An Acetylacetonate or a Pyrazole? Both! 3-(3,5-Dimethyl-pyrazol-4-yl)pentane-2,4-dione as a Ditopic Ligand

Article abstract of DOI:10.1021/acs.cgd.6b00710

The alternative coordination sites of 3-(3,5-dimethyl-pyrazol-4-yl)pentane-2,4-dione (H₂acacPz) differ with respect to Pearson hardness. The softer, heterocyclic moiety was used as N donor toward Zn(II) and Ag(I); it yielded a tetrahedral, neutral Zn complex in the former and a monocationic, linear bis(ligand) Ag complex in the latter case. After deprotonation with silver benzoate, the pyrazolyl ring may act as a monoanionic N,N′-bridge between neighboring cations in a hexanuclear Ag aggregate; in addition to ligand-supported Ag···Ag distances of ca. 3.2 ?, these aggregates feature ligand-unsupported argentophilic interactions of ca. 2.9 ?. With stronger bases and in the presence of oxophilic Mg cations, the harder hydroxyketone part of the H₂acacPz ligand may be deprotonated to a chelating acetylacetonate. The resulting bis(ligand) Mg complex has been used as starting compound for a bimetallic derivative: the ditopic ligand allows coordinating cadmium acetate to its dangling N donor site, thus, bridging divalent Mg and Cd in a bimetallic three-dimensional coordination network of pts topology.

Full text of DOI:10.1021/acs.cgd.6b00710

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Article
An acetylacetonate or a pyrazole? Both! 3-(3,5-dimethyl-
pyrazol-4-yl)pentane-2,4-dione as a ditopic ligand
Qianqian Guo, and Ulli Englert
Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b00710 • Publication Date (Web): 02 Aug 2016
Downloaded from http://pubs.acs.org on August 9, 2016
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An acetylacetonate or a pyrazole? Both! 3-
(3,5-dimethyl-pyrazol-4-yl)pentane-2,4-dione
as a ditopic ligand†
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Qianqian Guo and Ulli Englert∗
Institute of Inorganic Chemistry, RWTH Aachen University, Aachen, Germany
E-mail: ullrich.englert@ac.rwth-aachen.de
Phone: +49-241-8094666. Fax: +49-241-8092288
Abstract
The alternative coordination sites of 3-(3,5-dimethyl-pyrazol-4-yl)pentane-2,4-dione
(H2acacPz) differ with respect to Pearson hardness. The softer, heterocyclic moiety was
used as N donor towards Zn(II) and Ag(I); it yielded a tetrahedral, neutral Zn complex
in the former and a monocationic, linear bis(ligand) Ag complex in the latter case.
After deprotonation with silverbenzoate, the pyrazolyl ring may act as a monoanionic
N,N’-bridge between neighbouring cations in a hexanuclear Ag aggregate; in addition
to ligand-supported Ag· · · Ag distances of ca. 3.2 Å, these aggregates feature ligand-
unsupported argentophilic interactions of ca. 2.9 Å. With stronger bases and in the
presence of oxophilic Mg cations, the harder hydroxyketone part of the H2acacPz ligand
may be deprotonated to a chelating acetylacetonate. The resulting bis(ligand) Mg
complex has been used as starting compound for a bimetallic derivative: the ditopic
ligand allows to coordinate cadmium acetate to its dangling N donor site, thus, bridging
†Supporting Information available
∗To whom correspondence should be addressed
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divalent Mg and Cd in a bimetallic three-dimensional coordination network of pts
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topology.
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Introduction
Ligands with two or more coordination sites allow for assembling cations to coordination
polymers. The wide range of cations and the plethora of potential linkers have given rise
to considerable scientific efforts and to almost countless publications documenting synthe-
ses, structures and applications of such compounds. Ditopic ligands with two distinctly
different coordination sites allow to combine different metal centers and thus add an addi-
tional degree of freedom to these complex solids. Substituted acetylacetonates have often
been used in this context; we here focus on derivatives with a potential N donor substituent
in 3 position. Scheme 1 compiles three of these ditopic acetylacetones: for HacacCN, an
efficient synthesis was introduced by Silvernail et al..1 This ligand acts as a (substituted)
acetylacetonate towards many different cations but successive N coordination is limited to
Ag or Cu.2–8 A different coordination behaviour was observed for the pyridyl derivative Ha-
cacPy. It was first applied as linker in a discrete supramolecular structure.9 Complexes in
which this ligand acts as O10 or N11 donor and extended bimetallic structures in which it
links different cations10–15 have been described. Quite obviously, HacacPy is a significantly
better N donor than HacacCN. In addition to cation coordination, the pyridyl N has been
used as nucleophilic group in halogen bonds.16 We now wish to report our results concern-
ing the pyrazolyl-substituted ditopic ligand 3-(3,5-dimethyl-pyrazol-4-yl)pentane-2,4-dione,
H2acacPz. A beryllium complex of this compound was published by Boldog et al.17 Sim-
ilar to the aforementioned alternatives, H2acacPz offers O and N donor sites of different
Pearson hardness;18 in addition, both the pyrazolyl and the acetylacetone moiety may be
deprotonated, and the question about preferred O or N coordination has not yet been an-
swered. Moving from single site coordination to ditopic topology, H2acacPz should rank
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Scheme 1: Three N-donor substituted acetylacetonates with different M· · · M distances.
