A route to novel stable salts containing transition and main group metals

Article abstract of DOI:10.1134/S1070328407050090

Novel salts of the type [Cu(Dien)₂][Bu₃SnCl ₃], [Cu(Dien)₂][Ph₂SnCl₄], and [Cu(Dien)₂][SnCl₆] (Dien-diethylenetriamine) were prepared by the reaction of [Cu(Dien)₂]Cl₂ with Bu ₃SnCl, Ph₂SnCl₂ and SnCl₄ in MeOH in a 1:1 ratio, respectively, and characterized by elemental analyses, electronic, IR and ESR spectroscopy, magnetic susceptibility, electrochemistry, and conductivity measurements. The results revealed that the compounds are 1:1 electrolytes and the Cu²⁺ ion is paramagnetic in the octahedral field. The complexes exhibit a single-electron redox couple. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S1070328407050090

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2007, Vol. 33, No. 5, pp. 364–367. © Pleiades Publishing, Ltd., 2007.
A Route to Novel Stable Salts Containing Transition
and Main Group Metals1
F. M. A. M. Aqra and R. M. A. Q. Jamhour
Department of Chemistry, Faculty of Science, Hebron University, Hebron, West Bank, Palestin
Department of Applied Chemistry, Faculty of Science, Tafila Technical University, Tafila, Jordan
e-mail: fathiaqra@hotmail.com
Received April 5, 2006
Abstract—Novel salts of the type [Cu(Dien)2][Bu3SnCl3], [Cu(Dien)2][Ph2SnCl4], and [Cu(Dien)2][SnCl6]
(Dien—diethylenetriamine) were prepared by the reaction of [Cu(Dien)2]Cl2 with Bu3SnCl, Ph2SnCl2 and
SnCl4 in MeOH in a 1 : 1 ratio, respectively, and characterized by elemental analyses, electronic, IR and ESR
spectroscopy, magnetic susceptibility, electrochemistry, and conductivity measurements. The results revealed
that the compounds are 1 : 1 electrolytes and the Cu2+ ion is paramagnetic in the octahedral field. The complexes
exhibit a single-electron redox couple.
DOI: 10.1134/S1070328407050090
1
INTRODUCTION
EXPERIMENTAL
Binuclear copper(II) compounds have evoked con-
siderable worldwide interest in recent years and have
attracted much attention [1, 2] because they are good
electrocatalysts [3, 4] and have been widely used in the
biomimetic chemistry of copper(II) proteins and in the
substrate activation by metal centers [5, 6]. Salts con-
taining two transition metal ions have been thoroughly
investigated [7–12]. However, salts incorporating a
transition and a main group metal are probably less
common, and therefore, it was considered worthwhile
to prepare a series of salts containing Cu2+/Sn4+ ions
that could be useful in some future applications in order
to gain further insight into the above properties of
dimetallic complexes.
Diethylenetriamine (Koch Light), CuCl2 (BDH),
Bu3SnCl, Ph2SnCl2, and SnCl4. (Fluka) were used as
received. MeOH and DMSO were distilled and dried
before use. Microanalyses were made on a Carlo Erba
analyzer (model 1106). Molar conductances were mea-
sured at room temperature on a Digisun electronic con-
ductivity bridge. The IR spectra (200–4000 cm–1) were
recorded on a Carl Zeiss Specord M80 spectrometer in
nujol mulls. Electronic spectra were recorded on a Shi-
madzu UV Vis spectrometer (model 60). The ESR
spectra were measured on a Bruker Scientific X-band
spectrometer (ESP-300) using a 100 KHz field modula-
tion and quartz sample tubes. The g values determined
were calibrated with a DPPA powder (g = 2.0036).
Chlorine was estimated by a gravimetric method. Tin
was estimated as SnO2, whereas copper analysis was
made on a Schimadzu AA-6AO atomic absorp-
tion/flame emission spectrometer. Magnetic suscepti-
bilities were measured using a Cahn 2000 Faraday
magnetic balance calibrated with Hg[Co(NCS)4] at
room temperature. All reactions were carried out at
room temperature under nitrogen atmosphere. Cyclic
voltametric experiments were carried out on a Prince-
tonApplied Model, 273 potentiostat-galnvanostat using
a 0.001 M solution in DMF and Et4NClO4 as supporting
electrolyte. All experiments were performed under dry
N2 at 25°C, using a three-electrode assembly compris-
ing a platinum disk as the working electrode, a plati-
num wire as the auxiliary electrode, and a standard
calomel electrode (SCE) as the reference electrode. All
potentials were referred to SCE.
To extend this chemistry, attempts were made to uti-
lize the ability of tin(IV) in a salt with copper(II).
