Low-dimensional compounds containing cyano groups. XIX. Crystal structure, spectroscopic, thermal and magnetic properties of {[Cu(tn)2]3[Pt(CN)4]2}[Pt(CN)4] (tn = 1,3-diaminopropane) complex

Article abstract of DOI:10.1016/j.ica.2009.06.014

Violet prismatic crystals of {[Cu(tn)₂]₃[Pt(CN)₄]₂}[Pt(CN)₄] (tn = 1,3-diaminopropane) were crystallized from the water-methanol solution containing CuCl₂·2H₂O, tn and K₂

Full text of DOI:10.1016/j.ica.2009.06.014

Inorganica Chimica Acta 362 (2009) 4152–4157
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Low-dimensional compounds containing cyano groups. XIX. Crystal structure,
spectroscopic, thermal and magnetic properties of {[Cu(tn) ] [Pt(CN) ] }[Pt(CN) ]
2
3
4 2
4
(
tn = 1,3-diaminopropane) complex
a,*
a
b
c
d
d
ˇ
Ivan Poto cˇ nˇ ák , Martin Vavra , Erik Ci zˇ már , Michal Dušek , Thomas Müller , Dirk Steinborn
a
Department of Inorganic Chemistry, Institute of Chemistry, P.J. Šafárik University, Moyzesova 11, SK–04154 Košice, Slovakia
Centre of Low Temperature Physics, P.J. Šafárik University, Park Angelinum 9, SK–04154 Košice, Slovakia
Institute of Physics, Na Slovance 2, CZ–18221 Praha 8, Czech Republic
Institute of Chemistry, Inorganic Chemistry, Martin-Luther University Halle–Wittenberg, Kurt–Mothes–Street 2, D–06120 Halle, Germany
b
c
d
a r t i c l e i n f o
a b s t r a c t
Article history:
2 3 4 2 4
Violet prismatic crystals of {[Cu(tn) ] [Pt(CN) ] }[Pt(CN) ] (tn = 1,3-diaminopropane) were crystallized
Received 6 March 2009
Received in revised form 4 June 2009
Accepted 9 June 2009
from the water–methanol solution containing CuCl
2
ꢀ2H
2
O, tn and K
2
[Pt(CN)
4
]ꢀ3H
2
O. Prepared complex
was characterized using elemental analysis, infrared and UV–Vis spectroscopy, magnetic measurement
and thermal analysis. X-ray analysis revealed an ionic character of the complex containing mononuclear
Available online 13 June 2009
2
ꢁ
2+
square planar [Pt(CN)
4
]
2 4 2 4 2
complex anions and penta-nuclear [Cu(tn) -Pt(CN) -Cu(tn) -Pt(CN) -Cu(tn) ]
complex cations. The inner Cu(II) atom of the complex cation is hexa-coordinated, whereas two crystal-
lographically equivalent peripheral Cu(II) atoms are penta-coordinated in the shape of a deformed square
pyramid. Four v(C„N) absorption bands observed in the IR spectrum are in agreement with the higher
number of crystallographically different cyano groups and a broad highly asymmetric band observed
in the reflectance UV–Vis spectrum is consistent with the presence of both hexa- and penta-coordinated
Cu(II) atoms in the structure. The temperature dependence of the inverse susceptibility suggests the pres-
ence of a weak antiferromagnetic exchange coupling between Cu(II) ions. The complex is stable up to
Keywords:
X-ray crystal structure
Thermal studies
Spectroscopic studies
Magnetic studies
[
4 2
Pt(CN) ] -anion
210 °C when its two-stage thermal decomposition starts.
Ó 2009 Elsevier B.V. All rights reserved.