−
−
in-between the shorter acacCN and the longer acacPy linker: The former is associated
with metal· · · metal distances of ca. 8 Å, the latter of ca. 9.7 Å, whereas for the yet unex-
−
plored HacacPz bridge ca. 9 Å, were expected based on simple geometry considerations.
We here communicate the synthesis and characterization of N coordinated, N,N’ bridging, O
coordinated and O,N’ bimetallic complexes. Scheme 2 compiles the compounds synthesized
and structurally characterized in the context of this work.
Results and discussion
We start our survey of the coordination modes of H2acacPz by using the ligand as an N donor
without deprotonation. With ZnCl2, the neutral mononuclear complex [ZnCl2(H2acacPz)2],
1 is obtained. The metal cation is located on a twofold crystallographic axis and adopts an
almost undistorted tetrahedral coordination. This reaction product is depicted in Fig. 1. The
◦
N coordinated H2acacPz molecules subtend an interligand angle of 106.4 and unambiguously
correspond to the enol tautomer, with significantly different C-C and C-O bond distances in
acetylacetone moiety as shown in Scheme 3.
This enol geometry derived from the diffraction experiment matches the IR spectrum of
1, and we anticipate that the same pattern is encountered in the spectra of 2, 3 and that of
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+
Figure 2: Arrangement of [Ag(H2acacPz)2] cations and nitrate anions along the b axis.
Dashed lines indicate Ag· · · O contacts of ca. 2.8 Å, hydrogen atoms and orientational
disorder in the nitrate have been omitted.
pounds 3b and 3c two such independent residues. Therefore, five symmetrically independent
hexanuclear [Ag6(HacacPz)6] aggregates have been characterized in total and are compared
in the Supporting Information. In Fig. 3, we restrict our comparison to the Ag6N12 cores in
3a and 3b. In all independent [Ag6(HacacPz)6] molecules, pairs of Ag3 triangles form; their
Ag· · · Ag edges (dashed lines) range between 3.3 and 3.5 Å, and are bridged by monoanionic
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HacacPz ligands.
Aggregation of these triangles to a hexanuclear moiety is achieved via significantly shorter
Ag-Ag contacts of ca. 2.9 Å. In view of the fact that these interactions occur directly and
without any bridging ligand, even the term "cluster" might apply. Due to the concomitant
presence of ligand supported and ligand unsupported contacts, we prefer the more general
expression "aggregate". Table 1 compiles the Ag· · · Ag distances in the five symmetrically in-
dependent aggregates in 3a, 3b and 3c. Short Ag· · · Ag contacts are generally referred to as
"argentophilic",21–29 and this type of interactions has recently been reviewed.30 More specif-
ically, pyrazolyl-bridged Ag triangles represent a rather well-established oligonuclear aggre-
gate: In the CSD database,31,32 coordinates for 43 well-ordered and error-free occurences of
this fragment are available, with an average length for the pyrazolyl-bridged edges of 3.469
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Å. The second feature encountered in the case of our hexanuclear aggregates, namely short
ligand-unsupported argentophilic interactions to neighbouring triangles, is less popular. Fu-
jisawa and coworkers33 have contributed five analogous structures and also compiled related
examples from the literature. To the best of our knowledge, 3a exhibits the shortest Ag-Ag
distances between neighbouring [Ag3(pyrazolyl)3] moieties; slightly longer contacts between
2.9 and 3.0 Å have been reported in a few cases.34–36
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Figure 3: Ag6(HacacPz)6 cores in compound 3a (left) and 3b (middle and right). Symmetry
operations: A = 1-x, 1-y, 1-z; B = 1-x, 2-y, -z; C = 1-x, 1-y, 1-z.
In the solids 3a, 3b and 3c, solvent molecules fill the voids between the large [Ag6(HacacPz)6]
aggregates. 3a contains two molecules of ethanol per unit cell or hexanuclear aggregate. In
3b, eight molecules of ethanol per unit cell occupy two voids. A more complex situation was
encountered in the case of 3c: The compound contains a well-localized CH2Cl2 with half-
occupied atom sites in general position, i. e. one CH2Cl2 per unit cell and three strongly
disordered molecules of 2-butanol in two voids per unit cell (see Experimental).
