First row transition metal complexes of a hexadentate pyrazole-based bispidine ligand

Article abstract of DOI:10.1016/j.poly.2012.06.035

The efficient synthesis of a new hexadentate pyrazole-based bispidine-ligand and its first-row transition metal complexes (Fe^II, Co^II, Ni^II, Cu^II and Zn^II) is reported. There are interesting structural differences between the present and earlier hexadentate bispidine ligands (tetragonally versus trigonally distorted octahedral geometries). The structural analysis of the metal-free ligand and the five complexes shows that the structure enforced by the rigid pyrazole-based bispidine is best described as distorted trigonal prismatic, and this also emerges from the spectroscopic analysis.

Full text of DOI:10.1016/j.poly.2012.06.035

Polyhedron 52 (2013) 1239–1245
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First row transition metal complexes of a hexadentate pyrazole-based
bispidine ligand
⇑
Peter Comba , Michael Morgen, Hubert Wadepohl
Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, Heidelberg, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 27 June 2012
The efficient synthesis of a new hexadentate pyrazole-based bispidine-ligand and its first-row transition
metal complexes (FeII, CoII, NiII, CuII and ZnII) is reported. There are interesting structural differences
between the present and earlier hexadentate bispidine ligands (tetragonally versus trigonally distorted
octahedral geometries). The structural analysis of the metal-free ligand and the five complexes shows
that the structure enforced by the rigid pyrazole-based bispidine is best described as distorted trigonal
prismatic, and this also emerges from the spectroscopic analysis.
Keywords:
Bispidine
Trigonal prismatic
Crystallography
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
electronic forces are less important (see above) [1,2,21–25].2 The tri-
gonal twist of hexacoordinate complexes has had impact in various
Since Alfred Werner’s discovery of coordination chemistry,
octahedral structures are in the focus of transition metal coordina-
tion compounds. Smaller and larger coordination numbers and
other geometries for six-coordinate complexes (trigonal prismatic
versus trigonal antiprismatic) are known but less common – and
often ignored [1]. Square planar, square pyramidal and square
bipyramidal (octahedral) geometries satisfy the preferences ex-
erted by the d-orbital set of the metal center but, for classical coor-
dination compounds (i.e., relatively high oxidation states) ligand
dictation is more important in terms of coordination geometries
than the metal-ion-dependent electronic preferences [2–5].1 That
is, with a well chosen ligand system, ‘‘exotic’’ geometries may be en-
forced, and these may lead to specific and interesting stabilities,
selectivities, reactivities and electronic properties [6]. Trigonal pris-
matic structures in solids have been described as early as 1923 [7],
and for molecular compounds, trigonal prismatic structures have
been predicted shortly afterwards [8] and discovered and discussed
from the 1960s onwards [9,10]. Interestingly, the various models for
their description and rationalization include pure geometric ap-
proaches, steric considerations, ligand-field-based models and
molecular orbital descriptions [11–18]. Of interest is that with par-
ticular sets of first row transition metal hexamines, a ligand-field
based analysis [19] and a molecular mechanics approach without
any specific electronic effects included [20] lead to basically identical
results, and this stresses the assertion that coordination geometries
are largely enforced by the ligands, i.e., the metal-ion-based
areas [11–18], and the probably most obvious feature is related to an
isomerization pathway of chiral octahedral complexes, i.e., the Bailar
twist [26].
Bispidines (3,7-diazabicyclo[3.3.1]nonane; see Scheme 1) are
derived from the natural product sparteine and were first synthe-
sized by Mannich [27]; first transition metal complexes have been
reported in the 1950s [28,29]. As adamantane derivatives, these
ligands are extremely rigid [30–32] and the specifically distorted
cis-octahedral structures enforced have been shown to lead to a
widely variable and unique coordination chemistry [33]. The bispi-
dines are easily built-up by two consecutive double-Mannich reac-
tions and therefore are highly flexible in terms of their design. By
variation of the aldehyde- and/or amine-components a multitude
of aromatic and aliphatic moieties with donor atoms ranging from
nitrogen to oxygen and sulfur can be incorporated in the adaman-
tane-like backbone [34]. In the original bispidine ligands (L1 in
Scheme 1) the C2/C4 positions generally are substituted with aro-
matic nitrogen donors, and further donor groups, generally also
pyridine moieties, are introduced at N3/N7 for the pentadentate
and hexadentate ligands. This leads to square-pyramidal or
cis-octahedral coordination geometries of their transition metal
complexes (N3, pyC2, pyC4 and pyN7 in equatorial position; pyN3
and N7 in axial position). A second generation of bispidine ligands
(e.g., L2 in Scheme 1) [35] may have exclusively aliphatic nitrogen
donors which are introduced in the backbone by variation of the
amine component at N3/N7. These ligands enforce trigonal
2
⇑
Corresponding author.
