The structure determination was carried out by the X-ray powder diffraction
technique. The experimental data were collected using DRON-4 automatic
diffractometer, equipped with a secondary flat graphite monochromator in
conjunction with a scintillation detector. Cu Kα radiation was used
(λ1 = 1.54056 Å, λ2 = 1.54439 Å). The sample was prepared by
top-loading the standard quartz sample holder with cutting the excess of well
grained substance. The diffraction pattern was scanned with the step of 0.02°
2θ and counting time of 5 sec./step in the most informative angular range
from 9° to 115% 2θ at room temperature. Corundum was used as the external
standard. The powder pattern of cis-bis(methylamine) dichloro
platimun(II) is presented in Fig. 1. X-ray powder diffraction data have been
deposited in JCPDS-ICDD PDF2 database (ICDD, 2005). Cell parameters were
obtained from d-spaces by indexing and refining using programs described in
(Visser, 1969; Kirik et al., 1979). The space group was determined from
the analysis of systematic absences. The structural investigations were
carried out using a full-profile structure analysis package based on a
modified version of the Rietveld refinement program DBWS-9006PC (Wiles &
Young, 1981; Kirik, 1985). The intensities of 50 reflections were estimated
from the powder pattern by means of the full-profile fitting procedure (Le
Bail et al., 1988) and used in the Patterson synthesis. Atoms of Pt and
Cl were located directly from the Patterson map. Positions of light atoms N
and C were defined from a difference Fourier synthesis. The final refinement
was carried out by Rietveld method (Rietveld, 1969; Wiles & Young, 1981).
H-atoms were not located, but they were included in the refined structure
models and rigidly connected to their C and N atoms with N—H = 0.90 and
C—H = 0.96 Å and Uiso(H) = 0.152 Å2.
Structure description
top
The title complex, cis-[Pt(CH3NH2)2Cl2], has attracted attention
due to its biological activity especially in connection with cancer
chemotherapy (Clere & Hoechele, 1973; Clere, 1974). Reports on
cis-[Pt(CH3NH2)2Cl2] can be found in the literature as early as
the nineteen fifties (Grinberg & Gildengershel, 1951; Gildengershel, 1956).
X-ray diffraction data were published by Watt et al. (1967) and a
single-crystal structure was determined by Wimmer et al. (1988). This
group found the existence of two forms A and B. Concisely the form A is build
from molecules cis-[Pt(CH3NH2)2Cl2] in the conformation where
both methyl groups lie on the same side of the plane delimited by the two
chloride and the two nitrogen atoms (motif A). The form B consists of
molecules of two possible conformations: above mentioned motif A and a motif B
where methyl groups are on the both side of "platinum" plane. Unfortunately
the publication (Wimmer et al., 1988) does not present the 3-D
coordinates of the structures, and that hinders the detailed analysis of
reasons for the different types of conformations. Here we present the results
of crystal structure determination of cis-[Pt(CH3NH2)2Cl2] in
form A obtained applying another synthetic approach without using AgI as it
was done by Wimmer et al. (1988) following Dhara (1970). Another
important feature follows from application of the X-ray powder technique that
allows ascribing the structure to bulk sample of the substance.
The crystal structure of cis-bis(metylamine) dichloro platimun(II)
consists of discrete molecules. The geometry of the molecule is presented in
Fig. 2. The Pt atom has slightly distorted square-planar coordination
enviroment consisting of two N and two Cl atoms. The torsion angle
Cl2—Cl1—N1—N2 = 177.5°. The distances Pt1—N1, Pt1—N2, Pt1—Cl1 and
Pt1—Cl2 are 2.083 (14) Å, 2.088 (12) Å, 2.303 (5) Å and 2.343 (4) Å
respectively and these correspond well to known in literature values
(Arpalahti et al., 1988; Wimmer et al., 1988; Kirik et
al., 1996; Wells, 1984; Allen, 2002; ICSD, 2007). Metylamine as a ligand
does not induce essential distortions of the molecule. The N1—Pt1—N2 angle
is 90.0 (4)°. The N···Cl contacts in the molecule are of 3.081 (16) Å and
3.095 (15) Å. Methyl-groups are oriented to one side of the PtN2Cl2plane.
