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Acta Cryst. (2008). E64, m698-m699    [ doi:10.1107/S160053680801088X ]

Tetrakis(thiourea-[kappa]S)palladium(II) dithiocyanate

S. Nadeem, M. Khawar Rauf, M. Ebihara, S. A. Tirmizi and S. Ahmad

Abstract top

The title compound, [Pd(CH4N2S)4](SCN)2, consists of complex [Pd(TU)4]2+ [TU = thiourea, SC(NH2)2] cations and thiocyanate counter-anions. The PdII cation is situated on an inversion centre and exhibits an almost square-planar coordination by the S atoms of the TU ligands. The complex cations are connected through the thiocyanate ions via N-H...N [2.922 (3)-3.056 (3) Å] and N-H...S [3.369 (2)-3.645 (2) Å] hydrogen bonds.

Comment top

Thiourea (TU), SC(NH2)2, is a simple ambidentate ligand capable of binding to transition metals via the sulfur or the nitrogen atoms. Complex formation with such ligands provides model systems for the interaction of naturally occurring biomolecules possessing thioamido binding sites (Akrivos, 2001; Raper, 1996; Cusumano et al., 2005). The ability of TU to form stable adducts with a variety of transition metals, e.g. Cu, Ag, Au and Pt, is well established. The crystal structures of several such complexes have been determined (Bott et al., 1998; Gale et al., 2006). These studies demonstrate that TU can act both as a terminal ligand in monomeric complexes (Hunt et al., 1979), or as a bridging ligand in polymeric complexes (Taylor et al., 1974). In order to investigate other transition metal complexes of thiourea, we report here the crystal structure of a monomeric complex, viz. [Pd(SC(NH2)2)4](SCN)2, (I).

The crystal structure of (I) is composed of complex [Pd(TU)4]+2 cations and thiocyanate counter anions. The Pd2+ ion is situated on an inversion centre and, as expected for a d8 system, has an almost square planar environment with cis angles (S—Pd—S) ranging from 87.87 (2) to 92.13 (2)°, and trans angles (S—Pd—S) of 180.0°. The TU ligands are coordinated to PdII at almost equal distances. The Pd—S bond lengths of 2.3302 (8) and 2.3448 (7) Å (Table 1) are comparable to those of similar compounds reported in the literature (Gale et al., 2006). In the cationic complex, TU ligands behave as S–donors and all four ligands are binding in a terminal mode. Therefore no bridging of metal centers are found as it is observed in some other metal-thiourea compounds, for example, [Cu4(TU)7(SO4)2]NO3 (Bott et al., 1998) and [Ag2(TU)6](ClO4)2 (Dupa & Krebs, 1973). The C—S and C—N bond lengths of 1.723 (2) Å and 1.326 (3) Å, respectively, agree with those of coordinated thiourea molecules reported in the Cambridge Crystallographic database (Allen, 2002). In the crystal structure, the building units are connected via hydrogen bonds of the type N—H···N [2.922 (3)–3.058 (3) Å] and N—H···S [3.370 (2)–3.646 (2) Å] (see Table 2).

Related literature top

For the coordination chemistry of thiones and thionates, and for biomolecules possessing thioamido binding sites, see: Akrivos (2001); Raper (1996); Cusumano et al. (2005). For other structures listed in the Cambridge Structural Database (Allen, 2002) that contain transition metals and thiourea ligands, see: Bott et al. (1998); Dupa & Krebs (1973); Gale et al. (2006); Hunt et al. (1979); Taylor et al. (1974).

Experimental top

Crystals of (I) were obtained by adding 4 equivalents of thiourea in 15 ml methanol to a solution of K2[PdCl2] (0.326 g) in 15 ml of water and stirring for one h. The resulting orange solution was kept after filtration at room temperature for three d. Orange crystals of (I) were obtained on slow evaporation. The counter anion SCN- has apparently been introduced due to impurities (presumably KSCN), that were present in thiourea.

Refinement top

The H atoms attached to the N atoms were placed in idealized positions and refined with a N—H distance of 0.88 Å and Uiso(H) = 1.2Ueq(N).

Computing details top

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); cell refinement: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); data reduction: TEXSAN (Molecular Structure Corporation & Rigaku, 2004); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and TEXSAN (Molecular Structure Corporation & Rigaku, 2004).

