The trans-chlorometalation of hetero-substituted alkynes: A facile entry to unsymmetrical palladium YCY′ (Y, Y′ = NR2, PPh2, OPPh2, and SR) pincer complexes

Article abstract of DOI:10.1021/om011002a

A simple and efficient method for the preparation of unsymmetrical palladium YCY′PdCl (Y, Y′ = NR₂, Py, PPh₂, OPPh₂, and SR) pincer complexes has been disclosed from the chloropalladation of hetero-substituted alkynes. This method tolerates a variety of alkyne functional groups (amines, pyridine, thioethers, phosphines, and phosphinites) and allows the preparation of palladacycles containing different metalated ring sizes. Thus the reaction of Li₂PdCl₄ with hetero-substituted alkynes Me₂NCH₂C≡CCH₂CH₂Y (Y = S-t-Bu, NMe₂, PPh₂, and OPPh₂) 1-4 affords the pincer palladacycles (Me₂NCH₂(Cl)C=CCH₂CH₂Y-κN, κC,κY)PdCl 7-10, in high yields. Under the same reaction conditions the chloropalladation of o-MeSC₆H₄C≡CCH₂NMe₂, 5, and o-NC₅H₄C≡CCH₂CH₂S-t-Bu, 6, yields (C₆H₄(o-MeS)C= C(Cl)CH₂NMe₂-κS,κC,κN)PdCl, 11, and (t-BuSCH₂CH₂C=C(Cl)(o-NC₅H₄)-κ S,κC,κN)PdCl, 12, respectively. The molecular structures of compounds 7 and 11 have been ascertained by means of X-ray diffraction analyses. IR and NMR spectroscopic investigation of the species involved in these reactions suggests that the chloropalladation reaction proceeds through the coordination of only one donor group followed by coordination of the C≡C bond to the metal center. Selective intermolecular chloride nucleophilic addition on this activated unsaturated bond affords the more thermodynamically stable palladacyclic ring. Finally, coordination of the second donor group to the Pd center yields the pincer palladacycles.

Full text of DOI:10.1021/om011002a

Organometallics 2002, 21, 3221-3227
3221
Th e tr a n s-Ch lor om eta la tion of Heter o-Su bstitu ted
Alk yn es: A F a cile En tr y to Un sym m etr ica l P a lla d iu m
YCY′ (Y, Y′ ) NR2, P P h 2, OP P h 2, a n d SR) “P in cer ”
Com p lexes
Gunter Ebeling,† Mario R. Meneghetti,† Frank Rominger,‡ and J airton Dupont*,†
Laboratory of Molecular Catalysis, Institute of Chemistry, UFRGS, Av. Bento Gonc¸alves,
9500 Porto Alegre 91501-970 RS Brazil, and Organisch-Chemisches Institut der
Ruprecht-Karls-Universita¨t Heidelberg, Im Neuenheimer Feld 270,
D-69120 Heidelberg, Germany
Received November 20, 2001
A simple and efficient method for the preparation of unsymmetrical palladium YCY′PdCl
(Y, Y′ ) NR2, Py, PPh2, OPPh2, and SR) “pincer” complexes has been disclosed from the
chloropalladation of hetero-substituted alkynes. This method tolerates a variety of alkyne
functional groups (amines, pyridine, thioethers, phosphines, and phosphinites) and allows
the preparation of palladacycles containing different metalated ring sizes. Thus the reaction
of Li2PdCl4 with hetero-substituted alkynes Me2NCH2CtCCH2CH2Y (Y ) S-t-Bu, NMe2,
PPh2, and OPPh2) 1-4 affords the “pincer” palladacycles (Me2NCH2(Cl)CdCCH2CH2Y-
κN,κC,κY)PdCl 7-10, in high yields. Under the same reaction conditions the chloropalladation
of o-MeSC6H4CtCCH2NMe2, 5, and o-NC5H4CtCCH2CH2S-t-Bu, 6, yields (C6H4(o-MeS)Cd
C(Cl)CH2NMe2-κS,κC,κN)PdCl, 11, and (t-BuSCH2CH2CdC(Cl)(o-NC5H4)-κS,κC,κN)PdCl, 12,
respectively. The molecular structures of compounds 7 and 11 have been ascertained by
means of X-ray diffraction analyses. IR and NMR spectroscopic investigation of the species
involved in these reactions suggests that the chloropalladation reaction proceeds through
the coordination of only one donor group followed by coordination of the CtC bond to the
metal center. Selective intermolecular chloride nucleophilic addition on this activated
unsaturated bond affords the more thermodynamically stable palladacyclic ring. Finally,
coordination of the second donor group to the Pd center yields the “pincer” palladacycles.
In tr od u ction
will facilitate the investigation of their steric and
electronic properties by placing, for example, soft and
hard donating groups on the same metalated ligand. We
wish to disclose herein some of our results in the
establishment of a general method for the synthesis of
such palladacycles. The method is based on the chloro-
palladation reaction of propargylamines and -thioethers,
which has been successfully used for the preparation
Palladium complexes containing NCN, PCP, and SCS
“pincer” (tridentate and anionic six-electron donor)
ligands are a popular and widely investigated class of
palladacycles (Chart 1).1
These compounds exhibit a wide range of reactivity
and applications encompassing precursors for organo-
metallic catalysis, organometallic dendrimers, new ma-
terials, intermediates for organic synthesis, etc.2 With
rare exceptions3,4 these palladium YCY′ “pincer” com-
plexes are symmetrical (Y ) Y′) and their synthesis is
usually performed by direct palladation of the aryl
ring (C-H bond activation), transmetalation reactions
(mainly from aryllithium derivatives), by oxidative
addition of the hetero-substituted aryl halide onto Pd-
(0) precursors (Scheme 1) or more recently by transcy-
clometalation.1,2
(2) See for example: (a) Albrecht, M.; Kocks, B. M.; Spek, A. L.;
van Koten, G. J . Organomet. Chem. 2001, 624, 271-286. (b) Be-
letskaya, I. P.; Chuchurjukin, A. V.; Dijkstra, H. P.; van Klink, G. P.
M.; van Koten, G. Tetrahedron Lett. 2000, 41, 1075-1079. (c) Morales-
Morales, D.; Redon, R.; Yung, C.; J ensen, C. M. Chem. Commun. 2000,
1619-1620. (d) Bedford, R. B.; Draper, S. M.; Scully, P. N.; Welch, S.
L. New J . Chem. 2000, 24, 745-747. (e) Gruber, A. S.; Zim, D.; Ebeling,
G.; Monteiro, A. L.; Dupont, J . Org. Lett. 2000, 2, 1287-1290. (f)
Bergbreiter, D. E.; Osburn, P. L.; Liu, Y. S. J . Am. Chem. Soc. 1999,
121, 9531-9538. (g) Miyazaki, F.; Yamaguchi, K.; Shibasaki, M.
Tetrahedron Lett. 1999, 40, 7379-7383. (h) Steenwinkel, P.; Gossage,
R. A.; Maunula, T.; Grove, D. M.; van Koten, G. Chem. Eur. J . 1998,
4, 763-768. (i) Huck, W. T. S.; vanVeggel, F. C. J . M.; Reinhoudt, D.
