A one pot multi-component CuAAC click approach to bidentate and tridentate pyridyl-1,2,3-triazole ligands: Synthesis, X-ray structures and copper(II) and silver(I) complexes

Article abstract of DOI:10.1016/j.poly.2009.06.010

A one pot, multi-component CuAAC reaction has been developed for the generation of alkyl, benzyl or aryl substituted bi and tridentate pyridyl-1,2,3-triazole ligands from their corresponding halides, sodium azide and alkynes in excellent yields. The ligands have been fully characterized by elemental analysis, HR-ESMS, IR, ¹H and ¹³C NMR and in the ferrocenyl substituted cases the structures were confirmed by X-ray crystallography. Additionally, we have examined the coordination chemistry of these ligands and found that a variety of geometrically diverse Cu(II) and Ag(I) complexes, including interesting tri and tetrasilver complexes, can be formed.

Full text of DOI:10.1016/j.poly.2009.06.010

Polyhedron 29 (2010) 70–83
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
A one pot multi-component CuAAC ‘‘click” approach to bidentate and
tridentate pyridyl-1,2,3-triazole ligands: Synthesis, X-ray structures
and copper(II) and silver(I) complexes
*
James D. Crowley , Pauline H. Bandeen, Lyall R. Hanton
Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 9 June 2009
A one pot, multi-component CuAAC reaction has been developed for the generation of alkyl, benzyl or
aryl substituted bi and tridentate pyridyl-1,2,3-triazole ligands from their corresponding halides, sodium
azide and alkynes in excellent yields. The ligands have been fully characterized by elemental analysis,
HR-ESMS, IR, 1H and 13C NMR and in the ferrocenyl substituted cases the structures were confirmed
by X-ray crystallography. Additionally, we have examined the coordination chemistry of these ligands
and found that a variety of geometrically diverse Cu(II) and Ag(I) complexes, including interesting tri
and tetrasilver complexes, can be formed.
Keywords:
Click reactions
Cu(II) complexes
Ag(I) complexes
Heterocyclic ligands
Chelating ligands
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
development of such a method1 [65,66]. We show that a one pot,
multi-component CuAAC reaction can be used to generate alkyl, ben-
Despite the central importance of ligand design and synthesis in
modern coordination chemistry [1–17] there are very few modular,
facile and high yielding methods for the generation of functional-
ised ligand scaffolds. The recently discovered Cu(I)-catalyzed 1,3-
cycloaddition of organic azides with terminal alkynes [18,19]
(the CuAAC reaction) offers great promise in this regard. The
CuAAC methodology, a so-called ‘click’ [20] reaction, has been ap-
plied to functional molecule synthesis in a wide range of fields,
including the biological and materials sciences, due to its reliabil-
ity, mild reaction conditions and wide substrate scope [21–28]. Be-
cause the 1,4-functionalized 1,2,3-triazoles generated in the
CuAAC reaction have the potential to act as N donor ligands a num-
ber of authors have examined its use in the synthesis of a range of
mono [29–36], bi [33,37–44], tri [45–53] and polydentate [54–58]
ligand architectures.
zyl or aryl substituted bi and tridentate pyridyl-1,2,3-triazole ligands
from their corresponding halides, sodium azide and alkynes in excel-
lent yield. The potentially dangerous organic azides are generated
in situ then captured by copper(I) acetylides, providing the desired
pyridyl-1,2,3-triazole ligands in excellent yields. The method not
only improves the synthetic efficiency for preparing previously re-
ported bidentate and tridentate ligand architectures but also extends
this family of ligands and potentially enables the rapid synthesis of
functionalized ligand scaffolds. Finally, we have examined the coor-
dination chemistry of these ligands and found that a variety of geo-
metrically diverse Cu(II) and Ag(I) complexes, including interesting
tri and tetrasilver complexes, can be formed.
2. Experimental
We have a long standing interest in the design and synthesis of
functional ligand architectures [30,59–63] and became interested
in exploiting the CuAAC reaction to synthesize polydentate ligands
for the generation of metallosupramolecular architectures. How-
ever, retrosynthetic analysis of the desired target molecules indi-
cated that some of the required synthons were potentially
explosive low molecular weight polyazides [64]. Isolation of these
types of molecules is a safety hazard and therefore ill-advised.
Undeterred we set out to find a safe efficient method for the gen-
eration of polydentate ‘click’ chelators, herein we describe the
2.1. General
Unless otherwise stated, all reagents were purchased from com-
mercial sources and used without further purification. Dry CH2Cl2
and CH3CN were obtained by passing the solvent through an
activated alumina column on a PureSolvTM solvent purification
system (Innovative Technologies Inc., MA). 2,6-Diethynylpyridine
[67] was prepared according to the literature procedure. Petrol
refers to the fraction of petroleum ether boiling in the range
1
* Corresponding author. Tel.: +64 34797731; fax: +64 34797906.
E-mail address: jcrowley@chemistry.otago.ac.nz (J.D. Crowley).
During the preparation of this manuscript Schubert et al. has reported a similar
approach, see Ref. [65] and [66].
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.06.010

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
71
40–60 °C. Flash column chromatography was carried out using
Kiesegel C60 (Fisher) as the stationary phase. Analytical TLC was
performed on precoated silica gel plates (0.25 mm thick, 60F254,
Merck, Germany) and observed under UV light. All melting points
were determined using a Sanyo Gallenkamp apparatus and are
uncorrected. 1H NMR and 13C NMR spectra were recorded on a
300 MHz Varian UNITY INOVA or 400 MHz Varian 400 MR spec-
trometer at 298 K. Chemical shifts are reported in parts per million
and referenced to residual solvent. Coupling constants (J) are re-
ported in Hertz (Hz). Standard abbreviations indicating multiplic-
ity were used as follows: m = multiplet, quint. = quintet,
q = quartet, t = triplet, d = doublet, s = singlet, br = broad. IR spectra
were recorded on a Perkin–Elmer Spectrum BX FT-IR spectrometer
using KBr discs. Microanalyses were performed at the Campbell
Microanalytical Laboratory at the University of Otago. Electrospray
mass spectra (ESMS) were collected on a Bruker micro-TOF-Q
spectrometer.
Safety note: Sodium azide is very toxic and appropriate precau-
tions should be taken. As low molecular weight organic azides are
potential explosives, care must be taken during their handling [64].
Generally, when the total number of carbon (C) plus oxygen (O)
atoms is less than the total numbers of nitrogen atoms (N) by a ra-
tio of three, i.e., (C + O)/N < 3, the compound is considered as an
explosive hazard. A standard PVC blast shield was used when nec-
essary. Additionally, copper azides and acetylides are explosive
when dry, and their traces should be removed before the CuAAC
reaction products are dried. This is achieved by pouring the crude
reaction mixture into 100 mL of aqueous EDTA/NH4OH (1 M).
2.0 mmol, 1.02 equiv.) was added and the reaction mixture was
heated to 95 °C for 20 h. The resulting suspension was poured into
100 mL of aqueous EDTA/NH4OH (1 M). The orange precipitate was
isolated by filtration and washed with dilute EDTA/NH4OH (10 mL)
and H2O (10 mL) then vacuum dried. The solid was redissolved in
CH2Cl2 (100 mL) and the organic phase was washed with H2O
(100 mL) and brine (100 mL), dried (MgSO4) and the solvent removed
under reduced pressure giving 1b as an orange solid. If necessary the
product can be further purified by chromatography (CH2Cl2 then 20%
acetone in CH2Cl2). Yield: 0.58 g, 85%. Mp 174–175 °C; 1H NMR
(300 MHz, CDCl3) d: 8.55 (ddd, J = 0.9, J = 1.7, J = 4.8, 1H, Ha), 8.23–
8.11 (m, 1H, Hd), 8.05 (s, 1H, He), 7.76 (td, J = 1.8, J = 7.8, 1H, Hc),
7.21 (ddd, J = 1.2, J = 4.9, J = 7.5, 1H, Hb), 5.37 (s, 2H, Hf), 4.31 (t,
J = 1.8, 2H, Hg), 4.23 (t, J = 1.8, 2H, Hh), 4.21 (s, 5H, Hi); 13C NMR
(75 MHz, CDCl3) d: 150.4, 149.4, 148.3, 137.0, 134.2, 122.8, 121.4,
120.2, 80.5, 69.2, 69.1, 68.9, 50.3; I.R. (KBr):
t
(cmꢁ1) 3105, 3096,
3075, 2925, 1603, 1595, 1543, 1426, 1405, 1333, 1260, 1234, 1223,
1191, 1075, 1050, 996, 980, 928, 853, 824, 785, 743, 729; HRESI-MS
(CH2Cl2/MeOH): m/z = 367.0614 [M+Na]+ (calc. for C18H16FeN4Na
367.0617 [M+Na]+); Anal. Calc. for C18H16FeN4: C, 62.81; H, 4.69; N,
16.28. Found: C, 62.76; H, 4.86; N, 16.30%.
2.2.1.3. 2-(1-Octyl-1H-1,2,3-triazol-4-yl)pyridine (1c). To a stirred
solution of 2-ethynylpyridine (0.62 g, 6.0 mmol, 1 equiv.) in DMF/
H2O (15 mL, 4:1) was added NaN3 (0.47 g, 7.2 mmol, 1.2 equiv.),
Na2CO3 (0.65 g, 6.0 mmol, 1 equiv.), CuSO4ꢀ5H2O (0.30 g, 1.2 mmol,
0.2 equiv.) and ascorbic acid (1.05 g, 6.0 mmol, 1.0 equiv.). 1-Bro-
mooctane (1.27 g, 6.6 mmol, 1.1 equiv.) was added and the reac-
tion mixture was stirred at 95 °C for 20 h. The suspension was
then partitioned between aqueous NH4OH/EDTA (1 M, 100 mL)
and CH2Cl2 (100 mL) and the layers separated. The organic phase
was washed with H2O (100 mL) and brine (100 mL), dried (MgSO4)
and the solvent removed under reduced pressure. Chromatography
(CH2Cl2 then 10% acetone in CH2Cl2) gave 1c as a white solid. Yield:
0.71 g, 88%. Mp 67–68 °C; 1H NMR (300 MHz, CDCl3) d: 8.52–8.50
(m, 1H, Ha), 8.12 (d, J = 8.0, 1H, Hd), 8.07 (s, 1H, He), 7.71 (td,
J = 1.8, J = 7.8, 1H, Hc), 7.16 (ddd, J = 1.1, J = 4.9, J = 7.5, 1H, Hb),
4.35 (t, J = 7.2, 2H, Hf), 1.88 (p, J = 7.3, 2H, Hg), 1.24 (m, 10H,
Hh-l), 0.80 (t, J = 6.7, 3H, Hm); 13C NMR (75 MHz, CDCl3) d: 150.7,
149.6, 148.6, 137.1, 123.0, 122.9, 120.4, 50.8, 31.9, 30.5, 29.3,
2.2. Experimental procedures
2.2.1. Ligand synthesis
2.2.1.1. 2-(1-Benzyl-1H-1,2,3-triazol-4-yl)pyridine (1a). To a stirred
solution of 2-ethynylpyridine (0.62 g, 6.0 mmol, 1 equiv.) in DMF/
H2O (15 mL, 4:1) was added NaN3 (0.42 g, 6.6 mmol, 1.1 equiv.),
Na2CO3 (0.65 g, 6.0 mmol, 1 equiv.), CuSO4ꢀ5H2O (0.30 g,
1.20 mmol, 0.2 equiv.) and ascorbic acid (1.06 g, 6.0 mmol,
1.0 equiv.). Benzyl bromide (1.07 g, 6.3 mmol, 1.05 equiv.) was
added and the reaction mixture was stirred at room temperature
for 20 h. Upon completion (monitored by TLC or LC-MS), the crude
mixture was poured into 100 mL of aqueous EDTA/NH4OH (1 M).
The off-white precipitate was isolated by filtration and washed
with dilute aqueous EDTA/NH4OH (10 mL, 1 M) and H2O (10 mL)
and vacuum dried. The solid was redissolved in CH2Cl2 (100 mL)
and the organic phase was washed with H2O (100 mL) and brine
(100 mL), dried (MgSO4) and the solvent removed under reduced
pressure giving 1a as a white solid. If necessary the product can
be further purified by chromatography (CH2Cl2 then 20% acetone
in CH2Cl2). Yield: 1.3 g, 92%. Mp 115–116 °C; 1H NMR (300 MHz,
CDCl3): d = 8.56 (ddd, J = 4.9, J = 1.8, J = 1.0, 1H, Ha), 8.21 (d,
J = 8.5, 1H, Hd), 8.18 (s, 1H, He), 7.83 (td, J = 7.8, 1.7, 1H, Hc),
7.40–7.31 (m, 5H, Hg,h,i), 7.27–7.25 (m, 1H, Hb), 5.61 (s, 2H, Hf).
13C NMR (75 MHz, CDCl3) d: 150.2, 149.2, 148.6, 137.0, 134.3,
29.2, 26.7, 22.8, 14.3; I.R. (KBr):
t
(cmꢁ1) 3120, 3050, 2928, 1605,
1594, 1421, 1377, 1345, 1299, 1227, 1149, 1080, 1047, 996, 851,
798, 751; HRESI-MS (CH2Cl2/MeOH): m/z = 281.1755 [M+Na]+
(calc. for C15H22N4Na 281.1742 [M+Na]+); Anal. Calc. for
C15H22N4ꢀ(0.66H2O): C, 66.66; H, 8.70; N, 20.73. Found: C, 66.77;
H, 8.34; N, 20.82%.
2.2.1.4. 2-(1-Phenyl-1H-1,2,3-triazol-4-yl)pyridine (1d). To a stirred
argon degassed solution of iodobenzene (0.41 g, 2.2 mmol,
1.1 equiv.) in EtOH/H2O (10 mL, 7:3) was added NaN3 (0.16 g,
2.4 mmol, 1.2 equiv.), CuI (0.08 g, 0.4 mmol, 0.2 equiv.), N,N0-
Dimethylethylenediamine (0.05 g, 0.6 mmol, 0.3 equiv.) and so-
dium ascorbate (0.20 g, 1.0 mmol, 0.5 equiv.). The reaction was
then heated to reflux under an argon atmosphere for 2 h. After this
time had elapsed the reaction mixture was cooled to room temper-
ature and 2-ethynylpyridine (0.21 g, 2.0 mmol, 1 equiv.), Cu-
SO4ꢀ5H2O (0.10 g, 0.2 mmol, 0.2 equiv.) and sodium ascorbate
(0.20 g, 1.0 mmol, 0.5 equiv.) were added to the reaction mixture
and the resulting suspension was stirred at room temperature for
20 h. The reaction mixture was then poured into aqueous
NH4OH/EDTA (1 M, 100 mL). The resulting precipitate was isolated
by filtration and washed well with NH4OH/EDTA (10 mL) and H2O
(10 mL) then vacuum dried. Chromatography (CH2Cl2 then 19:1
CH2Cl2/acetone) gave 1d as a white solid. Yield: 0.39 g, 89%. Mp
90–91 °C; 1H NMR (300 MHz, CDCl3) d: 8.63 (ddd, J = 0.9, J = 1.7,
J = 4.9, 1H, Ha), 8.61 (s, 1H, He), 8.26 (m, 1H, Hd), 7.85–7.80 (m,
129.2, 128.9, 128.3, 122.7, 122.0, 120.3, 54.4; I. R. (KBr):
t )
(cmꢁ1
3102, 3090, 3066, 2924, 1603, 1595, 1421, 1345, 1224, 1150,
1072, 1045, 995, 786, 727. HRESI-MS (MeOH): m/z = 237.1138
[M+H]+ (calc. for C14H13N4 237.1140 [M+H]+), 259.0967 [M+Na]+
(calc. for C14H12N4Na 259.0959 [M+Na]+; Anal. Calc. for C14H12N4:
C, 71.17; H, 5.12; N, 23.71. Found: C, 70.77; H, 5.06; N, 23.77%.
2.2.1.2. 2-(1-Ferrocenylmethyl-1H-1,2,3-triazol-4-yl)pyridine (1b). To
a stirred solution of 2-ethynylpyridine (0.21 g, 2.0 mmol, 1 equiv.)
in DMF/H2O (15 mL, 4:1) was added NaN3 (0.15 g, 2.5 mmol,
1.25 equiv.), Na2CO3 (0.21 g, 2.0 mmol, 1 equiv.), CuSO4ꢀ5H2O
(0.20 g, 0.8 mmol, 0.4 equiv.) and ascorbic acid (0.35 g, 2.0 mmol,
1.0 equiv.). (Ferrocenylmethyl)trimethylammonium iodide (0.79 g,

