catena-Poly[[bis(thiocyanato-κN)cobalt(II)]-di-μ-thiourea-κ4 S:S]

In the title polymeric complex, [Co(NCS)2{SC(NH2)2}2]n, the asymmetric unit comprises a CoII ion, which is situated on an inversion centre, an N-bound thiocyanate anion and a μ2-bridging thiourea molecule. The CoII atom is coordinated in a distorted octahedral fashion within an N2S4 donor set. The bridging thiourea ligands link CoII ions into a polymeric chain extending along [100]. The molecular conformation is stabilized by intramolecular N—H⋯N hydrogen bonds, which generate S(6) ring motifs. The crystal packing is stabilized by N—H⋯S interactions, which connect the chains into a three-dimensional architecture.

In the title polymeric complex, [Co(NCS) 2 {SC(NH 2 ) 2 } 2 ] n , the asymmetric unit comprises a Co II ion, which is situated on an inversion centre, an N-bound thiocyanate anion and a 2bridging thiourea molecule. The Co II atom is coordinated in a distorted octahedral fashion within an N 2 S 4 donor set. The bridging thiourea ligands link Co II ions into a polymeric chain extending along [100]. The molecular conformation is stabilized by intramolecular N-HÁ Á ÁN hydrogen bonds, which generate S(6) ring motifs. The crystal packing is stabilized by N-HÁ Á ÁS interactions, which connect the chains into a three-dimensional architecture.

Comment
The interest in the coordination compounds possessing both thiourea and thiocyanato ligands dates back to the 1950's (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. The interest in these compounds is related either to their non-linear optical properties (Yuan et al., 1997, Yu et al., 2001 or with their possible use as single-source precursors of semiconducting materials. 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). For the above reasons and during our studies on new molecular precursors (Kropidłowska et al., 2008), we turned our attention to systems of this type, that is, complexes containing thiourea and thiocyanate ligands connected to a cobalt center.
The title complex, Fig. 1, is isostructural with the previously reported cadmium(II) complex (Wang et al., 2002). The Co II atom is located at the inversion centre and is octahedrally coordinated by two N atoms from two thiocynate groups and four S atoms from four thiourea molecules. The bridging thiourea ligands link Co II ions into a one dimensional polymeric chain along [100] (Fig. 2). The Co···Co distance along the chain is 3.855 (3) Å. The octahedral coordination sphere of the cobalt(II) cation is slightly distorted with distances in the range of 2.016 (1) Å to 2.623 (1) Å. The angles around the cobalt(II) atom range from 83.4 (1)° to 180°. The thiocynate group is almost linear with the N1-C1-S1 angle = 179.2 (1)°.

Experimental
Cobalt(II) chloride, ammonium thiocynate and thiourea were dissolved in aqueous solution in the molar ratio 1:2:2 and stirred well for 2 h to obtain an homogeneous mixture. The dark-brown crystals of the title compound were obtained after the filtrate and had been allowed to stand at room temperature for two weeks.

Refinement
H atoms were positioned geometrically, with N-H = 0.86 Å and constrained to ride on their parent atom, with U iso (H)=1.2U eq (N).

catena-Poly[[bis(thiocyanato-κN)cobalt(II)]-di-µ-thiourea-κ 4 S:S]
Crystal data [Co(NCS) 2 (CH 4 N 2 S) 2 ] M r = 327.33 Triclinic, P1 Hall symbol: -P 1 a = 3.855 (3)  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )