Complexes of late transition metals containing the mixed donor ligands 2,6-(RSCH2)2C5H3N (R = Ph, Me): Crystal structures of [{Cu(2,6-(PhSCH2)2C5H3N) (μ-X)}2] (X=Cl, Br) and [Ni(2,6-(PhSCH2)2C5H3N)Br 2]

Article abstract of DOI:10.1039/b104332n

A range of NiX₂ and CuX (X = halide) complexes containing the tridentate NS₂ ligands 2,6-bis(methylthiomethyl)pyridine (L¹) and 2,6-bis(phenylthiomethyl)pyridine (L²) were prepared. Reaction of CuX with 1 molar equivalent of L¹ or L² afforded the binuclear species [{CuL(μ-X)}₂] (L=L¹, X=Cl; L=L₂, X=Cl, Br, I). These compounds have been characterised by IR and ¹H NMR spectroscopies, mass spectrometry and microanalysis. Crystal structure determinations of [{CuL²(μ-X)}₂] (X=Cl, Br) confirm the dimeric nature of these complexes through bridging halide centres, with the NS₂ ligands coordinated through their pyridyl nitrogens and one of the sulfur atoms in a bidentate manner. Reaction of NiX₂ with 1 molar equivalent of L¹ or L² afforded mononuclear species for [NiLX₂] (L=L¹, X=I; L=L², X=Br, I) and binuclear species for [NiLX₂]₂ (L=L¹, X=Cl, Br; L=L², X=Cl). These compounds have limited solubility and were characterised through IR and UV-Vis reflectance spectroscopies and microanalysis. The crystal structure determination of [NiL²Br₂] confirms the compound to be monomeric with a five-coordinate, square pyramidal nickel centre.

Full text of DOI:10.1039/b104332n

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Complexes of late transition metals containing the mixed donor
ligands 2,6-(RSCH2)2C5H3N (R ؍ Ph, Me): Crystal structures of
[{Cu(2,6-(PhSCH2)2C5H3N)(ꢀ-X)}2] (X ؍ Cl, Br) and [Ni(2,6-
(PhSCH2)2C5H3N)Br2]
Rachel J. Ball,a Anthony R. J. Genge,a Alison L. Radford,b Brian W. Skelton,c
Vicki-Anne Tolhurst*b and Allan H. Whitec
a Department of Chemistry, University of Southampton, Highfield, UK SO17 1BJ
b School of Chemistry, University of Tasmania, Hobart TAS, 7001, Australia.
E-mail: VickiAnne.Tolhurst@utas.edu.au
c Department of Chemistry, University of Western Australia, Nedlands WA, 6097, Australia
Received 16th May 2001, Accepted 2nd August 2001
First published as an Advance Article on the web 7th September 2001
A range of NiX2 and CuX (X = halide) complexes containing the tridentate NS2 ligands 2,6-bis(methylthiomethyl)-
pyridine (L1) and 2,6-bis(phenylthiomethyl)pyridine (L2) were prepared. Reaction of CuX with 1 molar equivalent of
L1 or L2 afforded the binuclear species [{CuL(µ-X)}2] (L = L1, X = Cl; L = L2, X = Cl, Br, I). These compounds have
been characterised by IR and 1H NMR spectroscopies, mass spectrometry and microanalysis. Crystal structure deter-
minations of [{CuL2(µ-X)}2] (X = Cl, Br) confirm the dimeric nature of these complexes through bridging halide
centres, with the NS2 ligands coordinated through their pyridyl nitrogens and one of the sulfur atoms in a bidentate
manner. Reaction of NiX2 with 1 molar equivalent of L1 or L2 afforded mononuclear species for [NiLX2] (L = L1,
X = I; L = L2, X = Br, I) and binuclear species for [NiLX2]2 (L = L1, X = Cl, Br; L = L2, X = Cl). These compounds
have limited solubility and were characterised through IR and UV-Vis reflectance spectroscopies and microanalysis.
The crystal structure determination of [NiL2Br2] confirms the compound to be monomeric with a five-coordinate,
square pyramidal nickel centre.
