Hemilabile ligands are chelating ligands with two different donor centers and are used in coordination chemistry of
the transition metals to enhance the reactivity of metal complexes. The activating effect of such ligand results from
the different metal-ligand bond strengths: while the donor atom with the stronger bond remains coordinated to the
metal, the more weakly bonded second center de-coordinates easier and thus opens a vacant coordination site at the
metal. After reaction of a substrate molecule at the metal, the dangling center may re-coordinate with concomitant
elimination of product species. Hemilabile ligands thus promote both addition and elimi-nation reactions. Another
effect associated with this kind of chelate ligands is that due to the different donor/acceptor properties of the two
Lewis basic centers, the sites trans to the two donor atoms have different electronic properties.
In organometallic chemistry, many catalytic reactions benefit from the use of hemilabile ligands. In the chemistry
of metal-silicon compounds hemilabile auxiliary ligands are hardly used. This is rather surprising because
addition/elimination sequences play a much bigger role than in the organometallic chemistry of carbon compounds.
In addition, the activation of substituents at silyl ligands by the intermediate formation of silylene complexes can
be expected. Both possibilities have a huge potential tot metal-mediated trans-formations of organosilanes.
The goal of the project is to exploit the possibilities offered by the use of hemilabile ligands for the chemistry of
metal-silyl complexes and for the metal-mediated conversion of organosilicon products. We will investigate to
what extent catalytic or stoichiometric reactions of organosilanes known to proceed by oxidative addition/reductive
elimination sequences er E-bond metathesis reactions are promoted by the use of hemilabile co-ligands. The
reactivity of the system can be tailored by modifying the hemilabile ligand (ring size and conformation,
substituents at the donor atoms, etc.). Novel reactions of organosilanes are expected by a controlled access to metal
silylene intermediates, such as substituent exchange er dehydrocoupling reactions. Such reactions have a potential
tot new applications of organosilicon compounds.