72
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
3H, Hc,f), 7.59–7.52 (m, 2H, Hg), 7.46–7.43 (m, 1H, Hh), 7.27 (m, 1H,
100 mL) and CH2Cl2 (100 mL) and the layers separated. The organic
phase was washed with H2O (100 mL) and brine (100 mL), dried
(MgSO4) and the solvent removed under reduced pressure. Chro-
matography (CH2Cl2 then 2% acetone in CH2Cl2) gave 2c as a white
solid. Yield: 0.79 g, 88%. Mp 119–121 °C; 1H NMR (300 MHz, CDCl3)
d: 8.20 (s, 2H, Hc), 8.11 (d, J = 7.8, 2H, Hb), 7.88 (t, J = 7.8, 1H, Ha),
4.44 (t, J = 7.2, 4H, Hd), 1.98 (p, J = 7.4, 4H, He), 1.33 (m, 20H, Hf-j),
0.89 (t, J = 6.8, 6H, Hk); 13C NMR (75 MHz, CDCl3) d: 150.2, 148.4,
137.9, 122.0, 119.3, 50.6, 31.8, 30.4, 29.2, 26.6, 22.7, 14.2; I.R.
Hb); 13C NMR (75 MHz, CDCl3) d: 150.0, 149.5, 149.0, 137.2, 137.0,
129.9, 128.9, 123.1, 120.5, 120.4, 119.9; I. R. (KBr):
t
(cmꢁ1) 3117,
3049, 2925, 1599, 1592, 1567, 1543, 1411, 1353, 1273, 1237, 1146,
1090, 1073, 1036, 993, 842, 794, 758; HRESI-MS (CH2Cl2/MeOH):
m/z = 245.0813 [M+Na]+ (calc. for C13H10N4Na 245.0798
[M+Na]+); Anal. Calc. for C13H10N4: C, 70.26; H, 4.54; N, 25.21.
Found: C, 70.21; H, 4.73; N, 24.93%.
2.2.1.5. 2,6-Bis(1-benzyl-1H-1,2,3-triazol-4-yl)pyridine (2a). To
a
(KBr): t
(cmꢁ1) 3156, 3039, 2955, 1607, 1576, 1310, 1231, 1216,
stirred solution of 2,6-diethynylpyridine (0.38 g, 3 mmol, 1 equiv.)
in DMF/H2O (15 mL, 4:1) was added NaN3 (0.41 g, 6.2 mmol,
2.1 equiv.), Na2CO3 (0.63 g, 3.0 mmol, 1.0 equiv.), CuSO4ꢀ5H2O
(0.15 g, 0.6 mmol, 0.2 equiv.), and ascorbic acid (0.42 g, 3.0 mmol,
1 equiv.). Benzyl bromide (1.02 g, 6.1 mmol, 2.05 equiv.) was
added and the reaction mixture was stirred at room temperature
for 20 h. The suspension was then partitioned between aqueous
NH4OH/EDTA (1 M, 100 mL) and CH2Cl2 (100 mL) and the layers
separated. The organic phase was washed with H2O (100 mL) and
brine (100 mL), dried (MgSO4) and the solvent removed under re-
duced pressure. Chromatography (CH2Cl2 then 2% acetone in
CH2Cl2) gave 2a as a white solid. Yield: 1.06 g, 90%. Mp 196–
198 °C; 1H NMR (300 MHz, CDCl3) d: 8.09 (d, J = 7.7, 2H, Hb), 8.04
(s, 2H, Hc), 7.85 (t, J = 7.7, 1H, Ha), 7.45–7.28 (m, 10H, He,f,g), 5.59
(s, 4H, Hd); 13C NMR (75 MHz, CDCl3) d: 149.9, 148.8, 137.8,
1191, 1081, 1045, 992, 975, 797; HRESI-MS (CH2Cl2/CH3CN):
m/z = 460.3190 [M+Na]+ (calc. for C25H39N7Na 460.3159 [M+Na]+);
Anal. Calc. for C25H39N7: C, 68.61; H, 8.98; N, 22.40. Found: C,
68.74; H, 9.13; N, 22.66%.
2.2.1.8. 2,6-Bis(1-phenyl-1,2,3-triazol-4-yl)pyridine (2d). To a stirred
argon degassed solution of iodobenzene (0.86 g, 4.2 mmol,
2.1 equiv.) in EtOH/H2O (10 mL, 7:3) was added NaN3 (0.29 g,
4.4 mmol, 1.2 equiv.), CuI (0.08 g, 0.4 mmol, 0.2 equiv.), N,N0-
Dimethylethylenediamine (0.05 g, 0.6 mmol, 0.3 equiv.) and so-
dium ascorbate (0.20 g, 1.0 mmol, 0.5 equiv.). The reaction was
then heated to reflux under an argon atmosphere for 2 h. After this
time had elapsed the reaction mixture was cooled to room temper-
ature and 2,6-diethynylpyridine (0.26 g, 2.0 mmol, 1 equiv.), Cu-
SO4ꢀ5H2O (0.10 g, 0.2 mmol, 0.2 equiv.), and sodium ascorbate
(0.20 g, 1.0 mmol, 0.5 equiv.) were added to the reaction mixture
and the resulting suspension was stirred at room temperature for
20 h. The reaction mixture was then poured into aqueous
NH4OH/EDTA (1 M, 100 mL). The resulting precipitate was isolated
by filtration and washed well with H2O then vacuum dried. Chro-
matography (CH2Cl2 then 9:1 CH2Cl2/acetone) gave 2d as a yellow
solid. Yield: 0.64 g, 88%. Mp 201–202 °C; 1H NMR (300 MHz, CDCl3)
d: 8.67 (s, 2H, Hc), 8.23 (d, J = 7.8, 2H, Hb), 7.96 (t, J = 7.8, 1H, Ha),
7.87 (d, J = 7.7, 4H, He), 7.58 (t, J = 7.5, 4H, Hf), 7.49 (t, J = 7.3, 2H,
Hg); 13C NMR (75 MHz, CDCl3) d: 150.0, 149.1, 138.1, 137.2,
134.6, 129.2, 128.8, 128.1, 122.0, 119.5, 54.3; I. R. (KBr):
t )
(cmꢁ1
3105, 3056, 2946, 1603, 1595, 1421, 1345, 1224, 1150, 1072,
1045, 995, 786, 727. HRESI-MS (MeOH): m/z = 394.1704 [M+H]+
(calc. for C23H20N7 394.1780 [M+H]+), 416.1604 [M+Na]+ (calc. for
C23H19N7Na 416.1600 [M+Na]+; Anal. Calc. for C23H19N7: C, 70.21;
H, 4.87; N, 24.92. Found: C, 70.34; H, 4.79; N, 25.20%.
2.2.1.6. 2,6-Bis(1-ferrocenylmethyl-1H-1,2,3-triazol-4-yl)pyridine
(2b). To a stirred solution of (ferrocenylmethyl)trimethylammoni-
um iodide (1.08 g, 2.8 mmol, 2.1 equiv.) in DMF/H2O (15 mL, 4:1)
was added NaN3 (0.19 g, 2.9 mmol, 2.2 equiv.) and the reaction
mixture was stirred at 95 °C for 16 h. The reaction mixture was
cooled to room temperature and CuSO4ꢀ5H2O (0.17 g, 0.6 mmol,
0.5 equiv.), sodium ascorbate (0.27 g, 1.3 mmol, 1 equiv.) and 2,6-
diethynylpyridine (0.17 g, 1.3 mmol, 1 equiv.) were added and
the resulting suspension was stirred at room temperature for
20 h. The suspension was then partitioned between aqueous
NH4OH/EDTA (1 M, 100 mL) and CH2Cl2 (100 mL) and the layers
separated. The organic phase was washed with H2O (100 mL) and
brine (100 mL), dried (MgSO4) and the solvent removed under re-
duced pressure. Chromatography (CH2Cl2 then 8:2 acetone/CH2Cl2)
gave 2b as an orange/red solid. Yield: 0.63 g, 77%. Mp 165 °C (de-
comp.); 1H NMR (300 MHz, CDCl3) d: 8.08–8.04 (m, 4H, Hb,c),
7.83 (t, J = 7.5, 1H, Ha), 5.35 (s, 4H, Hd), 4.31 (t, J = 1.8, 4H, He),
4.23–4.21 (m, 14H, Hf,g); 13C NMR (75 MHz, CDCl3) d: 150.1,
130.1, 129.2, 120.7, 120.5, 120.0; I. R. (KBr):
t
(cmꢁ1) 3117, 3061,
2950, 1599, 1592, 1567, 1543, 1411, 1353, 1273, 1237, 1146,
1090, 1073, 1036, 993, 842, 794, 758; HRESI-MS (CH2Cl2/MeOH):
m/z = 388.1291 [M+Na]+ (calc. for C21H15N7Na 388.1281
[M+Na]+); Anal. Calc. for C21H15N7ꢀ(0.25H2O): C, 68.19; H, 4.22; N,
26.51. Found: C, 68.31; H, 4.40; N, 26.74%.
2.2.1.9. 2-[(4-Phenyl-1H-1,2,3-triazol-1-yl)methyl]pyridine (3a). To a
stirred solution of phenylacetylene (1.12 g, 11 mmol, 1.1 equiv.) in
DMF/H2O (20 mL, 4:1) was added NaN3 (0.78 g, 12 mmol,
1.2 equiv.), Na2CO3 (3.15 g, 30 mmol, 3 equiv.), CuSO4ꢀ5H2O
(0.49 g, 2.0 mmol, 0.2 equiv.), and ascorbic acid (1.40 g, 10 mmol,
1.0 equiv.). 2-(Bromomethyl)pyridine hydrobromide (2.52 g,
10 mmol, 1.0 equiv.) was added and the reaction mixture was stir-
red at room temperature for 16 h. The suspension was then parti-
tioned between aqueous NH4OH/EDTA (1 M, 100 mL) and CH2Cl2
(100 mL) and the layers separated. The organic phase was washed
with H2O (100 mL) and brine (100 mL), dried (MgSO4) and the sol-
vent removed under reduced pressure. Chromatography (CH2Cl2
then CH2Cl2/acetone 9:1) gave 3a as a white solid. Yield: 2.06 g,
88%. Mp 79–80 °C; 1H NMR (300 MHz, CDCl3) d: 8.62 (ddd,
J = 4.86, J = 1.70, J = 0.90 Hz, 1H, Ha), 7.93 (s, 1H, Hf), 7.86–7.80
(m, 2H, Hg), 7.70 (dt, J = 7.71, J = 7.71, J = 1.81 Hz, 1H, Hc), 7.44–
7.22 (m, 5H, Hb,d,h,i), 5.70 (s, 2H, He); 13C NMR (75 MHz, CDCl3) d:
154.6, 149.9, 148.4, 137.7, 130.7, 129.0, 128.4, 125.9, 123.7,
148.2, 137.7, 121.5, 119.3, 80.8, 69.1, 69.0, 68.9, 50.3; I.R. (KBr):
t
(cmꢁ1) 3105, 3009, 2940, 1603, 1595, 1421, 1345, 1224, 1150,
1072, 1045, 995, 786, 727; HRESI-MS (MeOH): m/z = 610.1037
[M+H]+ (calc. for C31H27Fe2N7 610.1100 [M+H]+), 632.0925
[M+Na]+ (calc. for C31H27Fe2N7Na 632.0920 [M+Na]+; Anal. Calc.
for C31H27Fe2N7ꢀ(H2O): C, 59.31; H, 4.41; N, 15.64. Found: C,
59.35; H, 4.66; N, 15.63%.
2.2.1.7. 2,6-Bis(1-octyl-1,2,3-triazol-4-yl)pyridine (2c). To a stirred
solution of 2,6-diethynylpyridine (0.38 g, 3.0 mmol, 1 equiv.) in
DMF/H2O (15 mL, 4:1) was added NaN3 (0.41 g, 6.2 mmol,
2.1 equiv.), Na2CO3 (0.63 g, 3.0 mmol, 1.0 equiv.), CuSO4ꢀ5H2O
(0.15 g, 0.6 mmol, 0.2 equiv.), and ascorbic acid (0.42 g, 3.0 mmol,
1 equiv.). 1-Bromooctane (1.18 g, 6.1 mmol, 2.05 equiv.) was added
and the reaction mixture was stirred at 95 °C for 16 h. The suspen-
sion was then partitioned between aqueous NH4OH/EDTA (1 M,
122.7, 120.4, 55.8; I.R. (KBr):
t
(cmꢁ1) 3105, 1603, 1592, 1345,
1217, 1200, 1073, 1044, 996, 976, 910, 850, 818, 801, 760, 727.
HRESI-MS (MeOH): m/z = 237.1135 [M+H]+ (calc. for C14H13N4
237.1140 [M+H]+), 259.0954 [M+Na]+ (calc. for C14H12N4Na
259.0959 [M+Na]+; Anal. Calc. for C14H12N4: C, 71.17; H, 5.12; N,
23.71. Found: C, 71.10; H, 5.15; N, 23.58%.

