A general and very straightforward route to the selective N-functionalization of 1,4,7-triazacyclononane with imidazole groups. Crystal structure determinations of nickel(II), copper(II) and zinc(II) complexes

Article abstract of DOI:10.1016/S0020-1693(99)00518-6

An easy, one-step procedure for the synthesis of the selectively substituted macrocycles 1-(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane, L¹, and 1,4-bis(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane, L², is reported. The potentially tetra-, L¹, and pentadentate, L², compounds yield nickel(II), copper(II) and zinc(II) complexes which have been isolated in the solid state. The crystal structures of [NiL¹(N₃)]₂[PF₆]₂ (1), [Cu₂L₂¹(OH)][PF₆]₃ (2), [ZnL¹Cl]BPh₄ (3), [NiL²-(H₂0)][BPh₄]₂-·C₂H₅OH (4) and [Ni₂L₂²(N₃)][PF₆]₃ (5) have been determined by X-ray diffraction studies. The L¹ and L² molecules provide four and, respectively, five nitrogens for complexation of the metal ions whose coordination requirements are completed by additional ligands either terminal (Cl, H₂O, compounds 3 and 4) or bridging two metal ions (N₃^-, compounds 1 and 5; OH^-, compound 2). In its complexes nickel(II) is six-coordinated in an approximately octahedral environment. Both copper(II) and zinc(II) are five-coordinated with geometries approximately square pyramidal and, respectively, trigonal bipyramidal. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00518-6

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 303 (2000) 61–69
A general and very straightforward route to the selective
N-functionalization of 1,4,7-triazacyclononane with imidazole
groups. Crystal structure determinations of nickel(II), copper(II)
and zinc(II) complexes
Massimo Di Vaira *, Fabrizio Mani, Piero Stoppioni
Dipartimento di Chimica, Uni6ersita` di Firenze, 6ia Maragliano 77, 50144 Florence, Italy
Received 5 July 1999; accepted 22 October 1999
Abstract
An easy, one-step procedure for the synthesis of the selectively substituted macrocycles 1-(1-methylimidazol-2-ylmethyl)-1,4,7-
triazacyclononane, L1, and 1,4-bis(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane, L2, is reported. The potentially tetra-,
L1, and pentadentate, L2, compounds yield nickel(II), copper(II) and zinc(II) complexes which have been isolated in the solid
state. The crystal structures of [NiL1(N3)]2[PF6]2 (1), [Cu2L21(OH)][PF6]3 (2), [ZnL1Cl]BPh4 (3), [NiL2(H2O)][BPh4]2·C2H5OH (4)
and [Ni2L22(N3)][PF6]3 (5) have been determined by X-ray diffraction studies. The L1 and L2 molecules provide four and,
respectively, five nitrogens for complexation of the metal ions whose coordination requirements are completed by additional
ligands either terminal (Cl, H2O, compounds 3 and 4) or bridging two metal ions (N3−, compounds 1 and 5; OH−, compound
2). In its complexes nickel(II) is six-coordinated in an approximately octahedral environment. Both copper(II) and zinc(II) are
five-coordinated with geometries approximately square pyramidal and, respectively, trigonal bipyramidal. © 2000 Elsevier Science
S.A. All rights reserved.
Keywords: Crystal structures; Nickel complexes; Copper complexes; Zinc complexes; Aza macrocycle complexes
to the polyazamacrocycle according to multistep pro-
cesses with low yields. Our interest in this field
prompted us to exploit a variety of alternative synthetic
methods to selectively functionalize polyazamacrocycles
and some time ago we reported the synthesis of 1,4-
bis(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclono-
nane with the use of 1,8-bis-(dimethylamino)-
naphthalene (Proton Sponge®) as the base [1,5]. Now
we have devised an improved and efficient strategy
which allows to obtain mono- and di-functionalized
[9]aneN3 with remarkable synthetic simplicity and in
high yields. From these compounds it is possible to
obtain unsymmetrically functionalized macrocycles by
means of routine organic procedures.
1. Introduction
We are interested in the synthesis of ligands through
the functionalization of 1,4,7-triazacyclononane ([9]-
aneN3) with pendant donor groups of different nature,
in order to improve the selectivity of the ligands and
the stability of the complexes [1]. To that purpose
mono- and di-functionalized derivatives of [9]aneN3
have to be readily available in high yields. While a large
number of hexadentate compounds derived from N-
functionalization of [9]aneN3 with three identical pen-
dant groups have recently been reported [2,3],
selectively N-functionalized compounds are compara-
tively rare [4]. This reveals the difficulties encountered
for the attachement of only one or two pendant groups
In this paper we describe the one-step synthesis of the
two compounds 1-(1-methylimidazol-2-ylmethyl)-1,4,7-
triazacyclononane, L1, and 1,4-bis(1-methylimidazol-2-
ylmethyl)-1,4,7-triazacyclononane, L2. The coordi-
nation properties of the two ligands have been inves-
* Corresponding author. Tel.: +39-055-321 631; fax: +39-055-
354 845.
