Binuclear copper(I) complexes containing bis(diphenylphosphino)ethane bridges: The crystal structure of bis[{μ-bis(diphenylphosphino)ethane}(pyridine-2-thione)copper(I) bromide]

Article abstract of DOI:10.1016/S0277-5387(00)00438-1

Treatment of copper(I) bromide with one equivalent of 1,2-bis(diphenylphosphino)ethane (dppe), followed by the addition of one equivalent of heterocyclic thione L {L = pyridine-2-thione (py2SH), pyrimidine-2-thione (pymtH), imidazole-2-thione (imtH), benz-1,3-imidazoline-2-thione (bzimtH₂), benz-1,3-thiazoline-2-thione (bztztH), 2-mercapto-1-methylimidazole (meimtH), 4,6-dimethylpyrimidine-2-thione (dmpymtH), and 6-ethoxybenz-1,3-thiazoline-2-thione (etObztztH) in dry acetone affords the dinuclear complexes [CuBr(dppe)(L)]₂ in ca. 60-80% yield. These compounds have been characterized by their IR, far-IR, UV-Vis and ¹H NMR spectroscopic data. The crystal structure of [CuBr(dppe)(py2SH)]₂ has been determined by single-crystal X-ray diffraction methods. In the dinuclear complex in which the two monomers are related by inversion, each Cu(I) centre exhibits a tetrahedral coordination sphere involving, besides the bromine, the exocyclic sulfur of one thione molecule and two phosphor atoms from two different diphosphine units. Vibrational, electronic and ¹H NMR spectral data of the complexes are discussed in relation to the structure. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00438-1

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 1615–1620
Binuclear copper(I) complexes containing
bis(diphenylphosphino)ethane bridges: the crystal structure of
bis[{m-bis(diphenylphosphino)ethane}(pyridine-2-thione)copper(I)
bromide]
P.J. Cox a, P. Aslanidis b,*, P. Karagiannidis b
a School of Pharmacy, Robert Gordon Uni6ersity, Schoolhill, Aberdeen, AB10 1FR, Scotland, UK
b Inorganic Chemistry Laboratory, Faculty of Chemistry, Aristotle Uni6ersity of Thessaloniki, PO Box 135, GR-540 06 Thessaloniki, Greece
Received 4 January 2000; accepted 18 May 2000
Abstract
Treatment of copper(I) bromide with one equivalent of 1,2-bis(diphenylphosphino)ethane (dppe), followed by the addition of
one equivalent of heterocyclic thione L {L=pyridine-2-thione (py2SH), pyrimidine-2-thione (pymtH), imidazole-2-thione (imtH),
benz-1,3-imidazoline-2-thione (bzimtH2), benz-1,3-thiazoline-2-thione (bztztH), 2-mercapto-1-methylimidazole (meimtH), 4,6-
dimethylpyrimidine-2-thione (dmpymtH), and 6-ethoxybenz-1,3-thiazoline-2-thione (etObztztH) in dry acetone affords the dinu-
clear complexes [CuBr(dppe)(L)]2 in ca. 60–80% yield. These compounds have been characterized by their IR, far-IR, UV–Vis
and 1H NMR spectroscopic data. The crystal structure of [CuBr(dppe)(py2SH)]2 has been determined by single-crystal X-ray
diffraction methods. In the dinuclear complex in which the two monomers are related by inversion, each Cu(I) centre exhibits a
tetrahedral coordination sphere involving, besides the bromine, the exocyclic sulfur of one thione molecule and two phosphor
1
atoms from two different diphosphine units. Vibrational, electronic and H NMR spectral data of the complexes are discussed in
relation to the structure. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Copper(I) bromide complexes; Heterocyclic thione complexes; Diphosphine complexes; Dinuclear complexes; Crystal structures
1. Introduction
parameters like the geometrical flexibility of the coinage
metals and electronic properties or bulkiness on the
part of the ligands make structural prediction of these
complexes virtually impossible, steric demands of the
phosphine ligands seems to be of major importance
causing significant changes on the coordination geome-
try of the metal atom [4]. To obtain further insight into
this very interesting field of research we, therefore,
decided to initiate a comparative investigation on sub-
stituting the unidentate triarylphosphines with acyclic
multidentate phosphine ligands.
