Copper(I) bromide complexes from 1,2-bis(diphenylphosphano) benzene and some heterocyclic thiones

Article abstract of DOI:10.1016/j.ica.2005.04.042

The synthesis, characterization and solid state emission properties of a series of mixed-ligand copper(I)bromide complexes containing 1,2-bis(diphenylphosphano)benzene (dppbz) and some heterocyclic thiones (L) are reported. The complexes are readily synthesized by the addition of the appropriate thione to a CuBr-diphosphane adduct in acetonitrile/methanol or acetone solution. The molecular structures of [CuBr(dppbz)(py2SH)], [CuBr(dppbz)(pymtH)] and [CuBr(dppbz)(imdtH₂)] were established by single-crystal X-ray diffraction. Each of these structures features a tetrahedral copper(I) centre with two phosphorus atoms from the chelating diphos ligand, one bromine and the exocyclic sulfur atom of the heterocyclic thioamide unit. Slow decomposition of the mixed-ligand complexes via ligand dissociation occurs when their chloroform solutions are left to stand at room temperature for several weeks. On the basis of elemental analysis, NMR and IR spectra, the resulting coloured crystals are found to contain phosphane-free coordination polymers of composition [CuBr(L)]. At room temperature, some of the molecular complexes in the solid state exhibit strong emission assigned to a metal-ligand charge transfer of type Cu(I) → π*(PPh₂).

Full text of DOI:10.1016/j.ica.2005.04.042

Inorganica Chimica Acta 358 (2005) 3048–3056
www.elsevier.com/locate/ica
Copper(I) bromide complexes from
1,2-bis(diphenylphosphano) benzene and some heterocyclic thiones
a
b,
a,
*
A. Kaltzoglou , P.J. Cox *, P. Aslanidis
a
Aristotle University of Thessaloniki, Faculty of Chemistry, Inorganic Chemistry Laboratory, P.O. Box 135, GR-541 24 Thessaloniki, Greece
b
School of Pharmacy, The Robert Gordon University Schoolhill, Aberdeen AB10 1FR, Scotland, United Kingdom
Received 8 November 2004; received in revised form 1 April 2005; accepted 22 April 2005
Abstract
The synthesis, characterization and solid state emission properties of a series of mixed-ligand copper(I)bromide complexes con-
taining 1,2-bis(diphenylphosphano)benzene (dppbz) and some heterocyclic thiones (L) are reported. The complexes are readily syn-
thesized by the addition of the appropriate thione to a CuBr-diphosphane adduct in acetonitrile/methanol or acetone solution. The
molecular structures of [CuBr(dppbz)(py2SH)], [CuBr(dppbz)(pymtH)] and [CuBr(dppbz)(imdtH2)] were established by single-crys-
tal X-ray diffraction. Each of these structures features a tetrahedral copper(I) centre with two phosphorus atoms from the chelating
diphos ligand, one bromine and the exocyclic sulfur atom of the heterocyclic thioamide unit. Slow decomposition of the mixed-
ligand complexes via ligand dissociation occurs when their chloroform solutions are left to stand at room temperature for several
weeks. On the basis of elemental analysis, NMR and IR spectra, the resulting coloured crystals are found to contain phosphane-free
coordination polymers of composition [CuBr(L)]. At room temperature, some of the molecular complexes in the solid state exhibit
strong emission assigned to a metal–ligand charge transfer of type Cu(I) ! p*(PPh2).
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Copper; Sulfur heterocycles; 1,2-bis(diphenylphosphano)benzene complexes; Crystal structures; Luminescence
1. Introduction
these typical soft acids tend to be coordinated by the
neutral thione unit exclusively through the exocyclic sul-
fur atom, either in a terminal or bridging mode. Our
work within this area of research has involved the incor-
poration of a tertiary arylphosphane as a second bulky
soft donor. This produced a large number of mixed-
ligand copper(I) complexes with a variety of structures
ranging from mononuclear three- or four-coordinate
species with trigonal planar and tetrahedral copper(I),
respectively, to double bridged dimers [4–10]. Within
this theme, our particular interest has been to under-
stand and control the factors which may affect the stoi-
chiometric and geometrical preferences of these
complexes. According to the observed characteristics
for the copper(I) complexes examined by us so far there
are indications that other parameters, apart from the
well known extraordinary flexibility of copper(I), are
The interaction of heterocyclic thiones with transition
metals has attracted much attention in the past, due to
the biochemical significance of such thiones [1] and their
use as medicinal substances [2,3]. The key feature of
these heterocyclic thioamides, with respect to their ligat-
ing properties, is based upon the presence of both nitro-
gen and sulfur as potential donating atoms. Hence, the
ability to bind to a metal in several ways is evident
and this can produce a rich variety of structural proto-
types. However, considering the univalent coinage
metals in general and the copper(I) halides in particular,
*
Corresponding authors. Tel.: +32310997694; fax: +32310997738.
