Abstract
White phosphorus ignition notoriously produces the phosphoric acid anhydride P(4)O(10), yet the intermediate oxidation steps remain undetermined. We report the first geometric and vibrational characterization of two P(4)O(2) isomers, P(3)OPO and P(3)PO(2), and substantiate a previously proposed cyclic P(4)O(2) isomer. We formally assign the infrared bands observed by Andrews and Mielke at 898 and 891 cm(-1) to the antisymmetric P-O-P vibrations of P(3)OPO species (Mielke and Andrews, 1990). Additional bands corresponding to terminal P═O and -PO(2) stretches of P(3)OPO and P(3)PO(2) discussed herein also went unrecognized due to the peculiar bonding of P(4)O(2) species compared to oxo-bridged P(4)O(x) (x = 3-6) species. Sequential addition of oxygen atoms to the P(4) tetrahedron appears to form P(3)OPO and P(3)PO(2), while cyclic P(4)O(2) is formed from P(2)O dimerization. CCSD(T) geometries, CCSD(T) + MP2[δVPT2] fundamental frequencies, and enthalpies of formation extrapolated using focal-point analysis are reported. The predicted enthalpies of formation relative to tetrahedral P(4) plus (3)Σ(g)(-) O(2) for bent-P(3)OPO, extended-P(3)OPO, P(3)PO(2), and cyclic-P(4)O(2) are -93, -88, -85, and -63 kcal mol(-1), respectively.