Macrocyclic [M2L(μ-L')]+ complexes (M = Ni II, ZnII; L' = Cl- or RCO2 -) incorporating thiophenolate and phenylsulfonate donor units: Preparation, reactivity, structure, and stability

Article abstract of DOI:10.1002/ejic.201200036

The effect of de-tert-butylation on the coordinating properties of the 24-membered hexaazadithiophenolate macrocycle 13,27-bis(tert-butyl)-3,6,9,17,20, 23-hexaazatricyclo[23.3.1.11.15]triaconta-1(28),11,13,15(30),25,26-hexaene-29, 30-dithiol (H₂L¹) has been examined. For this purpose, a series of mixed-ligand Ni^II and Zn^II complexes of the de-tert-butylated hexaaminedithiophenolate macrocycle H₂L ²were prepared and characterized, namely, [Ni^II ₂L²(Cl)]⁺(1b), [Zn^II ₂L²(OAc)]⁺ (2b), [Ni^II ₂L²(O₂CCH=CHPh)]⁺ (3b), [Zn ^II₂L²(O₂CCH=CHPh)]⁺ (4b), [Ni^II₂L²(O₂CC₁₄H ₁₇)]⁺ (5b), [Zn^II₂L ²(O₂CC₁₄H₁₇)]⁺ (6b, in which C₁₄H₁₇CO₂^- =3,4-dimethyl-6-phenylcyclohex-3-enecarboxylate), [Ni^II ₂L²(O₂CC₆H₄-3-OMe)] ⁺ (7b), and [Zn^II₂L²(O ₂CC₆H₄-3-OMe)]⁺ (8b). The synthesis and characterization data for complexes [Ni^II₂L ⁴(O₂CC₆H₄-3-OMe)]⁺ (7d) and [Zn^II₂L⁴(O₂CC₆H ₄-3-OMe)]⁺ (8d), in which H₂L⁴ represents the S-oxygenated (bis-sulfonate) derivative of H₂L ² are also reported. The de-tert-butylated macrocycles H ₂L² (and H₂L⁴) behave essentially in the same fashion as H₂L¹ (and H₂L³) producing dinuclear mixed-ligand [M₂L(μ-L')]⁺ complexes with analogous bioctahedral core structures in similar good yields and reaction times. The spectroscopic features of the [M₂L ²(μ-L')]⁺ and [M₂L⁴(μ-L')] ⁺ complexes resemble those of theanalogous complexes supported by the tert-butylated derivatives H₂L¹ and H₂L ³. One major difference between the [M₂L ^1,3(μ-L')]⁺ and [M₂L^2,4(μ-L')] ⁺ complexes concerns the depth of the binding pocket of the compounds, which is significantly reduced upon removing the tert-butyl substituents. Another significant difference associated with removal of the tert-butyl substituent concerns the less pronounced differences of the relative stability constants for the carboxylato-bridged [M₂L ²(μ-O₂CR)]⁺ complexes {as compared to the [M₂L¹(μ-O₂CR)]⁺ complexes}. These stability differences can be qualitatively explained in terms of less pronounced intramolecular CH...π and/or van der Waals interactions in the de-tert-butylated complex systems. Copyright

Full text of DOI:10.1002/ejic.201200036

FULL PAPER
DOI: 10.1002/ejic.201200036
Macrocyclic [M2L(μ-LЈ)]+ Complexes (M = NiII, ZnII; LЈ = Cl– or RCO2 )
–
Incorporating Thiophenolate and Phenylsulfonate Donor Units: Preparation,
Reactivity, Structure, and Stability
Steffen Käss[a] and Berthold Kersting*[a]
Keywords: Nickel / Zinc / Macrocyclic ligands
The effect of de-tert-butylation on the coordinating proper-
ties of the 24-membered hexaazadithiophenolate macro-
cycle 13,27-bis(tert-butyl)-3,6,9,17,20,23-hexaazatricyclo-
[23.3.1.11.15]triaconta-1(28),11,13,15(30),25,26-hexaene-
29,30-dithiol (H2L1) has been examined. For this purpose, a
series of mixed-ligand NiII and ZnII complexes of the de-tert-
butylated hexaaminedithiophenolate macrocycle H2L2
were prepared and characterized, namely, [NiII2L2(Cl)]+
(1b), [ZnII2L2(OAc)]+ (2b), [NiII2L2(O2CCH=CHPh)]+ (3b),
tially in the same fashion as H2L1 (and H2L3) producing di-
nuclear mixed-ligand [M2L(μ-LЈ)]+ complexes with analo-
gous bioctahedral core structures in similar good yields and
reaction times. The spectroscopic features of the [M2L2(μ-
LЈ)]+ and [M2L4(μ-LЈ)]+ complexes resemble those of the
analogous complexes supported by the tert-butylated deriva-
tives H2L1 and H2L3. One major difference between the
[M2L1,3(μ-LЈ)]+ and [M2L2,4(μ-LЈ)]+ complexes concerns the
depth of the binding pocket of the compounds, which is sig-
nificantly reduced upon removing the tert-butyl substituents.
Another significant difference associated with removal of the
tert-butyl substituent concerns the less pronounced differ-
ences of the relative stability constants for the carboxylato-
bridged [M2L2(μ-O2CR)]+ complexes {as compared to the
[M2L1(μ-O2CR)]+ complexes}. These stability differences can
be qualitatively explained in terms of less pronounced intra-
molecular CH···π and/or van der Waals interactions in the de-
tert-butylated complex systems.
[ZnII2L2(O2CCH=CHPh)]+ (4b), [NiII2L2(O2CC14H17)]+ (5b),
–
[ZnII2L2(O2CC14H17)]+ (6b, in which C14H17CO2
=
3,4-dimethyl-6-phenylcyclohex-3-enecarboxylate), [NiII2L2-
(O2CC6H4-3-OMe)]+ (7b), and [ZnII2L2(O2CC6H4-3-OMe)]+
(8b). The synthesis and characterization data for complexes
[NiII2L4(O2CC6H4-3-OMe)]+ (7d) and [ZnII2L4(O2CC6H4-3-
OMe)]+ (8d), in which H2L4 represents the S-oxygenated
(bis-sulfonate) derivative of H2L2 are also reported. The de-
tert-butylated macrocycles H2L2 (and H2L4) behave essen-
Introduction
The coordination chemistry of Robson-type polyaza-di-
thiophenolate ligands has been actively investigated over
the past several years,[1–3] because they are ideally suited as
supporting ligands for the preparation of model com-
pounds for dinuclear metalloenzymes,[4] for the stabilization
of unusual metal oxidation states,[5] and to understand,
achieve, and control dinuclear metal reactivity.[6,7]
We have investigated the coordination chemistry of the
octadentate hexaaza-dithiophenolate ligand H2L1 in much
detail (Figure 1). The specific feature of H2L1 is its capsular,
cleftlike structure reminiscent of the “cone” conformation
of the calixarenes[8] that it adopts in its mixed-ligand com-
plexes of composition [MII2L1(μ-LЈ)]+, in which LЈ is the
coligand and MII a first-row transition-metal ion.[9,10] This
conformation of (L1)2– provides a deep binding cavity that
considerably influences the complex stability[11,12] and reac-
tivity.[13,14]
The unique reactivity features of these complexes[15,16]
led us to investigate potential routes to derivatives of H2L1
[a] Institut für Anorganische Chemie, Universität Leipzig,
04103 Leipzig, Germany
Figure 1. Top: Structure of the ligands H2L1 and H2L2. Bottom: Per-
Fax: +49-341-973-6199
E-mail: b.kersting@uni-leipzig.de
spective view of the structure of complexes of the type [M2L1(μ-LЈ)]+.
