Sterically fixed dithiolate ligands and their zinc complexes: Derivatives of 1,8-dimercaptonaphthalene

Article abstract of DOI:10.1002/1099-0682(200105)2001:5<1183::AID-EJIC1183>3.0.CO;2-I

The synthesis of two new dithiols, 1,8-dimercapto-2,7-di(tert-butyl)naphthalene (H₂L¹) and 1,8-dimercaptonaphthoic anhydride (H₂L²), is described. They react with diethylzinc to yield the polymeric complexes L¹Zn and L²Zn. L¹Zn dissolves in the presence of pyridine to form [L¹Zn·py]_x, which is presumed to be dimeric. Both L¹Zn and L²Zn react with neocuproin. Structure determinations have confirmed the tetrahedral ZnN₂S₂ coordination in the resulting LZn·neo complexes.

Full text of DOI:10.1002/1099-0682(200105)2001:5<1183::AID-EJIC1183>3.0.CO;2-I

FULL PAPER
Sterically Fixed Dithiolate Ligands and Their Zinc Complexes: Derivatives of
1,8-Dimercaptonaphthalene
Markus Tesmer[a] and Heinrich Vahrenkamp*[a]
Keywords: S ligands / Alcohols / Zinc / Structure elucidation / Enzyme models
The synthesis of two new dithiols, 1,8-dimercapto-2,7-di(tert-
butyl)naphthalene (H2L1) and 1,8-dimercaptonaphthoic an- sumed to be dimeric. Both L1Zn and L2Zn react with neocup-
hydride (H2L2), is described. They react with diethylzinc to
roin. Structure determinations have confirmed the tetrahed-
yield the polymeric complexes L1Zn and L2Zn. L1Zn dissolves ral ZnN2S2 coordination in the resulting LZn·neo complexes.
in the presence of pyridine to form [L1Zn·py]x, which is pre-
Introduction
We are not aware that these principles have been applied
to chelating bis-thiolate ligands, and our attempts to do so
are reported in this paper. We wanted to synthesize a ligand
in which the two thiolate donors have fixed positions in
space. This should serve the purpose of preorganization (i.e.
good chelating properties) while at the same time the lack
of conformational freedom would reduce the oligonucleat-
ing tendency. We chose the 1,8-dimercaptonaphthalene
framework for our purposes. It strictly defines the locations
of the two sulfur atoms, while allowing the attachment of
bulky substituents at the 2- and 7-positions or the attach-
ment of electron-withdrawing substituents anywhere on the
naphthalene skeleton. The target ligands were H2L1 and
H2L2. This paper describes their synthesis and some prelim-
inary chemistry of their zinc complexes.
The chemistry of transition metal thiolates is a world of
thiolate-bridged oligomers and polymers.[1,2] This extends
into biology with the ubiquitous presence of the Fe4S4(SR)4
redox unit and the accumulation of copper, zinc or cad-
mium in the metallothioneins. Yet Nature is able to prevent
thiolate bridging and metal aggregation by isolating the
cysteine-thiolate donors and limiting the space available to
the metals, thereby making the cysteine sulfur one of the
prominent monodentate ligands for metals in biology.
Model studies of sulfur-rich metal environments in
metalloenzymes invariably suffer from this problem of com-
plex aggregation.[3,4] As a result, far-reaching advances have
often only been made in the exceptional situations where
thiolate bridging is not preferred, typical examples being
the bioinorganic chemistry of octahedral iron[5] or the
ZnN2S2 coordination motif of the zinc finger proteins.[6]
In the bioinorganic chemistry of zinc, model studies of
the alcohol dehydrogenases have met with this problem.[7,8]
The attachment of the metal to the protein by an NS2 (histi-
dine, cysteine, cysteine) ligation[9] calls for amine bis-thiol-
ates as model ligands. But to date no such thiolate[10,11] has
been found to produce mononuclear (NS2)ZnϪX com-
plexes that are free from thiolate bridging and that bear a
ligand X as a substitute for the substrate of the enzyme.
