Salt-like compounds

These represent a new elass, characterized by the following properties  

They are brittle in the solid state, and generally have low volatilities. 

An example of a compound of this type is of course salt itself (i.e. common salt , sodium chloride). This forms colourless, brittle crystals, which melt to a colourless liquid at 801 C, and boil to a colourless vapour at 1413 C. In the solid, it has the electrical conductivity of an insulator, but the liquid has a conductivity of about 10 Q m . When a direct current is passed through the melt, chlorine gas is evolved at the positive electrode (the anode) and metallic sodium is formed at the negative electrode (the cathode). This process is used industrially for the preparation of sodium, except that the temperature is lowered by the addition of another salt, e.g. calcium chloride, which depresses the freezing point of the sodium chloride. 

Sodium chloride also conducts electricity when dissolved in water. Strong solutions have a similar conductivity to the melt. A direct current again leads to chemical change at the electrodes, only this time hydrogen is produced at the cathode. This is to be expected, since sodium reacts with water to give 

Compounds that are good electrolytic conductors in the solid state are relatively rare. One example is silver iodide above about 150 °C. 

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Anionic polymerization of vinyl monomers can be effected with a variety of organometaUic compounds alkyllithium compounds are the most useful class (1,33—35). A variety of simple alkyllithium compounds are available commercially. Most simple alkyllithium compounds are soluble in hydrocarbon solvents such as hexane and cyclohexane and they can be prepared by reaction of the corresponding alkyl chlorides with lithium metal. Methyllithium [917-54-4] and phenyllithium [591-51-5] are available in diethyl ether and cyclohexane—ether solutions, respectively, because they are not soluble in hydrocarbon solvents vinyllithium [917-57-7] and allyllithium [3052-45-7] are also insoluble in hydrocarbon solutions and can only be prepared in ether solutions (38,39). Hydrocarbon-soluble alkyllithium initiators are used directiy to initiate polymerization of styrene and diene monomers quantitatively one unique aspect of hthium-based initiators in hydrocarbon solution is that elastomeric polydienes with high 1,4-microstmcture are obtained (1,24,33—37). Certain alkyllithium compounds can be purified by recrystallization (ethyllithium), sublimation (ethyllithium, /-butyUithium [594-19-4] isopropyllithium [2417-93-8] or distillation (j -butyUithium) (40,41). Unfortunately, / -butyUithium is noncrystaUine and too high boiling to be purified by distiUation (38). Since methyllithium and phenyllithium are crystalline soUds which are insoluble in hydrocarbon solution, they can be precipitated into these solutions and then redissolved in appropriate polar solvents (42,43). OrganometaUic compounds of other alkaU metals are insoluble in hydrocarbon solution and possess negligible vapor pressures as expected for salt-like compounds. 

Hydrides — True hydrides (i.e., those in which the hydrogen is in its anionic or most reduced form) are salt-like compounds in which the hydrogen is combined with alkali metals, either alone as simple hydrides or in association with other elements as complex hydrides. Hydrides react with water to release hydrogen. 

Carbides, which are binary compounds containing anionic carbon, occur as covalent and as salt-like compounds. The salt-like carbides are water-reactive and, upon hydrolysis, yield flammable hydrocarbons. Typical hydrolysis reactions include ... 

Lanthanide nitridoborates can be divided into three classes salt-like compounds, semiconductors, and conductors or superconductors, as already shown in Fig. 8.7. Salt-like structures are usually transparent materials, marked by the typical color of the lanthanide ion. Here we discuss only nitridoborate compounds of lanthanum. The compounds La3(B3N, ) [27], La5(B3N, )(BN3) [28], Lag(B3N6)(BN3)N [29], and La3(BN3)N all count as salt-like materials, with La, ... 

Note 4 Cubic mesophases have long been known in thermotropic salt-like compounds and in lyotropic liquid-crystals. 

Arsenic(III) halides are not salt-like compounds but typically non-metallic halides comparable to, for example, GeCl4 and SC12 besides their predecessors in Group 5, PX3. However AsC13 is not as reactive to nucleophilic attack as is PC13. 

Franklin developed an ammono-system of acids, bases, and salts in liquid ammonia and showed that in this solvent the amides of metals (e.g. KNH2) are bases, and the amides of metalloids (e.g. CO(NH2)2) are acids. They react with each other with the formation of salt-like compounds... 

The ternary systems display a variety of structural chemistry depending on the sizes of the alkaline and lanthanide metals (Scheme 3 Fig. 3 [43, 45-57]). The smaller alkali cations determine the expected coordination structures as found in salt-like compounds, e.g., Na3Y (NH2)6 or KY(NH2)4. Layer structures are observed in alkali metal poor systems like MLa2(NH2)7 while cesium derivatives, apart from the lanthanum compounds, form perowskit-like arrangements as in CsEu(NH2)3 and Cs3Ln2(NH2)9. The mono ammoniates of some Cs-systems are probably metastable. Preparation of analogous ternary systems with Li were unsuccessful in contrast to, e.g., LiAl(NH2)4 [58]. 

