Different crystal forms of Zn(II) compound with diethyl (pyridin-3-ylmethyl)phosphonate (3-pmpe) ligand: Zn(3-pmpe)Cl2

The synthesis and characterization of the new didentate ligand diethyl (pyridin-3-ylmethyl) phosphonate (3-pmpe) and three of its Zn(II) complexes are described. IR and X-ray analyses show that in the reaction of ZnCl2 with 3-pmpe in methanol three crystalline polymorphs are formed: [Zn(3-pmpe)Cl2]2 (1) and [Zn(3-pmpe)Cl2]n (2 and 3). In these crystals 3-pmpe acts as a didentate N,O-bridging ligand and Zn(II) are in a slightly distorted tetrahedral ZnNOCl2 environment. Zn2+ ions in 1 are doubly bridged by the 3-pmpe ligands, resulting in the formation of dinuclear species. In polymeric compounds 2 and 3 Zn2+ ions are singly bridged by the 3-pmpe, resulting in the formation of one-dimensional chains. Small differences in the conformation of the ligand in 1 and 2 have been found. The infrared spectra are in agreement with the structural data.