Rare stability

Stable in aq. solution Usually found with N-, Rare, stabilized by... 

Copper(O) is rarely stabilized the unstable Cu2(CO)g has been isolated in a matrix at low temperature. The highest oxidation state attained for copper is +4. 

Alkali-metal triamidozincates have been reported [80-82], but sterically hindered lithium dialkylamide and diamidozinc, e.g., LiHDMS and Zn(HDMS)2, are rarely stabilized as lithium triamidozincate [83]. In the case of TMP, although LiZn... 

In the chemistry of nickel, we observe the continuing tendency for the higher oxidation states to decrease in stability along the first transition series unlike cobalt and iron, the -e3 state is rare and relatively unimportant for nickel and the +2 state is the only important one. 

Good to excellent Hammett plots were obtained using substituent constants (see Figure 2.6). Surprisingly, literature examples of good Hammett correlations of stability constants are rare The p-values are shown in Table 2.7. 

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

Allyl Complexes. Allyl complexes of thorium have been known since the 1960s and are usually stabilized by cyclopentadienyl ligands. AEyl complexes can be accessed via the interaction of a thorium haUde and an aHyl grignard. This synthetic method was utilized to obtain a rare example of a naked aHyl complex, Th(Tj -C2H )4 [144564-74-9] which decomposes at 0°C. This complex, when supported on dehydroxylated y-alumina, is an outstanding heterogeneous catalyst for arene hydrogenation and rivals the most active platinum metal catalysts in activity (17,18). 

Mention has already been made of epoxide stabilisers. They are of two classes and are rarely used alone. The first class are the epoxidised oils, which are commonly employed in conjunction with the cadmium-barium systems. The second class are the conventional bis-phenol A epoxide resins (see Chapter 22). Although rarely employed alone, used in conjunction with a trace of zinc octoate (2 parts resin, 0.1 part octoate) compounds may be produced with very good heat stability. 

The early 1980s saw considerable interest in a new form of silicone materials, namely the liquid silicone mbbers. These may be considered as a development from the addition-cured RTV silicone rubbers but with a better pot life and improved physical properties, including heat stability similar to that of conventional peroxide-cured elastomers. The ability to process such liquid raw materials leads to a number of economic benefits such as lower production costs, increased ouput and reduced capital investment compared with more conventional rubbers. Liquid silicone rubbers are low-viscosity materials which range from a flow consistency to a paste consistency. They are usually supplied as a two-pack system which requires simple blending before use. The materials cure rapidly above 110°C and when injection moulded at high temperatures (200-250°C) cure times as low as a few seconds are possible for small parts. Because of the rapid mould filling, scorch is rarely a problem and, furthermore, post-curing is usually unnecessary. 

Antioxidants. Antioxidants are rarely needed because of the highly saturated nature of the polymer chains. If protection against severe environmental ageing conditions is needed, typical antioxidants (Ethanox 702, Irganox 1010) can be added. In some cases, zinc dibutyldithiocarbamate (0.05-0.2 wt%) or butylated hydroxytoluene (BHT) can be used as stabilizers. 

A broad range of solvents can be used in solvent-borne BR and PIB adhesives. Hydrocarbon (hexane, heptane, naphtha) and chlorinated solvents (perchloroethy-lene) can be used they provide higher viscosities. The presence of small amounts of stabilizer may cause cloudy solutions and settling is rarely produced. There is a logarithmic relationship between viscosity and solids content. In fact, a small... 

---