Solid-vapor reaction properties of copper(II) and cadmium(II) sulfonates with amines

Article abstract of DOI:10.1016/j.poly.2006.05.008

The solid-vapor reaction properties of three transition metal sulfonates and amines were investigated and the reaction products were characterized by EA, TGA, IR, PXRD and single crystal structure analyses. [Cu(1,5-nds)(H₂O)₄]_n<

Full text of DOI:10.1016/j.poly.2006.05.008

Polyhedron 25 (2006) 3045–3052
www.elsevier.com/locate/poly
Solid–vapor reaction properties of copper(II) and
cadmium(II) sulfonates with amines
a
a
b,
*
Ping Liu , Zhao-Xun Lian , Jiwen Cai
a
School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
b
School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510080, PR China
Received 5 January 2006; accepted 10 May 2006
Available online 16 June 2006
Abstract
The solid–vapor reaction properties of three transition metal sulfonates and amines were investigated and the reaction products
were characterized by EA, TGA, IR, PXRD and single crystal structure analyses. [Cu(1,5-nds)(H2O)4]n (I), [Cu(H2O)6](1,5-nds)
(II) (1,5-nds = 1,5-naphthalenedisulfonate) and [Cd(p-NH2C6H4SO3)2] (III) can react with primary alkyl amine vapors and form stable
monoamine-coordinated Cu(II) and Cd(II) complexes. All of the amine adducts are crystalline materials. The reactions between [Cd-
(p-NH2C6H4SO3)2] (III) and C2H5NH2 or n-C3H7NH2 produced single crystals in situ via the solid–vapor reaction process.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Copper(II); Cadmium(II); Sulfonate; Solid–gas reaction; Solid–vapor reaction; Alkyl amine
1. Introduction
pounds with flexible and tunable structures. We have
reported the amine-intercalating properties of two cad-
mium(II) arenesulfonate complexes, namely [Cd(1,5-nds)-
(H2O)2] (1,5-nds = 1,5-naphthalenedisulfonate) [2] and
[Cd(p-NH2C6H4SO3)2(H2O)2] [3]. Without excluding the
coordinated-water molecules to generate vacant coor-
dination sites, Cd(II) sulfonates can undergo solid–vapor
reactions with amine vapors and produce single-phase
monoamine-coordinated complexes that are otherwise diffi-
cult to obtain from homogeneous reactions. The reaction is
selective and reversible, which indicates that the metal sulfo-
nates could be developed into a new type of chemical sensor
for volatile amines [6].
In order to explore the general features of the solid–
vapor reactions between transition metal sulfonates, we
extended the metal center from Cd(II) to Cu(II), and inves-
tigated the solid–vapor reactions between [Cu(1,5-nds)-
(H2O)4]n (I) and [Cu(H2O)6](1,5-nds) (II) with a series of
alkyl amines. Moreover, the dehydrated metal sulfonate
[Cd(p-NH2C6H4SO3)2] (III), obtained from [Cd(p-NH2C6-
H4SO3)2(H2O)2] [3], was also investigated to compare the
influence of the coordinated water molecules on the reac-
tion properties.
Solid–vapor reactions between metal-organic com-
pounds and organic ligands to produce coordination com-
plexes have not been investigated broadly, probably due
to the difficulties in controlling the reaction processes and
characterizing the structure of the reaction products. Metal
phosphates are a unique group of compounds whose reac-
tion properties with amine vapors have been studied in
depth [1]. It was found that, after excluding water molecules
from the coordination sphere of the metal centers, metal
phosphates remain inorganic–organic lamellar structures
and can uptake amine molecules either via solid–vapor or
solid–liquid reactions [1]. The corresponding absorption
properties of the metal sulfonates have been investigated
recently by us [2–4] and others [5], in order to compare
the chemical properties between metal sulfonates, charac-
teristic of soft frameworks, with metal phosphate analogs,
characteristic of rigid inorganic–organic lamellar struc-
tures, as well as to search for functional coordination com-
*
Corresponding author. Tel.: +86 2084114215; fax: +86 2084112245.
E-mail address: puscjw@mail.sysu.edu.cn (J. Cai).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.05.008

