Early and Late Transition Metal Complexes Stabilised by Imidazopyridazine‐Substituted Bisamido Ligands

Abstract

AbstractThe preparation of a series of new imidazo[1,5‐b]pyridazine‐substituted diamines (5) is reported. They can be synthesised by the nucleophilic ring transformation of 2‐amino‐5‐methyl‐1,3,4‐oxadiazolium halogenides (1) with diaminoalkanes followed by condensation reactions with 1,3‐diketones. After deprotonation they were then used as bisamido ligands. These ligands stabilise early and late transition metal complexes as five‐membered chelates. The reaction with selected group 4 metals (titanium and zirconium) leads via amine elimination to unusual dark blue and purple mononuclear amido complexes. Deprotonation of the bisamido ligands using BuLi and further reaction with group 6 metals like chromium results in a dinuclear octahedral CrIII complex, where the different coordinated metal centres are bridged by two of the amido N atoms. The double deprotonation of 5 followed by reaction with the group 9 metals rhodium and iridium led to dinuclear complexes in a trans binding mode. The X‐ray structures of one of the novel bisamido ligands (protonated) and all complexes are reported and discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)