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

Abstract

Doubly oxido-bridged transition metal moieties, {M 2 (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 {Ru 2 III,IV (μ-O) 2 } 3+ with a carbonato bridged between the two ruthenium centers, M[{Ru III,IV (ebpma)} 2 (μ-O) 2 (μ-O 2 CO)] 2 (PF 6 ) 3 (M[1 CO3 ] 2 (PF 6 ) 3 ; Carbonato complex, ebpma; ethylbis(2-pyridymethyl)amine), and explores the interactions of this complex with cations (H + and M + ). M[1 CO3 ] 2 (PF 6 ) 3 was formed via reactions of a singly oxido-bridged complex, [{Ru III,IV Cl 2 (ebpma)} 2 (μ-O)]PF 6 •(CH 3 ) 2 CO, with M 2 CO 3 (M = K, Na) or with CO 2 (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 (PF 6 ) 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, {Ru 2 III,IV (μ-O) 2 } 3+ or {Ru 2 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.

Edge-sharing bi-octahedral diruthenium(iv,iv) compounds containing Ru–Ru bonds chelated and bridged by two carbonate and two oxo groups

“…23 As is known, compound 2 shows the smallest Ru–Ru distance value of 2.3808(6) Å for all known ESBO diruthenium compounds reported thus far (Table 1). 6–31 As shown in Fig. 2, the main structure of compounds 4 and 5 are isostructural, and the number of lattice water molecules is four and two for 1 and 2 , respectively.…”

“…Furthermore, the characterization of Ru–Ru bonds with short distances and high bond orders in electron-poor high-valent Ru 2 centers has boosted experimental and theoretical research. 5,29 To date, ESBO Ru⋯Ru interactions seem to present a broader range of distances (2.4334–3.733 Å, see Table 1) 6–32 than related paddle–wheel Ru–Ru bonds, which span a range from 2.248 to 2.2532(2.499(3)) Å. 1,2 In general, Ru⋯Ru interactions depend primarily on the electronic configuration of the Ru 2 core as well as the type of ligands; therefore, it is meaningfully interesting to search for the lower limit of ESBO Ru–Ru bond distance.…”