Eur. J. Inorg. Chem. 2012, 2389–2401
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that would provide more rigid and deeper binding cavities,
and many variants have now been prepared. The modifica-
tions included alteration of the N-methyl functions by sub-
stituents sterically more demanding than a methyl group
(e.g., R1 = Et, Pr),[17] installation of different N-alkyl
Results and Discussion
Preparation of the Ligands and Metal Complexes
The aminothiophenolate ligand H2L2 was synthesized
groups on the benzylic and central nitrogen atoms of the from 2-bromo-1,3-dimethylbenzene by a multistep pro-
linking diethylenetriamine units,[18] incorporation of pen- cedure as described in the literature.[16] The macrocycle was
dant donor R1 arms,[19] elongation of the diethylenetriam- isolated as the hexahydrochloride salt and stored under a
ine linker groups,[20] and S-oxygenation of the thiophenol- protective argon atmosphere due to its air sensitivity. The
ate sulfur atoms.[21,22] More recently, we have also been able synthesized complexes and their labels are depicted in Fig-
to alter the R2 substituents in the para position to the ure 2. All complexes of the de-tert-butylated macrocycle
thiophenolate sulfur atoms (e.g., R2 = H, Ph, 4-tBu- H2L2 are reported for the first time except 2b.[16] The metal
Ph).[16,23]
complexes supported by H2L1, namely, the chlorido-
This study focuses on the ligand H2L2, which represents (1a),[24] acetato- (2a),[25] cinnamato- (3a, 4a), and 3,4-di-
the de-tert-butylated derivative of the parent ligand H2L1. methyl-6-phenylcyclohex-3-enecarboxylato-bridged (5a, 6a)
We have prepared eight NiII and ZnII complexes of the li- NiII and ZnII complexes,[16] on the other hand, have all been
–
gand (L2)2– bearing Cl– and various RCO2 coligands 1b– reported previously and serve here merely as reference com-
8b (see Figure 2). Their properties are compared with the pounds.
analogous [M2L1(μ-LЈ)]+ complexes 1a–6a to establish
Complexes [Ni2L2(Cl)]+ (1b) and [Zn2L2(OAc)]+ (2b)
whether the choice of the substituent in the para position were readily obtained from stoichiometric complexation re-
of the thiophenolate head unit affects the structures and actions between the free ligand H2L2·6HCl and nickel(II)
properties of the complexes. The characterization of the chloride hexahydrate or zinc(II) acetate dihydrate, respec-
new compounds 7d and 8d, obtained by oxidation of 7b tively, in the presence of a solution of triethylamine in meth-
and 8b, respectively, is also reported.
anol (Scheme 1), followed by isolation as perchlorate salts.
–
Figure 2. Complexes studied in this work (C14H17CO2 = 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylate[26]).
Scheme 1. Synthesis of the [M2L2(μ-L)]+ and [M2L4(μ-L)]+ complexes 1b–8d (C14H17CO2 = 3,4-dimethyl-6-phenylcyclohex-3-enecarb-
–
oxylate).
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Nickel and Zinc Complexes with Macrocyclic Ligands
The latter were subjected to salt metathesis with NaBPh4 tion conditions to those given above. Conversion of the
to generate the corresponding tetraphenylborate salts. The thiophenolate head units in 7b to phenylsulfonate groups
complexation reactions appear to be unaffected by the in 7d was carried out in analogy to a previously described
choice of supporting ligand. The de-tert-butylated macro- method.[21] Thus, reaction of 7b with six equivalents of
cycle H2L2 reacts essentially in the same fashion as H2L1 meta-chloroperoxybenzoic acid (MCPBA) at 0 °C in MeCN
producing dinuclear mixed-ligand [M2L(μ-LЈ)]+ complexes generates a pale green solution, from which the lime-green
–
with analogous structures in similar good yields and reac- sulfonato complex 7d can be isolated as its ClO4 salt in
tion times.[17,27] The solubilities of 1b and 2b resemble those excellent yields (83%). It is worth noting that the 3-meth-
of 1a and 2a.
oxybenzoate coligand is not exchanged for the meta-chloro-
To obtain further pairs of analogous complexes sup- benzoate ion (which stems from the MCPBA) under these
ported by (L1)2– and (L2)2–, substitution reactions of 1b and conditions. It is indicative of a high kinetic inertness of the
2b were performed. Cinnamate and 3,4-dimethyl-6-phenyl- aminothiophenolate complex 7b and implies also that all
cyclohex-3-enecarboxylate were selected as coligands six S-oxygenation steps are not accompanied by complex
(Scheme 1). Treatment of the chlorido-bridged complex 1b disintegration. The oxidation of [Zn2L2(O2C-C6H4-3-
with a slight excess amount of the corresponding tri- OMe)]+ (8b) with MCPBA produces a product mixture
ethylammonium carboxylate in methanol at ambient tem- containing
[Zn2L4(O2C-C6H4-3-OMe)]+
(8d)
and
perature over the course of 2 h provided the carboxylato- [Zn2L4(O2C-C6H4-3-Cl)]+ (by NMR spectroscopy), the
bridged Ni2 complexes 3b and 5b in almost quantitative latter being produced by carboxylate exchange reactions
yield. It should be noted that these reactions are not simple with the meta-chlorobenzoate stemming from the MCPBA.
substitution reactions, because a simultaneous conforma- Attempts to purify this mixture failed. However, when
tional change of the supporting ligand (from structure type MCPBA was replaced by H2O2, the pure compound could
A present in 1b to type B in 3b and 5b) takes place (Fig- be isolated as its perchlorate salt in 40% yield.
ure 3). A similar behavior has been observed for complexes
All complexes are stable in air, both in solution and in
of H2L1.[18,28] This macrocycle adopts the bowl-shaped con- the solid state. They exhibit good solubility in polar aprotic
formation (type B) when LЈ is a large monoatomic (e.g., solvents such as acetonitrile, acetone, and dichloromethane,
–
S2–, SH–) or a multiatom bridging ligand (e.g., RCO2 ).[11,18] but are not very soluble in alcohols and are virtually insolu-
The change of the conformation can be traced back to a ble in water. The compounds gave satisfactory elemental
more favorable, less distorted octahedral coordination envi- analyses and were characterized by spectroscopic methods
ronment about the Ni2+ ions.[29]
(IR, UV/Vis, 1H and 13C NMR spectroscopy) and com-
The bridging acetate ion in the dizinc complex 2b could pounds 5b and 7d also by X-ray crystallography.
be replaced by cinnamate and 3,4-dimethyl-6-phenyl-
cyclohex-3-enecarboxylate ions as well to give complexes 4b
and 6b; however, a 10-fold excess amount of the entering
Spectroscopic Characterization of the Metal Complexes
carboxylate had to be used to drive these equilibrium reac-
tions to completion. Again, the reactivity of 2b is not mark-
Infrared Spectroscopy
edly different from that of 2a.[16]
Included in this study are the preparation and characteri-
FT infrared spectra of the dinuclear complexes were re-
zation data of the 3-methoxybenzoato-bridged complexes corded over the 4000–400 cm–1 range. Assignments of the
[M2L2(O2CC6H4-3-OMe)]+ [M = Ni (7b); M = Zn (8b)] and bands are based on comparisons between the individual
their oxidized derivatives [M2L4(O2CC6H4-3-OMe)]+ [M = complexes and on comparisons with the IR data for the
Ni (7d); M = Zn (8d)]. The thiophenolate complexes 7b and respective sodium carboxylates. Table 1 lists selected spec-
8b were obtained by substitution reactions between 3-meth- troscopic data. The corresponding data for analogous com-
oxybenzoate and 1b or 2b, respectively, using similar reac- plexes – if available – are included for comparison.[12]
Figure 3. Schematic representation of the two macrocycle conformations A and B in mixed-ligand [Ni2L1(μ-LЈ)]+ and [Ni2L2(μ-LЈ)]+
complexes.[18]
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Table 1. Selected spectroscopic data for compounds 1a–8d.[a]
Complex
νas, νs, Δ [cm–1][b]
λmax [nm] (ε [m–1 cm–1])[c]
Ref.
[18]
[Ni2L1(Cl)]+ (1a)
–
–
658 (41), 920 sh (59), 1002 (80)
662 (27), 920 sh (45), 1007 (62)
[Ni2L2(Cl)]+ (1b)
this work
[16]
[Zn2L1(OAc)]+ (2a)
1585, 1428, 157
1583, 1433, 150
1578, 1406, 172
1577, 1406, 171
1568, 1402, 166
1570, 1401, 169
1573, 1400, 173
1575, 1409, 166
1571, 1403, 168
1573, 1408, 165
1574, 1399, 175
1570, 1399, 171
1563, 1410, 153
1567, 1402, 165
–
–
[Zn2L2(OAc)]+ (2b)
this work
[12]
[Ni2L1(O2CCH=CHPh)]+ (3a)
[Ni2L2(O2CCH=CHPh)]+ (3b)
[Zn2L1(O2CCH=CHPh)]+ (4a)
[Zn2L2(O2CCH=CHPh)]+ (4b)
[Ni2L1(O2CC14H17)]+ (5a)[d]
[Ni2L2(O2CC14H17)]+ (5b)[d]
[Zn2L1(O2CC14H17)]+ (6a)[d]
[Zn2L2(O2CC14H17)]+ (6b)[d]
[Ni2L2(O2CC6H4-3-OMe)]+ (7b)
[Zn2L2(O2CC6H4-3-OMe)]+ (8b)
[Ni2L3(O2CC6H4-3-Cl)]+ (7c)
[Ni2L4(O2CC6H4-3-OMe)]+ (7d)
654 (27), 907 sh (40), 1125 (62)
658 (33), 908 sh (45), 1123 (69)
this work
[16]
–
–
this work
[16]
650 (29), 910 sh (29), 1112 (66)
650 (33), 909 sh (40), 1113 (61)
this work
[16]
–
–
this work
this work
650 (20), 909 sh (38), 1120 (45)
–
400 (47), 674 (14), 1126 (15)
400 (36), 678 (9), 1132 (12)
this work
[21]
this work
–
[1239 νs(RSO3 )]
1595, 1411, 184
[1202 νs(RSO3 )]
1567, 1400, 167
[21]
[Zn2L3(O2CCH3)]+ (8c)
–
–
–
[Zn2L4(O2CC6H4-3-OMe)]+ (8d)
this work
–
[1238 νs(RSO3 )]
–
–
–
[a] The complexes were isolated as ClO4 and BPh4 salts. [b] The data correspond to the ClO4 salts (see the Experimental Section for
–
–
the data of the BPh4 salts); Δ = νas – νs. [c] Solvent: CH3CN; concentration: approximately 10–3 m. [d] C14H17CO2 = 3,4-dimethyl-6-
phenylcyclohex-3-enecarboxylate.