E-mail addresses: p.j.cox@rgu.ac.uk (P.J. Cox), aslanidi@chem.
auth.gr (P. Aslanidis).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.04.042

A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
3049
also involved. For example, the steric and electronic
requirements on the part of the ligands and the reaction
conditions (stoichiometry, temperature, solvent) applied
might be expected to play a crucial role in determining
the preferred geometry in each case [5,6,8]. Sometime
ago, we started comparative studies into the substitution
of unidentate arylphosphanes with oligomethylene-
backboned symmetric diphosphanes of the type
Ph2P(CH2)nPPh2 (n = 1–6). We demonstrated that,
dependent on the nature of the phosphorus donors, it
is possible to prepare and isolate diphosphane com-
plexes of copper(I) of different nuclearity and stoichiom-
etry. Recently, we examined the coordination capability
of cis-1,2-bis(diphenylphosphano)ethene (cis-dppet) to-
ward copper(I) halides in the presence of a series of het-
erocyclic thione donor groups [11]. The results
prompted us to consider further chelating rigid diphos-
phanes, including 1,2-bis(diphenylphosphano)benzene
(dppbz), in our investigations. The present study con-
centrates on derivatives from the reactions of copper(I)
bromide with dppbz and various related heterocyclic
thiones.
priate thione (L) [L = pyridine-2-thione pyrimidine-2-
thione, 4,6-dimethyl-pyrimidine-2-thione, tetrahydro-
pyrimidine-2-thione or imidazolidine-2-thione] (Fig. 1)
in dry acetonitrile for 2 h at 50 ꢁC. The pure mixed-
ligand compounds were generally isolated in good yields
as the only product of the reaction. However, in a few
cases formation of an amorphous solid was observed
during the partial evaporation of the clear reaction solu-
tion. This solid could not be identified unambiguously
by spectroscopy or by elemental analysis. The composi-
tion of the solid depended on the extent of the evapora-
tion, indicating the presence of a mixture of two or more
products and attempts to isolate the individual compo-
nents of such mixtures were only partly successful. In
the case of pymtH, the compound that first separated
during the initial stages of the evaporation of the diluted
acetonitrile mother liquid was a greenish product. This
gave analytical and spectroscopic data identical with
those of the above copper/diphosphane intermediate.
One possible outcome was a mixture containing the
Cu/diphosphane intermediate adduct plus the desired
mixed-ligand complex and a phosphane-free species.
The separation of each of these compounds depended
on their relative solubilities in the solvent used. Thus, at-
tempts were made to direct the reaction course towards
the exclusive formation of the desired mixed-ligand
complexes. These attempts included treatment of the
intermediate after isolation by redissolving in appropri-
ate organic solvents or mixtures of them, as well as addi-
tion of the components in a reverse sequence. Respective
modifications of the original one-pot procedure leading
to efficient synthesis are given in the experimental sec-
tion as an alternative method.
In the solid state, complexes 1–5 can be stored at
room temperature for several months, but they were
found to decompose in solution over the course of a
couple of weeks. For example, separation of a dark
red microcrystalline solid was obtained from a chloro-
form solution of [CuBr(dppbz)(py2SH)]. Exposure to
daylight clearly accelerated the decomposition, and the
microcrystalline solid that was released quantitatively
could be spectroscopically identified as a phosphane-free
adduct of composition [CuBrL]. No other copper-con-
taining species, apart from the free dppbz, could be iden-
tified in the solution, thus, Scheme 1 can be used to show
this interesting phenomenon.
To check the photochemical nature of this process,
we performed photolytic experiments on degassed chlo-
roform solutions of some mixed-ligand complexes. UV
irradiation of these solutions containing 1, 2 or 3 at
k = 250–300 nm indeed caused complete decomposition
of the complex within 10–30 min. The process was mon-
itored spectroscopically and produced in each case the
corresponding phosphane-free polymer, while dppbz
was isolated from the solution as the only soluble pho-
toproduct (Fig. 2).
2. Results and discussion
2.1. Preparative investigations
Diphosphanes are by far the most frequently used
species for bridging or chelation of low oxidation state
transition metal centres. Previously, we attempted to
chelate copper(I) using acyclic diphosphanes of the type
Ph2P(CH2)nPPh2 and when 1,3-bis(diphenylphosp-
hano)propane (dppp) was used we observed formation
of six-membered chelate rings [12]. The bridging mode
of coordination was preferred for diphosphanes bearing
either a short or a long backbone. Our initial approach
to five-membered chelate rings using 1,2-bis(diphenyl-
phosphano)ethane (dppe) failed as the products ob-
tained were found to be diphosphane-bridged dimers
[13]. Nevertheless, use of the rigid cis-1,2-bis(diphenyl-
phosphano)ethene (dppet) led to the successful chelation
of copper(I) [11], and we focused once more on five-
membered chelate rings including cis-1,2-bis(diphenyl-
phosphano)benzene (dppbz) in our investigations. Note
that no copper(I) derivatives of this rigid diphosphane
are currently known, although dppbz has already found
extensive utilisation as a chelating ligand at many metal
centres [14–23].
For the preparation of the new compounds, we fol-
lowed the synthetic pathways that have already yielded
many mixed-ligand copper(I) halide complexes. Thus,
copper(I) bromide was first treated with an equimolar
quantity of 1,2-bis(diphenylphosphano) benzene
(dppbz) to produce an intermediate adduct. This was
then allowed to react with one equivalent of the appro-

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A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
CH3
NH
N
N
HN
NH
N
S
N
S
N
H
S
N
H
H
S
H
H3C
S
pymtH
tHpymtH
dmpymtH
imdtH2
py2SH
Fig. 1. The heterocyclic thione ligands used with their abbreviations.