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
73
2.2.1.10. 2-[(4-Ferrocenyl-1H-1,2,3-triazol-1-yl)methyl]pyridine
(3b). To a stirred solution of ethynylferrocene (2.73 g, 13 mmol,
1.2 equiv.) in DMF/H2O (15 mL, 4:1) was added NaN3 (0.84 g,
13 mmol, 1.3 equiv.), Na2CO3 (3.15 g, 30 mmol, 3 equiv.), Cu-
SO4ꢀ5H2O (0.50 g, 2 mmol, 0.2 equiv.), and ascorbic acid (1.40 g,
8.0 mmol, 0.8 equiv.). 2-(Chloromethyl)pyridine hydrochloride
(1.66 g, 10 mmol, 1.0 equiv.) was added and the reaction mixture
was stirred at room temperature for 24 h. The suspension was then
partitioned between aqueous NH4OH/EDTA (1 M, 100 mL) and
CH2Cl2 (100 mL) and the layers separated. The organic phase was
washed with H2O (100 mL) and brine (100 mL), dried (MgSO4)
and the solvent removed under reduced pressure. Chromatography
(CH2Cl2 then CH2Cl2/acetone 9:1) gave 3b as an orange solid. Yield:
2.80 g, 82%. Mp 162–163 °C; 1H NMR (300 MHz, CDCl3): d: 8.64 (d,
J = 4.5, 1H, Ha), 7.71 (td, J = 1.6, 7.7, 1H, Hc), 7.64 (s, 1H, Hf), 7.29 (t,
J = 6.2, 1H, Hb), 7.20 (d, J = 7.8, 1H, Hd), 5.69 (s, 2H, He), 4.74 (t,
J = 1.8, 2H, Hg), 4.31 (t, J = 1.8, 2H, Hh), 4.08 (s, 5H, Hi); 13C NMR
(75 MHz, CDCl3) d: 154.9, 149.9, 147.5, 137.6, 123.6, 122.5, 119.7,
Hd), 7.86–7.77 (m, 2H, Ha), 7.72 (t, J = 7.8, 1H, Hb), 7.36 (m, 8H,
He,f), 7.21 (d, J = 7.8, 2H, Hg), 5.70 (s, 4H, Hc); 13C NMR (75 MHz,
CDCl3) d: 154.9, 149.9, 147.5, 137.5, 123.7, 123.6, 122.5, 119.7,
119.6, 55.8; I.R. (KBr):
t
(cmꢁ1) 3105, 3067, 2976, 1603, 1592,
1345, 1217, 1200, 1073, 1044, 996, 976, 910, 850, 818, 801, 760,
727. HRESI-MS (MeOH): m/z = 394.4505 [M+H]+ (calc. for
C23H20N7 394.4518 [M+H]+), 416.1613 [M+Na]+ (calc. for
C23H19N7Na 416.1600 [M+Na]+. Anal. Calc. for C23H19N7: C, 70.21;
H, 4.87; N, 24.92. Found: C, 69.93; H, 4.95; N, 25.13%.
2.2.1.13. 2,6-Bis[(4-ferrocenyl-1H-1,2,3-triazol-1-yl)methyl]pyri-
dine (4b). To
a stirred solution of ethynylferrocene (1.38 g,
6.6 mmol, 2.2 equiv.) in DMF/H2O (20 mL, 4:1) was added NaN3
(0.45 g, 6.9 mmol, 2.3 equiv.), Na2CO3 (0.94 g, 8.9 mmol, 3 equiv.),
CuSO4ꢀ5H2O (0.40 g, 1.5 mmol, 0.5 equiv.) and ascorbic acid
(0.53 g, 3.0 mmol, 1.0 equiv.). 2-(Bromomethyl)pyridine hydrobro-
mide (1.34 g, 3.0 mmol, 1.0 equiv.) was added and the reaction
mixture was stirred at room temperature for 24 h. The suspension
was then partitioned between aqueous NH4OH/EDTA (1 M,
100 mL) and CH2Cl2 (100 mL) and the layers separated. The organic
phase was washed with H2O (100 mL) and brine (100 mL), dried
(MgSO4) and the solvent removed under reduced pressure. Chro-
matography (CH2Cl2 then gradient to CH2Cl2/acetone 8:2) gave
4b as an orange/red solid. Yield: 1.20 g, 65%. Mp 192–194 °C; 1H
NMR (300 MHz, CDCl3) d: 7.71 (t, J = 7.8, 1H, Ha), 7.58 (s, 2H, Hd),
7.13 (d, J = 7.8, 2H, Hb), 5.67 (s, 4H, Hc), 4.73 (t, J = 1.8, 4H, He),
4.31 (t, J = 1.8, 4H, Hf), 4.08 (s, 10H, Hg); 13C NMR (75 MHz, CDCl3)
d: 155.1, 147.7, 138.9, 121.9, 119.8, 76.1, 70.8, 69.4, 67.2, 55.4; I.R.
75.6, 69.82, 68.9, 66.9, 55.8; I.R. (KBr):
t
(cm-1) 3105, 3011, 2948,
1603, 1589, 1348, 1219, 1190, 1141, 1104, 1086, 1034, 1020,
942, 877, 815, 801, 763, 725; HRESI-MS (MeOH): m/z = 345.0785
[M+H]+ (calc. for C18H17FeN4 345.0797 [M+H]+), 367.0622
[M+Na]+ (calc. for C18H16FeN4Na 367.0617 [M+Na]+; Anal. Calc.
for C18H16FeN4: C, 62.81; H, 4.69; N, 16.28. Found: C, 62.71; H,
4.66; N, 16.19%.
2.2.1.11. 2-[(4-Octyl-1H-1,2,3-triazol-1-yl)methyl]pyridine (3c). To a
stirred solution of decyne (0.31 g, 2.2 mmol, 1.1 equiv.) in DMF/
H2O (20 mL, 4:1) was added NaN3 (0.13 g, 2.2 mmol, 1.1 equiv.),
Na2CO3 (0.90 g, 6.0 mmol, 3 equiv.), CuSO4ꢀ5H2O (0.20 g, 0.8 mmol,
0.4 equiv.), ascorbic acid (0.35 g, 2.0 mmol, 1.0 equiv.) and 2-(bro-
momethyl)pyridine hydrobromide (0.51 g, 2.0 mmol, 1.0 equiv.)
and the reaction mixture was stirred at room temperature for
16 h. The suspension was then partitioned between aqueous
NH4OH/EDTA (1 M, 100 mL) and CH2Cl2 (100 mL) and the layers
separated. The organic phase was washed with H2O (100 mL) and
brine (100 mL), dried (MgSO4) and the solvent removed under re-
duced pressure. Chromatography (CH2Cl2 then CH2Cl2/acetone
9:1) gave 3c as a white solid. Yield: 0.50 g, 91%. Mp 48–50 °C; 1H
NMR (300 MHz, CDCl3) d: 8.59 (d, J = 4.4, 1H, Ha), 7.68 (td, J = 1.8,
7.7, 1H, Hc), 7.42 (s, 1H, Hf), 7.25 (t, J = 7.6, 1H, Hb), 7.15 (d,
J = 7.8, 1H, Hd), 5.62 (s, 2H, He), 2.71 (t, J = 6.8, 2H, Hg), 1.64 (m,
2H, Hh), 1.28 (m, 10H, Hi,j,k,l,m), 0.87 (t, J = 6.7, 3H, Hn); 13C NMR
(75 MHz, CDCl3) d: 155.1, 149.8, 149.2, 137.5, 123.5, 122.5, 121.3,
(KBr):
t
(cmꢁ1) 3115, 3102, 3083, 2929, 1654, 1593, 1574, 1338,
1231, 1220, 1201, 1191, 1151, 1106, 1097, 1050, 1030, 999, 893,
878, 821, 807, 773, 761, 722; HRESI-MS (MeOH): m/z = 610.1146
[M+H]+ (calc. for C31H28Fe2N7 610.1100 [M+H]+), 632.0975
[M+Na]+ (calc. for C23H19N7Na 632.0920 [M+Na]+; Anal. Calc. for
C31H27Fe2N7: C, 61.11; H, 4.47; N, 16.09. Found: C, 61.37; H,
4.49; N, 16.39%.
2.2.1.14. 2,6-Bis[(4-octyl-1H-1,2,3-triazol-1-yl)methyl]pyridine
(4c). To a stirred solution of decyne (0.58 g, 4.2 mmol, 2.1 equiv.)
in DMF/H2O (20 mL, 4:1) was added NaN3 (0.27 g, 4.2 mmol,
2.1 equiv.), Na2CO3 (0.22 g, 2.0 mmol, 1 equiv.), CuSO4ꢀ5H2O
(0.20 g, 0.8 mmol, 0.4 equiv.), ascorbic acid (0.35 g, 2.0 mmol,
1.0 equiv.) and 2,6-(bromomethyl)pyridine (0.53 g, 2 mmol,
1.0 equiv.) and the reaction mixture was stirred at room tempera-
ture for 16 h. The suspension was then partitioned between aque-
ous NH4OH/EDTA (1 M, 100 mL) and CH2Cl2 (100 mL) and the
layers separated. The organic phase was washed with H2O
(100 mL) and brine (100 mL), dried (MgSO4) and the solvent re-
moved under reduced pressure to give 10c as a white solid. Yield:
0.86 g, 92%. Mp 114–115 °C; 1H NMR (300 MHz, CDCl3) d: 7.67 (t,
J = 7.8, 1H, Ha), 7.38 (s, 2H, Hd), 7.08 (d, J = 7.8, 2H, Hb), 5.62 (s,
4H, Hc), 2.74 (t, J = 6.8, 4H, He), 1.71–1.67 (m, 4H, Hf), 1.31 (m,
20H, Hg–j), 0.89 (t, J = 6.7, 6H, Hl); 13C NMR (75 MHz, CDCl3) d:
155.2, 149.3, 138.7, 121.7, 121.4, 55.3, 32.0, 29.7, 29.6, 29.5, 29.4,
55.7, 32.0, 29.7, 29.6, 29.5, 29.4, 25.9, 22.8, 14.3; I.R. (KBr):
t
(cmꢁ1) 3583, 3120, 3065, 1595, 1585, 1571, 1555, 1302, 1218,
1157, 1121, 1053, 1028, 966, 861, 834, 801, 761, 750; HRESI-MS
(MeOH): m/z = 273.2078 [M+H]+ (calc. for C15H25N4 273.2074
[M+H]+), 295.1939 [M+Na]+ (calc. for C16H24N4Na 295.1893
[M+Na]+; Anal. Calc. for C16H24N4ꢀ(0.33H2O): C, 69.04; H, 8.89; N,
20.13. Found: C, 68.93; H, 9.04; N, 20.24%.
2.2.1.12. 2,6-Bis[(4-phenyl-1H-1,2,3-triazol-1-yl)methyl]pyri-
dine (4a). To
a
stirred solution of phenylacetylene (1.12 g,
25.9, 22.8, 14.3; I.R. (KBr): t
(cmꢁ1) 3112, 3063, 2926, 1593,
11 mmol, 1.1 equiv.) in DMF/H2O (20 mL, 4:1) was added NaN3
(0.72 g, 11 mmol, 2.1 equiv.), Na2CO3 (0.53 g, 5 mmol, 1 equiv.),
CuSO4ꢀ5H2O (0.49 g, 2.0 mmol, 0.2 equiv.) and ascorbic acid
(0.88 g, 5.0 mmol, 1.0 equiv.). 2,6-(Bromomethyl)pyridine (1.32 g,
5.0 mmol, 1.0 equiv.) was added and the reaction mixture was stir-
red at room temperature for 16 h. The suspension was then parti-
tioned between aqueous NH4OH/EDTA (1 M, 100 mL) and CH2Cl2
(100 mL) and the layers separated. The organic phase was washed
with H2O (100 mL) and brine (100 mL), dried (MgSO4) and the sol-
vent removed under reduced pressure. Chromatography (CH2Cl2
then CH2Cl2/acetone 9:1) gave 4a as a white solid. Yield: 1.88 g,
90%. Mp 159–161 °C; 1H NMR (300 MHz, CDCl3) d: 7.89 (s, 2H,
1575, 1557, 1325, 1215, 1178, 1119, 1051, 1030, 997, 928, 863,
839, 824, 805, 770; HRESI-MS (MeOH): m/z = 488.3465 [M+Na]+
(calc. for C27H43N7Na 488.3472 [M+Na]+; Anal. Calc. for C27H43N7:
C, 69.64; H, 9.31; N, 21.05. Found: C, 69.23; H, 9.36; N, 21.31%.
2.2.2. Synthesis of CuCl2 complexes
2.2.2.1. [(1a)2CuCl](Cl). A solution (5 mL, MeOH) of anhydrous
CuCl2 (0.067 g, 0.5 mmol, 0.5 equiv.) was added dropwise slowly
to a CHCl3 (5 mL) solution of the ligand 1a (0.236 g, 1.0 mmol,
1 equiv.). The resulting blue-green solution was stirred at room
temperature for 1 h. The volume of solvent was reduced by half un-
der reduced pressure and a blue/green solid precipitated. The solid

