Preparation and characterization of mononuclear Ni complexes of tetradentate amine-thioether and amine-thiolate ligands

Article abstract of DOI:10.1515/znb-2007-0404

A short route for the preparation of tetradentate amine-thioether and amine-thiolate ligands derived from thiosalen is reported. The ligating properties of several of the synthesized ligands towards Ni(II) has been examined. The diamine-dithiophenolate li

Full text of DOI:10.1515/znb-2007-0404

Preparation and Characterization of Mononuclear Ni Complexes of
Tetradentate Amine-thioether and Amine-thiolate Ligands
Thorsten Fritzb, Gunther Steinfeldb, and Berthold Kerstinga
a Institut fu¨r Anorganische Chemie, Universita¨t Leipzig, Johannisallee 29, 04103 Leipzig, Germany
b Institut fu¨r Anorganische und Analytische Chemie, Universita¨t Freiburg, Albertstr. 21,
79104 Freiburg, Germany
Reprint requests to Prof. Dr. B. Kersting. Fax: +49/(0)341-97-36199.
E-mail: b.kersting@uni-leipzig.de
Z. Naturforsch. 2007, 62b, 508 – 518; received October 24, 2006
A short route for the preparation of tetradentate amine-thioether and amine-thiolate ligands derived
from thiosalen is reported. The ligating properties of several of the synthesized ligands towards Ni(II)
has been examined. The diamine-dithiophenolate ligands (L6)2− [H2L6 = N,Nꢀ-dimethyl-N,Nꢀ-di(2-
mercaptobenzyl)-ethane-1,2-diamine] and (L7)2− [H2L7 = N,Nꢀ-di(2-mercaptobenzyl)-piperazine]
support the formation of four-coordinate NiIIN2S2 complexes [NiII(L6)] (10) and [NiII(L7)] (11). By
contrast, the amine-thioethers 2 [Nꢀ,Nꢀꢀ-bis(2-(tert-butylthio)benzyl)ethane-1,2-diamine], L2 [8,11-
diaza-5,13-dibenzo-1,4-dithia-cyclotetradecane] and its N-methylated derivative L2,Me were found
to produce the six-coordinate Ni(II) complexes [NiIICl2(2)2] (9), [NiII2(µ-Cl)2(L2)2][ClO4]2 (12),
[NiII(NCS)2(L2)] (13), and [NiIICl2(L2,Me)] (14). The results of IR, NMR and UV/vis spectroscopy
and the crystal structures of complexes 9 – 13 are reported.
Key words: Nickel Complexes, Macrocyclic Ligands, N Donor, S Donor
Introduction
Koyama and coworkers prepared N,Nꢀ-bis(2-mercap-
tobenzyl)-ethylenediamine (H2L3) [7]. Until now only
The coordination chemistry of tetradentate N4 and a few more ligands of this sort have been reported in
S4 donor ligands has been well investigated in the the literature [8 – 12].
past several years [1, 2]. Far less is known about the
In recent work, we described the synthesis of
metal ion-binding of tetradentate N2S2 donor ligands. the pentadentate amine-thiophenol ligands H2L4 and
This is true in particular for the families of amine-thio- H2L5 [13]. We now find that the N2S2 ligands H2L6
ether and amine-thiolate ligands derived from thiosalen and H2L7 can be prepared in a similar manner. The
(H2L1, see Scheme 1) [3 – 5]. Lindoy et al. reported the synthesis of these ligands and their ligating properties
synthesis of the 14-membered N2S2 macrocycle L2 [6]. towards Ni(II) are reported herein.
Scheme 1. Structure of the ligands
H2L1 – H2L7.
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
509
Scheme 2. Synthesis of the
ligands used in this study.
Results and Discussion
Synthesis of ligands
The amine-thiolate ligands H2L6 and H2L7 were
isolated as their hydrochloride salts and stored under
an atmosphere of dry nitrogen. These ligands could
not be obtained in analytically pure form. Neverthe-
less, they were of sufficient purity for metal complex
syntheses.
The route used for the synthesis of the ligands
is depicted in Scheme 2. The preparations of proli-
gand 2 and H2L6 · 2HCl have already been reported
by other groups. Hinshaw and coworkers, for exam-
ple, prepared H2L6 in five steps starting from thiosal-
icylic acid and N,Nꢀ-dimethylethylenediamine in rel-
atively low yield (41 %) [10]. We adapted Sun’s
procedure [11], using 2-tert-butylthio-benzaldehyde
Synthesis and spectroscopic characterization of
complexes
Scheme 3 shows the complexes prepared and
(1) as starting material [14]. Thus, reductive ami- their labels. Treatment of amine-thioether 2 with
nation of 1 with ethylenediamine/NaBH4, followed NiCl2 · 6H2O in a 1 : 1 molar ratio in methanol solution
by Eschweiler-Clarke methylation of 2 furnished 3, produced the mononuclear 1 : 2 complex [NiIICl2(2)2]
which could be readily deprotected with Na/NH3 to (9) as a pale-blue, air-stable, microcrystalline solid
give H2L6 · 2HCl; an overall yield of 88 % was ob- in 81 % yield (based on 2). A 1 : 1 complex could
tained. The ligand H2L7 · 2HCl was prepared accord- not be obtained. Complex [NiII(L6)] (10) forms as
ing to a protocol used for the alkylation of triaza- the only isolable product, when H2L6 · 2HCl is treated
cyclononane [15]. The four-step method depicted in with NiCl2 · 6H2O and NEt3 in a 1 : 1 : 2 molar ra-
Scheme 2 provided H2L7 · 2HCl in 70 % yield. The tio in methanolic solution. Similarly, the reaction of
synthesis of the macrocycle L2 was first described by H2L7 · 2HCl with NiCl2 · 6H2O and NEt3 in methanol
Lindoy et al. [6]. We used a slight modification of produced the red neutral complex [NiII(L7)] (11). Ad-
the original procedure using commercially available 2- dition of NiCl2 · 6H2O to a solution of L2 in methanol,
nitro-benzaldehyde as starting material. The two-step followed by treatment with solid LiClO4, produced
method depicted in Scheme 2 is superior to the origi- a pale-blue microcrystalline solid of the composi-
nal procedure and leads to a significantly higher yield tion [NiII2Cl2(L2)2][ClO4]2 (12) in almost quantitative
of L2. Finally, the permethylated derivative L2,Me was yield. Treatment of NiCl2 · 6H2O with L2 in methanol,
obtained by Eschweiler-Clarke methylation of L2.
