Nickel thiolate complexes as ligands for copper and zinc: Novel additions to a library of binding modes

Article abstract of DOI:10.1002/ejic.200600645

The reactivity of the two nickel complexes [Ni(xbsms)] and [Ni(bsms) ₂] [H₂xbsms = α,α′-bis(4-mercapto-3,3- dimethyl-2-thiabutyl)-o-xylene; Hbsms = 4-mercapto-3,3-dimethyl-1-phenyl-2- thiabutane] towards copper iodide and zinc bromide has been investigated. The reactions yield novel aggregates of higher nuclearity with topologies that are different from previous reports; the nickel complexes in all cases can be considered as didentate S ligands. The X-ray structure of the novel octanuclear cluster [{Ni(bsms)₂}₃(CuI)₅] shows a unique arrangement in which the cis-NiS₂S′₂ units act as didentate ligands to a trigonal-bipyramidal array of five Cu^I ions. The tetranuclear structure of [{Ni(xbsms)CuI}₂] shows unprecedented asymmetric bridging of the thiolate sulfur atoms, with one of the thiolate groups binding to one copper ion and the other one μ₃-bridging to two copper ions. The complex is located on a crystallographic twofold axis and the complex in a single crystal is enantiomerically pure. The trinuclear complex [Ni₂(bsms)₃ZnBr₃] is formed as a result of dissociation of the didentate bsms ligand from part of the mononuclear complex and reassembly to form a dinuclear core to which the ZnBr₃ ^- unit is coordinated to a single thiolate sulfur atom. A complex of stoichiometry [Ni₃(xbsms)₂-(ZnBr₃)₂] has also been isolated and a structure proposal based on spectroscopic properties is given. All complexes have been characterised by analytical and spectroscopic methods. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600645

FULL PAPER
DOI: 10.1002/ejic.200600645
Nickel Thiolate Complexes as Ligands for Copper and Zinc: Novel Additions
to a Library of Binding Modes
Johanna A. W. Verhagen,[a] Christian Tock,[a] Martin Lutz,[b] Anthony L. Spek,[b] and
Elisabeth Bouwman*[a]
Keywords: Nickel / Copper / Zinc / S ligands / Cluster compounds
The reactivity of the two nickel complexes [Ni(xbsms)] and
[Ni(bsms)2] [H2xbsms = α,αЈ-bis(4-mercapto-3,3-dimethyl-2-
ion and the other one µ3-bridging to two copper ions. The
complex is located on a crystallographic twofold axis and the
complex in a single crystal is enantiomerically pure. The tri-
thiabutyl)-o-xylene; Hbsms
= 4-mercapto-3,3-dimethyl-1-
phenyl-2-thiabutane] towards copper iodide and zinc bro- nuclear complex [Ni2(bsms)3ZnBr3] is formed as a result of
mide has been investigated. The reactions yield novel aggre-
gates of higher nuclearity with topologies that are different
from previous reports; the nickel complexes in all cases can
be considered as didentate S ligands. The X-ray structure
of the novel octanuclear cluster [{Ni(bsms)2}3(CuI)5] shows a
unique arrangement in which the cis-NiS2SЈ2 units act as di-
dentate ligands to a trigonal-bipyramidal array of five CuI
ions. The tetranuclear structure of [{Ni(xbsms)CuI}2] shows
unprecedented asymmetric bridging of the thiolate sulfur
atoms, with one of the thiolate groups binding to one copper
dissociation of the didentate bsms ligand from part of the mo-
nonuclear complex and reassembly to form a dinuclear core
to which the ZnBr3 unit is coordinated to a single thiolate
–
sulfur atom.
A complex of stoichiometry [Ni3(xbsms)2-
(ZnBr3)2] has also been isolated and a structure proposal
based on spectroscopic properties is given. All complexes
have been characterised by analytical and spectroscopic
methods.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
discrete NiCu or NiNi dinuclear complexes[4,5,8,11] or linear
trinuclear Ni3 or Ni2Cu complexes;[8,15] or they may bind
to four different metal ions through µ3-S bridges in larger
Ni2Cu4 aggregates.[16] The nuclearity of the cluster and type
of aggregate that is formed is largely dependent on the stoi-
chiometry of the reactants and the presence or absence of
coordinating anions. In all of these clusters the nickel ion
in the parent complex remains divalent and low-spin in a
square-planar geometry. However, when using flexible li-
gands that allow for different geometries, in a reaction with
low-valent metal centres the nickel ion may be reduced and
expelled from the ligand[17,18] or it may result in clusters in
which the nickel centre is coordinated by the ligand in a
tetrahedral geometry and in which additional metal–metal
bonds are formed.[19,20]
Introduction
It is now generally accepted that the A-cluster of acetyl-
coenzyme-A-synthase/CO-dehydrogenase (ACS/CODH) in
its active state contains a dinuclear nickel site bound to an
iron–sulfur cluster.[1] However, due to the earlier reports of
Cu- or Zn-containing structures,[2,3] attempts to synthesise
structural models of the A-cluster have resulted in reports
of several new heteronuclear clusters.[4–11] In most of these
investigations, discrete mononuclear nickel complexes of
tetradentate N2S2 ligands have been used as building
blocks, and their reactivity towards transition metals such
as Fe, Ni, Cu, Zn, Ag, Pd and Hg have been studied. The
nickel complexes can be considered to react as didentate S
ligands. A wealth of structures has become available, and a
range of possible bridging modes for the thiolate sulfur
atoms have been reported.[7] The two cis-thiolate sulfur
atoms in the parent nickel complex may form single bridges
to two different metal ions in, for example, Ni3Cu2, Ni3Ag2
or Ni3Zn2 clusters[4,10,12,13] or Ni4Pd2 paddle wheels;[10,14]
they can act as a chelating ligand to one metal ion to form
Numerous CuI thiolate clusters have been reported.
