = 5.7 Hz, py5), 73.8 (s, CH2), 58.7 (s, CH2),
21.9 (s, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 59.7.
[Pd(η3-CHPhCHCH2)(ON-iPr)]SbF6 (12b). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol,
0.5 equiv), 2a (120 mg, 0.54 mmol), and AgSbF6 (172 mg, 0.50 mmol)
as starting materials. Yield: 329 mg (96%). Anal. Calcd for C20H28-
F6N2OPPdSb: C, 35.04; H, 4.12; N, 4.09. Found: C, 35.20; H, 4.14; N,
3.98. 1H NMR (δ, CD2Cl2, 20 ꢀC): 8.26 (s, 1H, py6), 7.81 (s, 1H, py3),
7.67ꢀ6.82 (m, 7H, Ph, py4,5), 6.44 (d, J = 9.3 Hz, 1H, NH), 6.28ꢀ6.08
(m, 1H, CH), 5.20ꢀ3.50 (m, 2H, CH2) 3.21 (s, 1H, CH), 2.65ꢀ1.80
(m, 2H, CH), 1.48ꢀ0.46 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 155.5 (s, py2), 152.3 (s, py6), 141.1 (s, py4), 136.2 (s, Ph), 129.2
(s, Ph), 128.8 (s, Ph), 127.9 (s, Ph), 119.3 (s, CH), 118.5 (s, py5), 109.4
(py3), 81.1 (s, CH), 56.0 (s, CH2), 26.5 (d, JCP = 110.7 Hz, CH), 15.3
(s, CH3), 14.7 (s, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 81.3.
[Pd(η3-CHPhCHCHPh)(ON-iPr)]SbF6 (13). This complex was
prepared analogously to complex 6a using 5e (167 mg, 0.25 mmol), 2b
(120 mg, 0.54 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 350 mg (92%). Anal. Calcd for C26H32F6N2OPPdSb:
C, 41.00; H, 4.23; N, 3.68. Found: C, 40.97; H, 4.13; N, 3.72. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 7.87ꢀ7.20 (m, 13H, Ph, NH, py), 7.11 (d, J =
8.2 Hz, 1H, py5), 6.64ꢀ6.37 (m, 2H, py5, CH), 6.28 (d, J = 10.8 Hz,
CH), 4.83 (bs, 1H, CH), 2.38ꢀ1.96 (m, 2H, CH), 1.11 (d, 14.7 Hz, 6H,
CH3), 0.86 (d, J = 11.5 Hz, 6H, CH3). 13C{1H} NMR (δ, CD2Cl2,
20 ꢀC): 155.2 (d, JCP = 4.8 Hz, py2), 150.2 (s, py6), 140.6 (s, py4), 136.8
(s, Ph), 131.0ꢀ129.2 (Ph), 128.9 (s, Ph), 128.1 (s, Ph), 119.1 (s, py5),
117.7 (s, CH), 117.6 (s, py3), 103.8 (s, Ph), 78.9 (s, CH), 73.8 (s, CH),
[Pd(η3-CH2CMeCH2)(SN-iPr)]SbF6 (15b). This complex was
prepared analogously to complex 6a using 5b (196 mg, 0.50 mmol),
3b (240 mg, 1.07 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 607 mg (95%). Anal. Calcd for C15H26F6N2SPPdSb: C,
28.17; H, 4.10; N, 4.38. Found: C, 28.19; H, 4.02; N, 4.48. 1H NMR (δ,
CD2Cl2, 20 ꢀC): 8.38 (d, J = 4.9 Hz, 1H, py6), 7.86 (t, J = 7.5 Hz, 1H,
py3), 7.35 (d, J = 8.3 Hz, 1H, py4), 7.10 (t, J = 6.3 Hz, 1H, py5), 6.34
(d, J = 6.9 Hz, 1H, NH), 4.20 (s, 1Hs, CH), 3.85 (s, 1Hs, CH2, 3.38 (s,
1Ha, CH), 2.97 (s, 1Ha, CH2), 2.78ꢀ2.46 (m, 2H, CH), 2.14 (s, 3H,
CH3), 1.47ꢀ1.13 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC):
154.1 (d, J = 5.0 Hz, py2), 152.2 (s, py6), 141.1 (s, py4), 133.7 (s, CCH3),
119.8 (d, JCP = 4.5 Hz, py3), 119.7 (s, py5), 71.9 (s, CH2), 57.7 (s, CH2),
30.4 (d, JCP = 57.1 Hz, CH), 23.0 (s, CH3), 15.8 (d, JCP = 24.2 Hz, CH3).