Scheme 1. Photochemical decomposition of 1.
phosphane (PPh3) in acetonitrile or acetone took place
very slowly and could not be driven to completion even
after heating under reflux for several days.
3. Characterization of the complexes
All prepared complexes are diamagnetic, air stable
microcrystalline solids soluble in acetonitrile and only
moderately soluble in chloroform and acetone. The
composition of the compounds has been confirmed
by elemental analysis. Their solutions in acetone and
chloroform are non-conducting. As far as possible,
we characterized all of the compounds by elemental
analyses, IR, NMR, and mass spectra. The molecular
structures of [CuBr(dppbz)(py2SH)], [CuBr(dppbz)-
(pymtH)] and [CuBr(dppbz)(imdtH2)] were determined
by X-ray crystallographic analyses. Room temperature
1H NMR spectra, recorded in deuterated chloroform,
exhibit a typical set of complex multiplets due to phe-
nyl/phenylene resonances, as well as signals attributable
to the aromatic protons of the thione groups. In some
cases, the extent of overlapping does not allow resolu-
tion between signals in the phenyl region, thus the cor-
responding thione resonances were not analyzed
further. Nevertheless, the observation of a broad sin-
glet in the ꢀ11–14 ppm region attributed to the NH
proton reflects the prevalence of the thione tautomer
in the complexes. In the 13C NMR spectrum of 1,
the signal of the thione-S bonded carbon atom, which
would be expected to be the most sensitive to coordina-
Fig. 2. UV–Vis absorbance changes in the course of the irradiation of
a 10ꢁ3 M chloroform solution of [CuBr(dppbz)(py2SH)]. (1) Spectrum
of the initial non-irradiated solution, (2)–(6) after irradiation for 2, 4,
6, 8 and 10 min, respectively.
The above decomposition seemed to be indicative of
the inherent lability of the coordinated dppbz and thione
ligands in solution and thus prompted us to investigate
the possibility of exchanging the chelating diphosphane
or thione ligand by other phosphane or thione units.
Refluxing reaction mixtures of [CuBr(dppbz)L] with a
3-fold excess of the appropriate thione L in acetonitrile
or acetone did lead to some reaction. However, intracta-
ble mixtures were normally formed, and only in the un-
ique case of the more basic dmpymtH, was
a
quantitative replacement of the coordinated thione L
achieved. On the other hand, analogous ligand-exchange
reactions on complexes 1–5 using an excess of triphenyl-

A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
3051
tion, is shifted by about 1.0 ppm to higher fields upon
complexation to the metal atom (d = 174.6 ppm com-
pared with d = 175.6 ppm for the free py2SH ligand
[24]). Shifts of the same order are also observed for
the corresponding carbon signals of compounds 2–5,
whereas no significant shifts are observed for the other
thione or the dppbz carbon atoms. The electronic
absorption spectra of the complexes 1–5 in chloroform
at room temperature show two intense broad bands
with maxima in the 243–255 and 285–310 nm regions,
respectively. With reference to the absorption bands
of the uncoordinated dppbz, the first one can be attrib-
uted to intraligand p* p transitions on the phenyl
group of the phosphane ligand, whereby the lower en-
ergy band, which lies in the region where the free thi-
tion of the residual CuBr which was completely re-
moved at 980 ꢁC.
The luminescence properties of compounds 1–5 in the
solid state were investigated at 298 K. Upon excitation
at 280 nm, compound 4 emits intensely at 483 nm,
whereas compounds 1–3 emit weakly with kmax values
in the 484–502 nm range which is typical of Cu–P con-
taining chromophores [27–29]. Thus, the excited-state
responsible for the luminescence of the monomeric spe-
cies can be assigned to a metal–ligand charge transfer
(MLCT) of the type Cu(I) ! p* (PPh2).
3.1. X-ray structural investigations
The X-ray crystal structures of [CuBr(dppbz)(py2-
SH)] (1), [CuBr(dppbz)(pymtH)] (2) and [CuBr(dppbz)-
(imdtH)] (4) (details of crystal and structure refinement
are shown in Table 4) corroborate the spectroscopic
results discussed above. Tables 1–3 list selected dis-
tances and angles of these complexes. Note that the
X-ray crystal structure determinations of these three
ones absorb, expressing
a small red shift as a
consequence of the coordination to CuI, should be con-
sidered as a thione-originating intraligand transition
which possesses some MLCT character [25,26]. The
presence of the pyridine-2-thione, pyrimidine-2-thione
and 4,6-dimethyl-pyrimidine-2-thione units in 1, 2 and
5 is further associated with absorptions at 465, 450
and 435 nm, respectively. The infrared spectra of com-
pounds 1–5, recorded in the range 4000–250 cmꢁ1
,
Table 1
˚
Selected bond lengths (A) and angles (ꢁ) for 1
show all the expected strong phosphane bands, which
remain practically unshifted upon coordination. More-
over, the spectra of these compounds contain all of the
bands originating from the presence of the heterocyclic
thione ligands with shifts due to coordination indica-
tive of an exclusive S-coordination mode.