E-mail address: peter.comba@aci.uni-heidelberg.de (P. Comba).
Note that this is different for typical organometallic compounds with lower
Note that there are electronically doped molecular mechanics approaches [20,21],
and these lead to slightly more accurate structural predictions of the complex
geometries. Note also that metal-ion based electronic effects clearly are of importance
for thermodynamic effects, reactivities and spectroscopy [1,2,22,23].
1
oxidation numbers, see Refs. [3–5].
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.06.035

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P. Comba et al. / Polyhedron 52 (2013) 1239–1245
O
9
1
O
O
Ph
MeOOC
COOMe
5
Ph
Ph
Ph
2
6
4
8
3N
N
N7
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
L3
L1
L2
Scheme 1. Examples of a hexadentate first generation bispidine (left) which results in a tetragonally elongated octahedral coordination geometry, a hexadentate second
generation bispidine which enforces a distorted trigonal prismatic geometry to transition metal ions (middle) and the new pyrazole-based bispidine ligand L3 (right).
geometries (distorted trigonal prismatic for the hexadentate ligand
L2 and distorted trigonal bipyramidal for the corresponding tetra-
and pentadentate ligands).
required chair–chair conformation. Complexes of divalent first-
row transition metal ions were obtained by stirring equimolar mix-
tures of L3 and the corresponding metal salts (as perchlorates or
tetrafluoroborates) in acetonitrile over night. Pure samples and
crystals for X-ray crystallography were isolated by ether diffusion
(Fig. 2).
Bispidines of the first generation find broad applications, and
this is due to their rigid structure and the coordination geometry
enforced to the metal ion. In particular, for CuII this leads to high
complex stabilities (e.g., with L1, log KCu(II) = 16.28; L2, log KCu(II)
=
19.48) [35–37]. Together with relatively fast complexation
processes (open-chain ligands) and the fact that there are func-
tional groups which may be coupled to biomolecules (ester groups
at C1/C5, carbonyl group at C9), these ligands have found
application as bifunctional chelators for PET-imaging (positron
emission tomography) [34]. In molecular catalysis, transition metal
complexes of bispidines of the first generation are used, for exam-
ple, in the CuII-catalyzed aziridination [38], and FeII-catalyzed
sulfoxidation [39], olefin-oxidation [40], CH-hydroxylation [41]
and halogenation reactions [42]. A common possibility to tune
catalytic activity is by tuning the coordination geometry. However,
due to the arrangement of the aromatic donors at C2/C4 distortion
of the (pseudo)octahedral coordination geometry is limited. The
development of rigid, well preorganized bispidines with different
coordination geometries, e.g., trigonal instead of tetragonal, still
is a demanding and valuable task.
2.2. Coordination chemistry
There are significant differences in the transition metal coordi-
nation chemistry between the 1st and 2nd generation bispidine
ligands, in particular also with CuII. With the tetradentate ligands,
the 1st generation bispidines form very stable end-on-peroxo-
dicopper(II) complexes [30,44,45] and lead to interesting catecho-
lase model compounds [46–48], while the 2nd generation
bispidine-copper(I) complexes with dioxygen lead to the reversible
formation of mononuclear superoxo complexes [49]. Also, there is
a striking difference in the copper-catalyzed aziridination in terms
of efficiency and reaction pathway, and this has been shown to be
related to
a large extent to differences in redox potentials
[35,38,50,51]. Due to a ligand-enforced tetragonal distortion of
the complexes with both types of bispidine ligands the CuII com-
plexes are particularly stable and, together with the fast complex
formation (non-cyclic ligands) and an efficient shielding of the me-
tal centers by the hexadentate derivatives, these are potent ligands
for radiopharmaceutical applications [35–37,52]. The significantly
different stability constants between [CuL1]2+ and [CuL2]2+ (about
three orders of magnitude) are also related to the corresponding
redox potentials [35,37,53], and this must be due to the different
coordination geometry, combined with differences in donor sets.