Recent interest in copper(I) bis(diphosphine) com-
plexes, which are mostly polynuclear species containing
bridging diphosphines, stems from their potential bio-
logical significance [5]. In this work, we report on the
reaction of copper(I) bromide with 1,2-bis(diphenyl-
phosphino)ethane (dppe) and several heterocyclic
thione ligands, as well as the structure of [CuBr(dppe)-
(py2SH)]2.
Owing to their relevance in biological systems, hete-
rocyclic thiones have attracted considerable attention as
ligands in metal complexes [1]. Because of their applica-
tion in catalytic functions, transition metal complexes
with phosphine ligands have also been studied exten-
sively [2]. In recent years, we have explored the group
IB metal complexes blending both heterocyclic thione
and tertiary arylphosphine ligands. In the course of our
investigations, whose major target was the study of the
factors that govern the coordination geometry of the
metal atom, a large set of compounds with an interest-
ing and in some cases unpredictable structural variety
has been observed [3]. Although the interplay of several
* Corresponding author. Tel.: +30-31-997-694; fax: +30-31-997-
738.
E-mail address: aslanidi@auth.gr (P. Aslanidis).
0277-5387/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(00)00438-1

1616
P.J. Cox et al. / Polyhedron 19 (2000) 1615–1620
1
2. Experimental
740 vs, 694 vs, 512 s, 478 m, 418 m. H NMR: l 12.43
(s, ꢀNH), 7.65–7.15 (m, aromatic), 2.17–2.50 (m,
PꢁCH2CH2ꢁP).
2.1. Materials and instruments
Copper(I) bromide, 1,2-bis(diphenylphosphino)-
ethane and all solvents are commercially available and
were used as obtained, while the thiones (E. Merck or
Aldrich) were recrystallized from hot ethanol prior to
their use. IR, UV, Vis and NMR spectra, conductivi-
ties, melting points and elemental analyses of carbon,
nitrogen and hydrogen were performed as described
previously [6].
2.2.4. [CuBr(dppe)(bztzH)]2
Yellow crystals. Yield: 66%, m.p. 177°C. Anal. Calc.
for C66H58Br2Cu2N2P4S4: C, 55.9; H, 4.5; N, 2.0.
Found: C, 54.8; H, 4.1; N, 2.1%. UV–Vis (u, log m): 328
(4.38); 244 (4.58). IR (cm−1): 3057 m, 2953 m, 1597 m,
1490 vs, 1458 s, 1428 vs, 1321 vs, 1170 s, 1099 s, 1076
m, 1031 vs, 1013 s, 745 vs, 693 s, 512 s, 423 m. H
NMR: l 12.90 (s, ꢀNH), 7.70–7.26 (m, aromatic),
2.03–2.59 (m, PꢁCH2CH2ꢁP).
1
2.2. Preparation of the complexes
2.2.5. [CuBr(dppe)(meimtH)]2
The complexes of the formula [CuBr(dppe)(L)]2 were
prepared according to the following general procedure.
A solution of 1,2-bis(diphenylphosphino)ethane (99.6
mg, 0.25 mmol) in dry acetone (20 ml) was added to a
stirred suspension of CuBr (35.3 g, 0.25 mmol) in 15 ml
of the same solvent and the mixture was stirred and
moderately heated. After the formation of a complete
clear solution, 0.25 mmol of the appropriate thione,
dissolved in dry acetone (30 ml), was added slowly and
the stirring was continued for 2 h. The resulting solu-
tion was filtered off and allowed to cool. Slow evapora-
tion of the solvent at room temperature (r.t.) gave the
microcrystalline solid, which was filtered off and dried
in vacuo.