˚
Bond length (A)
Cu(1)–Br(1)
Cu(1)–P(1)
Cu(1)–P(2)
Cu(1)–S(1)
2.4746(4)
2.2534(6)
2.2957(7)
2.3054(6)
S(1)–C(1)
P(1)–C(6)
C(6)–C(11)
P(2)–C(11)
1.706(3)
1.844(2)
1.406(3)
1.829(2)
Bond angles (ꢁ)
P(1)–Cu(1)–P(2)
P(1)–Cu(1)–S(1)
P(2)–Cu(1)–S(1)
P(1)–Cu(1)–Br(1)
P(2)–Cu(1)–Br(1)
S(1)–Cu(1)–Br(1)
The thermal behaviour of the new compounds was
investigated using simultaneous differential thermoanal-
ysis (DTA) and thermogravimetry (TG) in a nitrogen
atmosphere. In contrast to their photochemical insta-
bility, complexes 1–5 proved to be thermally stable to
at least 200 ꢁC. On further heating, their DTA/TG
curves showed similar decomposition patterns, gener-
ally consisting of two main stages. The low tempera-
ture initial stage observed in the TG curve at about
200–260 ꢁC was connected with two or three strong
endothermic events in the DTA curve and involved
overall weight loss indicative of gradual thermal break-
down of the corresponding thione ligand. Subsequent
thermal decomposition of 1, 2 and 5 showed two
strong endothermic effects in the temperature range
420–500 ꢁC, which were accompanied by a relative
mass loss consistent with burning of the diphosphane
ligand. At the same time, the process of dppbz removal
in the case of 3 and 4 was accompanied with an inten-
sive exothermic effect, which could be of particular
interest but difficult to explain. Although these two
derivatives contain non-aromatic thioamide units, it is
difficult to envisage any resulting Cu–P bonding situa-
tion that would lead to a differentiation in the thermal
destruction of the coordination framework. For all the
compounds, further heating caused gradual sublima-
86.61(2)
113.86(2)
109.73(2)
122.046(19)
110.980(19)
110.73(2)
C(1)–S(1)–Cu(1)
C(6)–P(1)–Cu(1)
C(11)–C(6)–P(1)
C(6)–C(11)–P(2)
C(11)–P(2)–Cu(1)
105.10(9)
101.28(7)
118.07(17)
117.59(17)
100.96(8)
Hydrogen bridge
N(1)–H(1)
NH(1)–Br(1)
0.8800
2.3400
Br(1). . .N(1)
Br(1). . .H(1)–N(1)
3.218(2)
174.6ꢁ
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for 2
˚
Bond length (A)
Cu(1)–Br(1)
Cu(1)–P(1)
Cu(1)–P(2)
Cu(1)–S(1)
2.4588(5)
2.2947(6)
2.2927(6)
2.2965(10)
S(1)–C(1)
P(1)–C(6)
C(6)–C(11)
P(2)–C(11)
1.691(3)
1.839(2)
1.390(3)
1.830(2)
Bond angles (ꢁ)
P(1)–Cu(1)–P(2)
P(1)–Cu(1)–S(1)
P(2)–Cu(1)–S(1)
P(1)–Cu(1)–Br(1)
P(2)–Cu(1)–Br(1)
S(1)–Cu(1)–Br(1)
85.28(2)
103.9(4)
C(1)–S(1)–Cu(1)
C(6)–P(1)–Cu(1)
C(11)–P(2)–Cu(1)
C(11)–C(6)–P(1)
C(6)–C(11)–P(2)
111.99(11)
100.78(7)
102.13(7)
116.72(16)
117.92(16)
112.83(3)
119.26(2)
113.51(2)
115.51(3)
Hydrogen bridge
N(1)–H(1)
NH(1)–Br(1)
0.8800
2.3300
Br(1). . .N(1)
Br(1). . .H(1)–N(1)
3.214(3)
177.7ꢁ

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A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
Table 3
As expected, the carbon atoms of the phenylene
˚
Selected bond lengths (A) and angles (ꢁ) for 4
backbone and the two adjacent phosphorus atoms
are coplanar with the lone-pair of electrons of the lat-
ter lying on the same side of the plane, thus the CuP-
CCP five-membered ring is in envelope conformation
with the metal atom out of the plane containing the
˚
Bond lengths (A)
Cu(1A)–Br(1A)
Cu(1A)–P(1A)
Cu(1A)–P(2A)
Cu(1A)–S(1A)
2.4557(4)
2.2577(6)
2.2981(6)
2.3214(7)
S(1A)–C(1A)
P(1A)–C(4A)
P(2A)–C(5A)
1.690(3)
1.837(2)
1.827(2)
˚
Bond angles (ꢁ)
four diphos ligand atoms by ꢁ0.999(2) A. Considering
P(1A)–Cu(1A)–P(2A)
P(1A)–Cu(1A)–S(1A)
P(2A)–Cu(1A)–S(1A)
P(1A)–Cu(1A)–Br(1A)
P(2A)–Cu(1A)–Br(1A)
S(1A)–Cu(1A)–Br(1A)
86.58(2)
110.58(3)
105.90(2)
125.24(2)
115.96(2)
109.53(2)
C(1A)–S(1A)–Cu(1A)
C(4A)–P(1A)–Cu(1A)
C(5A)–P(2A)–Cu(1A)
C(5A)–C(4A)–P(1A)
C(4A)–C(5A)–P(2A)
102.51(9)
101.16(7)
101.16(7)
117.71(17)
118.08(17)
the orientation of the two phenyl rings on each phos-
phorus atom, they are nearly perpendicular to each
other. However, the C(18)–C(23) and C(30)–C(35)
phenyl rings have their planes in an almost parallel
˚
arrangement with a 3.85 A p-stacking interaction be-
Hydrogen bridge
N(1A)–H(1A)
tween them. The two individual Cu–P distances of
2.2534(6)ꢁ and 2.2957(7)ꢁ are within the limits of the
value range expected for tetrahedrally coordinated
Cu(I). Within the heterocyclic thione ligand, which
exhibits a strictly planar six-membered ring, the bond
distances and angles are not altered significantly upon
coordination. Finally, the Cu–S and Cu–Br bond
lengths lie in the range normally observed for tetrahe-
drally coordinated copper(I) complexes with terminal
bromine and thione-sulfur donors.
