Accessing Pentagonal Bipyramidal Geometry with Pentadentate Pincer Amido-bis(amidate) Ligands in Group IV and V Early Transition Metal Complexes

A family of amido-bis­(amidate) proligands (1a–1d) [LH3] with sterically bulky carboxamide arms is described. The ligands can be used to promote pentagonal bipyramidal geometries in titanium complexes (2a–2d) [TiL­(NMe2)­(NHMe2)]. Using the bulkiest ligand (1d), heavier early transition metal elements can be incorporated by the chelate, giving rise to stable mononuclear complexes (3d, 4d: [ML­(NMe2)­(NHMe2)] (M = Zr, Hf); 5d, 6d: [ML­(NMe2)2] (M = Nb, Ta)) bolstering the versatility of this binding motif.