A chiral ligand accessible in one step: Synthesis of bis-((R)-(+)-bornyl)acenaphthenequinonediimine and of its zinc and nickel complexes

Abstract

A new neutral chiral nitrogen ligand was obtained in one step from commercially available acenaphthenequinone and (R)-(+)-bornylamine. Use of titanium tetraisopropoxide is the key to obtain good yields of the condensed product. Ring strain in the bicyclic system helps in stabilizing the otherwise unstable Alkyl-BIAN type derivative, but is not enough to render the free ligand indefinitely stable. However, complexes of the ligand with the ZnCl2 and NiBr2 fragment were prepared and are stable. The single crystal X-ray structure of ((R)-(+)-Bornyl-BIAN)NiBr2 has been determined.