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00518-6

62
M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
tigated towards some 3d metal ions and the X-ray
structure determinations of the complexes [NiL1(N3)]2-
[PF6]2 (1), [Cu2L21(OH)][PF6]3 (2), [ZnL1Cl]BPh4 (3),
[NiL2(H2O)][BPh4]2·C2H5OH (4) and [Ni2L22(N3)][PF6]3
(5) have been carried out.
under a N2 atmosphere using deaerated solvents. Solid
2-chloromethyl-1-methylimidazole hydrochloride (13.5
g, 0.0808 mol) was slowly added to a solution of
1,4,7-triazacyclononane (10.0 g, 0.0775 mol) in dry
DMF (400 ml). The reactants were stirred at room
temperature for 6 days, during which increasing
amounts of a solid compound formed. The solid com-
pound was separated from the solution by filtration
under N2, washed with an ethanol–diethyl ether mix-
ture (50–50 by volume), then with diethyl ether alone,
and was finally dried in a stream of N2 at about
40°C. This compound is the bis-hydrochloride of 1-
(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane,
L1, in fairly pure form. Yield (average) 9.2 g, 40%. The
purity of the compound was checked by means of 13C
NMR, verifying that the spectra exhibited the expected
resonances. 13C NMR (D2O): l 145.0 (C2 of imidazole),
123.4, 121.6 (C4, C5 of imidazole), 48.7 (bridge-CH2),
43.8, 42.5, 42.3 (CH2 of macrocycle), 33.3 (CH3 of
imidazole). The DMF solution was rotary evaporated
to dryness, the resulting solid was dissolved in water
and the pH of the solution was adjusted to 9 with
NaOH. The water solution was extracted with CHCl3
(30 ml) in order to remove possible traces of unreacted
[9]aneN3 and 2-chloromethyl-1-methylimidazole. The
water solution was made strongly basic with NaOH
and extracted two times with CHCl3 (50 ml each). After
drying the CHCl3 layer with anhydrous sodium sulfate,
rotary evaporation to dryness gave a crude product in
oily form which was found to contain 1,4-bis(1-
methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane,
L2, and traces of the monosubstituted compound L1
and of unreacted [9]aneN3. Yield (average) 6.1 g, 25%.
For its purification, the crude product was dissolved in
CHCl3 and eluted through a neutral alumina column
(Aldrich, type 507 C, 150 mesh) with a chloroform–
methanol mixture (95–5 by volume). 13C NMR (D2O):
l 146.7 (C2 of imidazole), 126.6, 123.3 (C4, C5 of
imidazole), 53.3 (bridge-CH2), 52.1, 50.5, 45.2 (CH2 of
macrocycle), 33.2 (CH3 of imidazole).
2. Experimental
2.1. Materials and methods
All reagents were reagent grade; commercial solvents,
when required by the synthetic procedures, were dried
according to standard methods and distilled just before
their use. Hydrated zinc perchlorate was prepared using
a standard procedure. The intermediate compounds
1,4,7-triazacyclononane [6] and 2-chloromethyl-1-
methylimidazole [7] were prepared according to pub-
lished procedures. The purity of the products was
checked by means of 13C NMR, verifying that the
spectra exhibited the expected resonances. Hydrated
metal(II) chlorides, hydrated CuCO3·Cu(OH)2, Na-
BPh4, TlPF6 and NaN3 are commercially available and
were used as received. Elemental analyses were per-
formed by the Microanalytical Laboratory of the De-
partment of Chemistry of the University of Florence.
The 13C NMR spectra of the compounds were obtained
with a Varian FT 80 spectrometer operating at 20.0
MHz. Infrared spectra were recorded with a Perkin–
Elmer 283 grating spectrophotometer as Nujol mulls
between KBr plates; electronic spectra were recorded in
the range 300–2000 nm with a Perkin–Elmer Lambda
9 spectrophotometer; the concentration of the solutions
was ca. 1.0×10−3 M.
2.2. Syntheses of the ligands
The procedure for the synthesis of the ligands is
outlined in Scheme 1. The reactions were carried out
Scheme 1.

M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
63
2.3. Syntheses of the complexes
2.3.4. [NiL2(H2O)][BPh4]2·C2H5OH (4)
A solution of hydrated NiCl2 (238 mg, 1.0 mmol)
and of L2 (317 mg, 1.0 mmol) in EtOH (40 ml) and a
solution of NaBPh4 (684 mg, 2.0 mmol) in acetone (20
ml) were mixed together at boiling temperature and
concentrated until a lilac crystalline compound was
obtained. Recrystallization of the compound from a
Me2COꢀEtOH mixture gave the crystals used for X-ray
analysis. Calc. for C66H75B2N7NiO2: C, 73.5; H, 7.01;
N, 9.09. Found: C, 73.5; H, 7.11; N, 9.12%. UV–Vis
(umax (nm); m (cm2 mmol−1)): diffuse reflectance 330,
540, 800(sh), 870; CH3CN solution: 340(29), 540(20),
800(sh), 870(25).
2.3.1. [NiL1(N3)]2[PF6]2 (1)
Solutions of hydrated NiCl2 (238 mg, 1.0 mmol) in
EtOH (20 ml), of L1·2HCl (296 mg, 1.0 mmol) in
MeOH (30 ml) and of NaN3 (65 mg, 1.0 mmol) in H2O
(20 ml) were mixed at boiling temperature. To the
resulting solution, solid Na2CO3 (200 mg) in excess to
the stoichiometric ratio was added followed by an
acetone solution (30 ml) of TlPF6 (349 mg, 1.0 mmol).
The suspension was stirred at 40°C for 10 min, cooled
to room temperature and filtered to remove solid TlCl.
Finally, the solution was concentrated to a small vol-
ume until a lilac crystalline compound was obtained.
Slow evaporation at room temperature of a MeCNꢀ
EtOH solution of the compound gave the crystals used
for X-ray analysis. Calc. for C22H42F12N16Ni2P2: C,
28.2; H, 4.52; N, 23.9. Found: C, 28.6; H, 4.64; N,
24.0%. UV–Vis (umax (nm); m (cm2 mmol−1): diffuse
reflectance 310, 560, 850(sh), 920; CH3CN solution
300(810), 560(15), 820(sh), 920(26). IR (KBr, w (cm−1)),
2075, w(N3).
2.3.5. [Ni2L22(N3)][PF6]3 (5)
This compound was prepared by the same procedure
as compound 1 but using L2 instead of L1·2HCl and
without addition of Na2CO3. Calc. for C32H54F18N17-
Ni2P3: C, 31.3; H, 4.44; N, 19.4. Found: C, 31.4; H,
4.50; N, 19.3%. UV–Vis (umax (nm); m (cm2 mmol−1)):
diffuse reflectance 330, 540, 800(sh), 890; CH3CN solu-
tion: 349(29), 540(20), 800(sh), 870(25). IR (KBr, w
(cm−1)), 2080, w(N3).
