Versatile, selective, and switchable coordination modes of pincer click ligands

Article abstract of DOI:10.1021/om900827g

Ligands possessing multiple complexation modes are an interesting class of compounds. Here we report that our recently established pincer click ligands (PCLs), prepared by copper-catalyzed cycloaddition of azides to alkynes, exhibit unique versatility in

Full text of DOI:10.1021/om900827g

Organometallics 2009, 28, 7001–7005 7001
DOI: 10.1021/om900827g
Versatile, Selective, and Switchable Coordination Modes of Pincer Click
Ligands
Elaine M. Schuster, Mark Botoshansky, and Mark Gandelman*
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel
Received September 24, 2009
Ligands possessing multiple complexation modes are an interesting class of compounds. Here we
report that our recently established pincer click ligands (PCLs), prepared by copper-catalyzed
cycloaddition of azides to alkynes, exhibit unique versatility in coordination ability. Nitrogens of the
triazole-based backbone can actively participate in metal ligation rather than being a spectator
backbone. Under selection of the reaction conditions these ligands can selectively acquire either bi- or
tridentate coordination upon reaction with a metal precursor. Both palladium and platinum
complexes with different coordination modes were prepared and fully characterized including
X-ray analysis. Moreover, the “rollover switch” of kinetically preferred bidentate complexes to the
thermodynamically controlled tridentate species is demonstrated.
Introduction
the metal center has generated extensive research into the use
of these complexes for catalysis, mechanistic studies, isolation
of elusive species, and materials science.5
Chelating ligands with multiple binding modes are an
interesting and versatile class of compounds that are of great
potential for catalytic applications, materials science, and
supramolecular chemistry.1,2 Such ligands with ambidentate
character can often be coordinated to a metal center in a
selective manner by modification of metal choice or its
oxidation state, ligand set, or reaction conditions. Particu-
larly attractive is the ability to selectively interconvert com-
plexes of different binding modes of the same ligand, which is
of great interest for the design of molecular switches, logic
gates, sensors, etc.3
Tridentate pincer-type ligands have found a variety of
valuable applications and, as such, represent a valuable target
for synthesis and studies.4 The pincer structure affords its
metal complex a high stability, which is widely attributed to the
protective, sheltered environment in which the metal is situ-
ated. The realization that pincer ligands offer both a unique,
highly protective environment for the coordinated metal center
and facility to fine-tune the steric and electronic properties of
We recently reported a novel combinatorial approach
toward the synthesis of triazole-based tridentate ligands.6
This methodology is based upon the Cu(I)-catalyzed [2þ3]
cycloaddition of azides and alkynes, decorated with donor
arms, to form triazole as the main tool for ligand assembly
(Scheme 1).7 Utilization of the triazole pattern for adaptable
ligand construction has received increasing interest in recent
years.8 In our methodology, this type of ligand construction
provided a triazole-based pincer frame with two donor arms
in 1,4-positions; the relatively acidic triazole hydrogen al-
lows for metal insertion to form tridentate complexes. The
initial library of aryl-substituted donors (P, N, and S) was
recently expanded to include bulky, electron-donating alkyl-
substituted phosphines, which further expanded the range of
ligands accessible by this route.9 We discovered significant
differences between the triazole-based pincer complexes as
(6) Schuster, E. M.; Botoshansky, M.; Gandelman, M. Angew.
Chem., Int. Ed. 2008, 47, 4555.
(7) (a) Meldal, A.; Tornoe, C. W. Chem. Rev. 2008, 108, 2952. (b)
Rostovtsev, V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew. Chem.,
e
*To whom correspondence should be addressed. E-mail: chmark@tx.
technion.ac.il.
Int. Ed. 2002, 41, 2596. (c) Tornoe, C. W.; Christensen, C.; Meldal, M.
e
(1) Burmeister, J. L. Coord. Chem. Rev. 1990, 105, 77.
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Pahor, N.; Randaccio, L. J. Am. Chem. Soc. 1986, 108, 4830. (b) Chi,
K.-W.; Addicott, C.; Arif, A. M.; Stang, P. J. J. Am. Chem. Soc. 2004, 126,
16569. (c) Teo, P.; Koh, L. L.; Hor, T. S. A. Inorg. Chem. 2003, 42, 7290. (d)
Chi, K.-W.; Addicott, C.; Moon, M.-E.; Lee, H. J.; Yoon, S. C.; Stang, P. J. J.
