Nickel(II) and zinc(II) complexes of N-substituted di(2-picolyl)amine derivatives: Synthetic and structural studies

Article abstract of DOI:10.1016/j.poly.2010.12.005

The interaction of di(2-picolyl)amine (1) and its secondary N-substituted derivatives, N-(4-pyridylmethyl)-di(2-picolyl)amine (2), N-(4-carboxymethyl- benzyl)-di(2-picolyl)amine (3), N-(4-carboxybenzyl)-di(2-picolyl)amine (4), N-(1-naphthylmethyl)-di(2-picolyl)amine (5), N-(9-anthracenylmethyl)-di(2- picolyl)amine (6), 1,4-bis[di(2-picolyl)aminomethyl]benzene (7), 1,3-bis[di(2-picolyl)aminomethyl]benzene (8) and 2,4,6-tris[di(2-picolyl)amino] triazine (9) with Ni(II) and/or Zn(II) nitrate has resulted in the isolation of [Ni(1)(NO₃)₂], [Ni(2)(NO₃)₂], [Ni(3)(NO₃)₂], [Ni(4)(NO₃)₂] ·CH₃CN, [Ni(5)(NO₃)₂], [Ni(6)(NO ₃)₂], [Ni₂(7)(NO₃)₄], [Ni₂(8)(NO₃)₄], [Ni₃(9)(NO ₃)₆]·3H₂O, [Zn(3)(NO₃) ₂]·0.5CH₃OH, [Zn(5)(NO₃)₂], [Zn(6)(NO₃)₂], [Zn(8)(NO₃)₂] and [Zn₂(9)(NO₃)₄]·0.5H₂O. X-ray structures of [Ni(4)(NO₃)₂]·CH₃CN, [Ni(6)(NO₃)₂] and [Zn(5)(NO₃)₂] have been obtained. Both nickel complexes exhibit related distorted octahedral coordination geometries in which 4 and 6 are tridentate and bound meridionally via their respective N₃-donor sets, with the remaining coordination positions in each complex occupied by a monodentate and a bidentate nitrato ligand. For [Ni(4)(NO₃)₂]·CH₃CN, intramolecular hydrogen bond interactions are present between the carboxylic OH group on one complex and the oxygen of a monodentate nitrate on an adjacent complex such that the complexes are linked in chains which are in turn crosslinked by intermolecular offset π-π stacking between pyridyl rings in adjacent chains. In the case of [Ni(6)(NO₃)₂], two weak CH?O hydrogen bonds are present between the axial methylene hydrogen atoms on one complex and the oxygen of a monodentate nitrate ligand on a second unit such that four hydrogen bonds link pairs of complexes; in addition, an extensive series of π-π stacking interactions link individual complex units throughout the crystal lattice. The X-ray structure of [Zn(5)(NO ₃)₂] shows that the metal centre once again has a distorted six-coordinated geometry, with the N₃-donor set of N-(1-naphthylmethyl)-di(2-picolyl)amine (5) coordinating in a meridional fashion and the remaining coordination positions occupied by a monodentate and a bidentate nitrato ligand. The crystal lattice is stabilized by weak intermolecular interactions between oxygens on the bound nitrato ligands and aromatic CH hydrogens on adjacent complexes; intermolecular π-π stacking between aromatic rings is also present.