1
. Introduction
The particular characteristics of the cyano ligand have accorded
an exchange path mediating the interaction among spins localized
on paramagnetic centers. Dimensionality of a magnetic subsystem
is fundamental for cooperation processes, but it does not mean that
the magnetic and structural dimensionality must be the same. The
increase of magnetic dimensionality can be caused by the influence
it wide-ranging interest in various research areas [1,2]. One of the
more interesting characteristics of C„N is its ability to act either
ꢁ
as a terminal or as a bridging ligand. When it acts as a bridging li-
gand, it usually gives rise to the formation of oligonuclear com-
plexes or to polymeric compounds with one– (1D), two– (2D) or
three–dimensional (3D) structures [3]. Several detailed reviews
on cyano metal complexes describing their structures, reactivity
and physical properties have been published over the years [4–6]
of hydrogen bonds (HBs),
[8].
p–p and also dipole–dipole interactions
Previous studies on the structure and magnetic properties of
[CuL
2
4
][M(CN) ] (L = en (ethylenediamine), men (N-methylethylen-
0
ediamine), dmen (N,N-dimethylethylenediamine), bmen (N,N -
dimethylethylenediamine), bpy (2,2 –bipyridine); M = Ni, Pd, Pt)
[7,9–14] revealed that despite the 1D chain-like character of their
structures they behave as 2D magnets, which could be explained
by the formation of HBs linking the neighboring chains and thus
serving as exchange paths for magnetic interactions.
0
2ꢁ
and the review of coordination modes of [Pt(CN)
been presented in our previous paper [7].
4
]
anion has
Recently, cyano complexes with various degrees of dimension-
ality have been the subject of magnetic studies. In this case, the cy-
ano group or cyano complex anion in addition to its structural
function also exhibits an important electronic function: it forms
Therefore, with the aim to modify the HBs system in low-
dimensional [CuL ][M(CN) ] tetracyanometallates and to decrease
2 4
the magnetic dimensionality to 1D, we have decided to prepare a
compound with a different ligand L, namely with a tn (1,3-diami-
nopropane) ligand. As a result of our efforts, the title compound,
Abbreviations: v, stretching; d, scissoring;
vibrations; vs, very strong; s, strong; m, middle; w, weak vibrations; sh, shoulder.
x, wagging; s, twisting; r, rocking
{
[Cu(tn)
2 3 4 2 4
] [Pt(CN) ] }[Pt(CN) ] (1), was prepared. In this paper,
*
Corresponding author. Tel.: +421 55/234 2335; fax: +421 55/62 221 24.
E-mail address: ivan.potocnak@upjs.sk (I. Poto cˇ nˇ ák).
we describe its preparation along with its characterization using
0
020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.06.014

I. Poto cˇ nˇ ák et al. / Inorganica Chimica Acta 362 (2009) 4152–4157
4153
infrared and UV–Vis spectroscopy, elemental, thermal and X-ray
crystal structure analyses and measurement of magnetic
properties.
Table 1
Crystal data and structure refinement of 1.
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
C30H60Cu N24Pt3
3
1532.91
120
2
. Experimental
0.71073
monoclinic
C 2/c
2.1. Materials
Space group
Unit cell dimensions (Å)
27.623(4)
1
1
4.715(2); 121.520(12)°
4.1070(17)
Copper chloride dihydrate (CuCl
of Merck quality and used as received. K
pared according to the literature [15].
