Cyanoplatinate Halides - Synthesis, Crystal Structure Analyses and Vibrational Spectroscopy of Compounds A2[Pt(CN)4X 2] (A = Rb, Cs; X = Cl, Br, I)

Article abstract of DOI:10.1515/znb-2010-0902

Crystal structures of the cyanoplatinates A₂[Pt(CN) ₄X₂] (A = Rb, Cs; X = Cl, Br, I) have been determined by single-crystal analysis and X-ray powder diffraction. The compounds were synthesizedb y metathesis from Ba[Pt(CN)₄]. 4 H₂O and alkali metal sulfates, and by subsequent oxidation with the respective halogens. The crystals were grown by slowly concentrating respective aqueous solutions. The Pt^IV cations are octahedrally coordinated by four cyanide ligands and two halogen atoms, the latter being located in trans positions. Rb ₂[Pt(CN)₄Cl₂]: triclinic, P^-1 (Z = 2), a = 6.7779(2), b = 9.3149(3), c = 9.6707(3) A, a = 89.37(0), β = 76.05(0), γ = 72.98(0)°, V = 565.42(2) A³, N′_hkl= 5616, R(F)_N′ = 0.0273; Rb ₂[Pt(CN)₄I₂]: monoclinic, P2₁/c (Z = 2), a = 7.4239(2), b = 9.2486(2), c = 9.1189(2) A, ss = 107.22(3)°, V = 598.04(6) A³, N_′hkl = 2917, R(F)N′ = 0.0295; Cs₂[Pt(CN)₄I₂]: monoclinic, P2₁/c (Z = 2), a = 7.6740(4), b = 9.5397(5), c = 9.3474(5) A , β = 106.46(0)°, V = 656.3(2) A³, Z = 2, N′_hkl = 2738, R(F)_N′ = 0.0283; Cs ₂[Pt(CN)₄Cl₂]: monoclinic, C2/c (Z = 4), a = 17.947(4), b = 7.395(2), c = 12.031(3) A, β = 131.904(1)°, V = 1188.4(5) A³, R-wp = 2.77; Cs₂[Pt(CN) ₄Br₂]: monoclinic, C2/c (Z = 4), a = 18.404(1), b = 7.2819(5), c = 12.4156(8) A, β = 132.156(1),° V = 1233.5(1) A³, N′_hkl = 2566, R(F)N′ = 0.0268. All compounds were characterized by differential thermal analysis, thermogravimetry, and infrared and Raman spectroscopy.

Full text of DOI:10.1515/znb-2010-0902

Cyanoplatinate Halides – Synthesis, Crystal Structure Analyses and
Vibrational Spectroscopy of Compounds A [Pt(CN) X ] (A = Rb, Cs;
2
4
2
X = Cl, Br, I)
Claus M u¨ hle, J u¨ rgen Nuss, Robert E. Dinnebier, and Martin Jansen
Max-Planck-Institut f u¨ r Festk o¨ rperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
Reprint requests to Prof. Dr. Dr. h. c. M. Jansen. Fax: +49(0)711 6891502.
E-mail: M.Jansen@fkf.mpg.de
Z. Naturforsch. 2010, 65b, 1066 – 1072; received May 21, 2010
Crystal structures of the cyanoplatinates A [Pt(CN) X ] (A = Rb, Cs; X = Cl, Br, I) have been de-
2
4 2
termined by single-crystal analysis and X-ray powder diffraction. The compounds were synthesized
by metathesis from Ba[Pt(CN) ] · 4 H O and alkali metal sulfates, and by subsequent oxidation with
4
2
the respective halogens. The crystals were grown by slowly concentrating respective aqueous solu-
IV
tions. The Pt cations are octahedrally coordinated by four cyanide ligands and two halogen atoms,
¯
the latter being located in trans positions. Rb [Pt(CN) Cl ]: triclinic, P1 (Z = 2), a = 6.7779(2), b =
2
4
2
˚
◦
˚ 3
ꢀ
9
.3149(3), c = 9.6707(3) A, α = 89.37(0), β = 76.05(0), γ = 72.98(0) , V = 565.42(2) A , N
=
hkl
5
616, R(F)N
ꢀ
= 0.0273; Rb [Pt(CN) I ]: monoclinic, P2 /c (Z = 2), a = 7.4239(2), b = 9.2486(2),
2
4 2
1
˚
◦
˚ 3
ꢀ
c = 9.1189(2) A, β = 107.22(3) , V = 598.04(6) A , N
= 2917, R(F) = 0.0295; Cs [Pt(CN) I ]:
ꢀ
hkl
N
2 4 2
˚
◦
monoclinic, P2 /c (Z = 2), a = 7.6740(4), b = 9.5397(5), c = 9.3474(5) A, β = 106.46(0) , V =
1
˚
3
ꢀ
56.3(2) A , Z = 2, N
hkl
6
= 2738, R(F)N = 0.0283; Cs [Pt(CN) Cl ]: monoclinic, C2/c (Z = 4),
ꢀ
2 4 2
˚
◦
˚ 3
a = 17.947(4), b = 7.395(2), c = 12.031(3) A, β = 131.904(1) , V = 1188.4(5) A , R-wp = 2.77;
˚
Cs [Pt(CN) Br ]: monoclinic, C2/c (Z = 4), a = 18.404(1), b = 7.2819(5), c = 12.4156(8) A, β =
2
4
2
◦
˚ 3 ꢀ
32.156(1) , V = 1233.5(1) A , N
hkl
1
= 2566, R(F) = 0.0268. All compounds were characterized
ꢀ
N
by differential thermal analysis, thermogravimetry, and infrared and Raman spectroscopy.
