Structural insight into the reaction mechanism of Pd-catalyzed nitrile hydration: Trapping the [Pd(H2O)4]2+ cation through a supramolecular complex

Four new bis(oxamato)palladate(II) complexes have been obtained and characterized by single crystal X-ray diffraction. All of them contain bis(oxamato)palladate(II) anions and bulky n-Bu4N+ cations, but two of them have also the out of the ordinary [Pd(H2O)4]2+ inorganic cation. Acetonitrile is present as lattice molecule in a compound and appealing acetamide are present in the other ones as the natural consequence of the acetonitrile hydration reaction during the oxamate-palladate(II) complexation. Interestingly, the use of a different oxamate ligand supports (through a molecular-recognition interaction) the structural grasping of the [Pd(H2O)4]2+ specie, which can be considered as a reaction intermediate for the nitrile hydration.