Copper(I) halide complexes from cis-1,2-bis(diphenylphosphino) ethylene and some heterocyclic thiones

Article abstract of DOI:10.1016/j.ica.2003.10.006

Reaction of copper(I) chloride or bromide with equimolar amounts of the diphos ligand cis-1,2-bis(diphenylphosphino)ethylene (dppet) and a heterocyclic thione (L) in acetonitrile/methanol solvent afforded mononuclear complexes of the type [CuX(dppet)(L)] with the diphosphine ligand acting as a chelating ligand. However, the same reaction carried out at higher temperatures proceeds, in some cases, with exclusion of the phosphine ligand from the coordination sphere leading to double-S-bridged dimers. In contrast, copper(I) iodide under the same conditions gave the thione-free dimeric compound [CuI(dppet)] ₂ which contains double-bridging iodine atoms. A notable exception was for the reaction with 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH) which, under the same conditions, gave rise to the unexpected, simultaneous formation of the monomer [CuI(dppet)(CH₃CN)] as well as the above mentioned dimeric [CuI(dppet)]₂. Furthermore treatment [CuX(dppet)(L)] with two equivalents of triphenylphosphine was found to cause replacement of the diphos ligand, while substitution of the chlorine atom under HCl elimination and formation of [Cu(dppet)(mftztH)₂] occured in the unique case of treating [CuCl(dppet)(mftztH)] with one additional equivalent of the same thione ligand. The structures of one representative for each of the above mentioned types of complexes, namely [CuBr(dppet)(mftztH)], [Cu(dppet)(mftztH) ₂], [Cu(μ-I)(dppet)]₂·[CuI(dppet)(CH ₃CN)] and [CuBr{μ-S(pymtH)}(pymtH)]₂ have been established by single-crystal X-ray diffraction.

Full text of DOI:10.1016/j.ica.2003.10.006

Inorganica Chimica Acta 357 (2004) 1063–1076
www.elsevier.com/locate/ica
Copper(I) halide complexes from cis-1,2-bis(diphenylphosphino)
ethylene and some heterocyclic thiones
a,
b,
a
a
P. Aslanidis *, P.J. Cox *, S. Divanidis , P. Karagiannidis
a
Inorganic Chemistry Laboratory, Faculty of Chemistry, Aristotle University of Thessaloniki, P.O. Box 135, Thessaloniki 541 24, Greece
b
School of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen, Scotland AB10 1FR, UK
Received 13 June 2003; accepted 18 October 2003
Abstract
Reaction of copper(I) chloride or bromide with equimolar amounts of the diphos ligand cis-1,2-bis(diphenylphosphino)ethylene
(dppet) and a heterocyclic thione (L) in acetonitrile/methanol solvent afforded mononuclear complexes of the type [CuX(dppet)(L)]
with the diphosphine ligand acting as a chelating ligand. However, the same reaction carried out at higher temperatures proceeds, in
some cases, with exclusion of the phosphine ligand from the coordination sphere leading to double-S-bridged dimers. In contrast,
copper(I) iodide under the same conditions gave the thione-free dimeric compound [CuI(dppet)]2 which contains double-bridging
iodine atoms. A notable exception was for the reaction with 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH) which, under the same
conditions, gave rise to the unexpected, simultaneous formation of the monomer [CuI(dppet)(CH3CN)] as well as the above
mentioned dimeric [CuI(dppet)]2. Furthermore treatment [CuX(dppet)(L)] with two equivalents of triphenylphosphine was found to
cause replacement of the diphos ligand, while substitution of the chlorine atom under HCl elimination and formation of
[Cu(dppet)(mftztH)2] occured in the unique case of treating [CuCl(dppet)(mftztH)] with one additional equivalent of the same
thione ligand. The structures of one representative for each of the above mentioned types of complexes, namely [CuBr(dp-
pet)(mftztH)], [Cu(dppet)(mftztH)2], [Cu(l-I)(dppet)]2 ꢀ [CuI(dppet)(CH3CN)] and [CuBr{l-S(pymtH)}(pymtH)]2 have been es-
tablished by single-crystal X-ray diffraction.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Copper(I) complexes; cis-1,2-Bis(diphenylphosphino)ethylene complexes; Heterocyclic thione complexes; Crystal structures
1. Introduction
thione and tertiary arylphosphine ligands [5–11]. Con-
sidering that neutral thione molecules with both nitro-
gen and sulfur as potential donating atoms can be
coordinated to a metal in a rich variety of ways, it is
noteworthy that in the complexes structurally charac-
terized by us, the copper(I) centre is bound exclusively
through the exocyclic sulfur atom either in a terminal or
bridging mode. Nonetheless, an outstanding variety of
structures ranging from mononuclear three- or four-
coordinate species with trigonal planar and tetrahedral
Cu(I), respectively, to double bridged dimers in which
the two copper centers are linked either by a double
halide or by a double thione-sulfur bridge were obtained
even within a closely related series of thione ligands. In
the course of our investigations, much effort has been
devoted to understanding the factors which affect the
stoichiometric and structural preferences of these com-
plexes. In the case of dimeric species of general formula
The interaction of the low valent coinage metals with
both tertiary arylphosphines and heterocyclic thiones
have been the focus of a considerable amount of work
for some time. Owing to their application in catalytic
functions [1–3] phosphine containing transition metal
complexes have received widespread attention, whereas
the significance of heterocyclic thiones, as ligands in
metal complexes, stems from their relevance in biologi-
cal systems [4]. As a contribution to this field of research
we have been engaged in the study of the mixed ligand
copper(I) halide complexes blending both heterocyclic
* Corresponding authors. Tel.: +32310997694; fax: +32310997738.
E-mail addresses: aslanidi@chem.auth.gr (P. Aslanidis), p.j.cox@
rgu.ac.uk (P.J. Cox).
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2003.10.006

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
[CuX(PR3)(thione)]2, for example, the coordination be-
haviour (terminal or bridging mode) of each ligand
should depend on the nature of the halogen present.
Thus, formation of halogen-bridges has been found to
be prefered rather for the ‘‘soft’’ iodine than for the
‘‘harder’’ chlorine base [7,8].
ture. X-ray diffraction data were collected on an Enraf–
Nonius Kappa CCD area-detector diffractometer. The
programs DENZO [13] and COLLECT [14] were used
in data collection and cell refinement. Details of crystal
and structure refinement are shown in Table 1. The
structures were solved using program SIR97 [15] and
refined with program SHELX-97 [16]. Molecular plots
were obtained with program ORTEP-3 [17].
Recently we started a comparative study into the
substitution of unidentate triarylphosphines with flexi-
ble oligomethylene-backboned diphosphines with a view
to forming chelated products. Using 1,3-bis(diph-
enylphosphino)propane, two different types of com-
pounds have been observed: monomeric with
tetrahedrally coordinated Cu(I) for X ¼ Cl and Br but
dimeric with double bridging iodine atoms for X ¼ I.
These form even under the same preparative conditions,
confirming once more the strong tendency of copper(I)
to bind the ‘‘soft’’ iodine [12]. Note that this tendency in
the above mentioned case is strong enough to cause the
exclusion of the thione ligand from the coordination
sphere. In order to obtain further information on this
very interesting aspect we have now investigated the
behaviour of rigid diphosphine cis-1,2-bis(diph-
enylphosphino)ethylene (dppet) towards coordination
of Cu(I) halides in the presence of several heterocyclic
thione ligands.
2.3. Computational
€
Extended Huckel calculations were performed using
the CACAO program [18]. The calculations were carried
out using crystallographic data of the studied molecules.
The EHT parameters for Cu were those established in
the literature.
2.4. Synthesis of complexes 1–13
The complexes were prepared according to the fol-
lowing general procedure. A suspension of copper(I)
halide (0.5 mmol) and cis-1,2-bis(diphenylphosph-
ino)ethylene (198.2 mg, 0.5 mmol) in 20 cm3 acetonitrile
was stirred until a white precipitation was formed. A
solution of the appropriate thione (0.5 mmol) in meth-
anol was then added and the new suspension was stirred
to clearness. The resulting solution was filtered off and
the clear solution was kept at room temperature. Slow
evaporation of the solvent at room temperature gave the
microcrystalline solid, which was filtered off and dried in
vacuo.
2. Experimental
2.1. Materials and instruments
Commercially available copper(I) chloride, copper(I)
bromide, copper(I) iodide and cis-1,3-bis(diph-
enylphosphino)ethylene 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. Infra-red spectra in the
region of 4000–250 cmꢁ1 were obtained in KBr discs
with a Perkin–Elmer 1430 spectrophotometer, while a
Perkin–Elmer-Hitachi 200 spectrophotometer was used
2.5. Synthesis of [Cu(dppet)(mftztH)2] (14)
An acetonitrile/methanol solution of [CuCl(dp-
pet)(mftztH)] (4) (133 mg, 0.2 mmol) was treated with
equimolar amount of mftzH (34 mg, 0.2 mmol) and
refluxed for 30 min. The resulting clear solution was
filtered off and kept at room temperature. Slow evapo-
ration of the solvent at room temperature gave the
crystalline solid, which was filtered off and dried in
vacuo.
1
to obtain the electronic absorption spectra. H NMR
spectra were recorded on a Brucker AM 300 spec-
trometer at 25 °C with positive chemical shifts given
downfield from TMS. Melting points were measured in
open tubes with a STUART scientific instrument and
are uncorrected. Molar conductivities, magnetic sus-
ceptibility measurements and elemental analyses for
carbon, nitrogen and hydrogen were performed as de-
scribed previously [4].
2.6. Synthesis of complexes 15–16
The two phosphane-free compounds were prepared
by refluxing equimolar quantities of copper(I) chloride
or bromide, cis-1,2-bis (diphenylphosphino)ethylene and
pyrimidine-2-thione in dry acetonitrile or acetone (30
ml) for 2 h and subsequent slow evaporation of the re-
sulting clear solution at room temperature. Alterna-
tively, refluxing of compound 2 or 8 in dry acetonitrile
for 4 h gave a clear yellow solution. Slow evaporation of
the solvent at room temperature gave the crystalline
solid, which was filtered off and dried in vacuo.
2.2. X-ray crystallographic study
Single crystals suitable for crystal structure analysis
were obtained by slow evaporation of acentonitrile/
methanol solutions of the complexes at room tempera-

