Mono- and dinuclear coordination compounds with directional bis(bidentate) ligands

Article abstract of DOI:10.1002/ejic.200900505

The benzene-o-dithiol/salicylimine (S-S/N-O) ligands H₃-1 and H₃-2 have been synthesized, representing the first examples of a new type of polydentate heterodonor ligands, Schiff-ba.se condensation of salicylaldehyde with an amine li

Full text of DOI:10.1002/ejic.200900505

FULL PAPER
DOI: 10.1002/ejic.200900505
Mono- and Dinuclear Coordination Compounds with Directional Bis(bidentate)
Ligands
Johannes Dömer,[a] Florian Hupka,[a] F. Ekkehardt Hahn,*[a] and Roland Fröhlich[b]
Keywords: Heterodonor ligands / S ligands / N,O ligands / Titanium / Nickel
The benzene-o-dithiol/salicylimine (S-S/N-O) ligands H3-1
and H3-2 have been synthesized, representing the first exam-
ples of a new type of polydentate heterodonor ligands.
Schiff-base condensation of salicylaldehyde with an amine
nuclear complex (Bu4N)2[Ni(H-1)2] or the dinuclear complex
(Bu4N)2[Ni2(1)2] depending on the stoichiometric conditions
employed. While (Bu4N)2[Ni(H-1)2] possesses a nickel(II)
center with an S4 coordination environment, the double-
linked to a benzene-o-dithiol donor group leads to the forma- stranded dinuclear complex (Bu4N)2[Ni2(1)2] contains two
tion of the ligands. Bis(cyclopentadienyl)titanium dichloride
reacts selectively at the S-S donor groups of H3-1 and H3-2 to
yield complexes [Cp2Ti(H-1)] and [Cp2Ti(H-2)], respectively.
{NiIIS2NO} centers and shows an antiparallel orientation of
the ligand strands.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Ligand H3-1 reacts with [Ni(OAc)2]·4H2O to yield the mono- Germany, 2009)
nium(IV) or gallium(III) ions gave triple-stranded homodi-
Introduction
nuclear helicates with an antiparallel orientation of the li-
gand strands. Contrary to this, reaction of the catechol/ami-
nophenol ligand with a 1:1 mixture of TiIV and GaIII ions
leads to a triple-stranded heterobimetallic helicate featuring
the parallel orientation of the ligand strands.
We have studied double- and triple-stranded homo- and
heterodinuclear complexes built from mixed benzene-o-di-
thiolato/catecholato ligands.[13] These ligands possess two
electronically different, but sterically similar binding sites
and form homo- and heterobimetallic helical complexes al-
most exclusively featuring a parallel orientation of the li-
gand strands. In fact, mixtures of complexes containing the
isomers with the parallel and antiparallel orientation of the
ligand strands have only been observed twice and the sepa-
ration of the isomers proved impossible.[13b]
Herein, we present the synthesis of mixed benzene-o-di-
thiol/salicylimine (S-S/N-O) ligands H3-1 and H3-2, which
possess two electronically and sterically different bidentate
binding sites. The coordination chemistry of these ligands
towards titanocene dichloride and nickel acetate has been
studied. Nickel(II) is known to adopt a square-planar coor-
dination geometry in complexes with benzene-o-dithiol-
ato,[14] salicylimine,[15] and (SNO)[16] ligands. We became in-
terested in the selective metalation of the two binding sites
in H3-1 and H3-2 and in the coordination chemistry of these
ligands (parallel vs. antiparallel orientation of the ligands
strands) in dinuclear double-stranded nickel(II) complexes.