3046
P. Liu et al. / Polyhedron 25 (2006) 3045–3052
2. Experimental
2.1. Materials and methods
EQUINOX 55 FTIR spectrometer. Thermogravimetry
was carried out with a Netzsch TG-209 analyzer under
flowing nitrogen.
All materials were commercially available and used
without further purification. Elemental analyses were con-
ducted using the Vario EL elemental analyzer. PXRD
(Powder X-ray diffraction) was performed on a Rigaku
D/Max-IIIA diffractometer operated using a 0.02ꢁ step
scan from 3ꢁ to 70ꢁ in 2h and 0.2 s preset time. Infrared
spectra were obtained as KBr pellets on a Bruker
2.2. Syntheses of compounds I, II and III
[Cu(1,5-nds)(H2O)4]n (I) and [Cu(H2O)6](1,5-nds) (II)
were obtained according to the reported procedure [7].
[Cd(p-NH2C6H4SO3)2] (III) was prepared by heating
[Cd(p-NH2C6H4SO3)2(H2O)2] [3] at 200 ꢁC for 2 h.
C10H14CuO10S2 (I): Anal. Calc. C, 28.47; H, 3.34. Found:
Table 1
TGA and EA results of amine complexes formed by [Cu(1,5-nds)(H2O)4] (I)
Compound
TGA (%)
Releasing T (ꢁC)
Elemental analyses
Calculateda
Observed
Calculated C, N, H (%)
Observed C, N, H (%)
Cu(1,5-nds)(H2O)2(CH3NH2)4
Cu(1,5-nds)(H2O)2(C2H5NH2)4
Cu(1,5-nds)(H2O)2(n-C3H7NH2)4
Cu(1,5-nds)(H2O)2(n-C4H9NH2)3
Cu(1,5-nds)(i-C4H9NH2)3
Cu(1,5-nds)(H2O)2(t-C4H9NH2)3
a
31.4
38.2
43.8
42.2
38.5
42.2
29.5
35.9
38.4
39.9
38.7
41.8
81–137, 176–320
93–151, 241–316
94–143, 252–306
108–300
32.97, 10.98, 5.93
38.18, 9.90, 6.76
42.46, 9.00, 7.45
43.66, 6.94, 7.16
46.42, 7.38, 6.91
43.66, 6.94, 7.16
33.06, 11.05, 5.72
38.18, 9.73, 6.49
41.86, 8.64, 7.15
44.47, 7.16, 7.10
47.15, 8.42, 7.27
43.13, 7.06, 7.09
90–320
124–277
Calculated weight loss includes water and amine molecules.
Table 2
TGA and EA results of amine complexes formed by [Cd(p-H2NC6H4SO3)2] (III)
Compound
TGA (%)
Releasing T (ꢁC)
Elemental analyses
Calculateda
Observed
Calculated C, N, H (%)
Observed C, N, H (%)
Cd(p-H2NC6H4SO3)2(CH3NH2)3
Cd(p-H2NC6H4SO3)2(H2O)2(C2H5NH2)4
Cd(p-H2NC6H4SO3)2(n-C3H7NH2)4
Cd(p-H2NC6H4SO3)2(i-C3H7NH2)
Cd(p-H2NC6H4SO3)2(n-C4H9NH2)4
a
16.9
32.1
34.1
11.5
39.0
15.7
30.9
32.5
12.4
38.9
102–314
57–90, 152–300
86–115, 141–310
134–175, 198–289
59–113, 150–321
32.76, 12.73, 4.95
35.69, 12.48, 6.59
41.58, 12.12, 6.98
34.92, 8.15, 4.10
44.88, 11.22, 7.53
32.63, 12.58, 5.14
37.41, 13.02, 6.55
40.68, 11.87, 7.11
34.89, 8.01, 4.36
44.77, 11.20, 7.27
Calculated weight loss includes water and amine molecules.
I / t-C H NH
4
9
2
I / i-C H NH
4
9
2
I / n-C H NH
4
9
2
I / i-C H NH
3
7
2
I / n-C H NH
3
7
2
I / C H NH
2
5
2
I / CH NH
3
2
I
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber/cm-1
Fig. 1. IR spectra of amine complexes formed by [Cu(1,5-nds)(H2O)4] (I).