Homoleptic CuI clusters with monodentate thiolate ligands
have been reported as [Cu4(SR)4] in a square-planar or cub-
ane arrangement, as [Cu4(SR)6] in a tetrahedral or ada-
mantane arrangement, or as clusters of varying stoichiome-
try such as [Cu5(SR)6], [Cu5(SR)7], [Cu6(SR)6], [Cu8(SR)8],
[Cu8(SR)12] and [Cu12(SR)12].[21] In addition, some CuI
clusters containing dithiolate ligands have been reported.[22]
The central cores in these homoleptic clusters are remarka-
bly similar to the heteronuclear clusters that can be ob-
tained with the nickel complexes, in which the [NiN2S2]
group acts as a didentate sulfur ligand.
[a] Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden
University,
P. O. Box 9502, 2300 RA Leiden, The Netherlands
Fax: +31-71-527-4550
E-mail: bouwman@chem.leidenuniv.nl
[b] Bijvoet Center for Biomolecular Research, Crystal and Struc-
tural Chemistry, Utrecht University,
Utrecht, The Netherlands
4800
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 4800–4808

Nickel Thiolate Complexes as Ligands to Copper and Zinc
FULL PAPER
Earlier we have synthesised nickel complexes as models stoichiometries have been obtained (Scheme 1). The reactiv-
for hydrogenases by making use of various ligands contain- ity of the complexes towards ZnBr2 and ZnCl2 appeared to
ing oxygen, nitrogen and sulfur donor atoms.[23–25] The re- be similar as analogous products were obtained; only the
activity of these nickel complexes with various iron sources results of the reactions with ZnBr2 are reported.
has resulted in novel compounds, in some cases of surpris-
Reactions of the related trinuclear nickel complexes
ing composition.[17–19] Recently, we have reported the mo- [Ni3(xbsms)2](BF4)2 and [Ni3(bsms)4](BF4)2 with either CuI
nonuclear complexes [Ni(bsms)2] and [Ni(xbsms)] in which or ZnBr2 did not generate any new compounds of different
the nickel ion is in an S4 coordination environment stoichiometries. The trinuclear complexes appeared to be
[H2xbsms = α,αЈ-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)- relatively inert, and the starting materials could be reco-
o-xylene; Hbsms = 4-mercapto-3,3-dimethyl-1-phenyl-2- vered from most of the reactions.
thiabutane].[26] The reactivity of these mononuclear com-
plexes towards nickel and iron has been studied and the
trinuclear nickel complexes [Ni3(bsms)4](BF4)2 and [Ni3-
(xbsms)2](BF4)2 have been reported.[15,27]
The reactivity of these complexes towards copper(I) and
zinc(II) salts has now been investigated, resulting in a
Structures of the Complexes
Structure of [{Ni(bsms)2}3(CuI)5] (1)
number of novel aggregates with unprecedented structures
that are described below.
The asymmetric unit contains two independent mole-
cules of [{Ni(bsms)2}3(CuI)5] together with four acetone
molecules and two diethyl ether molecules. The differences
between the two independent molecules are very small,
therefore the detailed geometry of only one of them is dis-
cussed. An ORTEP projection of the structure of
Results
Reactivity Studies
The reactivity of the mononuclear NiS4 complex [{Ni(bsms)2}3(CuI)5] is shown in Figure 1. Another projec-
[Ni(xbsms)] towards FeCl2, [Fe2(CO)9] and [Fe(CO)2(NO)2] tion showing the coordination environment of the nickel
appeared to be very similar to that reported for NiN2S2 and copper centres is given in Figure 2. Crystal data are
complexes,[28] with the nickel complex acting as a mono- given in the Experimental Section and selected bond
dentate or didentate chelating ligand to iron. Despite the lengths and angles are summarised in Table 1. Three
trans orientation of the two didentate ligands in [Ni- square-planar nickel(II) centres, three trigonal-planar cop-
(bsms)2] a similar reactivity towards FeCl2 has been ob- per(I) ions and two tetrahedrally coordinated copper(I) ions
served;[15] in aggregation reactions with nickel or iron the constitute the octanuclear cluster. The nickel ions have an
two ligands tend to rearrange to form a nickel complex with S2SЈ2 coordination, with the coordination environment con-
the cis-dithiolate conformation required for further binding. sisting of two didentate bsms ligands that bind through the
The reactivity of the mononuclear complexes [Ni(xbsms)] thiolate groups in the cis positions. The trigonal-planar
and [Ni(bsms)2] has now been investigated in reactions with copper ions have an S2I coordination environment and the
ZnBr2, ZnCl2 and CuI, with acetonitrile as the solvent and tetrahedral copper ions are in an S3I coordination environ-
in 1:1 molar ratios; interesting new products of unexpected ment.
Scheme 1. Synthesis of the novel clusters.
Eur. J. Inorg. Chem. 2006, 4800–4808
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J. A. W. Verhagen, C. Tock, M. Lutz, A. L. Spek, E. Bouwman
FULL PAPER
Table 1. Selected bond lengths [Å] and angles [°] in [{Ni(bsms)2}3-
(CuI)5] (1).
Cu(4)···Cu(5)
Cu(1)···Ni(1)
Ni(1)–S(11)
Ni(1)–S(13)
Cu(1)–S(13)
Cu(1)–S(21)
Cu(1)–I(1)
4.2012(12)
3.1381(13)
2.1868(17)
2.1970(18)
2.2481(18)
2.2775(18)
2.4903(10)
Cu(1)···Cu(4)
Ni(1)···Ni(2)
Ni(1)–S(12)
Ni(1)–S(14)
Cu(4)–S(11)
Cu(4)–S(21)
Cu(4)–S(31)
Cu(4)–I(4)
3.5855(12)
6.1880(15)
2.2010(19)
2.1966(18)
2.3252(18)
2.3548(18)
2.3354(18)
2.5801(9)
S(13)–Cu(1)–S(21)
S(13)–Cu(1)–I(1)
S(21)–Cu(1)–I(1)
S(11)–Cu(4)–S(21)
S(11)–Cu(4)–S(31)
S(11)–Cu(4)–I(4)
S(21)–Cu(4)–S(31)
S(21)–Cu(4)–I(4)
S(31)–Cu(4)–I(4)
110.34(7)
130.85(5)
118.73(5)
106.79(6)
115.73(7)
105.31(5)
104.64(7)
113.42(5)
111.11(5)
S(11)–Ni(1)–S(12) 91.64(7)
S(11)–Ni(1)–S(13) 91.15(6)
S(11)–Ni(1)–S(14) 169.77(8)
S(12)–Ni(1)–S(13) 169.19(8)
S(12)–Ni(1)–S(14) 87.84(7)
S(13)–Ni(1)–S(14) 91.25(7)
Cu(1)–S(13)–Cu(5) 112.11(7)
Cu(1)–S(13)–Ni(1) 89.81(6)
Cu(5)–S(13)–Ni(1) 129.75(8)
Figure 1. Displacement ellipsoid plot of one of the independent
molecules of [{Ni(bsms)2}3(CuI)5] (1), drawn at the 50% prob-
ability level. Hydrogen atoms and the solvent molecules have been
omitted and copper surroundings are indicated by dashed bonds
for clarity.
ion and two copper ions. Finally, the coordination environ-
ment of each copper ion is completed by one iodide ion.