Full text of DOI:10.1016/j.poly.2010.12.005

Polyhedron 30 (2011) 708–714
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Nickel(II) and zinc(II) complexes of N-substituted di(2-picolyl)amine
derivatives: Synthetic and structural studies
Linda Götzke a, Kerstin Gloe a, Katrina A. Jolliffe b, Leonard F. Lindoy b, Axel Heine a, Thomas Doert a,
Anne Jäger a, Karsten Gloe a,
⇑
a Department of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany
b School of Chemistry, University of Sydney, NSW 2006, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
The interaction of di(2-picolyl)amine (1) and its secondary N-substituted derivatives, N-(4-pyridylmethyl)-
di(2-picolyl)amine (2), N-(4-carboxymethyl-benzyl)-di(2-picolyl)amine (3), N-(4-carboxybenzyl)-di(2-
picolyl)amine (4), N-(1-naphthylmethyl)-di(2-picolyl)amine (5), N-(9-anthracenylmethyl)-di(2-picol-
yl)amine (6), 1,4-bis[di(2-picolyl)aminomethyl]benzene (7), 1,3-bis[di(2-picolyl)aminomethyl]benzene
(8) and 2,4,6-tris[di(2-picolyl)amino]triazine (9) with Ni(II) and/or Zn(II) nitrate has resulted in the isola-
tion of [Ni(1)(NO3)2], [Ni(2)(NO3)2], [Ni(3)(NO3)2], [Ni(4)(NO3)2]ÁCH3CN, [Ni(5)(NO3)2], [Ni(6)(NO3)2],
[Ni2(7)(NO3)4], [Ni2(8)(NO3)4], [Ni3(9)(NO3)6]Á3H2O, [Zn(3)(NO3)2]Á0.5CH3OH, [Zn(5)(NO3)2], [Zn(6)
(NO3)2], [Zn(8)(NO3)2] and [Zn2(9)(NO3)4]Á0.5H2O. X-ray structures of [Ni(4)(NO3)2]ÁCH3CN, [Ni(6)(NO3)2]
and [Zn(5)(NO3)2] have been obtained. Both nickel complexes exhibit related distorted octahedral coordi-
nation geometries in which 4 and 6 are tridentate and bound meridionally via their respective N3-donor
sets, with theremaining coordination positions ineach complex occupiedby amonodentate and abidentate
nitrato ligand. For [Ni(4)(NO3)2]ÁCH3CN, intramolecular hydrogen bond interactions are present between
the carboxylic OH group on one complex and the oxygen of a monodentate nitrate on an adjacent complex
Received 16 November 2010
Accepted 2 December 2010
Available online 16 December 2010
Keywords:
Nickel(II)
Zinc(II)
Polypyridyl
X-ray structure
Di(2-picolyl)amine
such that the complexes are linked in chains which are in turn crosslinked by intermolecular offset p–p
stacking between pyridyl rings in adjacent chains. In the case of [Ni(6)(NO3)2], two weak CHÁ Á ÁO hydrogen
bonds are present between the axial methylene hydrogen atoms on one complex and the oxygen of a mono-
dentate nitrate ligand on a second unit such that four hydrogen bonds link pairs of complexes; in addition,
an extensive series of p–pstacking interactions link individual complex units throughout the crystal lattice.
The X-ray structure of [Zn(5)(NO3)2] shows that the metal centre once again has a distorted six-coordinated
geometry, with the N3-donor set of N-(1-naphthylmethyl)-di(2-picolyl)amine (5) coordinating in a merid-
ional fashion and the remaining coordination positions occupied by a monodentate and a bidentate nitrato
ligand. The crystal lattice is stabilized by weak intermolecular interactions between oxygens on the bound
nitrato ligands and aromatic CH hydrogens on adjacent complexes; intermolecular
aromatic rings is also present.
p–p stacking between
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
[8–18] have appeared, although the N-substituted derivatives have
received less attention than those of dipic itself. Even so, individual
N-substituted ligand complexes of both metals have been employed
in a number of applied investigations – including for carbon dioxide
fixation [19] as well as for a range of studies focused on biological
and/or sensor applications [10,20–31,17,32–40].
In a recent paper we presented the results of an investigation of
the interaction of Cu(II) with both di(2-picolyl)amine (dipic, 1) and
a range of its N-substituted derivatives (including 2, 3 and 6–9
shown in Scheme 1) [41]. In parallel studies, we have also investi-
gated aspects of the metal ion chemistry of a number of related
N-substituted derivatives of 2,2-dipyridylamine with Cu(II) [42],
Pd(II) [42] and Ag(I) [43,44]. We now report the results of an exten-
sion of these studies that involve the interaction of the N-substituted
The interaction of transition and post-transition metal ions with
di- and polypyridyl ligands continues to receive much attention, in
part reflecting the coordination versatility of such ligands and their
importance in a number of biological, catalytic, photoactive and sen-
sor applications [1,2]. For example, the ‘classical’ di(2-picolyl)amine
ligand (dipic, 1), as well as its secondary nitrogen substituted deriv-
atives, yield strong complexes with a wide range of metal ions. In
particular, reports of the interaction of the parent dipic moiety and
its (uncharged) N-substituted derivatives with Ni(II) [3–7] and Zn(II)
⇑
Corresponding author. Tel.: +49 351 463 34357; fax: +49 351 463 31478.
