Insertion of substituted alkynes into the Pd-C bond of methyl and vinyl palladium(II) complexes bearing pyridylthioethers as ancillary ligands. The influence of ligand substituents at pyridine and sulfur on the rate of insertion

Article abstract of DOI:10.1021/om058005y

The palladium(II) chloro methyl complexes bearing the bidentate 6-R-C ₅H₃N-2-CH₂SR′ (RN-SR′; R = H, Me, Cl; R′ = Me, t-Bu, Ph) and the potentially terdentate 2,6-(CH ₂SR′)₂-C₅H₃N

Full text of DOI:10.1021/om058005y

Organometallics 2005, 24, 3297-3308
3297
Insertion of Substituted Alkynes into the Pd-C Bond of
Methyl and Vinyl Palladium(II) Complexes Bearing
Pyridylthioethers as Ancillary Ligands. The Influence of
Ligand Substituents at Pyridine and Sulfur on the Rate
of Insertion
Luciano Canovese,*,† Fabiano Visentin,† Gavino Chessa,† Paolo Uguagliati,†
Claudio Santo,† and Alessandro Dolmella‡
Dipartimento di Chimica, Universita` Ca' Foscari, Calle Larga S. Marta 2137, 30123 Venezia,
Italy, and Dipartimento di Scienze Farmaceutiche, Universita` di Padova, Via F. Marzolo 5,
35131 Padova, Italy
Received February 3, 2005
The palladium(II) chloro methyl complexes bearing the bidentate 6-R-C5H3N-2-CH2SR′
(RN-SR′; R ) H, Me, Cl; R′ ) Me, t-Bu, Ph) and the potentially terdentate 2,6-(CH2SR′)2-
C5H3N (S-N-S(R′); R′ ) Me, t-Bu, Ph) pyridylthioethers as ancillary ligands were synthesized,
characterized, and reacted with substituted alkynes ZCtCZ (Z ) COOMe, Z′ ) COOt-Bu,
1
Z′′ ) COOEt). The reactions were followed under second-order conditions by H NMR
technique, and the reaction rates were determined. The corresponding vinyl derivatives were
synthesized, and in the case of the complexes [PdCl(ZCdCZMe)(MeN-SPh)] and [PdCl(ZCd
CZMe)(C1N-St-Bu)] (Z ) COOMe) reaction rates for alkyne insertion yielding the corre-
sponding butadienyl complexes were also determined. The rate of insertion of the second
alkyne on the vinyl complex is more than 3 orders of magnitude lower than the first insertion
rate in both the studied complexes, thereby allowing easy separation between vinyl and
butadienyl derivatives and an easy preparation of mixed butadienyl esters. Furthermore,
the reaction rates are strongly dependent on the steric and electronic features of the ancillary
ligands. In particular, the distortion of the complex main coordination plane, induced by
the substituent in position 6 of the pyridine ring, was found to significantly influence the
substrate reactivity. The structures of the mono-inserted vinyl [PdCl(ZCdCZMe)(MeN-St-
Bu)] (1) and the bis-inserted butadienyl [PdCl((ZCdCZ)2Me)(MeN-St-Bu)] (2) complexes were
determined by X-ray diffraction, and the persistence of a structural distortion of the complex
skeleton was observed. Moreover, the distortion may be related to facile ancillary ligand
displacement, a feature that can be exploited for the synthesis of substrates that would not
be easily obtained otherwise.
Introduction
decided to extend our studies to the insertion reactions
of alkynes and in particular to the mechanism governing
the stoichiometric mono- and bis-insertion reaction on
methyl derivatives of palladium(II) bearing pyridylth-
ioethers as ancillary ligands. Olefin and alkyne insertion
We have recently shown that suitable steric and
electronic modifications of the pyridylthioether ligands
may impart a marked reactivity to the corresponding
palladium(II) methyl complexes with respect to the
insertion reactions of small unsaturated molecules
across the Pd-C bond.1 Since these kinds of reactions
identify an important path to C-C bond formation2 and
therefore represent a current topic in the field of
synthetic chemistry and copolymerization reactions,3 we
(2) (a) Shimuzu, I.; Tsuji, J. Chem. Lett. 1984, 203. (b) Ahmar, M.;
Cazes, B.; Gore, J. Tetrahedron Lett. 1984, 25, 4505. (c) Ahmar, M.;
Cazes, B.; Barieux, J. J.; Gore, J. Tetrahedron 1987, 43, 513. (d) Cazes,
B. Pure Appl. Chem. 1990, 62, 1867. (e) van Leeuwen, P. W. N. M.;
van Koten, G. In Catalysis: An Integrated Approach to Homogeneous,
Heterogeneous and Industrial Catalysis; Mouljin, J. A., et al., Eds.;
Elsevier Science: Amsterdam, 1993; and references therein. (f) Besson,
L.; Gore, J.; Cazes, B. Tetrahedron Lett. 1995, 36, 3853 and 3857. (g)
Delis, J. G.P.; Aubel, P. G.; Vrieze, K.; van Leeuwen, P. W. N. M.
Organometallics 1997, 16, 2948. (h) Kacker, S.; Sen, A. J. Am. Chem.
Soc. 1997, 119, 1028. (i) Grigg, R.; Monteith, M.; Sridharan, V.; Terrier,
C. Tetrahedron 1998, 54, 3885. (j) Zenner, J. M.; Larock, R. C. J. Org.
Chem. 1999, 64, 7312. (k) Yamamoto, A. J. Chem. Soc., Dalton Trans.
1999, 1027. (l) Mecking, S. Coord. Chem. Rev. 2000, 203, 325, and
references therein. (m) Zimmer, R.; Dinesh, C. U.; Nandanan, E.; Khan,
F. A. Chem. Rev. 2000, 100, 3067, and references therein. (n) Yagyu,
T.; Hamada, M.; Osakada, K.; Yamamoto, T. Organometallics 2001,
20, 1087. (o) Liu, W.; Malinoski, J.M.; Brookhart, M. Organometallics
2002, 21, 2836.
* To whom correspondence should be addressed. E-mail: cano@
unive.it.
† Universita` Ca' Foscari.
‡ Universita` di Padova.
(1) (a) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Bandoli,
G. Organometallics 2000, 19, 1461 (for the structural commentary
entry codes XEKVAK, XEKVEO). (b) Canovese, L.; Visentin, F.;
Chessa, G.; Santo, C.; Uguagliati, P.; Bandoli, G. J. Organomet. Chem.
2002, 650, 43 (for the structural commentary entry code HUGGAR).
(c) Canovese, L.; Chessa, G.; Santo, C.; Visentin, F.; Uguagliati, P.
Inorg. Chim. Acta, 2003, 346, 158. (d) Canovese, L.; Visentin, F.;
Chessa, G.; Uguagliati, P.; Santo, C.; Bandoli, G.; Maini, L. Organo-
metallics 2003, 22, 3230.
(3) Groen, J. H.; Elsevier, C. J.; Vrieze, K.; Smeets, W. J. J.; Spek,
A. L. Organometallics 1996, 15, 3445, and references therein.
10.1021/om058005y CCC: $30.25 © 2005 American Chemical Society
Publication on Web 05/20/2005

3298 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
reactions were first investigated in the 1970s by Maitlis4
and Clark,5 who studied the insertion into the Pd-C
bond of aryl or methyl palladium complexes, respec-
tively. More recently a number of papers dealing with
single and multiple alkyne insertion into the Pd-C bond
have appeared in the literature.6 In the case of aryl
derivatives, mono-insertion was achieved by reaction of
activated alkynes with neutral complexes, whereas poly-
insertion was obtained by the use of solvato species,
which often yield cyclic derivatives owing to their labile
and reactive vacant coordination site. The latter reac-
tion, however, hampers further insertion.6,7 The methyl
derivatives display a less predictable reactivity, and
generally the separation between the mono- and the bis-
inserted products is not obvious.5 Different types of
ancillary ligands were also employed in the alkyne
insertion reactions. Besides the more usual phosphines,
diphosphines, and diazotate amino or pyridine ligands,4-8
phosphoimines9 and ferrocene derivatives10 were used
as polydentate ligands.
Scheme 1
However, it is apparent that the mono- and poly-
insertion and in general the reaction degree of advance-
ment are not easily handled since less reactive sub-
strates preferentially give rise to mono-inserted species,
whereas the more reactive ones lead to mixtures of
mono- and poly-inserted derivatives.
Thus, with the aim of establishing whether the
pyridylthioether ligands impart to their palladium
methyl substrates an enhanced reactivity analogous to
that already observed in the case of entering allenesl
we decided to extend our study on the reaction of
insertion of several activated alkynes across the Pd-C
bond. Moreover these insertion reactions go smoothly
to completion, and the structure of the product is easily
identified. Thus, on the basis of the retention of config-
uration of the latter (or the lack thereof) and of some
other kinetic data, important information about the
nature of the intermediate and the involved mechanism
becomes available.
Scheme 2
exchange, of a wealth of vinyl and/or butadienyl deriva-
tives that are not easily obtainable otherwise.
The starting alkyl complexes and the ensuing vinyl
and butadienyl derivatives together with the employed
abbreviations are reported in Scheme 1.
Eventually, on the basis of our knowledge about the
coordinating lability of the pyridylthioeter ligands, we
programmed the synthesis, by simple metathetic ligand
Results and Discussion
(4) (a) Maitlis, P. M. Acc. Chem. Res. 1976, 9, 93. (b) Maitlis, P. M.
J. Organomet. Chem. 1980, 200, 161.
Synthesis and Solution Behavior of Palladium-
(II) Vinyl Complexes with Bidentate Pyridylthio-
ethers as Ancillary Ligands. Addition under inert
atmosphere of a slight excess of the appropriate alkyne
to a solution of palladium(II) pyridylthioether methyl
substrates in anhydrous CH2C12 at RT yields quanti-
tatively, promptly, and exclusively the corresponding
mono-inserted vinyl complexes (Scheme 2). The reaction
could also be carried out under uncontrolled conditions
(air and commercial CH2C12), in which case traces of
decomposition products render the crystallization pro-
cess more difficult. Only in the case of the stoichiometric
reaction between DMAD (dimethylacetylenedicarboxy-
late) and [PdCl(Me)(ClN-SPh)] was a mixture of mono-
(up to 95%), bis-, and poly-inserted derivatives obtained.
On the basis of the X-ray structural determination (vide
post) and theoretical and 1H NMR evidence, we suggest
that the complex representation in Scheme 2 (the vinyl
group in trans position to the pyridine nitrogen) agrees
with the predominant diastereoisomer (hereafter trans)-
(5) Clark, H. C.; Milne, C.R. C.; Wong, C. S. J. Organomet. Chem.
1977, 136, 265.
(6) (a) Samsel, E. G.; Norton J. R. J. Am. Chem. Soc. 1984, 106,
5505. (b) Dupont, J.; Pfeffer, M.; Daran, J. C.; Gouteron, J. J. Chem.
Soc., Dalton Trans. 1988, 2421. (c) Vicente, J.; Saura-Llamas, I.;
Ramirez de Arellano, M. C. J. Chem. Soc., Dalton Trans. 1995, 2529.
(d) Vicente, J.; Saura-Llamas, I.; Palin, M. G.; Jones, P. G. J. Chem.
Soc., Dalton Trans. 1995, 2535. (e) Vicente, J.; Abad, J. A.; Femandez
de Bobadilla, R.; Jones, P. G.; Ramirez de Arellano, M. C. Organome-
tallics 1996, 15, 24. (f) Vicente, J.; Abad, J. A.; Bergs, R.; Jones, P.G.;
Ramirez de Arellano, M. C. Organometallics 1996, 15, 1422. (g) Vicente,
J.; Abad, J. A.; Shaw, K. F.; Gil-Rubio, J.; Ramirez de Arellano, M. C.;
Jones, P. G. Organometallics 1997, 16, 4557. (h) La Pointe, A. M.;
Brookhart, M. Organometallics 1998, 17, 1530. (i) Vicente, J.; Abad,
J. A.; Martinez-Viviente, E.; Ramirez de Arellano, M. C.; Jones, P. G.
Organometallics 2000, 19, 52.
(7) (a) Yagyu, T.; Osakada, K.; Brookhart, M. Organometallics 2000,
19, 2125. (b) Yagyu, T.; Hamada, M.; Osakada, K.; Yamamoto, T.
Organometallics 2001, 20, 1087.
(8) (a) Bastero, A.; Ruiz, A.; Claver, C.; Milani, B.; Zangrando, E.
Organometallics 2002, 21, 5820. (b) Carfagna, C.; Gatti, G.; Mosca,
L.; Paoli, P.; Guerri, A. Organometallics 2003, 22, 3967.
(9) Reddy, K. R.; Surekha, K.; Lee, G.-H.; Peng, S.-M.; Liu, S.-T.
Organometallics 2001, 20, 5557.
(10) Pe´rez, S.; Lo´pez, C.; Cubet, A.; Pawelczyk, A.; Solans, X.; Font-
Bardia, M. Organometallics 2003, 22, 2396.

