Electrochemical evidence for a two-electron reduction process in a (.mu.-oxo)bis(.mu.-acetato)diruthenium(III) complex containing terminal 1-methylimidazole ligands

Sudha, Chellamma; Mandal, Sisir K.; Chakravarty, Akhil R.

doi:10.1021/ic00070a004

Cited by 46 publications

(22 citation statements)

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“…16 6 ]-(ClO 4 ) 2 (1-MeIm ) 1-methylimidazole). 27 The work is now extended using other imidazole bases viz., imidazole (ImH) and 4-methylimidazole (4-MeImH) and bridging aryl carboxylates. Herein, we report the full details of the results on complexes of composition [Ru 2 (3)).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, X-ray Structures, and Spectroscopic and Electrochemical Properties of (μ-Oxo)bis(μ-carboxylato)diruthenium Complexes Having Six Imidazole Bases as Terminal Ligands

1998

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Complexes [Ru 2 O(O 2 CR) 2 (1-MeIm) 6 ](ClO 4 ) 2 (1a-c), [Ru 2 O(O 2 CR) 2 (ImH) 6 ](ClO 4 ) 2 (2a,b), and [Ru 2 O(O 2 CR) 2 -(4-MeImH) 6 ](ClO 4 ) 2 (3a,b) with a (µ-oxo)bis(µ-carboxylato)diruthenium(III) core have been prepared by reacting Ru 2 Cl(O 2 CR) 4 with the corresponding imidazole base, Viz. 1-methylimidazole (1-MeIm), imidazole (ImH), and 4-methylimidazole (4-MeImH) in methanol, followed by treatment with NaClO 4 in water (R: Me, a; C 6 H 4 -pOMe, b; C 6 H 4 -p-Me, c). Diruthenium(III,IV) complexes [Ru 2 O(O 2 CR) 2 (1-MeIm) 6 ](ClO 4 ) 3 (R: Me, 4a; C 6 H 4 -p-OMe, 4b; C 6 H 4 -p-Me, 4c) have been prepared by one-electron oxidation of 1 in MeCN with K 2 S 2 O 8 in water. Complexes 1a, 2a‚3H 2 O, and 4a‚1.5H 2 O have been structurally characterized. Crystal data for the complexes are as follows: 1a, orthorhombic, P2 1 2 1 2 1 , a ) 7.659 (3) The complexes have a diruthenium unit held by an oxo and two carboxylate ligands, and the imidazole ligands occupy the terminal sites of the core. The Ru-Ru distance and the Ru-O oxo -Ru angle in 1a and 2a‚3H 2 O are 3.266(1), 3.272(1) Å and 122.4(4), 120.5(2)°, while in 4a‚1.5H 2 O these values are 3.327(1) Å and 133.6(2)°. The diruthenium(III) complexes 1-3 are blue in color and they exhibit an intense visible band in the range 560-575 nm. The absorption is charge transfer in nature involving the Ru(III)-dπ and O oxo -pπ orbitals. The diruthenium(III,IV) complexes are red in color and show an intense band near 500 nm. The diruthenium(III) core readily gets oxidized with K 2 S 2 O 8 forming quantitatively the diruthenium(III,IV) complex. The visible spectral record of the conversion shows an isosbestic point at 545 nm for 1 and at 535 nm for 2 and 3. Protonation of the oxide bridge by HClO 4 in methanol yields the [Ru 2 (µ-OH)(µ-O 2 CR) 2 ] 3+ core. The hydroxo species shows a visible band at 550 nm. The pK a value for 1a is 2.45. The protonated species are unstable. The 1-MeIm species converts to the diruthenium(III,IV) core, while the imidazole complex converts to [Ru(ImH) 6 ] 3+ and some uncharacterized products. Complex [Ru(ImH) 6 ]-(ClO 4 ) 3 has been structurally characterized. The diruthenium(III) complexes are essentially diamagnetic and show characteristic 1 H NMR spectra indicating the presence of the dimeric structure in solution. The diruthenium(III,IV) complexes are paramagnetic and display rhombic EPR spectral features. Complexes 1-3 are redox active. Complex 1 shows the one-electron reversible Ru III 2 /Ru III Ru IV , one-electron quasireversible Ru III Ru IV /Ru IV 2 , and two-electron quasireversible Ru III 2 /Ru II 2 couples near 0.4, 1.5, and -1.0 V Vs SCE in MeCN-0.1 M TBAP, respectively, in the cyclic and differential pulse voltammetric studies. Complexes 2 and 3 exhibit only reversible Ru III 2 /Ru III Ru IV and the quasireversible Ru III Ru IV /Ru IV 2 couples near 0.4 and 1.6 V Vs SCE, respectively. The observation of a quasireversible one-step two-electron transfer reduction process in 1 is significant considering its relevance to the r...

