Hanan El-Sharkawy Ali
Received August, 2015; Accepted October, 2015
In an effort to develop new classes of NHC (N-heterocyclic carbenes) complexes, two imidazoline-anchored quat and bis-quat ligand systems have been synthesized. The process is superior owing to two approaches: (i) a new synthesized phase transfer catalyst, namely, 1,1’-benzene-1,4-diyldipyridinium dibromide (BDPDB) used to catalyze the phase-transfer hoffmann reaction of two structurally varied amines, dodecylamine and 1-amino-9, 10-anthraquinone. The reaction successfully gave the corresponding isocyanides that display the highest reactivity in reasonable to good yields. (ii) a cycloaddition-rearrangement reaction between imine and isocyanides based on chloroform gives easy access to a diverse range of highly substituted 4- and 2-imidazolines. Furthermore, imidazoline based bis-NHC (N-heterocyclic carbenes) precursors have been prepared and complexed to copper cation (4-L and 2-L, Figure 1). The molecular structures of the representative metal-NHC and metal-carbene bonds of these complexes have been elucidated and proved by elemental analyses, FT-IR, 1H & 13C NMR, and atomic adsorption spectroscopy. In contrast to the common assumption that NHCs are pure α-donors, the prepared complexes revealed a significant π-backbonding in electron-rich metal NHC complexes.
Keywords: PT Catalysis, imidazoline complexes, aldimines, isocyanides, imidazolines, 1, 1′-(ethane- 1, 2-diyl) dipyridinium bistribromide, MCRs, heterocyclic carbenes.