Metal-heterocyclic thione interactions. 13. Pyridine-2-thione derivatives of copper(I): Crystal structure of dinuclear [bromo(pyridine-2-thione)(tri-p-tolylphosphine)copper(I)]2 complex

Article abstract of DOI:10.1016/S0277-5387(02)01006-9

The sulfur-bridged dinuclear copper (I) complex, [CuBr(η²-S-μ-C₅H₅NS) (p-Tol₃P)]₂ (1) was prepared by the reaction of insoluble CuBr₂(C₅H₅NS)₂ {from copper(II) bromide and pyridine-2-thione(C₅H₅NS) in ethanol} with excess tri-p-tolylphosphine (p-Tol₃P) in chloroform (1:2 mole ratio). Similarly, other copper(I) complexes of stoichiometry [CuX(C₅H₅NS)(Ph₃P)]₂ {X = Cl, 2 and 1, 3} were prepared. Compound 1 crystallised from a dichloromethane-chloroform-methanol mixture and exists as a centrosymmetric sulfur-bridged dimer with distorted tetrahedral geometry about each Cu atom; the other two positions of each Cu atom being occupied by a P atom from p-Tol₃P and a bromine atom. The central core Cu₂S₂ of the dimer is a parallelogram with the important interatomic parameters as follows: Cu-P, 2.2376(13), Cu-S, 2.3895(19), 2.415(2), Cu-Br, 2.4455(11), S-C(2), 1.717(4), Cu-Cu*, 3.250(2), S-S*, 3.539(3) A?; Cu-S-Cu*, 85.14(6), S-Cu-S*, 94.86(6), Cu-S-C(2), 108.41(14), 113.12(16)°. The dimer structure is stabilised by strong intramolecular N-H···Br hydrogen bonds [3.319(5) A?]. The X-ray study of 2 showed that it has transformed into monomer [CuCl(η¹-S-μ-C₅H₅NS) (Ph₃P)₂] (4) during crystal growth. The strong intramolecular N-H···Cl hydrogen bonding appears to stabilise the monomer. All the compounds were characterised using analytical data, IR and far-IR (4000-100 cm^-1), UV-Vis spectra, NMR (₁H, ¹³C) and for 1 and 4 using X-ray crystallography. The factors controlling Cu···Cu interaction in the sulfur-bridged dinuclear copper(I)-heterocyclic thione complexes are described.

Full text of DOI:10.1016/S0277-5387(02)01006-9

Polyhedron 21 (2002) 1603Á1611
/
www.elsevier.com/locate/poly
MetalÁ
/
heterocyclic thione interactions.
13. Pyridine-2-thione derivatives of copper(I): crystal structure of
dinuclear [bromo(pyridine-2-thione)(tri-p-tolylphosphine)copper(I)]2
complex
Tarlok S. Lobana a,*, Alfonso Castineiras b
a Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, Punjab, India
b Departamento de Quimica Inorganica, Universidade de Santiago, 15706 Santiago, Galicia, Spain
Received 10 December 2001; accepted 4 March 2002
Abstract
The sulfur-bridged dinuclear copper (I) complex, [CuBr(h2-Sꢀ
insoluble CuBr2(C5H5NS)2 {from copper(II) bromide and pyridine-2-thione(C5H5NS) in ethanol} with excess tri-p-tolylphosphine
(p-Tol3P) in chloroform (1:2 mole ratio). Similarly, other copper(I) complexes of stoichiometry [CuX(C5H5NS)(Ph3P)]2 {XꢀCl, 2
and I, 3} were prepared. Compound 1 crystallised from a dichloromethaneÁchloroformÁmethanol mixture and exists as a
/
m-C5H5NS)(p-Tol3P)]2 (1) was prepared by the reaction of
/
/
/
centrosymmetric sulfur-bridged dimer with distorted tetrahedral geometry about each Cu atom; the other two positions of each Cu
atom being occupied by a P atom from p-Tol3P and a bromine atom. The central core Cu2S2 of the dimer is a parallelogram with the
important interatomic parameters as follows: Cuꢀ
/
P, 2.2376(13), Cuꢀ
Cu*, 85.14(6), SꢀCuꢀS*, 94.86(6), Cuꢀ
structure is stabilised by strong intramolecular NꢀHÁ Á ÁBr hydrogen bonds [3.319(5) A]. The X-ray study of 2 showed that it has
transformed into monomer [CuCl(h1-Sꢀ
m-C5H5NS)(Ph3P)2] (4) during crystal growth. The strong intramolecular NꢀHÁ Á ÁCl
/
S, 2.3895(19), 2.415(2), Cuꢀ
/
Br, 2.4455(11), Sꢀ
/
C(2), 1.717(4),
˚
Cuꢀ
/
Cu*, 3.250(2), Sꢀ
/
S*, 3.539(3) A; Cuꢀ
/
Sꢀ
/
/
/
/
SꢀC(2), 108.41(14), 113.12(16)8. The dimer
/
˚
/
/
/
hydrogen bonding appears to stabilise the monomer. All the compounds were characterised using analytical data, IR and far-IR
(4000Á
/
100 cmꢁ1), UVÁ
/
Vis spectra, NMR (1H, 13C) and for 1 and 4 using X-ray crystallography. The factors controlling CuÁ Á ÁCu
interaction in the sulfur-bridged dinuclear copper(I)-heterocyclic thione complexes are described. # 2002 Elsevier Science Ltd. All
rights reserved.