Figures top
[Figure 1] Fig. 1. Molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 30% probability level. Unlabelled atoms and atoms labelled by superscript i) are related by the symmetry operator i) 1-x, y, z.
Tetrakis(thiourea-κS)palladium(II) dithiocyanate top
Crystal data top
[Pd(CH4N2S)4](SCN)2F000 = 528
Mr = 527.05Dx = 1.884 Mg m−3
Monoclinic, P21/cMo Kα radiation
λ = 0.71070 Å
Hall symbol: -P 2ybcCell parameters from 3103 reflections
a = 8.136 (3) Åθ = 3.4–27.5º
b = 12.966 (5) ŵ = 1.69 mm−1
c = 8.810 (3) ÅT = 123 (2) K
β = 91.12 (5)ºPrism, orange
V = 929.3 (6) Å30.30 × 0.25 × 0.22 mm
Z = 2
Data collection top
Rigaku/MSC Mercury CCD
diffractometer		2117 independent reflections
Radiation source: fine-focus sealed tube2040 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.025
T = 123(2) Kθmax = 27.5º
ω scansθmin = 3.9º
Absorption correction: integration
(NUMABS; Higashi, 1999)		h = −8→10
Tmin = 0.632, Tmax = 0.708k = −16→13
7301 measured reflectionsl = −11→11
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.022H-atom parameters constrained
wR(F2) = 0.043  w = 1/[σ2(Fo2) + 0.6382P]
where P = (Fo2 + 2Fc2)/3
S = 1.35(Δ/σ)max = 0.001
2117 reflectionsΔρmax = 0.66 e Å−3
106 parametersΔρmin = −0.48 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
[Pd(CH4N2S)4](SCN)2V = 929.3 (6) Å3
Mr = 527.05Z = 2
Monoclinic, P21/cMo Kα
a = 8.136 (3) ŵ = 1.69 mm−1
b = 12.966 (5) ÅT = 123 (2) K
c = 8.810 (3) Å0.30 × 0.25 × 0.22 mm
β = 91.12 (5)º
Data collection top
Rigaku/MSC Mercury CCD
diffractometer		2117 independent reflections
Absorption correction: integration
(NUMABS; Higashi, 1999)		2040 reflections with I > 2σ(I)
Tmin = 0.632, Tmax = 0.708Rint = 0.025
7301 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.022106 parameters
wR(F2) = 0.043H-atom parameters constrained
S = 1.35Δρmax = 0.66 e Å−3
2117 reflectionsΔρmin = −0.48 e Å−3
Special details top

