Framework Conversion of Oxido-Bridged Dinuclear Ruthenium Complexes

Abstract

Syntheses, properties, and reactions of hydroxido-or oxido-bridged dinuclear ruthenium complexes bearing a tridentate auxiliary ligand, ethylbis(2-pyridylmethyl)amine (ebpma) or benzylbis(2-pyridylmethyl)amine (bbpma), have been investigated. Reduction reactions of a singly oxidob r i d g e d d i r u t h e n i u m c o m p l e x b e a r i n g e b p m a , [{Ru III,IV Cl 2 (ebpma)} 2 (μ-O)] + ([2 Cl ] + ), by zinc in acetonitrile afforded an acetonitrile-substituted singly oxido-bridged complex in the Ru III −Ru III isovalent state, [{Ru III,III Cl(NCCH 3 )(ebpma)} 2 (μ-O)] 2+ ([2 CH 3 CN ] 2+ ). Chlorido ligand abstraction reactions using silver salts have also been attempted. Through a reaction of [2 Cl ] + with two equimolar amounts of AgNO 3 in water−acetone, a singly oxido-bridged complex having an aqua and a hydroxido, [{Ru III Cl(OH 2 )(ebpma)}(μ-O){Ru IV Cl-(OH)(ebpma)}] 2+ ([2 H 2 O-OH ] 2+ ), was obtained. Reactions with four equimolar amounts of AgL (L = CH 3 COO − or NO 3 − ) in water−acetone gave doubly oxido-and bidentate oxygen donor ligand-bridged diruthenium complexes of Ru(III)−Ru(IV), [{Ru III,IV (ebpma)} 2 (μ-O) 2 (μ-L)] 2+ ([3 L ] 2+ ; L = O 2 CCH 3 ; [3 CH 3 COO ] 2+ , L = O 2 NO; [3 NO 3 ] 2+ ). Reactions of [3 L ] 2+ under acidic conditions afforded a corresponding one-protonated species having the {Ru 2 (μ-O)(μ-OH)} core. Reactivity and electronic structure of the oxido-bridged diruthenium complexes were studied by electrochemical, spectroscopic, and theoretical methods.

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.…”

Pyrazine-Coordinated Dinuclear and Mononuclear Ruthenium Complexes Formed via the Conversion of the Triply Chlorido-Bridged Diruthenium(II) Complex

“…The two chlorido ligands also bound to the zinc(II) center, which was contained in the synthesis process, and zinc(II) forms a four-coordinate pseudotetrahedral geometry alongside two terminal chlorido ligands. The coordination manner, in which pyrazine locates at the trans to pyridine, is the same as the singly oxido-bridged complex with chlorido ligands, [{Ru III,IV Cl 2 (Rbpma)} 2 (μ-O)] + . From the viewpoint of the electrostatic characters of ligands, the geometry seems not favorable; however, there would be other factors, e.g., the stabilization of pyrazine owing to the Ru(dπ)-pz(π)-Ru(dπ) interactions.…”

“…In methanol under air, the chlorido ligand(s) was­(were) substituted for methoxido ligand(s) without framework conversion, affording [{Ru II,III (Rbpma)} 2 (μ-Cl) m (μ-OCH 3 ) 3– m ] 2+ ( m = 1, 2) . In contrast, in the presence of water, the triply bridged framework was converted into the singly bridged framework, bridged by an oxido ligand coming from water, [{Ru III,IV Cl 2 (Rbpma)} 2 (μ-O)] + . In this work, the reactions of [{Ru II,II (bbpma)} 2 (μ-Cl) 3 ] + ([ 1 ] + ) with pyrazine (pz), the N -donor ambidentate ligand, which could enable multinucleation, were attempted.…”

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

“…The electronic transition spectrum of [ 1 CO3 ] + in the UV-vis-NIR region in CH 3 CN showed two intense absorption bands at 249 and 362 nm and a weak broad band at ∼1067 nm (see the black broken line in Figure , as well as Table , both presented later in this work). Each absorption band was attributed to the π­(py)−π*­(py) transition of ebpma, the MLCT from dπ­(Ru) to π*­(py), , and the transitions on the {Ru 2 (μ-O) 2 } core, , respectively. The λ max values of the MLCT and the transition on the {Ru 2 (μ-O) 2 } core were in longer wavelengths for [ 1 CO3 ] + than those of [ 1 CH3COO ] 2+ and [ 1 NO3 ] 2+ , since the stronger electron-donating carbonate destabilized the dπ­(Ru) orbital energy level.…”