The molecule lacks crystallographic symmetry elements
and therefore every nickel centre and every copper centre is
unique. However, the molecule contains an approximate,
non-crystallographic threefold rotation axis running
through the apical copper ions that makes the differences
between the three nickel ions, the three equatorial copper
ions Cueq and the two tetrahedrally coordinated copper
ions Cuap very small. The nickel–thiolate distances vary
from 2.082(17) to 2.1861(18) Å, and are comparable to the
distances found in the starting complex [Ni(bsms)2], and
the nickel–thioether distances are 2.1966(18)–2.2108(19) Å,
slightly longer than those in [Ni(bsms)2].[26] The Cueq–thio-
late distances vary from 2.2328(19) to 2.2775(18) Å,
whereas the Cuap–thiolate distances are slightly longer and
vary from 2.3204(18) to 2.3548(18) Å. The Cueq–iodide dis-
tances are 2.4860(10)–2.4903(10) Å and the Cuap–iodide
distances are 2.5775(9)–2.5801(9) Å. Because of the rigid
conformation of the complex the nickel centres have a tetra-
hedral distortion with a dihedral angle varying from
12.09(10) to 18.44(10)° between the planes S(n1)–Ni(n)–
S(n2) and S(n3)–Ni(n)–S(n4). The geometry around the
Cueq ions deviates only slightly from planarity and the
angles around the tetrahedral Cuap ions are in the range
104.64(7)–115.73(7)°.
Figure 2. Projection of the central core and the coordination envi-
ronment of the copper and nickel centres in 1. View approximately
along the pseudo-threefold axis of the trigonal bipyramid; the tri-
gonal plane is indicated by solid lines.
The intramolecular Cu···Cu contacts vary from
3.4668(13) to 5.3666(14) Å, with the shortest distances be-
tween the apical and equatorial copper ions. The distances
between the nickel centres range from 6.0776(15) to
6.3023(14) Å.
The five copper ions are clustered in a trigonal-bipyrami-
dal array, with the three trigonal-planar copper ions in the
equatorial plane and the tetrahedral copper ions at the api-
ces. The NiS2SЈ2 units are each capping two edges of the
trigonal bipyramid with two µ3-bridging thiolate groups
that each connect two copper ions with one nickel ion; each
nickel complex thus binds to four different copper ions.
Each nickel dithiolate complex bridges two equatorial cop-
per ions to form a giant twelve-membered Ni3Cu3S6 ring.
The tetrahedral copper ions are coordinated to three thio-
late groups, each from a different NiS2SЈ2 unit, thus capping
the 12-membered crown on both sides, and as a result creat-
ing a cage. All thiolate sulfur atoms use three lone pairs in
Although the nickel(II) ions in the solid structure have a
significant tetrahedral distortion, in solution the NiII ions
are in a low-spin state, as shown by NMR experiments. In
1
the H NMR spectrum of the complex in [D6]DMSO only
one set of relatively sharp signals is observed for the ligand,
thus confirming its rather symmetrical structure in solution.
Structure of [{Ni(xbsms)CuI}2] (2)
A projection of the structure of [{Ni(xbsms)CuI}2] is
a distorted tetrahedral geometry in binding to one nickel shown in Figure 3. Crystal data are given in the Experimen-
4802
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Eur. J. Inorg. Chem. 2006, 4800–4808

Nickel Thiolate Complexes as Ligands to Copper and Zinc
FULL PAPER
tal Section and selected bond lengths and angles are given Table 2. Selected bond lengths [Å] and angles [°] in [Ni(xbsms)-
CuI]2 (2).
in Table 2. The compound crystallises in the trigonal space
group P3221. The disordered solvent contained in this crys-
tal structure was modelled as diffuse electron density (see
Experimental Section). One tetranuclear complex contains
two nickel(II) centres in square-planar surroundings and
two copper(I) ions in a tetrahedral geometry. The complex
is located on an exact, crystallographic twofold rotation
axis and the complex in a single crystal is enantiomerically
pure, with clockwise rotation along the positive c-axis. Be-
cause of the symmetry the compound can be considered as
being a dimer of a heterodinuclear nickel-copper complex.
The nickel centres have an S2SЈ2 coordination sphere con-
sisting of two thiolate sulfur atoms in enforced cis positions
and two thioether sulfur atoms. These nickel ions are in a
square-planar geometry with a small tetrahedral distortion
defined by a dihedral angle of 5.44(7)° between the planes
Ni(1)–S(6)–S(9) and Ni(1)–S(16)–S(19). The bonds of the
thioether sulfur atoms and the thiolate sulfur atoms to Ni
are slightly longer than in the parent nickel complex
[Ni(xbsms)][26] but are still unexceptional. Both thiolate sul-
fur atoms of the NiS4 unit are bound as a chelating ligand
to a single copper ion with one short Cu(2)–S(6) distance
of 2.3010(12) Å and one long Cu(2)–S(16) distance of
2.6229(9) Å. The latter thiolate S(16) is the one that binds
to the symmetry-related copper ion Cu(2a), with a short
copper–thiolate distance of 2.2929(9) Å, and is therefore µ3-
bridging between both copper ions and one nickel ion. The
copper centres additionally have one coordinated iodide ion
and are therefore in a tetrahedral S3I coordination environ-
ment. The tetranuclear molecules are arranged in a helical
motif around a 32 screw axis in the crystallographic c direc-
tion by π–π stacking of the xbsms ligands (Figure 4). The
geometric centres of the stacking phenyl rings are
3.636(3) Å apart and the phenyl rings have a dihedral angle
of 2.0(3)°. Large, solvent-accessible channels are located
along this 32 screw axis (see Experimental Section).
