Synthesis and Reactivity of a Paramagnetic Iron Phosphaethynolate Complex

The bulky iron(II) tris(carbene)borate complex PhB(AdIm)3FeCl reacts with equimolar NaPCO to afford PhB(AdIm)3Fe(PCO) as a rare example of a paramagnetic phosphaethynolate complex. Although thermally and photochemically unstable, there is no evidence that either of these conditions leads to the formation of an iron phosphido complex. However, in the presence of excess NaPCO, thermolysis of PhB(AdIm)3Fe(PCO) yields a dinuclear iron complex in which a new side-bound diphosphene ligand is stabilized by N-heterocyclic carbene and borate groups. These results hint at the utility of paramagnetic complexes for enlarging the scope of phosphaethynolate chemistry.