The purpose of the project is the synthesis of new phosphaalkenes with oligosilyl groups on phosphorus as stable
monomers, suitable for subsequent polymerization. The bulky silyl substituents RSi, such as Si(SiMe 3 ) 3 ,
SiMe(SiMe3 ) 2 , SiPh(SiMe 3 ) 2 , have two functions: 1) as stabilizers of the monomer (preventing the dimerization to
1,3-diphosphetaines) and 2) as leaving groups, after the polymerization in elimination-addition pathways to new
polymethylenephosphines.
The synthesis of the phosphaalkenes will be attempted by the reaction between
oligosilyl(trimethylsilyl)lithiumphosphides and ketones. The product will be used for a 1,2-addition of MeLi across
the P=C bond to get a polymer:
Eventually, treating oligosilyl(trimethylsilyl)lithiumphosphide with bis(trimethylsilyl)ketone will yield the first
persilylated phosphaalkene.
If the size of the RSi group is not sufficient to shield the Si-P bond (but big enough to stabilize the phosphaalkene)
and the R groups on carbon are not too large, the reaction of the polymer with H2 O or KO tBu, for example, should
proceed by the cleavage of the SiP-bond forming a functionalized polymethylenephosphines:
If the size of the RSi group is big enough to shield the Si-P bond (which is probably the case for RSi = hypersilyl
group Si(SiMe 3 ) 3 ), in agreement with the results of my Ph.D. thesis, the reaction with KO tBu proceeds via
cleavage of a Si-Si bond on RSi. The atom arrangement in P-Si-K is instable and the intermediate rearranges,
forming a phosphanide anion and a silylene (which can be trapped by 2,3-dimethyl-1,3-butadiene).
The obtained functionalized polymers will then be substituted using, for example, ClOR` or R`NHCl and giving
new polymers.