Ni(1)···Cu(2)
Ni(1)–S(6)
Ni(1)–S(9)
Ni(1)–S(16)
Ni(1)–S(19)
S(6)–Ni(1)–S(9)
S(6)–Ni(1)–S(16)
S(6)–Ni(1)–S(19)
S(9)–Ni(1)–S(16)
S(9)–Ni(1)–S(19)
2.7496(6)
2.1956(11)
2.1936(10)
2.1983(10)
2.2024(10)
89.94(4)
Cu(2)···Cu(2)[a]
Cu(2)–S(6)
Cu(2)–S(16)
2.5671(9)
2.3010(12)
2.6229(9)
2.5301(5)
2.2929(9)
76.12(4)
122.38(4)
114.86(4)
111.18(3)
Cu(2)–I(3)
Cu(2)–S(16)[a]
S(6)–Cu(2)–S(16)
S(6)–Cu(2)–I(3)
S(6)–Cu(2)–S(16)[a]
S(16)–Cu(2)–I(3)
87.77(4)
174.57(4)
176.73(4)
92.35(4)
S(16)–Cu(2)–S(16)[a] 117.23(3)
S(16)–Ni(1)–S(19) 89.73(4)
I(3)–Cu(2)–S(16)[a]
111.00(3)
[a] Symmetry position: x – y, –y, 1/3 – z.
Figure 4. Stacking plot of [{Ni(xbsms)CuI}2] (2), including the
ARU numbers. View along the 32 screw axis.
ened and only two CH2 resonances can be discerned: one
for the ethylene bridges and one for the xylyl-CH2 groups.
Furthermore, only one resonance is observed for all four
methyl groups. This indicates that both sides of one ligand
and both protons on a CH2 group are chemically equivalent
in solution on the NMR timescale at room temperature.
After cooling the sample to 238 K, the spectrum is sharp-
ened and four doublets are observed for the eight CH2 pro-
tons and two singlets are observed for the four methyl
groups. In addition, the protons within a CH2 group show
COSY and NOESY cross-peaks. This indicates that even at
low temperature both sides of one ligand are still chemically
equivalent: C7 and C17, C10 and C20, and C8 and C18 are
mutually equivalent. So, in solution the asymmetry of the
crystal structure is apparently released. Full assignment of
the resonance signals could be made from the COSY and
Figure 3. Displacement ellipsoid plot of [{Ni(xbsms)CuI}2] (2),
drawn at the 50% probability level. Hydrogen atoms and solvent
molecules have been omitted for clarity.
The NMR spectra of 2 were obtained in CDCl3 at room NOESY NMR spectra at 238 K. The signal of one of the
temperature and at 238 K. Due to the presence of the two- benzylic protons has shifted 1.8 ppm downfield to δ =
fold rotation axis, only one set of ligand signals is expected 5.6 ppm as compared to that in the parent nickel complex.
1
for the tetranuclear complex. The H NMR spectrum re- This rather large shift is comparable to the shift of the sig-
corded at room temperature displays signals that are broad- nal of one benzylic proton in [Ni(xbsms)Fe(CO)4].[28] From
Eur. J. Inorg. Chem. 2006, 4800–4808
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J. A. W. Verhagen, C. Tock, M. Lutz, A. L. Spek, E. Bouwman
FULL PAPER
the crystal structure, however, no apparent interactions can and a dihedral angle of only 2.9(2)°. The thiolate sulfur
be discerned that may be responsible for this downfield atom of this third bsms ligand is bridging between Ni(2)
shift; the shortest Ni···benzylic-H distance is 3.27 Å, and an and the zinc(II) ion, which has an SBr3 coordination envi-
iodine–H interaction of 3.1 Å is present.
ronment. The bond lengths to nickel are similar to those in
the parent nickel complex [Ni(bsms)2] and are unexcep-
tional.[26]
Structure of [Ni2(bsms)3ZnBr3] (3)
A projection of the structure of [Ni2(bsms)3ZnBr3] is
shown in Figure 5. Crystal data are given in the Experimen-
tal Section and selected bond lengths and angles in Table 3.
The asymmetric unit contains the trinuclear complex
[Ni2(bsms)3ZnBr3] and two molecules of acetone. The trinu-
clear complex is built up from two nickel(II) centres with
square-planar surroundings and a tetrahedral zinc(II) ion.
Ni(1) has an S2SЈ2 coordination environment originating
from two bsms ligands, with the two thiolate sulfur atoms
in cis positions. The square-planar coordination of this
nickel ion has a small tetrahedral distortion, with an in-
terplanar angle of 4.7(3)°. Both thiolate sulfur atoms are
bridging to the second nickel ion, Ni(2), which is in an S3SЈ
coordination environment consisting of the already men-
tioned bridging thiolate sulfur atoms and an additional di-
dentate bsms ligand. The Ni(2) ion is also in a rather perfect
square-planar geometry with a small tetrahedral distortion
The NMR spectroscopic results confirm the diamagnetic
properties of the complex, with two square-planar low-spin
nickel(II) centres and a zinc(II) ion, which is retained in
solution. Quite unexpectedly, only a single set of resonances
is discernible for the three ligands, which makes the spec-
1
trum quite similar to the H NMR spectrum of [Ni(bsms)2].
Structure of [Ni3(xbsms)2(ZnBr3)2] (4)
A structure proposal based on elemental analysis and IR,
NMR and ligand-field spectroscopy is shown in Figure 6.
