J. Cano, A. Benito, R. Martínez‐Máñez
Mar 15, 1995
Citations
0
Influential Citations
18
Citations
Journal
Inorganica Chimica Acta
Abstract
Ferrocenecarboxaldehyde reacts with 2-amino-benzoic acid, 2-amino-5-methyl-benzoic acid or 3-amino-2-naphthoic acid to give the corresponding Schiff-base derivatives 2-ferrocenylmethylidenimino-benzoic acid (1), 2-ferrocenylmethylidenimino-5-methyl-benzoic acid (2) and 3-ferrocenylmethylidenimino-2-naphthoic acid (3). 1, 2 and 3 are stable in the solid state but easily hydrolyze in solution. This hydrolysis has been studied kinetically in a methanol-water medium. In order to increase the stability in solution to use these compounds as ligands, the imino group from 1, 2 and 3 was reduced by NaBH4 to give the amino derivatives 2-ferrocenylmethylamino-benzoic acid (4), 2-ferrocenylmethylamino-5-methyl-benzoic acid (5) and 3-ferrocenylmethylamino-2-naphthoic acid (6). 4, 5 and 6 are stable, both in the solid state and in solution, and potential chelating NO donor ligands containing ferrocenyl groups. The protonation of 4–6 and their complex formation with copper(II) have been investigated by potentiometry in dimethyl sulfoxide (dmso)-water (80:20 wt./wt.) mixtures at 25 °C and 0.1 mol dm−3 KClO4. The molecular structure of 5 has been determined by single-crystal X-ray methods. It crystallizes in the triclinic system, space group P1, with a = 6.1747(7), b = 9.539(1), c = 13.511(4) A, α = 88.99(1), β = 87.00(1), γ = 82.34(1)°, V = 787.6(3) A3 and Z = 2. An unusual feature of the ferrocene-containing ligand 5 in its interaction with nickel(II) ions was found. Cleavage of the CN bond of the secondary amine 5 and molecular rearrangement yields the protonated tertiary amine 2-bis(ferrocenylmethyl)ammonium-5-methyl-benzoic acid perchlorate (7). Compound 7 crystallizes in the monoclinic system, space group P21/c with a = 9.702(9), b = 27.153(17), c = 22.326(6) A, β = 97.39(6)°, V = 5833(12) A3 and Z = 8. Typical reversible oxidation waves were found for 4–7 whereas some degree of irreversibility was detected for their parent imines.