RuII RuIII Research Articles

A ruthenium(IV) oxo complex that contains a tertiary diamine ligand

The complex [Ru(terpy)(tmen)(OH2)]2+(terpy = 2,2′:6′2″-terpyridine, tmen =N,N,N′,N′-tetra-methylethylenediamine) and its corresponding oxo complex have been prepared. Their spectral properties and redox properties in aqueous solution were investigated. Evidence for two one-electron redox processes has been obtained for the RuIV–RuIII and RuIII–RuII couples.The reactions of the new ruthenium(IV) oxo species with olefins have been found to proceed with second-order kinetics, rate =k2[RuIV][olefin] where k2=(3.3 ± 0.3)× l0–3 and (2.0 ± 0.2)× 10–2 dm3 mol–1 s–1 at 25 °C for norbornene and styrene respectively.

Synthesis, electrochemistry, and reactivities of trans-[RuVI(L)O2]2+(L =N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)propylenediamine

The synthesis and characterization of the ligand N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-propylenediamine (L) and the complex trans-[RuVI(L)O2]2+ are described. The complex has been characterized by u.v.–visible [dxy→dπ*(dπ*=dxz,dyz) at 380–420 nm] and i.r. [νasym(RuO2) at 860 cm–1] spectroscopy. At pH 1.0 it exhibits three reversible couples RuVI–RuIV, RuIV–RuIII, and RuIII–RuII at potentials of 0.89, 0.60, and 0.28 V respectively vs. saturated calomel electrode. The RuVI–RuIV couple splits into two reversible one-electron couples RuVI–RuV and RuV–RuIV in alkaline solutions (pH > 9). The complex is a powerful oxidant, capable of oxidizing toluene to benzaldehyde, alcohols to aldehydes/ketones, tetrahydrofuran to γ-butyrolactone, and norbornene to exo-2,3-epoxy-norbornane in high yields at room temperature. Oxidation of cis- and trans-stilbenes gave benzaldehyde and trans-stilbene oxides.

ChemInform Abstract: CHEMISTRY OF RUTHENIUM. PART 10. TRIAZENE 1‐OXIDE COMPLEXES OF BIS(2,2′‐BIPYRIDINE)RUTHENIUM(II) AND ‐(III). SYNTHESIS, SPECTRA, AND ELECTROCHEMISTRY

AbstractDie wie aufgezeichnet synthetisierten Ru(II)‐Titelkomplexe (III) werden durch Elementaranalysen, molare Leitfähigkeiten, elektronen‐ und IR‐spektroskopische Daten charakterisiert.

Luminescent metal complexes. Part 3. Electrochemical potentials of ground and excited states of ring-substituted 2,2′-bipyridyl and 1,10-phenanthroline tris-complexes of ruthenium

E ½ values for 21 tris-complexes of substituted 2,2′-bipyridyls and 1,10-phenanthrolines with RuII–RuIII in acetonitrile have been measured using cyclic voltammetry. A linear correlation exists between E½ and the Hammett σ constant for data obtained from complexes of 4,4′-and 5,5′-disubstituted 2,2′-bipyridyls. The reduction potential for the couple Ru(ligand)33+–*Ru(ligand)32+, where * refers to the excited state, have been calculated from the E½ values and a combination of data collected from luminescence and magnetic circular dichroism measurements.

ChemInform Abstract: CHEMISTRY OF RUTHENIUM. PART 8. NEW TRIS COMPLEXES OF RUTHENIUM(III). SYNTHESIS, SPECTRA, AND REDOX ACTIVITY

AbstractDie Reaktion einer siedenden EtOH‐Lösung von RuCl3 mit Triazen‐1‐oxiden liefert die Titelkomplexe (I) mit seltener mer‐Struktur, die durch IR‐ und Elektronenspektren charakterisiert wurden.

Chemistry of ruthenium. Part 10. Triazene 1-oxide complexes of bis(2,2′-bipyridine)ruthenium-(II) and -(III). Synthesis, spectra, and electrochemistry

Mixed ruthenium complexes of type [Ru(bipy)2L]ClO4·H2O derived from 2,2′-bipyridine (bipy) and triazene 1-oxides, RN(O)N–NH–C6H4X-p(HL: R = Et or Ph; X = Me, H, Cl, CO2Et, or NO2) are described. In solution they display two quasi-reversible reductions due to electron transfer to co-ordinated bipy units. The RuIII–RuII couple occurs in the range 0.16–0.44 V versus s.c.e. The formal potential of this couple is linearly related to the Hammett constant of substituent X. The low-spin ruthenium(III) analogue, [Ru(bipy)2L]2+, is furnished by both coulometric and chemical oxidations. The energy of the ligand-to-metal charge-transfer band of [Ru(bipy)2L]2+ correlates linearly with the RuIII–RuII formal potential.

