cis-Diiodido(N,N,N′,N′-tetra­methyl­ethylenediamine-κ²N,N′)platinum(II)

In the title complex, cis-[PtI₂(C₆H₁₆N₂)], the Pt atom lies on a crystallographic twofold axis and the mol­ecule exhibits C₂ symmetry. The Pt atom is four-coordinated by a chelating N,N,N′,N′-tetra­methyl­ethylenediamine ligand [Pt—N = 2.081 (9) Å] and two iodide ligands [Pt—I = 2.589 (2) Å], forming a distorted square-planar geometry.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.017 Å
• R factor = 0.047
• wR factor = 0.105
• Data-to-parameter ratio = 25.6

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT342_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...         17

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Pt1         (2)       0.96
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......         12

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

---

S1. Comment

During the course of our ongoing studies on the design of new antitumor prodrugs related to cisplatin Łakomska et al., 2007;Łakomska et al., 2004) we have isolated the title compound (I) (Fig. 1). The asymmetric unit comprises a half of the molecule as the Pt atom lies on a crystallographic twofold axis. The crystal structure displays a distorted square-planar geometry around Pt(II) which is coordinated by a chelating N,N,N',N'-tetramethylethylenediamine tmeda ligand (dihedral angle of N—C—C—N = -53.1 (12)°) and two iodo ligands. The largest deviation from the ideal geometry is imposed by N1—Pt—N1ⁱ angle of 84.1 (5)° (symmetry code:(i) -x, y, -z + 3/2), which reflects geometric constrains introduced by the bite angle of the ligand. This value is similar to the corresponding ones of 85.0 (5) and 84.0 (3)° in the cationic complex cis-[Pt(1-methylcytosine)₂(tmeda)]²⁺ (Preut et al., 1991) and cis-[Pt(pentafluorophenyl)₂(tmeda)] (Deacon et al., 1991), respectively. The coordinated ligand atoms and Pt(II) are coplanar within the limits of experimentl errors: I1 and N1 are displaced from the least square plane defined by five atoms (Pt I₂N₂) by -0.003 (2) and -0.004 (2) Å, respectively. Pt—I, Pt—N and the diamine ring distances compare well with the previously reported values (Hughes et al., 2004; Connick & Gray, 1994). The crystal structure of (I) is defined by the van der Waals interactions (Fig. 2).

Related literature

For related literature, see: Connick & Gray (1994); Deacon et al. (1991); Hughes et al. (2004); Preut et al. (1991); Łakomska et al. (2004, 2007).

S2. Experimental

To a solution of K₂PtCl₄ (1.605 g; 3.9 mmol) in 20 cm³ of water, an aqueous solution of KI (3.212 g, 19.3 mmol) was added and the reaction mixture was stirred at room temperature for 1 h. Then 0.88 cm³ (5.9 mmol) of N,N,N',N'-tetramethylethylenediamine (tmeda) was added dropwise, with vigorous stirring. The yellow-brown precipitate was filtered, washed several times with water and ethanol and dried under vacuum. Yield 1.938 g (88%). Analysis: calcd/exp. for C₆H₁₆I₂N₂Pt: C 12.8/12.7; N 5.0/4.9; H, 2.9/2.8. Crystals suitable for single-crystal X-ray diffraction were obtained by recrystallization from a water:methanol:2-propanol mixture (2:1:1).

S3. Refinement

H atoms were positioned geometrically (C—H = 0.98 and 0.99 Å) and constrained to ride on their parent atoms; U_iso(H) values were fixed at 1.2 times U_eq(C) (1.5 times for methyl H atoms).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 2001; Atwood & Barbour, 2003); software used to prepare material for publication: X-SEED (Barbour, 2001; Atwood & Barbour, 2003).

Figures

	Fig. 1. The molecular structure of (I) showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Unlabelled atoms are related to the labelled atoms by the symmetry operation -x, y, -z + 3/2. H atoms are shown as spheres of arbitrary radii.
	Fig. 2. Packing diagram of (I) viewed along [100].

cis-Diiodido(N,N,N',N'-tetramethylethylenediamine-κ²N,N')platinum(II)

Crystal data

[PtI2(C6H16N2)]	Z = 4
Mr = 565.10	F(000) = 1000
Monoclinic, C2/c	Dx = 3.227 Mg m^−3
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 7.937 (7) Å	µ = 17.32 mm^−1
b = 14.733 (14) Å	T = 100 K
c = 10.43 (1) Å	Plate, colourless
β = 107.513 (17)°	0.14 × 0.10 × 0.03 mm
V = 1163.1 (19) Å^3

