Catalysis heterobimetallic

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. 

The application of the heterobimetallic lanthanoid complexes of the LnMB type led to a breakthrough in establishing a highly efficient asymmetric catalytic route to a-hydroxy as well as a-amino phosphonic acid esters, which have attracted much attention due to their wide ranging biological activity [57-64]. The heterobimetallic catalysis described below represents the first and until now the only highly efficient asymmetric catalytic approach to both a-hydroxy and a-amino phosphonates by the attractive way of asymmetric catalytic hydrophos-phonylation. 

Cooperative Catalysis Besides Early-Late Heterobimetallic Catalysis. 141... 

A benchmark publication in the field of early-late heterobimetallic catalysis is certainly the smdy reported by Bergman in 1990 about catalytic hydrogenation, isomerization, and hydrosilylation of aUcenes by [Cp2Ta(p-CH2)2lr(CO)2](91)... 

Heterobimetallic Catalysis with Amide-Based Ligand 3.1 Anti-Selective Catalytic Asymmetric Nitroaldol Reaction... 

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