PREPARATION OF 2-SUBSTITUTED AND 4-SUBSTITUTED 3-HYDROXY-5-METHYLFURANS AND THE ALUMINUM AND GALLIUM COMPLEXES OF 3-HYDROXY-5-METHYL-2-(N-METHYLFORMAMIDO)FURAN

In model studies designed to study the synthesis of potentially hexadentate chelates based on the linkage of three furan rings to a triamine via amide linkages, new 2- and 1-substituted 3-hydroxy-5-methylfurans have been prepared. Particularly, 3-hydroxy-5-methyl-(N-methylformamido)fur (Hahm) and its Al and Ga complexes (M(ahm)(3)) have been prepared and thoroughly characterized by a variety of techniques, in the solid state and in solution. Solution equilibrium studies (mu = 0.6 M NaCl, 25 degrees C) uncovered a complicated set of equilibria in the Al3+/Hahm system; the solution potentiometric data were best explained by the presence of mixed ligand (HL = Hahm, L(-) = ahm(-)) hydroxo species [Al-3(OH)(4)L(3)](2+) and [AI(OH)(2)L(2)](-), in addition to the expected [AlL(n)]((3-n)+) (n = 1, 2, 3) species. Further solution studies at HL:M ratios of 3:1 (mu = 0.15 M NaCl, 25 degrees C) showed that Hahm is a relatively weak complexing agent for both Al and Ga, forming tris-ligand species with overall formation constants of 10(19.5) and 10(20.6), respectively.