5,6-Membered palladium pincer complexes of 1-thiophosphoryloxy-3- thiophosphorylbenzenes. Synthesis, X-ray structure, and catalytic activity

Article abstract of DOI:10.1039/b907644a

Novel unsymmetrical ligands, 1-thiophosphoryloxy-3-thiophosphorylbenzenes 3a-d, bearing phosphine sulfide and thiophosphoryloxy moieties as coordinating sites, were found to undergo cyclometalation at the C-2 position of the central benzene ring in a reac

Full text of DOI:10.1039/b907644a

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5,6-Membered palladium pincer complexes of 1-thiophosphoryloxy-3-
thiophosphorylbenzenes. Synthesis, X-ray structure, and catalytic activity†
V. A. Koz lov , a D. V. Aleksanyan,a Yu. V. Nelyubina,a K. A. Lyssenko,a E. I. Gutsul,a A. A. Vasil’ev,b
P. V. Pe t rov s k i i a and I. L. Odinets*a
Received 16th April 2009, Accepted 5th August 2009
First published as an Advance Article on the web 25th August 2009
DOI: 10.1039/b907644a
Novel unsymmetrical ligands, 1-thiophosphoryloxy-3-thiophosphorylbenzenes 3a–d, bearing
phosphine sulfide and thiophosphoryloxy moieties as coordinating sites, were found to undergo
cyclometalation at the C-2 position of the central benzene ring in a reaction with
bis(benzonitrile)palladium dichloride affording rare examples of nonsymmetrical pincer complexes,
namely [2-{(thiophosphoryl)oxy}-6-(diphenylthiophosphoryl)phenyl]palladium chlorides 4a–d,
3
containing 5- and 6-membered fused metallacycles with k -SCS¢-coordination. Molecular structures of
the complexes were characterized by X-ray diffraction. These complexes demonstrated high catalytic
activity for the Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid.
vinyl carbon atom). Such alterations allow additional possibilities
Introduction
of controlling steric and electronic properties of the pincer system
Pincer complexes containing anionic six-electron donor ligands
in total. Among such nonsymmetrical pincer complexes, those
bearing metallacycles of different size are rather scarce.13
of the type YCY are of unfailing interest due to their feasible
structural modifications with multiple choices of donor atoms and
their substituents (Y = NR2, SR, PR2, OPR2, etc.), high stability,
and remarkable catalytic activities with high TON and TOF values
in various processes such as dehydrogenation of alkanes, reduction
of ketones, aldol condensation, cross-coupling reactions and so
on.1 However, applications of pincer complexes are not restricted
only by catalysis. They may be used as building-blocks for the
synthesis of natural compounds2 and homo- and heterometallic
dendrimers,3,4b–d,g chemosensors for small molecules (e.g. SO2),4
biomarkers for peptides,5 liquid crystal materials,6 etc.
The most common are symmetrical pincer palladium and plat-
inum complexes of PCP, NCN, or SCS types having two identical
donor groups and two equivalent five-membered metallacycles.
Nevertheless, nonsymmetrical (hybrid) YCY¢ pincer complexes
possess a wider area of practically important properties as they can
combine the properties of a few symmetrical systems and manifest
unique reactivity and non-typical features compared with their
symmetric analogues. The routes of desymmetrization comprise
changes in donor moieties (introduction of different substituents
at the same donor atoms or different donor groups), variation
of linkers (changing of their length and nature), and central core
(shifting of the central aromatic core to give CYY¢ system, appli-
cation of different aromatic rings, and moieties bearing the C(sp2)
It should be mentioned that even though thiophosphoric acid
derivatives and phosphine sulfides are known to form complexes
with a variety of metals where the coordination bond is formed
via the soft sulfur atom of thiophosphoryl group,7 there are only
=
a few reports dealing with the application of P S containing
compounds in the synthesis of pincer-type complexes.8–10
For example, 1,3-bis(diphenylthiophosphoryl)benzene,8 1,3-bis-
(diphenylthiophosphoryl)pyridine,9
and
2,6-bis(diphenyl-
thiophosphoryl)phosphinane10 form symmetric platinum and
palladium pincer complexes I–III (Scheme 1). Among hybrid
11
=
P S pincer complexes known are only tin complex IV of 1-
diphenylthiophosphoryl-3-diisopropoxyphosphoryl-5-tert-butyl-
benzene and palladium complexes V12 of 3-diphenylthio-
phosphorylbenzoic acid thioamides reported by us recently.
aA.N. Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences, 28 Vavilova str., Moscow, 119991, Russia. E-mail:
odinets@ineos.ac.ru
bN.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 117913, Moscow, Russia
† Electronic supplementary information (ESI) available: Tables giving
complete data collection parameters, atomic coordinates, bond distances
and angles, and thermal parameters for 3b, 4a, 4c, as well as the
schematic view of complex 4c with the central fragment shown as a
superposition of two isomers. CCDC reference numbers 730242–730244.
For crystallographic data in CIF or other electronic format see DOI:
10.1039/b907644a
Scheme 1 Representatives of thiophosphoryl pincer complexes.
Dalton Trans., 2009, 8657–8666 | 8657
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SCS¢-Complexes V demonstrated high catalytic activity for the
Suzuki cross-coupling of aryl bromides with phenylboronic acid
and exhibited the luminescence at 77 and 300 K both in solid
state and in solutions.
In this communication we report the convenient synthesis of 1-
thiophosphoryloxy-3-thiophosphorylbenzenes suitable as pincer
ligands and their nonsymmetrical palladium complexes with fused
5- and 6-membered metallacycles proved to be active catalysts for
the Suzuki reaction.
performed under phase-transfer catalysis (PTC) conditions using
10% aq. NaOH/benzene system and triethylbenzylammonium
chloride (TEBA) as a catalyst.
The structures of 1-thiophosphoryloxy-3-thiophosphoryl-
benzenes 3a–d were unambiguously confirmed by NMR and
elemental analysis data. The 31P NMR spectra of 3a–d show two
singlets at ca. 43 ppm (region typical for phosphine sulfide group)
and in the range of 76.6–94.4 ppm (phosphorus resonances of
1
OP(S)R1R2 moiety). An interpretation of H NMR spectra in
the aromatic proton region is complicated by the presence of
signals of several peripheral phenyl rings while the resonances
of alkyl protons of NEt2, Me, OBu and NMe2 groups can be easily
identified. In contrast, the signals of carbon atoms of the central
benzene core in the 13C NMR spectra of 3a–d do not overlap with
the resonances of peripheral benzene CPh-atoms even in the case
of compound 3c containing five phenyl rings.
The structure of 3b was confirmed by a single crystal
X-ray diffraction analysis. In line with the molecular geometry
examination, the bond lengths and angles of 3b (Fig. 1) fall
into the range typical for compounds of this type. The mutual
Results and discussion
Synthesis of ligands
The synthetic route of novel SCS¢-ligands was elabo-
rated starting from commercially available 3-bromoanisole
(Scheme 2). Thus, reaction of the Grignard reagent prepared
from this compound with diphenylchlorophosphine afforded (3-
methoxyphenyl)diphenylphosphine converted via sulfur addition
to the corresponding phosphine sulfide 1. In contrast to the
literature data,14 the synthesis was performed as a one-pot
process using the original procedure. Treatment of the phosphine
sulfide 1 with pyridine hydrochloride resulted in formation of
thiophosphorylated phenol 2 in a reasonably good yield (69%).
