Two P, Ten\nP, White P, Red P: Mechanistic Exploration\nof the Oligomerization of Red Phosphorus from Diphosphorus with the\nAb Initio Nanoreactor

Phosphorus is critical to humans on many fronts, yet\nwe do not\nhave a mechanistic understanding of some of its most basic transformations\nand reactionsnamely the oligomerization of white phosphorus\nto red. With heat or under ultraviolet (UV) exposure, it has been\nexperimentally demonstrated that white phosphorus dissociates into\ndiphosphorus units which readily form red phosphorus. However, the\nmechanism of this process is unknown. The ab initio nanoreactor approach\nwas used to explore the potential energy surface of phosphorus clusters.\nDensity functional theory and metadynamics simulations were used to\ncharacterize potential reaction pathways. A mechanism for oligomerization\nis proposed to take place via diphosphorus additions at π-bonds\nand weak σ-bonds through three membered ring intermediates.\nDownhill paths through P<sub>6</sub> and P<sub>8</sub> clusters eventually\nresult in P<sub>10</sub> clusters that can oligomerize into red phosphorus\nchains. The initial, rate limiting step for this process has an energy\nbarrier of 24.2 kcal/mol.