Three- and four-coordinate copper(I) halide complexes of 2-(diphenylphosphano)benzaldehyde: Dimerization induced by thione-S ligation

Article abstract of DOI:10.1016/j.poly.2007.09.001

Reactions of copper(I) halides with 2-(diphenylphosphano)benzaldehyde (PCHO) in 1:2 molar ratio afforded mononuclear complexes of the type [CuX(PCHO)₂], whereas treatment of these compounds with equimolar amounts of pyridine-2-thione or pyrimidine-2-thione gave rise to the formation of mixed-ligand dimers of the formula [CuX(PCHO)(thione)]₂. The molecular structures of [CuCl(PCHO)₂], [CuBr(PCHO)₂] and [CuCl(PCHO)(pymtH)]₂ have been established by single-crystal X-ray diffraction. The two homoleptic complexes feature a trigonal copper(I) centre with the phosphane acting as a monodentate ligand via the P atom. In the structure of the dimeric mixed-ligand complex each of the two metal centres exhibit a distorted tetrahedral environment with the thione-S atoms acting in a doubly bridging mode.

Full text of DOI:10.1016/j.poly.2007.09.001

Available online at www.sciencedirect.com
Polyhedron 27 (2008) 175–180
www.elsevier.com/locate/poly
Three- and four-coordinate copper(I) halide complexes
of 2-(diphenylphosphano)benzaldehyde: Dimerization induced
by thione-S ligation
a
b
a,
*
M. Mamais , P.J. Cox , P. Aslanidis
a
Aristotle University of Thessaloniki, Faculty of Chemistry, Inorganic Chemistry Laboratory, P.O. Box 135, GR-541 24 Thessaloniki, Greece
b
School of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen AB10 1FR, Scotland, UK
Received 14 June 2007; accepted 5 September 2007
Available online 1 November 2007
Abstract
Reactions of copper(I) halides with 2-(diphenylphosphano)benzaldehyde (PCHO) in 1:2 molar ratio afforded mononuclear complexes
of the type [CuX(PCHO)2], whereas treatment of these compounds with equimolar amounts of pyridine-2-thione or pyrimidine-2-thione
gave rise to the formation of mixed-ligand dimers of the formula [CuX(PCHO)(thione)]2. The molecular structures of [CuCl(PCHO)2],
[CuBr(PCHO)2] and [CuCl(PCHO)(pymtH)]2 have been established by single-crystal X-ray diffraction. The two homoleptic complexes
feature a trigonal copper(I) centre with the phosphane acting as a monodentate ligand via the P atom. In the structure of the dimeric
mixed-ligand complex each of the two metal centres exhibit a distorted tetrahedral environment with the thione-S atoms acting in a dou-
bly bridging mode.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Copper(I) halide complexes; 2-(Diphenylphosphano)benzaldehyde; Heterocyclic thiones; Structures
1. Introduction
decades, largely because of their relevance to biological sys-
tems [4,5].
There is much current interest in copper(I) coordination
chemistry, mainly because of its participation in certain
biochemical redox reactions [1]. Due to the favorable soft
acid–soft base interaction, the chemistry of this closed-shell
d10 metal ion is largely based upon coordination to ligands
containing phosphorus and sulfur donor atoms. Thus, with
tertiary phosphanes, copper(I) produces a vast number of
complexes which feature an extraordinary stoichiometric
and geometrical variety. Many of these complexes have
been intensively employed in catalytic processes [2] and
some of them were even found to exhibit antitumor activity
[3]. As far as the sulfur containing ligands are concerned,
heterocyclic thioamides represent a class of compounds
that have attracted substantial interest over the last few
Based on the rich chemistry so far found for each of the
two aforementioned classes of ligands, we have been inter-
ested in examining univalent copper and silver mixed-
ligand complexes bearing both neutral heterocyclic thiones
and bulky triaryl phosphane ligands with respect to the fac-
tors that influence the structural characteristics of these
compounds [6,7]. Since our findings showed the coordina-
tion number to be related to the steric requirements on
the part of the phosphane ligand only [8], we recently
focused on phosphanes that may introduce imposed steric
effects around the metal centre. In the present work we
report on the synthesis and characterization of some CuI
complexes derived from 2-(diphenylphosphano)benzalde-
hyde (PCHO). Apart from its steric demands, the selection
of PCHO as ligand is further based on its salient feature to
bear, besides the ‘‘soft’’ phosphorus donor, a ‘‘hard’’ oxy-
gen atom, thus being capable of behaving as a P,O-chelate
[9].