Insertion of Substituted Alkynes into Pd-C
Organometallics, Vol. 24, No. 13, 2005 3299
Table 1. Freezing Temperature and Rotameric
Ratio of the Vinyl Derivatives (Z ) COOMe)
Scheme 3
freezing
rotameric
complex
temperature (K) ratio R1/R2
[PdCl(ZCdCZMe)(HN-SPh)]
[PdCl(ZCdCZMe)(MeN-SPh)]
[PdCl(ZCdCZMe)(MeN-St-Bu)]
[PdCl(ZCdCZMe)(ClN-St-Bu)]
243
243
263
243
1.4/1
1/1
2/1a
2.9/1a
a R1 ) endo rotamer.
being present in the solid state and in solution for all
the complexes studied. As a matter of fact (i) the H
rotamers and do not display steric characteristics
amenable to NOESY experiments.
1
NMR spectra of the vinyl derivatives show the presence
of only one isomer in solution; (ii) the trans influence of
sulfur is considerably higher than that of nitrogen; and
(iii) all the X-ray diffraction determinations performed
in this and in other papers for related methyl species
always identify the trans isomer.la,b
However, the addition of a small quantity of trieth-
ylbenzylammonium chloride (TEBACl) to solutions con-
taining methyl or vinyl derivatives induces a general-
ized fluxionality, which severely broadens the proton
signals; such a phenomenon is ascribed to the establish-
ment of a fast equilibrium between the trans and the
cis isomers promoted by the chloride ion.
With the aim of establishing whether some form of
regioselectivity would govern the reaction, the insertion
of an asymmetrically substituted alkyne was also
studied. Thus, ethyl-4,4,4-trifluoro-2-butynoate (F3CCt
CCOOEt) was reacted with the complex [PdCl(Me)-
(MeN-SPh)], leading rapidly to an equally distributed
population of isomers. Apparently, the substituent at
the unsaturated alkyne carbon does not influence the
overall reactivity.
Synthesis and Solution Behavior of Palladium-
(ll) Butadienyl Complexes with Bidentate Py-
ridylthioethers as Ancillary Ligands. The bis-
inserted butadienyl products can be obtained under
preparative conditions analogous to the formerly de-
scribed species by addition of an excess of DMAD to the
methyl or vinyl RN-SR′ derivatives (Scheme 2). The
choice of the starting complex is strategic, and in this
context the most useful substrates are those bearing
MeN-SPh or ClN-St-Bu as ancillary ligands. These
complexes display a peculiar reactivity that allows facile
separation of the required reaction products and an easy
control of the reaction degree of advancement, and thus
the synthesis of butadienyl derivatives bearing different
ester groups Z becomes accessible. Consequently, addi-
tion of a 1:5 excess of DMAD to a CHC13 solution of the
complexes [PdCl(Me)(RN-SR′)] or [PdCl(ZCdCZMe)(RN-
SR′)] (R ) Me, R′ ) Ph; R ) Cl, R′ ) t-Bu; Z ) COOMe)
yields quantitatively the bis-inserted product [PdCl-
((ZCdCZ)2Me)(RN-SR′)] in 24 h. As will be seen further
on, the most reactive substrates are the complexes
bearing ClN-SPh as the pyridylthioether ligand; how-
ever, such species do not represent the most suitable
starting materials, since their intrinsically high reactiv-
ity leads often to the formation of poly-inserted deriva-
tives. Conversely, the ligands bearing an unsubstituted
pyridine ring (HN-SR′) display a lower reactivity and
are not good substrates even toward mono-insertion
products, their reactivity being too low in any case. The
determination of the rate constants for mono- and bis-
insertion will be dealt with further on.
Moreover, the peculiar structure of the coordinated
vinyl group (which is orthogonal to the main coordina-
tion plane) allows the presence of two rotamers, corre-
sponding to the reciprocal positions of the sulfur sub-
stituent R′ and the vinyl group itself with respect to the
1
main molecular plane. The low-temperature H NMR
spectra of these derivatives display the contemporary
presence of the two species (Scheme 3). As can be seen
in Scheme 3 the existence of the rotamers must be
traced back to the rotation of the vinyl fragment around
the Pd-C bond since sulfur inversion is already “frozen”
at RT, as can be deduced from the presence of signals
(two doublets or an AB system) between 4 and 5 ppm
due to the diastereotopic endocyclic CH2-S protons.
Usually, inversion of the absolute configuration of sulfur
in pyridylthioether palladium complexes is a low-energy
process.11 However, when ligands with a 6-substituted
pyridine ring (R ) Me, Cl) are involved, it has been
noticed that the temperature of inversion of sulfur
configuration increases with respect to that of the
analogous derivatives bearing ligands with an unsub-
stituted pyridine. This fact was interpreted on the basis
of the weakening of the Pd-N bond generated by
distortion of the bond itself with consequent enhance-
ment of the palladium electrophilicity toward the sulfur
atom.1 The distribution between rotamers, summarized
in Table 1, is slightly dependent on the steric require-
ments of the sulfur substituent R. A (1H-2D)-NOESY
experiment carried out in CDCl3 at 233 K on the
complex [PdCl(ZCdCZMe)(MeN-St-Bu)] indicates that
the most abundant rotamer is the endo species (R1).
Such a conclusion can also be advanced for the [PdCl-
(ZCdCZMe)(ClN-St-Bu)] species, which displays similar
behavior in solution and analogous 1H NMR spectrum.
No generalization could be drawn for the other species
that are present in solution as nonequimolar couples of
The mono- and bis-inserted complexes undergo a
similar fluxional rearrangement in solution. The low-
1
temperature (228 K) H NMR spectra in CDCl3 of the
latter display the presence of two species that were
interpreted as the exo and endo rotamers, as was
suggested in the case of the mono-inserted derivatives.
X-ray Crystal Structures. The molecular structures
of [PdCl(ZCdCZMe)(MeN-St-Bu)] (1) and [PdCl((ZCd
CZ)2Me)(MeN-SPh)] (2) and the employed numbering
scheme are illustrated as ORTEP12 drawings, in Figures
(11) (a) Abel, E. W.; Evans, D. G.; Koe, J. R.; Sik, V.; Hursthome,
M. B.; Bates, P. A. J. Chem. Soc., Dalton Trans. 1989, 2315. (b) Abel,
E. W.; Dormer, J. C.; Ellis, K. J.; Hursthome, M. B.; Mazid, M. A. J.
Chem. Soc., Dalton Trans. 1991, 107.
(12) Johnson, C. K. ORTEP, Report ORNL-5138; Oak Ridge Na-
tional Laboratory: Oak Ridge, TN, 1976.

3300 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
around Pd in 1 and 2 agree with existing data. In
particular, the Pd-N bond in 1 (2.206(2) Å) is longer
than in 2 (2.148(4) Å), and it is the second longest
reported so far, following the one found in ref 1a (2.229-
(4) Å). The same bond of 2 approaches also the values
found in ref 1a, 2.162(5) Å, and in ref 1b, 2.16(1) and
2.17(1) Å. The Pd-S bond in 1 (2.276(1) Å) is shorter
than in 2 (2.283(2) Å), and the two distances compare
well with those of the complexes described in ref 15,
2.276(1), 2.281(1), and 2.273(1) Å. The bond in 2 is also
the third longest after those reported in ref 14 (average
value of 2.294 Å). The Pd-Cl distances in 1 and 2 are
2.340(1) and 2.318(2) Å, respectively, and they match
those described in ref 1b, 2.340(6) and 2.315(6) Å. The
Pd-C distances are 1.986(3) and 1.989(5) Å in 1 and 2,
respectively, and are close to the ones reported for ref
14 (average value of 1.984 Å).
These distances can be explained in terms of the trans
influence. In both complexes, the pyridine ligand and
the sulfur atom are faced by a negatively charged
σ-bonded C ligand and by a chloride, respectively. The
trans influence of these hard bases (combined with the
distortion induced by the presence of the pyridine
6-methyl group) leads to long Pd-N and Pd-S and
short Pd-C and Pd-Cl bonds. However, the different
Pd-N bond length in 1 and 2 cannot be explained only
with the greater amount of tetrahedral distortion found
in 1. The Pd-C distances deserve further comment. The
σ-bonded C atom in 1 and 2 belongs to an olefin moiety,
like in refs 14-16, while it belongs to a methide in refs
1a,b; the shortest Pd-C distance is found in the olefin
group (mean value of 1.984 Å for ref 14), the longest in
the methide group (2.048(5) Å for ref 1a). This is also
due to the trans influence. In fact, in the methide group
the C donor atom is always trans to the pyridine ligand,
whereas in the olefin group it is trans to a chloride (a
softer base).
Figure 1. ORTEP representation of complex 1. Hydrogen
atoms have been omitted for clarity. Thermal ellipsoids are
at the 40% probability level.
The chelate pyridine ligand forms a five-membered
ring showing an envelope (Cs) conformation in both
complexes. The atoms participating to the ring other
than Pd are N, C(5), C(7), and S in 1 and N, C(5), C(6),
and S in 2. In the former, these atoms do not deviate
more than 0.02 Å from the ring mean plane, except
sulfur (out by 0.76 Å). In the latter, the deviations are
-0.03, 0.07, -0.08, 0.04, and 1.03 Å for Pd, N, C(5), C(6),
and S, respectively.
Other sets are defined by the C-C(O)-OMe residues.
In 1, the C(12)-C(15)(dO(1))-O(2)-C(16) and C(13)-
C(17)(dO(3))-O(4)-C(18) moieties are defined with the
basal plane dihedral angles of 96.7° and 113.6°. In 2
there are four such residues (clockwise from the top in
Figure 2: I-IV), which are all approximately perpen-
dicular to the basal plane (dihedral angles of 78.7°,
89.7°, 109.8°, and 105.3° for I-IV, respectively). More
planes are defined in 2 by the C(14), C(15), C(16), and
C(17) atoms of the alkene ligand and by the phenyl ring
bound to sulfur. The former makes a dihedral angle of
85.1° with the basal plane, and the latter makes angles
of 109.2° with the basal plane and of 103.7° with the
pyridine plane.
Figure 2. ORTEP representation of complex 2. Figure
settings as for 1.
1 and 2, respectively. In both complexes the Pd core is
surrounded by a tetrahedrally distorted square planar
environment, whereas the vinyl and the butadienyl
moieties are perpendicular to the main coordination
plane. The configuration of complex 2 is E,E (both sets
of ester groups are cis disposed). In 1, the atoms Pd, S,
N, Cl, and C(12) deviate from the basal square plane
by 0.07, -0.23, 0.19, -0.20, and 0.24 Å. The dihedral
angle between the triangles S-Pd-N and Cl-Pd-C(12)
is 17.1°, and the angles S-Pd-Cl and Cl-Pd-C(12)
measure 164.2(1)° and 85.9(1)°, respectively. In 2, the
atoms Pd, S, N, Cl, and C(14) deviate from the main
plane by 0.17, -0.15, 0.14, -0.13, and 0.14 Å. The
dihedral angle between the triangles S-Pd-N and Cl-
Pd-C(14) is 15.6° and the S-Pd-Cl and Cl-Pd-C(14)
measure 164.4(1)° and 90.1(1)°, respectively. The
S-Pd-N “bite” angle is 84.2(1)° in 1 and 82.3(1)° in 2.
A search in the Cambridge Crystallographic Data-
base13 for similar Pd(II) square planar complexes show-
ing the Npyr, S, Cl, C (Npyr ) pyridine nitrogen) donor
set returned seven entries;1a,b,14-16 the bond distances
As for nonbonding interactions, in 1 the sole detect-
able interaction involves, within the same molecule, the
Pd atom and a hydrogen atom bonded to C(6) (Pd- - -
HC(6) distance 2.81 Å, Pd- - -H-C(6) angle 125.5°). In
(13) Allen, F. H. Acta Crystallogr. 2002, B58, 380-388; Cambridge
Structural Database (Version 5.25 of November 2003).

