Solvent effects ruthenium complexes

Another focus of this chapter is the alkynol cycloisomerization mediated by Group 6 metal complexes. Experimental and theoretical studies showed that both exo- and endo- cycloisomerization are feasible. The cycloisomerization involves not only alkyne-to-vinylidene tautomerization but alo proton transfer steps. Therefore, the theoretical studies demonstrated that the solvent effect played a crucial role in determining the regioselectivity of cycloisomerization products. [2 + 2] cycloaddition of the metal vinylidene C=C bond in a ruthenium complex with the C=C bond of a vinyl group, together with the implication in metathesis reactions, was discussed. In addition, [2 + 2] cycloaddition of titanocene vinylidene with different unsaturated molecules was also briefly discussed. 

The Schiff base ruthenium complex, (III), prepared by Fogg et al. (4) was effective in ring-closing metathesis reactions and used in polar protic solvents at elevated temperatures. 

There is a certain solvent effect on the quantum yields (QY) and lifetimes r of these probes. Even for the same solvent, deviant values can be found in the literature, e.g., for pyrene in cyclohexane (r = 382 ns) [56] or the ruthenium complexes in water [57]. Besides their long lifetimes, these transition metal complexes show another advantage with respect to time-resolved... 

Works CF, Ford PC. Photoreactivity of the ruthenium nitrosyl complex, ru(salen)(cl)(no). solvent effects on the back reaction of NO with the Lewis acid Rum(salen)(Cl). J Am Chem Soc 2000 122 7592. 

In asymmetric complexes of the type [(bpy)2RuCl(pi-pyz)Ru-(NH3)4L]4+, studies (94) revealed that there is a solvent donor-number (DN)-dependent contribution to the Frank-Condon barrier of approximately 0.006 eV/DN, which completely overwhelms the dielectric-continuum-theory-derived (l/Dop-l/Ds) solvent dependence typically observed in symmetrical dimers. In this case, variations in MMCT Eop with solvent give linear correlations when plotted against solvent dependent AEm, the difference in potential between the two ruthenium(III/II) couples, as shown in Fig. 10. The microscopic origin of this solvent effect was described by Curtis, Sullivan, and Meyer (122) in their study of solvatochromism in the charge transfer transitions of mononuclear Ru(II) and Ru(III) ammine complexes. The dependence... 

For the intermolecular hydroacylation of olefins and acetylenes, ruthenium complexes - as well as rhodium complexes - are effective [60-64]. In 1980, Miller reported the first example of an intermolecular hydroacylation of aldehydes with olefins to give ketones, during their studies of the mechanism of the rhodium-catalyzed intramolecular cydization of 4-pentenal using ethylene-saturated chloroform as the solvent [60]. A similar example of the hydroacylation of aldehydes with olefins using ruthenium catalyst is shown in Eq. 9.43. When the reaction of propionaldehyde with ethylene was conducted in the presence of RuCl2(PPh3)3 as the catalyst without... 

Recent work on dimeric ruthenium complexes demonstrated that there is reasonable agreement between experimental data and the band width and solvent dependence predictd by Hush for IT bands (29, 30, 31), The work with ruthenium complexes also revealed that the energies and intensities of IT bands vary systematically as a function of bridging and nonbridging ligand effects (29, 30,31,34), No IT band was observed... 

Ruthenium, (4,4 -bipyridyl)bis(pentaammine)-equilibrium constant solvent effect, 516 Ruthenium(ll) complexes magnetic behavior, 273 polymerization electrochemistry, 488 reactivity, 300 spectra, 254... 

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