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1065
Table 1
Crystal data and structure refinements for [CuBr(dppet)(mftztH)] (9), [Cu(dppet)(mftztH) (mftzt)] (14), [Cu(l-I)(dppet)]2 [CuI(dppet)(CH3CN)] (13)
and [CuBr{l-S(pymtH}(pymtH)]2 (16)
9
14
13
16
Chemical formula
C
30H26BrCuF3N3P2S
C34H29CuF6N6P2S2
C52H44Cu2I2P4 ꢀ C28H25
CuINP2 ꢀ C2H3N
1842.56
-
C16H16Br2Cu2N8S4
Formula weight
Temperature (K)
ꢀ
Wavelength (A)
722.99
120(2)
0.71073
825.23
120(2)
735.51
120(2)
0.71073
120(2)
0.71073
0.71073
monoclinic
P21=n
11.384(5)
18.927(5)
17.303(5)
90
Crystal system
Space group
triclinic
ꢁ
monoclinic
P21=c
18.1463(2)
12.04760(10)
35.9323(4)
90
triclinic
ꢁ
P1
P1
ꢀ
a (A)
9.8429(2)
11.3450(4)
14.6006(5)
100.6860(10)
106.870(2)
98.312(2)
1498.69 (8)
2
8.1729(2)
8.9811(3)
9.2616(3)
82.2910(10)
70.5960(10)
68.866(2)
598.00(3)
1
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
104.6900(11)
90
98.9870(10)
90
3
ꢀ
Volume (A )
3606(2)
4
1.520
7759.06(14)
4
1.577
Z
Density (calculated)
1.602
2.042
(mg/m3 A)
ꢀ
Absorption coefficient
(mmꢁ1
F(0 0 0)
2.283
0.876
2.176
5.491
)
728
0.22 ꢂ 0.14 ꢂ 0.06
2.98–27.54
1680
0.15 ꢂ 0.10 ꢂ 0.10
3.25–27.48
3656
0.30 ꢂ 0.18 ꢂ 0.08
2.92–27.52
360
0.16 ꢂ 0.16 ꢂ 0.10
3.03–27.51
Crystal size (mm)
h range for data collection
(°C)
Index ranges
ꢁ12 6 h 6 12
ꢁ14 6 k 6 14
ꢁ18 6 l 6 18
20 847
ꢁ14 6 h 6 9
ꢁ23 6 h 6 19
ꢁ15 6 k 6 13
ꢁ46 6 l 6 44
54 016
ꢁ10 6 h 6 10
ꢁ11 6 k 6 11
ꢁ11 6 l 6 11
5066
ꢁ24 6 k 6 23
ꢁ22 6 l 6 22
28 993
Reflections collected
Independent reflections
Completeness
6822 (Rint ¼ 0:0810)
98.7% (h ¼ 27:54°)
6822/0/371
8253 (Rint ¼ 0:1494)
99.7% (h ¼ 27:48°)
8253 /0/462
17665 (Rint ¼ 0:0828)
98.8% (h ¼ 27:48°)
17665/0/867
2715 (Rint ¼ 0:0310)
98.6% (h ¼ 27:51°)
2715/0/145
Data ½ðI > 2rðIÞꢃ/
restrains/parameters
Maximum and
0.8752 and 0.6336
0.9175 and 0.8798
0.8451 and 0.5613
0.6097 and 0.4736
minimum transmission
Refinement method
Goodness-of-fit on F 2
Final R indices ½ðI > 2rðIÞꢃ
full-matrix l.s. on F 2
1.026
full-matrix l.s. on F 2
1.020
full-matrix l.s. on F 2
0.990
full-matrix l.s. on F 2
1.024
R1 ¼ 0:0373,
wR2 ¼ 0:0811
R1 ¼ 0:0697,
wR2 ¼ 0:1479
R1 ¼ 0:0425,
wR2 ¼ 0:0938
R1 ¼ 0:0387
wR2 ¼ 0:0860
R indices (all data)
R1 ¼ 0:0589,
R1 ¼ 0:1326,
R1 ¼ 0:0704,
wR2 ¼ 0:1043
R1 ¼ 0:0549,
wR2 ¼ 0:0878
wR2 ¼ 0:1771
wR2 ¼ 0:0921
Final weighting schemea
Largest difference peak
a ¼ 0:0473, b ¼ 0:0407
0.457 and )0.764
a ¼ 0:0604, b ¼ 0:0245,
0.680 and )1.090
a ¼ 0:0473, b ¼ 0:0000,
1.122 and )1.352
a ¼ 0:0476, b ¼ 0:0000
0.676 and )0.836
3
ꢀ
and hole (e A )
2
a Calc: w ¼ 1=½r2ðFo2Þ þ ðaPÞ þ bPÞ, where P ¼ ðFo2 þ 2Fc2Þ=3.
2.6.1. [CuCl(dppet)(py2SH)] (1)
1604s, 1598vs, 1480vs, 1434vs, 1327vs, 1215s, 1176vs,
1098s, 976s, 744vs, 693vs, 539vs, 481s; UV–Vis ðkmax
Orange crystals (203 mg, 67%), m.p. 138 °C; Anal.
Calc. for C31H27ClCuNP2S: C, 61.38; H, 4.49; N, 2.31;
Found: C, 62.16; H, 4.55; N, 2.20%; IR (cmꢁ1): 3032w,
1652s, 1580vs, 1481s, 1434vs, 1370s, 1185s, 1133vs,
1099s, 1025m, 992s, 743vs, 693vs, 538vs, 485s, 448s;
UV–Vis ðkmax, log eÞ: (CHCl3): 248.5 (4.31), 295.0 (4.25),
398.5 (3.19).
,
log eÞ, (CHCl3): 248.5 (4.31), 295.0 (4.25), 398.5 (3.19).
2.6.3. [CuCl(dppet)(mtdztH)] (3)
Yellow crystals (185 mg, 59%), m.p. 153 °C; Anal.
Calc. for C29H26ClCuN2P2S2: C, 55.50; H, 4.18; N, 4.46;
Found: C, 56.05; H, 4.29; N, 4.52%; IR (cmꢁ1): 3042w,
1636s 1465m, 1433s, 1268s, 1185s, 1097m, 1051s, 730vs,
2.6.2. [CuCl(dppet)(pymtH)] (2)
692vs, 618m, 540vs, 484s; UV–Vis ðkmax
,
log eÞ:
Orange-red crystals (235 mg, 74%), m.p. 135 °C; Anal.
Calc. for C30H26ClCuN2P2S: C, 59.31; H, 4.31; N, 4.61;
Found: C, 59.67; H, 4.41; N, 4.61%; IR (cmꢁ1): 3043w,
(CHCl3); 248.5 (4.30), 306.0 (4.31); 1H NMR (CDCl3, d
ppm): 13.90 (br, 1H, NHmtdztH), 7.12–7.88 (m, 22H,
C6H5 + –CH@CH–), 2.45 (s, 3H, CH3)C).

