Syntheses and characterizations of zinc phosphites with new templates generated by N-alkylation transformations

Abstract

Two new organically templated zinc phosphites, [tmpip]0.5[Zn2(HPO3)2(H2PO3)] (1) and [dmdabco][Zn3(HPO3)4]·(H2O) (2), have been synthesized under solvothermal conditions, where tmpip=N,N,N′,N′-tetramethyl-piperazinium and dmdabco=N,N′-dimethyl-1,4-diazabicyclo[2,2,2]octane. Note that the templating agents tmpip2+ and dmdabco2+ originated from in situ N-methylation transformations between CH3OH solvent and corresponding cyclic aliphatic amine precursors, i.e. piperazine, 1-methylpiperazine or 1,4-dimethylpiperazine in 1, and 1,4-diazabicyclo[2,2,2]octane in 2. Distinct from conventional Eschweiler–Clarke methylation with excess formic acid and formaldehyde, such direct methylation transformation from methanol molecules is unique. Compound 1 consists of ZnO4 tetrahedra, HPO3 and HPO2(OH) pseudopyramids, exhibiting a complex double layered structure with 12-ring windows. Compound 2 is constructed from strictly alternating ZnO4 tetrahedra and HPO3 pseudopyramids, and possesses a (3,4)-connected interrupted architecture with intersecting 8- and 12-ring channels.