2
ꢀ2H
2
O) and tn (C
3
H
10
N
2
) were
2 4
[Pt(CN) ]ꢀ3H
2
O was pre-
Volume (Å3)
4888.1(11)
4; 2.083
9.885
Z; density (calculated) (g cm 3)
Absorption coefficient (mmꢁ1)
F(0 0 0)
ꢁ
2916
2
.2. Synthesis
Crystal shape, color
Crystal size (mm)
h Range for data collection (°)
Index ranges
Reflections collected
Independent reflections
Completeness to hmax
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
prism, violet
0.576 ꢂ 0.474 ꢂ 0.442
2.63–25.25
{
[Cu(tn)
methanol solution (1:1) of CuCl
tn (0.17 ml, 2 mmol) was added in one portion. After 30 min, aque-
ous solution of K [Pt(CN) ] (0.216 g of K [Pt(CN) O, 0.5 mmol)
]ꢀ3H
was added in one portion too. Four days later, the violet crystals of 1
2
]
3
[Pt(CN)
4
]
2
}[Pt(CN)
4
] (1). Into 20 ml of stirring water–
ꢁ33<=h<=33, ꢁ17<=k<=17, ꢁ16<=l<=16
2
(0.085 g of CuCl O, 0.5 mmol),
2
ꢀ2H
2
29 645
4429 [Rint = 0.0349]
2
4
2
4
2
99.9%
Full-matrix least-squares on F2
ꢁ1
were filtrated off and dried on air. Yield 81%. IR (4000–400 cm
KBr pellets): (N–H) = 3302 vs, 3277 m, 3252 s, 3167 m; (C–
H) = 2939 w, 2893 w; (C„N) = 2168 w, 2150 m, 2133 vs, 2125 s,
sh; d(ANH ) = 1630 w, 1605 s; d(ACH A) = 1470 w, 1460 w;
(ACH A) = 1433 m, 1406 m; (ANH ) = 1321 w, 1311 w;
(ACH A) = 1286 m; (ANH ) = 1165 s; (ANH ) = 1097 w; (C–
N) = 1026 s; (C–C) = 1013 vs; (ACH A) = 920 w, 905 s, 883 w;
(ANH ) = 694 s; (PtAC) = 494 m, 417 w, 405 m. UV–Vis (solid
1
state): 370 nm ( B1g ? E ? E). Anal. Calc. for
,
4429/0/274
1.038
m
m
Final R factors [I > 2
R factors (all data)
Largest difference in peak and hole
r(I)]
R
R
1
= 0.0141, wR
= 0.0169, wR
2
2
= 0.0341
m
1
= 0.0344
ꢁ3
2
2
0.830 and ꢁ0.977 e Å
x
s
2
x
2
2
x
2
s
2
m
m
r
2
3
. Results and discussions
.1. Preparation of the title complex
The title complex 1 has been prepared in a relatively facile way
r
2
v
2
2
2
2
g
), 420–450 nm ( B
3
: C, 23.51; H, 3.95; N, 21.93. Found: C, 23.48; H,
3
C
4
30
H
60
N
3
24Cu Pt
.51; N, 21.41%.
within our studies on the role of hydrogen bonds as possible ex-
change paths for magnetic interactions in low-dimensional com-
pounds. To prepare the desired complex, we have used the same
procedure as well as the same molar ratios between Cu(II), tn
2
.3. Physical measurements
Elemental analysis for C, H and N was carried out using an LECO
2ꢁ
and [Pt(CN)
chain-like [CuL
bpy) [7,13,14]. Although the results of the elemental analysis were
in good agreement with an expected [Cu(tn) ][Pt(CN) ] composi-
tion, the IR spectrum of 1 contained unusually high number of
(C„N) vibrations and thus indicated a different composition with
4
]
as were used in the preparation of previous
CHNS–932. IR spectrum was recorded on an Avatar 330 FT-IR Spec-
trometer from ThermoNicolet by the method of KBr pellets in the
range from 4000 to 400 cm . Reflectance UV–Vis spectrum was
measured with Perkin–Elmer UV/VIS/NIR Spectrometer Lambda
2
][Pt(CN) ] complexes (L = en, dmen, bmen and
4
ꢁ1
2
4
1
9. The thermal investigation was performed using a NETZSCH
v
STA 409C/CD thermal analyzer under air conditions with a heating
rate of 10 K/min to 900 °C. Measurement of magnetic susceptibility
was carried out on a powdered sample using a commercial SQUID
magnetometer in the temperature range from 2 to 300 K in mag-
netic field 0.1 T. The background contribution from the gelcap
and core diamagnetic contribution of the sample, estimated using
a more complicated structure. This was definitely confirmed by the
X-ray analysis which revealed that compound 1 is an ionic sub-
stance with the {[Cu(tn)
2 3 4 2 4
] [Pt(CN) ] }[Pt(CN) ] formula.