Pale-yellow crystals. Yield: 75%, m.p. 225°C. Anal.
Calc. for C60H60Br2Cu2P4N4S2: C, 54.9; H, 4.6; N, 4.3.
Found: C, 55.3; H, 4.9; N, 4.1%. UV–Vis (u, log m): 266
(4.31); 245 (4.25). IR (cm−1): 3131 m, 3046 m, 2940 w,
1572 vs, 1478 vs, 1433 vs, 1281 vs, 1254 m, 1153 s, 1095
s, 1025 m, 998 m, 883 m, 756 vs, 670 vs, 514 vs, 487 s,
416 m, 341 m. H NMR: l 12.50 (s, ꢀNH), 7.80–7.26
(m, aromatic), 6.80–6.75 (m, ꢁCHꢂCHꢁ), 3.67 (s, \
NꢁCH3), 2.03–2.17 (m, PꢁCH2CH2ꢁP).
1
2.2.6. [CuBr(dppe)(imtH)]2
Red–brown crystals. Yield: 65%, m.p. 171°C. Anal.
Calc. for C58H60Br2Cu2N4P4S2: C, 54.1; H, 4.7; N, 4.3.
Found: C, 53.7; H, 4.4; N, 4.9%. UV–Vis (u, log m): 290
(4.54); 243 (4.42). IR (cm−1): 3138 m, 3055 m, 2950 w,
1582 vs, 1480 s, 1438 vs, 1306 m, 1169 vs, 1115 vs, 989
m, 738 vs, 730 vs, 697 vs, 618 s, 535 vs, 511 vs, 406 m,
2.2.1. [CuBr(dppe)(py2SH)]2
Yellow crystals. Yield: 80%, m.p. 220°C. Anal. Calc.
for C62H58Br2Cu2N2P4S2: C, 57.0; H, 4.5; N, 2.1.
Found: C, 56.3; H, 4.5; N, 2.1%. UV–Vis (u, log m): 295
(4.46); 244 (4.52). IR (cm−1): 3048 m, 2960 m, 2897 s,
1610 s, 1577 vs, 1500 s, 1433 vs, 1366 s, 1132 vs, 1097
1
340 m. H NMR: l 13.10 (s, ꢀNH), 7.76–7.26 (m,
aromatic), 2.52 (s, NꢁCH2CH2ꢁN), 2.09–2.17 (m,
PꢁCH2CH2ꢁP).
1
s, 882 m, 745 vs, 695 vs, 518 s, 479 s, 448 s, 336 m. H
2.2.7. [CuBr(dppe)(dmpymtH)]2
NMR: l 14.25 (s, ꢀNH), 7.60–7.10 (m, aromatic),
Yellow crystals. Yield: 76%, m.p. 246°C. Anal. Calc.
for C64H64Br2Cu2N4P4S2: C, 56.3; H, 4.7; N, 4.1.
Found: C, 55.8; H, 4.5; N, 4.0%. UV–Vis (u, log m): 294
(4.80); 247 (4.74). IR (cm−1): 3148 m, 2910 w, 1614 vs,
1560 vs, 1483 s, 1433 vs, 1320 m, 1227 vs, 1189 s, 1098
s, 1027 m, 982 m, 885 m, 741 vs, 694 vs, 512 vs, 484 s,
2.17 (s, PꢁCH2CH2ꢁP).
2.2.2. [CuBr(dppe)(pymtH)]2
Orange–red crystals. Yield: 80%, m.p. 148°C. Anal.
Calc. for C60H56Br2Cu2N4P4S2: C, 55.1; H, 4.3; N, 4.2.
Found: C, 55.9; H, 4.4; N, 4.2%. UV–Vis (u, log m): 290
(4.69); 247 (4.66). IR (cm−1): 3066 m, 2923 w, 1606 m,
1564 vs, 1480 s, 1432 vs, 1324 s, 1175 vs, 1091 s, 1025
1
416 m, 341 m. H NMR: l 13.95 (s, ꢀNH), 7.66–7.08
(m, aromatic), 2.30 (s, CꢁCH3), 2.17 (s, PꢁCH2CH2ꢁP).
