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

Activation of white phosphorus (P4) to smaller Pn units by rare-earth compounds remains a synthetic challenge. Here, we show that the rare-earth dinitrogen complexes [{(Cpttt)2 M}2(μ-1,2-N2)] (M = Y, Gd; Cpttt = 1,2,4-tri(tert-butyl)cyclopentadienyl), reductively cleave P4 to give a homologous series of phosphorus anions of decreasing nuclearity, that is, [{(Cpttt)2 M}2(μ-P4)] (1M), [{(Cpttt)2 M}2(μ-η2:η2-P2)] (2M), and [{(Cpttt)2 M}2(μ-P)] (3M). Structural, spectroscopic, and computational studies show that 1M contains a bicyclobutane-like [P4]2- ligand, whereas 2M features a side-on coordinated [P═P]2- ligand, and 3M comprises a monatomic P2- ligand formulated as a phosphorus-centered radical with S = 1/2. The EPR spectrum of 3Y confirms hyperfine coupling to 31P and 89Y, while magnetic measurements on 3Gd 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 3M, 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.