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.已合成并表征了处于三角三(ditox)（ditox = tBu₂(Me)CO⁻）配体环境中的单核铁(II)与铁(III)配合物。该铁(III) ditox配合物不与亚碘酰苯（PhIO）这类氧化剂发生反应，而三甲基胺N-氧化物（NMe₃O）会取代轴向配位的四氢呋喃（THF），且未发生氧转移过程。与之形成鲜明对比的是，该铁(II) ditox配合物可在四氢呋喃或环己二烯中与亚碘酰苯或三甲基胺N-氧化物（Me₃NO）快速反应，生成一种高活性中间体；该中间体可断裂C-H键，得到铁(III)-氢氧化物配合物。当在1,2-二氟苯中生成该中间体时，可通过捕获该中间体将膦氧化为氧化膦。这类反应的快速速率被归因于三(烷氧基)辅助配体环境所赋予的极弱配体场。