Key words: Platinum, Cyanides, Crystal Structures, X-Ray Scattering, Vibrational Spectroscopy
Introduction
lations in this class of compounds have been re-
vealed by Williams [5], who studied also the crys-
Platinum in its most common oxidation states tal structures of Rb [Pt(CN) Cl ] · 3 H O [6] and
2
4
0.33
2
of +II and +IV displays preferably square-planar Cs [Pt(CN) Cl ] [7] and their electrical properties
2
4
0.30
or octahedral coordination geometries, respectively. [8]. A recent overview was given in 2009 [9], ad-
Oxidation of cyanoplatinate complexes by halogens dressing the potential for the development of sen-
has been known for more than 150 years [1], sors and other technological applications using plat-
+
2.33
and the prototype of partially oxidized Pt
in inum polymers with short Pt–Pt distances. Partly ox-
K [Pt(CN) Br ] · 3 H O has been extensively stud- idized cyanoplatinate halides are obtained from mix-
2
4
0.33
2
ied and is well characterized by the original work of tures of the tetracyanoplatinate and the fully oxidized
Krogmann [2, 3], and further investigations by Zeller platinum halide complex in aqueous solution, and it
[
4]. A characteristic feature of the atomic structure of appeared desirable to also know the crystal struc-
cyanoplatinates(II) is the presence of columns built tures of compounds A [Pt(CN) X ] (A = alkali metal,
2
4 2
by Pt in a square-planar coordination of cyanide X = halogen) and of related series of oxidation prod-
groups. The Pt atoms approach each other realiz- ucts of cyanoplatinates which are precursors for the
˚
ing distances as short as 2.88 A, which is only one-dimensional complexes. So far, only the crys-
˚
slightly longer than in metallic platinum (2.77 A), sug- tal structures of Na [Pt(CN) Br ] · 2 H O [10] and
2
4
2
2
gesting one-dimensional metallic character and rela- Rb [Pt(CN) Br ] [11] had been reported a few years
2
4
2
tively high electron conductivity due to overlap of ago, and we determined the structures of the potassium
only partially filled Pt dz orbitals. Since Krogmann’s cyanoplatinate halides [12] and the hydrogen peroxide
pioneering work, amazing physical-structural corre- adducts A [Pt(CN) ] · H O (A = alkali metal) [13].
2
2
4
2
2
0
932–0776 / 10 / 0900–1066 $ 06.00 ꢀc 2010 Verlag der Zeitschrift f u¨ r Naturforschung, T u¨ bingen · http://znaturforsch.com
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C. M u¨ hle et al. · Cyanoplatinate Halides
1067
Table 1. Crystallographic data and data collection from single-crystal measurements.
