Synthesis and spectroscopic/DFT structural characterization of coordination compounds of Nb(V) and Ti(IV) with bioactive carboxylic acids

The reactions are reported of NbX5 (X = Cl, Br), TiCl4 and Ti(OiPr)4 with a selection of carboxylic acids exhibiting a known biological role, in a chlorinated solvent. The reactions of NbX5 with acetylsalicylic acid (aspirin) proceeded with selective deacetylation of the organic reactant and formation of the salicylate complexes NbX4(C7H5O3) (1a, X = Cl; 1b, X = Br) in 60–65% yields. NbCl5 reacted with diclofenac and ethacrynic acid (EA-CO2H) to give NbCl3[κ3O,O,N-O2CCH2(C6H4)NC6H3Cl2], 2 (80% yield), and NbCl4(O2C-EA), 3 (72% yield), respectively. Ti(OiPr)4 reacted with ethacrynic acid giving Ti(OiPr)2(O2C-EA)2, 4, in 74% yield, as a mixture of two isomers. All the products were characterized by means of analytical and spectroscopic methods, moreover DFT studies were carried out to give insight into structural features.