We anticipated that the L2- and L3-based complexes might have
very similar coordination geometries, and the differences in donor
sets should then be the major factor to influence the complex sta-
bilities as well as the redox potentials and ligand field transitions.
The relative basicities (pKa-values (conjugate acids): tertiary
amines, ꢀ10; pyridine, 5.2 (2-methylpyridine: 6.0); 1H-imidazole,
7.0; 1-methylimidazole, 7.0; 1H-pyrazole 2.5) [54] and the ligand-
field parameters (e , e [cmꢁ1]; tertiary amine, 7100, 0; pyridine,
We therefore present here a new ligand which is structurally re-
lated to L2 but has aromatic N-donors similar to L1, i.e., the pyra-
zole-based bispidine ligand L3 with a bis-amine-tetrakis-pyrazole
donor set, and discuss the corresponding structural and solution
properties of first-row transition metal complexes with a special
emphasis on the CuII systems.
2. Results and discussion
2.1. Ligand synthesis
The amine component 5 of the ligand was synthesized in a
three-step procedure as reported before [43], starting from the
aminoacetaldehyde dimethylacetal 1, which is protected using
1,8-naphthalic acid anhydride 2, followed by substitution of the
methoxy groups with pyrazole, affording the protected dipyrazole-
amine 4. Finally, hydrazinolytic deprotection of 4 results in the free
amine 5. The ligand L3 was obtained in the usual way by a double
Mannich reaction of 1,3-diphenyl-2-propanone, paraformalde-
hyde, the amine 5 and acetic acid as reagent, in refluxing ethanol
(Scheme 2).
r
p
6200, 930; pyrazole, 5200, 700) [55–57])3 lead to the expectation
that the stabilities of the L2- and L3-based complexes must be very
similar, and the coordination geometry therefore plays a major role.
The coordination geometry and d-orbital splitting of L3-based
complexes are described in Scheme 3; each trigonal plane consists
of one of the tertiary amines from the bispidine backbone (N3 or
A crystal structure of the ligand L3 reveals that the most stable
form is the boat–chair conformer, as expected due to the size of the
amine substituents and the electron pair repulsion, emerging from
the nitrogen atoms N3 and N7 in the hypothetical chair–chair con-
formation of the bispidine backbone (Fig. 1) [33]. However, in the
presence of a metal ion, the bispidine backbone easily adopts the
3
Note that these are estimates based on a normalization to a reference Cu–N
distance of 2.03 Å [56].
4
Angle between a donor atom of one trigonal plane, the metal centre and the
projection of the closest donor atom of the opposite trigonal plane; the twist angle
of an ideal trigonal prism is 0° that of an ideal octahedron is 60 °C.
U

P. Comba et al. / Polyhedron 52 (2013) 1239–1245
1241
Scheme 2. Synthesis of the hexadentate pyrazole-based bispidine-ligand L3 and its corresponding metal complexes.
due to the fact that the pyrazole groups are free to rotate while
the aliphatic nitrogen donors of L2 are fixed in a diazepane ring.
However, the twist angles are slightly larger due to repulsion of
the pyrazole H-atoms.
As expected from the structural properties, the e0 set of orbitals
is nearly degenerate with a10 and, at least for CuII, due to the Jahn–
Teller instability and the ligand-enforced tetragonal distortion (see
Table 1 and Fig. 2) [35], there is a significant splitting of the e00 set
of orbitals. As a result, for CuII a dz2 ground state is expected, and
this clearly emerges from the corresponding EPR spectrum
(Fig. 3); the spin Hamiltonian parameters for [CuL2]2+ and
[CuL3]2+ indicate that the two copper(II) complexes have very sim-
ilar ground states. This also emerges from the ligand field spectra
(see Table 2). Based on the basicities and ligand field parameters
(see above), a slightly lower ligand field might have been expected
for [CuL3]2+ but the significantly higher symmetry and slightly
more octahedral geometry as well as slightly smaller bond dis-
tances all lead to an increasing ligand field.
