Monoanionic Quasi-Imido Ligands Based on 1-Methyl-4-Iminopyridine and Complexes with the Main Group Elements Mg, Al and Zn.

Abstract

The synthesis of a new class monoanionic nitrogen donor ligands based on (1-methylpyridin-4(1H)-ylidene)amide, abbreviated MQI (monoanionic quasi imide) and it chemistry with main group elements is reported. The electronic structure of the ligand allows delocalization of positive charge onto the N-heterocycle, which is accompanied by aromatization. The unsubstituted MQI ligand was found to form insoluble intractable products on reaction with non-transition metal alkyls, thus substituents were introduced to increase solubility and stability of those complexes and enable their study. The precursors 3,5-bis(3,5-dimethylphenyl)-1-methylpyridin-4(1H)-imine [MQIMe]H and 3,5-bis(3,5-di-tert-butylphenyl)-1-methylpyridin-4(1H)-imine [MQItBu]H both gave isolable complexes. The species {[MQItBu]MgCl(THF)}2, {[MQItBu]MgMe}2, {[MQItBu]AlMe2}2 , {[MQItBu]ZnMe}2 , and {[MQIMe]MgCl(THF)}2 were prepared. As well, [MQI]H precursors were coordinated with Lewis acidic boron- and aluminium-derived Lewis acids. Charge delocalization onto pyridine was examined by crystallography and NMR spectroscopy.