Keywords: Pyridine-2-thione; Tri-p-tolylphosphine; Triphenylphosphine; Sulfur-bridged dimer; Copper(I) complexes
1. Introduction
studied and it has shown several modes of bonding [5].
The interaction of transition and main-group metals
with heterocyclic thioamides have been the focus of
several investigations because these compounds contain
chemically active
groups and bind to metals both as neutral and depro-
ꢀ
/
N(H)ꢀ
/
C(ꢁ
/
S)ꢀ
/
X
/
ꢀ
/
Nꢁ
/
C(ꢀ
/
SH)ꢀ
/
tonated species via a variety of modes forming mono-
mers, dimers and oligomers [1Á4]. The simplest
/
prototype of heterocyclic-2-thiones, i.e. pyridine-2-
thione (hereafter C5H5NS, see I), has been intensively
* Corresponding author. Tel.: ꢂ
820
E-mail address: tarlok@angelfire.com (T.S. Lobana).
/
91-183-257-604; fax: ꢂ91-183-258-
/
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 0 6 - 9

1604
T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á1611
/
The coordination chemistry of copper is important for
(nCꢁ
Br) [7,8]. The crystals were grown from CH2Cl2Á
CHCl3ÁMeOH mixture.
/
S), 1098s (nPꢀ
/
C), 809s (rCꢀ
/
CH3), 219sb (nCuꢀ
/
a variety of reasons such as modelling its sites present in
biological systems, display of stereochemical diversity
on interaction with organic substrates, formation of
oligomers and polymers, interesting magnetic properties
/
/
etc. [1Á
/
23]. In view of our interest in the study of metalꢀ
/
2.1.2. [CuCl(C5H5NS)(Ph3P)]2 (2)
sulfur bonds, structural and spectroscopic properties of
interaction of heterocyclic thiones, thiosemicarbazones
and phosphine sulfuides/selenides with several transition
To CuCl(C5H5NS) {0.100 g, 0.48 mmol} suspended in
CHCl3 (15 cm3) was added a solution of Ph3P (0.125 g,
0.48 mmol) in CHCl3 (15 cm3) and the mixture was
refluxed for 2 h. The clear solution formed was filtered
and concentrated. A yellow solid started forming on
cooling to r.t., which was filtered, washed with EtOH
and non-transition metals have been reported [9Á42].
/
In the literature, neutral heterocyclic thiones form
sulfur-bridged dinuclear copper(I) complexes, namely
[Cu2(C5H5NS)4I2] (5) [24], [Cu2(imdtH2)4Cl2] (6) {im-
and dried in vacuo. Yield: 65%, m.p. 190Á192 8C. Anal.
/
dtH2ꢀ
[Cu2(meimtH)4Cl2] (7) [26], [Cu2(meimtH)4(SCN)2] (8)
[27], [Cu2(C5H5NS)6]X2 {XꢀCl, 9, Br, 10} [28,29],
[Cu2(meimtH)6](BF4)2 (11) {meimtHꢀ1-methylimida-
zoline-2-thione, III} [30], [Cu2(imdtH2)6](ClO4)2 (12)
[31], [Cu2(pymtH)2Cl2(p-Tol3P)2] (13) {pymtHꢀpyri-
/
1,3-imidazolidine-2-thione,
II}
[25],
Found: C, 57.6; H, 4.40; N, 2.94. Calc. for
C46H40Cl2Cu2N2P2S2: C, 58.5; H, 4.23; N, 2.97%. UV
data (lmax, nm): 367mb (CS), 285s (py), 250s (Ph). IR
/
/
data (cmꢁ1): 1126s (nCꢁ
Cl).
/
S), 1097s (nPꢀ
/
C), 327sb (nCuꢀ
/
/
midine-2-thione, IV] [32],[Cu2(C5H5NS)2Br2(m-Tol3P)2]
(14) [33], [Cu2(C5H5NS)2Br2(PPh3)2] (15) [34],
2.1.3. [CuI(C5H5NS)(Ph3P)]2 (3)
[Cu2(C5H5NS)2I2(p-Tol3P)2]
[Cu2(tzdtH)2Cl2(p-Tol3P)2] (17) (tzdtHꢀ
dine-2-thione, V} [35] and [Cu2(meimtH)5](SO4)×
(18) [36].