Fig. 1. ORTEP plot of the experimental structure of the metal-free ligand L3. Ellipsoids
are shown at a 30% probability level. H atoms are omitted for clarity.
N7) and the two appended pyrazolyl donors (N13, N18 or N25,
N30, respectively). The two corresponding trigonal planes are
almost parallel with
Unfortunately, only irreversible reduction signals are observed
in cyclovoltammetric experiments. The L3-based CuII complex
shows a peak at Ep = ꢁ245 mV (versus Fc/Fc+ in MeCN, see Sup-
porting Information). The corresponding L1- and L2-based com-
plexes have reversible potentials and, importantly, these are at
much more negative potentials. As mentioned in the Introduction,
bispidine ligands, in particular those of the 1st generation, lead to
very stable CuII complexes [37]. Interestingly, the redox potentials
of CuII complexes are correlated to the complex stabilities [53].
While general correlations of this type should not be expected,
the two groups of 1st and 2nd generation bispidine-copper com-
plexes have been shown to lead to rather good linear dependencies
of the CuII/I couples with the logKCu(II) values.
H
= 1.83° (for FeII) – 8.51° (for CuII), and the
inter-plane distance of 2.8–2.9 Å, is dictated by the rigid bispidine
backbone (distance of the donor atoms N3 and N7; see Fig. 2 for
plots of the experimental structures and Table 1 for the corre-
sponding structural parameters). The trigonal twist angles4 are be-
tween 15° and 20° for the N3ꢂ ꢂ ꢂN7 edge but between 35° and 41° on
average. That is, the complexes are best described as distorted trigo-
nal prismatic, and this is as expected (see above), a very similar sit-
uation to that with the ligand L2 with only tertiary amine donors and
a very similar backbone (note that the twist angles with L2 are very
similar but the trigonal planes are significantly more parallel with
L3) [35]. It appears that the L3-based complexes are less strained
Therefore, L3 forms less stable CuII complexes than the corre-
sponding 1st generation bispidine ligands, and this is due to (i) a
less preferential geometry (distorted trigonal prismatic versus dis-
torted cis-octahedral), and to (ii) the lower basicity of the aromatic
nitrogen donor (pKa = 2.5 of 1H-pyrazole and pKa = 5.2 of pyridine).
4
Angle between a donor atom of one trigonal plane, the metal centre and the
projection of the closest donor atom of the opposite trigonal plane; the twist angle
U
of an ideal trigonal prism is 0° that of an ideal octahedron is 60 °C.

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P. Comba et al. / Polyhedron 52 (2013) 1239–1245
Fig. 2. ORTEP plots of the experimental structures of the MII-complexes with the pyrazole-based bispidine L3. Ellipsoids are shown at a 30% probability level; counter ions,
solvent molecules and H atoms are omitted for clarity (for numbering see also Scheme 2).
Scheme 3. Presentation of an ideal trigonal prism (left), an ideal octahedron (right) and the corresponding d-orbital-splitting; the coordination geometry of metal complexes
with L3 are also shown (middle).

P. Comba et al. / Polyhedron 52 (2013) 1239–1245
1243
Table 1
Selected bond distances (Å) and angles (°) of the divalent transition metal-complexes with L3 (top), angles between the trigonal planes
H
and trigonal twist angles
U
(bottom).
M
M–N3
M–N7
M–N13 M–N18 M–N25 M–N30 N3ꢂꢂꢂN7 N3–M–
N7–M–
N13
N18–M–
N25
N3–M–
N7
N3–M–
N13
N13–M–
N30
N30–M–
N7
N30
FeII 2.252(2) 2.258(2) 2.166(2) 2.153(2) 2.148(2) 2.179(2) 2.834
CoII 2.214(3) 2.219(3) 2.131(3) 2.111(3) 2.104(3) 2.137(3) 2.826
NiII 2.166(4) 2.180(4) 2.083(4) 2.108(4) 2.103(4) 2.077(4) 2.806
CuII 2.065(2) 2.055(2) 2.301(2) 2.015(2) 1.992(2) 2.774(3) 2.815
ZnII 2.201(2) 2.231(2) 2.117(2) 2.232(2) 2.201(2) 2.101(2) 2.856
110.47(7) 112.92(7) 102.79(7)
108.79(11) 112.72(11) 101.13(11) 79.20(10) 80.34(10) 166.14(11) 79.81(11)
164.76(16) 163.36(16) 167.27(16) 80.44(15) 94.78(16) 94.14(17) 94.20(15)
77.85(6)
80.67(6)
165.18(7)
79.77(7)
116.40(8) 117.16(7)
91.12(8)
86.19(7)
80.23(6)
82.85(7)
93.10(6)
156.56(6)
101.14(7)
79.29(7)
90.96(6)
157.37(7) 161.30(6) 162.64(6)
H
U1 (N3/N7)
U2 (N13/N25)
U3 (N18/N30)
Uav
FeII
CoII
NiII
CuII
ZnII
1.83
4.07
5.08
8.51
3.51
20.17
20.43
23.74
15.10
18.65
44.46
47.82
48.26
57.58
43.64
43.03
43.76
52.38
38.73
42.81
35.89
37.34
41.46
37.14
35.03
of the solvent (CDCl3). Mass spectra were recorded on a Finnigan
MAT8230 and a Joel JMS-700 spectrometer. Elemental analyses
were performed on a CHN-O-vario EL by the ‘‘Mikroanalytische
Labor’’, Department of Organic Chemistry, University of Heidel-
berg. The electrochemical measurements were performed on CH
Instruments CHI660D electrochemical workstation (equipped with
a CH Instruments Picoamp Booster and Faraday Cage) with a three-
electrode setup consisting of a glassy-carbon working electrode, a
Pt wire as the auxiliary electrode and an Ag/AgNO3 reference elec-
trode (0.01 M Ag+, 0.1 M (Bu4N)(BF4) in MeCN). The solutions were
thoroughly degassed and a slight argon-stream was set above the
solution during the measurement; a scan rate of 100 mV sꢁ1 was
applied. UV–Vis-spectra were recorded on a Jasco V-570 UV–
Vis-near-IR spectrophotometer. Solution spectra were measured
from in situ-prepared complexes. For solid state UV–Vis-spectra
the isolated complexes were triturated with titanium(IV)oxide.
EPR measurements were performed on a Bruker ELEXSYS-E-500
instrument at 110 K using methanol as solvent. The spin Hamilto-
nian parameters were obtained by simulation of the spectra with
XSophe [58,59].
Fig. 3. EPR-spectrum of [CuIIL3][BF4]2. Experimental spectrum measured in MeOH
at 110 K, at frequency of 9.453599 GHz (solid line), simulated spectrum
a
(gx,y = 2.061, gz = 2.241, Ax,y = 12 G, Az = 170 G) (dashed line) [58,59].
3.2. Syntheses
3.2.1. Compound 3 (C16H15NO4; 285.29 g/mol)
3. Experimental
1,8-Naphthalic acid anhydride (19.82 g, 0.1 mol, 1.0 equiv) and
1-aminoacetaldehyde-dimethylacetal (12.49 g, 12.94 ml, 0.12 mol,
1.2 equiv) were dissolved in 250 ml of ethanol and heated to reflux
for 4 h. After allowing the reaction mixture to cool to room temper-
ature a brown solid precipitated. This brown solid was filtrated and
washed with ethanol (3 ꢃ 200 ml) to afford long white needles as
the pure product in a yield of 88.4% (25.22 g, 88.4 mmol). 1H NMR
(400 MHz, CDCl3): d = 3.42 (s, 6H, OCH3), 4.40 (d, J = 5.65 Hz, 2H,
NCH2CH(OMe)2), 4.92 (t, J = 5.65 Hz, 1H, NCH2CH(OMe)2), 7.76
(t, J = 7.78 Hz, 2H, Hnaph), 8.22 (d, J = 8.16 Hz, 2H, Hnaph), 8.61
(d, J = 7.40 Hz, 2H, Hnaph). 13C NMR (100 MHz, CDCl3): d = 40.82,
53.45, 100.58, 122.49, 126.91, 128.22, 131.39, 131.55, 134.00,
164.24. HR-ESI (pos): [M+Na]+ calc. 308.08988, obs. 308.08908;
[2M+Na]+ calc. 593.18999, obs. 593.18918. Elemental analysis
(Report No.: 29570): [M] calc. C, 67.36; H, 5.30; N, 4.91; obs.