followed by the addition of NaSCN, gave a purple,
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
Scheme 3. The complexes
prepared in this study and
their labels.
crystalline powder of [NiII(NCS)2(L2)] (13). Finally, geminal coupling constant was found to be 12 Hz. The
reaction of L2,Me with one equivalent of NiCl2 · 6H2O benzylic protons in 11 also form an AB system (δ =
yielded [NiIICl2(L2,Me)] (14) as a green powder. All 2.47 and 3.52 ppm) presumably as a consequence of
compounds gave satisfactory elemental analyses and a hindered inversion of the two six-membered chelate
were characterized by spectroscopic methods (IR, rings. These data suggest that both complexes main-
UV/vis, 1H and 13C NMR spectroscopy) and com- tain their solid state structures in the solution state (i. e.
pounds 9 – 13 also by X-ray crystallography.
trans orientation of the two methyl groups in 10, rigid
The infrared spectra of the complexes 9 – 11 and propeller-like structure of 11). Complexes 12 – 14 are
14 reveal mainly the various stretching and bending paramagnetic and could not be investigated by NMR
spectroscopy. The stereochemistry of 14 is unknown.
The electronic absorption spectra of 9 – 14 have
modes of the supporting ligands. The most significant
feature in the IR spectrum of crystalline 9 is the band
at 3294 cm−1, which can be readily assigned to the been recorded in the 300 – 1600 nm range in MeCN
N–H stretching vibrations of the coordinated amine or CH2Cl2. The spectra of the nickel complexes of the
donors [16]. Similar bands are observed for 12 and 13, amine-thioether ligands 2, L2, and L2,Me are similar but
but not for the complexes 10, 11, and 14 which con- not identical. Above 500 nm, each compound displays
tain only tertiary amine donors. The IR spectra of 12 two weak absorption bands. The absorption band in the
and 13 reveal additional bands for counter ions and 580 to 630 nm range can be attributed to the ν2 tran-
3
co-ligands. Thus, the IR spectrum of the perchlorate sition [3A2g(F) → T1g(F)] of an octahedral nickel(II)
salt 12 reveals a strong band at 1100 cm−1 for the (d8) ion. The bands between 1055 and 1100 nm can
ClO4 ions, whereas 13 shows two bands at 2107 and be assigned to the ν1 transition [3A2g(F) → T2g(F)].
2089 cm−1 characteristic of thiocyanate ions ν(NCS). The slight differences in the position of the d-d tran-
The values are similar to those of other octahedral sitions indicate that each complex retains its integrity
[NiII(NCS)2(macrocycle)] complexes, indicative of N- in solution. The spectra of the amine-thiolate com-
−
3
bound thiocyanates [17, 18].
plexes 10 and 11 reveal intense absorptions in the
The diamagnetic complexes 10 and 11 were further 300 to 600 nm region, characteristic of four-coordinate
characterized by 1H NMR spectroscopy. It is apparent N2S2NiII compounds. These absorptions can be at-
from the H NMR data that the two halves of (L6)2− tributed to RS− → NiII charge-transfer transitions.
1
in 10 and (L7)2− in 11 are equivalent. For example,
Description of the crystal structures
1
a single H NMR resonance is observed for the NMe
protons in 10 at δ = 2.49 ppm. The benzylic protons
The crystal structures of 9 – 13 were determined
form an AB system, the corresponding A and B dou- by X-ray crystallography to establish the geometries
blets being centered at δ = 2.22 and δ = 4.33 ppm. The about the metal ions as well as the bonding modes of
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
Table 1. Selected crystallographic data for 9 – 13.
511
Compound
Formula
[NiCl2(2)2] (9)
C48H72Cl2N4NiS4 C18H22N2NiS2 C18H20N2NiS2 C18H22Cl2N2NiO4S2
[Ni(L6)] (10)
[Ni(L7)] (11)
[Ni2(µ-Cl)2(L2)2][ClO4]2 (12) [Ni(NCS)2(L2)] (13)
C20H22N4NiS4
505.37
P21/n
10.271(2)
13.398(3)
16.788(2)
90
105.12(2)
90
2230.2(7)
4
1.505
1.259
1.97 – 30.04
14784
Mr [g mol−1
Space group
]
962.95
P1
389.21
P21/c
13.623(3)
10.658(2)
13.252(3)
90
115.83(3)
90
1731.9(6)
4
387.19
Pca21
15.362(3)
7.895(2)
14.032(3)
90
90
90
1701.8(7)
4
524.11
P21/c
10.0169(8)
19.914(2)
11.5659(9)
90
112.38(3)
90
2133.3(3)
4
¯
˚
a [A]
9.936(2)
10.042(2)
13.592(3)
85.15(3)
78.00(3)
71.67(3)
1259.0(5)
1
˚
b [A]
˚
c [A]
α [deg]
β [deg]
γ [deg]
3
˚
V [A ]
Z
dcalcd. [g cm−3
]
1.270
0.693
1.53 – 28.29
11386
5843
1.493
1.361
1.66 – 28.29
10468
4089
1.511
1.385
2.90 – 28.31
4775
1.632
1.384
2.05 – 28.30
18797
5115
µ(MoKα ) [mm−1
θ limits [deg]
]
Measured refl.
Independent refl.
Observed refl.a
No. parameters
R1b (R1 all data)
2765
6117
2094
262
4201
268
3048
208
2279
208
3615
262
0.0399 (0.0649)
0.0963 (0.1160)
0.0260 (0.0454) 0.0297 (0.0399) 0.0338 (0.0598)
0.0619 (0.0823) 0.0630 (0.0669) 0.0784 (0.0877)
0.0496 (0.2025)
0.0865 (0.1198)
0.531/−0.681
wR2c (wR2 all data)
3
˚
Max, min peaks [e/A ] 0.721/−0.309
0.372/−0.384
R1 = ΣꢁFo|−|Fcꢁ/Σ|Fo|.
