The chemistry of vanadate chelate esters of monoionized aromatic diols and methoxyphenolate

Two ONO donor tridentate Schiff base ligands, two aromatic 1,2-diols and a monomethyl ether derivative of aromatic 1,2-diol are used in this work. The ONO donor ligands are deprotonated forms of N-(1-hydroxyphenyl)salicylaldimine (H2L1) and N-(1-hydroxyphenyl)napthaldimine(H2L2) (general abbreviation H2L). The concerned diols are catechol (H2cat), its 3,5-Bu2t derivative (H2dbcat) and the monomethyl ether derivative of aromatic 1,2-diol is 2-methoxyphenol (HMecat), commonly known as guaiacol. The syntheses of hexa-/penta-coordinated vanadate esters of monoionized aromatic 1,2-diols and 2-methoxyphenolate, with diionized N-salicylidene/N-napthalidine-α-aminophenol as coligands are described and the reactivities of the compounds are reported. The concerned vanadate esters are [VO(L)(Hcat)], [VO(L)(Hdbcat)] and [VO(L)(Mecat)], where Hcat, Hdbcat and Mecat are monoionised forms of H2cat, H2dbcat and HMecat, respectively. The complexes are electroactive in MeCN solution. Molecular oxygen reacts smoothly with the oxovanadium(V) complexes quantitatively, furnishing the corresponding o-quinone. In the presence of the aromatic diol or guaiacol the reaction becomes catalytic. The X-ray structure of [VO(L2)(Mecat)] has also been reported.

The synthesis, characterization and reactivities of a family of vanadate esters of monoionized aromatic 1,2-diols [catechol− (Hcat) and its 3,5-Bu2t derivative (Hdbcat)] and 2-methoxyphenolate with diionized N-salicylidene/N-napthalidine-α-aminophenol (L) as coligands are reported. Molecular oxygen reacts smoothly with the vanadate esters quantitatively furnishing the corresponding o-quinone (Q) and in the presence of diol [catechol (H2cat) or its 3,5-Bu2t derivative (H2dbcat)] or 2-methoxyphenol the reaction becomes catalytic.Figure optionsDownload as PowerPoint slide