Herein, we performed the synthesis and characteriza-
tion of new compounds resulting from the reaction of
tin(IV) species with bis(diethylenetriamine)copper(II).
It is an established fact that tin(IV) is capable of extend-
ing its coordination number from four to six by accept-
ing two ligands. However, in this project, novel type of
salts made of mononuclear anionic and mononuclear
cationic metal complexes are described.
Attempts to recrystallize the compounds in order to
prepare single crystals for X-ray diffraction studies
were unsuccessful. It was not possible to record 1H, 13C,
and 119Sn NMR spectra for these compounds due to the
presence of paramagnetic copper(II), and this would
indeed be crucial to get experimental evidence for the
geometry of the tin atom in the compounds.
Synthesis of [Cu(Dien)2]Cl2 (I) was carried out by
a reported method [13].
1
The article was submitted by the authors in English.
364

A ROUTE TO NOVEL STABLE SALTS CONTAINING TRANSITION
365
Table 1. The elemental analyses data, molar conductances and some physical properties of compounds I–IV
Contents(found/calcd), %
Yield, M.p.,
Λ,
Compound
Colour
%
°C
Ohm−1 cm−2 mol–1
C
H
N
Cu
Sn
Cl
[Cu(Dien)2]Cl2 (I)
80 243 Blue
28.4/28.4 7.7/7.7 24.6/24.5 18.6/18.5
20.8/20.5
200
161
137
106
[Cu(Dien)2][Bu3SnCl3] (II) 46 210 Blue
36.0/36.3 8.0/8.0 12.6/12.6 9.5/9.3 17.8/17.5 15.9/15.8
[Cu(Dien)2][Ph2SnCl4] (III) 35 123 Yellow 35.1/35.2 5.3/5.3 12.2/12.2 9.2/9.1 17.3/17.0 20.7/20.5
[Cu(Dien)2][SnCl6] (IV)
65 205 Green- 14.3/14.5 3.9/3.9 12.5/12.5 9.4/9.2 17.6/17.2 31.1/31.0
ish-yel-
low
Synthesis of [Cu(Dien)2][Bu3SnCl3] (II). Bu3SnCl
(3.25 g, 0.01 mol) dissolved in carbon tetrachloride
(25 ml) was added dropwise to a methanolic solution
(25 ml) of [Cu(Dien)2]Cl2 (3.40 g, 0.01 mol). This mix-
ture was warmed and left at room temperature for
20 days until blue crystals precipitated. The crystals
were then filtered and dried in vacuo.
Bu3SnCl
[Cu(Dien)2][Bu3SnCl3]
(II)
MeOH Ph2SnCl2
SnCl4
[Cu(Dien)2]Cl2
[Cu(Dien)2][Ph2SnCl4].
(III)
(2)
[Cu(Dien)2][SnCl6]
(IV)
Synthesis of [Cu(Dien)2][Ph2SnCl4] (III). A solu-
tion of Ph2SnCl2 (3.40 g, 0.01 mol) in CCl4 was added
dropwise (25 ml) to a methanolic solution (25 ml) of
[Cu(Dien)2]Cl2 (3.40 g, 0.01 mol). Solution color
changed from blue to yellow, was warmed and kept
standing at ambient temperature for more than three
weeks until a yellow crystalline compound formed. The
crystals were filtered off and dried in vacuo.
The elemental analyses are in good agreement with
the proposed composition of the compounds. They are
slightly hygroscopic in nature and highly soluble in
water. The molar conductances of these salts in DMSO
at room temperature show that they are 1 : 1 electrolytes
[14]. These compounds are suggested to be formed by
the transfer of two chloride ions from [Cu(Dien)2]Cl2 to
tin(IV) tetrachloride or organotin(IV) chlorides. In this
way, the bis(diethylenetriamine)copper(II) cation is sta-
bilized by tin(IV) anionic species.
Synthesis of [Cu(Dien)2][SnCl6] (IV). This com-
pound was synthesized by a slow addition of SnCl4
(0.01 mol) dissolved in CCl4 (25 ml) to a methanolic
solution (25 ml) of [Cu(Dien)2]Cl2 (3.40 g, 0.01 mol).
The resulting precipitate was then stirred for 30 min,
At the room temperature ESR spectra of all the
polycrystalline samples (figure) are similar, showing a
signal with g|| = 2.268 and g⊥= 2.056 (g0 = 2.13), in
agreement with the tetragonally distorted stereochem-
filtered off, washed twice with MeOH, and dried under istry of the Cu2+ ion [15]. The nuclear hyperfine cou-
pling is observed in the g|| signal with three of the four
components resolved, the last one being obscured by
the g⊥ component. At lower temperature (110 K), nar-
rower signals with the same values are observed. There-
fore, the orbital ground state of copper(II), which con-
vacuo.