N. Angew. Chem., Int. Ed. Engl. 1996, 35, 1213-1215. (j) Loeb, S. J .;
Shimizu, G. K. H. J . Chem. Soc., Chem. Commun. 1993, 1395-1397.
(l) Portnoy, M.; BenDavid, Y.; Milstein, D. Organometallics 1993, 12,
4734-4735. (m) Haenel, M. W.; J akubik, D.; Kruger, C.; Betz, P. Chem.
Ber. 1991, 124, 333-336. (n) Dupont, J .; Beydoun, N.; Pfeffer, M. J .
Chem. Soc., Dalton Trans. 1989, 1715-1720. (o) Rimml, H.; Venanzi,
L. M. Phosphorus Sulfur 1987, 30, 297-300. (p) Errington, J .;
McDonald, W. S.; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1980,
2312-2314. (q) Moulton, C. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans.
1976, 1020-1024. (r) Dijkstra, H. P.; Albrecht, M.; van Koten, G. Chem.
Commun. 2002, 126-127.
It can be anticipated that the availability of unsym-
metrical palladium YCY′ (Y * Y′) “pincer” complexes
* E-mail: dupont@iq.ufrgs.br.
† Laboratory of Molecular Catalysis. Institute of Chemistry.
‡ Organisch-Chemisches Institut der Ruprecht-Karls-Universita¨t
Heidelberg.
(1) For recent reviews see: (a) Steenwinkel, P.; Gossage, R. A.; van
Koten, G. Chem. Eur. J . 1998, 4, 759-762. (b) Dupont, J .; Pfeffer, M.;
Spencer, J . Eur. J . Inorg. Chem. 2001, 4, 1917-1927. (c) Albrecht, M.;
van Koten, G. Angew. Chem., Int. Ed. 2001, 40, 3750-3781.
10.1021/om011002a CCC: $22.00 © 2002 American Chemical Society
Publication on Web 06/25/2002

3222 Organometallics, Vol. 21, No. 15, 2002
Ebeling et al.
Ch a r t 1. Exa m p les of Sym m etr ica l “P in cer
P a lla d a cyles”
Sch em e 3a
a
(i) HCHO/HNMe2, CuI, dioxane, reflux; (ii) Pd(PPh3)4, CuI,
NEt3, DMF, RT.
Sch em e 1a
Ch a r t 2. “P in cer ” P a lla d a cycles Com p lexes
Obta in ed via Ch lor op a lla d a tion Rea ction of th e
Heter o-Su bstitu ted Alk yn es
a
Z ) H, Li, MgCl, etc.; X ) Br, I, etc.
Sch em e 2a
a
(i) HCHO/HNMe2, CuI, dioxane, reflux; (ii) TsCl, CH2Cl2,
NEt3, 0 °C; (iii) t-BuSNa, EtOH, RT or HNMe2, CH2Cl2, RT or
NaPPh2, THF, 0 °C; (iv) ClPPh2, NEt3, CH2Cl2, 0 °C.
a dark red methanolic solution of Li2PdCl4 at 5 °C
affords almost instantaneously a dark yellow solution.
Palladacycles 7 and 8 where isolated in good yields from
these solutions by extraction with dichloromethane and
precipitation with hexanes. On the other hand, the
addition of an alkynes 3-6 to a methanolic solution of
Li2PdCl4 at 5 °C leads almost instantaneously to the
precipitation of a light yellow solid, which gradually
dissolves to afford a dark yellow solution after stirring
at room temperature for ca. 1-3 h. Evaporation of the
volatiles under reduced pressure, extraction with dichlo-
romethane, and filtration over a plug of Celite affords
a yellow solution. Concentration of these reaction solu-
tions under reduced pressure and addition of hexanes
affords the palladacycles 9-12 as yellow solids.
of various “classical” five-membered nitrogen- and sulfur-
containing palladacycles.5
Resu lts a n d Discu ssion
Syn th esis of th e Liga n d s. The hetero-substituted
alkynes 1-4 were prepared by Mannich reactions6 with
the homopropargyl alcohol followed by functionalization
with sodium thiolate, dimethylamine, lithiumdiphe-
nylphosphide, or chlorodiphenyl phosphine (Scheme 2).
Alternatively, the alkyne containing amino and thio-
ether groups 5 can be prepared directly from the easily
available 1-methylthio-2-ethynylbenzene7 (Scheme 3).
The alkyne 6 was prepared using a Sonogashira8
coupling as described in Scheme 3. All the alkynes were
Palladacycles 7-12 are light yellow air- and moisture-
stable crystalline solids, which are highly soluble in
most polar organic solvents such as dichloromethane
and acetone and slightly soluble in hexanes and diethyl
ether. Compounds 7-12 have relatively high thermal
stabilities. They start to decompose only above 140 °C.
The palladacycles 7-12 were characterized by means
1
characterized by GC-MS, IR, and H and 13C{1H} NMR
spectroscopy (see Experimental Section).
Syn th eses a n d Ch a r a cter iza tion of th e “P in cer ”
P a lla d a cyles. The palladium YCY′ “pincer” complexes
7-12 (Chart 2) were obtained in high yields (70-95%)
from the reaction of alkynes 1-6 with Li2PdCl4. Thus,
the addition of equimolar amounts of alkynes 1 or 2 to
1
of CHN combustion analysis, IR, and H and 13C{1H}
NMR spectroscopy. The CHN analyses indicated that
one PdCl2 fragment has been incorporated per alkyne
unit. The IR spectra of these compounds exhibit a band
between 1580 and 1650 cm-1, which is characteristic
for a ν(CdC) vibration. Two distinct resonances for the
nonaromatic CdC bond were observed in the 13C NMR
spectra of 7-12 in CDCl3: one at low field (140-150
ppm) and another at high field (110-125 ppm) charac-
teristic for sp2 carbons bonded to a chlorine atom and a
(3) Holton, R. A.; Sibi, M. P.; Murphy, W. S. J . Am. Chem. Soc. 1988,
110, 314-316.
(4) For metallacycles containing the (CNS)- terdentate group see:
Riera, X.; Lo´pez, C.; Caubet, A.; Moreno, V.; Solans, X.; Font-Bardia,
M. Eur. J . Inorg. Chem. 2001, 2135-2141, and references therein.
(5) (a) Dupont, J .; Basso, N. R.; Meneghetti, M. R. Polyhedron 1996,
15, 2299-2302. (b) Dupont, J .; Basso, N. R.; Meneghetti, M. R.;
Konrath, R. A.; Burrow, R.; Horner, M. Organometallics 1997, 16, 2386-
2391.
(6) Dyatkin, A. B.; Rivero, R. A. Tetrahedron Lett. 1998, 39, 3647-
3650.
(7) Klusener, P. A. A.; Hanekamp, J . C.; Brandsma, L.; Schleyer,
P. V. J . Org. Chem. 1990, 55, 1311-1321.
(8) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975,
4467-4470.