Metallosupramolecular chemistry allows for the genera-
tion of large and sophisticated molecular structures such
as cages,[1] grids,[2] catenanes,[3] and cylinders[4] using non-
convalent metal–ligand interactions. To gain a deeper un-
derstanding of the self-assembly process and self-organiza-
tion reactions leading to metallosupramolecular architec-
tures, simple molecules were initially studied. Helicates, in
turn, became the model compounds as metallosupramolec-
ular analogues to the perfect, natural example, DNA.[5]
Various double- and triple-stranded polynuclear helicates
using polydentate catecholato,[6] oligopyridine,[7] imine[8]
and, more recently, benzene-o-dithiolato[9] ligands have
been investigated. The use of directional ligands in dinu-
clear complexes is of particular interest since they can be
manipulated to form regioisomeric complexes with a paral-
lel or antiparallel orientation of the ligand strands.[10] How-
ever, investigations into complexes with ligands containing
two or more different donor units (i.e. specialized direc-
tional ligands) are comparatively rare.[11] Albrecht et al.
demonstrated in an impressive example that it is possible to
influence the regioselectivity in helicates using a ligand
which contains two electronically different binding sites.[12]
Reaction of a catechol/aminophenol ligand with either tita-
[a] Institut für Anorganische und Analytische Chemie, Westfäli-
sche Wilhelms-Universität Münster,
Corrensstraße 36, 48149 Münster, Germany
Fax: +49-25183-33013
E-mail: fehahn@uni-muenster.de
[b] Organisch-Chemisches Institut, Westfälische Wilhelms-Uni-
versität Münster,
Results and Discussion
Corrensstraße 40, 48149 Münster, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200900505.
The procedure followed for the preparation of ligands
H3-1 and H3-2 is similar to the method developed for the
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Mono- and Dinuclear Coordination Compounds
Scheme 1. Preparation of ligands H3-1 and H3-2.
synthesis of benzene-o-dithiol/catechol ligands.[13a,13b]
Scheme 1 shows the preparation of Ligand H3-1 in detail.
2,3-Bis(isopropylmercapto)benzoic acid[17] was converted
into the acid chloride 4 using oxalyl chloride. Reaction of
4 with the singly protected amine 3, synthesized from para-
phenylenediamine and Boc-ON, yields compound 5. After
removal of the Boc group with trifluoroacetic acid, the S-
isopropyl protection groups are cleaved by reaction with so-
dium and naphthalene in THF. Treatment with HCl yields
the bidentate S-S ligand precursor 7, which reacts in a
Schiff-base condensation with salicylaldehyde to yield H3-
1.
In order to prevent reduction of the imine function, it is
essential that the reductive cleavage of the S-iPr bonds to
give 7 is carried out before the Schiff-base condensation.
Ligand H3-2 was synthesized using the same procedure,
with the only difference being the use of 4,4Ј-diaminodi-
phenylmethane in lieu of para-phenylenediamine (see Sup-
porting Information).
Scheme 2. Preparation of complexes [Cp2Ti(H-1)] and [Cp2Ti(H-
2)].
Following a published procedure, complexes [Cp2Ti(H-
1)] and [Cp2Ti(H-2)] were synthesized from stoichiometric
amounts of titanocene dichloride and H3-1 and H3-2,
respectively (Scheme 2).[18] These dark green complexes are anion).[18] The five-membered C2S2Ti ring is significantly
stable in air and can be purified by column chromatography bent along the S-S vector, which is a common feature for
(silica gel, dichloromethane/methanol, 20:1, v:v).
[Cp2Ti(bdt)] and [Ti(bdt)3] complexes[9a,18c,19] but uncom-
Single crystals of [Cp2Ti(H-2)]·EtOH·0.5CHCl3, suitable mon for bdt2– complexes involving other transition met-
for an X-ray diffraction analysis, were obtained by layering als.[17a,18b,20] The structure analysis reveals selective binding
a chloroform solution of the complex with n-pentane. The of the Cp2Ti fragment to the benzene-o-dithiolato donor
structure analysis reveals the presence of two essentially while the salicylimine donor group remains uncoordinated.
identicalmolecules of [Cp2Ti(H-2)] in the asymmetric unit This type of discrimination between the potential binding
(Figure 1). Bond lengths and angles in [Cp2Ti(H-2)] re- units of an S-S/N-O ligand was initially surprising, since
semble those of comparable parameters reported for coordination of the hard titanium center to the hard N-O
[Cp2Ti(bdt)] complexes (bdt2– = benzene-o-dithiolato di- binding would have been expected. Neutralization of the
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J. Dömer, F. Hupka, F. E. Hahn, R. Fröhlich
FULL PAPER
positive charge at the titanium by the dithiolato donor unit
appears as a reasonable explanation for the observed selec-
tive binding situation.