Rb2[Pt(CN)4Cl2]
541.01
298(2)
Cs2[Pt(CN)4Br2]
724.81
298(2)
0.25 × 0.15 × 0.10
monoclinic
C2/c (15); 4
18.404(1)
7.2819(5)
12.4156(8)
90
132.156(1)
90
1233.49(14); 3.90
Smart APEX II
SADABS [17]
23.6
Rb2[Pt(CN)4I2]
723.91
298(2)
0.30 × 0.25 × 0.20
monoclinic
P21/c (14); 2
7.4232(5)
9.2468(6)
9.1165(6)
90
107.240(1)
90
597.65(7); 4.02
Smart APEX II
TWINABS [18]
24.9
Cs2[Pt(CN)4I2]
818.79
298(2)
0.25 × 0.20 × 0.12
monoclinic
P21/c (14); 2
7.6740(4)
9.5397(5)
9.3474(5)
−
1
Mr, g mol
Temperature, K
Crystal size, mm
Crystal system
3
0.15 × 0.18 × 0.25
triclinic
¯
Space group (no.); Z
P1 (2); 2
˚
a, A
6.7779(2)
9.3149(3)
9.6707(3)
89.373(1)
76.049(1)
72.978(1)
565.42(3); 3.18
Smart APEX II
SADABS [17]
21.4
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
90
106.461(1)
90
656.25(6); 4.14
Smart APEX I
SADABS [17]
20.8
˚
3
−3
V, A ; Dcalcd, g cm
Diffractometer
Absorption correction
µ(MoKα ), cm
−
1
F(000), e
476
1240
620
692
hkl range
−11 ≤ h ≤ +11
−29 ≤ h ≤ +29
−11 ≤ k ≤ +11
−19 ≤ l ≤ +19
2.99 – 34.35
9408 / 2566 / 0.029
62
−12 ≤ h ≤ +11
0 ≤ k ≤ +15
0 ≤ l ≤ +15
2.87 – 36.44
2913 / 2913 / 0
62
−12 ≤ h ≤ +11
−15 ≤ k ≤ +14
−14 ≤ l ≤ +14
2.77 – 34.90
9896 / 2738 / 0.0253
62
−
−
15 ≤ k ≤ +15
16 ≤ l ≤ +16
2
θ range, deg
2.17 – 37.45
14375 / 5616 / 0.046
122
ꢀ
Nall / N
/ Rint
uniqe
Param. refined
Extinction coefficient
0.0078(4)
0.00089(8)
0.0318 / 0.0268
0.0730 / 0.0697
0.0411 / 1.0348
1.057
0.0032(3)
0.0038(2)
a
R(F)N / R(F)N
wR(F )N / wR(F )
ꢀ
0.0435 / 0.0273
0.0719 / 0.0652
0.0286 / 0
0.0420 / 0.0310
0.0775 / 0.0750
0.0453 / 0
0.0272 / 0.0249
0.0613 / 0.0596
0.0289 / 1.5474
1.040
2
2
a
ꢀ
N
a
Weighting w: q1 / q2
2
b
GoF (F )
0.973
0.988
˚
−3
∆
ρfin (max / min), e A
2.05 / −2.23
1.64 / −2.13
1.79 / −5.82
2.12 / −2.08
Deposition no.
CSD-419370
CSD-421656
CSD-421673
CSD-421657
a
2
2
2
2
2
2 1/2
2
2
2
−1
2
2
R(F) = ΣꢁFo|−|Fcꢁ/Σ|Fo|, wR(F ) = [Σw(Fo −Fc ) /Σw(Fo ) ] , w = [σ (Fo ) + (q1P) + q2P] , where P = (Max(Fo , 0) + 2Fc )/3;
b
2
2
1/2
GoF = [Σw(Fo2−Fc ) /(nobs −nparam)]
.
In order to complete the consolidated findings and to green), Cs [Pt(CN) Br ] (yellow), and Cs [Pt(CN) I ] (red)
2
4
2
2
4 2
learn more about the influence of the kind of alkali were grown by slowly concentrating the solutions by keeping
metal on the crystal structure we investigated the ru- them at r. t.
bidium and cesium cyanoplatinate halides by X-ray
crystal diffraction, differential thermal analysis (DTA),
X-Ray structure determination
thermogravimetry (TG), and infrared (IR) and Raman
spectroscopy.
