metal-organic compounds
catena-Poly[[[bis(thiourea-κS)cadmium]-di-μ-thiocyanato-κ2N:S;κ2S:N] dihydrate]
aDepartment of Inorganic Chemistry, Chemical Faculty, Gdansk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdańsk, Poland
*Correspondence e-mail: anna.mietlarek-kropidlowska@pg.gda.pl
The title compound, {[Cd(NCS)2(CH4N2S)2]·2H2O}n, forms a one-dimensional chain parallel to the a axis, caused by the presence of the bridging thiocyanate groups. Two solvent molecules per complex are present in the lattice. The CdII ion is situated on an inversion centre and is coordinated in a distorted octahedral fashion by two N and two S atoms from four thiocyanate ligands and by two S atoms from two thiourea molecules. Weak O—H⋯S, N—H⋯O and N—H⋯N interactions reinforce the structure.
Related literature
For a general introduction to thiocyanato complexes, see: Nardelli et al. (1957). For the syntheses and structures of a series of cadmium complexes with thiourea derivatives and thiocyanato ligands, see: Wang et al. (2002); Cavalca et al. (1960); Zhu et al. (2000); Yang et al. (2001); Ahmad et al. (2008); Williams et al. (1992). For information on the properties of complexes incorporating these ligands, see: Yuan et al. (1997); Krunks et al. (1997); Amutha et al. (2011); Machura et al. (2011). For the use of CdII complexes with mixed S-donor ligands as precursors to CdS, see: Kropidłowska et al. (2008).
Experimental
Crystal data
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Refinement
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Data collection: CrysAlis PRO (Oxford Diffraction, 2008); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).
Supporting information
https://doi.org/10.1107/S1600536812030267/fj2575sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812030267/fj2575Isup2.hkl
The reaction was carried out between 0.50 g cadmium(II) thiocyanate, Cd(SCN)2, and 1.34 g thiourea (molar ratio 1:8) which were dissolved in a small amount of water. The mixture was heated to 70°C and stirred using magnetic stirrer for 50 minutes and then left for crystallization at room temperature. After a few days two types of crystals appeared in the flask: needles (0.2 g) and blocks (0.1 g), which were mechanically separated under the microscope. The structure of needle-like crystals [Cd(SCN)2{µ-SC(NH2)2}]n (m.p. 189°C) has been already described (Wang et al., 2002), while the block-like crystals appeared to be a new compound, crystallizing as diaqua solvate [[Cd{SC(NH2)2}2(SCN)2].2H2O]n (m.p. 187°C). The product, when taken from the mother liquor and dried using the filter paper, changes - becomes opaque and finally takes the form of a powder (most probably because of the removal of the solvent molecules). IR spectra were recorded using Mattson Genesis II Gold spectrometer equipped with Momentum Microscope as detector.
All N—H atoms were placed in calculated positions and refined as riding on their carrier atoms with N—H = 0.86 Å (NH2) and Uiso(H) = 1.2 times Ueq(N). Solvent O—H hydrogen atoms were found in the Fourier map and refined as constrained to: O–H bond length of 0.80 Å, H1C - H1D distance of 1.30 Å and Uiso(H) = 1.5 times Ueq(O) with the default uncertainties.
The interest in the coordination compounds possessing simultaneously thiourea and thiocyanato ligands dates back to the 1950s (e.g. Nardelli et al., 1957) when the nature of coordination compounds formed by divalent cations (M = Mn, Co, Ni, Cd, Pb) and organic molecules containing sulfur was extensively studied. Besides the polymeric catena-poly[bis(thiocyanato-κN)bis(µ-thiourea-κ2S:S)cadmium(II)] (Wang et al., 2002), also structures of four other complexes with thiourea derivatives of [Cd(SCN)2(TU)2]n type, where TU = ethylenethiourea (Cavalca et al., 1960), N,N'-diphenylthiourea (Zhu et al., 2000), N-phenylthiourea (Yang et al., 2001; Ahmad et al., 2008) or 1,3-dimethyl-2(3H)-imidazolethione (Williams et al., 1992), can be found. The interest in these compounds is related either with their non-linear optical properties (Yuan et al., 1997) or with the possibility to use them as single-source precursors of semiconducting materials based on CdS (Krunks et al., 1997; Amutha et al., 2011). Moreover, the use of SCN ligands, with bridging abilities, may lead to intriguing architectures and topologies, often generating one-dimensional chains (Machura et al., 2011). It was the reason why, during our studies on the new molecular precursors (Kropidłowska et al., 2008), we have turned our attention to systems of this type now and we have obtained a new complex containing thiourea and thiocyanato ligands connected to cadmium center.