(16)
[6],
1,3-thiazoli-
To CuI {0.100 g, 0.52 mmol} suspended in CHCl3 (20
cm3) was added solid C5H5NS (0.058 g, 0.52 mmol) and
a solution of Ph3P (0.138 g, 0.52 mmol) in CHCl3 (15
cm3) and the mixture was refluxed for 2 h. The clear
solution formed was filtered, concentrated to 1/3 of its
/
/3H2O
In this paper, copper(I) complexes with C5H5NS
containing tertiary phosphines as co-ligands are re-
ported with the objectives of: (i) understanding the
effect of substituents on Ph groups attached to P atoms
and anion on the Lewis acidity of the Cu(I) centre; (ii)
studying the Cu(I)Á Á ÁCu(I) interaction; and (iii) analys-
ing factors controlling the formation of sulfur-bridged
dinuclear copper(I) complexes with various heterocyclic
thioamides. It may be mentioned that preparations and
other details of the complexes have appeared elsewhere
[12,32,34].
initial volume and addition of 10 cm3 of petroleumÁ
ether (60Á80 8C) formed a bright yellow solid which
was filtered, washed with Et2O and dried in vacuo.
Yield: 70%, m.p. 218Á220 8C. Anal. Found: C, 49.2; H,
/
/
/
3.69; N, 2.56. Calc. for C46H40Cu2I2N2P2S2: C, 49.0; H,
3.55; N, 2.49%. UV data (lmax, nm): 355wb (CS), 285s
(py), 247 (Ph). IR data (cmꢁ1): 3105w (nNꢀ
/H), 1124s
(nCꢁ
/
S), 1096s (nPꢀ
/
C), 136sb (nCuꢀ
/I).
2.1.4. [CuCl(h1-Sꢀ
The crystallisation of 2 from CH2Cl2Á
resulted in the formation of the monomer 4 as revealed
/
m-C5H5NS)(Ph3P)2] (4)
/EtOH mixture
2. Experimental
by its X-ray crystal determination.
2.1. Preparation of complexes
2.1.1. [CuBr(h2-Sꢀ
NMR spectroscopy and also preparation details of
compound are described earlier [6]. To
CuBr2(C5H5NS)2 {0.100 g, 0.22 mmol} suspended in
CHCl3 (15 cm3) was added a solution of excess p-Tol3P
(0.136 g, 0.44 mmol) in CHCl3 (15 cm3) and the mixture
was refluxed for 2 h. The clear solution formed was
filtered and concentrated. A yellow solid started forming
on cooling to room temperature (r.t.), which was
filtered, washed with EtOH and dried in vacuo. Yield:
/
m-C5H5NS)(p-Tol3P)]2 (1)
2.2. Elemental analyses and spectroscopic techniques.
1
The C, H and N elemental analyses were obtained
with a Carlo-Erba 1108 microanalyser. The m.p. was
determined with a Gallenkamp electrically heated appa-
ratus. The electronic absorption spectra were recorded
on a Shimadzu Graphicord 240 UVÁ
ometer. The IR spectra were recorded in KBr pellets
(4000Á
400 cmꢁ1) or Nujol mull in polythene sheets
(500Á
100 cmꢁ1) on a Bruker IFS 66V spectrometer.
/Vis spectrophot-
/
/
70%, m.p. 208Á
/
210 8C. Anal. Found: C, 55.3; H, 4.22;
The NMR spectra were recorded in CDCl3 using a
Bruker AMX 300 spectrometer at 300.14, and 75.48
MHz probe frequencies (1H and 13C, respectively) with
TMS as the internal reference.
N, 2.50. Calc. for C52H52Br2Cu2N2P2S2: C, 55.9; H,
4.65; N, 2.50%. UV data (lmax, nm): 367mb (CS), 288s
(py), 251s (Ph). IR data (cmꢁ1): 3162w (nNꢀ
/
H), 1127s

T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á
/1611
1605
2.3. Crystal structure determinations
Table 1
Summary of crystal data for compounds 1 and 4
A yellow crystal of 1 (or yellow plate crystals of 4) was
mounted on a glass fibre and used for data collection.
Cell constants and orientation matrix for data collection
were obtained by least-squares refinement of the dif-
fraction data from 25 reflections in the range of
1
4
Empirical formula
C
P2S2
52H52Br2Cu2N2-
C41H35ClCuNP2S
Formula weight (MW)
T (K)
˚
l (A)
1117.92
293(2)
1.54184
triclinic
734.69
293(2)
14.0778B
for 4 on an EnrafÁ
ometer [43]. Data were collected at 293 K using Cu Ka
/
u B
/
42.2538 for 1 and 16.0368B
/
u B19.5978
/
1.54184
monoclinic
P21/c
/Nonius CAD 4 automatic diffract-
Crystal system
Space group
Unit cell dimensions
¯
/
P1/
˚
radiation (lꢀ1.54184 A) and the v-scan technique and
/
˚
a (A)
9.790(5)
10.391(7)
14.600(5)
83.64(4)
73.82(3)
62.16(4)
1261.0(11)
1
14.4776(13)
10.1609(14)
24.5402(9)
corrected for Lp effects [44]. A semi-empirical absorp-
tion correction (c-scan) was made [45].