Insertion of Substituted Alkynes into Pd-C
Organometallics, Vol. 24, No. 13, 2005 3301
Table 2. Second-Order Rate Constants for
by at least 3 orders of magnitude (see entries 1 and 3).
(3) The chloride in position 6 of the pyridine ring
imparts a higher reactivity than that of the correspond-
ing substrate bearing the methyl group as pyridine
substituent (see entries 2 and 4). (4) The reactivity of
the complexes also depends on the substituent at sulfur.
The complex bearing the less hindered and more
electron-withdrawing phenyl group is markedly more
reactive than that with the t-Bu moiety (see entries 2
and 3). (5) Complexes bearing different ancillary ligands
with analogous chelating capability17 show an enhanced
reactivity if the sulfur atom is present in the complex
backbone (see entries 3 and 5). (6) The iodo derivative
is more reactive (1 order of magnitude) than its chloro
analogue (see entries 3 and 6). (7) The dielectric
constant of the solvent does not influence appreciably
the rate constants (see entries 3, 7, and 8).
Reactions 1 (kI) and 2 (kII) at 298 K
kI (s-1 dm3 kII (s-1 dm3
a
b
solvent
complex
mol-1
)
mol-1
)
1
2
3
4
5
6
7
8
CDCl3
CDCl3
CDCl3
CDCl3
CDCl3
CDCl3
[PdCl(Me)(HN-SPh)]
1 × 10-4
1 × 10-1
[PdCl(Me)(MeN-St-Bu)] 2.1 × 10-3
[PdCl(Me)(MeN-SPh)]
2.5 × 10-4 c
[PdCl(Me)(ClN-St-Bu)] 1.17
∼6 × 10-4 c,d
[PdCl(Me)(N-N)] e
4.3 × 10-3
[PdI(Me)(MeN-SPh)]
1.34
Acetone [PdCl(Me)(MeN-SPh)]
CD3CN [PdCl(Me)(MeN-SPh)]
3.2 × 10-2
5.8 × 10-2
a Rate of first insertion reaction. b Rate of second insertion
reaction. c Value from second-order half-life expression: kII
)
ln((2B0 - A0)/B0)/(B0 - A0)t1/2 (A0 and B0 represent the initial
concentrations of complex and alkyne, respectively). d Uncertain
e
value due to partially obscured 1H NMR signals. N-N )
6-MeC5H3N-2-CHdN-C6H4-4-OMe.
For the sake of completeness, the insertion reaction
of DMAD across the Pd-C bond of the complex [PdCl-
(Me)(MeN-SPh)] was also studied at different temper-
atures in CDCl3, and the results are summarized in
Table 3.
2, the packing diagram shows that the pyridine rings
are stacked. The separation between the rings is 4.03
Å, compared to 3.40 Å in graphite. A similar, but less
efficient, stacking is also observed for the phenyl ring
1
bound to sulfur; the separation is about
sponding to 5.6 Å.
/ b, corre-
2
The activation parameters calculated by the reparam-
etrized Eyring equation18 are ∆Hq ) 7. 7 ( 1 kcal mol-1
Kinetics and Mechanism of the Alkyne Insertion
Reaction. The course of insertion of DMAD (reactions
1, 2) was monitored at 298 K by lH NMR spectrometry
since the UV/vis technique was hampered by the small
difference in absorbance between reactants and prod-
ucts. Thus, the reactions were independently followed
by mixing the complex under study ([PdCl(Me)(RN-
SR′)]0 ≈ 1.6 × 10-2 mol dm-3, [PdCl(Me)(RN-SR′)]0/
[DMAD]0 ) 1:1.2 for reaction 1 and [PdCl(ZCdCZMe)-
(RN-SR′)]0 ≈ 1.6 × 10-2 mol dm-3, [PdCl(ZCdCZMe)(RN-
SR′)]0/[DMAD]0 ) 1:5 for reaction 2) and recording the
disappearance of the Pd-CH3 proton signal at ∼1 ppm
(reaction 1) and the appearance or disappearance of the
most suitable signals in the case of reaction 2.
and ∆Sq ) - 6( 5 cal mol-l K-1
.
On the basis of these experimental findings we
propose the mechanistic Scheme 4.
Under pre-equilibrium conditions (migration of the
methyl group being the rate-determining step), with 1
. Ke[DMAD] the rate law becomes rate ) Kekm-
[complex][DMAD], where the experimentally deter-
mined k2 ) Kekm.
Scheme 4 directly comes from the well-established
theory of nucleophilic substitution of square planar
complexes. The pentacoordinate intermediate species
displays the alkyne molecule (entering group) lying in
the same trigonal plane as the methyl (leaving group)
and the pyridine nitrogen (group in trans position to the
leaving group itself). The rate-determining leaving
group migration to the cis coplanar alkyne gives rise to
the reaction product with retention of configuration, the
vinyl group being in trans position to the pyridine
nitrogen.
It is therefore apparent that the complexity of the
composite mechanism undermines any discussion about
the real meaning of activation parameters. In particular,
no conclusion could be drawn from the low negative
value of the activation entropy. Thus, Scheme 4 ac-
counts for the lack of influence of the solvent dielectric
constant on the overall reaction rates since no interme-
diates carrying or producing separation of charges are
involved, which would be the case if chloride ions were
[PdCl(Me)(RN-SR′)] + ZCtCZ f
[PdCl(ZCdCZMe)(RN-SR′)]
(kI) (1)
(kII) (2)
[PdCl(ZCdCZMe)(RN-SR′)] + ZCtCZ f
[PdCl((ZCdCZ)2Me)(RN-SR′)]
(Z ) COOMe )
The rate constants, which are summarized in Table
2, were determined by nonlinear fitting of concentration
vs time data by means of the customary integrated
second-order rate law or evaluated from the first half-
lives under second-order conditions. The second-order
conditions were dictated by the peculiar experimental
situation (fast reactions and uncertainty in the read-
ability of the NMR spectra owing to problems of mutual
scaling among the ensuing signals in the case of pseudo-
first-order conditions). Each value represents the aver-
age of two or three independent evaluations with an
estimated 10% relative error.
(14) Spencer, J.; Pfeffer, M.; DeCian, A.; Fischer, J. J. Org. Chem.
1995, 60, 1005 (entry code SUPMIZ).
(15) Spencer, J.; Pfeffer, M.; Kyritsakas, N.; Fischer, J. Organome-
tallics 1995, 14, 2214 (entry codes ZAFCUE, ZAFDEP).
(16) Dupont, J.; Basso, N. R.; Meneghetti, M. R.; Konrath, R. A.;
Burrow, R., Homer, M. Organometallics 1997, 16, 2386 (entry code
RUQVOO).
(17) (a) Crociani, B.; Antonaroli, S.; Di Bianca, F.; Canovese, L.;
Visentin, F.; Uguagliati, P. J. Chem. Soc., Dalton Trans. 1994, 1145.
(b) Canovese, L.; Visentin, F.; Uguagliati, P.; Di Bianca, F.; Antonaroli,
S.; Crociani, B. J. Chem. Soc., Dalton Trans. 1994, 3113. (c) Canovese,
L.; Visentin, F.; Uguagliati, P.; Chessa, G.; Pesce, A. J. Organomet.
Chem. 1998, 566, 61.
It is apparent that (1) the difference between the first
and the second insertion rates is large, spanning about
4 orders of magnitude. In other words the Pd-Me
derivatives are much more reactive than the vinyl
complexes (see entries 3 and 4). (2) The substituent in
position 6 of the pyridine ring enhances the reactivity
(18) Uguagliati, P.; Michelin, R. A.; Belluco, U.; Ros, R. J. Orga-
nomet. Chem. 1979, 169, 115.

3302 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
Table 3. Second-Order Rate Constants for Reaction 1 in CDC13 for the Complex [PdCl(Me)(MeN-SPh)] at
Different Temperatures
T (K)
273.15
283.15
298.15
313.15
323.15
kI (s-1 dm3 mol-1
)
6.6 × 10-3
2.67 × 10-2
1.1 × 10-1
3.1 × 10-1
6.8 × 10-1
Scheme 4
Scheme 5
the leaving group. The difference in reactivity among
similarly substituted complexes described in Table 2
arises from the presence of a substituted pyridine ring
in the ligand molecule. The induced distortion coupled
with adequate electronic effect (i.e., electron-withdraw-
ing capability of sulfur and pyridine substituents)
renders the methyl palladium complexes very reactive.
These effects were deeply discussed elsewhere,l and it
is apparent that, despite the fact that distortion would
render the starting substrate more similar to a penta-
coordinate intermediate, the chemical stability of the
complexes is warranted by the flexibility of the chelating
ring constituted by the pyridine nitrogen and the two
carbon and sulfur sp3 atoms. As a matter of fact, the
complex [PdCl(Me)(N-N)] (N-N ) 6-methyl-2-pyridyl-
carbaldimine) is not particularly reactive despite its
having a methyl group in position 6 of the pyridine ring
(Table 2). In other words, distortion makes the starting
substrate very reactive by enhancing its intrinsic ground
state energy and favoring association of alkynes in the
first step of reaction (increase of Ke).
However, the reactivity of complexes bearing the ClN-
SPh ligand is not immediately explained. It was noticed
that the complex [PdCl(Me)(ClN-SPh)] is present in
solution as an equilibrium mixture of cis and trans
isomers, the trans isomer being predominant ([trans]/
[cis] ≈ 10:1), since the 6-chloro-substituted pyridine is
less firmly bonded to the metal center.1b The presence
in solution of a less stabilized and more reactive species
would enhance the reactivity of the complex [PdCl(Me)-
(ClN-SPh)] toward insertion. Thus, also the present
reaction mechanism would be better explained by
admitting an alternative path via the more reactive cis
species, where the methyl group lies in trans position
with respect to sulfur. Moreover, since iodide displays
a higher trans effect than the chloride ion, the enhanced
reactivity of [PdI(Me)(MeN-SPh)] with respect to its
chloride analogue could be explained by invoking the
presence in solution of the more reactive cis species, as
can also be deduced from its 1H NMR spectrum, which
under the same experimental conditions appears con-
siderably more broadened than that of its chloride
analogue.1c Eventually, addition of chloride ion (TE-
BACl) to the reaction mixture would catalyze the
isomerization between trans and cis derivatives, giving
rise also in this case to the observed rate increment due
to the increased rate of formation of the cis isomer, a
substrate otherwise not available for the insertion
reaction.
The isomerization constant Ki (in the case of added
chloride) is obviously independent of chloride concentra-
tion and ionic strength, and its value should be ,1, as
can be deduced from the experimental results and from
the consideration that in the case of complex [PdCl(Me)-
(ClN-SPh)] (which represents the most favorable case)
Ki = 0.1.
The difference between the kI and kII values in Table
2 is easily traced back to the increased steric demand
of the vinyl with respect to the methyl group and to the
shortening with consequent strengthening of the Pd -N
bond (vide supra). Under these conditions the rate-
determining vinyl migration will be depressed due to
the lower Ke and km values. The insertion reaction of
the alkyne across the Pd-vinyl bond is also enhanced
by the addition of chloride but to a lesser extent than
the previously described reactions. Apparently, the
faster formation of the more reactive cis isomer can
hardly affect the reaction rate owing to the higher
stabilization of the vinyl with respect to the methyl
group (vide supra).
Synthesis, Solution Behavior, and Reactivity of
Palladium(lI) Vinyl Complexes with Terdentate
Pyridylthioethers as Ancillary Ligands. The inser-
tion of the activated alkyne DMAD across the Pd-C
bond in methyl complexes bearing terdentate pyridylth-
ioether ligands (SNS(R′)) under experimental conditions
analogous to those used in the synthesis of the bidentate
species yields the mono-inserted vinyl derivatives.
The reaction progress was detected by 1H NMR
technique following the shift of the signal of the methyl
group from ∼0.8 to ∼2.5 ppm upon transfer from the
metal to the vinyl moiety. The reactions were monitored
under second-order conditions, and the experimental
conditions and the half-life times for the insertion of
DMAD into different terdentate complexes are listed in
Table 4. These half-life times should be taken as raw
indicators of reactivity since the mechanistic picture
involving these substrates and their insertion reactions
is rather complicated and not amenable to a fully
fledged kinetic study. In fact, these potentially terden-
tate complexes are known1d to undergo equilibrium
displacement of one chelating arm by chloride, leading
The overall reaction mechanism should then be
described by Scheme 5, the lower part being operative
only under the favorable conditions described before.

