cis-Diamminedichloridoplatinum(II) N,N-dimethyl­formamide monosolvate

Abstract

In the title compound, cis-[PtCl₂(NH₃)₂]·C₃H₇NO, the metal complex mol­ecules are stacked parallel to the b axis, forming close Pt⋯Pt inter­actions of 3.4071 (7) and 3.5534 (8) Å and weak N—H⋯Cl hydrogen bonds between the ammine ligand and the Cl atoms of the neighboring complex. Conventional N—H⋯O hydrogen bonds are formed between ammine ligands and the O atom of adjacent N,N-dimethyl­formamide mol­ecules. The crystal was found to be a split crystal and was analyzed using two domains related by a rotation of ca 4.4° about the reciprocal axis (−0.351 1.000 0.742) and refined to give a minor component fraction of 0.084 (6).

Related literature  

For a review of platinum anti­cancer coordination compounds, see: Reedijk (2009 ▶). For the preparation of cis-diamminedichloridoplatinum(II), see: Kukushikin et al. (1998 ▶). For single-crystal X-ray and neutron diffraction studies of cis-diamminedichloridoplatinum(II), see: Milburn & Truter (1966 ▶); Ting et al. (2010 ▶). For vibrational studies, see: Nakamoto et al. (1965 ▶). For crystallographic studies of dimethyl­formamide solvates and complexes of cis-diamminedichlorido­platinum(II) and related compounds, see: Raudaschl et al. (1983 ▶, 1985 ▶); Raudaschl-Sieber et al. (1986 ▶); Alston et al. (1985 ▶). For a crystallographic study of palladium analogs, see: Kirik et al. (1996 ▶). For a detailed analysis of linear chainstructures in platinum(II) complexes, see: Connick et al. (1997 ▶). For an analysis of hydrogen bonding in platinum–ammine complexes, see: Brammer et al. (1987 ▶).

Experimental  

Crystal data  

• [PtCl₂(NH₃)₂]·C₃H₇NO

• M _r = 373.15

• Triclinic,

• a = 6.2344 (9) Å

• b = 6.8196 (11) Å

• c = 11.5833 (18) Å

• α = 105.285 (4)°

• β = 96.061 (4)°

• γ = 97.809 (4)°

• V = 465.47 (12) ų

• Z = 2

• Mo Kα radiation

• μ = 15.59 mm⁻¹

• T = 200 K

• 0.46 × 0.36 × 0.10 mm

Data collection  

• Bruker SMART X2S benchtop diffractometer

• Absorption correction: multi-scan (TWINABS; Bruker, 2009 ▶) T _min = 0.05, T _max = 0.30

• 7440 measured reflections

• 1620 independent reflections

• 1484 reflections with I > 2σ(I)

• R _int = 0.043

Refinement  

• R[F ² > 2σ(F ²)] = 0.028

• wR(F ²) = 0.072

• S = 1.07

• 1620 reflections

• 96 parameters

• H-atom parameters constrained

• Δρ_max = 1.44 e Å⁻³

• Δρ_min = −2.08 e Å⁻³

Data collection: APEX2 and GIS (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) and OLEX2 (Dolomanov et al., 2009 ▶); molecular graphics: PLATON (Spek, 2009 ▶), Mercury (Macrae et al., 2008 ▶) and POV-RAY (Cason, 2004 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Supplementary material file. DOI: 10.1107/S1600536812024014/pk2417Isup3.mol

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1E⋯Cl1i	0.91	2.51	3.389 (7)	161
N2—H2E⋯Cl2i	0.91	2.53	3.403 (7)	162
N1—H1D⋯O1ii	0.91	2.13	3.023 (9)	167
N2—H2F⋯O1iii	0.91	2.31	3.198 (9)	165

Symmetry codes: (i) ; (ii) ; (iii) .

supplementary crystallographic information

Comment

Cis-diamminedichloridoplatinum(II), also known as cisplatin, is a widely used anti-cancer drug that has been extensively studied since its clinical applications were first discovered (Reedijk, 2009). The structure of cisplatin was first determined crystallographically in 1966 (Milburn & Truter, 1966); a recent study has elaborated the structure of the two common polymorphs (Ting et al., 2010). A different DMF-solvate of cisplatin has been described previously (Raudaschl et al., 1983, Raudaschl et al. 1985, Raudaschl-Sieber et al. 1986). A crown ether complex of cisplatin has also been crystallographically characterized (Alston et al., 1985).