It should be noted that application of hydrobromic acid typ-
ically used for removing of methoxy protective group, yielded
3-diphenylphosphorylphenol, i.e. the phosphorylated analogue
of 2 bearing the P(O) group instead of the P(S) one. Further
thiophosphorylation of 3-diphenylthiophosphorylphenol 2 as a
single key precursor allowed a variety of SCS¢-pincer-type ligands
3a–d bearing different substituents at the phosphorus atom of the
thiophosphoryloxy moiety to be obtained.
=
disposition of P S groups is a transoid one. Although the torsion
angle S(1)P(1)P(2)S(2) is only 47.1(2)◦, P(1)–S(1) and P(2)–S(2)
lines are directed away from the central phenyl cycle into the
different directions. Such a configuration of the 3b molecule in
=
the crystal is stabilized by a number of relatively weak P S ◊ ◊ ◊ H
As mentioned above, thiophosphorylation of phenol 2 was
carried out by thiophosphorus acid chlorides bearing different
substituents at the phosphorus atom, namely thiophosphoric,
thiophosphonic and thiophosphinic acid chlorides (Scheme 2).
Depending on the nature of this reactant, different reaction
conditions were used. To avoid hydrolysis of thiophosphorylating
agents, anhydrous conditions were used for the synthesis of
tetraalkyldiamido- and (butoxy)methyl-substituted ligands 3a, 3b
and 3d. At that, the reaction of more active methylthiophosphonic
acid chloride in benzene in the presence of triethylamine as a base
resulted in 3d with a yield of 93%, while thiophosphorylation using
tetraalkyldiamido-derivatives did not afford reasonable yields of
the desired products 3a,b under these conditions. The optimized
conditions providing the desired 3a,b in 56–58% yields comprised
of using of triethylamine as a solvent and elevated temperature. In
the case of the most water-resistant Ph2P(S)Cl, the reaction was
Fig. 1 General view of compound 3b in representation of atoms via
◦
˚
thermal ellipsoids (p = 50%). The main bond lengths (A) and angles ( ):
P(1)–S(1) 1.9392(9), P(2)–S(2) 1.9555(9), P(1)–O(1) 1.6289(16), O(1)–C(1)
1.389(2), P(2)–C(3) 1.817(2), C(1)–C(2) 1.388(3), C(2)–C(3) 1.395(3);
C(1)–C(2)–C(3) 119.11(19), O(1)–P(1)–S(1) 112.49(7), C(3)–P(2)–S(2)
113.61(8).
Scheme 2 Synthesis of 1-thiophosphoryloxy-3-thiophosphorylbenzenes 3a–d.
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group region were either upfield or downfield shifted for 2.5–4 ppm
while those for phosphine sulfide groups were downfield shifted
for 0.5–2.5 ppm. In time, these signals transform to the single
pair of singlets assigned to the final pincer-type complexes. The
shifting of phosphorus resonances indicates the coordination by
metal center of sulfur atoms of a ligand.8–10,12
As for the structure of these intermediate compounds, one
can suggest the initial formation of dimeric complexes of 1 : 1
composition with the m-bridged chlorine atom, which may have
different structures. Namely, in these complexes Pd may be
coordinated either via the same or the different sulfur atoms
in the ligand. The signals also may be attributed to complexes
PdCl2L2 of 1 : 2 composition (rather trans than cis ones) and
non-cyclopalladated species with bridged Pd coordination via two
sulfur atoms of the same ligand being the precursor of final pincer
products. Unfortunately, all efforts were futile for the isolation
of such intermediate species in an individual form. Note also
that during the slow reaction in DCM the precipitation of PdCl2
was observed. In fact, transformation of m-bridged complexes
[PdCl2L]2 to PdCl2L2 species with liberation of PdCl2 was reported
in literature.15 Indeed, if 2 equivalents of the ligand were used
precipitation of PdCl2 was not observed as was demonstrated using
formation of 4c as a representative example.
Scheme 3 Cyclopalladation of 1-thiophosphoryloxy-3-thiophosphoryl-
benzenes.
˚
contacts (S ◊ ◊ ◊ C 3.656(4)–3.918(4) A). The latter leads to the
formation of corrugated layers, two molecules thick, which are
further assembled into 3D framework by stacking interaction
˚
between central rings (C ◊ ◊ ◊ C 3.376(4) A).
Synthesis of palladium pincer complexes
The reaction of 1-thiophosphoryloxy-3-thiophosphorylbenzenes
3a–d with (PhCN)2PdCl2 readily proceeded as cyclopalladation
of the central phenyl ring to form the corresponding SCS¢-pincer
palladium complexes 4a–d having in the molecule fused 5- and
6-membered palladacycles (Scheme 3). Such direct cyclopallada-
tion of 3a–d was performed either in benzene solution under reflux
for 2 h or in dichloromethane (DCM) or its mixture with methanol
(1 : 1) under ambient conditions over a few days.
The structure of the complexes 4a–d was assigned by NMR
(1H, 31P and 13C), IR spectra and elemental analysis data. As
compared with the corresponding free ligands, in the 31P NMR
spectra of complexes the signals of thiophosphoryloxy moieties
were shifted upfield to 8.7–13.1 ppm in contrast with the downfield
shifted (to 1.2–4.4 ppm) signals of the phosphine sulfide groups.
As mentioned above, the shifting of phosphorus resonances
unambiguously indicates the coordination by metal center of both
For the synthesis of dialkylamidophosphoryloxy derivatives
4a,b the reaction in benzene was found to be more convenient due
to the high rate of cyclopalladation comparing with the reaction
in CH2Cl2. When the diphenylthiophosphoryloxy analogue 3c
was used as a ligand, the yield of the corresponding complex 4c
estimated by 31P NMR spectra of reaction mixtures (C6H6, reflux,
2 h or CH2Cl2, 20 ◦C, 7 days), reached only ca. 20%. However,
addition of methanol to dichloromethane solution allowed not
only increasing the yield of pincer-type product 4c, but accelerating
the cyclopalladation too. Thus, the reaction of (PhCN)2PdCl2
with the ligand 3c in CH2Cl2–MeOH mixed solvent afforded
the corresponding complex 4c in the yield of ~70% over 24 h.
The complex 4d bearing the (butoxy)methylthiophosphoryloxy
group was obtained only under mild conditions (dichloromethane
solution, 5 days) in the yield of 19% while heating in benzene
or addition of methanol to CH2Cl2 solution lead to the de-
composition of the ligand 3d. In total, when cyclopalladation
was performed in dichloromethane solution the yields of the
corresponding complexes decreased in the range 4b > 4a > 4c >
4d depending on the substituents at the phosphorus atom of the
thiophosphoryloxy moiety.
Moreover, the low rate of cyclopalladation in CH2Cl2 allowed
the process of pincer-type complexes formation to be followed.
Thus, initially the 31P NMR spectra of the reaction mixtures
display a few pairs of signals corresponding to thiophosphoryloxy
and phosphine sulfide groups of the intermediate species (typically
3 pairs) along with the corresponding pair of signals of a ligand.
According the distribution of the integral intensities of the signals,
two intermediate complexes dominated in reaction mixtures (e.g.
