Double piperazinediium and 1,4-diazabicyclo[2.2.2]octanediium MII selenates (MII = CoII, NiII, CuII, ZnII) as effective catalysts for Henry reaction

New organically templated complexes {(C4H12N2)[MII(H2O)4(SeO4)2]}·2H2O [MII = Co (1), Cu (2) and Zn (3)] were prepared by slow evaporation of aqueous solution containing metal(II) carbonate, selenic acid and piperazine taken in 1:2:1 M ratio. The compounds 1–3 were characterized by IR spectroscopy, ESI-MS, elemental and single-crystal X-ray diffraction analyses. The structures of the compounds contain [C4H12N2]2+ cation, H2O molecules and the [MII(H2O)4(SeO4)2]2− anions interlinked by Ow–Hw⋯O and N–H⋯O hydrogen bonding. 1–3 and known analogous mixed salts (C6H14N2)[MII(H2O)6](SeO4)2 [MII = Ni (4), Zn (5)] (C6H12N2 = 1,4-diazabicyclo[2.2.2]octane) are effective catalysts in the synthesis of β-nitroalkanols from nitroethane and aliphatic or aromatic aldehydes with yields up to 93% and threo/erythro ratio up to 79:21.