3.2. X-ray crystallography
ꢁ9
3
ꢁ1
Pascal’s constants [16] to be
been subtracted.
v
DIA = ꢁ1.95 ꢂ 10 m mol , have
According to the result of CHN analysis a simple chain-like
[Cu(tn) ][Pt(CN) ]} structure of 1 was expected. An X-ray analysis
has revealed that the compound 1 has the same summary formula,
nevertheless the crystal structure of consists of discrete
anions and bulky penta-nuclear [Cu(tn) –Pt(CN)
{
2
4
n
2.4. X-ray data collection and structure refinement
1
2
ꢁ
[
Pt(CN)
4
]
2
4
–
2
+
2ꢁ
4
A summary of crystal data and structure refinement for 1 is pre-
Cu(tn) –Pt(CN)
2
4
–Cu(tn)
2
]
cations with two bridging [Pt(CN) ]
sented in Table 1. The crystal structure of 1 was determined using
an Oxford Diffraction diffractometer equipped with the CCD detec-
tor. Crysalis CCD [17] was used for data collection while Crysalis
RED [17] was used for cell refinement, data reduction and absorp-
tion correction. Structure was solved by the direct method with
SHELXS97 [18] and subsequent Fourier syntheses using SHELXL97
moieties (Fig. 1). The structure of 1 is rather unusual as there are
only a few tetracyanoplatinates containing oligonuclear moieties
described in the literature so far. To the best of our knowledge,
excluding four striking compounds with either tetradeca- (one
compound), or nonadeca- (one compound) or eicosi-nuclear (two
compounds) molecules or molecular cations in their solid state
structures [21], there are several bi-, tri-, tetra- and penta-nuclear
compounds known, which contain at least one bridging cyano
group. Namely, two bi-nuclear complexes with one cyano bridge
(Scheme 1a; M = Cu(II) [22,23]), six tri-nuclear complexes with
two bridging cyano groups (five of them with bridging cyano
groups in trans positions (Scheme 1b; M = 2 ꢂ Cu(II) [23], 2 ꢂ Ru(II)
[24] and Fe(III) [25]) and one of them with cis-arrangement of
[
18]. Anisotropic displacement parameters were refined for all
non-H atoms. The H atoms were placed in calculated positions
and refined riding on their parent C or N atoms with C–H and N–
H distances of 0.97 and 0.90 Å, respectively, and Uiso(H) = 1.2 Ueq(C
or N). An analysis of bond distances and angles was performed
using SHELXL97 and PARST [19]. DIAMOND [20] was used for molecular
graphics.

4
154
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N3
C3
C2i
C2 N2
Pt1
N30
Cu2
N21
Cu2i
C1
N1
N20
N31
N8
C8
N7
N10i
N11i
C7
Pt2 i
N10
Pt2
Cu1
C5
C6
N6
N5
N11
Fig. 1. The crystal structure of 1 with displacement ellipsoids (55% probability) and labeling of selected atoms. Symmetry transformation used to generate equivalent atoms:
i) ꢁx, y, ꢁz + ½.
(
N
C
bridging cyano groups (Scheme 1c; M = Ni(II) [26]), two tetra-nu-
clear square–like complexes with two bridging cyano groups in
cis mode (Scheme 1d; M = Cu(II) [3] and Ni(II) [27]) and, finally,
one penta-nuclear complex with all four bridging cyano groups
M
N
C
Pt
C
N
(Scheme 1e; M = Cu(II) [23]) have been observed. All of the above
C
N
mentioned complexes contain in their structure only one kind of
2
ꢁ
[
Pt(CN)
4
]
units with either one, two or four bridging cyano
2
ꢁ
groups, whereas in 1 there are two kinds of [Pt(CN)
4
]
units; one
1
a
of them with two bridging cyano groups, is a part of the complex
cation and the other one is a discrete anion with all four cyano
groups coordinated monodentatelly.
