Tetrakis(thiourea-κS)palladium(II) dithio­cyanate

Abstract

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 Pd^II 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.

Related literature

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

Crystal data

• [Pd(CH₄N₂S)₄](SCN)₂

• M _r = 527.05

• Monoclinic,

• a = 8.136 (3) Å

• b = 12.966 (5) Å

• c = 8.810 (3) Å

• β = 91.12 (5)°

• V = 929.3 (6) ų

• Z = 2

• Mo Kα radiation

• μ = 1.69 mm⁻¹

• T = 123 (2) K

• 0.30 × 0.25 × 0.22 mm

Data collection

• Rigaku/MSC Mercury CCD diffractometer

• Absorption correction: integration (NUMABS; Higashi, 1999 ▶) T _min = 0.632, T _max = 0.708

• 7301 measured reflections

• 2117 independent reflections

• 2040 reflections with I > 2σ(I)

• R _int = 0.025

Refinement

• R[F ² > 2σ(F ²)] = 0.022

• wR(F ²) = 0.043

• S = 1.35

• 2117 reflections

• 106 parameters

• H-atom parameters constrained

• Δρ_max = 0.66 e Å⁻³

• Δρ_min = −0.48 e Å⁻³

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2001 ▶); cell refinement: CrystalClear; 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 and TEXSAN.

Supplementary Material

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

Table 1. Selected geometric parameters (Å, °).

Pd1—S2	2.3302 (11)
Pd1—S1	2.3448 (8)

S2—Pd1—S2i	180
S2—Pd1—S1	87.86 (3)
S2i—Pd1—S1	92.14 (3)

Symmetry code: (i) .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1B⋯S3	0.88	2.58	3.369 (2)	150
N1—H1A⋯S2ii	0.88	2.60	3.466 (2)	166
N2—H2A⋯S3iii	0.88	2.78	3.615 (2)	158
N2—H2B⋯N5iv	0.88	2.04	2.922 (3)	178
N3—H3B⋯S3	0.88	2.82	3.645 (2)	157
N3—H3A⋯S1v	0.88	2.73	3.531 (2)	153
N4—H4B⋯S3vi	0.88	2.61	3.482 (2)	173
N4—H4A⋯N5vii	0.88	2.50	3.056 (3)	121

Symmetry codes: (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

supplementary crystallographic information

Comment

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 Pd^II 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).

Experimental

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

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 U_iso(H) = 1.2U_eq(N).

Figures

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.

Crystal data

[Pd(CH4N2S)4](SCN)2	F000 = 528
Mr = 527.05	Dx = 1.884 Mg m−3
Monoclinic, P21/c	Mo Kα radiation λ = 0.71070 Å
Hall symbol: -P 2ybc	Cell parameters from 3103 reflections
a = 8.136 (3) Å	θ = 3.4–27.5º
b = 12.966 (5) Å	µ = 1.69 mm−1
c = 8.810 (3) Å	T = 123 (2) K
β = 91.12 (5)º	Prism, orange
V = 929.3 (6) Å3	0.30 × 0.25 × 0.22 mm
Z = 2

Data collection

Rigaku/MSC Mercury CCD diffractometer	2117 independent reflections
Radiation source: fine-focus sealed tube	2040 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.025
T = 123(2) K	θmax = 27.5º
ω scans	θmin = 3.9º
Absorption correction: integration(NUMABS; Higashi, 1999)	h = −8→10
Tmin = 0.632, Tmax = 0.708	k = −16→13
7301 measured reflections	l = −11→11

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.022	H-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 reflections	Δρmax = 0.66 e Å−3
106 parameters	Δρmin = −0.48 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