Figure 1. Molecular structure of one of the two molecules of
[Cp2Ti(H-2)] in the asymmetric unit (hydrogen atoms and solvent
molecules have been omitted). Selected bond lengths [Å] and angles
[°] for molecule 1 [molecule 2]: Ti–S1 2.4109(12) [2.4074(13)], Ti–
S2 2.4194(12) [2.4201(12)], S1–C11 1.757(4) [1.752(4)], S2–C12
1.765(4) [1.761(4)]; S1–Ti–S2 82.05(4) [82.40(4)], Ti–S1–C11
96.63(13) [95.55(14)], Ti–S2–C12 95.37(13) [94.43(13)].
Scheme 3. Preparation of complexes (Bu4N)[Ni(H-1)2] and (Bu4N)2-
[Ni2(1)2].
Ligand H3-1 is also stepwise metalated by other metal
ions. Two equiv. of ligand H3-1 react in boiling methanol
with one equiv. of nickel acetate in the presence of sodium
hydroxide (Scheme 3). The ESI(–) mass spectrum of the
brown reaction mixture (Figure 2, A) shows the formation
of the complex anion [NiIII(H-1)2]– (m/z = 814.0) together
with some decomposition products. If exposed to air, the
brown color of the solution turned to green within a few
minutes. This color change indicates an aerobic oxidation
of [NiII(H-1)2]2– to [NiIII(H-1)2]–, which is a well known
behavior for {NiIIS4} centers.[17a,21] This oxidation process
can be followed by time-dependent UV/Vis spectroscopy,
wherein the intense band at λ = 464 nm (characteristic for
the {NiIIS4} chromophore) disappears within two minutes,
while a very intensive absorption at λ = 867 nm and a weak
absorption at λ = 352 nm, both characteristic for {NiIIIS4}
chromophores, appear.[17a,20] Addition of two equiv. of tet-
rabutylammonium bromide to the brown solution contain-
ing [NiII(H-1)2]2– followed by diffusion of diethyl ether into
the reaction mixture led to precipitation of brown (Bu4N)2-
[NiII(H-1)2].
Figure 2. ESI(–) mass spectra of the reaction products obtained in
the reaction of ligand H3-1 with [Ni(OAc)2] with different metal/
ligand ratios and reaction times (ratio, reaction time, main prod-
uct): A: 1:2, 24 h, [Ni(H-1)2]–; B: 2:2, 2 h, [Ni(H-1)2]– and [Ni2-
(1)2]2–; C: 2:2, 24 h, [Ni2(1)2]2–.
A comparison of the IR spectra of ligand H3-1 and com-
plex (Bu4N)2[Ni(H-1)2] supports the exclusive coordination
of the benzene-o-dithiolate donor groups in [NiII(H-1)2]2–. that the nickel atom in (Bu4N)2[Ni(H-1)2] is coordinated
The spectrum of the ligand shows a characteristic S–H vi- by two benzene-o-dithiolato donors, while the salicylimine
bration at ν = 2514 cm–1, which is absent in the spectrum groups remain uncoordinated.
˜
of (Bu4N)2[Ni(H-1)2] indicating coordination of both S-S
The reaction of two equiv. of ligand H3-1 with two equiv.
donor groups. Unfortunately, small quantities of a para- of nickel(II) ions in methanol, in the presence of sodium
magnetic nickel(III) species, obtained by rapid oxidation of hydroxide, initially also leads to a dark brown solution. This
the nickel(II), are present in samples of (Bu4N)2[Ni(H-1)2] solution was heated under reflux for 24 h (Scheme 3). The
preventing its NMR spectroscopic characterization. Based ESI(–) mass spectrum of the reaction products shows the
on ESI MS, UV/Vis, and IR spectra it can be concluded formation of dianionic double-stranded dinuclear complex
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Mono- and Dinuclear Coordination Compounds
anion [Ni2(1)2]2– (Figure 2, C). Besides the main product at
m/z = 436.0, traces of the mononuclear complex [Ni(H-1)2]–
are also observed (m/z = 814.0). A comparison of the ESI-
(–) mass spectra recorded after different reaction times
(Figure 2, B: 2 h; C: 24 h) with the spectrum for [Ni-
(H-1)2]– (Figure 2, A) indicates that the mononuclear com-
plex featuring exclusive coordination of the benzene-o-di-
thiolato binding units appears as a reaction intermediate.