˚
b (A)
˚
c (A)
The structure was solved by direct method [46] and
subsequent difference Fourier maps, and refined on F2
by a full-matrix least-squares procedure using anisotro-
pic displacement parameters [47]. For 1 all hydrogen
atoms were located from difference Fourier maps while
a (8)
b (8)
93.367(14)
g (8)
3
V (A )
˚
3603.8(6)
4
Z
Dcalc (g cmꢁ3
)
1.472
4.543
568
1.354
3.144
1520
m(Cu Ka) (mmꢁ1
F(000)
)
for 4 all hydrogens were located in their calculated
˚
H 0.93 A) except the one bonded to N1,
positions (Cꢀ
/
Scan type
v Á
0.30ꢃ0.10ꢃ0.05 0.20ꢃ0.20ꢃ0.10
3.15Á74.33 3.06Á64.92
ꢁ125h 50,
ꢁ125k 511,
185l 517
5438
/2u
v Á
/
2u
which was located from the Fourier map. The located
hydrogens were refined isotropically whereas calculated
ones were refined using a riding model. Atomic scatter-
ing factors were taken from International Tables for X-
ray crystallography [48] and molecular graphics from
ZORTEP [49]. A summary of the crystal data, experi-
mental details and refinement results are listed in Table
1. Tables 2 and 3 contain bond lengths and angles while
NMR data are given in Tables 4 and 5.
Crystal size (mm)
2u Range (8)
Index ranges
/
/
ꢁ175h 50,
05k 511,
ꢁ285l 528
6380
Reflections collected
Unique reflections, Rint
Max./min. transmission
Reflections with
5122, 0.0227
0.978 and 0.907
5122, 384
6117, 0.0672
0.910 and 0.803
6117, 429
[I ꢀ2s(I)], parameters
Final R indices
R1ꢀ0.0414,
wR2ꢀ0.1011
R1ꢀ0.0867,
wR2ꢀ0.1195
1.010
R1ꢀ0.0705,
wR2ꢀ0.1433
R1ꢀ0.2669,
wR2ꢀ0.2092
1.067
R indices (all data)
S on F2
3. Results and discussion
ꢁ3
˚
Peak and hole ( e A
3.1. Synthesis, IR and NMR spectral studies
)
0.324 and ꢁ0.711 0.466 and ꢁ0.410
Reaction of CuBr2(C5H5NS)2 with p-Tol3P in CHCl3
in a 1:2 mole ratio formed dinuclear compound 1 which
C5H5NS is not deprotonated in the complexes and a
strong n(Cꢁ
S) peak at 1139 cmꢁ1 in the free ligand
shifts to the low energy region, 1124Á
1127 cmꢁ1, again
as a strong peak in the complexes. This shows that
C5H5NS coordinates to the Cu(I) centre via its thione
sulfur and the magnitude of the coordination shift is
similar to that reported in the literature [6]. Tentative
yielded crystals in the CH2Cl2Á
/
CHCl3ÁCH3OH solvent
/
/
mixture. Similarly CuCl(C5H5NS) reacted with Ph3P in
CHCl3 (1:1 mole ratio) to form 2; while compound 3
was formed by reacting CuI with C5H5NS and Ph3P in a
1:1:1 mole ratio. The melting points of complexes 2 and
3 are different, though close, to the reported values {lit.
/
value [34], 2, 196Á
difference may be attributed to the different packing
densities. The crystallisation of 2 from a CH2Cl2Á
/
199 8C; 3, 210Á212 8C} and the
/
assignments to n(Cuꢀ
made (cf. Section 2) [6Á
The presence of a broad signal due to NH protons in
the range d 13.93Á14.92 ppm at a lowfield shows that
pyridine-2-thione is coordinating to the Cu(I) centre as a
neutral ligand (free ligand, dNH 13.40 ppm) (Table 4).
/
X) Xꢀ/halogen bands are also
/8].
/
C2H5OH mixture resulted in the formation of 4 as
revealed by X-ray crystallography. It is significant to
note that reaction of CuCl(C5H5NS) with Ph3P in a 1:2
mole ratio formed the monomer 4 [12]. Compound 3 did
not yield good quality crystals.
The IR spectra of the complexes showed characteristic
peaks due to C5H5NS and tertiary phosphines at altered
positions and some important ones are listed in Section
/
ꢀ
/
There is a lowfield shift in H(6), H(5) and H(4) protons
of C5H5NS, while H(3) protons remain nearly unaf-
3
fected. The J coupling constants show variable trends
for different ring protons; for example, the J5 value for
H(6) proton decreases, for H(4) proton J3 and J5
become equal, for H(3) J4 and for H(5) J4 and J6
2. The presence of a n(Nꢀ
/
H) peak in the region 3105Á
/
3164 cmꢁ1 as a weak peak in the complexes shows that

1606
T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á1611
/
Table 2
increased aromatic character of the pyridyl ring [6]. As
regards 13C NMR signals for the phosphines, the
behaviour is summarised as follows: (i) ipso-carbons
for both ligands show upfield shifts; (ii) ortho-carbons
for Ph3P also show the same behaviour, but for p-Tol3P
they are nearly unaffected; (iii) the para-carbon for Ph3P
also shows an upfield shift and for p-Tol3P it is reversed;
and finally (iv) for meta-carbons the trend is irregular
and nearly unaffected.
