Electron donor power

In 18, on the basis of the different electron donor power of the ligands and the metal-metal interaction, the expected pattern is 6-1-3. In practice, only a six-electron process is observed (Fig. 3 c) in the accessible potential window. 

An example of a system that can be switched reversibly in three different states through electrochemical control of the guest properties of one component is illustrated in Figure 10.1281 Tetrathia-fulvalene is stable in three different oxidation states, TTF(0), TTF+, and TTF2+. On oxidation, the electron-donor power of tetrathiafulvalene decreases with a... 

The preparation of carbonyl-lr—NHC complexes (Scheme 3.1) and the study of their average CO-stretching frequencies [7], have provided some of the earliest experimental information on the electron-donor power of NHCs, quantified in terms of Tolman s electronic parameter [8]. The same method was later used to assess the electronic effects in a family of sterically demanding and rigid N-heterocyclic carbenes derived from bis-oxazolines [9]. The high electron-donor power of NHCs should favor oxidative addition involving the C—H bonds of their N-substituents, particularly because these substituents project towards the metal rather than away, as in phosphines. Indeed, NHCs have produced a number of unusual cyclometallation processes, some of which have led to electron-deficient... 

Other important differences relevant to our discussion are (1) Os(Il) complexes are oxidized at potentials considerably less positive than Ru(II) complexes (2) the MLCT absorption and luminescence bands lie at lower energies for the Os(II) complexes than for the Ru(II) ones (3) the eneigy of the LUMO of the (mono-coordinated) ligands decreases in the series bpy > 2,3-dpp > 2,5-dR) > biq as a consequence, the lowest (luminescent) ML(TT level involves the lowest ligand of the above series which is present in the complex and (4) the electron donor power decreases in the ligand series bpy > biq > 2,3-dpp - 2,5-dpp. 

In general, substituent frequencies in azoles are consistent with those characteristic of the same substituents in other classes of compounds. Some characteristic trends are found, and these have been used to measure electronic effects. Thus, for example, the frequencies of v(C = 0) in 3-, 4- and 5-alkoxycarbonylisoxazoles (cfi 129) are respectively 9-12, 2-8 and 17-18 cm higher than those of the corresponding alkyl benzoates, indicating the following order of electron donor power phenyl > 4- > 3- > 5-position of isoxazole. Similar work has been reported for other ring systems and substituents (63PMH(2)l6l). 

The chemical reactivity most associated with dioxiranes is the electrophilic transfer of oxygen to electron-rich substrates (e.g., epoxidation, N-oxidation) as well as oxygen insertion reactions into unactivated C-H bonds. The reactivity-selectivity relationships among these types of reactions has been examined in depth by Curci. The reaction kinetics are dependent upon a variety of factors, including electron-donor power of the substrate, electrophilicity of the dioxirane, and steric influences (95PAC811]. 

Probably the higher one-electron donor power is responsible for the higher... 

You have a set of different ligands of the PR3 type, and a large supply of (CO)5W(thf), with which to make a series of complexes (CO)5W(PR3). How could you estimate the relative ordering of the electron-donor power of the different PR3 ligands ... 

As a partial conclusion, by considering a thermodynamic selectivity, which is the difference between ionization energies of reactant and product, various reactions of oxidation can be ranked. AI represents the electron acceptor power of the gas (liquid) phase reaction and is the analog of A, which represents the electron donor power of the selective solid catalyst. 

The linear correlations between A and AI have distinct slopes and intercepts (Table 10.5), which seem to depend on (i) the relative electron donor power or (Lewis-related) acidity/basicity of the reactant and (ii) on the extent of the considered oxidation reactions. Although it is not (yet) possible to explain all of these findings, we shall try to bring more light, on the one hand, by considering thermodynamics of redox systems to account for the particular nature of optical basicity, which looks like an intensive parameter, and on the other hand, by using the charge transfer theory to account for the linear nature of [A/, A] correlations. 

A simple criterion, which has the same nature as Ath of the catalyst, was used to represent the electron donor power during reaction the absolute value of the potential ionization difference. A/ = /r — /p, weighed by the ratio p/ r of carbon in product and reactant molecules respectively. The linear correlations obtained between A/ and Ath show that their slope is related to the electron donor power of the reactant, positive when C-C (alkanes, alkyl-aromatics) or C-H (alcohols) bonds are to be transformed, and negative when C=C bonds are concerned. The intercept depends on the extent of oxidation, and its absolute value increases from mild to total oxidation, respectively. A main difficulty is the actual state of cations at the steady state, but each time accurate experiments allow determining the mean valence state, the calculated Ath fits well the correlations. These lines may be used as a predictive trend, and allow, for example, to precise that more basic catalysts are needed for alkane ODH than for its mild oxidation to oxygenated compound. As a variety of solids have been catalytically experienced in literature, it would be worthwhile to consider far more examples than what is proposed here to refine the relationships observed. Finally, theoretical considerations are proposed to tentatively account for these linear relationships. Optical basicity would be closely related to the free enthalpy, and, as an intensive thermodynamic parameter, it is normal that it could be related to several characteristic properties, including now catalytic properties. 

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