C, 67.11; H, 5.35; N, 4.89%.
3.1. Materials and methods
Chemicals were purchased from Sigma–Aldrich Chemie GmbH
(Taufkirchen, Germany), ABCR GmbH
& Co. KG (Karlsruhe,
Germany) and Merck KGaA (Darmstadt, Germany) and were of
the highest available purity. Dry solvents were used as delivered
without further purification. NMR spectra were recorded on a
Bruker DRX 200, Bruker Avance II 400 or Bruker Avance III 600
spectrometer. The latter spectrometer was equipped with a direct
detection cryoprobe for maximum sensitivity in the detection of
13C. 1H and 13C NMR chemical shifts were referenced to the signals
Table 2
dd-transitions of the divalent transition metal complexes of the bisdipyrazole-based
ligand L3 in comparison with the CuII complexes of the hexadentate ligands L1 and L2.
Compound
dd transitions solution (nm)
dd transitions solid (nm)
3.2.2. Compound 4 (C20H15N5O2; 357.37 g/mol)
[FeL3]2+
[CoL3]2+
[NiL3]2+
[CuL3]2+
[CuL1]2+a
[CuL2]2+b
835 (max), 960 (sh)
480 (max), 950, 1040 (sh)
520, 640, 800 (sh), 960 (max)
650 (max), 900 (sh)
620
830 (max), 1010
2-(2,2-Dimethoxyethyl)-1H-benzo[d,e]isoquinoline-1,3(2H)-dione
(24.2 g, 84.83 mmol, 1.0 equiv), pyrazole (17.3 g, 254.11 mmol,
3.0 equiv) and para-toluene sulfonic acid monohydrate (350 mg)
were heated to 220 °C for 4 h in a distillation apparatus in order
to get rid of the resulting methanol. After allowing the reaction
mixture to cool to room temperature the brownish product crystal-
lized. The solid was suspended in 300 ml of dichloromethane,
475 (max), 940, 1060
530, 650, 820 (sh), 970 (max)
670 (max), 890 (sh)
622
a
Ref. [36].
Ref. [35].
b

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P. Comba et al. / Polyhedron 52 (2013) 1239–1245
filtrated and mortared. The solid was then washed with 1 l of a sat-
urated K2CO3-solution and 1 l of water. The remaining solid was
dried under high vacuum to afford a light brown solid as the pure
product in a yield of 87.85% (26.63 g, 74.52 mmol). 1H NMR
temperature in aꢁy+ield of 50.0% (85.9 mg, 0.10 mmol). HR-ESI
analysis (Report No.: IPMB24): [FeL3(ClO4)2.H2O] calc. C, 47.47;
(pos): [FeIIL3+ClO4
] calc. 767.19081, obs. 767.19303. Elemental
H, 4.33; N, 15.82; obs. C, 47.06; H, 4.47; N, 15.62%.
(400 MHz, CDCl3): d = 5.30 (d, J = 7.28 Hz, 2H, CH2CH(pz)2), 6.27
0
(t, J = 2.01 Hz, 2H, H4 ), 7.17 (t, J = 7.28 Hz, 1H, CH2CH(pz)2), 7.49
3.2.6. [CoIIL3][ClO4]2
0
(d, J = 1.25 Hz, 2H, H3 ), 7.73 (t, J = 7.72 Hz, 2H, Hnaph), 7.85 (d,
To a solution of the ligand L3 (0.2 mmol, 122.5 mg, 1.0 equiv) in
2.5 ml of acetonitrile was added Co(ClO4)2ꢂ6H2O (0.2 mmol,
73.19 mg, 1.0 equiv) dissolved in 2.5 ml of acetonitrile. This solu-
tion was stirred at room temperature over night. The solution
was then stored at ꢁ18 °C for several days. The solution was then
freed from white solid material that precipitated and subjected to
ether diffusion at room temperature. A red crystalline solid was ob-
tained in a yield of 70.0% (117.9 mg, 0.14 mmol). HR-ESI (pos):
[L3+Co]2+ calc. 335.62028, obs. 335.61996. Elemental analysis (Re-
port No.: IPMB21): [CoL3(ClO4)2ꢂCH3CN] calc. C, 48.75; H, 4.31; N,
16.90; obs. C, 49.43; H, 4.76; N, 16.24%.