74
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
was filtered off and was washed Et2O and petrol. Yield: 0.295 g,
95%. X-ray quality blue-green crystals were obtained by slow evp-
ouration of a methanol solution of [(1a)2CuCl](Cl). Mp 204 °C (de-
in the absence of light for 1 h, during which time a white solid
slowly precipitated. The volume of solvent was halved under re-
duced pressure and the solid was filtered off and was washed with
Et2O and petrol. X-ray quality colourless crystals were obtained by
vapour diffusion of acetone solution of [(1a)2Ag](SbF6) with meth-
anol. Yield: 0.132 g, 82%. Mp 220–221 °C; 1H NMR (300 MHz, d6-
acetone) d: 9.02 (s, 2H, He), 8.71 (d, J = 5.0, 2H, Ha), 8.16–8.06 (m,
4H, Hc,d), 7.58 (ddd, J = 2.5, 5.1, 6.2, 2H, Hb), 7.53–7.39 (m, 10H,
Hg,h,i), 5.85 (s, 4H, Hf); 13C NMR (75 MHz, d6-acetone) d 150.9,
147.4, 145.6, 139.4, 135.1, 129.2, 129.0, 128.6, 125.1, 124.4,
comp.); I.R. (KBr):
t
(cmꢁ1) 3500–3200 (br), 3081, 2925, 1616,
1580, 196, 1348, 1294, 1272, 1248, 1216, 1153, 1119, 1095,
1063, 1027, 995, 918, 867, 827, 798, 782, 735; HRESI-MS (MeOH):
m/z = 535.1436 [Cu(1a)2]+ (calc. for C28H24CuN8 535.1420
[Cu(1a)2]); KM (MeOH) = 145
X ; Anal. Calc. for
ꢁ1 cm2 molꢁ1
C28H24CuCl2N8ꢂ(3H2O): C, 50.87; H, 4.57; N, 16.95. Found: C,
51.19; H, 3.92; N, 17.16%.
122.3, 54.8; I.R. (KBr):
t
(cmꢁ1) 3136, 3077, 2936, 1601, 1570,
2.2.2.2. [(2a)CuCl2]. A solution (5 mL, MeOH) of anhydrous CuCl2
(0.078 g, 0.57 mmol, 1 equiv.) was added dropwise slowly to a
CH2Cl2 (5 mL) solution of the ligand 2a (0.226 g, 0.57 mmol,
1 equiv.). A green solid precipitated immediately and the resulting
suspension was stirred at room temperature for 1 h. The volume of
solvent was reduced by half under reduced pressure and the green
solid isolated by filtration and was purified by recrystallization
(hot CH3OH) to give copper complex [(2a)CuCl2] as a blue-green
1559, 1348, 1239, 1199, 1158, 1107, 1088, 1062, 1048, 1008,
992, 891, 833, 795, 783, 734; HRESI-MS (CH3CN): m/z = 343.0076
[1aAg]+ (calc. for C14H12N4Ag 343.0112 [1aAg]+), 579.1137
[1a2Ag]+ (calc. for C28H24N8Ag 579.1174 [1a2Ag]+); KM
(CH3CN) = 162
X
ꢁ1 cm2 molꢁ1; Anal. Calc. for C28H24AgF6N8Sb: C,
41.20; H, 2.96; N, 13.73. Found: C, 41.47; H, 2.96; N, 13.74%.
2.2.3.2. [(3a)2Ag](SbF6). A solution (acetone, 5 mL) of AgSbF6
(0.067 g, 0.2 mmol, 1 equiv.) was added dropwise slowly to a
(CH2Cl2, 5 mL) solution of the ligand 3a (0.94 g, 0.4 mmol, 2 equiv.).
The resulting colourless solution was stirred at room temperature
in the absence of light for 1 h. The volume of solvent was halved
under reduced pressure and the white solid isolated by filtration
and washed well with Et2O and petrol. The product was recrystal-
lized from acetone/Et2O. Yield: 0.090 g, 82%. Mp 148–149 °C; 1H
NMR (300 MHz, d6-acetone) d 8.87 (ddd, J = 0.7, J = 1.6, J = 5.1, 2H,
Ha), 8.81 (s, 2H, Hf), 8.21 (td, J = 1.7, J = 7.7, 2H, Hc), 8.03 (dd,
J = 0.9, J = 6.9, 2H, Hd), 7.87–7.79 (m, 4H, Hg), 7.70 (ddd, J = 1.3,
5.1, 7.7, 2H, Hb), 7.47–7.37 (m, 4H, Hh), 7.37–7.28 (m, 2H, Hi),
6.15 (s, 4H, He); 13C NMR (75 MHz, CDCl3) d 153.6, 153.5, 149.7,
141.6, 130.5, 130.1, 129.6, 127.4, 127.2, 126.6, 124.8, 56.8; I.R.
solid (0.280 g, 91%). Mp 236 °C (decomp.); I.R. (KBr):
t )
(cmꢁ1
3300–3200 b, 3130, 3075, 2936, 1617, 1585, 1268, 1210, 1157,
1119, 1063, 1051, 1025, 974, 813, 765, 719. HRESI-MS (MeOH):
m/z = 456.1012 [Cu(2a)]+ (calc. for C23H19CuN7 456.0998
[Cu(2a)]+), 424.6353 [Cu(2a)2]2+ (calc. for C46H38CuN14 424.6350
[Cu(2a)]+), 416.1572 (calc. for C23H19N7Na 416.1600 [Na(2a)]+);
KM (MeOH) = 94
X
ꢁ1 cm2 molꢁ1
;
Anal. Calc. for C23H19
Cl2CuN7ꢀH2O: C, 50.60; H, 3.88; N, 17.96. Found: C, 50.89; H,
3.84; N, 18.08%.
2.2.2.3. [(3a)2CuCl2]. A solution (5 mL, MeOH) of anhydrous CuCl2
(0.067 g, 0.5 mmol, 0.5 equiv.) was added dropwise slowly to a
CHCl3 (5 mL) solution of the ligand 3a (0.236 g, 1.0 mmol, 1 equiv.).
The resulting blue-green solution was stirred at room temperature
for 1 h. The volume of solvent was reduced by half under reduced
pressure and a blue/green solid precipitated. The solid was filtered
off and was washed with Et2O and petrol. Yield: 0.243 g, 80%. X-ray
quality blue-green crystals were obtained by slow evaporation of a
(KBr):
t
(cmꢁ1) 3500–3200 (br), 3143, 3088, 3030, 2951, 1600,
1574, 1557, 1309, 1231, 1195, 1149, 1090, 1056, 972, 825, 764,
723; HRESI-MS (CH3CN): m/z = 579.1150 [3a2Ag]+ (calc. for
C28H24N8Ag 579.1174 [3a2Ag]+); KM (CH3CN) = 122
X
ꢁ1 cm2
molꢁ1; Anal. Calc. for C28H24AgF6N8Sb: C, 41.20; H, 2.96; N, 13.73.
Found: C, 41.36; H, 2.90; N, 13.54. X-ray quality colourless crystals
were obtained by vapour diffusion of acetone solution of the prod-
uct with methanol.
methanol solution of [(3a)2CuCl2]. Mp 158–159 °C; I.R. (KBr):
t
(cmꢁ1) 3118, 3080, 3023, 2940, 1607, 1572, 1313, 1226, 1195,
1150, 1077, 1064, 1025, 973, 828, 758, 721. HRESI-MS (MeOH):
m/z = 535.1405 [Cu(3a)2]+ (calc. for C28H24CuN8 535.1420
[Cu(3a)2]); KM (MeOH) = 77
X
ꢁ1 cm2 molꢁ1; Anal. Calc. for C28H24
2.2.3.3. [(2a)Ag](SbF6). A solution (acetone, 5 mL) of AgSbF6
(0.034 g, 0.1 mmol, 1 equiv.) was added dropwise slowly to a
CH2Cl2 (2 mL) solution of the ligand 2a (0.039 g, 0.1 mmol,
1 equiv.). The resulting colourless solution was stirred at room
temperature in the absence of light for 1 h. The volume of solvent
was halved under reduced pressure and the white solid isolated by
filtration and was washed with Et2O (10 mL) and petrol (10 mL)
then vacuum dried (0.046 g, 62%). Mp 228 °C (decomp.); 1H NMR
(300 MHz, d6-acetone) d 8.92 (sb, 2H, Hc), 7.59 (t, J = 7.8, 1H, Ha),
7.50 (sb, 2H, Hb), 7.20 (s, 10H, He,f,g), 5.76 (s, 4H, Hd); 13C NMR
(75 MHz, d6-acetone) d 145.9, 145.1, 140.1, 134.1, 128.9, 128.8,
CuCl2N8: C, 55.40; H, 3.99; N, 18.46. Found: C, 55.42; H, 3.97; N,
18.21%.
2.2.2.4. [(4a)CuCl2]. A solution (5 mL, MeOH) of anhydrous CuCl2
(0.068 g, 0.50 mmol, 1 equiv.) was added dropwise slowly to a
CH2Cl2 (5 mL) solution of the ligand 4a (0.200 g, 0.50 mmol,
1 equiv.). A green solid precipitated immediately and the resulting
suspension was stirred at room temperature for 1 h. The volume of
solvent was reduced by half under reduced pressure and the green
solid isolated by filtration and was purified by recrystallization
(hot CH3OH) to give [(4a)CuCl2] as blue-green crystals (0.190 g,
128.0, 125.5, 121.9, 55.1; I.R. (KBr):
t
(cmꢁ1) 3146, 3034, 2926,
71%). Mp 159–160 °C; I.R. (KBr):
t
(cmꢁ1) 3130, 3079, 2930,
1606, 1582, 1564, 1497, 1453, 1438, 1405, 1381, 1346, 1268,
1245, 1194, 1159, 1115, 1098, 1074, 1057, 1022, 926, 848, 812,
782, 761, 705. HRESI-MS (MeOH/CH3CN): m/z = 500.0714
[(2a)Ag]+ (calc. for C23H19AgN7 500.0747), 416.1563 [(2a)+Na]+
(calc. for C23H19N7Na 416.1600); KM (CH3CN) = 135 Xꢁ1
cm2 molꢁ1; Anal. Calc. for C23H19AgF6N7Sb: C, 37.48; H, 2.60; N,
13.30. Found: C, 37.40; H, 2.69; N, 13.06%.
1609, 1578, 1316, 1277, 1250, 1192, 1165, 1085, 1019, 974, 833,
766, 722. HRESI-MS (MeOH): m/z = 456.0980 [Cu(4a)]+ (calc. for
C23H19CuN8 456.0998 [Cu(4a)]+), 416.1579 (calc. for C23H19N7Na
416.1600 [Na(4a)]+); KM (MeOH) = 62
X
ꢁ1cm2 molꢁ1; Anal. Calc.
for C23H19Cl2CuN7: C, 52.33; H, 3.63; N, 18.57. Found: C, 52.60;
H, 3.72; N, 18.68%.
2.2.3. Synthesis of silver(I) complexes
2.2.3.4. [(4a)Ag](SbF6). A solution (acetone, 5 mL) of anhydrous
AgSbF6 (0.034 g, 0.10 mmol, 1 equiv.) was added dropwise slowly
to a CH2Cl2 (2 mL) solution of the ligand 4a (0.039 g, 0.10 mmol,
1 equiv.). The resulting colourless solution was stirred at room
temperature in the absence of light for 1 h. The volume of solvent
2.2.3.1. [(1a)2Ag](SbF6). A solution (acetone, 5 mL) of AgSbF6
(0.067 g, 0.2 mmol, 1 equiv.) was added dropwise slowly to a solu-
tion (CH2Cl2, 5 mL) of the ligand 1a (0.094 g, 0.4 mmol, 2 equiv.).
The resulting colourless solution was stirred at room temperature

