Structures of copper complexes of the hybrid [SNS] ligand of bis(2-(benzylthio)ethyl)amine and facile catalytic formation of 1-benzyl-4-phenyl-1H-1,2,3-triazole through click reaction

Article abstract of DOI:10.1021/ic801690v

A hybrid ligand, bis(2-(benzylthio)ethyl)amine (SNS), with an amine and two thioether donors reacts with Cu(II) to give mononuclear [CuCl₂(SNS)] (1), [CuBr₂(SNS)] (2), [Cu(OTf)₂(SNS)(OH₂)] (3), and an one-dimens

Full text of DOI:10.1021/ic801690v

Inorg. Chem. 2009, 48, 1207-1213
Structures of Copper Complexes of the Hybrid [SNS] Ligand of
Bis(2-(benzylthio)ethyl)amine and Facile Catalytic Formation of
1-Benzyl-4-phenyl-1H-1,2,3-triazole through Click Reaction
Shi-Qiang Bai, Lip Lin Koh, and T. S. Andy Hor*
Department of Chemistry, National UniVersity of Singapore, 3 Science DriVe 3, Singapore 117543
Received September 3, 2008
A hybrid ligand, bis(2-(benzylthio)ethyl)amine (SNS), with an amine and two thioether donors reacts with Cu(II) to
give mononuclear [CuCl2(SNS)] (1), [CuBr2(SNS)] (2), [Cu(OTf)2(SNS)(OH2)] (3), and an one-dimensional Cu(I)
coordination polymer [Cu2I2(SNS)]n (4). All complexes have been characterized by single-crystal X-ray diffraction
analysis, and 1-3 were studied by EPR analysis at room temperature. Complexes 1 and 2 are penta-coordinated
with a distorted square pyramidal metal supported by a tridentate SNS ligand on the basal plane. Complex 3
shows a tetragonally distorted octahedral sphere with two trans and weakly bonding monodentate triflates. A 12-
membered ring in the solid lattice is formed by intermolecular H-bonding among the coordinated triflate and aqua
ligands from four neighboring molecules. Complex 4, the only Cu(I) in this series, shows a coordination polymer
chain [Cu4I4]n comprising tetrahedral Cu(I) centers stitched by the SNS ligand in a unique bridge-chelate mode in
the form of a helix. All four complexes are catalytically active at room temperature in a copper-catalyzed azide-alkyne
cycloaddition (CuAAA) three-component click reaction of benzyl chloride, sodium azide, and phenylacetylene in an
aqueous MeCN mixture to give good isolated yields of 1-benzyl-4-phenyl-1H-1,2,3-triazole, without the use of a
base or reducing agent.
Introduction
of immense significance. The classical pincer complexes5
and many other ligand sets with a mix of hard and soft donor
sites are among the myriad of examples. One of our current
foci is the use of the tridentate hybrid set [SNS] with
diagonally related donor atoms to support complexes that
are potentially unsaturated. An application of such a design
is found in the water-rich Pd(II) [SNS] complexes for
aqueous Suzuki coupling.6 Other representative developments
of [SNS]-stabilized complexes include those of the fluxional
Pd(II) allyl complexes,7a magnetically active dinuclear Ni(II)
S-substituted pyrazole complexes,7b brain-imaging agents
oxotechnetium(V) and oxorhenium(V) complexes,7c,d eth-
ylene trimerization catalyst Cr(III),7e,f a Cu2N2 diamond core
for electron transfer,8a and 1-D ribbons with Cu6I6
hexamers,8b among others.8c,d In this paper, we shall use such
The use of hybrid ligands,1 especially those with labile or
hemilabile2 functions, to promote dynamic properties such
as solution equilibria3 and catalytic reversibility4 is an area
* To whom correspondence should be addressed. Fax: +65-6873-1324.
E-mail: andyhor@nus.edu.sg.
(1) (a) Bell, S.; Wu¨stenberg, B.; Kaiser, S.; Menges, F.; Netscher, T.;
Pfaltz, A. Science 2006, 311, 642. (b) Braunstein, P.; Naud, F. Angew.
Chem., Int. Ed. 2001, 40, 680. (c) Huang, H.; Okuno, T.; Tsuda, K.;
Yoshimura, M.; Kitamura, M. J. Am. Chem. Soc. 2006, 128, 8716.
´
(d) Roseblade, S. J.; Ros, A.; Monge, D.; Alcarazo, M.; Alvarez, E.;
Lassaletta, J. M.; Ferna´ndez, R. Organometallics 2007, 26, 2570. (e)
Matano, Y.; Miyajima, T.; Ochi, N.; Nakabuchi, T.; Shiro, M.; Nakao,
Y.; Sakaki, S.; Imahori, H. J. Am. Chem. Soc. 2008, 130, 990. (f)
Dyson, G.; Frison, J.-C.; Simonovic, S.; Whitwood, A. C.; Douthwaite,
R. E. Organometallics 2008, 27, 281. (g) Willms, H.; Frank, W.;
Ganter, C. Chem.sEur. J. 2008, 14, 2719.
(2) (a) Yoon, T. P.; Jacobsen, E. N. Science 2003, 299, 1691. (b) Gischig,
S.; Togni, A. Eur. J. Inorg. Chem. 2005, 4745. (c) Weng, Z.; Teo, S.;
Hor, T. S. A. Acc. Chem. Res. 2007, 40, 676. (d) Kermagoret, A.;
Tomicki, F.; Braunstein, P. Dalton Trans. 2008, 2945. (e) Li, F.-W.;
Bai, S.-Q.; Hor, T. S. A. Organometallics 2008, 27, 672.
(3) (a) Chikkali, S.; Gudat, D.; Niemeyer, M. Chem. Commun. 2007, 981.
(b) Huynh, H. V.; Yeo, C. H.; Tan, G. K. Chem. Commun. 2006,
3833.
(5) (a) Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40,
3750. (b) Morales-Morales, D. ReV. Soc. Qu´ım. Me´x. 2004, 48, 338.
