Reactions with alkali metals

Whereas sulfolane is relatively stable to about 220°C, above that temperature it starts to break down, presumably to sulfur dioxide and a polymeric material. Sulfolane, also stable in the presence of various chemical substances as shown in Table 2 (2), is relatively inert except toward sulfur and aluminum chloride. Despite this relative chemical inertness, sulfolane does undergo certain reactions, for example, halogenations, ring cleavage by alkali metals, ring additions catalyzed by alkali metals, reaction with Grignard reagents, and formation of weak chemical complexes. 

The most simple way of preparing sodium caprolactam consists in dissolving the sodium metal in molten caprolactam. Although the solutions thus obtained are capable to induce a rapid polymerization, we meet with complications arising from the presence of reduction products formed such as hexamethyleneimine (53,69,80,81) and 6-aminohexanol (59,69). These by-products affect the course of the subsequent polymerization as they react with the active centers. The ratio neutralization/reduction in the alkali metal reaction with caprolactam depends strongly on the temperature. According to Hamann (41) and Yumoto (101) the reduction reaction takes place to 75% and 10—20% respectively. In order to suppress the reduction it is recommended to maintain the temperature during the dissolution of the sodium metal below 100° (42). 

There are three general types of metallation reactions (metal-hydrogen exchange) that are commonly used to synthesize organoalkali metal compoimds from organic molecules Direct reaction with an alkali metal, reaction with an alkali metal hydride, or reaction with an organo- or amido-alkali metal. Since these reactions involve acid/base equilibria, they are dependent on both the C-H acidity of the organic molecule and the basicity of the alkali metal source. 

The structural requirement described above places restrictions on the types of host lattices that are snitable for intercalation reactions. Nevertheless, many examples of one-, two-, and three-dimensional structures can be found with suitable properties. Studies of alkali metal reactions with Ceo see Carbon Fullerenes) have been discnssed in terms of intercalation in a host lattice of effectively zero dimensionahty. The different types of host lattice geometry are shown in Figure 1. 

Reviews of alkali-metal reactions with conjugated organic substrates are B. J. McClelland, Chem. Rev., 64, 301 (1964) V. Kalyanaraman, M. V. George, J. Organomet. Chem., 47, 225 (1973). 

Table 23-4 summarizes some reactions of the alkaline earth metals, which, except for stoichiometry, are similar to the corresponding reactions of the alkali metals. Reactions with hydrogen and oxygen were discussed in Sections 6-7 and 6-8. 

Hydrogen reacts direcdy with a number of metallic elements to form hydrides (qv). The ionic or saline hydrides ate formed from the reaction of hydrogen with the alkali metals and with some of the alkaline-eartb metals. The saline hydrides ate salt-like in character and contain the hydride, ie,, ion. Saline hydrides form when pure metals and H2 react at elevated temperatures (300—700°C). Examples of these reactions ate... 

Pyrazoles, and some indazoles, substituted on the nitrogen by B, Al, Ga, In, Si, Ge, Sn, P and Hg are known. Poly(pyrazol-1 -yl)borates have been studied by Trofimenko (72CRV497) who found that they were excellent ligands (Section 4.04.2.1.3(vi)). The parent ligands (282), (283) and (284) are available by the reaction of an alkali metal borohydride with pyrazole, the extent of substitution depending on the reaction temperature (Scheme 22). 

Novel electron-transfer reactions mediated by alkali metals complexed with crown ethers as macrocyclic ligands 98ACR55. 

Deb [1238] prepared thin films of inorganic azides (for optical studies) by reaction of an alkali metal azide with a heavy metal iodide, e.g. 

Salt Elimination Reaction of an Alkali Metal Silyl with a Transition Metal Halide... 

Two principle strategies have been employed for the synthesis of siloxide-containing molecular precursors. The first involves a silanolysis, or condensation, reaction of the Si - OH groups with a metal amido, alkyl, hahde, or alkoxide complex. The second method involves salt metathesis reactions of an alkali metal siloxide with a metal hahde. Much of our work has been focused on formation of tris(tert-butoxy)siloxide derivatives of the early transition metals and main group elements. The largely imexplored regions of the periodic table include the lanthanides and later transition metals. 

Karayannis NM, Mikulski CM, Strocko MJ, et al. 1971b. Reactions of alkali metal iodides with diisopropyl methylphosphonate. Inorg Chim Acta 5(3) 357-361. 