N
C
M
M
The inner Cu1 atom of the penta-nuclear complex cation, lo-
cated at the two-fold rotation axis, is six–coordinate in a slightly
deformed elongated tetragonal bipyramidal arrangement (4 + 2
form) with the tetragonality factor T of 0.819 [28]. The equatorial
plane of the tetragonal bipyramid is defined by the two nitrogen
atoms of a chelate bonded tn molecule (Cu1–N10 = 2.046(2) Å
and Cu1–N11 = 2.033(2) Å) and the corresponding nitrogen atoms
of the symmetrically arranged second tn molecule. The axial posi-
tions are occupied by the N5 atom of the bridging cyano group and
its symmetrically related partner at a significantly longer distance
N
N
N
C
C
C
C
M
N
C
Pt
C
N
M
Pt
C
N
N
1
b
1c
M
N
N
9
Cu1–N5 = 2.490(3) Å (Table 2), which is characteristic for d sys-
C
C
C
tems. The Cu1–N5 bonds are 7.64(8)° tilted from the normal to
Pt
4
the CuN equatorial plane.
N
C
i
The peripheral Cu2 atom (and its symmetrically related Cu2 ,
symmetry code: (i) ꢁx, y, ꢁz + ½) is five-coordinate by four nitro-
gen atoms of two crystallographically independent tn ligands in
the basal plane and one nitrogen atom (N8) from bridging cyano
group in the apical position, respectively. The Cu–N bond lengths
in the basal plane adopt similar values with an average value of
2.038(7) Å. The apical Cu2–N8 bond is significantly longer
C
N
N
N
M
M
M
N
C
Pt
C
N
M
N
C
N
C
C
C
C
Pt
(
4
2.216(2) Å) and is tilted from the normal to the CuN basal plane
M
by 1.17(8)° thus forming a slightly deformed square pyramidal
N
N
geometry with Cu2 atom raised from the basal plane by
0
.2342(4) Å. The s parameter of 12.6, which assigns values of 100
1
d
1e
for an ideal trigonal bipyramid and zero for an ideal square pyra-
mid [29], is in good agreement with a slightly deformed square
pyramidal coordination.
Scheme 1. Structural types of bi-, tri-, tetra- and penta-nuclear compounds of
tetracyanoplatinates.

I. Poto cˇ nˇ ák et al. / Inorganica Chimica Acta 362 (2009) 4152–4157
4155
Table 2
to the corresponding values in 1. On the other hand, as the inner
Cu(II) atom in the mentioned compound does not lie on a rotation
axis, the two Cu1–N(cyano) bonds of bridging cyano groups are
substantially different (2.458(3) and 2.828(3) Å) and the coordina-
tion polyhedron is described as an unsymmetrically deformed
octahedron (4 + 1 + 1 form). Moreover, although the peripheral
Cu2 atom is also in a square pyramidal coordination, still the
Cu2–N8 bond distance of 2.444(4) Å is somewhat longer than the
Selected bond lengths (Å) and bond angles (°) of 1.
Cu1–N5
2.490(3)
2.046(2)
2.033(2)
2.216(2)
2.047(2)
2.031(2)
2.040(2)
2.034(2)
N11–Cu1–N11i
N11–Cu1–N10
91.35(14)
88.22(10)
179.24(10)
92.22(14)
97.89(9)
90.41(9)
89.03(9)
82.74(9)
150.2(2)
Cu1–N10
Cu1–N11
Cu2–N8
Cu2–N20
Cu2–N21
Cu2–N30
Cu2–N31
i
N11–Cu1–N10
N10–Cu1–N10
i
N11–Cu1–N5
i
N11 –Cu1–N5
N10–Cu1–N5
i
N10 –Cu1–N5
respective distance in 1.