˚
Bond lengths (A) and angles (8) for compounds 1 and 4
Parameters
1
Parameters
4
Bond lengths
CuꢀP
2.2376(13)
CuꢀP1
CuꢀP2
CuꢀS1
2.300(2)
2.288(2)
2.381(2)
2.367(2)
1.688(9)
1.14(12)
1.94(12)
CuꢀS
CuꢀS*
CuꢀBr
CuꢀCu*
SꢀS*
S(1)ꢀC(2)
N(1)ꢀH(1)
H(1)Á Á ÁBr
2.3895(19)
2.415(2)
2.4455(11)
3.250(2)
3.539(3)
1.717(4)
0.93(5)
CuꢀCl
S(1)ꢀC(2)
N(1)ꢀH(1)
H(1)Á Á ÁCl
3.1.1. Crystal and molecular structures
The atomic numbering schemes of [CuBr(h2-Sꢀ
/
/
m-
[CuCl(h1-Sꢀ
m-
2.41(5)
C5H5NS)(p-Tol3P)]2
(1)
and
Bond angles
C5H5NS)(Ph3P)2] (4) are shown in Figs. 1 and 2,
respectively. The selected bond lengths and angles are
given in Table 2. The basic structural unit of 1 is a
centrosymmetric dimer with no interaction between the
dimers and the S atoms of C5H5NS molecules bridge
two Cu atoms forming a strictly planar Cu2S2 core.
Each Cu atom is further bonded to a P atom of p-Tol3P
and one bromine atom and thus Cu acquires a distorted
SꢀCuꢀS*
94.86(6)
85.14(6)
P(2)ꢀCuꢀP(1)
P(2)ꢀCuꢀCl
P(1)ꢀCuꢀCl
P(2)ꢀCuꢀS(1)
P(1)ꢀCuꢀS(1)
ClꢀCuꢀS(1)
CuꢀS(1)ꢀC(2)
122.31(9)
111.84(9)
99.46(8)
CuꢀSꢀCu*
CuꢀSꢀC(2)
Cu*ꢀSꢀC(2)
108.41(14)
113.12(16)
102.83(9)
111.10(9)
109.08(9)
113.3(4)
Symmetry transformations used to generate equivalent atoms:
ꢁxꢂ2, ꢁyꢂ1, ꢁzꢂ1.
tetrahedral geometry. Two tetrahedra share a Sꢀ
/
S edge
and the trans-bromine atoms stabilise the dimer with
strong intramolecular hydrogen bonds [Nꢀ
/
HÁ Á ÁBr,
decrease marginally. As regards phosphines, o-, m- and
p-protons show lowfield shifts but are unresolved for
Ph3P (Table 4).
˚
3.319(5); HÁ Á ÁBr, 2.41(5) A and Nꢀ
/
Hꢀ
/
Br bond an-
gleꢀ
/
163(5)8] similar to those observed in literature
[6,25]. The pyridyl ring of the thione ligand is planar
and makes an angle of 63.668 with the plane of the
Cu2S2 core.