The best approximation has been achieved by NS2 ligands
in which the sulfur donors are not of the thiolate type.[12]
The standard procedures for reducing the bridging tend-
ency of thiolate ligands (steric hindrance or increased elec-
tronegativity) have been applied successfully to zinc com-
plexes: tris(tert-butyl)benzene thiolate has been used to pro-
duce a tricoordinate Zn(SR)2·pyridine complex,[13] and we
have used pentafluorobenzene thiolate to model the
ZnNS2O ligation pattern of the alcohol dehydrogenase
enzymeϪsubstrate complexes.[14]
Results and Discussion
The Ligands
1,8-Dimercaptonaphthalene[15] and 1,8-dimercaptohex-
achloronaphthalene[16] have been described in the literature,
but not investigated extensively as ligands.[16,17] Our ap-
proach of generating the 1,8-dithiol functionality in H2L1
and H2L2 followed the established procedure of introducing
sulfur as the naphthalene-1,8-disulfide and then reducing it.
Scheme 1 describes this for H2L1, using the literature
method to prepare naphthalene-1,8-disulfide.[18] The overall
yield of H2L1 starting from bromonaphthalene was 8%.
H2L1 is a yellow crystalline solid which is soluble in weakly
polar organic solvents. It is easily identified by its simple
[a]
Institut für Anorganische und Analytische Chemie der
Universität Freiburg,
Albertstraße 21, 79104 Freiburg, Germany
Fax: (internat.) ϩ49-761/203-6001
E-mail: vahrenka@uni-freiburg.de
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0505Ϫ1183 $ 17.50ϩ.50/0
1183

M. Tesmer, H. Vahrenkamp
FULL PAPER
1H NMR spectrum (see Experimental Section). Upon expo- Zinc Complexes
sure to air, it is oxidized to the disulfide. Upon depro-
tonation, its colour in solution becomes a deeper yellow.
Diethyl zinc was found to be the best reagent to convert
H2L1 and H2L2 into the binary zinc complexes ZnL1 (1)
and ZnL2 (2), respectively, by hydrolytic cleavage in aprotic
media. The resulting compounds 1 and 2 were obtained in
very good yields. They dissolve only in very good donor
solvents, in agreement with the assumption that they are
oligomeric or polymeric. It is likely that they contain zinc
in a ZnS4 environment, i.e. each thiolate sulfur bridges two
zinc ions.
Some attempts were made to isolate adducts of ZnL with
monodentate donors. They were successful for the combina-
tion ZnL1/pyridine. Upon addition of equimolar amounts
of pyridine to a suspension of ZnL1 in chloroform, the com-
plex dissolved. However, a new precipitate of composition
ZnL1·pyridine (3) formed immediately; again, this complex
was of rather low solubility. This reaction did not occur
with ZnL2. Assuming the likely ZnNS3 coordination in this
species, it follows that one of the two thiolate functions acts
as a bridge. Thus a dimeric structure can be proposed for
3, in analogy with the one described by Kellogg for the zinc
complex of a sterically hindered pyridine-bis(thiolate) li-
gand.[10]
Scheme 1
The synthesis of H2L2 was performed according to
Scheme 2 starting from acenaphthene, using the literature
procedure[19] to generate its 1,8-dibromide. The overall yield
of H2L2 starting from acenaphthene was again 8%.
As expected, the highly preferred ZnN2S2 coordination
with 1 and 2 was readily found in the form of mononuclear
complexes. We chose neocuproin (2,9-dimethylphenanthro-
line, neo) as the bidentate nitrogen co-ligand, as we had
previously found it to be most suitable for this purpose.[20]
Compounds 1 and 2 dissolve in its presence, and cleanly
form the 1:1 complexes (neo)Zn(L1) (4) and (neo)Zn(L2)
(5), which are orange crystalline solids suitable for X-ray
analysis (see below). In complex 5, the electron-withdrawing
properties of ligand L2 can be confirmed by the positions
of its ν(CO-carboxylate) IR bands: these are shifted by ap-
proximately 20 cmϪ1 to lower wavenumbers than those of
H2L2.
Scheme 2
H2L2 is a yellow solid of low solubility which again has
a simple 1H NMR spectrum (see Experimental Section). Its
air sensitivity is similar to that of H2L1. Deprotonation
greatly enhances its solubility in polar solvents. Its solutions
are deep red, indicating the delocalized nature of the anion
according to the following valence structures.