A decision concerning keto-enol tautomerism in 3 is less obvious because the structure
models for these solids have to account for larger asymmetric units, comprise chlathrated
solvent molecules and hence are associated with higher standard uncertainties. The IR
spectra of 3, however, closely match those of 1 and 2 for which the diffraction results are
unambiguous. A synopsis of the IR spectra of H2acacPz, 1, 2 and 3 is provided in the Sup-
porting Information. The Ag-Ag vibrations in 3 are difficult to assign; they will necessarily
be observed at low wave numbers in the Raman spectra and probably not correspond to
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pure Ag-Ag stretching. A resonance at 83 cm has been associated with a metal· · · metal
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contact slightly shorter than 3 Å.37 Our experimental Raman spectrum of 3 (Fig. S12)
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shows a broad band with a shoulder between 100 and 50 cm but we do not have sufficient
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Table 1: Ag· · · Ag distances in Ag6(HacacPz)6 aggregates in compounds 3a, 3b and 3c.
ligand support
interaction range (Å) interaction (Å)
direct
Compound
3a
3.329 - 3.477
3.419 - 3.436
3.376 - 3.474
3.420 - 3.432
3.370 - 3.499
2.905
2.969
2.911
3.006
2.906
3b resd. 1
3b resd. 2
3c resd. 1
3c resd. 2
In all compounds discussed so far, the acetylacetone part is protonated but the hydroxyl
group is not involved in any short intermolecular interactions. Rather, intramolecular O-
H· · · O hydrogen bonds with donor· · · acceptor distances between 2.4 and 2.5 Å occur within
each Hacac moiety.
In the absence of soft coordination partners, more drastic conditions are required for
deprotonation in the O donor part of the ditopic ligand. Magnesium methoxide proved a
suitable reagent, combining the oxophilic nature of the cation with the required basicity of
the anion. Crystals of the target product 4 could be directly isolated from the reaction
mixture. The diffraction experiment revealed that 4 crystallizes in the orthorhombic space
group Pbca with the central Mg cation located on a crystallographic center of inversion. It
is coordinated by six oxygen atoms in a slightly distorted octahedral geometry. Four oxygen
atoms from two O,O’ chelating HacacPz ligands are coplanar, and two coordinated apical
MeOH molecules complete the coordination sphere with slightly longer Mg-O bonds (Fig.
4 left). In addition, 4 contains two molecules of uncoordinated MeOH per Mg complex.
The NH group of the pyrazolyl ring and the hydroxyl groups of the coordinated and the
uncoordinated methanol molecules act as donors, the unprotonated pyrazolyl N, one of the
Mg-coordinated HacacPz oxygen atoms and the oxygen of the uncoordinated MeOH as
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acceptors for classical hydrogen bonds; they subtend a three-dimensional network (Fig. 4
right and Table S2 in Supporting Information).
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Figure 4: Left: Mg(II) complex in the crystal structure of 4; ellipsoids are drawn at 50 %
probability, only the H atoms at N2 and O3 are shown. Symmetry operation: A = 1-x, 1-y,
1-z. Right: N-H· · · O and O-H· · · O interactions (dashed blue lines) in the crystal structure
of 4.
A comparison of 4 with the only prior structural result obtained for the ligand HacacPz,
its complex with the lighter congener Be,17 reveals clear differences. The alkaline earth
cation in the latter is only four-coordinated, in agreement with general trends: a search in
the CSD32 resulted in 109 structures with BeO4 fragments whereas only one example of
hexa-coordinated Be with dubious charge balance has been reported. In contrast, sixfold co-
ordination for Mg cations is unexceptional. The oxygen atoms in the BeO4 core investigated
by Boldog et al.17 subtend an almost undistorted tetrahedron, with Be-O distances of 1.60
Å, whereas the Mg-O distances in 4 range between 2.0 and 2.1 Å and the bite angle of the
◦
HacacPz ligand amounts to 86 .
With respect to Crystal Engineering, the N coordinated complexes 1 - 3 and the O
coordinated compound 4 show distinctly different behaviour: our attempts to crosslink the
dangling acetylacetone moieties in the former did not yet lead to isolated crystalline reaction
products whereas further N coordination of 4 was successful. In the following section, we
will discuss the resulting mixed-metal coordination compound 5.
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The Mg-O bonds to the coordinated MeOH molecules represent the predetermined break-
ing points in 4: equimolar reaction with cadmium acetate gives additional coordination of
a Cd coordinated acetate oxygen to the alkaline earth cation. In parallel, the pyrazolic N
donor completes the octahedral coordination about a symmetry-equivalent Cd(II). The re-
action stoichiometry and a first interpretation of the single crystal diffraction experiment
on solid 5 suggest the overall composition Mg(HacacPz)2Cd(OOCCH3)2. In line with this
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¯
hypothesis, a coordination sphere with 1 site symmetry made up entirely of oxygen atoms is
observed for Mg (Fig. 5 left) whereas the softer Cd cation is situated on a twofold axis in a
mixed nitrogen-oxygen N2O4 environment (Fig. 5 right). In the introduction, we suggested
an approximate cation· · · cation distance subtended by the HacacPz ligand of ca. 9 Å, and
we can now confirm this estimate: the ditopic ligand in 5 bridges a Mg· · · Cd of 9.1 Å.
