First example of a molecular Ce(III) phosphonate: synthesis, structural characterization and catalytic activity of [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4], structural diversity of Ph3CPO3H2

The X-ray structural characterization of tritylphosphonic acid, Ph3CPO3H2 (1), reveals that it possesses three different structural forms (a hexameric cage, a two-dimensional polymeric sheet and a dimer) depending upon the solvent used for crystallization. The reaction of cerium nitrate with 1 under solvothermal conditions afforded a molecular dinuclear Ce(III) phosphonate, [Ce-2{Ph3CPO2(OEt)}(4)(NO3)(2)(H2O)(4)] (2). The molecular structure of 2 reveals that the two cerium atoms are held together by two isobidentate phosphonate and nitrate ligands. The cerium atoms are enveloped by a 8 O coordination environment in a distorted dodecahedral geometry. 2 is found to be a good catalyst for the three-component Biginelli reaction.