*
Corresponding author.
E-mail addresses: p.j.cox@rgu.ac.uk (P.J. Cox), aslanidi@chem.
auth.gr (P. Aslanidis).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.09.001

176
M. Mamais et al. / Polyhedron 27 (2008) 175–180
2. Experimental
2.3.1. [CuCl(PCHO)2] (1)
Orange crystals (21 mg, 12%), m.p. 232 ꢁC; Anal. Calc.
for C38H30ClCuO2P2: C, 67.16; H, 4.45. Found: C, 67.24;
H, 4.58%. IR (cmÀ1): 3054m, 2824w, 2761m, 1696vs,
1668vs, 1583m, 1561m, 1481s, 1392m, 1295m, 1200vs,
2.1. Materials and instrumentation
Commercially available copper(I) halides and 2-(diphe-
nylphosphano)benzaldehyde (Aldrich) were used as
received while the thiones (Merck) were re-crystallized from
hot ethanol prior to their use (Scheme 1). 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 cmÀ1 were obtained in KBr discs with
Perkin–Elmer FT-IR Spectrum 1 spectrophotometer, while
a Perkin–Elmer-Hitachi 200 spectrophotometer was used to
1
1096s, 864m, 764m, 748vs, 696vs, 527vs, 508vs, 462s. H
NMR (CDCl3, d ppm): 9.98 (s, 1H, –CHO), 7.83 (d, 1H,
JH–H = 7.3 Hz, H3–PhCHO), 7.58 (t, 1H, JH–H = 7.3 Hz,
H5–PhCHO), 7.49 (t, 1H, JH–H = 7.3 Hz, H4–PhCHO),
7.40 (m, 4H, Ph, H2,6), 7.26 (m, 6H, Ph, H2,6), 6.99 (d,
JH–H = 7.3 Hz, H6-PhCHO).
2.3.2. [CuBr(PCHO)2] (2)
1
obtain the electronic absorption spectra. H NMR spectra
Orange crystals (45 mg, 24%), m.p. 230 ꢁC; Anal. Calc.
for C38H30BrCuO2P2: C, 63.04; H, 4.18. Found: C, 62.98;
H, 4.25%. IR (cmÀ1): 3061m, 2839m, 2745m, 1697s,
1676vs, 1560s, 1479s, 1435vs, 1393m, 1294s, 1203vs,
1094s, 1091vs, 846vs, 760vs, 749vs, 703vs, 691vs, 676s,
529vs, 509vs, 462s. 1H NMR (CDCl3, d ppm): 9.95 (s,
1H, –CHO), 7.84 (d, 1H, JH–H = 7.3 Hz, H3–PhCHO),
7.58 (t, 1H, JH–H = 7.3 Hz, H5–PhCHO), 7.50 (t, 1H,
JH–H = 7.3 Hz, H4–PhCHO), 7.40 (m, 4H, Ph, H2,6), 7.26
(m, 6H, Ph, H2,6), 6.99 (d, JH–H = 7.3 Hz, H6-PhCHO).
were recorded on a Brucker AM 300 spectrometer at
298 K with positive chemical shifts given downfield from
internal TMS. Melting points were measured in open tubes
with a STUART scientific instrument and are uncorrected.
2.2. Crystal structure determination
Single crystals suitable for crystal structure analysis were
obtained by slow evaporation of acetonitrile/methanol
solutions of the complexes at room temperature. X-ray dif-
fraction data were collected on an Enraf-Nonius Kappa
CCD area-detector diffractometer. The programs DENZO
[10] and COLLECT [11] were used in data collection and cell
refinement. Details of crystal and structure refinement are
shown in Table 1. The structures were solved using pro-
gram SIR97 [12] and refined with program SHELX-97 [13].
Molecular plots were obtained with program ORTEP-3 [14].