The structure proposal is based on the known type of trinu-
clear complexes of the form [Ni3(xbsms)2]2+, which are
composed of a zig-zag chain of three square planes similar
to that reported for [Ni3(bsms)4]2+ [15]
This arrangement
.
leaves space for two ZnBr3 units to coordinate above and
below the trinuclear complex, similar to the binding ob-
served in [Ni2(bsms)3ZnBr3]. The 1H NMR spectrum of this
compound again shows only one set of sharp signals, in
agreement with a symmetrical structure and square-planar
surrounding for the nickel(II) ions. The coordination of the
ZnBr3 groups apparently has a stabilizing effect on the flux-
ionality of the nickel ions as no sharp NMR spectrum
could be obtained for the parent trinuclear complex, even
at low temperature.[27]
Figure 6. Proposed structure of [Ni3(xbsms)2(ZnBr3)2] (4).
Figure 5. Displacement ellipsoid plot of [Ni2(bsms)3ZnBr3] (3),
drawn at the 50% probability level. Hydrogen atoms and solvent
molecules are omitted for clarity.
Table 3. Selected bond lengths [Å] and angles [°] in [Ni2(bsms)3-
ZnBr3] (3).
UV/Vis/NIR Spectroscopy of the Complexes
The square-planar surrounding of the nickel(II) ions in
all of the mixed-metal complexes discussed above is re-
flected in their ligand-field spectra. The UV/Vis/NIR data
are presented in Table 4. The nickel–copper complexes are
black solids that yield brown solutions both in chloroform
and in acetonitrile. These complexes show a very broad ab-
sorption band in the solid state with the diffuse reflectance
technique. The nickel–zinc complexes are brown solids that
also yield brown solutions in both chloroform and acetoni-
trile. [Ni3(xbsms)2(ZnBr3)2] (4) dissolves very poorly in
chloroform and therefore the ligand-field data of this com-
plex are only given for acetonitrile. For [Ni2(bsms)3ZnBr3]
(3), the differences in the ligand-field spectra of a solution
in chloroform and a solution in acetonitrile are very small,
Ni(1)···Ni(2)
Ni(1)–S(6)
Ni(1)–S(9)
Ni(1)–S(26)
Ni(1)–S(29)
2.864(3)
2.162(4)
2.211(5)
2.147(4)
2.192(4)
2.211(4)
2.212(4)
87.27(17)
80.93(15)
170.60(17)
168.03(18)
101.04(17)
Ni(2)···Zn(3)
Zn(3)–S(46)
Zn(3)–Br(61)
Zn(3)–Br(62)
Zn(3)–Br(63)
Ni(2)–S(46)
3.616(3)
2.414(4)
2.379(2)
2.406(2)
2.402(2)
2.175(4)
2.192(4)
170.85(16)
97.36(16)
91.77(15)
Ni(2)–S(6)
Ni(2)–S(26)
Ni(2)–S(49)
S(6)–Ni(1)–S(9)
S(6)–Ni(1)–S(26)
S(6)–Ni(1)–S(29)
S(9)–Ni(1)–S(26)
S(9)–Ni(1)–S(29)
S(26)–Ni(2)–S(46)
S(26)–Ni(2)–S(49)
S(46)–Ni(2)–S(49)
S(46)–Zn(3)–Br(61) 111.74(11)
S(46)–Zn(3)–Br(62) 100.99(11)
S(46)–Zn(3)–Br(63) 106.19(12)
Br(61)–Zn(3)–Br(62) 112.93(9)
Br(61)–Zn(3)–Br(63) 109.66(9)
Br(62)–Zn(3)–Br(63) 114.86(8)
S(26)–Ni(1)–S(29) 90.88(15)
S(6)–Ni(2)–S(26)
S(6)–Ni(2)–S(46)
S(6)–Ni(2)–S(49)
78.45(15)
92.46(16)
175.01(15)
4804
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Eur. J. Inorg. Chem. 2006, 4800–4808

Nickel Thiolate Complexes as Ligands to Copper and Zinc
FULL PAPER
Table 4. Electronic absorption maxima for the NiCu and NiZn complexes.
ν [103 cm–1] (ε [–1 cm–1])
˜
Solid state[a]
21.2
Chloroform
Acetonitrile
[{Ni(bsms)2}3(CuI)5] (1)
[{Ni(xbsms)CuI}2] (2)
[Ni2(bsms)3ZnBr3] (3)
22.6 (14×103)
28.0 (14×103)
26.2 (sh)
34.4 (sh)
38.1 (62×103)
40.3 (107×103)
47.6 (255×103)
14.5 (300)
14.5 (sh)
21.0
20.6 (2400)
26.2 (3100)
35.6 (14×103)
21.8 (630)
30.0 (sh)
35.1 (13×103)
40.3 (20×103)
13.6 (120)
15.1
20.2
24.1
19.3 (sh)
20.4 (sh)
25.0 (2200)
34.4 (sh)
25.8 (4500)
34.4 (sh)
36.7 (12×103)
37.2 (21×103)
19.7 (6600)
23.4 (19×103)
[Ni3(xbsms)2(ZnBr3)2] (4)
19.5
23.2
30.2
37.5
36.2 (54×103)
[a] Diffuse reflectance.
thus indicating that solvent coordination does not take ions do not have additional halogen ions coordinated and
place in this case. Coordination of acetonitrile cannot be the Cu···Cu distances are much smaller and are more likely
excluded for the nickel–copper complexes [{Ni(xbsms)- to indicate a metal–metal interaction.
CuI}2] and [{Ni(bsms)2}3(CuI)5]. The d–d transitions of the
nickel centres in all complexes are at slightly lower energy
and the ligand-to-metal charge-transfer transitions are at
higher energy compared with the starting complexes
[Ni(bsms)2] and [Ni(xbsms)] (see Table 4).[26] These changes
are just the opposite to the shifts in energy in ligand field
for the [{NiLFeX2}2] complexes [{Ni(xbsms)FeCl2}2],
[{Ni(xbsms)FeBr2}2] and [{Ni(xbsms)FeI2}2].[28] Appar-
ently, the somewhat softer CuI and ZnBr3 units accept more
electron density from the thiolate sulfur atoms.
The rearrangement of the didentate ligands in
[{Ni(bsms)2}3(CuI)5] to form cis-planar nickel complexes
would imply that a similar structure could possibly be ob-
tained from [Ni(xbsms)]. However, the resulting complex
[{Ni(xbsms)CuI}2] is obviously different and, as similar re-
action conditions were applied in the two syntheses, the re-
sulting dissimilar structures must be a consequence of pack-
ing effects. The reported[6,16] complex [{Ni(N2S2)}3(CuBr)2]
may be regarded as being derived from the present Ni3Cu5
complex by removal of the three equatorial CuI units.
