Polymerizations hexamethyldisilazide

Interesting examples of simple substituted heterometallic species are [(thf)M p-N(SiMe3)2 2M (th 2] (M/M = Li/Na, Li/K and Na/K) which were obtained from solutions of 1 1 mixtures of the metal salts.The unsolvated ( LiXtSiMe J , K- lSiXleO, ), has a polymeric, one-dimensional chain structure formed by alternating lithium and potassium centres bridged through the hexamethyldisilazides (Li—N= 1.935(1) A and K—N = 2.86(1) A) with linear coordination at K and almost linear coordination (N-Li= 176.4(3)°) atLi. ... 

The lithium enolate generated using lithium diisopropylamide [4111-54-0], lithium 2,2,6,6-tetramethylpiperidide [58227-87-1], or lithium hexamethyldisilazide [4039-32-17 is a chemical reagent that reacts with other reactants to give a variety of products (37). In the quest for improved stereospecificity, enolates with different cations such as silicon, aluminum, boron, and zinc have also been used (38). In group transfer polymerization, ketene silyl acetals, eg, (CH3)2C=C [OSi(CH3)3] (OCH3) are employed as initiators (39). 

Since most of the synthetically useful enolate anions described in the previous section are prepared by the reactions of enolizable substrates with alkali metal amide bases, it is appropriate to note a few structures of these amide bases. The common bases in synthetic organic chemistry include LDA and LHMDS. The structures of both of these bases are known as the THF solvates.Both of these compounds form bis-solvated dimers corresponding to structure (201). The diethyl ether solvate of LHMDS also forms a bis-solvated dimer (202).Sodium hexamethyldisilazide crystallizes as an unaggregated monomer from benzene solution.Two different cryst line forms of KHMDS are known as the polymeric dioxane solvate (203), ° and the unsolvated dimer (204). ... 

Hydrophilic branched oligo(ethylene glycol)-substituted PPV derivatives, poly(2,5-bis(l,3-bis(tri-ethoxymethoxy) propan-2-yloxy)-1,4-phenyleneviny-lene) and poly(2-methoxy-5-(l,3-bis(triethoxymeth-oxy) propan - 2-yloxy) -1,4-phenylenevinylene), have been described [23]. The polymerization reaction is carried out via the dithiocarbamate precursor route. Lithium hexamethyldisilazide is used as a base in order to get high-molecular-weight precursor polymers. After the thermal conversion of the precursor polymers into the fully conjugated systems, the solubility of the polymers has been examined. 

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