1
Pd(II) center, respectively. The H NMR signals related
to the NMe2, S-t-Bu, and SMe groups of palladacycles
7-12 appear at ca. 0.6-1.0 ppm downfield shifted

Unsymmetrical Palladium “Pincer” Complexes
Organometallics, Vol. 21, No. 15, 2002 3223
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 7 a n d 11
7
111
112
Bond Lengths
Pd-C4
Pd-N7
Pd-S
1.980(2) Pd-C8
2.126(2) Pd-N11
2.276(1) Pd-S1
2.393(1) Pd-Cl1
1.772(3) Cl2-C9
1.823(3) S1-C2
1.854(3) S1-C14
1.515(4) C2-C3
1.507(4) C3-C8
1.317(4) C8-C9
1.493(4) C9-C10
1.488(3) C10-N11
1.986(3)
2.091(3)
2.240(1)
2.388(1)
1.765(3)
1.783(4)
1.810(4)
1.405(5)
1.481(5)
1.323(4)
1.492(5)
1.495(4)
1.983(3)
2.091(3)
2.242(1)
2.394(1)
1.761(3)
1.784(4)
1.810(4)
1.395(5)
1.486(5)
1.333(4)
1.481(5)
1.492(5)
Pd-Cl1
Cl2-C5
S1-C2
S1-C11
C2-C3
C3-C4
C4-C5
C5-C6
C6-N7
F igu r e 1. Molecular structure of the complex (t-BuSCH2-
CH2CdC(Cl)CH2NMe2-κS,κC,κN)PdCl (7). Hydrogen atoms
were omitted for clarity.
Bond Angles
82.1(1) C8-Pd-N11
83.5(1) C8-Pd-S1
163.4(1) N11-Pd-S1
175.5(1) C8-Pd-Cl1
104.7(1) C2-S1-C14
99.2(1) C21-S1-Pd
118.2(1) C14-S1-Pd
109.7(2) C2-C3-C8
113.0(2) C9-C8-Pd
120.4(2) C3-C8-Pd
122.7(2) C8-C9-C10
123.0(2) C8-C9-Cl2
108.7(2) C9-C10-N11
105.7(2) C12-N11-C13
108.2(2) C10-N11-Pd
116.7(2) C13-N11-Pd
C4-Pd-N7
C4-Pd-S1
N7-Pd-S1
C4-Pd-Cl1
C2-S1-C11
C2-S1-Pd
C11-S1-Pd
C2-C3-C4
C5-C4-Pd
C3-C4-Pd
C4-C5-C6
C4-C5-Cl2
N7-C6-C5
C3-C2-S1
C6-N7-Pd
C9-N7-Pd
84.59(12) 84.0(1)
86.99(10) 85.9(1)
170.65(8) 169.1(1)
176.13(9) 176.7(1)
102.42(17) 103.3(2)
100.23(12) 100.0(1)
103.17(15) 106.3(2)
117.4(3)
111.3(3)
117.9(2)
122.0(3)
127.2(3)
109.1(3)
109.0(3)
106.6(2)
105.7(2)
66.4
116.4(3)
110.9(3)
118.6(2)
121.9(3)
126.4(3)
108.9(3)
108.6(3)
106.1(2)
105.9(2)
58.0
C11-S1-Pd-Cl1 45.0
C9-N7-Pd-Cl1 37.7
C11-S1-N7-C9 7.2
C14-S1-Pd-Cl1
C13-N11-Pd-Cl1 78.9
C14-S1-N11-C13 26.3
84.3
12.8
Ta ble 2. Su m m a r y of th e Cr ysta l Da ta a n d
Str u ctu r e Refin em en t for 7 a n d 11
7
11
chem formula
temperature (K)
wavelength (Å)
cryst syst
space group
Z
a (Å)
b (Å)
c (Å)
C
11H21Cl2NPdS
C12H15Cl2NPdS
200(2)
0.71073
monoclinic
P21/c
8
17.7871(1)
11.5507(1)
15.2392(1)
109.951(1)
2943.04(4)
1.73
200(2)
0.71073
monoclinic
P21/n
F igu r e 2. Molecular structures of the complex (C6H4-
(o-SMe)CdC(Cl)CH2NMe2-κS,κC,κN)PdCl (11). Hydrogen
atoms were omitted for clarity.
4
6.0892(1)
28.9582(3)
8.4416(1)
92.258(1)
1487.37(3)
1.68
1.72
0.86 and 0.73
polyhedron
compared to the resonances of the free ligands (1-6).
â (deg)
4
volume (Å3)
The typical spin-coupling values of J PH ) 2.5-2.9 Hz
calc (g/cm3)
3
F
and J PC ) 3.0 Hz between the P atom and the
µ (mm-1
)
1.744
hydrogens and carbons of the NMe2 group, respectively,
are strong indications of the trans relationship between
the NMe2 and PPh2 groups for compounds 9 and 10.
X-r a y Str u ctu r e of P a lla d a cycles 7 a n d 11. The
structures of compounds 7 and 11 were ascertained by
means of X-ray diffraction analysis. ORTEP drawings
of the structures of 7 and 11 are shown in Figures 1
and 2, respectively.
max./min. transm
cryst shape
0.95 and 0.71
polyhedron
0.28 × 0.18 × 0.12
2.14 to 27.49
cryst dimens (mm3) 0.44 × 0.14 × 0.11
θ range data collect. 1.4 to 27.5
(deg)
index range
-7 e h e 7,
-37 e k e 37,
-10 e l e 10
-23 e h e 18,
-14 e k e 8,
12 e l e 19
11 109
no. of collect. reflns 12 555
no. of ind reflns
no. of obsd reflns
(I >2σ(I))
no. of data/restr/
params
3389 (Rint ) 0.0360) 6340 (Rint ) 0.0312)
3051
Selected bond distances and angles are presented in
Table 1. Crystallographic data and details of the struc-
ture determination are presented in Table 2. Tables of
atomic coordinates, hydrogen coordinates, and aniso-
tropic thermal parameters are supplied as Supporting
Information.
In compound 7 the Pd(II) center is coordinated in a
distorted square-planar fashion by the N and the S
donor groups, a C(sp2) vinyl atom of the anionic ter-
dentate ligand system, and a Cl atom. The C(vinyl)-
Pd-Cl bond angle is 175.5° and the S and N donor
groups are also in mutual trans positions with a bond
angle of 163.4°, showing an angular deviation of 16.6°
4807
3389/0/150
6340/0/314
R-indices (I > 2σ(I)) R(F) ) 0.027,
R(F) ) 0.034,
wR2(F2) ) 0.075
0.90 and -0.88
wR2(F2) ) 0.056
0.38 and -0.62
largest peak/hole
(e Å-3
)
from exact trans coordination. This distortion from the
ideal square-planar arrangement is the result of the
small N-Pd-C(vinyl) and S-Pd-C(vinyl) bite angles
in the two five-membered rings of 83.0° and 83.5°,
respectively. The σ Pd-C(vinyl) single bond in 7 (1.980

3224 Organometallics, Vol. 21, No. 15, 2002
Ebeling et al.
Sch em e 4
Sch em e 5
Å) is slightly shorter than observed in similar com-
pounds, where the distances fall in the range between
1.991 and 2.011 Å.9 The two five-membered rings have
a distinct puckering; see Figure 1. This is due to the
presence or not of a double bond in each ring. The bulky
tert-butyl group, bounded to the S atom, is in an
equatorial position as expected.
