Hirotaka Nagao

Adduct between quadricyclane and (η5-cyclopentadienyl)(1,2-benzenedithiolato)cobalt(III): formation and structure

The reaction of (η5-cyclopentadienyl)(1,2-benzenedithiolato)cobalt(III) (1) in quadricyclane (Q) at 90°C gives 1:1 adducts of 1 and Q. The main adduct (40% yield) has a unique structure, in which the 5-and 7-positions of norbornene are bonded to Co and S of 1. A mechanism of the formation of the adduct (by the use of deuterium-labeled Q), including a skeletal rearrangement of Q, is proposed.

Synthesis, characterization and reactivity of a series of dinuclear copper complexes bearing the ligand bis[3-(2-hydroxybenzylideneamino)phenyl] sulfone and derivatives

Abstract The ligands bis[3-(X-2-hydroxybenzylideneamino)phenyl] sulfones (X=none: BHBAPS, X=3-tert-butyl: BH(t-Bu)BAPS and X=3,5-dichloro: BHCl2BAPS) were prepared. These, together with Cu(OAc)2 were used in the syntheses of the dinuclear copper complexes Cu2(BBAPS)(μ-OMe)2 (1), Cu2[B(t-Bu)BAPS] (μ-OH)2 (2), and Cu2[BCl2BAPS] (μ-OMe)2 (3). Complex 1 was crystallographically characterized. The structures of 2 and 3 are similar to 1 by comparison of IR, UV–Vis, FAB-MS and elemental analyses results. Complexes 1–3 (1 mol%) were used in the oxidation of 2,4- and 2,6-di-t-butylphenol (dtbp) at −50xa0°C with H2O2. The results show that (1) the coupling products are preferred when CH2Cl2 is used; and (2) the quinone yield increases when THF is utilized. In CH2Cl2 with 2,4-dtbp, the yield of the coupling product based on the complex amount, is in the order 2, 1, and 3 with yields of 6300,xa04700 and 200%, respectively. Low temperature UV–Vis results of the reaction of 1 with H2O2 showed the growth of peaks at 390 and 580 nm indicative of a μ-η2:η2-peroxo or μ-η1:η1-hydroperoxo intermediate. At −50xa0°C, this spectrum does not change. But when warmed to 0xa0°C, a spectrum similar to the original spectrum was obtained. This probably indicates hydrogen radical abstractions of the peroxo intermediate from solvents, and if excess H2O2 is present, the peroxo intermediate may again be formed. This reusability of the complex explains the high yield using 1 and 2.

Synthesis and characterization of polypyridineruthenium(II) complexes containing a linear ambidentate ligand, NCO− or NCS−, and reaction of isocyanato complexes under acidic conditions

Abstract Isocyanato and isothiocyanatopolypyridineruthenium complexes, [Ru(NCX)Y(bpy)(py)2]n+ (bpy=2,2′-bipyridine, py=pyridine; X=O, Y=NO2 for n=0, and Y=py for n=1; X=S, Y=NO2 for n=0, Y=NO for n=2, and Y=py for n=1), were synthesized by the reaction of polypyridineruthenium complexes with potassium cyanate or sodium thiocyanate salt. Isocyanatoruthenium(II) complexes, [Ru(NCO)(NO2)(bpy)(py)2] and [Ru(NCO)(bpy)(py)3]+, react under acidic conditions to form the corresponding ammineruthenium complexes, [Ru(NO)(NH3)(bpy)(py)2]3+. The molecular structures of [Ru(NCO)(bpy)(py)3]ClO4, [Ru(NCS)(NO)(bpy)(py)2](PF6)2 and [Ru(NO)(NH3)(bpy)(py)2](PF6)3 were determined by X-ray crystallography.

