Iron in a Trigonal Tris(alkoxide) Ligand Environment

Mononuclear Fe­(II) and Fe­(III) complexes residing in a trigonal tris­(ditox) (ditox = ^tBu₂(Me)­CO^–) ligand environment have been synthesized and characterized. The Fe­(III) ditox complex does not react with oxidants such as PhIO, whereas NMe₃O substitutes a coordinated tetrahydrofuran (THF) in the apical position without undergoing oxo transfer. In contrast, the Fe­(II) ditox complex reacts rapidly with PhIO or Me₃NO in THF or cyclohexadiene to furnish a highly reactive intermediate, which cleaves C–H bonds to afford the Fe­(III)–hydroxide complex. When generated in 1,2-difluorobenze, this intermediate can be intercepted to oxidize phosphines to phosphine oxide. The fast rates at which these reactions occur is attributed to a particularly weak ligand field imparted by the tris­(alkoxide) ancillary ligand environment.