Stepwise cyclopalladation of 2-phenacylthiopyridine to give C,C,N-pincer complexes

Article abstract of DOI:10.1039/c4dt02085e

Orthopalladation of the phenyl ring in the cyclopalladated complex [Pd{C,N-pyl-SCHC(O)Ph}(μ-X)]₂ (pyl = 2-pyridyl, X = Cl; 1·Cl) occurs upon reacting it with AgOAc (1+:+2) in MeCN to give the pincer complex [Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}(NCMe)] (2). The nature of the base and X plays a key role because palladation neither occurs with other bases nor when AgOAc is the base and X is Br, in which case 1·OAc is obtained. In addition, complex 2 is not obtained upon refluxing 1·OAc in MeCN. Complex 2 affords complexes [Pd{C,C,N,S-pyl-SCHC(O)C₆H₄-2}]_n, [Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}L] (L = PPh₃, ^tBuNC, XyNC) or Me₄N[Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}Cl] upon acetonitrile loss, or its replacement by neutral or anionic ligands, respectively. Some such complexes act as metallaligands towards AgClO₄ or [PdCl₂(NCPh)₂] giving rise to heterodinuclear [{Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}(PPh₃)}{Ag(PPh₃)}]ClO₄ or homodinuclear [{Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}(Cl)}{Pd(μ-Cl)}]₂, [{Pd{C,C,N-pyl-SCHC(O)C₆H₄-2}(Cl)}{Pd(Cl)(PPh₃}] complexes. Some derivatives of complexes 1 were also obtained. This journal is

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Stepwise cyclopalladation of
2-phenacylthiopyridine to give C,C,N-pincer
complexes†
Cite this: Dalton Trans., 2014, 43,
15170
María-Teresa Chicote,*a Concepción Rubio,a Delia Bautistab and José Vicentea
Orthopalladation of the phenyl ring in the cyclopalladated complex [Pd{C,N-pyl-SCHC(O)Ph}(μ-X)]2
(pyl = 2-pyridyl, X = Cl; 1·Cl) occurs upon reacting it with AgOAc (1 : 2) in MeCN to give the pincer
complex [Pd{C,C,N-pyl-SCHC(O)C6H4-2}(NCMe)] (2). The nature of the base and X plays a key role
because palladation neither occurs with other bases nor when AgOAc is the base and X is Br, in which
case 1·OAc is obtained. In addition, complex 2 is not obtained upon refluxing 1·OAc in MeCN. Complex 2
t
affords complexes [Pd{C,C,N,S-pyl-SCHC(O)C6H4-2}]n, [Pd{C,C,N-pyl-SCHC(O)C6H4-2}L] (L = PPh3, BuNC,
XyNC) or Me4N[Pd{C,C,N-pyl-SCHC(O)C6H4-2}Cl] upon acetonitrile loss, or its replacement by neutral
or anionic ligands, respectively. Some such complexes act as metallaligands towards AgClO4 or
[PdCl2(NCPh)2] giving rise to heterodinuclear [{Pd{C,C,N-pyl-SCHC(O)C6H4-2}(PPh3)}{Ag(PPh3)}]ClO4 or
homodinuclear [{Pd{C,C,N-pyl-SCHC(O)C6H4-2}(Cl)}{Pd(μ-Cl)}]2, [{Pd{C,C,N-pyl-SCHC(O)C6H4-2}(Cl)}-
{Pd(Cl)(PPh3}] complexes. Some derivatives of complexes 1 were also obtained.
Received 15th July 2014,
Accepted 12th August 2014
DOI: 10.1039/c4dt02085e
www.rsc.org/dalton
1. Introduction
Cyclopalladated complexes are increasingly important in
organic synthesis.1–3 Chiral cyclopalladated derivatives are
being used for both optical resolution purposes4 and enantio-
selective catalysis3,5 Many palladacycles have found use in the
preparation of metallomesogens6 and some show antitumor
activity.7 Cyclopalladation reactions involving a C(sp2)–H acti-
vation are by far the best known while those involving a
C(sp3)–H bond are in the minority,2,8–12 those concerning a
prochiral C(sp3) atom being particularly rare.11,12 We have pre-
viously reported the cyclopalladation13 and cycloauration14 of
2-R-carbonylmethylenethiopyridines pyl-SCH2C(O)R (pyl
=
2-pyridyl, R = Ph, Me, OMe). By reacting these ligands with
[PdCl2(NCPh)2], or the coordination complexes [Pd{pyl-SCH2-
C(O)R}2Cl2] (A, Scheme 1) with Na2CO3 or NaH, chiral com-
plexes with one (B) or two (C) five-membered C,N-metallacycles
were prepared (Scheme 1). Transmetallation reactions between
C and [PdCl2(NCPh)2] or deprotonation of B with Na2CO3
Scheme 1
allowed the syntheses of dinuclear complexes D. Reactions of
complex B or D (R = Ph) with excess Na2CO3, which we carried
out in an attempt to prepare pincer complexes resulting from
the additional cyclometalation of the phenyl group, were
unsuccessful. This was not surprising because, although
double C–H activation processes leading to various types of
doubly cyclopalladated compounds are well known,15 cyclo-
metalation reactions involving two C–H bond activations per
aGrupo de Química Organometálica, Departamento de Química Inorgánica, Facultad
de Química, Universidad de Murcia, Apartado 4021, 30071 Murcia, Spain.
E-mail: mch@um.es, jvs1@um.es
bSAI, Universidad de Murcia, Apartado 4021, 30071 Murcia, Spain.
E-mail: dbc@um.es
†Electronic supplementary information (ESI) available: Crystallographic data for
compounds 1·Br·CHCl3, 1·AcO and 7c. CCDC 1001640–1001642. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/
c4dt02085e
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metal atom are very rare, not only for palladium8,9,13 but also ladacycles that can adopt mutual cisoid- or transoid-
for any metal.16 However, in this paper we report that using disposition.
AgOAc as a base it is possible to prepare, from complex D
Complex 1·Cl was recovered unchanged after reacting it
(R = Ph), pincer complexes bearing a dianionic C(sp2),C(sp3),N- with KtBuO (1 : 1, in CH2Cl2) at room temperature for 3 h or,
donor ligand. Carbometalated pincer complexes were defined by additionally refluxing the reaction mixture for 2 h. However,
as “organometallic compounds bearing tridentate monocarb- the same complex reacted with AgOAc to give, after 4 h reflux-
anionic ligands that coordinate metals in a η3-mer fashion”.17 ing in MeCN, the C,C,N-pincer complex [Pd{C,C,N-pyl-SCHC-
Most complexes included in this general definition display one (O)C6H4-2}(NCMe)] (2). Although a small amount of colloidal
Csp2–M bond. However, only a few such complexes with a palladium also formed, complex 2 could be isolated in 77%
Pd–Csp3 bond are known, some of which have been found to yield. The different behavior of AgOAc with respect to Na2CO3
be more active catalysts than their Pd–Csp2 counterparts.8,18 or KtBuO suggests that the driving force for this reaction is the
On the other hand, as far as we are aware, very few palladium formation of an intermediate (I, in Scheme 2) in which the
complexes with dianionic pincer ligands have been reported acetato ligand interacts with the ortho hydrogen of the aryl
so far,8,19 only one of them bearing a C,C,N-pincer ligand.20 group, as has been suggested previously.27,28 This C–H acti-
We have recently reported the synthesis of the first family of vation is probably preferred to that of the CH group co-
stable Pd(IV) pincer complexes21,22 and the first generation of a ordinated to Pd, in spite of its vicinity to the carbonyl group,
coordinating side arm on a chelate complex giving rise to a because of the +I effect of the metallic moiety. This is con-
pincer complex.23 A few examples have been reported of firmed by the shift of the ν(CO) frequency towards the low
chelate complexes converting into palladium pincer derivatives energy region in all C,N-cyclopalladated complexes compared
as a consequence of the chelating ligand bearing a pendant aryl to that in N-coordinated [Pd]-pyl-SCH2C(O)Ph complexes.13 In
group that palladates intramolecularly by heating or by adding fact, we have failed other attempts to deprotonate the methine
a base (NaOAc).24 However, in these cases the ligand to be palla- group (see below). In addition, an intermediate similar to I
dated is a N^N neutral ligand while in the present work we involving the methine proton would probably be less favored
report the palladation of the side arm of a cyclopalladated from a steric point of view.
ligand, which is probably responsible for the difficulty in the
palladation process, which does not occur upon heating. A rela-
tively large number of cyclopalladated compounds containing a
dianionic C,N,O-pincer ligand has been reported.25
2. Results and discussion
2.1 Synthesis
Scheme 1 shows the results, previously reported by us,13 on
the reactivity of [PdCl2(NCPh)2] toward various 2-R-carbonyl-
methylenethiopyridines pyl-SCH2C(O)R (pyl = 2-pyridyl, R =
Ph, Me, OMe) including dehydrohalogenation reactions, spon-
taneous or induced by the use of a base such as Na2CO3 or
NaH, to give palladacyclic complexes of the type B or C,
respectively. However, further deprotonation of the methine
proton or of the R group did not occur even when an excess of
these bases was used.
With the purpose of further studying dehydrohalogenation
reactions on complexes [Pd{C,N-pyl-SCHC(O)R}(μ-Cl)]2 (D in
Scheme 1) to give C,C,N-pincer complexes, we attempted an
alternative synthesis of 1·Cl (D, R = Ph) because the previous
methods were rather cumbersome ([PdCl2(NCPh)2] → B → D or
[PdCl2(NCPh)2] → A → C → D).13 Thus, a double deprotonation
of [Hpyl-SCH2C(O)Ph]Cl (pyl- = 2-pyridyl),26 with Pd(OAc)2
(1 : 1, refluxing in acetone for 3 h), gave 92% yield of 1·Cl in a
single step. Similarly, its homologous [Pd{C,N-pyl-SCHC(O)Ph}-
(μ-Br)]2 (1·Br) was obtained in 83% yield from [pylH-SCH2C(O)-
Ph]Br26 and Pd(OAc)2 (1 : 1, refluxing in acetone for 3 h).