Insertion of Substituted Alkynes into Pd-C
Organometallics, Vol. 24, No. 13, 2005 3303
Table 4. Molar Ratio and Estimated Half-Life
Time for the Insertion Reaction of DMAD into the
Pd-Me Bond of Palladium Complexes Bearing
Potentially Terdentate Pyridylthioether Ligands
Conclusions
The reactivity and the selectivity toward mono- and
bis-insertion reaction of alkynes across the Pd-C bond
in pyridylthioether palladium methyl complexes were
investigated, and the peculiar behavior of these sub-
strates was confirmed. In particular, the reaction rate
in some cases is high and comparable with that of
solvento species bearing different ancillary ligands.
However, in our complexes no vacant coordinative
position is available, and therefore no undesired cyclic
species is formed. The modification induced by the
ancillary ligand to the geometry of the substrate was
confirmed to be very important since the starting
complex assumes a distorted configuration similar to
that of the reactive intermediate.
On the basis of kinetic and structural investigations
a simple mechanism for the reaction under study is
proposed that takes into account the electronic and
steric features of the sulfur and pyridine substituents
and the effect that the substituent trans to the pyridine
nitrogen exerts on the overall rate. There emerges that
the reactivity of the complex [PdCl(Me)(ClN-SPh)] is the
highest detected in the case of pyridylthioether com-
plexes and one of the highest found in the literature.
However, the stoichiometric reaction of the complex
[PdCl(Me)(ClN-SPh)] and DMAD yields a mixture of
mono-, bis-, and poly-inserted derivatives, and thus such
a substrate is not the best choice as far as the synthesis
of intermediates is concerned. The most suitable com-
plexes for mono- and bis-insertion are [PdCl(Me)(MeN-
SPh)] and [PdCl(Me)(ClN-St-Bu)], since their reactivity
allows the ready formation of [PdCl(ZCdCZMe)(RN-
SR′)] at 1:1 complex/alkyne and of [PdCl((CZdCZ)2Me)-
(RN-SR′)] at 1:5 complex/alkyne molar ratios, respec-
tively. Apparently, stoichiometric control of the insertion
products is easily achieved.
complex
[Pd]0/[DMAD]0
t1/2 (s)
[PdCl(Me)(SNS(Ph))]
[PdCl(Me)(SNS(Me))]
[PdCl(Me)(SNS(t-Bu))]
1.06 × 10 -2/1.17 × 10 -2
3.04 × 10 -2/3.49 × 10 -2
3.05 × 10 -2/3.49 × 10 -2
90
410
5200
to neutral bidentate methyl-chloride complexes with a
dangling wing. Insertion takes place only on the neutral
bidentate species to yield the inserted product, which
in turn is in chloride-mediated equilibrium with the
corresponding terdentate mono-inserted species. As
matter of fact, the terdentate methyl substrate, which
is easily obtained by dechloridation with AgClO4 of the
bidentate chloro methyl complex, is unreactive. As can
be seen, the reactivity of the potentially terdentate
ligands is similar to that of 6-methyl-substituted py-
ridylthioether bidentate derivatives despite their behav-
ing mostly as terdentate moieties in solution.1d Only in
the case of [PdCl(Me)(SNS(t-Bu))] do the bulky tert-butyl
groups exert a remarkable steric retardation. The most
prominent difference between the bidentate and the
terdentate derivatives arises from the fact that the
latter do not easily give rise to bis-inserted butadienyl
species. As a matter of fact, it is noteworthy that the
half-life time for the second insertion of DMAD into the
complex [PdCl(CZdCZMe)(SNS(Me))] (Z ) COOMe) is
about 72 h. Apparently the second insertion reaction is
sterically and electronically hampered (the vinyl group
is less reactive than the methyl group), and this very
fact can be exploited to produce in short time (with a
large excess of alkyne) the mono-inserted species, which
can be used as starting material in the synthesis of other
derivatives (vide post).
Vinyl and Butadienylpyridylthioether Palla-
dium Complexes as Starting Materials. Ligand
Exchange. It has been already noticed that the 6-sub-
stituted pyridylthioether ligands are easily displaced by
monodentate or chelating molecules. Thus, the reaction
of allylpyridylthioether derivatives with monodentate
amines yields the corresponding unreactive bis-amino
species,17c,19 and the palladium(0) olefin derivatives
easily exchange the pyridylthioether ligand with an
R-diimine moiety, in any case irrespectively of the
apticity of the pyridylthioether ligand itself.20 It is
noteworthy that the lability of the latter ligands and
the ease in controlling the insertion degree of advance-
ment when their derivatives are involved could be
exploited to synthesize vinyl or butadienyl complexes
with ligands that will not impart the adequate reactivity
to their methyl derivatives. Thus, the exchange reac-
tions between ligands according to Scheme 6 were
performed. The metathetic exchanges were followed in
CDCl3 under very mild conditions (complex/ligand )
1:1.02 molar ratio at room temperature). The reactions
are fast and complete with all the species studied, as
can be seen from the NMR spectra.
As a consequence, the synthetic operative conditions
allow the formation of mixed butadienyl derivatives
bearing different Z groups as butadiene chain substit-
uents whose importance is brought to bear when hy-
drolysis or trans-esterification reactions are involved.
The difference in reactivity of the various substituted
esters toward such reactions might gain primary im-
portance.21
Eventually, these compounds represent an interesting
class of starting substrates in the production of vinyl
and butadienyl complexes owing to the lability of
pyridylthioethers as ancillary ligands.
Experimental Section
Solvents and Reagents. CH2Cl2 was dried and distilled
on CaH2. All other chemicals were commercially available
grade products unless otherwise stated.
1
IR, NMR, and UV-Vis Measurements. The IR and H,
13C{lH}, and {1H-1H}-NOESY experiments and 31P{lH} NMR
spectra were recorded on a Perkin-Elmer Spectrum One
spectrophotometer and on a Bruker 300 Avance spectrometer,
respectively. The proton and carbon assignment was performed
1
by H-13C-HMQC and -HMBC experiments. UV-vis spectra
were taken on a Perkin-Elmer Lambda 40 spectrophotometer
equipped with a Perkin-Elmer PTP6 (Peltier temperature
programmer) apparatus.
(19) Canovese, L.; Visentin, F.; Chessa, G.; Niero, A.; Uguagliati,
P. Inorg. Chim. Acta 1999, 293, 44.
(20) (a) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.;
Dolmella, A. J. Organomet. Chem. 2000, 601, 1. (b) Canovese, L.;
Visentin, F.; Chessa, G.; Gardenal, G.; Uguagliati, P. J. Organomet.
Chem. 2001, 622, 155.
(21) Kocienski, P. J. In Protecting Groups; Georg Thieme Verlag,
2000; p 125.

3304 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
Scheme 6
Table 5. Summary of Crystal and Refinement
Data for 1and 2
Preliminary Studies and Kinetic Measurements: In-
sertion Reactions. In a typical NMR experiment 1.8 × 10-2
mmol of the complex under study was dissolved in 0.6 mL of
CDCl3, and the appropriate alkyne was added in order to
produce the molar ratio required by the particular process (1:l
or 1:5 for mono- or bis-insertion, respectively). The reaction
progress was followed at 298 K by recording selected inte-
grated signals of the reactants and products. The ensuing rate
constants were computed from nonlinear regression of the
concentration profiles vs time according to the customary
second-order rate law or (in the case of the slowest reactions)
from the estimated half-life time as k2 ≈ ln((2[Alk]0 - [Pd]0)/
[Alk]0)/([Alk]0 - [Pd]0)t1/2. In one case the asymmetric substi-
tuted alkyne 4,4,4-trifluoroacetylene-2-butynoato (F3CCt
CCOOMe) was also studied in order to gather some information
on the regioselectivity of the insertion reaction. However, from
1
2
empirical formula
fw
C
18H26ClNO4PdS
C26H28ClNO8PdS
656.4
494.3
cryst syst; space
group
triclinic; P1h
(No. 2)
monoclinic; P21/c
(No. 14)
a, Å
10.242(2)
10.271(2)
11.162(2)
81.30(3)
69.67(3)
71.66(3)
1044.0(4)
2; 1.573
0.71073; 11.4
3.6-29.5
4520
10.939(2)
b, Å
11.314(2)
c, Å
22.949(5)
R, deg
â, deg
101.84(3)
γ, deg
V, Å3
2780(1)
4; 1.568
0.71073; 8.9
3.3-26.0
4928
Z; Fcalcd, g cm-3
λ, Å; µ, cm-1
θ range, deg
reflns collected
reflns obsd
(I > 2σ(I))
data/params ratio
R1a (obsd reflns)
wR2b (obsd reflns)
GOFc on F2
largest peak, e Å-3
1
the H NMR spectra it can be deduced that the reaction will
3656
4769
yield both possible diastereoisomers (Pd(ZCdCZ′′′) and Pd-
(Z′′′CdCZ); Z′′′ ) CF3, Z ) COOMe) in equivalent molar ratio,
each species being present as a couple of rotamers (see Results
and Discussion).
Metathesis Reactions. The metathetic exchange reaction
among ligands was also followed in CDCl3 by NMR technique,
and under NMR experimental conditions ([Pd]0/[L-L]0, 1:1;
[Pd]0 ≈ 3 × 10-2 mol dm-3) all the reactions studied were
immediate.
4520/235
0.032
0.066
0.971
0.82
4928/344
0.051
0.112
1.361
0.44
a R1 ) ∑||Fo| - |Fc| |/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2
.
c GOF ) [∑w(|Fo | - |Fc |)2/(Nobsd - Nparams)]1/2
.
2
2
X-ray Analysis. Crystals of 1 and 2 suitable for X-ray
analysis were sealed in a glass capillary and mounted on the
goniometer head of two different four-circle automated dif-
fractometers equipped with a graphite monochromator in the
incident beam (Mo KR radiation). The crystals of 1 were
mounted on a Nicolet Siemens R3m/V; those of 2 on a Philips
PW-1100 (FEBO System). The intensities of the diffracted
beam were measured at room temperature, and unit cell
dimensions were obtained from a least-squares fit of 50 well-
centered reflections (for 1) and 30 reflections (for 2). Crystal
stability was checked periodically by monitoring the intensities
of three standard reflections. Data were collected by the ω-2θ
scan technique and corrected for Lorentz-polarization effects
and for absorption. The two structures were solved by the
heavy atom method and refined on F 2 by standard full-matrix
least squares. In the last cycles of refinement the non-H atoms
were allowed to vibrate anisotropically; H atoms were included
in ideal positions and refined as riding model. Crystallographic
data and reliability factors are reported in Table 5, while Table
6 lists the relevant bond distances and angles for both
complexes. The SHELXTL NT22 computer program was used
for structure solution and SHELXL-93 for structure refine-
ment.23
Table 6. Selected Bond Distances (Å) and Angles
(deg) for 1 and 2
1
2
Pd-Cl
2.340(1)
2.276(1)
2.206(2)
1.986(3)
1.808(3)
1.852(3)
1.334(4)
Pd-Cl
2.318(2)
2.283(2)
2.148(4)
1.989(5)
1.825(6)
1.784(5)
1.328(7)
1.346(7)
Pd-S
Pd-S
Pd-N
Pd-N
Pd-C(12)
S-C(7)
S-C(8)
C(12)-C(13)
Pd-C(14)
S-C(6)
S-C(8)
C(14)-C(15)
C(16)-C(17)
Cl-Pd-S
164.2(1)
103.1(1)
85.9(1)
Cl-Pd-S
164.4(1)
96.2(1)
Cl-Pd-N
Cl-Pd-N
Cl-Pd-C(12)
S-Pd-N
Cl-Pd-C(14)
S-Pd-N
90.1(1)
84.2(1)
82.3(1)
90.9(1)
173.1(2)
91.2(2)
111.0(2)
112.1(4)
127.7(4)
112.1(4)
123.1(4)
112.2(3)
S-Pd-C(12)
N-Pd-C(12)
Pd-S-C(7)
Pd-S-C(8)
S-C(7)-C(5)
Pd-N-C(1)
Pd-N-C(5)
88.7(1)
168.6(1)
95.3(1)
115.2(1)
114.6(2)
127.4(2)
114.7(2)
127.8(2)
109.1(2)
S-Pd- -C(14)
N-Pd-C(14)
Pd-S-C(6)
Pd-S-C(8)
S-C(6)-C(5)
Pd-N-C(1)
Pd-N-C(5)
Pd-C(12)-C(13)
Pd-C(12)-C(15)
Pd-C(14)-C(15)
Pd-C(14)-C(18)
Synthesis of the Bidentate and Terdentate Ligands.
The synthesis of the ligands 6-chloro-2-tert-butylthiometh-
ylpyridine (ClN-St-Bu), 6-chloro-2-phenylthiomethylpyridine
(ClN-SPh),20a 6-methyl-2-phenylthiomethylpyridine (MeN-
SPh), 6-methyl-2-methylthiomethylpyridine (MeN-SMe), 6-
methyl-2-tert-butylthiomethylpyridine (MeN-St-Bu), 2-phe-
nylthiomethylpyridine (HN-SPh),17c 2,6-bis(phenylthiomethyl)-
pyridine (S-N-S(Ph)), 2,6-bis(methylthiomethyl)pyridine (S-N-
S(Me)), and 2,6-bis(tert-butylthiomethyl)pyridine (S-N-S(t-
Bu))19,20 was carried out according to published procedures.17c,19,20
All other chemicals were commercial grade and were purified
or dried by standard methods where required.24
(22) Sheldrick, G. M. SHELXTL NT, Version 5.10; Bruker AXS
Inc.: Madison, WI, 1999.
(23) Sheldrick, G. M. SHELXL-93, Program for the Refinement of
Crystal Structures; University of Gottingen: Germany, 1993.
(24) Armarego, W. L. F.; Perrin., D. D. In Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: New York, 1988.