30 and 35%, respectively, in the case of 3c as a starting ligand), the
amount of non-coordinated ligand did not exceed 10–15%. For
the intermediate complexes the signals in the thiophosphoryloxy
1
sulfur atoms of phosphine sulfide groups.8–10,12 The H and 13C
NMR spectra of complexes 4a–d confirmed the occurrence of
C-metalation: the resonance of the C(2)-H proton was absent,
and the signal of the C(2)-carbon atom in the 13C NMR spectra
was strongly shifted downfield compared to the signal in the
corresponding free ligand. It should be mentioned that signals of
C(1)- and C(3)-carbon atoms in palladacycles were also downfield
shifted by ~14 and ~5 ppm, respectively, with regard to their
resonances in the parent ligands. Moreover, the 13C NMR data
for complexes 4a,b show clearly that metalation changes not
only the chemical shifts of C(1), C(2), and C(3) but also JPC
1
coupling constants which increase significantly. Thus, the JPC(3)
coupling constant averaged ca. 85 Hz for the starting ligands
3a,b increases to approximately 105.5 Hz for the corresponding
3
complexes; a JPC(2) coupling constant between the C2-carbon
and the phosphorus atom of the thiophosphoryloxy moiety being
equal to 11.8 Hz in 3b increases up to 22.5 Hz in 4b. The coupling
constants between the C(1) atom and both phosphorus nucleus
2
also changed from 5.3–5.9 Hz to 7.2–8.1 Hz in the case of JPC(1)
and from 15.8–16.1 Hz to 21.3–22.0 Hz for 3JPC(1). Also, it should be
noted that the signals of protons of central benzene ring in the 1H
NMR spectra of pincer complexes 4a–d can be easily interpreted
even in the case of compound 4c, which contains four additional
peripheral phenyl rings, as they are significantly shifted upfield and
do not overlapped with the signals of the other aromatic protons.
X-Ray diffraction analysis performed for 4a and 4c unam-
biguously confirmed formation of palladium pincer complexes.
According to the X-ray data the bond lengths and angles in 4a
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(Fig. 2) and 4c (Fig. 3) are close to those for the known palladated
SCS and SCS¢-ligands. It should be mentioned that due to strong
disorder at two positions of the central core of the complex 4c in
the crystal (Fig. 1S), the details of palladium-to-ligand binding
conformation with the deviation of S(2) atom from the plane of
˚
Pd(1), P(2), C(2) and C(3) atoms by as much as 1.02 A, and the
6-membered cycle by a conformation that can be described as
highly distorted chair with the deviation of S(1) atom from the
˚
=
will be mainly discussed for 4a. The P S groups in both 4a and
4c become longer by 0.04 A upon the complex formation, while
plane of Pd(1), P(1), O(1), C(1), C(2) by 1.32 A. The nonplanarity
˚
of Pd-containing cycles in comparison with those, for example, in
V,12 lead in turn to the distortion of the palladium square-planar
configuration with the dihedral angle between S(2)Pd(1)C(2)Cl(2)
and S(1)Pd(1)C(2)Cl(2) planes equal to 9.4◦. In other words, the
PdSSClC square is characterized by folding along Cl(1)Pd(1)C(2)
line with the deviation of S(2) and S(1) atoms from the corre-
sponding Pd(1)S(1)Cl(1)C(2) and Pd(1)S(2)Cl(1)C(2) planes equal
the C–C(2) bonds change only in a minor way. However, the value
of C(1)–C(2)–C(3) varies from 119.11(19)◦ in free 3b ligand to ca.
114◦ in the complexes. The analogous tendency was also observed
for the C(3)P(2)S(2) angle, which decreases to 105.65(8) in 4a and
101.6(2)◦ in 4c as compared with 113.61(8)◦ for 3b. On the other
hand, the binding of metal to the second sulfur atom does not lead
to such a distortion of the SPO angle.
˚
to 0.38 A. Furthermore, the significant puckering of the above
palladacycles leads to the rather high value (33.9◦) of the dihedral
angle between PdSSClC square and the central aromatic cycle.
Despite this fact, the Pd(1)–C(2) bond lengths are equal in 4a
and known symmetrical 5,5-membered complex II8 (2.008(2) and
˚
2.006 A, respectively). It should be mentioned that in hybrid
5,5-membered complexes V the corresponding Pd(1)–C(2) bond
12
˚
lengths were slightly shorter (1.973(1) A).
Analysis of supramolecular organization in crystals of these
complexes revealed that molecules 4a and 4c exhibit the similar
binding pattern despite the difference in the nature of substituents
=
at the phosphorus atom of the O–P S moiety. In both cases
˚
there are bifurcated H–C ◊ ◊ ◊ Cl bond (C ◊ ◊ ◊ Cl 3.573–3.676 A) and
˚
˚
one C–H ◊ ◊ ◊ S (C ◊ ◊ ◊ S 3.638 in 4a A and 3.583 A in 4c) contact
of comparable strength. In addition, the presence of aromatic
fragments in two complexes allows the occurrence of weaker p ◊ ◊ ◊ p
and C–H ◊ ◊ ◊ p contacts.
Fig. 2 General view of compound 4a in representation of atoms via
˚
thermal ellipsoids (p = 50%). The main bond lengths (A) and angles
(◦) are: Pd(1)–Cl(1) 2.4013(6), Pd(1)–S(1) 2.3376(6), Pd(1)–S(2) 2.3393(6),
Pd(1)–C(2) 2.008(2), P(1)–S(1) 1.9782(8), P(2)–S(2) 2.0065(8), C(1)–C(2)
1.399(3), C(2)–C(3) 1.406(3); C(1)–C(2)–C(3) 114.0(2), O(1)–P(1)–S(1)
111.21(7), C(3)–P(2)–S(2) 105.65(8).
Thus, summarizing the results of XRD data, we can mention
that the presence of the six-membered CCOPSPd cycle leads to
an increase of strain that is reflected in distortion of the palladium
configuration.
Catalytic studies
While the catalytic application of symmetrical pincer complexes
is well studied and actually presents the most important sphere of
their usage, there is far less information about the catalytic activity
of their unsymmetrical analogues. Palladacycles in general and
pincer palladium complexes in particular are known to be quite
efficient catalyst precursors in the palladium catalyzed Suzuki
cross-coupling of arylhalides with phenylboronic acids,1g being
one of the most powerful methods for CAr–CAr bond formation.
Because of the commercial availability of the starting materials,
the relatively mild reaction conditions required, the tolerance of a
broad range of functionalities, easy handling and removal of the
nontoxic boron-containing by-products, as well as the possibility
of using water as a solvent (or co-solvent) and solid-support
materials, this cross-coupling reaction has gained prominence
in recent years at an industrial level, mainly in the synthesis
of pharmaceuticals and fine chemicals. Recent advances also
involving non-conventional methodologies that have been applied
to the Suzuki reaction are well documented in the literature.16
In fact, the Suzuki coupling involving bromo- and iodo-arenes
substituted with electron-withdrawing groups is promoted by
almost any palladium salt or complex (e.g. palladium acetate17).