Complexes 1·Cl and 1·Br are obtained as a mixture of isomers
(see the Experimental section) which can be explained by the
fact that they bear two chiral CHPd carbon atoms and two pal-
Scheme 2
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Using 1·Br instead of 1·Cl in its reaction with AgOAc, under [PPN]Br, respectively (Scheme 3). Complex 4c·Br was obtained
the same reaction conditions, gave instead a mixture contain- as a mixture of the SP-4-3- and SP-4-4-isomers (see NMR dis-
ing, among other species, 1·Br and the bridging acetato cussion and the Experimental section).
complex [Pd{C,N-pyl-SCHC(O)Ph}(μ-O,O′-OAc)]2 (1·OAc) that we
We attempted the synthesis of [Pd{C,N-pyl-SCHC(O)C6H4-2}-
could not separate. When a dichloromethane solution of that (OAc){S(O)Me2}] (4c·OAc, analogous to 4c·Br) by reacting 1·OAc
mixture was layered with n-hexane, in an attempt to obtain with dmso under various reaction conditions (1 : 1 or 1 : 2, at
1·OAc, crystals of 1·Br grew instead, which were suitable for room temperature or refluxing in chloroform for 3 h or, as for
determining its crystal structure. However, pure 1·OAc was 4c·Br, 1 : 9 in acetone at room temperature for 2 h or even after
obtained after refluxing in acetone for 1.5 h an equimolar 3 h refluxing) in the hope that, if both of the possible isomers
mixture of pyl{SCH2C(O)Ph}-2 and Pd(OAc)2 in the presence of formed, the SP-4-4-one would be prone to form upon heating
AcOH (1 equiv.). The same result was obtained using an intermediate similar to I, replacing MeCN by dmso, giving
0.5 equiv. of AcOH and acetonitrile as the solvent. In the finally the pincer complex [Pd{C,C,N-pyl-SCHC(O)C6H4-2}(S(O)-
absence of an acid, some decomposition to Pd(0) was observed Me2)] homologous of 2. Unfortunately, from any of these reac-
causing a yield decrease. 1·OAc was also obtained as a mixture tions, neither the mononuclear dmso-complex 4c·OAc nor the
of isomers (see the Experimental section).
pincer complex could be detected by NMR. In fact, 1·OAc was
Although we cannot fully understand the different behavior recovered almost quantitatively in all cases. Also, 1·OAc was
of 1·Br and 1·Cl toward AgOAc it seems that the reaction start- isolated in 70% yield from the reaction of 1·Cl with AgOAc and
ing from 1·Cl favors the formation of the intermediate I while dmso (1 : 1 : 2, refluxing in acetone for 2 h). The acetyl-
that from 1·Br allows its irreversible conversion into 1·OAc acetonate complex 5 was recovered unchanged after refluxing
(Scheme 2). In fact, after stirring 1·OAc (0.1 mmol) with MeCN it in MeCN for 4 h in an attempt to prepare 2 upon acetyl-
(5 mL) at room or refluxing temperature for 5 or 3 h, respect- acetone loss. Similarly, refluxing 6 in acetonitrile for 5 h did
ively, the formation of 2 could not be evidenced by 1H NMR not give 2 or the anionic pincer PPN[Pd{C,C,N-pyl-SCHC(O)-
and 1·OAc was recovered unchanged.
C6H4-2}Br] and 6 was also recovered unchanged.
Complex 2 is soluble in MeCN and dmso and partially
From complex 2, neutral [Pd{C,C,N-pyl-SCHC(O)C6H4-2}L]
soluble in acetone. However it decomposed upon standing in (L = PPh3 (7a), tBuNC (7b), XyNC (7c)) or anionic Me4N[Pd{C,C,
CH2Cl2 or CHCl3 solutions to give the insoluble complex N-pyl-SCHC(O)C6H4-2}Cl] (8) complexes could be obtained
[Pd{C,C,S,N-pyl-SCHC(O)C6H4-2}]n (3) (Scheme 2) along with a upon replacement of the labile MeCN ligand by the appropriate
solution containing a mixture of products, likely to be oligo- ligands (Scheme 4). Complex 7a could be prepared using a
mers that we could not identify by 1H-NMR spectroscopy. 1 : 1 molar ratio of the reagents but it was best obtained by
Complex 3 presumably forms because the sulfur atom is slow addition of solid complex 2 to a solution of PPh3 in
capable of replacing the labile MeCN ligand in 2 (see below).
CH2Cl2 in order to minimize the formation of the polymer 3.
Complexes 1–3 have been used as starting materials for the The yield of 7b improved when an excess of the ligand (1 : 2)
synthesis of related complexes. Thus, neutral complexes [Pd- was used; otherwise some unidentified side-products also
{C,N-pyl-SCHC(O)Ph}X(L)] (L = XyNC (Xy = C6H3Me2-2,6), X = formed which we could not separate. In spite of the excess
Cl, (4a·Cl), Br (4a·Br) AcO (4a·OAc), L = PTol3 (Tol = C6H4Me-4), tBuNC in the reaction giving 7b, neither insertion of the
X = Br (4b·Br), L = dmso, X = Br (4c·Br)) and [Pd{C,N-pyl-SCHC-
(O)Ph}{O,O′-acac}] (acacH = acetylacetone, 5) or anionic PPN-
[Pd{C,N-pyl-SCHC(O)Ph}Br2] (6) (PPN = Ph3PvNvPPh3) were
prepared in good yields by reacting the appropriate complex 1
with neutral monodentate ligands, with Tl(acac) or with
Scheme 3
Scheme 4
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isocyanide into the Pd–Caryl bond nor replacement of the pyri- with elemental analyses suitable for the stoichiometry of A
dine moiety was observed. The reaction of 2 with pyridine gave with n = 2.5. These results suggest processes in which soluble
a product the spectroscopic data of which suggest the for- species resulting from bridge splitting of complexes A by RCN
mation of the corresponding neutral complex. However, its (R = Me, Ph) or acetone could be involved, giving rise to com-
elemental analyses indicate some contamination29 probably plexes with different stoichiometries depending on their solu-
with 3 that we could not resolve.
bility as well as on the reagents’ molar ratio.
Complexes 7a–c could also be obtained by reacting 3 with
The reaction of 9 with PPh3 (acetone, 1 : 1), or better that of
the appropriate ligand, but since this complex is obtained in 7a with [PdCl2(NCPh)2] (CH2Cl2, 1 : 1), gave [S,O-{Pd{C,C,N-pyl-
rather low yield, the former method was preferred. However, as SCHC(O)C6H4-2}Cl}{Pd(Cl)PPh3}] (10), which again is a deriva-
an example of its use, we describe in the Experimental section tive of the anionic metallaligand present in 8. The former of
the synthesis of [Pd{C,C,N-pyl-SCHC(O)C6H4-2}(CNXy)] (7c) by these reactions produced bridge splitting and coordination
slow addition of a CH2Cl2 solution of XyNC to a suspen- of the neutral ligand, while in the latter the interchange of
sion containing an equimolar amount of 3 in the same chloro and phosphine ligands provided a new example of
solvent (40 min, 72%). No insertion of XyNC was observed PPh3/carbon donor ligands transphobia.13,30–32 The proposed
either in the reaction of 3 with 3 equiv. XyNC in CHCl3 at geometry for 10 is based on those of related complexes in
room temperature or at 65 °C in a Carius tube for 6 h, giving which P- and O-donor ligands as well as Cl and S-donor ligands
only 7c.
are placed in mutually trans disposition.33 The reaction of
Since the sulfur and oxygen atoms in complexes 2 and 7 2 with (PPN)2[Pd2Cl6] (acetone, 2 : 1) intended to produce
bear lone electron pairs we have explored their behavior as the anionic dinuclear complex PPN[S,O-{Pd{C,C,N-pyl-SCHC-
ligands towards palladium(II) and silver(I). The reaction of 2 (O)Ph}Cl}(PdCl2)], led instead to the precipitation of 9 while
with [PdCl2(NCPh)2] in acetone gave different species depend- (PPN)Cl was recovered from the mother liquor.
ing on the molar ratio of reagents that can be considered
In turn, the reaction of 7a with AgClO4 and PPh3 (acetone,
derivatives of the anion of 8 acting as a ligand (Scheme 5). 1 : 1 : 1) produced a white suspension of 11 (57%, Scheme 6)
However, we have only been able to isolate pure the complex shown by 31P NMR to be an equilibrium mixture of complexes
[S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}Cl}{Pd(μ-Cl)}]2 (9) which [S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}PPh3}(AgPPh3)]ClO4 (11a)
immediately precipitates in the 1 : 1 reaction (Scheme 5). 9 and [S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}PPh3}{Ag(OClO3)PPh3}]
results from the replacement of all the nitrile ligands, (11b) (see below).
migration of one chloro ligand from [PdCl2(NCPh)2] to 2 and
Attempts to deprotonate the CHPd group by reacting 2 with
the necessary dimerization in order to provide Pd(II) with its AgOAc (acetone, 1 : 1) or 7a or 8 with [Ag(acac)(PPh3)] (acetone,
preferred square planar tetracoordination. When different 2 : 1 : 1)34 failed and the starting materials were recovered in all
[PdCl2(NCPh)2] molar ratios were used, ranging from 1 : 2 to cases. We have also reacted 7a or 8 with an excess of Cl2 in
1 : 4, precipitation of variable amounts of 9 occurred and, from CCl4 or with a stoichiometric amount of Cl2IPh, respectively,
the solutions, mixtures were obtained (by 1H NMR) with in an attempt to produce Pd(IV) complexes, as we have reported
elemental analyses approaching those for A with n = 1 with other pincer complexes.22 However, complex mixtures
(Scheme 5). The reaction of 2 with PdCl2 (1 : 1 in acetone) were obtained in the reactions with Cl2 and no reaction was
intended to produce 9 gave instead a red insoluble compound observed in those with Cl2IPh.