Single crystals of Rb [Pt(CN) Cl ], Cs [Pt(CN) Br ],
2 4 2 2 4 2
Rb [Pt(CN) I ], and Cs [Pt(CN) I ] were selected under a
2
4 2
2
4 2
microscope, and sealed in Lindemann glass capillaries. Their
experimental intensity data were collected with graphite-
monochromatized MoKα radiation on a Smart APEX I (or
APEX II) CCD diffractometer (Bruker AXS, Karlsruhe, Ger-
Experimental Section
Synthesis
A concentrated aqueous solution of Ba[Pt(CN) ] · 4 H O many). The collection, done at 298(2) K, and reduction of
4
2
(
Chempur, 99.9 %) was added to excess amounts of aque- data were carried out with the BRUKER SUITE software
ous solutions of Rb SO (Sigma-Aldrich, 99.8 %) or Cs SO package [15]. Rb [Pt(CN) Cl ] crystallizes in the triclinic
2
4
2
4
2
4
2
¯
(Alfa-Aesar, 99.99 %), as already described [12, 14]. Af- space group P1 (no. 2), Cs [Pt(CN) Br ] monoclinically
2 4 2
ter removing BaSO4 by filtration, the respective halogen in C2/c (no. 15), and Rb [Pt(CN) I ] and Cs [Pt(CN) I ]
2
4 2
2
4 2
as chlorine gas, liquid bromine or an ethanolic solution of both monoclinically in P2 /c (no. 14). The structures were
1
iodine was added to the clear filtrates containing rubid- solved and refined using the program SHELXTL [16]. For
ium or cesium tetracyanoplatinate, and boiled afterwards Rb [Pt(CN) Cl ] and Cs [Pt(CN) Br ], the atomic posi-
2
4
2
2
4
2
for one hour to remove the excess of halogen. Colorful tions of platinum, halogen and the alkali metal atoms were
needles of Rb [Pt(CN) Cl ] (green), Rb [Pt(CN) Br ] (yel- found by Direct Methods, and the positions of the cyanide
2
4
2
2
4
2
low), Rb [Pt(CN) I ] (dark red), Cs [Pt(CN) Cl ] (light groups were located from Difference Fourier maps. For
2
4 2
2
4
2
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1068
C. M u¨ hle et al. · Cyanoplatinate Halides
Rb [Pt(CN) I ] and Cs [Pt(CN) I ], the atomic coordinates Table 2. Crystallographic data of the powder structure refine-
2
4 2
2
4 2
ment for Cs [Pt(CN) Cl ].
of the isotypic K [Pt(CN) I ] [12] were used as starting
model for the refinement. Such an approach was necessary,
especially for Rb [Pt(CN) I ], because all crystals under in-
vestigation were systematically twinned (dove-tail twins),
the volume ratio of the two twin components of the crystal
under investigation being 0.907(1)/0.093(1). The intensities
of all crystals were corrected for absorption effects applying
a semi-empirical method [17, 18] (Table 1).
X-Ray powder diffraction data of Cs [Pt(CN) Cl ]
Fig. 1) were collected at r. t. using a Bruker D8 diffractome-
ter in Debye-Scherrer geometry (primary beam Johannson-
type Ge(220) monochromator for MoK radiation, one-
dimensional LynxEye PSD with silicon strips of 500 µm
thickness and an opening angle of 3.5 ) with the sample con-
tained in a sealed borosilicate glass capillary of 0.2 mm di-
2
4
2
2
4 2
−
1
Mr, g mol
535.67
295
Temperature, K
2
4 2
Space group (no.); Z
C2/c (15); 4
17.947(4)
7.395(2)
12.031(3)
131.904(1)
1188.4(5); 3.55
0.7093
1.93
2.04
2.77
1.20
1.44
˚
a, A
˚
b, A
˚
c, A
β deg
V, A˚ ; D
3
−3
calcd
, g cm
˚
Wavelength, A
2
4
2
a
R-exp, %
(
R-p, %a
a
R-wp, %
α1
2
a
R−F , %
GoF
◦
θ range, deg
Step width, deg
Time/scan, h
5.0 – 50.0
0.0085
42
◦
ameter. Patterns were collected in the range 2θ = 4 – 52 with
◦
No. of variables
36
a step width of 0.0085 in 2θ. There was no Bragg contri-
◦
Deposition no.
CSD-421674
bution to the pattern at angles higher than 50 in 2θ which
a
R-exp, R-p, R-wp, and R-F2 as defined in TOPAS (Bruker AXS
was excluded from the analysis. The sample was spun dur-
ing measurements for better particle statistics. For indexing
GmbH) [19].
and refinement of the powder pattern of Cs [Pt(CN) Cl ],
2
4
2
struments and used as starting values in the LeBail refine-
the program TOPAS [19] was used. Indexing was performed
by iterative use of singular value decomposition (LSI) [20],
leading to the lattice parameters given in Table 2. The peak
profiles and precise lattice parameters for all three phases
were first determined by a LeBail fit [21] using the funda-
mental parameter (FP) approach of TOPAS [22]. Since the
LynxEye and the Stoe PSD detectors are not fully described
by the current implementation of the fundamental parame-
ters approach in TOPAS, the instrument parameters were re-
fined on respective measurements of a NIST standard mate-
ments. A cylindrical 2θ correction according to Sabine et al.
