Chlorine reaction + metal atoms

Even chlorine which is bound to phosphorus coordinated to a metal atom can be exchanged for fluorine, but higher temperatures are required. So the four-membered phosphido-bridged metal complex 16 is fluorinated at temperatures over 100C, whereas the exchange reaction in the case of the corresponding iodide proceeds at room temperature and for the bromide at over 60CC in 80% yield each.77... 

Investigation of the kinetics of the reaction of 4-chloro-2-pentene, an allylic chloride model for the unstable moiety of polyfvinyl chloride), with several thermal stabilizers for the polymer has led to a better understanding of the stabilization mechanism. One general feature of the mechanism is complexing of the labile chlorine atom by the metal atom of the stabilizer. A second general feature is substitution of the complexed chlorine atom by a ligand (either carboxylate or mercaptide) bound to the metal. Stabilization requires that the new allylic substituent (ester or sulfide) be more thermally stable than the allylic chlorine. The isolation of products from stabilizer-model compound reactions supports the substitution hypothesis of poly(vinyl chloride) stabilization. 

In view of the presence of metal atoms in stabilizers and the bi-molecular nature of reactions of the allylic chloride with stabilizer, it is reasonable to postulate that the first step in the reaction is complexing of the chlorine atoms by the metal, and the second step is transfer of a ligand from the metal to the allyl chloride with concomitant transfer of chlorine atom to the metal. This is depicted in Reaction 7. 

In order for it to function as a Lewis acid catalyst, the dimer AbCU can undergo the less energetic opening of only one of the two chlorine bridges to form the half-bridged structure 3 [Eq. (2.2)] in which the three-coordinate metal atom can function as a strong Lewis acid. " Similar half-bridged structures in dimeric aluminum alkyls and other associated metal alkyls can be expected to play roles in their reactions with bases. 

As we saw in Chapter 3, this transfer of electrons from metal atoms to nonmetal atoms is the general process for the formation of any binary ionic compound from its elements. For example, when sodium chloride is formed from the reaction of metallic sodium with gaseous chlorine, each sodium atom loses an electron, and each chlorine atom gains one. 

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