A third polymorph of the zwitterionic complex trichlorido-((dimethylphosphoryl)methanaminium-κO)zinc(II)

Abstract

By the reaction of (dimethylphosphoryl)methanamine (dpma) with one equivalent of zinc(II) chloride in a concentrated hydrochloric acid solution and subsequent slow evaporation of the solvent, the title compound (dpmaH)ZnCl3 was obtained in quantitative yield. The primary reaction product mainly consists of larger brick-shaped colorless and smaller cuboide colorless crystals. Long-time storage over several months of these crystals in the mother liquor yielded a third polymorph (P21/n; a = 9.6639(1); b = 10.0271(1); c = 11.2446(1) Å; β = 98.964(1)°) of this compound. Similar to the two other modifications, its crystal structure consists of a zwitterionic dpmaHZnCl3 complex containing the cationic dpmaH+ ligand, which coordinates the zinc atom through its oxygen atom. Hydrogen bonds connect neighboring zwitterionic complexes to a layered structure. The motif of a hydrogen bonded dimer, similar to that found in the chain structure of polymorph I, is also present, but in the title structure these dimers form hydrogen bonds in two dimensions.