and both sulfur atoms,10–16 with one exception where bidentate
Introduction
ligation is observed.17 In solution, although the ligand can
Extensive studies into the bonding and structural features of
behave as a bidentate, chelating metal centres through the
transition metal complexes containing multidentate thioether
pyridyl nitrogen and one sulfur atom, it can readily undergo
ligands have been conducted.1 Similarly, studies of mixed
fluxional processes.18–20 Very few reports of complexes con-
multidentate phosphine/thioether ligand containing complexes
taining these ligands have considered bonding comparisons
have also been reported.2 The structures of complexes contain-
between ligands containing alkyl-thioethers and aryl-thioether
ing these multidentate ligands vary from mononuclear com-
groups, and even fewer have made comparisons between dif-
pounds which have not contributed to supramolecular motifs
ferent halide complexes of the same metal. One study of CuCl2
complexes containing NS2 ligands have shown that alkyl-
thioether ligands are less π-acidic than aryl-thioether ligands
within the infinite structure,1b–e to complexes which form ion
channels and two-dimensional sheets.3 Solution studies of a
large number of these complexes have also been reported with
significant conclusions being drawn concerning bonding
patterns within groups of metals as well as ligands.
and that the latter ligand has a higher ability to stabilise low
oxidation state metals.14
Complexes containing nitrogen/sulfur mixed donor ligands
have recently attracted increasing interest. Ligands such as
these are used for the preparation of complexes designed as
enzyme mimics.4 Enzymes such as nickel hydrogenase and
copper proteins have the metal centres surrounded by histidine
(N-donor) and cysteine (S-donor) groups.5,6 Related to this,
complexes containing multidentate mixed donor ligands con-
sisting of hard N-donor and softer S-donor atoms have been
investigated as catalysts for a number of catalytic reactions.7
2,6-(Rthiomethyl)pyridine ligands (I) (R = alkyl, aryl) have
been studied less. Their applications include metal selectivity
such as the selective extraction of palladium from mixtures of
palladium() and copper() in aqueous solutions by polymer
bound 2,6-bis(methylthiomethyl)-3-hydroxypyridine.8 This
application can also extend to the preparation of sensors.9 This
ligand type contains three donor atoms, allowing for the ligand
to act as a tridentate (II) or bidentate ligand (III). In the
solid-state, these ligands generally behave as tridentate ligands,
bonding to metal centres through the pyridyl nitrogen centre
Herein we report the preparation of a number of Ni() and
Cu() halide complexes containing the ligands 2,6-bis(methyl-
thiomethyl)pyridine (L1) and 2,6-bis(phenylthiomethyl)-
pyridine (L2). We show that for nickel() complexes, changing
both the ligand and halide results in a change in structure of the
complexes, through spectral characterisation as well as single
crystal X-ray diffraction studies. We also illustrate a difference
DOI: 10.1039/b104332n
J. Chem. Soc., Dalton Trans., 2001, 2807–2812
This journal is © The Royal Society of Chemistry 2001
2807

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in the ability of the two ligands to stabilise low oxidation state
complexes when the electron density of the metal is varied from
our studies of copper() halide complexes. We also report the
monomeric and dimeric structures of three metal complexes
containing 2,6-bis(phenylthiomethyl)pyridine, the dimeric
structure being the first reported for a Cu() metal complex
containing this type of ligand.
Results and discussion
Nickel
The stoichiometric reaction of NiX2 (X = Cl, Br, I) with ligands
L1 or L2 in ethanol at ambient temperature affords the com-
plexes [NiLX2] in low to good yield as green [L = L1, X = Cl (1a),
Br (1b), I (1c); L = L2, X = Cl (2a)] or brown powders [L = L2,
X = Br (2b), I (2c)], see Scheme 1. The nickel complexes are air
Fig. 1 Molecular projection of [NiL2Br2], showing atom labelling
scheme. Thermal ellipsoids are drawn at the 50% probability level.
the larger halide ion. The monomeric nature of the larger halide
complexes also can be attributed to the decreased bridging
ability of the halide.
X-Ray structure determination of [NiL2Br2] (2b)
Crystals suitable for X-ray diffraction studies were grown by the
liquid diffusion of the two reagents using ethanol (containing
NiBr2) and isopropanol (containing L2) as solvent. [NiL2Br2]
crystallises as orange/brown plate-like crystals in the triclinic
space group P1 (no. 2) with the asymmetric unit comprised of
a monomeric species containing a five-coordinate nickel centre
with distorted square pyramidal geometry (Fig. 1). Crystallo-
graphic data of [NiL2Br2] are listed in Table 1. Important bond
distances and angles of [NiL2Br2] are listed in Table 2. The
ligand acts as a tridentate ligand, chelating the metal centre
in a meridional fashion through the nitrogen and two sulfur
centres, occupying three basal positions of the square pyramid.