[
[
23] was applied. Starting values for the Rietveld refinement
24, 25] were taken from isostructural Cs [Pt(CN) Br ] in
2
4
2
space group C2/c (see Tables 1 and 3). Due to the fact that
free refinement of the atomic coordinates of the CN groups
resulted in meaningless distortions, for the description of the
2−
[
Pt(CN) Cl ] octahedron a regular rigid body was con-
4
2
structed in the rigid body editor of TOPAS. The rigid body
was defined in a way allowing for the refinement of the Pt–Cl,
Pt–C (2×), and average C–N distances. Due to the fixed posi-
tion of the rigid body at the origin of the unit cell, only three
rial, SRM 660a (LaB ) over the whole 2θ range of the in-
6
2−
rotations for the [Pt(CN) Cl ] octahedron as external de-
4
2
grees of freedom were subjected to global optimization. The
structure giving the best fit to the data was validated by a
Rietveld refinement. During the Rietveld refinement, the in-
ternal degrees of freedom as well as isotropic displacement
parameters were refined.
The crystallographic data of all compounds under investi-
gation are collected in Tables 1 and 2, the positional and dis-
placement parameters are listed in Table 3, selected atomic
distances and angles are given in Tables 4 and 5.
Further details of the crystal structure investigations
may be obtained from Fachinformationszentrum Karlsruhe,
7
6344 Eggenstein-Leopoldshafen, Germany (fax: +49-7247-
Fig. 1. Scattering X-ray intensities for Cs [Pt(CN) Cl ] at
2
4
2
808-666; e-mail: crysdata@fiz-karlsruhe.de, http://www.fiz-
informationsdienste.de/en/DB/icsd/depot anforderung.html)
on quoting the deposition numbers given in Tables 1 and 2.
ambient conditions, as a function of the diffraction angle
2
θ. Shown are the observed pattern (diamonds), the best
Rietveld-fit profile (line a), the difference curve between ob-
served and calculated profile (line b), and the reflection mark-
Physical properties
˚
ers (vertical bars). The wavelength is λ = 0.7093 A. The
higher angle part of the plot is enlarged by a factor of five
Differential thermal analysis (DTA) and thermogravime-
try (TG) in combination with mass spectrometry (QMS 421,
◦
starting at 2θ = 42 .
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C. M u¨ hle et al. · Cyanoplatinate Halides
1069
Table 3. Atomic positions and equivalent isotropic displace-
The infrared spectra were recorded on an IR-Spectrometer
113v, Bruker, Germany) from 2 – 3 mg samples thoroughly
˚
2
ment parameters Ueq (A ), with estimated standard devia-
(
tions in parentheses.
mixed and ground with ∼400 mg of KBr (Aldrich, 99+ %,
◦
dried at 200 C in vacuo) and subsequently pressed into pel-
Atom Site
x
y
z
Ueq
lets with a diameter of 13 mm.
¯
Rb2[Pt(CN)4Cl2], P1
Pt1
1a
1h
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
0
0
1/2
0
1/2
0.02225(5)
0.02003(4)
The Raman spectra were measured by a laser with 0.4 W
and a wavelength of 632 nm in a Confocal Microscope Laser
Raman System (Model LabRam 1, Jobin-Yvon, France).
Pt2
1/2
Rb1
Rb2
Cl1
0.87406(6) 0.82270(4) 0.95215(4) 0.03855(9)
0.71063(6) 0.65796(4) 0.95215(4) 0.03730(9)
0.3214(1)
0.2582(2)
0.0672(5)
0.1077(6)
0.1523(6)
0.2424(7)
0.2838(6)
0.1634(6)
0.3936(6)
0.3424(7)
0.0205(1)
0.4709(1)
0.0758(4)
0.1190(4)
0.8572(1)
0.3760(1)
0.1727(4)
0.2682(4)
0.0362(2)
0.0358(2)
0.0287(6)
0.0454(8)
0.0314(7)
0.0493(9)
0.0284(6)
0.0450(8)
0.0307(7)
0.0505(9)
Results and Discussion
Cl2
C11
N11
C12
N12
