Phosphorus ylide complexes, carbonyl stabilized

Carbonyl-stabilized phosphorus ylides are less nucleophilic and hence do not react with (phosphine)gold(I) halides, but their gold(I) complexes can be generated from precursors such as [Au(acac)(PPh3)] or [AuCl(SC4Hg)] by reaction with phosphonium salts and ylides, respectively, and again both mono- and bis(yhde) complexes have been obtained (equation 48 and Scheme 8)206 207. The ylide carbon atoms in these complexes are centres of chirality, but no stereospecificity was observed in the coordination process and racemic mixtures are formed throughout. 

SCHEME 8. Synthesis of gold(I) complexes containing carbonyl-stabilized phosphorus ylides... 

Related dinuclear complexes with carbonyl-stabilized phosphorus ylide ligands (6) are accessible from the reaction of the phosphonium chlorides [Ph2P(CH2C02R)2]Cl (R = Me, Et) with Ag2C03 (equation 6)18. The precipitation of AgCl is regarded as the driving force of these reactions. 

Kawashima and co-workers attempted to prepare the phosphorus ylide-sta-bilized AYC ligand 129 which could, however, not be isolated because of an intramolecular rearrangement giving 130. The intermediate formation of 129 was confirmed by its reaction with sulfur to give 131 and by the formation of the rhodium complexes 132 and 133 (Scheme 1.17). Infrared spectroscopy of the carbonyl complex 133 confirmed the superb donor properties of AYC 129. A palladium complex bearing the phosphorus ylide-stabilized NHC was also prepared. Fiirstner et al. synthesized the analogous... 

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