1
m, 744 vs, 697 vs, 511 s, 481 m, 448. H NMR: l 14.80
2.2.8. [CuBr(dppe)(etObztztH)]2
(s, ꢀNH), 7.50–7.20 (m, aromatic), 2.17 (s,
Pale-yellow crystals. Yield: 70%, m.p. 177°C. Anal.
Calc. for C70H66Br2Cu2N2O2P4S4: C, 55.8; H, 4.4; N,
1.8. Found: C, 55.3; H, 4.6; N, 2.0%. UV–Vis (u, log m):
331 (4.37); 247 (4.30). IR (cm−1): 3033 m, 2925 w, 1601
vs, 1483 vs, 1427 vs, 1398 s, 1332 s, 1260 s, 1224 vs,
1099 s, 1044 vs, 1026 vs, 943 m, 877 m, 740 vs, 692 vs,
668 s, 584 s, 512 vs, 489 s, 421 m. H NMR: l 13.84 (s,
ꢀNH), 7.86–7.05 (m, aromatic), 4.07 (q, OꢁCH2ꢁC),
2.16 (s, PꢁCH2CH2ꢁP), 1.45 (t, CH3ꢁC).
PꢁCH2CH2ꢁP).
2.2.3. [CuBr(dppe)(bzimtH2)]2
Pale-yellow crystals. Yield: 60%, m.p. 146°C. Anal.
Calc. for C66H60Br2Cu2N4P4S2: C, 57.3; H, 4.4; N, 4.1.
Found: C, 57.8; H, 4.2; N, 4.1%. UV–Vis (u, log m): 309
(4.95); 248 (5.09). IR (cm−1): 3049 s, 2925 m, 1618 m,
1500 vs, 1463 s, 1434 vs, 1359 s, 1172 s, 1099 s, 1026 m,
1

P.J. Cox et al. / Polyhedron 19 (2000) 1615–1620
1617
Table 2
2.3. Collection and reduction of X-ray data
,
Bond lengths (A) and angles (°)
The unit cell and intensity data were collected on a
Delft Instruments FAST diffractometer using the rou-
tines ENDEX, REFINE and MADONL in the MADNES
software [7] and processed using ABSMAD [8]; detailed
procedures are described by Darr et al. [9]. Absence of
crystal decay in the X-ray beam was confirmed by
checking equivalent reflections at the beginning and end
of data collection, which lasted about 8 h. The structure
was solved with SIR-92 [10] and refined with SHELX93
[11]. Details of crystal data and structure refinement
BrꢁCu
2.5693(12)
2.2564(13)
2.2778(12)
2.3456(13)
1.709(4)
1.827(4)
1.830(4)
1.843(4)
1.824(4)
1.838(4)
1.837(4)
2.2564(13)
1.331(5)
1.356(5)
1.409(6)
1.352(6)
1.391(6)
1.375(6)
1.362(6)
1.399(6)
1.394(6)
1.350(7)
C(9)ꢁC(10)
C(10)ꢁC(11)
C(12)ꢁC(13)
C(12)ꢁC(17)
C(13)ꢁC(14)
C(14)ꢁC(15)
C(15)ꢁC(16)
C(16)ꢁC(17)
C(18)ꢁC(19)
C(20)ꢁC(25)
C(20)ꢁC(21)
C(21)ꢁC(22)
C(22)ꢁC(23)
C(23)ꢁC(24)
C(24)ꢁC(25)
C(26)ꢁC(27)
C(26)ꢁC(31)
C(27)ꢁC(28)
C(28)ꢁC(29)
C(29)ꢁC(30)
C(30)ꢁC(31)
1.373(7)
1.380(6)
1.359(6)