P. Liu et al. / Polyhedron 25 (2006) 3045–3052
3047
C, 28.31; H, 3.37%. C12H12CdN2O6S2 (III): Anal. Calc. C,
2.4. Characterization
31.55; N, 6.13; H 2.65. Found: C, 31.55; N, 6.15; H, 2.76%.
[Cu(H2O)6](1,5-nds) (II) was characterized by its PXRD
which matched the simulated PXRD from its single crystal
structure.
The reaction products were characterized by EA, TGA,
IR and PXRD. Since the final products formed by com-
pounds I and II have the same PXRD patterns, only the
results of I are presented. The EA and TGA results are
showed in Tables 1 and 2. All complexes have similar IR
patterns and only those obtained from I is shown in
Fig. 1. The PXRD is shown in Fig. 2.
2.3. Solid–vapor reaction
Compounds I–III and the amine liquids were placed in
two different but connected vessels and the reactions were
carried out at room temperature. The reaction process
was monitored via the net weight gain. It took a few days
to 2 weeks for the reaction process to be complete. All reac-
tion products were placed in an N2 flow to remove the
deposited amine and moisture on the crystalline surface
before submission for characterization.
2.5. X-ray structure analysis
Diffraction data of [Cd(n-C3H7NH2)4(H2O)2](p-H2NC6-
H4SO3)2 were collected on a Bruker Smart 1000 CCD area
detector diffractometer with graphite monochromated
˚
Mo Ka radiation (k = 0.71073 A) at room temperature.
I / t-C H NH
4
9
2
I / i-C H NH
4
9
2
I / n-C H NH
4
9
2
I / n-C H NH
3
7
2
I / C H NH
2
5
2
I / CH NH
3
2
I
10
20
30
40
2theta/o
III / n-C H NH
4
9
2
III / i-C H NH
3
7
2
III / n-C H NH
3
7
2
III / C H NH
2
5
2
III / CH NH
3
2
III
Cd (H NC H SO ) (H O)
6 4 3 2 2
2
2
10
20
30
40
2theta/o
Fig. 2. PXRD of the amine complexes formed by [Cu(1,5-nds)(H2O)4] (I) and [Cd(p-H2NC6H4SO3)2] (III).

