Abstract

The synthesis of neutral dinuclear iron-nickel unsymmetrical Schiff base complexes 3 and 4 was achieved via a template reaction involving equimolar amounts of alkyl or aryl "half-unit" precursors, respectively, Fc-C(O)CH=C(CH 3)N(H)R (1: R = CH 2CH 2NH 2; 2: R = o-C 6H 4NH 2; Fc = CpFe(η 5-C 5H 4); Cp = η 5- C 5H 5), 5-bromosalicylaldehyde and nickel(II) acetate tetrahydrate in a refluxing CH 2Cl 2/MeOH (1:1) mixture. The ionic trinuclear unsymmetrical complex 5 was prepared by reacting its dinuclear precursor 3 with the arenophile source, [Cp*Ru(NCCH 3) 3]PF 6 (Cp* = η 5-C 5(CH 3) 5), in refluxing CH 2Cl 2 for 2 h, whereas the trinuclear species 6 was formed upon regioselective π-complexation of the 5-bromosalicylidene ring of 4 by [Cp*Ru] + at room temperature overnight. All the new compounds were adequately characterized by analytical and spectroscopic techniques and, in addition, the crystal and molecular structures of the "half-unit" 1, the binuclear complex 4 and its hemisolvate adduct 4 • 0.5CH 3OH, the trinuclear Schiff base compound 5 • 2(CH 3) 2CO, and the mixed sandwich metalloligand 7 have been determined by X-ray crystallography. Both organometallic-inorganic hybrids 5 and 6 contain the neutral electron-releasing ferrocenyl group, and the cationic electron-withdrawing ruthenium mixed sandwich, linked through the unsymmetrical tetradentate Schiff base complex {Ni(ONNO)}. UV-vis, 1H and 13C NMR as well as electrochemical data clearly indicate a mutual donor-acceptor electronic influence between the organometallic termini. Furthermore, X-ray crystal structure analysis of 5 • 2(CH 3) 2CO reveals the partial delocalization of bonding electron density throughout the dinucleating nickel Schiff base ligand. © 2007 Springer Science+Business Media, LLC.