LONE-PAIR STEREOCHEMISTRY OF ANTIMONY(III) POLYAMINOCARBOXYLATES - CRYSTAL-STRUCTURE OF [AMMONIUM DIAMINETETRAACETATO)ANTIMONATE]CENTER-DOT[AMMONIUM CHLORIDE]

The antimony atom in the crystal structure of [ammonium 1,2,diaminetet raacetato)antimonate(III)].[ammonium chloride], which is (4O + 2N) che lated by the diaminetetracarboxylato group [Sb-O = 2.216(5), 2.433(6), Sb-N = 2.325(5) Angstrom], exists in a psi-pentagonal bipyramidal geo metry in which the lone pair occupies an equatorial site. The yclohexa ne-1,2-diaminetetraacetato)antimonate(III) anion lies on a two-fold ax is, and is linked to two adjacent anions through the carboxyl oxygen a tom that forms the longer Sb-O bond to result in a zig-zag chain. If t hese weak interactions [(SbO)-O-... = 3.153(6) Angstrom; O(...)Sb1(... )O3 = 108.1(2)degrees] are regarded as formal bonds, the eight-coordin ate antimony atom shows distorted dodecahedral coordination. Lone-pair stereochemistry is discussed quantitatively in relation to the struct ures of the previously reported polyaminocarboxylate complexes of anti mony(III) and bismuth(III). Crystal data: C14H26N4O8ClSb, FW = 535.59, monoclinic, C2/c, a = 12.534(2), b = 23.570(3), c = 8.708(1) Angstrom , beta = 133.22(1)degrees, DX-ray = 1.898 g cm(-3), mu = 13.77 mm(-1), F(000) = 1080 for Z = 4.