The two thioether moieties are coordinated to the nickel centre,
meso relative to each other. The two bromine atoms occupy
the remaining apical position and the axial position. These
structural features are also observed in the copper()
compound [Cu{2,6-bis(ethylthiomethyl)pyridine}Cl2].12 The
related complex [Ni{2,6-bis(benzylthiomethyl)pyridine}Br(µ-
Br)]2 has a considerably different structure where the molecule
is dimeric through bridging bromide atoms with octahedral
nickel centres,16 2,6-bis(benzylthiomethyl)pyridine also acting
as a tridentate ligand and coordinating to the metal centres
in a meridional fashion. A terminally bound bromide atom
occupies the remaining coordination site. In the case of [{Ni-
[2,6-bis(benzylthiomethyl)pyridine]Br(µ-Br)}2], the methylene
spacer reduces the effective bulk of the phenyl group in the
vicinity of the sulfur, and hence, the nickel, thus accommo-
dating the bridging bromide atoms, resulting in a dimeric
stucture.16
Scheme 1 Preparation of nickel() halide complexes 1a–c and 2a–c.
stable but insoluble in most common solvents, thus limiting
solution spectroscopic studies. FAB mass spectra for the com-
plexes [NiL2X2] (3-NOBA matrix) show fragments corre-
sponding to the [NiL2X2] ions, with further loss of halide and
nickel leading to the observation of the [NiL2X] and [L2] ions,
respectively. The ion [NiL2Cl3Ni] is also observed in the FAB
mass spectrum of [NiL2Cl2]2 suggesting that the compound is
dinuclear. On heating the brown monomeric complex [NiL2Br2]
in acetonitrile for 30 min, a green solid is formed, presumably
either an octahedral binuclear [{NiL2Br2}2] complex or an
octahedral monomeric complex containing a coordinated
MeCN molecule.
Solid-state electronic spectra were obtained for all nickel
halide complexes. The reflectance UV/vis spectra of the dimeric
complexes [NiL1Cl2]2, [NiL1Br2]2 and [NiL2Cl2]2 show bands
which are consistent with high spin d8 metal centres with
pseudo octahedral geometry, additional splitting being due to
the loss of symmetry. The spectra exhibit two d–d transition
bands in the regions 7900–11000 and 13100–14500 cmϪ1 with a
third near the charge transfer bands corresponding to the
The Ni–N bond distance of 2.057(5) Å in [NiL2Br2] is com-
parable with that in [{Ni[bis(benzylthiomethyl)pyridine]Br-
(µ-Br)}2] [2.057(5) Å]16 and similar to those found in
[Ni([18]aneN2S4)]2ϩ [2.065(13), 2.126(13) Å] {[18]aneN2S4
=
3
3
3
3
3
3A2g T2g, A2g T1g and A2g T1g(P) allowed transitions,
respectively.21 In contrast, the UV-Vis spectra of [NiL1I2],
[NiL2Br2] and [NiL2I2] exhibit bands in the ranges 5400–6300,
8169–11100, 9328–13600, and 23000–24500 cmϪ1, which can
be assigned to 3B1 3E (2 bands), 3B1 3B2, 3B1 3A2(P)
1,10-diaza-4,7,13,16-tetrathiacyclooctadecane}, where the
macrocyclic ligand coordinates to the octahedral nickel centre
through all six donors.22 The average Ni–N bond distance
in (2,11-dithia[3,3](2,6)pyridinophane)nickel() of 2.08 Å23 is
slightly longer than that of [NiL2Br2] which can be attributed to
the increased strain within the macrocyclic ligands associated
with the square planar nickel centre. The Ni–S bond distances
found in [NiL2Br2] are 2.370(2) and 2.397(2) Å, similar Ni–S
bond distances being observed in (2,11-dithia[3,3](2,6)-
pyridinophane)nickel() [2.385(1), 2.407(1) Å].23 Longer Ni–S
and B1 3E(P) transitions, respectively, of a high spin penta-
3
coordinate nickel species with square pyramidal geometry.21
The difference in structure between the complexes suggests that
the presence of the more bulky ligand imparts considerable
steric constraints within the molecule as does the presence of
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Table 1 Crystallographic data for [NiL2Br2] and [{CuL2(µ-X)}2]
[NiL2Br2]
[{CuL2(µ-Cl)}2]
[{CuL2(µ-Br)}2]
Formula
M
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
C19H17NS2NiBr2
C38H34N2S4Cu2Cl2
844.97
C38H34N2S4Cu2Br2
933.84
541.98
Triclinic
P1 (no. 2)
8.294(3)
17.025(4)
7.520(4)
95.86(3)
109.48(3)
99.24(2)
974.2(6)
1.848
2
52.7
0.35, 0.73
50.0
3412
Triclinic
P1 (no. 2)
7.8258(5)
9.7175(6)
12.9919(8)
105.981(1)
105.008(1)
95.913(1)
901.1(2)
1.557
Triclinic
P1 (no. 2)
10.035(2)
13.133(6)
7.866(2)
105.25(3)
96.69(2)
106.58(3)
937.8(6)
1.653
1
35.2
0.21, 0.35
50.0
3302
β/Њ
γ/Њ
U/Å3
Dc/g cmϪ3
Z
1
15.9
µ/cmϪ1
a
T (min, max)
2θmax/Њ
No. unique reflections
0.66, 0.83
75.0
9279a
No. observed data
R
2275
0.037
7335
0.030
2286
0.051
RЈ
0.041
0.035
0.082
a Rint = 0.025.