C5–N5–Cu1
2ꢁ
Square planar [Pt(CN)
4
]
moiety (and its symmetrical unit), as
N20–Cu2–N8
N21–Cu2–N8
N30–Cu2–N8
N31–Cu2–N8
N21–Cu2–N20
N30–Cu2–N20
N31–Cu2–N20
N21–Cu2–N30
N21–Cu2–N31
N31–Cu2–N30
C8–N8–Cu2
94.74(9)
99.70(9)
94.67(9)
a part of the penta-nuclear complex cation in 1, connects Cu1 and
Cu2 atoms by two cis–arranged bridging cyano groups forming a
Cu2ꢀ ꢀ ꢀPt2ꢀ ꢀ ꢀCu1ꢀ ꢀ ꢀPt2ꢀ ꢀ ꢀCu2 metal chain within one complex cat-
97.39(10)
87.70(10)
170.41(10)
89.56(10)
88.95(10)
162.86(10)
91.00(10)
154.3(2)
ion. According to our knowledge, the cis-arrangement of two bridg-
2ꢁ
ing cyano groups within a [Pt(CN)
4
]
unit has been observed only
in one 1D [32] and in three polynuclear complexes. Two of them
are above mentioned tetra-nuclear square-like complexes [3,27]
whereas the third one is one of the above mentioned tri-nuclear
complexes [26]. Despite the different character of the cyano groups
in 1, the Pt2–C and C„N bond distances as well as Pt2–C„N angles
for bridging and terminal cyano groups are very similar and in ex-
pected ranges. On the other hand, the cyano groups coordinate to
the copper(II) centers in a significantly bent way as evidenced from
the Cu1–N5„C5 and Cu2–N8„C8 angles of 150.2(2) and
154.3(2)°, respectively. Such values are not unusual and indicate
a contribution of the ionic character to the Cu–N bond [7,33,34].
Symmetry transformations used to generate equivalent atoms: (i) ꢁx, y, ꢁz + ½.
The Cu–tn metallocycles in both coordination polyhedra are in a
chair conformation, exhibiting usual values of bond distances and
angles within the tn molecules.
2
There are 14 structures with (tn) Cu–N„C moieties listed in the
2
ꢁ
Cambridge Structural Database [30]. Seven of them contain hexa-
coordinated Cu(II) atoms, whereas five structures are with penta-
coordinated Cu(II) atoms. Nevertheless, the bond distances and
bond angles around the two types of Cu(II) atoms are comparable
with the corresponding values in 1. The remaining two structures
contain both hexa- and penta-coordinated Cu(II) atoms. One of
The Pt1 atom in the mononuclear [Pt(CN)4] complex anion in
1, located at the same two-fold rotation axis as the Cu1 atom, is, as
expected, in a square planar geometry of four cyano groups, which
are terminally coordinated at the same distance (within 3 r), with
the average Pt1–C bond distance of 1.991(5) Å. The C„N bonds and
Pt1–C„N angles adopt usual values (1.152(4) Å and 179.2(8)° on
average) observed also in other tetracyanoplatinates [3,23].
All nitrogen atoms of terminal cyano groups of both kinds of
them, {[Cu(tn)
Ni(CN) –Cu(tn)
penta-nuclear cations in 1 in missing one peripheral Cu(tn)
2
]
2
[Ni(CN)
4
]
2
}ꢀH
2
O, is formed by tetra-nuclear
] molecules, which differ from
moi-
[
4
2
–Ni(CN)
4
–Cu(tn)
2
2
ꢁ
2
[Pt(CN)4] moieties in 1 are involved in a complicated system
of intermolecular N–Hꢀ ꢀ ꢀN hydrogen bonds (Fig. 2, Table 3), which
contribute to the stabilization of the structure and which
ety [31]. The bond distances between two kinds of Cu(II) atoms
and nitrogen atoms of tn molecules in this compound are similar
N11
N11
N6
N3
N6vi
N2i
Pt1
N2
N7
N30i
Cu2i
N21i
N20i
N30
N7vi
N31i
N31
Cu2
N21
N30
N1
N31
N11
N11
N31
Pt2
N6
N20
N10
Cu1
N7
N7i
N30
Pt2i
N10i
N6
N6v
N6i
N11i
N7ii
N11
N20
N7
N31
N20
N31
N3iii
Fig. 2. Hydrogen bonds (dashed lines) in 1. Only NH
2
groups of tn molecules are shown because of clarity. Symmetry transformations used to generate equivalent atoms: (i)
ꢁ
x, y, ꢁz + ½; (ii) x ꢁ ½, ꢁy + 1½, z ꢁ ½; (iii) x, y ꢁ 1, z; (v) ꢁx + ½, ꢁy + 1½, ꢁz + 1; (vi) x, ꢁy + 2, z ꢁ ½.