The main challenges in this cross-coupling pertain to the use of
less reactive chloro- and bromo-arenes bearing electron donating
Fig. 3 General view of compound 4c. The disordering◦is omitted for clar-
˚
ity (see Fig. S1) The main bond lengths (A) and angles ( ) are: Pd(1)–Cl(1)
2.3742(10), Pd(1)–S(1) 2.3298(10), Pd(1)–S(2) 2.3428(10), Pd(1)–C(2)
2.055(7), P(1)–S(1) 1.9914(13), P(2)–S(2) 1.9738(14), C(1)–C(2) 1.386(9),
C(2)–C(3) 1.410(9); C(1)–C(2)–C(3) 114.1(6), O(1)–P(1)–S(1) 115.99(15),
C(3)–P(2)–S(2) 101.6(2).
Unlike the 5,5-membered palladium complexes I–V having two
8,9
P S groups or P S and C S groups12 bonded directly with the
=
=
=
=
central phenyl ring, the P S bonds in 4a,c significantly deviate
from the plane of the central core. The latter is reflected in
significant puckering of both 5- and 6-membered metallacycles.
Indeed, in 4a the 5-membered cycle is characterized by an envelope
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Table 2 Influence of catalyst 4b amount on the conversion in the Suzuki
groups and in these cases only a few pincer complexes displayed
catalytic activity. It is noteworthy that the best results for coupling
of chloro-arenes were obtained just with phosphorus containing
pincer complexes or with palladacycles modified by carbenes.
That was related to the extra stability provided by these ligands
towards the low-ligated catalytically active Pd(0) species involved
in catalytic cycle.1g
Therefore, the complexes obtained were examined as the
catalytic precursors in a standard Suzuki reaction. This selection
gives us the possibility for comparison to other above mentioned
SCS-pincer complexes. All experiments were carried out in DMF
solution at 120 ◦C for 5 h similar to the procedure suggested
for testing of pincer palladium complexes formed by 1,3-bis[(tert-
butylthio)methyl]benzene.18 In all cases the normal dependence on
the electronic properties of the substituent X at the aryl bromide
was observed and the complete conversions were reached for acti-
vated substrates using 1 mol% of 4a–d. In the range of complexes
tested, complexes 4a,b bearing dialkylaminothiophosphoryloxy
group demonstrated higher activity, with 4b being the best one.
This fact may be explained by the difference in electronic factors
of the ligands. However, as electronic factors in 4a,b are almost
identical, the higher activity of 4b should be attributed to steric
factors, namely more bulky substituents on the nitrogen atoms in
4b compared with 4a.
It should be noted that preformed palladacycles 4 demonstrated
higher catalytic activity comparing with catalysts formed in situ
from the corresponding free ligand and (PhCN)2PdCl2. Thus, 4b
afforded 93% yield of 4-methoxy-1,1¢-biphenyl (see Table 1) while
catalysts formed in situ in DCM or DMF over 30 min provided
68% and 56% yield of the product respectively. This fact can be
easily explained by slow rate of pincer-type complex formation.
Using the best catalyst (4b) in this series as a representative
example, it was demonstrated that for the most active substrate,
bromoacetophenone, the catalyst loading might be lowered to
0.01% and still result in practically quantitative conversion. High
TON values were observed even at very low catalyst loading of
0.001 mol%. At the same time, for less active 4-bromoanisole,
the amount of a catalyst was crucial for effective cross-coupling
(Table 2), apparently due to catalyst destruction during the process
of intermediates formation at decreased reaction rate.
cross-coupling
X
Cat. mol%
Yield (%)
TON
100
333
998
3303
9300
15 667
38 000
Ac
1
0.3
0.1
0.03
0.01
0.003
0.001
100
100
99.8
99.1
93
47
38
OMe
1
93
65
68
51
7
93
217
680
1700
700
0.3
0.1
0.03
0.01
group. Thus, in the 31P NMR spectra of the mixtures obtained after
the reactions catalyzed by diaminothiophosphoryloxy-substituted
complexes 4a,b two singlets in 1 : 1 ratio were observed: the
first one situated in the region typical for non-coordinated
thiophosphoryloxy group of the free ligand (80 ppm and 73 ppm
for 4a and 4b correspondingly) and the second one at 57–58 ppm
characteristic for coordinated CArP(S) moiety.12 Therefore, in this
particular case we can suggest the ‘opening’ of the coordinated
bond formed by thiohophoryloxy-group resulting in formation of
monopalladacycle species 5a,b.
The 31P NMR spectra for the mixtures obtained after catalysis
using complexes 4c,d having Ph2P(S)O- and Me(BuO)P(S)O-
groups respectively, demonstrated 3 signals in 2 : 1 : 1 ratio. In
both cases one signal (at 42.8 ppm and 41.6 ppm for 4c and 4d,
respectively) is close to that of the coordinated phosphine sulfide
group in the starting complexes. In the case of 4c two other signals
were observed at 26 ppm and 15 ppm while for 4d at 43 ppm and
21 ppm. Based on the NMR data, we may suppose a cleavage of the
6-membered metallacycle with subsequent rupture of P–OAr bond
leading to a monopalladacycle complex 6 formed by thiophospho-
rylated phenol 2 along with non-coordinated species (Scheme 4).
Naturally, one should take into account the possible changing of
the Cl anion for the bromide one in the presence of Bu4NBr and
bromo-arenes being the components of a reaction mixture. How-
ever, such anion exchange should not significantly influence on the
chemical shift of the complexes in the 31P NMR spectra due to the
distant location of both phosphorus atoms from the Pd-centre.
The products 5a,b, and 6 of the decomposition also showed the
catalytic activity and catalyzed the reaction of a new portion of
aryl bromide and phenylboronic acid added to the same reaction
Complexes 4a–d are stable and do not undergo any transforma-
tion during 40 days in DMF solution under ambient conditions.
However, the31P NMR monitoring of the reaction mixtures
obtained after catalysis revealed the decomposition of initial pal-
ladacycles 4 proceeding in different ways depending on the nature
of the substituents at the phosphorus atom of thiophosphoryloxy
Table 1 Palladacycles 4 catalyzed the Suzuki cross-coupling
Yield (%)
Catalyst (1 mol%)
R1, R2
C(O)Me
F
OMe
NMe2
4a
4b
4c
4d
R1 = R2 = NMe2
R1 = R2 = NEt2
R1 = R2 = Ph
100
100
100
100
91
98
96
89
85
93
70
80
54
60
6
R1 = Me, R2 = OBu
20
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these 5,6-membered catalytic precursors are less stable than 5,5-
membered SCS-pincer complexes and though they provided
higher reactivity it might be that it is not the pincer compound
that does the catalysis.
Conclusion
To summarize the results presented, we developed the synthetic
route to novel SCS¢-pincer ligands, namely 1-thiophosphoryloxy-
3-thiophosphorylbenzenes. Direct cyclopalladation of these lig-
ands at the C-2 position of the central benzene ring resulted in non-
symmetrical pincer complexes having fused 5- and 6-membered
palladacycles. These compounds possess a very distorted geometry
of both the palladium ‘square’ and even the ligand. Despite these
5,6-membered palladium SCS-pincer complexes demonstrated
higher catalytic activity in the Suzuki cross-coupling reaction than
5,5-membered SCS-pincer compounds their pincer conformation
is unstable under severe catalytic conditions.