Table 2 Selected bond distances (Å) and angles (Њ) of [NiL2Br2]
position of the octahedron, and preventing dimerisation
through halide bridges.
Ni–Br(1)
Ni–Br(2)
Ni–S(1)
Ni–S(2)
Ni–N
2.434(1)
2.417(1)
2.397(2)
2.370(2)
2.057(5)
S(1)–C(1)
S(1)–C(11)
S(2)–C(2)
S(2)–C(21)
1.807(6)
1.772(7)
1.799(7)
1.765(7)
Copper
Reaction of CuX (X = Cl, Br, I) with one molar equivalent of L
(L = L1 or L2) in refluxing CH2Cl2 for 2 hours gave green to
brown coloured solutions. Addition of diethyl ether afforded
[{CuLX}2] as green [L = L1, X = Cl (3a); L = L2, X = Cl (4a),
I (4c)] or yellow solids [L = L2, X = Br (4b)] in low yields,
see Scheme 2. Attempts to prepare the complexes [{CuL1X}2]
Br(1)–Ni–Br(2)
Br(1)–Ni–S(1)
Br(1)–Ni–S(2)
Br(1)–Ni–N
104.57(4) Br(2)–Ni–S(1)
101.31(6) Br(2)–Ni–S(2)
99.50(6) Br(2)–Ni–N
94.5(2)
91.89(6)
92.96(6)
160.9(2)
Torsion angles
S(1)–C(1),C(7)–N(1)
Ϫ22.3(8)
S(2)–C(2),C(3)–N(1)
8.9(8)
bond distances are recorded for the dimeric complex [{Ni[2,6-
bis(benzylthiomethyl)pyridine]Br(µ-Br)}2] [2.427(2), 2.459(2)
Å],16 consistent with the increased coordination number of
the nickel, while the significantly longer Ni–S bonds in [Ni-
([18]aneN2S4)]2ϩ [2.403(6)–2.430(5) Å]22 and [Ni([9]aneN2S)2]2ϩ
[2.418(1) Å], {[9]aneN2S = 1-thia-4,7-diazacyclononane},24
which contain N-alkyl rather than N-aryl moieties within the
ligand, suggest the thioether to be a stronger donor to nickel in
the presence of aromatic nitrogen donor moieties. The Ni–Br
bond distances of [NiL2Br2] are 2.434(1) and 2.417(1) Å where
the longer bond distance is associated with the bromine atom
occupying the apical position. These bond distances are signifi-
cantly shorter than the distance involving the terminally bound
bromide in [{Ni[2,6-bis(benzylthiomethyl)pyridine]Br(µ-Br)}2]
[2.529(1) Å], again consistent with the increased coordination
number of the nickel centre.16
The least-square plane of best fit defined by the atoms Br(2),
S(1), N(1) and S(2) has an r.m.s. deviation of 0.041 and the
nickel centre is 0.409 Å out of the least-square plane inside
the polyhedron. The angle between the least-square plane of
best fit defined by the base atoms and S(1), Br(1), S(2) is 88.7Њ,
and, with N(1), Br(1), Br(2), is also 88.7Њ. The angle between
the two intersecting planes perpendicular to the base least-
square plane is 89.9Њ. The distortion of the polyhedron can
partly be attributed to the Br(1) ؒ ؒ ؒ Br(2) repulsion [Br(1)–Ni–
Br(2) = 104.57(4)Њ]. The bite angles of the ligand are also
restrictive on the polyhedron [N–Ni–S = 83.3(2), 84.7(2)Њ]. The
Br(2)–Ni–S bond angles of 92.96(6) and 91.89(6)Њ are slightly
larger than ideal to help alleviate strain within the molecule.
The phenyl groups are orientated away from the Br(1) atom,
the meso arrangement of the phenyl groups blocking the sixth
Scheme 2 Preparation of copper() halide complexes 3a and 4a–c.
(X = Br, I) only resulted in the isolation of the CuX reagent.
