Ruthenium complex, anion

Giannelis, E.P., Nocera, D. G., and Pinnavaia, T. J. 1987. Anionic photocatalysts supported in layered double hydroxides intercalation and photophysical properties of a ruthenium complex anion in synthetic hydrotalcite. Inorg. Chem. 26 203-05. 

Ruthenium, iridium and osmium Baths based on the complex anion (NRu2Clg(H20)2) are best for ruthenium electrodeposition. Being strongly acid, however, they attack the Ni-Fe or Co-Fe-V alloys used in reed switches. Reacting the complex with oxalic acid gives a solution from which ruthenium can be deposited at neutral pH. To maintain stability, it is necessary to operate the bath with an ion-selective membrane between the electrodes . 

The chemistry of these compounds has not been investigated in detail. Scheme 12 summarizes some of the chemistry that has been established for the ruthenium complex RugClCO) (192). In general, the octahedral metal-carbido skeleton is maintained, substitution reactions occurring with phosphine, phosphites, and arsine ligands. Base attack leads to the production of the anion [Ru8C(CO)16P, which is... 

Acidification of the anion leads progressively to [HOs6(CO)18] and H2Os6(CO)i8. These two compounds may be compared with the related ruthenium complexes. The dihydride, H2Ru (CO)x8, was initially prepared by interaction of [Mn(CO)5] with Ru3(CO)12 (222). However, a... 

Anionic rhodium complexes, 32 356-364 Anionic ruthenium complexes, 32 402-406 Anions, 32 224 Anisole... 

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating Hgands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19]. In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

A special application of bimetallic ruthenium complexes was found in the olefin metathesis reaction vide infra) The two metal centers were closely attached to one another through /r-halide anions. The labile assembly was the key feature to the formation of highly active catalysts. 

The stoichiometric interaction of an enyne and [RuCl(PCy3)(pcymene)]B(Ar )4 XVIIIa containing a bulky non-coordinating anion B(ArF)4 showed by NMR at —30 ° C the formation of the alkenyl alkylidene ruthenium complex and acrolein. This formation could be understood by the initial formation of a vinylidene intermediate and transfer of a hydride from the oxygen a-carbon atom to the electrophilic vinylidene carbon, as a retroene reaction step (Scheme 8.13) [54]. 

Like other peroxides, also dioxetanes are sensitive to the presence of metal ions and their complexes, which catalyze the decomposition of the dioxetane molecule. In most cases, this decomposition is dark, i.e. no chemiluminesce is generated in such a catalytic cleavage42. An informative exception, for instance, constitutes the chemiluminescent decomposition of the dioxetane 19 in Scheme 13, initiated by the ruthenium complex Ru(bipy)3Cl243. It has been shown that this chemiexcitation derives from the valence change of the ruthenium ion in the process Ru3+ I e — Ru2+, for which the efficiency of the excited-state generation may be as much as 40%44. Hence, when the radical anion of the carbonyl cleavage fragment from the dioxetane and the Ru3+ ion are formed in... 

In order to obtain high conversion efficiencies, optimization of the short-circuit photocurrent (z sc) and open-circuit potential (Voc) of the solar cell is essential. The conduction band of the TiO is known to have a Nernstian dependence on pH [13,18], The fully protonated sensitizer (22), upon adsorption, transfers most of its protons to the TiO surface, charging it positively. The electric field associated with the surface dipole generated in this fashion enhances the adsorption of the anionic ruthenium complex and assists electron injection from the excited state of the sensitizer in the titania conduction band, favoring high photocurrents (18-19 inA/cm ). However, the open-circuit potential (0.65 V) is lower due to the positive shift of the conduction-band edge induced by the surface protonation. 

Similarities between [Ru(bpy),]2+ (discussed in Chapter 13) and [Pt,(pop)J4 are apparent. Reactive excited states are produced in each when it is subjected to visible light. The excited state ruthenium cation, [Ru(bpy)3]" +, can catalytically convert water to hydrogen and oxygen. The excited slate platinum anion, [Pt,(pop)J 4-, can catalytically convert secondary alcohols to hydrogen and ketones. An important difference, however, is that the ruthenium excited stale species results from (he transfer of an electron from the metal to a bpy ligand, while in the platinum excited state species the two unpaired electrons are metal centered. As a consequence, platinum reactions can occur by inner sphere mechanisms (an axial coordination site is available), a mode of reaction rot readily available to the 18-clectron ruthenium complex.-03... 

Several calixarenes 17-20 bridged on the lower rim with ruthenium(II) and rhenium(I) bipyridyl complexes have been prepared and studied for anion recognition [19]. When compared to acyclic receptor 21 having a similar active structure (ruthenium complex), all receptors show significantly better complexation of AcO" and chloride in DMSO-d6. Thus, calixarene 17 exhibits an almost 30 times higher association constant for AcO (Kl7=9,990 M 1 vs K21=... 

The stereoselective synthesis of 1,4-disubstituted-l,3-dienes proceeds by head-to-head oxidative coupling of two alkynes with formation of an isolable metallacyclic biscarbene ruthenium complex [23], as shown in Scheme 6. Several key experiments involving labeled reagents and stoichiometric reactions and theoretical studies support the formation of a mixed Fischer-Schrock-type biscarbene complex which undergoes protonation at one carbene carbon atom whereas the other becomes accessible to nucleophilic addition of the carboxylate anion (Scheme 6) [23]. 

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