Scheme 5
Scheme 6
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2.2. X-ray crystal structures
The crystal structures of complexes 1·Br·CHCl3 (Fig. 1), 1·AcO
(Fig. 2) and 7c (Fig. 3) were determined by X-ray diffraction
studies. Details on crystal data, data collection, and refine-
ments are summarized in the ESI.† The crystal structure of
1·Br·CHCl3 corresponds to the RS-transoid isomer and is
centrosymmetric while that of 1·OAc corresponds to the
RR-cisoid isomer, the SS-one being also present in the centro-
symmetric unit cell. All the structures display some common
features. Thus, in all cases, the Pd atom is in a distorted
square-planar environment, the mean deviation from planarity
for the Pd atom and its four immediate neighbors being
≤0.05 Å, except for Pd1 in 1·OAc (0.08 Å). The five membered
C–Pd–N ring adopts in complexes 1·Br and 1·OAc an envelope
conformation. However in 7c it is nearly planar (mean devi-
ation from planarity being 0.065 Å, the C1 atom being the
most deviated, +0.0833 Å) while the other five membered
C–Pd–C palladacycle adopts an envelope conformation. In
Fig. 2 Thermal ellipsoid representation plot (50% probability) of com-
pound 1·AcO. Selected bond lengths (Å) and angles (°): Pd(1)–N(1)
2.012(3), Pd(1)–C(6) 2.027(3), Pd(1)–O(2) 2.033(2), Pd(1)–O(3) 2.134(2),
N(1)–C(1) 1.358(4), C(1)–S(1) 1.735(3), C(6)–S(1) 1.811(3), C(7)–O(1)
1.229(4); N(1)–Pd(1)–C(6) 85.39(12), C(6)–Pd(1)–O(2) 92.99(11),
N(1)–Pd(1)–O(3) 93.44(10), O(2)–Pd(1)–O(3) 88.33(9), C(1)–S(1)–C(6)
98.05(15), S(1)–C(6)–Pd(1) 109.07(16), O(1)–C(7)–C(6) 122.0(3),
O(1)–C(7)–C(11) 119.3(3).
1·OAc the two acetato ligands subtend an angle of 91.7°. The
Pd–C(sp3) bond distances (similar in all complexes: 2.042(6) Å
in 1·Br, 2.027(3) and 2.035(3) Å in 1·OAc, 2.049(4) Å in 7c) are
longer than the Pd–C(sp2) and Pd–C(sp) bond distances in 7c
(2.0072(17) and 1.9904(16) Å, respectively). The trans influence
sequence C > Br > O is responsible for the slightly different
Pd–N bond distances in these complexes (2.1080(16) (7c) >
2.036(5) (1·Br) > 2.012(3), 2.007(3) Å (1·OAc)). All other struc-
tural parameters are unremarkable. The bite angles of the N,C-
chelating ligand in 1·Br and 1·OAc (N(1)–Pd–C(6), 85.5(2) and
85.39(12)°, respectively) are similar while in the pincer
complex 7c the homologous N(1)–Pd(1)–C(1) bond angle is
similar (86.47(6)°) and the C(1)–Pd(1)–C(31) one rather nar-
rower (80.98(7)°). Intermolecular hydrogen bonds are present
in all the structures. In 1·Br and 7c, chains parallel to the a
axis form through C–H⋯O bonds with participation of the car-
bonyl oxygen and the ortho-CH(phenyl) (1·Br) or the ortho-CH
(phenyl) plus one CH in the Me (xylyl) fragment. In 1·AcO a
3D net forms through various C–H⋯O hydrogen bonds with
participation of CH groups in the pyridine, phenyl and methyl
fragments and both acetato and phenacyl oxygen atoms.
2.3. NMR spectra
The NMR spectra of complexes 1·OAc, 4–8, 10 and 12 were
recorded in CDCl3 (1·Br also in dmso-d6) while the instability
(2, 4c·Br) or the insolubility of the other complexes in non-
donor solvents required the use of CD3CN (2) or dmso-d6 (3,
4c·Br, 9 and 11), which means that the NMR spectra of the
latter probably correspond to species resulting from solvent
coordination. As mentioned above, various isomeric forms are
possible for complexes 1·Cl, 1·Br and 1·OAc. The presence in
Fig. 1 Thermal ellipsoid representation plot (50% probability) of com-
pound 1·Br. Selected bond lengths (Å) and angles (°): Pd(1)–N(1)
2.036(5), Pd(1)–C(6) 2.042(6), Pd(1)–Br(1) 2.4351(8), Pd(1)–Br(1A)
2.5266(8), N(1)–C(1) 1.354(8), C(1)–S(1) 1.740(6), C(6)–S(1) 1.811(6),
C(7)–O(1) 1.225(7); N(1)–Pd(1)–C(6) 85.5(2), C(6)–Pd(1)–Br(1) 92.41(16),
N(1)–Pd(1)–Br(1A) 95.36(13), Br(1)–Pd(1)–Br(1A) 86.63(3), C(1)–S(1)–C(6)
98.5(3), S(1)–C(6)–Pd(1) 108.3(3), O(1)–C(7)–C(6) 123.2(6), O(1)–
C(7)–C(11) 119.7(5).
1
their H NMR spectra, measured in CDCl3, of various CHPd re-
sonances at 5.22, 5.58, 5.64 (1·Cl, relative intensities 1 : 1 : 0.5),
5.24, 5.62, 5.66 (1·Br, relative intensities 1 : 1 : 0.5) and 4.78,
4.86, 5.90, 6.20, 6.34 (1·OAc, relative intensities
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with the neutral ligand disposed trans to nitrogen in order to
avoid the high transphobia of the C/C and C/P couples.13,30–32
The room temperature 31P{1H}-NMR spectrum of 11 in
CDCl3 shows a singlet at 31.04 ppm, assignable to the phos-
phine ligand coordinated to palladium and two broad reson-
ances centered at 15.5 and 11.5 ppm, with relative intensities
1 : 3, attributable to PPh3 coordinated to silver. At −60 °C the
resonance at higher frequency splits into two singlets at 32.6
and 34.0 ppm, with relative intensities 3 : 1 while that at
15.5 ppm splits into two broad peaks at 18.1 and 12.7 ppm
(separated 660 Hz approx.) and that at 11.5 resolves into two
doublets centered at 12.0 ppm (due to coupling with 109Ag and
107Ag; JAgP = 564 and 489 Hz, respectively). These data support
the existence of two isomeric species in solution (11a and 11b)
and, as bigger J values correspond to the larger s-character of
the hybrid orbital involved and thus to smaller coordination
numbers, Ag(I) should be tricoordinate in the less abundant
species (δ = 15.5) in solution (structure 11a) while the most
abundant one (δ = 11.5) should contain tetracoordinate
Ag(I) (structure 11b).
The 13C{1H}-NMR spectrum of complex 9 could not be
recorded because its dmso solution is not stable for long enough.
In the remaining complexes, the CHPd carbon resonance
appears in the ranges of 39.8–45.6 or 55.2–67.4 ppm for
quelate or pincer complexes, respectively, while the CS and
CO resonances (in the ranges 171.22–178.00 and
187.02–199.55 ppm, respectively) do not show noticeable
differences among both types of complexes.13
The IR spectra of pincer complexes show one CO band in
the 1634–1658 cm−1 range, at lower energy than that of the
2-(phenacylthio)pyridine ligand (1678 cm−1) and similar to
that in the cyclometallated complexes C,N-Pd{pyl-SCHC(O)Ph}
here or previously reported,13 in the range 1623–1652 cm−1
.
Coordination of Ag(I) or Pd(II) to the carbonyl group in com-
plexes 9–11 must be weak as it does not affect significantly the
energy of the ν(CO) band. Weak to medium bands in the
1540–1590 cm−1 region can be assigned to ν(CC) and ν(CN)
from the aryl and pyridyl rings.35 The chloro complexes show
one (4a·Cl, 267; 8, 293 cm−1) or two (9, 322, 265; 10, 355,
255 cm−1) ν(PdCl) bands. We assign those below 300 cm−1 to
ν(PdCl) trans to carbon because of its higher trans influence.
Complexes bearing an isocyanide ligand display an intense
ν(CuN) absorption in the 2179–2209 cm−1 range. The pres-
ence of a strong ν(SvO) band at 1117 cm−1 in the spectrum of
4c·Br is indicative of the S-coordination of the dmso ligand.36
The IR spectrum of 11 shows strong perchlorate bands at
around 1100 and 620 cm−1. Both bands are narrow pointing to
a species with tricoordinate silver (structure 11a). The molar
conductivity of 11 in acetone solution corresponds to that of
an 1 : 1 electrolyte (118 Ω−1 cm−2 mol−1).37
Fig. 3 Above: thermal ellipsoid representation plot (50% probability) of
compound 7c. Selected bond lengths (Å) and angles (°): Pd(1)–C(11)
1.9904(16), Pd(1)–C(31) 2.0072(17), Pd(1)–C(1) 2.0494(16), Pd(1)–N(1)
2.1080(16), C(1)–S(1) 1.7971(18), C(1)–C(7) 1.493(2), C(11)–N(2) 1.154(2);
C(11)–Pd(1)–C(31) 94.10(7), C(31)–Pd(1)–C(1) 80.98(7), C(1)–Pd(1)–N(1)
86.47(6), C(11)–Pd(1)–N(1) 97.63(6), C(2)–S(1)–C(1) 101.44(7), S(1)–C(1)–
Pd(1) 113.45(8), C(7)–C(1)–Pd(1) 104.65(10), C(32)–C(7)–C(1) 109.42(13).