Sch em e 6
The crystal structure of 11 consists of two indepen-
dent molecules found in the asymmetric unit, with a
close nonbonding contact between the two Pd centers
(3.77 Å). These two structures are quite similar to each
other and show a coordination environment around each
Pd(II) center similar to the one encountered in the
“pincer” palladacycle 7. In both molecules of 11 the
distances between the Pd(II) center and the coordinated
atoms are rather similar to that observed in the
analogous compound 7 (see Table 1). Both molecules of
11 exhibit a Pd(II) center coordinated in a distorted
square-planar fashion by the N and the S donor groups,
a C(sp2) vinyl atom of the anionic terdentate ligand
system, and a Cl atom as in 7. The average C(vinyl)-
Pd-Cl bond angle of the two structures is 176.4°, and
the S and N donor groups are in mutual trans positions
with an average bond angle of 169.9°. As observed in
compound 7, the distortion from the ideal square-planar
arrangement for both crystallographic structures of 11
results from the small N-Pd-C(vinyl) and S-Pd-
C(vinyl) bite angles in the two five-membered rings of
84.3° and 86.4°, respectively.
Ch lor op a lla d a tion Rea ction P a th . It has been
proposed earlier that the chloropalladation of hetero-
substituted alkynes such as PhCtCCH2NMe2 proceeds
through the coordination of the N atom followed by
interaction of the triple bond to the metal center.
Intermolecular selective nucleophilic attack of the chlo-
ride anion to the activated triple bond yields the
thermodynamically favored five-membered palladacycle
(Scheme 4).5
absence of the CtC bond and the presence of a CdC
bond.
Further evidence for the chloropalladation reaction
path was obtained from the spectroscopic data of the
yellow precipitate 14 formed immediately after the
addition of 6 to a methanolic solution of Li2PdCl4 at
room temperature. This compound slowly (2-3 h) rear-
ranges in solution and/or in suspension (methanol or
dichloromethane) to afford quantitatively the “pincer”
1
palladacycle 12 (Scheme 6). The H NMR spectrum of
the 14, immediately after dissolution in CDCl3, shows
the resonances of the ortho H of the substituted pyridine
moiety and t-Bu hydrogens at 8.66 and 1.71 ppm,
respectively. This is a strong indication that in 14 ligand
6 is coordinated to the Pd center through its sulfur
group only (compare the selected spectroscopic data of
ligand 6 and compounds 12 and 14 in Table 3). The
presence of characteristic resonances of a CtC bond at
80.5 and 96.3 ppm in the 13C NMR spectra and νCtC at
2230 cm-1 in the IR spectra of 14 indicates that the
chloropalladation had not yet taken place.
These results indicate that it is most likely that the
chloropalladation reaction of these hetero-substituted
alkynes occurs through the coordination of only one
donor group to afford compounds such as 14. This is
probably followed by coordination of the CtC bond to
the metal center to generate intermediates of the type
15 and 16 (Chart 3). The intermolecular Cl- nucleophilic
addition occurs on the carbon that will generate the
thermodynamically more stable palladacyclic ring, i.e.,
five-membered ring rather than four-membered in the
case of 15 or six-membered in the case of 16. Finally,
coordination of the pendant donor group through dis-
placement of the chloro ligand yields the “pincer”
We have observed that in the earlier stages of the
reaction of 4 with Li2PdCl4 the precipitation of an
intermediate compound that is gradually and quanti-
tatively transformed into the “pincer” palladacycle 10
(Scheme 5). Although it was impossible to isolate this
intermediate in pure form, spectroscopic data allow us
to propose a structure 13, as depicted in Scheme 5. The
presence of a singlet at 2.81 ppm for the NMe2 moiety
1
in the H NMR spectra is a strong indication that 4 is
coordinated to the Pd center through its N atom only.
IR and the 13C{1H} NMR spectrum clearly show the
(9) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Robin Taylor, R. J . Chem. Soc., Dalton Trans 1989, S1-S83.

Unsymmetrical Palladium “Pincer” Complexes
Organometallics, Vol. 21, No. 15, 2002 3225
Ta ble 3. Selected Sp ectr oscop ic Da ta of Obser ved Com p ou n d s in th e Ch lor op a lla d a tion of 4 a n d 6
compd
IR (cm-1
)
1H NMR (δ, ppm)
2.27 (NMe2)
2.87 (NMe2)
2.81 (NMe2)
1.36 (t-BuS); 8.57 (H0-Py)
1.68 (t-BuS); 9.17 (H0-Py)
1.71 (t-BuS); 8.66 (H0-Py)
13C NMR (δ, ppm)
4
10
13
6
12
14
CtC n.o.a
1601 (νCdC
1616 (νCdC
2226 (νCtC
1594 (νCdC
2230 (νCtC
76.9 and 81.7 (CtC)
121.1 and 142.9 (CdC)
119.0 and 138.8(CdC)
81.2 and 89.2 (CtC)
119.4 and 163.8(CdC)
80.5 and 96.3 (CtC)
)
)
)
)
)
a
n.o.) not observed.
atmosphere in oven-dried Schlenk tubes. The alkynols were
prepared according to a known procedure.11 Solvents were
dried with adequate drying agents and distilled under argon
prior to use. All the other chemicals were purchased from
commercial sources and used without further purification.
Elemental analyses were performed by the Analytical Central
Service of IQ-USP (Brazil). NMR spectra were recorded on a
Varian Inova 300 spectrometer. Infrared spectra were per-
formed on a Bomem B-102 spectrometer. Mass spectra were
obtained using a GC/MS Shimadzu QP-5050 (EI, 70 eV). Gas
chromatography analyses were performed with a Hewlett-
Packard-5890 gas chromatograph with a FID and 30 m
capillary column with a dimethylpolysiloxane stationary phase.
Ch a r t 3. P ostu la ted In ter m ed ia tes in th e
Ch lor op a lla d a tion Rea ction
Ch a r t 4. Mod el System s for th e Coor d in a tion of
th e CC Tr ip le Bon d
X-r a y Str u ctu r es An a lysis of 7 a n d 11. Crystals were
mounted on a glass fiber with perfluoropolyether. The mea-
surements were made on a Bruker SMART-CCD diffractome-
ter with graphite-monochromated Mo KR radiation. For 7,
frames corresponding to a sphere of data were collected using
the ω-scan technique, and 20 s exposures of 0.3 deg in ω were
taken. For 11, frames corresponding to at least one complete
set of independent reflections (one asymmetric unit of recipro-
cal space) were collected using the ω-scan technique, and 10 s
exposures of 0.3 deg in ω were taken. An absorption correction
was applied, in each case, using SADABS12 based on the laue
symmetry of the reciprocal space, and the data were corrected
for Lorentz and polarization effects. The structures were solved
by direct methods and expanded using Fourier techniques. All
non-hydrogen atoms were refined with anisotropic displace-
ment parameters; hydrogen atoms could be located in the
Fourier map, but then were considered at calculated positions.
The full-matrix least-squares refinement against F2 converged.