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
75
was halved under reduced pressure and the white solid isolated by
filtration and was washed with Et2O (10 mL) and petrol (10 mL)
then vacuum dried (0.064 g, 86%). Mp >250 °C; 1H NMR
(300 MHz, d6-acetone) d 8.91 (s, 2H, Hd), 8.31 (t, J = 7.8, 1H, Ha),
8.05 (d, J = 7.7, 2H, Hb), 7.72 (d, J = 7.5, 4H, He), 7.39 (t, J = 7.3, 3H,
Hg), 7.24 (t, J = 7.4, 4H, Hf), 6.05 (s, 4H, Hc); 13C NMR (75 MHz,
d6-acetone) d: 154.3, 150.3, 142.7, 130.9, 130.3, 128.9, 127.3,
solved by direct methods using SIR97 [68] with the resulting Fourier
map revealing the location of all non-hydrogen atoms. Weighted full
matrix refinement on F2 was carried out using SHELXL-97 [69] with all
non-hydrogen atoms being refined anisotropically. The hydrogen
atoms were included in calculated positions and were refined as rid-
ing atoms with individual (or group, if appropriate) isotropic dis-
placement parameters. The [3a2CuCl2] crystal studied has an
inversion twin with a 0.47(2):0.52(2) domain ratio. The space group
for this structure was examined carefully and the structure was
found to solve and refine in P21 satisfactorily. However in the space
group P21/c no solution was found. In [2aCuCl2], one of the benzyl
substituents was disordered over two sites and was modeled satis-
factorily with 60:40 contributions for the two orientations. Crystals
of [3a2Ag](SbF6) were of modest quality, and while the [3a4Ag3]3+
cation and the acetone and methanol solvate molecules were well
resolved, two of the SbF6 anions and the [3a2Ag]+ cation were disor-
dered. The silver (I) ion of the [3a2Ag]+ cation is disordered over two
sites about a crystallographic center of inversion. This disorder could
not be satisfactorily resolved and as such some of the thermal
parameters associated with this cationic fragment are large. All ORTEP
[70] diagrams have been drawn with 50% probability ellipsoids.
Crystal data and collection parameters are given in Table 1.
127.2, 125.7, 57.4; I.R. (KBr):
t
(cmꢁ1) 3127, 3085, 3028, 2945,
1711, 1607, 1593, 1575, 1485, 1462, 1437, 1359, 1330, 1266,
1219, 1200, 1159, 1092, 1082, 1074, 1044, 1009, 985, 976, 850,
838, 818, 764, 725; HRESI-MS (MeOH/CH3CN): m/z = 500.0718
[(2a)Ag]+ (calc. for C23H19AgN7 500.0747), 416.1571 [(2a)+Na]+
(calc. for C23H19N7Na 416.1600), 394.1753 [(2a)+H]+; KM
(CH3CN) = 141
X ; Anal. Calc. for C23H19AgF6N7Sb
ꢁ1 cm2 molꢁ1
ꢀ(C2H6O): C, 38.34; H, 3.22; N, 12.52. Found: C, 38.72; H, 3.19; N,
12.24%.
2.3. X-ray data collection and refinement
X-ray data for 1c, 2c, 3b, 4b, [2aCuCl2], [3a2CuCl2], [1a2Ag](SbF6),
[2aAg](SbF6), [3a2Ag](SbF6) and [4aAg](SbF6) were recorded using a
Bruker APEX II CCD diffractometer at 90(2) K. The structures were
Table 1
Crystal data and structure refinement for ligands 1c, 2c, 3b, 4b, copper(II) and silver(I) complexes.
1c
2c
3b
4b
[(3a)2CuCl2]
Identification
code
CCDC 728064
CCDC 728065
CCDC 728062
CCDC 728063
CCDC 728300
Empirical formula
Formula weight
T (K)
C
18H16FeN4
C31H27N7Fe2
609.30
90(2)
C18H16N4Fe
344.20
90(2)
C31H27N7Fe2
609.30
90(2)
C28H24N8Cl2Cu
606.99
90(2)
344.20
90(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
5.7798(6)
28.458(3)
9.3468(9)
90.00
98.859(5)
90.00
1519.0(3)
4
monoclinic
P21/n
15.551(2)
9.480(1)
17.927(3)
90.00
100.198(8)
90.00
2601.1(8)
4
monoclinic
P21/c
9.063(1)
14.830(1)
11.598(1)
90.00
104.229(3)
90.00
1511.0(12)
4
1.513
1.002
triclinic
P1
8.372(7)
8.763(7)
18.257(14)
94.633(4)
98.838(4)
101.370(4)
1289.0(17)
2
monoclinic
P21
12.122(5)
8.282(3)
13.269(5)
90.00
92.000(2)
90.00
1331.3(9)
2
ꢀ
a
(°)
b (°)
c
(°)
V (Å3)
Z
qcalc (mg mm3)
1.505
0.997
1.556
1.152
1.570
1.162
1.514
1.056
l
(mmꢁ1
)
Crystal size, color, 0.44 ꢃ 0.25 ꢃ 0.13,
0.52 ꢃ 0.47 ꢃ 0.33,
0.74 ꢃ 0.43 ꢃ 0.31, orange, rhomb.
0.64 ꢃ 0.22 ꢃ 0.12 mm,
red, block
R1 = 0.0232
wR2 = 0.0569
R1 = 0.0246
wR2 = 0.0584
0.55 ꢃ 0.32 ꢃ 0.06, blue,
irregular
R1 = 0.0388
wR2 = 0.1109
R1 = 0.0399
wR2 = 0.1119
habit
orange, plate
R1 = 0.0398
wR2 = 0.1528
R1 = 0.0472
wR2 = 0.1581
red, rod
Final R indexes
[I > 2r(I)]
Final R indexes
[all data]
R1 = 0.0345
wR2 = 0.0884
R1 = 0.0376
wR2 = 0.0908
R1 = 0.0243
wR2 = 0.0638
R1 = 0.0248
wR2 = 0.0643
Identification
code
Empirical formula
Formula weight
T (K)
[(2a)CuCl2] CCDC
728301
[(1a)2Ag](SbF6) CCDC
728302
C28H24N8SbAgF6
816.17
[(3a)4Ag3](SbF6)3 + 0.5[(3a)2Ag](SbF6) {[(4a)Ag](SbF6)}1 CCDC
{[(2a)Ag](SbF6)}4 CCDC
728432
C94H76Ag4F24N28O6Sb4
3068.35
CCDC 728303
C74H66O4F32Ag4Sb5N20
2492.64
728304
C26H25AgF6N7OSb
795.15
C
79H64O5Cl6Cu3N21
3399.47
90(2)
90(2)
90(2)
90(2)
90(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1
monoclinic
P21/c
10.294(5)
23.221(1)
12.259(6)
90.00
93.143(2)
90.00
2926(2)
triclinic
P1
monoclinic
P21/c
13.050(3)
15.467(3)
14.283(4)
90.00
96.451(12)
90.00
2864.7(12)
4
tetragonal
I41cd
21.737(11)
21.737(11)
ꢀ
ꢀ
14.147(1)
15.295(1)
20.095(2)
98.474(4)
95.836(4)
111.901(4)
3932.0(9)
6
17.0758(7)
17.654(7)
18.227(7)
114.50(2)
95.97(2)
110.52(2)
4477(4)
2
a
(°)
90.00
90.00
90.00
22519(30)
8
b (°)
c
(°)
V (Å3)
Z
4
qcalc (mg mm3)
1.436
1.071
1.853
1.665
1.842
1.883
1.844
1.700
1.810
1.728
l
(mmꢁ1
)
Crystal size, color, 0.44 ꢃ 0.30 ꢃ 0.16,
0.50 ꢃ 0.25 ꢃ 0.15,
colourless, irregular
R1 = 0.0253
wR2 = 0.0589
R1 = 0.0302,
wR2 = 0.0619
0.52 ꢃ 0.23 ꢃ 0.22, colourless,
0.40 ꢃ 0.14 ꢃ 0.03,
colourless, needle
R1 = 0.0307
wR2 = 0.0603
R1 = 0.0385,
wR2 = 0.0637
0.39 ꢃ 0.19 ꢃ 0.06,
colourless, irregular
R1 = 0.1288
wR2 = 0.3105
R1 = 0.1720
wR2 = 0.3245
habit
green, rhomb.
R1 = 0.0651
rhomb.
Final R indexes
R1 = 0.0749
wR2 = 0.2090
R1 = 0.0985
wR2 = 0.2369
[I>2
Final R indexes
r
(I)]
wR2 = 0.1759
R1 = 0.0756
[all data]
wR2 = 0.1855