Data collection

Bruker APEX CCD area-detector diffractometer	1359 independent reflections
Radiation source: fine-focus sealed tube	1175 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.051
ω scans	θmax = 28.3°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −10→10
Tmin = 0.145, Tmax = 0.593	k = −19→16
3585 measured reflections	l = −13→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.105	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0423P)^2 + 24.7364P] where P = (Fo^2 + 2Fc^2)/3
1359 reflections	(Δ/σ)max < 0.001
53 parameters	Δρmax = 3.38 e Å^−3
12 restraints	Δρmin = −2.98 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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	0.0000	0.01766 (4)	0.7500	0.01035 (18)
I1	0.21455 (11)	0.14405 (5)	0.87331 (8)	0.0226 (2)
N1	−0.1649 (12)	−0.0872 (6)	0.6530 (9)	0.0125 (19)
C2	−0.0594 (15)	−0.1730 (8)	0.6785 (12)	0.018 (2)
H2A	0.0124	−0.1773	0.6158	0.021*
H2B	−0.1396	−0.2260	0.6632	0.021*
C4	−0.3189 (16)	−0.0968 (9)	0.7077 (12)	0.022 (3)
H4A	−0.3890	−0.1500	0.6673	0.033*
H4B	−0.3928	−0.0423	0.6859	0.033*
H4C	−0.2753	−0.1044	0.8055	0.033*
C3	−0.2406 (15)	−0.0778 (8)	0.5058 (12)	0.020 (3)
H3A	−0.1448	−0.0725	0.4650	0.031*
H3B	−0.3147	−0.0233	0.4853	0.031*
H3C	−0.3124	−0.1313	0.4694	0.031*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1	0.0099 (3)	0.0105 (3)	0.0116 (3)	0.000	0.0048 (2)	0.000
I1	0.0261 (5)	0.0206 (4)	0.0206 (5)	−0.0096 (3)	0.0061 (4)	−0.0026 (3)
N1	0.012 (2)	0.011 (2)	0.014 (2)	−0.0021 (18)	0.0025 (18)	−0.0021 (17)
C2	0.019 (3)	0.016 (3)	0.018 (3)	0.0004 (19)	0.0054 (19)	0.0004 (19)
C4	0.021 (6)	0.032 (7)	0.012 (6)	0.003 (6)	0.005 (5)	0.001 (5)
C3	0.015 (6)	0.023 (6)	0.021 (6)	−0.013 (5)	0.003 (5)	0.000 (5)

Geometric parameters (Å, º)

Pt1—N1	2.081 (9)	C2—H2A	0.9900
Pt1—N1^i	2.081 (9)	C2—H2B	0.9900
Pt1—I1	2.5891 (18)	C4—H4A	0.9800
Pt1—I1^i	2.5891 (18)	C4—H4B	0.9800
N1—C3	1.478 (15)	C4—H4C	0.9800
N1—C2	1.495 (14)	C3—H3A	0.9800
N1—C4	1.503 (14)	C3—H3B	0.9800
C2—C2^i	1.51 (2)	C3—H3C	0.9800
N1—Pt1—N1^i	84.1 (5)	C2^i—C2—H2B	109.9
N1—Pt1—I1	177.9 (3)	H2A—C2—H2B	108.3
N1^i—Pt1—I1	94.0 (3)	N1—C4—H4A	109.5
N1^i—Pt1—I1^i	177.9 (3)	N1—C4—H4B	109.5
I1—Pt1—I1^i	88.02 (8)	H4A—C4—H4B	109.5
C3—N1—C2	107.2 (9)	N1—C4—H4C	109.5
C3—N1—C4	106.3 (9)	H4A—C4—H4C	109.5
C2—N1—C4	109.2 (9)	H4B—C4—H4C	109.5
C3—N1—Pt1	115.8 (7)	N1—C3—H3A	109.5
C2—N1—Pt1	107.7 (7)	N1—C3—H3B	109.5
C4—N1—Pt1	110.5 (7)	H3A—C3—H3B	109.5
N1—C2—C2^i	109.1 (7)	N1—C3—H3C	109.5
N1—C2—H2A	109.9	H3A—C3—H3C	109.5
C2^i—C2—H2A	109.9	H3B—C3—H3C	109.5
N1—C2—H2B	109.9
N1^i—Pt1—N1—C3	−133.8 (9)	I1^i—Pt1—N1—C4	−74.1 (7)
I1^i—Pt1—N1—C3	46.8 (8)	C3—N1—C2—C2^i	164.6 (10)
N1^i—Pt1—N1—C2	−13.9 (5)	C4—N1—C2—C2^i	−80.7 (13)
I1^i—Pt1—N1—C2	166.7 (6)	Pt1—N1—C2—C2^i	39.4 (12)
N1^i—Pt1—N1—C4	105.3 (8)

Symmetry code: (i) −x, y, −z+3/2.