Linear oxygen-donor ligands derived from gallic acid methyl ester: Ligand synthesis and preliminary coordination studies

The new ligands 3a-c-H-4 with two catechol-type oxygen-donor binding sites and ether-linked spacers are synthesized in three step procedures starting from gallic acid methyl ester 4. After protection of two OH-functions as be nzophenone ketale, a Williamson ether synthesis introduces the spacer, and finally the ketale is removed again. Preliminary coordination studies with 3a (or 3b, 3c) and titanium(IV) ions show that dinuclear triple-stranded co mplexes M-4[(3a)(3)Ti-2] (land K-4[(3b/c)(3)Ti-2]) are formed in the presen ce of alkali metal (M = Li, Na, K, Cs) as well as ammonium cations (M = NH4 , PhCH2NH3, i-Pr2NH2).