0
J = 2.38 Hz, 2H, H5 ), 8.20 (d, J = 8.16 Hz, 2H, Hnaph), 8.56 (d,
J = 7.28 Hz, 2H, Hnaph). 13C NMR (100 MHz, CDCl3): d = 42.40,
72.04, 106.70, 121.97, 126.92, 128.20, 129.56, 131.53, 131.61,
134.31, 140.26, 163.94. HR-ESI (pos): [M+H]+ calc. 358.13040,
obs. 358.12980; [M+Na]+ calc. 380.11234, obs. 380.11175; [M+K]+
calc. 396.08628, obs. 396.08571; [2M+H]+ calc. 737.23492, obs.
737.23340. Elemental analysis (Report No.: 29569): [M] calc. C,
67.22; H, 4.23; N, 19.60; obs. C, 66.93; H, 4.26; N, 19.38%.
3.2.3. Compound 5 (C8H11N5; 177.21 g/mol)
2-(2,2-Dipyrazol-1-yl-ethyl)-benzo[d,e]iso-quinoline-1,3-dione
(30.72 g, 85.96 mmol, 1.0 equiv) was suspended in 200 ml of warm
toluene. Then hydrazine monohydrate (31.9 g, 31.0 ml, approx.
1.0 mol, approx. 10.0 equiv) was added and this suspension was
refluxed over night whereupon a yellow precipitate formed. The
suspension was allowed to cool to room temperature and excess
of hydrazine hydrate and toluene were removed by a rotary
evaporator. In order to extract the free amine the precipitate was
washed with water (4 ꢃ 50 ml). The aqueous solution was concen-
trated under high vacuum to afford an oily brown solid as the pure
3.2.7. [NiIIL3][ClO4]2
To a solution of the ligand L3 (0.2 mmol, 122.5 mg, 1.0 equiv) in
2.5 ml of acetonitrile was added Ni(ClO4)2ꢂ6H2O (0.2 mmol,
73.1 mg, 1.0 equiv) dissolved in 2.5 ml of acetonitrile. This solution
was stirred at room temperature over night. Pink needles were ob-
tained by ether diffusion of this solution at 2 °C in a yield of 50.0%
(91.0 mg, 0.10 mmol). HR-ESI (pos): [NiIIL3ClO4ꢁ]+ calc. 769.19121,
obs. 769.19475. Elemental analysis (Report No.: 30092):
[NiL3(ClO4)2ꢂ0.5H2O] calc. C, 47.81; H, 4.24; N, 15.93; obs.
C, 47.81; H, 4.05; N, 15.92%.
product in
a
quantitative yield. 1H NMR (400 MHz, CDCl3):
d = 1.67 (br. s, 2H, NH2), 3.77 (d, J = 7.03 Hz, 2H, CH2CH(pz)2),
0
6.30 (t, J = 2.13 Hz, 2H, H4 ), 6.36 (t, J = 6.96 Hz, 1H, CH2CH(py)2),
3.2.8. [CuIIL3][BF4]2
0
0
7.58 (d, J = 1.63 Hz, 2H, H3 ), 7.60 (d, J = 2.38 Hz, 2H, H5 ). 13C NMR
(100 MHz, CDCl3): d = 44.93, 77.37, 106.66, 128.94, 140.33.
HR-FAB (pos): [M+H]+ calc. 178.1093, obs. 178.1090. Elemental
analysis (Report No.: 29202): [M+1/5H2O] calc. C, 53.14; H, 6.36;
N, 38.73; obs. C, 53.31; H, 6.26; N, 38.46%.
To a solution of the ligand L3 (0.2 mmol, 122.5 mg, 1.0 equiv) in
2.5 ml of acetonitrile was added dry Cu(BF4)2 (0.2 mmol, 47.5 mg,
1.0 equiv) dissolved in 2.5 ml of acetonitrile. This solution was
stirred at room temperature over night. Blue needles were ob-
tained by ether diffusion of this solution at room temperature in
a yield of 50.0% (81.9 mg, 0.10 mmol). HR-ESI (pos): [CuII+L3+BF4]+
calc. 762.23988, obs. 762.23994. Elemental analysis (Report No.:
29745): [CuL3(BF4)2ꢂ2H2O] calc. C, 47.45; H, 4.55; N, 15.81; obs.
