Synthesis of Carbonato- and Doubly Oxido-Bridged Diruthenium(III,IV) Complex and Reactions with Cations.

Doubly oxido-bridged transition metal moieties, {M(μ-O)}, play important roles as oxidation reaction centers in nature. This work features a diruthenium(III,IV) complex with a doubly oxido-bridged core {Ru(μ-O)} with a carbonato bridged between the two ruthenium centers, M[{Ru(ebpma)}(μ-O)(μ-OCO)](PF) (M[](PF); , ebpma; ethylbis(2-pyridymethyl)amine), and explores the interactions of this complex with cations (H and M). M[](PF) was formed via reactions of a singly oxido-bridged complex, [{RuCl(ebpma)}(μ-O)]PF(CH)CO, with MCO (M = K, Na) or with CO(), adjusted to around pH 12 with NaOH(aq.), in a water-acetone mixed solvent. The Carbonato complex was isolated as a powder in the form of M[](PF) (M = K, Na), because of the interactions between the carbonato moiety and K or Na in the solid structure. In acidic aqueous solutions, unexpectedly, the carbonato ligand remained bound to the doubly bridged core, {Ru(μ-O)} or {Ru(μ-O)(μ-OH)}, without decarboxylation even under pH 1.0. Two-step one-protonation/deprotonation occurred reversibly between pH 1.0 and 13.2 to the bridging oxido and carbonato ligands. The structures of the corresponding one- and two-protonated complexes ([] and []) were successfully characterized.