One- and two-dimensional coordination networks of the tetracyanoethylene anion-radicals with potassium counter-ions

Abstract

Potassium-mirror reduction of tetracyanoethylene (TCNE) acceptor in tetrahydrofuran affords K(THF) 2 TCNE salt ( 1) showing double TCNE/K chains assembled via unusual μ 3-TCNE-bridging of potassium cations. These parallel ladder-type chains are further tethered by pairs of THF bridges between potassium centers and by intermolecular π-bonding in (TCNE ) 2 2− dimers, and this results in formation of quasi-2-D coordination networks. In the presence of crown-ether ligand, the same potassium-mirror reduction lead to formation of [K(18-crown-6)(THF) 2]TCNE salt ( 2) in which monomeric tetracyanoethylene anion-radicals are positioned between bulky [K +(18-crown-6)(THF) 2] counter-ions. In comparison, crystallization of tetracyanoethylene anion-radicals with K +(18-crown-6) counter-ions in dichloromethane affords K(18-crown-6)TCNE salt ( 3) consisting of 1-D chains with 1,2-( N,N’)-TCNE bindings of potassium cations (nested in the crown-ether cavities). Temperature-dependent magnetic susceptibility study revealed essentially isolated tetracyanoethylene anion-radicals ( S = 1/2) in this 1-D coordination polymer.