Previous cyclic voltammetry studies on copper() chloride
complexes containing NS2 ligands indicated that complexes
containing ligands with aryl-thioether moieties had enhanced
capacity for stabilising low oxidation states of copper compared
to ligands containing alkyl-thioether moieties.14 The less π-
acidic S-alkyl ligand is unable to compensate for the increased
electron density of the copper() centre on varying the halide
from chloride to iodide with consequent failure to prepare these
heavier halide complexes. FAB mass spectra of [{CuL2Cl}2],
[{CuL2Br}2] and [{CuL2I}2] show peaks at m/z 809, 853 and
901, respectively, with the correct isotopic pattern correspond-
ing to [L2–Cu–X–Cu–L2]ϩ, suggesting the presence of dimeric
species. Further loss of halide is observed with the peak
corresponding to [CuL2]ϩ also present in all spectra.
1
The 297 K H NMR spectra of the [{CuL2X}2] complexes
show aromatic protons as multiplets at 6.8–7.7 ppm. The
resonances are broadened, suggesting fluxionality and inversion
of the ligand via κ3-coordination of the ligand, when bound to
J. Chem. Soc., Dalton Trans., 2001, 2807–2812
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Table 3 Selected bond distances (Å) and angles (Њ) of [{CuL2(µ-X)}2]
[X = Cl (4a), X = Br (4b)]
4a
4b
Cu–X(1)
Cu–X(1*)
Cu–S(1)
Cu–N(1)
S(1)–C(1)
S(2)–C(2)
S(1)–C(11)
S(2)–C(21)
2.2649(4)
2.4380(4)
2.3501(3)
2.067(1)
1.821(1)
1.808(1)
1.784(1)
1.774(1)
2.3905(11)
2.5452(12)
2.383(2)
2.074(4)
1.820(6)
1.791(7)
1.778(6)
1.783(8)
Cu–X(1)–Cu*
X(1*)–Cu–X(1)
X(1)–Cu–S(1)
X(1)–Cu–N(1)
X(1*)–Cu–S(1)
X(1*)–Cu–N(1)
S(1)–Cu–N(1)
72.61(1)
107.39(1)
124.41(1)
126.23(3)
104.88(1)
104.59(3)
86.02(3)
67.03(4)
112.97(4)
120.58(6)
125.32(13)
103.59(6)
104.22(12)
85.58(14)
Fig.
2
Molecular projection of [{CuL2(µ-Br)}2], showing atom
the metal centre. The methylene proton resonances are also very
broad and are non-observable for [{CuL2X}2] and [{CuL1Cl}2].
The resonance corresponding to the methyl protons of
[{CuL1Cl}2] is also broad. The spectrum of [{CuL2I}2] shows
the methylene protons to be equivalent as a single resonance
at 4.64 ppm. The aromatic region is also better resolved but
does not show inequivalence of the aromatic thioether rings.
Low temperature NMR studies were carried out to investigate
the intramolecular fluxional process but even at 220 K, the
methylene resonances could not be resolved, with only a
slight improvement in the resolution of the aromatic region.
This contrasts with similar studies of rhenium carbonyl com-
plexes containing L1 where the ambient temperature spectrum
shows the presence of two non-exchanging invertomers, both
having one coordinated and one non-coordinated MeS arm.20
On heating the sample, the four resonances of the methyl
protons exhibited exchange broadening and coalesced to a
single resonance. Studies of the line shape changes suggested
concurrent pyramidal sulfur inversion and intramolecular
exchange of the uncoordinated and coordinated MeS groups.
labelling scheme. Thermal ellipsoids are drawn at the 50% probability
level.
imposed on the copper centre in the latter by the macrocyclic
ligand, as well as stronger bonds to the metal centre associated
with the macrocyclic effect. The Cu–N bond distances for
[{CuL2(µ-X)}2] [2.067(1) (4a), 2.074(4) Å (4b)] are significantly
shorter than the Cu–N bond in [Cu2(Me2[18]aneN2S4)-
(NCMe)2]2ϩ [2.165(7) Å]26 but are comparable to that of Cu-
[2-(tert-butylthiomethyl)pyridine]2Br [2.109(9) Å],25 suggesting
that the pyridyl ring is a stronger donor than the sp3 nitrogen
centre of the macrocyclic ligand. The C–N bond distances in
[{CuL2(µ-X}2] are comparable to those in other four-coordinate
Cu() complexes containing pyridine ligands, e.g. [Cu(pyr)4]-
[ClO4] [2.05(1) Å].27 The Cu–X bond distances for [{CuL2(µ-
X}2] [2.2649(4), 2.4380(4) Å (X = Cl), 2.3905(11), 2.5452(12) Å
(X = Br)] are consistent with some degree of weak bonding
through the bridging halide atoms to the second metal centre.