E-mail address: karsten.gloe@chemie.tu-dresden.de (K. Gloe).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.12.005

L. Götzke et al. / Polyhedron 30 (2011) 708–714
709
N
N
N
N
N
N
N
N
H
N
N
N
N
4
1
2
3
COOH
N
COOMe
N
N
N
N
N
N
N
N
N
N
N
N
N
5
7
6
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
8
9
Scheme 1.
di(2-picolyl)amine derivatives 2–9 with Ni(II) and 2, 3, 5, 6, 8 and 9
with Zn(II).
N
17
16
N
13
12
N
11
15
14
2. Experimental
6
10
1
2
9
2.1. Physical methods
5
4
8
NMR spectra were determined on a DRX-500 Bruker or Varian
300 MHz spectrometer. Column chromatography was performed
on silica gel 60 (0.040–0.063 mm Merck) or neutral Al2O3 (FH
300 mm, HNS 29 Por.0). ESI-MS were determined on a Micromass
LCT-TOF mass spectrometer.
3
7
Scheme 2.
t, 16-H); 7.39 (1H, t, 8-H); 7.45 (4H, m, 1/2/14-H); 7.60 (3H, m,
9/15-H); 7.72 (1H, d, 7-H); 7.80 (1H, d, 3-H); 8.12 (1H, d, 6-H);
8.52 (2H, d, 17-H). 13C NMR (CDCl3, 300 K): d (ppm) 57.06 (11-
C); 60.46 (12-C); 121.97 (16-C); 123.19 (14-C); 124.50 (6-C);
125.20 (8-C); 125.48 (1-C); 125.52 (2-C); 127.36 (9-C); 127.86
(7-C); 128.38 (3-C); 132.28 (10-C); 133.76 (5-C); 134.53 (4-C);
136.37 (15-C); 148.77 (17-C); 159.50 (13-C).
2.2. Ligand synthesis
Di(2-picolyl)amine (1) was obtained commercially. The synthe-
ses of 2 [41], 3 [36,45], 4 [46], 6 [33], 7 [47], 8 [47] and 9 [48] have
been reported previously. A preparation for 5 has also been re-
ported [49] but the modified procedure given below was employed
in the present study.
2.3. Synthesis of Ni(II) and Zn(II) complexes
The metal complexes were washed with ether and dried under
vacuum before microanalysis. Crystals for X-ray analysis were
removed from the reaction solution and used directly for the
X-ray study. The synthesis and characterisation of [Ni(1)(NO3)2],
[Ni(2)(NO3)2], [Ni(3)(NO3)2], [Ni(5)(NO3)2], [Ni2(7)(NO3)4], [Ni2(8)
(NO3)4], and [Ni3(9)(NO3)6]Á3H2O, [Zn(3)(NO3)2]Á0.5CH3OH, [Zn(6)
(NO3)2], [Zn(8)(NO3)2] and [Zn2(9)(NO3)4]Á0.5H2O, all of which
were not employed for X-ray diffraction studies, are presented in
the Supplementary data.
2.2.1. N-(1-naphthylmethyl)-di(2-picolyl)amine (5, Scheme 2)
1-(Chloromethyl)naphthalene (0.883 g, 5.00 mmol) in acetone
(20 mL) was added dropwise to di(2-picolyl)amine (1.003 g,
5.03 mmol) and a suspension of K2CO3 (0.967 g, 7.00 mmol). After
25 h of heating under reflux, the solvent was removed on a rotary
evaporator. The residue was washed well with water and then
extracted several times with chloroform. The combined chloroform
phases were washed three times with water then dried over
MgSO4 and the solvent was removed on a rotary evaporator. The
orange oil that remained was purified by chromatography on an
alumina column [eluent: ethylacetate/heptane (1:1), Rf = 0.43].
The purified product was obtained as a yellow oil. Yield: 1.37 g
(80%). ESI-MS m/z = 340.1 [M+H]+. 1H NMR (500 MHz, CDCl3,
300 K): d (ppm) 3.87 (4H, s, 12-H); 4.14 (2H, s, 11-H); 7.12 (2H,
2.3.1. [Ni(4)(NO3)2]ÁCH3CN
Nickel nitrate hexahydrate (0.022 g, 0.076 mmol) in warm
acetonitrile (2 mL) was added to 4 (0.025 g, 0.075 mmol) in warm
acetonitrile (2 mL). The solution was let stand at 4 °C under an

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L. Götzke et al. / Polyhedron 30 (2011) 708–714
Table 1
Crystal data and structure refinement for [Ni(4)(NO3)2]ÁCH3CN, [Ni(6)(NO3)2] and [Zn(5)(NO3)2].