76
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
3. Results and discussion
3.1. Ligand synthesis
An examination of the literature showed that there are a num-
ber of one pot CuAAC methodologies in which the organic azides
are generated in situ from alkyl, benzyl and aryl halides [71–77].
Using the synthesis of the known ligands 1a [37,40,78,79] and 2a
[80] we screened these methods and found the conditions of Fokin
[71] to be the most convenient. Simply mixing either 2-ethynyl-
pyridine or 2,6-diethynylpyridine, benzyl bromide, NaN3, Cu-
SO4ꢀ5H2O, Na2CO3 and ascorbic acid in DMF/H2O (4:1) then
stirring at room temperature for 20 h (Scheme 1) provided, after
work up, the desired ligands in excellent yields (1a, 92% and 2a,
90%) without the need for isolating the potentially hazardous ben-
zyl azide. Indeed the yields of the ligands 1a and 2a obtained from
the one pot method are comparable if not better than those re-
ported using preformed isolated benzyl azide [37,40,78–80]. Fol-
lowing on from this initial success we then attempted the
synthesis of the ferrocenylmethyl2 [81] (1b and 2b) and octyl (1c
and 2c) substituted ligands. Under the standard Fokin conditions
only modest yields of the desired products were obtained presum-
ably because the substitution of the halide (or pseudo halide) leaving
groups by azide was slow at room temperature. However, simply
increasing the temperature of the reaction to 95 °C enabled the de-
sired ligands to be generated in excellent isolated yields (Scheme 1).
By modifying [82–84] the one pot CuAAC method developed by
Liang [74,77] we were also able to synthesise the aryl (phenyl)
substituted ligands (1d and 2d)3. Iodobenzene, NaN3, CuI, DMEDA
and sodium ascorbate were refluxed in a degassed EtOH/H2O (7:3)
solution for 2 h, to generate azidobenzene in situ, then the reaction
mixture was cooled to room temperature. CuSO4ꢀ5H2O, sodium
ascorbate and either 2-ethynylpyridine or 2,6-diethynylpyridine
were added as solids to the reaction mixture and the resulting solu-
tion was stirred at room temperature for 20 h, yielding the desired
aryl functionalized ligands (Scheme 1).
Scheme 1. (i) NaN3, CuSO4ꢀ5H2O, ascorbic acid, Na2CO3, DMF/H2O (4:1), RT or
95 °C, 20 h; (ii) a) NaN3, CuI, DMEDA, EtOH/H2O (7:3), 100 °C, 2 h, (b) CuSO4ꢀ5H2O,
ascorbic acid, Na2CO3, RT, 20 h. Isolated yield after chromatography.
Additionally, we were also able to exploit the one pot CuAAC
methodology to generate methylene bridged, aryl and alkyl substi-
tuted pyridyl-1,2,3-triazole ligands (3a-c and 4a-c) in excellent
yields (Scheme 2).
The ligands 1a–d, 2a–d, 3a–c and 4a–c have been fully charac-
terized by elemental analysis, HR-ESMS, IR, 1H and 13C NMR. These
pyridyl-1,2,3-triazole derivatives were characterized by the lack of
an azide (ꢄ2095 cmꢁ1) or alkyne (ꢄ2150 cmꢁ1) band in their IR
spectra and by the diagnostic singlet of the triazole unit (found be-
tween 8.6 and 7.5 ppm) in their 1H NMR spectra (see Supporting
information). In the case of the ferrocene substituted ligands (1c,
2c, 3b and 4b) the structures were confirmed by X-ray crystallog-
raphy (Fig. 1 and Fig. 2, Table 1).
The compounds 1c and 2c both crystallise in the monoclinic
space group P21/n and the structures of 1c and 2c are consistent
with the other collected experimental data (Fig. 1). The cp rings
of the ferrocene units are eclipsed, the triazoles rings are planar
1,4 substituted isomers. The pyridine and triazole units are essen-
tially coplanar (the N–C–C–N dihedral angles vary from 3° to 14°),
and the bond lengths and angles are similar to those observed in
related structures [40,43,85]. Additionally, the nitrogen donor
atoms of the chelating units adopt the anti (1c) or anti–anti (2c)
conformations as is commonly observed in related heterocyclic li-
gands [40,46,86].
Scheme 2. (i) NaN3, CuSO4ꢀ5H2O, ascorbic acid, Na2CO3, DMF/H2O (4:1), RT, 20 h.
The structures of 3b and 4b along with the bond length and an-
gles are shown in Fig. 2. Compound 3b crystallises in the mono-
clinic space group P21/n whereas 4b crystallises in the triclinic
2
Ferrocene containing compounds have found applications as sensors, catalysts
ꢀ
space group P1. Like 1c and 2c the cp rings of the ferrocene units
and as drugs, see Ref. [81]. As such the attempted incorporation of the ferrocene
functional group seemed a logical choice.
are once again found in the expected eclipsed conformation and
the triazoles rings are planar 1,4 substituted isomers. The triazole
units are twisted away from the pyridine rings presumably to
3
The synthesis of these ligands has been recently reported by Fletcher et al., see
Ref. [52].

