Anion interaction acetone

This equation accounts for experimental association constant values higher than theoretical ones because KA > Ki. Moreover, we may deduce that when cations are equal, KA is smaller for smaller anions, which means that they have a greater charge density and thus are more basic, since K2 is lower for them. On the contrary, KA values decreasing with an increase in the size of the anion have been observed in aprotic solvents like TMS (II), acetone (41), nitrobenzene (42), nitromethane (43), acetonitrile (44), and 1,1,3,3-tetramethylurea (45). This order can be understood if one considers that in this class of solvents the anions are scarcely solvated so that association is affected mainly by the strength of cation-anion interaction, which, with the cations being equal, increases with an increase in the anion charge density. 

We referred to Avent et al. s work [27] to interpret these spectra. We assumed that both of the ionic liquids were solvated to free ions in acetone, while the cation and the anion interacted somehow under solventless conditions, with the chemical shifts indicating the relative basicity of these anions. In fact, as can be seen in Table 3.2, the P"stereoselectivity of the glycosylation reactions with glucosyl fluoride was... 

With the long alkyl chain substitutions on the A-heterocyclic carbenes, lamella-structured silver(i) carbene complexes 27a and 27b (Figure 14) were isolated.74 It is interesting to note that the synthetic procedures for the two complexes are the same except for the use of different solvents of crystallization. The dinuclear 27a was obtained from recrystallization in dichloromethane- -hexane while the tetranuclear 27b was obtained from acetone. The structure of 27a could be interpreted as the dimeric form of [Ag(carbene)Br] bridged by intermolecular Ag-Br interactions. The Ag-G bond has a distance of 2.094(5) A. The tetranuclear 27b, on the other hand, could be regarded as two monocationic bis(carbene)silver(i) bridged by an [Ag2Br4]2 anion, with the presence of short Ag(cationic)-Ag(anionic) contact (3.0038(18) A) and comparable Ag-G bond distances (2.0945(5), 2.138(13) A). A related... 

The reaction of the tetranuclear mercuracarborand 166 with 2 or 3 equiv. of KNO3/I8-C-6 in acetone affords two different nitrate complexes namely [166-(N03)2(H20)]2 and [166-(N03)2]2 (Figures 15 and 16). In both cases, the nitrate anions are ligated to the mercury centers by Hg-O interactions ranging from 2.60 to 3.08 A. In [166-(N03)2]2, the two anions coordinate with all four mercury atoms in a face-on trihapto fashion from either side of the plane.216... 

Several arylplatinum complexes of Tl+ have been reported (Table 15). The anionic /rreacts with T1N03 to produce a chain polymer 120, in which successive Pt atoms are bridged to each other by two Tl+ ions (Scheme 28).112 The compound is an acetone solvate, and there also appear to be weak Tl F interactions in the solid-state structure. Upon irradiation (A = 441 nm), the complex exhibits an intense emission with a maximum at 678 nm. The luminescence is attributed to MLCT transitions. 

The Au-Au distances are 3.1882(1) A and they are considered to be responsible for the emission band that appears at 460 nm at room temperature. When the anion in the carbene complex is BF4, the structure is similar although the Au-Au distances are substantially longer (3.4615(2) A). The different distance leads to a different emission band that is blue-shifted. This indicates a greater orbital interaction in the former, consistent with its shorter Au-Au distance. Nevertheless, the behavior in solution is similar for both. Thus, at room temperature in solution they lose their emissive properties but they recover them in frozen solutions at 77 K. Interestingly, the emission differs in color, depending on the solvent, ranging from orange (acetone) to blue (pyridine), which would seem to result from the self-association... 

Discrete dimers of the head-to-head type have been found in the structures of the Ag+ complex of (145)570 and the Na+ complex of (145)571 respectively. The complexes were recrystallized from carbon tetrachloride. In both complexes each metal is five-coordinated in the cavity provided by one anion, and there is an additional reaction with the second anion [through an Ag+-phenyl interaction or an Na+-carboxylate oxygen atom (Figure 32a)]. When the Na+ complex was crystallized from a solvent of medium polarity, acetone, the head-to-head dimer was recovered.571 In contrast, recrystallization from a polar medium, methanol, gave a monomeric complex in which one methanol of solvation was also present.572 In all of these complexes an intramolecular head-to-tail hydrogen bond was present to hold the ligand in its pseudo-macrocyclic conformation. 

In an attempt to maximize interactions between the metal dithiolene anions, Underhill and Ahmad studied the lithium salt of the [Pt S2C2(CN)2 2] cation.121,122 Slow aerial oxidation of a 50% aqueous acetone solution of H2[Pt S2C2(CN)2 2] and LiCl yielded a black microcrystalline product of small shining black needles and black platelets. Four-probe DC conduction studies on the needle-shaped crystals showed the room temperature conductivity along the needle axis to be 100 Q i cm-1. 

Fig. 25 A portion of the structure of crystalline [AuI C(NHMe)2 2](PF6)-0-5(acetone), which emphasizes aurophilic interactions and the hydrogen bonding interactions between two cations and a hexafluorophosphate anion. The Au--- Au distance is 3.1882(1) A. From [48]...

The nucleophilic reactivity of the lithium salts changes in the same order as in protic solvents (I > Br > Cl cf. Table 5-15). However, the order is completely reversed for the ammonium salts (Cl > Br > I ), and this latter order is the same as that found in dipolar non-HBD solvents such as A,A-dimethylformamide [278]. The small lithium cation, with its high charge density, has a strong tendency to form ion pairs with anions, whereas the electrostatic interaction between the large tetraalkylammonium ion and anions is comparatively weak. Quaternary ammonium salts, therefore, should be practically fully dissociated in acetone solution. Thus, the reactivity order obtained with these salts corresponds to that of the free, non-associated halide ions. On the other hand, the sequence obtained with the lithium salts also reflects the dissociation equilibria of these salts in acetone solution [279]. 

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