Org. Chem. 2006, 71, 6662. (e) Zelikovich, L.; Libman, J.; Shanzer, A.
Nature 1995, 374, 790. (f) Kalny, D.; Elhabiri, M.; Moav, M.; Vaskevich, A.;
Rubinstein, I.; Shanzer, A.; Albrecht-Gary, A.-M. Chem. Commun. 2002,
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(3) Balzani, V., Credi, A.; Venturi, M. Molecular Devices and Ma-
chines, 2nd ed.; Wiley-VCH: New York, 2008.
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3750. (b) van der Boom, M. E.; Milstein, D. Chem. Rev. 2003, 103, 1759.
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(b) Dai, Q.; Gao, W.; Liu, D.; Kapes, L. M.; Zhang, X. J. Org. Chem. 2006,
71, 3928. (c) Detz, R. D.; Heras, S.; de Gelder, R.; van Leeuwen, P. W. N. M.;
Hiemstra, H.; Reek, J. N. H.; van Maarseveen, J. H. Org. Lett. 2006, 8, 3227.
(d) Dolhem, F.; Johansson, M. J.; Antonsson, T.; Kann, N. J. Comb. Chem.
2007, 9, 477. (e) Detz, R. D.; Delville, M. M. E.; Hiemstra, H.; van
Maarseveen, J. H. Angew. Chem., Int. Ed. 2008, 47, 3777. (f) van Assema,
S. G. A.; Tazelaar, C. G. J.; Bas de Jong, G.; van Maarseveen, J. H.; Schakel,
M.; Lutz, M.; Spek, A. L.; Slootweg, J. C.; Lammertsma, K. Organometallics
2008, 27, 3210. (g) Rheingold, A. L.; Liable-Sands, L. M.; Trofimenko, S.
Angew. Chem., Int. Ed. 2000, 39, 3321. (h) Mindt, T. L.; Schweinsberg, C.;
Brans, L.; Hagenbach, A.; Abram, U.; Tourwe, D.; Garcia-Garayoa, E.;
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Organometallics 2009, 28, 5025.
r
2009 American Chemical Society
Published on Web 11/13/2009
pubs.acs.org/Organometallics

7002 Organometallics, Vol. 28, No. 24, 2009
Schuster et al.
Scheme 1. Assembly of PCLs and Formation of Pd-Based
Complexes
Scheme 2. Formation of Pt Complex 3
Figure 1. X-ray structure of a molecule of 3. Hydrogen atoms
are omitted for clarity.
compared with their phenyl-based counterparts, both in
catalytic activity and in their coordination chemistry. This
new class of ligands demonstrates a modifiable coordination
mode: under certain conditions, the nitrogens of the triazole-
based backbone do not behave as innocent bystanders. In
this paper, we report the selective formation of either biden-
tate or tridentate complexes upon reaction of these ligands
with both palladium and platinum precursors. It should be
noted that this is the first example of Pt complexes with
pincer click ligands. A selective “switch” from bidentate-to-
tridentate mode of coordination via C-H bond cleavage is
demonstrated. Thus, our triazole-based system represents an
intriguing example of “rollover” cyclometalation, which
mainly has been demonstrated for bipyridine-derived and
related complexes in both solution and gas phase.10
Figure 2. Phenyl-based pincer 4.
˚
Table 1. Selected bond lengths [A] and angles [deg] of Molecule 3
Pt(1)-C(25)
1.908(30)
2.348(13)
159.7(3)
82.2(9)
Pt(1)-Cl(1)
2.401(15)
2.261(11)
177.3(9)
79.0(9)
Pt(1)-P(2)
Pt(1)-P(1)
P(1)-Pt(1)-P(2)
C(25)-Pt(1)-P(1)
P(2)-Pt(1)-Cl(1)
C(25)-Pt(1)-Cl(1)
C(25)-Pt(1)-P(2)
P(1)-Pt(1)-Cl(1)
99.3(3)
99.7(3)
Scheme 3. Formation of Bidentate Complexes 5a-da
Results and Discussion
The tridentate pincer-type coordination ability of our
ligands upon reaction with Pd precursors under heating
and in the presence of base was previously demonstrated in
our laboratories (Scheme 1).6,9 Our interest in Pt-based
catalysis promoted exploration of these new ligands with
platinum precursors. Gratifyingly, heating PCP ligand 2
with (COD)PtCl2 (COD = cyclooctadiene) in the presence
of triethylamine resulted in selective formation of PCP-
platinum chloride complex 3 (Scheme 2). This complex was
fully characterized by multinuclear NMR. The 31P{1H}
NMR spectrum of compound 3 exhibits two doublets at
δ=38.13 and 28.58 ppm with JPP=445 Hz, a typical P-P
trans coupling. The 195Pt-P satellites for both doublets with
JPPt = 2813 and 3084 Hz, respectively, clearly indicate
coordination of both phosphine arms to the platinum center.