[Ni(4)(NO3)2]ÁCH3CN
[Ni(6)(NO3)2]
[Zn(5)(NO3)2]
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
22H22N6NiO8
C27H23N5NiO6
572.21
198(2)
C23H21N5O6Zn
528.84
120
557.17
198(2)
0.71073
monoclinic
P21
0.71073
triclinic
0.71073
triclinic
ꢀ
ꢀ
P1
P1 (No. 2)
8.583(2)
9.402(1)
8.3038(3)
b (Å)
13.871(3)
10.133(1)
8.6756(3)
c (Å)
10.635(2)
90
14.225(2)
103.62(1)
16.6453(7)
78.638(1)
a
(°)
b (°)
110.33(3)
103.33(1)
83.272(2)
c
(°)
90
1187.3(4)
2
107.96(1)
1183.6(2)
2
70.568(1)
1106.94(7)
2
Volume (Å3)
Z
Dcalc (mg/m3)
1.559
1.606
1.587
Absorption coefficient (mmÀ1
Crystal size (mm3)
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
)
0.878
0.877
1.162
0.51 Â 0.27 Â 0.09
0.30 Â 0.13 Â 0.13
0.32 Â 0.15 Â 0.12
33922
55652
20511
6714 [Rint = 0.1046]
4481/1/336
1.043
6886 [Rint = 0.0594]
5238/7/353
1.017
6912 [Rint = 0.029]
5528/0/316
1.020
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0514, wR2 = 0.0766
R1 = 0.1035, wR2 = 0.0886
0.539 and À0.387
R1 = 0.0487, wR2 = 0.1157
R1 = 0.0731, wR2 = 0.1267
1.352 and À1.099
R1 = 0.0377, wR2 = 0.0884
R1 = 0.0531, wR2 = 0.0957
1.00 and À0.52
Largest differences in peak and hole (e ÅÀ3
)
Fig. 3. Offset
p–p stacking in the crystal lattice of [Ni(4)(NO3)2]ÁCH3CN; Cg–Cg
3.752(2) Å, aromatic planes are not parallel (a = 5.5(2)°), b = 17.1°/22.5° [58],
symmetry operation: 1 + x, y, z.
2.3.2. [Ni(6)(NO3)2]
Fig. 1. ORTEP representation of [Ni(4)(NO3)2]ÁCH3CN (50% thermal ellipsoids).
Selected bond lengths [Å] and angles [°]: Ni–N1 2.086(3), Ni–N4 2.023(2), Ni–N11
2.030(2), Ni–O1 2.157(2), Ni–O2 2.120(3), Ni–O4 2.070(2); N1–Ni–N4 82.7(1), Ni–
Ni–N11 82.7(1), N1–Ni–O1 92.2(1), N1–Ni–O4 96.32(9), N4–Ni–O1 87.4(1), N4–Ni–
O2 94.0(1), N4–Ni–O4 91.5(1), N4–Ni–O1 91.5(1), N4–Ni–O2 98.1(1), N11–Ni–O4
91.7(1), O1–Ni–O2 59.6(1), O2–Ni–O4 111.8(1).
Nickel nitrate hexahydrate (0.037 g, 0.128 mmol) in warm ace-
tonitrile (3 mL) was added to 6 (0.050 g, 0.128 mmol) in warm ace-
tonitrile (3 mL). Diethyl ether (2 mL) was added and the solution
was let stand at 4 °C under an atmosphere of diethyl ether to yield
grey-blue crystals. A crystal from this batch was used directly for
the X-ray structure analysis. Anal. Calc. for C27H23N5NiO6: C,
56.67; H, 4.05; N, 12.24. Found: C, 56.41; H, 4.12; N, 12.57%. ESI-
MS m/z = 446.1 [6+NiÀH]+; 1080.1 [2(6)+2Ni+3NO3]+. UV–Vis
atmosphere of diethyl ether to yield dark blue crystals. A crystal
from this batch was used directly for the X-ray structure analysis.
