Redox state switching of transition metals by deprotonation of the tridentate ligand 2,6-bis(imidazol-2-yl)pyridine

The chemistry of the ligand 1, 2,6-bis(imidazol-2-yl) pyridine with manganese, cobalt, nickel and ruthenium has been investigated. The ligand binds as a meridional tridentate ligand as shown by the crystal structures of [Mn(1)(2)](CF3SO3)2.Et2O and [Ru(1)(2)](PF6)(2).2CH(3)CN.H2O. The coordinated ligand is deprotonated in mildly basic solution, and this leads to a drop in the metal M(III)/ M(II) reduction potential for cobalt and ruthenium of roughly 1.3 V. The crystal structure of Na-2(PPN)[Co(1 - 2H)(2)](2)(OH).MeOH.2H(2)O confirms the deprotonation and shows sodium to bind to the deprotonated nitrogen atoms. No stabilisation of the M(III) oxidation state was observed for nickel and manganese.