Some binuclear acetonitrile 'solvated' complexes of copper(I) chloride and bromide with triphenylarsine

Article abstract of DOI:10.1016/j.ica.2005.12.014

Reaction of copper(I) chloride and bromide, CuX (X = Cl or Br), with triphenylarsine in acetonitrile solution has resulted in two adducts, respectively, of 2:3:1, [(Ph₃As)₂Cu(μ-Cl)₂Cu(AsPh₃)(NCMe)] (1), and 1:1:2 stoichiometry, [(Ph₃As)(MeCN)Cu(μ-Br)₂Cu(NCMe)(AsPh₃)] · 2MeCN (2), characterized by elemental analysis, IR, ESI MS and NMR spectroscopy, and room temperature single crystal X-ray structure determinations. The environments of the two four-coordinate copper(I) atoms in 1 are different, being As₂Cu(μ-Cl)₂ and As,NCu(μ-Cl)₂. (2) is also binuclear, being a centrosymmetric dimer with the two four-coordinate, symmetry-related copper atoms having As,NCu(μ-Br)₂-environments.

Full text of DOI:10.1016/j.ica.2005.12.014

Inorganica Chimica Acta 359 (2006) 2178–2182
www.elsevier.com/locate/ica
Some binuclear acetonitrile ‘solvated’ complexes of copper(I)
chloride and bromide with triphenylarsine
a
a
b,
a
Robert D. Hart , John D. Kildea , Claudio Pettinari *, Brian W. Skelton ,
a
Allan H. White
a
Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia
b
`
Dipartimento di Scienze Chimiche, Universita degli Studi di Camerino, via S. Agostino 1, 62032 Camerino MC, Italy
Received 2 November 2005; accepted 11 December 2005
Available online 25 January 2006
Abstract
Reaction of copper(I) chloride and bromide, CuX (X = Cl or Br), with triphenylarsine in acetonitrile solution has resulted in two
adducts, respectively, of 2:3:1, [(Ph3As)2Cu(l-Cl)2Cu(AsPh3)(NCMe)] (1), and 1:1:2 stoichiometry, [(Ph3As)(MeCN)Cu(l-Br)2Cu(NC-
Me)(AsPh3)] Æ 2MeCN (2), characterized by elemental analysis, IR, ESI MS and NMR spectroscopy, and room temperature single crys-
tal X-ray structure determinations. The environments of the two four-coordinate copper(I) atoms in 1 are different, being As2Cu(l-Cl)2
and As,NCu(l-Cl)2. (2) is also binuclear, being a centrosymmetric dimer with the two four-coordinate, symmetry-related copper atoms
having As,NCu(l-Br)2-environments.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Copper; Triphenylarsine; X-ray; Acetonitrile complexes
1. Introduction
[1,2], and [(Ph3P)2AgBr] [3]; binuclear [(Ph3E)2M(l-
X)2M(EPh3)2] have been recorded previously only for
M = Ag, X = Cl, Br as chloroform solvates in systems in
which there is a pronounced complex/solvent interaction
[3]. The origins of this dichotomy may be possibly steric
in origin, a consequence of possible difficulty in accommo-
dating four Ph3E ligands around the M(l-X)2M core, with
the four E atoms coplanar; although the E4 disposition dif-
fers, a similar situation is evident in the extreme situation
of collapse of the array to a single metal atom, Cu at the
limit, resulting in an ME4 environment distorted relative
to those found in ‘larger’ systems where M is Ag or E is
As or Sb [10,11]. This viewpoint is reinforced by noting
the propensity of CuX:PPh3 systems to form 2:3 rather
the 2:4 dimers, incorporating E2M(l-X)2 environments in
combination with the less crowded (l-X)2ME array [12–
16].