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
2.6.4. [CuCl(dppet)(mftztH)] (4)
3018w, 1618m, 1583m, 1480vs, 1436vs, 1278vs, 1206s,
1154s, 1093vs, 734vs, 696vs, 541vs, 517s, 475s, 432m;
UV–Vis ðkmax, log eÞ: (CHCl3); 255.0 (4.39), 298.5 (4.09);
1H NMR (CDCl3, d ppm): 14.25 (br, 1H, NHmtdztH),
7.07–7.69 (m, 22H, C6H5 + –CH@CH–), 3.55 (s, 3H,
CH3)N).
Yellow crystals (153 mg, 45%), m.p. 186 °C; Anal.
Calc. for C30H26ClCuF3N3 P2S: C, 53.10; H, 3.86; N,
6.19; Found: C, 53.77; H, 4.22; N, 6.19%; IR (cmꢁ1):
3028m, 1652s, 1480vs, 1435vs, 1280vs, 1203vs, 1147vs,
1091vs, 731vs, 693vs, 579s, 541vs, 471vs; UV–Vis ðkmax
,
log eÞ: (CHCl3); 253.0 (4.36), 293.5 (4.01); 1H NMR
(CDCl3, d ppm):14.05 (br, 1H, NHmtdztH), 7.06–7.67 (m,
22H, C6H5 + –CH@CH–), 3.58 (s, 3H, CH3)N).
2.6.10. [CuBr(dppet)(bzoxtH)] (10)
Brown crystals (197 mg (57%), m.p. 198 °C; Anal.
Calc. for C33H27BrCuNP2OS: C, 57.36; H, 3.94; N, 2.03;
Found: C, 57.12; H, 3.95; N, 1.97%; IR (cmꢁ1): 3040w,
1616s, 1511vs, 1480vs, 1434vs, 1284s, 1252vs, 1187s,
1140vs, 1099vs, 934vs, 749vs, 732vs, 696vs, 540vs, 476s,
423s; UV–Vis ðkmax, log eÞ: (CHCl3); 245.0 (3.99), 306.0
(4.11); 1H NMR (CDCl3, d ppm): 13.65 (br, 1H,
NHbzoxtH); 7.13–7.56 (m, 26H, C6H5 + –CH@CH–
+ CHbzoxtH).
2.6.5. [CuCl(dppet)(bzoxtH)] (5)
Pale yellow crystals (187 mg, 58%), m.p. 134 °C; Anal.
Calc. for C33H27ClCuNP2OS: C, 61.30; H, 4.21; N, 2.17;
Found: C, 61.26; H, 4.19; N, 2.26%; IR (cmꢁ1): 3042w,
1634s, 1511vs, 1480s, 1448vs, 1434vs, 1252s, 1191s,
1142vs, 1093s, 932s, 732vs, 695vs, 540vs, 476s, 424m;
UV–Vis ðkmax, log eÞ: (CHCl3); 245.0 (4.11), 302.0 (4.25);
1H NMR (CDCl3, d ppm): 13.95 (br, 1H, NHbzoxtH);
7.12–7.87 (m, 26H, C6H5 + –CH@CH–).
2.6.11. [CuBr(dppet)(mbzimtH2)] (11)
Yellow crystals (162 mg, 46%), m.p. 140 °C; Anal.
Calc. for C34H30 BrCuN2P2 S: C, 58.00; H, 4.29; N,
3.98; Found: C, 58.92; H, 4.26 N, 3.97%; IR (cmꢁ1):
3047w, 1615s, 1512s, 1481vs, 1434vs, 1374s, 1324s,
1181vs, 1098vs, 998s, 802s, 741vs, 692vs, 628s, 541vs,
514s, 391s; UV–Vis ðkmax, log eÞ: (CHCl3); 246.0 (4.09),
2.6.6. [CuCl(dppet)(mbzimtH2)] (6)
Yellow crystals (191 mg, 58%), m.p. 138 °C; Anal.
Calc. for C34H30ClCuN2P2S: C, 61.91; H, 4.58; N, 4.25;
Found: C, 62.18; H, 4.77; N, 4.48%; IR (cmꢁ1): 3046w,
1616s, 1514s, 1457vs,1438vs, 1374s, 1325vs, 1183vs,
1097vs, 998s, 802s, 740vs, 697vs, 630s, 542vs, 470s,
392m; UV–Vis ðkmax, log eÞ: (CHCl3); 251.5 (4.36), 308.5
(4.38); 1H NMR (CDCl3, d ppm): 10.45 (br, 2H,
NHmbzimtH2); 6.91–7.65 (m, 25H, PC6H5+ PCH ¼ CHP,
+CHmbzimtH2), 2.28 (s, 3H, CH3 ) CPh).
1
313.5 (4.13); H NMR (CDCl3, d ppm): 11.35 (br, 2H,
NHmbzimtH2); 6.86–7.52 (m, 25H, PC6H5 + PCH@CHP,
+CH mbzimtH2), 2.14 (s, 3H, CH3)CPh).
2.6.12. [CuI(dppet)]2 (12)
Colourless crystals (202 mg, 69%), m.p. 241 °C; Anal.
2.6.7. [CuBr(dppet)(py2SH)] (7)
Calc. for C52H44Cu2I P4: C, 53.21; H, 3.78; Found: C,
2
Yellow crystals (202 mg, 62%), m.p. 153 °C; Anal.
Calc. for C31H27BrCuNP2S: C, 57.19; H, 4.18; N, 2.15;
Found: C, 57.10; H, 4.23; N, 2.08%; IR (cmꢁ1): 3046w,
1606s, 1574vs, 1480s, 1433vs, 1370s, 1183s,
1132vs,1098vs, 992s 743vs, 692vs, 538vs, 483s, 447s;
UV–Vis ðkmax, log eÞ: (CHCl3): 248.0 (4.25), 296.5 (4.21),
53.29; H, 3.84%; IR (cmꢁ1): 3046w, 1606w, 1480s,
1433vs, 1370s, 1183s, 1132vs,1098vs, 992s 743vs, 692vs,
538vs, 483s, 447s; UV–Vis ðkmax, log eÞ: (CHCl3): 248.0
1
(4.25), 296.5 (4.21); H NMR (CDCl3, d ppm): 7.42–
6.89 (m, C6H5 + –CH@CH–).
1
386.5 (3.79); H NMR (CDCl3, d ppm): 14.35 (br, 1H,
2.6.13. [CuI(dppet)(CH3CN)] ꢀ [CuI(dppet)]2 CH3
CN (13)
NHpy2SH), 7.62–7.26 (m 25H, C6H5 + –CH@CH–
+ CHpy2SH), 6.73 (t, 1H, CHpy2SH).
Yellow crystals (120 mg, 39%), m.p 240 °C, Anal.
Calc. for C82H72 Cu3I3 N2P6: C, 53.11; H, 3.94; N, 1.52;
Found: C, 53.11; H, 3.73; N, 1.46%; IR (cmꢁ1): 3031w,
1606s, 1558s, 1474s, 1426s, 1331s, 1191s, 984s, 722m,
732vs, 691vs, 541vs, 511s, 469s; UV–Vis ðkmax, log eÞ:
(CHCl3); 248.0 (4.17), 306.0 (4.40); 1H NMR (CDCl3, d
ppm): 7.13–7.67 (mm 66H, C6H5), 2.00 (s, 3H,
H3C)CN).
2.6.8. [CuBr(dppet)(mtdztH)] (8)
Yellow crystals (171 mg, 51%), m.p. 141 °C; Anal.
Calc. for C29H26BrCuN2P2S2: C, 51.83; H, 3.90; N, 4.17;
Found: C, 52.19; H, 4.10; N, 4.26%; IR (cmꢁ1): 3048w,
1636m, 1481s, 1457m, 1433vs, 1265s, 1158m, 1097s,
1054s 740vs, 692vs, 515vs, 515s, 470m; UV–Vis ðkmax
,
log eÞ: (CHCl3); 246.0 (4.14), 307.0 (4.04); 1H NMR
(CDCl3, d ppm): 13.82 (br, 1H, NHmtdztH), 7.60–7.06 (m,
22H, C6H5 + –CH@CH–), 2.41 (s, 3H, CH3)C).
2.6.14. [Cu(dppet)(mftztH)(mftzt)] (14)
Yellow crystals (67 mg, 42%), m.p. 232.5 °C; Anal.
Calc. for C34H29CuF6N6 P2S2: C, 49.49; H, 3.54; N,
10.18; Found: C, 49.46; H, 3.64; N, 10.15%; IR (cmꢁ1):
3054w, 1585m, 1526vs, 1482vs, 1435vs, 1258vs, 1202vs,
1144vs, 1090vs, 758s, 735vs, 695vs, 532vs, 519s, 468s,
349m; UV–Vis ðkmax, log eÞ: (CHCl3); 256.5 (4.12), 289.0
2.6.9. [CuBr(dppet)(mftztH)] (9)
Yellow crystals (246 mg, 68%), m.p. 204 °C; Anal.
Calc. for C30H26BrCuF3N3 P2S: C, 49.84; H, 3.62; N,
5.81; Found: C, 50.05; H, 3.62; N, 5.77%; IR (cmꢁ1):