Structures
The structure determinations of 4 and 5 (see Figure 1 and
2) confirmed the identities and compositions of the species
described here, and gave some information about the ligat-
ing properties of L1 and L2. The crystalline structure of
compound 4 has an asymmetric unit with two molecules
that are quite similar. The overall coordination geometries
in 4 and 5 are as expected, with ZnϪN and ZnϪS distances
1184
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188

Sterically Fixed Dithiolate Ligands and Their Zinc Complexes
FULL PAPER
in the normal range and with relatively small NϪZnϪN formational requirements of the sulfur atoms which do not
and relatively large SϪZnϪS angles.
allow for the zinc ions to reside together with them in the
planes of the naphthalene rings. The necessity for small
ZnϪSϪC angles (101Ϫ108°) together with the given ZnϪS
bond lengths enforces an out-of-plane motion of the zinc
ions and/or both sulfur atoms. This geometry is highlighted
in Figure 1 and 2. In these figures, the bisector of the
SϪZnϪS angle is in the plane of the paper with a viewing
direction normal to the plane of the neocuproin ligand. The
naphthalene rings are bent away from the bisector, and
partly rotated with respect to their expected orientation per-
pendicular to the plane of the paper. This relieves the tor-
sional strain at the sulfur atoms and the intramolecular re-
pulsive forces.
More specifically, in both independent molecules of 4,
the sulfur atoms are bent away in opposite directions from
˚
the naphthalene plane by approximately 1.0 and 1.2 A. The
carbon atoms attached to them follow this movement to a
lesser degree. The out-of-plane displacement of the sulfur
atoms is reversed for the zinc ion which is roughly in the
naphthalene plane again. Concomitantly, the naphthalene
plane is tilted by only 8° with respect to the bisector of the
SϪZnϪS angle. In 5, the sulfur atoms are also bent away
from the naphthalene plane in opposite directions, but this
Figure 1. Molecular structure of 4 (one of the two independent
˚
molecules); bond lengths [A]: ZnϪS1 2.227(1)/2.222(1), ZnϪS2
2.229(1)/2.226(1), ZnϪN1 2.086(3)/2.085(3), ZnϪN2 2.091(3)/
2.092(3); bond angles [°]: S1ϪZnϪS2 103.06(4)/103.51(4),
N1ϪZnϪN2 80.1(1)/80.5(1), S1ϪZnϪN1 126.1(1)/126.6(1),
S1ϪZnϪN2 114.5(1)/115.7(1), S2ϪZnϪN1 113.0(1)/109.0(1),
S2ϪZnϪN2 120.4(1)/122.0(1)
˚
time by only 0.75 A on average. Contrary to the case in
compound 4, both SϪZn bonds in 5 are tilted in the same
direction, thereby causing the observed tilt of 30° of the
naphthalene ring with respect to the bisector of the
SϪZnϪS angle. The reason for this difference between 4
and 5 may lie in the tert-butyl substituents of 4, which pre-
vent the pronounced tilting owing to their van der Waals
interactions with the methyl groups of the neocuproin li-
gand. Generally, the observed asymmetry of 4 and 5 seems
to effect the necessary relief from the inherent steric strain,
thereby making ligand L1 and L2 suitable for their inten-
ded purpose.
The ZnN2S2 ligation in complexes 4 and 5 is also the
most common one in zinc finger motifs.[6] The geometric
features of the ZnN2S2 units in these complexes and in the
zinc fingers compare reasonably well but, as was discussed
in detail for zinc-neocuproin complexes of bis(cysteinyl)-
peptides,[20] the geometric constraints induced by the small
bite angle of the neocuproin ligand make the NϪZnϪN
angles smaller and concomitantly the SϪZnϪS angles
larger than the situation in the proteins.
Conclusions
The ligands H2L1 and H2L2 were accessible. They are two
new members of a hitherto unexplored group of sterically
fixed dithiolate ligands that are geometrically similar to the
dithiolene ligands. The ligand H2L1 is sterically crowded
owing to the favourable positioning of its tert-butyl sub-
stituents, whereas the Ligand H2L2 is electron poor. At the
˚
Figure 2. Molecular structure of 5; bond lengths [A]: ZnϪS1
2.230(2), ZnϪS2 2.260(2), ZnϪN1 2.058(5),ZnϪN2 2.050(4); bond
angles [°]: S1ϪZnϪS2 103.04(7),N1ϪZnϪN2 81.6(2), S1ϪZnϪN1
125.1(1),
S1ϪZnϪN2
122.7(1),
S2ϪZnϪN1
111.8(1),
S2ϪZnϪN2 112.0(1)
However, both complexes are severely distorted from same time, the dianion L2 should have ligating properties
their ideal C2v symmetry. The reason for this lies in the con- for hard metal ions at its carboxylate oxygen atoms, as in-
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188
1185

M. Tesmer, H. Vahrenkamp
FULL PAPER
1
42.40, H 1.19; found C 42.22, H 1.19. Ϫ H NMR (CDCl3): δ ϭ
dicated by its resonance structures and the IR spectroscopic
data of its zinc complex 5.
