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

Abstract

The title salt, (1,4,7,10,13,16-hexaoxacyclooctadecane-kappa(6)O)[(isothiocyanato)triphenylborato-kappaS]potassium(I), [K(C(19)H(15)BNS)(C(12)H(24)O(6))] or [K(SCNBPh(3))(18-crown-6)], where 18-crown-6 is 1,4,7,10,13,16-hexaoxacyclooctadecane and [SCNBPh(3)](-) 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 BPh(3) in a micro(2) 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 [SCNBPh(3)](-) anion, with a K-S distance of 3.2617 (17) A (100 K). The trans-axial ligand is an unexpected eta(2)-bound C=C bond of a phenyl group (meta- and para-C atoms) that belongs to the BPh(3) moiety of a neighboring molecule. The K-C bond distances span the range 3.099 (3)-3.310 (3) A (100 K) and are apparently retained in CDCl(3) solution (as evidenced by (13)C 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 [SCNBPh(3)](-) ion.