2.3.3. [CuI(PCHO)2] (3)
Yellow crystals (33 mg, 17%), m.p. 241 ꢁC; Anal. Calc.
for C38H30ClCuO2P2: C, 59.19; H, 3.92. Found: C, 60.09;
H, 4.01%. IR (cmÀ1): 3058m, 2839m, 2744m, 1697s,
1675vs, 1560m, 1479s, 1435vs, 1385m, 1294s, 1203vs,
1094m, 1091s, 847s, 759vs, 744s, 703s, 691vs, 677s, 529vs,
509vs, 462s. 1H NMR (CDCl3, d ppm): 9.95 (s, 1H,
–CHO), 7.88 (d, 1H, JH–H = 7.3 Hz, H3–PhCHO), 7.60
2.3. Synthesis of complexes 1–3
(t, 1H, JH–H = 7.3 Hz, H5–PhCHO), 7.52 (t, 1H, JH–H
=
7.3 Hz, H4–PhCHO), 7.38 (m, 4H, Ph, H2,6), 7.24 (m,
A suspension of 0.25 mmol of copper(I) halide (24.75 mg
for CuCl, 35.85.7 mg for CuBr, 47.6 mg for CuI) in 30 cm3
of dry acetonitrile was stirred at 50 ꢁC until a clear yellow
solution was formed. To this, a solution of 145 mg
(0.5 mmol) of 2-(diphenylphosphano)benzaldehyde in
25 cm3 of dry acetonitrile was added and the mixture was
stirred for 2 h at 50 ꢁC. The resulting bright yellow solution
was filtered off and left to evaporate at ambient. The micro-
crystalline solid, which was deposited upon standing for
several days, was filtered off and dried in vacuo.
6H, Ph, H2,6), 7.00 (d, JH–H = 7.3 Hz, H6-PhCHO).
2.4. Synthesis of complexes 4–6
To a stirred solution of 0.25 mmol of copper(I) halide
(24.75 mg for CuCl, 35.85.7 mg for CuBr) was suspended
in 60 cm3 of dry acetonitrile, solid 2-(diphenylphosphan-
o)benzaldehyde (145 mg, 0.5 mmol) was suspended and
the mixture was stirred for 2 h at 50 ꢁC. The resulting clear
solution was then treated with the appropriate thione
(0.5 mmol) dissolved in a small amount (ꢀ20 cm3) of meth-
anol. The new reaction mixture was stirred for additional
two hours at 50 ꢁC and then was filtered off and left several
days at ambient to provide a yellow microcrystalline
product.
N
NH
NH
O
2.4.1. [CuBr(PCHO)(py2SH)]2 (4)
Yellow crystals (32 mg, 23%), m.p. 179 ꢁC; Anal. Calc.
for C48H40Br2Cu2N2O2P2S2: C, 52.90; H, 3.70, N: 2.57.
Found: C, 64.47; H, 4.81; N, 3.47%. IR (cmÀ1): 3049m,
2965m, 2901m, 1691vs, 1606s, 1575vs, 1505s, 1436vs,
1366s, 1261s, 1200s, 1125vs, 1094s, 1080s, 996s, 822m,
747vs, 695vs, 521vs, 483s, 443m. 1H NMR (CDCl3, d
S
S
PPh2
PCHO
pymtH
py2SH
Scheme 1. The phosphane and the heterocyclic thiones used as ligands
with their abbreviations.

