cis-(1,4-Di­thia­ne-S,S')­di­iodo­platinum(II)

The title compound, [PtI₂(S₂C₄H₈)], consists of a 1,4-di­thia­ne and two iodo ligands coordinated to a Pt atom in a distorted square-planar cis-system with Pt on a twofold axis. The di­thiane forms a bidentate chelate with Pt, bonding via the S atoms. The Pt-I bonds are 2.6035 (5) Å and the Pt-S bonds 2.2751 (16) Å. The Pt-S bond is influenced mainly by the cis-chelate effect and the Pt-I bond by the trans-influence of sulfur.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.011 Å
• R factor = 0.026
• wR factor = 0.049
• Data-to-parameter ratio = 37.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



ABSTM_02  Alert C The ratio of expected to reported Tmax/Tmin(RR) is > 1.10
          Tmin and Tmax reported:      0.168     0.268
          Tmin and Tmax expected:      0.142     0.288
          RR =      1.274
          Please check that your absorption correction is appropriate.

PLAT_711  Alert C BOND    Unknown or Inconsistent Label ........       PT
                           PT     S1

PLAT_711  Alert C BOND    Unknown or Inconsistent Label ........       PT
                           PT     S1

PLAT_711  Alert C BOND    Unknown or Inconsistent Label ........       PT
                           PT     I1

PLAT_711  Alert C BOND    Unknown or Inconsistent Label ........       PT
                           PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           S1     PT     S1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           S1     PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           S1     PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           S1     PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           S1     PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           I1     PT     I1

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           C2     S1     PT

PLAT_712  Alert C ANGLE   Unknown or Inconsistent Label ........       PT
                           C1     S1     PT

General Notes



FORMU_01  There is a discrepancy between the atom counts in the
          _chemical_formula_sum and _chemical_formula_moiety. This is
          usually due to the moiety formula being in the wrong format.
          Atom count from _chemical_formula_sum:   C4 H8 I2 Pt1 S2
          Atom count from _chemical_formula_moiety:

ABSTM_02  When printed, the submitted absorption T values will be replaced
          by the scaled T values. Since the ratio of scaled T's is
          identical to the ratio of reported T values, the scaling does
          not imply a change to the absorption corrections used in the
          study.
          Ratio of Tmax expected/reported      1.074
          Tmax scaled      0.288 Tmin scaled      0.180

REFLT_03
         From the CIF: _diffrn_reflns_theta_max           31.98
         From the CIF: _reflns_number_total               1625
         Count of symmetry unique reflns         1050
         Completeness (_total/calc)            154.76%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured       575
         Fraction of Friedel pairs measured     0.548
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 13 Alert Level C = Please check

---

S1. Comment

1,4-Dithiane [dit, S(C₂H₄)₂S] is the thioether analogue of the antitumor agent piperazine (Ciccarese et al., 1998). Very few compounds with 1,4-dithiane as a bidentate ligand have been crystallographically characterized. The only metal–organic compound with a chelating dithiane found in the Cambridge Structural Database (CSD; Allen & Kennard, 1993) is an osmium cluster (Adams et al., 1995). Platinum halide compounds with thioether ligands have been investigated earlier and it is found that most of the chloro and bromo compounds structurally characterized adopt a cis-configuration, while the trans-configuration is mainly observed for iodo complexes (Lövqvist, 1996). Only two cis-platinum–iodo–thioether complexes are found in the CSD, both with chelating thioethers, diiodo[1,2-bis(phenylsulfanyl)ethane]platinum(II) (Marangoni et al., 1995) and diiodo(1,3,5,7-tetrametyl-2,4,6,8-tetrathiaadamantane)platinum(II) (Levy & Long, 1975).