Scheme 4 Possible way of decomposition of the complexes 4a–d over the
catalytic cycle.
mixture (a biaryl derivative obtained at the first catalytic cycle was
considered as an inert component). However, the catalytic activity
of the monopalladacycle species was lower comparing with that
for pincer-type complexes 4. Thus, using the most active 4b as a
catalyst, the reaction of 4-bromoacetophenone was performed at
the first catalytic cycle to afford quantitative yield of the biphenyl
product. To the liquid phase obtained after separation of solids 4-
bromoanisole as a substrate was added along with fresh portions
of phenylboronic acid and K3PO4, and the reaction resulted in
the corresponding biaryl in 69% yield (for comparison, complex
4b gave 93% of the same product, see Table 1). In the second
experiment, the reaction of 4-bromoanisole was carried out at the
first catalytic cycle under the catalytic action of 4b (93% yield of
the product, Table 1) and followed by the second catalytic cycle
where 4-bromoacetophenone was used as a substrate. In this case,
the arylation at the second cycle proceeded in the quantitative
yield confirming rather high catalytic activity of monopalladacycle
formed over the catalytic reaction.
In the absence of tetrabutylammonium bromide—a salt known
to stabilize palladium nanoparticles19—approximately 15% de-
crease of the yield of the final product was observed for the
reaction mixtures catalyzed by 4b. Therefore we cannot exclude the
competitive mechanism including the cleavage of the palladium–
carbon bond and/or formation of palladium nanoparticles as
the active form of the catalysts. To elucidate the detailed the
peculiarities of the catalytic cycle in this particular case further
investigation exceeding the bounds of the above study will be
performed in future and published elsewhere.
In general, the catalytic activity in the Suzuki cross-coupling of
the new 5,6-membered complexes 4a–d is higher comparing with
the activity for other pincer complexes with SCS-coordination re-
ported in the literature. Thus, the above mentioned 5,5-membered
nonsymmetrical complexes V (there being more active catalyst
precursors in this reaction that symmetric SCS-complexes formed
by 1,3-bis[(tert-butylthio)methyl]benzene12) provided up to 83% of
4-methoxy-1,1¢-biphenyl at the typical catalyst loading of 3 mol%
while complexes 4 gave up to 90% of the same product being used
in 1 mol%. Note also that the data concerning the catalytic activity
for palladium SCS complexes I–IV are absent in the literature.
Taking into account that the pincer conformation of com-
pounds 4a–d does not survive the conditions of catalytic reaction,
Experimental
General remarks
If not noted otherwise, all manipulations were carried out
without taking precautions to exclude air and moisture. THF
was distilled from sodium benzophenone ketyl under argon
atmosphere. The starting diphenylchlorophosphine sulfide
Ph2P(S)Cl,20
N,N,N¢,N¢-tetramethyl-phosphorodiamidothioic
chloride (Me2N)2P(S)Cl,21 its tetraethyl analogue (Et2N)2P(S)Cl22
and (BuO)MeP(S)Cl23 were obtained according to the literature
procedures. All other solvents and chemicals were used as
purchased without further purification.
NMR spectra were recorded on Bruker Avance-300 and Bruker
Avance-400 spectrometers and the chemical shifts (d) were in-
ternally referenced by the residual solvent signals relative to
tetramethylsilane (1H and 13C) or externally to H3PO4 (31P). The
13C NMR spectra were registered using the JMODECHO mode;
the signals for the C atoms bearing odd and even numbers of
protons have opposite polarities. The numeration for carbon atoms
of the central benzene ring in the descriptions of the H and 13C
1
spectral data is in agreement with IUPAC nomenclature used
for the ligands. The same principle of numbering was used for
description of solid-state molecular structures characterized by
X-ray crystallography.
IR spectra were recorded in KBr on a Fourier-spectrometer
“Magna-IR750”(Nicolet), resolution 2 cm-1, 128 scans. The
assignment of the absorption bands in IR spectra was made
according to ref. 24. Flash chromatography was carried out using
Merck silica gel 60 (230–400 mesh ASTM). Melting points were
determined with an Electrothermal IA9100 Digital Melting Point
Apparatus and were uncorrected.
Synthesis of ligands
(3-Methoxyphenyl)diphenylphosphine sulfide 1. A solution of
diphenylchlorophosphine (27.6 g, 125 mmol) in THF (30 mL) was
slowly added dropwise to the Grignard reagent, prepared from
magnesium (3.0 g, 125 mmol), 3-bromoanisole (24.3 g, 130 mmol)
and THF (300 mL), in an argon atmosphere at 0–5 ◦C. The
reaction mixture was heated at 50–55 ◦C for 2 h, cooled down and
8662 | Dalton Trans., 2009, 8657–8666
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stirred overnight at ambient temperature. Then, the mixture was
treated successively with a saturated aqueous solution of NH4Cl
and diluted hydrochloric acid (15 mL of conc. HCl/90 mL of
water). The desired product was extracted with benzene (150 mL).
The organic layer was separated, dried over anhydrous Na2SO4 and
filtered. Then, finely powdered sulfur (4.0 g, 125 mmol) was added
to benzene filtrate and the obtained mixture was stirred under
ambient conditions for 3 days. The solvent was removed under
reduced pressure and the resulting residue was twice crystallized
from hexane (2 ¥ 70 mL) to give 1 (26.9 g, 66%) as a white solid.
(N,N,N¢,N¢-Tetramethyl)diamidothiophophosphoric acid O-(3-
diphenylthiophosphoryl)phenyl ester 3a. 3a was obtained by
analogous procedure excluding using of N,N,N¢,N¢-tetramethyl-
phosphorodiamidothioic chloride (0.88 g, 4.7 mmol) instead of
(Et2N)2P(S)Cl. Yield: 1.0 g, 56%, white solid. M.p.: 95–97 ◦C
1
(hexane). 31P{ H} NMR (167.98 MHz, CDCl3): d 43.07 (P(S)Ph2),
1
81.24 (OP(S)(NMe2)2) ppm. H NMR (400.13 MHz, CDCl3): d
2.62 (d, 3JPH = 12.3 Hz, 12H, CH3), 7.22–7.25 (m, 1H, HAr), 7.31–
7.35 (m, 1H, HAr), 7.38–7.55 (m, 8H, HAr), 7.70–7.75 (m, 4H,
1
2
HAr). 13C{ H} NMR (75.47 MHz, CDCl3): d 36.82 (d, JPC
=
◦
M.p.: 110–111 C (hexane). 31P{ H} NMR (121.49 MHz, CDCl3):
d 43.88 ppm. 1H NMR (300.13 MHz, CDCl3): d 3.81 (s, 3H, CH3),
7.04–7.06 (m, 1H, HAr), 7.16–7.22 (m, 1H, HAr), 7.32–7.39 (m, 2H,
HAr), 7.43–7.55 (m, 6H, HAr), 7.69–7.77 (m, 4H, HAr) (cf.25). Anal.
Calcd. for C19H17OPS: C, 70.35; H, 5.28; S, 9.89%. Found: C,
70.37; H, 5.29; S, 9.67%.