Insertion of Substituted Alkynes into Pd-C
Organometallics, Vol. 24, No. 13, 2005 3305
8-Diphenylphosphanyl-2-methylquinoline (DPPQ-Me).
A 2 g (9 mmol) sample of 8-bromo-2-methylquinoline25 was
dissolved in 35 mL of anhydrous THF under inert atmosphere
(Ar). To the solution at -78 °C was added dropwise 6.2 mL
(9.9 mmol) of n-BuLi, and the reaction mixture was stirred
for 1 h. Then, 1.62 mL (9 mmol) of chlorodiphenylphosphine
was added by a syringe and the solution was brought to room
temperature by removing the cooling bath. The resulting
solution was stirred at 30 °C for 30 min, and eventually 5 mL
of water was added in order to remove the reactants in excess.
The solvent was removed under reduced pressure, and the
residue was dissolved in CH2Cl2 and washed twice with a 5%
aqueous solution of NaHCO3. The organic phase was separated
and dried on MgSO4. Addition of diethyl ether to the concen-
trated solution yielded the title product, which was filtered
off on a gooch, washed with cold diethyl ether, and dried.
Yield: 30% (0.9 g, 2.7 mmol, white microcrystals). 1H NMR
(CDCl3, T ) 295 K, ppm): methyl protons, δ, 2.59 (s, 3H, CH3),
quinoline protons 7.10 (m, 3H, H2, H6, H7), 8.03 (d, 1H, H4, J
) 9 Hz), 7.66 (d, 1H, H5, J ) 9 Hz), phenyl protons 7.33 (m,
10H).
The following complexes were prepared under conditions
analogous to those of [PdCl(ZCdCZMe)(MeN-SPh)] using the
appropriate starting substrates. The reaction time for each
complex is reported in parentheses.
Bidentate Complexes. [PdCl(ZCdCZMe)(MeN-SMe)].
(21 h) Yield: 81% (pale yellow microcrystals). 1H NMR (CDCl3,
T ) 298 K, ppm): pyridine protons, δ, 7.71 (t, 1H, H4, J ) 7
0.7 Hz), 7.26 (d, 1H, H3, J ) 7 0.7 Hz), 7.24 (d, 1H, H5, J ) 7
0.7 Hz), thiomethyl protons 4.53 (broad AB system, 2H, Pyr-
CH2-S), carboxylic protons 3.84 (s, 3H, COOCH3R), 3.68 (s, 3H,
COOCH3â), methyl protons 3.11 (s, 3H, Pyr-CH3), 2.49 (bs, 3H,
dCCH3), thiomethyl protons 2.32 (bs, 3H, S-CH3).
1H NMR (CDCl3, T ) 243 K, ppm) major rotamer: pyridine
protons, δ, 7.75 (t, H4′, J′ ) 7 0.7 Hz), 7.33 (d, H3′, J′ ) 7.7
Hz), 7.26 (d, H5′, J′ ) 7.7 Hz), thiomethyl protons 4.68, 4.07
(d, Pyr-CH2′-S, Jd′ ) 16.2 Hz), carboxylic protons 3.87 (s,
COOCH3′R), 3.68 (s, COOCH3′ â), methyl protons 3.09 (s, Pyr-
CH3′), methyl protons 2.46 (s, dCCH3′), methyl protons 2.27
(s, S-CH3′).
1H NMR (CDCl3, T ) 243 K, ppm) minor rotamer: pyridine
protons, δ, 7.74 (t, H4′′, J′′ ) 7 0.7 Hz), 7.33 (d, H3′′, J′′ ) 7.7
Hz), 7.26 (d, H5′′, J′′ ) 7.7 Hz), thiomethyl protons 4.49, 4.44
(AB system, Pyr-CH2′′-S, JAB′′ ) 15.1 Hz), carboxylic protons
3.86 (s, COOCH3′′R), 3.68 (s, 3H, COOCH3′′â), methyl protons
3.08 (s, Pyr-CH3′′), methyl protons 2.55 (s, dCCH3′′), methyl
protons 2.43 (s, S-CH3′′).
Synthesis of the Methyl Complexes. All the palladium
methyl complexes (Scheme 1) were prepared by addition of the
appropriate ligand to a solution of [PdCl(Me)(COD)]26 in
toluene or THF under inert atmosphere (N2) according to
published procedures.1
The complex [PdI(Me)(MeNSt-Bu)] was prepared according
to a published procedure by metathetic exchange between
[PdCl(Me)(MeNSt-Bu)] and NaI.lc
Rotameric ratio ≈ 1.5:1.
IR: (KBr pellet) νCdO 1710.4, 1698.2 cm-l, νCN 1602.8 cm-l.
Anal. Calcd for C15H20ClNO4PdS: C 39.84, H 4.46, N 3.10.
Found: C 39.93, H 4.48, N 3.01.
Synthesis of the Vinyl Complexes. [PdCl(ZCdCZMe)-
(MeN-SPh)], Z ) COOMe. To 0.1936 g (0.52 mmol) of the
complex [PdCl(Me)(MeN-SPh)] dissolved in 30 mL of freshly
distilled (CaH2) CH2Cl2 was added 72.3 µL (83.84 mg, 0.59
mmol) of dimethylacetylenedicarboxylate (DMAD) under inert
atmosphere (Ar). The reaction mixture was stirred for 4 h at
RT, and the resulting yellow solution was concentrated by
evaporation under reduced pressure. Addition of diethyl ether
caused the precipitation of the title complex as yellow micro-
crystals, which were filtered off, washed with small aliquots
of ether, and dried under vacuum (0.237 g; yield 89%).
1H NMR (CDCl3, T 298 K, ppm): phenyl protons, δ, 7.67
(d, 2H, Hortho, J ) 6.8 Hz), 7.36-7.26 (m, 3H, Hmeta, Hpara),
pyridine protons 7.56 (t, 1H, H4, J ) 7.7), 7.15 (d, 1H, H3, J )
7.3 Hz), 7.07 (d, 1H, H5, J ) 7.5 Hz), thiomethyl protons 4.99,
(d, 1H, Pyr-CH2-S, J ) 16.0 Hz), 4.34 (d, 1H, Pyr- CH2-S, J )
16.0 Hz), carboxylic protons 3.81 (bs, 3H, COOCH3R), 3.65 (s,
3H, COOCH3â), methyl protons 3.15 (s, 3H, Pyr-CH3), 2.49 (bs,
3H, dCCH3).
[PdCl(ZCdCZMe)(MeN-St-Bu)]. (48 h) Yield: 89% (yellow
1
microcrystals). H NMR (CDCl3, T ) 298 K, ppm): pyridine
protons, δ, 7.68 (t, 1H, H,4 J ) 7.7 Hz), 7.24 (d, 1H, H3, J )
7.7 Hz), 7.21 (d, 1H, H,5 J ) 7.7 Hz), thiomethyl protons 4.78-
4.13 (broad AB system, 2H, Pyr-CH2-S), carboxylic protons 3.67
(s, 3H, COOCH3R), 3.82 (s, 3H, COOCH3â), methyl protons
3.15, 3.10 (bs, 3H, Pyr-CH3′, Pyr-CH3′′), 2.62, 2.46 (s, 3H, d
CCH3′, dCCH3′′), tert-butyl protons 1.28, 1.25 (s,9H, S-
C(CH3)3′, S-C(CH3)3′′).
1H NMR (CDCl3, T ) 323 K, ppm): pyridine protons, δ, 7.67
(t, 1H, H4, J ) 7.7 Hz), 7.24 (d, 1H, H3, J ) 7.7 Hz), 7.20 (d,
1H, H5, J ) 7.9 Hz), thiomethyl protons 4.5 (broad AB system,
2H, Pyr-CH2-S), carboxylic protons 3.81 (s, 3H, COOCH3R) 3.67
(s, 3H, COOCH3â), methyl protons 3.14 (s, 3H, Pyr-CH3), 2.55
(bs, 3H, dCCH3), tert-butyl protons 1.28 (s, 9H, S-C(CH3)3).
1H NMR (CDCl3, T ) 263 K, ppm) major rotamer: pyridine
protons, δ, 7.70 (t, H4′, J′ ) 7.7 Hz), 7.24 (d, H3′, J′ ) 7.7 Hz),
7.20 (d, H5′, J′ ) 7.7 Hz), thiomethyl protons 4.75, 4.10 (d, Pyr-
CH2′-S, J′ ) 17.1 Hz), carboxylic protons 3.82 (s, COOCH3′R),
3.67 (s, COOCH3′â), methyl protons 3.14 (s, Pyr-CH3′), 2.62
(s, dCCH3′), tert-butyl protons 1.24 (s, S-C(CH3)3′).
1H NMR (CDCl3, T ) 243 K, ppm): phenyl protons, δ, 7.69,
7.67 (d, 2H, H′ortho, H′′ortho, J′, J′′ ) 6.4 Hz), 7.41-7.29 (m, 3H,
H
meta, Hpara), pyridine protons 7.60 (t, 1H, H4, J ) 7.9 Hz), 7.17
(d, 1H, H3, J ) 7.9 Hz), 7.09 (d, 1H, H5, J ) 7.9 Hz), thiomethyl
protons 5.0, 4.98, 4.34, 4.31 (d, 2H, Pyr-CH2′-S, Pyr-CH2′′-S,
J′ ) 15.8, J′′ ) 16.2 Hz), carboxylic protons 3.87, 3.66 (s, 3H,
COOCH3′R, COO CH3′′R), 3.65, 3.64 (s, 3H, COOCH3′â,
COOCH3′′â), methyl protons 3.17, 3.13 (s, 3H, Pyr-CH3′R, Pyr-
CH3′′R), 2.54, 2.47 (s, 3H, dCCH3′â, dCCH3′′â).
1H NMR (CDCl3, T ) 263 K, ppm) minor rotamer: pyridine
protons, δ, 7.71 (t, H4′′, J′′ ) 7.7 Hz), 7.24 (d, H3′′, J′′ ) 7.7
Hz), 7.20 (d, H5′′, J′′ ) 7.7 Hz), thiomethyl protons 4.81, 4.20,
(d, Pyr-CH2′′-S, J′′ ) 17.3 Hz), carboxylic protons 3.85 (s,
COOCH3′′R), 3.67 (s, COOCH3′′ â), methyl protons 3.07 (s, Pyr-
CH3′′), 2.46 (s, dCCH3′′), tert-butyl protons 1.28 (s, S-C(CH3)3′′).
Rotameric ratio ≈ 2:1.
Rotameric ratio ≈ l:1 (see Results and Discussion).
13C NMR (CDCl3, T ) 298 K, ppm): carboxylic carbons, δ,
171.6 (COOCH3 R), 163.2 (COOCH3 â), pyridine carbons
163.7 (C6pyr), 155.7 (C2pyr), 125.6 (C5pyr), 121.2 (C3pyr), phenyl
carbons 132. 8, 130.9, 130.0, 129.3, vinyl carbons 147.2, 128.3,
thiomethyl carbons 50.0 (CH2-S), methyl carbons 52.3, 52.1
(COOCH3R, COOCH3â), 27.3 (Pyr-CH3), 21.6 (dCCH3). IR
(KBr pellet): νCdO 1710.8, 1699.2 cm-l, νCN 1602.8 cm-l. Anal.
Calcd for C20 H22ClNO4PdS: C 46.70, H 4.31, N, 2.72. Found:
C 46.67, H 4.33, N, 2.62.
IR: (KBr pellet) νCdO 1711.6 cm-l, νCN 1597.1 cm-l. Anal.
Calcd for C18H26ClNO4PdS: C 43.73, H 5.13, N 2.83. Found:
C 43.59, H 5.47, N 2.81.
[PdCl(ZCdCZMe)(HN-SPh)]. (24 h) Yield: 93% (yellow
1
microcrystals). H NMR (CDCl3, T ) 298 K, ppm): pyridine
protons, δ, 9.39 (d, 1H, H6, J ) 6.0 Hz), 7.85 (bt, 1H, H4),
pyridine and phenyl protons 7.49-7.31 (m, 5H, H3, H5, Hortho
,
H
para), phenyl protons 7.65 (bs, 2H, Hmeta), thiomethyl protons
4.73-4.31 (broad AB system, 2H, Pyr-CH2-S), carboxylic
protons 3.84, 3.37 (s, 3H, COOCH3′R, COO CH3′′R), 3.62 (bs,
3H, COOCH3â), methyl protons 2.52, 2.04 (bs, 3H, dCCH3′,
dCCH3′′).
(25) Leir, C.M. J. Org. Chem.1997, 42, 911.
(26) (a) Ru¨lke, R. E.; Ernsting, J.; Spek, A. L.; Elsevier, C. J.; van
Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769. (b)
Rudler-Chavin, M.; Rudler, H. J. Organomet. Chem. 1977, 134, 15.