Chemistry of ruthenium. Part 9. Electrophilic addition of a ruthenium nitrosyl complex to alkylidenearylhydrazones. Arylazo-oximates of bis(2,2′-bipyridyl)ruthenium(II)

The electrophilic addition of [Ru(bipy)2(NO)Cl][ClO4]2 to alkylidenearylhydrazones, RCHNNHR′(R = Me, Ph, or C6H4Me-p; R′= Ph or C6H4Me-p) in methanol containing sodium methoxide affords the new complex [Ru(bipy)2(A)][ClO4]·H2O (2)[HA = RC(NOH)NNR′; bipy = 2,2′-bipyridyl]. An alternative synthesis of (2) is provided by the reaction of cis-[Ru(bipy)2Cl2] with NaA. The protonation of (2) by HClO4 in methanol gives [Ru(bipy)2(HA)][ClO4]2·H2O (5). The proton dissociation constants (pK) of (5) and of HA in dioxan–water (1 : 1) are respectively ca. 10 and ca. 3. All complexes display a ν(NO) of the arylazo-oximate chelate ring at ca. 1 240 cm–1 in the i.r. and one or more t2(ruthenium)→π*(ligand) charge-transfer transition(s) in the visible region, 400–500 nm. A quasi-reversible RuIII–RuII couple occurs in (2) near 0.8 V versus s.c.e. with ΔEPca. 75 mV (cyclic voltammetry in acetonitrile). The RuIII species [Ru(bipy)2(A)]2+ is unstable and generally decomposes with a pseudo-first-order rate constant of 0.4–0.6 s–1(298 K). In (5) the RuIII–RuII couple is at ca. 1.0 V.

Chemistry of ruthenium. Part 8. New tris complexes of ruthenium(III). Synthesis, spectra, and redox activity

A group of new low-spin tris complexes of ruthenium(III) has been synthesized using triazene 1-oxides, RN(O)N–NH–C6H4X-p(HL; R = Et or Ph, X = Me, H, Cl, CO2Et, or NO2) as ligands. The green to yellow-green complexes [RuL3] are believed to have a meridional RuN3O3 co-ordination sphere. They display ligand → metal charge-transfer transitions in the region 550–750 nm. In acetonitrile solution the [RuL3] complexes exhibit a quasi-reversible RuIII–RuII couple (E2980, –0.6 to –1.2 V vs. s.c.e.) and a nearly reversible RuIV–RuIII couple (E2980, 0.2–0.7 V vs. s.c.e.) at a platinum working electrode. The E2980 values of both couples correlate linearly with the Hammett constant of substituent X. The reaction constants lie in the range 0.1–0.2 V. The electronic spectra of [RuL3]– and [RuL3]+ are briefly reported. The former complex is unstable.

ChemInform Abstract: CHEMISTRY OF RUTHENIUM. PART 6. BIS(2,2′‐BIPYRIDINE)(ISONITROSOKETONATO)RUTHENIUM(II) PERCHLORATE MONOHYDRATE. SYNTHESIS, SPECTRA, AND ELECTROCHEMISTRY

AbstractDie Titelkomplexe (III) werden durch Umsetzung der Dichloro‐Ru(II)‐Komplexe (I) mit den Hydroxyiminoketonen (IIa‐d) oder durch Addition eines im Komplex (V) koordinierten Nitrosyls an die aktivierte Form von Acetophenon dargestellt.

Chemistry of ruthenium. Part 6. Bis(2,2′-bipyridine)(isonitrosoketonato)ruthenium(II) perchlorate monohydrate. Synthesis, spectra, and electrochemistry

New ruthenium(II) complexes of type [Ru(bipy)2(L)](ClO4)·H2O are formed by the reaction of [Ru(bipy)2Cl2] with HL and in one case by chelative nitrosation of ketones with [Ru(bipy)2(NO)Cl]2+[HL = RC(NOH)C(O)R′, bipy = 2,2′-bipyridine]. These display metal-to-ligand charge-transfer transitions in the visible region (450–490 nm), a reversible RuIII–RuII couple near 0.9 V versus s.c.e., and one or more ligand reduction couples below –I V. Trends of E298° values for a group of related complexes are rationalised. The oxidised complex [Ru(bipy)2(L)]2+ is unstable and has a ligand-to-metal charge-transfer transition near 600 nm. Its energy correlates linearly with E298° of the RuIII–RuII couple. In acetonitrile, [Ru(bipy)2(L)]+ can be protonated to [Ru(bipy)2(HL)]2+. The RuIII–RuII couple of the protonated complex is at a higher (∼1.0 V) potential than that of [Ru(bipy)2(L)]+. The chemistries of [Ru(bipy)2(L)]+ and [RuX2(HL)(L)] are compared.

Near i.r. transition of the µ-quinoxaline-bis(penta-ammineruthenium)(5+) ion

Although the π* system of the bridging ligand in the µ-quinoxaline-bis(penta-ammineruthenium)(5+) ion (2) is considerably lower in energy than the π* system of the bridging ligand in the previously reported µ-pyrazine-bis(penta-ammineruthenium)(5+) ion (1), the near i.r. transition for (2)(νmax 5900 cm–1) occurs at essentially the same energy as that for (1)(νmax 6300 cm–1), a result suggestive of the mixed-valence RuII–RuIII representation of the ion as opposed to a delocalized RuII½–RuII½ description.