31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 99.8.
[Pd(η3-CHPhCHCH2)(SN-Ph)]SbF6 (16a). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol),
3a (165 mg, 0.53 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 362 mg (98%). Anal. Calcd for C26H24F6N2SPPdSb: C,
1
40.57; H, 3.14; N, 3.64. Found: C, 40.62; H, 3.18; N, 3.50. H NMR
(δ, CD2Cl2, 20 ꢀC): 8.03ꢀ7.80 (m, 9H, py6, Ph), 7.80ꢀ7.59 (m, 9H,
py3, Ph), 7.33 (d, J = 18.0 Hz, 2H, Ph), 7.18 (d, J = 3.1 Hz, 1H, py4), 7.07
(s, 1H, NH), 7.03ꢀ6.80 (m, 1H, py5), 6.62 (bs, 1Hc, CH), 5.51 (bs, 1Hs,
CH), 4.61 (d, J = 11.5 Hz, 1Ha, CH), 3.92 (d, J = 3.6 Hz, 1Ha, CH).
13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 149.9 (s, py2), 140.5 (s, py6), 134.0
(d, JCP = 2.9 Hz, py4), 131.2 (d, JCP = 12.5, Hz, Ph), 130.14ꢀ129.02
(Ph), 127.81 (s, Ph), 119.0 (s, CH), 116.5 (d, JCP = 6.8 Hz, py3), 110.37
(s, py5), 92.6 (s, CH), 57.33 (s, CH2). 31P{1H} NMR (δ, CD2Cl2,
20 ꢀC): 60.0.
26.4 (d, JCP = 82.6 Hz, CH), 15.0 (d, JCP = 36.9 Hz, CH3), 14.3 (d, JCP
=
40.0 Hz, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 80.9.
[Pd(η3-CH2CHCH2)(SN-Ph)]SbF6 (14a). This complex was pre-
pared analogously to complex 6a using 5a (184 mg, 0.50 mmol), 3a
(330 mg, 1.06 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 622 mg (90%). Anal. Calcd for C20H20F6N2SPPdSb: C,
1
34.64; H, 2.91; N, 4.04. Found: C, 34.55; H, 2.89; N, 4.12. H NMR
(δ, CD2Cl2, 20 ꢀC): 8.28 (d, J = 5.7 Hz, 1H, py6), 7.96ꢀ7.77 (m, 5H,
py4, Ph), 7.77ꢀ7.66 (m, 2H, Ph), 7.66ꢀ7.50 (m, 4H, Ph), 7.27 (d, J =
8.4 Hz, 1H, py3), 7.05 (t, J = 7.1 Hz, 1H, py5), 6.93 (d, J = 5.3 Hz, 1H,
NH), 5.09 (m, 1H, CH), 4.25 (bs, 1Hs, CH), 3.91 (bs, 1Hs, CH), 3.25
(bd, J = 11.8 Hz, 1Ha, CH), 2.72 (bd, J = 10.6 Hz, 1Ha, CH). 13C{1H}
NMR (δ, CD2Cl2, 20 ꢀC): 153.8 (d, J = 4.0 Hz, py2), 152.3 (s, py6),
[Pd(η3-CHPhCHCH2)(SN-iPr)]SbF6 (16b). This complex was
prepared analogously to complex 6a using 5d (129 mg, 0.25 mmol),
3b (125 mg, 0.52 mmol), and AgSbF6 (172 mg, 0.50 mmol) as starting
materials. Yield: 334 mg (95%). Anal. Calcd for C20H28F6N2PPdSSb: C,
141.1 (s, py4), 134.0 (s, Ph), 131.2 (d, JCP = 12.5 Hz, Ph), 129.5 (d, JCP
=
1
34.24; H, 4.02; N, 3.99. Found: C, 34.10; H, 4.14; N, 3.98. H NMR
14.2 Hz, Ph), 119.1 (s, CH), 117.8 (d, JCP = 6.8 Hz, py3), 117.6 (s, py5),
75.0 (s, CH2), 59.7 (s, CH2). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 60.9.