(c) Schuster, E. M.; Botoshansky, M.; Gandelman, M. Angew. Chem.,
Int. Ed. 2008, 47, 4555. (d) Snelders, D. J. M.; Kreiter, R.; Firet, J. J.;
van Koten, G.; Gebbink, R. J. M. K. AdV. Synth. Catal. 2008, 350,
262. (e) Neo, K. E.; Huynh, H. V.; Koh, L. L.; Henderson, W.; Hor,
T. S. A. J. Organomet. Chem. 2008, 693, 1628.
(4) (a) Bergbreiter, D. E.; Osburn, P. L.; Liu, Y.-S. J. Am. Chem. Soc.
1999, 121, 9531. (b) Wass, D. F. Dalton Trans. 2007, 816.
(6) Bai, S.-Q.; Hor, T. S. A. Chem. Commun. 2008, 3172.
10.1021/ic801690v CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 3, 2009 1207
Published on Web 01/05/2009

Bai et al.
Scheme 1. Schematic Representation of the Formation of CuI/II [SNS] Complexes 1-4
a hybrid ligand to promote different structural motifs in a
geometrically versatile metal such as copper9 and to introduce
labile ligands to the coordination sphere. A major impetus
of the latter is to promote potentially unsaturated species for
active aqueous-based catalysis. This is demonstrated by their
activities in Cu(I)-catalyzed azide-alkyne cycloaddition
(CuAAA) reactions in aqueous MeCN. The CuAAA reaction
is one of the most popular Huisgen’s dipolar cycloadditions,
as it provides a facile pathway to functional 1,2,3-triaz-
oles.10,11 The active catalytic mixture usually contains Cu(II)
with a reducing agent (usually sodium ascorbate).10c,d Direct
entry with Cu(I) or metallic copper or its clusters is possible
but met with problems such as undesirable alkyne-alkyne
homocoupling.10b The use of nitrogen,11a-d phosphorus,11e,f
and N-heterocyclic carbene ligands11g to protect the Cu(I)
is noteworthy. Sulfur-containing ligands have also been
applied in a range of catalytic systems,12a including the well-
known aminoarenethiolato Cu(I) in asymmetric conjugate
addition reactions and amination of aryl bromides.12b,c We
herein present a structural array of Cu(I)/(II) [SNS] com-
plexes supported by halides (Cl-, Br-, I-) and a labile
pseudohalide (OTf-) (Scheme 1) as well as the crystal-
lographic identification of [CuCl2(SNS)] (1), [CuBr2(SNS)]
(2), [Cu(OTf)2(SNS)(OH2)] (3), and [Cu2I2(SNS)]n (4) and
their potential uses in the CuAAA click reaction.
Results and Discussion
The tridentate [SNS] ligand is represented by bis(2-
(benzylthio)ethyl)amine6,7e with a central secondary amine
flanked by two thioether functional groups. Addition reac-
tions with CuCl2 · 2H2O or CuBr2 in MeOH and Cu(OTf)2
in THF result in Cu(II) five-coordinated [CuCl2(SNS)] (1),
[CuBr2(SNS)] (2), and six-coordinated [Cu(OTf)2(SNS)-
(OH2)] (3), respectively. Complexes 1 and 2 can also be
obtained by adding methanolic NaCl or KBr in situ to a
mixture of [SNS] and Cu(ClO4)2 ·6H2O. The use of KI under
similar conditions leads to a loss of coloration and formation
of the reduced [Cu2I2(SNS)]n (4), which is expected since
the redox potential would favor the reduction. The IR spectra
of these complexes invariably show a prominent band in the
(7) (a) Canovese, L.; Visentin, F.; Uguagliati, P.; Lucchini, V.; Bandoli,
G. Inorg. Chim. Acta 1998, 277, 247. (b) Konrad, M.; Meyer, F.;
Heinze, K.; Zsolnai, L. J. Chem. Soc., Dalton Trans. 1998, 199. (c)
Mastrostamatis, S. G.; Papadopoulos, M. S.; Pirmettis, I. C.; Paschali,
E.; Varvarigou, A. D.; Stassinopoulou, C. I.; Raptopoulou, C. P.;
Terzis, A.; Chiotellis, E. J. Med. Chem. 1994, 37, 3212. (d)
Zablotskaya, A.; Segal, I.; Lukevics, E.; Belyakov, S.; Spies, H. Appl.
Organometal. Chem. 2007, 21, 288. (e) McGuinness, D. S.; Wasser-
scheid, P.; Morgan, D. H.; Dixon, J. T. Organometallics 2005, 24,
552. (f) Temple, C. N.; Gambarotta, S.; Korobkov, I.; Duchateau, R.
Organometallics 2007, 26, 4598.
(8) (a) Harkins, S. B.; Peters, J. C. J. Am. Chem. Soc. 2004, 126, 2885.
(b) Amoore, J. J. M.; Hanton, L. R.; Spicer, M. D. Dalton Trans.
2003, 1056. (c) Pavlishchuk, V. V.; Strizhak, P. E.; Yatsimirskii, K. B.
Inorg. Chim. Acta 1988, 151, 133. (d) Kapoor, R.; Kataria, A.; Kapoor,
P.; Pannu, A. P. S.; Hundal, M. S.; Corbella, M. Polyhedron 2007,
26, 5131.
(9) (a) Bouwman, E.; Driessen, W. L.; Reedijk, J. Coord. Chem. ReV.
1990, 104, 143. (b) Lu, J. Y. Coord. Chem. ReV. 2003, 246, 327. (c)
Vitale, M.; Ford, P. C. Coord. Chem. ReV. 2001, 219-221, 3.
(10) (a) Huisgen, R.; Szeimies, G.; Mo¨bius, L. Chem. Ber. 1967, 100, 2494.
(b) Tornøe, C. W.; Christensen, C.; Meldal, M. J. Org. Chem. 2002,
67, 3057. (c) Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless,
K. B. Angew. Chem., Int. Ed. 2002, 41, 2596. (d) Rodionov, V. O.;
Presolski, S. I.; D´ıaz, D. D.; Fokin, V. V.; Finn, M. G. J. Am. Chem.
Soc. 2007, 129, 12705. (e) Fischler, M.; Sologubenko, A.; Mayer, J.;
Clever, G.; Burley, G.; Gierlich, J.; Carell, T.; Simon, U. Chem.