1:2 Adducts of coinage metal(I) halides, MX, M = Cu,
Ag; X = Cl, Br, I with triphenylpnicogens, EPh3, E = P,
As, Sb, are commonly found in two structural types: mono-
nuclear [(Ph3E)2MX] with quasi-trigonal planar/three-
coordinate E2MX metal atom environments [1–3], also
found in their gold(I) analogues [2,4,5], and binuclear
[(Ph3E)2M(l-X)2M(EPh3)2], with four coordinate E2M(l-
X)2 environments [3]. More recently, it has become evident
that complexes of the former type may be obtained with
systems involving the smaller metal atom (Cu(I)) and/or
the smaller pnictide(s) (P), while systems of the latter binu-
clear type, may be obtained with larger metal atoms and/or
the larger pnictides [6–9]. Systems [(Ph3E)2MX] have thus
far been obtained for [(Ph3P)2CuX], X = all Cl, Br, I
More recently, we have described 1:2 binuclear
MX:EPh3 adducts for combinations of MX:E of CuX:Sb,
AgX:As, Sb [6–9]. At the interface between those circum-
stances favouring the formation of mononuclear 1:2
*
Corresponding author. Tel.: +39 0737 402234; fax: +39 0737 637345.
E-mail address: claudio.pettinari@unicam.it (C. Pettinari).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.014

R.D. Hart et al. / Inorganica Chimica Acta 359 (2006) 2178–2182
2179
adducts and their binuclear counterparts, it therefore seems
2.1. Syntheses
that the unusual may be encountered, as evidenced by the
occurrence of the 2:3 species mentioned above [12–16].
Given the availability of less sterically demanding donors,
the possibility of the formation of solvated species may
exist, thus accessing the potential maximum four-coordi-
nate possibility in a binuclear array without undue steric
strain, as an intermediate in the further spectrum possible
in the mixed-ligand array
2.1.1. Synthesis of copper(I)
chloride:triphenylarsine:acetonitrile (2:3:1) (1)
Triphenylarsine (AsPh3) (0.92 g, 3.0 mmol) was added at
room temperature to a suspension of CuCl (0.198 g,
2.0 mmol) in MeCN (10 ml). After the addition, a colour-
less precipitate slowly formed and the suspension was stir-
red for 24 h under reflux. The precipitate was then filtered
off and identified as complex 1 (75% yield), a few more sub-
stantial crystals depositing from the mother liquor on
standing. M.p. 154–157 ꢁC dec. 1H NMR (CD3CN,
293 K): d 2.2 (br, 3H, CH3CN), 7.3–7.5 (m, 45H, C6H5).
13C NMR (CD3CN, 293 K): d 129.95s, 130.04, 134.50,
139.53. IR (nujol, cmꢀ1): 3060w, 2300br, 1585w, 1579w,
1076m, 1023m, 998m, 734s, 690s, 482m, 469m, 325m,
266br. ESI MS (+): 145(10) ½CuðMeCNÞ2þꢁ; 410(55)
[Cu(AsPh3)(MeCN)+]; 426(10) [Cu(AsPh3)(MeCN)+ + O];
675(100) ½CuðAsPh3Þ2þꢁ; 719(10) [Cu(AsPh3)2(MeCN)+];
775(25) [Cu2(AsPh3)2(Cl)+]. Anal. Calc. for C56H48As3Cl2-
Cu2N: C, 58.10; H, 4.18; N, 1.21. Found: C, 58.23; H,
½LL0Mðl ꢀ XÞ2MLL0ꢁ ꢀ ½LL0Mðl ꢀ XÞ2ML2ꢁ
ꢀ ½L2Mðl ꢀ XÞ2L2ꢁ.