[Pd(η3-CH2CHCH2)(SN-iPr)]SbF6 (14b). This complex was pre-
pared analogously to complex 6a using 5a (366 mg, 1.00 mmol), 3b
(δ, CD2Cl2, 20 ꢀC): 7.78ꢀ7.15 (m, 8H, py, Ph), 6.97 (d, J = 6.9 Hz, 1H,
py3), 6.62 (s, 1H, NH), 6.16 (bs, 1Hc, CH), 5.00 (d, J = 11.1 Hz, 1Hs,
CH), 4.08 (bs, 1Ha, CH), 3.11 (bs, 1Ha, CH), 2.59 (s, 2H, CH),
1.65ꢀ0.89 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC):
5939
dx.doi.org/10.1021/om200766y |Organometallics 2011, 30, 5928–5942

Organometallics
ARTICLE
153.9 (s, py2), 149.7 (s, py6), 140.3 (s, py4), 129.5 (s, Ph), 129.0 (s, Ph),
127.7 (s, Ph), 119.7 (s, CH), 118.8 (s, py3), 109.8 (s, py5), 90.6 (s, CH),
55.4 (s, CH2), 30.7 (d, JCP = 44.6 Hz, CH), 29.8 (d, JCP = 41.8, CH),
16.1 (s, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 99.5.
py5), 113.6 (s, CH), 109.8 (s, py3), 70.6 (s, CH2), 53.0(s, CH2), 31.0 (d, JCP
= 14.9 Hz, CH), 29.8 (d, JCP = 16.0 Hz, CH), 16.6 (s, CH3). 31P{1H} NMR
(δ, C6D6, 20 ꢀC): 64.2.
X-ray Structure Determination. X-ray data for (ON-Ph) (2a),
(ON-iPr) (2b), [Pd(η3-CH2CMeCH2)(PN-iPr)]SbF6 (7b), [Pd(η3-
CHPhCHCH2)(PN-iPr)]SbF6 (8b), [Pd(η3-CHPhCHCHPh)(PN-
iPr)]SbF6 (9),[Pd(η3-CH2CHCH2)(ON-iPr)]SbF6 (10),[Pd(η3-CH2CH-
CH2)(SN-iPr)]CF3SO3 (14b), [Pd(η3-CH2CMeCH2)(SN-Ph)]SbF6
(15a), [Pd(η3-CH2CMeCH2)(SN-iPr)]SbF6 (15b), [Pd(η3-CH2CH-
CH2)(SeN-iPr)]CF3SO3 (17b), [Pd(η3-CH2CMeCH2)(k1(N)-ON-
Ph)Cl] 1/2CH2Cl2 (18 1/2CH2Cl2), and [Pd(η3-CH2CHCH2)-
[Pd(η3-CH2CHCH2)(SeN-Ph)]SbF6 (17a). This complex was
prepared analogously to complex 6a using 5a (184 mg, 0.50 mmol),
4a (390 mg, 1.09 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 629 mg (85%). Anal. Calcd for C20H20F6N2PPdSbSe:
C, 32.44; H, 2.72; N, 3.78. Found: C, 32.53; H, 2.68; N, 3.81. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 8.32 (d, J = 5.6 Hz, 1H, py6), 7.94ꢀ7.78 (m, py3,
Ph), 7.77ꢀ7.48 (m, 6H, py4, Ph), 7.26 (d, J = 8.4 Hz, 1H, py5), 7.06
(t, J = 6.6 Hz, 1H, py), 6.92 (s, J = 6.30 Hz, 1H, NH), 5.01ꢀ4.81 (m, 1H,
CH), 4.34 (s, 1Hs, CH2), 3.88 (s, 1Hs, CH2), 3.21 (s, 1Ha, CH2), 2.52 (s,
1Ha, CH2). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 153.9 (d, JCP = 19.1 Hz,
py2), 151.8 (s, py6), 144.6 (s, py4), 140.9 (s, Ph), 133.9 (s, Ph), 131.1
(d, JCP = 12.8 Hz, Ph), 129.4 (d, JCP = 14.2 Hz, Ph), 119.0 (s, CH), 117.8
(d, JCP = 6.7 Hz, py3), 116.7 (s, py5), 76.4 (s, CH2), 57.9 (s, CH2).