3306 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
1H NMR (CDCl3, T ) 323 K, ppm): pyridine protons, δ, 9.42
(d, 1H, H6, J ) 4.9 Hz), 7.83 (t, 1H, H4, J ) 7.9 Hz), pyridine
and phenyl protons 7.48-7.32 (m, 5H, H3, H5, Hortho, Hpara),
phenyl protons 7.67 (d, 2H, Hmeta, J ) 6.1 Hz), thiomethyl
protons 4.49 (bs, 2H, Pyr-CH2-S), carboxylic protons 3.63, (s,
6H, COOCH3R, COOCH3â), methyl protons 2.25 (bs, 3H, d
CCH3).
Pyr-CH3′), methyl protons 2.45 (s, dCCH3′), tert-butyl protons
1.45 (s, COOC(CH3)3′R), 1.44 (s, COOC(CH3)3′â).
1H NMR (CDCl3, T ) 243 K, ppm) minor rotamer: phenyl
protons, δ, 7.66 (d, H′′ortho, J′′ ) 6.6 Hz), 7.36-7.29 (m, H′′meta
,
H′′para), pyridine protons 7.56 (t, H4′′, J′′ ) 7 0.7 Hz), 7.15 (d,
H5′′, J′′ ) 7 0.7 Hz), 7.03 (d, H3′′, J′′ ) 7.7 Hz), thiomethyl
protons 5.00, 4.33 (d, Pyr-CH2′′-S, J′′ ) 16.0 Hz), methyl
protons 3.16 (s, Pyr-CH3′′), methyl protons 2.34 (s, dC CH3′′),
tert-butyl protons 1.61 (s, COOC(CH3)3′′R), 1.42 (s, COOC-
(CH3)3′′â).
1H NMR (CDCl3, T ) 243 K, ppm) major rotamer: pyridine
protons, δ, 9.35 (d, H6′, J′ ) 6.0 Hz), 7.92 (t, H4′, J′ ) 7.6 Hz),
pyridine and phenyl protons 7.52-7.32 (m, H3′, H5′, H′ortho
,
H′para), phenyl protons 7.60 (d, H′meta J′ ) 6.0 Hz), thiomethyl
protons 4.79, 4.35 (d, Pyr-CH2′-S, J′ ) 16.8 Hz), carboxylic
protons 3.87 (s, COOCH3′R), 3.61 (s, COOCH3′â), methyl
protons 1.99 (s, dCCH3′).
Rotameric ratio ≈ 1:09.
IR: (KBr pellet) νCdO 1716.3, 1683.8 cm-l, νCN 1603.2 cm-l.
Anal. Calcd for C26H34ClNO4PdS: C 52.18, H 5.73, N 2.34.
Found: C 52.07, H 5.81, N 2.37.
1H NMR (CDCl3, T ) 243 K, ppm) minor rotamer: pyridine
protons, δ, 9.35 (d, H6′′, J ) 6.0 Hz), 7.87 (t, H4′′, J′′ ) 7.6
Hz), pyridine and phenyl protons 7.52-7.32 (m, H3′′, H5′′,
H′′ortho, H′′para), phenyl protons 7.70 (d, H′′meta, J′′ ) 6.0 Hz),
thiomethyl potons 4.74, 4.23 (d, Pyr-CH2′′-S, J′′ ) 16.6 Hz),
carboxylic protons 3.63 (s, COOCH3′′R), 3.29 (s, COOCH3′′â),
methyl protons 2.52 (s, dCCH3′′).
[PdCI(Z′′CdCZ"Me) (MeN-SPh)], Z′′ ) COOEt. (5 h)
Yield: 93% (pale yellow microcrystals). 1H NMR (CDCl3, T )
298 K, ppm): phenyl protons, δ, 7.69 (bd, 2H, Hortho), 7.35-
7.27 (m, 3H, Hmeta, Hpara), pyridine protons 7.55 (t, 1H, H4, J
) 7.8 Hz), 7.14 (d, 1H, H3, J ) 7.8 Hz), 7.06 (d, 1H, H5, J )
7.8 Hz), thiomethy1 protons 4.99, 4.35 (d, 2H, Pyr-CH2S,
J ) 15.6 Hz), ethyl protons 4.22 (bs, 2H, COOCH2CH3R), 4.10
(d, 2H, COOCH2CH3â, J ) 7.2 Hz), 1.35, 1.09 (bs, 3H,
COOCH2CH3R′, COOCH2CH3 R′′), 1.23 (t, 3H, COOCH2CH3â),
methyl protons 3.15 (s, 3H, Pyr-CH3), 2.49 (bs, 3H, dCCH3).
1H NMR (CDCl3, T ) 228 K, ppm): phenyl protons, δ, 7.75,
7.69 (d, 2H, H′meta, H′′meta, J′ ) J′′ ) 6.9 Hz), 7.35-7.27 (m,
3H, Hortho, Hpara), pyridine protons 7.60 (t, 1H, H4, J ) 7.8 Hz),
7.14 (d, 1H, H3, J ) 7.8 Hz), 7.10, 7.09 (d, 1H, H5′, H5′′, J′ )
J′′ )7.8 Hz), thiomethyl protons 4.99, 4.34, 4.28 (d, 2H, Pyr-
CH2′-S, Pyr-CH2′′-S, J′ ) J′′ ) 16.2 Hz), ethyl protons 4.23-
3.95 (m, 4H, COOCH2CH3), 1.41, 0.93 (t, 3H, COOCH2CH3R,
J ) 7.2 Hz), 1.24,1.23 (t, 3H, COOCH2CH3â, J ) 7.2 Hz),
methyl protons 3.18, 3.14 (s, 3H, Pyr-CH3′, Pyr-CH3′′), 3.46,
2.54 (s, 3H, dCCH3′, dCCH3′′).
Rotameric ratio ≈ 1.4:1.
IR: (KBr pellet) νCdO 1722.9, 1695.5 cm-l, νCN 1611.0 cm-l.
Anal. Calcd for C19H20ClNO4PdS: C 45.61, H 4.03, N 2.80.
Found: C 45.75, H 3.99, N 2.71.
[PdCl(ZCdCZMe)(ClN-St-Bu)]. (0.5 h) Yield: 80% (yel-
low microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm): pyridine
protons, δ, 7.78 (t, 1H, H4, J ) 7.6), 7.44 (d, 1H, H3, J ) 7.6
Hz), 7.39 (d, 1H, H5, J ) 7.6 Hz), thiomethyl protons 4.78, 4.18
(bd, bm 2H, Pyr-CH2′-S, Pyr-CH2′′-S), carboxylic protons 3.82
(s, 3H, COOCH3R), 3.68 (s, 3H, COOCH3â), methyl protons
2.65, 2.46 (bs, 3H, dCCH3′, dC CH3′′), tert-butyl protons 1.30
(bs, 9H, S-C(CH3)3).
1H NMR (CDCl3, T ) 243 K, ppm) major rotamer: pyridine
protons, δ, 7.83 (t, H4′, J′ ) 7.8 Hz), 7 0.46 (d, H5′, J ) 7.8
Hz), 7.44 (d, H3′, J ) 7.8 Hz), thiomethyl protons 4.76, 4.16
(d, Pyr-CH2′-S, J′ ) 17.5 Hz), carboxylic protons 3.83 (s,
COOCH3′R), 3.66 (s, COOCH3′â), methyl protons 2.66 (s, d
CCH3′), tert-butyl protons 1.28 (s, S-C(CH3)3′).
Isomeric ratio ≈ 1:1.
IR: (KBr pellet) νCdO 1709.7 cm-l, νCN 1601.1 cm-l. Anal.
Calcd for C22H26ClNO4PdS: C 48.72, H 4.83, N 2.58. Found:
C 48.65, H 4.88, N 2.67.
Terdentate Complexes. [PdCl(ZCdCZMe)(SNS(Me))],
Z ) COOMe. (3 h) Yield: 89% (fairly unstable pale yellow
1H NMR (CDCl3, T ) 243 K, ppm) minor rotamer: pyridine
protons, δ, 7.84 (t, H4′′, J′′ ) 7.8 Hz), 7 0.46 (d, H5′′, J′′ ) 7.8
Hz), 7.44 (d, H3′′, J′′ ) 7.8 Hz), thiomethyl protons 4.82, 4.27
(d, Pyr-CH2′′-S, J′′ ) 17.6 Hz), carboxylic protons 3.86 (s,
COOCH3′′R), 3.66 (s, COOCH3′′â), methyl protons 2.45 (s, d
CCH3′′), tert-butyl protons 1.32 (s, S-C(CH3)3′′).
1
microcrystals). H NMR (CDCl3, T ) 298 K, ppm): pyridine
protons, δ, 7.97 (t, 1H, H4, J ) 7.7 Hz), 7.75 (d, 2H, H3, H5, J
) 7.9 Hz), thiomethyl protons 5.10 (s, 4H, Pyr-CH2-S), car-
boxylic protons 3.82 (s, 3H, COOCH3R), 3.71 (s, 3H, COOCH3â),
thiomethyl protons 2.91 (s, 6H, S-CH3), methyl protons 2.41
(s, 3H, dCCH3).
Rotameric ratio ≈ 2.9:1.
IR: (KBr pellet) νCdO 1701.1 cm-l, νCN 1591.2 cm-l. Anal.
Calcd for C17H24ClNO4PdS: C 42.51, H 5.04, N 2.92. Found:
C 42.69, H 4.97, N 2.83.
IR: (KBr pellet) νCdO 1703.1 cm-l, νCN 1597.8 cm-l. Anal.
Calcd for C16H22C1NO4PdS2: C 38.56, H 4.45, N 2.81. Found:
C 38.43, H 4.58, N 2.79.
[PdCl(Z′CdCZ′Me)(MeN-SPh)]; Z′ ) COOt-Bu. (5 h)
Yield: 92% (pale yellow microcrystals). 1H NMR (CDCl3, T )
298 K, ppm): phenyl protons, δ, 7.68 (bs, 2H, Hortho), 7.36-
7.25 (bm, 3H, Hmeta, Hpara), pyridine protons 7.53 (bt, 1H, H4),
7.12 (d, 1H, H5, J ) 7.5 Hz), 7.02 (bs, 1H, H3), thiomethyl
protons 4.99, 4.33 (d, bt, 2H, Pyr-CH2′-S, Pyr-CH2′′-S, J′ ) 16.0
Hz), methyl protons 3.16 (s, 3H, Pyr-CH3), methyl protons 2.46,
2.32 (bs, 3H, dCCH3′, dCCH3′′), tert-butyl protons 1.60, 1.49
(bs, 9H, COOC(CH3)3′R, COOC(CH3)3′′R), 1.45 (s, 9H, COOC-
(CH3)3 â).
[PdCl(ZCdCZMe)(SNS(t-Bu))]. (11 h) Yield: 94% (pale
yellow microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm):
pyridine protons, δ, 8.18 (d, 2H, H3, H5, J ) 7.6 Hz), 8.03 (t,
1H, H4, J ) 7.6 Hz), thiomethyl protons 5.19, 4.98 (br AB
system, 4H, Pyr-CH2-S), carboxylic protons 3.79 (s, 3H,
COOCH3R), 3.71 (s, 3H, COOCH3â), methyl protons 2.36 (s,
3H, dCCH3), tert-butyl protons 1.55 (bs, 9H, S-C(CH3)3).
13C NMR (CDCl3, T ) 298 K, ppm): δ, 172.7, 164.5
(COOCH3), 159.6 (C6pyr,C2pyr), 146.7, 132.0 (olefin carbons),
141.3 (C4pyr), 123.6 (C5pyr, C3pyr), 56.0 (CH2-S), 52.4, 52.0
(COOCH3R, COOCH3 â), 44.8 (C((CH3)3), 31.0 (C(CH3)3), 23.4
(dCC3). IR: (KBr pellet) νCdO 1709.7 cm-l, νCN 1597.6 cm-l.
Anal. Calcd for C22H34ClNO4PdS2: C 45.36, H 5.88, N 2.40.
Found: C 45.17, H 5.92, N 2.47.
[PdCl(ZCdCZMe)(SNS(Ph))]. (1 h) Yield: 84% (orange
microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm): phenyl and
pyridine protons, δ, 7.88 (t, 1H, H4, J ) 7.4 Hz), 7.66-7.59
(m, 6H, Hmeta, H3, H5), 7.38-7.31 (m, 6H, Hortho, Hpara),
thiomethyl protons 5.21 (s, 4H, Pyr-CH2-S), carboxylic protons
3.61 (s, 3H, COOCH3R), 3.52 (s, 3H,COOCH3â), methyl protons
2.12 (s, 3H, dCCH3). IR: (KBr pellet) νCdO 1703.1 cm-l, νCN
1H NMR (CDCl3, T ) 328 K, ppm): phenyl protons, δ, 7.68
(d, 2H, Hortho, J ) 6.9 Hz), 7.36-7.24 (bm, 3H, Hmeta, Hpara),
pyridine protons 7.53 (t, 1H, H4, J ) 7.7 Hz), 7.12 (d, 1H, H,5
J ) 7.7 Hz), 7.02 (d, 1H, H3, J ) 7.7 Hz), thiomethyl protons
4.98, 4.37 (bs, 2H, Pyr-CH2-S), methyl protons 3.16 (s, 3H, Pyr-
CH3), methyl protons 2.39 (s, 3H, dCCH3), tert-butyl protons
1.55 (bs, 9H, COOC(CH3)3R) 1.46 (s, 9H, COOC(CH3)3â).
1H NMR (CDCl3, T ) 243 K, ppm) major rotamer: phenyl
protons, δ, 7 0.73 (d, H′ortho, J′ ) 6.6 Hz), 7 0.36-7.29 (m, H′meta
,
H′para), pyridine protons 7.55 (t, H4′, J′ ) 7 0.7 Hz), 7.14 (d,
H5′, J′ ) 7 0.7 Hz), 7.06 (d, H3′, J′ ) 7.7 Hz), thiomethyl protons
4.96, 4.31 (d, Pyr-CH2′-S, J′)15.7 Hz), methyl protons 3.14 (s,