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1067
(3.89); 1H NMR (CDCl3, d ppm): 10.94 (br, 1H,
NHmtdztH), 7.71–7.69 (m, 22H, C6H5 + –CH@CH–), 2.32
(s, 3H, CH3)C).
H
CH3
CF3
N
S
N
N
N
N
S
S
S
N
H
S
N
H
N
CH3
H
2.6.15. [CuCl{l-S(pymtH)}(pymtH)]2 (15)
mftztH
pymtH
mtdztH
py2SH
Violet crystals (103 mg 32%), m.p. 242 °C; Anal. Calc.
for C16H16Cl2Cu2N8S4: C, 29.72; H, 2.49; N, 17.33;
Found: C, 29.10; H, 2.28; N, 17.12%; IR (cmꢁ1): 3059w,
1583s, 1493vs, 1419vs, 1316s, 1171s, 998vs, 789vs, 740vs,
464s, 406s; UV–Vis ðkmax, log eÞ: (CHCl3); 248.5 (4.31),
313.0, (4.14), 429.5 (3.20).
H
H
H
CH3
N
N
N
S
S
O
bzoxtH
mbzimtH2
2.6.16. [CuBr{l-S(pymtH)}(pymtH)]2 (16)
Scheme 1. The heterocyclic thione ligands used with their abbrevia-
tions.
Violet crystals (103 mg, 28%), m.p. 223.5 °C; Anal.
Calc. for C16H16Br2Cu2 N8S4: C, 26.13; H, 2.19; N,
15.23; Found: C, 26.25; H, 2.21; N, 15.20%; IR (cmꢁ1):
3046m, 1598vs, 1564vs, 1481vs, 1420vs, 1322vs, 1218s,
1179vs, 1097s, 980s, 784s, 770vs, 742vs, 636m, 470s,
459s, 385s; UV–Vis ðkmax, log eÞ: (CHCl3); 243.5 (2.86),
293,0 (2.86), 410.5 (2.79).
Ph2
HN
X
S
P
30-40oC
HN
+ S
CuX +
Ph2P
Cu
CH3CN/CH3OH
PPh2
P
Ph2
1-11, X=Cl, Br
Scheme 2.
3. Results and discussion
3.1. General considerations
somewhat more detail. Moreover, efforts were made to
obtain crystal structures not only for key complexes but
also for related products obtained during this explora-
tion.
Diphosphines are generally good candidates for
bridging or chelation of low oxidation state transition
metal centers. Among the acyclic diphosphines of the
type Ph2P(CH2)nPPh2, 1,2-bis(diphenylphosphino)eth-
ane (dppe) was used for our first attempt to chelate
copper(I), but it was an inappropriate choice, since dppe
appears to act as a bridging, rather than as a chelating,
ligand [19]. However, using the larger 1,3-bis(diph-
enylphosphino)propane (dppp) we recently succeeded in
chelating Cu(I) [12], and we now focus once more on
five-membered chelate rings including cis-1,2-bis(diph-
enylphosphino)ethylene (dppet) in our investigations.
The reaction of equimolar quantities of copper(I)
chloride or bromide and cis-1,2-bis(diphenylphosphino)-
ethylene (dppet) followed by the addition of one equiva-
lent of the apropriate thione (L) [L ¼ pyridine-2-thione
(py2SH), pyrimidine-2-thione (pymtH), 5-methyl-1,3,
4-thiadiazole-2-thione (mtdztH), 4-methyl-5-trifluorom-
ethyl-4H-1,2,4-triazoline-3(2H)-thione (mftztH), benz-
1,3-oxazoline-2-thione (bzoxtH) and 5-methyl-benz-1,
3-imidazole-2-thione (mbzimtH2) (Scheme 1) in dry
acetonitrile/methanol solution at 30 °C afforded mono-
meric mixed ligand complexes of the type [CuX(dppet)L]
(compounds 1–11, Scheme 2).
Initially we investigated the influence of temperature.
A mixture of CuCl or CuBr with one equivalent of both
dppet and the appropriate thione was refluxed for two
hours in a 1:1 acetonitrile/methanol mixture. The iden-
tity of the amorphous solid that occurred during the
subsequent evaporation at ambient temperature of the
resulting clear solution could, however, not be con-
firmed by elemental analysis or spectroscopy. The
composition depended on the state of the evaporation,
indicating the presence of a mixture of two or more
products. Only in the case of L ¼ pymtH were dark vi-
olet crystals of the pure phosphane-free dimers [CuX{l-
S(pymtH)}(pymtH)]2 (compounds 15 and 16) isolated
during the initial stages of the evaporation (Scheme 3).
In addition, examining the influence of the rations of
the thione applied, solutions of the monomeric copper(I)
HN
NH
X
HN
Cu S
RF
CH3CN/CH3OH
S
+ S
CuX +
Ph2P
During the preparation stage we noticed that the
formation of the above mixed-ligand complex was re-
lated to the reaction temperature, such that the desired
product was only obtained when the temperature was
kept below 40 °C. Hence, a major objective of the
present work was to explore the reaction course in
S
PPh2
S Cu
X
HN
NH
15, X=Cl
16, X=Br
Scheme 3.

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
chloride complexes were treated with a two- or threefold
excess of the apropriate thione ligand, with no effect
such as phosphine substitution, even at higher temper-
atures. In one unique case, however, treatment of a
CH3CN solution of [CuCl(dppet)(mftztH)] with one
additional equivalent of the same thione ligand pro-
duced a new product causing the replacement of the
chlorine atom by the thione. In the new halogene-free
product (compound 14, Scheme 4), one of the thione
units was found to be coordinated in its thiolate form as
a consequence of deprotonation. It should be noted that
this type of coordination has been previously observed
in the case of [Cu(PPh3)2(bztzdtH)(bztzdt)] [20] which
was formed under similar experimental conditions. This
thiolate coordination – due to a spontaneous HX elim-
ination of unknown origin – has occurred, apparently,
in only a few cases and it is a very interesting phenom-
enon which needs to be investigated further.
The analogous reaction of copper(I) iodide, carried
out under the same conditions as for the monomerics of
general formula [CuX(dppet)L], always gave the thione-
free dimeric compound [CuI(dppet)]2 which contains
double-bridging iodine atoms. Furthermore, an inter-
esting exception was observed for the reaction between
copper(I) iodide, dppet and pymtH. The latter, carried
out under the same experimental conditions as usual,
proceeded in a unique way (Scheme 5) to give crystals
which were found to contain two totally different thione-
free molecules, namely the dimeric complex
[CuI(dppet)]2 (compound 13a) and also the monomer
[CuI(CH3CN)(dppet)] (compound 13b). In light of the
pronounced tendency of copper(I) iodide mixed ligand
complexes toward dimerization [2], the formation of the
former dimer [Cu(l-I)(dppet)] was not surprising, how-
ever,it was fully unexpected for the soft Cu(I) to form
the later monomeric compound because of its preference
for the soft sulphur of the thione over the harder ni-
trogen base of acetonitrile.
CuI +
Ph2P
PPh2
N
CH3CN/CH3OH
N S
H
CH3
Ph2
P
Ph2
P
Ph2
P
C
I
N
+
Cu
Cu
Cu
I
I
P
P
P
Ph2
Ph2
Ph2
13a
13b
Scheme 5.
On the contrary, no substitution was observed when the
dimers [CuX{l-S(pymtH)}(pymtH)]2 were treated under
similar conditions. Likewise, the mixture of [CuI(dppet)]2
and [CuI(CH3CN)(dppet)] (compound 13) could not be
forced to undergo any alterations, e.g., when treated with
triphenylphosphine or with excess of a thione at the
temperature of refluxing acetone or THF.
All prepared complexes are coloured, diamagnetic,
air stable, microcrystalline solids that are moderately
soluble in acetonitrile and only marginally 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.
3.2. Spectroscopy
The electronic absorption spectra of the complexes in
chloroform solutions appear to be mainly of intraligand
character, presenting two broad bands with maxima in
the 243–255 and 280–310 nm regions, respectively. The
first one can be attributed to intraligand pꢄ p tran-
sitions on the phenyl group of the phosphine ligand,
since the uncoordinated cis-1,2-bis(diphenylphosphino)
ethylene reveals a strong absorption at 258 nm which
usually remain unshifted upon coordination to Cu(I).
The lower energy band lies in the region where the free
thiones absorb, expressing a small red shift as a conse-
quence of the coordination to Cu(I) and should be,
therefore, considered as a thione-originating intraligand
transition which possess some MLCT character [21,22].
The infrared spectra of compounds 1–14, recorded in
the range 4000–250 cmꢁ1show all the expected strong
phosphine bands, which remain practically unshifted
upon coordination. Moreover, the spectra of com-
pounds under investigation contain, with the exception
of that of the iodo-compounds (12, 13), all of the bands
required by the presence of the heterocyclic thione li-
gands. In detail, they exhibit the usual four ‘‘thioamide
The above variety of products seemed to be indicative
of the lability of the coordinated dppet and this prompted
us to investigate the possibility of substitution of the
chelated diphosphine. When a threefold excess of tri-
phenylphosphine (PPh3) was refluxed with [CuX(dp-
pet)L] in acetonitrile/methanol mixture, or in acetone, the
products obtained were of the formula [CuX(PPh3)2L].
N
CF3
H3C
F3C
Ph2
P
N
N
N
X
N
S
H
Ph2
P
N
CH3
Cu
N
N
S
N
H
+
HCl
H
S
P
Cu
N
Ph2
CH3CN/CH3OH
N
CF3
S
P
H3C
Ph2
N
CF3
H3C
bands’’ in the regions ꢅ 1510, 1320, 1000 and 750 cmꢁ1
,
14
although in some cases partly masked by strong phos-
phine absorptions, as well as the characteristic NH
Scheme 4.