The IR spectra of the chlorido-bridged complexes 1a[24] for these complexes. The chlorido complex 1b shows two
and 1b are almost superimposable. However, complex 1b weak absorption bands at 662 and 1007 nm that can be as-
3
3
3
exhibits an additional band at 773 cm–1 that can be attrib- signed to the spin-allowed A2g Ǟ T1g (ν2) and A2g
Ǟ
uted to a δ(CH) bending vibration of a 1,2,3-trisubstituted 3T2g (ν1) transitions of a nickel(II) (S = 1) ion.[38] There is
arene ring.[30] The asymmetric [νas(CO)] and symmetric also a weak shoulder around 920 nm attributable to a spin-
3
1
stretching [νs(CO)] frequencies and their separation Δ [=νas- forbidden A2g Ǟ Eg(D) transition that is indicative of a
(CO) – νs(CO)] can be used as spectroscopic probes to significant distortion from octahedral symmetry.
identify the carboxylate binding mode.[31–33] In the present
Upon going from the chlorido complex 1b to the carbox-
study, the νas(CO) stretching frequencies are observed in a ylato complexes 3b, 5b, and 7b, the coordination environ-
narrow range (1583–1567 cm–1) as are the νs(CO) fre- ment of the NiII ions changes from N3S2Cl to N3S2O.
quencies (1428–1399 cm–1). The carboxylate stretching fre- Therefore, a shift of the ν1 transition – which is related to
quencies of the complexes supported by (L2)2– are very sim- the octahedral splitting parameter Δo (Δo [cm–1] = 107/ν1
ilar to those supported by (L1)2–, which is indicative of a [nm])[34] – can be expected. This is indeed the case. The ν1
–
common μ1,3-RCO2 bridging mode.[34,35] The infrared transitions are redshifted by about 110–120 nm relative to
spectrum of 7d displays a strong band at 1239 cm–1, a value 1b. The ν1 and ν2 values of the three pairs of analogous
–
typical for a sulfonate group [ν(RSO3 )].[36] The carboxylate [Ni2L1(O2CR)]+ and [Ni2L2(O2CR)]+ complexes are not
stretches at 1567 cm–1 [νas(CO)] and 1402 cm–1 [νs(CO)] re- markedly different from one another. A dependence of the
semble those of the parent complex 7b, which suggests that energy of these transitions on the substituent in the 4-posi-
the meta-methoxybenzoate moiety in 7d is also present in tion of the thiophenolate ligand is not significant.
the μ1,3-bridging mode. The IR spectrum of the dizinc com-
The electronic absorption spectrum of the pale green sul-
plex 8d compares well with that of 7d, which shows distinct fonato complex 7d lacks the intense thiolate-to-NiII charge-
bands for the bridging meta-methoxybenzoate (1567 and transfer (CT) transitions seen in 7b. This is in agreement
1402 cm–1) and sulfonate groups (1238 cm–1). The IR data with its formulation. The lack of the CT transitions in 7d
of 7d and 8d are similar to the sulfonate complexes 7c and on the other hand, should facilitate an observation of the
8c coligated by 3-chlorobenzoate and acetate groups.[21] spin-allowed A2g(F) Ǟ T1g(P) (ν3) transition [typical for
3
3
Again a dependence of the IR absorptions of the coligands NiII (S = 1 ions) in an octahedral coordination environ-
on the choice of the supporting ligand is not significant.
ment]. Indeed, there is a weak absorption at 400 nm that
can be attributed to this d–d transition. Values of 400 nm
for the ν3 transition are typical for octahedral NiIIN3O3
chromophores.[21]
UV/Vis Spectroscopy
Electronic absorption spectra for the paramagnetic nickel
complexes[37] were registered in acetonitrile in the 300–
1600 nm range. The UV/Vis spectra of the chlorido-bridged
nickel(II) complexes 1a and 1b are very similar, which is
NMR Spectroscopy
To determine the solution structures, the zinc complexes
indicative of analogous face-sharing bioctahedral structures were subjected to H and 13C NMR spectroscopic studies.
1
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Nickel and Zinc Complexes with Macrocyclic Ligands
1
1
Figure 4. H NMR spectra of 2a (top) and 2b (bottom) in CD3CN at 295 K (4.5–0.6 ppm). The box shows the H NMR spectra in the
7.15–6.80 ppm regions. The resonances for the complexes are listed in Table 2 and Table 3.
1
1
The H and 13C NMR spectra were recorded for sample
The H and 13C NMR spectroscopic data of zinc com-
solutions in CD3CN at ambient temperature. Figure 4 plexes 4b and 8b are also in accord with a C2v-symmetric
1
shows the H NMR spectrum of the acetato-bridged com- structure (type B). Note, however, that 6b reveals only 15
plex 2b, which is representative of all the diamagnetic zinc 13C NMR spectroscopic signals and thus only half as many
thiophenolate complexes 4b, 6b, and 8b. The 1H NMR spec- signals as expected for a C1-symmetric species (C1 sym-
trum of 2a is displayed for comparative purposes. Tables 2 metry imparted on the complex by the asymmetric co-
1
and 3 list the H and 13C NMR spectroscopic data. The ligand, which has two stereo centers). The observation of
NMR spectroscopic data for 2a, 4a, 6a, and 8a are included the 15 signals implies a fast rotation of the carboxylate resi-
for comparative purposes.
due about the O2C–R bond, which leads to a time-averaged
1
The H NMR spectrum of complex 2b displays one sig- C2-symmetric structure on the NMR spectroscopy time-
nal set indicative of the presence of a single isomer in solu- scale. A time-averaged C2 symmetry is also evident in the
tion. The six N-methyl groups give rise to two singlets 1H NMR spectrum, particularly because the four CH3
(4ϫC5H3, 2ϫC6H3), a clear indication for a C2v-symmetric groups on the benzylic nitrogen atoms give rise to just two
(type B, Figure 3) structure of the [Zn2L2(OAc)]+ cation. signals (instead of four for a species with a nonrotating
The 13C NMR spectrum is also in agreement with structure carboxylate residue). A similar behavior was reported for
B in that it reveals only 9 signals for the 30 carbon atoms the parent zinc complex 6a.[16]
of the [Zn2L2]2+ fragment. The methyl protons of the acet-
The H NMR spectrum of the sulfonate complex 8d dif-
1
ate group are observed at δ = 0.82 ppm, significantly high- fers significantly from that of its parent complex 8b. Par-
field shifted (Δδ = –1.01 ppm) relative to free NaOAc (δ ticularly affected are the chemical shifts of the aromatic
=1.83 ppm). A similar high-field shift was observed for protons of this complex (Figure 5). A clear shift pattern is
2a.[25] The high-field shift is attributable to the fact that the detectable. Thus, upon oxygenation the aromatic protons of
CH3 protons of the acetate group are located above the cen- the supporting ligand (C3H and C4H) are all low-field
ter of the two phenyl rings of H2L2 in the shielding re- shifted, whereas the ones of the coligand are all shifted to
gion.[21]
higher field.
