Abstract
Sodium propynoate, Na(O2CC≡CH) 1, was synthesized from propynoic acid and sodium hydroxide in methanol solution. Irradiation of solid 1 with 60Co γ-rays (654 kGy dose) leads to an amorphous dark-colored acetylenic polymer in high yield. An X-ray structure determination of compound 1 shows that the sodium ion is five-coordinate, with a square-pyramidal geometry. The five-coordinate local moiety is part of an unusual two-dimensional polymer in the crystal bc plane. Crystal packing of the two-dimensional, solid-state polymers leads to a bilayer motif, and the relatively short metal–metal distance of 3.575 Å promotes close packing of the organic tails with parallel acetylene moieties and a very short –C≡C–···–C≡C– contact of 3.29 Å along the crystallographic b direction. Crystal data for 1: orthorhombic, space group Pna21, a=19.837(6), b=3.575(1), and c=5.232(1) Å; V=371.0 Å3; Z=4; R=0.0262; Rw=0.0327 for 427 data for which I>1.96σ(I).