LEAD SEQUESTERING AGENTS .1. SYNTHESIS, PHYSICAL-PROPERTIES, AND STRUCTURES OF LEAD THIOHYDROXAMATO COMPLEXES

In an approach to the synthesis of ligands specific for Pb2+, lead complexes with mono-and bis(thiohydroxamic acids) have been prepared and characterized on the basis of their elemental analyses and their infrared, NMR, and UV spectra. The structures of the two compounds bis(N-methylthiobenzohydroxamato)lead(II) (2) and bis(N-methylthioacetohydroxamato) lead(II) (5) have been determined by single-crystal X-ray diffraction using automated counter methods. The structure of 2 is based on a five-coordinate geometry in which the sulfur atoms and the stereochemically active electron lone pair on Pb2+ occupy the equatorial positions of a trigonal bipyramid. The axial positions are occupied by the oxygen atoms and weak, outer-sphere coordination occurs from ligation by the thiohydroxamate oxygen atoms of adjacent molecules. Compound 5 exists in a similar pseudotrigonal-bipyramidal geometry in the solid state, but the equatorial positions are occupied by the lone electron pair on lead, one oxygen atom, and one sulfur atom. Additional weak coordination is formed by two oxygen atoms and one sulfur atom from neighboring molecules. Bis(N-methylthiobenzohydroxamato)lead(II) (2) crystallizes in space group C2/c with Z = 4, a = 18.067 (2) Å, b = 12.518 (2) Å, c = 8.103 (1) Å and β = 101.93 (1)°. Full-matrix least-squares refinement using 1805 reflections with F02 > 3σ(F0)2, with all non-hydrogen atoms given anisotropic temperature factors, converged to unweighted and weighted R factors of 1.7 and 1.9%, respectively. Bis(acetothiohydroxamato)lead(II) (5) crystallizes in space group P21/n with Z = 4, a = 7.958 (2) Å, b = 7.445 (1) Å, c= 19.007 (3)Å, and β = 98.74 (2)°. Full-matrix least-squares refinement using 1924 reflections with F02 > 3σ(F0)2, with allnon-hydrogen atoms given anisotropic temperature factors, converged to unweighted and unweighted R factors of 4.1 and 5.1%, respectively. © 1990, American Chemical Society. All rights reserved.