4
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I. Poto cˇ nˇ ák et al. / Inorganica Chimica Acta 362 (2009) 4152–4157
Table 3
1
1
1
.9
.8
.7
Hydrogen bonds for 1 (Å and °).
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
<(DHA)
8
00
N10–H10Aꢀ ꢀ ꢀN1
N21–H21Aꢀ ꢀ ꢀN2
N30–H30Bꢀ ꢀ ꢀN2
N11–H11Aꢀ ꢀ ꢀN7
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
0.90
2.28
2.18
2.32
2.22
2.26
2.26
2.31
2.17
2.28
2.46
3.161(4)
3.044(4)
3.197(4)
3.069(4)
3.153(4)
3.153(4)
3.174(4)
3.023(4)
3.138(3)
3.238(3)
167.7
161.8
165.5
157.9
168.9
168.9
159.7
158.4
159.5
144.3
g = 2.11
ii
1.6
1.5
1.4
600
400
200
0
Θ = -0.35 K
iii
iv
v
N11–H11Bꢀ ꢀ ꢀN3
N11–H11Bꢀ ꢀ ꢀN3
N31–H31Aꢀ ꢀ ꢀN6
v
N20–H20Bꢀ ꢀ ꢀN6
N31–H31Bꢀ ꢀ ꢀN7
N30–H30Aꢀ ꢀ ꢀN6
vi
vi
χ
1
1
1
1
.3
.2
.1
.0
Symmetry transformations used to generate equivalent atoms: (ii) x ꢁ ½, ꢁy + 1½,
z ꢁ ½; (iii) x, y ꢁ 1, z; (iv) ꢁx, y ꢁ 1, ꢁz + ½; (v) ꢁx + ½, ꢁy + 1½, ꢁz + 1; (vi) x,
ꢁ
y + 2, z ꢁ ½.
0
50 100 150 200 250 300
T (K)
connects single moieties of the structure in a 3D network. This
system of hydrogen bonds is more complicated than hydrogen
0
50
100
150
200
250
300
T (K)
2 4
bond systems observed in 1D [CuL ][Pt(CN) ] (L = en, dmen and
bmen) [7,13] compounds which contain only one or two crystalo-
graphically different terminal cyano groups in their structures in-
volved in hydrogen bonds. Thus, we could expect increased
magnetic dimensionality in 1 in comparison with the mentioned
compounds.
Fig. 3. Effective magnetic moment of 1. The inset shows the temperature
dependence of the inverse susceptibility (circles) with a fit to the Curie-Weiss
law (solid line).
ature range, with observed weight loss of 17%, involves the one-
step decomposition of cyanides which includes oxidation of twelve
CN groups to form six cyanogen molecules. Simultaneously, for-
3
.3. Spectroscopic studies
ꢁ
The IR spectrum of 1 comprises bands confirming the presence
mation of copper(II) oxide during reduction of three Pt(II) atoms
and one and a half oxygen molecules from the air ambient (calcu-
lated 17%) is observed. This process is accompanied by a strong
exothermic effect (maximum at 439 °C) as a consequence of the
cyanogen molecules pyrolysis. The final thermal decomposition
product is a mixture of CuO and metallic Pt (solid residue 55%; cal-
culated 54%). Thus, the most likely thermal decomposition scheme
for 1 is:
of all characteristic functional groups in the prepared complex
2ꢁ
[
35]. The presence of [Pt(CN)
4
]
anion in the prepared complex
is proved by
v(C„N) stretching vibrations whose positions are an
important tool to distinguish between terminal and bridging char-
acter of cyano group. According to [36,37], one can infer that the
bridging C„N group more strongly bound to the copper atom,
C8„N8, gives rise to the band at 2168 cm , whereas the
C5„N5, whose Cu1–N5 bond distance is longer, results in the band
at 2152 cm . The bands recorded at 2135 and 2125 cm can be
assigned to (C„N) stretching vibrations of terminal cyano groups.