The title compound, (I), crystallizes in the tetragonal space group P4₃2₁2 with the Pt atom on a twofold rotation axis. The dithiane forms a bidentate chelate with platinum(II), forcing the compound to adopt cis-configuration with the two I atoms in trans-positions to the dithiane S atoms (Fig. 1). The dithiane molecule must assume the boat conformation to be able to bind as a bidentate ligand. Bond lengths and angles are shown in Table 1. The complex exhibits a distorted square-planar geometry with angles around Pt from 79.74 (8) to 93.76 (4)°. The S—C distances, 1.818 (7) and 1.810 (7) Å, and the S—C—C angles, 111.6 (5) and 112.9 (5)°, are close to those found in free dithiane, even though the free form adopts the chair conformation (Marsh, 1955). The C—C bond seems to get elongated, 1.538 (10) versus 1.490 (18) Å, and the C—S—C angles become smaller, 97.4 (4) versus 99.0 (6)°, upon bidentate complexation with platinum. The closest contact between the complexes is S1···C1(-0.5 + x, 1.5 - y, 0.25 - z) of 3.729 (1) Å and the shortest Pt···Pt distance is 6.213 (1) Å.

In Table 2, cis- and trans-diiodoplatinum compounds with thioethers from the literature are listed. There are only two cis-compounds found and they both have bidentate chelating thioethers. The Pt—I bond distance in the title compound, 2.6035 (5) Å, is close to those reported for the other cis-compound. The Pt—I distances in the trans-compounds shows a wider range, 2.6039 (8) to 2.616 (1) Å.

The range of Pt—I bond distance trans to simple bidentate N-donor ligands with two C atoms between the N atoms in the CSD are 2.574 (2)–2.591 (2) Å (Casas et al., 1998; Ciccarese et al., 1998; Clark et al., 1995; Connick & Gray, 1994; Fanizzi et al., 1996; Mégnamisi-Bélombé & Endres, 1985) with one exception, 4,7-Ph₂-phen (phen = 1,10-phenanthroline), where the Pt—I distances are 2.558 (2) Å (Fanizzi et al., 1996). In chelating bidentate ligand complexes trans to P atoms, the Pt—I bond distances are in the range 2.6480 (9)–2.662 (2) Å (Wilson et al., 1994; Dahlenburg & Kurth, 1998). The differences in Pt—I bond length trans to S, N and P are thus consistent with the trans-influence series, where P > S > N (Greenwood & Earnshaw, 1997). The difference between P and S trans-influence is clearly shown in [PtI₂(PhPC₆H₁₂S)], where I is trans to both S and P, with Pt—I distances 2.598 (3) and 2.639 (2) Å, respectively.

In Table 2, the Pt—S distances in the above mentioned thioether compounds are shown. In the cis-compounds the Pt—S bond distances are 2.265 (2) and 2.280 (8) Å. The Pt—S bond of 2.2751 (16) Å for [PtI₂(dit)] lies within the range for the above-mentioned values obtained from literature. The average Pt—S bond distance for systems with S atoms trans to each other and cis to I is 2.305 (2) Å. These differences in the Pt—S bonds may be due to a cis-chelate effect, even though sulfur has a larger trans-influence than iodine. The cis-chelate effect is mainly referred to as a kinetic effect, but Marangoni et al. (1995) have performed comparative studies between Pt—S(thioether) bonds from both chelating and simple thioethers with the same atom in trans-position for a number of different Pt^II compounds. The chelating compounds yield shorter bond lengths, independent of the atom in trans-position and this is most probably due to electronic effects; the empty orbitals of sulfur is properly orientated towards the filled d_xy orbitals of platinum, resulting in easier π(d–d) back-donation.

The bite angle of the bidentate dithiane, 79.74 (8)°, is larger than the angle for N-methylpiperazine, 70.1 (7)° (Ciccarese et al., 1998). This difference is probably due to the larger atomic radius of sulfur compared to nitrogen, but the bite angle for PhS(CH₂)₂SPh is larger than for both the others, 91.00 (8)°, as would be expected because only one-carbon chain forms the chelating backbone in the latter (Marangoni et al., 1995).

S2. Experimental

PtI₂ (100 mg, 0.223 mmol) was added to an ethanol solution (5 ml) of 1,4 dithiane (30 mg, 0.245 mmol). The solution was stirred for 5 h at ambient temperature. The orange precipitate was filtered and washed with water (2 × 5 ml), ethanol (2 × 5 ml) and chloroform (3 × 5 ml) (yield 96 mg, 76%). Crystals of good quality were obtained by recrystallization from hot DMSO.

