Phosphine hgands complexes

The bis-phosphine complex must live long enough to capture a further phosphine Hgand or else nickel metal precipitates.) It is predicted that other metals should be effective in such physical mixtures, in which case the idea has greater potential. 

Scheme 14 Influence of phosphine hgand in the synthesis of stericaUy hindered NHC-Pd complexes...

The coordination chemistry of phosphinoenolato complexes has been reviewed. In certain cases the phosphinoenolate complex acts as a plain phosphine hgand for example. 

Fig. 2.4 Hydrogenase model by Schwartz (2009). As compared to the natural cyanide, tiimethyl phosphine hgands in the model complex will increase redox potentials of the Fe(ll) centers while reducing M-H acidity of hydride (cp. Franzle 1992). This diminishes...

The results of fhe phosphine dissociation experiments for the various ruthenium complexes were surprising in fhat fhe second-generation catalysts exchange phosphine hgands slower fhan the first-generation analogs (Tab. 6.2). 

Other catalytic systems were used recently, namely a Ddppi system (67, Scheme 8.14) for dicyclopentadiene and di(methylcyclopentadiene) [96] and imino-phosphine complexes (Scheme 8.19, 97 and 98) or hybrid terdentate carbene hgand complexes (99) [133] for norbornene. Furtlierrnore, the copolymerization of various substituted norbomadienes and norbomenes has been achieved with Rh6(CO)i6 under water gas shift reaction conditions (55 ""C, water and 100 atm CO) [134],... 

An interesting approach to develop an asymmetric allylic alkylation catalyst by using a peptide-based phosphine hgand was examined by Gilbertson (Scheme 3.70) [135]. Phosphine-sulfide amino acid 211 was incorporated into a peptide sequence on a polymer support After reduchon of the phosphine sulfide to phosphine, the polymer-supported pephde sequence having phosphine-(support-Gly-Pps-D-Ala-Pro-Pps-D-Ala-Ac) was prepared. The complex of the peptide with Pd was uhhzed for the asymmetric addition of dimethyl malonate 202 to 3-acetoxycy-clopentene 212 to give 213 in 59% yield and 66% ee. 

Significant advances have been made in asymmetric nucleophilic additions to -ir-allyl palladium complexes using chiral ligands. Substitution of allylic acetates in the presence of the chiral phosphine hgand 224 (or other chiral phosphine ligands) can occur with very high levels of enantioselection (1.224). The reaction works best with diaryl-substituted allylic acetates. 

---