2.3.2. [Cu2L12 (OH)][PF6]3 (2)
2.3.6. [CuL2][PF6]2 (6)
Solid CuCO3·Cu(OH)2·nH2O (110 mg, ca. 0.5 mmol)
was added to a boiling solution in EtOH (50 ml) of
L1·2HCl (296 mg, 1.0 mmol). After dissolution of the
copper compound, a water solution of Na2CO3 (106
mg, 1.0 mmol) and an acetone solution (20 ml) of
TlPF6 (698 mg, 2.0 mmol) were added in the order to
the reactant solution. The suspension was stirred for 10
min at 40°C, cooled to room temperature and filtered
to remove solid TlCl. Slow evaporation of the solution
gave a blue crystalline compound. Crystals suitable for
X-ray analysis were grown from a MeCNꢀEtOH solu-
tion of the compound. Calc. for C22H43Cu2F18N10OP3:
C, 25.8; H, 4.23; N, 13.6. Found: C, 25.8; H, 4.36; N,
13.6%. UV–Vis (umax (nm); m (cm2 mmol−1)): diffuse
reflectance 610, 700(sh), 950; CH3CN solution 630(120),
970(27).
Warm solutions of hydrated CuCl2 (170 mg, 1.0
mmol), of L2 (317 mg, 1.0 mmol) in EtOH (40 ml) and
of TlPF6 (698 mg, 2.0 mmol) in acetone (30 ml) were
mixed together and the suspension was stirred at 40°C
for 10 min. Afterward the suspension was cooled to
room temperature, TlCl discarded by filtration and the
resulting solution was concentrated until a blue crys-
talline compound was obtained. Recrystallization was
carried out with a MeCNꢀEtOH mixture. Calc. for
C16H27CuF12N7P2: C, 28.6; H, 4.10; N, 14.6. Found C,
28.7; H, 4.20; N, 14.5%. UV–Vis (umax (nm); m (cm2
mmol−1)): diffuse reflectance 380(sh) 610, 960; CH3CN
solution: 380(sh), 620(145), 970(30).
2.3.7. [ZnL2][ClO4]2 (7)
The solution of hydrated Zn(ClO4)2 (372 mg, 1.0
mmol) and L2 (317 mg, 1.0 mmol) in EtOH (40 ml) was
concentrated until a white crystalline product was ob-
tained which was recrystallized from water. Calc. for
C16H27Cl2N7O8Zn: C, 33.0; H, 4.69; N, 16.8. Found: C,
33.3; H, 4.91; N, 16.7%. 13C NMR (D2O): l 146.6 (C2),
123.9, 123.7 (C4, C5), 52.9, 51.7, 51.4, 43.4 (unresolved
CH2), 32.0 (CH3 of imidazole).
2.3.3. [ZnL1Cl]BPh4 (3)
Warm solutions of hydrated Zn(ClO4)2 (372 mg, 1.0
mmol) in EtOH (20 ml) and of L1·2HCl (296 mg, 1.0
mmol) in MeOH (20 ml) were mixed and solid Na2CO3
(159 mg, 1.5 mmol) was added to the resulting solution.
The suspension was allowed to boil for 10 min and
filtered to remove unreacted Na2CO3. Then NaBPh4
(342 mg, 1.0 mmol) dissolved in acetone (30 ml) was
added to the resulting solution. The solution was con-
centrated until a white crystalline compound was ob-
tained which was recrystallized from a Me2COꢀEtOH
mixture. Calc. for C35H41BClN5Zn: C, 65.3; H, 6.42; N,
10.9. Found C, 65.0; H, 6.79; N, 10.6%. The complex is
scarcely soluble in the common deuterated solvents.
2.4. X-ray data collections, structure determinations
and refinements
X-ray diffraction data were collected for the com-
pounds [NiL1(N3)]2[PF6]2 (1), [Ni2L22(N3)][PF6]3 (5),
[NiL2(H2O)][BPh4]2·C2H5OH (4), [Cu2L21(OH)][PF6]3
(2) and [ZnL1Cl]BPh4 (3) at room temperature on a

64
M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
Table 1
Crystallographic data for [NiL1(N3)]2[PF6]2 (1), [Ni2L22(N3)][PF6]3 (5), [NiL2(H2O)][BPh4]2·C2H5OH (4), [Cu2L21(OH)][PF6]3 (2) and [ZnL1Cl]BPh4
(3)
1
5
4
2
3
Formula
M
C22H42F12N16Ni2P2
938.08
C32H54F18N17Ni2P3
1229.25
C66H75B2N7NiO2
1078.66
C22H43Cu2F18N10OP3
1025.65
C35H41BClN5Zn
643.36
Crystal system
Space group
monoclinic
C2/c (no. 15)
25.642(1)
11.651(1)
13.168(2)
90.00
113.93(1)
90.00
3595.8(6)
4
monoclinic
C2/c (no. 15)
18.776(3)
18.993(4)
15.884(6)
90.00
118.36(3)
90.00
4985(2)
triclinic
orthorhombic
P21nb (no. 33)
10.762(2)
17.019(4)
20.265(5)
90.00
90.00
90.00
3712(1)
4
monoclinic
P21/n (no. 14)
9.335(4)
21.755(6)
16.175(4)
90.00
96.40(3)
90.00
3264(2)
(
P1 (no. 2)
,
a (A)
11.021(6)
13.581(4)
19.606(8)
96.45(3)
91.06(4)
96.14(3)
2898(2)
2
,
b (A)
,
c (A)
h (°)
i (°)
g (°)
3
,
U (A )
Z
4
4
Dc (g cm−3
)
1.733
1.638
1.236
1.835
1.309
Crystal size (mm)
0.20×0.25×0.40
3.12
0.17×0.33×0.70
0.966
0.15×0.40×0.60
0.386
0.10×0.25×0.50
3.83
0.50×0.60×0.70
0.866
v (mm−1
)
Radiation
Cu Ka
Mo Ka
Mo Ka
Cu Ka
Mo Ka
,
,
,
,
,
(u=1.5418 A)
(u=0.71069 A)
(u=0.71069 A)
(u=1.5418 A)
(u=0.71069 A)
Data collected a
Scan type
9h, +k, +l
ꢀ–2q
9h, +k, +l
ꢀ–2q
9h, 9k, +l
ꢀ–2q
redundant
ꢀ
9h, +k, +l
ꢀ–2q
2q range (°)
Reflections collected
Unique reflections
7–140
3919
3198
5–50
4567
4386
5–45
7491
7491
7–113
13924
4196
5–52
7141
6070
Unique observed reflections, 3086
3276
4379
3932
4409
with I\2|(I)
Absorption correction
No. parameters
„ scan method
247
no
328
empirical, DIFABS
725
empirical, SADABS
507
no
478
R1 (observed reflections)
R1 (all unique reflections)
wR2
0.051
0.052
0.138
1.076
0.051
0.077
0.146
1.037
0.55, −0.38
0.081
0.157
0.222
1.063
0.053
0.056
0.146
1.057
0.046
0.080
0.136
1.028
0.67, −0.50
Goodness-of-fit
Largest features (max, min)
0.83, −0.53
0.49, −0.42
0.55, −0.54
−3
,
in final DF map (e A
)
a Data collections performed with P4 (1), CAD4 (5, 4 and 3) and CCD (2) instruments.