Figure 5: Coordination of an Mg(II) cation (left) and Cd(II) (right) in the crystal structure
of 5. Ellipsoid are drawn at 50 % probability level. Symmetry operation: A = 0.5 -x, 1.5-y,
1-z; B = 0.5 +x, 0.5+y, z; C = 0.5 -x, 0.5+y, 1.5-z; D = 1 -x, y, 1.5-z.
Closer inspection of the diffraction results, however, indicated a slightly more complicated
situation: refinement of the well-ordered structure model as described above converged with
an unrealistically small displacement parameter for the Mg cation. This exclusively O co-
ordinated site is not completely occupied by the alkaline earth cation but also to a minor
extend by Cd(II). Fig. S2 in the Supporting Information compiles displacement parame-
ter plots for tentative variations in the occupancy factors: visual inspection confirms a low
Cd(II) content. Our final structure model is based on site occupancy refinement in which
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the sum of the occupancies was constrained to unity; it converged for 93.5(3)% of Mg and
6.5(3)% of Cd. We recall that the solid thus characterized, 5a, was obtained from a reaction
with 4 : Cd(OOCCH3)2 = 1 : 1 stoichiometry. Our interpretation of the disordered cation
site is corroborated by the existence of an isomorphous solid: 5b crystallizes in the presence
of an excess of cadmium actetate and shows a Mg : Cd = 86.3(4) : 13.7(4) ratio for the
occupancy of the oxygen-coordinated cation. The information about partial occupancy of
the O six-coordinated cation site by Cd stems mostly from the very pronounced difference
in electron density between Mg and Cd; we also note, however, that cation-oxygen distances
in 5b are slightly longer than in 5a, in agreement with the more pronounced site occupancy
by the larger Cd(II) cation. 5a and 5b represent two individual compositions of a solid
solution 5 in which the Mg(II) cation may be partially replaced by Cd(II). How surprising
is this type of substitutional disorder? The elements Mg and Cd both adopt hexagonal
close packing but clearly differ in their intermetal distances. As for their divalent cations,
Cd(II) (1.09 Å) is significantly larger than Mg(II) (0.86 Å)38 and much softer with respect
to Pearson hardness.39 Towards oxygen, both cations prefer coordination number 6; a com-
pilation of CSD-based32 frequencies for different coordination numbers is provided in the
Supporting Information (Fig. S20). We are aware of only one crystal structure for which
substitutional disorder between Mg(II) and Cd(II) has been reported: Yao and coworkers40
have encountered a related case of a six-coordinated cation site preferentially occupied by
Mg(II), together with a small (7%) Cd(II) content.
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5 forms a three-dimensional coordination network (Fig. 6 left). With respect to topology,
each Mg and Cd dication may be perceived as a 4-connected node. The resulting binodal (4,4)
net can be assigned the vertex symbol (4.4.82.82.88.88)(4.4.87.87.87.87),41 which corresponds
to a pts net.42 A simplified view of the topology is shown in Fig. 6 right.43
−1
The Raman spectra for solids 4 and 5 show a band at ca. 400 cm which is absent in
those of 1-3. We tentatively assign this resonance to Mg-O stretching.
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Figure 6: Perspective view of the 3D network of the bimetallic coordination polymer 5. Six
coordinated Cd is drawn in polyhedron mode (left); schematic illustrating the 3D topology
in 5. Color code: pink node, Mg(II) center; black node, Cd(II) center; pink stick, acetate
−
linker; black stick, HacacPz linker (right).
Conclusion
Employing cations of different Pearson hardness, we have been able to selectively deprotonate
the soft N and the hard O donor site of the pyrazolyl-substituted acetylacetone H2acacPz.
Future work will be dedicated to the fluorescence properties of the discrete molecular species
3. We will also attempt to synthesize mixed-metal coordination polymers involving Ag and
Yb cations: decomposition of such compounds has led to catalytically active agglomerates
of silver nanoparticles and rare-earth oxide.44
Experimental
Materials and Methods
All chemicals were used without further purification: ZnCl2 (99%, Grüssing), AgNO3 (KMF),
silver benzoate (99%, Acros), Mg (99.8%, Fluka), cadmium acetate (97%, Kraft Bernd) and
dimethyl sulfoxide-d6 (99.9 atom %D, Aldrich).
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IR spectra were recorded on a Nicolet Avatar 360 E.S.P. spectrometer in KBr windows.
Raman spectra were obtained with a Horiba LABRAM HR instrument equipped with a 633
nm HeNe excitation laser. The electron-impact mass spectrum of H2acacPz was recorded on a
Finnigan MAT-95 at a nominal electron energy of 70 eV. CHN microanalyses were carried out
at the Institute of Organic Chemistry, RWTH Aachen University, using a HERAEUS CHNO-
Rapid. Powder diffraction experiments were performed at room temperature on flat samples
with a Stoe & Cie STADI P diffractometer equipped with an imageplate detector with
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constant ω angle of 55 using germanium-monochromated Cu-Kα1 radiation (λ = 1.54051 Å).
