{[Ethyl(pyridin-4-ylmethyl)carbamothioyl]sulfanido-κ2 S,S′}(1,4,7,10,13,16-hexaoxacyclooctadecane-κ6 O)potassium

The asymmetric unit of title salt co-crystal, [K(C9H11N2S2)(C12H24O6)], comprises a K+ cation, an −S2CN(Et)py anion and a 18-crown-6 molecule. Substantial delocalization of π-electron density is evident in the dithiocarbamate anion, as indicated by the equivalent C—S bond lengths. The K+ cation sits within an O6S2 donor set lying 0.7506 (6) Å out of the least-squares plane through the six O atoms (r.m.s. deviation = 0.1766 Å) of the 18-crown-6 molecule with the two S atoms being on one side of this plane. Supramolecular layers in the bc plane, sustained by C—H⋯O and C—H⋯π interactions, feature in the crystal packing.

The asymmetric unit of title salt co-crystal, [K(C 9 H 11 N 2 S 2 )(C 12 H 24 O 6 )], comprises a K + cation, an À S 2 CN(Et)py anion and a 18-crown-6 molecule. Substantial delocalization of -electron density is evident in the dithiocarbamate anion, as indicated by the equivalent C-S bond lengths. The K + cation sits within an O 6 S 2 donor set lying 0.7506 (6) Å out of the least-squares plane through the six O atoms (r.m.s. deviation = 0.1766 Å ) of the 18-crown-6 molecule with the two S atoms being on one side of this plane. Supramolecular layers in the bc plane, sustained by C-HÁ Á ÁO and C-HÁ Á Á interactions, feature in the crystal packing.
We gratefully thank the Ministry of Higher Education (Malaysia) for funding structural studies through the High-Impact Research scheme (UM.C/HIR-MOHE/SC/03).

Comment
The supramolecular chemistry of dithiocarbamate ( -S 2 CNR 2 ) compounds compared with their xanthate ( -S 2 COR 2 ) counterparts is rather limited owing to the strong chelating ability of the anion, which often precludes the possibility of forming intermolecular M···S interactions (Tan et al., 2013). One way of overcoming this is to functionalize the dithiocarbamate ligand, as in the title salt co-crystal, (I), where the dithiocarbamate ligand carries a pyridyl residue. Crystal structures containing this dithiocarbamate ligand have been reported in recent years (Barba et al., 2012;Singh et al., 2011;Rajput et al., 2012).
The asymmetric unit of (I), Fig. 1, comprises a K + cation, an -S 2 CN(Et)py anion and a 18-crown-6 molecule. The dithiocarbamate ligand exhibits the expected features with equivalent C-S bond lengths and a short C-N bond, Table 1, consistent with a significant contribution of the (2-) S 2 C=N (+) (Et)py canonical form to the overall electronic structure. The ethyl and pyridyl substituents lie to either side of the S 2 CN plane, as is normally the case for dithiocarbamate anions.
The K + cation is coordinated by the six oxygen atoms of the 18-crown-6 molecule and the two sulfur atoms of the dithiocarbamate anion, Table 1 In the crystal packing, molecules assemble into supramolecular layers in the bc plane by a combination of pyridyl-C-H···O and methylene-C-H···π interactions, Table 2

Refinement
C-bound H-atoms were placed in calculated positions (C-H = 0.95-0.99 Å) and were included in the refinement in the riding model approximation with U iso (H) set to 1.2-1.5U eq (C). One reflection, i.e. (2 0 0), was omitted from the final refinement owing to poor agreement.  (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).  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 > 2σ(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.