Syntheses and characterization of homodinuclear manganese and cobalt complexes bridged by a hemiacetal or by an acetato group in a μ-(η2:η1) bridging mode

Abstract The complex [Mn2(BPMAPS)(μ-OAc)2(hemi)]PF6 (1), where hemi is the hemiacetal group, methoxy(2-pyridyl)methoxo, was prepared from bis[3-(2-pyridylmethyleneamino)phenyl] sulfone (BPMAPS), 2-pyridinecarbaldehyde, and manganese(II) acetate in methanol. The complexes Mn2(BPMAPS)(μ-OAc)2(μ-1,1-OAc)(η1-OAc) (2) and Co2(BPMAPS)(μ-OAc)2-[μ-(η2:η1)OAc](η1-OAc) (3) were prepared from manganese(II) acetate and cobalt(II) acetate, respectively, with BPMAPS in methanol. All three complexes were characterized by elemental analysis, FT-IR, MS, UV–Vis spectroscopy, and X-ray crystallography. The manganese ions of complex 1 are bridged by a hemiacetal through the oxygen atom of the alkoxo with the nitrogen atom of the pyridine group coordinating to one of the manganese atoms. The metal ions of complexes 2 and 3 are bridged by acetato groups in μ-1,1 or μ-η2:η1 modes, respectively.

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.

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.

Electrochemical behavior of the oxo complex of Ru(IV), trans-[RuCl(O)(py)4]+, in both non-aqueous and aqueous solvents

Abstract The electrochemical behavior of trans -[Ru IV Cl(O)(py) 4 ] + , and that of its related complexes, trans -[Ru III Cl(OH)(py) 4 ] + and trans -[Ru II Cl(H 2 O)(py) 4 ] + , were investigated in both acetonitrile and aqueous solvents. The reduction process of trans -[Ru IV Cl(O)(py) 4 ] + was an irreversible one; it converted into trans -[Ru II Cl(OH)(py) 4 ] 0 in CH 3 CN and trans -[Ru II Cl(H 2 O)(py) 4 ] + in aqueous solvent by a one-step two-electron reduction. The oxo complex undergoes a one-electron oxidation to give a reactive trans -[Ru V Cl(O)(py) 4 ] 2+ , which is the species capable of oxidizing organic substances.

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.

Reactions of [RuCl2(NO)(terpy)]+ (terpy = 2,2′ : 6′,2″-terpyridine) with mono anions such as NO2−, Br− and N3−, and structural studies on terpyridineruthenium having a nitrosyl ligand

[RuCl2(NO)(terpy)]PF6 ([1]PF6) has been synthesized by the reaction of K2[RuCl5(NO)] with terpy and characterized by single-crystal X-ray crystallography. [1]PF6 has a structure in which the two chloro ligands are located trans to each other with the nitrosyl ligand on the plane of the terpy ligand. Reactions of [1]PF6 with mono anions such as NO2−, Br− and N3− have been investigated. Its reactions with NO2− in H2O and CH3OH afford nitrosylterpyridineruthenium complexes, [Ru(OH)(NO2)(NO)(terpy)]PF6 ([2]PF6) and [RuCl(OCH3)(NO)(terpy)]PF6 ([3]PF6), respectively, whose geometrical configurations differ from that of [1]+. The Br−-substituted complex of [1]+, [RuBr2-(NO)(terpy)]PF6 ([4]PF6), and two solvated complexes, [RuCl2(CH3CN)(terpy)] ([5]) and [RuCl(CH3CN)2(terpy)]PF6 ([6]PF6), have been formed in its reactions with Br− and N3−. Structures of [2]PF6, [3]PF6 and [4]PF6 have been determined by singal-crystal X-ray crystallography and compared with each other.

A mixed-valence diruthenium complex, triply bridged by mixed-moieties of chloro and methoxo ligands

A mixed-valence diruthenium complex, whose metal centres were triply bridged by one chloro and two methoxo ligands, was synthesized and characterized by X-ray structural analysis, electrochemistry and spectroscopy, and its mixed-valence state was classified into Class III.