The bite angles (N–Cu–S) of the bidentate ligand in the
two complexes of 86.02(3) (4a) and 85.58(14)Њ (4b) are similar
to the bite angle of the chelating ligand in Cu[2-(tert-butyl-
thiomethyl)pyridine]2Br [N–Cu–S = 85.4(3)Њ],25 these small
angles contributing to the distortion from ideal tetrahedral
geometry of the copper centres. The N–Cu–X (X = Cl, Br)
bond angles are larger than ideal to compensate for the small
bite angles, while the N–Cu–X(1*) and S–Cu–X(1*) bond
angles for both compounds are close to ideal. The X(1)–Cu–
X(1*) bond angles are also slightly larger than ideal.
X-Ray structure determinations of [{CuL2(ꢀ-X)}2] [X ؍ Cl (4a),
Br (4b)]
Crystallographic data for [{CuL2(µ-X)}2] are listed in Table 1,
important bond distances and angles being given in Table 3.
Suitable crystals of [{CuL2(µ-X)}2] crystallised in the triclinic
space group P1 (no. 2) with the molecules being dimeric
through unsymmetrical halide bridges, containing two four-
coordinate copper centres having distorted tetrahedral geom-
etries (Fig. 2) (X = Br, that for X = Cl is similar). The asymmetric
units are comprised of one half of each dimer, the second half
being generated through a crystallographic inversion centre,
the molecules having an obligate planar Cu2X2 four-membered
ring core. The two remaining coordination sites on each copper
centre are occupied by the pyridyl nitrogen and one sulfur
atom of the ligand, forming a five-membered chelate ring. The
two uncoordinated sulfur atoms arrange themselves anti with
respect to the pyridyl ring and do not participate in any inter-
or intra-molecular bonding.
The Cu–S bond distances of 2.3501(3) and 2.383(2) Å (4a
and 4b, respectively) are comparable to distances seen in related
thiopyridyl complexes.25 An elongation in the Cu–S bond dis-
tance from the chloride to bromide complex is concomitant
with increased electron density on the copper centre imparted
by the heavier halide. The Cu–S bond distances are signifi-
cantly longer than those found in [Cu2(Me2[18]aneN2S4)-
(NCMe)2]2ϩ [2.317(4), 2.286(4) Å] which is a dinuclear complex
in which each Cu() centre is bound tetrahedrally by two sulfur
and one nitrogen atoms of the macrocycle.26 The difference in
bond distances may be attributed to geometrical restrictions
Conclusions
A number of nickel() halide and copper() halide complexes
containing the NS2 ligands 2,6-bis(methylthiomethyl)pyridine
(L1) and 2,6-bis(phenylthiomethyl)pyridine (L2) have been
prepared from the stoichiometric reaction of the metal halide
with the appropriate ligand.
Structural features vary between the nickel() complexes,
depending on both the ligand used as well as the choice of
halide. Green dimeric complexes, most probably through
bridging halide atoms, are obtained when the ligand L1 is
present, in both the chloride and bromide complexes. The
analogous iodide complex, which is brown in colour, appears to
be monomeric. When the more sterically demanding ligand,
L2, is used in conjunction with the larger halides, bromide and
iodide, the brown compounds become monomeric in structure,
most probably containing a five-coordinate, square pyramidal
nickel centre, based on comparisons of the spectroscopic data
of these complexes with that of the structurally authenticated
complex NiL2Br2. A dimeric complex is obtained containing
this ligand when the smaller chloride ligand is present.
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The copper() halide complexes obtained are dimeric in struc-
ture, by way of bridging halides. [{CuL2X}2] complexes (X = Cl,
Br, I) were prepared, while reactions of copper() bromide
and copper() iodide with L1 only resulted in the isolation of
the copper halide. The difference in reactivity between the two
ligands illustrates the difference in their electronic properties,
with the aryl-thioether ligand being able to stabilise low oxid-
ation state metals more effectively than the alkyl-thioether
ligand, the electron density on the metal centre increasing on
varying the halide from chloride to iodide. The structures of
[{CuL2X}2] (X = Cl, Br) show the ligand to act as a bidentate
ligand, the first showing the ligand type to behave in this
fashion in the solid-state.
CH2Cl2 requires C, 33.3; H, 2.7; N, 1.9%); νmax/cmϪ1 1598w,
1481m, 1454m, 1441m, 1390s, 1359s, 1106w, 1019s, 999s, 885m,
834w, 795m, 744s, 733s, 683m, 613w, 476w, 423vw, 304vw,
257w, 228w, 212w (CsI); m/z 504 (Mϩ Ϫ I), 377 (Mϩ Ϫ 2I), 319
(L2); λmax/cmϪ1 (BaSO4) 23000, 13100, 11100, 5400.
