Mono and dinuclear group 12 phosphonates derived from a sterically encumbered phosphonic acid: Observation of esterification

Metal phosphonates [Zn2(dtbhp)2(TMEDA)2(H2O)2]·0.5CH3CN (1), Cd2(dtbhp)2(TMEDA)2(H2O)2]·0.5CH3CN (2), [Cd2(mdtbhp)2(1,10-phenanthroline)4]·(ClO4)2(CH3OH)2 (3), and [Cd(dtbhp-H)2(2,2′-bpy)2](dtbhp-H2) (4) have been synthesized at room temperature from a reaction between a suitable metal precursor, 3,5-di-tert-butyl-2-hydroxybenzylphosphonic acid (dtbhp-H2) and an ancillary ligand, tetramethylenethylene diamine (TMEDA), 1,10-phenanthroline and 2,2′-bipyridine; Single crystal X-ray structure determination reveals that compound 1 crystallizes in the orthorhombic Fdd2 space group, while compounds 3 and 4 crystallize in the triclinic P 1 ¯ space group. A rare P–O–H bond esterification is observed in compound 3, presumably catalyzed by perchloric acid formed in the reaction. Compounds 1–3 are discrete dinuclear complexes while monomeric complex 4 forms a 1D polymeric chain through extended intermolecular hydrogen bonding, aided by free P–OH and PO groups of the coordinated as well as the lattice phosphonic acid.