Commun. 2008, 169. (f) Aucagne, V.; Berna´, J.; Crowley, J. D.;
Goldup, S. M.; Ha¨nni, K. D.; Leigh, D. A.; Lusby, P. J.; Ronaldson,
V. E.; Slawin, A. M. Z.; Viterisi, A.; Walker, D. B. J. Am. Chem.
Soc. 2007, 129, 11950.
(11) (a) Lutz, J.-F.; Bo˜rner, H. G.; Weichenhan, K. Macromol. Rapid
Commun. 2005, 26, 514. (b) Donnelly, P. S.; Zanatta, S. D.; Zammit,
S. C.; White, J. M.; Williams, S. J. Chem. Commun. 2008, 2459. (c)
Candelon, N.; Laste´coue`res, D.; Diallo, A. K.; Aranzaes, J. R.; Astruc,
D.; Vincent, J.-M. Chem. Commun. 2008, 741. (d) Meldal, M.
Macromol. Rapid Commun. 2008, 29, 1016. (e) Pe´rez-Balderas, F.;
Ortega-Mun˜oz, M.; Morales-Sanfrutos, J.; Herna´ndez-Mateo, F.;
Calvo-Flores, F. G.; Calvo-As´ın, J. A.; Isac-Garc´ıa, J.; Santoyo-
Gonza´lez, F. Org. Lett. 2003, 5, 1951. (f) Seela, F.; Sirivolu, V. R.;
Chittepu, P. Bioconjugate Chem. 2008, 19, 211. (g) D´ıez-Gonza´lez,
S.; Correa, A.; Cavallo, L.; Nolan, S. P. Chem.sEur. J. 2006, 12,
7558. (h) Zhao, Y.-B.; Yan, Z.-Y.; Liang, Y.-M. Tetrahedron Lett.
2006, 47, 1545. (i) Johnson, J. A.; Finn, M. G.; Koberstein, J. T.;
Turro, N. J. Macromol. Rapid Commun. 2008, 29, 1052.
(12) (a) Bayo´n, J. C.; Claver, C.; Masdeu-Bulto´, A. M. Coord. Chem. ReV.
1999, 193-195, 73. (b) Arink, A. M.; Braam, T. W.; Keeris, R.;
Jastrzebski, J. T. B. H.; Benhaim, C.; Rosset, S.; Alexakis, A.; van
Koten, G. Org. Lett. 2004, 6, 1959. (c) Jerphagnon, T.; van Klink,
G. P. M.; de Vries, J. G.; van Koten, G. Org. Lett. 2005, 7, 5241.
1208 Inorganic Chemistry, Vol. 48, No. 3, 2009

Catalytic Formation of 1-Benzyl-4-phenyl-1H-1,2,3-triazole
Figure 1. EPR spectra of the solid samples of complexes 1 (a), 2 (b), and
3 (c) at 298 K with frequencies at 9.7761, 9.7759, and 9.7765 GHz,
respectively.
3200-3240 cm-1 region attributed to the N-H group of the
[SNS] ligand. Solid X-band EPR spectra were recorded for
1-3 at 298 K (Figure 1). Complex 1 shows a three g-value
anisotropic EPR pattern with g1 ) 2.13, g2 ) 2.09, and g3
) 2.07 (Figure 1a). Complex 2 exhibits a broad quasi-
isotropic signal centered at giso ) 2.07 (Figure 1b), corre-
sponding to the ∆MS ) (1 transition. The EPR spectrum
of 3 also reveals a three g-value anisotropic EPR spectrum
with g1 ) 2.21, g2 ) 2.07, and g3 ) 2.04, (Figure 1c) which
is consistent with the tetragonally distorted Cu(II).13
Single-crystal structural analysis of 1 and 2 shows that
they are mononuclear and penta-coordinated Cu(II) adducts
of CuX2 with the [SNS] ligand. The tridentate hybrid ligand
in the two complexes occupies the basal plane of a distorted
square-pyramidal (structural indices τ14 ) 0.05 for 1 and
0.12 for 2) metal sphere with a unique apical halide. (Max
deviations of +0.0327 to -0.0368 Å in the least-squares
plane {SNSCl} in 1 and +0.0651 to -0.0561 Å in the
{SNSBr} plane in 2) (Figures 2a and 3a). Its chelation results
in two five-membered rings fused at the Cu-N bond. Similar
coordination modes are found in some related CuX2L (L )
tridentate ligand) complexes.15 The slightly larger chelate
angle of 1 (av. 85.3°) compared to that of 2 (av. 84.8°)
probably reflects the higher steric influence of bromide. In
1, intermolecular H-bonding interactions are observed be-
tween the skeletal methylene C-H and secondary amine
Figure 2. (a) Thermal ellipsoids at 30% probability of the molecular
structure of 1. Selected bond distances [Å] and angles [deg]: Cu1-N1
2.001(4), Cu1-S1 2.353(1), Cu1-S2 2.380(1), Cu1-Cl2 2.241(1), Cu1-Cl1
2.518(1), N1-Cu1-Cl2 162.4(1), N1-Cu1-S1 85.4(1), N1-Cu1-S2
85.3(1), N1-Cu1-Cl1 92.3(1), S1-Cu1-S2 165.44(5), S1-Cu1-Cl1
94.39(4), S2-Cu1-Cl1 97.07(4), Cl2-Cu1-Cl1 105.29(5), Cl2-Cu1-S1
92.84(5), Cl2-Cu1-S2 92.76(5). (b) A crystal structure representation
showing secondary intermolecular H bonding in 1. (Cu1 · · ·Cu1A 5.829 Å,
symmetry code A: x, 1.5 - y, -0.5 + z.)
(13) (a) Ribas Gispert, J. Coordination Chemistry; Wiley-VCH Verlag
GmbH & Co. KGaA: Weinheim, 2008; pp 341-373. (b) Hathaway,
B. J.; Billing, D. E. Coord. Chem. ReV. 1970, 5, 143. (c) Bertini, I.;
Gatteschi, D.; Scozzafava, A. Coord. Chem. ReV. 1979, 29, 67. (d)
Le, X.-Y.; Shi, J.-E. Chin. J. Inorg. Chem. 1999, 15, 128. (e)
Sakaguchi, U.; Addison, A. W. J. Chem. Soc., Dalton Trans. 1979,
600.
Figure 3. (a) Thermal ellipsoids at 30% probability of the molecular
structure of 2. Selected bond distances [Å] and angles [deg]: Cu1-N1
1.990(8), Cu1-S1 2.337(3), Cu1-S2 2.341(3), Cu1-Br1 2.744(2), Cu1-Br2
2.364(2), N1-Cu1-S1 85.0(2), N1-Cu1-S2 84.5(2), N1-Cu1-Br1
93.2(2), N1-Cu1-Br2 168.8(2), S1-Cu1-S2 161.8(1), S1-Cu1-Br1
91.40(8), S1-Cu1-Br2 94.65(8), S2-Cu1-Br1 103.98(8), S2-Cu1-Br2
92.75(9), Br2-Cu1-Br1 97.98(6). (b) A crystal structure representation
showing secondary intermolecular H bonding in 2. (Cu1 · · ·Cu1A 5.699 Å,
symmetry code A: 1.5 - x, -0.5 + y, 0.5 - z)
(14) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C.
J. Chem. Soc., Dalton Trans. 1984, 1349.
(15) (a) Astner, J.; Weitzer, M.; Foxon, S. P.; Schindler, S.; Heinemann,
F. W.; Mukherjee, J.; Gupta, R.; Mahadevan, V.; Mukherjee, R. Inorg.
Chim. Acta 2008, 361, 279. (b) Dhanalakshmi, T.; Suresh, E.; Stoeckli-
Evans, H.; Palaniandavar, M. Eur. J. Inorg. Chem. 2006, 4687.
(16) (a) van Albada, G. A.; Mutikainen, I.; Turpeinen, U.; Reedijk, J.
J. Chem. Cryst. 2006, 36, 259. (b) Manson, J. L.; Donovan, J.;
Twamley, B. Polyhedron 2008, 27, 2650. (c) van Albada, G. A.;
Dominicus, I.; Viciano-Chumillas, M.; Mutikainen, I.; Turpeinen, U.;
Reedijk, J. Polyhedron 2008, 27, 617. (d) van Albada, G. A.; Smeets,
W. J. J.; Spek, A. L.; Reedijk, J. J. Chem. Cryst. 2000, 30, 11. (e)
Schmu¨lling, M.; Grove, D. M.; van Koten, G.; van Eldik, R.; Veldman,
N.; Spek, A. L. Organometallics 1996, 15, 1384. (f) Zhang, F.;
Jennings, M. C.; Puddephatt, R. J. Organometallics 2004, 23, 1396.
(g) Stang, P. J.; Cao, D. H.; Poulter, G. T.; Arif, A. M. Organometallics
1995, 14, 1110.
N-H of the ligands and the coordinated chlorides of the
neighboring molecule [C10-H · · · Cl2 3.65, C3-H · · ·Cl1
3.81, C12-H · · · Cl1 3.70, N1-H · · · Cl1 3.24 Å] in the c
direction (Figure 2b and Table 1). Complex 2 is similarly
Inorganic Chemistry, Vol. 48, No. 3, 2009 1209

Bai et al.
Table 1. Hydrogen-Bond Parameters (Å) in Complexes 1, 2, and 3
D-H· · ·Aa (Å) D-H (Å) D · · ·A (Å) H · · ·A (Å) ∠D-H· · ·A (deg)
Complex 1
C10-H· · ·Cl2A
C3-H· · ·Cl1A
C12-H· · ·Cl1A
N1-H· · ·Cl1A
0.97
0.97
0.97
0.88
3.647(5)
3.808(5)
3.702(5)
3.244(4)
2.89
2.89
2.79
2.40
135
157
158
162
Complex 2
3.443(8)
3.533(7)
3.80(1)
3.61(1)
3.62(1)
N1-H· · ·Br1A
N1-H· · ·Br2A
C3-H· · ·Br1A
C10-H· · ·Br2A
C14-H· · ·Br2B
C11-H· · ·S1A
0.91
0.91
0.97
0.97
0.93
0.97
2.66
2.91
2.92
3.05
2.95
2.79
145
127
151
119
131
168
3.75(1)
Complex 3
3.015(3)
3.199(4)
2.668(4)
2.625(4)
N1-H· · ·O4A
C2-H· · ·O3A
O1-H· · ·O6B
O1-H· · ·O5C
0.86
0.97
0.87
0.87
2.34
2.33
2.04
1.76
136
149
128
168
a Symmetry codes: for 1, A, x, 1.5 - y, -0.5 + z; for 2, A, 1.5 - x,
-0.5 + y, 0.5 - z; B, x - 1, y, z; for 3, A, x - 1, y, z; B, 1 + x, y, z; C,
-x, -y, -z.
stabilized by secondary intermolecular H-bond interactions
[N1-H · · · Br1 3.44, N1-H · · · Br2 3.53, C3-H · · · Br1
3.80,C10-H · · · Br23.61,C11-H · · · S13.75,C14-H · · · Br2
3.62 Å] (Figure 3b and Table 1).
Complex 3 shows a tetragonally distorted octahedral Cu(II)
sphere with tridentate [SNS] and monodentate aqua forming
the equatorial plane (max deviations +0.1025 to -0.0973
Å in the least-squares plane of {SNSO}) and two mono-
dentate triflates at the axial positions (Figure 4a). A
combination of the Jahn-Teller effect and weak basicity of
the triflate oxygen results in two very weak axial Cu-O
interactions [Cu1-O2 2.415(2), Cu1-O7 2.574(3) Å], which
are comparable with the axial Cu-O (triflate oxygen) bonds
in complexes [Cu(OTf)2(bpyNO)2] (2.397(2) Å;16a bpyNO
) 2,2′-bipyridine-N-oxide), [Cu(OTf)2(2-mepyz)2(OH2)2]
(2.420(4) and 2.423(6) Å;16b 2-mepyz ) 2-methylpyrazine),
[Cu(OTf)2(OH2)2(pyz)] (2.402(2) Å;16b pyz ) pyrazine), and
[Cu3(OTf)2(µ-aapm)2(µ-dca)2(Haapm)2] (2.534(3) Å;16c Haapm
) N-(pyrimidin-2-yl)acetamide) but are shorter and presum-
ably stronger than those in complex [Cu(OTf)2(ampym)2-
(OH2)2](ampym)2(ampym)2 (2.749(2) Å;16d ampym ) 2-ami-
nopyrimidine). The equatorial Cu-O (1.932(2) Å) is
comparable with its counterpart in [Cu(OH2)6]2+ (∼1.95 Å)
and [Cu(OTf)2(ampym)2(OH2)2](ampym)2(ampym)2 (1.937(2)
Å).16d The resultant [4 + 2] coordination of the metal readily
provides two potential axial sites for substrate entry in the
catalytic process.
The lattice structure shows significant intermolecular
H-bonding between the amine, methylene, and coordinated
aqua hydrogen with triflate oxygen [N1-H · · · O4 3.02,
C2-H· · ·O3 3.20, O1-H· · ·O6 2.67 Å] along the a direction
(Figure 4b and Table 1) and between the coordinated aqua
hydrogen and triflate oxygen [O1-H · · · O5 2.63 Å] in the b
direction (Table 1). The two ligands (triflate and water) thus
play a major role in stabilizing the solid lattice. Enclaved
among four molecules is a 12-membered ring formed by the
association of two coordinated triflates and two coordinated
aqua ligands through H-bonding (Figure 4c). Similar ring
structures are found in [Pt{C6H3(CH2NMe2)2-2,6}(OH2)]-
Figure 4. (a) Thermal ellipsoids at 30% probability of the molecular
structure of 3. Selected bond distances [Å] and angles [deg]: Cu1-N1
1.976(2), Cu1-S1 2.3573(8), Cu1-S2 2.3738(8), Cu1-O1 1.932(2),
Cu1-O2 2.415(2), Cu1-O7 2.574(3), N1-Cu1-S1 85.64(7), N1-Cu1-S2
87.28(7), N1-Cu1-O1 178.2(1), N1-Cu1-O2 89.72(8), N1-Cu1-O7
80.4(1), S1-Cu1-O1 93.67(8), S1-Cu1-O2 97.33(5), S1-Cu1-O7
86.48(8), S1-Cu1-S2 167.16(3), S2-Cu1-O1 93.09(8), S2-Cu1-O2
93.33(5), S2-Cu1-O7 81.79(7), O1-Cu1-O2 92.01(9), O1-Cu1-O7
97.9(1), O2-Cu1-O7 169.16(9). (b) H-bonding supramolecular structure
in 3. (c) O-H· · ·O H-bonding cyclic structure in 3.
(OTf),16e [Cu(OTf)2(2-mepyz)2(OH2)2],16b [{PtMe3(OH2)}2(1,3-
16f
BAIB)](OTf)2 (1,3-BAIB ) 1,3-C6H4(CHdNCH2CH2-
NMe2)2), and also in the complex [Pd(OTf)2(OH2)2(dppp)]16g
(dppp ) cis-(1,3-bis(diphenylphosphino)propane)), which
shows a pseudobutterfly configuration.
X-ray structural analysis of 4 shows an asymmetric unit
with two independent copper atoms. The structure reveals a
novel one-dimensional coordination polymer formed by a
chainoftwotypesof[Cu2I2]parallelograms(Cu1-Cu1A-I1-I1A
and Cu2-Cu2B-I2-I2A) interconnected orthogonally by
triply bridging iodides and chelate-bridging SNS (Figure 5a).
The latter coordination mode, which is not found in the
earlier Cu(II) complexes, shows a N,S chelated to one Cu
and S-bonded to its Cu neighbor in the next Cu2 sphere. The
1210 Inorganic Chemistry, Vol. 48, No. 3, 2009

Catalytic Formation of 1-Benzyl-4-phenyl-1H-1,2,3-triazole
terminal alkyne. We are seeking higher click efficiency by
carrying out a room temperature three-component reaction
using phenylacetylene, benzyl chloride, and an inorganic
azide (NaN3) as a one-pot mixture in MeCN/H2O (v/v 2:1,
6 mL) in the air. Similar success was reported in an aqueous
ionic liquid medium but under a fairly high level (15%) of
Cu(I) catalysts and in the presence of a base (Na2CO3).11h
The reaction readily proceeds to give 1-benzyl-4-phenyl-1H-
1,2,3-triazole without the need to introduce either a base or
reducing agent. The presence of MeCN, which is usually
not a desirable solvent, as it could saturate the active Cu(I)
catalyst, presumably promotes the reduction of Cu(II) to
Cu(I) (for 1-3).10f,18 The product, 1-benzyl-4-phenyl-1H-
1,2,3-triazole,11g,19 was purified (by column chromatogra-
20
phy), isolated, and confirmed by H and 13C NMR and
X-ray crystallographic analyses.19 Some representative cata-
lytic data are summarized in Table 2. All four complexes
give good isolated yields, with up to 98% for catalyst 3 (5%
loading; entry 16) or 87% for 4 (2% loading; entry 19). The
yields drop to 49-75% when the catalyst loading is reduced
to the lower limit of 0.5 mol % (entries 3, 9, 15, 21). All
catalysts are still active in pure water, even at 0.5 mol %
loading (entries 6, 12, 18, 24), but the yields are generally
lower. Good activities of [CuX(NHC)] (NHC ) N-hetero-
cyclic carbene) on similar click chemistry but using organic
azide have been reported.11g Within this system, 3 generally
shows the highest activities, possibly attributed to the ready
formation of catalytically active unsaturated species through
facile dissociation of triflate and water, as well as its higher
solubility and stability in the aqueous-based media.