The former have been obtained for R3P/N-base combina-
tions for N-base = ‘one-’,‘two-,’ or ‘three-’ dimensional’ ar-
rays such as nitriles [17,18], pyridine [19,20] and piperidine
bases [21], the intermediate type as yet undescribed. An ini-
tial essay in the present exercise was the attempted synthe-
sis of 1:2 CuX:AsPh3 adducts [6]; in the event binuclear
arrays were obtained for the chloride and bromide as chlo-
roform solvates, but, in the process, attempts involving
other solvents, in particular acetonitrile, were undertaken,
leading to the formation of adducts of the [LL0M(l-
X)2MLL0] and [LL0M(l-X)2ML2] types, as described here-
in, respectively, for the CuBr/Ph3As/MeCN and CuCl/
Ph3As/MeCN combinations.
In an accompanying contribution [22], we define the nat-
ure of an array of solvated species obtained by the crystal-
lization of diverse CuX:dpex combinations from
acetonitrile (‘dpex’ = Ph2E(CH2)xEPh2, E = P, As, Sb), a
context in which it is appropriate to record the results of
the present study.
4.36; S, 1.10%. Km (CH2Cl2, 10ꢀ3 M): 1.0 Xꢀ1 mol2 cmꢀ1
.
2.1.2. Copper(I) bromide:triphenylarsine:acetonitrile
(2:2:2) Æ 2MeCN (2 Æ 2MeCN)
Triphenylarsine (AsPh3) (0.61 g, 2.0 mmol) was added at
room temperature to a suspension of CuBr (0.286 g,
2.0 mmol) in MeCN (20 ml). After the addition, a colour-
less precipitate immediately formed and the suspension
was stirred for 12 h at 40 ꢁC. The precipitate was then fil-
tered off and identified as complex 2 Æ 2MeCN (55% yield),
a few more substantial crystals depositing from the mother
liquor on standing. M.p. 164–166 ꢁC dec. 1H NMR
(CD3CN, 293 K): d1.98 (s, 6H, CH3CN), 2.17 (s, 6H,
CH3CN), 7.3–7.5 (m, 30H, C6H5). 13C NMR (CD3CN,
293 K): d 129.90s, 130.02, 134.49, 139.36. IR (nujol, cmꢀ1):
3050w, 2290br sh, 1582w, 1576w, 1077m, 1023m, 998m,
736s, 692s, 482m, 469m, 458sh, 333m, 324m, 315sh,
247w, 226w, 205w. ESI MS (+): 145(85) ½CuðMeCNÞ2þꢁ;
2. Experimental
All syntheses and handling were carried out in the atmo-
sphere. All chemicals were purchased from Aldrich and
used without further purification. Elemental analyses (C,
H, N) were performed in-house with a Fisons Instruments
1108 CHNS-O Elemental Analyser. IR spectra were
recorded from 4000 to 100 cmꢀ1 with a Perkin–Elmer Sys-
tem 2000 FT-IR instrument. 1H and 13C NMR spectra
were recorded on a Mercury Plus Varian 400 NMR spec-
410(90) [Cu(AsPh3)(MeCN)+]; 675(100) ½CuðAsPh3Þ þꢁ;
2
719(20) [Cu(AsPh3)2(MeCN)+]; 818(30) [Cu2(AsPh3)2-
(Br)+]. Anal. Calc. for C44H42As2Br2Cu2N4: C, 49.69; H,
3.98; N, 5.27. Found: C, 49.76; H, 3.83; NS, 5.33%. Km
1
trometer (400 MHz for H and 100 MHz for 13C). H and
(CH2Cl2, 10ꢀ3 M): 1.5 Xꢀ1 mol2 cmꢀ1
.
C chemical shifts are reported in ppm versus SiMe4. The
electrical conductances of the acetonitrile solutions were
measured with a Crison CDTM 522 conductimeter at room
temperature. Positive and negative electrospray mass spec-
tra were obtained with a Series 1100 MSI detector HP spec-
trometer, using an acetonitrile mobile phase. Solutions
(3 mg/mL) for electrospray ionization mass spectrometry
(ESI-MS) were prepared using reagent grade acetone or
acetonitrile. For the ESI-MS data, masses and intensities
were compared to those calculated by using the IsoPro Iso-
topic Abundance Simulator Version 2.1 [23]; peaks con-
taining copper ions are identified as the centres of
isotopic clusters.