[NiL1I2]. Following the above procedure with L1 (31%)
(Found: C, 26.5; H, 2.8; N, 3.4. NiCl2NS2C9H13 requires C,
21.1; H, 2.6; N, 2.7%); νmax/cmϪ1 3062vw, 2916vw, 1599s, 1570s,
1457vs, 1414s, 1358s, 1163m, 1094s, 1016s, 995m, 895w, 874w,
793m, 761w, 692vw, 235vw (CsI); λmax/cmϪ1 (BaSO4) 9300,
8200, 6300.
[{CuL2Cl}2]. A solution of L2 (160 mg, 0.49 mmol) and CuCl
(50 mg, 0.51 mmol) in degassed CH2Cl2 (20 ml) was refluxed for
2 hours. The green solution was cooled and the solvent volume
was reduced in vacuo (ca. 2 ml). Addition of Et2O afforded a
light green precipitate, which was collected and recrystallised,
from CH2Cl2 and Et2O (10 mg, 25%) (Found: C, 53.6; H,
3.9; N, 3.3. CuClNS2C19H17 requires C, 54.0; H, 4.1; N, 3.3%);
νmax/cmϪ1 2918w, 2852w, 1596m, 1452w, 1359s, 1090s, 1022m,
885w, 796w, 740m, 690m, 612w, 488w, 204w (CsI); δH (CDCl3)
7.7–6.5 (13H, m, C5H3N, C6H5); m/z 809 (Mϩ Ϫ Cl), 427 (Mϩ Ϫ
Cu Ϫ L2 Ϫ 2Cl ϩ MeCN), 386 (Mϩ Ϫ Cu Ϫ L2 Ϫ 2Cl), 324
(L2).
Experimental
Infrared spectra were measured as CsI discs using a Perkin-
Elmer 983 spectrometer over the range 200–4000 cmϪ1. Reflec-
tance UV-Vis spectra were recorded using a Perkin-Elmer
Lambda19 UV-Vis spectrometer. Mass spectra were run by
fast-atom bombardment (FAB) using 3-NOBA (3-nitro-
benzyl alcohol) as matrix on a VG Analytical 70-250-SE
Normal Geometry Double Focusing Mass Spectrometer or by
1
positive electrospray (ESϩ) using a VG Biotech Platform. H
NMR spectra were recorded using Bruker AM300 or AM360
spectrometers operating at 300 and 360 MHz, respectively.
Microanalyses were performed by the microanalytical service
of Strathclyde University and the CSL Laboratory at the
University of Tasmania. 2,6-Bis(methylthiomethyl)pyridine
(L1)8 and 2,6-bis(phenylthiomethyl)pyridine (L2)14 were
prepared using literature procedures.
[{CuL1Cl}2]. Following the procedure for the preparation of
[{CuL2Cl}2] using L1 (19%) (Found: C, 35.1; H, 4.6; N, 5.0.
CuClNS2C9H13 requires C, 36.2; H, 4.4; N, 4.7%); νmax/cmϪ1
2918w, 1596s, 1568m, 1453s, 1359s, 1261m, 1098vs, 805m, 614s,
303m, 251w (CsI); δH (CDCl3) 7.7–7.3 (3H, m, C5H3N), 1.4
(6H, s, CH3).
Syntheses
[{CuL2Br}2]. Following the above procedure with CuBr
(28%) (Found: C, 48.9; H, 3.7; N, 3.0. CuBrNS2C19H17 requires
C, 48.3; H, 3.4; N, 2.8%); νmax/cmϪ1 1587w, 1432w, 1436w,
1359s, 1091s, 990m, 885w, 834w, 792w, 749m, 739vw, 690m,
614w, 342w, 202w, 189w (CsI); δH (CDCl3) 7.5–7.0 (13H, m,
C5H3N, C6H5); m/z 853 (Mϩ Ϫ Br), 386 (Mϩ Ϫ Cu Ϫ L2 Ϫ 2Br),
324 (L2).
[NiL2Cl2]2. A colourless solution of L2 (110 mg, 0.34 mmol)
i
in PrOH (ca. 5 ml) was layered on a green solution of NiCl2ؒ
6H2O (80 mg, 0.51 mmol) in EtOH. The mixture was allowed to
stand for 24 h at room temperature to afford a green precipitate.
The solid was collected, washed with EtOH and dried (59 mg,
77%) (Found: C, 50.3; H, 3.7; N, 3.1. NiCl2NS2C19H17 requires
C, 50.4; H, 3.8; N, 3.1%). νmax/cmϪ1 1598w, 1454w, 1359vs,
1089m, 996s, 740m, 690m, 566w, 322w, 208w (CsI); m/z 412
(Mϩ Ϫ Cl), 377 (Mϩ Ϫ 2Cl), 319 (L2); λmax/cmϪ1 (BaSO4) 23800,
14500, 8000.
