Noriharu Nagao

One-pot and selective synthesis of a series of [RuCl6−2nLn] (L=bidentate ligand, n=0−3) types of complexes with polypyridyl ligands; another example of the synthetic utility of ‘ruthenium-blue’ solution

Abstract Convenient (one-pot) and selective syntheses of a series of ruthenium complexes with polypyridyl ligands, [RuL3]2+, cis-[RuCl2L2]+ and [RuCl4L]- (L=bpy, phen or Hdpa (di-2,2-dipyridylamine)), including [RuCl6]3−, have been reported as further examples of the synthetic utility of ‘ruthenium-blue’ solution. The methods developed here are also useful for synthesizing selectively such pair complexes as [RuIIICl3(terpy)]-[RuII(terpy)2]2+ and [RuIIICl4py2]−-[RuIICl2py4].

Syntheses, characterization, structure and redox behavior of cis-[Ru(NO)X(bpy)(py)2]z (X=monodentate) type complexes of nitrosylruthenium(II) and their related complexes

Abstract Nitrosyl complexes which have both 2,2′-bipyridine and pyridine as co-existing ligands were synthesized and characterized as cis-[Ru(NO)(X)(pby)(py)2]z+ (X=OH, Cl, NO2 for z=2; X=py for z=3). Their characteristics were investigated under the condition of both chemical oxidation and electrochemical reduction. The molecular of cis-[Ru(NO)(OH)(pby)(py)2](PF6)2 was determined: Ru20N5H19O2P2F12,FW=752.40, orthorhombic, a=15.942(2), b=26.541(4), c=12.670(5) A , V=5360(1) A 3 , space group Pbca, Z=8, Dcalc=1.864 g cm−3, Dobs=1.857 g cm−3, μ (Mo Kα)=8.18 cm−1, no. of observations (I>3.00σ(I))=2232, R=0.050, Rw=0.042. The related nitro and oxo complexes which were obtained from the nitrosyl complexes are also reported.

Evidence for a new nitrosyl-to-nitro reaction and an acetamide formation in the {RuNO}6-type complex, cis-[Ru(NO)(CH3CN)(bpy)2]3+

Abstract The reaction between cis-[Ru(NO)(CH3CN)(bpy)2]3+ and a free NO2− gives an appreciable amount of the nitro species cis-[Ru(NO2)(CH3CN)(bpy)2]+. Although definitive evidence for the mechanistic illustration of the nitrosyl-to-nitro conversion is still unavailable, an oxide abstraction from NO2− to the nitrosyl ligand appears to be the key reaction. In addition, cis-[Ru(NO)(CH3C(O)NH)(bpy)2]2+ having an acetamide ligand is formed during the reaction. The structure of the complex, used as a starting material of the present reaction, was determined by single-crystal X-ray diffraction methods; for cis-[Ru(NO)(CH3CN)(bpy)2](ClO4)3·CH3CN: FW=823.91, monoclinic, P21/n, a=12.471(3), b=15.041(7), c=17.598(4) A, β=94.65(2)°, V=3289(1) A3, Z=4, R=0.081, Rw=0.050.

Preparation and characterization of cis- and trans-[Ru(OAc)(2mqn)2NO] (OAc=acetate, 2mqn=2-methyl-8-quinolinolate), and their mutual photoisomerization reactions

Abstract A mixture of hydrated nitrosylruthenium(III) chloride and 2-methyl-8-quinolinol (H2mqu) (1:4 molar ratio) in acetic acid aqueous solution adjusted to pH 5.5 and warmed at c. 70 °C for 2 h led to preparation of cis- [Ru(OAc)(2mqn)2NO] which has cis(0,0) and trans(N,N) configuration for the ligating atoms of the 2mqn ligands. The trans isomer was photochemically prepared from the cis isomer in CH2Cl2 using an Xe lamp as the light source. The photoisomerization in deaerated CH2Br2 was examined at −5 to 30 °C using a super high-pressure Hg lamp (436 mm). Quantum yields of the cis to trans and the trans to cis isomerizations were 1–2.5×10−3 and 8–11×10−3, respectively. Solvent effect studies by adding liquid paraffin to the CH2Br2 solution on the photoreaction and the NO scramble on the irradiation in the presence of 15NO gas showed that RuNO bond rupture takes part in the isomerization.