7.93 (d, J ϭ 7.6 Hz, 2 H, H4,7), 8.27 (d, J ϭ 7.6 Hz, 2 H, H3,8).
The preliminary complexation reactions with zinc have
outlined the coordinating potential of both ligands. While
the binary ZnL compounds 1 and 2 could be expected to
be polymeric, addition of one pyridine ligand to 1 is suffi-
cient to break up its polymeric structure. The excellent co-
ligand neocuproin ensured the formation of the 1:1:1 com-
plexes 4 and 5, with a ZnN2S2 coordination. Their structure
determinations have revealed the basic ligation properties
of the naphthalene-1,8-dithiolates. The conformational re-
quirements of the sulfur atoms do not allow for a planar
arrangement of the naphthalene rings, the sulfur atoms and
the zinc ion. However, the two complex geometries that
were observed show that a strain-free and strong metal-di-
thiolate coordination is present.
b) 1,8-Dibromonaphthoic Anhydride: 1,8-Dibromoacenaphthene-
dione (6.23 g, 18.3 mmol) was dissolved in a mixture of 1,4-dioxane
(400 mL) and NaOH (2 , 400 mL) and heated to 100 °C. A solu-
tion of H2O2 (10%, 400 mL) was added slowly to the stirred solu-
tion. After stirring for a further 30 min. at 100 °C, the mixture was
cooled to room temp. and filtered. The filtrate was acidified with
conc. HCl producing a voluminous precipitate. This was separated
by centrifugation, washed twice with water and dried in vacuo.
Recrystallization from acetic anhydride (2.5 L) yielded 1,8-dibro-
monaphthoic anhydride (4.84 g, 74%) as a light brown powder, m.p.
260 °C. Ϫ C12H4Br2O3 (356.0): calcd. C 40.49, H 1,13; found C
1
40.45, H 1.11. Ϫ H NMR ([D6]acetone): δ ϭ 7.95 (d, J ϭ 7.5 Hz,
2 H, H5,8), 8.17 (d, J ϭ 7.5 Hz, 2 H, H4,9).
c) Naphthoic Anhydride-1,8-disulfide: Na (1.56 g, 67.9 mmol) and
sulfur (2.18 g, 68.0 mmol) were suspended in DMF (40 mL). The
mixture was stirred at 100 °C until the vigorous reaction had pro-
duced a voluminous precipitate. A suspension of 1,8-dibromo-
naphthoic anhydride in DMF (20 mL) was quickly added, upon
which the mixture turned deep purple. After heating at 140 °C for
10 min, it was poured while hot into water (300 mL). The resulting
orange suspension was acidified with conc. HCl, and the precipitate
was isolated by centrifugation, washed twice with water and dried
in vacuo. Recrystallization from 1,4-dioxane (1.6 L) in the presence
of activated charcoal (1 g) yielded naphthoic anhydride-1,8-disulf-
ide (2.41 g, 68%) as a red solid, m.p. 330 °C (dec.). Ϫ C12H4O3S2
(356.0): calcd. C 55.37, H 1.55; found C 55.32, H 1.59. Ϫ 1H NMR
([D6]acetone): δ ϭ 7.83 (d, J ϭ 8.0 Hz, 2 H, H3,9), 8.37 (d, J ϭ
8.0 Hz, 2 H, H4,8).
Experimental Section
For general preparative and measuring procedures, see ref.[21] All
reactions were carried out under a nitrogen atmosphere. Starting
materials were obtained commercially or prepared according to the
references given.