0.280/−0.428
0.937/−0.594
Observation criterion: I ≥ 2σ(I).
wR2 = {Σ[w(Fo −Fc2)2]/Σ[w(Fo2)2]}
.
a
b
c
2
1/2
the supporting ligands. Suitable crystals of 14 could
not be obtained. Experimental crystallographic data
are summarized in Table 1.
[NiIICl2(2)2] (9). This compound crystallizes in
¯
the triclinic space group P1 with one formula unit per
unit cell. The neutral complex exhibits crystallographi-
cally imposed inversion symmetry. A perspective view
of the molecular structure is depicted in Fig. 1. Se-
lected bond lengths and angles are given in the figure
caption. The Ni atom is coordinated by four nitrogen
atoms from the two amine-thioether ligands and two
trans-oriented chloro ligands in a distorted octahedral
fashion. The thioether functions point away from the
Ni atom; the intramolecular Ni···S(1) and Ni···S(2)
˚
distances of 5.234 and 4.959 A being out of range of
Fig. 1. Structure of the complex 9. Thermal ellipsoids are
drawn at the 50 % probability level. Hydrogen atoms, except
H(1) and H(2), are omitted for clarity. Selected bond lengths
bonding interactions. There are no unusual features as
far as bond lengths and angles are concerned. The av-
˚
(A) and angles (deg): Ni–N(1) 2.172(2), Ni–N(2) 2.133(2),
˚
erage Ni–N and Ni–Cl bond lengths are at 2.152(2) A
Ni–Cl 2.4186(8); L–Ni–Lcis 83.6 – 96.4◦, L–Ni–Ltrans 180◦.
Symmetry code used to generate equivalent atoms: 1 − x,
1−y, −z.
˚
and 2.4186(8) A, respectively. Similar distances are
seen in other octahedral NiIIN4Cl2 complexes [19].
[NiII(L6)] (10). Crystals of 10 grown by slow dif-
fusion of methanol into an acetonitrile solution are Ni, N(1), N(2), S(1) and S(2) being only 0.082 A. The
˚
˚
monoclinic, space group P21/c. The crystal struc- average Ni–S bond length of 2.175(1) A resembles that
ture determination revealed the presence of discrete
in [NiII(L3)] [20] and other planar NiN2S2 structures
molecules of the neutral complex (Fig. 2). The Ni atom [21 – 25]. The average Ni–N bond length in 10 is sig-
II
3
˚
is coordinated by the two N and two S atoms from nificantly longer than in [Ni (L )] (by 0.108 A), as
(L6)2− in an almost planar fashion; the maximum de- expected for the conversion of secondary into tertiary
N donors. Similar effects have been observed for Ni
viation from the least-squares plane through the atoms
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512
T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
Fig. 2. Structure of the neutral complex [NiII(L6)] (10).
Thermal ellipsoids are drawn at the 50 % probability level.
Hydrogen atoms are omitted for clarity. Selected bond
˚
lengths (A) and angles (deg): Ni–N(1) 1.974(2), Ni–N(2)
1.965(2), Ni–S(1) 2.1686(7), Ni–S(2) 2.182(1); N(1)–
Ni–N(2) 89.00(8), S(1)–Ni–S(2) 83.08(3), S(1)–Ni–N(1)
94.54(6), S(1)–Ni–N(2) 173.38(6), S(2)–Ni–N(1) 173.76(5),
S(2)–Ni–N(2) 93.95(6).
Fig. 4. ORTEP representation of the structure of complex
[NiII2(µ-Cl)2(L2)2]2+ in crystals of 12. Hydrogen atoms
have been omitted for clarity. Selected bond lengths and an-
gles are listed in Table 2. Symmetry code used to generate
equivalent atoms: 2−x, −y, −z.
complexes of other N donor ligands and their methy-
lated derivatives [26], the two methyl groups are lo-
cated at opposite sides of the five-membered ring.
[NiII(L7)] (11). This compound crystallizes in the
non-centrosymmetric space group Pca21. The crys-
tal structure determination revealed the presence of
discrete molecules (Fig. 3). The neutral complex ex-
hibits idealized C2 symmetry. Again, the Ni atom is
four-coordinate by two cis-oriented S and N donors
from (L7)2−. The distortion from planarity is less pro-
nounced than in 10, the maximum deviation from the
least-squares plane through the atoms Ni, N(1), N(2),
most significant structural differences between 10 and
11 concern the bond angles around the Ni atom. The
deviations from the ideal values are more pronounced
in 11. For example, the N–Ni–N bond angle in 11
(76.4(1)◦) is much more acute than in 10 (89.00(8)◦)
most likely as a consequence of the steric constraints
of the piperazine backbone.
[NiII2(µ-Cl)2(L2)2][ClO4]2 (12). This salt crys-
tallizes in the monoclinic space group P21/c.
The cystal structure consists of dinuclear [NiII2(µ-
Cl)2(L2)2]2+ dications (Fig. 4) and perchlorate coun-
teranions. Selected bond lengths and angles are given
in Table 2. Unlike in trans-[NiCl2(cyclam)] [29], the
14-membered N2S2 macrocycle L2 adopts a folded
conformation such that the two bridging chloride
atoms are arranged in cis positions. This can be
traced back to the longer Ni–S bonds (mean value =
˚
S(1) and S(2) being only 0.053 A. The average Ni–S
˚
˚
(2.165(1)A) and Ni–N bond lengths (1.954(3) A) com-
pare well with those in 10 and other four-coordinate
Ni(II) complexes with N2S2 coordination [27, 28]. The
˚
2.4037(8) A), which are only compatible with the
folded conformation. The average Ni–N bond length
˚
at 2.084 A closely compares with that in trans-
[NiCl2(cyclam)] and other octahedral nickel(II) com-
plexes.
