Stabilizing P≡P: P22–, P2⋅–, and P20 as bridging ligands

Summary In contrast to its lighter congener N2, neutral diphosphorus with a P≡P triple bond is a highly reactive species observable only in the gas phase and by matrix isolation. Previous stabilization efforts with Lewis bases (e.g., carbenes) or by transition-metal coordination led to charge transfer to highly electrophilic P2 and thus to significant reduction of the bond order. Here, we report the crystallographic, spectroscopic, and quantum chemical characterization of the redox series [(μ2,η1:η1-P2){Pt(PNP)}2] (PNP = N(CHCHPtBu2)2), which features (P2)2–, (P2)⋅–, and (P2)0 as bridging ligands. Although common for N2, the stabilization as a neutral, triply bonded P≡P ligand is unprecedented for the heavier homolog. It was enabled by coordination of the dipnictogen to redox-inactive Lewis-acidic metal fragments and gave rise to the controlled release of P2 in the condensed phase.