M. Mamais et al. / Polyhedron 27 (2008) 175–180
177
Table 1
Crystal data and structure refinements for [CuCl(PCHO)2] (1), [CuBr(PCHO)2] (2) and [CuCl(PCHO)(pymtH)]2 (5)
1
2
5
Molecular formula
Formula weight
Temperature (K)
C38H30ClCuO2P2
679.55
120(2)
0.71073
monoclinic
P21/n
11.55790(10)
17.1727(3)
16.3545(3)
90
C38H30BrCuO2P2
724.02
120(2)
0.71073
monoclinic
C2/c
18.1960(6)
9.8615(3)
19.6831(8)
90
C46.13H38Cl2Cu2N4O2.13P2S2a
1006.63
120(2)
0.71073
monoclinic
P21/n
14.6594(3)
12.0067(3)
24.9499(6)
90
˚
Wavelength (A)
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.5490(10)
90
3184.03(9)
4
116.936(1)
90
3148.76(16)
4
91.9370(10)
90
4388.95(18)
4
3
˚
Volume (A )
Z
Dcalc (Mg/m3)
1.418
1.527
1.523
Absorption coefficient
0.904
2.099
1.303
(mmÀ1
)
F(000)
1400
1472
2056
Crystal size (mm)
h Range for data
collection (ꢁ)
0.40 · 0.25 · 0.18
3.09–27.49
0.52 · 0.24 · 0.20
2.42–27.61
0.46 · 0.36 · 0.30
3.18–27.49
Index ranges
À14 6 h 6 14,
À22 6 k 6 22,
À21 6 l 6 21
36828
7247 [Rint = 0.0439]
27.49ꢁ, 99.4%
7247/0/397
À23 6 h 6 23,
À12 6 k 6 12,
À25 6 l 6 25
28527
3639 [Rint = 0.0488]
27.61ꢁ, 99.5%
3639/0/200
À19 6 h 6 19,
À15 6 k 6 15,
À32 6 l 6 24
47805
10023 [Rint = 0.0544]
27.49ꢁ, 99.4%
10023/0/550
Reflections collected
Independent reflections
Completeness to h
Data/restraints/
parameters
Maximum and minimum
transmission
Refinement method
Goodness-of-fit on F2
0.8541 and 0.6368
0.6789 and 0.5233
0.6958 and 0.5495
full-matrix least square on F2
1.031
full-matrix least square on F2
1.044
full-matrix least square on F2
1.018
Final R indices [I > 2r(I)] R1 = 0.0330, wR2 = 0.0779
R1 = 0.0261, wR2 = 0.0638
R1 = 0.0352, wR2 = 0.0677
calc w = 1/
[r2(F2o) + (0.0358P)2 + 2.9145P]
where P = (F2o + 2Fc2)/3
0.305 and À0.520
R1 = 0.0344, wR2 = 0.0768
R1 = 0.0529, wR2 = 0.0829
calc w = 1/
[r2(F2o) + (0.0351P)2 + 2.8449P]
where P = (F2o + 2Fc2)/3
0.454 and À0.419
R indices (all data)
Final weighting scheme
R1 = 0.0526, wR2 = 0.0845
calc w = 1/
[r2(F2o) + (0.0438P)2 + 0.7341P]
where P = (F2o + 2Fc2)/3
Largest differencÀe3in peak 0.406 and À0.522
˚
and hole (e A
)
a
Decimal points for the number of C and O atoms due to a small impurity of doubly CHO-substituted phosphane.
ppm): 14.08 (br, 1H, NH), 10.35 (s, 1H, –CHO), 7.88 (d,
Found: C, 50.60; H, 3.48; N, 5.13%. IR (cmÀ1): 3063m,
2925w, 2853w, 1677vs, 1603vs, 1584vs, 1568vs, 1474s,
1425s, 1321vs, 1210s, 1173vs, 989s, 973s, 751s, 743s, 698s,
530s, 504s, 462s.
1H, JH–H = 7.3 Hz, H3–PhCHO), 7.60 (t, 1H, JH–H
=
7.3 Hz, H5–PhCHO), 7.52 (t, 1H, JH–H = 7.3 Hz, H4–
PhCHO), 7.36–7.28 (m, 10H, PPh), 7.00 (d, JH–H
=
7.3 Hz, H6-PhCHO), 7.00 (t, 1H, Hp3y2SH), 6.89 (t, 1H,
H5py2SH).
3. Results and discussion
2.4.2. [CuCl(PCHO)(pymtH)]2 (5)
3.1. Synthesis
Yellow crystals (25 mg, 20%), m.p. 196 ꢁC; Anal. Calc.
for C46H38Cl2Cu2N4O2P2S2: C, 55.09; H, 3.81, N: 5.59.
Found: C, 54.98; H, 3.91; N, 5.66%. IR (cmÀ1): 3054m,
2827m, 2632m, 1690vs, 1600s, 1572vs, 1479s, 1425s,
1326vs, 1196s, 1167vs, 1043s, 984s, 762s, 747s, 696vs,
528vs, 501s, 481s, 457s.
