Volume 59, Issue 10 pp. m407-m412

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

Orde Q. Munro

Orde Q. Munro

School of Chemical and Physical Sciences, University of Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa

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Nicole Pearson

Nicole Pearson

School of Chemical and Physical Sciences, University of Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa

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First published: 09 June 2004
Citations: 2
Orde Q. Munro, e-mail: [email protected]

Abstract

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.

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