The iso­thio­cyanate complex of tri­phenyl­borane forms an unusual coordination polymer with [K(18‐crown‐6)]+, both in the solid state and in solution

The title salt, (1,4,7,10,13,16‐hexa­oxa­cyclo­octa­decane‐κ⁶O)(iso­thio­cyanato)­tri­phenyl­borato‐κS]­potassium(I), K(C₁₉H₁₅BNS)(C₁₂H₂₄O₆)] or K(SCNBPh₃)(18‐crown‐6)], where 18‐crown‐6 is 1,4,7,10,13,16‐hexaoxa­cyclo­octa­decane and SCNBPh₃]^? is the (iso­thio­cyanato)­tri­phenyl­borate anion, exhibits a supramol­ecular structure that is best described as a helical coordination polymer or molecular screw. This unusual supramolecular structure is based on a framework in which the SCN^? ion bridges the chelated K⁺ ion and the B atom of BPh₃ in a μ₂ fashion. The X‐ray crystal structure of the title salt has been determined at 100 (1) and 293 (2) K. The K⁺ ion exhibits axial ligation by the S atom of the SCNBPh₃]^? anion, with a K—S distance of 3.2617 (17) Å (100 K). The trans‐axial ligand is an unexpected η²‐bound C=C bond of a phenyl group (meta‐ and para‐C atoms) that belongs to the BPh₃ moiety of a neighboring mol­ecule. The K—C bond distances span the range 3.099 (3)–3.310 (3) Å (100 K) and are apparently retained in CDCl₃ solution (as evidenced by ¹³C NMR spectroscopy). By virtue of the latter interaction, the supramolecular structure is a helical coordination polymer, with the helix axis parallel to the b axis of the unit cell. IR spectroscopy and semi‐empirical molecular orbital (AM1) calculations have been used to investigate further the electronic structure of the SCNBPh₃]^? ion.