Structures have been reported of [{Ni(N2S2)}2Cu2]2+, which
have the same nickel/copper ratio as [{Ni(xbsms)CuI}2] but
which do not contain coordinated halides and in which the
sulfur binding is different.[5,7]
Discussion
The ability of [NiN2S2] complexes to act as a ligand to
The reaction of NiN2S2 complexes with copper and zinc
other metal ions has long been recognized, but intense ef- halides has been shown to result in similar structures in
forts to study the binding of mononuclear [NiN2S2] to tran- some cases,[12] although different topologies have also been
sition metal ions were triggered by the publication of the reported.[7] Our new nickel–zinc complexes [Ni2(bsms)3-
X-ray structure of ACS. Many examples of the versatile ZnBr3] and [Ni3(xbsms)2(ZnBr3)2] are noticeably different
binding of nickel dithiolate complexes − as compared with from these earlier reported structures, and are also quite
“normal” didentate sulfur ligands − have now been re- different from each other, as a result of dissociation of the
ported. As the reactivity of the mononuclear NiS4 com- didentate bsms ligand from part of the mononuclear com-
plexes [Ni(xbsms)] and [Ni(bsms)2] towards iron sources is plex and re-assembly to form a dinuclear core similar to
rather similar to that of NiN2S2 complexes, the unique that of the nickel ethanedithiolate compound [Ni2(edt)3].[30]
–
products formed with copper and zinc salts were quite un- The binding of the ZnBr3 group to one thiolate sulfur
expected. Regarding the NiS4 complexes as dithiolate li- atom is similar to the binding observed in the dinuclear
gands makes the novel octanuclear compound [{Ni- complex [Ni(N2S2)ZnCl2(dmf)].[7] The proposed structure
(bsms)2}3(CuI)5] a [Cu5(“S2”)3] cluster. Numerous CuI thio- of the pentanuclear complex of general formula
late clusters have been reported; however, only two clusters [Ni3(xbsms)2(ZnBr3)2] is based on the assumption of a sim-
–
have been reported with a related Cu5(SR)6 arrangement.[29] ilar binding of the ZnBr3 groups; binding at two sides of
The copper centres in these complexes are also in a trigo- the trinuclear core is proposed for reasons of steric bulk
nal-bipyramidal array, each axial–equatorial edge of which and the existence of a symmetrical structure as indicated by
is bridged by a thiolate sulfur atom. However, the copper NMR spectroscopy.
Eur. J. Inorg. Chem. 2006, 4800–4808
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4805

J. A. W. Verhagen, C. Tock, M. Lutz, A. L. Spek, E. Bouwman
FULL PAPER
Acros or Aldrich and were used without further purification. The
complexes were synthesised under argon using standard Schlenk
techniques. Solvents were deoxygenated and dried with molecular
sieves. The synthesis of [Ni(bsms)2] and [Ni(xbsms)] has been re-
ported earlier.[26]
The structures of the products of the reactions of the
mononuclear complexes [Ni(xbsms)] and [Ni(bsms)2] with
copper and zinc salts are remarkably different from those
that have been reported earlier, and the reactivity of these
products as well as that of the trinuclear nickel complexes
also differ from the analogous NiN2S2 compounds. A
study[6] of the reactivity of the complexes [{Ni(N2S2)}3-
(ZnCl)2]2+, [{Ni(N2S2)}3(CuBr)2] and [{Ni(N2S2)}2Ni]2+
towards nickel, copper and zinc salts resulted in a qualita-
tive ranking of metal ion affinity by the nickel dithiolate
ligand, i.e. Zn2+ Ͻ Ni2+ Ͻ Cu+. With this in mind the
nickel–zinc complexes [Ni2(bsms)3ZnBr3] and [Ni3(xbsms)2-
(ZnBr3)2] have been tested for their reactivity towards
Ni(BF4)2 and CuI. Both complexes show no reactivity
towards Ni(BF4)2 and only the starting complexes were re-
covered after 24 h. The complex [Ni2(bsms)2ZnBr3], how-
ever, does show reactivity towards CuI; this reaction again
gives the stable octanuclear cluster [{Ni(bsms)2}3-
(CuI)5]. The complex [Ni3(xbsms)2(ZnBr3)2] does not show
reactivity towards CuI, which may be related to the low
solubility of this complex. The trinuclear nickel complexes
appear to be comparatively inert, and from most of the re-
actions only the starting materials could be recovered.
Physical Measurements: IR spectra were recorded with a Perkin–
Elmer FT-IR Paragon 1000 spectrophotometer equipped with a
golden-gate ATR device, using the reflectance technique (4000–
300 cm–1; resolution 4 cm–1). Elemental analyses were carried out
with a Perkin–Elmer series II CHNS/O analyzer 2400. Metal analy-
ses were performed with a Perkin–Elmer 3100 atomic absorption
(AAS) and flame emission spectrometer using a linear calibration
method. Due to the presence of variable amounts of solvent encap-
sulated in the complexes, some of the analytical data may be con-
sidered not satisfactory. Ligand-field spectra were obtained with a
Perkin–Elmer Lambda 900 spectrophotometer. The diffuse reflec-
tance technique, with MgO as a reference, was used for the solid
compounds. Ligand-field spectra of the solutions were obtained
with the solvent in the reference beam. NMR spectra were recorded
with a Bruker WM 300 MHz spectrometer or a Jeol FX-200
1
Teqmac. H and 13C chemical shifts are quoted in ppm relative to
tetramethylsilane (TMS).
