A new type of heteroleptic complex of divalent lead and synthesis of the P-plumbyleniophosphasilene, R_2Si=P-Pb(L): (L = β-diketiminate)

摘要

The synthesis and structures of the first heteroleptic β-dikeri-minato complexes of lead(II) with terminal phenolato, bis(trimethylsilyl)amido, bis(trimethylsilyl)phosphanido and silylidenephosphanido ligands are reported; ~(207)Pb NMR spectroscopic data indicate that lead(II) can serve as a σ-donor or acceptor centre, depending on the electronegativity of the terminal ligand. The β-diketiminate ligand is a particularly versatile ligand for the stabilisation of single-site metal centres in unusual low valence states. Their coordination feature resembles those of related N-heterocyclic ligands which were used for the synthesis of unusual low-coordinate metal complexes. The low-valent (or low-coordinate) metal centres in such complexes benefit from intramolecular N→M donor-acceptor bonds and the presence of sterically demanding substituents at the nitrogen atoms. Diketiminato metal complexes were employed as pre-catalysts for polymerisation and C-X coupling processes in homogeneous catalysis. In line with that, main-group metal complexes can be employed for a better understanding and a rational design of particular molecular catalysts.