Ir(2-Phenylpyridine)₂(benzene-1,2-dithiolate) Anion as a Diastereoselective Metalloligand and Nucleophile: Stereoelectronic Effect, Spectroscopy, and Computational Study of the Methylated and Aurated Complexes and their Oxygenation Products

The anionic complex [Ir­(2-phenylpyridine)₂(benzene-1,2-dithiolate)]⁻ ([IrSS]⁻) is a nucleophile and metalloligand that reacts with methyl iodide and AuPR₃⁺ (R = Ph or Et) to form S-methylated complexes (thiother–thiolate and dithiother complexes) and S-aurated complexes, respectively. The reactions are completely diastereselective, producing only the enantiomers ΛS and ΔR or ΛSS and ΔRR. The diastereoselectivity is stereoelectronically controlled by the orientation of the highest occupied molecular orbital (HOMO) of [IrSS]⁻ arising from filled dπ–pπ antibonding interactions, and the chirality of the iridium ion. Methylation or auration removes the high-energy lone pair of the thiolate S atom, leading to low-lying HOMOs composed mainly of the Ir d-orbital and the 2-phenylpyridine π (ppyπ) orbital. The methylated and aurated complexes can be oxidized by H₂O₂ or peracid to give sulfinate–thiother, disulfoxide, and sulfinate–sulfoxide complexes, and the oxygenation further stabilizes the HOMO. All the complexes are luminescent, and their electronic spectra are interpreted with the aid of time-dependent density functional theory calculations. The thiother–thiolate complex exhibits ligand­(S)-to-ligand­(π* of ppy)-charge-transfer/metal-to-ligand-charge-transfer absorption (LLCT/MLCT) and a relatively low-energy ³LLCT/MLCT emission, while the other complexes display ³ππ*/MLCT emissions.