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1
Table 2. Selected H NMR spectroscopic data for zinc complexes 2a–8d.[a,b]
[a] The data refer to the perchlorate salts. Resonances for the supporting ligands are assigned according to the structure shown in
Figure 4. [b] Solvent: CD3CN.
complexes – also has to be taken into account. As is shown
below, the S-oxygenation leads to a drastic decrease of the
folding angle between the two aryl residues of the support-
ing ligand by approximately 45°. This in turn leads to much
shorter distances between the coligand and the aryl rings of
the macrocycle, such that the coligand senses a larger ring
current. One would expect that this effect is larger for the
ortho protons C3HЈ and C7HЈ (as they are closer to the aryl
rings of H2L4) in the coligands. This is indeed the case. The
C3HЈ and C7HЈ signals are shifted by approximately
0.4 ppm. This value should be compared with much smaller
shifts of only 0.10 and 0.02 ppm for the C6HЈ (meta) and
Figure 5. 1H NMR resonances in the aromatic region (7.2–
C5HЈ (para) signals, respectively.
6.4 ppm) of the 1H NMR spectra of complexes 8b (top) and 8d
(bottom). The arrows indicate the up-field and down-field shifts of
the resonances of the supporting ligand (C3H, C4H) and coligand
(C5HЈ, C6HЈ, C7HЈ, C3HЈ).
Description of the Crystal Structures
Single crystals of X-ray quality were obtained for the
The shift pattern noted above is not just a result of the perchlorate salt of complex 5b and the tetraphenylborate
conversion of the thiophenolate to sulfonate groups. The salt of complex 7d. Ball-and-stick models of the structures
structural changes – that is the more pronounced folding of of the two complexes are provided in Figures 6 and 8,
the phenyl rings of the supporting ligand in the sulfonate respectively. Table 4 lists selected bond lengths and angles.
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Eur. J. Inorg. Chem. 2012, 2389–2401

Nickel and Zinc Complexes with Macrocyclic Ligands
Table 3. Selected 13C NMR spectroscopic data for zinc complexes
Table 4. Selected bond lengths [Å] and angles [°] in complexes
2a–8d.[a,b]
5a,[16] 5b, 7c,[21] and 7d.
2b[16] [2a]
4b [4a][16]
6b [6a][16]
8b
8d
5a[16]
5b
7c[21]
7d
[Zn2L2]2+ or [Zn2L1]2+ fragment
Ni1–O1/O7
Ni1–N1
Ni1–N2
2.043(2)
2.285(2)
2.173(2)
2.223(2)
2.480(1)
2.4487(8)
1.994(2)
2.265(2)
2.159(2)
2.293(2)
2.4982(7)
2.4256(9)
2.233(2)
1.999(2)
2.345(2)
2.141(2)
2.204(2)
2.479(1)
2.456(1)
2.016(2)
2.238(2)
2.155(2)
2.288(2)
2.493(1)
2.442(2)
2.229(2)
2.008(2)
2.468(1)
1.765(2)
3.473(1)
2.040(5)
2.230(7)
2.136(6)
2.265(6)
2.111(5)
2.073(5)
2.009(5)
2.266(6)
2.131(7)
2.254(7)
2.102(5)
2.109(5)
2.214(7)
2.024(5)
2.099(5)
1.783(8)
4.584(2)
1.986(3)
2.263(4)
2.129(4)
2.231(4)
2.048(3)
2.098(3)
2.004(3)
2.268(4)
2.119(3)
2.215(3)
2.106(3)
2.075(3)
2.204(4)
1.995(3)
2.082(3)
1.784(3)
4.535(1)
C1 147.8 [143.62] 147.16 [143.2]
C2 136.2 [135.25] 136.24 [134.9]
147.5 [143.7]
135.7, 135.9
[135.3, 135.7]
131.7, 132.0
[128.8, 128.9]
123.1 [146.1]
47.2, 46.9
147.40 145.07
135.57 133.87
Ni1–N3
Ni1–S1/O1
Ni1–S2/O5
Ni2–O2/O8
Ni2–N4
Ni2–N5
Ni2–N6
C3 132.3 [128.95] 131.82 [128.7]
C4 123.2 [145.98] 122.78 [145.8]
131.76 132.17
122.79 127.76
47.11 43.78
C5 47.2 [46.84]
46.94 [46.9]
[46.6, 47.1]
49.9 [49.9]
57.9, 58.7
C6 50.2 [50.08]
C7 58.4 [58.59]
49.79 [49.8]
58.36 [58.4]
49.84 44.00
58.42 51.51
Ni2–S1/O2
Ni2–S2/O4
Ni–N[a]
[58.0, 58.6]
59.4, 60.0
[59.5, 60.1]
64.1, 64.5
C8 60.0 [59.74]
C9 64.7 [64.59]
59.61 [59.6]
64.32 [64.4]
59.73 56.11
64.31 62.86
Ni–O(carboxylate)[a] 2.019(2)
Ni–S/O(sulfonate)[a]
C–S[a]
2.463(1)
1.763(2)
3.487(1)
[64.6, 64.9]
– [34.5]
– [31.6]
Ni···Ni
C10 – [34.64]
C11 – [31.68]
– [34.3]
– [31.4]
–
–
–
–
O1/O7–C39–O2/O8
Ni1–S1–Ni2
Ni1–S2–Ni2
Ph/Ph[b]
126.88(18)
88.92(3)
91.33(2)
86.5
126.9(2)
88.62(4)
90.35(4)
80.0
129.4(7)
–
–
44.5
126.9(4)
–
–
44.2
Coligand
C1 175.5 [174.97] 169.71 [169.6]
39.5 [40.0]
28.9 [29.5]
124.3 [123.8]
125.3 [126.0]
32.0 [31.5]
48.1 [48.1]
168.97 166.28
137.83 134.38
C2 19.1 [22.94]
125.27 [125.2]
128.16 [128.1]
129.63 [129.5]
130.04 [129.8]
140.22 [139.9]
C3
C4
C5
C6
C7
C8
C9
–
–
–
–
–
–
–
114.47 113.28 [a] Average values. [b] Folding angle between the normals of the
160.40 158.02 planes of the two phenyl rings of the supporting ligand.
117.54 117.46
129.74 129.40
122.01 122.12
55.63 54.59
obsc.[c] [118.3] 177.6 [178.0]
Selected crystallographic data are given in Table 6; see the
CIF files for complete listings. The metrical parameters of
complexes 5a[16] and [Ni2L3(O2CC6H4-3-Cl)]+,[21] in which
(L3)2– represents the amine-sulfonate derivative of (L1)2–,
have been included for comparative purposes. A common
labeling scheme for the core structures of analogous com-
plexes was applied to facilitate structural comparisons.
–
–
–
–
–
–
18.9 [19.0]
19.0 [19.4]
147.0 [146.5]
126.5 [126.5]
127.7 [127.8]
129.0 [129.3]
–
–
–
–
–
–
–
–
–
–
C10 –
C11 –
C12 –
C13 –
[a] The data refer to the perchlorate salts. Resonances for the co-
ligands and supporting ligands are assigned according to the struc-
tures shown in Figure 4 and Table 2. [b] Solvent: CD3CN. [c] obsc.
= obscured signal.
Description of the Crystal Structure of 5b[ClO4]·MeCN
¯
This salt crystallizes in the triclinic space group P1. The
structure consists of well-separated [Ni2L2(μ-3,4-dimethyl-
–
6-phenylcyclohex-3-enecarboxylate)]+
cations,
ClO4
anions, and MeCN solvate molecules. There are no unusual
features as far as bond lengths and angles around the di-
valent Ni atoms are concerned. The average Ni–N, Ni–S,
and Ni–O distances are 2.229(2), 2.468(1), and 2.008(2) Å,
respectively. Similar values were observed in the parent
complex 5a [Ni–N 2.233(2) Å; Ni–S 2.463(1) Å; Ni–O
2.019(2) Å][16] and other carboxylato-bridged Ni2 com-
plexes of (L1)2–.[28,29,41] The mean C–S bond lengths in 5a
and 5b are identical within experimental error. These C–S
bonds are not affected upon conversion of the tBu substitu-
ent to a H substituent.
It is worth noting that the phenyl and carboxylate groups
of the coligand in 5b assume bis-axial (ax,ax) positions, a
conformation that is also seen for the parent complex 5a.[16]
Generally, adjacent cyclohexene-ring substituents assume a
more stable bis-equatorial (eq,eq) conformation (Fig-
ure 7).[42,43] The presence of the ax,ax conformation is at-
tributable to confinement, for example, to the form- (and
size-) selective binding constraints of the cleftlike [Ni2L2]2+
structure. A coordination of the cyclohexenecarboxylate in
the alternative eq,eq conformation would inevitably lead to
Figure 6. Molecular structure of the [Ni2L2(μ-3,4-dimethyl-6-phen-
ylcyclohex-3-enecarboxylate)]+ cation in crystals of 5b[ClO4]·
MeCN. Hydrogen atoms are omitted for clarity.