Bruker-AXS P4 diffractometer (1) using graphite-
monochromated Cu Ka radiation, on an Enraf–
Nonius CAD4 diffractometer (5, 4 and 3) with
graphite-monochromated Mo Ka radiation, and on a
Bruker–AXS CCD platform (2) with Cu Ka radiation
from a rotating anode generator equipped with Go¨bel
mirrors. Crystal data and details about data collection
and structure refinements are given in Table 1. Unit-cell
parameters were obtained from the settings of 30 reflec-
tions with 20BqB30° (1), of 24 reflections with 15B
qB16° (5), 13BqB15° (4) and 13BqB16° (3), and
of 6069 reflections with 3BqB56° (2). No crystal
decay was observed during data collections. Empirical
corrections for absorption based on „ scans (1) or using
DIFABS [8] (4) or SADABS [9] (2) were applied, but no
corrections were applied for 5 and 3, for which „ scan
data were not available and DIFABS failed to yield
significant improvements. A small correction for extinc-
tion effects had to be applied to the data of 1. The main
programs used in the crystallographic calculations are
listed in Refs. [8–13].
The structures were solved by direct (SIR [10]) and
heavy-atom (SHELXL 93 [11]) methods and were refined
by full-matrix least-squares on Fo2. In the final refine-
ment cycles on all structures the non-hydrogen atoms,
including the fractional atoms of the solvent in 4 (see
below) were assigned anisotropic temperature factors.
The positional parameters of the hydrogen atoms of the
water molecule in 4 were refined with one geometrical
restraint; also those of most hydrogens in 3 were refined
with three separate and soft restraints for the NꢀH, the
aromatic and the aliphatic hydrogens of the dangling
group of L1. The hydrogens of the macrocyclic ring of
3, whose sites were affected by relatively high thermal
motion, all the hydrogen atoms in 4 (except those of the
H2O molecule) as well as those of the other structures
were in calculated positions, riding on the carrier atoms
(methyls being treated as rigid groups). In all cases the
H temperature factors were assigned according to the
eq
C,N
expression UH=1.2U
(UH=1.5UCeq for methyl hy-
drogens). A soft restraint was imposed on the CꢀC

M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
65
distances of the phenyl groups in 4. The ethanol solvate
molecule in the same structure, affected by disorder,
was refined as being distributed between two orienta-
tions with fixed complementary population parameters,
assigned on the basis of refinement cycles performed
with an overall temperature factor for all the fractional
sites of the solvent model. Common restraints were
imposed on corresponding bond distances in the two
fractions of the ethanol molecule; the short CꢀC value
obtained should be attributed to effects of thermal
motion and/or disorder. The absolute configuration for
the acentric structure of 2 could not be assigned on the
basis of Flack’s test [14], probably due to the small
anomalous dispersion effects for this compound with
Cu Ka radiation (actually, the absolute configuration
could be assigned for a different crystal of 2, based on
Mo Ka data collected on the CAD4 instrument; those
data, however, were considered to be of overall worse
quality than the present ones).
groups, in no case such deprotonation occurred upon
reaction with the Ni(II), Cu(II) and Zn(II) salts even in
basic conditions, as shown by the stoichiometries of the
complexes obtained. Moreover the IR spectra of the
complexes exhibit strong absorptions in the 3200–3280
region due to NꢀH stretching. The L1 and L2 com-
pounds provide four and, respectively, five nitrogen
donors for complexation of the metal ions thus favour-
ing the binding of additional ligands to the [ML]2+
(L=L1, L2) moieties in order to satisfy the coordina-
tion requirements of the metal ions, which generally
exceed the denticities of both ligands.
