Half-sandwich imido complexes of niobium bearing alkyne, benzyne and benzylidene ligands: relatives of the zirconocene family

Reactions of Pentafulvene Complexes of Titanium with Carbonyl Compounds − Diastereoselective Synthesis of σ,π-Chelate Complexes with Cp~O Ligands

“…Calculations of the electrostatic potential22 of 1 indicate a high electron density at the “backside” induced by the lone pairs of the chlorine atom (Figure 3). This suggests that from the electronic point of view the nucleophilic attack of the carbonyl oxygen atom from the “backside” is strongly disfavoured compared with the “frontal” attack, because the lone pairs of the oxygen and chlorine atoms should repel each other.…”

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl] (Ar=2,6-Me2C6H3)

“…Half-sandwich group 5 metal imido compounds [21,22] are isolobal with dicyclopentadienyl group 4 metal complexes, the chemistry of which has been widely studied [23]. However, constrained geometry group 5 metal compounds are still a field to be explored.…”

Synthesis and Reactivity of Oxametallacyclic Niobium Compounds by Using α,β‐Unsaturated Carbonyl Ligands

“…Coordination of the carbonyl group to the Nb atom favors stabilization of complex 4 increasing the electron count and preventing possible side-reactions due to the β-hydrogen atoms of the new alkyl chain. [25][26][27][28][29] This proposal was supported by NMR spectroscopy (see below) and by comparison with the reported analogous tantalum derivative, which was isolated by transmetalation with a zinc enolate compound. [29] Complex 4 was unstable in chlorinated solvents giving a mixture of unidentifiable compounds.…”