The cadmium atom in catena-Poly[[[bis(thiourea-κS)cadmium]-di-µ-thiocyanato-κ2N:S;κ2S:N] dihydrate] is located at the inversion center and is octahedrically coordinated by two S atoms and two N atoms from four thiocyanate groups as well as by two S atoms from thiourea molecules. The neighbouring CdII ions are bridged by two µ-SCN-κ2N:S ligands, thus forming eight-membered ring of [Cd-SCN]2 type with the Cd···Cd distance of 5.853 Å, which is close to the values observed in other bridged systems (Machura et al., 2011). These units form one-dimensional chains of slightly distorted edge-shared Cd-centered octahedra along the [100] crystallographic direction. The Cd—S i Cd—N distances are typical for cadmium(II) thiocyanate complexes. The IR spectra clearly show the presence of the thiocyanato groups (with the maxima of νCN absorption at 2078 cm-1).
In the structure of [[Cd{SC(NH2)2}2(SCN)2].2H2O]n, several weak interactions may be assumed, leading to the alternating arrangement of water and complex molecules. Each water molecule interacts with S or N atoms from the three neighboring polymeric chains. Thus, it can serve as a donor of a weak hydrogen bond to the sulfur atom from one of the thiourea moieties (O1(H1D)—S1viii) in one chain, as well as to sulfur from one thiocyanato ligand (O1(H1C) —S2) in the other. The oxygen lone pairs act as acceptors towards NH2 groups from thiourea moieties located within the third chain (N2(H2B) —O1vii, N1(H1A) —O1v, N2(H2A)—O1v). Finally, one "interchain" interaction, N1—H1B···N3i, operates between NH2 and SCN groups.
For a general introduction to thiocyanato complexes, see: Nardelli et al. (1957). For the syntheses and structures of a series of cadmium complexes with thiourea derivatives and thiocyanato ligands, see: Wang et al. (2002); Cavalca et al. (1960); Zhu et al. (2000); Yang et al. (2001); Ahmad et al. (2008); Williams et al. (1992). For information on the properties of complexes incorporating these ligands, see: Yuan et al. (1997); Krunks et al. (1997); Amutha et al. (2011); Machura et al. (2011). For the use of CdII complexes with mixed S-donor ligands as precursors to CdS, see: Kropidłowska et al. (2008).
Data collection: CrysAlis PRO (Oxford Diffraction, 2008); cell
CrysAlis PRO (Oxford Diffraction, 2008); data reduction: CrysAlis PRO (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).Fig. 1. Molecular structure and atom-numbering scheme for [[Cd{SC(NH2)2}2(SCN)2].2H2O]n with displacement ellipsoids drawn at 50% probability level. H atoms are represented as arbitrary circles. Symmetry codes: (i) x+1, y, z; (ii) -x, -y+1, -z; (iii) -x+1, -y+1, -z. | |
Fig. 2. Weak interaction present in the crystal structure of [[Cd{SC(NH2)2}2(SCN)2].2H2O]n between the water and complex molecules (on the left). The arrangement of water and complex molecules in the crystal (on the right). Dashed lines denote the possible weak interactions. |
[Cd(NCS)2(CH4N2S)2]·2H2O | Z = 1 |
Mr = 416.84 | F(000) = 206 |
Triclinic, P1 | Dx = 1.946 Mg m−3 |
Hall symbol: -P 1 | Melting point: 460 K |
a = 5.8533 (3) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.3527 (3) Å | Cell parameters from 4676 reflections |
c = 8.8630 (4) Å | θ = 2.9–33.8° |
α = 73.413 (4)° | µ = 2.12 mm−1 |
β = 76.926 (4)° | T = 293 K |
γ = 88.856 (4)° | Block, colourless |
V = 355.69 (3) Å3 | 0.53 × 0.42 × 0.23 mm |