The nickel(II) compounds have the formulae
NiL1N3PF6 (1), NiL2H2O(BPh4)2·C2H5OH (4) and
Ni2(L2)2N3(PF6)3 (5). Their electronic spectra recorded
on the solid samples and in MeCN solutions are all
indicative of a six-coordinate environment of high-spin
nickel(II). In particular, the marked splitting of the
low-energy band at 800–900 nm is typical of trigonally
distorted symmetry [15]. In the nickel complexes 1 and
5 the ligands block four (L1) and five (L2) coordination
sites of an octahedral environment thus leaving sites
available for possible N3− coordination. The stoi-
chiometry of the copper(II) complex Cu2(L1)2-
(OH)(PF6)3 suggests a dinuclear structure with one
bridging hydroxide and a five-coordinate metal envi-
ronment. Comparison of the electronic spectra of the
solid compound and of its MeCN solution suggests that
the dinuclear structure is disrupted in solution where
the hydroxide ion is most likely replaced by a solvent
molecule. The 13C NMR spectrum of ZnL2(ClO4)2 in
D2O exhibits one resonance from each group of chemi-
cally equivalent carbon atoms suggesting that only a
single symmetric species, presumably five-coordinate, is
present in solution. The ZnL1ClBPh4 complex is not
sufficiently soluble in the common deuterated solvents
to give meaningful 13C NMR spectra.
3. Results and discussion
The selectively substituted macrocycles 1-(1-methyl-
imidazol-2-ylmethyl)-1,4,7-triazacyclononane, L1, ob-
tained as the bis-hydrochloride salt, and 1,4-bis-
(1-methylimidazol-2-ylmethyl)-1,4,7-triazacyclononane,
L2, were prepared by a very simple one-step procedure
which involves the reaction of 2-chloromethyl-1-
methylimidazole hydrochloride with 1,4,7-triazacy-
clononane in a molar ratio close to 1:1. The synthetic
route is summarized in Scheme 1. The reactants in
DMF were allowed to react for 6 days at room temper-
ature; then the L1 ligand was separated from the reac-
tion mixture as the bis-hydrochloride in fairly pure
form and in good yield. After removal of the solid
L1·2HCl from the DMF solution, the L2 ligand was
recovered as a byproduct by means of standard
workup. The purity of the ligands was checked by
means of their 13C NMR spectra in D2O. In the above
synthetic procedure the macrocycle to be functionalized
acts as the base and the protonation of the secondary
amines of the macrocycle prevents their functionaliza-
tion. The molar ratio of the two reactants, the choice of
the solvent and the temperature and the extent of the
reaction time were found to be crucial factors for the
success of the synthesis. The experimental conditions
reported (see Section 2) are those which gave the best
yields of L1 and L2 (65% overall with respect to
[9]aneN3).
In the structures of the nickel compounds each of the
metal atoms is six-coordinated in an approximately
octahedral environment, being surrounded by all the
donor atoms of the substituted macrocyclic ligand and
by N3− nitrogen or water oxygen atoms. In each case
the three macrocycle nitrogens span one face of the
octahedron about the metal atom forming NꢀNiꢀN
angles B90°. This may be at the origin of the trigonal
distortion suggested by the electronic spectra of the
compounds.
The dimeric [NiL1(N3)]22+ cation of 1 (Fig. 1 and
Table 2) possesses a twofold symmetry axis normal to
the N3− anions, which are substantially parallel to each
other and bridge the two metal atoms. Two N3− nitro-
gens and the methylimidazole donor atom define the
face of the octahedron about the nickel atom lying
trans to the face occupied by the macrocycle nitrogens.
Probably due to the effects of packing forces, the two
The complexes were prepared by the reactions of
compounds L1·2HCl or L2 and the appropriate
metal(II) salts in EtOHꢀMeOH mixtures. The syntheses
of the complexes with L1·2HCl require a basic medium.
Even if the ligands have potentially deprotonable NH

66
M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
Table 3
2
,
Selected bond lengths (A) and angles (°) for [Ni2L2 (N3)][PF6]3 (5)
NiꢀN(1)
NiꢀN(2)
NiꢀN(3)
NiꢀN(4)
2.080(4)
2.111(3)
2.122(4)
2.048(4)
NiꢀN(6)
NiꢀN(8)
N(8)ꢀN(9)
2.059(4)
2.095(4)
1.169(4)
N(1)ꢀNiꢀN(2)
N(1)ꢀNiꢀN(3)
N(1)ꢀNiꢀN(4)
N(1)ꢀNiꢀN(6)
N(1)ꢀNiꢀN(8)
N(2)ꢀNiꢀN(3)
N(2)ꢀNiꢀN(4)
N(2)ꢀNiꢀN(6)
83.31(14)
83.9(2)
99.3(2)
163.8(2)
91.1(2)
84.57(13)
81.64(13)
96.63(14)
N(2)ꢀNiꢀN(8)
N(3)ꢀNiꢀN(4)
N(3)ꢀNiꢀN(6)
N(3)ꢀNiꢀN(8)
N(4)ꢀNiꢀN(6)
N(4)ꢀNiꢀN(8)
N(6)ꢀNiꢀN(8)
NiꢀN(8)ꢀN(9)
174.2(2)
165.34(13)
79.93(14)
96.4(2)
96.7(2)
97.8(2)
89.2(2)
119.5(3)
Fig. 1. A view of the dimeric [NiL1(N3)]22+ cation in the structure of
1, showing the atom numbering scheme for the symmetry indepen-
dent part of the cation. A twofold axis passes through atoms N(7)
and N(9).
