Salt with Lewis bases

Earlier, Ahland and coworkers56 noticed that metal and metallic salts which form complexes with Lewis bases can be divided into two classes, namely one which interacts mostly with the donors bearing a first row element as a center and a second which coordinates preferentially with those of second and third row elements. 

An extension of the research on silver complexes with Lewis base-functionalized mono(A-heterocyclic carbene) ligands has been made toward the better-studied and stronger coordinating phosphine systems. The reaction of a diphenylphosphine-functionalized imidazolium salt with silver oxide in dichloromethane affords a trinuclear silver carbene complex 50, as confirmed by electrospray-ionization mass spectrometry.96,97 Metathesis reaction of 50 in methanol using silver nitrate gives 51 in 33% yield. The crystal structures of 51 were found to be different when different solvents were used during crystallization (Scheme 12).97 One NO3- anion was found to be chelated to... 

Chloryl fluoride, like most of the other known chlorine fluorides and oxyfluorides, possesses amphoteric character. Owing to its weak and polar (p—jr )a Cl—F bond (see Section II, C), it exhibits a much stronger tendency to form adducts with Lewis acids than with Lewis bases. The adducts with Lewis acids result in salts containing ClOg" cations, and those with bases result in ClOgFj" salts. Both ions are discussed in detail in Sections III, G and H, respectively. 

Shi and coworkers have reported that the rate and product distribution of Baylis-Hillman reactions of aldehydes with a,/ -unsaturated ketones can be drastically affected by the reaction temperature and by the presence of Lewis bases [18]. When the reaction was carried out at -78 °C using catalytic amounts of quaternary ammonium salts as Lewis bases, in the presence of titanium] IV) chloride, chlorinated syw-aldol adducts were obtained as the major products. Quaternary ammonium bromides and iodides showed higher catalytic activity than... 

Some salts contain metal ions that can act as Lewis acids in solution. These often form complex ions when in solutions with Lewis bases like water or ammonia. In the presence of these Lewis bases, the anions form complex ions. The formation of these complex ions reduces the concentration of the anion, which will cause the equilibrium to shift right (or increase dissolving). 

The matrix isolation technique has been applied, in conjunction with the salt/molecule reaction technique, to model the high temperature gas phase reactions of alkali halide salt molecules. The reactions with Lewis acids such as SiFi, HF and CO2 yielded ion pair products which were quenched into inert matrices for spectroscopic study. Difficulties arising from lattice energy considerations in alkali halide salt reactions are minimized by the initial vaporization of the salt reactant. The reaction of such salt molecules with Lewis bases, including H2O and NH3, yielded complexes similar in nature to transition metal coordination complexes, with binding through the alkali metal cation to the base lone pair. 

Alkali Halide Salt Reactions with Lewis Bases... 

The application of the salt/molecule reaction technique to the study of reactions with Lewis bases such as H2O and NH3 presents the possibility for a different type of interaction which may find some cinalogy in transition metal coordination chemistry. The structure of small complexes such as MX H20 are of considerable interest both experimentally and theoretically. These studies were initiated as a result of the observation of several beinds in the spectrum of alkali halide salts in argon which could not readily be assigned to the isolated salt species. Rather, it was shown that these bands were due to reaction of the salt with impurity H2O, which was always present in these experiments to some degree. A study was then initiated to investigate these beinds, and the nature of the reaction conplex. 

Other compounds are the explosive C102F that is formed by hydrolysis of chlorine fluorides and reacts with Lewis bases to give salts of the C102 ion,53 C10F3 and I02F3. The latter is made by the reactions... 

The formation of ionic liquids by the reaction of halide salts with Lewis acids (most notably AICI3) dominated the early years of this area of chemistry. The great breakthrough came in 1951 with the report by Hurley and Weir on the formation of a salt that was liquid at room temperature based on the combination of 1-butylpyridinium with AICI3 in the relative molar proportions 1 2 (X = 0.66) [26]. ... 

Many reactions involving arachno-B4H1Q with Lewis bases are known and Figure 13.31 illustrates cleavage with NH3 (a small base) to give an ionic salt and by a more stericaUy demanding base to give neutral adducts. Compare these... 

Polybutadiene. Unlike cis- and trans-1,4-polybutadiene, high vinyl 1,2-polybutadiene has a chiral center which can exist in one of three different stere-ochemically related forms. The material can either be atactic, leading to an amorphous elastomer, or it can be isotactic or syndiotactic, both of which are crystalline. The elastomeric amorphous form has found utility in tire tread applications (271) and although certain molybdenum (272) coordination catalysts can produce this material, commercialization has focused on anionic alkali metal initiators modified with Lewis bases. Of the two crystalline forms, isotactic 1,2-polybutadiene with a melting temperature of 126° C is the most elusive isomer. A few chromium systems based on soluble salts and aluminum alkyls have been reported to give 45% of the isotactic polymer in a mixture of the atactic isomer (273,274). 

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