Below: chain parallel to axis a formed in 7c through C–H⋯O hydrogen
bonds. Hydrogen atoms were omitted except those involved in these
bonds.
0.16 : 1 : 0.21 : 0.11 : 0.18) as well as various MeCO2 resonances
in 1·OAc at 1.13, 1.48, 1.74, 1.77, and 1.95 ppm (relative inten-
sities 0.16 : 0.11 : 1 : 0.18 : 0.21) is indicative of the presence of
different isomers in solution. Supporting the fact that these
extra resonances are not arising from impurities, only one set
of resonances is observed for the R + S enantiomers in the
NMR spectra of their mononuclear derivatives, except in the
case of 4c·Br. Its 1H NMR spectrum, which coincides with that
of 1·Br in dmso-d6, shows two CHPd resonances at 5.33 and
5.56 ppm that we attribute to the SP-4-3- and SP-4-4-isomers.
The same occurs in the 1H NMR spectrum of 9 in dmso-d6. We
assume the geometry of the remaining complexes 4 to be that
The FAB+-MS of complexes 7a–c show the M+ ion at m/z
595.89 (7a) and 416.85 (7b), respectively. Additionally, the
molecular weight of 7a measured in chloroform by vapor-
pressure osmometry (560) demonstrates the mononuclear
nature of this complex in solution. The spectra of 7b (as well
as that of 8) show also a peak at m/z 333.8 corresponding to
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the fragment “Pd{pyl-{SCHC(O)C6H4-2}”. The spectrum of 4.1. Single-crystal X-ray structure determination
complex 11 shows peaks corresponding to M+ − ClO4 and M+
− AgClO4 − PPh3, which support the structure proposed. In Crystals suitable for X-ray diffraction of compounds
the spectra of complexes 2, 3, 9 and 10, only peaks of the 1·Br·CHCl3, 1·OAc and 7c were mounted in inert oil on a loop
matrix were observed.
and transferred to a Bruker D8 Quest diffractometer. Data were
recorded at 100(2) K using multilayer-monochromated Mo Kα
radiation (λ = 0.71073 Å) and ω-scan mode. The frames were
integrated with the Bruker SAINT software package using a
narrow-frame algorithm. Data were corrected for absorption
3. Conclusion
We report the synthesis of a family of palladium C,C,N-pincer effects using the multi-scan method (SADABS).
complexes derived from 2-phenacylthiopyridine obtained by
Solution and refinements: crystal structures were solved by
an unprecedented stepwise double cyclopalladation process. direct methods and all non-hydrogen atoms were refined
The second step was successful using AgAcO as the base and anisotropically on F2 using the program SHELXL-9739 for
dehalogenating reagent. Other attempts with various bases or 1·Br·CHCl3 and 7c and SHELXTL-201340 for 1·OAc. The methyl
monocyclopalladated precursors, some of them reported here groups were refined using rigid groups (AFIX 137), and the
for the first time, were unsuccessful. We have shown that the other hydrogens were refined using a riding model.
pincer complex containing MeCN as the ligand polymerizes,
Synthesis of [Pd{C,N-pyl-SCHC(O)Ph}(μ-Br)]2 (1·X)(X = Cl
most likely because the sulfur and carbonyl oxygen atoms (1·Cl), Br (1·Br)).. A suspension containing Pd(OAc)2 (for 1·Cl,
make the pincer moiety a chelating metallaligand. We have 298 mg, 1.33 mmol; for 1·Br, 387 mg, 1.72 mmol) and the
supported this idea by reacting it with neutral ligands and by appropriate amount of [Hpyl-SCH2C(O)Ph]X (X = Cl, 353 mg,
preparing Ag(I) and Pd(II) derivatives of such a ligand.
1.33 mmol; Br, 535 mg, 1.72 mmol) in acetone (30 mL) was
refluxed for 4 h. During that time a solution initially formed
which gradually transformed into a suspension. After allowing
the suspension to cool at room temperature, it was filtered and
the solid collected was washed with acetone (5 mL) and Et2O
4. Experimental section
IR spectroscopy, elemental analyses, conductance measure- (2 × 5 mL) and dried, first by suction and then in an oven at
ments in acetone and melting point determination were 75 °C for 4 h to give a yellow (1·Cl) or orange (1·Br) solid.
carried out as described earlier.38 The neutral complexes 2,
1·Cl: Yield 436 mg, 1.18 mmol, 89%). Mp: 225 °C. Anal.
4a–d, and 9 are non-conducting in acetone. The molar conduc- Calcd for C13H10ClNOPdS: C, 42.18; H, 2.72; N, 3.78, S, 8.66.
tivities of complexes 3, 6 and 8 could not be measured because Found: C, 41.85; H, 2.71; N, 3.82, S, 8.54. IR (cm−1): ν(CvO),
1
of their very low solubility in acetone. Unless otherwise stated 1644; ν(CvC), (CvN), 1590, 1552. H NMR (300 MHz, dmso-
3
the reactions were carried out at room temperature without d6): δ 5.20 (s, 1H, CHPd), 7.27 (ddd, 1H, H5, pyl, JHH = 7 Hz,
4
special precautions against moisture. The 1H, 13C{1H} and 3JHH = 6 Hz, JHH = 1 Hz), 7.37–7.96 (various m, 7H, H3 + H4,
3
4
31P{1H} NMR spectra were recorded with 200, 300 and 400 MHz pyl + Ph), 8.57 (dd, 1H, H6, pyl, JHH = 6 Hz, JHH = 1 Hz). Re-
Varian spectrometers and chemical shifts are referenced to sonances for the minor isomer (21% with respect to the major
TMS [1H, 13C{1H}] or H3PO4 [31P{1H}]. Mass spectra (FAB+) one, see Discussion) are also observed. Most of them are
were recorded with a Fisons VG-Autospec spectrometer using obscured in part by those of the major isomer, except those at
3-nitrobenzyl alcohol as the dispersing matrix. The molecular δ 5.52 (s, 1H, CHPd), 7.18 (ddd, 1H, H53JHH = 7 Hz, 3JHH = 6 Hz,
weight was determined with a vapor-pressure osmometer. 4JHH = 1 Hz). In CDCl3 (200 MHz) three CHPd resonances
The synthesis of 6 required the use of [PPN]Br which we pre- appear at 5.22, 5.58 and 5.64 ppm with relative intensities
pared as a dichloromethane solvate from the commercial 1 : 1 : 0.5 while the aromatic region is poorly resolved (see
chloride and excess NaBr (1 : 3, in acetone, 4 h). The suspen- Discussion).
sion was concentrated to dryness, the residue was stirred with
1·Br: Yield, 584 mg, 1.41 mmol, 82%. Mp: 206 °C. Anal.
CH2Cl2, and the suspension was filtered through a short pad Calcd for C13H10BrNOPdS: C, 37.61; H, 2.60; N, 3.38, S, 7.73.
of Celite. The solution was concentrated (1 mL) and Et2O Found: C, 37.75; H, 2.54; N, 3.45, S, 7.44. IR (cm−1): ν(CvO),
1
(15 mL) was added. The suspension was filtered and the solid 1641; ν(CvC), (CvN), 1588, 1553. H NMR (300 MHz, dmso-
3
collected was recrystallized from CH2Cl2 and Et2O and dried, d6): δ 5.33 (s, 1H, CHPd), 7.27 (ddd, 1H, H5, pyl, JHH = 8 Hz,
4
3
first by suction and then in an oven at 70 °C for 2 h to give 3JHH = 6 Hz, JHH = 2 Hz), 7.47 (“t”, 2H, Ph, JHH = 7 Hz), 7.58
[PPN]Br·CH2Cl2 as a white solid. Yield: 84%. Mp: 252 °C. Anal. (“t”, 1H, Ph, 3JHH = 7 Hz), 7.73–7.84 (m, 3H, H3, pyl + Ph), 7.86
Calcd for C37H32Cl2BrNP2: C, 63.17; H, 4.58; N, 1.99. Found: C, (td, 1H, H4, pyl, JHH = 8 Hz, JHH = 2 Hz), 8.78 (dd, 1H, H6,
3
4
1
3
4
62.86; H, 4.59; N, 2.04. H NMR (400 MHz, CDCl3): δ 5.30 (s, pyl, JHH = 6 Hz, JHH = 1 Hz). Resonances for the minor
2H, CH2Cl2), 7.30–7.50 (various m, 24H, ortho- + meta-Ph), 7.65 isomer (36% with respect to the major one, see Discussion) are
(tdd, 6H, para-Ph, JHH = 7 Hz, JHH = 1 Hz). 13C{1H} NMR also observed at δ 5.56 (s, 1H, CHPd). 7.21 (“t”, 1H, H5, pyl,
3
4
(100 MHz, CD3CN): δ 126.8 (d, ipso-C, 1JCP = 108 Hz), 129.5 (m, 3JHH = 6 Hz), 7.39 (“t”, 2H, Ph, JHH = 7 Hz), 7.51 (t, 1H, Ph,
3
meta-CH), 132.0 (m, ortho-CH), 133.9 (para-CH). 31P{1H} NMR 3JHH = 7 Hz), 7.74 (“d”, 1H, H3, pyl, JHH = 8 Hz), 7.92 (m, 3H,
3
3
4
(121 MHz, CDCl3): δ 21.11 (s).