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H NMR spectra were measured with a Bruker Avance II UltrashieldTM plus 400 instrument
(400 MHz, referenced to TMS).
Syntheses
Synthesis of H2acacPz.
The H2acacPz ligand was prepared according to the literature method by W. L. Mosby.45–47
1
Spectroscopic data: H NMR (d6-DMSO): δ = 16.98 (s, 1H, -OH), 12.33 (s, 1H, -NH), 2.06
(s, 6H, -CH3), 1.87 (s, 6H, -CH3). Broadening of the signal at 2.06 ppm associated with
the methyl groups in the acetylacetone part of the ligand (Fig. S21) is due to keto-enol
tautomerism. Deprotonation of this part of the ligand as in 4 results in a narrow line.48–51
+
MS-EI: m/z calcd for [C10H14N2O2] : 194.1055; found: 194.1.
Synthesis of Zn(H2acacPz)2Cl2, 1.
H2acacPz (9.7 mg, 0.05 mmol) and ZnCl2 (3.4 mg, 0.025 mmol) were dissolved in methanol (2
mL) and stirred for 10 min at ambient temperature. The clear solution was left unperturbed
for slow evaporation. Colorless crystals grew over a period of one week. Yield: 10.2 mg
(0.019 mmol, 76%). Phase purity of the product was confirmed by powder diffraction of the
bulk material (see Fig. S15, Supporting Information).
Anal. Calcd. for C20H28Cl2N4O4Zn: C: 45.78, H: 5.38, N: 10.68.
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Found: C: 45.04, H: 5.95, N: 10.20.
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Synthesis of [Ag(H2acacPz)2]NO3·H2O, 2.
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AgNO3 (4.2 mg, 0.025 mmol) was dissolved in one drop of water and 1 mL of methanol was
added. H2acacPz (9.7 mg, 0.05 mmol) was dissolved in MeOH (1 mL). These two solutions
were combined and stirred for 10 min at ambient temperature. The clear reaction mixture
was left unperturbed for slow evaporation. Colorless crystals grew over a period of one week.
Yield: 7.2 mg (0.012 mmol, 48%). Phase purity of the product was confirmed by powder
diffraction of the bulk material (see Fig. S16, Supporting Information).
Anal. Calcd. for C20H30AgN5O8: C: 41.68, H: 5.25, N: 12.15.
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Found: C: 42.01, H: 5.67, N: 11.61.
Synthesis of [Ag6(HacacPz)6]·2EtOH, 3a, [Ag6(HacacPz)6]·4EtOH, 3b
and [Ag6(HacacPz)6]·0.5CH2Cl2·1.5C4H10O, 3c.
Solutions of Ag(PhCOO) (11.5 mg, 0.05 mmol) in THF (2 mL) and H2acacPz (9.7 mg, 0.05
mmol) in MeOH (2 mL) were combined. The mixture was stirred for 12 h at ambient temper-
ature and the phases were separated by centrifugation. The supernatant liquid was discarded
and the solid residue was washed twice with MeOH (2 mL). Yield: 9.6 mg of Ag6(HacacPz)6
(0.0053 mmol, 64%). Colorless block-shaped crystals of 3a and 3b were obtained by slow
diffusion of EtOH into a CH2Cl2 solution of Ag6(HacacPz)6 within two days. Crystals of
3c were prepared in an analogous way using 2-butanol instead of EtOH as antisolvent in
diffusion. All solvates of 3 lose solvent very fast as evidenced by powder diffraction. When
solid 3a is freshly isolated, hardly ground and subjected to powder diffraction with the pro-
tection of perfluoropolyallyether, the powder pattern of the bulk is in agreement with the
expectation from the single crystal structure (see Supporting Information Fig. S17). No
fully satisfactory elemental analysis has been obtained for 3.
Anal. Calcd. for C60H78Ag6N12O12: C: 39.89, H: 4.35, N: 9.30.
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Found: C: 37.43, H: 4.37, N: 9.34.
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Synthesis of [Mg(HacacPz)2(MeOH)2]·2MeOH, 4
9
Magnesium methoxide was prepared by reaction of Mg (23.9 mg, 1 mmol) with dry MeOH
(10 mL) at room temperature; standard Schlenk technique was used to exclude moisture
and oxygen. This magnesium methoxide solution was combined with a solution of H2acacPz
(388.5mg, 2 mmol) in dry MeOH and stirred for 3 h. The colorless precipitate consisted of
larger crystals. It was recovered by filtration and washed with ca. 0.5 mL of cold MeOH and
dried in a desiccator. Yield: 299.3 mg (0.63 mmol, 63%). The methanol solvate 4 undergoes
fast desolvation as evidenced by powder diffraction. When solid 4 is freshly isolated, hardly
ground and subjected to powder diffraction with the protection of perfluoropolyallyether,
the powder pattern indicates concomitant presence of solvated and desolvated material (see
Supporting Information Fig. S18).
