Synthesis of two covalently linked bis(2,2′∶6′,2′′-terpyridine) (terpy) chelating ligands with different length spacers, comparison of the crystal structures of their mononuclear nickel(II) complexes, and kinetic and mechanistic studies of the reaction of one ligand with [Fe(terpy)2]2+
Abstract
Two new covalently linked bis(2,2′∶6′,2′′-terpyridine)-chelating hexadentate ligands, 1,3-bis(2,2′∶6′,2′′-terpyridyl-5-ylmethylsulfanyl)propane (L1), and 1,4-bis(2,2′∶6′,2′′-terpyridyl-5-ylmethylsulfanyl)butane (L2), and their six-coordinate mononuclear metal complexes [ML][PF6]2 (M = Fe and Ni; L = L1 and L2) have been prepared and characterised. The X-ray structures of [NiL](PF6)2 (L = L1 and L2) have been compared to establish that L2 has the optimum length of linker to give the least strained mononuclear complex. The marked stability of [ML]2+ is demonstrated by kinetic studies that show that one equivalent of L1 is capable of substituting both 2,2′∶6′,2′′-terpyridine (terpy) ligands of [Fe(terpy)2]2+ to give [FeL1]2+ in a two stage kinetic process.