1.403(6)
1.400(7)
1.350(8)
1.377(7)
1.373(7)
1.525(5)
1.389(5)
1.398(6)
1.370(6)
1.372(6)
1.380(6)
1.387(6)
1.372(5)
1.393(5)
1.390(5)
1.354(6)
1.374(7)
1.391(5)
a
CuꢁP(2)c1
CuꢁP(1)
CuꢁS
SꢁC(1)
P(1)ꢁC(6)
P(1)ꢁC(12)
P(1)ꢁC(18)
P(2)ꢁC(20)
P(2)ꢁC(26)
P(2)ꢁC(19)
P(2)ꢁCu(1)c1
N(1)ꢁC(1)
N(1)ꢁC(2)
C(1)ꢁC(5)
C(2)ꢁC(3)
C(3)ꢁC(4)
C(4)ꢁC(5)
C(6)ꢁC(11)
C(6)ꢁC(7)
C(7)ꢁC(8)
C(8)ꢁC(9)
,
and bond lengths (A) and angles (°) are given in Tables
1 and 2, respectively. The copper, bromine, sulfur,
phosphorus, nitrogen and carbon atoms were refined
with anisotropic temperature factors. The hydrogen
atoms were allowed to ride on their attached atoms
with common isotropic temperature factors for methyl
and non-methyl hydrogens. An absorption correction
was made with DIFABS [12].
P(2)c1ꢁCuꢁP(1)
P(2)c1ꢁCuꢁS
P(1)ꢁCuꢁS
123.14(4)
105.64(5)
109.06(5)
107.38(4)
101.25(3)
109.98(3)
108.7(2)
102.7(2)
99.5(2)
107.3(2)
118.54(13)
111.62(12)
115.63(13)
104.5(2)
103.0(2)
101.8(2)
C(4)ꢁC(5)ꢁC(1)
C(11)ꢁC(6)ꢁC(7)
C(11)ꢁC(6)ꢁP(1)
C(7)ꢁC(6)ꢁP(1)
C(8)ꢁC(7)ꢁC(6)
C(9)ꢁC(8)ꢁC(7)
C(8)ꢁC(9)ꢁC(10)
C(9)ꢁC(10)ꢁC(11)
C(6)ꢁC(11)ꢁC(10)
C(13)ꢁC(12)ꢁC(17) 117.8(4)
C(13)ꢁC(12)ꢁP(1)
C(17)ꢁC(12)ꢁP(1)
C(12)ꢁC(13)ꢁC(14) 121.3(5)
C(15)ꢁC(14)ꢁC(13) 119.7(6)
C(14)ꢁC(15)ꢁC(16) 120.6(5)
C(17)ꢁC(16)ꢁC(15) 119.5(5)
C(16)ꢁC(17)ꢁC(12) 121.1(5)
C(19)ꢁC(18)ꢁP(1)
C(18)ꢁC(19)ꢁP(2)
119.5(5)
117.6(4)
119.3(3)
123.0(3)
120.3(5)
120.2(5)
120.2(5)
119.5(5)
122.1(4)
Table 1
Crystal data and structure refinement
P(2)c1ꢁCuꢁBr
P(1)ꢁCuꢁBr
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C31H29BrCuNP2S
653.00
150(2)
0.71073
monoclinic
P21/n
SꢁCuꢁBr
C(1)ꢁSꢁCu
C(6)ꢁP(1)ꢁC(12)
C(6)ꢁP(1)ꢁC(18)
C(12)ꢁP(1)ꢁC(18)
C(6)ꢁP(1)ꢁCu
C(12)ꢁP(1)ꢁCu
C(18)ꢁP(1)ꢁCu
C(20)ꢁP(2)ꢁC(26)
C(20)ꢁP(2)ꢁC(19)
C(26)ꢁP(2)ꢁC(19)
,
125.6(4)
116.6(4)
Unit cell dimensions
,
a (A)
11.783(5)
15.539(5)
16.157(5)
93.375(5)
2953(2)
4
1.469
2.293
1328
0.21×0.14×0.05
1.82–25.05
−135h510
−165k517
,
b (A)
,
c (A)
i (°)
3
,
Volume (A )
Z
C(20)ꢁP(2)ꢁCuc1 109.71(14)
C(26)ꢁP(2)ꢁCuc1 117.06(13)
C(19)ꢁP(2)ꢁCuc1 119.00(14)
115.2(2)
112.3(2)
Dcalc (Mg m−3
)
Absorption coefficient (mm−1