[NiII(NCS)2(L2)] (13). The crystal structure de-
termination of 13 confirmed the formulation of the
title compound (Fig. 5). Table 2 lists selected bond
lengths and angles. The conformation of the macro-
cycle resembles that found in 12, such that the
N-bound thiocyanate ions are in cis positions. The
Ni–S and Ni–N(macrocycle) bond lengths are some-
what longer than in 12. The Ni–N(isothiocyanate)
Fig. 3. Structure of the neutral complex [NiII(L7)] (11).
Thermal ellipsoids are drawn at the 50 % probability level.
Hydrogen atoms are omitted for clarity. Selected bond
˚
lengths (A) and angles (deg): Ni–N(1) 1.951(3), Ni–N(2)
1.956(3), Ni–S(1) 2.161(1), Ni–S(2) 2.170(1); N(1)–Ni–
N(2) 76.40(12), S(1)–Ni–S(2) 88.62(4), S(1)–Ni–N(1)
97.52(9), S(2)–Ni–N(2) 97.67(9). S(1)–Ni–N(2) 172.43(9),
S(2)–Ni–N(1) 173.34(9).
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
513
Table 2. Selected bond lengths and angles of complexes 12
and 13.
The individual complexes appear to be weakly in-
termolecularly hydrogen-bonded to each other. The
corresponding NH···S (thiocyanate) distances lie at
12
13
Ni−S(1)
Ni−S(2)
Ni−N(1)
Ni−N(2)
Ni−Cl(1)
Ni−Cl(1ꢀ)a
M–Nb
2.3792(7)
2.4281(8)
2.077(2)
2.090(2)
2.4272(7)
2.4189(8)
2.084(2)
2.4037(8)
2.4231(8)
Ni–S(1)
Ni–S(2)
Ni–N(1)
Ni–N(2)
Ni–N(3)
Ni–N(4)
2.436(2)
2.515(2)
2.103(4)
2.073(4)
2.034(5)
2.037(4)
2.088(4)
2.476(2)
2.036(4)
ꢀ
˚
˚
2.686 A [for N(1)H(1)···S(3 )] and at 2.565 A [for
N(2)H(2)···S(3ꢀꢀ)] [30]. These values are normal for
NH···S hydrogen bonds [31 – 34]. In 12 and 13 the
N-bound H atoms are located on the same side of the
five-membered ring.
M–Sb
M–Lb
Conclusion
N(1)–Ni–N(2)
N(1)–Ni–S(1)
N(1)–Ni–S(2)
N(2)–Ni–S(2)
N(1)–Ni–Cl(1ꢀ)a
N(2)–Ni–Cl(1)
N(2)–Ni–Cl(1ꢀ)a
S(1)–Ni–Cl(1)
S(1)–Ni–Cl(1ꢀ)a
S(2)–Ni–Cl(1)
S(1)–Ni–S(2)
85.40(8)
91.95(6)
96.33(7)
89.72(6)
86.50(6)
96.11(6)
95.84(6)
87.00(3)
88.21(3)
90.17(3)
86.36(3)
86.89(3)
N(1)–Ni–N(2)
N(1)–Ni–S(1)
N(1)–Ni–S(2)
N(2)–Ni–S(2)
N(1)–Ni–N(4)
N(2)–Ni–N(3)
N(2)–Ni–N(4)
S(1)–Ni–N(3)
S(1)–Ni–N(4)
S(2)–Ni–N(3)
S(1)–Ni–S(2)
N(3)–Ni–N(4)
83.9(2)
90.9(1)
94.7(1)
87.5(1)
85.3(2)
97.2(2)
96.3(2)
88.4(1)
92.4(1)
87.3(1)
83.78(5)
92.7(2)
In this study, a new synthetic strategy was em-
ployed for the synthesis of two known and two new
N2S2 ligands derived from thiosalen. This method is
superior and leads to a considerably higher yield of
these ligands. It has been demonstrated that the amine-
thiophenolate ligands support the formation of planar
NiN2S2 complexes, whereas the amine-thioethers pro-
duce octahedral cis-[Ni(Lꢀ)2(L2)]n+ complexes (Lꢀ =
Cl, NCS). Finally, it has also been demonstrated that
the complexes exist as single isomers in the solution
state.
Cl(1)–Ni–Cl(1ꢀ)a
N(1)–Ni–Cl(1)
N(2)–Ni–S(1)
Cl(1ꢀ)–Ni–S(2)a
Ni–Cl–Niꢀ
173.34(6)
175.01(6)
173.95(2)
N(3)–Ni–N(1)
N(2)–Ni–S(1)
N(4)–Ni–S(2)
177.8(2)
169.4(1)
176.2(1)
Experimental Section
Materials and methods
93.11(3)
–
–
a
Symmetry code used to generate equivalent atoms: 2 − x, −y, −z.
b
Mean values.
Unless otherwise noted, all preparations were carried
out under an atmosphere of argon. Reagent grade solvents
were used throughout. 2-tert-Butylthio-benzaldehyde was
prepared according to the literature procedure [35]. All other
reagents were obtained from standard commercial sources
and used without further purification. Melting points were
determined in open glass capillaries and are uncorrected.
Infrared spectra were recorded on a Bruker VECTOR 22
FT-IR-spectrometer, NMR spectra on a Bruker AVANCE
DPX-200 spectrometer at 300 K. Chemical shifts refer to
solvent signals converted to TMS. The electronic absorp-
tion spectra were measured on a Jasco V-570 UV / VIS /
NIR spectrometer. Elemental analyses were carried out with
a VARIO EL – elemental analyzer.
CAUTION! Perchlorate salts are potentially explosive
and should therefore be prepared only in small quantities and
handled with appropriate care.
Fig. 5. ORTEP representation of the molecular structure of
complex 13 at 50 % probability ellipsoids. Hydrogen atoms
˚
have been omitted for clarity. Selected bond lengths (A) and
Preparation of intermediate 2
angles (deg) are listed in Table 2.