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1069
stretching vibrations observed in the ꢅ3150 cmꢁ1region.
The shifts observed for these bands due to coordination
in combination with the lack of m(SH) bands at ca. 2500–
2600 cmꢁ1, signify the exclusive S-coordination mode of
the thione ligands. Because of poor solubility in the
common deuterated solvents, the NMR study of the
prepared complexes is unfortunately incomplete. For
and should be considered as quite normal but the second
one is unexpected large, much larger than the two P–
Cu–S angles including the sterically bulky thione ligand.
These structural parameters contrast with those of some
monomeric copper(I) bromide complexes which contain
one heterocyclic thione and two monodentate triphe-
nylphosphane ligands, exhibiting the same CuSP2Br
core but also with the structure of [CuBr(dppp)(pymtH)]
[12] containing the non-rigid 1,2-propanebis(diphenyl-
phosphine). The CuPCCP five-membered ring is twisted
about the Cu(1)–P(2) bond adopting a half-chair con-
1
the most soluble, however, H NMR spectra were re-
corded in deuterated chloroform and displayed the sig-
nals expected for the phosphine and thione ligands, as
well as a single broad resonance at ꢅ11–14 ppm at-
tributed to the NH proton reflecting the prevailance of
the thione tautomer in the complexes.
ꢀ
formation with deviations of 0.2073 and )0.1955 A for
Cu(1) and P(2), respectively, from the plane defined by
P(1), C(5) and C(6). As a consequence of the lack of
coplanarity within the chelate ring no significant p
bonding interaction should be expected throughout the
coordination plane and the ethene bridge, a fact that is
further indicated by the aliphatic double bond length of
3.3. Description of the structures
The X-ray crystal structures of complexes 9, 14, 13a,
13b and 16 (details of crystal and structure refinement
are shown in Table 1) have been determined. The
common structural feature of all five compounds is the
tetrahedral coordination of the copper(I), whereas
compounds 9, 13a, 13b and 16 contain the diphosphine
unit coordinated in the expected chelating fashion.
3.3.1. [CuBr(dppet)(mftztH)] (9)
C25
Main bond lengths and angles for compound 9 are
given in Table 2, and a perspective drawing showing the
atom numbering is shown in Fig. 1.
C19
P2
C5
C6
C13
C7
In the monomeric complex copper(I) exhibits a highly
distorted tetrahedral co-ordination geometry, with the
metal atom being surrounded by two P, one S and one
bromine atoms. The largest deviation from the ideal
geometry is reflected by the P(1)–Cu(1)–P(2) and P(1)–
Cu(1)–Br(1) angles whose values of 91.45(3)° and
127.00(2)°, respectively, are markedly different than the
tetrahedral value of 109.4°. The first angle corresponds
to the bite angle of the rigid chelating phosphane ligand
F1
Br1
N2
N1
N3
P1
Cu1
F2
C1
C2
C3
F3
S1
C4
Fig. 1. A view of compound 9 with atom labels. Displacement ellip-
soids are shown in the 50% probability level.
Table 2
ꢀ
Selected bond lengths (A) and angles (°) for 9
Cu(1)–Br(1)
Cu(1)–P(1)
2.4118 (4)
2.2302 (7)
2.2893 (7)
2.3495 (7)
1.685 (3)
1.824 (2)
91.45(3)
P(1)–C(7)
P(1)–C(5)
1.828 (3)
1.830 (3)
1.824 (3)
1.331 (4)
1.815 (3)
1.835 (3)
122.19 (9)
102.39(9)
104.51(12)
105.55(12)
99.86(12)
118.74(8)
100.90(8)
123.56(8)
121.6(2)
Cu(1)–P(2)
Cu(1)–S(1)
P(2)–C(6)
C(5)–C(6)
S(1)–C(1)
P(1)–C(13)
P(2)–C(19)
P(2)–C(25)
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)
C(1)–S(1)–Cu(1)
C(13)–P(1)–C(7)
C(13)–P(1)–C(5)
C(7)–P(1)–C(5)
C(13)–P(1)–Cu(1)
Cu(7)–P(1)–Cu(1)
C(5)–P(1)–Cu(1)
C(19)–P(2)–C(6)
C(19)–P(2)–C(25)
C(6)–P(2)–C (25)
C(19)–P(2)–Cu(1)
C(6)–P(2)–Cu(1)
C(25)–P(2)–Cu(1)
C(6)–C(5)–P(1)
C(5)–C(6)–P(2)
106.15(3)
102.03(2)
127.00(2)
111.51(2)
114.00(2)
99.72 (8)
104.41(11)
105.25(11)
98.40(11)
120.50(8)
121.1(2)

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
ꢀ
1.331(4) A which remains practically unchanged upon
chelation [23].
F1
C3
F2
An additional striking feature of the present structure
is the Cu(1)–S(1)–C(1) angle of 99.78(8)° which is the
smallest one observed among the thione-S coordinated
copper(I) complexes structurally characterized by us so
far and can be associated with the presence of a strong
hydrogen bond between the halogen and the N(1)H.
Because of their extraordinary inequality, which may be
considered as rather unusual for a chelating diphos-
phane, the two individual Cu–P distances of 2.2302(7)°
and 2.2893(7)° are placed in the lower and upper limit
respectively of the value range expected for tetrahedrally
coordinated Cu(I). Moreover, the planes of the two ar-
omatic rings of each PPh2 moiety are essentially per-
pendicular to one another. Within the heterocyclic
thione ligand which exhibits a strictly planar five-mem-
bered 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 tetrahedrally coordinated copper(I) complexes with
terminal bromine and thione–sulphur donors.
C4
N3
F3
C29
P2
C2
N2
C1
C10
S1
N1
C9
P1
C17
C11
C23
Cu1
N4
N5
C6
S2
C5
F4
N6
C7
F5
F6
C8
Fig. 2. A view of compound 14 with atom labels. Displacement ellip-
soids are shown in the 50% probability level.
sidered as obviously closer to the ideal bite angle of the
phosphine ligand since it is associated with the forma-
tion of an almost planar five-membered chelate ring.
The copper, the P(1) atom and the ethene bridge are
nearly coplanar and the deviations from least-sqares
plane througt the following atoms are as follows: Cu(1),
0.0008; P(1), )0.0015; C(9), 0.0022; C(10), )0.0014;
3.3.2. [Cu(dppet)(mftztH)(mftzt)] (14)
Main bond lengths and angles are listed in Table 3,
and a view of the structure showing the atom numbering
appears in Fig. 2. The four-coordinate monomer reveals
a copper coordination sphere consisting of two P atoms
of one dppet and two S atoms from two mftztH ligands.
In connection with the above discussed structure for 9,
there exist a few marked differences, which should be
commended upon, since they emerge from the substi-
tution of the halogen by a thione ligand.
ꢀ
P(2), )0.1448 A.
In accordance to that later fact the C–C double bond
length of 1.325(6) A is slightly shorter compared to the
ꢀ
ꢀ
value of 1.334(4) A observed for the free phosphine [24],
probably as a result of partial charge delocalization
throughout the chelate ring. These more ‘‘regular’’
conditions are additionally reflected in the values of the
two individual Cu–P distances (2.2541(14)° and
2.2682(15)°), which are nearly equal against their re-
markable inequality within the structure of 9.
Comparison of the CuPCCP framework of the two
complexes shows the slightly reduced P–Cu–P angle of
90.25(5)° in 14 (vs. 91.45(3)° in 9) which could be con-
Table 3
ꢀ
Selected bond lengths (A) and angles (°) for 14
Cu(1)–P(1)
Cu(1)–P(2)
2.2541(14)
2.2682(15)
2.2947(14)
2.3538(14)
1.716(5)
P(1)–C(11)
P(1)–C(9)
1.827(5)
1.830(5)
1.833(5)
1.819(5)
1.829(5)
1.843(5)
Cu(1)–S(1)
Cu(1)–S(2)
P(1)–C(17)
P(2)–C(10)
P(2)–C(23)
P(2)–C(29)
S(1)–C(1)
S(2)–C(5)
C(9)–C(10)
1.690(5)
1.325(6)
90.25(5)
P(1)–Cu(1)–P(2)
P(1)–Cu(1)–S(1)
P(2)–Cu(1)–S(1)
P(1)–Cu(1)–S(2)
P(2)–Cu(1)–S(2)
S(1)–Cu(1)–S(2)
C(1)–S(1)–Cu(1)
C(5)–S(2)–Cu(1)
C(11)–P(1)–C(9)
C(11)–P(1)–C(17)
C(9)–P(1)–C(17)
C(11)–P(1)–Cu(1)
C(9)–P(1)–Cu(1)
C(17)–P(1)–Cu(1)
C(10)–P(2)–C(23)
C(10)–P(2)–C(29)
C(23)–P(2)–C(29)
C(10)–P(2)–Cu(1)
C(23)–P(2)–Cu(1)
C(29)–P(2)–Cu(1)
C(10)–C(9)–P(1)
C(9)–C(10)–P(2)
115.14(14)
104.45(16)
124.20(16)
102.1(2)
123.50(5)
118.61(5)
98.06(5)
106.03(5)
115.90(5)
101.24(17)
107.40(16)
101.7(2)
100.6(2)
102.6(2)
102.90(16)
120.17(14)
124.43(16)
119.3(4)
103.9(2)
104.9(2)
122.7(4)

