Coligand Modulated Oxidative O-demethylation of Methylether Appended Tetradentate N-Ligand on Co(II) Complexes
Two Co(II) complexes of the formula CoLOMeX2 (X= Cl- (1a); X= I- (1b)), where LOMe is 2-methoxy-N,N-bis(pyridin-2-ylmethyl) aniline were synthesized and their structure, spectroscopy and reactivity were studied. Upon oxidation of 1a and 1b, the ligand LOMe undergo demethylation at the metal centre resulting in the formation of Co(III) complexes with modified phenoxide ligand. This is the very first examples of oxidative O-demethylation reported at a Co(II) centre. The oxidative behaviour shows striking dependance on the nature of coligands coordinated to the metal centre. The Co(II) complex 1a with stronger chloro coligands requires a strong oxidising agent like t-BuOOH for oxidative demethylation and the subsequent formation of a mononuclear Co(III) complex with demethylated ligand, CoLO-Cl2 (2). On the other hand, the complex 1b with weaker iodo coligands undergoes oxidation in presence of weak oxidant O2 to form a dihydroxo bridged binuclear Co(III) complex [Co2(LO-)2(OH)2]2+ (3) with modified phenoxide ligand. The oxidation of 1b to 3 is monitored and the intermediate Co(II) iodo aqua complex, [CoLOMeI(H2O)]+ and Co(II) diaqua complex, [CoLOMe(H2O)2]2+ are isolated and characterised.