H4, pyl +Ph, JHH = 7 Hz), 8.00 (d, br, H6, pyl, JHH = 5 Hz).
15176 | Dalton Trans., 2014, 43, 15170–15182
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In CDCl3 (300 MHz) three CHPd resonances appear at 5.24, (CH), 131.5 (C), 136.1 (CH), 137.9 (CH), 150.0 (CH), 173.2 (CS),
5.62 and 5.66 ppm with relative intensities 1 : 1 : 0.5 while the 199.7 (CO).
aromatic region is poorly resolved (see Discussion).
Synthesis of [Pd{N,C,C,S-pyl-SCHC(O)C6H4-2}]n (3). A solu-
Crystals of 1·Br suitable for an X ray diffraction study were tion of 2 (84 mg, 0.22 mmol) in CH2Cl2 (10 mL) was stirred at
obtained by the slow diffusion of n-hexane in a dichloro- room temperature for 1 h during which time a white suspen-
methane solution of a mixture obtained in the reaction of 1·Br sion formed which was allowed to stir for 24 h and then fil-
with AgOAc (see Discussion).
tered. The solid was washed with CH2Cl2 (3 × 5 mL) and air-
Synthesis of [Pd{C,N-pyl-SCHC(O)Ph}(μ-OAc)]2 (1·OAc). dried to give 3 as a white solid. Yield, 29 mg, 0.09 mmol, 39%.
Pd(OAc)2 (248 mg, 1.10 mmol) and AcOH (0.1 mL, 1.2 mmol) Mp: 248 °C. Anal. Calcd for C13H9NOPdS: C, 46.79; H, 2.72; N,
were added to
a solution of pyl-SCH2C(O)Ph (253 mg, 4.20, S, 9.61. Found: C, 46.56; H, 2.56; N, 4.36, S, 9.31. IR
1.10 mmol) in acetone (15 mL). After refluxing the reaction (cm−1): ν(CvO), 1658, ν(CvC), (CvN), 1590, 1580, 1556.
mixture for 1.5 h, the solution was concentrated under 1H NMR (300 MHz, dmso-d6): δ 5.68 (s, 1H, CHPd), 6.98–7.19
vacuum to 1 mL and the suspension formed was filtered. The (m, 4H, pyl + C6H4), 7.49 (“d”, 2H, C6H4, 3JHH = 9 Hz), 7.70 (“t”,
3
6
solid collected was washed with acetone (2 mL) and Et2O (3 × 1H, pyl, JHH = 8 Hz), 8.29 (“d”, 1H, H6, pyl, JHH = 6 Hz).
5 mL) and dried, first by suction and then in an oven at 70 °C 13C{1H} NMR (50 MHz, dmso-d6): δ 55.2 (CH), 119.3 (CH), 121.4
for 2 h, to give 1·OAc as an orange/red solid. Yield, 365 mg, (CH), 123.8 (CH), 123.9 (CH), 129.3 (CH), 134.2 (CH), 137.8
0.93 mmol, 84%. Mp: 242 (decomp) °C. Anal. Calcd for (CH), 146.5 (C), 148.8 (CH), 152.1 (C), 171.2 (CS), 199.1 (CO).
C15H13NO3PdS: C, 45.76; H, 3.33; N, 3.56, S, 8.14. Found: C,
Synthesis of [Pd{N,C-pyl-SCHC(O)Ph}X(L)] (L = CNXy, Xy =
46.03; H, 3.12; N, 3.51, S, 8.41. IR (cm−1): ν (CvO), 1653; νasym C6H3Me2-2,6, X = Cl (4a·Cl), Br (4a·Br), AcO (4a·OAc); L =
(CO2), 1562 ν(CvC), (CvN), 1590, 1551. 1H NMR (400 MHz, PTol3, Tol = C6H4Me-4, X = Br (4b·Br). A solution containing
CDCl3): δ 1.74 (s, 3H, Me, AcO), 4.86 (s, 1H, CHPd), 7.03 (ddd, an appropriate amount of complex 1 (for 4a·Cl, 1·Cl, 53 mg,
3
3
4
1H, H5, pyl, JHH = 8 Hz, JHH = 6 Hz, JHH = 2 Hz), 7.36 (m, 0.07 mmol; for 4a·Br or 4b·Br, 1·Br, 82 mg, 0.1 mmol or
2H, meta-Ph), 7.43–7.47 (m, 2H, para-Ph + H3, pyl), 7.63 (ddd, 100 mg, 0.12 mmol, respectively; for 4a·OAc, 1·OAc, 100 mg,
3
3
4
1H, H4, pyl, JHH = 9 Hz, JHH = 8 Hz, JHH = 2 Hz), 7.77 (m, 0.25 mmol) and ligand (for 4a·Cl or 4a·Br or 4a·OAc, XyNC,
3
2H, ortho-Ph), 8.13 (dm, 1H, H6, pyl, JHH = 6 Hz). Various 18.8 mg, 0.14 mmol, 26 mg, 0.2 mmol, or 33.3 mg, 0.25 mmol,
other minor resonances are also found at 1.13, 1.49, 1,77, and respectively; for 4b·Br, PTol3, 110 mg, 0.36 mmol) in CH2Cl2
1.96 ppm (Me, OAc, relative intensities 0.16, 0.11, 0.18 and (10 mL) was stirred for 1 h or 30 min (4a·OAc, 4b·Br, respect-
0.21 with respect to that at 1.74 ppm) and at 4.78, 5.90, 6.20, ively), filtered through a short pad of Celite and concentrated
and 6.34 ppm (CHPd, relative intensities 0.16, 0.21, 0.11 and under vacuum (1 mL). Upon addition of Et2O (15 mL) or
0.18 with respect to that at 4.86 ppm) which indicate the pres- pentane (4a·OAc) a suspension formed which was filtered and
ence of four other isomers (see Discussion). 13C{1H} NMR the yellow or pale tan (4a·OAc) solid collected was washed with
(100 MHz, CDCl3): δ 23.9 (Me, AcO), 39.8 (CHPd), 119.4 (CH5, Et2O (2 × 2 mL) or pentane (4a·OAc, 2 × 3 mL) and dried by
py), 120.8 (CH3, py), 127.9 (ortho-CH, Ph), 128.4 (meta-CH, Ph), suction. In the case of 4a·Br, a second crop precipitated when
131.9 (para-CH, Ph), 137.6 (CH4, py), 138.0 (ipso-C, Ph), 149.8 n-hexane (15 mL) was added to the concentrated filtrate. 4b·Br
(CH6, py), 176.9 (CS), 182.5 (CO2, AcO), 196.8 (CvO). Crystals was recrystallized from CH2Cl2–Et2O.
suitable for an X ray diffraction study were obtained by the
slow diffusion of Et2O into a CDCl3 solution of 1·OAc.
4a·Cl: Yield, 55 mg, 0.11 mmol, 78%. Mp: 160 °C. Anal.
Calcd for C22H19ClN2OPdS: C, 52.71; H, 3.82; N, 5.59, S, 6.40.
Synthesis of [Pd{C,C,N-pyl-SCHC(O)C6H4-2}(NCMe)] (2). To Found: C, 52.79; H, 3.75; N, 5.52, S, 6.31. IR(cm−1): ν(CuN),
a suspension of 1·Cl (215 mg, 0.29 mmol) in MeCN (20 mL) 2199; ν(CvO), 1650; ν(CvC), ν(CvN), 1591, 1578, 1555;
solid AgOAc (97 mg, 0.58 mmol) was added and the mixture ν(PdCl), 267. 1H NMR (300 MHz, CDCl3): δ 2.21 (s, 6H, Me,
was refluxed for 4 h. The suspension was filtered through Xy), 5.73 (s, 1H, CHPd), 7.03 (d, 2H, meta-CH, Xy), 7.11 (ddd,
3
3
4
anhydrous MgSO4 to remove AgCl and a small amount of 1H, H5, pyl, JHH = 8 Hz, JHH = 6 Hz, JHH = 2 Hz), 7.17–7.21
palladium, the resulting brown solution was concentrated to (m, 3H, meta-CH, Ph + para-CH, Xy), 7.24 (m, 1H, para-Ph),
3
3
ca. 1 mL, and Et2O (15 mL) was added. The suspension was fil- 7.57 (d, 1H, H3, pyl, JHH = 9 Hz), 7.65 (ddd, 1H, H4, pyl, JHH
3
4
tered and the solid was dried, by suction to give 2 as a brown = 9 Hz, JHH = 8 Hz, JHH = 2 Hz), 7.90 (m, 2H, ortho-Ph), 9.04
solid. Yield, 138 mg, 0.37 mmol, 63%. Mp: 215 °C (decomp). (dm, 1H, H6, pyl, JHH = 6 Hz). 13C{1H} NMR (75 MHz, CDCl3):
3
Anal. Calcd for C15H12N2OPdS: C, 48.08; H, 3.23; N, 7.48, S, δ 18.5 (Me, Xy), 45.6 (CHPd), 119.9 (CH5, pyl), 120.3 (CH3, pyl),
8.56. Found: C, 47.98; H, 2.91; N, 7.27, S, 8.44. IR (cm−1): 127.7 (ortho-CH, Ph), 127.8 (meta-CH, Xy), 128.1 (meta-CH, Ph),
ν(CvO), 1644; ν(CvC), (CvN), 1588, 1574, 1550. 1H NMR 129.9 (para-CH, Xy), 131.9 (para-CH, Ph), 135.5 (ortho-C, Xy),
(200 MHz, CD3CN): δ 1.97 (m, Me + solvent), 5.71 (s, 1H, 137.5 (ipso-C, Ph), 138.4 (CH4, pyl), 151.0 (CH6, pyl), 173.0
3
CHPd), 7.03–7.09 (m, 2H, C6H4), 7.12 (ddd, 1H, H5, pyl, JHH
=
=
=
=
(CS), 196.5 (CvO).