F(000)
)
C(1)ꢁN(1)ꢁC(2)
N(1)ꢁC(1)ꢁC(5)
N(1)ꢁC(1)ꢁS
125.4(4)
116.1(4)
121.6(3)
122.3(4)
119.6(4)
117.9(4)
121.5(5)
C(25)ꢁC(20)ꢁC(21) 117.6(4)
C(25)ꢁC(20)ꢁP(2)
C(21)ꢁC(20)ꢁP(2)
123.9(3)
117.9(3)
Crystal size (mm)
q range for data collection (°)
Index ranges (°)
C(5)ꢁC(1)ꢁS
C(22)ꢁC(21)ꢁC(20) 121.2(4)
C(21)ꢁC(22)ꢁC(23) 120.9(4)
C(22)ꢁC(23)ꢁC(24) 118.9(4)
C(23)ꢁC(24)ꢁC(25) 120.7(4)
C(29)ꢁC(28)ꢁC(27) 120.4(4)
C(28)ꢁC(29)ꢁC(30) 120.8(4)
C(29)ꢁC(30)ꢁC(31) 119.6(4)
C(30)ꢁC(31)ꢁC(26) 119.6(4)
C(3)ꢁC(2)ꢁN(1)
C(2)ꢁC(3)ꢁC(4)
C(5)ꢁC(4)ꢁC(3)
C(24)ꢁC(25)ꢁC(20) 120.6(4)
C(27)ꢁC(26)ꢁC(31) 119.8(4)
C(27)ꢁC(26)ꢁP(2)
C(31)ꢁC(26)ꢁP(2)
C(26)ꢁC(27)ꢁC(28) 119.8(4)
−165l518
12213
Reflections collected
Independent reflections
Observed reflections [I\2|(I)]
Refinement method
Number of parameters
Goodness-of-fit on F2 (S)
Final R indices [I\2|(I)]
R indices (all data)
4526 [Rint=0.0761]
3171
122.3(3)
117.7(3)
full-matrix least squares on F2
335
0.884
a Atomic coordinates transposed by −x+3/2, −y+1/2, −z+1.
R1=0.0335, wR2=0.0709
R1=0.0521, wR2=0.0815
Calc.
Final weighting scheme
w=1/[|2(Fo2)+(0.0146P)2]
where P=(Fo2+2Fc2)/3
0.371
3. Results and discussion
Residual diffraction max.
The complexes were prepared by reacting equimolar
quantities of copper(I) bromide and 1,2-bis-
(diphenylphosphino)ethane (dppe), followed by the ad-
dition of one equivalent of the appropriate thione (L) in
−3
,
(e A
)
Residual diffraction min.
−0.342
−3
,
(e A
)

1618
P.J. Cox et al. / Polyhedron 19 (2000) 1615–1620
dry acetone solution. This procedure, frequently used
for the preparation of copper(I) halide complexes con-
taining both heterocyclic thiones and triphenyl- or tri-
tolylphosphine ligands, gave monomeric complexes of
are, however, of the type [Cu2(dppe)3L2] [18–23], in
which the diphosphine units act at the same time both
as chelating ligands for each of the copper atoms and as
a bridge between them. The double bridging coordina-
tion mode realized in the case of the complex under
investigation is quite common for univalent Group 1B
metal complexes of bis(diphenylphosphino)methane
(dppm) [24–27].