Insertion of Substituted Alkynes into Pd-C
Organometallics, Vol. 24, No. 13, 2005 3307
1604.4 cm-l. Anal. Calcd for C26H26ClNO4PdS2: C 50.17, H
4.21, N 2.25. Found: C 50.31, H 4.29, N 2.18.
7.44 (t, 1H, H4, J ) 7. 7 Hz), 7.03 (d, 1H, H3, J ) 7.7 Hz), 6.92
(bd, 1H, H5), thiomethyl protons 5.30 (bs, 2H, Pyr-CH2-S),
carboxylic protons 3.85, (s, 3H, COOCH3â),3.60 (bs, 3H,
COOCH3R), methyl protons 3.10 (s, 3H, Pyr-CH3), 2.26 (bs,
3H, dCCH3), tert-butyl protons 1.62 (s, 9H, C(CH3)3), 1.43 (s,
9H, C(CH3)3).
[PdCl(Z′CdCZ′Me)(SNS(Ph))], Z′ ) COOtBu. (1 h) Yield
75% (orange microcrystals). 1H NMR (CDCl3, T ) 298 K,
ppm): phenyl and pyridine protons, δ, 7.94 (bt, 1H, H4), 7.
71-7.65 (m, 4H, H5, H3, Hmeta), 7.34-7.32 (m, 6H, Hortho, Hpara),
thiomethyl protons 5.22 (bs, 4H, Pyr-CH2-S), methyl protons
1.95 (s, 3H, dCCH3), tert-butyl protons 1.42 (s, 18H, S-
C(CH3)3). IR: (KBr pellet) νCdO 1699.2 cm-l, νCN 1600.8 cm-l.
Anal. Calcd for C32H38ClNO4PdS2: C 54.39, H 5.42, N 1.98.
Found: C 54.52, H 5.57, N 1.92.
[PdCl(Z′′CdCZ′′Me)(SNS(Ph))], Z′′ ) COOEt. (1 h) Yield
88% (orange microcrystals). 1H NMR (CDCl3, T ) 298 K,
ppm): phenyl and pyridine protons, δ, 7.85 (t, 1H, H4, J ) 7.
7 Hz), 7.65 (d, 4H, Hmeta, J ) 6.7 Hz), 7.57 (d, 2H, H5, H3, J )
7. 7 Hz), 7.40-7.30 (m, 6H, Hortho, Hpara), thiomethyl protons
5.17 (bs, 4H, Pyr-CH2-S), ethyl protons 4.07 (q, 2H, COOCH2-
CH3R, J ) 7.1 Hz), 4.04 (q, 2H, COO CH2CH3â, J ) 7.1 Hz),
methyl protons 2.15 (s, 3H, dCCH3), 1.21 (t, 3H, COOCH2-
CCH3R , J ) 7 Hz), 1.15 (t, 3H, COOCH2CH3â, J ) 7.1 Hz).
IR: (KBr pellet) νCdO 1696.5 cm-l, νCN 1604.4 cm-l. Anal. Calcd
IR: (KBr pellet) νCdO 1709.7 cm-l, νCN 1606.1 cm-l. Anal.
Calcd for C32H40ClNO8PdS: C 51.90, H 4.79, N 1.89. Found:
C 51.77, H 4.71, N 1.78.
[PdCl(Z′CdCZ′-CZdCZMe)(MeN-SPh)], Z′ ) COOt-Bu,
Z ) COOMe. (30 h) Yield: 99% (yellow microcrystals). 1H
NMR (CDCl3, T ) 298 K, ppm): phenyl protons, δ, 7.77 (m,
2H, Hortho), 7.31-7.22 (bm, 3H, Hmeta, Hpara), pyridine protons
7.48 (t, 1H, H4, J ) 7.7 Hz), 7.03 (d, 2H, H3, H5, J ) 7.7 Hz),
thiomethyl protons 5.55, 4.50 (bs, 2H, Pyr-CH2-S), carboxylic
protons 3.86 (s, 3H, COOCH3), 3.66 (s, 3H, COOCH3), methyl
protons 3.03 (s, 3H, Pyr-CH3), 2.37 (bs, 3H, dCCH3), tert-butyl
protons 1.59 (s, 9H, COOC(CH3)3 â), 1.28 (bs, 9H, COOC(CH3)3
R).
IR: (KBr pellet) νCdO 1729.4 cm-l, νCN 1602.0 cm-l. Anal.
Calcd for C32H40ClNO8PdS: C 51.90, H 4.79, N 1.89. Found:
C 52.03, H 4.68, N 1.93.
for C28H30ClNO4PdS2: C 51.69, H 4.65, N 2.15. Found:
51.57, H 4.61, N 2.19.
C
Complexes from Ligand Metathesis. [PdCl(ZCdCZMe)-
(DPPQ-Me)], Z ) COOMe. To a suspension of 0.050 g (0.097
mmol) of [PdCl(ZCdCZMe)(MeN-SPh)] in 6 mL of freshly
distilled anhydrous CH2Cl2 was added 0.0325 g (0.099 mmol)
of DPPQ-Me, and the reaction mixture was stirred for 30 m.
The solution was concentrated under reduced pressure, and
the complex was precipitated as a whitish solid by addition of
diethyl ether. The product was filtered off, washed with small
aliquots of diethyl ether, and dried under vacuum (0.058 g,
yield 93%). 1H NMR (CDCl3, T ) 298 K, ppm): quinoline
protons, δ, 8.17 (d, 1H, H4, J ) 6.5 Hz), 7.78-7.51 (m, 4H),
phenyl protons 8.03-7.88 (m, 4H), 7.50-7.37 (m, 6H), car-
boxylic protons 3.66 (s, 3H, COOCH3), 3.46 (s, 3H, COOCH3),
methyl protons 3.41 (s, 3H, Pyr-CH3), 1.85 (s, 3H, dCCH3).
31P NMR (CDCl3, T ) 298 K, ppm): δ, 37.7 (s, 1P). IR: (KBr
pellet) νCdO 1716.3 cm-l, νCN 1606.6 cm-l. Anal. Calcd for
C29H27ClNO4PPd: C 55.61, H 4.34, N 2.24. Found: C 55.73,
H 4.23, N 2.27.
Synthesis of Butadienyl Complexes. [PdCl((ZCd
CZ)2Me)(MeN(SPh))], Z ) COOMe. To a solution of 0.098 g
(0.19 mmol) of [PdCl(ZCdCZMe)(MeN-SPh)] in 6 mL of freshly
distilled anhydrous CH2C12 was added 69.95 µL (0.57 mmol)
of DMAD, and the mixture was stirred at RT for 22 h. The
yellow solution was concentrated at reduced pressure, and the
title complex was precipitated by addition of diethyl ether. The
yellow microcrystals were filtered off, washed with small
aliquots of diethyl ether, and dried under vacuum (0.095 g;
yield 77%).
1H NMR (CDCl3, T ) 328 K, ppm): phenyl protons, δ, 7.73-
7.70 (m, 2H, Hortho), 7.29-7.25 (m, 3H, Hmeta, Hpara), pyridine
protons 7.47 (t, 1H, H4, J ) 7.7 Hz), 7.05 (d, 1H, H3, J ) 7.7
Hz), 6.96 (d, 1H, H5, J ) 7.7 Hz), thiomethyl protons 4.75 (bs,
2H, Pyr-CH2-S), carboxylic protons 3.87, 3.86, 3.67 (s, 9H,
COOCH3â, γ, δ), 3.41 (bs, 3H, COOCH3R), methyl protons 3.10
(s, 3H, Pyr-CH3), 2.18 (s, 3H, dCCH3).
1H NMR (CDCl3, T ) 258 K, ppm) major rotamer: phenyl
protons, δ, 7.82-7.63 (m, H′ortho), 7.40-7.22 (m, H′meta, H′para),
pyridine protons 7.48 (t, H4′, J′ ) 7.6 Hz), 7.06 (d, H3′, J ) 7.6
Hz), 6.92 (d, H5′, J′ ) 7.6 Hz), thiomethyl protons 5.15, 4.13
(d, Pyr-CH2′-S, J′ ) 15.6 Hz), carboxylic protons 3.93, 3.88,
3.62, 2.64 (s, COOCH3′), methyl protons 3.12 (s, Pyr-CH3′), 2.41
(s, dCCH3′).
[PdCl((ZCdCZ)2Me)(DPPQ-Me)], Z ) COOMe. The syn-
thesis of the title complex is analogous to that of the former
species, starting from the appropriate substrate (0.5 h).
Yield: 89% (pale yellow microcrystals). 1H NMR (CDCl3, T )
298 K, ppm): quinoline protons, δ, 8.14 (d, 1H, H,4 J ) 6.5
Hz), quinoline and phenyl protons 7.91-7.38 (m, 14H), car-
boxylic protons 3.88 (s, 3H, COOCH3), 3.56 (s, 3H, COOCH3),
3.37 (s, 3H, COOCH3), 3.34 (s, 3H, COOCH3), methyl protons
3.32 (s, 3H, Pyr-CH3), 2.09 (s, 3H, dCCH3). 31P NMR (CDCl3,
T ) 298 K, ppm): δ, 36.3 (s, lP). IR: (KBr pellet) νCdO 1724.3,
1699.2 cm-l, νCN 1604.4 cm-l. Anal. Calcd for C35H33ClNO8-
PPd: C 54.70, H 4.33, N 1.82. Found: C 54.57, H 4.39, N 1.87.
The following complexes were separated from the NMR test
tube by concentration of the reaction mixture and precipitation
with diethyl ether. Each single species was characterized by
1H NMR and IR spectroscopy but not elementally analyzed.
[PdCl(ZCdCZMe)(DPPE)], Z ) COOMe. Yield ≈ 75%
(whitish microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm):
phenyl protons, δ, 8.07 (m, 2H), 7.72 (m, 6H), 7.59-7.32 (m
14H), carboxylic protons 3.57 (s, 3H, COOCH3), 3.52 (s, 3H,
COOCH3), methylenic protons 2.75-2.34 (m, 3H), 1.81-1.65
(m, 1H), methyl protons 1.62 (s, 3H, dCCH3). 31P NMR (CDCl3,
T ) 298 K, ppm): δ, 55.75 (d, 1P, J ) 23.8), 40.01 (d, 1P, J )
23.8). IR: (KBr pe1let) νCdO 1709.7 cm-l, νCN 1591.2 cm-l.
[PdCl((ZCdCZ)2Me)(DPPE)], Z ) COOMe. Yield ≈ 70%
(whitish microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm):
phenyl protons, δ, 7.91 (m, 4H), 7.68 (m, 4H), 7.51-7.18 (m
12H), carboxylic protons 3.75 (s, 3H, COOCH3), 3.64 (s, 3H,
COOCH3), 3.61 (s, 3H, COOCH3), 3.13 (s, 3H, COOCH3),
methylenic protons 2.81-2.20 (m, 3H), 1.78-1.62 (m, 1H),
methyl protons, 1.65 (s, 3H, dCCH3). 31P NMR (CDCl3, T )
1H NMR (CDCl3, T ) 258 K, ppm) minor rotamer: phenyl
protons, δ, 7.82-7.63 (m, H′′ortho), 7.40-7.22 (m, H′′meta, H′′para),
pyridine protons 7.54 (t, H4′′, J′′ ) 7 0.6 Hz), 7.06 (d, H3′′, J )
7.6 Hz), 7.01 (d, H5′′, J′′ ) 7.6 Hz), thiomethyl protons 5.60,
4.33 (d, Pyr-CH2′′-S, J′′ ) 16.2, J′′ ) 15.6 Hz), carboxylic
protons 3.97, 3.88, 3.79, 3.69 (s, COOCH3′′), methyl protons
3.01 (s, Pyr-CH3′′), 2.14 (bs, dCCH3′′).
13C NMR (CDCl3, T ) 298 K, ppm): δ, 171.6 (COOCH3),
163.4 (C6pyr), 161.8 (COOCH3), 156.0 (C2pyr), 139.0 (C4pyr), 133.0
(broad, CdC), 130.7, 130.1, 129.1 (phenyl carbons), 125.3(C5pyr),
121.1 (C3pyr), 52.7, 52.5 (COOCH3), 50.8 (broad, CH2-S), 26.4
(Pyr-CH3), 19.4 (broad dCCH3).
Rotameric ratio ≈ 1.4:1.
IR: (KBr pellet) νCdO 1736.0, 1709.7, 1689.9 cm-l, νCN 1604.4
cm-l. Anal. Calcd for C26H28ClNO8PdS: C 47.57, H 4.30, N
2.13. Found: C 47.73, H 4.22, N 2.18.
The following complexes were prepared under conditions
analogous to those of [PdCl((ZCdCZ)2Me)(MeN-SPh)] using the
appropriate starting substrates. The reaction time for each
complex is reported in parentheses.
[PdCl(ZCdCZ-CZ′dCZ′Me)(MeN-SPh)], Z ) COOMe, Z′
) COOt-Bu. (30 h) Yield: 90% (whitish microcrystals). 1H
NMR (CDCl3, T ) 328 K, ppm): phenyl protons, δ, 7.71 (m,
2H, Hortho), 7.30-7.20 (m, 3H, Hmeta, Hpara), pyridine protons

