Half-Sandwich Iridium Complexes Bearing a Diprotic Glyoxime Ligand: Structural Diversity Induced by Reversible Deprotonation.

Synthesis and deprotonation reactions of half-sandwich iridium complexes bearing a vicinal dioxime ligand were studied. Treatment of [{Cp*IrCl(µ-Cl)}2 ] (Cp*=η5 -C5 Me5 ) with dimethylglyoxime (LH2 ) at an Ir:LH2 ratio of 1:1 afforded the cationic dioxime iridium complex [Cp*IrCl(LH2 )]Cl (1). The chlorido complex 1 undergoes stepwise and reversible deprotonation with potassium carbonate to give the oxime-oximato complex [Cp*IrCl(LH)] (2) and the anionic dioximato(2-) complex K[Cp*IrCl(L)] (3) sequentially. Meanwhile, twofold deprotonation of the sulfato complex [Cp*Ir(SO4 )(LH2 )] (4) resulted in the formation of the oximato-bridged dinuclear complex [{Cp*Ir(µ-L)}2 ] (5). X-ray analyses disclosed their supramolecular structures with one-dimensional infinite chain (1 and 2), hexagonal open channels (3), and a tetrameric rhomboid (4) featuring multiple intermolecular hydrogen bonds and electrostatic interactions.