Table 2
1
,
Selected bond lengths (A) and angles (°) for [NiL (N3)]2[PF6]2 (1)
NiꢀN(1)
NiꢀN(2)
NiꢀN(3)
NiꢀN(4)
2.126(2)
2.083(3)
2.084(3)
2.051(3)
NiꢀN(6)
NiꢀN(8)
N(6)ꢀN(7)
N(8)ꢀN(9)
2.153(3)
2.086(3)
1.175(3)
1.169(3)
N(1)ꢀNiꢀN(2)
N(1)ꢀNiꢀN(3)
N(1)ꢀNiꢀN(4)
N(1)ꢀNiꢀN(6)
N(1)ꢀNiꢀN(8)
N(2)ꢀNiꢀN(3)
N(2)ꢀNiꢀN(4)
N(2)ꢀNiꢀN(6)
N(2)ꢀNiꢀN(8)
83.38(10)
83.51(10)
80.96(10)
94.12(11)
174.45(10)
83.01(11)
97.00(11)
174.09(11)
91.10(11)
N(3)ꢀNiꢀN(4)
N(3)ꢀNiꢀN(6)
N(3)ꢀNiꢀN(8)
N(4)ꢀNiꢀN(6)
N(4)ꢀNiꢀN(8)
N(6)ꢀNiꢀN(8)
NiꢀN(6)ꢀN(7)
NiꢀN(8)ꢀN(9)
164.36(11)
91.40(11)
95.26(11)
87.87(12)
100.37(11)
91.32(12)
121.0(2)
Fig. 3. A view of the [NiL2(H2O)]2+ cation in the structure of 4.
NiꢀN(N3−) distances differ significantly (Table 2), the
shorter one lying trans to the longest of the NiꢀN
distances formed by the macrocycle nitrogens. The
,
metal atom deviates by 50.16 A from each of the three
122.7(2)
planes (hereafter ‘equatorial’ planes) of the idealized
octahedron, each defined by four donor atoms mutually
trans in pairs. In addition to the dimetal cations, the
structure of 1 contains isolated PF6− anions.
The dimeric [Ni2L22(N3)]3+ cation of 5 (Fig. 2, Table
3) has a twofold axis normal to the bridging N3− anion.
Each metal atom is coordinated by the five L2 nitrogen
donor atoms and one N3− nitrogen. The axis of the
N3− ligand forms an angle close to 120° with the
direction of the NiꢀN(N3−) bond (Table 3). Similar
values of the corresponding angles are formed by the
two bridging anions in 1 (Table 2). The metal atom in
,
5 deviates from the equatorial planes by 50.15 A. In
addition to one half of the dimetal cation, the asymmet-
ric unit of 5 contains one PF6− anion lying in general
position and one half of a second PF6− anion, which
lies in special position on a twofold axis.
The structure of 4 contains [NiL2(H2O)]2+ cations,
BPh4− anions and (disordered) solvate ethanol
molecules. The coordination in the monomeric cation
(Fig. 3, Table 4) is provided by the five donor atoms of
Fig. 2. A view of the dimeric [Ni2L22 (N3)]3+ cation in the structure of
5. Atom N(9) lies on a twofold axis. Only atoms forming the
asymmetric unit are labelled.

M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
67
the L2 ligand and by the water oxygen. The conforma-
tion of the L2 molecule is substantially similar to that
attained in 5, with the planes through the two
methylimidazole groups forming closely related,
91.2(3)° 4 and 88.1(2)° 5, dihedral angles in the two
structures. However, if the angles formed by the above
two planes and the plane through the macrocycle nitro-
gens in each structure are compared (43.6(3) and
52.8(3)° in 4, 51.5(2) and 54.6(2)° in 5), one of the
angles in 4 is found to differ sensibly from the others.
This is probably an effect of hydrogen bond interac-
tions in 4 (see below). The metal atom in 4 deviates
Table 4
Selected bond lengths (A) and angles (°) for [NiL2(H2O)]-
[BPh4]2·C2H5OH (4)
,
NiꢀN(1)
NiꢀN(2)
NiꢀN(3)
2.085(6)
2.105(6)
2.095(6)
NiꢀN(4)
NiꢀN(6)
NiꢀO(1)
2.017(6)
2.056(6)
2.105(6)
,
from the equatorial planes by 50.13 A.
The mean values of the metal-donor atom distances
,
,
in the nickel(II) derivatives (2.097 A 1, 2.086 A 5, 2.077
A 4) decrease regularly going from the dimeric cation
N(1)ꢀNiꢀN(2)
N(1)ꢀNiꢀN(3)
N(1)ꢀNiꢀN(4)
N(1)ꢀNiꢀN(6)
N(1)ꢀNiꢀO(1)
N(2)ꢀNiꢀN(3)
N(2)ꢀNiꢀN(4)
N(2)ꢀNiꢀN(6)
83.3(2)
83.2(2)
97.0(2)
163.6(2)
94.0(2)
84.2(2)
82.3(2)
96.8(2)
N(2)ꢀNiꢀO(1)
N(3)ꢀNiꢀN(4)
N(3)ꢀNiꢀN(6)
N(3)ꢀNiꢀO(1)
N(4)ꢀNiꢀN(6)
N(4)ꢀNiꢀO(1)
N(6)ꢀNiꢀO(1)
177.3(2)
166.3(2)
80.5(2)
96.1(2)
99.3(2)
97.5(2)
86.0(2)
,
with a double N3− bridge to the monobridged one and
then to the monomeric cation. Actually, part of this
trend (from 1 to 5) is substantially determined by the
values of the NiꢀN(N3−) distances (Tables 2 and 3) and
may result from comparatively high space demand
within the coordination sphere by the charged ligands,
particularly when there are two N3− anions closely
spaced, as in 1. If only the NiꢀN distances formed by
the chelating ligands are considered, their mean values
are found to be closely similar for the two N3− deriva-
,
,
tives (2.086 A 1, 2.084 A 5), both being only slightly
,
smaller than the 2.089 A mean found for the nickel(II)
complex of the completely methylimidazol-functional-
,
ized macrocycle [16]. On the other hand, the 2.072 A
mean value of the NiꢀN distances, all formed by L2, in
4 is sensibly smaller than all of the former mean values.
This could be due to the formation of (strongly bent)
hydrogen bonds or related electrostatic interactions
within the coordination sphere of 4, between the water
molecule and nitrogen atoms of L2. Actually, the two
candidate N atoms for such interactions, according to
the PARST analysis [13] of the structure, the aminic N(1)
and the methylimidazole N(4) nitrogen, form the short-
est NiꢀN bonds of the respective type in 4 (Table 4).