In the case of [CuBr(dppbz)(pymtH)] (2), which
crystallizes in the monoclinic space group P21/n with
four formula units in the unit cell, two different orien-
tations were refined for the bromine atoms and the
atoms of the pymtH ligand, with an occupancy of
93% for the major and 7% for the minor orientation
respectively (Fig. 5). The four-coordinate monomer
(Fig. 4) reveals a copper coordination sphere with
0.8800
2.7200
Br(1A). . .N(1A)
3.543(3)
NH(1A)–Br(1A)
Br(1A). . .H(1A)–N(1A)
156.1ꢁ
complexes are the first to be carried out on copper(I)
compounds containing dppbz.
The structures of the three mixed-ligand compounds
are similar having a common tetrahedral coordination
of the copper(I) centres, which are surrounded by one
Br, the S donor of the thione ligand and two P atoms
of the chelating dppbz unit. Complex 1 crystallizes in
ꢀ
the triclinic space group P1 with two formula units in
the unit cell. Fig. 3 depicts a perspective of the molecule
showing the atom numbering. The tetrahedral environ-
ment of the copper atom is considerably distorted, with
the largest deviation from the ideal geometry being re-
flected by the P(1)–Cu(1)–P(2) and P(1)–Cu(1)–Br(1) an-
gles whose values of 86.61(2)ꢁ and 122.046(19)ꢁ,
respectively, are markedly different than the ideal tetra-
hedral value.
C15
C16
C15
C14
C16
C14
C13
C17
C13
C17
C12
C4
C3
C8
C12
N2
C2
C23
C7
C1
N1
C22
C8
C7
P1
C6
C18
S1
P1
C6
C23
C18
S1
C22
Cu1
Br1
C19
C9
C10
C30
C21
C11
C20
C1
C19
C5
C20
C11
C21
Br1
C9
C10
C30
C35
C34
C4
P2
C24
N1
C2
C35
P2
C24
C25
C34
C26 C25
C31
C33
C3
C32
C31
C26
C27
C33
C32
C29
C27
C29
C28
C28
Fig. 4. Molecular structure of 2 with disorder removed to show only
the major (93% occupancy) orientation (ORTEP drawing, 50%
probability ellipsoids).
Fig. 3. A view of compound 1 with atom labels. Displacement
ellipsoids are shown in the 50% probability level.

A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
3053
distances are essentially equal against their remarkable
inequality within the structure of 1. Moreover, com-
parison of the CuPCCP framework with that of 1
shows a slightly reduced P–Cu–P angle of 85.28(2)ꢁ
(vs. 86.61(2)ꢁ in 1).
C3
C300
C400
C4
C2
N1
[CuBr(dppbz)(imdtH2)] (4) crystallizes in the triclinic
C200
N200
N2
ꢀ
space group P1 with four discrete molecules in the unit
N100
cell. The asymmetric unit contains two independent
molecules (A and B) with small differences in the bond
distances and angles. One of these (molecule A) is de-
picted in Fig. 6.
Similarly to the structure of 2 and 3, the PCCPCu
five-membered ring is in an envelope conformation with
C100
C1
H1
H100
S1
S2
Br1
Br2
˚
the intraligand P–Cu–P angle 86.58(2) A in molecule A
˚
and 86.61(2) A in molecule B. The most striking feature
Cu1
between molecules A and B is the inclination of the five-
membered imidazoline-ring to the C(22)–C(27) ring. The
dihedral angle between mean planes through these two
rings is 15.4(2)ꢁ in molecule A and 45.6(1)ꢁ in molecule
P1
P2
˚
B. As a consequence, a 3.78 A closest contact distance
between these two rings in the former molecule is
observed.
Likewise, the almost parallel arrangement of two
Fig. 5. A section of molecule 2 showing the orientations of the
disordered bromine atoms and thione units.
additional phenyl substituents [rings C(16A)–C(21A)
˚
bond lengths in the ranges documented in the litera-
ture. As in the structure of 1, the CuPCCP five-mem-
bered ring is in envelope conformation with the metal
atom out of the plane containing the four diphos li-
and C(28A)–C(33A)] results in a 3.89 A p-stacking inter-
action between them. Although these interligand inter-
actions are small, they may be considered to
contribute in some degree to the overall stabilization
of the molecule.