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Anal. Calcd. for C22H34MgN4O6 (desolvation of uncoordinated MeOH): C: 55.65, H: 7.22,
N: 11.80.
Found: C: 54.60, H: 6.62, N: 12.70.
Synthesis of Mg1−xCdx(HacacPz)2Cd(OOCCH3)2, 5
In a test tube, 4 (9.5 mg, 0.02 mmol) was dissolved in a mixture of MeOH/CH2Cl2 (1 mL/1
mL). The solution was layered by a mixture of 0.5 mL CH2Cl2 and 0.5 mL MeOH. A top layer
of Cd(OOCCH3)2 ·H2O (5.3 mg, 0.02 mmol) in 1 mL of MeOH was added and the test tube
was left unperturbed at room temperature for crystallization by diffusion. Colorless crystals
of 5a formed within two days. The composition Mg1−xCdx(HacacPz)2Cd(OOCCH3)2 , x
= 0.065(3) was determined by single crystal X-ray diffraction. Yield: 8.2 mg (0.013 mmol,
65%). Phase purity of the product was confirmed by powder diffraction of the bulk material
(see Fig. S19, Supporting Information).
When an excess of cadmium acetate was used by changing the reaction stoichiometry 4 :
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Cd(OOCCH3)2·H2O to 1 : 2, the solid 5b was obtained. It is isomorphous to 5a, with x
= 0.137(4). Yield: 9.7 mg (0.015 mmol, 75%). No fully satisfactory elemental analysis was
obtained for 5.
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Crystallographic Studies
The diffraction experiments were performed with a Bruker D8 goniometer equipped with
an Incoatec microsource (Mo-Kα, λ = 0.71073 Å, multilayer optics) and an APEX CCD
detector; a sample temperature of 100(2) K was maintained with an Oxford Cryostream 700
instrument. Intensity data were integrated with SAINT+52 and corrected for absorption by
multi-scan methods using the program SADABS.53
The crystal structures were solved with Patterson or Direct methods, and refinements
were accomplished with full matrix least-squares procedures as implemented in SHELXL-
13.54 All non-hydrogen atoms were assigned anisotropic displacement parameters; hydrogen
atoms were placed in idealized positions and included as riding with constrained isotropic
displacement parameters. In 1 - 5, the hydrogen atoms of the hydroxyl group and secondary
amine were located according to the following strategy: 1. tentative assignment of local
electron density maxima from Fourier difference maps, followed by refinement with distance
restraints; 2. in the absence of geometrically acceptable electron density maxima, positions
in the direction of a suitable hydrogen bond acceptor were calculated and also subjected to
distance restraints; 3. if neither matching electron density maxima nor suitable hydrogen
bond acceptors were available, H atoms were calculated in standard distance in arbitrary
orientation.
In 2, the nitrate anion and the water molecule are disordered about a crystallographic
center of inversion; the situation is depicted in Fig. S1. For reasons of symmetry and charge
balance, the mutually exclusive components were assigned half occupancy and a common
isotropic displacement parameter in the least squares refinement. In 3a, the solvent molecule
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was refined as ethanol with similarity restraints for its displacement parameters. The as-
signment of EtOH to the electron density in the solvent-containing void was in agreement
with a tentative SQUEEZE55 calculation. Electron density in the solvent-accessible voids of
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3b was handled with the SQUEEZE55 algorithm. The H NMR spectra for 3c confirmed
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the identity of the chlathrated solvents CH2Cl2 and 2-butanol. Distance and displacement
similarity restraints were used for the refinement of the CH2Cl2 molecule; its occupancy
converged to ca. 0.5. No structure model could be obtained for 2-butanol because of severe
disorder. Therefore, in the final structure model for 3c, atoms in the CH2Cl2 molecule were
assigned half occupancy and the electron density in the remaining solvent-accessible voids
was handled with the SQUEEZE55 algorithm. In 5a, the exclusively O-coordinated cation
showed substitutional disorder: in addition to its major occupancy by Mg, a minor site oc-
cupancy of Cd was detected. Coordinates and displacement parameters for the alternative
cations were constrained to be equal and the sum of their site occupancies was constrained
to unity; relative site occupancy converged to a Mg : Cd ratio of 93.5(3) : 6.5(3). The
same type of substitutional disorder was detected in 5b, albeit with a higher Cd content of
13.7(4)%. After refinement of the disorder model for 5b, a list of disagreeable reflections
showed a clear tendency for F2(obs.)≫F2(calc.). A test with the TwinRotMat option in
PLATON56 confirmed non-merohedral twinning for this sample, with 375 out of 3066 re-
flections overlapping. An appropriately modified set of intensity data taking the partially
overlapped diffraction of both domains into account (HKLF5 format in SHELXL9757) gave
significantly improved convergence results and relative domain fractions of 0.82 and 0.18.