Ligand H2L1: a) 2,7-Di(tert-butyl)naphthalene-1,8-disulfide: Naph-
thalene-1,8-disulfide[18] (3.00 g, 15.8 mmol) was dissolved at 50 °C
in a mixture of nitromethane (37 mL) and tert-butyl chloride
(4.38 g, 47.3 mmol). Anhydrous AlCl3 (400 mg, 3.00 mmol) was ad-
ded and the mixture was stirred at 50 °C for 20 min. After cooling
to room temp. the product precipitated. Washing with nitrometh-
ane and recrystallization from acetone yielded 2,7-di(tert-butyl)-
naphthalene-1,8-disulfide (1.82 g, 38%) as orange crystals, m.p. 129
°C. Ϫ C18H22S2 (302.5): calcd. C 71.47, H 7.33; found C 71.55, H
d) HL2: Naphthoic anhydride-1,8-disulfide (0.32 g, 1.20 mmol) was
suspended in methanol (10 mL). After the addition of NaBH4
(94 mg, 2.50 mmol) the mixture turned purple. After stirring for
2 h, the mixture was filtered and the filtrate treated with conc. HCl
(1 mL) and stirred for 1 h. The resulting yellow precipitate was
washed with water and methanol and dried in vacuo to afford H2L2
as a yellow powder (0.23 g, 73%), m.p. 280 °C (dec.). Ϫ C12H6O3S2
(262.3): calcd. C 54.95, H 2.31; found C 54.18, H 2.59. Ϫ IR (KBr):
1
7.37. Ϫ H NMR (CDCl3): δ ϭ 1.50 (s, 18 H, tBu), 7.36 (d, J ϭ
8.0 Hz, 2 H, H5,6), 7.42 (d, J ϭ 8.0 Hz, 2 H, H4,7).
b) H2L1: A solution of 2,7-di(tert-butyl)naphthalene-1,8-disulfide
(5.43 g, 28.5 mmol) in THF (50 mL) was treated with LiAlH4
(1.08 g, 28.5 mmol) and heated at reflux for 1 h. After cooling to
room temp., water (1 mL) and 10  HCl (15 mL) were added drop-
wise to the stirred solution. After extraction with dichloromethane
(100 mL), the organic layer was separated, washed with water (3 ϫ
30 mL) and dried over Na2SO4. The solvent was removed in vacuo
and the residue was recrystallized from cyclohexane/THF (5:1).
H2L1 was obtained as a yellow powder (8.25 g, 95%), m.p. 137 °C.
Ϫ C18H24S2·C6H12 (304.5 ϩ 84.2): calcd. C 74.16, H 9.34; found C
75.40, H 9.31. Ϫ IR (KBr): ν˜ ϭ 2544 (SH) cmϪ1. Ϫ 1H NMR
(CDCl3): δ ϭ 1.50 (s, 12 H, C6H12), 1.64 (s, 18 H, tBu), 4.41 (s, 2
H, SH), 7.48 (d, J ϭ 8.6 Hz, 2 H, H4,5), 7.50 (d, J ϭ 8.6 Hz, 2
H, H3,6).
1
ν˜ ϭ 2537 (SH) cmϪ1. Ϫ H NMR ([D6]acetone): δ ϭ 5.51 (s, 2 H,
SH), 7.80 (d, J ϭ 8.2 Hz, 2 H, H5,8), 8.42 (d, J ϭ 8.2 Hz, 2 H, H4,9).
Compound 1: A solution of H2L1 (0.20 g, 0.66 mmol) in chloroform
(10 mL) was treated dropwise with a solution of diethyl zinc
(81 mg, 0.66 mmol) in n-hexane (2.0 mL). The resulting precipitate
was filtered off, washed with chloroform and dried in vacuo, leav-
ing behind compound 1 (0.23 g, 95%) as a yellow powder, m.p. 160
°C (dec.). Ϫ C18H22S2Zn (367.9): calcd. C 58.77, H 6.03, Zn 17.77;
1
found C 57.38, H 5.97, Zn 17.32. Ϫ H NMR ([D6]DMSO): δ ϭ
1.68 (s, 18 H, tBu), 7.06 (d, J ϭ 8.5 Hz, 2 H, H4,5), 7.25 (d, J ϭ
8.5 Hz, 2 H, H3,6).
Compound 2: Prepared in the same manner as 1 from H2L2 (0.10 g,
0.38 mmol) in toluene (15 mL) and diethyl zinc (47 mg,
0.38 mmol). Compound 2 was obtained as a pale orange powder
(0.12 g, 97%), m.p. 175 °C (dec.). Ϫ C12H4O3S2Zn (325.7): calcd.