Bond lengths and angles are given in Table 2. The
atomic arrangement in the complex is shown in Fig. 1.
The basic structural unit of [Cu(dppe)(py2SH)Br]2 is a
dimer in which the two monomers are related by inver-
sion. The two copper atoms are doubly bridged by two
dppe ligands to form a ten-membered Cu2P4C4 ring.
The slightly distorted tetrahedral coordination around
copper is completed by one sulphur atom from the
thione ligand and one bromine atom.
the
formula
[CuX(PPh3)2L]
[3]
or
dimers
[CuX(PPh3)L]2 with the two copper centres being
bridged either by the halogen [13] or by the thione-S
atom [14]. In this work we expected that replacement of
the monodentate phosphine by the bidentate dppe
would lead to the formation of chelated products;
however, this was not the case.
All the complexes are coloured solids soluble in
chloroform, methanol, ethanol, acetone and acetoni-
trile. They are stable in air and moisture and can be,
after the isolation, manipulated in air without apprecia-
ble decomposition. Their solutions are non-conducting
in acetone and chloroform. Room temperature mag-
netic measurements confirm the diamagnetic nature of
the compounds.
The CuꢁS and CuꢁBr bond lengths lie in the range
normally observed for tetrahedrally coordinated cop-
per(I) complexes with terminal bromine and thione-sul-
phur donors [28]. The two individual CuꢁP distances of
3.1. Spectroscopy
,
2.2564(13) and 2.2778(12) A are somewhat shorter than
The electronic absorption spectra of the complexes in
chloroform solutions are dominated by broad bands in
the regions 240–250 and 280–330 nm attributable to
intraligand transitions of the dppe, since the uncoordi-
nated dppe also absorbs strongly in this region.
those found for bridging dppe in other dimeric cop-
,
per(I) complexes, e.g. [Cu2Cl2(dppe)3] (2.284(6) A) [20]
,
and [Cu2(3-Me3Sipyt)2(dppe)3] (2.294(3) A) [23].
The irregularities in the tetrahedral coordination ge-
ometry about the copper(I) centre are best reflected in
the values of the bond angles, since only three of them
are close to the ideal tetrahedral value. As expected, the
largest angle [PꢁCuꢁP=123.14(4)°] arises between the
two most bulky ligands, whereas the presence of in-
tramolecular hydrogen bonds between the bromine and
the N(1)H, C(4)H(4) and C(19)H(19A) hydrogen
The infrared spectra of the compounds, recorded in
the range 4000–250 cm−1, show, apart from the exis-
tence of strong phosphine bands, all of the bands
required by the presence of the heterocyclic thione
ligands. In detail they exhibit the usual four ‘thioamide
bands’ in the regions ꢀ1510, 1320, 1000 and 750
cm−1, although in some cases partly masked by strong
phosphine absorptions, as well as the characteristic NH
stretching vibrations observed in the 3050–3160 cm−1
region. The shifts observed for these bands due to
coordination (upward shifts of 15–35 cm−1 for
thioamide I, downward shifts of 10–30 cm−1 for
thioamide II and III) in combination with the lack of
w(SH) bands at ca. 2500–2600 cm−1 [15] signify the
exclusive S-coordination mode of the thione ligands.