Compound (Bu4N)2[Ni2(1)2] can be isolated in analyti-
cally pure form after addition of two equiv. of tetrabutyl-
ammonium bromide, followed by gas diffusion of ethyl
ether into the crude reaction mixture. The compound crys-
tallized as small reddish-brown needles. The ESI(–) mass
spectrum of these needles exhibits exclusively peaks for the
dianionic double-stranded dinuclear complex [Ni2(1)2]2– at
m/z = 436.0 and for the complex anion with one counterion
attached ([(Bu4N)[Ni2(1)2]]– at m/z = 1114.24 and [K[Ni2-
(1)2]]– at m/z = 920.9).
1
Figure 3. H NMR spectrum of complex (Bu4N)2[Ni2(1)2] in [D7]-
DMF at room temperature (δ, ppm, * = DMF, # = methanol).
Contrary to the bis(benzene-o-dithiolato) complex
(Bu4N)2[Ni(H-1)2], the dinuclear compound (Bu4N)2[Ni2-
(1)2] is stable in air indicating the absence of {Ni(bdt)2}
polyhedra. This assumption is corroborated by the UV/Vis
spectrum showing besides the typical π-π* benzene ring ab-
sorptions of the ligands at λ ≈ 300 nm two absorptions at λ
= 424 and 523 nm. These values are consistent with pre-
viously reported data for {NiIIS2NO} centers[16a] and indi-
cate an antiparallel orientation of the ligand strands in
anion [Ni2(1)2]2–.
membered C2S2Ni and six-membered C3NONi rings are ne-
arly perfectly planar and coplanar to each other. The amide
N–H proton maintains only a weak hydrogen bond to the
o-sulfur atom of the benzene-o-dithiolato unit as predicted
by NMR spectroscopy. The weak nature of this interaction
is illustrated by the long nitrogen (N1)-sulfur(S2*) distance
of 3.04 Å.
1
The H NMR spectrum of (Bu4N)2[Ni2(1)2] shows only
one set of signals for both ligand strands (Figure 3), indicat-
ing that only one of the two possible regioisomers with a
parallel or antiparallel orientation of the ligand strands,
respectively, is present. Since both a parallel orientation of
the ligand strands (C2-symmetry) and an antiparallel orien-
tation (inversion symmetry) would lead to a highly symmet-
ric complex anion, the NMR spectrum is consistent with
both possible orientations of the ligand strands. The reso-
nance for the NH proton (δ = 10.62 ppm) appears at an
almost unchanged chemical shift compared to the free li-
gand H3-1 (δ = 10.73 ppm) which was taken as an indica-
tion for the presence of only weak intramolecular N–H···S
hydrogen bonds. Such hydrogen bonds have been shown to
be structure determining in related complexes with cate-
choylamide ligands[1a,22] but are rarely observed for ben-
zene-o-dithiolato complexes.[9,13]
X-ray quality crystals of (Bu4N)2[Ni2(1)2] were obtained
by gas diffusion of diethyl ether into a solution of the salt in
methanol. The compound crystallizes in the orthorhombic
space group Fdd2 with Z = 8. The complex dianion [Ni2-
(1)2]2–, shown in Figure 4, resides on a crystallographic two-
fold axis which passes through the midpoint of the complex
anion. The complex dianion contains two identical pseudo-
square-planar benzene-o-dithiolato/salicylimine nickel(II)
complex units, as predicted by UV/Vis spectroscopy. The
Figure 4. Molecular structure of the [Ni2(1)2]2– anion in (Bu4N)2-
[Ni2(1)2] (the anion resides on a crystallographic twofold axis, hy-
drogen atoms have been omitted for clarity). Selected bond lengths
[Å] and angles [°]: Ni–S1 2.156(2), Ni–S2 2.169(2), Ni–O2 1.881(4),
Ni–N2 1.937(6), C8–N2 1.286(8); S1–Ni–S2 89.31(7), S1–Ni–O2
82.23(15), S1–Ni–N2 176.0(2), S2–Ni–O2 171.54(15), S2–Ni–N2
94.6(2), O2–Ni–N2 93.8(2).