The C(2) signal of coordinated C5H5NS shows a
significant upfield shift relative to the free ligand; C(6)
and C(3) signals show small lowfield shifts; C(4) signals
are nearly unaffected and finally C(5) signals also show
upfield shift (Table 5). The upfield shift of C(2) signals
shows that coordination of Cu(I) to the S atom of
C5H5NS increases the aromatic character of the pyridyl
ring. The anionic C5H4NSꢁ shows upfield shifts if it
binds to a metal centre via S only and it is attributed to
˚
Br bond distance, 2.446 A, is shorter than
˚
that (2.493 A) in [Cu2(C5H5NS)2Br2(m-Tol3P)2] (14) [33]
The Cuꢀ
/
˚
(the sum of ionic radii, 2.73 A) [50]. The two short and
˚
S bonds, 2.389 and 2.415 A form a
parallelogram of the Cu2S2 core, similar to other dimeric
two longer Cuꢀ
/
Cu(I) complexes listed in Table 3 and bond lengths are
˚
P bond distance of 2.238 A is
similar in value. The Cuꢀ
/
Table 3
˚
Bond lengths (A) and angles (8) for Cu2S2 core of dinuclear copper(I)-heterocyclic thione complexes
Compound
CuÁ Á ÁCu
SÁ Á ÁS
CuꢀSbbr
CuꢀSꢀCu
SꢀCuꢀS
Reference
1
3.250
3.139
4.506
2.914
2.861
2.950
2.907
3.007
2.686
3.316
2.691
3.420
3.263
3.508
3.308
3.539
2.389, 2.415
2.328, 2.577
2.204, 2.631
2.301, 2.572
2.377, 2.457
2.308, 2.498
2.297, 2.534
2.358, 2.459
2.362, 2.490
2.356, 2.470
2.335, 2.488
2.383, 2.392
2.393, 2.425
2.386, 2.470
2.243, 2.151
85.14
79.4
137.3
73.2
72.6
74.3
73.8
77.2
67.2
86.7
67.7
91.5
85.2
87.5
94.8
94.9
96.1
this work
[24]
[25]
5
6
7
106.8
107.4
105.7
106.2
110.1
112.8
93.2
[26]
[27]
8
9
[28,29]
[28,29]
[30]
10
11
12
13
14
15
16
17
18
3.766
[31]
[32]
3.508
4.005
3.332
3.545
112.3
88.5
94.7
[33]
[34]
[6]
[35]
92.5
[36]

T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á
/1611
1607
Table 4
1H NMR data (d ppm, J, Hz) for the compounds
a
CH3
o-H
m-H
p-H
b
p-Tol3P
Ph3P
2.36s
7.23t (6H) (7.8,3JHꢀH,3JHꢀP
)
7.15d (6H) (7.3,3JHꢀH
)
c
7.23m
7.30dd (6H) (8.1,3JHꢀH, 10.3,3JHꢀP
b
3
1
2.27s
7.07d (6H) (7.4, JHꢀH
)
c
c
c
c
2
3
7.39Á
/
7.45m
7.51m
7.23Á
/
7.31m
7.39Á
/
7.45m
c
c
7.44Á
/
7.29Á
/
7.36m
7.44Á
/
7.51m
H(6)
H(4)
H(3)
H(5)
b
1
7.71d (4.1, J5)
7.70
7.43td (8.9, J3, J5, 1.6, J6)
c
7.46d (7.3, J4)
c
6.84td (6.2, J4, J6, 2.0, J3)
6.81td (6.4, J4, J6, 1.6, J3)
6.91td (5.9, J4, J6, 2.7, J3)
2
c
c
3
C5H5NS
7.70d (6.2, J5)
7.56ddd (6.3, J5, 1.6, J4, 0.8, J3)
b,d
7.34ddd (8.7,
J
3, 7.0, J5, 1.8, J6)
7.49dt (8.7, J4, 0.8, J5, J6) 6.73td (6.7, J4, J6,1.2, J3)
a
d, doublet; t, triplet; dd, doublet of doublets; td, triplet of doublets; dt, doublet of triplets.
From Ref. [6].
Unresolved signals.
b
c
d
Unresolved signals dNH for 1Á3 and ligand are 14.43, 14.92, 13.93, 13.40 ppm, respectively.
/
˚
comparable to that (2.243 A) in analogous [Cu2(C5H5N-
S)2I2(p-Tol3P)2] (16) [6], but shorter than in monomeric
˚
[51]. The HÁ Á ÁCl bond separation of 1.94(12) A in 4 is
˚
much shorter than that (2.23 A) in analogous monomer
[Cu(bztzdtH)Cl(PPh3)2] (23) {bztzdtHꢀbenz-1, 3-thia-
zolidine-2-thione} [52] as well as that (2.30 A) in the
related dimer [Cu2(pymtH)2Cl2(p-Tol3P)2] (13)
{pymtHꢀpyrimidine-2-thione} [32].
tetrahedral complexes [12,33]. The Cꢀ
/
S bond distance of
1.717 A is longer than (1.690 A) in analogous 16, but
close to those in 13 [32], 14 [33] and 15 [34]. The CuꢀSꢀ
/
˚
˚
˚
/
/
C angles (108.418, 113.128) are similar to those
(107.0(4)8, 116.5(5)8) in analogous 16.
