FERRIC ION SEQUESTERING AGENTS .23. SYNTHESIS OF TRIS(HYDROXYPYRIDINETHIONE) LIGANDS AND THEIR FERRIC COMPLEXES - X-RAY STRUCTURE-ANALYSIS OF N,N',N''-TRIS((1,2-DIDEHYDRO-1-HYDROXY-2-THIOXOPYRID-6-YL)CARBONYL)-2,2',2''-TRIAMINO-TRIETHYLAMINATO)IRON(III)

Hexadentate thiohydroxamate ligands derived from 2-mercaptopyridine-6-carboxylic acid 1-oxide and triamines have been prepared by reaction of the amines with the active amide produced from the carboxylic acid and 1,1'-carbonyldiimidazole in DMF. The triamides isolated are N,N',N''-tris((1,2-didehydro-1-hydroxy-2-thioxopyrid-6-yl)carbonyl)-2,2',2''-triaminotriethylamine, N,-N',N''-tris((1,2-didehydro-1-hydroxy-2-thioxopyrid-6-yl)carbonyl)-1,-5,10-triazadecane, and 1,3,5-tris((N-methyl-N-((1,2-didehydro-1-hydroxy-2-thioxopyrid-6-yl)carbonyl)amino)methyl)benzene. These ligands have been characterized by their elemental analyses and IR and NMR spectra, and the ferric complexes have also been prepared and characterized. The structure of the complex N,N',N''-tris((1,2-didehydro-1-hydroxy-2-thioxopyrid-6-yl)carbonyl)-2,2',2''-triaminotriethylaminato)iron(III).0.5CHCl3 has been determined by single-crystal automated-counter X-ray diffraction. The complex crystallizes in the triclinic space group PlBAR with z = 4, a = 11.073 (1) angstrom, b = 13.858 (1) angstrom, c = 22.401 (2) angstrom, alpha = 70.216 (8)-degrees, beta = 71.847 (8)-degrees, gamma = 68.104 (8)-degrees. Two crystallographically independent molecules of the ferric complex and one disordered chloroform molecule are in the asymmetric unit. Full-matrix least-squares refinement using 6000 reflections with F(o)2 > 3-sigma-(F(o))2, with all non-hydrogen atoms given anisotropic temperature factors, converged to R = 0.040 and R(W) = 0.058. The coordination polyhedron around the ferric ion is intermediate between octahedral and trigonal-prismatic geometries and is similar to that of the ferric complex of 1-hydroxy-2(1H)-pyridinone.