PtS-Related {[Cu^I(F₄TCNQ^II–)]⁻}_∞ Networks

Abstract

A series\nof compounds of composition A­[Cu^I­(F₄­TCNQ^II–)] (A = a quaternary ammonium\nor phosphonium cation, F₄­TCNQ^II– = the dianionic form of 2,3,5,6-tetra­fluoro-7,7,8,8-tetra­cyano­quino­dimethane)\nhave been synthesized and structurally characterized. In each structure,\nan anionic [Cu^I­(F₄­TCNQ^II–)]⁻ framework possessing the topology of PtS is\nformed with the Cu­(I) center serving as a tetrahedral 4-connecting\ncenter and the F₄­TCNQ^2– anion acting\nas a planar 4-connecting unit. Although a PtS topology is observed\nfor six different compounds, the anionic framework shows significant\ngeometric variation depending upon the identity of the cation. Very\nsimilar structures are obtained when the organic cation is NMe₄⁺, NMe₂­Pr₂⁺, or NMe₂­Bu₂⁺. A distorted\nanionic structure possessing the same connectivity is generated when\nthe cation is NEt₄⁺, and anionic frameworks\nwith a different connectivity, but still related to PtS, are obtained\nwhen the much larger quaternary phosphonium cations are employed.\nOf interest in the structures containing quaternary phosphonium cations\nare π-stacking interactions involving phenyl groups of the cation\nand F₄­TCNQ^2– ligands. These face-to-face\ninteractions between the electron-rich F₄­TCNQ^2– ligands and a phenyl group of the cation appear to\nbe responsible for the color exhibited by these compounds.