Oxford Diffraction KM-4-CCD diffractometer | 1985 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.036 |
ω–scan | θmax = 31°, θmin = 2.9° |
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2008), based on expressions derived by Clark & Reid (1995)] | h = −8→8 |
Tmin = 0.558, Tmax = 0.725 | k = −10→10 |
7642 measured reflections | l = −12→12 |
2268 independent reflections |
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) = 0.062 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0266P)2] where P = (Fo2 + 2Fc2)/3 |
2268 reflections | (Δ/σ)max < 0.001 |
85 parameters | Δρmax = 0.47 e Å−3 |
3 restraints | Δρmin = −0.51 e Å−3 |
[Cd(NCS)2(CH4N2S)2]·2H2O | γ = 88.856 (4)° |
Mr = 416.84 | V = 355.69 (3) Å3 |
Triclinic, P1 | Z = 1 |
a = 5.8533 (3) Å | Mo Kα radiation |
b = 7.3527 (3) Å | µ = 2.12 mm−1 |
c = 8.8630 (4) Å | T = 293 K |
α = 73.413 (4)° | 0.53 × 0.42 × 0.23 mm |
β = 76.926 (4)° |
Oxford Diffraction KM-4-CCD diffractometer | 2268 independent reflections |
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2008), based on expressions derived by Clark & Reid (1995)] | 1985 reflections with I > 2σ(I) |
Tmin = 0.558, Tmax = 0.725 | Rint = 0.036 |
7642 measured reflections |
R[F2 > 2σ(F2)] = 0.028 | 3 restraints |
wR(F2) = 0.062 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.47 e Å−3 |
2268 reflections | Δρmin = −0.51 e Å−3 |
85 parameters |
Experimental. CrysAlisPro, (Oxford Diffraction, 2008). Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by (Clark & Reid, 1995). |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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. |
x | y | z | Uiso*/Ueq | ||
Cd1 | 0.5 | 0.5 | 0 | 0.03082 (8) | |
S1 | 0.24899 (10) | 0.38566 (9) | 0.30122 (7) | 0.03890 (15) | |
S2 | 0.25651 (10) | 0.82898 (8) | −0.03961 (7) | 0.03377 (13) | |
N1 | 0.6502 (3) | 0.3430 (3) | 0.3988 (3) | 0.0424 (5) | |
H1A | 0.7326 | 0.2965 | 0.4686 | 0.051* | |
H1B | 0.7155 | 0.4193 | 0.3061 | 0.051* | |
N2 | 0.3288 (4) | 0.1803 (3) | 0.5771 (3) | 0.0481 (6) | |
H2A | 0.4141 | 0.1352 | 0.6452 | 0.058* | |
H2B | 0.1813 | 0.1488 | 0.6023 | 0.058* | |
N3 | −0.1946 (3) | 0.6528 (3) | 0.0619 (3) | 0.0391 (5) | |
C1 | 0.4240 (4) | 0.2975 (3) | 0.4340 (3) | 0.0321 (5) | |
C2 | −0.0091 (4) | 0.7257 (3) | 0.0194 (3) | 0.0281 (4) | |
O1 | 0.1962 (4) | 0.9249 (3) | 0.3133 (2) | 0.0524 (5) | |
H1C | 0.216 (7) | 0.902 (5) | 0.229 (3) | 0.079* | |
H1D | 0.193 (7) | 1.038 (3) | 0.296 (4) | 0.079* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cd1 | 0.02632 (12) | 0.03241 (13) | 0.03125 (13) | −0.00184 (9) | −0.00529 (9) | −0.00613 (10) |
S1 | 0.0255 (3) | 0.0545 (4) | 0.0282 (3) | 0.0010 (3) | −0.0048 (2) | 0.0002 (3) |
S2 | 0.0298 (3) | 0.0265 (3) | 0.0402 (3) | −0.0021 (2) | −0.0038 (2) | −0.0050 (2) |
N1 | 0.0333 (10) | 0.0557 (13) | 0.0361 (11) | −0.0005 (10) | −0.0120 (9) | −0.0065 (10) |
N2 | 0.0454 (12) | 0.0560 (13) | 0.0333 (11) | −0.0053 (11) | −0.0110 (10) | 0.0044 (10) |
N3 | 0.0330 (10) | 0.0371 (11) | 0.0500 (13) | −0.0009 (9) | −0.0106 (9) | −0.0158 (10) |
C1 | 0.0357 (12) | 0.0316 (11) | 0.0295 (11) | 0.0009 (9) | −0.0074 (9) | −0.0100 (9) |
C2 | 0.0335 (11) | 0.0264 (10) | 0.0266 (10) | 0.0050 (9) | −0.0101 (9) | −0.0088 (8) |
O1 | 0.0662 (13) | 0.0522 (11) | 0.0412 (11) | −0.0028 (11) | −0.0197 (10) | −0.0113 (10) |
Cd1—N3i | 2.3734 (19) | N1—H1A | 0.86 |
Cd1—N3ii | 2.3734 (19) | N1—H1B | 0.86 |