1
Figure 5. (a) Thermal ellipsoids at 30% probability of the molecular
structure of 4. Selected bond distances [Å] and angles [deg]: Cu1-N1
2.085(5), Cu1-S1 2.307(2), Cu1-I1 2.5831(9), Cu1-I1A 2.7463(9),
Cu1-Cu1A 2.525(2), Cu2-S2 2.332(2), Cu2-I1A 2.6816(8), Cu2-I2
2.6329(9), Cu2-I2B 2.6509(8), Cu2-Cu2B 2.844(2), N1-Cu1-S1 91.2(2),
N1-Cu1-I1 119.4(1), N1-Cu1-I1A 100.4(1), N1-Cu1-Cu1A 134.4(1),
S1-Cu1-I1 112.96(5), S1-Cu1-Cu1A 131.02(7), S1-Cu1-I1A 103.68(5),
I1-Cu1-I1A 123.53(3), Cu1A-Cu1-I1A 58.50(3), Cu1A-Cu1-I1
65.03(3), Cu1-I1-Cu2A 113.02(3), Cu1-I1-Cu1A 56.47(3), S2-Cu2-I1A
107.51(5), S2-Cu2-I2 113.94(5), S2-Cu2-I2B 99.10(5), S2-Cu2-Cu2B
121.55(6), I2-Cu2-I2B 114.88(3), I2-Cu2-I1A 109.54(3), I2B-Cu2-I1A
111.33(3), I2-Cu2-Cu2B 57.75(3), I2B-Cu2-Cu2B 57.14(3), I1A-
Cu2-Cu2B 130.45(4), Cu2A-I1-Cu1A 93.79(2), Cu2-I2-Cu2B 65.12(3).
(symmetry codes: A, 1 - x, -y, 1 - z; B, 1 - x, 1 - y, 1 - z; C, x, y -
1, z; D, x, 1 + y, z). (b) [Cu4I4]n coordination polymer chain along the b
direction.
overall polymer chain thus shows intercalation of doubly
bridging µ2- and singly bridging µ3-iodides with Cu4 as the
repeating unit, namely, [Cu4I4]n. The triply bridging iodide
also brings a set of copper atoms to within bonding distance
(Cu1-Cu1A 2.525 Å), which is significantly shorter than the
other pair (Cu2-Cu2A 2.844 Å). The SNS ligand crosses
between two Cu2 moieties with longer separations (Cu1· · ·Cu2
3.963 Å), whereas the remaining metal separation is even longer
(Cu1 · · ·Cu2A 4.391 Å). There are no apparent interchain
interactions, either via H-bonding or Cu · · ·Cu interactions
(Cu1 · · ·Cu1E 7.211 Å, symmetry code E: 2 - x, -y, 1 - z).
This Cu(I) coordination polymer is assembled by bridging
iodides and the [SNS] hybrid ligand. The latter effectively
stitches the two rhombic Cu2I2 entities by traversing across
two metal centers, thereby fixing two Cu2I2’s into a Cu4I4
core (Figure 5b). This results in an unusual form of helical
arrangement of the SNS hybrid ligand wrapping around the
tetrahedral copper atoms along the metal chain. A myriad
of CuI discrete molecular entities, as well as 1-D and 2-D
structures, have been reported in recent years.8b,9b,c,17 The
known 1-D polymer system contains the likes of a zigzag
[CuI]n chain,17a,b [CuI]n columnar chain,17e staircase [CuI]n
chain,17f-k [Cu8I7]nn+ cluster-based stair-like double chain,17l
double six-membered rings [Cu6I6]n core-based chains,17m
[Cu14I18]4- anion,17n [Cu6I5]nn+ and [Cu2I]nn+ chains, and so
forth.17o The connected rhombic [Cu4I4]n motif of 4 is a new
addition to this range of 1-D polyiodocuprates.
(17) (a) The´bault, F.; Barnett, S. A.; Blake, A. J.; Wilson, C.; Champness,
N. R.; Schro¨der, M. Inorg. Chem. 2006, 45, 6179. (b) Caradoc-Davies,
P. L.; Hanton, L. R.; Hodgkiss, J. M.; Spicer, M. D. J. Chem. Soc.,
Dalton Trans. 2002, 1581. (c) Li, M.; Li, Z.; Li, D. Chem. Commun.
2008, 3390. (d) Blake, A. J.; Brooks, N. R.; Champness, N. R.; Crew,
M.; Deveson, A.; Fenske, D.; Gregory, D. H.; Hanton, L. R.;
Hubberstey, P.; Schro¨der, M. Chem. Commun. 2001, 1432. (e) Blake,
A. J.; Brooks, N. R.; Champness, N. R.; Cooke, P. A.; Deveson, A. M.;
Fenske, D.; Hubberstey, P.; Li, W.-S.; Schro¨der, M. J. Chem. Soc.,
Dalton Trans. 1999, 2103. (f) Blake, A. J.; Brooks, N. R.; Champness,
N. R.; Hanton, L. R.; Hubberstey, P.; Schro¨der, M. Pure Appl. Chem.
1998, 70, 2351. (g) Peng, R.; Li, D.; Wu, T.; Zhou, X.-P.; Ng, S. W.
Inorg. Chem. 2006, 45, 4035. (h) Persky, N. S.; Chow, J. M.;
Poschmann, K. A.; Lacuesta, N. N.; Stoll, S. L.; Bott, S. G.; Obrey,
S. Inorg. Chem. 2001, 40, 29. (i) Fitchett, C. M.; Steel, P. J. Inorg.
Chem. Commun. 2007, 10, 1297. (j) Kim, T. H.; Shin, Y. W.; Kim,
J. S.; Lee, S. S.; Kim, J. Inorg. Chem. Commun. 2007, 10, 717. (k)
Cariati, E.; Roberto, D.; Ugo, R.; Ford, P. C.; Galli, S.; Sironi, A.
Inorg. Chem. 2005, 44, 4077. (l) Cheng, J.-W.; Zheng, S.-T.; Yang,
G.-Y. Inorg. Chem. 2007, 46, 10261. (m) Li, G.; Shi, Z.; Liu, X.;
Dai, Z.; Feng, S. Inorg. Chem. 2004, 43, 6884. (n) Allen, D. W.;
Gelbrich, T.; Hursthouse, M. B. Inorg. Chim. Acta 2001, 318, 31. (o)
Wu, T.; Li, M.; Li, D.; Huang, X.-C. Cryst. Growth Des. 2008, 8,
568. (p) Cheng, J.-W.; Zhang, J.; Zheng, S.-T.; Yang, G.-Y.
Chem.sEur. J. 2008, 14, 88.
(18) Kratochvil, B.; Zatko, D. A.; Markuszewski, R. Anal. Chem. 1966,
38, 770.
(19) (a) Lokanath, N. K.; Sridhar, M. A.; Shashidhara Prasad, J.; Bhadre
Gowda, D. G.; Rangappa, K. S. Z. Kristallogr. New Cryst. Struct.