All calculations were performed using the SHELXTL crystal-
lographic software package of Bruker.13
palladacycles. Moreover, preliminarily theoretical cal-
culations of full optimized geometries on the model
systems A and B (Chart 4) using the Gaussian 98
package (DFT-B3LYP/3-21G*) indicated that both in-
termediates are prone to the formation of five-membered
palladacycles rather than a four-membered ring in the
case of A or a six-membered ring in the case of B.10
Con clu sion s. These results clearly show that the
chloropalladation of hetero-substituted alkynes is a
simple and efficient method for the preparation of a
large variety of unsymmetrical palladium YCY′ “pincer”
complexes. Various functional donor groups can be
introduced in the metalated fragment such as amines,
pyridine, thioethers, phosphines, and phosphinites.
Moreover, metallacycles of different ring sizes, i.e., five-
and six-membered rings, can be generated and this
selectivity is under thermodynamic control. The exten-
sion of this method for the preparation of other transi-
tion metal “pincer” complexes and the investigation of
their catalytic properties in C-C coupling processes
such as Heck and Suzuki reactions are currently under
investigation in our laboratory.
Syn th esis of 5-Dim eth yla m in o-3-p en tyn -1-ol. A mixture
of 3-butyn-1-ol (4.2 g, 60 mmol), paraformaldehyde (2.2 g, 72
mmol), dimethylamine (50% aqueous solution, 11 mL), dioxane
(35 mL), and cuprous iodide (0.150 g) was refluxed for 3 h.
Filtration of the reaction mixture through a plug of Celite,
evaporation of the solvent under reduced pressure, and bulb-
to-bulb distillation of the residue (bp 130 °C/5 mm Hg) afforded
the desired amino alcohol as pale yellow oil. Yield: 6.1 g, 80%.
IR (film, cm-1): 2266 (νCtC). GC-MS (m/z, rel int, [peak]): 127,
60, [M]•+; 126, 74, [M - 1]+; 109, 2.5, [Me2NCH2CdCCHCH2]•+;
108, 26, [Me2NCHdCdCdCHCH2]+; 96, 36, [Me2NCH2Cd
CCH2]+; 94, 41, [MeNdCHCdCCH2CH2]+; 58, 46, [Me2Nd
CH2]+; 53, 78, [H2CdCdCHCH2]+. 1H NMR (CDCl3): δ 4.00
Exp er im en ta l Section
Gen er a l Meth od s. All reactions involving organometallic
compounds were carried out under an argon or nitrogen
3
(br s, 1H, OH); 3.63 (t, 2H, CH2O, J HH ) 6.6 Hz); 3.10 (br s,
2H, CH2N); 2.39 (m, 2H, CH2CdC); 2.22 (s, 6H, NMe2). 13C-
{1H} NMR (CDCl3): δ 82.2 and 76.4 (CdC); 60.9 (CH2O); 48.1
(CH2N); 44.1 (NMe2); 23.0 (CH2CdC).
(10) Calculations for the model systems A and B were performed
with the Gaussian 98 program package: Frisch, M. J .; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J . R.;
Zakrzewski, V. G.; Montgomery, J . A. J r.; Stratmann, R. E.; Burant,
J . C.; Dapprich, S.; Millam, J . M.; Daniels, A. D.; Kudin, K. N.; Strain,
M. C.; Farkas, O.; Tomasi, J .; Barone, V.; Cossi, M.; Cammi, R.;
Mennucci, B.; Pomelli, C.;. Adamo, C.; Clifford, S.; Ochterski, J .;
Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J . B.; Cioslowski, J .; Ortiz,
J . V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi,
I.; Gomperts, R.; Martin, R. L.; Fox, D. J .; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P.
M. W.; J ohnson, B.; Chen, W.; Wong, M. W.; Andres, J . L.; Gonzalez,
C.; Head-Gordon, M.; Replogle, E. S.; Pople, J . A. Gaussian 98, Revision
A.5; Gaussian, Inc.: Pittsburgh, PA, 1998.
Syn th esis of 5-Dim eth yla m in o-3-p en tyn yl-p-tolu en e-
su lfon a te. Triethylamine (2 mL) was slowly added to a
vigorously stirred solution of 5-(dimethylamino)-3-pentyn-1-
ol (0.640 g, 5.00 mmol) and p-toluenesulfonyl chloride (0.850
(11) Brandsma, L.; Verkruijsse, H. D. Synthesis of Acetylenes, Allenes
and Cumulenes; Elsevier: Amsterdam, 1981.
(12) Sheldrick, G. M. SADABS; Bruker AXS, Inc.: Madison, WI,
1996.
(13) Sheldrick, G. M. SHELXTL V5.10; Bruker AXS, Inc.: Madison,
WI, 1997.

3226 Organometallics, Vol. 21, No. 15, 2002
Ebeling et al.
g, 5.00 mmol) in dichloromethane (10 mL) at 0 °C. The
resulting suspension was stirred at this temperature for 1 h.
Aqueous 10% Na2CO3 solution (20 mL) was then added and
stirred for an additional 30 min at room temperature. The
layers were separated, the aqueous phase was extracted with
dichloromethane, and the combined organic extracts were
dried with MgSO4. Evaporation of the solvent afforded the
desired compound as a clear yellow oil, sufficiently pure for
further work. Yield: 0.785 g, 56%. IR (film, cm-1): 2271
(νCtC). GC-MS (m/z, rel int, [peak]): 237, 72, [p-MeC4H6SO3-
(CH2)2CdCCH2]+; 236, 95, [M - Me2NH]•+; 109, 33, [Me2-
NCH2CdCCHCH2]•+; 108, 48, [Me2NCHdCdCdCHCH2]+; 94,
100, [MeNdCHCdCCH2CH2]+; 82, 93, [Me2NCH2CdC]+; 66,
72, [MeNdCHCdC]+; 65, 63, [CH2dCHCdCCH2]+; 58, 75,
[Me2NdCH2]+. 1H NMR (CDCl3): δ 7.80 (d, 2H, CH arom, 3J HH
continued for 5 min. The layers were separated, the organic
phase was washed with water and dried with MgSO4, and the
solvent was evaporated. The crude product was purified by
column chromatography under argon (basic alumina, activity
grade II, hexanes then hexanes/EtOAc, 50:50), giving a pale
yellow oil, easily oxidizable by atmospheric oxygen. Yield:
1
0.470 g, 57%. IR (film, cm-1): 2269 (νCtC). H NMR (CDCl3):
δ 7.55-7.20 (m, 10H, CH arom); 3.20 (br s, 2H, CH2N); 2.40-
2.25 (m, 4H, PCH2CH2CdC); 2.30 (s, 6H, NMe2). 13C{1H} NMR
1
(CDCl3): δ 138.2 (d, C arom quat, J PC ) 12.5 Hz); 132.9 (d,
CH arom, 2J PC ) 18.5 Hz); 129.0, 128.8, 128.7, (CH arom); 85.1
3
(d, CdC, J PC ) 16.0 Hz); 76.2 (CdC); 48.4 (CH2N); 44.5
(NMe2); 28.1 (d, CH2CdC, 2J PC ) 13.0 Hz); 16.0 (d, CH2P, 1J PC
) 21.5 Hz). 31P{1H} NMR (CDCl3): δ -16.2.