The title compound has a square-planar geometry (Fig. 1) and forms stacked chains along the crystallographic b axis with Pt—Pt distances of 3.4071 (7) and 3.5534 (8) Å and Pt—Pt—Pt angle of 156.90 (2) degrees as shown in Figures 2 and 3. Formation of extended platinum chains through stacking is a common motif in square-planar platinum compounds (Connick et al., 1997). Hydrogen bonds are formed between the ammine hydrogen atoms and the chlorine atoms on the closer of the two neighboring complexes. This type of hydrogen bonding has been proposed or observed in previous studies on cisplatin and related complexes (Milburn & Truter, 1966; Brammer et al., 1987; Ting et al., 2010).

Additional hydrogen bonds are formed between the ammine hydrogen atoms and the oxygen atom of the N,N-dimethylformamide as illustrated in Figure 4. Similar interactions are seen in the DMF-solvated cisplatin structure previously described (Raudaschl et al., 1983, Raudaschl et al., 1985, Raudaschl-Sieber et al., 1986). Interestingly, the previously described DMF solvate of cisplatin does not display stacking of the metal complexes seen in the title compound.

Experimental

The title complex was prepared by refluxing 2.00 g (4.82 mmol) of K₂[PtCl₄] with 1.60 g (20.8 mmol) of ammonium acetate and 2.0 g (26.8 mol) of KCl in 25 ml of water for two hours, during which the solution changed from a dark red to green. The solution was hot filtered and a greenish-yellow powder formed on cooling. The powder was recrystallized by vapor diffusion of diethylether into a DMF solution of the complex yielding yellow-orange crystals. Infrared spectra were in agreement with literature values (Nakamoto et al., 1965)

Data sets on multiple crystals showed evidence of at least two independent domains, either from agglomeration or from the crystal being cracked or split, perhaps during rapid cooling to 200 K.

Refinement

The matrix relating the two domains, [1.007 0.033 - 0.041 - 0.010 1.013 - 0.022 0.118 0.060 0.975], corresponding to a rotation of 4.4 degrees about the reciprocal axis (-0.351 1.000 0.742), was determined using the CELL_NOW program (Bruker AXS, 2009). Integration and absorption correction (TWINABS, Bruker AXS 2009) gave 1558 unique reflections in domain 1, 1560 unique reflections in domain 2, and 211 unique overlapping reflections, or 14 percent overlapping reflections. The structure was solved using merged reflections from both domains (type HKLF 4 in SHELXL-97). The structure was refined using corrected reflections from only the major component including overlaps (type HKLF 5 in SHELXL-97).

Refinement produced a minor component fraction of 0.084 (6). All hydrogen atoms were positioned geometrically and refined with the atom positions constrained to appropriate positions with N—H distances of 0.91 Å and C—H distances of either 0.95 Å (amide) or 0.98 Å (methyl groups). A riding model was used for all H atoms with U_iso(H) = 1.2 times U_iso (amine, amide) or 1.5 times U_iso (methyl carbon atoms).

Figures

Fig. 1.

The molecular structure of the title compound drawn with 50% probability displacement ellipsoids for non-H atoms.

Fig. 2.

The packing of the title compound viewed along the b axis drawn with 50% probability displacement ellipsoids for non-H atoms.

Fig. 3.