Cd1—S1 | 2.6431 (6) | N2—C1 | 1.318 (3) |
Cd1—S1iii | 2.6431 (6) | N2—H2A | 0.86 |
Cd1—S2iii | 2.7585 (6) | N2—H2B | 0.86 |
Cd1—S2 | 2.7585 (6) | N3—C2 | 1.154 (3) |
S1—C1 | 1.714 (2) | N3—Cd1iv | 2.3734 (19) |
S2—C2 | 1.649 (2) | O1—H1C | 0.797 (17) |
N1—C1 | 1.317 (3) | O1—H1D | 0.805 (17) |
N3i—Cd1—N3ii | 180 | C1—S1—Cd1 | 111.15 (8) |
N3i—Cd1—S1 | 95.01 (6) | C2—S2—Cd1 | 96.75 (7) |
N3ii—Cd1—S1 | 84.99 (6) | C1—N1—H1A | 120 |
N3i—Cd1—S1iii | 84.99 (6) | C1—N1—H1B | 120 |
N3ii—Cd1—S1iii | 95.01 (6) | H1A—N1—H1B | 120 |
S1—Cd1—S1iii | 180 | C1—N2—H2A | 120 |
N3i—Cd1—S2iii | 89.81 (5) | C1—N2—H2B | 120 |
N3ii—Cd1—S2iii | 90.19 (5) | H2A—N2—H2B | 120 |
S1—Cd1—S2iii | 92.043 (19) | C2—N3—Cd1iv | 148.15 (19) |
S1iii—Cd1—S2iii | 87.957 (19) | N1—C1—N2 | 118.6 (2) |
N3i—Cd1—S2 | 90.19 (5) | N1—C1—S1 | 122.51 (18) |
N3ii—Cd1—S2 | 89.81 (5) | N2—C1—S1 | 118.87 (18) |
S1—Cd1—S2 | 87.957 (19) | N3—C2—S2 | 179.5 (2) |
S1iii—Cd1—S2 | 92.043 (19) | H1C—O1—H1D | 108 (3) |
S2iii—Cd1—S2 | 180.00 (3) | ||
N3i—Cd1—S1—C1 | −43.20 (10) | N3ii—Cd1—S2—C2 | 30.81 (10) |
N3ii—Cd1—S1—C1 | 136.80 (10) | S1—Cd1—S2—C2 | −54.18 (8) |
S2iii—Cd1—S1—C1 | 46.79 (9) | S1iii—Cd1—S2—C2 | 125.82 (8) |
S2—Cd1—S1—C1 | −133.21 (9) | Cd1—S1—C1—N1 | 22.3 (2) |
N3i—Cd1—S2—C2 | −149.19 (10) | Cd1—S1—C1—N2 | −157.98 (17) |
Symmetry codes: (i) x+1, y, z; (ii) −x, −y+1, −z; (iii) −x+1, −y+1, −z; (iv) x−1, y, z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1v | 0.86 | 2.26 | 3.049 (3) | 153 |
N1—H1B···N3i | 0.86 | 2.3 | 3.147 (3) | 167 |
N2—H2A···O1v | 0.86 | 2.4 | 3.159 (3) | 147 |
N2—H2B···O1vi | 0.86 | 2.19 | 3.050 (3) | 175 |
O1—H1C···S2 | 0.80 (2) | 2.54 (2) | 3.340 (2) | 177 (4) |
O1—H1D···S1vii | 0.81 (2) | 2.59 (2) | 3.377 (2) | 165 (3) |
Symmetry codes: (i) x+1, y, z; (v) −x+1, −y+1, −z+1; (vi) −x, −y+1, −z+1; (vii) x, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | [Cd(NCS)2(CH4N2S)2]·2H2O |
Mr | 416.84 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 5.8533 (3), 7.3527 (3), 8.8630 (4) |
α, β, γ (°) | 73.413 (4), 76.926 (4), 88.856 (4) |
V (Å3) | 355.69 (3) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 2.12 |
Crystal size (mm) | 0.53 × 0.42 × 0.23 |
Data collection | |
Diffractometer | Oxford Diffraction KM-4-CCD |
Absorption correction | Analytical [CrysAlis PRO (Oxford Diffraction, 2008), based on expressions derived by Clark & Reid (1995)] |
Tmin, Tmax | 0.558, 0.725 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7642, 2268, 1985 |
Rint | 0.036 |
(sin θ/λ)max (Å−1) | 0.725 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.062, 1.05 |
No. of reflections | 2268 |
No. of parameters | 85 |
No. of restraints | 3 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.47, −0.51 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2006), WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1i | 0.86 | 2.26 | 3.049 (3) | 153 |
N1—H1B···N3ii | 0.86 | 2.3 | 3.147 (3) | 167 |
N2—H2A···O1i | 0.86 | 2.4 | 3.159 (3) | 147 |
N2—H2B···O1iii | 0.86 | 2.19 | 3.050 (3) | 175 |
O1—H1C···S2 | 0.797 (17) | 2.544 (18) | 3.340 (2) | 177 (4) |
O1—H1D···S1iv | 0.805 (17) | 2.593 (19) | 3.377 (2) | 165 (3) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x+1, y, z; (iii) −x, −y+1, −z+1; (iv) x, y+1, z. |
Acknowledgements
The research was supported by grants from the Polish Ministry of Education and Science (grant Nos. N N204 543339 and N N204 150237).
