A reversible intramolecular hydrogen-bonding interaction involving second-sphere co-ordination of a water ligand

Abstract

The crystal structure of [Cu{HB(pypz)₃}(H₂O)][PF₆]{HB(pypz)₃= hydrotris[3-(2-pyridyl)pyrazol-1-yl]borate} has been determined and reveals a square-pyramidal Cu^II centre co-ordinated by two of the three bidentate arms of the ligand and an axial water molecule, while the third, pendant, bidentate ligand arm is involved in a ‘chelating’ hydrogen-bonding interaction with one of the protons of the axial water molecule; this interaction is not maintained in solution.