ANTIMONY(III) ACETATE AND THIOACETATE - SPECTRA AND CRYSTAL-STRUCTURES
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abstract
Antimony(III) tris(monothioacetate) has been prepared from thioacetic acid and antimony(III) oxide as a water-stable compound, in contrast to the extreme instability to water of the analogous triacetate. X-Ray structure determinations, however, show similar molecular structures for the two compounds. Crystals of antimony triacetate are monoclinic, space group P21, Z = 2, with a = 7.463(5), b = 9.346(5), c = 7.740(5) , and = 116.20(5), whereas those of antimony tris(monothioacetate) are monoclinic, space group P21/c, Z = 4, with a = 8.884(5), b = 16.819(5), c = 8.964(5) , and = 117.26(5). Primary bonding in the former is to three oxygen atoms (mean Sb-O, 2.06 ) but to three sulphur atoms (mean Sb-S, 2.47 ) in the latter. Vibrational spectra suggest the presence of secondary bonding in both compounds, which has been confirmed by the observation of three weak intramolecular interactions (Sb-O, 2.596-2.775 in the acetate and 2.745-2.918 in the thioacetate). One of the ligands, in addition to behaving as a chelate, bridges between molecules (Sb-O, 2.600 and 3.043 for the acetate and thioacetate respectively) leading to polymeric chains in the solid. The overall co-ordination polyhedron, which includes the stereochemically active lone pair, is best described in terms of a distorted dodecahedron.
