Synthesis, characterization and selective de-esterification of diorganotinbis(O-methylphosphite)s

Studies on the Genesis and Proton Conductivity of Imidazole-Based Linear and Open-Framework Zinc Phosphites

Three new zinc phosphites, [HIm]₂[Zn₃(HPO₃)₄] (1), [Zn₂(HPO₃)₂Im₂] (2), and [Zn(HPO₃)Im] (3) (Im = imidazole), have been synthesized from the hydro/solvothermal reaction of zinc acetate, dimethyl phosphite, and imidazole by varying the temperature and solvent of the reaction medium. The structure of 1 is built from vertex-sharing of four HPO₃-capped Zn₃P₃ units and adopts an open framework with 12-ring channels stabilized by HIm cations via N-H···O hydrogen bonds. For 2, the inorganic skeleton is comprised of alternating ZnO₄ and HPO₃ tetrahedra, while the coordinatively associated ZnN₂O₂ fragments occupy the 12-ring hexagonal channels. Compound 3 adopts a ladder-type one-dimensional structure and exhibits N-H···O hydrogen-bonding interactions to afford a supramolecular assembly. A plausible rationale on the genesis of 1-3 has been put forth by reacting the preformed inorganic zinc phosphites Zn{OP(O)(OMe)H}₂ or [Zn₂(HPO₃)₂(H₂O)₄]·H₂O with imidazole as the structure-directing ligand. Alternating-current impedance measurements reveal that 1 and 3 exhibit proton conductivities on the order of 10^-3-10^-4 S cm^-1 between 25 and 100 °C under 35 and 77% relative humidity in repeated impedance cycles (E_a = 0.22-0.35 eV). On the contrary, the conduction property is completely impaired in 2 under similar conditions.

Reactivity of Elemental Tin and Zinc toward Organophosphonic Acid Dialkyl Esters: A New One-Pot Recipe for the Synthesis of Coordination Assemblies Derived from O-Alkylorganophosphonate Ligands

A new recipe for the synthesis of diorganotin bis(O-alkylorganophosphonate)s, R¹₂Sn{O(P)(O)(OR¹)R}₂ [R = R¹ = methyl (1); R¹ = ethyl and R = methyl (2), allyl (3), 2-thienyl (4), benzyl (5)], has been developed from the direct reaction of elemental tin (powder) with organophosphonic acid dialkyl esters, RP(O)(OR¹)₂, in the presence of a catalytic amount of potassium iodide under ambient conditions (130 °C, 18-20 h). The key steps in the proposed catalytic cycle involve the monodealkylation of phosphonate diester and in situ generation of a R¹SnI or R¹₂SnI₂ intermediate via the oxidative addition of alkyl iodide on tin. Evidence in support of the formation of organotin species comes from the isolation of Me₂Sn{O(P)(O)(OⁱPr)Me}₂ (6) from the direct reaction of tin metal with MeP(O)(OⁱPr)₂ in the presence of methyl iodide. The method has also been extended to isolate Zn{OP(O)(OMe)Me}₂ (7) using metallic zinc as the precursor. All of the compounds have been characterized by IR and NMR studies as well as X-ray crystallography for 2, 4, 6, and 7.

Synthesis, characterization and hydrolytic stability of diorganotin(IV)bis(O-alkyl alkylphosphonate)s

Diorganotinbis(O-alkyl alkylphosphonate)s, R2Sn(O2P(OR1)R1)2 [R1 = Me, R = Me (1), Et (2), n-Bu (3); R1 = Et, R = Me (4), Et (5), n-Bu (6)] have been synthesized from the reaction between dimethyl/diethyl/di-n-butyltin dichloride and dialkyl alkylphosphonates, (R1O)2P(O)R1, in a solvent-free medium (120 °C, 18 h). X-ray crystal structure of 1 reveals two independent molecules in the unit cell that form one-dimensional polymeric motifs by virtue of bridging bidentate phosphonate groups. The structural attribute of each polymeric chain represents an orderly infinite array of -[Sn-O-P-O-]2 8-membered puckered cyclic rings with hexa-coordinated tin atoms. The structure of 2 resembles that of 1 and exhibits nearly identical structural parameters. The presence of C–H···O hydrogen bonding interactions involving P-OMe and (or) phosphonate (P=O) groups in both 1 and 2 afford the formation of two- and three-dimensional structural motifs, respectively. The phase purity and structural integrity of the bulk sample of 1 upon exposure to water has been ascertained by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the compounds reported herein have been characterized by IR and multinuclear (1H, 13C, 31P, 119Sn) NMR spectral studies.