Dual Functionalization of White Phosphorus: Formation, Characterization, and Reactivity of Rare‐Earth‐Metal Cyclo‐P3 Complexes

: The [3+1] fragmentation reaction of rare-earth metallacyclopentadienes 1 a-c with 0.5 equivalents of P4 affords a series of rare-earth metal cyclo-P3 complexes 2 a-c and a phospholyl anion 3. 2 a-c demonstrate an unusual η3 coordination mode with one P-P bond featuring partial π-bonding character. 2 a-c are the first cyclo-P3 complexes of rare-earth metals, and also the first organo-substituted polyphosphides in the category of Group 3 and f-block elements. Rare-earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels-Alder reaction. Compounds 2 a-c can coordinate to one or two [W(CO)5 ] units, yielding 4 a-c or 5 c, respectively. Furthermore, oxidation of 2 a with p-benzoquinone produces its corresponding phospholyllithium and regenerated P4 .