The prevailance of the thione tautomer in the com-
,
,
[N(1)···Br=3.226(3) A, N(1)ꢁH=0.880(4) A, H···Br=
,
2.367(3) A, N(1)ꢁHꢁBr=165.1(3)°; C(4)···Br=3.585(5)
,
,
,
,
A, C(4)ꢁH(4)=0.951(7) A, H(4)···Br=2.902(5) A,
C(4)ꢁH(4)ꢁBr=129.6(5)°; C(19)···Br=3.582(4) A,
,
,
C(19)ꢁH(19)=0.990(5) A, H(19)···Br=2.703(4) A,
C(19)ꢁH(19)ꢁBr=148.1(4)°] could be responsible for
the moderate narrowing of the P(1)ꢁCuꢁBr angle
[101.25(3)°]. It is interesting to note that all these angles
are in qualitative agreement with the corresponding
values already observed for a series of monomeric
copper(I) halide complexes that contain one hetero-
cyclic thione and two monodentate triphenylphosphine
ligands, exhibiting the same CuSP2X core [28]. Given
that steric constrains between the ligands are of signifi-
cance in achieving minimum energy arrangements
around the metal centre, this fact indicates that the
steric requirements of the bridging dppe units within
the dimer [Cu(dppe)(py2SH)Br]2 are approximately of
the same magnitude as those of the triphenylphosphine
ligands in the monomeric complexes [Cu(PPh3)2(S)X]
[29]. It seems plausible, therefore, to invoke steric rea-
sons in order to explain the feature of the complex
under investigation, the most energetically favourable
1
plexes is further confirmed by the H NMR spectra of
the compounds, which display, apart from the signals
expected for the phosphine and thione ligands, a single
resonance at lꢀ12–14 ppm attributed to the NH
proton.
3.2. Description of the structure
The ability of 1,2-bis(diphenylphosphino)ethane
(dppe) to chelate Cu(I) is well known and a few double-
chelated cationic Cu(dppe)2+ species have been ob-
served [16,17]. Most of the structurally characterized
binuclear copper(I) complexes involving dppe ligands

P.J. Cox et al. / Polyhedron 19 (2000) 1615–1620
1619
Fig. 1. A view of the complex with atom labels. Displacement ellipsoids are shown at the 50% probability level.
[4] S.K. Hadjikakou, P. Aslanidis, P. Karagiannidis, A. Aubry, S.
Skoulika, Inorg. Chim. Acta 193 (1992) 129.
situation being manifested by the appearance of doubly
bridged dppe ligands but not by the formation of
five-membered chelate rings.
[5] (a) S.J. Berners-Price, P.J. Sandler, Struct. Bonding 70 (1988) 70.
(b) J.S. Lewis, J. Zweit, J.L.J. Dearling, B.C. Rooney, P.J.
Blower, Chem. Commun. (1996) 1093. (b) J. Lewis, S.L. Heath,
A.K. Powell, J. Zweit, P.J. Blower, J. Chem. Soc., Dalton Trans.
(1997) 855.
[6] P. Karagiannidis, S.K. Hadjikakou, P. Aslanidis, A. Hountas,
Inorg. Chim. Acta 178 (1990) 27.
[7] J.W. Pflurgrath, A. Messerschmidt, MADNES, Version 11 Sep-
tember 1989, Distributed by Delft Instruments, Delft, The
Netherlands.
4. Supplementary material
Supplementary data are available free of charge
from: The Director, CCDC, 12 Union Road, Cam-
bridge, CB2 1EZ, UK (fax: +44-1223-336-033; e-mail:
deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.
ac.uk) quoting the deposition number CCDC-114060.
[8] A.I. Karaulov, ABSMAD, Program for FAST data Processing,
University of Wales, Cardiff, 1992.
[9] J.A. Darr, S.R. Drake, M.B. Hursthouse, K.M.A. Malik, Inorg.
Chem. 32 (1993) 5704.
[10] A. Altomare, M.C. Burla, M.C. Camalli, G. Cascarano, C.
Giacovazzo, A. Guagliardi, G. Polidori, J. Appl. Cryst. 27
(1994) 435.
Acknowledgements
[11] G.M. Sheldrick, SHELXL-93, Program for the Refinement of
Crystal Structures, University of Go¨ttingen, Germany, 1994.
[12] N. Walker, D. Stuart, Acta Crystallogr., Sect. A 39 (1983) 158.
[13] S.K. Hadjikakou, P. Aslanidis, P. Karagiannidis, A. Hountas, A.
Terzis, Inorg. Chim. Acta 184 (1991) 161.
We thank the EPSRC X-ray crystallographic service
at the University of Wales, Cardiff for data collection.
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