Crystal structures of methyltriphenylarsonium and methyltriphenylphosphonium bis-(ααα′α′-tetracyanoquinodimethanide){di-[3,6-bis(dicyanomethylene)cyclohexa-1,4-dienes]}

Abstract

Methyltriphenylarsonium bis-(ααα′α′-tetracyanoquinodimethanide) crystallizes in the triclinic system, space group P, with a= 9·01, b= 12·89, c= 18·18 Å, α= 121·80°, β= 90·58°, γ= 97·30°. The methyltriphenylphosphonium salt is isomorphous with unit-cell parameters a= 9·01, b= 12·82, c= 18·02 Å, α= 121·48°, β= 90·80°, γ= 97·52°. Atomic parameters were obtained by Patterson and Fourier syntheses and refined by full-matrix least-squares calculations. The final R for the methyltriphenylarsonium salt is 0·104 over 6134 independent reflexions and 0·088 over 5590 independent reflexions for the methyltriphenylphosphonium salt. The crystals contain columns of ααα′α′-tetracyanoquinodimethane molecules the bond lengths of which are intermediate between those for formally 0 and –1 charged species. Within the columns a tetrad of molecules having similar nearest-neighbour overlap and interplanar spacing of 3·20 Å may be recognized. Between the tetrads the overlap differs from that within the tetrads and the interplanar spacing is increased to 3·58 Å. The cation occupy the spaces between the columns.