C21
N21
C22
N22
Crystal structures
−0.2104(4) 0.0398(4)
The six representatives with the general formula
−0.3286(4) 0.0635(5)
A [Pt(CN) X ] (A = Rb, Cs; X = Cl, Br, I) crystallize
0.4992(4)
0.4899(4)
0.7259(4)
0.8516(4)
0.6842(3)
0.7861(4)
0.4936(4)
0.4853(5)
2
4 2
in three different types of structures: Rb2[Pt(CN)4Cl2]
¯
(
Fig. 2) crystallizes in the triclinic space group P1;
Rb [Pt(CN) I ] (Fig. 3) and Cs [Pt(CN) I ] crystal-
2
4 2
2
4 2
Cs2[Pt(CN)4Cl2], C2/c
lize in the already known Rb [Pt(CN) Br ]-type struc-
2
4
2
Pt1
Cs1
Cl1
C1
N1
C2
4a
8 f
8 f
8 f
8f
8 f
8f
0
0
0
0.0197
0.0365
0.0298
0.0713
0.0713
0.0713
0.0713
ture (monoclinic space group P2 /c) [11], which is also
0.1715(1)
0.0735
−0.0601
−0.0941
−0.1274
−0.1941
0.4956(9)
0.2396
0.1733
0.2712
0.0142
0.0217
0.0385(2)
0.1738
−0.1616
−0.2530
−0.0251
−0.0382
1
realized by K2[Pt(CN)4X2] (X = Cl, Br, I) [12], and
N2
Cs2[Pt(CN)4Br2], C2/c
Pt1
Cs1
Br1
C1
N1
C2
4a
8 f
8 f
8 f
8f
8 f
8f
0
0
0
0.02523(7)
0.18103(2) 0.49385(3) 0.03952(3) 0.04222(8)
0.07197(3) 0.26460(5) 0.16893(4) 0.0417(1)
0.1209(3)
0.1915(3)
0.0629(2)
0.1016(3)
−0.0186(4) 0.0288(5)
−0.0349(6) 0.0500(6)
−0.1743(5) 0.1669(4)
−0.2766(5) 0.2614(4)
0.0358(7)
0.057(1)
0.0382(7)
0.060(1)
N2
Cs2[Pt(CN)4I2], P21/c
Pt1
Cs1
I1
C1
N1
C2
N2
2a
4e
4e
4e
4e
4e
4e
0
0
0
0.02380(6)
0.47802(4) 0.78147(3) 0.61611(3) 0.03687(7)
0.07943(4) 0.27477(3) 0.03036(3) 0.03754(7)
0.8061(5)
0.6916(6)
0.1837(5)
0.2935(5)
0.0265(4)
0.0423(5)
0.9612(4)
0.9382(4)
0.1036(4)
0.1586(5)
0.1969(4)
0.3058(4)
0.0298(6)
0.0432(8)
0.0298(6)
0.0398(7)
Fig. 2. Perspective representation of the crystal structure of
Rb [Pt(CN) Cl ], with the margins of the unit cell (black).
2
4
2
Rb2[Pt(CN)4I2], P21/c
Pt1
Rb1
I1
2a
4e
4e
4e
4e
4e
4e
0
0
0
0.01674(6)
0.47700(7) 0.78204(6) 0.61738(5) 0.0330(1)
0.09041(4) 0.28164(3) 0.02936(4) 0.02912(8)
0.8003(6)
0.6805(7)
0.1934(6)
0.3089(6)
C1
N1
C2
N2
0.0333(5)
0.0529(6)
0.9601(5)
0.9358(5)
0.1053(5)
0.1591(5)
0.2028(5)
0.3140(4)
0.0231(8)
0.0353(9)
0.0220(7)
0.0308(8)
Balzers, Wiesbaden, Germany) for analyzing the volatile
decomposition products were performed with a computer-
controlled thermal analyzer (STA 409, Netzsch GmbH, Ger-
many). Powder samples of 20 mg were placed in a corundum
−1
crucible, heated to 1173 K with a rate of 10 K min , and Fig. 3. Perspective representation of the crystal structure of
then cooled down to r. t. with the same rate under argon.
Cs2[Pt(CN)4Br2], with the margins of the unit cell (black).
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1070
C. M u¨ hle et al. · Cyanoplatinate Halides
˚
Table 4. Selected distances (A) and angles (deg) of Rb [Pt(CN) Cl ] with estimated standard deviations in parentheses.
2
4
2
Atom
Pt1
Distance
Atom
Pt2
Distance
Atom
Angle
–C11
2.019(3) × 2
2.012(3) × 2
2.3399(9) × 2
3.484(1)
–C22
–C21
–Cl2
–Cl1
2.020(4) × 2
2.017(3) × 2
2.3267(9) × 2
3.459(1)
3.885(1)
3.342(1)
2.993(4)
3.061(4)
3.051(4)
3.051(4)
C11–Pt1–C12
C21–Pt2–C22
Pt1–C11–N11
Pt1–C12–N12
Pt2–C21–N21
Pt2–C22–N22
Cl1–Pt1–C11
Cl1–Pt1–C12
Cl2–Pt2–C21
Cl2–Pt2–C22
91.5(2)
87.0(2)
178.8(4)
178.3(3)
175.9(3)
176.9(3)
90.2(1)
90.5(1)
88.8(1)
88.8(1)
–
C12
–Cl1
Rb1
–Cl1
Rb2
–Cl2
3.490(1)
3.511(1)
–Cl2
–N12
–
–
N11
N22
3.016(3)
2.983(4)
3
3
.430(5)
.442(5)
–N21
C11
C12
–N11
–N12
1.134(5)
1.142(5)
C21
C22
–N21
–N22
1.139(5)
1.128(5)
˚
Table 5. Selected distances (A)
and angles (deg) with esti-
mated standard deviations in
parentheses.
