Ring geometry and secondary interactions in a salt of S3N2Cl+; the crystal structure of 1-chloro- 1,2,4-trithia-3,5-diazolium tetrachloroferrate(III)

The structure of the title compound has been determined using single crystal X-ray methods. The tetrachloroferrate(III) ion is approximately tetrahedral, with three FeCl bonds at 2.178(2), 2.182(2) and 2.183(2) Å, and one, FeCl(2), at 2.215(2) Å, which is weakened by interactions between Cl(2) and two sulphurs of the cation. The four sulphur-nitrogen distancesl.546(6)1.604(6) Å, mean 1.578 Å] are typical of a delocalised SN system; the two-coordinate atoms (only) are coplanar within experimental error. The S(2)S(3) bond 2.181(2) Å] and exocyclic S(2)Cl(1) bond 2.086(2) Å] are respectively 0.045 Å longer and 0.08 Å shorter than in S₃N₂Cl⁺Cl^?; this is interpreted as being due to weaker cation-anion interaction in the tetrachloroferrate (III) salt. Ring angles at S(1) 105.8(3)°], N(2) 121.5(4)°], S(3) 95.6(2)°] S(2) 95.9(2)°] and N(1) 119.6(4)°] are under compression due to constraint within the small ring.