C, 47.73; H, 4.66; N, 15.91%.
3.2.4. L3 (C35H36N10O; 612.73 g/mol)
1,3-Diphenyl-2-propanone (3.56 g, 16.93 mmol, 1.0 equiv),
paraformaldehyde (2.03 g, 67.72 mmol, 4.0 equiv) and acetic acid
(5.08 g, 4.84 ml, 84.65 mmol, 5.0 equiv) were mixed in 100 ml of
ethanol and slowly heated to 60 °C. At this temperature 2,2-
di(1H-pyrazol-1-yl)ethanamine (6.00 g, 33.86 mmol, 2.0 equiv)
was added to the reaction mixture and heated to reflux over night.
The solution was allowed to cool to room temperature whereupon
a pale yellow precipitate formed which was filtrated and washed
with ethanol to afford a white solid as the product in a yield of
44.36% (4.60 g, 7.51 mmol). Crystals suitable for X-ray diffraction
were obtained by recrystallization from acetonitrile. 1H NMR
(400 MHz, CDCl3): d = 3.17 (d, J = 10.67 Hz, 4H, CHaxHeq), 3.36 (d,
3.2.9. [ZnIIL3][ClO4]2
To a warm solution of the ligand L3 (0.2 mmol, 122.5 mg,
1.0 equiv) in 2.5 ml of acetonitrile was added Zn(ClO4)2ꢂ6H2O
(0.2 mmol, 74.5 mg, 1.0 equiv) in 2.5 ml of warm acetonitrile. The
resulting suspension was stirred at room temperature over night
and afterwards stored at ꢁ18 °C. The solution was removed from
the precipitate and separately allowed to stand at room tempera-
ture whereupon the solvent slowly evaporated. Colorless crystals
were obtained in a yield of 45.0% (80.0 mg, 0.09 mmol). Elemental
analysis (Report No.: 30091): [ZnL3(ClO4)2ꢂ2H2O] calc. C, 46.04; H,
4.42; N, 15.34; obs. C, 45.90; H, 4.36; N, 15.21%.
J = 10.67 Hz, 4H, CHaxHeq), 3.61 (d, J = 7.40 Hz, 4H, CH2CH(pz)2),
0
6.33 (t, J = 2.07 Hz, 4H, H4 ), 6.53 (t, J = 7.40 Hz, 2H, CH(pz)2), 6.93
(d, J = 7.03 Hz, 4H, Ph), 7.20–7.31 (m, 6H, Ph), 7.58 (d, J = 1.51 Hz,
0
0
4H, H3 ), 7.67 (d, J = 2.26 Hz, 4H, H5 ). 13C NMR (100 MHz, CDCl3):
d = 54.27, 58.58, 65.00, 73.41, 106.81, 126.55, 126.78, 127.97,
128.90, 140.19, 142.00, 209.74. HR-ESI (pos): [M+H]+ calc.
613.31518, obs. 613.31452; [M+Na]+ calc. 635.29713, obs.
635.29697; [M+K]+ calc. 651.27106; obs. 651.27115. Elemental
analysis (Report No.: 30169): [M] calc. C, 68.61; H, 5.92; N,
22.86; obs. C, 68.57; H, 6.11; N, 22.74%.
Acknowledgments
Generous financial support by the German Science Foundation
(DFG) and the University of Heidelberg is gratefully acknowledged.
Appendix A. Supplementary data
3.2.5. [FeIIL3][ClO4]2
CCDC 878253–878258 contains the supplementary crystallo-
graphic data for this paper. 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,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
posit@ccdc.cam.ac.uk. Supplementary data associated with this
To a solution of the ligand L3 (0.2 mmol, 122.5 mg, 1.0 equiv) in
2.5 ml of acetonitrile was added Fe(ClO4)2ꢂ10H2O (0.2 mmol,
87.0 mg, 1.0 equiv) dissolved in 2.5 ml of acetonitrile. This solution
was stirred at room temperature over night. Pale brown needles
were obtained by ether diffusion of this solution at room

P. Comba et al. / Polyhedron 52 (2013) 1239–1245
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