1997, 212, 35. (b) Suijkerbuijk, B. M. J. M.; Aerts, B. N. H.; Dijkstra,
H. P.; Lutz, M.; Spek, A. L.; van Koten, G.; Gebbink, R. J. M. K.
Dalton Trans. 2007, 1273.
(20) NMR data for catalytic product of 1-benzyl-4-phenyl-1H-1,2,3-triazole:
1H NMR (500 MHz, CDCl3, 25°C): δ 5.57 (s, 2H, CH2), 7.26-7.41
(m, 8H), 7.66 (s, 1H), 7.79 and 7.80 (d, 2H). 13C NMR (125.77 MHz,
CDCl3, 25°C): δ 54.2, 119.4, 125.7, 128.0, 128.1, 128.8, 129.1, 130.5,
134.6, 148.2.
CuAAA Click Reaction Catalyzed by 1-4. A typical
Cu-catalyzed Huisgen reaction couples organoazide with a
Inorganic Chemistry, Vol. 48, No. 3, 2009 1211

Bai et al.
Table 2. Catalytic Formation of 1-Benzyl-4-phenyl-1H-1,2,3-triazole from a CuAAA Click Reaction Promoted by Copper Complexes with [SNS]
Hybrid Ligand
entry
catalyst
solvent
reaction time, h
catalyst loading, mol %
isolated yield, %
1
2
3
4
5
6
7
8
1
1
1
1
1
1
2
2
2
2
2
2
3
3
3
3
3
3
4
4
4
4
4
4
MeCN/H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
H2O
24
24
24
1
15
24
24
24
24
1
15
24
24
24
24
1
15
24
24
24
24
1
2
1
0.5
5
5
0.5
2
1
0.5
5
5
0.5
2
1
0.5
5
5
0.5
2
1
0.5
5
5
82
74
49
91
54
37
86
84
75
92
87
57
92
89
72
98
75
36
87
85
72
83
77
54
H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
H2O
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
H2O
H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
MeCN/H2O
H2O
15
24
H2O
0.5
procedures.7e,6 Elemental analyses for C, H, and N were performed
on a Perkin-Elmer PE 2400 CHNS elemental analyzer. Infrared
spectra were obtained on the Shimadzu IR-470 spectrometer from
samples in KBr discs. The NMR spectra were measured at 25 °C
using a Bruker ACF 500 NMR spectrometer. EPR spectra were
measured at Nanjing University using a Bruker ER 200-D-SRC
spectrometer for solid samples at 298 K. The general procedure
for a CuAAA catalytic preparation is given:
The ability of the hybrid ligand [SNS] to stabilize complex
formation in both Cu(II) and Cu(I) is an advantage of the
current system. It offers practical convenience to the prepara-
tion of a catalyst precursor and a ready stabilizing source
for the metal in both oxidation states. The high air and water
stability and the avoidance of potentially hazardous organic
azides are additional advantages.
Isolation of these complexes under similar conditions
suggests that the hybrid ligand uses its mix of soft-hard
functions to support different redox states of the metal (Cu(I)/
(II)) and ligand demands (denticity and lability). Not only
can it adapt to different metal geometries (square-pyramidal,
octahedral, and tetrahedral) but it also adjusts its coordination
modes to adapt to the metal nuclear and topological as-
semblies (mono- and polymeric). These electronic, geo-
metrical, steric, and conformational adaptations of the SNS
ligand help it support complexes with dynamic behaviors.
Ligands of this nature are probably best used in a complex
environment when the metal needs to consistently switch
between saturation and unsaturated states and among dif-
ferent redox states, nuclearities, and even topologies. This
ability to support dynamic changes within a self-contained
system is probably the single most important feature of a
hybrid ligand. Ongoing efforts in our laboratory are directed
at the exploitation of such potential.
In a vial fitted with a screw cap, benzyl chloride (0.5 mmol),
sodium azide (0.6 mmol), phenylacetylene (1.0 mmol), and
Cu(II)/(I) [SNS] complexes (1-4) were added to a solvent
[MeCN/H2O (v/v 2:1, 6 mL) mixture or pure water (6 mL)].
The reaction mixture was stirred at room temperature in the air.
The product was obtained by extraction with Et2O and purified
1
by column chromatography and confirmed by H and 13C NMR
and X-ray structural analyses.
Caution! Sodium azide is potentially explosiVe and hence must
be handled with great caution.
Syntheses. [CuCl2(SNS)] (1). A MeOH solution (5 mL) of
CuCl2 ·2H2O (0.1 mmol, 0.017 g) was added to a MeOH solution
(5 mL) of the SNS ligand (0.1 mmol, 0.032 g), and the mixture
was stirred at room temperature. Slow evaporation of the resulting
solution afforded blue crystals of 1 after ∼2 weeks. Yield: 0.019 g
(42%). Anal. calcd for C18H23Cl2CuNS2 (451.93): C, 47.84; H, 5.13;
N, 3.10. Found: C, 47.94; H, 4.98; N, 3.17%. IR bands (cm-1):
3210m, 3084m, 2928m, 1601m, 1490m, 1454m, 1417m, 1078m,
969m, 762m, 701vs.
Experimental Section
CuBr2(SNS)] (2). Complex 2 (green crystals) was prepared
similarly to 1, using CuBr2 as the substrate. Yield: 0.042 g (78%).
Anal. calcd for C18H23Br2CuNS2 (540.85): C, 39.97; H, 4.29; N,
Materials and Physical Measurements. All of the starting
chemicals were used as purchased. The SNS ligand of bis(2-
(benzylthio)ethyl)amine was prepared according to the literature
1212 Inorganic Chemistry, Vol. 48, No. 3, 2009

Catalytic Formation of 1-Benzyl-4-phenyl-1H-1,2,3-triazole
2.59. Found: C, 40.13; H, 4.14; N, 2.81%. IR bands (cm-1): 3207m,
3052m, 2968m, 2932m, 1598m, 1492m, 1454m, 1413m, 1071m,
1001m, 963m, 761m, 696vs.
heavy atoms, followed by difference maps for the light non-
hydrogen atoms. Anisotropic thermal parameters were refined for
the rest of the non-hydrogen atoms. Hydrogen atoms were placed
geometrically and refined isotropically. CCDC reference numbers:
692260 (1), 692261 (2), 692262 (3), and 692263 (4).
