Main Group Metal Chemistry (Dec 2015)
Two structurally related, hydrogen-bonded polymorphs 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 hydrochloric acid solution and subsequent slow evaporation of the solvent, the title compound dpmaHZnCl3 was obtained in almost quantitative yield. The reaction product mainly consists of brick-shaped colorless crystals. Additionally, some smaller cuboid colorless crystals could be separated from the mother liquor. Structure analyses of two differently shaped crystals revealed that the block-shaped crystals 6a show a monoclinic diffraction pattern with the space group P21/c, whereas the cuboid-shaped crystals 6b possess tetragonal symmetry with the non-centrosymmetric space group P41. Both crystal structures consist of zwitterionic dpmaHZnCl3 complexes containing the cationic dpmaH+ ligand, which coordinates the zinc metal center through its oxygen atom. One more common feature of both structures is an intramolecular N-H···Cl hydrogen bond that fixes the conformation about the central P-C bond of the dpmaH+ ligand. The polymorphs differ with regard to their intermolecular hydrogen bonding schemes. In the structure of polymorph 6a, one out of the two chlorido ligands, not involved in the intramolecular hydrogen bond, forms two N-H···Cl hydrogen bonds to aminium groups of two adjacent complexes, whereas the third chlorido ligand is uninvolved in any classical hydrogen bonding. This connection scheme constructs layers in the ab plane. In the crystal structure of polymorph 6b, both chlorido ligands that are not involved in the intramolecular hydrogen bond form intermolecular NH···Cl connections. This connectivity scheme results in one-dimensional polymers running perpendicular to the c direction. Common to both structures is that each aminium group form three unbifurcated N-H···Cl hydrogen bonds.
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