Synthesis of and Structural Insights into Contact Ion Pair and Solvent-Separated Ion Pair Diphenyliridate Complexes

Lithium diphenyliridate
complexes bearing cycloocta-1,5-diene (COD)
as a ligand were synthesized by treating [IrCl­(cod)]2 with
phenyllithium and subsequent recrystallization. X-ray crystallographic
analysis of the complexes showed both contact ion pair and solvent-separated
ion pair structures depending on the coordination environment around
the Li cation. Natural bond orbital analysis revealed that the anionic
charge formally described on Ir efficiently delocalizes to not only
the phenyl moieties but also the COD ligand. This result contrasts
to the rhodium-analogues, where the anionic charge is more localized
at the metal center, suggesting stronger π-back-donation from
Ir to ligands than that of Rh.