C 44.26, H 1.24, Zn 20.08; found C 44.07, H 1.16, Zn 19.89. Ϫ 1H
NMR ([D6]DMSO): δ ϭ 7.84 (d, J ϭ 8.2 Hz, 2 H, H5,8), 8.37 (d,
J ϭ 8.2 Hz, 2 H, H4,9).
Ligand H2L2: a) 1,8-Dibromoacenaphthenedione: 1,8-Dibromoace-
naphthene[19] (8.51 g, 27.3 mmol) was dissolved in acetic anhydride
(1 L) at 110 °C. CrO3 (21.1 g, 211 mmol) was added carefully to
the stirred solution over a period of 2 h. The resulting green sus-
pension was stirred at 160 °C for 30 min., and then poured while
hot onto crushed ice (1 kg). Conc. HCl (20 mL) was added and the
mixture was filtered. The brownish precipitate was washed with
water, dried in vacuo and recrystallized from acetic anhydride (2 L).
Compound 3: A suspension of 1 (0.20 g, 0.54 mmol) in chloroform
(10 mL) was treated with a solution of pyridine (44 mg, 0.55 mmol)
1,8-Dibromoacenaphthenedione (6.23 g, 67%) was obtained as a in chloroform (2 mL). A clear solution was formed from which a
light brown solid, m.p. 239 °C. Ϫ C12H4Br2O2 (340.0): calcd. C
yellow solid precipitated after a few seconds. The precipitate was
1186
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188

Sterically Fixed Dithiolate Ligands and Their Zinc Complexes
FULL PAPER
filtered off, washed with chloroform and dried in vacuo, leaving
behind compound 3 as a yellow powder (0.21 g, 85%), m.p. 105 °C
(dec.). Ϫ C23H27NS2Zn (447.0): calcd. C 61.80, H 6.09, N 3.13, Zn
Structure Determinations:[22] Crystals of 4 were obtained by
layering a dichloromethane solution with hexane, and crystals of
5 were obtained by layering a chloroform solution with hexane.
Diffraction data were recorded with the ω/2θ technique on a Non-
14.63; found C 59.48, H 5.97, N 3.05, Zn 14.50. Ϫ IR (KBr): ν˜ ϭ
1
1609 (CϭN) cmϪ1. Ϫ H NMR ([D6]DMSO): δ ϭ 1.68 (s, 18 H, ius CAD4 diffractometer fitted with a molybdenum tube (Mo-Kα,
tBu), 7.06 (d, J ϭ 8.5 Hz, 2 H, H4,5), 7.25 (d, J ϭ 8.5 Hz, 2 H, λ ϭ 0.7107 A) and a graphite monochromator. No absorption cor-
˚
H3,6), 7.41 (m, 2 H, py), 7.82 (m, 1 H, py), 8.58 (m, 2 H, py).
rections were applied. The structures were solved by direct methods
and refined anisotropically with the SHELX program suite.[23] Hy-
drogen atoms were included with fixed distances and isotropic tem-
perature factors which were 1.5 times the value of those of their
attached atoms. Parameters were refined against F2. The R values
Compound 4: A solution of H2L1 (0.20 g, 0.66 mmol) and neocup-
roin hydrate (0.14 g, 0.67 mmol) in chloroform (10 mL) was treated
with diethyl zinc (81 mg, 0.66 mmol) in n-hexane (2.0 mL). After
stirring for 20 min. the volume was reduced to 2 mL in vacuo.
Addition of petroleum ether (4 mL) produced a precipitate which
was filtered off and washed with petroleum ether. Recrystallization
from dichloromethane/hexane (1:1) yielded 4 as orange crystals
(0.36 g, 95%), m.p. 115 °C (dec.). Ϫ C32H34N2S2Zn·CH2Cl2 (576.2
ϩ 84.9): calcd. C 59.96, H 5.49, N 4.24, Zn 9.89; found C 59.82,
H 5.54, N 3.98, Zn 10.03. Ϫ IR (KBr): ν˜ ϭ 1621 and 1591 (CϭN)
are defined as R1 ϭ Σ|Fo Ϫ Fc|/ΣFo and wR2 ϭ [Σ[w(F2o
Ϫ
F2c)2]Σ[w(F2o)2]]1/2. Drawings were produced with SCHAKAL.[24]
Table 1 lists the crystallographic data.