To a solution of 2-tert-butylthio-benzaldehyde 1 (10.0 g,
51.5 mmol) in ethanol (100 mL) was added a solution of eth-
ylenediamine (1.54 g, 25.6 mmol). After the reaction mixture
was stirred for 24 h, sodium borohydride (3.00 g, 79.3 mmol)
was added. The reaction mixture was stirred for further 24 h,
water was added (50 mL), and the pH of the solution ad-
bond lengths are normal for six-coordinate nickel(II)
isothiocyanate complexes [17]. The nickel atom fea-
tures a slightly distorted octahedral coordination en-
vironment. This is manisfested in the L–Ni–Lcis and
L–Ni–Ltrans bond angles which vary from 83.78(5)◦
to 97.2(2)◦ and from 169.4◦ to 177.8◦, respectively. justed to 1 by addition of conc. hydrochloric acid. After
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
all volatiles had been distilled off, the residue was taken the thiolate functions. Solid ammonium chloride was added
up in 3 M aqueous potassium hydroxide solution (100 mL) in small portions at −78 ◦C to destroy excess reducing agent.
and dichloromethane (100 mL). The layers were separated The resulting colorless suspension was allowed to warm to
and the aqueous layer was extracted with dichloromethane r. t. After 12 h, the remaining solvent was distilled off at re-
(3 × 50 mL). The organic layers were combined and evap- duced pressure. The residue was taken up in water (20 mL)
orated in vacuo. The resulting oily residue was dissolved in and the pH of the suspension adjusted to ≈ 1 to give a pale-
ethanol (20 mL) and treated with conc. aqueous hydrochlo- yellow solution of H2L6 as the dihydrochloride salt. To re-
ric acid to give a colorless precipitate of the dihydrochlo- move the inorganic salts the solution was concentrated in
ride salt 2 · 2HCl. The crude material was recrystallized from vacuum to a volume of ≈ 20 mL. Methanol (ca. 25 mL) was
ethanol. The hydrochloride was suspended in aqueous potas- then added and the resulting solution was filtered off from
sium hydroxide solution (pH = 13) and the free amine 2 ex- NaCl and NH4Cl. The latter two steps were repeated sev-
tracted with dichloromethane. The combined organic frac- eral times in this order, until no more salts precipitated upon
tions were dried over K2CO3 and filtered. Evaporation of the addition of MeOH. Concentration of the filtrate afforded
solvent gave compound 2 as a colorless oil (10.1 g, 94 %). – the title compound as a pale-yellow, air-sensitive powder.
1H NMR (200 MHz, CD3OD): δ = 1.15 (s, 18 H, tBu), Yield: 2.47 g (99 %). – 1H NMR (200 MHz, D2O/CD3OD):
2.58 (s, 4 H, NCH2CH2N), 3.89 (s, 4 H, ArCH2), 7.12 – δ = 2.90 (s, 6 H, NCH3), 3.72 (s, 4 H, NCH2CH2N), 4.48
1
1
7.46 (m, 8 H, ArH). – 13C{ H} NMR (50.3 MHz, CD3OD): (s, 4 H, ArCH2), 7.30 – 7.58 (m, 8 H, ArH). – 13C{ H}
δ = 32.1 (C(CH3)3), 48.5 (SC(CH3)3), 49.2 (NCH2), 53.3 NMR (50.3 MHz, CD3OD): δ = 41.3 (NCH3), 52.1 (NCH2),
(ArCH2), 128.8, 130.8, 131.4, 133.9, 140.5, 146.3. The spec- 60.3 (ArCH2), 128.9, 130.4 (CH), 132.7 (CH), 134.8, 134.9,
troscopic data for the dihydrochloride salt are given in the 135.2. This material was used in the next step without further
literature [11].
purification.
Preparation of intermediate 3
Preparation of intermediate 4
The amine-thioether 2 (7.64 g, 18.30 mmol) was dissolved
To a solution of aldehyde 1 (5.00 g, 25.7 mmol) in ethanol
in 96 % formic acid (9.57 g, 0.200 mol). To the clear so- (50 mL) was added NaBH4 (500 mg, 13.2 mmol), and the
lution was added a 35 % aqueous solution of formaldehyde resulting reaction mixture was stirred for 12 h. The excess
(9.24 g, 108 mmol). The reaction mixture was heated under reducing agent was destroyed by careful addition of conc.
reflux for 20 h, after which time it was concentrated to dry- hydrochloric acid. Water (50 mL) was added and the pH
ness. Water (50 mL) and dichloromethane (100 mL) were of the aqueous phase was adjusted to 13 by the addition
added to the slicky residue, the pH of the aqueous phase of 3 M aqueous potassium hydroxide solution. The solu-
was adjusted to 13 by the addition of 3 M aqueous potas- tion was evaporated to dryness and the product extracted
sium hydroxide solution, and the heterogeneous mixture was with dichloromethane. The combined organic fractions were
stirred vigorously for 30 min. The layers were separated dried over MgSO4 and filtered. Evaporation of the solvent
and the aqueous phase was extracted with dichloromethane gave compound 4 as a colorless oil (4.18 g, 83 %). This
(3 × 100 mL). The combined organic fractions were dried material was used in the next step without further purifica-
over K2CO3 and filtered. Evaporation of the solvent gave tion.
compound 3 as a colorless oil (7.91 g, 97 %). – 1H NMR
(200 MHz, CD3OD): δ = 1.12 (s, 18 H, C(CH3)3), 2.07
(s, 6 H, NCH3), 2.50 (s, 4 H, NCH2CH2N), 3.74 (s, 4 H,
ArCH2), 7.06 – 7.25 (m, 4 H, ArH), 7.40 – 7.45 (m, 4 H,
Preparation of intermediate 5
A solution of PBr3 (1.92 g, 7.10 mmol) in dichlorometh-
ane (20 mL) was slowly added to a solution of 4 (4.18 g,
21.3 mmol) in CH2Cl2 (20 mL) at 0 ◦C. The reaction mixture
was allowed to stirr for 3 h. Water was then added, the or-
ganic layers were separated, and the aqueous phase extracted
several times with dichloromethane. The combined organic
phases were dried over MgSO4, filtered and concentrated in
vacuo to give 5 as a pale-yellow oil. Yield: 4.14 g (75 %). –
1H NMR (200 MHz, CDCl3): δ = 1.23 (s, 9 H, C(CH3)), 4.79
1
ArH). – 13C{ H} NMR (50.3 MHz, CD3OD): δ = 32.2
(C(CH3)3), 43.7 (NCH3), 48.3 (SC(CH3)3), 56.7 (NCH2),
61.6 (ArCH2), 128.5, 130.6 (CH), 132.0 (CH), 134.6, 140.4,
145.4. This material was used in the next step without further
purification.