˚
gand atoms by 1.0463 A. The two individual Cu–P
C3a
N2a
C1a
C2a
S1a
N1a
C27a
C22a
C12a
C26a
Br1a
C11a
C13a
Cu1a
C25a
C10a
P1a
C9a
C16a
P2a
C24a
C4a
C14a
C5a
C23a
C15a
C6a
C33a
C28a
C21a
C20a
C8a
C17a
C7a
C32a
C31a
C29a
C18a
C19a
C30a
Fig. 6. A view of compound 4 with atom labels. Displacement ellipsoids are shown at the 50% probability level.

3054
A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
4. Conclusion
The programs DENZO [30] and COLLECT [31] were used
in data collection and cell refinement. Details of crystal
and structure refinement are shown in Table 4. The
structures were solved using program SIR-97 [32] and re-
fined with program SHELX-97 [33]. Molecular plots were
obtained with program ORTEP-3 [34].
The aim of this work was the study of the coordina-
tion capability of the rigid diphos ligand 1,2-bis(diphe-
nylphosphano)benzene (dppbz) toward Cu(I) bromide.
We have found that dppbz readily forms a copper/
diphosphane intermediate, which proves to be a good
precursor for the preparation of other derivatives; in
the course of the present study it was chosen for the syn-
thesis of monomeric complexes which contain, besides
the chelating dppbz, some heterocyclic thioamides
bonded to the metal via the thione-S atom. These com-
plexes are light sensitive, undergoing slow decomposition
when exposed to daylight or intense UV irradiation. The
mixed-ligand derivatives exhibit in the solid state at
room temperature strong luminescence, the excited-state
responsible for the emission assigned to a metal to ligand
charge transfer (MLCT) of type Cu(I) ! p* (PPh2).
5.3. General synthesis of complexes 1–3
To a suspension of copper(I) bromide (71.7 mg,
0.5 mmol) in 30 cm3 of dry acetonitrile, 223.2 mg
(0.5 mmol) of 1,2-bis(diphenylphosphano) benzene was
added and the mixture was stirred for 2 h at 50 ꢁC dur-
ing which time a greenish precipitate was formed. To
this was added a solution of the appropriate thione
(0.5 mmol) in a small amount (ꢀ20 cm3) of methanol
and the new reaction mixture was heated under reflux
for two hours whereupon the precipitate gradually dis-
appeared. The resulting clear solution was filtered off
and left to evaporate at ambient temperature. The
microcrystalline solid, which was deposited upon stand-
ing for several days, was filtered off and dried in vacuo.
5. Experimental
5.1. Materials and instrumentation
5.4. Alternative method
Commercially available copper(I) bromide and 1,2-
bis(diphenylphosphano)benzene were used as received,
while the thiones (Merck or Aldrich) were recrystallized
from hot ethanol prior to their use. All the solvents were
purified by respective suitable methods and allowed to
stand over molecular sieves. Infrared spectra in the re-
gion of 4000–250 cmꢁ1 were obtained in KBr discs with
a Perkin–Elmer Spectrum-1 spectrophotometer, while a
Perkin–Elmer-Hitachi 200 spectrophotometer and a
Perkin–Elmer 350 S10 fluorescence spectrophotometer
were used to obtain the electronic absorption spectra
and the luminescence spectra, respectively. 1H NMR
spectra were recorded on a Brucker AM 300 spectrom-
eter at 25 ꢁC with positive chemical shifts given down-
field from TMS. TGA were performed under dry N2
using a SETSYS-1200 machine with DTG facility. Sam-
ple sizes were in the range 8–10 mg and open Pt crucibles
were used. The heating rate was 10ꢁ/min. For the photo-
lyses, an Osram high pressure HBO 200 W/4 lamp was
used. Melting points were measured in open tubes with
a STUART scientific instrument and are uncorrected.
Molar conductivities, magnetic susceptibility measure-
ments and elemental analyses for carbon, nitrogen and
hydrogen were performed as described previously [6].
To a stirred suspension of 4 (236 mg, 0.2 mmol) in
50 cm3 of dry acetone, a solution of the appropriate thi-
one (0.4 mmol) in 20 cm3 acetone was added dropwise
and the mixture was heated under reflux to clearness.
Slow evaporation of the mother liquid over a period
of a few days gave the microcrystalline solid which
was filtered off and dried in vacuo.
5.5. [CuBr(dppbz)(py2SH)] (1)
Bright yellow crystals (272 mg, 78%), m.p. 232 ꢁC;
Anal. Calc. for C35H29BrCuNP2S: C, 59.96; H, 4.17;
N, 2.00. Found: C, 59.93; H, 4.07; N, 2.20%. IR
(cmꢁ1): 3469m, 3049w, 1618m, 1575vs, 1481s, 1435vs,
1369s, 1180m, 1132vs, 1096s, 992s, 755s, 753vs, 693vs,
518vs, 493s, 482s, 446m. UV–Vis (kmax, log e), (CHCl3):
290 (4.14), 366 (3.75), 465 (2.11). 1H NMR (CDCl3,
d ppm): 14.33 (br, 1H, NHpy2SH), 7.48 (dd, 1H,
H6py2SH), 7.18–7.34 (m, 24H, 4C6H5 + C6H4), 7.29 (over-
lapping t, 1H, H4py2SH), 7.29 (t, 1H, Hp4y2SH), 6.70 (t, 1H,
H5py2SH). 13C NMR (CDCl3, d ppm): [128.18, 128.24,
128.30(t)], 129.18, 129.83, 130.28, 132.51, [132.90,
133.10, 133.29(t)], [133.68, 133.77, 133.81, 133.90(q)],
134.00, 134.06, 137.00,137.26, [142.41, 142.80,
143.19(t)], 174.60(s).