Eur. J. Inorg. Chem. 2012, 2389–2401
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2395

S. Käss, B. Kersting
FULL PAPER
Figure 7. Top: The two possible eq,eq and ax,ax conformations of 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylic acid. Bottom: Represen-
tation of the solid-state structures of 5a and 5b with the 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylate coligand in the ax,ax conforma-
tion, and the structure of the hypothetical complex 5bЈ with the cyclohexenecarboxylate in an alternative eq,eq conformation. Steric
interactions between supporting ligands and coligands are indicated by double arrows. The primed C and O atoms in structure 5a define
the dihedral angle τ that is used in the text.
repulsive interactions between the phenyl rings of the co-
ligand and the backbone of the supporting ligand as indi-
cated in Figure 7 for a hypothetical structure of 5bЈ. This
stabilization of unusual ligand conformations by confine-
ment is of general interest in supramolecular coordination
chemistry.[44]
The only other significant structural differences between
complexes 5a and 5b concern a smaller twist angle of the
carboxylate substituent with respect to the cyclohexene ring
in 5b (expressed by the dihedral angle τ, see legend to Fig-
ure 7); and a smaller folding angle between the planes
through the two aryl rings of the supporting ligand in 5b.
The smaller τ value in 5b of 163.5° (O2–C31–C32–C33) as
opposed to 174.8° (O2–C39–C40–C45) in 5a can be attrib-
uted to the absence of repulsive interactions between the
tBu groups of the supporting ligand and CH3 groups of the
coligand (indicated by the hypothetical structure of 5bЈ in
Figure 7). The same arguments can be invoked to explain
the decrease of the folding angle between the two aryl rings
from 86.5° in 5a to 80.0° in 5b.
Figure 8. Molecular structure of the [Ni2L4(μ-O2CC6H4OMe)]+
cation (ball-and-stick model) in crystals of 7d[BPh4]·
0.5MeCN·0.5H2O. Hydrogen atoms are omitted for clarity.
Description of the Crystal Structure of
7d[BPh4]·0.5MeCN·0.5H2O
The crystal structure of 7d[BPh4]·0.5MeCN·0.5H2O con-
firms the formulation of 7d as a dinuclear nickel(II) com-
plex supported by the deprotonated macrocyclic amine-sul- is of length 1.995(3) Å and significantly shorter than the
fonate ligand (L4)2–. The crystal structure consists of dis- average Ni–Osulfonate bonding length of 2.082(3) Å, thereby
–
crete [Ni2L4(O2CC6H4-3-OMe)]+ cations, BPh4 anions, indicating stronger Ni–Ocarboxylate bonds. This is not sur-
MeCN, and H2O solvate molecules. Figure 8 provides a prising given that carboxylate ligands are generally much
ball-and-stick model of the structure of cation 7d. Table 4 better donor ligands than sulfonate ligands.[45] The mean
lists selected bond lengths and angles. The carboxylate and Ni–N and Ni–O distances at 2.204(2) and 2.053(3) Å,
both sulfonate groups bridge the divalent Ni ions in a μ1,3 respectively, resemble those in the amine-sulfonate complex
fashion at a Ni···Ni distance of 4.535(1) Å, a distance ap- [Ni2L3(O2CC6H4-3-Cl)]+ (7c), in which (L3)2– represents
proximately one Å larger than in the thiophenolate com- the amine-sulfonate derivative of (L1)2– [2.214(7),
plexes. The amine nitrogen atoms of (L4)2– occupy the re- 2.074(5) Å].[21]
maining positions and complete the pseudo-octahedral
Of note is a very acute angle of 44.2° at which the best
N3O3 coordination spheres. The mean Ni–Ocarboxylate bond planes through the two phenyl rings of the amine-sulfonate
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Eur. J. Inorg. Chem. 2012, 2389–2401

Nickel and Zinc Complexes with Macrocyclic Ligands
macrocycle intersect. A similar value of 44.5° is observed in the binding constant, the maximum value being reached for
7c, the only other example of a Ni2 complex of a Robson- the benzoato-bridged complexes. However, the stability dif-
type amino-sulfonate complex that has been characterized ferences are much less pronounced in the complexes of the
crystallographically so far.[21] The two complexes are essen- de-tert-butylated macrocycle (L2)2–. This observation can be
tially isostructural and the corresponding bond lengths and traced back to the less extensive CH···π or van der Waals
angles lie within very narrow ranges. Based on the NMR interactions in the [Zn2L2(O2CR)]+ complexes. In contrast
spectroscopic data, a similar decrease of the folding angle to 7d, for example, complex 7c reveals short distances (3.23
is likely for the zinc complex 8d.
and 3.31 Å) between the coligand and the tert-butyl protons
of the supporting macrocycle.
Complex Stability
Conclusion
We decided to determine the relative stability constants
of some analogous zinc complexes supported by H2L1 and
H2L2 to probe whether the presence or absence of the two
tert-butyl substituents affects the thermodynamic stability
of the complexes. For this purpose the relative stability con-
stants (Krel) of the formiato-, acetato-, palmitato-, chloro-
acetato-, and benzoato-bridged zinc complexes 2a, 2b, and
9a–12b were determined by the exchange experiments in
Equation (1).
In summary, a series of novel nickel(II) and zinc(II) com-
plexes supported by macrocyclic amine thiophenolate and
amine phenylsulfonate ligands have been synthesized and
characterized, namely, [NiII2L2(Cl)]+ (1b), [ZnII2L2(OAc)]+
(2b), [NiII2L2(O2CCH=CHPh)]+ (3b), [ZnII2L2(O2CCH=
CHPh)]+ (4b), [NiII2L2(O2CC14H17)]+ (5b), [ZnII2L2-
(O2CC14H17)]+ (6b, in which C14H17CO2– = 3,4-dimethyl-6-
phenylcyclohex-3-enecarboxylate),
[NiII2L2(O2CC6H4-3-
OMe)]+ (7b), [ZnII2L2(O2CC6H4-3-OMe)]+ (8b), [NiII2L4-
(O2CC6H4-3-OMe)]+ (7d), and [ZnII2L4(O2CC6H4-3-
OMe)]+ (8d). The de-tert-butylated macrocycles H2L2 and
H2L4 behave essentially in the same fashion as H2L1 (and
H2L3) by producing dinuclear mixed-ligand [M2L2(μ-LЈ)]+
complexes with analogous calixarene-like structures as
shown by X ray crystallography and NMR spectroscopy.
The major difference between the [M2L1(μ-LЈ)]+ and
[M2L2(μ-LЈ)]+ complexes concerns the size of the binding
pocket of the compounds, which is greatly reduced upon
going from H2L1 to H2L2. This causes significant structural
differences between complexes 5a and 5b, for instance,
through a smaller twist angle of the carboxylate substituent
with respect to the cyclohexene ring in 5b, and a smaller
folding angle between the planes through the two aryl rings
of the supporting ligand in 5b. The smaller τ value in 5b of
163.5° (O2–C31–C32–C33) as opposed to 174.8° (O2–C39–
C40–C45) in 5a can be attributed to the absence of repulsive
interactions between the tert-butyl groups of the supporting
ligand and CH3 groups of the coligand. Another significant
difference associated with removal of the tert-butyl substit-
uents concerns the less pronounced differences of the rela-
tive stability constants for the carboxylato-bridged
[M2L2(μ-O2CR)]+ complexes {as compared to the [M2L1(μ-
O2CR)]+ complexes}. These stability differences can be ex-
plained in terms of less pronounced intramolecular CH···π
and/or van der Waals interactions in the de-tert-butylated
complex systems.
The reactions were performed in a 1:1 molar ratio, and
the equilibria are attained within sample preparation. The
relative concentrations of the complexes were determined
by integration of the 1H NMR spectroscopic signals for the
methyl protons for the free acetate ion (δ = 1.83 ppm) and
the acetato ligand of complexes 2a (δ = 0.85 ppm) or 2b (δ =
0.86 ppm), respectively. The relative stability constants were
then calculated with the mass action law in Equation (2).
Table 5 lists the stability constants (relative to 2a or 2b)
and the pKa values of the corresponding carboxylic ac-
ids.[46] As can be seen, the equilibrium constants differ by
as much as two orders of magnitude and do not correlate
with the pKa values of the carboxylates. The complex sta-
bility constants can be ranked as follows 9a Ͻ 2a Ͻ 11a Ͻ
10a Ͻ 12a for the [Zn2L1(O2CR)]+ complexes and 9b Ͻ 11b
Ͻ 2b Ͻ 10b Ͻ 12b for the [Zn2L2(O2CR)]+ complexes. For
both series, a clear trend is seen. Thus, the larger the or-
–
ganic residue R of the carboxylate anion (RCO2 ) the larger
Table 5. Relative stability constants of the zinc complexes 2a, 2b,
and 9a–12b.