Acknowledgement
Financial support by China Scholarship Council (Q. Guo) is gratefully acknowledged. We
thank Irmgard Kalf for help with the Raman spectra.
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Supporting Information Available
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The following files are available free of charge.
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• Crystallographic information in CIF format.
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• Illustration of the disordered nitrate anion and water molecule in 2.
• Illustration of the refinement results with variable minor site occupancy by Cd(II) in
5a.
• Infrared spectra for H2acacPz, 1, 2, 3, 4 and 5.
• Raman spectra for 1-5.
• Powder patterns for 1-5.
• Histogram showing coordination numbers for Mg(II) and Cd(II) in exclusively O-
coordinated environments.
1
• H NMR spectrum of H2acacPz in d6-DMSO.
1
• H NMR spectrum of 4 in d6-DMSO.
• Ag· · · Ag distances of Ag6(HacacPz)6 aggregates in compounds 3a, 3b and 3c.
• hydrogen bond information of 4.
This material is available free of charge via the Internet at http://pubs.acs.org/.
References
(1) Silvernail, C. M.; Yap, G.; Sommer, R. D.; Rheingold, A. L.; Day, V. W.; Belot, J. A.
Polyhedron 2001, 20, 3113–3117.
(2) Burrows, A. D. CrystEngComm 2011, 13, 3623–3642.
18
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Page 19 of 25
Crystal Growth & Design
1
2
3
4
5
6
(3) Kondracka, M.; Englert, U. Inorg. Chem. 2008, 47, 10246–10257.
(4) Merkens, C.; Englert, U. Dalton Trans. 2012, 41, 4664–4673.
7
8
9
(5) Merkens, C.; Becker, N.; Lamberts, K.; Englert, U. Dalton Trans. 2012, 41, 8594–8599.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(6) Burrows, A. D.; Cassar, K.; Mahon, M. F.; Warren, J. E. Dalton Trans. 2007, 2499–
2509.
(7) Merkens, C.; Pecher, O.; Steuber, F.; Eisenhut, S.; Görne, A.; Haarmann, F.; En-
glert, U. Z. Anorg. Allg. Chem. 2013, 639, 340–346.
(8) Guo, Q.; Merkens, C.; Si, R.; Englert, U. CrystEngComm 2015, 17, 4383–4393.
(9) Mackay, L. G.; Anderson, H. L.; Sanders, J. K. M. Chem. Commun. 1992, 43–44.
(10) Vreshch, V. D.; Chernega, A. N.; Howard, J. A. K.; Sieler, J.; Domasevitch, K. V.
Dalton Trans. 2003, 1707–1711.
(11) Merkens, C.; Truong, K.-N.; Englert, U. Acta Crystallogr. 2014, B70, 705–713.
(12) Chen, B.; Fronczek, F. R.; Maverick, A. W. Inorg. Chem. 2004, 43, 8209–8211.
(13) Vreshch, V. D.; Lysenko, A. B.; Chernega, A. N.; Howard, J. A. K.; Krautscheid, H.;
Sieler, J.; Domasevitch, K. V. Dalton Trans. 2004, 2899–2903.
(14) Vreshch, V. D.; Lysenko, A. B.; Chernega, A. N.; Sieler, J.; Domasevitch, K. V. Poly-
hedron 2005, 24, 917–926.
(15) Zhang, Y.; Chen, B.; Fronczek, F. R.; Maverick, A. W. Inorg. Chem. 2008, 47, 4433–
4435.
(16) Merkens, C.; Pan, F.; Englert, U. CrystEngComm 2013, 15, 8153–8158.
(17) Boldog, I.; Rusanov, E. B.; Chernega, A. N.; Sieler, J.; Domasevitch, K. V. Angew.
Chem. Int. Ed. 2001, 40, 3435–3438.
19
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Page 20 of 25
1
2
3
4
(18) Pearson, R. G. Chemical Hardness. Applications from Molecules to Solids; Wiley-VCH,
5
6
Weinheim, 1997.
7
8
9
(19) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds.
Part B: Applications in Coordination, Organometallic and Bioinorganic Chemistry, 6th
Edition; Wiley-VCH, Weinheim, 2009.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(20) Creighton, J.; Albrecht, M.; Hester, R.; Matthew, J. Chemical Physics Letters 1978,
55, 55–58.
(21) Omary, M. A.; Webb, T. R.; Assefa, Z.; Shankle, G. E.; Patterson, H. H. Inorg. Chem.
1998, 37, 1380–1386.
(22) Chu, Q.; Swenson, D. C.; MacGillivray, L. R. Angew. Chem. Int. Ed. 2005, 44, 3569–
3572.