Syn th esis of 5-Dim eth yla m in o-3-p en tyn yld ip h en yl-
p h osp h in ite (4). Chlorodiphenylphosphine (95% pure, 1.80
g, 8.00 mmol) dissolved in CH2Cl2 (5 mL) was added slowly,
under argon, to a stirred solution of 5-(dimethylamino)-3-
pentyn-1-ol (1.02 g, 8.00 mmol) and triethylamine (3 mL) in
CH2Cl2 (10 mL). After addition, stirring was continued for an
additional 30 min. The organic solution was washed with
aqueous 10% Na2CO3 solution and water then dried with
MgSO4, and the solvent was evaporated, affording a pale
yellow oil. Yield: 2.13 g, 85%. IR (film, cm-1): 2267 (νCtC).
GC-MS (C19H22NOP, 311.36); (m/z, rel int, [peak]): not
detected, [M]•+; 201, 3, [Ph2PdO]+; 58, 100, [Me2NdCH2]+. 1H
NMR (CDCl3): δ 7.45-7.55 (m, 4H, CH arom); 7.32-7.41 (m,
3
) 8.6 Hz); 7.35 (d, 2H, CH arom, J HH ) 8.5 Hz); 4.09 (t, 2H,
CH2O, 3J HH ) 7.1 Hz); 3.14 (t, 2H, CH2N, 5J HH ) 2.2 Hz); 2.59
3
5
(tt, 2H, CH2CdC, J HH ) 7.1 Hz and J HH ) 2.2 Hz); 2.46 (s,
3H, CH3); 2.24 (s, 6H, NMe2). 13C{1H}NMR (CDCl3): δ 281.36;
145.2 and 133.1 (C arom quat); 130.1 and 128.2 (CH arom);
79.3 and 77.9 (CtC); 69.2 (CH2O); 48.2 (CH2N); 44.4 (NMe2);
21.9 (CH3); 19.9 (CH2CdC).
Syn t h esis of 5-ter t-Bu t ylt h io-1-(d im et h yla m in o)-2-
p en tyn e (1). Into a solution of sodium thio-tert-butoxide,
prepared from a suspension of sodium ethoxide (0.408 g, 6.0
mmol) and 2-methyl-2-propanethiol (0.451 g, 5.0 mmol) in
ethanol (50 mL), was added a solution of 5-(dimethylamino)-
3-pentynyl-p-toluenesulfonate (1.40 g, 5.0 mmol) in ethanol (5
mL). After 6 h, the suspension was concentrated in vacuo, and
brine (50 mL) and diethyl ether (50 mL) were added. The
organic phase was washed with brine (3 × 20 mL) and dried
in MgSO4. Evaporation of the solvent afforded the desired
compound as a clear yellow oil. Yield: 0.797 g, 80%. GC-MS
3
3
6H, CH arom); 3.99 (dt, 2H, CH2OP, J PH ) 9.6 Hz and J HH
5
) 7.0 Hz); 3.19 (t, 2H, CH2N, J HH ) 1.9 Hz); 2.62 (tt, 2H,
CH2CdC, 3J HH ) 7.0 Hz and 5J HH ) 1.9 Hz); 2.27 (s, 6H, NMe2).
13C{1H} NMR (CDCl3): δ 141.0 (d, C arom quat, J PC ) 17.5
1
2
Hz); 130.6 (d, CH arom, J PC ) 21.5 Hz); 129.6 (CH arom);
128.6 (d, CH arom, J PC ) 6.5 Hz); 81.7 and 76.9 (CdC); 68.8
3
(C11H21NS, 199.35); (m/z, rel int, [peak]): not detected, [M]•+
;
2
(d, CH2OP, J PC ) 20.0 Hz); 48.3 (CH2N); 44.3 (NMe2); 22.1
142, 70, [M - 57]+; 117, 10, [M - 82]; 82, 10, [M - 117]; 57,
(d, CH2CdC, J PC ) 8.0 Hz). 31P{1H} NMR (CDCl3): δ 113.7.
3
1
5
100, [M - 142]+. H NMR (CDCl3): δ 3.14 (t, 2H, CH2N, J HH
Syn th esis of 1-(2-Meth ylth ioph en yl)-3-(dim eth ylam in o)-
1-p r op yn e (5). A mixture of 2-methylthiophenylacetylene7
(0.833 g, 5.60 mmol), paraformaldehyde (0.185 g, 6.20 mmol),
dimethylamine (50% aqueous solution, 0.8 mL), dioxane (5
mL), and cuprous iodide (0.014 g) was refluxed for 9 h. The
solvent was evaporated and the residue was purified by column
chromatography (basic alumina, activity grade II, hexanes/
EtOAc, 50:50 v/v), furnishing a pale yellow oil. Yield: 0.970
g, 85%. IR (film, cm-1): 2262 (νCtC). GC-MS (m/z, rel int,
[peak]): 205, 2, [M]•+; 204, 10, [M - 1]+; 190, 15, [M - 15]+;
160, 100, [M - Me2NH]•+; 82, 12, [Me2NCH2CdC]+; 58, 18,
[Me2NdCH2]+. 1H NMR (CDCl3): δ 7.44-7.06 (m, 4H, CH
arom); 3.59 (s, 2H, CH2N); 2.43 (s, 3H, SMe); 2.18 (s, 6H,
NMe2). 13C{1H} NMR (CDCl3): δ 147.1 and 121.5 (C arom
quat); 132.8, 128.8, 124.4, 124.1 (CH arom); 91.6 and 83.0
(CtC); 48.9 (CH2N); 44.4 (NMe2); 15.2 (SMe).
3
) 2.20 Hz), 2.64 (t, 2H, CH2S, J HH ) 7.00), 2.40 (tt, 2H,
CH2CH2S, 3J HH ) 7.00 Hz, 5J HH ) 2.20 Hz), 2.22 (s, 6H, NMe2),
1.27 (s, 9H, t-BuS). 13C{1H}NMR (CDCl3): δ 83.56, 76.57
(CtC), 48.11 (CH2N), 44.16 (NMe2), 42.35 (C(CH3)3), 30.95
(C(CH3)3), 27.86, 20.38 (CH2CH2).
Syn t h esis of 1,5-Bis(d im et h yla m in o)-2-p en t yn e (2).
Into a Schlenk containing 5-(dimethylamino)-3-pentynyl-p-
toluenesulfonate (2.81 g, 10 mmol) dimethylamine (30 mL) was
condensed. After 16 h of reaction at room temperature brine
(50 mL) and dichloromethane (50 mL) were added. The layers
were separated, and the aqueous layer was extracted with
dichloromethane (3 × 20 mL). The combined organic extract
was dried with MgSO4, and evaporation of the solvent afforded
the desired compound as a clear yellow oil. Yield: 1.43 g, 72%.
Anal. Calcd for C9H18N2 (154.26): C, 70.08; H, 11.76; N, 18.16.