2.2. Structure determinations
General procedures are given in Ref. [22]; specific details
are as follows, a single counter instrument being used to
acquire unique data sets at ca. 295 K. CCDC 286436,
286437.
2.2.1. [(Ph3As)2Cu(l-Cl)2Cu(AsPh3)(NCMe)]
(1) ” C56H48As3Cl2Cu2N, M = 1157.8
1
˚
ꢀ
˚
Triclinic, space group, P1ðCi No. 2Þ, a = 21.857(2) A,
˚
b = 12.763(7) A, c = 10.013(3) A. a = 71.46(5)ꢁ, b = 81.88(1)ꢁ,
3
ꢀ3
˚
c = 73.56(3)ꢁ, V = 2540 A . Dc (Z = 2 dimers) = 1.516 g cm
.

2180
R.D. Hart et al. / Inorganica Chimica Acta 359 (2006) 2178–2182
l
Mo = 28 cmꢀ1; specimen: 0.22 · 0.24 · 0.52 mm; Tmin,max
=
vibrations have been found in the 2300–2280 cmꢀ1 region,
as expected.
0.50, 0.60 (Gaussian correction). 2hmax = 50ꢁ; N = 8475,
No = 5673; R = 0.041, Rw = 0.042.
In the 1H and 13C NMR spectra of 1 and 2 in CD3CN (or
in CDCl3) (see Section 2), the signals due to the arsine show a
different pattern with respect to those found for the free
donor, confirming the existence, at least partial, of the com-
plexes in solution. The presence of coordinated MeCN is con-
firmed by the presence of broad signals at ca 2.2 ppm [28]. In
2.2.2. [(Ph3As)(MeCN)Cu(l-Br)2Cu(NCMe)(AsPh3)] Æ
2MeCN (2) ” C40H36As2Br2Cu2N2Æ2CH3CN, M = 1063.2
Monoclinic, space group P21/c (C52h, No. 14), a =
9.239(1) A,
93.572(8)ꢁ, V = 2178 A .
˚
˚
˚
b = 13.682(2) A,
c = 17.265(2) A,
b =
3
1
˚
l
Mo = 43.6 cmꢀ1
;
specimen:
the H NMR spectrum of 2 a sharp signal at d ca. 2 ppm,
0.70 · 0.22 · 0.16 mm; Tmin,max = 0.38, 0.54 (analytical
correction). 2hmax = 50ꢁ; N = 4066, No = 3123; R = 0.039,
Rw = 0.047.
likely due to the non-coordinated MeCN, is also present.
The positive electrospray mass spectra of complexes 1
and 2 (the most relevant data are reported in Section 2
and a typical spectrum is reported in Fig. 1) indicate that
these derivatives exist as dinuclear species also in solution.
The isotopic distribution of these species is in accord with
the calculated composition. However, the major peaks are
those derived from mononuclear species containing one or
two AsPh3 and one or two MeCN ligands bonded to a cop-
per centre. The aggregation behaviour is dependent on the
solvent employed, no adducts containing MeCN being
detected in acetone or alcohols, and also dependent on
the concentration, the dinuclear species [Cu2(AsPh3)2(X)+]
increasing with increasing concentration of 1 or 2 in solu-
tion. Under our conditions the linear aggregate containing
a copper centre and two triphenylarsine donors dominates
significantly over adducts containing different ligand to
metal ratio. Oxidation of the arsine is evident in solution,
some weak peaks due to [Cu(AsPh3)(MeCN)+ + O] being
often present [29]. No fragments containing two positive
charges have been detected. The negative electrospray spec-
tra of 1 and 2 are dominated by the presence of peaks due
to [CuX2]ꢀ.
