Diferrocenophosphaborin: A Planar-Chiral, Redox-Active and Anion-Responsive Ambiphilic Ligand

A new class of Janus-like ambiphilic ligands is introduced. The rigid diferrocene backbone in heterocycles 4-SnP and 4-BP creates an unprecedented chiral environment as demonstrated by multinuclear NMR and single-crystal X-ray studies. In addition, the ligands are redox-responsive and the Lewis acidic borane moiety in 4-BP can be exploited to further tune the properties: a clear decrease in the CO stretching frequency of a Vaska-type RhI complex 5-BP is observed upon addition of fluoride ions. Thus, the Lewis acid and Lewis base sites influence each other and their strength can be modulated by redox chemistry and anion binding.