Found: C, 69.88; H, 11.69; N, 17.89. IR (film, cm-1): 2257
(νCtC). GC-MS (C9H18N2, 154.26); (m/z, rel int, [peak]): not
detected, [M]•+; 109, 10, [M - 57]+; 58, 100, [M - 96]+. 1H NMR
(CDCl3): δ 3,26 (t, 2H, CH2CH2N, 3J HH ) 6,92 Hz); 3.11(t, 2H,
CH2N, 5J HH ) 1.71 Hz), 2.40 and 2.39 (2 s, 12H, 2 NMe2), 2.25
Syn th esis of 4-(ter t-Bu tylth io)-1-(2-p yr id in yl)-1-bu tyn e
(6). A mixture of diethylamine (20 mL), DMF (1.0 mL), 1-tert-
butylthio-3-butyne (1.00 g, 7.04 mmol), 2-bromopyridine (0.948
g, 5.92 mmol), PdCl2(PPh3)2 (0.070 g, 0.10 mol), and CuI (0.038
g, 0.20 mmol) was stirred under argon for 16 h at room
temperature. The reaction mixture was concentrated; brine
(50 mL) and dichloromethane (50 mL) were added. The layers
were separated, and the aqueous layer was extracted with
dichloromethane (3 × 20 mL). The combined organic extract
was washed with brine (1 × 20 mL) and dried with MgSO4.
The volatiles were removed in vacuo, affording the desired
compound as dark yellow oil. Yield: 0.777 g, 60%. IR (film,
cm-1): 2226 (νCtC). GC-MS (C13H17NS, 219.34); (m/z, rel int,
[peak]): 219,5, [M]•+; 162, 95, [M - 57]+; 130, 50, [M - 89];
57, 100, [M - 162]+. 1H NMR (CDCl3): δ 8.57 (d, 1H, py, 3J HH
3
5
(tt, 2H, CH2CH2N, J HH ) 6.29 Hz, J HH ) 1.71 Hz). 13C{1H}
NMR (CDCl3): δ 83.44, 76.07 (CtC), 58.88 (CH2CH2N), 48.49
(CH2N), 45.45 and 44.46 (2 NMe2), 17.91 (CH2CH2N).
Syn th esis of 5-Dim eth yla m in o-3-p en tyn yld ip h en yl-
p h osp h in e (3). A lithium diphenylphosphide solution was
prepared under argon by stirring, for 3 h, a mixture of
chlorodiphenylphosphine (95% pure, 0.660 g, 2.80 mmol) and
lithium pieces (0.100 g, excess) in dry THF (15 mL) containing
dry TMEDA (2 mL). The lithium diphenyl phosphide solution,
separated from the residual lithium pieces, was added slowly,
under argon, to a vigorously stirred suspension of 5-(dimethy-
lamino)-3-pentynyl-p-toluenesulfonate (0.785 g, 2.80 mmol) in
dry THF (5 mL). After addition, stirring was continued for 10
min, the solvent was evaporated under reduced pressure,
water (10 mL) and CH2Cl2 (20 mL) were added, and stirring
3
) 7.41 Hz), 7.64 (t, 1H, py, J HH ) 7.69 Hz), 7.39 (d, 1H, py,
3J HH ) 7.96 Hz), 7.21 (dd, 1H, py, 3J HH ) 7.69 Hz, 3J HH ) 7.41
Hz), 2.85 and 2.71 (2t, 4H, 3J HH ) 7.69 Hz), 1.36 (s, 9H, CH3).
13C{1H}NMR (CDCl3): δ 150.12, 143.81, 136.32, 127.12, 122.75

Unsymmetrical Palladium “Pincer” Complexes
Organometallics, Vol. 21, No. 15, 2002 3227
(py), 89.19, 81.24 (CtC), 42.87 (C(CH3)3), 31.25 (CH3), 27.55,
21.34 (CH2CH2).
Addition of hexanes (10 mL), filtration, and evaporation of the
solvent afforded a pale yellow solid. Yield: 0.586 g, 60%. Anal.
Calcd for C19H22Cl2NOPPd (488.7): C, 46.70; H, 4.54; N, 2.87.
Found: C, 46.83; H, 4.77; N, 2.77. dp: 163-164 °C. IR (Nujol,
cm-1): 1601 (νCdC). 1H NMR (CDCl3): δ 8.05-7.90 (m, 4H, CH
arom); 7.55-7.40 (m, 6H, CH arom); 3.97 (dt, 2H, CH2OP, 3J PH
Syn th esis of P a lla d a cycle (7). A Li2PdCl4 solution was
prepared by dissolving PdCl2 (0.285 g, 1.60 mmol) and LiCl
(0.170 g, 4.00 mmol) in methanol (10 mL) with gentle heating.
A solution of 1 (0.318 g, 1.60 mmol) in methanol (10 mL) was
then added to the former at 5 °C. The resulting dark yellow
solution was then stirred for 1 h. The mixture was concen-
trated in vacuo, leading to a dark solid. Dichloromethane (3
mL) was added, and the afforded solution was filtered through
a plug of Celite. A yellow precipitate was obtained by addition
of hexane to the formed solution. The solid was recuperated
by filtration, washed with hexane, and dried in vacuo, afford-
ing a yellow solid. Yield: 0.361 g, 60%. Anal. Calcd for
3
) 18.0 Hz and J HH ) 5.3 Hz); 3.55 (q, 2H, CH2N, J ) 2.1 Hz);
4
2.87 (d, 6H, NMe2, J PH ) 2.9 Hz); 2.43 (m, 2H, CH2CdC).
13C{1H} NMR (CDCl3): δ 142.9 (CdC); 134.0 (d, C arom quat,
2
1J PC ) 61 Hz); 133.4 (d, CH arom, J PC ) 19.6 Hz); 131.8 (d,
4
3
CH arom, J PC ) 2.5 Hz); 128.5 (d, CH arom, J PC ) 11.6 Hz);
2
3
121.2 (d, CdC, J PC ) 5.6 Hz); 72.3 (d, CH2N, J PC ) 3.0 Hz);
69.3 (d, CH2OP, 2J PC ) 4.5 Hz); 50.5 (d, NMe2, 3J PC ) 3.0 Hz);
32.1 (d, CH2CdC, J PC ) 8.1 Hz). 31P{1H} NMR (CDCl3): δ
3
C
11H21Cl2NPdS (376.68): C, 35.08; H, 5.62; N, 3.72. Found:
114.6.
C, 35.33; H, 5.59; N, 3.76. Mp ) 142 °C. IR (Nujol, cm-1): 1632
Syn th esis of Cyclop a lla d a te (11). The methanolic solu-
tion of Li2PdCl4 was prepared using the same procedure in
the synthesis of 7, with PdCl2 (0.337 g, 1.88 mmol) and LiCl
(0.200 g, 4.70 mmol) in methanol (10 mL). The former solution
was allowed to react with a solution of 5 (0.385 g, 1.88 mmol),
dissolved in methanol (5 mL). The resulting suspension was
stirred for 1 h. The volatiles were removed under reduced
pressure, and the residue was taken up in a minimum amount
of CH2Cl2. Subsequent chromatographic purification (column,
silica gel, EtOAc) afforded a yellow solid. Yield: 0.480 g, 67%.
Anal. Calcd for C12H15Cl2NSPd (382.6): C, 37.67; H, 3.95; N,
3.66. Found: C, 37.97; H, 4.11; N, 3.67. Dp ) 148-150 °C. IR
(Nujol, cm-1): 1590 (νCdC). 1H NMR (CDCl3): δ 8.51 (d, 1H,
1
(νCdC). H NMR (CDCl3): δ 3.68 (br s, 2H, CH2N), 2.90 (s, 6H,
NMe2), 2.77 (br t, 2H, CH2S, J HH ) 7.50 Hz), 2.40 (br s, 2H,
3
CH2CH2S), 1.59 (s, 9H, C(CH3)3). 13C{1H} NMR (CDCl3): δ
157.45 (Cl-Cd), 115.83 (Pd-Cd), 75.91 (CH2N), 52.36 (NMe2),
50.80 and 36.22 (CH2CH2), 37.38 (C(CH3)3), 30.61 (C(CH3)3).
