Lithium Hexaphenylrhodate(III) and -Iridate(III): Structure in the Solid State and in Solution

Anionic homoleptic organo–transition metal complexes can be prepared from organolithium reagents and transition metal salts and are key reactive intermediates in C–C bond formation. However, the interaction between the anionic component and cationic counterparts of multianionic homoleptic organo–transition metal complexes in solution remains unclear, unlike well-studied monoanionic complexes such as organocuprates. Here we have prepared and structurally characterized lithium hexaphenylrhodate­(III) and -iridate­(III) complexes, [Li­(12-crown-4)2]­[MPh6{Li­(thf)}2] (M = Rh and Ir), as the first examples of hexaaryl complexes of d6 metals. In the crystals, two Li cations contact the trianionic MPh6 moiety, while the other exists as a solvent-separated ion pair. In THF, hexaphenylrhodate decomposed within 1 h. In contrast, the Ir analog was stable. 7Li NMR and X-ray absorption fine structure analysis revealed the solution-phase structure of hexaphenyliridate, which maintained a partially contacted ion pair structure even in THF, a coordinating solvent.