3
4
3
8 Hz, JHH = 6 Hz, JHH = 2 Hz), 7.28 (ddd, 1H, H3, pyl, JHH
8 Hz, 4JHH = 2 Hz, 5JHH = 0.4 Hz)), 7.42 (dm, 1H, H4, pyl, 3JHH
4a·Br: Yield, 95 mg, 0.17 mmol, 87%. Mp: 159 °C. Anal.
Calcd for C22H19BrN2OPdS: C, 48.42; H, 3.51; N, 5.13, S, 5.87.
Found: C, 48.35; H, 3.28; N, 5.12, S, 5.72. IR (cm−1): ν(CuN),
3
8 Hz), 7.55–7.65 (m, 2H, C6H4), 8.35 (dm, 1H, H6, pyl, JHH
6 Hz). 13C{1H} NMR (50 MHz, CD3CN): δ 57.1 (CHPd), 119.6 2196; ν(CvO), 1648; ν(CvC), ν(CvN), 1591, 1578, 1555.
(CH), 121.8 (CH), 124.68 (CH), 124.8 (CH), 128.8 (C), 130.2 1H NMR (300 MHz, CDCl3): δ 2.22 (s, 6H, Me, Xy), 5.80 (s,
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2
1H, CHPd), 7.03 (d, 2H, meta-CH, Xy, JHH = 8 Hz), 7.10 (ddd, trum of 4c·Br in dmso-d6 is identical to that of 1·Br in the
3
3
4
1H, H5, pyl, JHH = 7 Hz, JHH = 6 Hz, JHH = 2 Hz), 7.15–7.25 same solvent.
(various m, 4H, meta-CH, Ph + para-CH, Ph + para-CH, Xy),
Synthesis of [Pd{C,N-pyl-SCHC(O)Ph}(O,O′-acac)] (5). To a
3
7.58 (dm, 1H, H3, pyl, JHH = 7 Hz), 7.64 (ddd, 1H, H4, pyl, suspension of 1·Br (106 mg, 0.26 mmol) in CH2Cl2 (15 mL)
3
4
3JHH = 8 Hz, JHH = 7 Hz, JHH = 2 Hz), 7.89 (m, 2H, ortho-Ph), was added Tl(acac) (77.6 mg, 0.26 mmol). A yellow suspension
9.24 (dm, 1H, H6, pyl, JHH = 6 Hz). 13C{1H} NMR (75 MHz, immediately formed which was stirred for 1 h and then fil-
3
CDCl3): δ 18.6 (Me, Xy), 47.3 (CHPd), 120.2 (CH5, pyl), 120.4 tered. The solution was concentrated under vacuum to
(CH3, pyl), 127.7 (ortho-CH, Ph), 127.8 (meta-CH, Xy), 128.2 ca. 2 mL and n-hexane (20 mL) was added. The resulting sus-
(meta-CH, Ph), 129.9 (para-CH, Xy), 131.9 (para-CH, Ph), 135.5 pension was filtered, and the solid collected was washed with
(ortho-C, Xy), 137.7 (ipso-C, Ph), 138.4 (CH4, pyl), 152.5 (CH6, n-hexane 2 mL and dried, first by suction and then in an oven
pyl), 172.8 (CS), 196.1 (CO).
at 70 °C for 2 h to give 5 as a yellow solid. Yield, 89 mg,
4a·OAc: Yield, 98 mg, 0.19 mmol, 75%. Mp: 145 °C. Anal. 0.20 mmol, 80%. Mp: 188 °C (decomp). Anal. Calcd for
Calcd for C24H22N2O3PdS: C, 54.92; H, 4.22; N, 5.34, S, 6.11. C18H17NO3PdS: C, 49.84; H, 3.95; N, 3.23, S, 7.39. Found: C,
Found: C, 54.71; H, 3.91; N, 5.31, S, 5.99. IR (cm−1): ν(CuN), 49.56; H, 3.80; N, 3.27, S, 7.36. IR (cm−1): ν(CvO), 1637;
2209; ν(CvO), 1642; νasym(CO2), 1620; ν(CvC), ν(CvN), 1591, ν(CvC), (CvN), 1578, 1557. 1H NMR (200 MHz, CDCl3): δ 1.67
1
1553. H NMR (400 MHz, CDCl3): δ 2.04 (s, 3H, Me, OAc), 2.19 (s, Me, acac), 1.95 (s, Me, acac), 5.20 (s, 1H, CHPd), 5.53 (s, 1H,
3
3
(s, 6H, Me, Xy), 5.51 (s, 1H, CHPd), 7.00 (d, 2H, meta-CH, Xy, CH, acac), 6.93 (ddd, 1H, H5, pyl, JHH = 7 Hz, JHH = 6 Hz,
3JHH = 7 Hz), 7.08 (ddd, 1H, H5, pyl, JHH = 8 Hz, JHH = 6 Hz, 4JHH = 2 Hz), 7.31–7.59 (various m, 5H, pyl + Ph), 8.05 (m, 2H,
3
3
4JHH = 2 Hz), 7.14–7.17 (various m, 3H, meta-CH, Ph + para- ortho-Ph), 8.24 (dm, 1H, H6, pyl, JHH = 6 Hz). 13C{1H} NMR
3
3
CH, Ph), 7.21 (d, 1H, para-CH, Xy, JHH = 7 Hz), 7.53 (d, 1H, (50 MHz, CDCl3): δ 26.2 (Me, acac), 27.4 (Me, acac), 41.7
H3, pyl, JHH = 8 Hz), 7.64 (ddd, 1H, H4, pyl, JHH = 8 Hz, JHH (CHPd), 100.1 (CH, acac), 118.8 (CH5, pyl), 120.7 (CH3, pyl),
3
3
3
4
= 7 Hz, JHH = 2 Hz), 7.90 (m, 2H, ortho-Ph), 8.36 (dm, 1H, H6, 127.2 (ortho-CH, Ph), 128.9 (meta-CH, Ph), 131.6 (para-CH,
pyl, JHH = 6 Hz). 13C{1H} NMR (100 MHz, CDCl3): δ 18.4 (Me, Ph), 137.4 (CH4, pyl), 137.9 (ipso-C, Ph), 148.8 (CH6, pyl),
3
Xy), 23.8 (Me, OAc), 41.7 (CHPd), 119.4 (CH5, pyl), 120.3 (CH3, 176.9 (CS), 185.334 (CO, acac), 187.2 (CO, acac), 197.1 (CvO).
pyl), 127.7 (ortho-CH, Ph), 127.8 (meta-CH, Xy), 128.1 (meta-
Synthesis of PPN[Pd{C,N-pyl-SCHC(O)Ph}Br2] (6). To a sus-
CH, Ph), 129.7 (para-CH, Xy), 131.8 (para-CH, Ph), 135.6 pension of 1·Br (62 mg, 0.15 mmol) in CH2Cl2 (10 mL) was
(ortho-C, Xy), 137.7 (ipso-C, Ph), 138.4 (CH4, pyl), 149.3 (CH6, added [PPN]Br·CH2Cl2 (105.2 mg, 0.15 mmol). The resulting
pyl), 173.8 (CS), 176.4 (CO2, OAc), 198.1 (CO).
solution was stirred for 30 min, filtered through a short pad of
4b·Br: Yield, 202 mg, 0.28 mmol, 78%. Mp: 232 °C Celite and concentrated under vacuum (1 mL). Upon the
(decomp). Anal. Calcd for C34H31BrNOPPdS: C, 56.80; H, 4.35; addition of Et2O a suspension formed which was filtered. The
N, 1.95: S, 4.46. Found: C, 56.56; H, 4.35; N, 1.92; S, 4.19. IR solid collected was recrystallized from CH2Cl2 and Et2O to give
1
(cm−1): ν(CvO), 1644; ν(CvC), ν(CvN), 1588, 1555. H NMR 6 as an orange solid. Yield, 135 mg, 0.13 mmol, 87%
(200 MHz, CDCl3): δ 2.35 (s, 9H, Me, Tol), 4.48 (d, 1H, CHPd
,
Mp: 97 °C. Anal. Calcd for C49H40Br2N2OP2PdS: C, 56.97; H,
3JHP = 3 Hz), 7.07–7.13 (m, 12H, Tol + Ph + pyl), 7.30–7.37 (m, 3.90; N, 2.71; S, 3.10. Found: C, 56.90; H, 3.91; N, 2.87; S, 3.07.