A view showing the platinum-platinum interactions and hydrogen bonding between the ammine ligands and the chlorine atoms on neighboring complexes. Additional donor/acceptor distances and angles are listed in Table 1. [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (iv) x, y + 1, z; (v) -x + 1, -y + 2, -z + 1.]

Fig. 4.

An illustration of the hydrogen bond interactions between the ammine ligands and the N,N-dimethylformamide solvent molecules. Additional donor/acceptor distances and angles are listed in Table 1. [Symmetry codes: (ii) -x + 2, -y + 2, -z + 2; (iii) x - 1, y, z - 1; (v) -x + 1, -y + 2, -z + 1.]

Crystal data

[PtCl2(NH3)2]·C3H7NO	Z = 2
Mr = 373.15	F(000) = 344
Triclinic, P1	Dx = 2.662 Mg m−3
a = 6.2344 (9) Å	Mo Kα radiation, λ = 0.71073 Å
b = 6.8196 (11) Å	Cell parameters from 1090 reflections
c = 11.5833 (18) Å	θ = 3.3–24.8°
α = 105.285 (4)°	µ = 15.59 mm−1
β = 96.061 (4)°	T = 200 K
γ = 97.809 (4)°	Plate, clear yellow
V = 465.47 (12) Å3	0.46 × 0.36 × 0.10 mm

Data collection

Bruker SMART X2S benchtop diffractometer	1620 independent reflections
Radiation source: fine-focus sealed tube	1484 reflections with I > 2σ(I)
Doubly curved silicon crystal monochromator	Rint = 0.043
Detector resolution: 8.3330 pixels mm-1	θmax = 25.1°, θmin = 3.1°
ω scans	h = −7→7
Absorption correction: multi-scan (TWINABS; Bruker, 2009)	k = −8→7
Tmin = 0.05, Tmax = 0.30	l = 0→13
7440 measured reflections

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.072	H-atom parameters constrained
S = 1.07	w = 1/[σ2(Fo2)]
1620 reflections	(Δ/σ)max = 0.001
96 parameters	Δρmax = 1.44 e Å−3
0 restraints	Δρmin = −2.08 e Å−3

Special details

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Pt1	0.55286 (4)	0.74780 (4)	0.49265 (2)	0.01388 (13)
Cl1	0.6813 (3)	0.6374 (3)	0.31075 (18)	0.0250 (4)
Cl2	0.8971 (3)	0.7991 (3)	0.60324 (18)	0.0244 (4)
N1	0.4361 (11)	0.8403 (11)	0.6522 (6)	0.0211 (15)
H1D	0.5443	0.9266	0.7089	0.025*
H1E	0.3894	0.7281	0.6772	0.025*
H1F	0.3222	0.9076	0.6419	0.025*
N2	0.2485 (11)	0.6999 (11)	0.3960 (6)	0.0236 (15)
H2D	0.1706	0.7943	0.4345	0.028*
H2E	0.1786	0.5706	0.3897	0.028*
H2F	0.2604	0.7135	0.3208	0.028*
O1	1.2567 (10)	0.8302 (10)	1.1506 (5)	0.0335 (15)
N3	0.9601 (11)	0.7534 (9)	1.0048 (6)	0.0254 (17)
C1	0.7242 (15)	0.7227 (15)	0.9760 (9)	0.041 (2)
H1A	0.6598	0.7511	1.0510	0.061*
H1B	0.6694	0.5797	0.9279	0.061*
H1C	0.6836	0.8165	0.9294	0.061*
C2	1.0852 (17)	0.7125 (15)	0.9063 (8)	0.037 (2)
H2A	1.2411	0.7612	0.9374	0.055*
H2B	1.0389	0.7845	0.8476	0.055*
H2C	1.0608	0.5637	0.8667	0.055*
C3	1.0583 (16)	0.8090 (13)	1.1198 (7)	0.027 (2)
H3	0.9686	0.8339	1.1818	0.032*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Pt1	0.01315 (19)	0.01376 (19)	0.01392 (18)	0.00092 (13)	0.00190 (12)	0.00322 (13)
Cl1	0.0266 (11)	0.0290 (11)	0.0192 (10)	0.0044 (9)	0.0089 (8)	0.0044 (8)
Cl2	0.0164 (10)	0.0311 (12)	0.0230 (10)	0.0032 (9)	−0.0005 (8)	0.0049 (9)
N1	0.018 (4)	0.022 (4)	0.019 (3)	−0.001 (3)	0.000 (3)	0.003 (3)
N2	0.020 (4)	0.029 (4)	0.023 (4)	0.005 (3)	0.003 (3)	0.010 (3)
O1	0.030 (4)	0.037 (4)	0.025 (3)	0.005 (3)	−0.005 (3)	−0.001 (3)
N3	0.031 (5)	0.020 (4)	0.022 (4)	0.003 (3)	0.001 (3)	0.003 (3)
C1	0.036 (6)	0.040 (6)	0.045 (6)	−0.001 (5)	−0.007 (5)	0.017 (5)
C2	0.049 (6)	0.038 (6)	0.022 (5)	0.008 (5)	0.001 (4)	0.009 (4)
C3	0.042 (6)	0.023 (5)	0.013 (4)	0.006 (4)	0.001 (4)	0.001 (4)