The elemental analyses data, molar conductances
and some physical properties of compounds are given
in Table 1.
tains an unpaired electron, would be basically dx
2 – y2
and the CuN6 would statistically be distorted (N is a
donor atom in a macrocyclic complex).
RESULTS AND DISCUSION
Copper(II) chloride reacts with diethylenetriamine
(Dien) in a 1 : 2 ratio in MeOH to yield [Cu(Dien)2]Cl2
(Eq. (1)), which in turn reacts efficiently with tin(IV) tet-
rachloride and organotin(IV) chlorides to yield polycrys-
talline [Cu(Dien)2][Bu3SnCl3], [Cu(Dien)2][Ph2SnCl4],
and [Cu(Dien)2][SnCl6] (Eq. (2)).
The electronic absorption spectra for [Cu(Dien)2]Cl2
and for the newly synthesized copper species were
recorded in MeOH and DMSO at 25C°, respectively,
and expanded wherever possible. The electronic spec-
tral bands of compounds in a ranges 200–400 and 400–
750 nm are 256, 302, 300, 295 and 620, 600, 589, 585,
respectively.
The
electronic
spectrum
of
[Cu(Dien)2]Cl2 exhibits a high intensity charge-transfer
MeOH
[Cu(Dien)2]Cl2
(I)
CuCl2 + 2Dien
(1)
band at 256 nm. A clear d–d band observed at 620 nm
2
is characteristic of Eg
2T2g transition in the dis-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

366
AQRA, JAMHOUR
(b)
g||
(a)
g||
g_
g_
|
|
DPPH
(H = 3322 G)
(c)
(d)
g||
g||
A|| = 83 G
g_
g_
|
|
2700 2800 2900 3000 3100 3200 3300 3400 3500 2700 2800 2900 3000 3100 3200 3300 3400 3500
H, G
ESR spectra of polycrystalline samples of the compounds: (a) I, (b) II, (c) III, and (d) IV.
torted octahedral environment of Cu2+ ion. The elec-
tronic absorption spectra of the salts exhibit a band at
~302 nm assigned to the ligand-to-metal charge trans-
fer [16]. The d–d bands centered at ~600 nm are char-
The IR spectral bands of all the compounds are
given in Table 2. The IR spectrum of [Cu(Dien)2]Cl2
shows two adjacent bands at 3230 and 3145 cm–1 attrib-
utable to ν(RNH) of the primary and secondary amines
of the diene, respectively. The δ(RNH) appears at
1590 cm–1. Two sharp absorption bands (1062 and
1384 cm–1) are due to ν(C–C) and ν(C–N) modes,
respectively. A band of medium intensity is observed at
405 cm–1 assigned to ν(Cu–N). All these bands remain
in their positions in the IR spectra of the salts. However,
the IR spectra of the new species exhibit some worth
mentioning additional bands. [Cu(Dien)2][Bu3SnCl3]
exhibits one band at 530 cm–1 due to ν(Sn–C). Others
two bands, observed at 290 and 320 cm–1 are assigned
to ν(Sn–Cl) of the [Bu3SnCl3]2– anion [17, 18]. Com-
pound [Cu(Dien)2][Ph2SnCl4] shows similar bands at
same positions. The IR spectrum of the
[Cu(Dien)2][SnCl6] salt exhibits also two distinct bands
in the far-IR region at 296 and 322 cm–1 due to
ν(Sn−Cl) of the [SnCl6]2– moiety.
acteristic of the dx
dz2 transition in the d9 sys-
2 – y2
tem of the Cu2+ ion in a hexacoordinated configuration.
The observed magnetic moments of all compounds
are ~1.78 µB due to the presence of one spin electron.
Since the Cu+2 + ion is always d9, it can hardly be imag-
ined what an alternative expectation to paramagnetism
might be. The diene ligand normally forms octahedral
complexes and, therefore, it is claimed that the Cu2+ ion
maintains an octahedral geometry. On this basis, it is
not surprising to say that the presence of tin(IV) in
these salts does not change the paramagnetism of the
Cu2+ ion, and therefore, rules out the possibility of anti-
ferromagnetic exchange because Sn(IV) contains no
unpaired electron. Thus, the metal sites in such a salt
would not be expected to exhibit any interaction with
one anther, and experimentally they do not.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007

A ROUTE TO NOVEL STABLE SALTS CONTAINING TRANSITION
367
Table 2. IR and far IR-bands (cm–1) of the compounds I–IV and their asignments
Compound
ν(N–H)
δ(RNH)
ν(C–C)
ν(C–N)
ν(Cu–N)
ν(Sn–C)
ν(Sn–Cl)
I
3230
3145
3230
3145
3230
3145
3230
3145
1590
1061
1384
405
II
1600
1600
1595
1061
1061
1061
1384
1384
1384
405
405
405
503
515
320
290
320
290
322
296
III
IV
6. Rockliffe, D.A. and Martell, A.E. Inorg. Chem., 1993,
Cyclic voltammetric data for [Cu(Dien)2][SnCl6]
salt in DMF were measured in the potential range from
1 to –15V at room temperature. A reversible redox cou-
ple occurs with a reduction peak of –0.63V and the cor-
responding oxidation peak at –0.50 V with ∆Ep =
130 mV. Therefore, the complex shows a singleelectron
redox couple as anticipated. It seems that the prepara-
tion of such type salts is valuable, and in the near future
the reactivity differences between the starting copper
salt and the newly synthesized copper salts can be
investigated.