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P. Liu et al. / Polyhedron 25 (2006) 3045–3052
Table 3
4 moles of CH3NH2, C2H5NH2 and n-C3H7NH2, 3 moles
of i-C3H7NH2, n-C4H9NH2, i-C4H9NH2 and t-C4H9NH2,
and form stable coordination compounds.
Crystallographic data for [Cd(n-C3H7NH2)4(H2O)2](p-H2NC6H4SO3)2
Empirical formula
Formula weight
Temperature (K)
C24H52CdN6O8S2
729.24
293(2)
0.71073
triclinic
It is noted that the reaction process of [Cu(1,5-
nds)(H2O)4]n (I) with amine was accompanied by a color
change, depending on the different amine molecules that
the reactant was exposed to. With CH3NH2 and i-C3H7-
NH2, the color changed from light blue to purple; with
C2H5NH2, n-C3H7NH2, n-C4H9NH2 and i-C4H9NH2, the
light blue deepened; with t-C4H9NH2, the color became
brown.
[Cd(l2-N,O-p-NH2C6H4SO3)2(H2O)2] is a layered coor-
dination compound with a 2D structure [3]. It can react
with amine vapors and produce mono-amine coordinated
complexes. [Cd(p-NH2C6H4SO3)2] (III) was obtained by
dehydrating [Cd(l2-N,O-p-NH2C6H4SO3)2(H2O)2] and is
also a crystalline material. [Cd(p-NH2C6H4SO3)2] (III)
can uptake 3 moles of CH3NH2, 4 moles of C2H5NH2, n-
C3H7NH2 and n-C4H9NH2, and 1 mole of i-C3H7NH2. It
is interesting to note that III has a much stronger amine-
intercalation property for amines with a longer chain than
that of [Cd(l2-N,O-p-NH2C6H4SO3)2(H2O)2]. [Cd(p-NH2-
C6H4SO3)2] (III) can uptake 4 moles of n-C4H9NH2, while
its hydrated form can only uptake 1 mole of n-C4H9NH2.
This observation can be explained by the result that dehy-
dration creates vacant reaction sites in Cd(II) that are more
accessible for amines with longer carbon chains.
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
ꢀ
P1
˚
a (A)
8.093(3)
9.907(3)
11.212(4)
76.573(5)
78.813(5)
83.288(5)
855.4(5)
1
1.416
0.810
382
0.48 · 0.45 · 0.42
2.12–27.00
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Dcalc (Mg/m3)
Absorption coefficient (mmÀ1
F(000)
)
Crystal size (mm)
h Range for data collection (ꢁ)
Limiting indices
À10 6 h 6 10,
À12 6 k 6 12,
À14 6 l 6 13
7288/3665 [0.0163]
97.8
Reflections collected/unique [Rint
Completeness to h = 27.00 (%)
Absorption correction
Maximum and minimum transmission
Refinement method
]
empirical
0.7272 and 0.6971
full-matrix least-squares on F2
3665/3/192
1.079
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Largest different peak and hole (e A
R1 = 0.0222, wR2 = 0.0591
R1 = 0.0240, wR2 = 0.0605
0.259 and À0.352
All complexes release amine molecules at temperatures
higher than 50 ꢁC, after the boiling points of the free amine
molecules, indicating the coordinative nature of the amine
ligands to the metal centers. Considering the compatible
coordination strength of H2O and –SO3, whether the water
molecules or the sulfonate groups occupy the spare coordi-
nation sites of the metal centers is not clear.
À3
˚
)
Absorption corrections were applied by SADABS [8]. The
structure was solved by direct methods and refined using
full-matrix least-squares/difference Fourier techniques by
SHELXTL [9]. All non-hydrogen atoms were refined with
anisotropic displacement parameters. After that, all hydro-
gen atoms of the ligands were placed in idealized positions
and refined as riding atoms with the relative isotropic
parameters. Crystal data are listed in Table 3.
There are strong peaks around 3150–3350 cmÀ1 in the
IR spectra of all the amine complexes, corresponding to
the stretching bands of the coordinated N–H groups. There
are alkyl C–H stretching bands observed around 2900–
3000 cmÀ1 that are contributed by the alkyl amines, con-
firming the existence of the adducted amine molecules.
The broad bands around 3500 cmÀ1 are contributed by
the O–H stretching of the water molecules.
3. Results and discussion
3.1. Syntheses and characterization
All the amine-coordinated complexes obtained via the
solid–vapor reactions are crystalline materials, similar to
that observed in the Cd(II) analogs [2,3]. The C2H5NH2
and n-C3H7NH2 products of [Cd(p-NH2C6H4SO3)2] (III)
grow into single crystals in situ in the solid–vapor reac-
tion, which makes direct structure characterization
possible.
[Cu(1,5-nds)(H2O)4]n (I) and [Cu(H2O)6](1,5-nds) (II)
were obtained via the reaction between CuCl2 and 1,5-
naphthalenedisulfonate acid (1,5-nds) in aqueous media
at different temperatures [7]. In I, Cu(II) is coordinated
by the sulfonate group as well as by 4 water molecules,
while one –SO3 group coordinates as a g2 l2 ligand to
two different [Cu(H2O)4]+ ions in syn/anti fashion, result-
ing in a one-dimensional structure, as shown in Fig. 3. In
II, Cu(II) is coordinated by 6 water molecules and the sul-
fonate is the counter anion. They show different reactivity
toward amine vapors, with II being more reactive than I.
However, they produce the same final amine-coordinated
complexes. Both complexes can quantitatively take up to
3.2. Reaction selectivity and preference
[Cu(1,5-nds)(H2O)4] (I) and [Cu(H2O)6](1,5-nds) (II) do
not react with (C2H5)3N and PhNH2. [Cd(p-NH2C6H4-
SO3)2] (III) does not react with NH2CH2CH2NH2,
(C2H5)2NH and PhNH2.In order to reveal the reaction
preferences toward different amines, the absorption exper-