Molecules conjugate in pairs due to (Cl···H—N) intermolecular bounding with
centrosymmetric orientation respectively each other. N···Cl contacts between
nearest molecules are of 3.296 (16) Å and 3.462 (16) Å. The shortest
(Pt···Pt) distance in pairs equals to 3.372 (2) Å. The pairs comprise double
layers stretched along (ac)-plane with methylamine ligands protruding
from layers forming organic interlayers (Fig. 3). This type of packing is also
typical for other methylamine containing compound (Kirik & Starkov, 2007).
The title compound was previously reported by Watt et al. (1967) and
Wimmer et al. (1988). For related compounds, see: Arpalahti et
al. (1988); Clere (1974); Clere & Hoechele (1973); Dhara (1970);
Gildengershel (1956); Grinberg & Gildengershel (1951); Kirik & Starkov (2007);
Kirik et al. (1996); Wells (1984). Searches were conducted using the
Cambridge Structural Database (Version?; Allen, 2002) and the Inorganic
Crystal Structure Database (Version 2007–1; ICSD, 2007). X-ray powder
diffraction data have been deposited in the JCPDS-ICDD PDF-2 database (ICDD,
2005). For analysis techniques, see: Kirik (1985); Kirik et al. (1979);
Le Bail et al. (1988); Rietveld (1969); Visser (1969); Wiles & Young
(1981). [Original long list of references has been rearranged to make it
more informative. Please check.]
Data collection: DRON-4 data collection software; cell refinement: POWDER (Kirik et al., 1979); data reduction: DRON-4 data collection software; program(s) used to solve structure: modified DBWM (Wiles & Young, 1981); program(s) used to refine structure: modified DBWM (Wiles & Young, 1981); molecular graphics: SHELXTL (Siemens, 1989); software used to prepare material for publication: SHELXTL (Siemens, 1989).
The title complex, cis-[Pt(CH3NH2)2Cl2], has attracted attention due to its biological activity especially in connection with cancer chemotherapy (Clere & Hoechele, 1973; Clere, 1974). Reports on cis-[Pt(CH3NH2)2Cl2] can be found in the literature as early as the nineteen fifties (Grinberg & Gildengershel, 1951; Gildengershel, 1956). X-ray diffraction data were published by Watt et al. (1967) and a single-crystal structure was determined by Wimmer et al. (1988). This group found the existence of two forms A and B. Concisely the form A is build from molecules cis-[Pt(CH3NH2)2Cl2] in the conformation where both methyl groups lie on the same side of the plane delimited by the two chloride and the two nitrogen atoms (motif A). The form B consists of molecules of two possible conformations: above mentioned motif A and a motif B where methyl groups are on the both side of "platinum" plane. Unfortunately the publication (Wimmer et al., 1988) does not present the 3-D coordinates of the structures, and that hinders the detailed analysis of reasons for the different types of conformations. Here we present the results of crystal structure determination of cis-[Pt(CH3NH2)2Cl2] in form A obtained applying another synthetic approach without using AgI as it was done by Wimmer et al. (1988) following Dhara (1970). Another important feature follows from application of the X-ray powder technique that allows ascribing the structure to bulk sample of the substance.
The crystal structure of cis-bis(metylamine) dichloro platimun(II) consists of discrete molecules. The geometry of the molecule is presented in Fig. 2. The Pt atom has slightly distorted square-planar coordination enviroment consisting of two N and two Cl atoms. The torsion angle Cl2—Cl1—N1—N2 = 177.5°. The distances Pt1—N1, Pt1—N2, Pt1—Cl1 and Pt1—Cl2 are 2.083 (14) Å, 2.088 (12) Å, 2.303 (5) Å and 2.343 (4) Å respectively and these correspond well to known in literature values (Arpalahti et al., 1988; Wimmer et al., 1988; Kirik et al., 1996; Wells, 1984; Allen, 2002; ICSD, 2007). Metylamine as a ligand does not induce essential distortions of the molecule. The N1—Pt1—N2 angle is 90.0 (4)°. The N···Cl contacts in the molecule are of 3.081 (16) Å and 3.095 (15) Å. Methyl-groups are oriented to one side of the PtN2Cl2plane. Molecules conjugate in pairs due to (Cl···H—N) intermolecular bounding with centrosymmetric orientation respectively each other. N···Cl contacts between nearest molecules are of 3.296 (16) Å and 3.462 (16) Å. The shortest (Pt···Pt) distance in pairs equals to 3.372 (2) Å. The pairs comprise double layers stretched along (ac)-plane with methylamine ligands protruding from layers forming organic interlayers (Fig. 3). This type of packing is also typical for other methylamine containing compound (Kirik & Starkov, 2007).