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1071
ꢀ
Interestingly, the C–S bonds but also the adjacent C–
N bonds of both thione molecules do not differ signifi-
cantly, retaining most of their double bond character,
despite the deprotonation in one of these units. On the
other hand the deprotonated thione ligand is bonded to
the metal center with the ‘‘short’’ Cu(1)–S(1) bond dis-
A which is too long to invoke any appreciable metal–
metal interaction. The strongly distorted tetrahedral
coordination around each copper(I) central atom is
completed by the two P donor atoms of the chelating
dppet unit. The tendency of copper(I) iodide to form
dimeric complexes with two iodine atoms serving as
bridges between the two copper atoms is already well
established and can be attributed to its strong preference
to be ligated from soft donors such as iodine. Thus,
among the structures of mixed-ligand copper(I) halide
complexes containing tertiary arylphosphines and het-
erocyclic thiones characterized by us so far, dimeric
species with a Cu(l-I)2PS core are quite common,
whereas in the presence of the harder chlorine dimer-
ization have been achieved via the softer thione-S donor
atom.
Moreover, we recently observed this tendency to be
accompanied with an additional interesting effect,
namely the exclusion of the thione ligand from the co-
ordination sphere, when a bidentate phosphine ligand
such as 1,3-propanebis(diphenylphosphine) (dppp) or
1,5-pentanebis(diphenylphosphine) (dpppe) is used in-
stead of the simple monodentate arylphosphines. The
same type of behaviour is once more observed in the
present structure, which displays an additional quite
unexpected feature namely a remarkable non-planarity
within the Cu2I2 central core. Unlike in the analogous
dimeric complex [Cu(l-I)(dppp)]2[dppp ¼ 1.3-propane-
bis(diphenylphosphine)] with a strictly planar Cu2I2
core, in the structure under investigation the two main
planes through I(1), Cu(1), I(2) and I(1), Cu(2), I(2)
form a dihedral angle of 139.16(2)°, with I(2) being
displaced from the mean plane defined by Cu(1), I(1)
ꢀ
tance of 2.2947(14) A which is comparable with the value
ꢀ
of 2.302(4) A observed for [CuBr(py2SH)(PPh3)2] [24]
bearing the heterocyclic thione ligand also in its de-
protonated form, whereby the neutral thione unit par-
ticipates in the significantly longer Cu(1)–S(2) bond
ꢀ
distance of (2.3538(14) A) which is usual for tetrahe-
drally coordinated copper(I) and compares well with the
one observed in 9. An additional striking feature of this
structure is the one-sided inclination of the two five-
membered triazoline-rings which are twisted with respect
to each other to be nearly coplanar. This orientation
further contributes to the distortions of the tetrahedral
geometry around copper(I) and should be attributed to
the presence of a strong hydrogen bond [N(4)–H(4)ꢀ ꢀ ꢀ
ꢀ
ꢀ
N(1); N(4)–H(4) ¼ 0.8804 A, H(4)ꢀ ꢀ ꢀN(1) ¼ 1.8572 A,
ꢀ
N(4)ꢀ ꢀ ꢀN(1) ¼ 2.726(5) A, N(4)–H(4)ꢀ ꢀ ꢀN(1) ¼ 168.62°].
3.3.3. [Cu(l-I)(dppet)]2 (13a) and [CuI(dppet)-
(CH3CN)] (13b)
The title compounds 13a and 13b co-crystallize in the
monoclinic space group P21=c with eight discrete mol-
ecules (four of each) in the unit cell. Selected bond
lengths and angles for compounds 13a and 13b are given
in Tables 4 and 5 and respective drawings showing the
atom numbering are shown in Figs. 3 and 4, respec-
tively. Both molecules possess no crystallographically
imposed symmetry.
ꢀ
In the dimeric complex 13a, the two copper(I) centers
are joined by two iodine bridges to form a four-mem-
bered Cu2I2 core with a Cuꢀ ꢀ ꢀCu separation of 3.0144(7)
and Cu(2) by 1.0788(7) A. It seems likely that this re-
markable feature stems from crystal packing effects.
Moreover, within the Cu2I2 backbone, there are four
Table 4
ꢀ
Selected bond lengths (A) and angles (°) for 13a
Cu(1)–I(1)
Cu(1)–I(2)
2.6658 (5)
2.6063 (5)
2.6380 (5)
2.6087 (5)
2.2752 (11)
2.2704 (11)
2.2843 (11)
3.0144(7)
69.701(15)
70.169(15)
90.44(4)
Cu(2)–P(4)
P(1)–C(49)
C(49)–C(50)
C(50)–P(2)
P(3)–C(51)
C(51)–C(52)
C(52)–P(4)
2.2805 (11)
1.813 (4)
1.337 (6)
1.829 (4)
1.829 (4)
1.328 (5)
1.828 (4)
Cu(2)–I(2)
Cu(2)–I(1)
Cu(1)–P(1)
Cu(1)–P(2)
Cu(2)–P(3)
Cu(1)–Cu(2)
Cu(1)–I(1)–Cu(2)
Cu(2)–I(2)–Cu(1)
P(1)–Cu(1)–P(2)
P(2)–Cu(1)–I(2)
P(1)–Cu(1)–I(2)
P(2)–Cu(1)–I(1)
P(1)–Cu(1)–I(1)
I(2)–Cu(1)–I(1)
P(4)–Cu(2)–P(3)
P(4)–Cu(2)–I(1)
P(3)–Cu(2)–I(1)
P(4)–Cu(2)–I(2)
P(3)–Cu(2)–I(2)
I(1)–Cu(2)–I(2)
115.79 (3)
110.55(3)
104.959(18)
103.38(13)
103.22(14)
102.67(13)
102.22(13)
121.5(3)
121.40(3)
122.18(3)
113.78(3)
103.81(3)
104.236(18)
90.43(4)
C(49)–P(1)–Cu(1)
C(50)–P(2)–Cu (1)
C(51)–P(3)–Cu(2)
C(52)–P(4)–Cu(2)
C(50)–C(49)–P(1)
C(49)–C(50)–P(2)
C(52)–C(51)–P(3)
C(51)–C(52)–P(4)
121.0(3)
120.8(3)
122.3(3)
116.74(3)
118.42(3)

