Chiral synthesis of a mononuclear nickel(Il) complex formed from an achiral tripodal amine ligand: spontaneous resolution

Abstract

A neutral chiral mononuclear Ni(ll) complex cis-[Ni(NCS)2(tren)] (1) [tren = tris(2-aminoethyl)amine] has been isolated in a reaction of nickel(ll) salt with an achiral ligand tren and NH4SCN in a MeOH-H2O (1:1) mixture. The crystal structure of 1 reveals the encapsulation of Ni(ll) ions in a facial {NiN6} coordination environment that includes four nitrogen donors from the tetradentate chelate tren and two nitrogen donors from two cis-NCS (mono-dentate) ligands. The chirality of 1 arises from symmetry breaking of the cis-(NCS)2-Ni(ll) octahedral complex by the tetradentate chelate tren. Compound 1 exhibits both its enantiomers in a DMF solution through a Pfeiffer effect when/- and d-arabinose are used as environment substances. The particular synthesis, described herein, offers total spontaneous resolution, as is evidenced from crystal structure and circular dichroism spectral studies. © 2009 American Chemical Society.