Anal. Calc. for C22H22N6NiO8: C, 47.43; H, 3.98; N, 15.08. Found: C,
(CH3CN): kmax in nm (e
in L molÀ1 cmÀ1) = 572 (19.9), 943 (14.7)
47.60; H, 3.89; N, 15.14%. ESI-MS m/z = 255.0 [4+2Ni+NO3ÀH]2+
;
(the spectrum is in accord with a pseudo octahedral ligand field;
it also contained the ‘tail’ of an intense charge transfer absorption
390.1 [4+NiÀH]+.
Fig. 2. Hydrogen bonding interactions present in the crystal lattice of [Ni(4)(NO3)2]ÁCH3CN; OH24Á Á ÁO6 1.94 Å (O24–H24Á Á ÁO6 150°), symmetry operation: x, À1 + y, z;
CH2AÁ Á ÁN101 2.59 Å (C2–H2AÁ Á ÁN101 151°); CH9BÁ Á ÁN101 2.62 Å (C9H9BÁ Á ÁN101 153°), symmetry operation: 2 À x, À0.5 + y, 1 À z.

L. Götzke et al. / Polyhedron 30 (2011) 708–714
711
Fig. 4. ORTEP representation of the X-ray structure of [Ni(6)(NO3)2] showing
selected atom labels (50% thermal ellipsoids); disorder in the monodentate nitrate
ligand not shown. Selected bond lengths [Å] and angles [°]: Ni–N1 2.099(3), Ni–N4
2.046(2), Ni–N11 2.032(2), Ni–O1 2.139(2), Ni–O3 2.114(3), Ni–O4A 2.032(7); N1–
Ni–N4 81.69(8), N1–Ni–N11 82.26(8), N1–Ni–O1 102.03(7), N1–Ni–O3 162.71(8),
N1–Ni–O4A 95.3(2), N4–Ni–N11 163.93(8), N4–Ni–O1 92.39(8), N4–Ni–O3
97.10(8), N4–Ni–O4A 82.4(2), N11–Ni–O191.77(8), N11–Ni–O3 98.48(8), N11–Ni–
O4A 98.2(2), O1–Ni–O3 60.71(7), O1–Ni–O4A 161.0(2).
Fig. 7. ORTEP representation of the structure of [Zn(5)(NO3)2] showing selected
atom labels (50% thermal ellipsoids). Selected bond lengths [Å] and angles [°]: Zn1–
N1 2.059(1), Zn1–N2 2.281(1), Zn1–N3 2.053(2), Zn1–O3 2.079(1), Zn1–O5
2.114(1), Zn1–O4 2.471(2), Zn1–O1 2.728(2); N(1)–Zn1–N(2) 78.01(6), N(1)–Zn1–
N(3) 155.95(6), N(1)–Zn1–O(3) 101.01(6), N(1)–Zn1–O(4) 84.47(5), N(1)–Zn1–O(5)
94.82(6), N(2)–Zn1–N(3) 78.28(6), N(2)–Zn1–O(3) 138.39(6), N(2)–Zn1–O(4)
85.91(5), N(2)–Zn1–O(5) 141.19(5), N(3)–Zn1–O(3) 99.34(6), N(3)–Zn1–O(4)
89.89(5), N(3)–Zn1–O(5) 101.13(6), O(3)–Zn1–O(5) 80.36(5), O(4)–Zn1–O(5)
55.32(5).
2.3.3. [Zn(5)(NO3)2]
Zinc nitrate hexahydrate (0.033 g, 0.112 mmol) in methanol
(1 mL) was added to 5 (0.038 g, 0.112 mmol) in methanol (2 mL)
and the solution was let stand for several days under an atmo-
sphere of ether to yield the product as a white precipitate. Anal.
Calc. for C23H21N5O6Zn: C, 52.24; H, 4.00; N, 13.24. Found: C,
51.99; H, 4.02; N, 13.26%. ESI-MS m/z = 340.2 [5+H]+; 402.2
[5+ZnÀH]+; 465.1 [5+Zn+NO3]+. 1H NMR (500 MHz, DMSO-d6,
300 K): d [ppm] = 3.73 (2H, d, 12a-H); 4.26 (4H, m, 11/12b-H);
7.52 (2H, d, 14-H); 7.59 (2H, m, 2/8-H); 7.68 (5H, m, 1/7/9/16-
H); 8.06 (2H, m, 3/6-H); 8.14 (2H, t, 15-H); 8.72 (2H, d, 17-H).