Treatment of 2-(diphenylphosphano)benzaldehyde and
CuX (X = Cl, Br, I) resulted in the formation of orange-
yellow colored crystalline compounds formulated as
[CuX(PCHO)2] (compounds 1–3), regardless of the molar
ratio (1:1 or 2:1) applied. Aiming to obtain phosphane/thi-
one mixed-ligand complexes, we further treated the solu-
tions of these precursors, skipping their isolation, with a
methanolic solution of 1 equiv. of a heterocyclic thione.
Stirring of such a mixture at 50 ꢁC gradually caused slight
2.4.3. [CuBr(PCHO)(pymtH)]2 (6)
Yellow crystals (29 mg, 21%), m.p. 191 ꢁC; Anal. Calc.
for C46H38Br2Cu2N4O2P2S2: C, 50.60; H, 3.51, N: 5.13.

178
M. Mamais et al. / Polyhedron 27 (2008) 175–180
Table 2
darkening of the solution, from which, on slow evapora-
tion, microcrystalline or powdery solids were deposited.
These proved, however, to correspond to the desired pure
compounds only in a few cases, although the described
one-top two-step synthetic procedure applied has already
produced a number of such copper(I) halide derivatives,
virtually for any thione and copper(I) halide applied. In
particular, pyridine-2-thione (py2SH) and pyrimidine-2-
thione (pymtH) yielded small amounts of well-formed
bright orange crystals, which could be satisfactory defined
as compounds 4–6, but inseparable mixtures of two or
more products resulted in all the other cases. All prepared
compounds are air stable diamagnetic solids, moderately
soluble in acetonitrile, chloroform and acetone. Their solu-
tions in common organic solvents are non-conducting.
˚
Selected bond lengths (A) and angles (ꢁ) for 1 and 2
Compound 1
Compound 2
Cu(1)–P(1)
Cu(1)–Cl(1)
Cu(1)–P(2)
2.2266(5)
2.2448(5)
2.2486(5)
Cu(1)–P(1)
Cu(1)–Br(1)
Cu(1)–P(1)a
2.2366(4)
2.3364(4)
2.2366(4)
P(1)–Cu(1)–P(2)
Cl(1)–Cu(1)–P(2)
P(1)–Cu(1)–Cl(1)
a
130.17(2)
108.350(18)
120.177(19)
P(1)–Cu(1)–P(1)a
Br(1)–Cu(1)–P(1)
P(1)1–Cu(1)–Br(1)
123.53(2)
118.234(12)
118.234(12)
Symmetry transformations used to generate equivalent atoms: Àx + 1,
y, Àz + 1/2.
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for 5
Cu(1)–Cl(1)
Cu(1)–P(1)
Cu(1)–S(2)
Cu(1)–S(1)
Cu(2)–P(2)
Cu(2)–Cl(2)
2.3350(6)
2.2506(6)
2.3469(6)
2.4025(6)
2.2387(6)
2.3279(6)
Cu(2)–S(1)
Cu(2)–S(2)
S(1)–C(20)
S(2)–C(43)
Cu(1)Á Á ÁCu(2)
2.3608(6)
2.4227(6)
1.722(2)
1.723(2)
2.9766(4)
3.2. Spectroscopy
1
The room temperature H NMR spectra of the com-
S(2)–Cu(1)–S(1)
P(1)–Cu(1)–S(2)
P(1)–Cu(1)–S(1)
P(1)–Cu(1)–Cl(1)
Cl(1)–Cu(1)–S(1)
S(2)–Cu(1)–Cl(1)
P(2)–Cu(2)–Cl(2)
P(2)–Cu(2)–S(1)
Cl(2)–Cu(1)–S(1)
103.23(2)
112.33(2)
123.13(2)
105.12(2)
100.19(2)
112.32(2)
118.93(2)
111.39(2)
109.20(2)
P(2)–Cu(2)–S(2)
Cl(2)–Cu(2)–S(2)
S(1)–Cu(2)–S(2)
C(20)–S(1)–Cu(2)
C(20)–S(1)–Cu(1)
C(43)–S(2)–Cu(1)
C(43)–S(2)–Cu(2)
Cu(1)–S(2)–Cu(2)
Cu(2)–S(1)–Cu(1)
113.46(2)
99.89(2)
102.23(2)
113.18(7)
99.62(7)
110.94(7)
110.08(7)
77.211(18)
77.344(18)
plexes under investigation, recorded in deuterated chloro-
form, are dominated by the presence of two separated
multiplets in the regions d = 7.40 and d = 7.25 ppm attrib-
uted to the resonances of the non-substituted phenyl rings
of the PCHO ligand. With respect to the complex multiplet
assigned to the PPh2 resonances of the un-coordinated
phosphane, this splitting indicates coordination to the
metal through the P atom which causes a typical upfield
shift of the ortho-positioned protons by ca. 0.20 ppm.
