Synthesis of Oligosilyphosphaalkenes for Polymerization

    Project: Research project

    Project Details

    Description

    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(SiMe3)3,
    SiMe(SiMe3)2, SiPh(SiMe3)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 H2O or KOtBu, 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(SiMe3)3), in agreement with the results of my Ph.D. thesis, the reaction with KOtBu 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.
    StatusFinished
    Effective start/end date1/10/071/10/08