Geometric parameters (Å, º)

Pt1—N1	2.034 (6)	N3—C3	1.339 (10)
Pt1—N2	2.037 (6)	N3—C2	1.437 (11)
Pt1—Cl1	2.3088 (19)	N3—C1	1.447 (11)
Pt1—Cl2	2.313 (2)	C1—H1A	0.9800
N1—H1D	0.9100	C1—H1B	0.9800
N1—H1E	0.9100	C1—H1C	0.9800
N1—H1F	0.9100	C2—H2A	0.9800
N2—H2D	0.9100	C2—H2B	0.9800
N2—H2E	0.9100	C2—H2C	0.9800
N2—H2F	0.9100	C3—H3	0.9500
O1—C3	1.229 (11)
N1—Pt1—N2	91.8 (3)	C3—N3—C2	120.9 (8)
N1—Pt1—Cl1	178.99 (19)	C3—N3—C1	120.9 (8)
N2—Pt1—Cl1	87.6 (2)	C2—N3—C1	118.1 (8)
N1—Pt1—Cl2	87.9 (2)	N3—C1—H1A	109.5
N2—Pt1—Cl2	179.34 (18)	N3—C1—H1B	109.5
Cl1—Pt1—Cl2	92.63 (7)	H1A—C1—H1B	109.5
Pt1—N1—H1D	109.5	N3—C1—H1C	109.5
Pt1—N1—H1E	109.5	H1A—C1—H1C	109.5
H1D—N1—H1E	109.5	H1B—C1—H1C	109.5
Pt1—N1—H1F	109.5	N3—C2—H2A	109.5
H1D—N1—H1F	109.5	N3—C2—H2B	109.5
H1E—N1—H1F	109.5	H2A—C2—H2B	109.5
Pt1—N2—H2D	109.5	N3—C2—H2C	109.5
Pt1—N2—H2E	109.5	H2A—C2—H2C	109.5
H2D—N2—H2E	109.5	H2B—C2—H2C	109.5
Pt1—N2—H2F	109.5	O1—C3—N3	124.3 (8)
H2D—N2—H2F	109.5	O1—C3—H3	117.8
H2E—N2—H2F	109.5	N3—C3—H3	117.8
C2—N3—C3—O1	0.3 (12)	C1—N3—C3—O1	177.2 (8)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1E···Cl1i	0.91	2.51	3.389 (7)	161
N2—H2E···Cl2i	0.91	2.53	3.403 (7)	162
N1—H1D···O1ii	0.91	2.13	3.023 (9)	167
N2—H2F···O1iii	0.91	2.31	3.198 (9)	165

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, −y+2, −z+2; (iii) x−1, y, z−1.