[{Ni(bsms)2}3(CuI)5] (1): A solution of CuI (0.072 g, 0.38 mmol) in
80 mL of CH3CN was added to a solution of [Ni(bsms)2] (0.18 g,
0.37 mmol) in 170 mL of CH3CN, and the solution was stirred for
20 h. The solvent was then evaporated and the crude product was
recrystallised from acetone/diethyl ether. Dark-red crystals suitable
for X-ray diffraction were formed in a yield of 0.146 g (75%). IR:
Conclusions
Four new heteronuclear aggregates of various composi-
tion have been synthesised and characterised by using the
NiS4 compounds [Ni(xbsms)] and [Ni(bsms)2] as a ligand
for copper and zinc salts. Despite the similar reactivity of
these two complexes towards iron salts, the products of the
reactions with CuI and ZnBr2 are diverse. The novel octan-
uclear structure of [{Ni(bsms)2}3(CuI)5] shows a unique ar-
rangement of copper and nickel centres, with a central tri-
gonal-bipyramidal array of copper ions to which the three
NiS2SЈ2 units act as capping ligands. This remarkable com-
plex represents another important example of the structural
versatility possible for the reaction products of nickel di-
ν
= 2960 m, 2907 m, 1495 m, 1454 m, 1386 m, 1368 m, 1256 w,
˜
max
1228 w, 1199 w, 1139 m, 1083 m, 1071 m, 1028 w, 955 w, 925 w,
1
889 w, 772 m, 696 vs, 668 m, 476 m cm–1. H NMR (300.13 MHz,
[D6]dmso, 298 K): δ = 7.31 (m, 30 H, Ph), 3.68 (s, 12 H, Ph-CH2-
S), 2.26 [s, 12 H, C(CH3)2-CH2-S], 1.21 (s, 36 H, CH3) ppm.
C66H90Cu5I5Ni3S12 (2396.5): calcd. C 33.08, H 3.79, Cu 13.26, Ni
7.35, S 16.05; found C 33.25, H 4.17, Cu 13.05, Ni 7.71, S 15.44.
[{Ni(xbsms)CuI}2] (2): CuI (0.19 g, 1.0 mmol) in 80 mL of CH3CN
was slowly added to a solution of [Ni(xbsms)] (0.4 g, 1.0 mmol) in
100 mL of CH3CN, and the solution was stirred for 23 h. After
evaporation of the solvent, the product was recrystallised from dmf/
diethyl ether in a yield of 0.46 g (78%). Dark-red crystals suitable
thiolate complexes as ligands to other transition metal ions. for X-ray diffraction were obtained. IR: ν˜max = 2963 m, 2926 m,
1676 m, 1660 vs, 1497 m, 1454 m, 1437 m, 1382 m,1362 m, 1253 m,
1227 m, 1190 w, 1134 m, 1079 s, 956 m, 890 m, 768 s, 759 m, 743 w,
691 s, 668 s, 660 m, 606 m, 579 w, 488 m, 462 m cm–1. 1H NMR
(300.13 MHz, CDCl3, 238 K): δ = 7.28 (m, 4 H, C23-H, C26-H),
7.18 (m, 4 H, C24-H, C25-H), 5.65 (d, 2J = 12.4 Hz, 4 H, C10/20HH),
The tetranuclear structure [{Ni(xbsms)CuI}2] shows un-
precedented asymmetric bridging of the thiolate sulfur atoms,
with one of the thiolate groups binding to one copper ion
and the other one µ3-bridging to two copper ions. The tri-
nuclear complex [Ni2(bsms)3ZnBr3] is formed as a result of
dissociation of the didentate bsms ligand from part of the
mononuclear complex and reassembly to form the dinuclear
core. The trans binding of the didentate ligand in the start-
ing complex [Ni(bsms)2] appears not to limit its ability to
3.55 (d, J = 12.4 Hz, 4 H, C10/20HH), 2.84 (d, J = 12.9 Hz, 4 H,
C7/17HH), 2.45 (d, 2J = 12.9 Hz, 4 H, C7/17HH), 1.74 (s, 12 H,
CH3), 1.48 (s, 12 H, CHЈ3) ppm; see Figure 3 for numbering
scheme. C32H48Cu2I2Ni2S8 (1187.5): calcd. C 32.37, H 4.07, Cu
10.70, Ni 9.89, S 21.60; found C 33.24, H 4.45, Cu 10.55, Ni 9.86,
2
2
bind to other transition metal ions as a chelating ligand; it S 18.94.
does, however, result in the formation of new, unexpected
[Ni2(bsms)3ZnBr3] (3): ZnBr2 (0.23 g, 1.0 mmol) in 50 mL of
aggregates. The formation of these cluster compounds as
opposed to the desired dinuclear complexes emphasises the
importance of the site isolation in metalloenzymes and the
difficulty of controlling the product formation in vitro.
CH3CN was added to a solution of [Ni(bsms)2] (0.50 g, 1.04 mmol)
in 200 mL of CH3CN. The solution changed colour from light
brown to dark brown and was stirred for 19 h. The solvent was
evaporated and the obtained product was recrystallised from ace-
tone/hexane. A yield of 0.48 g of red crystals suitable for X-ray
diffraction was obtained (80%). IR: νmax = 2957 w, 2920 w, 1601 w,
˜
Experimental Section
Chemicals: All preparations were carried out in reagent-grade sol-
1495 m, 1463 m, 1455 m, 1417 m, 1385 w, 1362 m, 1264 m, 1240 m,
1221 m, 1195 m, 1141 m, 1082 m, 1070 m, 1030 w, 953 m, 879 w,
806 m, 767 s, 736 w, 699 vs, 668 w, 620 w, 585 w, 528 m, 487 s,
vents. All chemicals used in the syntheses were obtained from
4806
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 4800–4808

Nickel Thiolate Complexes as Ligands to Copper and Zinc
Table 5. Crystal and structure-refinement data for [{Ni(bsms)2}3(CuI)5] (1), [{Ni(xbsms)CuI}2] (2) and [Ni2(bsms)3ZnBr3] (3).