Conclusions
We have prepared new directional ligands with a mixed
Ni–S distances [2.156(2) and 2.169(2) Å] are within the typi- benzene-o-dithiolato/salicylimine (S-S/N-O) donor set. The
cal range for [NiII(bdt)2] complexes,[14,17a] while the Ni–O tetradentate ligands H3-1 and H3-2 are preferentially met-
[1.881(4) Å], and Ni–N [1.937(6) Å] bond lengths are com- alated by TiIV and NiII at the benzene-o-dithiolato donor
parable to salicylimine nickel(II) complexes.[15] The five- function. This feature can be beneficial in subsequent syn-
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J. Dömer, F. Hupka, F. E. Hahn, R. Fröhlich
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(N=CH), 154.6, 146.6, 141.6, 140.8, 138.2, 137.5, 134.0, 133.4,
130.8, 130.5, 129.7, 128.3, 127.8, 126.0, 125.4, 122.1, 121.1, 119.7,
117.3, 115.9 (Ar-C), 41.0 (CH2) ppm. C27H22N2O2S2 (470.11):
calcd. C 68.91, H 4.71, N 5.95, S 13.63; found C 68.73, H 5.06, N
5.86, S 13.28.
theses of heterodinuclear metal complexes. The reactivity of
ligand H3-1 towards nickel(II) showed that a variation of
the metal-to-ligand ratio results in two different coordina-
tion motives of the nickel centers. A metal-to-ligand ratio
of 1:2 leads to the mononuclear complex [Ni(H-1)2]2– with
a {NiII(S-S)2} coordination polyhedron, while a ratio of 2:2
favours the formation of a double-stranded dinuclear com-
plex with two identical {NiII(S-S)(N-O)} coordination poly-
hedra. Complex anion [Ni(H-1)2]2– functions as a reaction
intermediate in the formation of the dinuclear complex
[Ni2(1)2]2–. In summary, we have described a new S-S/N-O
ligand type which reacts in different stoichiometric amounts
with NiII ions to yield two structurally and electronically
different types of metal complexes.
[Cp2Ti(H-1)]: Ligand H3-1 (100 mg, 0.26 mmol) and bis(cyclopen-
tadienyl)titanium dichloride (70 mg, 0.28 mmol) were suspended in
THF (10 mL). After addition of triethylamine (0.3 mL), the mix-
ture was stirred for 12 h at ambient temperature. Subsequently, the
solvent was removed in vacuo. The resulting dark green solid was
purified by column chromatography (SiO2, CH2Cl2/methanol, 20:1,
1
v:v); yield 61 mg (42%). H NMR (400 MHz, CDCl3, 25 °C): δ =
13.33 (s, 1 H, OH), 9.36 (s, 1 H, NH), 8.65 (s, 1 H, N=CH), 7.87–
6.95 (m, 11 H, Ar-H), 6.11 (br. s, 10 H, C5H5) ppm. 13C NMR
(100 MHz, CDCl3): δ = 196.6 (Ar-C-OH), 166.3 (C=O), 159.3
(N=CH), 166.3, 161.1, 152.7, 144.4, 137.4, 135.1, 133.7, 133.0
132.4, 126.7, 124.7, 121.8, 121.0, 119.1, 117.2 (Ar-C), 113.2 (C5H5)
ppm. C30H24N2O2S2Ti (556.52): calcd. C 64.75, H 4.35, N 5.03, S
11.52; found C 64.48, H 4.16, N 5.26, S 11.46.
Experimental Section
General: 2,3-Bis(isopropylmercapto)benzoyl chloride 4[17] and com-
pounds 3, 5, and 6 were prepared according to literature pro-
cedures.[13b]
[Cp2Ti(H-2)]: Complex [Cp2Ti(H-2)] was synthesized as described
for [Cp2Ti(H-1)] from H3-2 (76 mg, 0.16 mmol), [Cp2TiCl2] (40 mg,
0.16 mmol) and triethylamine (0.2 mL) in THF; yield 78 mg (75%).