S3. Refinement

H atoms were refined with fixed individual displacement parameters [U(H) = 1.2U_eq(C)] using a riding model with C—H = 0.97 Å.

Computing details

Data collection: SMART (Bruker, 1995); cell refinement: SAINT (Bruker, 1995); data reduction: SAINT (Bruker, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. Numbering scheme with displacement ellipsoids (30% probability) for the title compound.

(I)

Crystal data

[PtI2(C4H8S2)]	Dx = 3.818 Mg m^−3
Mr = 569.11	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212	Cell parameters from 4610 reflections
a = 8.9850 (13) Å	θ = 2.8–29°
c = 12.265 (3) Å	µ = 20.75 mm^−1
V = 990.2 (3) Å^3	T = 293 K
Z = 4	Prism, orange
F(000) = 992	0.10 × 0.09 × 0.06 mm

Data collection

Bruker SMART CCD diffractometer	1625 independent reflections
Radiation source: rotating anode	1387 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.061
Detector resolution: 512 pixels mm^-1	θmax = 32.0°, θmin = 2.8°
ω scans	h = −13→12
Absorption correction: empirical (using intensity measurements) absorption corrections using SADABS (Sheldrick, 1996)	k = −12→13
Tmin = 0.168, Tmax = 0.268	l = −13→18
10493 measured reflections

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.026	w = 1/[σ^2(Fo^2) + (0.0174P)^2 + 1.0607P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.049	(Δ/σ)max < 0.001
S = 1.05	Δρmax = 1.04 e Å^−3
1625 reflections	Δρmin = −1.06 e Å^−3
43 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.00217 (15)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983)
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.009 (7)

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	0.41705 (2)	0.41705 (2)	0.0000	0.02798 (9)
I1	0.16998 (4)	0.38139 (5)	0.10777 (4)	0.04066 (13)
S1	0.47268 (18)	0.63627 (18)	0.08341 (14)	0.0395 (4)
C1	0.6621 (8)	0.5942 (9)	0.1253 (6)	0.0539 (18)
H1A	0.7119	0.6857	0.1463	0.065*
H1B	0.6598	0.5293	0.1885	0.065*
C2	0.5186 (9)	0.7505 (8)	−0.0334 (6)	0.0482 (17)
H2A	0.4282	0.7955	−0.0614	0.058*
H2B	0.5844	0.8301	−0.0103	0.058*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1	0.02567 (10)	0.02567 (10)	0.03261 (16)	−0.00257 (12)	0.00085 (9)	−0.00085 (9)
I1	0.0309 (2)	0.0475 (3)	0.0436 (2)	−0.00299 (17)	0.00695 (17)	0.00693 (18)
S1	0.0319 (7)	0.0351 (8)	0.0515 (10)	−0.0032 (6)	0.0032 (7)	−0.0146 (7)
C1	0.042 (4)	0.063 (5)	0.057 (4)	−0.001 (4)	−0.008 (3)	−0.012 (4)
C2	0.052 (4)	0.026 (3)	0.066 (5)	−0.002 (3)	−0.004 (4)	0.003 (3)

Geometric parameters (Å, º)

Pt—S1	2.2751 (16)	S1—C2	1.810 (7)
Pt—S1^i	2.2751 (16)	S1—C1	1.818 (7)
Pt—I1^i	2.6035 (5)	C1—C2^i	1.538 (10)
Pt—I1	2.6035 (5)	C2—C1^i	1.538 (10)
S1—Pt—S1^i	79.74 (8)	C2—S1—C1	97.4 (4)
S1—Pt—I1^i	173.50 (4)	C2—S1—Pt	100.7 (2)
S1^i—Pt—I1^i	93.76 (4)	C1—S1—Pt	98.8 (2)
S1—Pt—I1	93.76 (4)	C2^i—C1—S1	111.6 (5)
S1^i—Pt—I1	173.50 (4)	C1^i—C2—S1	112.9 (5)
I1^i—Pt—I1	92.74 (2)

Symmetry code: (i) y, x, −z.