3
6H, Tol), 7.54 (t, br, 1H, pyl, JHH = 8 Hz), 7.60 (td, 1H, pyl, IR (cm−1): ν(CvO), 1630; ν(CvC), (CvN), 1586, 1575, 1552. 1H
4
3
3JHH = 8 Hz, JHH = 2 Hz), 9.25 (m, 1H, H6, pyl, JHH = 6 Hz). NMR (200 MHz, CDCl3): δ 5.71 (s, 1H, CHPd), 6.81 (m, 1H, H4,
31P{1H} NMR (121 MHz, CDCl3):
δ
26.4. 13C{1H} NMR pyl), 7.27–7.44 (various m, 7H, H3 + H5, pyl, +Ph), 7.48 (m,
(150 MHz, CDCl3): δ 21.3 (Me, Tol), 51.3 (CHPd), 120.21 (CH5, 24H, PPN), 7.67 (m, 6H, PPN), 8.17 (d, 1H, H6, pyl, JHH
=
3
pyl), 120.23 (CH3, pyl), 127.6 (ortho-CH, Ph), 128.0 (meta-CH, 7 Hz). 31P{1H} NMR (81 MHz, CDCl3): δ 21.2. 13C{1H} NMR
Ph), 128.2 (d, ipso-C, Tol, JCP = 46 Hz), 128.9 (d, meta-CH, Tol, (50 MHz, CDCl3): δ 42.9 (CHPd), 119.2 (CH5, pyl), 120.2 (CH3,
1
3JCP = 12 Hz), 131.1 (para-CH, Ph), 134.6 (d, ortho-CH, Tol, pyl), 127.2 (ortho-CH, Ph), 127.9 (ipso-C, PPN), 129.4 (meta-CH,
2JCP = 12 Hz), 137.5 (CH4, pyl), 139.1 (ipso-C, Ph), 140.7 Ph), 129.6 (meta-CH, PPN), 130.9 (para-CH, Ph), 132.0 (ortho-
(d, para-CH, Tol, JCP = 2 Hz), 152.2 (CH6, pyl), 170.4 (CS), PPN), 133.8 (para-PPN), 136.2 (CH4, pyl), 137.9 (ipso-C, Ph),
4
196.8.1 (CvO).
144.2 (CH6, pyl), CS, CvO not observed.
Synthesis of [Pd{N,C-pyl-SCHC(O)Ph}Br(dmso)] (4c·Br). To a
Synthesis of [Pd{C,C,N-pyl-SCHC(O)Ph}(PPh3)] (7a). To a
suspension containing 1·Br (100 mg, 0.24 mmol) in acetone solution of PPh3 (95 mg, 0.36 mmol) in CH2Cl2 (20 mL) was
(5 mL) was added dmso (0.15 mL, 2.11 mmol). After 2 h of stir- added complex 2 (136 mg, 0.36 mmol). The resulting brown-
ring, the resulting solution was concentrated under vacuum to orange solution was stirred for 1 h, concentrated to ca. 2 mL
2 mL and Et2O (20 mL) was added. Partial evaporation of the and Et2O (20 mL) was added to give a solid which was recrys-
solvents’ mixture under vacuum, and the concomitant cooling, tallized from CH2Cl2 and Et2O to give 7a as a pale brown solid.
caused the precipitation of a yellow solid which was filtered, Yield, 181 mg, 0.31 mmol, 85%. Mp: 205 °C. Anal. Calcd for
washed with Et2O (2 mL) and dried by suction to give 4c·Br. C31H24NOPPdS: C, 62.48; H, 4.06; N, 2.35; S, 5.38. Found: C,
Yield, 95 mg, 0.19 mmol, 80%. Mp: 138 °C. Anal. Calcd for 62.53; H, 4.18; N, 2.59, S, 5.86. IR (cm−1): ν(CvO), 1634;
C15H16BrNO2S2Pd: C: 36.56; H: 3.27; N, 2.84; S: 13.01. Found: ν(CvC), ν(CvN), 1588, 1576, 1548. 1H NMR (300 MHz,
3
C: 36.63; H: 3.47; N, 2.92; S: 12.98. IR (cm−1): ν(CvO), 1643; CDCl3): δ 5.92 (d, 1H, CHPd, JHP = 12 Hz), 6.15–6.19 (m, 1 H),
ν(CvC), ν(CvN), 1588, 1577; ν(SvO), 1117. The 1H NMR spec- 6.51–6.53 (m, 1 H), 6.90–6.95 (m, 1 H), 6.99–7.01 (m, 1 H),
15178 | Dalton Trans., 2014, 43, 15170–15182
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7.21–7.26 (m, 14 H), 7.59–7.65 (m, 5 H). 13C{1H} NMR
Synthesis of Me4N[Pd{C,C,N-pyl-SCHC(O)C6H4-2}Cl] (8). To
(50 MHz, CDCl3): δ 67.4 (d, CHPd
,
2JCP = 72 Hz), 117.3 (CH), a suspension of 2 (144 mg, 0.38 mmol) in acetone (20 mL),
2
121.5 (CH), 123.9 (CH), 124.3 (CH), 128.0 (d, CH, JCP = 2 Hz), solid Me4NCl (42 mg, 0.38 mmol) was added. The resulting
128.5 (d, CH, 2JCP = 10 Hz), 130.3 (d, CH 2JCP = 2 Hz), 131.4 (C), suspension was stirred for 7 h, the solvent was then removed
132.1 (C), 134.8 (d, CH, JCP = 14 Hz), 135.8 (CH), 136.9 (d, CH, under vacuum and the residue was extracted with CH2Cl2 (3 ×
JCP = 12 Hz), 147.2 (d, C, JCP = 9 Hz), 147.6 (C), 151.2 (d, CH, 5 mL). The combined extracts were filtered through Celite.
2JCP = 2.82 Hz), 177.4 (CS), 195.8 (d, CO, JCP = 6 Hz). 31P{1H} Concentration of the brown-orange solution under vacuum (to
NMR (121 MHz, CDCl3): δ 27.8 (s). Mass spectrum (FAB+) m/z ca. 2 mL) and addition of Et2O (15 mL) gave a solid that was fil-
(% abundance) 595.89 (M+, 10.43%). Molecular weight in tered and dried in an oven at 80 °C overnight to give 8 as an
chloroform, 560.
Synthesis
orange-brown solid. Yield 159 mg, 0.36 mmol, 94%. Mp:
of
[Pd{C,C,N-pyl-SCHC(O)C6H4-2}(tBuNC)] 178 °C. Anal. Calcd for C17H21ClN2OPdS: C, 46.06; H, 4.78; N,
(7b). To a suspension of 2 (ca. 0.1–0.5 mmol) in acetone 6.32; S, 7.23. Found: C, 46.15; H, 5.08; N, 6.50; S, 6.97. IR
t
(10–20 mL) one equivalent of BuNC was added. The resulting (cm−1): ν(CvO), 1637; ν(CvC), ν(CvN), 1582, 1568, 1547;
red brown solution was stirred for 1 h, concentrated (2 mL) ν(PdCl), 293. ΛM, 61 Ω−1 cm−2 mol−1 1H NMR (300 MHz,
.
and n-hexane (15 mL) was added to precipitate a dark red solid CDCl3): δ 3.15 (s, 12H, NMe4), 5.83 (s, 1H, CHPd), 6.85 (ddd,
3
3
4
which was filtered and air dried. Yield, 204 mg, 0.49 mmol, 1H, H5, pyl, JHH = 7 Hz, JHH = 6 Hz, JHH = 2 Hz), 6.97 (m,
92%. Mp: 158 °C. Anal Calcd for C18H18N2OPdS: C, 51.87; H, 2H, C6H4), 7.26–7.30 (m, 1H, H3, pyl), 7.33–7.53 (m, 3H, pyl +
3
4.35; N, 6.72; S, 7.69%. Found: C, 51.65; H, 4.76; N, 7.12, S, C6H4), 7.90 (d, 1H, C6H4, JHH = 8 Hz), 8.90 (dm, 1H, H6, pyl,
7.38. IR (cm−1): ν(CuN), 2179; ν(CvO), 1636; ν(CvC), 3JHH = 6 Hz). 13C{1H} NMR (75 MHz, CDCl3): δ 55.9 (t, NMe4,
1
ν(CvN), 1583, 1568, 1546. H NMR (300 MHz, CDCl3): δ 1.65 1JCN = 4 Hz), 58.2 (s, CHPd), 118.4 (CH5, pyl), 120.8 (CH3, pyl),
t
(s, 9H, Me, Bu), 5.57 (s, 1H, CHPd), 6.87 (m, 1H, H5, pyl), 123.8 (CH, C6H4), 127.7 (CH, C6H4), 128.9 (CH, C6H4), 136.2
7.10–7.14 (m, 2H, C6H4), 7.27–7.54 (m, 4H, pyl + C6H4), 8.24 (CH4, pyl), 136.8 (CH), 147.4 (Pd–C, C6H4), 150.0 (CH6, pyl),
3
(d, 1H, H6, pyl, JHH = 5 Hz). 13C{1H} NMR (75 MHz, CDCl3): δ 151.1 (C(O)C, C6H4), 174.1 (CS), 198.6 (s, CO). Mass spectrum
30.4 (Me, tBu), 57.6 (CMe3), 61.7 (CHPd), 118.5 (CH5, pyl), (FAB+) m/z (% abundance): 333.81 (M+ − NMe4Cl, 7.25%).
121.7 (CH4, pyl), 124.6 (CH, C6H4), 125.3 (CH, C6H4), 128.3
Synthesis
of
[S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}Cl}-
(C), 129.7 (CH, C6H4), 136.3 (CH3, pyl), 137.5 (CH, C6H4), {Pd(μ-Cl)}]2 (9). To a suspension of 2 (203 mg, 0.54 mmol) in
147.8 (Pd–C, C6H4), 148.4 (C(O)C–C6H4), 150.5 (CH6, pyl), acetone (20 mL) was added solid [PdCl2(NCPh)2] (208 mg,
177.0 (CS), 196.7 (CO). Mass spectrum (FAB+) m/z (% abun- 0.54 mmol). Immediately an orange suspension formed which
dance) 416.86 (M+, 27.34%), 333.77 (M+ − tBuNC, 16.38%).
was stirred for 1 h. It was then filtered and the solid was
Synthesis of [Pd{C,C,N-pyl-SCHC(O)C6H4-2}(CNXy)] (7c). To washed with acetone (3 × 5 mL) to give a solid. A second crop
a suspension of complex 3 (51 mg, 0.15 mmol) in CH2Cl2 was obtained upon concentration of the mother liquor.
