Cu^II and Zn^II β-diketonate coordination polymers based on pyrimidin-2-amine, pyrazine and 1,2-bis(4-pyridyl)ethane

Copper(II) and zinc(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionato) compounds with pyrimidin-2-amine (pyr2a), pyrazine (pyz) and 1,2-bis(4-pyridyl)ethane (dpet) were prepared and solid-state structures of coordination polymers [M(tfpb)₂(pyr2a)]_∞ [M = Cu (1), Zn (2); tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate], [M(tfpb)₂(pyz)]_∞ [M = Cu (3), Zn (4a, 4b)] and [Cu(tfpb)₂(dpet)]_∞ (5), respectively, were determined by single-crystal X-ray analysis. The coordination of metal centers in all compounds is octahedral with nitrogen ligands occupying the axial positions. Compound (1) crystallizes in the triclinic space group P\bar 1, whereas (2) crystallizes in the monoclinic space group P2/n. Differences are due to the different orientation of adjacent M(tfpb)₂ units, whereas the orientation of pyrimidin-2-amine is the same in both compounds. Polymeric chains in (1) and (2) contain intramolecular N-H...O hydrogen bonding between amino and carbonyl groups. Room-temperature structures (3) and (4a) are isomorphous adopting the monoclinic space group C2/m; however, on cooling crystals (4a) to 150 K a single-crystal-to-single-crystal transformation to (4b) possessing the triclinic space group P\bar 1 was observed. Compound (5) crystallizes in the triclinic space group P\bar 1 and contains a parallel aggregation of chains in contrast to the known structure of the non-fluorinated benzoylacetonato ligand, where chains aggregate in a perpendicular fashion. In the compounds studied intramolecular C-H...O and/or C-H...F interactions are present. The neighboring chains are linked by π...π interactions and in some compounds also by C-H...π interactions [(1), (4b), (5)].