Ferrocene containing chelating ligands Part 2. Synthesis, characterization, electrochemical behaviour and crystal structure of 2-ferrocenylmethylamino-benzoic acid

Abstract

Ferrocenecarboxaldehyde reacts with 2-amino-benzoic acid in benzene to give the Schiff base derivative 2-ferrocenyl- methylidenimino-benzoic acid (η 5-C 5H 5)Fe[(η 5-C 5H 4)CH NC 6H 4COOH] ( 1). 1 is stable as a solid but easily hydrolyzes in solution. Selective hydrogenation of the imine group can be performed using NaBH 4 to obtain the parent amine (η 5- C 5H 5) Fe[(η 5-C 5H 4)CH 2NH& z.sbnd;C 6H 4COOH]. ( 2). The molecular structure of 2 has been determined by single-crystal X-ray methods. It crystallizes in the space group P2 1/ c, a=11.077(9), b =7.430(2), c=19.194(9) Å, β=111.02(4)°, V=1474(2) Å 3, Z=4. Refinement of the structure gave final R factor of 0.038 ( R w=0.035) for 1106 unique reflections having F o 2>2.8σ( F o 2). 2 is stable both in the solid state and solution, and a potential chelating N,O-donor ligand containing a ferrocenyl group. A one-electron oxidation process was found by cyclic voltammetry (0.1 M NBu n 4PF 6, CH 2Cl 2) for 1 and 2 at 0.74 and 0.51 V, respectively.