The resonances attributed to the formylated phenyl ring
appear as well separated signals assignable to the discrete
aromatic protons only for the thione-free compounds
1–3, whereas for compounds 4–6 the extent of overlapping
makes assignments of the splitting pattern for the individ-
ual phosphane and thione resonances very difficult.
The infrared spectra of compounds 1–6, recorded in the
range 4000–250 cmÀ1 display strong vibrational phosphane
bands, which remain practically unshifted upon coordina-
tion. In addition, the spectra of the mixed-ligand com-
plexes 4–6 contain the expected characteristic ‘‘thioamide
bands’’, with shifts due to coordination indicative of an
exclusive S-coordination mode. As expected, upon coordi-
nation no significant shift is noticed for the m(C@O) vibra-
tion of the PCHO ligand.
Hydrogen bridges
N(2)–H(2)
NH(2)–Cl(2)
N(4)–H(4)
0.8800
2.2000
0.8800
2.1600
Cl(2)Á Á ÁN(2)
3.0650(18)
168.8
3.0419(18)
179.5
Cl(2)Á Á ÁH(2)–N(2)
Cl(12)Á Á ÁN(4)
NH(4)–Cl(1)
Cl(1)Á Á ÁH(4)–N(4)
that there is a small impurity in the structure of 5, indicated
by the presence of a formyl substituent attached to C(25),
apparently due to a small amount of doubly formylated
phosphane. Hence a population parameter of 0.13 corre-
sponds to C(47), O(3) and H(47), whereas the population
parameter of H(25) is 0.87 (see also Table 1).
By comparison to the vast number of known four-coor-
dinate species, examples of three coordination among CuI
complexes are far less common, mostly represented by cat-
ions of the type CuL3+. The more rarely reported neutral
complexes of the formula CuL2X are usually formed by
bulky ligands such as triarylphosphanes or aromatic
amines. A literature search of published data on CuI com-
plexes of 2-(diphenylphosphano)benzaldehyde revealed
that there were structures of six cationic species known
[15,16], featuring tetrahedral or trigonal planar environ-
ment around CuI, thus the three structures presented here
are the first examples of neutral CuI complexes bearing
PCHO.
3.3. X-ray structural investigations
The X-ray crystal structures of [CuCl(PCHO)2] (1),
[CuBr(PCHO)2] (2) and [CuCl(PCHO)(pymtH)]2 (5)
(details of crystal and structure refinement are shown in
Table 1) corroborate the spectroscopic results discussed
above. Tables 2 and 3 list selected distances and angles of
these complexes.
Compounds 1 and 2 crystallize in the monoclinic space
group P21/n and C2/c respectively, both with four discrete
formula units in the unit cell. Likewise, compound 5 crys-
tallizes in the monoclinic space group P21/n with four dis-
crete formula units in the unit cell. It should be mentioned
The crystal structures of compounds 1 and 2 (Figs. 1
and 2) are quite similar having in common trigonal coordi-
nation of the copper(I) centre. Nevertheless, considering
the interligand bond angles involving the central metal
atom in the two structures described here, there are some

M. Mamais et al. / Polyhedron 27 (2008) 175–180
179
Fig. 1. A view of compound 1 with atom labels. Displacement ellipsoids
are shown in the 50% probability level.
