The Influence of Redox-Innocent Donor Groups in Tetradentate Ligands Derived from -Phenylenediamine: Electronic Structure Investigations with Nickel.

The continued development of redox-active ligands requires an understanding as to how ligand modifications and related factors affect the locus of redox activity and spin density in metal complexes. Here we describe the synthesis, characterization, and electronic structure of nickel complexes containing triaryl NNNN () and SNNS () ligands derived from -phenylenediamine. The tetradentate ligands in and were investigated and compared to those in metal complexes with compositionally similar ligands to determine how ligand-centered redox properties change when redox-active flanking groups are replaced with redox-innocent NMe or SMe.

Uranyl Functionalization Mediated by Redox-Active Ligands: Generation of O-C Bonds via Acylation.

A series of uranyl compounds with the redox-active iminoquinone ligand have been synthesized, and their electronic structures elucidated using multinuclear NMR, EPR, electronic absorption spectroscopies, SQUID magnetometry, and X-ray crystallography. Characterization and analysis of the iminoquinone (iq) complex, (iq)UO(OTf)THF (1-iq), the iminosemiquinone (isq) complex, (isq)UOTHF (2-isq), and the amidophenolate (ap) complex, [(ap)UOTHF][K(18-crown-6)(THF)](3-ap crown) show that reduction events are ligand-based, with the uranium center remaining in the hexavalent state. Reactivity of 2-isq with B-chlorocatecholborane or pivaloyl chloride leads to U-O bond scission and reduction of U(VI) to U(IV) concomitant with ligand oxidation along with organic byproducts.

Expanding the Library of Uranyl Amide Derivatives: New Complexes Featuring the tert-Butyldimethylsilylamide Ligand.

New uranyl derivatives featuring the amide ligand, -N(SiHMe) Bu, were synthesized and characterized by X-ray crystallography, multinuclear NMR spectroscopy, and absorption spectroscopies. Steric properties of these complexes were also quantified using the computational program Solid-G. The increased basicity of the free ligand -N(SiHMe) Bu was demonstrated by direct comparison to -N(SiMe), a popular supporting ligand for uranyl.

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 (L ) derivative, ( iq) NdI (1-iq), the iminosemiquinone (L ) compound, ( isq) NdI(THF) (1-isq), and the amidophenolate (L ) [K(THF) ][( ap) Nd(THF) ] (1-ap) and [K(18-crown-6)][( ap) Nd(THF) ] (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)][( isq) Nd(S )] (2-isq crown) and [K(18-crown-6)(THF)][( isq) Nd(Se )] (3-isq crown), which are characterized to contain a 6-membered twist-boat ring.