31P{1H} NMR (δ, CD2Cl2, 20 ꢀC): 50.3 (d, JPꢀSe = 651.2 Hz).
[Pd(η3-CH2CHCH2)(SeN-iPr)]SbF6 (17b). This complex was
prepared analogously to complex 6a using 5a (184 mg, 0.50 mmol),
4a (3.05 mg, 1.05 mmol), and AgSbF6 (343 mg, 1.00 mmol) as starting
materials. Yield: 578 mg (86%). Anal. Calcd for C14H24F6N2PPdSbSe:
C, 25.01; H, 3.60; N, 4.17. Found: C, 25.15; H, 3.49; N, 4.20. 1H NMR
(δ, CD2Cl2, 20 ꢀC): 8.66 (d, J = 3.6 Hz, 1H, py6), 8.44 (s, 1H, NH), 7.97
(t, J = 7.7 Hz, 1H, py3), 7.53 (d, J = 7.7 Hz, 1H, py4), 7.20 (t, J = 5.1 Hz,
1H, py5), 5.96ꢀ5.73 (m, 1H, CH), 4.62 (bs, 1Hs, CH), 4.12 (bs, 1Hs,
CH), 3.75 (bs, 1Ha, CH), 3.09 (bs, 1Ha, CH), 2.98ꢀ2.68 (m, 2H, CH),
1.45ꢀ1.14 (m, 12H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 ꢀC): 155.2
3
3
(SNH-iPr)] (19) were collected at T = 100 K on a Bruker Kappa
APEX-2 CCD area detector diffractometer using graphite-monochro-
mated Mo Kα radiation (λ = 0.71073 Å) and j- and ω-scan frames
covering complete spheres of the reciprocal space with θmax = 30ꢀ.
Corrections for absorption and λ/2 effects were applied.43 After
structure solution with the program SHELXS97 and direct methods,
refinement on F2 was carried out with the program SHELXL97.44 Non-
hydrogen atoms were refined anisotropically. Most hydrogen atoms
were placed in calculated positions and thereafter treated as riding. The
allyl groups in 10, 14b, 17b, and 19 showed orientation disorder with the
central allyl carbon atom adopting two complementary positions (up
and down orientation of the allyl group relative to the Pd coordination
plane). This feature was taken into account in the refinement. All
substituted allyl groups were ordered. Allyl group hydrogen atoms were
handled with instructions AFIX 23 for CH2 and AFIX 43 for CH. The
two triflate salts 14b and 17b, [Pd(η3-CH2CHCH2)(EN-iPr)]CF3SO3
with E = S or Se, are isostructural. Compound 18 crystallized as a stable
stoichiometric dichloromethane solvate (2:1) with two independent Pd
complexes differing in conformation and one solvent molecule. All
(d, JCP = 6.04 Hz, py2), 151.6 (s, py6), 140.5 (s, py4), 120.5 (d, JCP
=
4.4 Hz, CH), 119.2 (s, py3), 116.0 (s, py5), 74.8 (s, CH2), 55.4 (s, CH2),
30.6 (d, JCP = 46.4 Hz, CH), 16.6 (d, JCP = 3.2 Hz, CH3). 31P{1H} NMR
(δ, CD2Cl2, 20 ꢀC): 94.5 (d, JPꢀSe = 634.8 Hz). The same complex with
complexes except 18 1/2CH2Cl2 and 19 showed intermolecular hydro-
3
gen bonds between the NꢀH group of the chelate ligand and the
counteranion. In 19 the deprotonated nitrogen atom N2 is an acceptor
of a weak CꢀH N interaction from CH of a isopropyl group, C N =
ꢀ
CF3SO3 as counterion was obtained by using AgCF3SO3 as halide
scavenger.