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
77
Fig. 1. Labelled ORTEP diagrams of (a) 1c and (b) 2c. The thermal ellipsoids are shown at the 50% probability. Selected bond lengths (Å) and angles (ꢁ) for 1c: N2–N3
1.3144(14), N3–N4 1.3474(13), N4–C7 1.3525(14), N2–C6 1.3656(14), N2–C6–C7 108.51(9), N3–N3–C6 108.69(9), N2–N3–N4 107.51(9), N4–C6–C7 104.24(9), N3–N4–C7
111.06(9). Selected bond lengths (Å) and angles (ꢁ) for 2c; C4–N2 1.355(3), C4–C5 1.340(3), N2–N3 1.316(3), N3–N4 1.352(3); N3–N2 C4 108.6(2), N2–N4 107.2(2), C5–N4–N3
110.7(2), C5–N4–C6 128.8(2), N3–N4–C6 120.4(2).
Fig. 2. Labelled ORTEP diagrams of (a) 3b and (b) 4b. The thermal ellipsoids are shown at the 50% probability. Selected bond lengths (Å) and angles (ꢁ) for 3b: C8–N4 1.362(2),
C8–C7 1.373(2), C7–N2 1.347(2), N4–N3 1.3172(19), N3–N2 1.3453(18); N4–C8–C7 108.22(13), N3–N2–C6 120.32(12), N4–C8–C9 121.79(13), C7–N2–C6 128.54(13), C7–C8–
C9 129.98(13), N2–C7–C8 104.73(12), N2–C6–C5 113.00(12), N3–N4–C8 108.94(13), N4–N3–N2 107.09(12), N3–N2–C7 111.02(12). Selected bond lengths (Å) and angles ꢁ()
for 4b: C5–N2 1.352(2), C5–C6 1.377(2), C6–N4 1.370(2), N2–N3 1.3523(19), N3–N4 1.3168(19); C5–N2–N3 111.21(12), C5–N2–C4 129.54(13), N3–N2–C4 119.05(13), N4–
N3–N2 107.06(13), N3–N4–C6 108.92(13) .
remove any repulsive interactions between the nitrogen atoms
lone pairs of electrons.
Having successfully developed a facile one pot method for the
generation of pyridyl-1,2,3-triazole ligands we then examined

78
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
their metal complexation properties. Because the complexation
chemistry of related pyridyl-1,2,3-triazoles with metal ions that
exhibit a rigid octahedral geometry (Fe(II), Ru(II), Re(I), Tc(I)) has
already been well studied [33,37–53], we investigated the coordi-
nation chemistry of these ligands with the more geometrically
flexible copper(II) and silver(I) metal ions.
filtration (Scheme 3). Recrystallization from hot methanol fur-
nished green or blue crystals suitable for X-ray crystallography.
Elemental analysis indicated that the bidentate ligands (1a and
3a) formed copper(II) chloride complexes of a 1:2 metal:ligand
stoichiometry whereas the tridentate ligands (2a and 4a) formed
1:1 metal:ligand complexes. These formulations were further sup-
ported by the electrospray mass spectrometry (ESMS). The ESMS
spectra of the copper(II) chloride complexes of the ligands 1a
and 3a in acetonitrile solution both showed a signal at m/z = 535
corresponding to a [L2Cu]+ ion, whereas spectra of the CuCl2 com-
plexes of the tridentate ligands, 2a and 4a, contained signals
m/z = 456 and 416 due to the [LCu]+ and [LNa]+ ions, respectively.
Additionally, a weak signal was observed at m/z = 424 in the
spectra of the Cu(II) complex of 2a which corresponds to the
[(2a)2Cu]2+ ion. Conductivity measurements in methanol indicate
that the copper(II) complexes formed with 2a, 3a, and 4a are
non-electrolytes, suggesting that the anionic chloride ligands are
3.2. Synthesis of Cu(II) complexes
The rich and varied coordination chemistry of copper(II) with
nitrogen heterocycles has been extensively studied [87–90], and
as such it was of interest to explore how copper(II) would interact
with the pyridyl-1,2,3-triazole ligands. The complexes were pre-
pared by adding an ethanol solution of CuCl2 (1 equiv.) to a chloro-
form solution of one of the ligands (1a, 2a, 3a, or 4a, 1 or 2 equiv.).
The suspension which formed was then heated at 60 °C for 1 h and
the resulting blue-green microcrystalline powders were isolated by
Scheme 3. (i) CuCl2, EtOH, CHCl3, 60 °C, 1 h.
Fig. 3. A representative labelled ORTEP diagram of one of the independent molecules of [(2a)CuCl2] in the unit cell. The thermal ellipsoids are shown at the 50% probability.
Selected bond lengths (Å) and angles ꢁ() for [(2a)CuCl2]: N3A–Cu1A 2.021(4), N4A–Cu1A 2.017(4), N5A–Cu1A 2.035(4), Cl1A–Cu1A 2.4483(13), Cl2A–Cu1A 2.2395(14); N4A–
Cu1A–N3A 78.19(15), N4A–Cu1A–N5A 77.86(15), N3A–Cu1A–N5A 155.13(15), N4A–Cu1A–Cl2A 152.15(11), N3A–Cu1A–Cl2A 98.10(12), N5A–Cu1A–Cl2A 99.93(11), N4A–
Cu1A–Cl1A 100.39(11), N3A–Cu1A–Cl1A 97.50(11), N5A–Cu1A–Cl1A 93.29(11), Cl2A–Cu1A–Cl1A 107.46(5).

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
79
Fig. 4. A labelled ORTEP diagram of [(3a)2CuCl2]. The thermal ellipsoids are shown at the 50% probability. Selected bond lengths (Å) and angles ꢁ() for [(3a)2CuCl2]: N1A–Cu1
2.043(4), N1–Cu1 2.040(3), Cl1–Cu1 2.287(2), Cl2–Cu1 2.295(2), N3A–Cu1 2.693(2), N3–Cu1 2.672(2); N1–Cu1–N1A 179.4(3), N1–Cu1–Cl1 88.98(15), N1A–Cu1–Cl1
91.52(14), N1–Cu1–Cl2 91.07(15), N1A–Cu1–Cl2 88.43(14), Cl1–Cu1–Cl2 178.63(7).
Scheme 4. (i) Acetone, CH2Cl2, RT, 1 h.
coordinated to the Cu(II) ions, while the conductivity of the Cu(II)
complex of 1a is in the range usually observed for a 1:1 electrolyte
[91], presumably because one of the chloride ions is acting as a
non-coordinating counterion (Scheme 3).
lengths range from 2.01 to 2.04 Å. The chloride ligand that makes
up the square plane is slightly bent out of the planarity (N4A–
Cu1A–Cl2A 152.15(11)°) at
a distance Cl2A–Cu1A 2.2395(14),
whereas the axial Cu1A–Cl1A bond is slightly longer at 2.4483(13).
It is of interest to note that overall the structure is very similar to
that reported for a related [Cu(terpy)Cl2] complex [93].
X-ray crystallography was used to determine the molecular
structures of the complexes formed with the ligands 2a and 3a.
Fig. 3 shows a perspective view of the structure of the copper com-
plex formed with the tridentate 2a. The compound crystallises in
The copper(II) complex formed with 3a crystallises in the
monoclinic space group P21 with one complete molecule of
[(3a)2CuCl2] in the asymmetric unit. The copper(II) ion lies in a
Jahn–Teller distorted octahedral coordination environment
(Fig. 4). The pyridyl and chloride donor units adopt a square planar
array around the Cu(II) ion and the Cu–N (ca. 2.04 Å) and Cu–Cl (ca.
2.28 ) bond lengths of these ligands are in the expected ranges. The
Cu–N bond lengths between the Cu(II) ion and the axial triazole
donors are much longer (ca. 2.68 Å) on the edge of what would
normally be considered to constitute a bonding interaction5[94,95].
However, we note that the triazole rings are oriented such that the
N-donor atom is directed toward Cu(II) ion, as such the coordination
geometry is best described as a distorted octahedron.
ꢀ
the triclinic space group P1 and there are three independent mol-
ecules within the unit cell. Compound [(2a)CuCl2] adopts a dis-
torted square pyramidal coordination geometry (Fig. 3) with a s5
parameter [92] of 0.05 (the other independent molecules of
[(2a)CuCl2] have s5 parameters of 0.065 and 0.097, respectively).4
Although there is some disorder associated with the peripheral ben-
zyl rings, the metal coordination core in each of the independent
molecules is well defined and almost identical. The coordination core
of tridentate ligand, 2a, is essentially planar and the Cu–N bond
4
The s5 parameter was introduced (s5 = b ꢁ a/60) for penta-coordinated com-
plexes. This parameter serves as a semiquantitative criterion to distinguish between
trigonal bipyramidal (TB) ( 5 = 1 for regular TB stereochemistry) and square based
pyramidal (SBP) ( 5 = 0 for regular SBP stereochemistry) geometries. The 5 parameter
s
5
s
s
A search of the Cambridge Structural Database (CSD) Version 5.3, showed that the
calculated for [2aCuCl2] of 0.05 indicates that the coordination geometry of is best
described as a distorted square based pyramid.
Cu–N bond distances for six-coordinate Cu(II)–triazine complexes range from 1.81 to
2.82 Å with a mean distance of 2.07 Å.

