Isao Ando

The effect of second-sphere coordination. 7. Isolation of 18-crown-6 ether adducts of ruthenium-ammine complexes

Abstract 18-Crown-6 ether adducts were isolated for ruthenium(II)- and ruthenium(III)-ammine complexes, and the mixed-valence binuclear ruthenium-ammine complex. The adducts were characterized by electronic and IR spectroscopy. Ruthernium-ammine complexes form adducts with 18-crown-6 ether through hydrogen bonding between ammines coordinating to the ruthenium and ether oxygens of 18-crown-6 ether. The composition of the adducts is dependent on the valence of the metal canter: the composition was found to be 1:12, 1:2, and 1.3 (complex to 18-crown-6 ether) for the ruthenium (III complex, and the mixed-valence binuclear binuclear complex respectively. The adduct of the ruthenium (III) complex has a unusual composition: two molecules of 18-crown-6 ether are involved in the adduct. Furthermore, the delocalized mixed-valence binuclear complex formed an asymmetric adduct similar to that formed by a binuclear complex with fixed valence.

The effect of second-sphere coordination—II. Adduct formation between [Ru(NH3)5L](PF6)n (n = 2 and 3) and 18-crown-6 ether in solution and the effect on redox behaviour☆

Abstract The adduct formation of [Ru(NH3)5L](PF6)n (n = 2 for L = isonicotinamide and pyrazine; n = 3 for L = 4-aminopyridine and 4-dimethylaminopyridine) with 18-crown-6 ether (18C6) was investigated spectrophotometrically and electrochemically in non-aqueous solution. The adduct formation gave a red shift of the MLCT band for [Ru(NH3)5L](PF6)2 and a blue shift of the LMCT band for [Ru(NH3)5L](PF6)3. The magnitude of the shifts is linearly dependent on the reciprocal of the dielectric constant of the solvents examined. The adduct formation was interpreted in terms of the hydrogen bonding between the ammine coordinating to ruthenium and the ether oxygen of 18C6. The stoichiometry of the adducts in non-aqueous solution was determined to be 1 : 1 (complex: 18C6) for [Ru(NH3)5L](PF6)2 and 1 : 2 for [Ru(NH3)5L](PF6)3. The potential of a ruthenium(III)/ruthenium(II) redox couple in acetonitrile solution was measured at various concentrations of 18C6 by cyclic voltammetry. The redox couples shifted to more negative potentials with an increasing 18C6 concentration, where no additional redox peak appeared. The shift of redox potentials was about − 130 mV at 0.10 mol dm−3 18C6 concentration, irrespective of the nature of L. Thus, it becomes possible to tune the redox potential of the ruthenium complexes by second-sphere coordination with 18C6.

The effect of second-sphere coordination of 18-crown-6 ether on electronic spectra and electrochemical properties of [Ru(NH3)5L](PF6)3 and [Ru(NH3)5L](PF6)2

Abstract Ruthenium(III) complexes [Ru(NH3)5L](PF6)3 (L = 4-aminopyridine or 4-dimethylaminopyridine) and ruthenium(II) complexes [Ru(NH3)5L](PF6)2 (L = isonicotinamide or pyrazine) form adducts with 18-crown-6 ether in acetonitrile giving a blue shift of the LMCT band for the ruthenium(III) complex, a red shift of the MLCT band for the ruthenium(II) complex and a negative shift of the ruthenium(III)/ruthenium(II) redox potential for all the complexes.

pH Dependence of the distribution coefficients of monomeric oxo anions of phosphorus in gel chromatography with tightly cross-linked gels

Abstract Sodium phosphinate, sodium phosphonate and potassium dihydrogen orthophosphate were chromatographed on a Sephadex G-10, G-15 or G-25 column with six kinds of eluents containing different alkali metal halides at various pH values. The distribution coefficient ( K d ) on a tightly cross-linked gel column varies significantly depending on the pH of the eluent and is effectively insensitive to the kind of the eluent used. The pH profile of the K d value is characteristic of the corresponding oxo acid of phosphorus and resembles closely its pH titration curve. The pH dependence of the K d value of the oxo anion is discussed in terms of the distribution of the species in different dissociation states, which depends on the pH of the eluent.