Crystals of the solvate [Cp2Ti(H-2)]·EtOH·0.5CHCl3 were obtained
1
at ambient temperature from a chloroform/n-pentane solution. H
4Ј-[2,3-Bis(mercapto)benzamido]-4-aminobenzene (7): Compound 6
(1.87 g, 5.2 mmol), naphthalene (1.66 g, 13 mmol), and sodium
(598 mg, 26 mmol) were suspended in THF (30 mL) and stirred for
12 h at ambient temperature. Subsequently, methanol (15 mL) was
added and then all solvents were removed in vacuo. The residue
was dissolved in water (20 mL) and the aqueous phase was washed
with diethyl ether (3ϫ20 mL) and filtered. Addition of hydrochlo-
ric acid gave a pale yellow precipitate which was isolated by fil-
tration, washed with water and diethyl ether and dried in vacuo;
yield 1.15 g (80.1%). 1H NMR (400 MHz, [D7]DMF, 25 °C): δ =
10.93 (s, 1 H, NH), 8.36 (br. s, 2 H, NH2), 7.91–7.11 (m, 7 H, Ar-
H), 3.80 (br. s, 2 H, SH) ppm. 13C NMR (100 MHz, [D7]DMF,
25 °C): δ = 168.2 (C=O), 138.4, 137.1, 135.5, 132.5, 131.9, 131.6,
126.5, 125.5, 123.1, 121.8 (Ar-C) ppm. C13H12N2OS2 (276.38):
calcd. C 56.49, H 4.38, N 10.14, S 23.20; found C 56.59, H 4.25,
N 10.25, S 22.94.
NMR (200 MHz, CDCl3, 25 °C): δ = 13.32 (s, 1 H, OH), 9.12 (s,
1 H, NH), 8.62 (s, 1 H, N=CH), 7.84–6.92 (m, 15 H, Ar-H), 6.09
(br. s, 10 H, C5H5), 3.99 (s, 2 H, CH2) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C): δ = 196.7 (Ar-C-OH), 166.3 (C=O), 159.1 (N=CH),
162.0, 161.1, 152.6, 146.5, 140.2, 136.8, 136.5, 135.4, 133.0, 132.2,
129.8, 129.4, 126.4, 124.7, 121.2, 119.8, 119.2, 119.0, 117.2 (Ar-C),
113.2 (C5H5), 40.9 (CH2) ppm. C37H30N2O2S2Ti (646.64): calcd. C
68.72, H 4.68, N 4.33, S 9.92; found C 68.93, H 4.70, N 4.11, S
10.29.
(Bu4N)2[Ni(H-1)2]: Ligand H3-1 (64 mg, 0.17 mmol) and sodium
hydroxide (20 mg, 0.5 mmol) were dissolved in methanol (10 mL).
After addition of nickel(II) acetate tetrahydrate (23 mg, 0.09 mmol)
in methanol (2 mL) the reaction mixture was heated under reflux
for 12 h. After cooling to ambient temperature, the mixture was
filtered and tetrabutyl ammonium bromide (55 mg, 0.17 mmol) was
added to the filtrate. Slow vapour diffusion of diethyl ether into this
solution gave a brown precipitate which was collected and dried in
Ligand H3-1: Compound 7 (1.3 g, 4.7 mmol) was suspended in
methanol (10 mL) and salicylaldehyde (0.58 g, 4.7 mmol) in meth-
anol (5 mL) was added. The reaction mixture was stirred for 12 h
at ambient temperature. A yellow precipitate formed during this
time which was isolated by filtration, washed with methanol and
vacuo; yield 18 mg (15%). IR (KBr): ν = 3275 (NH), 2959, 2872
˜
(CH), 1636 (C=O), 1612 (C=C), 1513 (C=N) cm–1. UV/Vis (DMF):
λmax (ε) = 313 (28000), 350 (20400) 464 nm (4100 mol–1 dm3 cm–1).
MS (ESI, negative ions): m/z = 814.04 [Ni(H-1)2]–, 710.01 [[Ni(H-
1)2]-C7H4O]–. C72H100N6NiO4S4 (1300.56): calcd. C 66.49, H 7.75,
N 6.46, S 9.86; found C 66.55, H 7.90, N 6.53, S 10.01.
