Influence of Hydrogen Bonds on the Stability of Some Cationic Monoaminocarbene Tantalum Complexes Containing Tridentate Bis(phenolato) [OSO]-Type Ligands

A series of new cationic aminocarbene tantalum complexes have been synthesized and characterized. A significant contribution of the anion−cation interaction to the stability of the cationic moiety has been revealed. The complexes with a triflate or chloride counterion are very stable, even in air, while the corresponding tetraphenylborate derivatives are very unstable species. This stabilizing behavior can be explained by the establishment of hydrogen bonds between the electronegative atoms of the anion and the amine and hydroxyl protons of the cation. The presence of the hydrogen bonds has been detected by spectroscopic and structural techniques.