3. Results and discussion
Reaction of three equivalent of triphenylarsine (AsPh3)
with two equivalents of CuCl in refluxing acetonitrile
resulted in the formation of derivative 1 (Chart 1). A 3:2
ligand to metal molar ratio and reaction times greater than
12 h are rigorously required. When a ligand to metal ratio
greater than 2:1 was employed the well-known dinuclear
[(AsPh3)2Cu(l-Cl)2Cu(AsPh3)2] formed. The 3:2 adduct 1
was afforded only when the reaction was carried out in
MeCN, whereas in MeOH the 2:1 species always formed.
Reaction between CuBr and AsPh3 in MeCN in 1:1
ligand to metal molar ratio yielded the derivative
2 Æ 2MeCN (Chart 1); a similar iodide analogue has been
previously recorded [24].
Compounds 1 and 2 are air-stable, colourless materials,
insoluble in diethyl ether and ethanol and soluble in ace-
tone, acetonitrile, DMSO. The conductivity measurements
are in accordance with a non-ionic formulation also in
solution, K being in acetonitrile, for 1 and 2, 1.0 and
1.5 Xꢀ1 cm2 molꢀ1, respectively.
The infrared spectra (Section 2) are consistent with the
formulations proposed, showing all of the bands required
by the presence of the arsine ligand [25]. In the far-IR spec-
tra we assigned, on the basis of previous reports, the broad
absorptions near 500 cmꢀ1 and those at 480–400 cmꢀ1 to
Whiffen’s y and t vibrations [26]. No bands assignable to
terminal Cu–Cl and Cu–Br stretching vibrations have been
found. On the other hand two broad bands at ca. 160 and
180 cmꢀ1 have been detected in the spectrum of 1. Analo-
gous bands have been previously assigned to m(Cu–Cl) in
complexes containing a bridging halide group [27] in accor-
dance with the Cu(l-X)2Cu (X = Cl or Br) environments
found in the solid state. Broad signals due to CN stretching
The results of the room-temperature single crystal X-ray
studies described herein are consistent with the description
of the above complexes as an interesting pair of binuclear
arrays with Cu(l-X)2Cu molecular cores involving four-
coordinate copper(I) atoms, the latter coordination envi-
ronments being completed by different aggregates of
Group V/15 unidentate ligands.
Complex 2, [(Ph3As)(MeCN)Cu(l-Br)2Cu(NCMe)(As-
Ph3)], Fig. 2, has close counterparts in (o-tolyl)Ph2P/CuBr
and Ph3As/CuI arrays [17,24]; in all three complexes one
half of the binuclear, centrosymmetric dimer comprises
the asymmetric unit of the structure, a crystallographic
inversion centre lying at the centre of the Cu(l-X)2Cu core.
Core geometries are presented comparatively in Table 1
(together with those of complex 1), those of the present
array disposed largely as expected with respect to those
of the two counterpart complexes in consequence of the
different component differences. Complex 1, [(Ph3As)2-
Cu(l-Cl)2Cu(NCMe)(AsPh3)], an adduct of 2:3:1 CuX:-
Ph3E:MeCN stoichiometry, appears to be the first
structurally authenticated example of the intermediate sol-
vated species (Fig. 2). The geometries about the two differ-
ent copper atoms are tabulated independently in Table 1,
again showing broadly the anticipated variations
consequent upon their different substitution patterns.
Ph3As
Ph3As
Cl
AsPh3
H3CCN
Ph3As
Br
AsPh3
Cu
Cu
Cu
Cu
Cl
NCCH3
Br
NCCH3
2
1
Chart 1.

R.D. Hart et al. / Inorganica Chimica Acta 359 (2006) 2178–2182
2181
*MSD1 SPC, time=0.153:0.208 of PT\05090507.D API-ES, Pos, Scan, 30
Norm.