(23) Dobrzan`ska, L.; Raubenheimer, H. G.; Barbour, L. J. Chem. Commun. 2005, 5050–
5052.
(24) Park, B. I.; Lee, J. W.; Lee, Y.-A.; Hong, J.; Jung, O.-S. Bull. Chem. Soc. Jpn. 2005,
78, 1624–1628.
(25) Kalf, I.; Braun, M.; Wang, Y.; Englert, U. CrystEngComm 2006, 8, 916–922.
(26) Liu, X.; Guo, G.-C.; Fu, M.-L.; Liu, X.-H.; Wang, M.-S.; Huang, J.-S. Inorg. Chem.
2006, 45, 3679–3685.
(27) Wang, Y.; Şerb, M.; Englert, U. Struct. Chem 2010, 21, 203–211.
(28) Wang, Y.; Englert, U. Inorg. Chim. Acta 2010, 363, 2539–2545.
(29) Kalf, I.; Mathieu, P.; Englert, U. New J. Chem. 2010, 34, 2491–2495.
(30) Schmidbaur, H.; Schier, A. Angew. Chem. Int. Ed. 2015, 54, 746–784.
20
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Page 21 of 25
Crystal Growth & Design
1
2
3
4
5
6
(31) Groom, C. R.; Allen, F. H. Angew. Chem. Int. Ed. 2014, 53, 662–671.
(32) CSD Version 5.36, including updates until Feb. 2016.
7
8
9
(33) Morishima, Y.; Young, D. J.; Fujisawa, K. Dalton Trans. 2014, 43, 15915–15928.
(34) Dias, H. R.; Diyabalanage, H. V. Polyhedron 2006, 25, 1655–1661.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(35) Mohamed, A. A.; Pérez, L. M.; Fackler Jr, J. P. Inorg. Chim. Acta 2005, 358, 1657–
1662.
(36) Veronelli, M.; Kindermann, N.; Dechert, S.; Meyer, S.; Meyer, F. Inorg. Chem. 2014,
53, 2333–2341.
(37) Puszynska-Tuszkanow, M.; Staszak, Z.; Misiaszek, T.; Klepka, M. T.; Wolska, A.;
Drzewiecka-Antonik, A.; Faltynowicz, H.; Cieslak-Golonka, M. Chem. Phys. Lett. 2014,
597, 94–98.
(38) Shannon, R. D. Acta Crystallogr. 1976, A32, 751–767.
(39) Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533–3539.
(40) Zhang, X.; Huang, Y.-Y.; Lin, Q.-P.; Zhang, J.; Yao, Y.-G. Dalton Trans. 2013, 42,
2294–2301.
(41) Lamberts, K.; Merkens, C.; Wang, R.; Englert, U.; Hons, D.; Grüter, S.; Guo, Y.;
Porsche, S.; Hamacher, A.; Bündgens, D.; Kuhlen, T. Z. Kristallogr. Suppl. 2012, 32,
117.
(42) O’Keeffe, M.; Peskov, M. A.; Ramsden, S. J.; Yaghi, O. M. Accts. Chem. Res. 2008,
41, 1782–1789.
(43) Dolomanov, O. V.; Blake, A. J.; Champness, N. R.; Schröder, M. J. Appl. Cryst. 2003,
36, 1283–1284.
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2
3
4
(44) Konkol, M.; Kondracka, M.; Kowalik, P.; Próchniak, W.; Michalska, K.; Schwedt, A.;
5
6
Merkens, C.; Englert, U. Appl. Cat. B: Environ. 2016, 190, 85–92.
7
8
9
(45) Charles, R. G. Organic Syntheses 1963, 4, 869.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
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41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(46) Ponomarova, V. V.; Komarchuk, V. V.; Boldog, I.; Krautscheid, H.; Domasevitch, K. V.
CrystEngComm 2013, 15, 8280.
(47) Mosby, W. L. J. Chem. Soc. 1957, 3997–4003.
(48) Drexler, E. J.; Field, K. W. J. Chem. Educ. 1976, 53, 392–393.
(49) Fokendt, M. M.; Weiss-Lopez, B. E.; Cbauvel Jr., P. J.; True, N. S. J. Phys. Chem.
1985, 89, 3347–3352.
(50) Martínez-Richa, A.; Díaz, G. M.; Joseph-Nathan, P. Appl. Spectrosc. 1996, 50, 1408–
1412.
(51) Abood, N. A.; Ajam, A. F. J. Chem. Soc. Pak. 1985, 7, 1–6.
(52) SAINT+ (version 7.68). Program for reduction of data collected on Bruker CCD area
detector diffractometer. 2009.
(53) Sheldrick, G. M. SADABS (version 2.03). Program for empirical absorption correction
of area detector data. 2004.
(54) Sheldrick, G. M. Acta Crystallogr. 2015, C71, 3–8.
(55) van der Sluis, P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194–201.
(56) Spek, A. L. Acta Crystallogr. 2009, D65, 148–155.
(57) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
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