1
dried in vacuo; yield 1.0 g (55%). H NMR (400 MHz, [D7]DMF,
25 °C): δ = 10.73 (s, 1 H, NH), 9.06 (s, 1 H, N=CH), 7.98–6.99 (m,
11 H, Ar-H), 3.55 (br. s, 2 H, SH) ppm. 13C NMR (100 MHz, [D7]-
DMF, 25 °C): δ = 166.3 (C=O), 154.65 (N=HC), 140.8, 140.6,
139.9, 130.3, 129.7, 128.5, 128.3, 127.8, 126.1, 124.7, 124.5, 121.8,
(Bu4N)2[Ni2(1)2]: Ligand H3-1 (31 mg, 0.08 mmol) and sodium hy-
droxide (10 mg, 0.25 mmol) were dissolved in methanol (10 mL).
After addition of nickel acetate tetrahydrate (23 mg, 0.09 mmol) in
methanol (2 mL) the reaction mixture was heated under reflux for
12 h. After cooling to ambient temperature, tetrabutyl ammonium
bromide (55 mg, 0.18 mmol) was added to the mixture. The mixture
was filtered and slow vapour diffusion of diethyl ether into the
filtrate gave a red-brown precipitate which was collected and dried
121.5, 121.3, 119.7, 115.9 (Ar-C) ppm. IR (KBr): ν = 3292 (NH),
˜
2514 (SH), 1653 (C=O), 1637 (C=C), 1570 (C=N) cm–1.
C20H16N2O2S2 (380.48): calcd. C 63.13, H 4.24, N 7.36, S 16.85;
found C 63.14, H 4.33, N 7.49, S 16.90.
Ligand H3-2: Ligand H3-2 was synthesized as described for H3-1
from N-[2,3-bis(mercapto)benzamido]bis(4-aminophenyl) methane
(700 mg, 1.9 mmol) and salicylaldehyde (280 mg, 2.3 mmol) in in vacuo. X-ray-quality crystals of (Bu4N)2[Ni2(1)2] were obtained
methanol. For the preparation of N-[2,3-bis(mercapto)benzamido]-
by slow gas diffusion of diethyl ether into a solution of the salt in
bis(4-aminophenyl) methane and its precursors see Supporting In-
methanol; yield 11 mg (10%). 1H NMR (400 MHz, [D7]DMF,
formation; yield 714 mg (80%). 1H NMR (400 MHz, [D7]DMF, 25 °C, for assignment of resonances see Figure 3): δ = 10.62 (s, 2
3
25 °C): δ = 10.48 (s, 1 H, NH), 9.01 (s, 1 H, N=CH), 7.82–6.96 (m,
H, NH), 7.92 (s, 2 H, N=CH), 7.67 [d, JH,H = 8.4 Hz, 4 H, Ar-
15 H, Ar-H), 4.76 (br. s, 2 H, SH), 4.03 (s, 2 H, CH2) ppm. 13C H(d)], 7.27 [d, JH,H = 8.4 Hz, 4 H, Ar-H(e)], 7.25 [m, 4 H, Ar-
3
3
3
NMR (100 MHz, [D7]DMF, 25 °C): δ = 166.0 (C=O), 161.7
H(c, g)], 7.10 [t, JH,H = 7.9 Hz, 2 H, Ar-H(i)], 6.96 [d, JH,H =
3604
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3600–3606

Mono- and Dinuclear Coordination Compounds
3
7.5 Hz, 2 H, Ar-H(a)], 6.58 [t, JH,H = 7.5 Hz, 2 H, Ar-H(b)], 6.50
Acknowledgments
3
3
[d, JH,H = 7.9 Hz, 2 H, Ar-H(j)], 6.36 [t, JH,H = 7.4 Hz, 2 H, Ar-
H(h)], 3.38 (m, 16 H, NCH2), 1.75 (m, 16 H, CH2CH2CH2), 1.39
(qt, 3JH,H = 7.4 Hz, 16 H, CH2CH3), 0.96 (t, 3JH,H = 7.4 Hz, 24 H,
CH3) ppm. 13C NMR (100 MHz, [D7]DMF, 25 °C): δ = 168.1
(C=O), 166.7 (N=CH), 166.9, 165.3, 152.4, 150.1, 146.3, 137.5,
134.6, 134.0, 132.9, 127.9, 124.9, 122.7, 122.2, 121.01, 119.9, 113.6
(Ar-C), 58.9 (NCH2), 24.2 (CH2CH2CH2), 20.2 (CH2CH3), 13.8
This work was supported by the Deutsche Forschungsgemeinschaft
(DFG) (IRTG 1444) and the Fonds der Chemischen Industrie. We
thank Dr Alexander Hepp for measuring the NMR spectra and Dr
Heinrich Luftmann for measuring the mass spectra.