Preparation of ligand H2L6 · 2HCl
To a solution of sodium (1.10 g, 47.8 mmol) in liquid (s, 2 H, ArCH2Br), 7.12 – 7.30 m (2 H, ArH), 7.45 – 7.50 (m,
ammonia (100 mL) was added a solution of compound 3 2 H, ArH). – 13C{ H} NMR (50.3 MHz, CDCl3): δ = 29.5
1
(2.74◦g, 6.16 mmol) in tetrahydrofuran (30 mL) dropwise at (C(CH3)3), 30.9 (ArCH2Br), 45.6 (C(CH3)), 126.6, 127.7,
−78 C. The resulting blue reaction mixture was stirred at 129.3, 130.8, 137.1, 141.1 (ArC). This material was used in
◦
−78 C for further 1 h to ensure complete deprotection of the next step without further purification.
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515
Preparation of intermediate 6
with water and dried in air. The crude material was recrys-
tallized from a mixed dichloromethane/cyclohexane solvent
to give a pale-yell◦ow microcrystalline solid. Yield: 22.8 g
(76 %). M. p. 123 C. – 1H NMR (200 MHz, CDCl3): δ =
3.12 (s, 4 H, SCH2CH2S), 7.25 – 7.32 (m, 4 H, ArH), 7.40 –
To a solution of 5 (4.14 g, 16.0 mmol) and piperazine
(688 mg, 8.00 mmol) in acetonitrile (100 mL) was added
K2CO3 (2.43 g, 17.6 mmol) and the resulting mixture was
stirred for 2 d at ambient temperature. The mixture was evap-
orated to dryness, water was added to the residue, and the
product extracted with dichloromethane. The combined or-
ganic phases were dried over MgSO4, filtered, and concen-
trated in vacuo to ≈ 10 mL. Addition of methanol resulted
in the formation of colorless crystals of 6, which were fil-
tered and dried in air. Yield: 2.17 g (77 %). – 1H NMR
(200 MHz, CDCl3): δ = 1.20 (s, 18 H, C(CH3)3), 2.44
(s, 8 H, NCH2CH2N), 3.76 (s, 4 H, ArCH2), 7.09 – 7.25
(m, 4 H, ArH), 7.43 – 7.54 (m, 4 H, ArH). – 13C NMR
(50.3 MHz, CDCl3): δ = 31.6 (C(CH3)3), 47.5 (C(CH3)3),
53.7 (NCH2CH2N), 60.8 (ArCH2), 126.8, 129.2, 130.1,
132.9, 139.1, 144.1 (ArC).
1
7.48 (m, 2 H, ArH). – 13C{ H} NMR (50.3 MHz, CDCl3):
δ = 32.7 (SCH2), 126.7, 129.3, 132.6, 134.5, 135.1, 140.1
(CAr), 191.8 (CHO). This material was used in the next step
without further purification.
Preparation of ligand L2
Solutions of 8 (3.02 g, 10.0 mmol) in dichloromethane
(100 mL) and ethylenediamine (601 mg, 10.0 mmol) in
ethanol (100 mL) were added simultaneously over a period
of 5 h to a mixture of dichloromethane (400 mL) and ethan-
ol (200 mL). After complete addition, the reaction mixture
was stirred for 24 h at r. t. A solution of sodium borohydride
(1.50 g, 38.7 mmol) in ethanol (150 mL) was added. After
stirring at r. t. for 24 h, the reaction mixture was acidified to
pH = 1 with conc. hydrochloric acid and the resulting color-
less suspension was evaporated to dryness. Water (150 mL)
and dichloromethane (300 mL) were added to the residue,
the pH of the aqueous phase was adjusted to 13 with 3 M
aqueous potassium hydroxide and the heterogeneous mix-
ture was stirred vigorously for 30 min. The layers were sep-
arated and the aqueous phase was extracted with dichloro-
methane (5×50 mL). The combined organic fractions were
dried over anhydrous sodium sulfate. Evaporation of the sol-
vent gave a colorless oil which was purified by column chro-
matography on SiO2 using CH2Cl2/MeOH (10 : 1) as eluent.
Addition of cyclohexane to a solution of L2 in CH2Cl2 af-
forded colorless crystals. Yield: 2.28 g (69 %). M. p. 86 ◦C. –
1H NMR (200 MHz, CDCl3): δ = 2.83 (s, 4 H, NCH2CH2N),
3.81 (s, 4 H, SCH2CH2S), 3.74 (s, 4 H, ArCH2), 7.05 –
Preparation of ligand H2L7 · 2HCl
To a solution of sodium (1.00 g, 43.5 mmol) in liquid am-
monia (100 mL) was added a solution of compound 6 (2.71 g,
6.12 mmol) in tetrahydrofuran (25 mL) dropwise at −78 ◦C.
The resulting blue reaction mixture was stirred at –78 ◦C for
1 h to ensure complete deprotection of the thiolate functions.
Solid ammonium chloride was added in small portions at
−78 ◦C to destroy excess reducing agent. The resulting col-
orless suspension was allowed to warm to room temperature.
After 12 h, the remaining solvent was distilled off at reduced
pressure. The residue was taken up in water (20 mL) and the
pH of the suspension adjusted to ≈ 1 to give a pale-yellow
solution of H2L7 as the dihydrochloride salt. To remove the
inorganic salts the solution was concentrated in vacuum to a
volume of ≈ 20 mL. Methanol (ca. 25 mL) was then added
and the resulting solution was filtered off from NaCl and
NH4Cl. The latter two steps were repeated several times in
this order, until no more salts precipitated upon addition of
MeOH. Concentration of the filtrate afforded the title com-
pound as a pale-yellow, air-sensitive powder. Yield: 2.42 g
1
7.34 (m, 8 H, ArH). – 13C{ H} NMR (50.3 MHz, CDCl3):
δ = 34.3 (SCH2CH2S), 48.0 (NCH2CH2N), 52.3 (ArCH2),
127.6, 128.4, 131.5, 132.1, 134.2, 141.8. This material was
used in the next step without further purification.
