Metal-controlled reactivity of a pincer-type, sigma-coordinated naphthyl radical anion

Reduction of the new, naphthalene-based pincer complex [(C10H5(CH2PiPr2)2)Rh(eta1-N2)] with potassium metal gave the corresponding sigma-coordinated naphthyl radical anion complex, with a ring-centered radical and no change in the formal metal oxidation state. This paramagnetic complex can be reoxidized to the diamagnetic one with [Cp2Fe][BF4], the structural integrity being retained. Unexpectedly, treatment of a THF solution of the reduced complex with water leads to the immediate evolution of dihydrogen, with reoxidation to the starting complex. This is in striking contrast with the well-known reactivity of the naphthide radical anion, which undergoes ring protonation by water to form 1,4-dihydronaphthalene and naphthalene in a 1:1 ratio.