[{CuL2I}2]. Following the above procedure with CuI (20%)
(Found: C, 44.4; H, 3.3; N, 2.7. CuINS2C19H17 requires C, 44.0;
H, 3.1; N, 2.6%); νmax/cmϪ1 1587m, 1452w, 1358s, 1091s, 988w,
885w, 835w, 749s, 690m, 540w, 484w (CsI); δH (CDCl3) δ 7.6–7.1
(13H, m, C5H3N, C6H5), 4.65 (4H, s, CH2); m/z 901 (Mϩ Ϫ I),
386 (Mϩ Ϫ Cu Ϫ L2 Ϫ 2I), 324 (L2).
[NiL1Cl2]2. Following the above procedure with L1 (51%)
(Found: C, 32.7; H, 3.8; N, 3.9. NiCl2NS2C9H13 requires C,
32.9; H, 4.3; N, 4.0%); νmax/cmϪ1 3055vw, 2901vw, 1592s,
1570m, 1457s, 1420m, 1395m, 1358s, 1095m, 1019s, 991s, 870m,
796s, 698w, 254m, 207w (CsI); λmax/cmϪ1 (BaSO4) 27100, 13100,
10800.
Structure determinations
Single crystals of [NiL2Br2] were grown from liquid diffusion of
alcoholic solutions of the reagents at room temperature. Single
crystals of [{CuL2(µ-Br)}2] were obtained from a solution
of the complex in nitromethane at Ϫ30 ЊC. Single crystals
of [{CuL2(µ-Cl)}2] were obtained from vapour diffusion of
Et2O into a solution of the complex in nitromethane. For
each compound the selected crystal was coated with mineral
oil and mounted on a glass fibre. Data collection for [NiL2-
[NiL2Br2]. Following the above procedure for [NiL2Cl2]2 with
NiBr2 (65%) (Found: C, 42.1; H, 2.9; N, 2.2. NiBr2NS2C19H17
requires C, 42.1; H, 3.2; N, 2.6%); νmax/cmϪ1 3064vw, 2933vw,
2891vw, 1593w, 1570w, 1481w, 1458m, 1442w, 1358vs, 1106s,
1017s, 1000s, 887w, 834w, 802w, 745m, 734m, 683m, 613w,
476w, 319vw, 275vw, 203vw (CsI); m/z 461 (Mϩ Ϫ Br), 382
(Mϩ Ϫ 2Br), 319 (L2); λmax/cmϪ1 (BaSO4) 24500, 21100, 13600,
10300, 5700.
Br2] and [{CuL2(µ-Br)}2] used
a single counter Rigaku
AFC7S diffractometer at 150 K (for [NiL2Br2]) or 297 K (for
[{CuL2(µ-Br)}2]), (ω–2θ scans); for [{CuL2(µ-Cl)}2], a full
sphere of data was measured using a Bruker AXS CCD
instrument (18631 reflections; T ca. 153 K). “Empirical”/multi-
scan absorption corrections were applied, monochromatic
Mo-Kα radiation being employed for all determinations. In
the full matrix least-squares refinements, anisotropic thermal
parameter forms were refined for the non-hydrogen atoms;
for the Cu/Cl/L2 adduct, (x, y, z, Uiso)H were refined, these
parameters being included constrained at estimated values
in the other two. Conventional R, RЈ on |F| are quoted at
[NiL1Br2]2. Following the above procedure with L1 (41%)
(Found: C, 26.8; H, 3.4; N, 3.2. NiCl2NS2C9H13 requires C,
25.9; H, 3.1; N, 3.4%); νmax/cmϪ1 3064vw, 1599m, 1571m,
1458m, 1410m, 1206w, 1172w, 1098m, 1018m, 984m, 961w,
871m, 797m, 763m, 697m, 589w, 557w, 382vw, 321vw, 273w,
240m, 225m (CsI); λmax/cmϪ1 (BaSO4) 23300, 14500, 9000.
[NiL2I2]. Following the above procedure for [NiL2Cl2]2 with
NiI2 (74%) (Found: C, 32.8; H, 3.1; N, 2.3. NiCl2NS2C19H17ؒ
J. Chem. Soc., Dalton Trans., 2001, 2807–2812
2811

View Article Online
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Pertinent results are given above and in the figures and tables.
CCDC reference numbers 164471, 164472 and 168826.
See http://www.rsc.org/suppdata/dt/b1/b104332n/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We thank the University of Southampton, and Professor
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