Oxidation of elemental antimony by substituted ortho-benzoquinones

Abstract

The oxidation of elemental antimony by the o-quinones Y₄C₆O₂-o(Y = Cl or Br) in diethyl ether gives the unusual antimony(V) products Sb(O₂C₆Y₄)_2.5·nEt₂O (Y = Cl, n= 1.5; Y = Br, n= 1). The same quinones, and 3,5-di-tert-butyl-1,2-benzoquinone, upon treatment with Sb +½X₂(X = Br or I) in toluene, give the antimony(III) derivatives Sb(cat)X (cat = substituted catecholate anion). The oxidations are shown by electron spin resonance spectroscopy to proceed via the o-semiquinone intermediates. Adducts of Sb(cat)I with bidentate neutral donors have been prepared. The structure of Sb(dbc)I(bipy)(dbc = 3,5-di-tert-butylcatecholate, bipy = 2,2′-bipyridine) has been shown to be that of a pseudo-octahedral molecule with a stereochemically active lone pair of electrons. Crystal parameters for Sb(dbc)I(bipy)·0.5bipy: triclinic, space group P, a= 9.779(4), b= 18.554(7), c= 8.944(3)Å, α= 100.94(3), β= 115.11(3), γ= 86.82(4)°, Z= 2 and R= 0.044 for 3307 unique reflections.