1
Preparation of ligand L2,Me
(98 %). – H NMR (200 MHz, D2O/CD3OD/K2CO3): δ =
3.02 (s, 8 H, NCH2CH2N), 4.00 (s, 4 H, ArCH2), 7.09 – 7.42
The macrocyclic amine-thioether L2 (2.28 g, 6.90 mmol)
was dissolved in 96 % formic acid (2.39 g, 50.0 mmol). To
the clear solution was added a 35 % aqueous solution of
formaldehyde (2.31 g, 108 mmol). The reaction mixture was
heated under reflux for 20 h, after which time it was con-
centrated to dryness. Water (50 mL) and dichloromethane
(100 mL) were added to the slicky residue, the pH of the
1
(m, 8 H, ArH). – 13C{ H} NMR (50.3 MHz, CD3OD, D2O):
δ = 51.3 (NCH2CH2N), 60.6 (ArCH2), 129.6, 131.2 133.1,
135.2, 135.4, 136.0. This material was used in the next step
without further purification.
Preparation of intermediate 8
A mixture of 2-nitrobenzaldehyde (30.0 g, 0.199 mmol), aqueous phase was adjusted to 13 by the addition of 3 M
potassium carbonate (32.9 g, 238 mmol), and ethanedithiol aqueous potassium hydroxide solution and the heteroge-
(9.35 g, 99.3 mmol) in DMF (80 mL) was stirred for 5 d neous mixture was stirred vigorously for 30 min. The lay-
at ambient temperature. After dropwise addition of water ers were separated and the aqueous phase was extracted with
(500 mL), the resulting precipitate was filtered off, washed dichloromethane (3×100 mL). The combined organic frac-
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
tions were dried over K2CO3 and filtered. Evaporation of (200 MHz, [D6]DMSO): δ = 2.47 (d, 2J = 6.1 Hz, 2 H, CH2),
the solvent gave L2,Me as a colorless oil (2.40 g, 97 %). – 3.16 (m, 8 H, CH2), 3.52 (d, 2J = 6.1 Hz, 2 H, CH2), 6.81 –
1H NMR (200 MHz, CDCl3): δ = 2.04 (s, 6 H, NCH3), 6.98 (m, 6 H, ArH), 7.28 (m, 2 H, ArH). – C18H20N2NiS2
2.79 (s, 4 H, NCH2CH2N), 3.14 (s, 4 H, SCH2CH2S), 3.66 (387.19): calcd. C 55.84, H 5.21, N 7.24; found C 55.79,
(s, 4 H, ArCH2), 7.01 – 7.19 (m, 4 H, ArH), 7.33 – 7.38 (m, H 5.28, N 7.23.
4 H, ArH). – 13C{ H} NMR (50.3 MHz, CDCl3): δ =
1
[NiII2(µ-Cl)2(L2)2](ClO4)2 (12)
34.1 (SCH2CH2S), 43.6 (NCH3), 48.4 (NCH2CH2N), 61.8
(ArCH2), 127.4, 128.1, 131.8, 132.3, 134.2, 141.0. This ma-
terial was used in the next step without further purification.
To a solution of L2 (500 mg, 1.51 mmol) in methanol
(20 mL) was added a solution of NiCl2 · 6H2O (357 mg,
1.50 mmol) in methanol (5 mL). The resulting blue reaction
Preparation of [NiIICl2(2)] (9)
mixture was stirred for one hour. Then solid LiClO4 · 3H2O
To a solution of 2 (417 mg, 1.00 mmol) in methanol (481 mg, 3.00 mmol) was added. The resulting micro-
(10 mL) was added NiCl2 · 6H2O (238 mg, 1.00 mmol). crystalline solid was isolated by filtration, washed with
The resulting pale-blue solid was isolated by filtration and isopropanol and dried in air. The crude material was re-
recrystallized from methanol. Yield: 390 mg (81 %). M. p. crystallized from acetonitrile. Yield: 513 mg (65 %). M. p.
213 ◦C (decomp.). – IR (KBr): ν = 3294, 3251, 3055, 290 ◦C (decomp.). – IR (KBr): ν = 3435, 3279, 2943,
2967, 2864, 1436, 1363, 1007, 928, 905, 816, 765, 751, 2886, 2012, 1629, 1591, 1469, 1435, 1393, 1365, 1295,
680, 629 cm−1. – UV/vis (CH2Cl2): λmax(εmax) = 288 1275, 1259, 1213, 1198, 1164, 1097, 1035, 1016, 992,
(2620), 380 (36), 628 (21), 1068 nm (19 M−1cm−1). – 964, 948, 925, 903, 866, 773, 731, 688, 623, 582, 505,
C48H72Cl2N4NiS4 (865.46): calcd. C 59.87, H 7.54, N 5.82; 463, 449 cm−1. – UV/vis (CH2Cl2): λmax(εmax) = 580
found C 59.80, H 7.54, N 5.79.
(56), 1032 nm (50 M
−1cm−1). – C36H44Cl4N4Ni2O8S4
(1048.22): calcd. C 41.25, H 4.23, N 5.34, S 12.24; found
C 41.25, H 3.79, N 5.45, S 12.49.