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Section: Introductionmentioning

confidence: 99%

Synthesis, X-ray Structures, and Spectroscopic and Electrochemical Properties of (μ-Oxo)bis(μ-carboxylato)diruthenium Complexes Having Six Imidazole Bases as Terminal Ligands

1998

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“…The diruthenium tetracarboxylates react with imidazole bases to form tribridged complexes containing six terminal imidazole bases (figure 4) (Sudha et al 1993). The corr/plexes of formulation [Ru 2 O(O 2 CR) 2 (Rim) 6 ] (CIO 4)2 (R = H, Me) exhibit interesting redox properties (figure 5, table 1).…”

Section: Tribridged Species Containing Imidazole Basesmentioning

confidence: 99%

Tribridged diruthenium complexes: A new structural motif

Chakravarty

1996

Proc. Indian Acad. Sci. (Chem. Sci.)

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Dinuclear complexes containing a (lt-oxo)bis(#-carboxylato) diruthenium (III) core have been prepared by a novel synthetic route using metal-metal bonded diruthenium(II, III) tetracarboxylates as precursors. The complexes have been structurally characterized and they are redox active. The terminal ligands play an important role in tuning the electronic structure of the core. The stability of the core is found to be dependent on the size and 7r-acidic nature of the terminal ligand cis-to the/~-oxo ligand. The chemistry of such tribridged complexes is relatively new. The rapid growth of this chemistry is based on the discovery of similar core structures in several non-heme iron'and manganese-containing metaUoproteins. The tribridged core presents a new structural motif in coordination chemistry. The chemistry of diruthenium complexes with a [Ru 2 (/1-O) ~-O 2 CR)22 +] core has been reviewed.

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“…In the study of the functions and biological mechanisms of diiron enzymes, second‐ and third‐row transition metal complexes have been resorted to for over several decades as substitutes of the more labile iron complexes with the general formula [Fe III 2 ( μ ‐O)( μ ‐RCO 2 ) 2 L n ] m + (L: terminal ligand). Particularly, a number of diruthenium complexes with various ligands, which mimic their iron congeners, have been extensively synthesized and studied from the viewpoints of structure, electrochemistry, spectroscopy, catalysis and kinetic behavior …”

Section: Introductionmentioning

confidence: 99%

The First Bis(μ‐acetato)(μ‐oxido)diruthenium(III) Complexes Containing Sulfur Donor Ligands

et al. 2019

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Novel diruthenium(III) complexes of general formula [RuIII2(μ‐O)‐(μ‐CH3CO2)2(bpy)2L2](PF6)2 (L: tetrahydrothiophene, (3); 4,5‐dihydro‐3(2H)‐thiophenone, (4); thiazole, (5); 4‐methylthiazole, (6); bpy: 2,2’‐bipyridine), which contain sulfur or nitrogen donor ligands at the trans‐to‐oxido sites, have been synthesized. The Ru–S bond distance in 4 is determined by X‐ray crystallography to be 2.447 Å, and the Ru–N(trans‐to‐oxido) length in 5 (2.157 Å) is similar to that of the complex having pyridine as the L ligand, 1. The spectroscopic properties and redox behavior of the complexes bearing sulfur donor ligands have been investigated and compared with those containing nitrogen donor ligands. The potentials of the redox couples of Ru2II,III/Ru2III,III and Ru2III,III/Ru2III,IV for 3 and 4 shift to positive regions compared with those of complexes with nitrogen donor ligands, 1, 5 and 6. The density functional theory (DFT) calculations reveal that the contribution of the trans ligand to the visible absorption is larger in 3 and 4 than in 1, 2 (L: CH3CN), 5 and 6.

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Electrochemical evidence for a two-electron reduction process in a (.mu.-oxo)bis(.mu.-acetato)diruthenium(III) complex containing terminal 1-methylimidazole ligands

Cited by 46 publications

References 1 publication

Synthesis, X-ray Structures, and Spectroscopic and Electrochemical Properties of (μ-Oxo)bis(μ-carboxylato)diruthenium Complexes Having Six Imidazole Bases as Terminal Ligands

Synthesis, X-ray Structures, and Spectroscopic and Electrochemical Properties of (μ-Oxo)bis(μ-carboxylato)diruthenium Complexes Having Six Imidazole Bases as Terminal Ligands

Tribridged diruthenium complexes: A new structural motif

The First Bis(μ‐acetato)(μ‐oxido)diruthenium(III) Complexes Containing Sulfur Donor Ligands

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