The structure of 3 was confirmed by X-ray analysis. Single
a Conditions: 5, MCl2 = K2PdCl4 or (TMEDA)PdCl2; 6, MCl2
(COD)PdCl2.
=
monoclinic crystals suitable for X-ray analysis were obtained
by slow diffusion of ether into a DMF solution of 3. The
platinum atom is located in the center of a distorted square-
planar structure with the chloride group occupying a posi-
tion trans to the carbon atom of the triazole (Figure 1). The
two phosphine groups are located in a mutual trans position
with a P-Pd-P angle of 159.65. Interestingly, the analogous
phenyl-substituted phosphine ligand arms in the phenyl-
based counterpart 411 (Figure 2) are twisted out of the plane
with a torsional angle P2-C7-C2-C1 of 33°,12 as compared
to the analogous angle P1-C27-C26-C25 in our triazole-
based ligand of 10°. This lack of planarity in complex 4 is
likely in order to release strain of metal-containing rings,
imposed by the geometry of substitution in the six-membered
(10) For representative examples in solution, see: (a) Nord, G.;
Hazell, A. C.; Hazell, R. G.; Farver, O. Inorg. Chem. 1983, 22, 3429.
(b) Spellane, P. J.; Watts, R. J.; Curtis, C. J. Inorg. Chem. 1983, 22, 4060. (c)
Braterman, P. S.; Heat, G. H.; Mackenzie, A. J.; Noble, B. C.; Peacock, R. D.;
Yellowlees, L. J. Inorg. Chem. 1984, 23, 3425. (d) Zucca, A.; Droppin, A.;
Cinellu, M. A.; Stoccoro, S.; Minghetti, G.; Manassero, M. Organometallics
2002, 21, 783. (e) Minghetti, G.; Stoccoro, S.; Cinellu, M. A.; Soro, B.;
Zucca, A. Organometallics 2003, 22, 4770. For mechanistic studies of
(11) Bennett, M. A.; Jin, H.; Willis, A. C. J. Organomet. Chem. 1993,
451, 249.
(12) For crystallographic details of 4, see: Fischer, S.; Wendt, O. F.
€
rollover metalation in gas phase, see: Butschke, B.; Schlangen, M.; Schroder,
D.; Schwarz, H. Chem.;Eur. J. 2008, 14, 11050.
Acta Crystallogr. Sect. E 2004, E60, m69.

Article
Organometallics, Vol. 28, No. 24, 2009 7003
Figure 3. X-ray structure of molecules 5b and 5c. Hydrogen atoms are omitted for clarity.
˚
Table 2. Selected Bond Lengths [A] and Angles [deg] for Com-
plexes 5b and 5c
phenyl ring of the backbone, as compared with our five-
membered triazole-based backbone in complex 3 (compare
corresponding angles C1-C2-C7 = 117.4° in
4 vs
complex 5b
complex 5c
C25-C26-C27=125° in 3). Selected bond lengths and bond
angles of 3 are given in Table 1.