vol. 32, no. 14, p. 3143.
7. Bailer, J.C. Jr and Busch, D.H., Chemistry of the Coor-
dination Compounds, New York: Reinhold Publishing
Corp., 1956.
8. Flores-Velez, L.M., Rivadeneyra, J.S., Torres, M.E.S.T.,
et al., Dalton Trans., 1991, no. 12, p. 3243.
9. Bellingham, R.K., Graham, J.T., Jones, P.J., et al. Dal-
ton Trans., 1991, no. 12, p. 3387.
10. Shaviv, R., Redmond, M.E., and Carlin, R.L., Inorg.
Chem., 1992, vol. 31, no. 10, p. 1762.
In conclusion, the possibility of antiferromagnetic
spin exchange is ruled out. Such salts and other binu-
clear metal complexes with identical or different metals
can find many applications, such as the investigation of
interactions between metal ions in the active sites of
metalenzymes, e.g., cytochrome C oxidase [19], bovine
erythrocyte superoxidase dismutase [20], and halperox-
idases [21]. They can also play an important part in the
search for appropriate systems for binding and activat-
ing simple molecules and in investigations concerning
the mutual influences of two metal centers on the elec-
tronic, magnetic, and electrochemical properties of
such heterodinuclear complexes [22, 23].
11. Shaviv, R. and Carlin, R.L., Inorg. Chem., 1992, vol. 31,
no. 4, p. 710.
12. Carlin, R.L., Comments Inorg. Chem., 1992, vol. 11,
p. 215.
13. Stephens, F.S., J. Chem. Soc. A, 969, no. 6, p. 883.
14. Geary, W.J., Coord. Chem. Rev., 1971, vol. 7, no. 1,
p. 81.
15. Soto, L., Garcia, J., Escriva, E., and Legros, J.P., Poly-
hedron, 1992, vol. 11, p. 647.
16. Vrengdenhil, W., Haasnoot J.G., and Reedijk, J., Inorg.
Chem. Acta, 1990, vol. 167, no. 1, p. 109.
17. Janas, Z., Sobota, P., and Lis, T., Polyhedron, 1988,
vol. 7, p. 2655.
REFERENCES
18. Thomas, T.E., and Orville-Thomas, W.J., J. Inorg. Nucl.
Chem., 1972, vol. 34, p. 839.
1. Arion, V.B., Gerbeleu, N.V., Veaceslav, G., et al., Dal-
ton Trans, 1994, no. 13, p. 1913.
19. Palmer, G., Babcock, G.T., and Vickery, L.E. Proc.
Natl. Acad. Sci. U.S.A., 1976, vol. 73, p. 2206.
2. Shakir, M. Mohamed, A.M . Verkey S.P., and Nas-
man, O.S.M., Indian J. Chem., 1996, vol. 35 A,
p. 935.
20. Richardson, J.S., Thomas, K.A., Rubin, B.H., and Rich-
ardson, D.C. Proc. Natl. Acad. Sci. U.S.A., 1975, vol. 72,
p. 1394.
3. Collin, J.P., Jouaiti A., and Sauvage, J.P., Inorg. Chem.,
21. Halcow, M.A., and Christou, G., Chem. Rev., 1994,
1988, vol. 27, no. 1, p. 1986.
vol. 94, p. 2421.
4. Beley, M., Collin, J.P., Ruppert R.,and Sauvage, J.P.,
22. Sinn, E. and Harris, C.M., Coord. Chem. Rev., 1969,
J. Am. Chem. Soc., 1986, vol. 108, no. 24, p. 7461.
vol. 4, p. 391.
5. Ling, J., Farooq, A.K., Karlin, D., et al., Inorg. Chem.,
23. Pilkington, N.H. and Robson, R., Aust. J. Chem., 1970,
1992, vol. 31, no. 12, p. 2552.
vol. 23, p. 2225.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 5 2007