3.5 Hz, CH3), 124.62, 124.68, 124.77 (overlapped C2+C5), 128.00
1
(d, 3JPC = 10.4 Hz, C6), 128.45 (d, 3JPC = 12.5 Hz, m-C in PC6H5),
2
129.66 (d, JPC = 14.5 Hz, C4), 131.58 (s, p-C in PC6H5), 132.07
(d,2JPC = 11.1 Hz, O-C in PC6H5), 132.35 (d, 1JPC = 85.1 Hz, ipso-
1
2
C in PC6H5), 134.24 (d, JPC = 84.4 Hz, C3), 150.60 (dd, JPC
=
5.3 Hz, 3JPC = 15.8 Hz, C1). Anal. Calcd. for C22H26ON2P2S2: C,
57.38; H, 5.69; N, 6.08%. Found: C, 57.42; H, 5.88; N, 5.61%.
3-(Diphenylthiophosphoryl)phenol 2. A mixture of compound
1 (6.3 g, 20 mmol) and pyridine hydrochloride (6.8 g, 60 mmol)
Diphenylthiophosphinic acid O-(3-diphenylthiophosphoryl)-
phenyl ester 3c. 3-Diphenylthiophosphorylphenol 2 (2.00 g,
6.5 mmol) was added portion-wise to a stirred mixture of 10%
aq. NaOH (0.26 g, 6.5 mmol), TEBA-Cl (0.07 g, 0.325 mmol,
5 mol%) and benzene (6 mL). Then a solution of Ph2P(S)Cl
(1.63 g, 6.65 mmol) in benzene (10 mL) was slowly added
dropwise to the obtained suspension. The reaction mixture was
stirred for 30 min at room temperature and 2 h at 55–60 ◦C.
After that, it was poured into separating funnel and diluted with
water (50 mL). The mixture was extracted with benzene (2 ¥
50 mL). The combined organic layers were dried over anhydrous
Na2SO4, filtered and evaporated to dryness. The resulting residue
was crystallized from ether (40 mL) and recrystallized from
ethyl acetate (20 mL) to give 3c (3.00 g, 89%) as a white solid.
◦
was heated under stirring at 180–190 C (oil bath) for 5 h. After
cooling to room temperature, the reaction mixture was diluted
with ethyl acetate, washed with water, dried over anhydrous
Na2SO4 and evaporated under reduced pressure. The obtained
residue was purified by silica gel column chromatography (eluent:
ethyl acetate–hexane (1 : 3)) followed by recrystallization from
ethyl acetate–hexane mixture (1 : 1, 25 mL) to yield 2 (4.3 g,
69%) as a white solid. M.p.: 132–134 ◦C (ethyl acetate–hexane
1
1
(1 : 1)).31P{ H} NMR (121.49 MHz, CDCl3): d 43.59 ppm. H
NMR (300.13 MHz, CDCl3): d 7.02 (d, 3JHH = 7.98 Hz, 1H, HAr),
7.18 (dd, 3JHH = 7.93 Hz, 3JPH = 11.91 Hz, 1H, HAr),7.38 (t, 3JHH
=
7.93 Hz, 1H, HAr), 7.46–7.60 (m, 7H, HAr+o-H, p-H in C6H5P),
3
3
7.77 (dd, JHH = 7.32 Hz, JPH = 12.78 Hz, 4H, m-H in C6H5P),
7.69–7.77 (m, 4H, HAr) (cf. m.p. 132–133 ◦C14).
M.p.: 128–130 ◦C. 31P{ H} NMR (121.49 MHz, CDCl3): d
1
1
42.83 (P(S)Ph2), 83.59 (OP(S)Ph2) ppm. H NMR (300.13 MHz,
(N,N,N¢,N¢-Tetraethyl)diamidothiophophosphoric acid O-(3-
diphenylthiophosphoryl)phenyl ester 3b. A mixture of phenol
2 (1.45 g, 4.7 mmol) and (Et2N)2P(S)Cl (1.15 g, 4.7 mmol)
in triethylamine (2 mL) was heated at 115–120 ◦C in an oil
bath for 3 h. After cooling to room temperature, the reaction
mixture was dissolved in dichloromethane (25 mL) and washed
with diluted hydrochloric acid (3 mL conc. HCl/50 mL of
water). The organic phase was dried over anhydrous Na2SO4,
filtered and concentrated in vacuo. The resulting residue was
purified by silica gel column chromatography (eluent: hexane–
acetone (5 : 1)) followed by recrystallization from hexane to give
3b as white crystals (1.40 g, 58%). M.p.: 81–82 ◦C (hexane).
1
CDCl3): d 7.29–7.72 (m, 20H), 7.91–7.99 (m, 4H). 13C{ H} NMR
4
3
(100.61 MHz, CDCl3): d 124.88 (dd, JPC = 2.6 Hz, JPC
=
2
3
4.4 Hz, C6), 125.37 (dd, JPC = 10.9 Hz, JPC = 5.2 Hz, C2),
128.34, 128.47, 128.48, 128.55 (overlapped signals of C5, m-C in
2
OP(S)C6H5 and m-C in P(S)C6H5), 129.63 (d, JPC = 14.3 Hz,
2
C4), 131.20 (d, JPC = 11.7 Hz, o-C in P(S)C6H5), 131.44 (d,
4JPC = 2.9 Hz, p-C in P(S)C6H5), 132.05 (d, JPC = 10.6 Hz, o-C
2
1
in OP(S)C6H5), 132.10 (s, p-C in OP(S)C6H5), 132.22 (d, JPC
=
85.8 Hz, ipso-C in P(S)C6H5), 133.46 (d, 1JPC = 111.1 Hz, ipso-C
in OP(S)C6H5), 134.43 (d, 1JPC = 84.0 Hz, C3), 150.19 (dd, 2JPC
=
8.4 Hz, JPC = 16.1 Hz, C1). IR (KBr, n/cm-1: 508, 641,645
3
=
(P S), 689, 719, 733, 807, 927,1103, 1207(CPh–O), 1408, 1434,
1
31P{ H} NMR (161.98 MHz, CDCl3): d 43.16 (P(S)Ph2), 76.61
1438 (P–CPh), 1467, 1479, 1570, 1586, 3048. Anal. Calcd. for
C30H24OP2S2: C, 68.43; H, 4.59; S, 12.18%. Found: C, 68.21; H,
4.62; S, 12.29%.
1
(OP(S)(NEt2)2) ppm. H NMR (400.13 MHz, CDCl3): d 1.04 (t,
3JHH = 7.1 Hz, 12H, CH3), 2.99–3.20 (m, 8H, CH2), 7.25–7.27
(m, 1H, HAr), 7.34–7.57 (m, 9H, HAr), 7.70–7.75 (m, 4H, HAr).
1
13C{ H} NMR (100.61 MHz, CDCl3): d 13.57 (d, 4JPC = 2.9 Hz,
Methylthiophosphonic acid O-butyl-O-(3-diphenylthiophos-
phoryl)phenyl ester 3d. A solution of Me(BuO)P(S)Cl (0.75 g,
4.0 mmol) in benzene (5 mL) was slowly added dropwise to a
stirred solution of 3-diphenylthiophosphorylphenol 2 (1.2 g,
3.9 mmol) and triethylamine (0.45 g, 4.5 mmol) in C6H6 (35 mL).