Rb2[Pt(CN)4I2]
Cs2[Pt(CN)4Cl2]
Cs2[Pt(CN)4Br2]
Cs2[Pt(CN)4I2]
Pt1
A
–C1
2.014(5) × 2
2.010(4) × 2
2.6829(3) × 2
3.043(5)
1.95(3) × 2
2.10(2) × 2
2.360(8) × 2
3.178(4)
3.714(4)
3.929(3)
3.11(3)
2.007(4) × 2
2.006(4) × 2
2.4773(4) × 2
3.214(5)
3.435(4)
3.853(4)
2.010(4) × 2
2.008(4) × 2
2.6879(3) × 2
3.168(4)
3.214(4)
3.311(4)
–
C2
–X
–N1
3
3
.235(5)
.418(5)
–
N2
3.022(5)
3.129(4)
3.242(4)
3
3
.031(4)
.187(5)
3.593(7)
3.920(2)
3.628(4)
3.876(3)
3.983(4)
1.10(2)
3.566(4)
4.175(4)
3.7049(5)
3.9454(5)
3.9870(5)
1.146(6)
3.406(5)
3.466(5)
4.0059(4)
4.0475(4)
4.1060(4)
1.143(5)
–X
3.8273(6)
3
4
.8601(6)
.0237(7)
C1
C2
–N1
–N2
1.151(6)
1.139(6)
1.10(2)
1.146(6)
1.146(5)
C1–Pt1–C2
Pt1–C1–N1
Pt1–C2–N2
X–Pt1–C1
X–Pt1–C2
89.1(2)
177.0(4)
176.7(4)
90.1(1)
90.2(1)
90
91.7(2)
176.9(6)
176.9(3)
89.8(1)
90.4(1)
89.7(2)
177.9(4)
177.1(3)
90.1(1)
89.8(1)
180
180
90
90
finally, the two isotypic compounds Cs [Pt(CN) Cl ]
2
4
2
and Cs [Pt(CN) Br ] (Fig. 4) crystallize also in the
2
4
2
monoclinic system but in space group C2/c, c. f. Tables
– 3.
In all alkali metal tetracyanoplatinate halides men-
1
tioned above, the platinum(IV) atoms are in an octa-
hedral coordination. The carbon atoms of the cyanide
groups provide a square-planar basis, and the halo-
gen atoms are located in the axial (trans) positions of
2
−
the [Pt(CN) X ] octahedron. The bond lengths Pt–C
4
2
Fig. 4. Perspective representation of the crystal structure of
Rb [Pt(CN) I ], with the margins of the unit cell (black).
and C–N correspond to the expected values. A slight
decrease of both lengths is observed from the iodine
2
4 2
√
√
to the chlorine compounds, which correlates with in- ture type [26], with b 2 ≈ c 2 ꢀ a(K PtCl ).
2
6
creasing of IR vibrational frequencies (Tables 4 and 5). In the case of the other representatives a face-
The arrangement of the platinum atoms, as the centered arrangement is observed: Cs2[Pt(CN)4Cl2]
centers of the octahedra, is body-centered I in and Cs2[Pt(CN)4Br2] face-centered C (Fig. 3);
Rb [Pt(CN) Cl ] (Fig. 2), showing the same ar- Rb2[Pt(CN)4I2] and Cs2[Pt(CN)4I2] face-centered A
2
4
2
rangement as in the F centered K PtCl struc- (Fig. 4).
2
6
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C. M u¨ hle et al. · Cyanoplatinate Halides
1071
Table 6. IR vibrational frequencies (cm 1) of
−
−1
−1
2174 cm (X = Cl), and for A = Cs at 2158 cm
a
−1 −1
A [Pt(CN) X ] (A = Rb, Cs; X = Cl, Br, I) .