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
Table 5
ꢀ
Selected bond lengths (A) and angles (°) for 13b
Cu(3)–P(5)
Cu(3)–P(6)
2.2829 (12)
2.2670 (11)
2.014 (3)
P(5)–C(77)
P(6)–C(78)
C(77)–C(78)
C(79)–C(80)
1.824 (4)
1.823 (4)
1.332 (6)
1.454 (5)
Cu(3)–N(1)
Cu(3)–I(3)
N(1)–C(79)
2.5993 (6)
1.132 (5)
N(1)–Cu(3)–P(5)
N(1)–Cu(3)–P(6)
P(6)–Cu(3)–P(5)
P(5)–Cu(3)–I(3)
P(6)–Cu(3)–I(3)
N(1)–Cu(3)–I(3)
112.86(11)
119.20(10)
88.84(4)
C(77)–P(5)–Cu(3)
C(78)–P(6)–Cu(3)
C(78)–C(77)–P(5)
C(77)–C(78)–P(6)
Cu(3)–N(1)–C(79)
N(1)–C(79)–C(80)
102.66(14)
103.43(13)
120.7(3)
120.3(3)
166.9(4)
175.5(5)
119.26(3)
113.81(3)
103.49(10)
iodo(pyridine-2-thione)(tri-m-tolylphosphine)copper(I)]
[5].
C4
The two five-membered chelate rings are ordered al-
most parallel to each other including an angle of only
4.0°. The double bond lengths within the two ethene
C35
C7
C25
P3
I1
ꢀ
bridges are somewhat different (1.337(6) and 1.328(5) A,
C49
C50
Cu1
Cu2
P1
respectively). Interestingtly, the former value, being
somewhat longer than the ideal aliphatic double bond
length, corresponds to the almost planar chelate ring
formed by Cu(1), P(1), C(49), C(50) and P(2) whereby
the second distingtly distorted ring contains the shorter
aliphatic bond. Thus these aliphatic double bond values
hardly can be connected with the presence of any es-
sential p bonding interaction throughout the five-mem-
bered P2C2Cu arrangements. The four individual Cu–P
C51
C52
I2
P4
P2
C37
C13
C43
C46
ꢀ
bonds lie in the narrow range 2.2704(11)–2.2843(11) A
Fig. 3. A view of compound 13a with atom labels. Displacement el-
lipsoids are shown in the 50% probability level.
and are very similar to those observed in [Cu
(dppet)2]PF6 [23] and also in other copper(I) diphos-
phine complexes having a tetrahedral structure, e.g., in
[Cu(l-I)(dppp)]2.
The bite angles of the two phosphane ligands
(90.44(4)° and 90.43(4)°, respectively) are well below
what is ideal for a tetrahedrally coordinated metal ion
but very close to the intraligand P–Cu–P values of
89.69(7)° and 89.90(7)° observed in the above-men-
tioned [Cu(dppet)2]PF6.
C80
C79
N1
C66
In complex 13b, copper(I) exhibits a highly distorted
tetrahedral coordination geometry, with the metal atom
being surrounded by two P, one I, and one N donor
atoms. A particularly striking feature of this structure is
the coordination of the hard base nitrogen even in the
presence of a thione containing the soft base sulphur.
The largest deviation from the ideal geometry is reflected
by the P(5)–Cu(3)–057P(6) angle whose value of 88.84
(4)° is markedly lower than the tetrahedral value of
109.4°.
C65
C53
Cu3
I3
P5
P6
C54
C78
C77
C72
C71
C59
C60
It is interesting to note that for a series of tetrahedraly
coordinated copper(I) halide complexes which contain
two monodentate triphenylphosphine ligands, the larg-
est angle was found, as expected, between the two most
bulky phosphine ligands. In the complex under investi-
gation, however, the chelating dppet ligand is bonded to
the copper(I) center with an acute bite angle which is
Fig. 4. A view of compound 13b with atom labels. Displacement el-
lipsoids are shown in the 50% probability level.
clearly different Cu–I bond distances lying in the range
ꢀ
2.6063(5)–2.6658(5) A which are somewhat shorter than
the corresponding bond distances observed in bis[l-

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1073
even somewhat smaller than the corresponding P–Cu–P
bite angles in complex 13a. This lower angle is coun-
terbalanced by an appropriate expansion of the two
angles P(5)–Cu(3)–I(3) and N(1)–Cu(3)–P(6) whose
values of 119.26 (3)° and 119.20 (10)° are clearly larger
than the tetrahedral angle.
present structure is the extremly large asymmetry in the
two bridging distances. By comparison, these distances
ꢀ
are 2.444(1) and 2.386(2) A in bis[l-S(benzimidazo-
line-2-thione)(tmtp)copper(I)chloride]
(tmtp ¼ tri-m-
ꢀ
tolylphosphine) and 2.4879(7) and 2.3348(9) A in
bis[l-S(pyridine-2-thione)(tmtp)copper(I)bromide].
The two terminally bonded bulky thione ligands are
The inequality of the two Cu–P bonds whose values
ꢀ
are 2.28.29 (12) and 2.26.70 (11) A is somewhat larger
trans-disposed with
a
Cu–S bond distance of
ꢀ
than in complex 13a. Moreover, these values are shorter
than those found in [Cu(dppp)2]BF4 [25] or in other
monomeric copper(I) complexes with chelating diphos-
phines, e.g., in [Cu(dppe)2]ClO4. Finally, the Cu–I and
Cu–N bond lengths lie in the range normally observed
for tetrahedrally coordinated copper(I) complexes with
terminal iodine and nitrogen donors.
2.2776(10) A, which is equal to the ‘‘short’’ one in the
Cu–S–Cu bridge and thus significantly shorter than
the values normaly observed for the terminal Cu–S
bond of tetrahedraly coordinated copper(I) complexes.
ꢀ
The Cu–Br bond distance of 2.4556(5) A lies between
the values observed in the two above-mentioned di-
meric copper(I) bromide compounds with double
bridging sulphur atoms, thus confirming the previously
observed association of this bond length with the S–
Cu–S angle. In fact, an elongation of the Cu–Br bond
results as a consequence of the opening up of the S–
Cu–S angle and the shortening of the Cuꢀ ꢀ ꢀCu sepa-
ration. Finally, the S–Cu–S and Cu–S–Cu angles of
111.25(3)° and 68.75(3)°, respectively, are close to the
ideal values (109.5° and 70.5°) predicted for symmetric
dimers.
3.3.4. [CuBr{l-S(pymtH)}(pymtH)]2 (16)
Main bond lengths and angles are given in Table 6
and an ORTEP view of molecule 16 showing the atom
numbering scheme is given in Fig. 5. The basic structural
unit of [CuBr{l-S(pymtH)(pymtH)]2 is a dimer in which
ꢀ
the two copper atoms, separated by 2.7409(9) A, are
doubly bridged by two S atoms of the thione ligands to
form a strictly planar four-membered Cu2S2 core. The
highly distorted tetrahedral coordination around each
copper is completed by the S atom of a terminally
bonded pyrimidine-2-thione ligand and one bromine
atom. Each of the two trans-positioned bromine atoms
stabilize the complex with two strong intramolecular
3.4. Computational study
Searching for the factors which determine the local
metal environment in monovalent copper coordination
compounds, one can suggest that, besides steric effects,
the Lewis basicity of the ligands should be of major
importance. However, in view of the remarkable variety
of structures obtained within the closely related series of
thione ligands used in the past but also in this work,
additional considerations are required in order to ex-
plain the formation of the energetically favorable ge-
ometry in each particular case. The computations
performed in the present paper are an attempt to explore
the possibility of electronic factors in affecting the
chemical and structural behaviour of the above-men-
tioned compounds.
ꢀ
hydrogen bonds [N(1)ꢀ ꢀ ꢀBr(1) ¼ 3.598(3) A, H(1)ꢀ ꢀ ꢀ
ꢀ
Br(1) ¼ 2.7406 A, N(1)–H(1)ꢀ ꢀ ꢀBr(1) ¼ 164.85° and
ꢀ
ꢀ
[N(3)ꢀ ꢀ ꢀBr(1) ¼ 3.311(3) A, H(3)ꢀ ꢀ ꢀBr(1) ¼ 2.4372 A,
N(3)–H(3)ꢀ ꢀ ꢀBr(1) ¼ 172.02°]. atom. Each of the two
trans-positioned bromine atoms stabilize the complex
with two strong intramolecular hydrogen bonds [N(1)ꢀ ꢀ ꢀ
ꢀ
ꢀ
Br(1) ¼ 3.598(3) A, H(1)ꢀ ꢀ ꢀBr(1) ¼ 2.7406 A, N(1)–
ꢀ
H(1)ꢀ ꢀ ꢀBr(1) ¼ 164.85° and [N(3)ꢀ ꢀ ꢀBr(1) ¼ 3.311(3) A,
ꢀꢀꢀ
ꢀ
H(3) Br(1) ¼ 2.4372 A, N(3)–H(3)ꢀ ꢀ ꢀBr(1) ¼ 172.02°].
Each of the two inequivalent Cu–S bonds of
ꢀ
2.5634(10) and 2.2727(9) A are within the range ex-
pected for binuclear Cu(I) complexes with double
bridging sulfur atoms but the marked feature of the
Table 6
ꢀ
Selected bond lengths (A) and angles (°) for 16
Cu(1)–S(2)#1
Cu(1)–S(1)
2.2727(9)
2.2776(10)
2.4556(5)
2.5634(10)
Cu(1)–Cu(1)#1
S(1)–C(1)
S(2)–C(5)
2.7409(9)
1.697(3)
1.707(3)
2.2727(9)
Cu(1)–Br(1)
Cu(1)–S(2)
S(2)–Cu(1)#1
S(2)#1–Cu(1)–S(1)
S(2)#1–Cu(1)–Br(1)
S(1)–Cu(1)–S(2)
Br(1)–Cu(1)–S(2)
S(2)#1–Cu(1)–Cu(1)#1
S(1)–Cu(1)–Cu(1)#1
Br(1)–Cu(1)–Cu(1)#1
105.76(4)
S(1)–Cu(1)–Br(1)
S(2)#1–Cu(1)–S(2)
C(1)–S(1)–Cu(1)
S(2)–Cu(1)–Cu(1)#1
C(5)–S(2)–Cu(1)#1
C(5)–S(2)–Cu(1)
Cu(1)#1–S(2)–Cu(1)
121.01(3)
119.65(3)
102.55(3)
94.41(3)
60.65(3)
115.37(3)
118.82(3)
111.25(3)
106.22(13)
50.60(2)
110.71(12)
107.80(12)
68.75(3)
#1 Symmetry transformation ꢁx þ 2, ꢁy,ꢁz used to generate equivalent atoms.