Experimental Section
Coligand
pKa
Krel
ΔΔG[a]
Krel
ΔΔG[a]
(2a) [kJmol–1] (2b)
[kJmol–1]
General: Unless otherwise noted the preparations were carried out
under an argon atmosphere by using standard Schlenk techniques.
The ligand H2L2 [24] and 3,4-dimethyl-6-phenylcyclohex-3-enecar-
boxylic acid[47] were prepared as described in the literature. Melting
points were determined in capillaries. The infrared spectra were
recorded as KBr discs using a Bruker VECTOR 22 FTIR spectro-
–
9a,b HCO2
3.75
0.10
7.50
1.10
9.30
–5.71
5.00
0.24
5.53
0.20
3.30
0.30
3.75
–4.00
2.96
–2.98
3.28
–
10a,b C15H31CO2 5.70
–
11a,b CH2ClCO2 2.82
–
12a,b PhCO2
4.20
[a] Krel = exp(ΔΔG/RT).
Eur. J. Inorg. Chem. 2012, 2389–2401
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2397

S. Käss, B. Kersting
FULL PAPER
–
photometer. Electronic absorption spectra were recorded on a Ja-
sco V-570 UV/Vis/near-IR spectrophotometer. ESI-FTICR mass
spectra were recorded with a Bruker-Daltronics Apex II instrument
using dilute CH2Cl2/MeOH solutions. NMR spectra were recorded
on a Bruker AVANCE DPX-200, a Varian Unity 300, or Bruker
400 and 500 spectrometers at 295 K. Chemical shifts refer to sol-
vent signals.
(s) [νs(RCO2 )], 1366 (w), 1351 (w), 1337 (w), 1298 (w), 1267 (w),
1202 (w), 1171 (w), 1092 (s), 1040 (s), 1003 (w), 965 (m), 921 (m),
894 (w), 868 (w), 828 (m), 806 (w), 765 (m), 726 (w), 708 (w), 687
(w), 670 (w), 622 (m), 599 (w), 564 (w), 537 (w), 524 (w), 485 (w),
436 (w), 415 (w) cm–1.
[Zn2L2(μ-O2CCH=CHPh)][ClO4] (4b[ClO4]): A solution of trieth-
ylammonium cinnamate [prepared in situ from cinnamic acid
(524 mg, 3.54 mmol) and triethylamine (179 mg, 1.77 mmol)] in
methanol (5 mL) was added to a solution of 2b[ClO4] (300 mg,
0.354 mmol) in methanol (50 mL). After stirring for 12 h at ambi-
ent temperature, the solvent was removed under reduced pressure
to a final volume of approximately 10 mL. The colorless solid was
isolated by filtration and washed with cold methanol (5 mL). To
remove traces of unreacted starting compound 2b[ClO4], the prod-
uct was treated again with a tenfold molar excess amount of trieth-
ylammonium cinnamate as described above. Recrystallization from
a mixed ethanol/acetonitrile solvent system gave the title com-
pound in an analytically pure form; yield 240 mg (73%); m.p. 325–
328 °C (dec.). C39H55ClN6O6S2Zn2 (934.25): calcd. C 50.14, H
5.93, N 9.00, S 6.86; found C 49.66, H 6.07, N 8.97, S 7.01. IR
Caution! Perchlorate salts of transition-metal complexes are hazard-
ous and may explode. Only small quantities should be prepared and
handled with great care.
[Ni2L2(μ-Cl)][ClO4] (1b[ClO4]): A solution of NiCl2·6H2O (183 mg,
0.77 mmol) in methanol (5 mL) was added to a solution of
H2L2·6HCl (0.300 g, 0.385 mmol) in methanol (20 mL) followed by
triethylamine (0.311 g, 3.08 mmol). After stirring for 2 d at room
temperature, solid LiClO4·3H2O (1.00 g, 6.23 mmol) was added.
The yellow solid was filtered and washed with diethyl ether. An
analytical sample was obtained by recrystallization from
acetonitrile; yield 0.221 g (71%); m.p. 341–342 °C (dec.).
C30H48Cl2N6Ni2O4S2 (809.16): calcd. C 44.53, H 5.98, N 10.39, S
7.93; found C 44.03, H 6.41, N 10.16, S 7.88. IR (KBr): ν = 3011
(m), 2967 (m), 2860 (s), 2811 (m), 1633 (w), 1486 (m), 1461 (s),
1418 (m), 1394 (w), 1368 (w), 1355 (w), 1342 (w), 1290 (w), 1260
(w), 1209 (w), 1198 (w), 1180 (w), 1095 (s) ν3(ClO4 ), 1030 (w), 957
(w), 932 (m), 921 (m), 897 (w), 832 (w), 822 (m), 795 (w), 773 (s),
˜
(KBr): ν = 2991 (m), 2860 (s), 1641 (m) [ν(C=C)], 1570 (s)
[νas(CO)], 1485 (m), 1460 (s), 1433 (s), 1401 (s) [νs(CO)], 1367 (m),
1352 (w), 1333 (w), 1312 (w), 1296 (m), 1269 (m), 1204 (w), 1172
(w), 1093 (vs) [ν3(ClO4 )], 1043 (s), 1003 (m), 969 (m), 917 (m), 893
(w), 871 (w), 825 (s), 803 (w), 765 (s), 727 (w), 707 (w), 687 (w),
666 (w), 623 (s) [ν4(ClO4 )], 594 (w), 561 (w), 535 (w), 522 (w), 483
˜
–
–
–
753 (w), 735 (w), 671 (w), 651 (w), 623 (s) ν4(ClO4 ), 570 (w), 544
–
(w), 496 (w), 459 (w), 422 (w) cm–1.
(w), 454 (w), 409 (w) cm–1.
[Zn2L2(μ-OAc)][ClO4] (2b[ClO4]): A solution of Zn(OAc)2·2H2O
(283 mg, 1.28 mmol) in methanol (5 mL) was added to a solution
of H2L2·6HCl (500 mg, 0.643 mmol) in methanol (20 mL). A solu-
tion of triethylamine (520 mg, 5.14 mmol) in methanol (5 mL) was
added and the resulting clear solution was stirred for 2 d at room
temperature. Solid LiClO4·3H2O (1.00 g, 6.23 mmol) was then
added. The resulting colorless precipitate was isolated by filtration,
washed with methanol, and dried in air. The product was recrys-
tallized from an acetonitrile/ethanol mixture; yield 468 mg,
0.550 mmol (86%); m.p. 320–321 °C. C32H51ClN6O6S2Zn2·H2O
(846.15 + 18.02): calcd. C 44.48, H 6.18, N 9.73, S 7.42; found C
[Ni2L2(μ-O2CC14H17)][ClO4] (5b[ClO4]): A solution of triethylam-
monium 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylate [pre-
pared in situ from 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylic
acid (58 mg, 0.25 mmol) and triethylamine (25.3 mg, 0.25 mmol)]
in methanol (5 mL) was added to a solution of 1b[ClO4] (100 mg,
0.124 mmol) in methanol (50 mL). After stirring for 2 h at ambient
temperature, the product was precipitated by the addition of solid
LiClO4·3H2O (301 mg, 1.87 mmol). The green microcrystalline so-
lid was isolated by filtration, washed with cold methanol (2 mL),
and recrystallized once from
a mixed ethanol/acetonitrile
solvent system; yield 89 mg (72%); m.p. 289–290 °C (dec.).
C45H65ClN6Ni2O6S2 (1003.00): calcd. C 53.89, H 6.53, N 8.38, S
44.10, H 5.81, N 9.69, S 7.95. IR (KBr): ν = 2979 (s), 2993 (s),
˜
2851 (s), 2805 (s), 1583 (s) [νas(OAc)], 1460 (s), 1433 (s) [νs(OAc)],
1395 (m), 1365 (m), 1350 (w), 1312 (w), 1295 (m), 1269 (m), 1203
(w), 1171 (m), 1095 (vs) [ν(ClO4)], 1042 (s), 1060 (s), 1003 (m), 959
(w), 915 (m), 894 (w), 824 (m), 749 (w), 728 (w), 663 (m), 622 (s),
561 (m), 533 (w), 523 (w), 482 (w), 411 (w) cm–1. The tetraphen-
ylborate salt, [Zn2L2(OAc)]BPh4 (2b[BPh4]), was prepared by add-
ing NaBPh4 (342 mg, 1.00 mmol) to a solution of 2b[ClO4] (85 mg,
0.100 mmol) in methanol (40 mL). The colorless microcrystalline
solid was isolated by filtration, washed with ethanol, and dried in
air.