Fig. 3. A view of compound 5 with atom labels. Displacement ellipsoids
are shown in the 50% probability level.
the exactly planar CuP2Br core can be considered as essen-
tially regular with the largest P–Cu–P angle deviating only
by 3.5ꢁ from the ideal trigonal expectation of 120ꢁ. The
˚
Cu–P bond distances of 2.2266(5) and 2.2448(5) A in 1 and
˚
2.2366(4) A in 2 are comparable to those found in
PCHO ligated cationic CuI complexes such as [Cu
(PCHO)2(CH3CN)]BF4 or [Cu(PCHO)3]BF4 [15]. Moreover
the PCHO units have both their formyl groups oriented
toward the copper atom with a short CuÁ Á ÁO separation of
˚
3.002(2) A. As a further difference between the two structures,
the co-planarity within the formyl groups and the C atoms of
the attached phenyl rings in 2 is substantially distorted.
In the dimeric complex 5 each copper atom displays a
distorted tetrahedral environment formed by one P atom
from PCHO, one Br atom and two inequivalent bridging
S atoms from the thione ligands. Within the essentially pla-
nar Cu2S2 central core respective bond lengths and angles
around the two copper atoms differ slightly. This is in con-
trast to other related structures with simple monodentate
arylphosphane ligands like triphenylphosphane or tri-tolyl-
phosphanes, where doubly bridging S atoms were found to
generate a Cu2S2 rhombus with the dimeric molecule gen-
erally having a crystallographic centre of symmetry. None-
theless, this is another example of dicopper(I) halide
complex comprising a neutral thione ligand coordinated
in a l2-S bridging mode, which is in line with our assump-
tion that primary control of the coordination behavior (ter-
minal or bridging) of the thione and halide ligands can be
achieved by the choice of the halide ligand, with the ‘‘soft’’
iodide being capable to serve as bridging ligand rather than
the ‘‘hard’’ chloride which prefers, at least in the presence
of a ‘‘soft’’ thione-S donor atom, the terminal coordination
mode [18] (Fig. 3).
Fig. 2. A view of compound 2 with atom labels. Displacement ellipsoids
are shown in the 50% probability level.
obvious differences. Thus, angular deviations from the
ideal trigonal value in 1 are remarkable but not at all unex-
pected, at least regarding the appropriate opening up of the
angle between the sterically demanding groups of the
PHCO units. The sum of the three angles around Cu is
358.72ꢁ, and the Cu atom is displaced from the basal trigo-
˚
nal plane by 0.1465(3) A. Another remarkable feature of 1
is the different orientation of the formyl groups of the two
PCHO ligands, one of them having oriented its oxygen
atom toward the copper atom to
2.804(2) A, whereas the second one is twisted outwards.
a distance of
˚
This short Cu(1)Á Á ÁO(1) contact is less than the sum of
˚
the van der Waal radii (1.40 (Cu) + 1.52 (O) = 2.92A)
and may be considered as a dipole–ion interaction
[16,17]. The carbon–oxygen bond distance of the formyl
group in the two individual PCHO units remains essential
the same. Moreover, the formyl groups are both essentially
coplanar with the C atoms of the attached phenyl rings.
Contrary to that, 2 exhibits a symmetric arrangement of
the two PCHO units. Here the trigonal environment within
An interesting structural feature within molecule 5 is the
almost parallel orientation of each of the six-membered
pyrimidine rings relative to the formylated phenyl ring of
the respective PCHO unit. The dihedral angle between the

180
M. Mamais et al. / Polyhedron 27 (2008) 175–180
C13–C18 and N1,N2,C20–C23 rings is 12.68(8)ꢁ and the
dihedral angle between rings C36–C41 and N3,N4,C43–
C46 is 16.12(5)ꢁ. The respective stacking distances between
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˚
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The aim of this work was the study of the coordination
capability of 2-(diphenylphosphano)benzaldehyde (PCHO)
toward copper(I) halides. We have found that PCHO acts
as a monodentate, coordinating to the metal exclusively via
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bridging) of the thione and halide ligands in such dimers
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Acknowledgement
We thank the EPSRC X-ray crystallography service at
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Appendix A. Supplementary material
CCDC 612610, 612611 and 612609 contain the supple-
mentary crystallographic data for 1, 2 and 5. These data
can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit
@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2007.09.001.