Synthesis and characterisation of ammonium mediated assembly of two neutral nickel(II) Schiff base fragments

The 1:2 condensation of o-phenelenediamine and o-vanilline yields a compartmental N2O4 ligand N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) [H2L]. When nickel(II) thiocyanate is added to the methanol solution of H2L, followed by addition of ammonium thiocyanate, an unusual nickel(II) compound, [NH4(NiL)2SCN]·H2O (1), is separated out in which an ammonium ion is sandwiched between two neutral square planner NiL moieties. Hydrogen bonding interactions are observed among the ammonium ion, NiL moieties, the thiocyanate anion and the water of crystallization. The compound is characterized by C, H, N analysis, UV–VIS and IR spectroscopy, room temperature magnetic susceptibility measurement and X-ray crystal diffraction study. The compound crystallizes in monoclinic space group P21/n with a = 13.8636(7) Å, b = 14.0267(7) Å, c = 22.2715(10) Å and β = 94.301(3)°.

When nickel(II) thiocyanate is added to the methanol solution of N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine), followed by ammonium thiocyanate, an unusual nickel(II) compound is separated out, in which ammonium ion is sandwiched between two neutral Ni-Schiff base moieties.Figure optionsDownload as PowerPoint slideHighlights
► Use of the compartmental Schiff base N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) to form compound with Ni(II).
► Sandwiched ammonium ion between two neutral Ni-Schiff base moieties.
► Structure elucidated on the basis of X-ray crystallography.