FULL PAPER
Complex
1
2
3
C66H90Cu5I5Ni3S12 (C3H6O)2
(C4H10O)0.9
2579.41
C32H48Cu2I2Ni2S8 + disordered sol- C33H45Br3Ni2S6Zn
Empirical formula
vent
(C3H6O)2
1172.73
red
Formula mass
Crystal colour
Crystal dimensions [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
1187.48a
dark red
0.15×0.15×0.42
trigonal
P3221 (no. 154)
13.0141(1)
13.0141(1)
26.9539(2)
90
dark red
0.42×0.27×0.09
triclinic
0.03×0.42×0.48
triclinic
¯
¯
P1 (no. 2)
P1 (no. 2)
14.5217(19)
14.5596(6)
46.735(4)
98.451(7)
97.003(9)
93.656(6)
9667.3(16)
4
10.249(3)
11.549(3)
21.388(7)
104.28(3)
96.52(2)
97.44(2)
2404.9(12)
2
α [°]
β [°]
90
120
γ [°]
V [Å3]
3953.49(5)
3
Z
Dcalcd. [Mgm–3]
1.772
3.545
analytical
1.496[a]
3.006[a]
multi-scan
0.45–0.63
0.61
1.620
4.054
analytical
0.11–0.83
0.48
µ [mm–1]
Absorption correction
Absorption correction range 0.36–0.81
(sinθ/λ)max [Å–1]
0.61
No. of measured reflns
No. of independent reflns
100932
34944
0.0465/0.0965
0.0691/0.1050
1.162
62695
5001
0.0253/0.0609
0.0284/0.0619
1.104
19594
4453
0.0726/0.1814
0.0831/0.1904
1.110
[c]
R1[b]/wR2[c] [I Ͼ 2σ(I)]
R1[b]/wR2 (all refl.)
S[d]
No. of refined parameters
No. of restraints
Flack x parameter
1873
195
–
212
0
0.008(14)
489
300
–
2
[a] Derived parameters do not contain the contribution of the disordered solvent. [b] R = Σ(||Fo| – |Fc||)/Σ|Fo|. [c] wR2 = {Σ[w(Fo
–
2 2
2
2 2
Fc ) ]/Σ[w(Fo2)2]}1/2. [d] S = {Σ[w(Fo – Fc ) ]/(n – p)}1/2
.
411 w, 328 m cm–1. 1H NMR (300.13 MHz, [D6]dmso, 298 K): δ =
612515 (1), -612516 (2), and -612517 (3) contain the supplementary
7.49 (m, 6 H, Ph-ortho-H), 7.34 (m, 6 H, Ph-meta-H), 7.28 (m, 3 crystallographic data for this paper. These data can be obtained
H, Ph-para-H), 4.04 (s, 6 H, Ph-CH2-S), 2.25 [s, 6 H, C(CH3)2-CH2- free of charge from the Cambridge Crystallographic Data Centre
S], 1.42 (s,18 H, CH3) ppm. C33H45Br3Ni2S6Zn (1056.6): calcd. C
37.51, H 4.29, Ni 11.11, S 18.21, Zn 6.19; found: calcd. C 37.92,
H 4.41, Ni 11.61, S 17.13, Zn 6.67.
via www.ccdc.cam.ac.uk/data_request/cif. 1: The diethyl ether sol-
vent molecule was refined with an occupancy of 0.9. 2: The crystal
structure contains large, solvent-accessible channels along the 32
screw axis (1078.9 Å3 per unit cell) filled with disordered solvent
molecules. Their contribution to the structure factors was secured
by back Fourier transformation using the SQUEEZE routine of
the program PLATON,[33] amounting to 267 electrons in the unit
cell. 3: The crystal appeared to be non-merohedrally twinned with
a 180° rotation about uvw = [100] as the twin operation. Addition-
ally, there was a large anisotropic mosaicity about hkl = (100) pres-
ent. The intensity data were evaluated with EvalCCD.[34] The twin
refinement[35] resulted in a twin fraction of 0.331(3).
[Ni3(xbsms)2(ZnBr3)2] (4): ZnBr2 (0.23 g, 1.0 mmol) in 50 mL of
CH3CN was slowly added to a solution of [Ni(xbsms)] (0.4 g,
1.0 mmol) in 100 mL of CH3CN. The colour changed from dark
green to dark brown and the solution was stirred for 20 h. A pale-
brown product (0.415 g) was collected by filtration and recrystal-
lised from dmf/diethyl ether. After 2 d, a brown precipitate was
collected by filtration in a yield of 0.11 g (22%). IR: νmax = 2960 m,
˜
2925 m, 1647 vs, 1490 w, 1456 m, 1436 m, 1383 s, 1371 s, 1252 m,
1137 m, 1115 m, 1088 m, 957 w, 865 w, 774 s, 688 m, 658 m, 606 w,
1
492 w, 467 w cm–1. H NMR (300.13 MHz, [D6]dmso, 298 K): δ =
7.34 (m, 8 H, Ph), 4.10 (s, 8 H, Ph-CH2-S), 2.00 [s, 8 H, C(CH3)2-
CH2-S], 1.65 (s, 24 H, CH3) ppm. C32H48Br6Ni3S8Zn2 (1475.6) +
DMF: calcd. C 27.15, H 3.58, N 0.90, Ni 11.37, S 16.56, Zn 8.44;
found C 28.19, H 3.66, N 1.10, Ni 11.82, S 16.81, Zn 8.40.
Acknowledgments
These investigations were supported in part (M. L. and A. L. S.) by
the Netherlands Foundation for Chemical Research, with financial
aid from the Netherlands Organisation of Scientific Research (CW-
NWO). C. T. (University of Strasbourg) was involved in the project
through the Socrates student exchange programme. The authors
thank Prof. Dr. Jan Reedijk for stimulating discussions.
Crystal Structure Determinations: X-ray intensities were measured
with a Nonius KappaCCD diffractometer with rotating anode and
graphite monochromator (λ = 0.71073 Å) at a temperature of
150(2) K. Numerical data and details of the data collection and
refinement are presented in Table 5. The structures were solved by
direct methods (SHELXS-97[31] for compounds 1 and 3; SIR-97[32]
for compound 2) and refined with SHELXL97 against F2 of all
reflections.[31] Non-hydrogen atoms were refined freely with aniso-
tropic displacement parameters; hydrogen atoms were refined as
rigid groups. Molecular illustrations, structure checking and calcu-
lations were performed with the PLATON package.[33] CCDC-
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4807

J. A. W. Verhagen, C. Tock, M. Lutz, A. L. Spek, E. Bouwman
FULL PAPER
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Received: July 10, 2006
Published Online: October 10, 2006
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