Fig. 5. Hydrogen bonding between pairs of complex units in [Ni(6)(NO3)2];
CH9AÁ Á ÁO5A 2.53 Å (C9–H9A–O5A 137°); CH2BÁ Á ÁO5A 2.54 Å (C2–H2B–O5A
133°); symmetry operation: 2 À x, Ày, Àz.
2.4. Crystallography
X-ray structures of [Ni(4)(NO3)2]ÁCH3CN and [Ni(6)(NO3)2] were
band that extended into the visible region and obscured the high-
est energy d–d transition expected for this geometry).
determined on a Bruker Nonius Kappa CCD with
x and u scans at
198(2) K. Data collections were undertaken with COLLECT [50], cell
Fig. 6. Intermolecular
p–p
stacking present in the crystal lattice of [Ni(6)(NO3)2]; Cg(1)–Cg(2) 3.795(2) Å, aromatic planes are not parallel (
a = 12.2(1)°), b = 27.6°/15.5°,
symmetry operation: 3 À x, 1 À y, 1 À z; Cg(1)–Cg(3) 3.905(2) Å, aromatic planes are not parallel (
a
= 14.6(1)°), b = 21.1°/24.2°; symmetry operation: x, À1 + y, z [58].

712
L. Götzke et al. / Polyhedron 30 (2011) 708–714
Fig. 8. Three views of the lattice structure of [Zn(5)(NO3)2] showing the intermolecular CHÁ Á ÁO interactions as dotted lines; CH3Á Á ÁO1 2.44 Å (C3–H3Á Á ÁO1 132°), symmetry
operation: x, 1 + y, z; CH16Á Á ÁO1 2.57 Å (C16–H16Á Á ÁO1 148°), symmetry operation: À1 + x, y, z; CH6AÁ Á ÁO6 2.70 Å (C6–H6AÁ Á ÁO6 145°), symmetry operation: Àx, 1 À y, 2 À z;
CH7BÁ Á ÁO6 2.62 Å (C7–H7BÁ Á ÁO6 144°), symmetry operation: Àx, 1 À y, 2 À z; CH9Á Á ÁO3 2.48 Å (C9–H9Á Á ÁO3 164°), symmetry operation: À1 + x, y, z; CH10Á Á ÁO4 2.57 Å (C10–
H10Á Á ÁO4 155°), symmetry operation: Àx, Ày, 2 À z; CH12Á Á ÁO5 2.47 Å (C12–H12Á Á ÁO5 124°), symmetry operation: 1 À x, Ày, 2 À z.
Both diffractometers employed graphite-monochromated Mo
Ka radiation generated from a sealed tube (0.71073 Å). Multi-scan
empirical absorption corrections were applied to all data sets using
the program SADABS [56]. All structures were refined and extended
with SHELXL-97 [57].
3. Results and discussion
3.1. Complex synthesis
During attempts to obtain crystalline products suitable for
X-ray analysis, interaction of 1–9 with nickel nitrate hexahydrate
in acetonitrile and/or zinc nitrate hexahydrate in methanol, aceto-
nitrile or methanol/ethyl acetate led to isolation of the range of 1:1
(metal nitrate:N-substituted di(2-picolyl)amine derivative) com-
plexes listed above (also see Supplementary data). The 1H NMR
spectra of the Zn(II) complexes in DMSO-d6 confirmed complexa-
tion of the respective substituted di(2-picolyl)amine ligands in
each case with, as expected, the majority of the ligand proton sig-
nals occurring at lower field for the complexes relative to those for
the corresponding free ligand (see Supplementary data). Mass
spectral and microanalysis data for all complexes were in accord
with their respective formulations. In our hands only [Ni(4)
(NO3)2]ÁCH3CN, [Ni(6)(NO3)2] and [Zn(5)(NO3)2] yielded suitable
crystals for X-ray structure determinations and only these are
now discussed (Table 1). Further details for the remaining com-
plexes are presented in the Supplementary data.