1
cmϪ1. Ϫ H NMR (CDCl3): δ ϭ 1.77 (s, 18 H, tBu), 3.19 (s, 6 H,
Acknowledgments
CH3), 5.35 (s, 2 H, CH2Cl2), 7.27 (d, J ϭ 8.6 Hz, 2 H, H4,5), 7.45
(d, J ϭ 8.6 Hz, 2 H, H3,6), 7.74 (d, J ϭ 8.4 Hz, 2 H, neo-H3,8), 7.94
(s, 2 H, neo-H5,6), 8.44 (d, J ϭ 8.4 Hz, 2 H, neo-H4,7).
This work was supported by the Deutsche Forschungsgemeinschaft
and by the Fonds der Chemischen Industrie.
Compound 5: A suspension of 2 (0.10 g, 0.31 mmol) in chloroform
(3 mL) was treated with neocuproin hydrate (70 mg, 0.31 mmol).
The resulting clear solution formed a precipitate upon addition of
hexane (6 mL), which was filtered off, washed with hexane and
dried in vacuo, leaving behind compound 5 as orange crystals
(0.13 g, 77%), m.p. 140 °C (dec.). Ϫ C26H16N2O3S2Zn·C6H14 (533.9
ϩ 86.2): calcd. C 61.98, H 4.88, N 4.52, Zn 10.54; found C 62.52,
H 5.55, N 4.33, Zn 10.11. Ϫ IR (KBr): ν˜ ϭ 1734 and 1700 (Cϭ
[1]
B. Krebs, G. Henkel, Angew. Chem. 1991, 103, 785Ϫ804; An-
gew. Chem. Int. Ed. Engl. 1991, 30, 769Ϫ788.
[2]
J. R. Dilworth, J. Hu, Adv. Inorg. Chem. 1993, 40, 411Ϫ459.
W Kaim, B. Schwederski, Bioanorganische Chemie, Teubner,
Stuttgart, 1995.
S. J. Lippard, J. M. Berg, Principles of Bioinorganic Chemistry,
University Science Books, Mill Valley, 1994.
D. Sellmann, J. Sutter, Acc. Chem. Res. 1997, 30, 460Ϫ469.
B. A. Krizek, B. T. Amann, V. J. Kilfoil, D. L. Merkle, J. M.
Berg, J. Am. Chem. Soc. 1991, 113, 4518Ϫ4523.
Zinc and its Role in Biology and Nutrition (Ed.: H. Sigel), Mar-
cel Dekker, New York, 1983.
Zinc Enzymes (Eds.: I. Bertini, C. Luchinat, W. Maret, M. Zep-
pezauer), Birkhäuser, Basel, 1986.
C. I. Bränden, H. Eklund, B. Nordström, T. Boiwe, G. Söder-
[3]
[4]
1
O), 1617 and 1590 (CϭN) cmϪ1. Ϫ H NMR ([D6]acetone): δ ϭ
[5]
0.88 (m, 6 H, hexane-CH3), 1.27 (m, 8 H, hexane-CH2), 2.76 (s, 6
H, CH3), 7.99 (d, J ϭ 8.2 Hz, 2 H, H5,8), 8.09 (d, J ϭ 8.2 Hz, 2 H,
H4,9), 8.11 (d, J ϭ 8.3 Hz, 2 H, neo-H3,8), 8.27 (s, 2 H, neo-H5,6),
8.90 (d, J ϭ 8.3 Hz, 2 H, neo-H4,7).
[6]
[7]
[8]
[9]
Table 1. Crystallographic details
lund, E. Zeppezauer, I. Ohlsson, A. Akeson, Proc. Natl. Acad.
Sci. USA 1973, 70, 2439Ϫ2442; H. Cho, S. Ramaswamy, B. V.
Plapp, Biochemistry 1997, 36, 382Ϫ389.