5.2. Crystal structure determination
Single crystals suitable for crystal structure analysis
were obtained by slow evaporation of acentonitrile/
methanol solutions of the complexes at room tempera-
ture. X-ray diffraction data were collected on an En-
raf-Nonius Kappa CCD area-detector diffractometer.
5.6. [CuBr(dppbz)(pymtH)] (2)
Red crystals (151 mg, 43%), m.p. 219 ꢁC; Anal. Calc.
for C34H28BrCuN2P2S: C, 58.17; H, 4.02; N, 3.99.
Found: C, 58.15; H, 3.90; N, 3.97%. IR (cmꢁ1):

A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
3055
Table 4
Crystal data and structure refinements for (1), (2) and (4)
1
2
4
Molecular formula
Formula weight
Temperature (K)
C35H29BrCuNP2S
C34H28BrCuN2P2S
702.03
120(2)
C33H30BrCuN2P2S
692.04
120(2)
701.04
120(2)
0.71073
˚
Wavelength (A)
0.71073
monoclinic
P21/n
0.71073
triclinic
Crystal system
Space group
Unit cell dimensions
triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
9.5559(2)
12.8262(2)
13.4081(3)
14.1790(3)
15.9576(3)
90
13.0253(2)
15.8994(2)
16.2348(2)
107.5050(10)
112.1780(10)
90.6270(10)
2939.56(7)
4
˚
b (A)
˚
c (A)
13.1234(3)
86.773(2)
a (ꢁ)
b (ꢁ)
c (ꢁ)
76.0370(10)
84.578(2)
1553.04(5)
99.2110(10)
90
3
˚
Volume (A )
2994.64(11)
4
1.557
Z
2
1.499
Dcalc (mg/m3)
Absorption coefficient (mmꢁ1
F(000)
1.564
2.309
1408
)
2.186
712
2.268
1424
Crystal size (mm)
h Range for data collection
Index ranges
0.36 · 0.24 · 0.06
3.01–27.46ꢁ
ꢁ126 h6 12,
ꢁ166 k6 16,
ꢁ17 6 l6 16
31501
0.30 · 0.26 · 0.22
2.96–27.49ꢁ
ꢁ176 h6 17,
ꢁ186 k6 18,
ꢁ186 l6 20
41226
0.26 · 0.22 · 0.12
3.13–27.53ꢁ
ꢁ166 h6 16,
ꢁ206 k6 20,
ꢁ196 l6 21
56774
Reflections collected
Independent reflections [Rint
Completeness (h)
Data/restraints/parameters
]
7100 [0.0617]
99.7% (27.46ꢁ)
7100/0/370
0.8800 and 0.5067
full-matrix least-squares on F2
1.020
6855 [0.0666]
99.7% (27.49ꢁ)
6855/19/409
0.6353 and 0.5494
full-matrix least-squares on F2
1.032
13439 [0.0552]
99.3% (27.53ꢁ)
13439/0/721
0.7691 and 0.5851
full-matrix least-squares on F2
1.020
R1 = 0.0351, wR2 = 0.0747
Maximum and minimum transmission
Refinement method
Goodness-of-fit on F2
Final R indices [(I) > 2r(I)]
R indices (all data)
R1 = 0.0352, wR2 = 0.0775
R1 = 0.0543, wR2 = 0.0843
R1 = 0.0339, wR2 = 0.0685
R1 = 0.0555, wR2 = 0.0743
R1 = 0.0561, wR2 = 0.0815
c
a
b
Final weighting scheme
˚
3
Largest differential peak and hole (e/A )
0.403 and ꢁ0.653
0.414 and ꢁ0.501
0.476 and ꢁ0.748
2
a
b
c
Calc w ¼ 1=½r2ðF o2Þ þ ð0.0451PÞ þ 0.1329Pꢂ; where P ¼ ðF o2 þ 2F 2cÞ=3.
2
Calc w ¼ 1=½r2ðF o2Þ þ ð0.0280PÞ þ 1.8928Pꢂ; where P ¼ ðF o2 þ 2F 2cÞ=3.
2
Calc w ¼ 1=½r2ðF o2Þ þ ð0.0402PÞ þ 10.2513Pꢂ; where P ¼ ðF o2 þ 2F 2cÞ=3.
3468m, 3052w, 1605s, 1570vs, 1472s, 1435vs, 1331vs,
1217s, 1177vs, 1095s, 977s, 744vs, 691vs, 517vs, 493s,
480m. UV–Vis (kmax, log e), (CHCl3): 243 (3.59), 285.0
(3.56), 328 (3.47), 450.0 (2.60). 1H NMR (CDCl3,
d ppm): 14.75 (br, 1H, NHpymtH), 7.17–7.37 (m, 24H,
4C6H5 + C6H4), 7.50 (m, 2H, H4p;y6mtH), 6.70 (t, 1H,
Hp5ymtH). 13C NMR (CDCl3, d ppm):128.31, 128.37,
129.28, 129.92, 130.28, [132.61, 132.80, 133.00(t)],
[133.68, 133.77, 133.81, 133.90(q)], 133.97, 134.03,
[142.28, 142.70, 143.09(t)], 180.58(s).
