Solvent coordinating property

Solvent coordinating property and electron-donor ability... 

Hie solid-state structure of Cu2Li2Pb4iDMS) is closely related to tliat observ ed for Cu2Li2Pb4iOEt2)2, except tliat one of tlie litliium atoms bete is now four-coordinate as a result of coordination of two DMS molecides [114]. Hiis observation shows tliat even slight clianges in tlie coordinating properties of donor solvent molecules may cliange tlie overall structure of tlie cuprate. 

Depending on the coordinative properties of the anion and on the degree of the cation s reactivity, the ionic liquid can be regarded as an innocent solvent, as a ligand (or ligand precursor), as a co-catalyst, or as the catalyst itself... 

There are many good reasons for applying ionic liquids as alternative solvents in transition metal catalysed reactions. Besides their very low vapour pressure and then-good thermal stability [33], an important advantage is the possibility of tuning then-solubility [34] and acidity/coordination properties [35] by varying the nature of the anions and cations systematically. 

Nonequilibrium solvent effects can indeed by significant at the kcal level-maybe even at a greater level, but so far there is no evidence for that when the reaction coordinate involves protonic or heavier motions. Our goal in this section has been to emphasize just how powerful and general the equilibrium model is. In addition, in both the previous section and the present section, we have emphasized the use of models based on collective solvent coordinates for calculating both equilibrium and nonequilibrium solvation properties. 

For the overall process of ionization both, the coordinating properties and the dielectric constant of the solvent must be considered. 

Thus it is apparent that the ionizing properties of a solvent are determined by the sum of its coordinating properties, e.g. a factor must be added to its dono-city which accounts for the solvation of the anion under consideration. 

For the consideration of the ionizing properties of a solvent it is therefore imperative to consider both the coordinating and the dielectric properties 101. An illustrative example is given in Table 8, in which three different donor solvents Dj.Da and D3 are considered. Dt and D3 are assumed to have the same dielectric constant while Dj and D2 are assumed to have the same coordinating properties. The values for e and A Ion have arbitrarily been selected. From Aion and ATdiss the sum of associated and dissociated ions can readily be calculated and the result shows that in D3 the overall process of ionization is progressing further than in D2, which has a much higher dielectric constant, but has somewhat smaller coordinating properties than D3. 

It is worth mentioning that there are some solvents that combine good solvency power with coordinating properties. The most salient example is 1,2-dimethoxyethane as a solvent in the reduction of organic acceptors by alkali metals. The acceptors transform into anion-radicals, and alkali metals into their cations. These cations are bound in chelates with 1,2-dimethoxyethane, and the one-electron reduction of the acceptors becomes more energy advantageous. 

ESI and APCI produce predominantly pseudo-molecular ions [M + H] + species in a positive mode and [M — H] in negative ion mode, with variable fragmentation depending upon the cone voltage used and, in the case of APCI, on the temperamre used. Adduct ions are very often seen in ESI, and it is these that can cause most problems to inexperienced users, but they can be useful. Their formation depends on the coordinating properties, polarity and concentration of the analyte and to some extent on the solvent being used. 

In the last few years the phenomenon has been extensively studied by Sacconi and his colleagues, who have investigated the physical properties of a series of bis(N-alkylsalicylaldimine)nickel compounds the alkyl chains have always been unbranched. Measurements of atom polarizations (221a, 225) and of dipole moments (225) indicate that there are no tetrahedral species in these solutions the dipole moments of both diamagnetic and of paramagnetic species are almost certainly zero, and so the tram-planar configuration (Du, symmetry) is common to both forms. The retention of D2h symmetry in the paramagnetic form does not exclude the possibility of solvent coordination 011 the z-axis. 

We would like to reiterate our initial suggestion (153) that studies of the structures of these compounds with highly hydrophobic ligands, in nonaqueous media, may reveal interesting aggregation characteristics. Such aggregations may persist in the solid state, particularly if these compounds are recrystallized from water-free, nonpolar solvents. Very little is known about the coordination properties of the alkaline earth—sulfur ligand compounds. 

In summary, in this subsection we have attempted to give a physical basis of C(t) in terms of different definitions of the solvent coordinate. We have not yet described how the time evolution of C(t) is related to dynamical properties of the medium, which is the subject of the next two subsections and Section II.E of this review. 

Consider the case of a single collective solvent coordinate y. This coordinate is linearly coupled to the solute at the transition state by generalized Langevin theory [71-75], (It is not necessary to couple the solvent to the solute for the calculation of reactant properties because we retain the equilibrium-reactant approximation.) The form of the coupling is [60,61]... 

To measure the donor power of a solvent, Gutmann18 has proposed that one determines the enthalpy of coordination of the donor solvent toward a standard reference acceptor (SbCl5) in a reference solvent of low donor power such as 1,2-dichloroethane. The quantity — A//D SbClj is easily determined at high dilution and may be considered a semiquantitative measure of the coordinating properties of a donor solvent toward an acceptor molecule. It has been termed... 

Given the association of solvent ions with charged solutes, one would anticipate that the solvation properties of ions should be very sensitive to the chemical structure of the IL. This fact has been exploited in the creation of task specific ILs, in which relatively small modifications are made to known ILs to alter their coordination properties with a given solute ion. Visser et al. 

The coordinating properties of solvents often control the yield and nature of the photosubstitution of transition metal complexes, as in the frans,-[Cr(NCS)4(NH3)2] complex, which is inactive photochemically in nitromethane (0 = 0), whereas in... 

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