Type I ionic compounds

The following rules apply for Type I ionic compounds ... 

Type I Ionic compounds with metals that always form a cation with the same charge... 

In the ionic compounds considered previously (Type I), the metal involved forms only a single type of cation. That is, sodium forms only Na+, calcium forms only Ca2+, and so on. However, as we will see in more detail later in the text, many metals can form more than one type of positive ion and thus form more than one type of ionic compound with a given anion. For... 

In this section we will consider binary ionic compounds of two types based on the cations they contain. Certain metal atoms form only one cation. For example, the Na atom always forms Na", never Na or Na ". Likewise, Cs always forms Cs, Ca always forms Ca, and A1 always forms Al. We will call compounds that contain this type of metal atom Type I binary compounds and the cations they contain Type 1 cations. Examples of Type 1 cations are Na, Ca, Cs, and AL. ... 

Section 5.7 Naming Ionic Compounds has been revised. The terms "Type I" and "Type 11" ionic compounds have been eliminated, and the subsections and worked Examples dealing with naming binary ionic compounds have been renamed and revised. 

Several additional, more complicated structure types are known for ionic compounds. For example, according to the radius ratio, one could expect the rutile type for strontium iodide (rSr2+ /i = 0.54). In fact, the structure consists of Sr2+ ions with a coordination number of 7 and anions having two different coordination numbers, 3 and 4. 

Cations [(RR C=Se)2I]+ In the case of A-methylbenzothiazole-2(3//)-selone (mbts), one equivalent of iodine provides a molecular adduct in dichloromethane solution 50 crystallisation, however, leads to a ionic compound of the type [(RR C Se)2I]+I3, 43 This compound was the first one reported in the literature featuring a two coordinated iodine(I) complex with two donor molecules containing selenocarbonyl groups. In the solid state two molecules of mbts are linearly coordinating a central I+ ion to give a slightly... 

Type I spectra are associated with hydrated ionic compounds such as the MnCl2 4H2O and with many other compounds having a single octahedral coordination sphere. These spectra are sensitive to ionic charge and to radius of coordination sphere. 

One hundred and forty-four meso-ionic heterocycles of type A (13, 19) and 84 meso-ionic heterocycles of type B (14, 20) are possible. The numbers of these two types which are now known (Table I type A, 44 representatives) and (Table II type B, 8 representatives) encourage us to put forward the proposal that the term meso-ionic should in future be restricted to five-membered heterocycles belonging to type A (13, 19) and type B (14,20). This clear restriction upon the use of the term meso-ionic has obvious advantages. It still embraces 228 different classes of heterocycles with a common structural characteristic, and the many types of meso-ionic compounds included in the authoritative review by Ohta and Kato " are included. Needless to say, the restriction upon the definition of the term meso-ionic to five-mem red heterocycles of type A and type B still includes, for example, benz derivatives such as the compounds 67, 71, 110, 123, 133, 151, 206, 209, 226, 255, and 258. 

The following references extend the literature coverage up to December 31, 1975. The preparation of derivatives of one previously unknown type A meso-ionic system has come to the attention of the authors since the completion of the Appendix. These new meso-ionic compounds are l,2,3-thiadiazole-5-ones [Table A-I (page 111) a = S, b = N, c = NR, d = CR, e = C, f = O]. They are the first examples of sulfur analogs of the sydnones (1). 

This reaction is based on a stoichiometric reaction of multifunctional olefins (enes) with thiols. The addition reaction can be initiated thermally, pho-tochemically, and by electron beam and radical or ionic mechanism. Thiyl radicals can be generated by the reaction of an excited carbonyl compound (usually in its triplet state) with a thiol or via radicals, such as benzoyl radicals from a type I photoinitiator, reacting with the thiol. The thiyl radicals add to olefins, and this is the basis of the polymerization process. The addition of a dithiol to a diolefin yields linear polymer, higher-functionality thiols and alkenes form cross-linked systems. 

Among binary (i.e., two-element) ionic compounds, six simple types of unit cell structures are commonly encountered, although many more exist ... 

---