The bond angles around Cu in compound 4 reveal a
/
From the reactions of copper(I) halides with tertiary
phosphines reported to date, it is noted that there is no
monomeric tetrahedral complex with a substituted
tertiary phosphine; however monomeric trigonal planar
copper(I) complexes, viz. [CuBr(o-tol3P)(thiazolidine-2-
thione)] [37], [CuCl(o-tol3P)(pyrimidine-2-thione)] and
[CuI(o-tol3P)(pyridine-2-thione)] [38] have been re-
ported. The large cone angles of substituted tertiary
phosphines appear responsible for the different beha-
viour [39]. Our efforts to get tetrahedral or trigonal
planar complexes using pyridine-2-thione and m- or p-
tol3P resulted in the formation of dinuclear copper(I)
complexes [6]. However, copper(I) bromide with unsub-
stituted tertiary phosphines, e.g. triphenyl phosphine,
formed both monomeric [Cu(C5H5NS)Br(PPh3)2] (22)
distorted tetrahedral geometry with different Cuꢀ
/
P and
CuꢀS bond distances unlike those observed in the dimer
/
1 (Table 2). The structural parameters are similar to the
ones reported earlier in literature [12]. In 1, the non-
˚
bonded H(1)Á Á ÁBr bond distance of 2.41(5) A is longer
˚
than that (2.348(2) A) in [Cu2(C5H5NS)2Br2(m-Tol3P)2]
˚
(14) [33], but shorter than that (2.49 A) in
[Cu2(C5H5NS)2Br2(PPh3)2] (15) [34]; all these are longer
˚
A)
than
that
(2.39
in
the
monomer
[Cu(C5H5NS)Br(PPh3)2] (22) [34]. The HÁ Á ÁBr separa-
˚
tion is about 0.6 A shorter than the sum of the van der
˚
3.45 A) [50] and therefore fulfils
Hamilton’s criterion for hydrogen bond formation
Walls radii (3.00Á
/
Table 5
13C NMR data (d ppm, J, Hz) for the compounds
Compound
CH3
i-C (1JCꢀP
)
o-C (2JCꢀP
)
m-C (3JCꢀP
)
p-C (4JCꢀP
)
a
p-Tol3P
PPh3
20.30
133.0 (8.8)
132.5 (10.0)
131.0
132.6 (19.5)
134.2 (19.5)
132.8 (15.1)
132.9 (14.9)
133.0 (14.5)
128.3 (7.2)
137.6
128.9 (10.8)
128.4 (9.9)
129.5 (9.4)
127.6 (9.4)
129.1 (9.3)
138.9
128.8
a
1
20.38
2
3
131.7
131.9
128.9
C(2)
C(6)
C(4)
C(5)
C(3)
a
1
171.5
173.3
170.6
175.6
137.8
137.6
137.8
137.0
136.0
136.2
128.7
131.0
131.3
132.8
114.6
114.4
114.6
113.4
2
3
a
C5H5NS
135.9
a
From Ref. [6].

1608
T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á1611
/
Fig. 1. A perspective view of the structure of compound 1 with atomic numbering scheme.
Fig. 2. A perspective view of the structure of compound 4 with atomic numbering scheme.

T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á
/1611
1609
and dimeric [Cu2(C5H5NS)2Br2(PPh3)2] (15) [34] com-
plexes. Similarly, with copper(I) iodide there are mono-
meric [CuI(PPh3)2(pyrimidine-2-thione)] (24) with a
(ii) compounds, with each Cu bonded to four S atoms,
˚
3.007 A) vary in the
the CuÁ Á ÁCu distances (2.686Á
/
sequence: 12B10B9B11 and it is certainly the
/
/
/
˚
NHÁ Á ÁI separation of 2.65 A [40] and probably dinuclear
[Cu2(C5H5NS)2I2(PPh3)2] (structurally uncharacterised)
[34]. Whereas pyridine-2-thione with copper(I) chloride
formed only the monomeric [Cu(C5H5NS)Cl(PPh3)2]
complex [12], benzothiazole-2-thione however stabilised
the dinuclear complex [CuCl(benzothiazole-2-thio-
ne)(PPh3)]2 (25) [41]. Relatively strong NHÁ Á ÁCl hydro-
gen bonding in 4 favours the monomeric complex while
˚
dinuclear 25 has a NHÁ Á ÁCl separation of 2.169 A
indicating a weak interaction [41].The analytical data of
the stoichiometric reaction of copper(I) chloride with
Ph3P presumably showed the formation of a dinuclear
complex (cf complex 2, Section 2); however, the crystal-
lisation of 2 led to the formation of the monomer 4 and
it creates doubt about the existence of the dinuclear
copper(I) chloride complex 2 [34]. It may be concluded
from the above discussion that the intramolecular
NHÁ Á ÁX(halogen) bonding and nature of the hetero-
cyclic thioamide both determine the formation of
monomeric or dimeric copper(I) complexes.