80
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
Disappointingly, despite collecting X-ray diffraction data sets
and in general, the spectra show a simple pattern containing one
set of proton signals, suggesting the formation of single symmetric
species. Compared with the spectra of the ligands 1a, 3a and 4a,
the proton signals of the corresponding silver complexes are sharp
and shifted downfield indicative of metal complexation in solution.
However, the silver complex of 2a exhibits a broad 1H NMR spec-
trum. The singlet due to the triazole ring is shifted downfield com-
pared to the ligand 2a, whereas all the other proton signals of the
silver complex are upfield shifted compared to the free ligand (see
Supporting information). We postulate that this is due to the for-
mation of a dimeric (or higher oligomeric) species such as 5, sim-
ilar to those observed in related Ag-Terpy structures [102–104],
but note that we do not see any evidence for this or larger aggre-
from the crystals of [(1a)2CuCl](Cl) and [(4a)CuCl2] we have been
unable to satisfactorily solve the structures of these molecules.
However, the inspection of the electron density maps indicated
that [(1a)2CuCl](Cl) adopts a distorted square pyramidal coordina-
tion geometry while [(4a)CuCl2] has a trigonal bipyramidal struc-
ture similar to those found in related pyridine containing CuCl2
complexes [96,97].
3.3. Synthesis of silver(I) complexes
The coordination chemistry of silver(I) with nitrogen heterocy-
cles has undergone a renaissance in recent times [7,98–101], due
to this motif’s usefulness in constructing metallosupramolecular
architectures. With this in mind we attempted to synthesize and
structurally characterise silver(I) complexes of the pyridyl-1,2,3-
triazole ligands. The complexes were prepared by adding an ace-
tone solution of AgSbF6 (1 equiv.) to a dichloromethane solution
of one of the ligands (1a, 2a, 3a, or 4a, 1 or 2 equiv.) and stirring
the resulting solutions at room temperature for 1 h (Scheme 4).
Addition of diethyl ether to the reaction mixtures led to the precip-
itation of white microcrystalline powders which were isolated by
filtration.
Elemental analysis indicated that both the bidentate ligands (1a
and 3a) formed silver(I) complexes of a 1:2 metal:ligand ratio
while the tridentate ligands (2a and 4a) formed complexes of a
1:1 metal:ligand stoichiometry with AgSbF6. Consistently, the
ESMS spectrum of [(1a)2Ag](SbF6) in acetonitrile showed two sig-
nals at m/z = 343 and 579 corresponding to the species [(1a)Ag]+
and [(1a)2Ag]+ whereas the mass spectrum of the isomeric
[(3a)2Ag](SbF6) contained a single signal at m/z = 579 correspond-
ing to [(3a)2Ag]+. The ESMS spectra of silver(I) complexes of the tri-
dentate ligands, 2a and 4a, contained two signals at m/z = 500 and
416 corresponding to the species [LAg]+ and [LNa]+. Conductivity
measurements in acetonitrile indicated that the silver(I) com-
plexes formed with 1a, 2a, 3a, and 4a are 1:1 electrolytes [91] with
Fig. 5. A labelled ORTEP diagram of [(1a)2Ag](SbF6). The thermal ellipsoids are
shown at the 50% probability. Selected bond lengths (Å) and angles (ꢁ) for
[(1a)2Ag](SbF6): Ag1–N2 2.230(2), Ag1–N2A 2.234(2), Ag–N1A 2.439(2), Ag–N1
2.442(2); N2–Ag1–N2A 144.41(8), N2–Ag1–N1A 136.52(8), N2A–Ag1–N1A
72.41(8), N2–Ag1–N1 71.29(9), N2A–Ag1–N1 138.55(8), N1A–Ag1–N1 91.54(8).
ꢁ
the SbF6 anion acting, as expected, as a non-coordinating counter-
ion. 1H NMR spectra of the silver(I) complexes were recorded at
room temperature in d6-acetone (see Supporting information)
Fig. 6. Three views of the molecular structure of the[(3a)4Ag3]3+ cation, (a) a labelled ORTEP diagram, (b) a ball and stick diagram, and (c) a space filling diagram. The thermal
ellipsoids are shown at the 50% probability. Selected bond lengths (Å) and angles (ꢁ) for [(3a)4Ag3]3+: Ag1–N1A 2.258(7), Ag1–N3 2.279(7), Ag1–N1 2.365(7), Ag1–N3A
2.443(7), Ag2–N4C 2.312(7), Ag2–N4A 2.316(7), Ag2–N4B 2.356(6), Ag2–N4 2.378(7), Ag3–N1C 2.301(7), Ag3–N1B 2.319(9), Ag3–N3B 2.369(7), Ag3–N3C 2.391(7); N1A–
Ag1–N3 150.6(3), N1A–Ag1–N1 106.3(2), N3–Ag1–N1 87.5(3), N1A–Ag1–N3A 85.5(3), N3–Ag1–N3A 105.1(2), N1–Ag1–N3A 131.0(3), N4C–Ag2–N4A 114.7(2), N4C–Ag2–N4B
109.5(2), N4A–Ag2–N4B 107.0(2), N4C–Ag2–N4 106.7(3), N4A–Ag2–N4 109.5(2), N4B–Ag2–N4 109.4(2), N3–Ag1–N3A 105.1(2), N1–Ag1–N3A 131.0(3), N1C–Ag3–N1B
113.7(3), N1C–Ag3–N3B 140.4(3), N1B–Ag3–N3B 87.0(3), N1C–Ag3–N3C 86.8(2), N1B–Ag3–N3C 134.8(3), N3B–Ag3–N3C 102.3(2) .

J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
81
Fig. 7. (a) A labelled ORTEP diagram showing a representative coordination environment for the polymeric {[(4a)Ag](SbF6)}1 and the presence of symmetry related Ag1 ions.
The SbF6 counter ion has been omitted for clarity, the thermal ellipsoids are shown at the 50% probability level. Selected bond lengths (Å) and angles ꢁ() for {[(4a)Ag](SbF6)}1:
Ag1–N1 2.321(3), Ag1–N4 2.317(2), Ag–N6 2.493(3), Ag1–N7 2.233(3); N7–Ag1–N4 135.42(9), N70–Ag1–N1 111.79(9), N4–Ag1–N1 106.70(9), N70–Ag1–N6 108.84(9), N4–
Ag1–N6 82.48(9), N1–Ag1–N6 103.40(9). (symmetry codes: 1 ꢁ x, ꢁy, 1 ꢁ z).
gates in the ESMS spectrum of the complex. However, we have
confirmed crystallographically that the 1,2,3-triazole unit can act
as a bridging ligand in related examples, see Figs. 6 and 7.
only the expected [(3a)2Ag]+ cation (Supporting information) but
also the trisilver complex [(3a)4Ag3]3+ (Fig. 6). The trisilver cation
[(3a)4Ag3]3+ is well resolved, but there is some disorder in the
[(3a)2Ag]+ cation and two of the hexafluoroantimonate counteri-
ons. The [(3a)2Ag]+ complex adopts a rare square planar [99] coor-
dination geometry
(s4 = 0.25), but because the silver ion is
disordered over two sites the Ag–N bond length and angles are
unreliable (Fig. 5, Supporting information). Conversely, the silver
ions of the trisilver unit [(3a)4Ag3]3+ are found to be tetrahedrally
coordinated to the 3a ligands with all the Ag–N bond lengths in
the range 2.25–2.39 Å. The trisilver complex is composed of two
[(3a)2Ag]+ units sandwiching the third Ag (I) ion and the phenyl
substituents of the two [(3a)2Ag]+ cations are interdigitated. The
central silver ion (Ag2) is tetrahedrally (s4 = 0.97) coordinated to
each of the ‘‘spare” triazole nitrogen atoms of the 3a ligands, while
the silver ions at the ends of the trimer adopt distorted tetrahedral
Single crystals of the silver complexes of 1a, 2a, 3a and 4a, suitable
for X-ray crystallography, were obtained by vapour diffusion of
methanol into acetone solutions of the complexes. Fig. 5 shows a
perspective view of the structure of the silver(I) complex formed
with the bidentate ligand 1a. The molecule crystallises in the mono-
or seesaw coordination environments (for Ag1,
s4 = 0.56, for Ag3,
s4 = 0.60). As far as we are aware this is only the second crystallo-
graphically characterized example of a 1,2,3-triazole acting as a
bridging ligand [56], however, 1,2,4-triazoles have been exten-
sively exploited as metal bridging ligands [106–108]. The trisilver
clinic space group P21/c and has
a
molecular formula
complex is further stabilized by a p–p interaction between the
[(1a)2Ag](SbF6) which is consistent with the other collected exper-
iment data. The silver(I) ion adopts a distorted tetrahedral coordi-
phenyl group on one ligand with the 1,2,3 triazole unit of
another ligand. Although the three silver ions adopt a linear
arrangement (Ag1–Ag2–Ag3 176.85°), the silver–silver distances
(Ag1–Ag2 4.073 Å, Ag2–Ag3 4.137 Å) preclude any additional sta-
bilization from Ag(I)–Ag(I) interactions. It appears that the forma-
tion of the trisilver complex is driven by crystal packing forces. The
crystal used for the X-ray crystallography was dissolved in acetoni-
trile and the ESMS spectrum acquired. Disappointingly, only the
[3a2Ag]+ fragment at m/z = 579 was observed, suggesting that the
trisilver unit is either not stable under the conditions of the ESMS
experiment or is unstable in solution, potentially because the elec-
trostatic repulsion generated between the three cationic silver ions
is enough to overcome the relatively weak Ag–N coordination
bonds.
nation geometry (s4 = 0.56, indicative of a distorted tetrahedral or
seesaw structure)6 [100] with the ligands coordinated through both
the pyridyl and triazole donors in the expected bidentate fashion
(Fig. 5). Interestingly, the Ag–N bond length to the triazole units
(ca. 2.23 Å) are much shorter than the corresponding bond length
between the pyridyl units and the silver ion (ca. 2.44 Å).
The X-ray crystallography of the silver(I) complex formed with
the bidentate 3a was surprising. The complex crystallises in the tri-
ꢀ
clinic space group P1 and interestingly, shows the presence of not
6
Inspired by the s5 parameter, Houser et al. (Ref. [105]) have developed a similar
semiquantitative method for determining the coordination geometry of
coordinated complexes, 4. The s4 parameter ( 4 = 360° ꢁ (b + )/141°) is used to
distinguish between tetrahedral ( 4 = 1) and square planar ( 4 = 0) geometries.
a four
Despite the solution data indicating that [(4a)Ag](SbF6) forms a
discrete complex the molecule crystallises as a coordination poly-
s
s
a
s
s

82
J.D. Crowley et al. / Polyhedron 29 (2010) 70–83
mer, where the ligand 4a does not interact in the expected triden-
Appendix A. Supplementary material
tate manner. The asymmetric unit contained one silver(I) ion, one
ꢁ
ligand, one molecule of acetone and one SbF6 counterion. The sil-
CCDC 728064, 728065, 728062, 728063, 728301, 728300,
728302, 728303, 728304 and 728432 contain the supplementary
crystallographic data for 1c, 2c, 3b, 4b, [(2a)CuCl2], (3a)2CuCl2],
[(1a)2Ag](SbF6)], [(3a)4Ag3](SbF6)3 + 0.5[(3a)2Ag](SbF6), [(4a)Ag]
ver ion is tetrahedrally (s4 = 0.80) coordinated to four nitrogen do-
nor atoms. The pyridyl (N4) and one of the triazole (N6) units of 4a
from a bidentate chelate with the silver ion and the other two coor-
dination sites are taken by triazole units from different molecules
of 4a. The triazole unit that forms the bidentate chelate is addition-
ally coordinated, in a bridging fashion, to an adjacent silver ion
through N7 and the final coordination site is occupied by the tria-
zole unit (N1) in the other arm of the ligand 4a. This arrangement
gives rise to a 4,4 net (Supporting information).
(SbF6)] and [(2a)4Ag4](SbF6)4]. These data can be obtained free
1
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2009.06.010.
The X-ray crystallography of the silver(I) complex formed with
the tridentate ligand 2a was also surprising. The complex crystal-
lises in the tetragonal space group I41cd and shows the presence
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