3 3 3
3 3 3
[Pd(η3-CH2CMeCH2)(j1(N)-ON-Ph)Cl] (18). A mixture of 5b
(100 mg, 0.25 mmol) and 2a (160 mg, 0.54 mmol) in CH2Cl2 (10 mL)
was stirred for 30 min. After that, the solvent was removed under
reduced pressure. The remaining solid was washed with diethyl ether
and dried under vacuum. Yield: 246 mg (100%). Anal. Calcd for
C21H22ClN2OPPd: C, 51.35; H, 4.51; N, 5.70. Found: C, 51.39; H,
4.59; N, 5.68. 1H NMR (δ, CD2Cl2, 20 ꢀC): 8.28 (d, J = 4.6 Hz, 1H py6),
8.05ꢀ7.89 (m, 4H, py, Ph), 7.70ꢀ7.40 (m, 7H, py, Ph), 7.27 (d, J =
8.3 Hz, 1H, py4), 6.87 (t, J = 5.9 Hz, 1H, py5), 5.35 (s, 1H, NH), 3.79
(s, 2H, CH2), 2.91 (s, 2H, CH2), 2.05 (s, 3H, CH3). 13C{1H} NMR
(δ, CD2Cl2, 20 ꢀC): 154.7 (s, py), 150.6 (s, py), 139.0 (s, py), 132.4
(d, JCP = 2.8 Hz, py), 131.7 (d, JCP = 10.5 Hz, Ph), 130.3 (d, JCP = 23.3
Hz, Ph), 128.8 (d, JCP = 13.2 Hz, Ph), 117.3 (s, CH), 114.2 (s, Ph), 61.5
(s, CH2), 55.3 (s, CH2), 22.8 (s, CH3). 31P{1H} NMR (δ, CD2Cl2,
20 ꢀC): 31.7.
3.57 Å. Crystallographic data are listed in Table S2. Selected geometric data
are given in Table S1.
Computational Details. All calculations were performed using
the Gaussian 03 software package45 and the PBE0 functional, without
symmetry constraints. That functional uses a hybrid generalized gradient
approximation, including a 25% mixture of HartreeꢀFock46 exchange
with DFT35 exchangeꢀcorrelation, given by the Perdew, Burke, and
Ernzerhof functional (PBE).47 The optimized geometries were obtained
with a LanL2DZ basis set48 augmented with an f-polarization function49
for Pd and a standard 6-31G(d,p)50 for the remaining elements (basis b1).
Transition-state optimizations were performed with the synchronous
transit-guided quasi-Newton method (STQN) developed by Schlegel
et al.,51 following extensive searches of the potential energy surface.
Frequency calculations were performed to confirm the nature of the
stationary points, yielding one imaginary frequency for the transition
states and none for the minima. Each transition state was further
confirmed by following its vibrational mode downhill on both sides
and obtaining the minima presented on the energy profiles. A natural
population analysis52 and the resulting Wiberg indices36 were used to
study the electronic structure and bonding of the optimized species.
The energy profiles reported result from single-point energy calcula-
tions using an improved basis set (basis b2) and the geometries
optimized at the PBE0/b1 level. Basis b2 consisted of the Stuttgart/
Dresden ECP basis set53 with an added f-polarization function49 for Pd
and standard 6-311++G(d,p)54 for the remaining elements. Solvent
effects (CH3CN) were considered in the PBE0/b2//PBE0/b1 energy
calculations using the polarizable continuum model initially devised by
Tomasi and co-workers55 as implemented in Gaussian 03.56 The
molecular cavity was based on the united atom topological model
applied on UAHF radii, optimized for the HF/6-31G(d) level.