(2 mL) was added dropwise a solution of XyNC (20.1 mg, Complex 9 was obtained as an orange solid by treating both
0.15 mmol) in the same solvent (5 mL). After 1 h of stirring, samples in an oven at 80 °C overnight. Yield 267 mg,
the resulting solution was filtered through a short pad of 0.26 mmol, 97%. Mp: 267 °C. Anal. Calcd for
Celite, concentrated to 1 mL and Et2O (10 mL) was added. The C26H18Cl4N2O2Pd4S2: C, 30.56; H, 1.78; N, 2.74; S, 6.27. Found:
suspension was filtered and the solid collected was recrystal- C, 31.06; H, 2.00; N, 2.80; S, 6.06. IR (cm−1): ν(CvO), 1638;
1
lized from CH2Cl2 and Et2O to give 7c (52 mg, 0.11 mmol) as ν(CvC), (CvN), 1587, 1569, 1541; ν(PdCl), 322, 265. H NMR
an off white solid which was dried by suction. Yield, 52 mg, (200 MHz, dmso-d6): δ 4.62 (s, br, 1H, CHPd), 6.8–8.1 (various
0.11 mmol, 72%. Mp: 160 °C. Anal Calcd for C22H19ClN2OPdS overlapping multiplets, 4H, pyl + C6H4), 8.55 (d, 1H, H6, py,
C, 52.71; H, 3.82; N, 5.69; S, 6.40. Found: C, 52.79; H, 3.75; N, 2JHH = 6 Hz). Minor resonances are observed for another
5.52, S, 6.31. IR (cm−1): ν(CuN), 2199; (CvO), 1650; ν(CvC), isomer at 5.64 (s, 0.2H, CHPd), and 8.50 (m, br, 0.2H, H6, pyl)).
1
ν(CvN), 1591, 1578, 1555. H NMR (300 MHz, CDCl3): δ 2.53 The remaining resonances are obscured by those of the major
(s, 6H, Me, Xy), 5.70 (s, 1H, CHPd), 6.87 (ddd, 1H, H5, pyl, isomer.
3JHH = 7 Hz, 3JHH = 6 Hz, 4JHH = 2 Hz), 7.11 (m, 2H, C6H4), 7.20
Synthesis of [S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}Cl}{Pd(Cl)-
(PPh3}] (10). To a solution of 7a (80 mg, 0.13 mmol) in CH2Cl2
3
3
(d, 2H, meta-Xy, JHH = 8 Hz), 7.32 (dd, 1H, para-Xy, JHH
=
8 Hz, 3JHH = 7 Hz), 7.39 (d, 1H, H3, pyl, 3JHH = 8 Hz), 7.48 (ddd, (15 mL) solid [PdCl2(NCPh)2] (52 mg, 0.13 mmol) was added.
3
3
4
1H, H4, pyl, JHH = 8 Hz, JHH = 6 Hz, JHH = 2 Hz), 7.55 (m, An orange color developed immediately and the solution was
3
2H, C6H4), 8.43 (d, 1H, H6, pyl, JHH = 6 Hz). 13C{1H} NMR stirred for 20 h. It was filtered through anhydrous MgSO4, con-
(75 MHz, CDCl3): δ 19.1 (Me, Xy), 62.5 (CHPd), 118.6 (CH5, centrated under vacuum (to ca. 2 mL) and Et2O (15 mL) was
pyl), 121.9 (CH3, pyl), 124.8 (CH, C6H4), 125.5 (CH, C6H4), added to give 10 as a yellow solid. Yield 63 mg, 0.26 mmol,
126.1 (ipso-C, Xy), 128.5 (meta-CH, Xy), 129.8 (CH, C6H4), 129.9 61%. Mp: 210 °C. Anal. Calcd for C31H24Cl2NOPPd2S: 48.15; H,
(para-CH, Xy), 135.5 (ortho-C, Xy), 136.5 (CH4, pyl), 147.7 3.13; N, 1.81; S, 4.15. Found: C, 47.96; H, 3.03; N, 1.85, S, 3.98.
(Pd–C, C6H4), 148.5 (C(O)C, C6H4), 150.8 (CH6, py), 177.0 (CS), IR (cm−1): ν(CvO), 1634; ν(CvC), ν(CvN), 1583, 1565, 1546;
196.8 (CO). Crystals of 7c suitable for an X ray diffraction study ν(PdCl), 355, 255. 1H NMR (300 MHz, CDCl3): δ 3.75 (s, br, 1H,
were obtained by the liquid diffusion method from CH2Cl2– CHPd), 6.81 (m, 1H, H5, pyl), 7.03 (m, 1H, C6H4), 7.27 (m, 1H,
Et2O.
pyl), 7.30–7.65 (m, 14H, C6H4 + ortho- + meta-PPh3) 7.92 (m,
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3
4H, C6H4 + para-PPh3), 8.21 (d, 1H, pyl, JHH = 8 Hz), 8.92 (m,
1H, H6, pyl). 13C{1H} NMR (50 MHz, CDCl3): δ 45.9 (CHPd),
122.9 (CH), 124.89 (CH), 125.25 (CH), 128.44 (CH, PPh3),
128.66 (CH), 129.58 (C), 130.43 (C), 130.68 (CH, PPh3), 131.13
M. A. Stark and C. J. Richards, Tetrahedron Lett., 1997, 38,
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5094; B. Xiao, T.-J. Gong, J. Xu, Z.-J. Liu and L. Liu, J. Am.
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Commun., 2012, 48, 6744.
3
(d, ortho-CH, PPh3, JCP = 1 Hz), 134.81 (CH), 135.03 (CH,
PPh3), 138.64 (CH), 140.00 (C), 150.5 (CH6, pyl), 175.2 (CS),
187.0 (CO). 31P{1H} NMR (121 MHz, CDCl3): δ 29.79 (s).
Synthesis of [S,O-{Pd{C,C,N-pyl-SCHC(O)C6H4-2}(PPh3)}Ag-
(PPh3)ClO4] (11). To a suspension of 7a (115 mg, 0.19 mmol)
in acetone (20 mL) solid AgClO4 (40 mg, 0.19 mmol) was
added. After 10 min of stirring a solution of PPh3 (101 mg,
0.39 mmol) in acetone (20 mL) was added and the resulting
suspension was stirred for 24 h. It was filtered through Celite,
the pale orange solution was concentrated under vacuum (to
ca. 2 mL) and Et2O (20 mL) was added to give a solid which
was recrystallized from CHCl3 and Et2O and dried in an oven
at 80 °C overnight to give 11 as a pale brown solid. Yield
119 mg, 0.11 mmol, 59%. Mp: 154 °C. Anal. Calcd for
C49H39AgClNO5P2PdS: C, 55.23; H, 3.69; N, 1.31; S, 3.01.
Found: C, 54.88; H, 3.68; N, 1.13; S, 2.78. IR (cm−1): ν(CvO),
1652; ν(CvC), ν(CvN), 1586, 1573, 1558, ClO4, 1190, 622. ΛM
2 W. A. Herrmann, C. Brossmer, K. Ofele, C. P. Reisinger,
T. Priermeier, M. Beller and H. Fischer, Angew. Chem., Int.
Ed. Engl., 1995, 34, 1844.
(acetone) = 118 Ω−1 cm−2 mol−1. H NMR (300 MHz, CDCl3): δ
3 T. W. Lyons and M. S. Sanford, Chem. Rev., 2010, 1147.
4 M. Chiang, Y. Li, K. Deepa, S. Pulllarkat, K. H. Ng and
P.-H. Leung, Eur. J. Inorg. Chem., 2010, 1413; Y. Ding,
M. Chiang, S. A. Pulllarkat, Y. Li and P.-H. Leung, Organo-
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S. Watanabe, V. Subbarayan, H. Sato and T. Takahasi,
Organometallics, 2013, 32, 4997; C. E. Barday, G. Deeble,
R. J. Doyle, S. A. Elix, G. Salem, T. L. Jones, S. B. Wild and
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hedron: Asymmetry, 1994, 5, 321.
1
5.74 (d, 1H, CHPd, JHP = 10.2 Hz), 6.41–6.54 (m, 1H, H4, py),
3
7.68–7.16 (m, 37 H). 13C{1H} NMR (75 MHz, CDCl3): δ 62.4
(CHPd), 119.7 (CH), 122.3 (CH), 124.3 (CH), 124.6 (CH), 129.2
(CH), 130.2 (C), 130.7 (C), 130.9 (CH), 131.00 (CH), 132.0 (CH),
132.1 (CH), 133.8 (CH), 134.9 (CH), 135.0 (CH), 137.8 (CH),
147.3 (C), 151.6 (CH), 174.2 (CS), 194.6 (CO). 31P{1H} NMR
(121 MHz, CDCl3, see Discussion): δ (20 °C) 11.5 (v br,
AgPPh3), 15.5 (v br, AgPPh3), 31.0 (s, PdPPh3); (–60 °C) δ 12.0
[two d, AgPPh3, J(109Ag31P) = 564 Hz, J(107Ag31P) = 489 Hz],
12.7 (br, AgPPh3), 18.1 (br, AgPPh3), 32.6 (s, PdPPh3), 34.0 (s,
PdPPh3). Mass spectrum (FAB+) m/z (% abundance): 966
(M+ − ClO4, 5.34%); 595.97 (M+ − AgClO4 − PPh3).
Acknowledgements
We thank Ministerio de Educación y Ciencia (Spain), FEDER
(CTQ2011-24016) and Fundación Séneca (04539/GERM/06 and
03059/PI/05) for financial support.
5 C. Chen, E. Zhan, Y. Li and W. Shen, J. Mol. Catal., 2013,
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Notes and references
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