Metal-directed assembly of combinatorial libraries - principles and establishment of equilibrated libraries with oligopyridine ligands

The cobalt(II) complexes [Co(bpy)(3)][PF6](2), [Co(Me(2)bpy)(3)][ PF6](2) (Me(2)bpy = 4,4' dimethyl- 2,2'-bipyridine) and [Co( phen)(3)][ PF6] (2) give paramagnetically shifted 1 H NMR spectra which may be fully assigned; the complexes are labile and ligand exchange is complete within mixing time in CD3CN solutions to give libraries of heteroleptic complexes which have been fully characterised by one- and two-dimensional (1) H NMR spectroscopy. A library comprising mer and fac isomers of [CoL3](2+) ( L = 2,2'- bipyridine-5-carbaldehyde) can be amplified by specific reaction of the fac stereoisomer with a triamine to give a new hexadentate ligand, although other ligand exchange processes compete.