Synthesis and electrochemistry of niobium complexes incorporating asymmetrically substituted ansa-ligands

Abstract

The following asymmetric ansa-niobocene(IV) dichloride complexes have been prepared: [Nb{Me 2Si(η 5-C 5Me 4)(η 5-C 5H 3R)}Cl 2] (R=H ( 1a), Me ( 2a), SiMe 3 ( 3a), Pr i ( 4a), PPh 2 ( 5a)). The ESR spectra of 1a– 5a have been recorded. Oxidation and reduction potentials have also been measured and compared with non ansa-niobocene complexes. The new niobocene complexes [Nb(η 5-C 5H 4R) 2}Cl 2] (R=Pr i ( 6a), PPh 2 ( 7a)) have been also synthesized. In addition, reduction of 1a in the presence of ligand (RCCR) (R=Me, Ph) to give [Nb{Me 2Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl(RCCR)] (R=Me ( 8a), Ph ( 9a)) is described.