Syn th esis of P a lla d a cycle (8). Compound 8 was prepared
using the same procedure and workup described in the
synthesis of 7. The methanolic solution of Li2PdCl4, prepared
from PdCl2 (0.285 g, 1.60 mmol) and LiCl (0.170 g, 4.00 mmol)
in methanol (10 mL), reacted with a solution of 2 (0.247 g,
1.60 mmol) in methanol (10 mL), affording the desired complex
as a yellow solid. Yield: 0.382 g, 72%. Anal. Calcd for C9H18
-
3
Cl2N2Pd (331.58): C, 32.60; H, 5.47; N, 8.45. Found: C, 31.75;
H, 5.47; N, 7.36. Dp ) 135-138 °C. IR (Nujol, cm-1): 1639
(νCdC). 1H NMR (CDCl3): δ 3.56 (t, 2H, CH2N, 5J HH ) 2.02 Hz),
CH arom, J HH ) 7.7 Hz); 7.43-7.28 (m, 3H, CH arom); 3.95
(s, 2H, CH2N); 3.00 (s, 6H, NMe2); 2.87 (s, 3H, SMe). 13C{1H}
NMR (CDCl3): δ 147.8, 145.1, 138.6, 118.3 (C quat); 130.8,
129.4, 128.8, 127.0 (CH arom); 77.8 (CH2N); 52.1 (NMe2); 26.7
(SMe).
3
2.88 and 2.78 (2 s, 12H, 2 NMe2) 2.74 (t, 2H, CH2CH2N, J HH
3
5
) 6.58 Hz), 2.30 (tt, 2H, CH2CH2N, J HH ) 6.58 Hz, J HH
)
2.02 Hz). 13C{1H} NMR (CDCl3): δ 153.95 (Cl-Cd), 112.74
(Pd-Cd), 76.6 1 (dC-CH2N), 68.62 (CH2CH2N), 53.32 and
51.53 (2 NMe2), 33.06 (CH2CH2N).
Syn th esis of P a lla d a cycle (12). The methanolic solution
of Li2PdCl4 was prepared using the same procedure in the
synthesis of 7, with PdCl2 (0.337 g, 1.88 mmol) and LiCl (0.200
g, 4.70 mmol) in methanol (10 mL). The former solution was
allowed to react with a solution of 6 (0.412 g, 1.88 mmol),
dissolved in methanol (5 mL). Immediately after the addition
of the alkyne a yellow solid is formed. After 15 mim the former
suspension became a dark yellow solution. After 3 h the mix-
ture was concentrated and the residue dissolved in a minimum
amount of CH2Cl2. The resulting solution was filtered through
a plug of Celite, and a yellow solid was obtained by addition
of hexane. The solid was recuperated by filtration and dried
in vacuo. Yield: 0.671 g, 90%. Anal. Calcd for C13H17Cl2NPdS
(396.67): C, 39.36; H, 4.32; N, 3.53. Found: C, 39.06; H, 4.54;
N, 3.33. Dp ) 157 °C. IR (Nujol) (cm-1): 1594 (νCdC). 1H NMR
Syn th esis of P a lla d a cycle (9). The methanolic solution
of Li2PdCl4 was prepared using the same procedure in the
synthesis of 7, PdCl2 (0.285 g, 1.60 mmol), and LiCl (0.170 g,
4.00 mmol) in methanol (10 mL). The former solution was
allowed to react with a solution of 3 (0.470 g, 1.60 mmol) in
methanol (10 mL) at 5 °C. The resulting suspension was
stirred for 1 h and filtered, and the precipitate was washed
with cold methanol and dried under reduced pressure. Solu-
bilization in dichloromethane, filtration through a plug of
Celite, and precipitation with hexanes afforded the desired
compound as a yellow solid, which was recuperated by filtra-
tion and dried in vacuo. Yield: 0.500 g, 66%. Anal. Calcd for
C
19H22Cl2NPPd (472.7): C, 48.28; H, 4.69; N, 2.96. Found: C,
3
(CDCl3): δ 9.16 (d, 1H, py, J HH ) 5.70 Hz), 7.85 (t, 1H, py,
47.91; H, 4.32; N, 2.74. Dp ) 153-155 °C. IR (Nujol, cm-1):
1616 (νCdC). 1H NMR (CDCl3): δ 8.05-7.75 (m, 4H, CH arom);
7.60-7.40 (m, 6H, CH arom); 3.68 (br s, 2H, CH2N); 2.91 (d,
6H, NMe2, 4J PH ) 2.5 Hz); 2.55-2.30 (m, 4H, PCH2CH2CdC).
13C{1H} NMR (CDCl3): δ 159.4 (CdC); 133.2 (d, CH arom, 2J PC
3
3J HH ) 8.10 Hz), 7.35 (d, 1H, py, J HH ) 8.10 Hz), 7.21 (t, 1H,
3
3
py, J HH ) 6.60 Hz), 3.03 (t, 2H, CH2S, J HH ) 6.59 Hz), 2.87
(br s, 2H, CH2), 1.69 (s, 9H, CH3). 13C{1H} NMR (CDCl3): δ
179.44, 119.38 (CdC), 163.77, 149.43, 139.77, 121.94, 119.48
(py), 51.48 (C(CH3)3), 37.73, 36.72 (CH2CH2), 30.61 (CH3).
4
) 11.6 Hz); 131.3 (d, CH arom, J PC ) 2.6 Hz); 130.7 (C arom
quat); 129.0 (d, CH arom, 3J PC ) 10.6 Hz); 117.6 (d, CdC, 3J PC
3
3
Ack n ow led gm en t. This work was supported by
grants from FAPERGS and CNPq (Brazil). M.R.M.
thanks the CNPq for a visiting scientific grant.
) 4.7 Hz); 74.4 (d, CH2N, J PC ) 2.5 Hz); 50.8 (d, NMe2, J PC
1
) 3.0 Hz); 34.1 (d, CH2P, J PC ) 34.5 Hz); 33.2 (d, CH2CdC,
2J PC ) 10.6 Hz). 31P{1H} NMR (CDCl3): δ 57.2
Syn th esis of Cyclop a lla d a te (10). The methanolic solu-
tion of Li2PdCl4 was prepared using the same procedure in
the synthesis of 7, with PdCl2 (0.355 g, 2.00 mmol) and LiCl
(0.213 g, 5.00 mmol) in methanol (10 mL). The former solution
was allowed to react with a solution of 4 (0.622 g, 2.00 mmol)
dissolved in methanol (5 mL) at 5 °C. The resulting suspension
was stirred overnight at room temperature, and the solvent
was evaporated under reduced pressure. The residue was
taken up in dichloromethane (10 mL) and set aside overnight.
Su p p or tin g In for m a tion Ava ila ble: Tables of full crystal
data, atomic coordinates, calculated hydrogen coordinates,
anisotropic thermal parameters, and a complete list of bond
lengths and angles are available as Supporting Information.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM011002A