6.39; found C 53.75, H 6.44, N 8.13, S 6.02. IR (KBr): ν = 2996
˜
(m), 2856 (s), 1575 (s) [νas(CO)], 1488 (w), 1461 (s), 1425 (s), 1409
(m) [νs(CO)], 1309 (w), 1297 (w), 1266 (w), 1201 (w), 1172 (w),
1094 (s) [ν3(ClO4)], 1041 (m), 1002 (m), 956 (w), 917 (m), 893 (w),
827 (m), 805 (w), 770 (m), 749 (w), 717 (w), 700 (w), 670 (w), 623
(s), 564 (w), 536 (w) cm–1.
[Zn2L2(μ-O2CC14H17)][ClO4] (6b[ClO4]): A solution of triethylam-
monium 3,4-dimethyl-6-phenylcyclohex-3-encarboxylate [prepared
in situ from 3,4-dimethyl-6-phenylcyclohex-3-enecarboxylic acid
[Ni2L2(μ-O2CCH=CHPh)][ClO4] (3b[ClO4]): A solution of trieth- (272 mg, 1.18 mmol) and triethylamine (119 mg, 1.18 mmol)] in
ylammonium cinnamate [prepared in situ from cinnamic acid
(37 mg, 0.25 mmol) and triethylamine (25.3 mg, 0.25 mmol)] in
methanol (5 mL) was added to a solution of 1b[ClO4] (100 mg,
0.124 mmol) in methanol (20 mL). After stirring for 2 h at ambient
temperature, the product was precipitated by the addition of solid
LiClO4·3H2O (301 mg, 1.87 mmol). The green microcrystalline so-
lid was isolated by filtration, washed with cold methanol (2 mL),
methanol (5 mL) was added to a solution of 2b[ClO4] (100 mg,
0.118 mmol) in methanol (20 mL). After stirring for 12 h at ambi-
ent temperature, the solvent was removed under reduced pressure
to a final volume of approximately 10 mL. The colorless solid was
isolated by filtration and washed with cold methanol (2–3 mL). To
remove traces of unreacted starting compound 2b[ClO4] the prod-
uct was treated again with a tenfold molar excess amount of tri-
ethylammonium 3,4-dimethyl-1,6-phenylcyclohex-3-enecarboxylate
as described above. Recrystallization from a mixed ethanol/
acetonitrile solvent system gave the title compound in analytically
pure form; yield 90 mg (75%); m.p. 275–276 °C (dec.).
and recrystallized once from
a mixed ethanol/acetonitrile
solvent system; yield 80 mg (70%); m.p. 318–319 °C (dec.).
C39H55ClN6Ni2O6S2·H2O (920.86 + 18.02): calcd. C 49.89, H 6.12,
N 8.95, S 6.83; found C 49.94, H 6.34, N 8.99, S 7.25. IR (KBr):
ν = 2996 (m), 2966 (m), 2861 (s), 2811 (s), 1642 (m) [ν(C=C)], 1577 C45H65ClN6O6S2Zn2 (1016.40): calcd. C 53.18, H 6.45, N 8.27, S
˜
(s) [νas(C–O)], 1491 (m), 1461 (s), 1450 (s), 1435 (m), 1424 (s), 1406 6.31; found C 53.03, H 6.74, N 7.85, S 5.42. IR (KBr): ν = 3057
˜
2398
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 2389–2401

Nickel and Zinc Complexes with Macrocyclic Ligands
(w), 2292 (m), 2856 (s), 1573 (s) [νas(CO)], 1483 (m), 1460 (s), 1426 (60.0 mg, 0.175 mmol) to
a solution of 7d[ClO4] (60 mg,
(s), 1408 (s) [νs(CO)], 1367 (w), 1352 (w), 1311 (m), 1295 (m), 1269 0.059 mmol) in acetonitrile (20 mL) provides, after addition of eth-
(m), 1202 (w), 1172 (w), 1095 (s) [ν3(ClO4)], 1002 (w), 1005 (m), anol (20 mL) and concentration to approximately 10 mL, pale
957 (w), 925 (w), 915 (m), 893 (w), 843 (w), 825 (m), 802 (w), 771
green crystals of crude product, which can be purified by
from ethanol/acetonitrile; yield 50 mg
(0.040 mmol, 68%); m.p. 298–299 °C. C62H75BN6Ni2O9S2
(1240.62): calcd. C 60.02, H 6.09, N 6.77, S 5.17; found C 59.85,
(m), 728 (w), 716 (w), 700 (w), 666 (w), 623 (s) [ν4(ClO4)], 580 (w), recrystallization
560 (w), 536 (w), 523 (w) cm–1.
[Ni2L2(μ-O2CC6H4-3-OMe)][ClO4]
(7b[ClO4]):
Triethylamine
H 5.74, N 6.88, S 5.27. IR (KBr): ν = 3494 (m), 3053 (m), 3032
˜
(37.5 mg, 0.37 mmol) was added to a solution of 3-methoxybenzoic
acid (56.4 mg, 0.371 mmol) in methanol (5 mL). This solution was
added to a solution of 1b[ClO4] (150 mg, 0.185 mmol) in methanol
(20 mL). After stirring for 2 h, solid LiClO4·3H2O (300 mg,
1.95 mmol) was added. The green solid was filtered, washed with
MeOH, and dried under vacuum. The crude product was purified
by recrystallization from acetonitrile/ethanol; yield 148 mg
(0.160 mmol, 86% based on 1b); m.p. 337–338 °C (dec.).
C38H55ClN6Ni2O7S2 (924.849): calcd. C 49.35, H 5.99, N 9.09, S
(m), 2997 (m), 2868 (m), 1598 (m) [ν(CC)], 1569 (s) [νas(CO)], 1478
(s), 1426 (m), 1401 (s) [νs(CO)], 1357 (w), 1312 (w), 1240 (s), 1204
(s) [ν(SO)], 1174 (w), 1141 (m), 1087 (s), 1033 (s), 993 (w), 974 (w),
917 (w), 907 (w), 831 (w), 809 (w), 777 (m), 762 (m), 737 (s)
[ν(BPh4)], 700 (s) [ν(BPh4)], 662 (w), 651 (w), 624 (s), 615, (w), 582
(w), 568 (w), 528 (w), 498 (w), 474 (w), 430 (w) cm–1.
[Zn2L3(μ-O2CC6H4-3-OMe)][ClO4] (8d[ClO4]): Hydrogen peroxide
(2.00 mL, 35 wt.-% solution in water, 20.6 mmol) was added to a
solution of 8b[ClO4] (250 mg, 0.270 mmol) in methanol (50 mL).
The reaction mixture was left at reflux for 5 h and was then filtered.
After cooling to room temperature, the solution was concentrated
to give the crude product as a white powder. Recrystallization from
ethanol/acetonitrile provided pure 8d[ClO]4 (105 mg, 38%); m.p.
358–359 °C. C38H55ClN6O13S2Zn2·H2O (1034.22 + 18.02): calcd. C
43.37, H 5.46, N 7.99, S 6.09; found C 43.02, H 5.00, N 8.21, S
6.93; found C 49.64, H 5.88, N 9.21, S 7.22. IR (KBr): ν = 3517
˜
(m), 2994 (m), 2967 (s), 2860 (s), 1598 (m) [ν(CC)],[48] 1574 (s)
[νas(CO)], 1487 (m), 1462 (s), 1426 (s), 1399 (s) [νs(CO)], 1363 (m),
1335 (w), 1312 (m), 1298 (m), 1279 (w), 1265 (w), 1254 (m), 1201
–
(w), 1170 (w), 1095 (vs) [ν3(ClO4 )], 1040 (s), 1000 (m), 957 (w),
918 (m), 894 (w), 866 (w), 828 (m), 806 (m), 788 (m), 763 (s), 726
–
(w), 691 (w), 670 (w), 623 (m) [ν4(ClO4 )], 565 (w), 537 (w), 526
(w), 492 (w), 461 (w), 440, (w), 416 (w) cm–1.
6.32. IR (KBr): ν = 2981 (s), 2871 (s), 1599 (s), 1567 (s) [ν (CO)],
˜
as
1462 (s), 1426 (m), 1400 (s) [νs(CO)], 1359 (w), 1312 (w), 1238 (s)
[ν(SO3)], 1211 (s), 1088 (s) [ν3(ClO4)], 1030 (s), 976 (w), 918 (w),
828 (w), 781 (m), 763 (m), 742 (w), 697 (m), 653 (w), 622 (s)
[ν4(ClO4)], 566 (m), 525 (w), 499 (w), 426 (w) cm–1.
