The Preparation and Crystal Structure of Polymeric Anhydrous Sodium Hydrogen o-Phenylenedioxydiacetate

Abstract

The crystal structure of anhydrous sodium hydrogen o-phenylenedioxydiacetate , [Na₂( Hbdda )₂]n, has been determined by X-ray methods and refined to a residual R 0.031 for 1234 observed reflections. Crystals are monoclinic, space group C2/c with Z 4 in a cell of dimensions a 18.415(6), b 7.4667(7), c 16.354(7) Å ,β112.61(2)º. The dimeric repeating unit has two centrosymmetrically related pentagonal pyramidal Na-O₆ complex centres [Na-0, 2.272-2.439(2) Å ] bridged by carboxylate oxygens. The pentagonal plane comprises four oxygens from the Hbdda ligand as well as one providing the bridging link. The axial bond gives the step-polymer link while the carboxylic acid proton is hydrogen bonded to a carboxylate oxygen of the inversion-related Hbdda ligand [O…O, 2.469(2) Å ].