Our requirements for certain applications called for the preparation of block copolymers of styrene and alkali metal methacrylates with molecular weights of about 20,000 and methacrylate contents of about 10 mol%. In this report we describe the preparation and reactions of S-b-MM and S-b-tBM. In the course of our investigation, we have found several new methods for the conversion of alkyl methacrylate blocks into methacrylic acid and/or metal methacrylate blocks. Of particular interest is the reaction with trimethylsilyl iodide. Under the same mild conditions, MM blocks are completely unreactive, while tBM blocks are cleanly converted to either methacrylic acid or metal methacrylate blocks. As a consequence of this unexpected selectivity, we also report the preparation of the new block copolymers, poly(methyl methacrylate-b-potassium methacrylate) (MM-b-MA.K) and poly(methyl methacrvlate-b-methacrylic acid) (MM-b-MA). 

Preparation and Reactions of S-b-MM. As mentioned in the introduction, we were interested in block copolymers of styrene and alkali metal methacrylates with overall molecular weights of about 20,000 and methacrylate contents on the order of 10 mol%. The preparation of such copolymers by the usual anionic techniques is not feasible. An alternative is to prepare block copolymers of styrene and methacrylic esters by sequential anionic polymerization, followed by a post-polymerization reaction to produce the desired block copolymers. The obvious first choice of methacrylic esters is methyl methacrylate. It is inexpensive, readily available, and its block copolymers with styrene are well-known. In fact, Brown and White have reported the preparation and hydrolyses of a series of S-b-MM copolymers of varying MM content using p-toluenesulfonic acid (TsOH) (6). The resulting methacrylic acid copolymers were easily converted to their sodium carboxylates by neutralization with sodium hydroxide. 

During the time of the Olin reports, the first examples of oligomeric boron-bridged (l-pyrazolyl)borate systems appeared from the laboratory of Trofimenko at DuPont Chemicals 24 He reported the synthesis of poly(l-pyrazolyl)borates (6) (Fig. 5) from the reactions of alkali metal borohydrides with the pyrazole ligand. The (l-pyrazolyl)borate ligand was obtained from two pyrazole units when bridged by a BR2 unit on one side and by a metal or onium ion on the other. Even though reports... 

The importance of alkali metal binding with available 7r-electron density in the formation of CIPs was also demonstrated by Niemeyer in the structural elucidation of the first monomeric non-solvated lithium cuprate, [(2,6-Mcs2(LI L)2CuLi] 450, formed from the reaction of 2 equiv. of (2,6-Mcs2Gf,I L)Li with /-BuOCu in pentane.447 The complex crystallizes as two different independent molecules in which the C-Cu-C angles differ (171.1° and 173.8°) as does the mode of coordination to the Li cations C pso and rf to one pendant Ph in molecule 1, with an additional rf interaction to a second Ph group in molecule 2. In the second molecule, the Li site is 10% occupied by a Cu ion. 

Numerous methods have been used for the synthesis of R2P(S)-S -P(S)R2 compounds. However, probably the most convenient and generally applicable for a range of alkyl, aryl, alkoxy and aryloxy R substituents is the reaction of alkali metal dithiophosphinates with thiophosphinic bromides for n = 1 (Equation 11), or the oxidation of dithiophosphinic acids or their alkali metal salts with I2, SC12 or S2C12 for n = 2, 3 or 4 respectively (Equations 12-14).1,34... 

The metal and ammonium salts of dithiophosphinic acids tend to exhibit far greater stability with respect to this thermal decomposition reaction, and consequently these acids are often prepared directly in their salt form for convenience and ease of handling. Alkali-metal dithiophosphinates are accessible from the reaction of diphosphine disulfides with alkali-metal sulfides (Equation 22) or from the reaction of alkali-metal diorganophosphides with two equivalents of elemental sulfur (Equation 23). Alternatively, they can be prepared directly from the parent dithiophosphinic acid on treatment with an alkali-metal hydroxide or alkali-metal organo reagent. Reaction of secondary phosphines with elemental sulfur in dilute ammonia solution gives the dithiophosphinic acid ammonium salts (Equation 24). 

In all cases, dithio-phosphorus acids can be liberated from their alkali-metal salts by reacting them with acids such as HC1. Thio-ester derivatives of the dithio-phosphorus acids can be synthesised via reaction of the acids themselves with an alcohol or phenol (Equation 26) or from reaction of their alkali-metal salt with an alkyl halide (Equation 27). 

Arbuzova, S.N., Brandsma, L., Gusarova, N.K., Nikitin, M.V., and Trofimov, B.A., Reaction of alkali metal acetylides with red phosphorus, Mendeleev Commun., 66, 2000. 

There is a limited number of examples of preparations involving the reaction of stannyl-alkali metal compounds with a substituted heteroarene, for example, Equations (58)-(60).88,197,198 Some of these reactions (e g Equation (58)) occur only with photoirradiation, showing that they involve SRN1 processes, but others may be straightforward nucleophilic heteroaromatic substitutions. 

The reactions of the alkali-metal atoms with halogens such as... 

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