100
Max: 25962
[Cu(AsPh3)2+]
80
60
40
20
0
[Cu(MeCN)2+]
[Cu(AsPh3)(MeCN)+]
[Cu(AsPh3)2(MeCN)+]
[Cu2(AsPh3)2(Br)+]
200
400
600
800
1000
m/z
Fig. 1. ESI MS spectrum (positive mode) of compound 2.
Fig. 2. Projections of (a) [(Ph3As)2Cu(l-Cl)2Cu(NCMe)(AsPh3)], (b) [(Ph3As)(MeCN)Cu(l-Br)2Cu(NCMe)(AsPh3)] (i) normal to the central Cu(l-X)2Cu
plane, and (ii) through the central Cu(l-X)2Cu planes, normal to the Cuꢂ ꢂ ꢂCu line in each case.

2182
R.D. Hart et al. / Inorganica Chimica Acta 359 (2006) 2178–2182
Table 1
Molecular core geometries
E/X
[(Ph3E)(MeCN)Cu(l-X)2Cu(NCMe)(EPh3)]
[(Ph3As)2Cu(l-Cl)2Cu(NCMe)(AsPh3)]b
P/Bra
As/Brb
As/Ic
2.690(1)
2.637(1)
2.779(1)
4.545(1)
2.381(1)
2.022(3)
As/Cl(As(11,12))
As/Cl(As(21))
˚
Distances (A)
Cu–X
2.569(2)
2.465(2)
3.215(2)
3.827(2)
2.228(3)
2.008(10)
2.529(1)
2.340(2)
2.362(2)
2.965(1)
2.338(2)
2.377(2)
Cu–X0
Cuꢂ ꢂ ꢂCu
Xꢂ ꢂ ꢂX0
Cu–E
2.4568(9)
2.950(1)
4.0204(8)
2.3562(9)
2.029(5)
2.355(2)
2.357(1)(As)
2.353(2)
2.019(5)
Cu–N
Angles (ꢁ)
Cu–X–Cu
X–Cu–X0
X–Cu–E
X–Cu–N
X0–Cu–E
X0–Cu–N
E–Cu–N
Cu–N–C
N–C–C
79.35(5)
100.65(6)
108.69(9)
103.6(3)
118.01(9)
107.2(3)
116.5(3)
174.3(6)
178(1)
72.53(3)
107.47(3)
107.10(3)
104.0(2)
114.70(2)
113.0(2)
109.8(1)
164.4(5)
178.2(7)
62.88(2)
117.12(2)
102.99(2)
104.1(1)
111.4(2)
108.6(1)
112.5(1)
176.0(3)
179.6(3)
77.89(6)
101.82(6)
104.25(6)
112.19(6)(As)
110.79(6)
78.22(7)
101.42(6)
117.66(7)
105.9(2)
115.01(5)
111.7(2)
105.0(1)
166.3(4)
178.5(7)
102.46(6)(As)
123.41(4)(As)
Torsion angles (ꢁ) (cation atoms denoted by number only)
Cu–E–11–12
Cu–E–21–22
Cu–E–31–32
ꢀ51(1)
ꢀ46.4(9)
ꢀ36(1)
ꢀ23.0(5)
ꢀ19.4(4)
ꢀ24.7(4)
36.3(1)
35.3(2)
58.6(2)
17.4(5), 66.0(7)
21.4(6), ꢀ10.3(7)
52.2(5), 57.0(6)
9.7(7)
62.2(6)
30.0(5)
˚
Deviations from the Cu(l-X)2Cu plane (A)
dE
dN
a
1.737(2)
ꢀ1.824(2)
1.874(2)
ꢀ1.704(6)
1.954(2)
ꢀ1.702(3)
2.182(2)
ꢀ 1.934(2)(As)
ꢀ1.505(2)
Ref. [17], R3 = (o-tolyl)Ph2.
b
This work.
Ref. [24].
c
[16] J.C. Dyason, L.M. Engelhardt, C. Pakawatchai, P.C. Healy, A.H.
White, Aust. J. Chem. 38 (1985) 1243.
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