Such interactions may also be responsible for the devia-
tion, mentioned above, of the plane of a methylimida-
zole group in 4 (the one containing N(4)) from the
expected orientation with respect to other planes in the
structure.
Fig. 4. A view of the [Cu2L21 (OH)]3+ cation in the structure of 2.
Table 5
1
,
Selected bond lengths (A) and angles (°) for [Cu2L2 (OH)][PF6]3 (2)
The structure of 2 consists of dimetal [Cu2L21(OH)]3+
cations and PF6− anions. Each of the two metal atoms
(Fig. 4, Table 5) is five-coordinated by the four nitrogen
donor atoms of the L1 ligand and by the oxygen atom
of the bridging OH− anion. The coordination geometry
about each copper(II) atom is approximately square
pyramidal, however with different arrangements of the
two L1 ligands. In the square pyramid about Cu(1) the
donor atom in the apical position, N(1), is the macrocy-
cle nitrogen bearing the pendant group, whereas in the
Cu(2) polyhedron the apical atom, N(8), is one of the
unsubstituted macrocycle nitrogens. As a consequence
of this in the Cu(1) environment the methylimidazole
plane is almost perpendicular to the basal plane of the
square pyramid, with which it forms a 96.2(2)° dihedral
Cu(1)ꢀN(1)
Cu(1)ꢀN(2)
Cu(1)ꢀN(3)
Cu(1)ꢀN(4)
Cu(1)ꢀO
2.271(6)
2.079(5)
2.021(6)
1.986(6)
1.913(4)
Cu(2)ꢀN(6)
Cu(2)ꢀN(7)
Cu(2)ꢀN(8)
Cu(2)ꢀN(9)
Cu(2)ꢀO
2.085(6)
2.005(7)
2.200(7)
1.989(6)
1.925(5)
N(1)ꢀCu(1)ꢀN(2)
N(1)ꢀCu(1)ꢀN(3)
N(1)ꢀCu(1)ꢀN(4)
N(1)ꢀCu(1)ꢀO
N(2)ꢀCu(1)ꢀN(3)
N(2)ꢀCu(1)ꢀN(4)
N(2)ꢀCu(1)ꢀO
N(3)ꢀCu(1)ꢀN(4)
N(3)ꢀCu(1)ꢀO
N(4)ꢀCu(1)ꢀO
80.5(2)
84.2(2)
80.0(2)
117.0(2)
83.8(2)
96.0(2)
161.6(3)
164.0(3)
92.0(2)
92.9(2)
135.2(3)
N(6)ꢀCu(2)ꢀN(7)
N(6)ꢀCu(2)ꢀN(8)
N(6)ꢀCu(2)ꢀN(9)
N(6)ꢀCu(2)ꢀO
N(7)ꢀCu(2)ꢀN(8)
N(7)ꢀCu(2)ꢀN(9)
N(7)ꢀCu(2)ꢀO
N(8)ꢀCu(2)ꢀN(9)
N(8)ꢀCu(2)ꢀO
N(9)ꢀCu(2)ꢀO
82.1(3)
83.8(3)
82.3(2)
168.9(2)
83.5(4)
155.8(3)
95.1(3)
112.9(3)
106.6(2)
96.6(2)
Cu(1)ꢀOꢀCu(2)

68
M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
of the L1 ligand in 3 differs considerably from those
attained in 1 and 2: with reference to the angle formed
by the methylimidazole plane and the plane through the
macrocycle nitrogens, this is found to measure 89.4(2)°
in 3, whereas it is 50.8(1)° in 1 and it possesses the
55.5(2)° and 67.0(3)° values in the two parts of the
cation of 2.
Overall, the present results point to considerable
flexibility of the ligands, particularly of L1, which ap-
pears to comply easily with the geometrical preferences
of specific metal ions, in combination with a variety of
monodentate coligands. It is likely that even higher
versatility will be exhibited by properly designed new
ligands which may be synthesized according to the
procedures outlined here and in the previous report [1].
Fig. 5. A view of the [ZnL1Cl]+ cation in the structure of 3.
Table 6
1
,
Selected bond lengths (A) and angles (°) for [ZnL Cl]BPh4 (3)
4. Supplementary material
ZnꢀN(1)
ZnꢀN(2)
ZnꢀN(3)
2.346(3)
2.079(3)
2.080(3)
ZnꢀN(4)
ZnꢀCl
1.982(3)
2.324(1)
Crystallographic data (without structure factors) for
the structural analyses have been deposited with the
Cambridge Crystallographic Data Centre, as CCDC
No. 127626 (1), 127629 (2), 127630 (3), 127627 (4) and
127628 (5). Copies of this information may be obtained
free of charge from: The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ UK, fax. +44-1223-
336033.
N(1)ꢀZnꢀN(2)
N(1)ꢀZnꢀN(3)
N(1)ꢀZnꢀN(4)
N(1) ꢀZnꢀ Cl
N(2)ꢀZnꢀN(3)
80.00(11)
79.51(12)
77.24(11)
176.05(8)
85.4(2)
N(2)ꢀZnꢀN(4)
N(2)ꢀZnꢀCl
N(3)ꢀZnꢀN(4)
N(3)ꢀZnꢀCl
N(4)ꢀZnꢀCl
132.79(13)
100.56(10)
129.22(14)
104.42(10)
99.72(9)
angle, whereas the angle between the corresponding
planes in the Cu(2) environment measures 29.1(2)°. The
metal atoms deviate by different amounts (Cu(1),
Acknowledgements
,
,
0.048(1) A; Cu(2), 0.250(1) A), each in the direction of
the apical atom of its polyhedron, from the best plane
through the four donor atoms forming the base of the
respective square pyramid. The mean value of the metal
to donor atom distances formed by Cu(1) is slightly
We acknowledge financial support by the Italian
Ministero dell’Universita` e della Ricerca Scientifica e
Tecnologica.
