Molybdenum(0) Dinitrogen Complexes Supported by Pentadentate Tetrapodal Phosphine Ligands: Structure, Synthesis, and Reactivity toward Acids

The syntheses of
two pentadentate tetrapodal phosphine (pentaPodP) ligands,
P2PhPP2Ph and P2MePP2Ph, are reported, which derive
from the fusion of a tripod and a trident ligand. Reaction of the
ligand P2PhPP2Ph with
[MoCl3(THF)3] followed by an amalgam reduction
under N2 does not lead to well-defined products. The same
reactions performed with the ligand P2MePP2Ph afford the mononuclear molybdenum dinitrogen
complex [MoN2(P2MePP2Ph)]. Because of the unprecedented topology of the pentaphosphine
ligand, the Mo–P bond to the phosphine in the trans position to N2 is significantly shortened, explaining
the very strong activation of the dinitrogen ligand (ν̃NN = 1929 cm–1). The reactivity of this complex
toward acids is investigated.