3308 Organometallics, Vol. 24, No. 13, 2005
Canovese et al.
298 K, ppm): δ, 53.7 (d, 1P, J ) 9.3), 44.6 (d, 1P, J ) 19.3).
IR: (KBr pe1let) νCdO 1716.6 cm-l, νCN 1598.9 cm-l.
Hz), 7.05 (d, 1H, H5, J ) 7. 7 Hz), thiomethyl protons 5.02
(bs, 1H, Pyr-CH2-S), 4.32 (bs, 1H, Pyr-CH2-S), carboxylic
protons 3.76 (bs, 3H, COOCH3R), 3.65 (s, 3H, COOCH3â),
methyl protons 3.20 (s, 3H, Pyr-CH3), 2.41 (s, 3H, dCCH3).
1H NMR (CDCl3, T ) 243 K, ppm) major rotamer: phenyl
protons, δ, 7.61 (d, H′ortho), 7.38-7.26 (m, H′meta, H′para), pyridine
protons 7.57 (t, H4′, J′ ) 7.7 Hz), 7.16 (d, H3′, J′ ) 7.7 Hz),
7.08 (d, H5′, J′ ) 7.7 Hz), thiomethyl protons 5.08 (d, Pyr-CH2′-
S, J′ ) 16.1 Hz), 4.31 (d, Pyr-CH2′-S, J′ ) 16.1 Hz), carboxylic
protons 3.74 (s, COOCH3′R), 3.66 (s, COOCH3′â), methyl
protons 3.18 (s, Pyr-CH3′), 2.44 (s, dCCH3′).
1H NMR (CDCl3, T ) 243 K, ppm) minor rotamer: phenyl
protons, δ, 7.64 (d, H′′ortho), 7.38-7.26 (m, H′′meta, H′′para),
pyridine protons 7.57 (t, H4′′, J′′ ) 7.7 Hz), 7.17 (d, H3′′, J′′
) 7.7 Hz), 7.09 (d, H5′′, J′′ ) 7.7 Hz), thiomethyl protons
5.06 (d, Pyr-CH2′′-S, J′′ ) 15.5 Hz), 4.37 (d, Pyr-CH2′′-S, J′′ )
15.5 Hz), carboxylic protons 3.86 (s, COOCH3′′R), 3.64 (s,
COOCH3′′â), methyl protons 3.23 (s, Pyr-CH3′′), 2.39 (s,
dCCH3′′).
[PdCl(ZCdCZMe)(bipy)], Z ) COOMe. Yield ≈ 70%
(whitish microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm):
bipyridyl protons, δ, 9.27, 9.02 (d, 2H, H2, H12, J ) 5.2 Hz),
8.07 (m, 4H, H4, H5, H8, H9), 7.59 (m, 2H, H6, H10), carboxylic
protons 3.84 (s, 3H, COOCH3), 3.73 (s, 3H, COOCH3), methyl
protons 2.51 (s, 3H, dCCH3). IR: (KBr pe1let) νCdO 1701.7
cm-l, νCN 1585.2 cm-l.
[PdCl((ZCdCZ)2Me)(bipy)], Z ) COOMe. Yield ≈ 70%
(whitish microcrystals). 1H NMR (CDCl3, T ) 298 K, ppm):
bipyridyl protons, δ, 9.23, 9.03 (d, 2H, H2, H12, J ) 5.2 Hz),
8.04 (m, 4H, H4, H5, H8, H9), 7.55 (m, 2H, H6, H10), carboxylic
protons 3.90 (s, 3H, COOCH3), 3.74 (s, 3H, COOCH3), 3.71 (s,
3H, COOCH3), 3.33 (s, 3H, COOCH3), methyl protons 2.12 (s,
3H, dCCH3). IR: (KBr pe1let) νCdO 1736.0, 1729.4, 1689,0
cm-l, νCN 1601.2 cm-l.
Complex from Halide Metathesis. [PdI(ZCdCZMe)-
(MeN-SPh)], Z ) COOMe. To a solution of 0.080 g (0.16
mmol) of [PdCl(ZCdCZMe)(MeN-SPh)] in 8 mL of freshly
distilled anhydrous CH2Cl2 was added 0.145 g (0.96 mmol) of
NaI under inert atmosphere (Ar). The heterogeneous mixture
was stirred for 1 h, and the pink-orange solution was separated
from the undissolved NaCl by filtration. The solution was
washed twice with 10 mL of water in a separatory funnel to
remove the dissolved inorganic salts and treated with CaCl2
for 2 h. The solid CaCl2 was filtered off, and the solution was
concentrated under reduced pressure. Addition of diethyl ether
yielded the title product, which was washed with several
aliquots of diethyl ether and dried under vacuum (0.076 g,
yield 80%). 1H NMR (CDCl3, T ) 298 K, ppm): phenyl protons,
δ, 7.63 (bd, 2H, Hortho), 7.31-7.29 (m, 3H, Hmeta, Hpara), pyridine
protons 7.54 (t, 1H, H4, J ) 7.7 Hz), 7.14 (d, 1H, H3, J ) 7.7
Rotameric ratio ≈ 1.2:1.
IR: (KBr pellet) νCdO 1716.3,1706.1 cm-1,νCN 1599.1 cm-1
.
Anal. Calcd for C20H22INO4PdS: C 39.65, H 3.66, N 2.31.
Found: C 39.63, H 3.71, N 2.28.
Supporting Information Available: Text giving details
of the X-ray crystal structure studies and table of crystal
structure determination data, atomic coordinates, anisotropic
thermal parameters, bond lengths and angles (CIF files) and
NOESY graphic output are available free of charge via the
Internet at http://pubs.acs.org.
OM058005Y