Reductive Activation of White Phosphorus to [P₄]^2-, [P₂]^2-, and a Formal P^2- Radical by Rare-Earth Dinitrogen...

Activation of white phosphorus (P₄) to smaller P_n units by rare-earth compounds remains a synthetic challenge. Here, we show that the rare-earth dinitrogen complexes [{(Cp^ttt)₂ M}₂(μ-1,2-N₂)] (M = Y, Gd; Cp^ttt = 1,2,4-tri(tert-butyl)cyclopentadienyl), reductively cleave P₄ to give a homologous series of phosphorus anions of decreasing nuclearity, that is, [{(Cp^ttt)₂ M}₂(μ-P₄)] (1_M), [{(Cp^ttt)₂ M}₂(μ-η²:η²-P₂)] (2_M), and [{(Cp^ttt)₂ M}₂(μ-P)] (3_M). Structural, spectroscopic, and computational studies show that 1_M contains a bicyclobutane-like [P₄]^2- ligand, whereas 2_M features a side-on coordinated [P═P]^2- ligand, and 3_M comprises a monatomic P^2- ligand formulated as a phosphorus-centered radical with S = 1/2. The EPR spectrum of 3_Y confirms hyperfine coupling to ³¹P and ⁸⁹Y, while magnetic measurements on 3_Gd reveal strong antiferromagnetic exchange between the Gd³⁺ ions and the radical ligand. Density functional theory supports a three-center π-type M-P-M interaction in 3_M, with the unpaired spin localized primarily on phosphorus and only weak delocalization onto the metal centers. These findings represent progressive fragmentation of P₄ to diatomic and monatomic phosphorus anions by rare-earth reagents, thereby extending the chemistry of multiply bonded phosphorus and persistent phosphorus radicals into the rare-earth series.