Crystal Refinement Data. [CuCl2(SNS)] (1). Formula:
C18H23Cl2CuNS2, blue rod crystal, monoclinic space group P21/c;
a ) 13.957(2), b ) 13.636(2), c ) 11.479(2) Å; ꢀ ) 112.206(3)°;
V ) 2022.6(6) Å3; Z ) 4. Crystal size: 0.40 × 0.14 × 0.08 mm3;
GOF ) 1.064. Reflections collected: 13 716. Independent reflec-
tions: 4639 [Rint ) 0.0547]; R1 ) 0.0661; wR2 ) 0.1599.
[CuBr2(SNS)] (2). Formula: C18H23Br2CuNS2, green thin plate
crystal, monoclinic space group P21/n; a ) 8.957(2), b ) 11.332(2),
c ) 21.243(4) Å; ꢀ ) 90.554(4)°; V ) 2155.9(7) Å3; Z ) 4. Crystal
size: 0.20 × 0.10 × 0.02 mm3; GOF ) 1.034. Reflections collected:
11 725. Independent reflections: 3806 [Rint ) 0.0738]; R1 ) 0.0724;
wR2 ) 0.1890.
[Cu(OTf)2(SNS)(OH2)] (3). The THF solution (3 mL) of
Cu(OTf)2 (0.1 mmol, 0.036 g) was added to a THF (5 mL) solution
of SNS (0.1 mmol, 0.032 g), and the mixture was stirred. Slow
evaporation of the resulting solution afforded green crystals of 3
after ∼4 weeks. Yield: 0.036 g (52%). Anal. calcd for C20H25-
CuF6NO7S4 (697.19): C, 34.45; H, 3.61; N, 2.01. Found: C, 34.65;
H, 3.46; N, 2.05%. IR bands (cm-1): 3212m, 1656m, 1604m,
1494m, 1457m, 1424m, 1286b, 1262b, 1243b, 1172s, 1079m,
1032m, 771m, 706m, 635m, 572m, 516m.
[Cu2I2(SNS)]n (4). A MeOH solution (5 mL) of Cu(ClO4)2 ·6H2O
(0.1 mmol, 0.037 g) was added to the MeOH solution (5 mL) of
the SNS ligand (0.1 mmol, 0.032 g), and the mixture was stirred
for about 5 min. A methanol solution (5 mL) of KI (0.2 mmol,
0.033 g) was added. The solution readily changed from green to
brown with some white precipitates. MeCN was then added to
dissolve the precipitate completely. Slow evaporation of the
resulting weak brown solution afforded colorless crystals of 4 after
∼4 weeks. Yield: 0.031 g (45%). Anal. calcd for C18H23Cu2I2NS2
(698.37): C, 30.96; H, 3.32; N, 2.01. Found: C, 31.43; H, 2.90; N,
2.14%. IR bands (cm-1): 3239m, 3026m, 2928m, 2912m, 2851m,
1601m, 1493m, 1450m, 1409m, 1083m, 950m, 849m, 810m, 770m,
698vs.
[Cu(OTf)2(SNS)(OH2)] (3). Formula: C20H25CuF6NO7S4, green
j
plate crystal, triclinic space group P1; a ) 8.3046(8), b ) 11.467(1),
c ) 16.216(2) Å; R ) 104.804(2), ꢀ ) 91.809(2), γ ) 105.428(2)°;
V ) 1430.9(2) Å3; Z ) 2. Crystal size: 0.60 × 0.40 × 0.10 mm3;
GOF ) 1.027. Reflections collected: 18 481. Independent reflec-
tions: 6559 [Rint ) 0.0331]; R1 ) 0.0477; wR2 ) 0.1378.
[Cu2I2(SNS)]n (4). Formula: C18H23Cu2I2NS2, colorless plate
j
crystal, triclinic space group P1; a ) 9.1552(6), b ) 10.7244(7),
X-Ray Crystallography. All measurements were conducted at
room temperature on a Bruker AXS SMART APEX diffractometer,
equipped with a CCD area detector using Mo KR radiation (λ )
0.71073 Å). The collecting of frames of date, indexing reflection,
and determination of lattice parameters and polarization effects were
performed with the SMART suite of programs.21 The integration
of intensity of reflections and scaling was carried out by SAINT.21
The empirical absorption correction was performed by SADABS.22
The space group determination, structure solution and least-squares
refinements on |F|2 were carried out with SHELXS-97 and SHELXL-
97.23 The structures were solved by direct methods to locate the
c ) 12.2586(8) Å; R ) 93.343(1), ꢀ ) 100.822(1), γ )
105.480(1)°; V ) 1131.8(1) Å3; Z ) 2. Crystal size: 0.36 × 0.20
× 0.04 mm3; GOF ) 1.099. Reflections collected: 14 980.
Independent reflections: 5182 [Rint ) 0.0344]; R1 ) 0.0478; wR2
) 0.1182.
Acknowledgment. We thank Professor Jing-Lin Zuo
(Nanjing University, China) for EPR measurements and
helpful discussions. We are also grateful to G. K. Tan for
crystallographic assistance. This work was supported by the
Agency for Science, Technology & Research (R143-000-
277-305), Ministry of Education (R-143-000-361-112), and
the National University of Singapore.
(21) SMART, Version 5.631, Software Reference Manual; SAINT, Version
6.63, Software Reference Manual; Bruker AXS GmbH: Karlsruhe,
Germany, 2000.
(22) Software for Empirical Absorption Correction: Sheldrick, G. M.
SADABS; University of Go¨ttingen: Go¨ttingen, Germany, 2001.
(23) (a) Program for Crystal Structure Solution: Sheldrick, G. M. SHELXS-
97; University of Go¨ttingen: Go¨ttingen, Germany, 1997. (b) Program
for Crystal Structures Refinement: Sheldrick, G. M. SHELXL-97;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Supporting Information Available: X-ray crystallographic file
in CIF format for the four molecules (1-4). This material is
available free of charge via the Internet at http://pubs.acs.org.
IC801690V
Inorganic Chemistry, Vol. 48, No. 3, 2009 1213