P. Liu et al. / Polyhedron 25 (2006) 3045–3052
3049
(a)
(b)
Fig. 3. Structures of [Cu(1,5-nds)(H2O)4]n (I) (a) and [Cu(H2O)6](1,5-nds) (II) (b). The dashed lines represent the hydrogen bonds formed between the –
SO3 groups and H2O.
iments of I and II with mixed amines CH3NH2/C2H5NH2
and C2H5NH2/(C2H5)2NH were conducted, and the results
are shown in Fig. 4. The PXRD spectra of the resulting
amine adduct is identical to that observed for Cu(1,5-nds)-
(H2O)2(C2H5NH2)4, indicating that compound I has pref-
erential reaction behavior, a similar observation made in
its Cd(II) analogs [2,3].
C6H4SO3)2(H2O)2] [3]. The crystal obtained in the case of
C2H5NH2 exposure has the cell parameters a = 10.751(3),
˚
b = 7.876(2), c = 18.994(5) A, a = 90, b = 100.432(5), c =
90ꢁ, similar to that of [Cd(C2H5NH2)4(H2O)2](p-H2NC6-
H4SO3)2 [3], suggesting that water molecules were taken up
from the C2H5NH2 solution and the same complex as that
from [Cd(l2-N,O-p-NH2C6H4SO3)2(H2O)2] was formed.
It is noted that there are two forms of crystals produced
in the case of n-C3H7NH2 exposure. One of them has cell
3.3. Crystal structure of [Cd(n-C3H7NH2)4(H2O)2]
(p-H2NC6H4SO3)2
˚
parameters a = 8.016(2), b = 15.422(4), c = 15.680(4) A,
a = 89.097(3), b = 88.123(3), c = 78.069(3)ꢁ, similar to that
recorded for [Cd(n-C3H7NH2)4(p-H2NC6H4SO3)2] Æ C3H7-
NH2 [3]. The other one is [Cd(n-C3H7NH2)4(H2O)2]-
(p-H2NC6H4SO3)2. The coordination structure of [Cd-
(n-C3H7NH2)4(H2O)2](p-H2NC6H4SO3)2, as well as that
of [Cd(n-C3H7NH2)4(p-H2NC6H4SO3)2] Æ C3H7NH2 [3] are
When exposed to C2H5NH2 and n-C3H7NH2, the powder
compound [Cd(p-NH2C6H4SO3)2] (III) became moisturized
and single crystals were formed after 2–4 weeks which could
be used directly for single crystal structure analysis, a phe-
nomenon similar to that observed for [Cd(l2-N,O-p-NH2-

