Metal-Element Multiple Bonds Stabilized by Trisamidophosphines: Synthesis, Structure and Reactivity

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Numerous chemical transformations, such as alkene or alkyne metathesis, rely on metal complexes with multiply-bound heteroelements (E), which often play key roles in these trans-formations. The studies proposed herein are focused on group (IV) and group (V) metal complexes that contain M=ER and ME building blocks (E = CR, N, P, As, etc.) with metal-element double and triple bonds. In order to stabilize the reactive ME fragments, the use of trisamidophosphine ligand scaffolds is planned. As the latter ligands have been studied in detail already, the intended synthetic efforts are directed mainly towards the coordination chemistry of this new class of ligands and the reactivity of ME motifs. Anionic alkylidenes, imides and phosphinidenes of titanium, zirconium and hafnium are targeted initially and subsequent reactivity studies are meant to exploit the expected nucleophilicity of such M=ER anions (M = Ti, Zr, Hf; E = N, P, As) in order to reveal potential applications of these compounds. The synthesis of anionic vanadium, niobium and tantalum complexes with terminal nitrido, phosphido and arsenido moieties is going to play a crucial role as well. The development of new synthetic pathways to complexes containing ME triple bonds (M = V, Nb, Ta; E = N, P, As) is of fundamental relevance, while reactivity studies will gain in importance over the course of the work. In the long term, the latter reactivity studies are meant to discover and establish applications of such metal complexes, for example in homogeneous catalysis. As M=SiR2 and M=BR substructures have not been studied in much detail in case of early transition metals, the frontier-crossing use of trisamidophosphins to stabilize such structural motifs will be examined and directed towards possible applications of these systems.