4
5
[10]
B. Kaptein, L. Wang-Griffin, G. Barf, R. M. Kellogg, J. Chem.
Formula
C32H34N2S2Zn
576.2
C26H16N2O3S2Zn·CHCl3
Soc., Chem. Commun. 1987, 1457Ϫ1459; B. Kaptein, G. Barf,
R. M. Kellogg, F. van Bolhuis, J. Org. Chem. 1990, 55,
1890Ϫ1901.
Mol. wt
533.9 ϩ 119.4
Crystal size [mm]
Space group
Z
1.2 ϫ 0.9 ϫ 0.8 0.7 ϫ 0.5 ϫ 0.4
¯
[11]
P21/c
8
P1
U. Brand, H. Vahrenkamp, Z. Anorg. Allg. Chem. 1996, 622,
213Ϫ218.
C. Kimblin, T. Hascall, G. Parkin, Inorg. Chem. 1997, 36,
5680Ϫ5681.
2
˚
a [A]
26.231(5)
10.400(2)
22.065(4)
90
9.737(2)
11.834(2)
13.847(3)
67.95(3)
84.66(3)
66.48(3)
1353.9(5)
1.60
[12]
˚
b [A]
˚
c [A]
[13]
M. Bochmann, G. C. Bwembya, R. Grinter, A. K. Powell, K.
α [°]
β [°]
γ [°]
J. Webb, M. B. Hursthouse, K. M. Abdul Malik, M. A. Mazid,
108.29(3)
90
Inorg. Chem. 1994, 33, 2290Ϫ2296.
[14]
3
˚
B. Müller, A. Schneider, M. Tesmer, H. Vahrenkamp, Inorg.
Chem. 1999, 38, 1900Ϫ1907.
W. B. Price, S. Smiles, J. Chem. Soc. 1928, 2372Ϫ2374; A.
Zweig, A. K. Hoffmann, J. Org. Chem. 1965, 30, 3997Ϫ4001.
W. P. Bosman, H. G. M. van der Linden, J. Chem. Soc., Chem.
Commun. 1977, 714Ϫ715.
W. Baratta, I. Bernal, F. Calderazzo, J. D. Korp, L. S. Magill,
F. Marchetti, D. Vitali, Gazz. Chim. Ital. 1996, 126, 469Ϫ474.
S. A. Gamage, R. A. J. Smith, Tetrahedron 1990, 46,
2111Ϫ2128.
Y. Kai, M. Morita, N. Yasuoka, N Kasai, Bull. Chem. Soc.
Jpn. 1985, 58, 1631Ϫ1635.
A. Meissner, W. Haehnel, H. Vahrenkamp, Chem. Eur. J. 1997,
3, 261Ϫ267.
M. Förster, R. Burth, A. K. Powell, T. Eiche, H. Vahrenkamp,
Chem. Ber. 1993, 126, 2643Ϫ2648.
V [A ]
5715(2)
1.34
d (calc.) [g·cmϪ3
]
[15]
Temp. [K]
273
1.03
183
1.39
µ (Mo-Kα) [mmϪ1
hkl range
]
[16]
h: Ϫ31 to 32
k: 0 to 12
l: Ϫ27 to 0
11909
h: Ϫ10 to 10
k: Ϫ13 to 12
l: Ϫ15 to 15
6312
[17]
Refl. measd.
Indep. refl.
11588
3892
[18]
Obs. refl. [I Ͼ 2σ(I)] 6693
2463
Parameters
667
381
[19]
Refl. refined
11588
0.042
0.127
ϩ0.6
Ϫ0.5
3892
R1 (obs. refl.)
wR2 (all refl.)
Residual el. density
0.060
[20]
0.150
ϩ0.6
Ϫ3
˚
[21]
[e/A
]
Ϫ0.5
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188
1187

M. Tesmer, H. Vahrenkamp
FULL PAPER
[22]
[23]
[24]
Crystallographic data for the structures reported in this paper
G. M. Sheldrick, SHELX-86 and SHELXL-93, Programs for
Crystal Structure Determination, Universität Göttingen, 1986
and 1993.
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-150527 (for 4)
and -150528 (for 5). Copies of these data can be obtained free
of charge on application to CCDC, 12 Union Road, Cam-
bridge CB2 1EZ [Fax: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
E. Keller, SCHAKAL for Windows, Universität Freiburg, 1998.
Received October 9, 2000
[I00380]
1188
Eur. J. Inorg. Chem. 2001, 1183Ϫ1188