Ru V Complexes

Relatively few oxonithenateCV) complexes were known, but there has recently been more activity in this area. Che and Yam have reviewed complexes in this category [20]. All of the complexes in this section contain a single oxo ligand. 

K[Ru(0)(EDTA)].3H30 (liDTA=(ethylenediamine tetra-acetate) ). The chemistry of Ru-EDTA complexes has been reviewed [628]. This complex is made by reaction 

K[Ru(0)(PDTA)].3Hj0 and Ru(0)(HEDTA) (PDTA=(propylenediaminetetra-acetate) -) are made by oxidation of K[Ru Cl(PDTA.H)] or K[Ru Cl(EDTA.H)] with PhIO electronic and ESR spectra were recorded. Rates and activation energies for epoxidation by stoich. Ru(0)(PDTA)] or Ru(0)(HEDTA)/water-dioxane of cyclo-alkanes were measured, as were those for oxidation of cyclohexane to cyclohexanol and cyclohexanone [632], 

As stoich. [Ru(0)((N 0)p7CH3CN it oxidised primary alcohols to aldehydes, secondary alcohols to ketones, alkenes to aldehydes, tetrahydrofuran to y-butyrolactone. Styrene, cis- and tran -stilbenes gave benzaldehyde and adamantane gave 1-adamantol exclusively, while cyclohexanol gave cyclohexanone, suggesting that the complex is an effective oxidant for unactivated C-H bonds [636]. Immobilisation of the catalyst within Nation films on a basal plane pyrohtic graphite electrode was achieved, but the 

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K[RuCl3(saloph)] (saloph=fcix(salicylaldehyde)o-phenylenediamine) is made from K3[Ru(H30)Cl3] and the ligand. As [RuCl3(saloph)] /03/water-dioxane it oxidised cyclohexane and adamantane. The intermediacy of Ru(lV) and Ru(V) complexes was proposed [796]. 

The [Ruv(N40)(0)]2+ complex is shown to oxidize a variety of organic substrates such as alcohols, alkenes, THF, and saturated hydrocarbons, which follows a second-order kinetics with rate = MRu(V)][substrate] (142). The oxidation reaction is accompanied by a concomitant reduction of [Ruv(N40)(0)]2+ to [RuIII(N40)(0H2)]2+. The mechanism of C—H bond oxidation by this Ru(V) complex has also been investigated. The C—H bond kinetic isotope effects for the oxidation of cyclohexane, tetrahydrofuran, propan-2-ol, and benzyl alcohol are 5.3 0.6, 6.0 0.7, 5.3 0.5, and 5.9 0.5, respectively. A mechanism involving a linear [Ru=0"H"-R] transition state has been suggested for the oxidation of C—H bonds. Since a linear free-energy relationship between log(rate constant) and the ionization potential of alcohols is observed, facilitation by charge transfer from the C—H bond to the Ru=0 moiety is suggested for the oxidation. 

Sassoon and Rabani [79, 83] constructed an intriguing photoinduced ET system in which the back ET was greatly retarded by the electrostatic repulsion between two different polycations. They prepared poly(3,3-ionene) covalently linked with Ru(bpy)f + (26) and with an iY,Af,/V, Ar -tetraalkyl-/>-phenylenediamine derivative (27). The latter is an electron donor quencher toward the photoexcited Ru(II) complex. 

The Ru(IV)/Ru(III) redox potential is 0.78 V, so that Ru(III) or even Ru(II) species may be present in vivo. Indeed, the related Ru(III) complex 32 is also active (171), and the pendant arms in these octahedral polyaminocarboxylate complexes increase the rate of substitution reactions. Complex 32 binds rapidly to the blood proteins albumin and transferrin (172), and the ruthenium ion appears to remain in the... 

Ru(bpy)2(CO)2]. The former is reduced to provide HC02 (Scheme 127). Product-selective electroreduction of CO2 to either CO or formate in an MeCN-Bu4NPF6-(Pt) system has been shown to occur using precursor complexes such as [Ru(trpy)(dppe)Cl]+ or [cis-Rh(bpy)2(TFMS)2] (trpy = 2,2 2"-tripyridine TFMS = trifluoromethane-sulfonyl anion) [338]. The Ru(II) complex is found to be a good CO2 reduction catalyst at a potential of —1.4 V (SCE) and the electrolysis results in the exclusive formation of CO (Scheme 128a). In contrast, the electroreduction of CO2... 

On the basis of the reduction potential of Rh(phen) (Eo = — 0.75 V/SCE) and of its nn energy (2.75 eV), Rh(phen)3 in the nn state is expected to be a very powerful oxidising agent (with a reduction potential of 2.0 V/SCE [133]), making it a stronger oxidant than the MLCT states of the Ru(II) complexes discussed above. Electron transfer from aromatic amines [134] or di-and tri-methoxybenzenes [135] to excited Rh(III) polypyridyl complexes have indeed been observed. 

This chapter focuses on several recent topics of novel catalyst design with metal complexes on oxide surfaces for selective catalysis, such as stQbene epoxidation, asymmetric BINOL synthesis, shape-selective aUcene hydrogenation and selective benzene-to-phenol synthesis, which have been achieved by novel strategies for the creation of active structures at oxide surfaces such as surface isolation and creation of unsaturated Ru complexes, chiral self-dimerization of supported V complexes, molecular imprinting of supported Rh complexes, and in situ synthesis of Re clusters in zeolite pores (Figure 10.1). 

Table 5 UV-visible spectral data of irawi-dioxo(macrocyclic tertiary amine) complexes of Ru(VI), Ru(V),...

A paramagnetic imidoruthenium(V) complex, [Ru N(CgHii) (OCEt2C02)2], has been obtained via interaction of the corresponding amidoruthenium(IV) species [Ru NH(CgHn) (0CEt2C02)2] (116) with O2. The formulation of the complex is supported by EPR. 

In aqueous solution, cA-[Ru (0)(pyen)Cl] has also been generated electrochemically from cA-[Ru (pyen)Cl(OH2)] (see Figure 3 for structure of ligand). This Ru 0x0 complex has an ii°(Ru ) value of 1.29 V vs. SCE and it is an active catalyst for the electrochemical oxidation of alcohols and THF. The rate constants for the oxidation of PhCH20H, CH3OH, CH3OD, and... 

A monooxoruthenium(V) complex containing a pentadentate N40 ligand, [Ru (0)(N40)]-(0104)2 (N4OH = bis(2-(2-pyridyl)ethyl)(2-hydroxy-2-(2-pyridyl)ethyl)amine) (Figure 14), has been obtained by oxidation of [Ru (N40)(0H2)](C104)2 with The complex has a... 

Reaction of [Ru04] with H4PHAB] gives the paramagnetic monoxoruthenium(V) complex (NPr°4)[Ru(0)PHAB] (109). It has a i/(Ru=0) stretch at 887 cm X-ray diffraction studies reveal that it has a distorted trigonal bipyramidal geometry, with a Ru=0 distance of 1.702 A. 

Monooxoruthenium(V) complexes [Ru(0)(salophen)X]" [salophen = V,V -bis(salicylidene)-o-phenylenediaminato X = Cl, Im(Imidazole), 2-Me-Im(2-methyl-imdazole)f and [Ru(0)(edta)f have also been claimed, but further characterization of these species is desirable. 

In the [Ru(CO)3(dppe)] catalysed carbonylation of para-nitrotoluene (Eq. (6)) HP IR spectroscopy indicated conversion of the Ru(0) complex into an oxidised species with v(CO) bands at higher frequency [41]. A mechanism involving single-electron-transfer from the nitroaromatic to the Ru complex was proposed. 

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