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P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
Fig. 5. A view of compound 16 with atom labels. Displacement ellipsoids are shown in the 50% probability level.
As menthioned above, there is an unusual bend of the
and the model structure II respectively. In both cases the
bonding nature of these metal–metal interactions is of
negligible importance to the formation of the dimeric
structure. Besides, the stabilizing effect of a metal–metal
interaction could be important for Cuꢀ ꢀ ꢀCu separations
Cu2I2 central core in compound 13a which may be at-
tributed to crystal packing effects. To examine whether
it is true, calculations were made on two model struc-
tures (I and II) constructed on the basis of the prototype
compound by altering only the positional parameters of
the atoms within the Cu2I2 framework in such a way
that a strictly planar centrosymmetric moiety is being
formed in each case, keeping the rest of the molecule
unchanged (Fig. 6).
In both model structures, the same Cu(1)–I(1) bond
distance, taken as the mean value of the experimentally
observed Cu(1)–I(1) and Cu(2)–I(2) distances, as well as
the same Cu(1)–I(2) bond distance, equal to the mean
value of the experimentally observed Cu(1)–I(2) and
Cu(2)–I(1) ones, were used. Model structure I was
chosen to display I–Cu–I angles equal to the mean value
observed in the original structure to keep the distortions
at a minimum with respect to the overal geometry
around the two copper(I) centers, which are now sepa-
ꢀ
below the value of 2.80 A proposed to be the sum of two
copper van der Waals radii. Thus, the corresponding
overlap population of 0.015 e calculated for the rather
ꢀ
short Cuꢀ ꢀ ꢀCu distance of 2.7409(9) A in [CuBr{l-
S(pymtH}(pymtH)]2 (16), may be an evidence for such a
stabilization. Nevertheless, it is of interest to notice that
ꢀ
for the given Cuꢀ ꢀ ꢀCu separation of 3.0144(7) A the
calculated copper–copper interaction loses slightly in
bonding character on going from the ‘‘real’’ molecule to
the planar model structure II, but this fact hardly can be
considered as a factor contributing to the bending of the
Cu2I2 central core in complex 13a. The least favourable
structure relative to this aspect is, however, model
structure I in which the interaction between the consid-
erably withdrawed copper atoms becomes, as expected,
antibonding in character ()0.001 e). Moreover, the
HOMO–LUMO gap of 2.081 eV in the true structure
remains practicaly constant in the two model structures
(2.056 and 2.057 eV for I and II, respectively), as a con-
sequence of the fact that no orbitals belonging to copper
or iodine atoms do participate in these two frontier or-
bitals. Thus, it remains unclear whether the structures
bearing a planar Cu2I2 central core could be energeticaly
more favourable with regard to the ‘‘real’’ one.
ꢀ
ꢀ
rated by 3.216 A (against the value of 3.014 A in the real
molecule). On the other hand, maintaining the Cu–I–Cu
angles intact, therefore increasing the separation be-
tween the two bulkier iodine atoms, produces the more
realistic model structure II in which the Cuꢀ ꢀ ꢀCu sepa-
ration remains unaffected.
The calculated overlap populations between the two
ꢀ
metal centers, which are separated by 3.0144(7) A, are
0.005 e and 0.004 e for the ‘‘real’’ dimeric structure 13a
I
I
I
I
Cu
Cu
Cu
Cu
Cu
Cu
I
I
(a)
(c)
(b)
Fig. 6. Sketches of the Cu2I2 core: (a) side view of the real molecule, (b) top view of model I, (c) top view of model II.

P. Aslanidis et al. / Inorganica Chimica Acta 357 (2004) 1063–1076
1075
The calculated overlap populations for the Cu(1)–I(1)
and Cu(1)–I(2) bonds in 13a are 0.244 e and 0.315 e,
respectively. Upon coordination the Cu(I) metal center
accepts electron density from both the iodide and the
phosphine ligands. Considering these particular bonds,
several interesting facts can be noticed. Each of the two
Cu(I) centers acquires a slightly differed net charge with
the difference being greater in the two model structures
bearing the planar C2I2-moieties. The sum of the com-
puted bond overlap populations of the four individual
Cu–I bonds bonds drops slightly on going from the
‘‘real’’ molecule to the any of the model structures. The
same holds true also for the total overlap population of
the four Cu–P bonds. For each of the two chelate rings
in the ‘‘real’’ molecule, the calculated overlap popula-
tions of the individual Cu–P bonds, ranging between
0.534 and 0.546 e, are much closer to each other as in the
two model structures, illustrating the bend conforma-
tion of the C2I2-core to allow a better copper–phosphine
interaction. Thus, electronic effects are likely to be
causal for the bend structure adopted by molecule 13a.
Considering the energetic conditions in the two co-
crystallized complexes 13a and 13b, the lowest unoccu-
pied molecular orbitals (LUMO) for 13a and 13b are
2.081 and 3.442 eV, respectively, higher than their
highest occupied molecular orbitals (HOMO). This
large difference in the HOMO–LUMO gaps of the two
complexes clearly indicates the monomeric compound to
be more stable than its dimeric counterpart and may be
essential in view of the simultaneous formation of the
two species.
analogous reaction when copper(I) iodide was used.
Working at higher temperatures, however, copper(I)
chloride and bromide clearly showed preference for the
soft sulphur donor forming pseudo-tetrahedral dimerics
with the thione ligand adopting both the bridging and
the terminal coordination mode, as we were able to
demonstrate in the case of pyrimidine-2-thione. Among
the structures obtained in the course of the present work
particular attention belongs to that of [Cu(dppet)
(mftztH)(mftzt)] derived from [CuCl(dppet)(mftztH)],
since it contains the second thione unit coordinated in
the thiolate form. Given that such a thiolate coordina-
tion takes place under spontaneous HX elimination
which is apparently of unknown origin, this very
interesting phenomenon needs further extensive
examination.
As for the two thione-free molecules 13a and 13b,
formation of the dimer [Cu(l-I)(dppet)]2 was by no
means unexpected, given the well established strong
tendency of copper(I) iodide to form halo-bridged di-
mers, in some cases even under exclusion of the thione
ligand from the coordination sphere. In the second one,
[CuI(dppet)(CH3CN)], however, the coordination of the
hard donor nitrogen, instead of the soft sulphur of the
thione present, despite Cu(I) being soft and thiophillic,
should be considered as rather strange. Nevertheless, a
question related to the simultaneous formation of these
two species still remains to be answered. Finally, ex-
€
tended Huckel calculations provide some evidence for
electronic interactions to be responsible for the uncom-
mon non-planarity adopted by the Cu2I2 moiety in
[Cu(l-I)(dppet)]2.
4. Conclusions
5. Supplementary material
The coordination capability of the rigid diphosphane
cis-1,2-bis(diphenylphosphino) ethylene (dppet) toward
Cu(I) halides in the presence of heterocyclic thione do-
nor groups has been studied. Continuing our investiga-
tions on the factors governing the stereochemical
preferences of copper(I) compounds, we were primary
interested in preparing complexes bearing dppet as a
chelating ligand. Indeed, dppet was found to adopt the
desired coordination mode in all the new complexes, but
this was the only common feature among the diverse
structures that occurred as a result of reaction stoichi-
ometries and conditions chosen. Thus, the well-known
extraordinary flexibility of Cu(I) was once more dis-
played during the present investigation in a fascinating
manner. In particular, according to previous observa-
tions, treating an acetonitrile suspension of copper(I)
chloride or bromide with stoichiometric amounts of
methanolic solutions of dppet and a heterocyclic thione
ligand, the complexes formed at ambient temperature
were of the formula [CuX(dppet)L], whereby the thione-
free dimer [Cu(l-I)(dppet)]2 was the main product of the
CCDC-211226 (9), CCDC-211224 (14), CCDC-
211223 (13) and CCDC-211225 (16) contain the sup-
plementary crystallographic data for this paper. These
data can be obtained free of charge at www.code.ca-
m.ace.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; Fax: (internat.) + 44-1223/336-
033; E-mail: deposit@ccdc.cam.ac.uk].
Acknowledgements
We thank the EPSRC X-ray crystallography service
at the University of Southampton for collecting the X-
ray data.
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