N(1)-Pd(1)
P(1)-Pd(1)
2.015(19) N(1A)-Pd(1A)
2.034(19)
2.213(5)
2.358(9)
2.298(23)
83.1(2)
2.220(21) Pd(1A)-P(1A)
2.300(24) Pd(1A)-Cl(2A)
2.358(22) Pd(1A)-Cl(1A)
During investigation of the mechanism of PCL-metal
complex formation, we discovered that the triazole back-
bone of these ligands is not an innocent bystander and can
coordinate to the metal center via the triazole nitrogens
(Scheme 3). Moreover, PCL reactivity can be tuned, by
modification of reaction conditions, to participate selectively
in either bidentate or tridentate coordination modes to the
metal. Triazole derivatives have recently found widespread
use as transition metal ligands by coordination through
nitrogen atoms.8,13 Thus, addition of either (CH3CN)2PdCl2,
K2PdCl4, or (tmeda)PdCl2 (tmeda = tetramethylethylene-
diamine) to ligands 1a-d in DMF resulted in selective
formation of the P-N bidentatate complexes 5 (Scheme 3).
This product was obtained even in the presence of base when
the reaction was performed at room temperature, and no
coordination to the sulfide arm was observed. This indicates
that the formation of bidentate complexes (rather than their
tridentate counterparts) giving a relatively stable five-mem-
bered coordination ring is kinetically favored. In the case of
P-S ligands 1, these products could be isolated in a quanti-
tative yield.
Pd(1)-Cl(2)
Pd(1)-Cl(1)
N(1)-Pd(1)-P(1)
84.2(2)
N(1A)-Pd(1A)-P(1A)
Cl(2A)-Pd(1A)-Cl(1A) 92.6(1)
Cl(1)-Pd(1)-Cl(2) 94.4(1)
Single crystals of compounds 5b and 5c suitable for X-ray
analysis were obtained by addition of THF to the reaction
mixture. In both complexes, the palladium atom is located in
the center of distorted square-planar structures, with the P
and N coordinating atoms occupying mutual cis positions
(Figure 3). The two chloride groups are mutually cis to one
another; the chloride that is trans to the triazole nitrogen
exhibits a shorter Pt-Cl bond length than that which is trans
to the phosphorus atom due to the weaker trans influence of
nitrogen. Selected bond lengths and bond angles for both 5b
and 5c are given in Table 2.
Figure 4. X-ray structure of a molecule of 6b. Hydrogen atoms
˚
are omitted for clarity. Selected bond lengths [A] and angles
[deg]: N1-Pt1 2.016(37), P1-Pt1 2.216(34), Pt1-Cl1 2.301(43),
Pt1-Cl2 2.373(40), N1-Pt1-P1 81.98(20), Cl2-Pt1-Cl1
91.69(8).
temperature exclusively affords bidentate complex 6b in
quantitative yield. The X-ray structure of 6b is similar to
that of corresponding palladium analogues 5 and is repre-
sented in Figure 4.
These bidentate kinetic products could be selectively
“switched” to the thermodynamically favored tridentate
complexes. For example, when complex 5a or 5b, obtained
at room temperature in the presence of triethyl amine, is
heated at 70 °C, the smooth conversion of bidentate species 5
to pincer-type complex 7 takes place. Apparently, at elevated
temperatures, an efficient on/off coordination of palladium
to the nitrogen donor of the triazole takes place followed by
This bidentate coordination was observed also using Pt(II)
precursors. Thus, reaction of 1b with (COD)PtCl2 at room
(13) For selected examples in addition to those in ref 8, see: (a)
Suijkerbuijk, B. M. J. M.; Aerts, B. N. H.; Dijkstra, H. P.; Lutz, M.;
Spek, A. L.; van Koten, G.; Klein Gebbink, R. J. M. Dalton Trans. 2007,
1273. (b) Huffman, J. C.; Flood, A. H.; Li, Y. Chem. Commun. 2007, 2692.
(c) Struthers, H.; Spingler, B.; Mindt, T. L.; Schibli, R. Chem.;Eur. J. 2008,
14, 6173. (d) Schweinfurth, D.; Hardcastle, K. I.; Bunz, U. H. F. Chem.
Commun. 2008, 2203.

7004 Organometallics, Vol. 28, No. 24, 2009
Schuster et al.
Scheme 4. Bidentate-to-Tridentate “Switch” and Pincer Com-
plex Formation via Lithiation
or tridentate coordination mode. Namely, triazole nitrogens
could participate in complexation rather than being a spec-
tator backbone of the ligand. Moreover, we can selectively
prepare bidentate or tridentate complexes by selection of
reaction conditions. The kinetically controlled bidentate
complexes can be “switched” via rollover C-H cleavage to
the thermodynamically preferred tridentate ones quite sim-
ply. We also reported both tridentate and bidentate platinum
complexes. The bidentate complexes of ligand 1 formed with
P-M-N coordination leave the sulfide arm free; which
could conceivably be exploited to form either hetero- or
homobimetallic complexes upon addition of a second metal
center. Studies on applications of these ligands in the forma-
tion of bimetallic complexes as well as application of the
prepared new Pd- and Pt-based compounds to catalytic
transformations are currently underway in our laboratories.
