Two new [Ni(tren)2]2+ complexes: [Ni(tren)2]Cl2 and [Ni(tren)2]WS4

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Crystallography

Background:

• The synthesis and structural characterization of metal complexes are fundamental to understanding chemical bonding and reactivity.
• Nickel(II) complexes with polydentate amine ligands are of interest due to their diverse coordination geometries and potential applications.

Purpose of the Study:

• To synthesize and elucidate the crystal structures of two novel nickel(II) complexes: bis[tris(2-aminoethyl)amine]nickel(II) dichloride ([Ni(tren)(2)]Cl(2)) and bis[tris(2-aminoethyl)amine]nickel(II) tetrathiotungstate ([Ni(tren)(2)]WS(4)).
• To investigate the coordination environment of the nickel(II) ion and the role of the tris(2-aminoethyl)amine (tren) ligand.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the molecular and crystal structures of both compounds.
• Analysis of bond lengths, bond angles, and coordination geometry around the central nickel atom.

Main Results:

• The structures confirm the presence of the [Ni(tren)(2)](2+) cation in both complexes, where tren acts as a tridentate ligand.
• Compound (I) features a Ni(II) ion on a center of inversion with one independent tren molecule, while compound (II) shows the Ni(II) ion coordinated to two independent tren molecules.
• Both complexes exhibit a distorted octahedral coordination geometry around the Ni atoms, formed by six nitrogen atoms from the chelating tren ligands, with chloride anions in (I) and tetrahedral [WS(4)](2-) anions in (II). Hydrogen bonding was observed in both structures.

Conclusions:

• The study provides detailed structural insights into two distinct nickel(II) complexes with the tris(2-aminoethyl)amine ligand.
• The findings highlight the versatility of the tren ligand in forming stable nickel(II) complexes with varying counter-ions and coordination environments.