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(CH ) ppm. IR (KBr): ν = 3218 (NH), 2958, 2874 (CH), 1684
˜
3
(C=O), 1654 (C=C), 1609 (C=N) cm–1. UV/Vis (DMF): λmax (ε) =
301 (29000), 424 (6200), 523 nm (1700 mol–1 dm3 cm–1). MS (ESI,
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X-ray Diffraction Studies: Diffraction data for [Cp2Ti(H-2)]·
EtOH·0.5CHCl3 and (Bu4N)2[Ni2(1)2] were collected with a Bruker
AXS APEX CCD diffractometer equipped with a rotation anode
at 153(2) K using graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å) for [Cp2Ti(H-2)]·EtOH·0.5CHCl3 or Cu-Kα radiation (λ
= 1.54178 Å) for (Bu4N)2[Ni2(1)2], respectively. Diffraction data
were collected over the full sphere and were corrected for absorp-
tion. The data reduction was performed with the Bruker
SMART[23] program package. Structure solutions were found with
the SHELXS-97[24] package using the heavy-atom method or the
direct methods and were refined with SHELXL-97[25] against |F2|
using first isotropic and later anisotropic thermal parameters for all
non-hydrogen atoms. Hydrogen atoms were added to the structure
models on calculated positions.
CCDC-691379 {for [Cp2Ti(H-2)]·EtOH·0.5CHCl3} and -734840
{for Bu4N)2[Ni2(1)2]} contain the supplementary 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.
Crystal Data for [Cp2Ti(H-2)]·EtOH·0.5CHCl3: C39.5H35.5N2-
Cl1.5O3S2Ti, M = 751.39, µ = 0.510 mm–1, ρ = 1.398 gcm–3, mono-
clinic, P21/n, Z = 8, a = 12.1019(4), b = 16.5718(6), c =
35.7715(13) Å, β = 95.6730(10)°, V = 7138.8(4) Å3, 72140 measured
reflections, 17115 unique reflections (Rint = 0.0577), R = 0.0754,
wR2 = 0.1940 for 11683 contributing reflections [IՆ2σ(I)], refine-
ment against |F2|with anisotropic thermal parameters for all non-
hydrogen atoms and hydrogen atoms on calculated positions. The
asymmetric unit contains two essentially identicalmolecules of
[Cp2Ti(H-1)], two molecules of EtOH and one disordered molecule
of CHCl3.
Crystal Data for (Bu4N)2[Ni2(1)2]: C72H98N6Ni2O4S4, M = 1357.22,
µ = 2.120 mm–1, ρ = 1.251 gcm–3, orthorhombic, Fdd2, Z = 8, a =
36.989(2), b = 44.083(3), c = 8.8366(6) Å, V = 14409(2) Å3, 20469
measured reflections, 6315 unique reflections (Rint = 0.1263), R =
0.0773, wR2 = 0.1536 for 4986 contributing reflections [IՆ2σ(I)],
refinement against |F2| with anisotropic thermal parameters for all
non-hydrogen atoms and hydrogen atoms on calculated positions.
The complex anion resides on a crystallographic twofold axis pass-
ing through its midpoint. Some residual electron density on and
close to the twofold axis was found but could not be refined as
solvent molecules (methanol or diethyl ether).
Supporting Information (see also the footnote on the first page of
this article): Detailed experimental data for the preparation of H3-
2.
Eur. J. Inorg. Chem. 2009, 3600–3606
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3605

J. Dömer, F. Hupka, F. E. Hahn, R. Fröhlich
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3600–3606