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 (Å2) top
xyzUiso*/Ueq
Pd10.00000.50000.50000.00900 (6)
S1−0.19061 (6)0.37251 (3)0.56476 (5)0.01265 (10)
C1−0.1354 (2)0.26304 (14)0.4664 (2)0.0140 (4)
N1−0.0189 (2)0.26297 (13)0.36425 (19)0.0197 (4)
H1A0.00680.20540.31750.024*
H1B0.03320.32050.34290.024*
N2−0.2134 (2)0.17612 (13)0.49809 (19)0.0199 (4)
H2A−0.18740.11870.45110.024*
H2B−0.29110.17590.56610.024*
S20.13159 (6)0.47003 (4)0.73312 (5)0.01300 (10)
C20.3204 (2)0.41505 (14)0.7012 (2)0.0141 (4)
N30.3774 (2)0.39827 (14)0.56415 (18)0.0201 (4)
H3A0.47430.36930.55340.024*
H3B0.31840.41600.48350.024*
N40.4105 (2)0.38793 (14)0.82155 (19)0.0219 (4)
H4A0.50730.35910.80960.026*
H4B0.37360.39880.91340.026*
S30.22933 (7)0.42269 (4)0.17265 (6)0.02044 (12)
C30.4076 (3)0.36611 (15)0.2055 (2)0.0186 (4)
N50.5334 (2)0.32525 (15)0.2287 (2)0.0260 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Pd10.00878 (10)0.00771 (9)0.01049 (9)0.00000 (7)−0.00061 (7)0.00047 (7)
S10.0121 (2)0.0103 (2)0.0156 (2)−0.00127 (17)0.00147 (17)−0.00054 (16)
C10.0152 (10)0.0128 (9)0.0137 (9)−0.0004 (7)−0.0027 (7)0.0001 (7)
N10.0228 (10)0.0129 (8)0.0238 (9)−0.0030 (7)0.0077 (7)−0.0057 (6)
N20.0248 (10)0.0115 (8)0.0236 (9)−0.0039 (7)0.0073 (7)−0.0027 (7)
S20.0111 (2)0.0163 (2)0.0115 (2)0.00134 (17)−0.00052 (16)0.00123 (16)
C20.0126 (9)0.0124 (9)0.0172 (9)−0.0010 (7)−0.0007 (7)0.0011 (7)
N30.0166 (9)0.0275 (9)0.0162 (8)0.0096 (7)0.0005 (7)0.0019 (7)
N40.0170 (9)0.0309 (10)0.0176 (8)0.0108 (8)−0.0040 (7)0.0005 (7)
S30.0193 (3)0.0202 (2)0.0220 (2)0.0026 (2)0.0054 (2)0.00404 (19)
C30.0235 (12)0.0183 (10)0.0144 (9)−0.0049 (8)0.0061 (8)−0.0029 (7)
N50.0232 (11)0.0256 (9)0.0292 (10)0.0018 (8)0.0031 (8)−0.0007 (8)
Geometric parameters (Å, °) top
Pd1—S22.3302 (11)N2—H2B0.8800
Pd1—S2i2.3302 (11)S2—C21.721 (2)
Pd1—S12.3448 (8)C2—N31.320 (3)
Pd1—S1i2.3448 (8)C2—N41.325 (3)
S1—C11.727 (2)N3—H3A0.8800
C1—N11.320 (3)N3—H3B0.8800
C1—N21.326 (3)N4—H4A0.8800
N1—H1A0.8800N4—H4B0.8800
N1—H1B0.8800S3—C31.646 (2)
N2—H2A0.8800C3—N51.167 (3)
S2—Pd1—S2i180.0C1—N2—H2B120.0
S2—Pd1—S187.86 (3)H2A—N2—H2B120.0
S2i—Pd1—S192.14 (3)C2—S2—Pd1108.72 (7)
S2—Pd1—S1i92.14 (3)N3—C2—N4119.29 (18)
S2i—Pd1—S1i87.86 (3)N3—C2—S2123.27 (15)
S1—Pd1—S1i180.0N4—C2—S2117.44 (15)
C1—S1—Pd1106.11 (7)C2—N3—H3A120.0
N1—C1—N2119.74 (17)C2—N3—H3B120.0
N1—C1—S1122.68 (15)H3A—N3—H3B120.0
N2—C1—S1117.57 (15)C2—N4—H4A120.0
C1—N1—H1A120.0C2—N4—H4B120.0
C1—N1—H1B120.0H4A—N4—H4B120.0
H1A—N1—H1B120.0N5—C3—S3179.5 (2)
C1—N2—H2A120.0
S2—Pd1—S1—C1−101.78 (7)S1—Pd1—S2—C2112.12 (7)
S2i—Pd1—S1—C178.22 (7)S1i—Pd1—S2—C2−67.88 (7)
Pd1—S1—C1—N1−6.95 (19)Pd1—S2—C2—N32.44 (18)
Pd1—S1—C1—N2172.15 (14)Pd1—S2—C2—N4−176.95 (14)
Symmetry codes: (i) −x, −y+1, −z+1.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···S30.882.583.369 (2)150
N1—H1A···S2ii0.882.603.466 (2)166
N2—H2A···S3iii0.882.783.615 (2)158
N2—H2B···N5iv0.882.042.922 (3)178
N3—H3B···S30.882.823.645 (2)157
N3—H3A···S1v0.882.733.531 (2)153
N4—H4B···S3vi0.882.613.482 (2)173
N4—H4A···N5vii0.882.503.056 (3)121
Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) −x, y−1/2, −z+1/2; (iv) x−1, −y+1/2, z+1/2; (v) x+1, y, z; (vi) x, y, z+1; (vii) x, −y+1/2, z+1/2.
Table 1
Selected geometric parameters (Å, °) top
Pd1—S22.3302 (11)Pd1—S12.3448 (8)
S2—Pd1—S2i180.0S2i—Pd1—S192.14 (3)
S2—Pd1—S187.86 (3)
Symmetry codes: (i) −x, −y+1, −z+1.
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···S30.882.583.369 (2)150
N1—H1A···S2ii0.882.603.466 (2)166
N2—H2A···S3iii0.882.783.615 (2)158
N2—H2B···N5iv0.882.042.922 (3)178
N3—H3B···S30.882.823.645 (2)157
N3—H3A···S1v0.882.733.531 (2)153
N4—H4B···S3vi0.882.613.482 (2)173
N4—H4A···N5vii0.882.503.056 (3)121
Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) −x, y−1/2, −z+1/2; (iv) x−1, −y+1/2, z+1/2; (v) x+1, y, z; (vi) x, y, z+1; (vii) x, −y+1/2, z+1/2.
Acknowledgements top

M. K. Rauf is grateful to the Higher Education Commission of Pakistan for financial support for a PhD programme.

references
References top

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