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
Pd1	0.0000	0.5000	0.5000	0.00900 (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)
H1A	0.0068	0.2054	0.3175	0.024*
H1B	0.0332	0.3205	0.3429	0.024*
N2	−0.2134 (2)	0.17612 (13)	0.49809 (19)	0.0199 (4)
H2A	−0.1874	0.1187	0.4511	0.024*
H2B	−0.2911	0.1759	0.5661	0.024*
S2	0.13159 (6)	0.47003 (4)	0.73312 (5)	0.01300 (10)
C2	0.3204 (2)	0.41505 (14)	0.7012 (2)	0.0141 (4)
N3	0.3774 (2)	0.39827 (14)	0.56415 (18)	0.0201 (4)
H3A	0.4743	0.3693	0.5534	0.024*
H3B	0.3184	0.4160	0.4835	0.024*
N4	0.4105 (2)	0.38793 (14)	0.82155 (19)	0.0219 (4)
H4A	0.5073	0.3591	0.8096	0.026*
H4B	0.3736	0.3988	0.9134	0.026*
S3	0.22933 (7)	0.42269 (4)	0.17265 (6)	0.02044 (12)
C3	0.4076 (3)	0.36611 (15)	0.2055 (2)	0.0186 (4)
N5	0.5334 (2)	0.32525 (15)	0.2287 (2)	0.0260 (4)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Pd1	0.00878 (10)	0.00771 (9)	0.01049 (9)	0.00000 (7)	−0.00061 (7)	0.00047 (7)
S1	0.0121 (2)	0.0103 (2)	0.0156 (2)	−0.00127 (17)	0.00147 (17)	−0.00054 (16)
C1	0.0152 (10)	0.0128 (9)	0.0137 (9)	−0.0004 (7)	−0.0027 (7)	0.0001 (7)
N1	0.0228 (10)	0.0129 (8)	0.0238 (9)	−0.0030 (7)	0.0077 (7)	−0.0057 (6)
N2	0.0248 (10)	0.0115 (8)	0.0236 (9)	−0.0039 (7)	0.0073 (7)	−0.0027 (7)
S2	0.0111 (2)	0.0163 (2)	0.0115 (2)	0.00134 (17)	−0.00052 (16)	0.00123 (16)
C2	0.0126 (9)	0.0124 (9)	0.0172 (9)	−0.0010 (7)	−0.0007 (7)	0.0011 (7)
N3	0.0166 (9)	0.0275 (9)	0.0162 (8)	0.0096 (7)	0.0005 (7)	0.0019 (7)
N4	0.0170 (9)	0.0309 (10)	0.0176 (8)	0.0108 (8)	−0.0040 (7)	0.0005 (7)
S3	0.0193 (3)	0.0202 (2)	0.0220 (2)	0.0026 (2)	0.0054 (2)	0.00404 (19)
C3	0.0235 (12)	0.0183 (10)	0.0144 (9)	−0.0049 (8)	0.0061 (8)	−0.0029 (7)
N5	0.0232 (11)	0.0256 (9)	0.0292 (10)	0.0018 (8)	0.0031 (8)	−0.0007 (8)

Geometric parameters (Å, °)

Pd1—S2	2.3302 (11)	N2—H2B	0.8800
Pd1—S2i	2.3302 (11)	S2—C2	1.721 (2)
Pd1—S1	2.3448 (8)	C2—N3	1.320 (3)
Pd1—S1i	2.3448 (8)	C2—N4	1.325 (3)
S1—C1	1.727 (2)	N3—H3A	0.8800
C1—N1	1.320 (3)	N3—H3B	0.8800
C1—N2	1.326 (3)	N4—H4A	0.8800
N1—H1A	0.8800	N4—H4B	0.8800
N1—H1B	0.8800	S3—C3	1.646 (2)
N2—H2A	0.8800	C3—N5	1.167 (3)
S2—Pd1—S2i	180.0	C1—N2—H2B	120.0
S2—Pd1—S1	87.86 (3)	H2A—N2—H2B	120.0
S2i—Pd1—S1	92.14 (3)	C2—S2—Pd1	108.72 (7)
S2—Pd1—S1i	92.14 (3)	N3—C2—N4	119.29 (18)
S2i—Pd1—S1i	87.86 (3)	N3—C2—S2	123.27 (15)
S1—Pd1—S1i	180.0	N4—C2—S2	117.44 (15)
C1—S1—Pd1	106.11 (7)	C2—N3—H3A	120.0
N1—C1—N2	119.74 (17)	C2—N3—H3B	120.0
N1—C1—S1	122.68 (15)	H3A—N3—H3B	120.0
N2—C1—S1	117.57 (15)	C2—N4—H4A	120.0
C1—N1—H1A	120.0	C2—N4—H4B	120.0
C1—N1—H1B	120.0	H4A—N4—H4B	120.0
H1A—N1—H1B	120.0	N5—C3—S3	179.5 (2)
C1—N2—H2A	120.0
S2—Pd1—S1—C1	−101.78 (7)	S1—Pd1—S2—C2	112.12 (7)
S2i—Pd1—S1—C1	78.22 (7)	S1i—Pd1—S2—C2	−67.88 (7)
Pd1—S1—C1—N1	−6.95 (19)	Pd1—S2—C2—N3	2.44 (18)
Pd1—S1—C1—N2	172.15 (14)	Pd1—S2—C2—N4	−176.95 (14)

Symmetry codes: (i) −x, −y+1, −z+1.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···S3	0.88	2.58	3.369 (2)	150
N1—H1A···S2ii	0.88	2.60	3.466 (2)	166
N2—H2A···S3iii	0.88	2.78	3.615 (2)	158
N2—H2B···N5iv	0.88	2.04	2.922 (3)	178
N3—H3B···S3	0.88	2.82	3.645 (2)	157
N3—H3A···S1v	0.88	2.73	3.531 (2)	153
N4—H4B···S3vi	0.88	2.61	3.482 (2)	173
N4—H4A···N5vii	0.88	2.50	3.056 (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.