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The interest in the coordination compounds possessing simultaneously thiourea and thiocyanato ligands dates back to the 1950s (e.g. Nardelli et al., 1957) when the nature of coordination compounds formed by divalent cations (M = Mn, Co, Ni, Cd, Pb) and organic molecules containing sulfur was extensively studied. Besides the polymeric catena-poly[bis(thiocyanato-κN)bis(µ-thiourea-κ2S:S)cadmium(II)] (Wang et al., 2002), also structures of four other complexes with thiourea derivatives of [Cd(SCN)2(TU)2]n type, where TU = ethylenethiourea (Cavalca et al., 1960), N,N'-diphenylthiourea (Zhu et al., 2000), N-phenylthiourea (Yang et al., 2001; Ahmad et al., 2008) or 1,3-dimethyl-2(3H)-imidazolethione (Williams et al., 1992), can be found. The interest in these compounds is related either with their non-linear optical properties (Yuan et al., 1997) or with the possibility to use them as single-source precursors of semiconducting materials based on CdS (Krunks et al., 1997; Amutha et al., 2011). Moreover, the use of SCN ligands, with bridging abilities, may lead to intriguing architectures and topologies, often generating one-dimensional chains (Machura et al., 2011). It was the reason why, during our studies on the new molecular precursors (Kropidłowska et al., 2008), we have turned our attention to systems of this type now and we have obtained a new complex containing thiourea and thiocyanato ligands connected to cadmium center.
The cadmium atom in catena-Poly[[[bis(thiourea-κS)cadmium]-di-µ-thiocyanato-κ2N:S;κ2S:N] dihydrate] is located at the inversion center and is octahedrically coordinated by two S atoms and two N atoms from four thiocyanate groups as well as by two S atoms from thiourea molecules. The neighbouring CdII ions are bridged by two µ-SCN-κ2N:S ligands, thus forming eight-membered ring of [Cd-SCN]2 type with the Cd···Cd distance of 5.853 Å, which is close to the values observed in other bridged systems (Machura et al., 2011). These units form one-dimensional chains of slightly distorted edge-shared Cd-centered octahedra along the [100] crystallographic direction. The Cd—S i Cd—N distances are typical for cadmium(II) thiocyanate complexes. The IR spectra clearly show the presence of the thiocyanato groups (with the maxima of νCN absorption at 2078 cm-1).
In the structure of [[Cd{SC(NH2)2}2(SCN)2].2H2O]n, several weak interactions may be assumed, leading to the alternating arrangement of water and complex molecules. Each water molecule interacts with S or N atoms from the three neighboring polymeric chains. Thus, it can serve as a donor of a weak hydrogen bond to the sulfur atom from one of the thiourea moieties (O1(H1D)—S1viii) in one chain, as well as to sulfur from one thiocyanato ligand (O1(H1C) —S2) in the other. The oxygen lone pairs act as acceptors towards NH2 groups from thiourea moieties located within the third chain (N2(H2B) —O1vii, N1(H1A) —O1v, N2(H2A)—O1v). Finally, one "interchain" interaction, N1—H1B···N3i, operates between NH2 and SCN groups.