Metal salts phosphite structure

Phosphorus containing additives include esters of phosphoric acids, derivatives of thiophosphoric acids, phosphites (Davey, 1950 Sakuri and Sato, 1970), and the metal salts of dithiophosphoric acid diesters, the best known of these compounds being the ZDDPs. The structure of ZDDP films, the composition of the film formed, and the mechanism of action on the molecular level are summarized in Chapter 4. 

Dialkyl H-phosphonates furnish in general two types of metal salts alter appropriate treatment. The first type is obtained through deprotonation of the hydrogen atom of the P-H group and has a phosphite structure. 

In this section, the alkaline metal derivatives of the first type of metal salts of dialkyl H-phosphonates are described, namely, those having phosphite structure. The reactivity of these metal salts has been already discussed in the preceding chapters, since in most of the cases they are generated as intermediates and used in situ as phosphorylation reagents. 

Heterobimetallic catalysis mediated by LnMB complexes (Structures 2 and 22) represents the first highly efficient asymmetric catalytic approach to both a-hydro and c-amino phosphonates [112], The highly enantioselective hydrophosphonylation of aldehydes [170] and acyclic and cyclic imines [171] has been achieved. The proposed catalytic cycle for the hydrophosphonylation of acyclic imines is shown representatively in Scheme 10. Potassium dimethyl phosphite is initially generated by the deprotonation of dimethyl phosphite with LnPB and immediately coordinates to the rare earth metal center via the oxygen. This adduct then produces with the incoming imine an optically active potassium salt of the a-amino phosphonate, which leads via proton-exchange reaction to an a-amino phosphonate and LnPB. 

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