[Zn2L2(μ-O2CC6H4-3-OMe)][ClO4] (8b[ClO4]): A solution of tri-
ethylammonium 3-methoxybenzoate [prepared in situ from 3-meth-
oxybenzoic acid (269 mg, 1.77 mmol) and triethylamine (178 mg,
1.77 mmol)] in methanol (5 mL) was added to a solution of
2b[ClO4] (150 mg, 0.177 mmol) in methanol (20 mL). After stirring
for 12 h at ambient temperature, the solvent was removed under
reduced pressure to a final volume of approximately 10 mL. The
colorless solid was isolated by filtration and washed with cold
methanol (5 mL). To remove traces of unreacted starting com-
pound 2b[ClO4], the product was treated again with a tenfold molar
excess amount of triethylammonium 3-methoxybenzoate as de-
scribed above. Recrystallization from a mixed ethanol/acetonitrile
solvent system then gave the title compound in analytically
pure form; yield 145 mg (87%); m.p. 345 °C (dec.).
C38H55ClN6O7S2Zn2·H2O (938.24 + 18.02): calcd. C 47.73, H 6.01,
N 8.79, S 6.71; found C 47.31, H 5.61, N 8.47, S 7.21. IR (KBr):
Crystallography: Suitable crystals of compound 5b[ClO4]·MeCN
and 7d[BPh4]·0.5MeCN·0.5H2O were selected and mounted on the
tip of a glass fiber (Table 6). The data sets were collected at
213(2) K using a STOE IPDS-2T diffractometer equipped with
graphite-monochromated Mo-Kα radiation (0.71073 Å). The inten-
sity data were processed with the program STOE X-AREA. An
Table 6. Crystallographic data for 5b[ClO4]·MeCN and 7d[BPh4]·
0.5MeCN·0.5H2O.
5b[ClO4]·MeCN
7d[BPh4]
·0.5MeCN·0.5H2O
Formula
C47H68ClN7Ni2O6S2 C63H77.5BN6.50Ni2O9.50S2
ν = 3525 (m), 2991 (m), 2857 (s), 1598 (m), 1570 (s) [ν (CO)], 1484
˜
as
Mr [gmol–1]
Space group
a [Å]
1044.07
P1
1268.65
C2/c
(m), 1462 (s), 1426 (s), 1399 (s) [νs(CO)], 1367 (m), 1352 (m), 1333
¯
(m), 1313 (m), 1297 (m), 1280 (m), 1269 (m), 1251 (m), 1204 (w),
12.7350(7)
14.0924(7)
14.6442(8)
85.01(4)
70.86(4)
70.95(4)
2346.3(8)
2
36.727(3)
16.2006(13)
24.9993(19)
90.00
115.484(8)
90.00
–
1172 (w), 1096 (vs) [ν3(ClO4 )], 1042 (s), 1003 (m), 959 (w), 916
b [Å]
c [Å]
α [°]
β [°]
(m), 894 (m), 868 (w), 825 (m), 803 (m), 784 (m), 764 (s), 727 (w),
–
688 (w), 666 (w), 623 (m) [ν4(ClO4 )], 562 (w), 536 (w), 523 (w),
483 (w), 433 (w), 410 (w) cm–1.
γ [°]
[Ni2L4(μ-O2CC6H4-3-OMe)][ClO4] (7d[ClO4]): A solution of MCPBA
(81 mg, 0.47 mmol) in acetonitrile (2 mL) was added dropwise at
0 °C to a solution of 7b[ClO4] (60 mg, 0.065 mmol) in acetonitrile
(20 mL). After stirring for 10 min at room temperature, solid
LiClO4·3H2O (500 mg, 3.26 mmol) was added followed by ethanol
(20 mL). The product precipitated upon evaporation to a final vol-
ume of approximately 5 mL. The resulting lime-green solid was fil-
tered and purified by recrystallization from acetonitrile/ethanol;
yield 55 mg (0.054 mmol, 83%); m.p. 317–318 °C (dec.). IR (KBr):
V [Å3]
13427.2(18)
8
Z
dcalcd. [gcm–3]
Crystal size [mm3]
μ(Mo-Kα) [mm–1]
θ limits [°]
Measured reflections
Indep. reflections
Obsd. reflections[a]
Parameters
R1[b] (R1 all data)
1.478
0.10ϫ0.10ϫ0.10
1.006
3.35–26.00
23395
9218
1.255
0.27ϫ0.22ϫ0.22
0.680
5.53–24.09
35779
9930
6430
764
0.0482 (0.0723)
0.1238 (0.1306)
0.641/–0.499
8154
632
ν = 3555 (s), 3497 (m), 2992 (m), 2871 (s), 1603 (s) [ν(CC)], 1567
˜
0.0632 (0.0699)
wR2[c] (wR2 all data) 0.1644 (0.1672)
(s) [νas(CO)], 1461 (s), 1426 (s), 1399 (s) [νs(CO)], 1359 (w), 1312
–
Max./.min peaks
2.934/–2.577
(w), 1208 (s) [νs(SO3)], 1178 (s), 1134 (s), 1088 (vs) [ν3(ClO4 )], 1035
[eÅ–3]
(s), 993 (w), 975 (w), 910 (m), 869 (w), 832 (m), 810 (w), 781 (s),
–
762 (s), 742 (w), 700 (s), 661 (w), 651 (w), 624 (s) [ν4(ClO4 )], 586
[a] Observation criterion: IϾ2σ(I). [b] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [c]
wR2 = {Σ[w(F2o – F2c)2]/Σ[w(F2o)2]}1/2
(w), 567 (m), 527 (w), 497 (w), 430 (w) cm–1. Addition of NaBPh4
.
Eur. J. Inorg. Chem. 2012, 2389–2401
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2399

S. Käss, B. Kersting
FULL PAPER
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empirical absorption correction was performed with the program
SADABS.[49] Structures were solved by direct methods[50] and re-
fined by full-matrix least squares on the basis of all data against
F2 using SHELXL-97.[51] PLATON was used to search for higher
symmetry.[52] Drawings were produced with Ortep-3.[53] Hydrogen
atoms were placed at calculated positions and refined as riding
atoms with isotropic displacement parameters. All non-hydrogen
atoms were refined anisotropically. In the crystal structure of
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[18] M. Gressenbuch, B. Kersting, Eur. J. Inorg. Chem. 2007, 90–
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5b[ClO4]·MeCN the ClO4 ions was found to be disordered over
102.
two positions. A split-atom model has been used to account for this
disorder using the AFIX 3 and EADP instructions implemented in
the SHELXL program suite. The site-occupancy factors of the two
orientations were refined as O3A–O6A/O3B–O6B = 0.60:0.40. In
the crystal structure of 7d[BPh4]·0.5MeCN·0.5H2O the occupancy
factors of the MeCN and H2O solvate molecules were fixed at 0.50.
No hydrogen atoms were calculated for the solvate molecules.
[19] M. Gressenbuch, B. Kersting, Dalton Trans. 2009, 5281–5283.
[20] U. Lehmann, B. Kersting, unpublished results.
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[26] The chemical formula of this compound is shown in Scheme 1.
[27] All attempts to prepare a chlorido-bridged zinc complex
[Zn2L2(Cl)]+ invariably proved unsuccessful, as was also ob-
served in the case of H2L1 in the literature.[24]
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[30] M. Hesse, H. Meier, B. Zeeh, Spektroskopische Methoden in der
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[37] The magnetic properties of these complexes are assumed to be
similar to other carboxylato-bridged [Ni2L1(O2CR)]+ com-
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state as observed in [Ni2L1(OAc)]+ and [Ni2L1(O2CPh)]+. See
J. Hausmann, M. H. Klingele, V. Lozan, G. Steinfeld, D. Sieb-
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[41] V. Lozan, A. Buchholz, W. Plass, B. Kersting, Chem. Eur. J.
2007, 13, 7305–7316.
CCDC-837598 (for 5b) and -837599 (for 7d) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgments
We are thankful to Prof. Dr. H. Krautscheid for providing facilities
for X-ray crystallographic measurements. This work was supported
by the Deutsche Forschungsgemeinschaft (DFG) (Graduate School
“BuildMona”).
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2400
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 2389–2401

Nickel and Zinc Complexes with Macrocyclic Ligands
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Published Online: March 23, 2012
Eur. J. Inorg. Chem. 2012, 2389–2401
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2401