Redox behavior of a binuclear ruthenium complex having a di-μ-nitrosyl ligand, [Ru(acac)22(μ-NO)2] (acac = acetylacetonato)

Abstract The title complex, which has two cis -Ru(acac) 2 fragments connected doubly by μ-N (O) bridges, undergoes both a one-electron reversible and a second one-electron irreversible reduction, in addition to a one-step, two-electron irreversible oxidation. In the oxidation process, the binuclear structure is disintegrated to give two moles of cis -[Ru(NO)(CH 3 CN)(acac) 2 ] + from one mole of the title complex.

One-electron oxidation behavior of {MNO}6-type nitrosyl complexes having acetylacetonato ligand, [M(NO)Cl5−2n(acac)n]m (M=Ru, Os; n=1, 2; acac=acetylacetonato)

Abstract The electrochemical behavior of several complexes with the general formula [M(NO)Cl 5−2 n (acac) n ] m (M=Ru, Os; n =1, 2; acac=acetylacetonato) was investigated: mer -[Ru(NO)Cl 3 (acac)] − ( 1 , n =1), cis -[Ru(NO)Cl(acac) 2 ] ( 2 , n =2), mer -[Os(NO)Cl 3 (acac)] − ( 3 , n =1), cis -[Os(NO)Cl(acac) 2 ] ( 4 , n =2). The study includes the known corresponding n =0 complexes, [M(NO)Cl 5 ] 2− (M=Ru, Os), for comparison. All these complexes undergo a one-electron oxidation, which is rather unusual redox behavior in the {MNO} 6 -type nitrosyl complexes. The behavior of some of these complexes as electrophiles was also described. Molecular structures with a meridional configuration were established for the n =1 complexes ([Ru(NO)Cl 3 (acac)] − ( 1 ) and [Os(NO)Cl 3 (acac)] − ( 3 )) by X-ray structure determinations. Crystal data for 1 (Bu 4 N salt): C 21 H 43 N 2 O 3 Cl 3 Ru, a =31.443(9), b =21.86(1), c =19.852(6) A, β =119.65(2)°, monoclinic, C 2/ c , Z =16. Crystal data for 3 (Cs salt): C 5 H 7 NO 3 Cl 3 OsCs, a =7.942(1), b =12.602(2), c =7.451(2) A, α =105.91(2), β =98.20(2), γ =90.31(1)°, triclinic, P 1 , Z =2.

Ligand nature of coordinated NO2− in the oxidation reaction of Ru(II) complexes, [Ru(NO2)(OH2)(py)4−2n(bpy)n]+(n=0, 1, 2), and their related complexes

Abstract Under the chemical conditions using NaClO, the title complexes undergo an oxidation which gives different products: [Ru IV (ONO)(O)(py) 4 ] + (for n =0), [Ru IV (NO 2 )(O)(py) 2 (bpy)] + (for n =1) and [Ru 2 III,III O(NO 2 ) 2 (bpy) 4 ] 2+ (for n =2). All these complexes retain the original nitro nitrogen. However, the electrochemical oxidation proceeds along basically the same mechanistic pathway; each of the title complexes undergoes a one-electron oxidation to give the corresponding Ru(III) complexes; then the formation of a dimeric intermediate consisting of both nitro and nitrito complexes of Ru(III) results in the generation of a nitrosyl complex of Ru(II). This pathway suggests that a metal-nitrite bond breaking process is involved in the electrochemical oxidation. We also investigated the oxidation of the μ-oxo complex of Ru(III,III) with nitro ligand, [Ru 2 O(NO 2 ) 2 (bpy) 4 ] 2+ , which was isolated as the product species in the chemical oxidation of the complex with n =2. In this oxidation, an intramolecular electron transfer process is operating; a one-electron oxidized (NO 2 − Ru III ORu IV NO 2 − ) 3+ moiety first changes to (NO 2 − Ru III ORu III NO 2 0 ) 3+ ; this change brings about the liberation of the non-charged NO 2 , along with the formation of solvation species containing the (NO 2 − Ru III ORu III CH 3 CN) 3+ moiety.