3050
P. Liu et al. / Polyhedron 25 (2006) 3045–3052
I / CH NH -C H NH
3
2
2 5
2
I / C H NH
2
5
2
I / CH NH
3
2
I
10
20
30
40
2theta/o
II / C H NH - (C H ) NH
2 5 2 5 2
2
II / (C H ) NH
2 5 2
II / C H NH
2
5
2
II
10
20
30
40
2theta/o
Fig. 4. PXRD of I and II with mixed amines.
shown in Fig. 5. In [Cd(n-C3H7NH2)4(H2O)2](p-H2NC6-
H4SO3)2, four C3H7NH2 molecules substitute the p-H2-
C3H7NH2 crystals decayed and lost reflection power
quickly when exposed to air [3], while [Cd(n-C3H7NH2)4-
(H2O)2](p-H2NC6H4SO3)2 is much more stable.
NC6H4SOÀ ligands from the Cd(II) coordination sphere,
3
and there are two water molecules coordinated to the metal
center. The Cd–N distances are 2.3483(15) and 2.3231(16)
A, which are consistence with those observed in its analogs
The TGA behavior of the n-C4H9NH2 complex of III is
similar to that of C2H5NH2 and n-C3H7NH2, suggesting
that the n-C4H9NH2 complex could have a similar coordina-
tion structure as that of [Cd(C2H5NH2)4(H2O)2](p-H2NC6-
H4SO3)2 and [Cd(n-C3H7NH2)4(H2O)2](p-H2NC6H4SO3)2,
with 4 n-C4H9NH2 and 2 water molecules coordinated to
Cd(II).
˚
[3]. In [Cd(n-C3H7NH2)4(p-H2NC6H4SO3)2] Æ C3H7NH2,
four amines replace the two coordinated water molecules
and –NH2 groups of the two p-H2NC6H4SOÀ ligands,
3
and the two sulfonates remain coordinated to Cd(II).
The PXRD obtained for the final absorption powder is
identical to that simulated for the single crystal structure of
[Cd(n-C3H7NH2)4(H2O)2](p-H2NC6H4SO3)2, as shown in
Fig. 6, indicating that [Cd(n-C3H7NH2)4(p-H2NC6H4-
SO3)2] Æ C3H7NH2 could be an intermediate product which
is not stable and transforms into [Cd(n-C3H7NH2)4(H2O)2]-
(p-H2NC6H4SO3)2. This conclusion is also supported by the
observation that [Cd(n-C3H7NH2)4(p-H2NC6H4SO3)2] Æ
4. Summary
The solid–vapor reaction between metal sulfonates and
amines has been extended from cadmium(II) to cop-
per(II), and the properties of three transition metal com-
pounds [Cu(1,5-nds)(H2O)4]n (I), [Cu(H2O)6](1,5-nds) (II)
and [Cd(p-NH2C6H4SO3)2] (III) with alkyl amines were

P. Liu et al. / Polyhedron 25 (2006) 3045–3052
3051
(a)
(b)
Fig. 5. The coordination structures of [Cd(n-C3H7NH2)4(H2O)2](p-H2NC6H4SO3)2 (a) and [Cd(n-C3H7NH2)4(p-H2NC6H4SO3)2] Æ C3H7NH2 (b).
Hydrogen bonds are represented as dashed lines. Both Cd(II) centers locate on the symmetric centers and only the independent atoms are labelled.
Hydrogen atoms bonded to carbon atoms are omitted for clarity.
investigated and the reaction products were characterized.
The results show that the single phase monoamine-coordi-
nated copper(II) and cadmium(II) complexes could be
obtained without using any solvent or involving any puri-
fication process. The distinctive heterogeneous reaction
can be employed as a solvent-free method to synthesize
monoamine-coordinated Cu(II) and Cd(II) complexes.
Furthermore, single crystals of the reaction products
could be obtained in situ of the heterogeneous reaction
process, which represents a unique method to obtain a
single crystal via a green route [10].
5. Supplementary data
Crystallographic data for [Cd(n-C3H7NH2)4(H2O)2]
(p-H2NC6H4SO3)2 has been deposited with the Cambridge
Crystallographic Data Center as supplementary publica-
tion number CCDC 290252. Copies of the data can be

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P. Liu et al. / Polyhedron 25 (2006) 3045–3052
III / n-C H NH
3 7
2
Simulated by crystal structure of
Cd C H NH H O H NC H SO
3 7 2 4 6 4 3 2
2
2
2
Simulated by crystal structure of
Cd C H NH H NC H SO
C H NH
3 7 2
3 7 2 4 6 4 3 2
2
10
20
30
40
2theta/o
Fig. 6. PXRD of the n-C3H7NH2 complex obtained from the reaction powder and the simulated PXRD from single crystal structures.
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obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44(0)
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