Experimental Section
General Methods. Oxygen- and moisture-sensitive reactions
were carried out under an atmosphere of purified nitrogen in a
glovebox equipped with an inert gas purifier or by using
standard Schlenk techniques. Dry Et3N was obtained by dis-
tillation from CaH2. Solvents were purified by passing through a
column of activated alumina under inert atmosphere. All com-
mercially available reagents were used as received, unless other-
wise indicated. NMR spectra were recorded at 300 MHz/75
MHz (1H/13C NMR) in CDCl3 unless otherwise stated on a
Bruker AVANCE 300 MHz spectrometer at 23 °C. Chemical
shifts (δ) are reported in parts per million, and the residual
solvent peak was used as an internal standard (CDCl3: δ 7.261/
Scheme 5. Reaction of Ligand 8 with Pd Precursor
phosphine arm rotation (around the C1-C2 bond in 5b, for
instance), C-H bond cleavage, and sulfide-arm coordina-
tion to afford compound 7. The overall switch represents a
“rollover” cyclometalation process, which has found appre-
ciable interest with regard to metal-assisted C-H bond
activation.10
Alternatively, we found that tridentate complex 7 could be
prepared by independent direct synthesis. Thus, ligand 1 is
selectively lithiated at the triazole carbon by butyllithium at
-78 °C (Scheme 4). The abstracted proton is relatively
acidic, and the resulting compound is presumably stabilized
by chelation of Li to the neighboring sulfide arm. These
species formed in situ are trapped with a Pd(II) precursor,
leading, via transmetalation, to selective formation of pincer
complexes 7.14
Such selective behavior is not observed with PCP ligands
bearing two phosphine arms. Complicated mixtures of inter-
mediates are obtained upon addition of ligand 2 to Pd(II) or
Pt(II) precursors at room temperature. These mixtures are
fully converted to the tridentate pincer-type complex as a
single product upon heating with triethyl amine.
Additionally, reaction of PCN ligand 8 with a Pd(II)
precursor at room temperature without the presence of an
external base gave a mixture of both bidentate and tridentate
complexes, presumably using the pyridine moiety as an
internal base. Again, this mixture is smoothly converted to
the tridentate complex when heated in the presence of excess
triethyl amine.
1
77.0, H/13C NMR). 31P NMR signals are in ppm and refer-
enced to external 85% H3PO4. Data are reported as follows:
chemical shift, multiplicity (s=singlet, d=doublet, t=triplet, q=
quartet, p=pentet, m=multiplet, b=broad), integration, and
coupling constant(s) (Hz). Compounds 7a,b and 9 are compared
to the previously reported spectroscopic data for these species.6
Preparation of Complex 3. To a solution of 2 (21 mg, 0.045
mmol) in DMF (2 mL) was added a solution of (COD)PtCl2
(17 mg, 0.045 mmol) in DMF (2 mL) and triethyl amine (63 μL,
0.45 mmol). The reaction mixture was placed in a sealed vessel
and heated to 70 °C for 18 h. The solvent was removed under
reduced pressure, and the crude residue was washed with ether
(3 ꢀ 3 mL) and extracted with toluene/THF. The combined
extracts were evaporated to give 3 (32 mg, 100%) as a grayish
solid. 31P{1H} NMR (121 MHz, CD2Cl2) δ: 38.13 (d, JPP=445
Hz, JPPt=2813 Hz), 28.58 (d, JPP=445 Hz, JPPt=3084 Hz). 1H
NMR (500 MHz, CD2Cl2) δ: 7.96-7.92 (m, 8H, Ar), 7.58-7.51
(m, 12H, Ar), 5.27 (d, JHP=7.0 Hz, 2H, P-CH2-N), 3.83 (d, JHP
=
10.5 Hz, 2H, P-CH2-C). 13C{1H} NMR (125 MHz, CD2Cl2)
δ: 152.0 (d, Cipso) 135.0 (q, JCP=12.1 Hz), 133.8, 132.9, 131.2 (d,
J
CP=11.0 Hz), 130.9 (d, JCP=10.6 Hz), 54.5 (d, JCP=45.2 Hz,
P-CH2-N), 32.1 (d, JCP =41.2 Hz, P-CH2-C). MS-ESI: (M þ
H)þ 695.0812 C28H25N3P2ClPt.