effect of the ligands and the non-bonded anions. It may
be noted that the shortest CuÁ Á ÁCu distance is observed
in 12 among all the dinuclear compounds listed in Table
3. Similarly, in type (iii) compounds with each Cu
bonded to two S, one P atom and one halogen atom,
˚
3.508 A
CuÁ Á ÁCu distances fall in the range 3.250Á
/
˚
except compound 14 which has a distance of 2.691 A
close to that in 12. Finally in type (iv) compounds with
one S atom bridging the two Cu atoms, the CuÁ Á ÁCu
˚
4.506 A) are among the longest.
distances (3.308Á
/
3.2. CuÁ Á ÁCu bond distances in homologous dinuclear
Some general trends in CuÁ Á ÁCu bond distances are
copper(I) complexes
revealed as follows: (i) when each copper is bonded to
four sulfur atoms, the CuÁ Á ÁCu bond distances decrease
Table 3 contains a list of dinuclear copper(I) com-
plexes with a series of heterocyclic-2-thiones namely
pyridine-2-thione (C5H5NS), 1,3-imidazolidine-2-thione
(imdtH2), 1-methylimidazoline-2-thione (meimtH), pyr-
imidine-2-thione (pymtH) and 1,3-thiazolidine-2-thione
(tzdtH) with tertiary phosphines as co-ligands in some
cases. These compounds can be categorised into four
˚
(2.686Á
/
3.007 A; compounds 8, 9Á
/12) because the
electron rich Cu atoms enhance metalÁmetal interac-
/
tion; (ii) when each copper is bonded to two S, one P
and one halogen atom, the CuÁ Á ÁCu distances increase
˚
(3.250Á
/
3.508 A; compounds 1, 13Á
/17, except 14) and
this behaviour can be explained in terms of reduction in
electron density at the Cu centres in view of pi-bonding
from the metal to d-orbitals on phosphorus and this
increases the CuÁ Á ÁCu distance. Whereas complex 14,
having a m-tol3P ligand, showed the short CuÁ Á ÁCu
types: (i) [Cu2(m-Sꢀ
NH)6]X2 (9, 10, 11, 12); (iii) [Cu2(m-Sꢀ
13, 14, 15, 16, 17); and (iv) [Cu2(m-SꢀNH)(Sꢀ
(6), [Cu2(m-SꢀNH)(SꢀNH)4](SO4)×3H2O (18) {m-Sꢀ
indicates bridging S-bonding and SꢀNH indicates
terminal S-bonding; Xꢀhalogen, and Lꢀa tertiary
/
NH)2X2] (5, 7, 8); (ii) [Cu2(m-Sꢀ
NH)2X2L2] (1,
NH)3Cl2]
NH
/
/
/
/
/
/
/
/
˚
distance of 2.691 A, the same was not true for
/
[Cu2Br2(thiazolidine-2-thione)2(m-tol3P)2] (26) [42] in
˚
/
/
which the CuÁ Á ÁCu distance increased to 3.347 A. It
phosphine}. Except in type (iv), all other complexes
contain a Cu2S2 core with two heterocyclic-2-thione
ligands bridging the Cu centres via S-donor atoms and
in these compounds it can be noted that CuÁ Á ÁCu and
SÁ Á ÁS distances (based on reported values) vary in a
shows that CuÁ Á ÁCu distance varies with the nature of
the thione ligand and is independent of the substituent
on the Ph group.
For compounds having three S atoms (2.914Á
˚
3.139 A;
/
compounds 5, 7) and one halogen bonded to each Cu
atom, though many examples are not available, the
distances in between the two extremes are observed.
Finally in type (iv) compounds (6, 18), the CuÁ Á ÁCu
complementary manner. Generally
a decrease in
CuÁ Á ÁCu bond distance is accompanied by an increase
in SÁ Á ÁS distance.
In the parallelogram Cu2S2, the CuÁ Á ÁCu bond
distances vary with the change in ligand and the anion
and in type (i) compounds (5, 7, 8), the shortest distance
is observed in 8 with each copper bonded to four S
˚
distance is longest (4.506 A) in 6 because one Cu is
bonded to three S and one halogen atom and the second
Cu is bonded to two S and one halogen atom and this
decreases electron density at the Cu centres thus
weakening the CuÁ Á ÁCu interaction. Interestingly in 18,
with each Cu bonded to three S atoms, the distance
atoms unlike three S and one halogen atom to each Cu
˚
in 5 and 7 (distances 2.861Á3.139 A). Thus the more
/
polarisable SCNꢁ group has a strong influence in
˚
(3.308 A) is quite short and comparable to that observed
bringing two Cu atoms closer for interaction. In type

1610
T.S. Lobana, A. Castineiras / Polyhedron 21 (2002) 1603Á1611
/
[13] T.S. Lobana, P.K. Bhatia, D.C. Povey, G.W. Smith, J. Crystal-
logr. Spectrosc. Res. 21 (1991) 9.
in the compounds 1, 13Á17. In short, an electron
/
withdrawing halogen or a metal to ligand pi-bonding
group decreases CuÁ Á ÁCu interaction and an increase in
number of sulfur groups bonded to Cu enhances
CuÁ Á ÁCu interaction.
[14] E.R.T. Tiekink, T.S. Lobana, Randhir Singh, J. Crystallogr.
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The Cuꢀ
/
Sꢀ
/
Cu and Sꢀ
/
Cuꢀ/S bond angles in com-
pounds with a Cu2S2 core vary with CuÁ Á ÁCu distance.
A shorter distance is accompanied by smaller CuꢀSꢀCu
and larger SꢀCuꢀS bond angles and vice versa and for
type (iv) compounds the CuꢀSꢀCu bond angles are the
largest. It is interesting to note that the angular
flexibility at S is very large (67.28Á137.38) and is of
great consequence for controlling metalÁmetal interac-
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One of us (T.S.L.) is thankful to Professor J.S. Casas
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