[NiII(L6)] (10)
To a solution of H2L6 · 2HCl (2.40 g, 5.92 mmol) in
methanol (40 mL) was added 5.93 mL of a 1.0 M solu-
tion of NiCl2 · 6H2O in methanol. To the resulting pale-
[NiII(NCS)2(L2)] (13)
To a solution of L2 (500 mg, 1.51 mmol) in methanol
green solution was added dropwise a solution of triethyl- (20 mL) was added a solution of NiCl2 · 6H2O (357 mg,
amine (2.39 g, 23.7 mmol) in methanol (2 mL). The result- 1.50 mmol) in methanol (5 mL). The resulting blue-purple
ing dark-green solid was isolated by filtration and recrystal- solution was stirred overnight and treated with a solution of
◦
lized from acetonitrile. Yield: 1.49 g (65 %). M. p. 184 C NaSCN (243 mg, 3.00 mmol) in water (5 mL). The reac-
(decomp.). – IR (KBr): ν = 3053, 3018, 2905, 1584, 1559, tion mixture was stirred for one hour to give a purple crys-
1466, 1437, 1416, 1072, 1054, 1040, 839, 829, 796, 739, talline powder, which was isolated by filtration, washed with
683 cm−1. – UV/vis (CH2Cl2): λmax(εmax) = 514 (251), isopropanol and dried in air. The crude material was puri-
1
656 nm (313 M−1cm−1). – H NMR (200 MHz, CD3CN): fied by recrystallization from a mixed acetonitrile/methanol
2
δ = 2.22 (d, J = 12 Hz, 2 H, CH2), 2.49 (s, 6 H, NCH3), solvent. Large blue blocks. Yield: 515 mg (68 %). M. p.
2
2
◦
3.08 – 3.25 (q, J = 12 Hz, 4 H, CH2), 4.33 (d, J = 12 Hz, > 300 C (decomp.). – IR (KBr): ν = 3237, 3206 ν(NH),
2 H, CH2), 6.81 – 6.98 (m, 6 H, ArH), 7.28 (m, 2 H, ArH). – 3060, 2967, 2922, 2866, 2107, 2089 ν(SCN), 1474, 1462,
C18H22N2NiS2 (389.20): calcd. C 55.55, H 5.70, N 7.20; 1445, 1430, 1388, 1364, 1334, 1298, 1271, 1260, 1238,
found C 55.43, H 5.72, N 7.19.
1216, 1206, 1198, 1159, 1147, 1130, 1080, 1068, 1036,
1017, 1001, 959, 942, 937, 927, 904, 870, 867, 851, 795,
790, 773, 752, 690 683, 618, 606, 581, 510, 475, 472,
467, 463, 442 cm−1. – UV/vis (CH2Cl2): λmax(εmax) = 592
(78), 1055 nm (63 M−1cm−1). – C20H22N4NiS4 (505.37):
calcd. C 47.53, H 4.39, N 11.09; found: C 47.82, H 4.22,
N 10.93.
[NiII(L7)] (11)
To a solution of H2L7 · 2HCl (2.10 g, 5.21 mmol) in
methanol (30 mL) was added 5.21 mL of a 1.0 M solution
of NiCl2 · 6H2O in methanol. To the resulting brown-green
solution was added dropwise a solution of triethylamine
(2.39 g, 23.7 mmol) in methanol (10 mL). The resulting dark-
red solid was isolated by filtration and recrystallized from
acetonitrile. Yield: 1.45 g (72 %). M. p. 167 ◦C (decomp.). –
[NiIICl2(L2,Me)] (14)
To a solution of L7,Me (500 mg, 1.39 mmol) in methanol
IR (KBr): ν = 2883, 2865, 1579, 1556, 1459, 1434, 1385, (20 mL) was added 1.39 mL of a 1.0 M solution of
1201, 1090, 1062, 803, 764, 673 cm−1. – UV/vis (CH2Cl2): NiCl2 · 6H2O in methanol to give a pale-green solution. A
λ
max(εmax) = 488 (597), 566 nm (233 M−1cm−1). – 1H NMR green solid was obtained upon concentration of the solution.
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T. Fritz et al. · Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands
517
This material was filtered and recrystal◦lized from acetoni- calculated positions and treated isotropically using the 1.2-
trile. Yield: 306 mg (72 %). M. p. 202 C (decomp.). – IR fold Uiso value of the parent atom except methyl protons,
(KBr): ν = 3052, 2865, 1579, 1471, 1424, 1370, 1266, 1067, which were assigned the 1.5-fold Uiso value of the parent
1035, 841, 610 cm−1. – UV/vis (CH3CN): λmax(εmax) = C atoms. All non-hydrogen atoms were refined anisotropi-
626 (21), 1082 nm (19 M−1cm−1). – C20H26Cl2N2NiS2 cally.
(488.16): calcd. C 49.21, H 5.37, N 5.74; found: C 49.20,
H 5.31, N 5.73.
In the crystal structure of 11 the Flack x parameter (abso-
lute structure parameter) was calculated to be 0.02(1) for the
present structure and 0.98(2) for the inverted structure pro-
viding strong evidence that the absolute structure has been
assigned correctly.
CCDC 624429 (9), CCDC 624430 (10), CCDC 624431
(11), CCDC 624432 (12), and CCDC 624433 (13) con-
tain supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data request/cif.
X-Ray crystallography
Crystals of 9 were grown by diffusion of MeOH into a
CH2Cl2 solution. Crystals of 10 were obtained by diffusion
of MeOH into a CH3CN solution. Crystals of 11 and 12
were produced by recrystallization from acetonitrile. Crys-
tals of 13 were grown by recrystallization from a mixed ace-
tonitrile/methanol solvent. Crystal data and data collection
details are reported in Table 1. The diffraction experiments
were carried out at 210(2) K on a BRUKER CCD X-ray
diffractometer using MoKα radiation. The data were pro-
cessed with SAINT [36] and corrected for absorption using
Acknowledgements
This work was supported by the Deutsche Forschungs-
SADABS [37]. Structures were solved by Direct Methods and gemeinschaft (project KE 585/3-1,2,3). We thank Prof. Dr.
refined by full-matrix least-squares on the basis of all data H. Vahrenkamp for providing facilities for X-ray crystallo-
against F2 using SHELXL-97 [38]. H atoms were placed in graphic measurements.
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ꢀ
ꢀꢀ
◦
◦
˚
[30] N(1)···S(3 ) = 3.433 A; N(1) – H(1) – S(3 ) = 140 ;
ꢀꢀ
˚
N(2)···S(3 ) = 3.387A; N(2) – H(2)···S(3 ) = 150.5 .
Symmetry code used to generate equivalent atoms:
−0.5+x, 1.5−y, −0.5+z(ꢀ); 2−x, 2−y, 2−z(ꢀꢀ).
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