Four (C„N) absorption bands observed in the spectrum of 1 are in
agreement with the higher number of crystallographically differ-
ent cyano groups in its structure; they are seven; and, moreover,
because there are eight terminal cyano groups in comparing with
four bridging cyano groups in one formula unit of 1, higher band
intensity for terminal groups is recorded.
ꢁ1
ꢄ
ꢁ1
ꢁ1
210ꢁ424 C
f½CuðtnÞ ꢃ ½PtðCNÞ ꢃ g½PtðCNÞ ꢃ
!
3Cu½PtðCNÞ4ꢃ
2
3
4
2
4
ꢁ
6tn
v
v
ꢄ
4
24ꢁ450 C
3Cu½PtðCNÞ ꢃ þ 3=2O
2
!
3CuO þ 3Pt
4
ꢁ6ðCNÞ
2
3.5. Magnetic properties
The reflectance UV–Vis spectrum of 1 consists of a broad, highly
asymmetric band with maximum at 370 nm with a shoulder,
which is not exactly distinctive somewhere between 420 and
From the susceptibility at T = 300 K, the effective magnetic mo-
ment may be quantified and yields a value typical for a Cu(II) cat-
9
ion with d configuration, namely
eff B
l /l = 1.83 (see Fig. 3). The
4
50 nm. Usually, one absorption band for six-coordinate and two
temperature dependence of the inverse susceptibility is character-
absorption bands for five-coordinate copper(II) complexes are
observed [28]. Therefore we suppose that the asymmetric band
in 1 is caused by an overlapping of absorption bands originating
ized by a Curie-like behavior with Curie temperature
H
= ꢁ0.35 K
and g = 2.11 suggesting the presence of a weak antiferromagnetic
exchange coupling between Cu(II) ions. As observed in our previ-
ous work [7], the exchange coupling mediated along the covalent
bonds is very weak in compounds from the same class and mag-
netic properties are governed by hydrogen-bond-mediated
exchange. We expect an increased magnetic dimensionality in
complex 1 due to the extended network of hydrogen bonds. A pos-
sible long-range magnetic order at very low temperatures is the
subject of further experimental studies.
from the CuN
.4. Thermal studies
The usual way of thermal decomposition of cyano complexes
6 5
and CuN chromophores.
3
with N-donor ligands is characterized by the liberation of N-donor
ligands followed by the separated decomposition of all cyano
groups in one-step. In accordance with this and with the results
of thermal decompositions of previously studied similar com-
pounds [7,13], the thermal decomposition of 1 is a two-stage pro-
cess. During the first stage, in the 210–424 °C temperature range, a
total weight loss of 27% corresponding to the release of six tn mol-
ecules (calculated 29%) is observed during two-step process (these
steps are overlapped). The second stage in the 424–450 °C temper-
4
. Conclusions
In this article, the synthesis, crystal structure, spectral, thermal
2 3 4 2 4
and magnetic properties of new {[Cu(tn) ] [Pt(CN) ] }[Pt(CN) ] (1)
complex have been investigated. The ionic structure of 1, con-
tains penta-nuclear [Cu(tn) –Pt(CN) –Cu(tn) –Pt(CN) –Cu(tn) ]
2 4 2 4 2
2+

I. Poto cˇ nˇ ák et al. / Inorganica Chimica Acta 362 (2009) 4152–4157
4157
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lic Pt being the final thermal decomposition product.
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