The reaction mixture was refluxed for 12 h. After cooling to
room temperature the precipitate of triethylamine chlorohydrate
was filtered off. The filtrate was washed with H2O (50 mL), the
separated water phase was additionally extracted with benzene
(30 mL). The combined organic layer was dried over anhydrous
3
3
CH3), 39.89 (d, JPC = 5.1 Hz, CH2), 124.64 (dd, JPC = 5.5 Hz,
4JPC = 2.6 Hz, C5), 124.86 (dd, 2JPC = 5.1 Hz, 3JPC = 11.8 Hz, C2),
127.72 (d, 2JPC = 9.5 Hz, C4), 128.31 (d, 3JPC = 12.5 Hz, m-C in
PC6H5), 129.41 (d, 3JPC = 14.7 Hz, C6), 131. 34 (d, 4JPC = 2.9 Hz,
p-C in PC6H5), 132.08 (d, 2JPC = 11.0 Hz, O-C in PC6H5), 132.40
1
1
(d, JPC = 85.8 Hz, ipso-C in PC6H5), 133.88 (d, JPC = 85.1 Hz,
C3), 150.81 (dd, 2JPC = 5.9 Hz, 3JPC = 16.1 Hz, C1). Anal. Calcd.
for C26H34NO2P2S2: C, 60.44; H, 6.63; N, 5.42%. Found: C, 60.51;
H, 6.59; N, 5.44%.
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Na2SO4, filtered and evaporated to dryness. The resulting
residue was purified by silica gel column chromatography (eluent
hexane–ethyl acetate (8 : 1)) to give 3d as viscous white oil. Yield:
2JPC = 5.1 Hz, CH2), 120.91 (dd, C5, 3JPC = 8.1 Hz, 4JPC = 2.9 Hz),
2
3
124.90 (d, C4, JPC = 15.4 Hz), 126.66 (d, C6, JPC = 15.4 Hz),
3
1
128.62 (d, JPC = 12.5 Hz, m-C in P(S)C6H5), 129.56 (d, JPC
=
1
2
1.65 g (93%). 31P{ H} (161.98 MHz, CDCl3): d 42.86 (P(S)Ph2),
80.0 Hz, ipso-C in P(S)C6H5), 132.20 (d, JPC = 11.0 Hz, O-C in
P(S)C6H5), 132.43 (d, 4JPC = 2.2 Hz, p-C in P(S)C6H5), 144.90 (dd,
94.38 (OP(S)(OBu)Me) ppm. 1H NMR (400.13 MHz, CDCl3): d
3
3
1
0.88 (t, JHH = 7.4 Hz, 3H, CH3), 1.26–1.36 (m, 2H, CH2CH3),
2JPC = 5.8 Hz, JPC = 22.5 Hz, C2), 147.98 (d, JPC = 105.6 Hz,
C3), 155.06 (dd, 2JPC = 8.1 Hz, 3JPC = 21.3 Hz, C1). Anal Calcd
for C26H33ClN2OP2PdS2: C, 47.49; H, 5.06; N, 4.26%. Found: C,
47.54; H, 5.06; N, 4.22%.
2
1.51–1.60 (m, 2H, OCH2CH2), 1.93 (d, JPH = 15.5 Hz, 3H,
PCH3), 3.82–3.90 (m, 1H, OCH2), 4.05–4.13 (m, 1H, OCH2),
7.27–7.30 (m, 1H, HAr), 7.39–7.58 (m, 9H, HAr), 7.69–7.74 (m,
4H, HAr). Anal Calcd. for C23H26O2P2S2: C, 59.98; H, 5.70; S,
13.92%. Found: C, 60.01; H, 5.77; S, 13.98%.
{2-[(Diphenylthiophosphoryl)oxy]-6-(diphenylthiophosphoryl)-
phenyl}-palladium chloride 4c. A dichloromethane solution
(2 mL) of PdCl2(PhCN)2 (84.3 mg, 0.22 mmol) was added
dropwise to a solution of 3c (115.8 mg, 0.22 mmol) in 3.5 mL
of CH2Cl2. In one hour the reaction mixture was slowly poured
into methanol (7.5 mL) and left under ambient conditions for
4 days, then filtered and evaporated to dryness. The ether (10 mL)
was added to the oily residue to give yellow solid, which was
filtered off and recrystallized from CH2Cl2–Et2O mixture (1 : 2,
15 mL◦) to give 4c (95.3 mg, 65%) as a yellow crystalline solid. M.p.:
Preparation of Pd(L)Cl complexes
Complexes 4a,b. Method A (general procedure). A benzene
solution (7 mL) of (PhCN)2PdCl2 (54.1 mg, 0.141 mmol) was
slowly added dropwise to a solution of 3a or 3b (0.141 mmol) in
8 mL of C6H6. A reaction mixture was refluxed for 2 h under
stirring, filtered and evaporated to dryness. The resulting oily
residue was washed with ether (10 mL) to give solid which was
filtered off and recrystallized from CH2Cl2–Et2O mixture (1 : 3,
12 mL) to give the corresponding complexes.
1
>250 C (decomp). 31P{ H} NMR (161.98 MHz, DMSO-d6): d
1
47.24 (P(S)Ph2), 74.92 (OP(S)Ph2) ppm. H NMR (300.13 MHz,
3
3
CDCl3/DMSO-d6): d 6.73 (dd, JPH = 10.7 Hz, JHH = 7.0 Hz,
Method B (general procedure). A dichloromethane solution
(4 mL) of (PhCN)2PdCl2 (98.0 mg, 0.255 mmol) was slowly added
dropwise to a solution of 3a or 3b (0.255 mmol) in 3 mL of CH2Cl2.
The resulting mixture was left under ambient conditions for 5 days
and evaporated to a volume of ~1 mL. Addition of ether (15 mL) to
the reaction solution afforded precipitation of the corresponding
complexes which were filtered off, washed with 15 mL of Et2O and
dried in vacuum.
1H, H–C4), 7.12 (m, 1H, H–C5), 7.20 (d, 3JHH = 7.8 Hz, 1H, H–
1
C6), 7.57–7.73 (m, 16H, HAr), 7.95–8.02 (M, 4H, HAr). 13C{ H}
NMR (100.61 MHz, DMSO-d6) (due to the low solubility of
the compound the signals of carbon atoms of central benzene
ring were not observed): d 129.60, 129.75, 129.90 (overlapped
signals of m-C in OP(S)C6H5 and m-C in P(S)C6H5), 131.94 (d,
2
2JPC = 12.1 Hz, o-C in P(S)C6H5), 132.68 (d, JPC = 11.1 Hz, o-
C in OP(S)C6H5), 133.80 (s, p-C in P(S)C6H5), 134.34 (s, p-C in
OP(S)C6H5). Anal. Calcd for C30H23ClOP2PdS2: C, 53.98; H, 3.47;
S, 9.61%. Found: C, 53.90; H, 3.64; S, 9.51%.
[2-{[Bis(dimethylamino)thiophosphoryl]oxy}-6-(diphenylthio-
phosphoryl)phenyl]-palladium chloride 4a. Yield: 60.2 mg
(method A, 71%), 104.6 mg (method B, 68%), yellow crystalline
solid. M.p.: >175 ◦C (decomp.). 31P{ H} NMR (121.49 MHz,
1
[2-{[Butoxy(methyl)thiophosphoryl]oxy}-6-(diphenylthiophos-
phoryl)phenyl]-palladium chloride 4d. A dichloromethane solu-
tion (4 mL) of PdCl2(PhCN)2 (109.4 mg, 0.29 mmol) was slowly
added dropwise to a solution of 3d (131.4 mg, 0.29 mmol) in
3 mL of CH2Cl2. The reaction mixture was left under ambient
conditions for 5 days and poured into hexane (7 mL). In
an hour, the resulting mixture was filtered and evaporated to
dryness. The obtained residue was washed with Et2O (10 mL) and
dissolved in CH2Cl2 (7 mL). Slow evaporation of solvent from
this solution under ambient conditions resulted in 4d as a yellow
crystalline solid. Yield: 33.2 mg (19%). M.p.: >168 ◦C (decomp.)
