Bis(2,6-pyrazolyl)pyridines as a New Scaffold for Coordination Polymers

Two coordination polymers, Fe(L(OBF)(3))(CH(3)COO)(CH(3)CN)(2)](n)•nCH(3)CN and [Fe(L(O−))(2)AgNO(3)BF(4)•CH(3)OH](n)•1.75nCH(3)OH•nH(2)O (L(O−) = 3,3′-(4-(4-cyanophenyl)pyridine-2,6-diyl)bis(1-(2,6-dichlorophenyl)-1H-pyrazol-5-olate)), were obtained via a PCET-assisted process that uses the hydroxy-pyrazolyl moiety of the ligand and the iron(II) ion as sources of proton and electron, respectively. Our attempts to produce heterometallic compounds under mild conditions of reactant diffusion resulted in the first coordination polymer of 2,6-bis(pyrazol-3-yl)pyridines to retain the core N(3)(L)MN(3)(L). Under harsh solvothermal conditions, a hydrogen atom transfer to the tetrafluoroborate anion caused the transformation of the hydroxyl groups into OBF(3) in the third coordination polymer of 2,6-bis(pyrazol-3-yl)pyridines. This PCET-assisted approach may be applicable to produce coordination polymers and metal–organic frameworks with the SCO-active core N(3)(L)MN(3)(L) formed by pyrazolone- and other hydroxy-pyridine-based ligands.