The new Reinecke-salt-like compounds K[Cr(NCS)4L ] (n = 1 or 2 L = o- or m-phenylenediamine, respectively) have been prepared by the reaction of K3[Cr-(NCS)6] with L and their thermal stabilities investigated.179 Diquinolino- and di-iodoquinolino-silver(i) iodide salts of the anions [Cr(NCS)6]3- and [Cr(NCS)4L2] (L = aniline, o- or p-toluidine) have been prepared and characterized.180 Chro-mium(m) thiocyanato-complexes with biguanide derivatives, K[Cr(NCS)4L] [L = phenyl-, p-chlorophenyl-, tolyl-, or 1-(p-chlorophenyl-5-isopropyl)biguanide], have been prepared by the reaction of K3[Cr(NCS)6] with L in anhydrous EtOH and their i.r. and electronic spectra reported.181 cis- and trans-[Cr(en)2(NH3XNCS)]2 + have been prepared and both shown to have a Amax value at 476 nm, but with the expected relative magnitudes of s values, cis > trans, as 120 to 80.182 The thermal decompositions of the salts [Cr(NH3)6 x(NCS)x](NCS)3 x (x = 0. 1. or 2) have been characterized. Under d.t.a. conditions [Cr(NH3)6](NCS)3 changes stepwise to [Cr(NH3)5(NCS)](NCS)2, trans-[Cr(NH3)4(NCS)2](NCS), and finally to merfac-[Cr(NH3)3(NCS)3].183... 

For a crystal, built up of molecules, the lattice energy is but small, as evidenced by the volatility, for example, of most organic substances (see however p. 160 about diamond etc.) in contrast to the hardly volatile salt-like compounds, which crystallize in an ionic lattice. 

In combinations of two metals which differ greatly in electronegativity, salt-like compounds, according to the ionic valence, are formed which are often characterized by a high melting point and a large heat of formation. As examples we may cite ... 

Upon reaction with basic transition metal complexes the general tendency of electronically unsaturated boranes to form Lewis acid-base adducts should result in the formation of borane complexes (I). [CpzWILfBFs)] (1), which is known from many textbooks represents the best known example for such a compound. Recently, however, the proposed constitution of 1 was disproved, and it was shown that reactions of [Cp2WH2] with boranes yield salt like compounds 2 and zwitterionic species 3, respectively. For the formation of 2 one equivalent of HF is required, and in this reaction the borane acts as a fluoride source, while the WH2 moiety supplies a proton (Figure 3). Until now no structurally authentic borane complex was reported. 

Amines are basic, as already shown, and so will react with acids to form salt-like compounds in a similar way to ammonia. 

The solid state structure of the centrosymmetric dilithium tetraphenylporphyrin bis(diethylethe-rate) differs from the salt-like compounds, in that the [Li(Et20)] moiety is coordinated to both faces of the porphyrin in a square pyramidal fashion (Li-N = 2.23-2.32 A). A related motif is found in the case of sodium octaethylporphyrinate X-ray crystallography reveals two Na(THF)2 moieties symmetrically bound to all four nitrogen atoms, one on each face of the porphyrin ring (Na—N (ay) = 2.48 A). The structure of the potassium derivative K2(py)4(OEP) is similar (K—N (av) = 2.84A). ... 

The long-acting insulins in use today are mainly protamine insulin and zinc insulins. Protamine insulins are the salt-like compounds formed between the acid (insulin) polypeptide and the polypeptide protamine, which consists primarily of arginine. They are used in the form of neutral suspensions of protamine insulin crystals (isophane insulin). 

This chapter deals with activated amides , i.e. salt-like compounds, imino derivatives of carboxylic acids as well as compounds which formally arise by complete esterification or amidation of carboxylic orthoacids. 

For the imides Strecker s rule gives a basicity of zero while Gerhardt s leads to a basicity of one Strecker cites this Ann, 103, 335) in favor of his rule, and yet we know that succinimide, for instance, forms salt-like compounds with silver oxide and mercuric oxide, while cyanic acid is almost universally considered the imide of carbonic acid, and at the same time as a monobasic acid. 

Although we have included these B subgroup hydrides with the salt-like compounds it is possible that the bonding is at least partially covalent in some or all of these compounds an obvious suggestion for BeH2 is a hydrogen-bridged structure like that of Be(CH3)2. 

Since not very many of these compounds are at present well authenticated we group them together in Table 8.2 their structures suggest that they include both salt-like compounds and also compounds more akin to the transition-metal compounds of the last section. Methods of preparation include the action of hydrogen on a mixture of the metals (for example, BaliHs from Ba + Li at 700° C)... 

Anionic surfactants are those which bear a negative charge and migrate toward the anode or positive charge in solution. This class of salt like compounds include the soaps and many of the popular synthetics (Fig. 4-6). When fats are hydrolysed... 

Translational (lattice) modes of hydroxides display TO/LO splittings in the same order of magnitude as other salt-like compounds. Those of pure OH -type vibrations are small [60]. 

The interstitial structures comprise the compounds of certain metallic elements, notably the transition metals and those of the lanthanide and actinide series, with the four non-metallic elements hydrogen, boron, carbon and nitrogen. In chapter 8 we discussed the structures of a number of hydrides, borides, carbides and nitrides of the most electropositive metals, and these we found to be typical salt-like compounds with a definite composition and with physical properties entirely different from those of the constituent elements they are generally transparent to light and poor conductors of electricity. The systems now to be considered are strikingly different. They resemble... 

Salt-like compounds (R3NH]+[(Cl3Si)2NJ" are formed on the addition of pyridine, or trimethyl- or triethyl-amine, to solutions of (CI3SO.2NH in petroleum ether. The [Cl3Si)2N] ion shows the strongest Si—bonds so far known, with a bond order of two in accordance with the formulation... 

In a number of instances such salt-like compounds have been isolated and characterized. In particular, many ternary complexes of the composition A H Y M Y (Y — halogen) can be considered as salts of the complex acids HMY j, i.e. the salts AH MY j. To these belong the compounds A HF BFj, A HF PFj, A HF SbFj, A HCl AICI3, A HCl SbClj and A HBr AIBFj. When using aluminium halogenide as Lewis-type acid one can also obtain the ternary complexes A HCl 2 AlQj and A HBr 2 AlBrj which are salts of the hypothetical acids HAljY,. The formation of the salts AH Al Yj. j with m > 2 is not excluded either For the complexes A HQ 2 GaClj see... 

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