General Procedure for the Preparation of Complexes 5. 5a: To
a solution of 1a (15 mg, 0.032 mmol) in THF (1 mL) was added a
solution of (CH3CN)2PdCl2 (8.4 mg, 0.032 mmol) in THF
(1 mL). A pale yellow color indicated the formation of the
bidentate complex. The solvent was removed under reduced
pressure, and the crude residue was washed with ether (3 ꢀ
3 mL) and toluene (3 ꢀ 3 mL) and extracted with THF and
DMF. The combined extracts were evaporated to give 18 mg
In conclusion, we have demonstrated that our pincer click
ligands possess ambidentate character in either a bidentate
1
(100%) as a white solid. 31P{1H} NMR (DMF-d7) δ: 48.3. H
NMR (DMF-d7) δ: 8.42 (s, 1H, triazole-H), 8.0-7.95 (m, 4H,
aromatic), 7.67-7.59 (m, 5H, aromatic), 7.43-7.29 (m, 4H,
aromatic), 6.14 (s, 2H, CH2-S), 4.12 (d, JHP=13 Hz, CH2-P).
13C{1H} NMR (DMF-d7) δ: 148.3 (d, JCP =9 Hz), 133.6 (d,
JCP=15 Hz), 132.4 (d, JCP=3.3 Hz), 131.9, 131.8, 129.5, 129.2
(14) A similar lithiation-transmetalation approach was used for
preparation of
a
ruthenium NCN-based complex (NCN =
[C6H3(CH2NMe2)2-2,6]-): Sutter, J.-P.; James, S. L.; Steenwinkel, P.;
Karlen, T.; Grove, D. M.; Veldman, N.; Smeets, W. J. J.; Spek, A. L.;
van Koten, G. Organometallics 1996, 15, 941.

Article
Organometallics, Vol. 28, No. 24, 2009 7005
(d, JCP=12 Hz), 128.5, 127.9 (d, JCP=57 Hz), 123.9 (d, JCP
14 Hz), 55.0 (s, CH2-S), 27.0 (d, JCP=30 Hz).
=
solution of 1a (10 mg, 0.026 mmol) in DMF (1 mL). A bright
yellow color indicated the formation of the bidentate complex.
The solvent was removed under reduced pressure, and the crude
residue was washed with ether (3 ꢀ 3 mL) and toluene (3 ꢀ 3 mL)
and extracted with THF and CH2Cl2. The combined extracts
were evaporated to give 6 as a white solid. 31P{1H} NMR
(DMF-d7) δ: 22.2 (s, JPPt = 3646 Hz). 1H NMR (DMF-d7)
δ: 8.63 (s, 1H, triazole-H), 8.17-8.13 (m, 5H), 7.78-7.52 (m,
10H), 6.33 (s, 2H, CH2-S), 4.13 (d, JHP = 11 Hz, CH2-P).
13C{1H} NMR (DMF-d7) δ: 152.4, 135.3 (d, JCP = 156 Hz),
134.0 (d, JCP=3 Hz), 133.9, 133.7, 131.5, 131.0 (d, JCP=12 Hz),
130.4, 129.7 (d, JCP =64 Hz), 126.0 (d, JCP =13 Hz), 57.2 (s,
C-CH2-S), 28.9 (d, JCP=37.9 Hz, C-CH2-P). Anal. Calcd: C,
40.31; H, 3.08. Found: C, 39.18; H, 4.56.