[Pd(η3-CH2CHCH2)(SNH-iPr)] (19). A solution of 14b (191 mg,
0.30 mmol) in THF (10 mL) was cooled to 0 ꢀC using an ice bath. Then,
KOtBu (34 mg, 0.30 mmol) dissolved in THF was added dropwise to
this solution, and the mixture was allowed to stir for 30 min. After that,
the solvent was evaporated under reduced pressure. The solid was
dissolved in benzene, the remaining potassium salt was filtered off, and
the solvent was removed under vacuum to give analytically pure 25.
Yield: 116 mg (99%). Anal. Calcd for C14H23N2PPdS: C, 43.25; H, 5.96;
N, 7.21. Found: C, 43.30; H, 5.88; N, 7.32. 1H NMR (δ, C6D6, 20 ꢀC):
7.99 (d, J = 5.1 Hz, 1H, py6), 7.27 (t, J = 7.6 Hz, 1H, py3), 6.66 (d, J =
8.5 Hz, 1H, py4), 6.27 (t, J = 6.0 Hz, 1H, py5), 5.64ꢀ5.43 (m, 1H, CH),
4.01 (d, J = 6.4 Hz, 1Hs, CH2), 3.65 (d, J = 6.5 Hz, 1Hs, CH2), 3.30 (d, J =
12.5 Hz, 1Ha, CH2), 2.75 (d, J = 12.3 Hz, 1Ha, CH2), 2.33ꢀ2.05 (m, 2H,
CH), 1.36ꢀ1.02 (m, 12H, CH3). 13C{1H} NMR (δ, C6D6, 20 ꢀC): 164.6
(s, py2), 152.5 (s, py6), 136.7 (d, JCP = 3.2 Hz, py4), 122.7 (d, JCP = 18.3 Hz,
5940
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Organometallics
ARTICLE
SuzukiꢀMiyaura Cross-Coupling Reactions. General Pro-
cedure. In a glovebox, a vial equipped with a magnetic stir bar was
charged with a solution of phenylboronic acid (1.5 mmol), aryl bromide
(1 mmol), and KOtBu (2 mmol) in 2-propanol (5 mL, HPLC grade),
and the required amount of palladium catalyst solution (prepared from a
0.01 M solution of the catalyst in CH2Cl2) was added by syringe. The
reaction mixture was stirred at room temperature unless otherwise
indicated. After 12 h the reaction was quenched with a saturated
NaHCO3 solution. The product was then extracted with diethyl ether
(3 ꢁ 5 mL). The combined organic layers were washed with brine, dried
over Na2SO4, and filtered, and the solvent was evaporated under
vacuum. When necessary the product was purified by flash chromatog-
raphy on silica gel.
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’ ASSOCIATED CONTENT
S
Supporting Information. Complete crystallographic data
b
and technical details in CIF format and tabular form for com-
pounds 2a, 2b, 7b, 8b, 9, 10, 14b, 15a, 15b, 17b, 18 1/2CH2Cl2,
3
and 19. Molecular structures of 2a and 2b (Figures S1 and S2).
Energy profiles for η3-allyl pseudorotation in 6b+ (Figure S3)
and η3ꢀη1ꢀη3 allyl isomerization in 14b+ (Figure S4). Atomic
coordinates for all optimized species. This material is available
free of charge via the Internet at http://pubs.acs.org.
(18) Benito-Garagorri, D.; Mereiter, K.; Kirchner, K. Collect. Czech.
Chem. Commun. 2007, 72, 527–540.
’ AUTHOR INFORMATION
(19) Vrieze, K. Fluxional Allyl Complexes. In Dynamic Nuclear
Magnetic Resonance Spectroscopy; Jackman, L. M.; Cotton, F. A., Eds.;
Academic Press: New York, 1975; pp 441ꢀ483.
Present Addresses
^Visiting Professor at the Institute of Applied Synthetic Chemistry
(Sept 2010ꢀAug 2011).
(20) Faller, J. W. In Dynamic NMR Spectroscopy in Organometallic
Chemistry, Comprehensive Organometallic Chemistry III; Crabtree, R. H.;
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’ ACKNOWLEDGMENT
L.F.V. acknowledges UTL/Santander and Fundac-~ao para a
Ci^encia e Tecnologia (FCT, project PEst-OE/QUI/UI0100/
2011) for financial support.
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