2
4
2
(X = I), 2166 cm (X = Br) or 2171 cm (X =
Rb2[Pt(CN)4Cl2] Rb2[Pt(CN)4Br2] Rb2[Pt(CN)4I2] Cl), which are assigned to the valence vibration of the
ν(C≡N)
ν(Pt–C)
2174 vs
2170 vs
494 s, 476 s
404 s
2159 vs
490 s, 473 s
405 s
C≡N groups [27]. With increasing size and decreas-
ing electronegativity of the halogen atoms the frequen-
cies ν(C≡N) are shifted to lower values, but are still
above the ν(C≡N) values of cyanoplatinates(II) like
492 s, 477 s
δ(Pt–C≡N) 403 s
Cs2[Pt(CN)4Cl2] Cs2[Pt(CN)4Br2] Cs2[Pt(CN)4I2]
2171 vs
487 s, 468 s
ν(C≡N)
ν(Pt–C)
2166 vs
487 s, 471 s
409 vs
2158 vs, 2129 s
490 s
407 s
−
1
Rb2[Pt(CN)4] (2132 cm ) [28]. The charge of the
platinum atom of the complex has a significant influ-
ence on the C≡N bonding character, whereas the type
of cation has only a marginal influence. The strong
δ(Pt–C≡N) 408 vs
a
vs = very strong, s = strong, w = weak.
Table 7. Raman vibrational frequencies (cm 1) of
−
−
1
−1
a
bands at 487 to 494 cm and 468 to 477 cm are
assigned to the valence vibrations of the Pt–C bonds
[28]. The absorption band of the deformation vibra-
A [Pt(CN) X ] (A = Rb, Cs; X = Cl, Br, I) .
2
4 2
Rb2[Pt(CN)4Cl2] Rb2[Pt(CN)4Br2] Rb2[Pt(CN)4I2]
ν(C≡N)
2196 s
187 w
2192 s
2184 w
468 s
198 vs
146 vs
2185 s
2174 w
467 s
149 s
140 vs
−
1
2
tion of the Pt–C≡N groups occurs at 403 to 409 cm
ν(Pt–C)
ν(Pt–X)
469 s
327 vs
[
39, 30].
δ(Pt–C≡N) 151 vs
Raman spectroscopy
Cs2[Pt(CN)4Cl2] Cs2[Pt(CN)4Br2] Cs2[Pt(CN)4I2]
ν(C≡N)
2197 s
187 w
472 s
2193 s
2183 w
469 s
204 vs
143 s
2186 s
2175 w
471 w
143 vs
140 vs
The Raman spectra (Table 7) of all representatives
2
of the type A [Pt(CN) X ] with A = Rb, Cs, and X =
2
4 2
ν(Pt–C)
ν(Pt–X)
333 vs
Cl, Br, I show two bands of the ν(C≡N) vibration be-
−
1
δ(Pt–C≡N) 150 s
tween 2174 and 2197 cm [31] with decreasing fre-
quencies, depending on the halogen atom, from X = Cl
to I. The electronegativity effect of the halogen atoms
on the force constants of the Pt–C bonds at frequencies
a
vs = very strong, s = strong, w = weak.
Thermogravimetric analysis
−
1
The thermal decomposition of Cs [Pt(CN) Br ], of 467 to 472 cm and on the δ(Pt–C≡N) deforma-
2
4
2
−
1
tion vibrations, decreasing from 151 cm (X = Cl) to
40 cm (X = I) in both cyanoplatinate halides, is not
measured exemplarily by DTA and TG-MS, starts with
−
1
◦
1
a separation of part of the cyanide at 300 C. At higher
temperature, the CN and (CN) groups and halogen very pronounced. The bands of the ν(Pt–X) vibration
are evolved progressively, until elemental platinum is
left as the only solid residue. All other rubidium and
cesium cyanoplatinate halides A [Pt(CN) X ] (A = Rb, at 149 cm (X = I), 198 cm (X = Br) and 327 cm
Cs; X = Cl, Br, I) behave similarly, thus corresponding
to the potassium cyanoplatinate halides investigated
previously [12].
−
2
have a very high intensity as observed in the potassium
tetracyanoplatinate halides [12] and occur for A = Rb
−
1
−1
−1
−1
2
4 2
−
1
(
(
X = Cl), and for A = Cs at 143 cm (X = I), 204 cm
X = Br) and 333 cm (X = Cl). Again, the frequen-
−
1
cies decrease with the increasing size and the decreas-
ing electronegativity of the halogen atoms, but are not
affected by the cation size.
Infrared spectroscopy
Acknowledgement
The infrared spectra (Table 6) of all alkali metal
cyanoplatinate halides A [Pt(CN) X ] (A = Rb, Cs; X =
2
4
2
The authors would like to thank W. K o¨ nig for the IR,
Cl, Br, I) show a sharp strong absorption band for A = A. Schulz for the Raman and Th. Pilz for the DTA/TG mea-
−
1
−1
Rb at 2159 cm (X = I), 2170 cm (X = Br) or surements.
[
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