7.25–7.57 (m, 24H, 4C6H5 + C6H4), 3.35 (dt, 2H,
H3tHpymtH), 1.85 (q, 2H, Ht4HpymtH). 13C NMR (CDCl3,
d ppm): 137.29, 133.90, 133.74, 132.51, 132.44, 129.37,
129.27,128.40.
5.8. [CuBr(dppbz)(imdtH2)] (4)
Pale green crystals (326 mg, 94%), m.p. 231 ꢁC; Anal.
Calc. for C33H30BrCuN2P2S2: C, 57.27; H, 4.37; N, 4.05.
Found: C, 56.81; H, 4.32; N, 4.01%. IR (cmꢁ1): 3428s,
3051w, 1618m, 1522vs, 1500vs, 1479vs, 1435s, 1319s,
1282s, 1188s, 1095s, 1028m, 747vs, 695vs, 518vs,
489vs, 418m. UV–Vis (kmax, log e), (CHCl3); 251
(3.77), 297 (3.80), 328 (3.69). 1H NMR (CDCl3, d ppm):
14.75 (br, 1H, NHimtH), 7.17–7.59 (m, 24H,
4C6H5 + C6H4), 2.32 (dt, 4H, –(CH2)2–). 13C NMR
(CDCl3, d ppm):128.20, 128.27, 128.33, 128.62, 128.79,
128.88, [129.13, 129.20, 129.27(t)], [132.25, 132.31,
132.37, 132.43(q)], [133.64, 133.77, 133.86, 133.96(q)],
[136.97, 137.13, 137.29(t)].
5.7. [CuBr(dppbz)(tHpymtH)] (3)
Colorless crystals (324 mg, 92%), m.p. 245 ꢁC; Anal.
Calc. for C34H32BrCuN2P2S: C, 57.83; H, 4.57; N,
3.97. Found: C, 57.47; H, 4.36; N, 3.81%. IR (cmꢁ1):
3430m, 3175w, 3050w, 1566vs, 1479s, 1435vs, 1366s,
1214s, 1162s, 1096s, 753s, 746vs, 694vs, 516vs, 490s,
418m. UV–Vis (kmax, log e), (CHCl3): 278 (3.65), 257
(3.69). 1H NMR (CDCl3, d ppm): 7.93 (s, 1H, NH),

3056
A. Kaltzoglou et al. / Inorganica Chimica Acta 358 (2005) 3048–3056
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5.9. Synthesis of [CuBr(dppbz)(dmpymtH)] (5)
To a suspension of copper(I) bromide (71.7 mg,
0.5 mmol) in 60 cm3 of dry acetone, 223.2 mg
(0.5 mmol) of 1,2-bis(diphenylphosphano) benzene was
added and the mixture was stirred for 30 min at 50 ꢁC
during which time a greenish precipitate was formed.
To this was added a solution of 4,6-dimethylpyrimi-
dine-2-thione (70.5 mg, 0.5 mmol) in a small amount
(ꢀ20 cm3) of acetone and the new reaction mixture
was heated under reflux for 20 min whereupon the pre-
cipitate gradually disappeared. The resulting clear solu-
tion was filtered off and left to evaporate at ambient
temperature. The microcrystalline solid, which was
deposited upon standing for two days, was filtered off
and dried in vacuo. Orange crystals (305 mg, 84%),
m.p. 278 ꢁC; Anal. Calc. for C34H32BrCuN2P2S: C,
59.22; H, 4.42; N, 3.84. Found: C, 59.06; H, 4.64; N,
3.76%. IR (cmꢁ1): 3468m, 3047w, 2905m, 1612s,
1562vs, 1480s, 1434vs, 1228vs, 1186s, 1095s, 980s,
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753s, 744vs, 695vs, 518vs, 491s, 462s. UV–Vis (kmax
,
[16] W.-M. Xue, M.C.-W. Chan, Z.-M. Su, K.-K. Cheung, S.-T. Liu,
C.-M. Che, Organometallics 17 (1998) 1622.
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(3.17). 1H NMR (CDCl3, d ppm): 14.24 (br, 1H,
NHpymtH), 7.37 + 7.19 (m, 24H, 4C6H5+ C6H4), 6.38
(s, 1H, H5pymtH), 2.41 (s, 6H, CH3). 13C NMR (CDCl3,
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132.96, 133.16(t)], [142.38, 142.80, 143.19(t)], 179.55.
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6. Supplementary data
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CCDC-243704 (1), CCDC-243705 (2) and CCDC-
243706 (4) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge at www.code.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK, fax: (intrnat.)
+44 1223/336 033; e-mail: deposit@ccdc.cam.ac.uk].
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Acknowledgements
[29] H.-K. Yip, H.-M. Lin, K.-K. Cheung, C.-M. Che, Y. Wang,
Inorg. Chem. 33 (1994) 1644.
We thank the EPSRC X-ray crystallography service
at the University of Southampton for collecting the
X-ray data.
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