Structural characterization of a tetrametallic diamine-bis(phenolate) complex of lithium and synthesis of a related bismuth complex

• Published in: Polyhedron 2015-12, Vol.102, p.60-68
• Main Authors: Drover, Marcus W., Murphy, Jennifer N., Flogeras, Jenna C., Schneider, Céline M., Dawe, Louise N., Kerton, Francesca M.
• Format: Article
• Language: English
• Subjects: Bismuth; Coordination compounds; Lithium; N, O ligands; NMR studies
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2015.07.071

A tetra-lithium amine-bis(phenolate) ‘daisy-chain’ complex is shown to reversibly dissociate to give a centrosymmetric di-lithium species in solution. It can be used as a precursor for an amine-phenolate complex of bismuth. [Display omitted] A novel lithium complex was prepared from the reaction of 1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)imidazolidine H2[O2N2]BuBuIm (L1H2) with n-butyllithium to provide the corresponding tetralithium amine-bis(phenolate) complex {Li2[L1]}2·4THF, 1. Variable temperature 7Li NMR revealed that this complex is labile in solution, dissociating at elevated temperatures to afford two dilithium entities. Additionally, 7Li MAS NMR was performed on 1 to provide information regarding the lithium coordination environment in the bulk solid-state. The reactivity of 1 was assessed in the ring-expansion polymerization of ε-caprolactone (ε-CL), which was first order in ε-CL with an activation energy of 50.9kJmol−1. Reaction of 1 and a related Li complex (formed in situ) with BiCl3 afforded hydrolytically unstable bismuth phenolate species, as evidenced by the isolation and structural characterization of [Bi4(Cl)3(μ-Cl)(μ-O)(O)2{[O2N2]BuBuPip}2], 2, where [O2N2]BuBuPip is the homopiperazine-containing analog of L1.