Ligand effects on the structures and reactivity of main-group and transition metal complexes

A series of bis(indenyl)chromium(II) complexes has been synthesized with a variety of alkyl or silyl substituents. The data collected in this study indicate that, while Ind′₂Cr species are normally high spin, subtle changes in the indenyl ligand environment may induce pronounced changes in the structural and magnetic properties of these compounds. The subsequent reactivity of Ind′₂Cr with small molecules also appears to be influenced by the spin state of the metal center.; A mechanistic study of the reduction of nitroarenes has been investigated with samarium(II). Both the products of non-aqueous and aqueous work up were examined and three moisture-sensitive samarium(III) complexes were structurally authenticated. It has been shown that 6 equivalents of samarium(II) are required for the reduction of a nitrogroup to an amine and that the reaction proceeds cleanly in aromatic solvents at room temperature in a moisture-free environment.; The first uncomplexed phosphonium diylide has been crystallographically characterized as an ion pair with a CaI(thf)₅+ cation. The diylide is not particularly nucleophilic as it does not bind calcium or barium. Density functional theory (DFT) calculations were also performed for this complex with model compounds that reproduce the structural features of the diylide complex.; A neutral organocalcium complex has been prepared that allows direct structural comparisons with trivalent lanthanide complexes. A ligand based on an ansa-phosphonium bridge was used that allowed for the formation of a complex of the general form “Cp′₂AeX”. The potential of this ligand set as a “valence-boosting” ligand will allow for the synthesis of metal complexes in oxidation states that are either unavailable or difficult to stabilize otherwise.