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

• Published in: Inorganic chemistry 2021-07, Vol.60 (13), p.9996-10005
• Main Authors: Misawa-Suzuki, Tomoyo, Mafune, Sota, Nagao, Hirotaka
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c01262

Doubly oxido-bridged transition metal moieties, {M2(μ-O)2}, play important roles as oxidation reaction centers in nature. This work features a diruthenium­(III,IV) complex with a doubly oxido-bridged core {Ru2 III,IV(μ-O)2}3+ with a carbonato bridged between the two ruthenium centers, M­[{RuIII,IV(ebpma)}2(μ-O)2(μ-O2CO)]2(PF6)3 (M­[1 CO3 ]2(PF6)3; Carbonato complex, ebpma; ethylbis­(2-pyridymethyl)­amine), and explores the interactions of this complex with cations (H+ and M+). M­[1 CO3 ]2(PF6)3 was formed via reactions of a singly oxido-bridged complex, [{RuIII,IVCl2(ebpma)}2(μ-O)]­PF6 ·(CH3)2CO, with M2CO3 (M = K, Na) or with CO2(g), 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[1 CO3 ]2(PF6)3 (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, {Ru2 III,IV(μ-O)2}3+ or {Ru2 III,IV(μ-O)­(μ–OH)}4+, 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 ([1 CO3 H]2+ and [1 CO3 2H]3+) were successfully characterized.