Between T and Y: Asymmetry in the Interaction of LAu(I) with Bipy and β‐Diiminate‐like Ligands

Abstract

AbstractThe combination of an LAu(I) fragment with a potentially chelating ligand can result in different coordination modes of : strictly monodentate, symmetrically bidentate, or intermediate with asymmetric bidentate binding of . Density Functional calculations indicate that for π‐acceptor ancillary ligands L (C2H4, CO) and bis(nitrogen) donors (bipyridine, phenanthroline, β‐diiminate) symmetric chelate structures are obtained. With primarily σ‐donating ancillary ligands L (Me−, Cl−, MeCN) the asymmetric coordination mode is the norm. Phosphine ancillary ligands L are on the edge and display the highest sensitivity to ligand variation. Asymmetry increases when (a) going from anionic (β‐diiminate) to neutral (bipyridine, phenanthroline) bidentates ; (b) making less electron‐rich e. g. through having aryl instead of alkyl groups at N or through introduction of CF3 substituents. Inversion of the asymmetry through “gold hopping” is remarkably facile (barrier mostly <6 kcal/mol, often ∼1 kcal/mol). The high‐temperature fluxionality reported for two (PPh3)Au(β‐diiminate) complexes is tentatively assigned to imine inversion (rather than gold hopping) as the rate‐limiting step.