,
longer, by 0.02 A, than that of the distances formed by
Cu(2), the difference being substantially due to the
longer apical bond formed by Cu(1) (Table 5).
References
[1] M. Di Vaira, F. Mani, P. Stoppioni, Inorg. Chim. Acta 273
(1998) 151.
In the structure of 3, formed by monomeric
[ZnL1Cl]+ cations and BPh4− anions, the zinc(II) atom
is five-coordinated by the four nitrogen atoms of the L1
ligand and by the chlorine atom, with approximately
trigonal bipyramidal geometry (Fig. 5, Table 6), which
represents yet another coordination type within this
series of compounds. The apical positions of the
bipyramid are occupied by the chlorine and by one of
the macrocycle nitrogens. This nitrogen, N(1), forms
[2] K. Wieghardt, U. Bossek, P. Chaudhuri, W. Herrman, B.C.
Menke, J. Weiss, Inorg. Chem. 21 (1982) 4308. B.A. Hammer-
shoi, A.M. Sargeson, Inorg. Chem. 22 (1983) 3554. B.A. Sayer,
J.P. Michael, R.D. Hancock, Inorg. Chim. Acta 77 (1983) L63.
K. Wieghardt, E. Scho¨ffmann, B. Nuber, J. Weiss, Inorg. Chem.
25 (1986) 4877. U. Auerbach, U. Eckert, K. Wieghardt, B.
Nuber, J. Weiss, Inorg. Chem. 29 (1990) 938. R. Ziessel, J.M.
Lehn, Helv. Chim. Acta 73 (1990) 1149. C.J. Broan, K.
Jankowski, R. Kataky, D. Parker, J. Chem. Soc., Dalton Trans.
(1990) 1738. I.A. Fallis, L.J. Farrugia, N.M. Macdonald, R.D.
Peacock, J. Chem. Soc., Dalton Trans. (1993) 2759.
,
the longest bond to the metal (2.346(3) A) among those
formed by nitrogen atoms in any of the present struc-
tures. The best line through the apical atoms and the
metal is almost perpendicular to the equatorial plane,
defined by N(2), N(3) and N(4), forming an angle of
2.0(1)° with its normal. The zinc(II) atom deviates by
[3] M. Di Vaira, B. Cosimelli, F. Mani, P. Stoppioni, J. Chem. Soc.,
Dalton Trans. (1991) 331. G. de Martino Norante, M. Di Vaira,
F. Mani, S. Mazzi, P. Stoppioni, J. Chem. Soc., Dalton Trans.
(1992) 361. M. Di Vaira, F. Mani, P. Stoppioni, J. Chem. Soc.,
Dalton Trans. (1994) 3739. M. Di Vaira, M. Guerra, F. Mani, P.
Stoppioni, J. Chem. Soc., Dalton Trans. (1996) 1173. M. Di
Vaira, F. Mani, P. Stoppioni, J. Chem. Soc., Dalton Trans.
(1997) 1375.
,
0.40(1) A from that plane, in the direction of the
chlorine atom. The arrangement of the dangling group

M. Di Vaira et al. / Inorganica Chimica Acta 303 (2000) 61–69
[7] R.G. Jones, J. Am. Chem. Soc. 71 (1949) 383.
69
[4] G.R. Weisman, D.J. Vachon, V.B. Johnson, D.A. Gronbeck, J.
Chem. Soc., Chem. Commun. (1987) 886. M. Studer, A. Riesen,
T.A. Kaden, Helv. Chim. Acta 72 (1989) 307. N.W. Alcock, F.
McLaren, P. Moore, G.M. Pike, S.M. Rae, J. Chem. Soc.,
Chem. Commun. (1989) 629. D.G. Fortier, A. McAuley, J.
Chem. Soc., Dalton Trans. (1991) 101. G.A. McLachlan, G.D.
Fallon, R.L. Martin, B. Moubaraki, K.S. Murray, L. Spiccia,
Inorg. Chem. 33 (1994) 4663. D. Schulz, T. Weyhermu¨ller, K.
Wieghardt, B. Nuber, Inorg. Chim. Acta 240 (1995) 217. D.
Ellis, L.J. Farrugia, D.T. Hickman, P.A. Lovatt, R.D. Peacock,
Chem. Commun. (1996) 1817. L.J. Farrugia, P.A. Lovatt, R.D.
Peacock, Inorg. Chim. Acta 246 (1996) 343.
[5] M. Di Vaira, F. Mani, N. Nardi, P. Stoppioni, A. Vacca, J.
Chem. Soc., Dalton Trans. (1996) 2679.
[6] T.J. Atkins, J.E. Richman, W.F. Oettle, Org. Synth. 58 (1978)
86. K. Wieghardt, W. Schmid, B. Nuber, J. Weiss, Chem. Ber.
112 (1978) 2220.
[8] N. Walker, D. Stuart, Acta Crystallogr., Sect. A 39 (1983) 158.
[9] G.M. Sheldrick, SADABS, Program for CCD data absorption
correction, University of Go¨ttingen.
[10] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, C. Giaco-
vazzo, A. Guagliardi, G. Polidori, SIR 92, J. Appl. Crystallogr.
27 (1994) 435.
[11] G.M. Sheldrick, SHELXL 93, Program for Crystal Structure
Refinement, University of Go¨ttingen, 1993.
[12] C.K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge Na-
tional Laboratory, Oak Ridge, TN, 1976.
[13] M. Nardelli, PARST, J. Appl. Crystallogr. 28 (1995) 659.
[14] H.D. Flack, Acta Crystallogr., Sect. A 39 (1983) 876.
[15] L.J. Zompa, T.N. Margulis, Inorg. Chim. Acta 45 (1980)
L263.
[16] M. Di Vaira, F. Mani, P. Stoppioni, J. Chem. Soc., Chem.
Commun. (1989) 126.
.