Synthesis, Structure, and Reactivity of a Diphosphadiferratetrahedrane with a Fe−Fe Double Bond

The short thermolysis of the butterfly molecule [{Cp′′′(OC)2Fe}2P4] affords, besides [Cp′′′FeP5] and [{Cp′′′Fe}2P4], the diphosphadiferratetrahedrane [{Cp′′′Fe}2(μ-CO)(μ-η2:η2-P2)] with a Fe−Fe double bond in 18 % yield. The P2 building block was split photochemically into two μ-P ligands with elimination of CO. In the resulting dinuclear complex 1, the 31P NMR signal is shifted to extremely low field (δ=1406.9), and the rhombic Fe2P2 four-membered ring is almost orthogonal to the eclipsed Cp′′′ five-membered rings (see picture); Cp′′′=tBu3C5H2.