5b: 31P{1H} NMR (DMSO-d6) δ: 76.7. 1H NMR (DMSO-d6)
δ: 8.25 (s, 1H, triazole-H), 7.32-7.43 (m, 5H, Ar), 6.02 (s, 2H,
CH2-S), 3.27 (d, JHP = 11.4 Hz, CH2-P), 2.15-2.33 (m, 2H),
1.54-1.76 (m, 10H), 1.31-1.50 (m, 10H). 13C{1H} NMR
(DMSO-d6) δ: 149.5 (d, JCP = 6.5 Hz, CAr), 131.8, 131.5,
129.7, 128.7, 123.1 (d, JCP = 11.4 Hz, CArH), 54.6 (CH2-S),
36.1, 33.3 (d, JCP=28.7 Hz, CH2-P), 31.1, 26.3 (d, JCP=14.4
Hz), 26.1 (d, JCP=10.3 Hz), 25.6. HRMS-ESI: (M þ H)þ 576.04
C22H31N3PSCl2Pd calcd mass 576.0388. Anal. Calcd: C, 45.65;
H, 5.57. Found: C, 45.89; H, 5.61.
1
5c: 31P{1H} NMR (DMF-d7) δ: 42.3. H NMR (500 MHz,
DMF-d7) δ: 8.50 (s, 1H, triazole-H), 8.03-8.01 (m, 2H),
7.87-7.84 (m, 3H), 7.74 (d, 2H), 7.55 (d, 2H), 7.43-7.40 (m,
2H), 7.30-7.27 (m, 2H), 6.34 (s, 2H, CH2-S), 3.91 (s, 6H,
O-CH3), 3.80 (s, 2H, CH2-P). 13C{1H} NMR (125 MHz,
DMF-d7) δ: 162.3, 138.4 (d, JCP=12 Hz), 136.6, 134.2, 133.3,
131.6 (d, JCP=10 Hz), 130.3, 122.7 (d, JCP=13 Hz), 114.1 (d,
6b: 31P{1H} NMR (81 MHz, DMF-d7) δ: 46.11 (s, JPPt=3482
Hz). 1H NMR (200 MHz, DMF-d7) δ: 8.55 (s, 1H, triazole-H),
7.68-7.56 (m, 5H, Ar), 6.30 (s, CH2-S), 3.36 (d, JHP=10 Hz,
CH2-P), 2.52-2.33 (m, 4H), 1.94-1.45 (m, 18H). 13C{1H}
NMR (200 MHz, DMF-d7) δ: 151.6, 132.0, 131.9, 129.7,
123.2, 55.2, 27.0, 26.9, 26.3, 26.0, 25.9, 25.7. MS-ESI: (M þ
H)þ 665.1035 C22H31N3PSCl2Pt calcd mass 665.1001. Anal.
Calcd: C, 39.58; H, 4.83. Found: C, 40.16; H, 5.13.
JCP=5.0 Hz), 69.3 (s, CH2-S), 57.7 (s, OCH3), 25.8 (d, JCP=108
Hz). Anal. Calcd: C, 45.99; H, 3.86. Found: C, 44.99; H, 3.55.
5d: 31P{1H} NMR (DMF-d7) δ: 83.4. 1H NMR (DMF-d7) δ:
8.45 (s, 1H, triazole-H), 7.37-7.52 (m, 5H, Ph), 6.17 (s, 2H,
CH2-S), 3.37 (d, JHP=11.4 Hz, CH2-P), 2.53-2.65 (m, 2H, CH),
1.44 (dd, JHH =7.12 Hz, JHP =18.3 Hz, 6H, CH3), 1.17 (dd,
Acknowledgment. Financial support from Israel
Science Foundation (Grant No. 1292/07) and The FIRST
Program of the Israel Science Foundation (Grant No.
1514/07) is acknowledged. E.M.S. is a recipient of the
Schulich Graduate Fellowship.
J
HH=6.84 Hz, JHP=16.7 Hz, 6H, CH3). 13C{1H} NMR (DMF-
d7) δ: 149.4 (d, JCP=7.05 Hz, CAr), 131.9, 129.4, 128.5, 123.3 (d,
CP=12.5 Hz, CArH), 54.9 (CH2-S), 24.8 (d, JCP=28.3, CH-
J
CH3), 17.8 (d, JCP=28.3 Hz, CH2-P), 17.4, 16.7. Anal. Calcd: C,
38.53; H, 4.85. Found: C, 39.84; H, 5.72.
Supporting Information Available: Crystallographic data are
available free of charge via the Internet at http://pubs.acs.org.
General Procedure for the Preparation of Compounds 6. 6a: To
a suspension of (COD)PtCl2 in DMF (1 mL) was added a