Mono-anionic acetophenone imine ligands: synthesis, ortho-lithiation and first examples of group (V) metal complexes.

A series of niobium and tantalum imido complexes with mono-anionic ortho-metallated acetophenone imine ligands have been prepared and characterized using NMR spectroscopy, mass spectrometry and elemental analysis. These low symmetry complexes are produced with only one or two structural isomers in all cases and display interesting correlations between the steric bulk of the ligands employed and the isomers formed. Crystal structures of several new niobium and tantalum complexes are presented as confirmation of the connectivity in these structural isomers.