CDCl3): d 44.58 (P(S)PPh2), 68.15 (OP(S)(NMe2)2) ppm. 1H NMR
(300.13 MHz, CDCl3): d 2.86 (d, 2JPH = 12.5 Hz, 12H, CH3), 6.69
3
3
3
(dd, JHH = 7.6 Hz, JPH = 10.4 Hz, 1H, H-C4), 6.79 (d, JHH
=
8.0 Hz, 1H, H-C6), 6.96 (m, 1H, H-C5), 7.49–7.62 (m, 6H, HAr),
7.77–7.84 (m, 4H, HAr). 13C{ H} NMR (100.61 MHz, CDCl3): d
1
37.07 (d, 2JCP = 4.3 Hz, CH3), 120.75 (dd, 4JPC = 3.2 Hz, 3JPC
=
=
2
3
8.6 Hz, C5), 125.12 (d, JPC = 15.5 Hz, C4), 126.85 (d, JPC
15.5 Hz, C6), 128.82 (d, 3JPC = 12.6 Hz, m-C in P(S)C6H5), 129.70
(d, 1JPC = 80.2 Hz, ipso-C in P(S)C6H5), 132.36 (d, 2JPC = 11.2 Hz,
4
O-C in P(S)C6H5), 132.64 (d, JPC = 2.9 Hz, p-C in P(S)C6H5),
1
31P{ H} NMR (161.98 MHz, CDCl3): d 45.75 (P(S)Ph2), 84.16
144.38 (dd, 4JPC = 5.0 Hz, 3JPC = 23.4 Hz, C2), 147.89 (d, 1JCP
=
(OP(S)(OBu)Me) ppm. 1H NMR (400.13 MHz, CDCl3): d 0.91 (t,
3JHH = 7.4 Hz, 3H, CH3), 1.36–1.46 (m, 2H, CH2CH3), 1.67–1.76
2
3
105.4 Hz, C3), 155.77 (dd, JPC = 7.2 Hz, JPC = 22.0 Hz, C1).
Anal Calcd. for C22H25ClN2OP2PdS2: C, 43.94; H, 4.19; N, 4.66%.
Found: C, 43.89; H, 4.19; N, 4.51%.
2
(m, 2H, OCH2CH2), 2.24 (d, JPH = 15.3 Hz, 3H, PCH3), 4.46–
3
4.60 (m, 2H, OCH2), 6.71–6.76 (m, 1H, H–C4), 6.84 (d, JHH
=
[2-{[Bis(diethylamino)thiophosphoryl]oxy}-6-(diphenylthiophos-
phoryl)phenyl]-palladium chloride 4b. Yield: 60.0 mg (method A,
65%),◦147.8 mg (method B, 88%), yellow crystalline solid. M.p.:
8.0 Hz, 1H, H–C6) 6.95–7.04 (m, 1H, H–C5), 7.59–7.65 (m, 2H,
HAr), 7.49–7.56 (m, 4H, HAr), 7.73–7.86 (m, 4H, HAr). Anal. Calcd
for C30H23ClOP2PdS2: C, 45.93; H, 4.19; S, 10.66%. Found: C,
45.78; H, 4.03; S, 10.37%.
1
>185 C (decomp.). 31P{ H} NMR (161.98 MHz, CDCl3): d 44.33
1
(P(S)Ph2), 64.88 (OP(S)(NEt2)2) ppm. H NMR (400.13 MHz,
3
CDCl3): d 1.20 (t, JPH = 7.1 Hz, 12H, CH3), 3.24–3.41 (m, 8H,
Catalytic experiments
CH2), 6.72 (dd, 3JPH = 11.2 Hz, 3JHH = 7.2 Hz, 1H, H–C4), 6.79
3
(d, JHH = 8.0 Hz, 1H, H–C6), 7.00 (m, 1H, H–C5), 7.51–7.56
In a typical experiment, a solution of 1 mmol of aryl bromide,
1.5 mmol of PhB(OH)2, 2 mmol of K3PO4, 0.2 mmol of Bu4NBr,
and the mentioned amount of the corresponding palladium
(m, 4H, HAr), 7.61–7.64 (m, 2H, HAr), 7.81–7.86 (m, 4H, HAr).
1
13C{ H} NMR (100.61 MHz, CDCl3): d 13.52 (s, CH3), 40.15 (d,
8664 | Dalton Trans., 2009, 8657–8666
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◦
complex in 5 mL of DMF was heated at 120 C over 5 h. After
Acknowledgements
cooling the reaction mixture was immediately filtered, treated with
water, extracted with benzene and analyzed by GC and 31P NMR.
The authors are grateful to Russian Basic Research Foundation
(grant 08-03-00508) for the financial support.
Crystal structure determination and data collection
References
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were carried out with a SMART APEX2 CCD diffractometer
for 4a and 4c and with a SMART 1000 CCD diffractometer
for 3b, using graphite monochromated Mo-Ka radiation (l =
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0.71073 A, w-scans) at 100 K (4a and 4c) and 120 K (3b). The
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structures were solved by direct methods and refined by the full-
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calculations were performed using the SHELXTL software.26
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Table 3 Crystal data and structure refinement parameters for 3b, 4a and
4c
3b
4a
4c
CCDC number 730242
730243
730244
Empirical
formula
Formula weight 516.61
C26H34N2OP2S2 C22H25ClN2OP2- C30H23ClOP2PdS2
PdS2
601.35
100(1)
667.39
100(1)
Monoclinic
P21/n
4
T/K
120(1)
Crystal system
Space group
Z
Triclinic
Triclinic
¯
¯
P1
P1
2
2
˚
a/A
9.1250(16)
11.081(3)
14.998(3)
83.718(16)
78.009(16)
66.27(2)
1357.4(6)
1.264
8.6417(4)
10.3955(5)
13.6809(7)
95.103(5)
98.150(5)
95.827(5)
1203.64(10)
1.659
12.2080(13)
8.7616(8)
26.551(3)
90.00
102.341(5)
90.00
2774.3(5)
1.598
10.55
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
V/A
Dc (g cm-1)
Linear
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3.35
12.07
absorption,
m/cm-1
F(000)
548
58
15045
608
54
8467
1344
56
13205
2qmax (◦)
Reflections
measured
Independent
reflections (Rint)
Observed
7182 (0.0507)
4787
5205 (0.0195)
4534
6636 (0.0456)
4859
reflections [with
I > 2s(I)]
Parameters
R1 for observed 0.0507
refl.
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15.
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302
284
0.0265
372
0.0426
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wR2 for
independent refl.
GOF
0.1224
0.0626
0.0936
1.004
0.604/-0.305
1.004
0.553/-0.504
1.004
0.980/-1.034
Drmax, Drmin/e
-3
˚
A
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8657–8666 | 8665
©

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©