Neodymium(III) Complexes Capable of Multi-Electron Redox Chemistry.

A family of neodymium complexes featuring a redox-active ligand in three different oxidation states has been synthesized, including the iminoquinone (L0 ) derivative, (dipp iq)2 NdI3 (1-iq), the iminosemiquinone (L1- ) compound, (dipp isq)2 NdI(THF) (1-isq), and the amidophenolate (L2- ) [K(THF)2 ][(dipp ap)2 Nd(THF)2 ] (1-ap) and [K(18-crown-6)][(dipp ap)2 Nd(THF)2 ] (1-ap crown) species. Full spectroscopic and structural characterization of each derivative established the +3 neodymium oxidation state with redox chemistry occurring at the ligand rather than the neodymium center. Oxidation with elemental chalcogens showed the reversible nature of the ligand-mediated reduction process, forming the iminosemiquinone metallocycles, [K(18-crown-6)][(dipp isq)2 Nd(S5 )] (2-isq crown) and [K(18-crown-6)(THF)][(dipp isq)2 Nd(Se5 )] (3-isq crown), which are characterized to contain a 6-membered twist-boat ring.