Complexes phosphane

Terminal palladium-complexed, phosphane-functionalised carbosilane dendrimers have been used as potential catalysts in membrane reactors [87]. 

Alkylation of the anion 2 with iodomethane or other haloalkanes provides alkyldicarbonyl(t/5-cyclopentadienyl)iron complexes such as 53,0 (see also Houben-Weyl, Vol. 13/9a, p 209). Migratory insertion of carbon monoxide occurs on treatment with phosphanes or phosphites9 -11 (see also Houben-Weyl, Vol. d3/9a, p257) to provide chiral iron-acyl complexes such as 6. This is the most commonly used preparation of racemic chiral iron-acyl complexes. 

Another route to enantiomcrically pure iron-acyl complexes depends on a resolution of diastereomeric substituted iron-alkyl complexes16,17. Reaction of enantiomerically pure chloromethyl menthyl ether (6) with the anion of 5 provides the menthyloxymethyl complex 7. Photolysis of 7 in the presence of triphenylphosphane induces migratory insertion of carbon monoxide to provide a racemic mixture of the diastereomeric phosphane-substituted menthyloxymethyl complexes (-)-(/ )-8 and ( + )-( )-8 which are resolved by fractional crystallization. Treatment of either diastereomer (—)-(/J)-8 or ( I )-(.V)-8 with gaseous hydrogen chloride (see also Houben-Weyl, Vol 13/9a, p437) affords the enantiomeric chloromethyl complexes (-)-(R)-9 or (+ )-(S)-9 without epimerization of the iron center. 

Incorporation of a chiral phosphane allowed resolution of the complex 6 which was obtained in enantiomerically pure form. Reaction of 6 with 2,2-dimethylpropanal provided the adduct 7 as the sole observable aldol product13. Oxidation of the metal center of 7 with ferric chloride induced decomplexation via reductive elimination, to provide the enantiomerically pure cy-clobutanone 8. 

Equation (3) shows that when tri(2-pyridyl)phosphane 9 [44] is treated directly with trimethyl aluminum in diethyl ether the adduct complex Me3Al(/r-Py)PPy2 10 is obtained which has structurally been characterised,... 

Table 2. P-NMR spectroscopic data for pyridyl phosphanes and their complexes...

Scheme 9) [63-65], Table 2 and Fig. 6 show the trends in phosphorus NMR data for pyridyl phosphanes on complexation.

In an excellent review by Roesky et al. in 1994 [70a] a vast number of examples for coordination complexes of cyclic phosphazanes and phosphazenes and other related systems have already been compiled. In the following section, an attempt is made to cover the latest features of group 13 systems along with some earlier examples with phosphorus-nitrogen based systems other than pyridyl phosphanes. 

Tetrasubstituted phosphinous amides of the type R2NPPh2 have been successfully arylated at phosphorus by the action of bromobenzene, in a process catalyzed by NiBr2, to give the aminophosphonium bromides [R2NPPh3] Br [109]. Other representative members of this class form phosphane-borane complexes [62], are aminated at phosphorus by chloramine to yield bis(amino)phos-phonium salts [110] and have been claimed to be protonated at phosphorus by ethereal tetrafluoroboric acid, as determined by NMR analysis [111]. 

Aqueous HCI solutions hydrolyze the P-N bond to give the amine hydrochloride and R2P-OH, which then disproportionates and is oxidized to diphenylphosphinic acid. A free phosphinous amide anion, with the countercation complexed by a crown ether, has been shown to be hydrolyzed and oxidized to the corresponding phosphinite with unusual ease [119]. Formic acid in toluene can be utilized for converting P,P-disubstituted phosphinous amides into their respective phosphane oxides [30]. 

A recent development that has gained attention is the characterization of a remarkable series of complexes resulting from the multiple metallation of primary phosphanes, and also a smaller number of the heavier group 15... 

Reviews covering the chemistry of group 2 metal complexes with phosphorus-stabilized carbanions,279 and of molecular clusters of magnesium dimetallated primary phosphanes, are available.2 u Magnesium phosphanes remain rare compounds.281 Lithiation of bromide 98 with BuLi in the presence of tmeda in pentane produces a lithium phosphine dimer subsequent treatment with MgCl2 in EtzO gives the phosphane 99 in 69% overall yield (Equation (19)). The centrosymmetric 99 has Mg-C = 2.217 A Mg-P = 2.77 A (av.).282... 

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