Effect of second-sphere coordination.: 10. Contribution of π-electron acceptability of ancillary ligand to stability of 18-crown-6 ether adduct of ruthenium complex

Abstract Redox potentials of rutheniumpentaammine complexes, [Ru(NH 3 ) 5 (pz)](PF 6 ) 2 and [Ru(NH 3 ) 5 (pzMe)](PF 6 ) 3 {pz=pyrazine, pzMe= N -methylpyrazinium}, were measured in acetonitrile solution in the presence of 18-crown-6 ether. Stability constants of 18-crown-6 ether adducts were evaluated from the dependence of redox potentials on the concentrations of 18-crown-6 ether. The stability constants were also evaluated from the dependences of diffusion coefficient of the complexes determined by chronocoulometry and the chemical shift of the ammine protons of the complexes determined by 1 H NMR spectroscopy on the concentrations of 18-crown-6 ether. The factors contributing to stability of the 18-crown-6 ether adducts were discussed on the basis of these stability constants obtained.

Effect of second-sphere coordination 6. Adduct formation of monoammine-, diammine-, triammine- and tetraamineruthenium(II) complexes with 18-crown-6 ether

Abstract Adduct formation was spectrophotometrically and electrochemically investigated for monoammine-, diammine-, triammine- and tetraamineruthenium(II) complexes. It was found that an adduct was formed through hydrogen bonding between the coordinating ammonia ligands to the ruthenium(II) and the ether oxygens of 18-crown-6 ether. The stoichiometry of adduct formation was determined to be a 1:1 ratio of complex to 18-crown-6 ether. The electrochemical results offer the evidence that the increased electron density around the metal center by formation of the hydrogen bond is redistributed over the whole complex through pπ-dπ back donation. The electrochemical behavior in the presence of 18-crown-6 ether revealed the concurrent electrode reactions for the ruthenium(II)-ammine complexes with fewer ammine ligands.

Effect of second-sphere coordination. 11. Selectivity in adduct formation of polypyridineruthenium(II) complexes with crown ethers

Adduct formation of polypyridineruthenium(II) complexes involving a different type of protic ligand was investigated for a series of crown ethers with different ring size. Changes in redox potential and in absorption spectra of the complex were measured on addition of crown ether to the complex solution. The magnitude of the change in both properties is dependent on the ring size of crown ethers. Chemical shifts of protic ligand of the complexes were measured at various concentrations of crown ethers. The stability constants of crown ether adduct were determined from the dependences of the chemical shift on crown ether concentration. It is found from their stability constants that the individual complex shows the different selectivity in adduct formation with crown ethers.

Bis(2,2′-bipyridine)(pyridin-2-olato)ruthenium(II) hexa­fluorido­phosphate benzene hemisolvate

In the title compound, [Ru(C5H4NO)(C10H8N2)2]PF6·0.5C6H6, the Ru2+ cation has a distorted octahedral RuN5O coordination environment. This complex is more distorted than the closely related ruthenium complex containing a pyridine-2-thiolate ligand [Santra et al. (1997 ▶). J. Chem. Soc. Dalton Trans. pp. 1387–1393]. The distortion is caused by the difference in size between the O and S atoms. The benzene solvent molecule is situated on a twofold rotation axis.

Crystal structure of bis­(1,10-phenanthroline-κ2N,N′)(1,3-thia­zole-2-thiol­ato-κ2S2,N)nickel(II) hexa­fluorido­phosphate 1,4-dioxane sesquisolvate

2-Mercaptothiazolate is generally used as a monodentate and bridging ligand. We report here the crystal structure of a new type of nickel(II) complex in which the 2-mercaptothiazolate ligand acts as a chelating and non-bridging ligand.

Bis[(5-bromo­pyridin-2-yl)methano­lato-κ2N,O]copper(II) monohydrate

In the title compound, [Cu(C6H5BrNO)2]·H2O, the CuII ion has a square-planer N2O2 coordination environment. Slipped π–π stackings [centroid-centroid distances: 3.625u2005(3), 3.767u2005(3), 3.935u2005(3) and 4.255u2005(3)u2005Å] between pyridine rings and Cu⋯π interactions (centroid-to-CuII distance: 3.56u2005Å) between Cu2+ ions and pyridine rings lead to a layered arrangement parallel to (010). Intermolecular Br⋯O interactions [Br⋯O distances: 2.904u2005(3) and 3.042u2005(3)u2005Å] and O—H⋯O hydrogen bonds form a three-dimensional network structure.