2-Pyridylmethylphosphonic acid: A flexible, multi-dentate ligand for metal phosphonates

Abstract

In a systematic investigation, 2-pyridylmethylphosphonic acid, 2PyCH 2PO3H2 (Py = pyridine), was reacted with specifically selected metal salts to examine the influence of the preferred metal geometry, role of the anion and coordination preferences of the ligand. From this study a series of metal phosphonates were isolated: [{M(2PyHCH 2PO3H)(H2O)}ClO4]n, M = Mn, 1 and Co, 2; a tetranuclear iron phosphonate cage, [Fe 4(2PyHCH2PO3)4(H2O) 12(Cl)(ClO4)7·xH2O], 3, and two polymeric iron phosphonate chains: 4, [Fe2(2PyHCH 2PO3H)2(ClO4)]n, and 5, [Fe(2PyHCH2PO3H)(H2O)(ClO4)] n. Meanwhile, the stoichiometric reaction of Pb(NO3) 2 and Ag(SO3CF3) with 2PyCH2PO 3H2 afforded a bimetallic Ag/Pb network, 6, [AgPb(2PyCH2PO3)(NO3)]n. The individual components of this reaction, Pb(NO3)2 and Ag(SO3CF3), when reacted with 2PyCH2PO 3H2 yielded [Pb(2PyHCH2PO3H)(NO 3)2]n, 7, and a luminescent silver polymer 8, [Ag3(2PyHCH2PO3)(SO3CF 3)2]n, that are used for structural comparison to 6. All products were characterized in the single crystal and bulk form. The electrochemical properties of 1, 2 and 3 were studied, and X-ray photoelectron spectroscopy (XPS) employed to investigate the bimetallic polymer, 6, and the tetrameric iron phosphonate, 3. © 2011 The Royal Society of Chemistry.