Fig. 9. The three
[Zn(5)(NO3)2]:
Cg(2) 3.747(1) Å, aromatic planes are not parallel
symmetry operation: x, 1 + y, z); intermolecular stacking between adjacent pyridyl
rings (Cg(2)–Cg(2) 3.711(1) Å, aromatic planes parallel, b = 24.2°, symmetry oper-
p
–
p
interaction types present in the crystal lattice of
stacking interactions along the crystallographic b-axis (Cg(1)–
= 3.9(1)°), b = 22.1°/25.6°,
p–p
(
a
ation: Àx, Ày, 2 À z) and two intermolecular
naphthalene rings to form a dimer (Cg(3)–Cg(4) 3.812(2) Å, aromatic planes not
parallel (
= 4.2(1)°), b = 22.92°/26.55°, symmetry operation: Àx, 1 À y, 1 À z) [58].
p–p stacking interactions between
a
3.2. Discussion of the X-ray structures
refinement with Dirax/lsq [51] and data reduction with EvalCCD
[52]. The X-ray-data for structure [Zn(5)(NO3)2] were collected
on a Bruker-AXS Kappa Apex II CCD diffractometer at 120 K.
Programs used: APEXII [53], SAINT [54], and DIAMOND3.1 [55].
The structure of the dark blue crystalline complex, [Ni(4)
(NO3)2]ÁCH3CN, formed from reaction of N-(4-carboxybenzyl)-
di(2-picolyl)amine (4) with nickel nitrate in acetonitrile, shows

L. Götzke et al. / Polyhedron 30 (2011) 708–714
713
that the Ni(II) centre exhibits a distorted octahedral coordination
geometry with 4 acting as a tridentate ligand, bound meridionally
(mer) via its N3-donor set (Fig. 1). The remaining three coordina-
tion sites are occupied by a monodentate and a bidentate nitrato
ligand. The acetonitrile molecule is not bound to the nickel but
occupies a void in the lattice structure; there is a bifurcated hydro-
gen bond to N101 of the acetonitrile from the methylene protons
CH2a and CH9b (Fig. 2). In part, the large distortion from Oh sym-
metry present in this complex is a consequence of the small bite
angle associated with the four-membered chelate ring formed on
coordination of the bidentate nitrato ligand. It is interesting to
compare this structure with those recently reported for two nickel
nitrate complexes of the related di(2-picolyl)amine derivative
incorporating a t-butyl N-substituent. This latter ligand forms 1:1
metal:ligand complexes which crystallize with both facial and
meridional conformations in the same unit cell [3]. In the case of
the mer derivative the coordination geometry is quite similar to
that observed in [Ni(4)(NO3)2]ÁCH3CN.
(NO3)2]ÁCH3CN, [Ni(6)(NO3)2] and [Zn(5)(NO3)2] have been deter-
mined. While related coordination sphere geometries were found
for all three complexes, quite different interesting lattice structures
in the form of extended framework arrangements involving both
multiple hydrogen bond and
each case.
p–p stacking interactions occur in
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft, the Australian
Research Council and the International Program Development
Fund of The University of Sydney for support. L.G. gratefully
acknowledges the TU Dresden for a grant. We thank Dr. J.K. Clegg,
University of Sydney, for assistance.
Appendix A. Supplementary data
CCDC 798320, 798321 and 798322 contains the supplementary
crystallographic data for ([Ni(6)(NO3)2]), ([Ni(4)(NO3)2]ÁCH3CN)
and ([Zn(5)(NO3)2]). These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2010.12.005.
The non-coordinated carboxylic –OH of 4 in each complex unit
is intermolecularly hydrogen bonded to an O-atom of a monoden-
tate nitrate ligand in an adjacent complex unit such that individual
complexes are linked in chains that are directed along the crystal-
lographic b-axis (Fig. 2). Adjacent pairs of pyridine rings are also in-
volved in intermolecular offset
p–p stacking to produce a further
chain-like arrangement that is orientated along the crystallo-
graphic a-axis (Fig. 3).
The X-ray structure of the dark blue crystalline complex,
[Ni(6)(NO3)2], obtained by reaction of N-(9-anthracenylmethyl)-
di(2-picolyl)amine (6) with nickel nitrate in acetonitrile, shows
that the Ni(II) centre once again exhibits a distorted octahedral
coordination geometry, with 6 being bound meridionally via its
N3-donor set (Fig. 4). The remaining three coordination sites are
filled by a (disordered) monodentate and a bidentate nitrato
ligand, with the coordination sphere in [Ni(6)(NO3)2] being thus
quite similar to that in [Ni(4)(NO3)2]ÁCH3CN.
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