The Triplet Hydroxyl Radical Complex of Phosphorus Monoxide

Abstract

Phosphorus monoxide (CPO) is a key intermediate in phosphorus chemistry, and its association with the hydroxyl radical (COH) to yield metaphosphorous acid (cis-HOPO) contributes to the chemiluminescence in the combustion of phosphines. When photolyzing cis-HOPO in an Ar-matrix at 2.8 K, the simplest dioxophosphorane HPO 2 and an elusive hydroxyl radical complex (HRC) of CPO form. This prototypical radical-radical complex reforms into cis-HOPO at above 12.0 K by overcoming a barrier of 0.28 AE 0.02 kcal mol À1. The vibrational spectra of this HRC and its D-and 18 Oisotopologues suggest a structure of COH•••OPC, for which a triplet spin multiplicity with a binding energy of À3.20 kcal mol À1 has been computed at the UCCSD(T)-F12a/aug-cc-pVTZ level.

Carbodiphosphorane-Stabilized Parent Dioxophosphorane: A Valuable Synthetic HO2P Source

“…The correct molecular ion with an m / z value of 601.1633 (calculated for [C 37 H 31 O 2 P 3 + H] + : 601.1610) was detected using high-resolution mass spectrometry, while single-crystal X-ray diffraction (Figure ) confirmed its structural connectivity. The double-bond characteristic for each PO bond was evident by their respective bond distance values of 1.4956(11) and 1.4990(11) Å. ,, Additionally, the two OPO stretching vibrations were observed by Fourier transform infrared spectroscopy at 1435 (asymmetric) and 1205 (symmetric) cm –1 . ,, …”

“…have generated considerable scientific interest due to their potential as phosphorylation/phosphonylation reagents − as well as their participation as intermediates/final products of combustion reactions involving warfare agents and flame retardants. , Dioxyphosphorane ( 1 , Figure ) and cis / trans -alkoxyphosphanone ( 2 , 3 ) are the structural isomers that these molecules are capable of adopting. The former, formally a P­(V) species, is thermodynamically more favorable for all species regardless of the nature of the R substituent − ,− with the exception of the parent compound (i.e., R = H). − In fact, parent dioxophosphorane 1a has been predicted to be more than 40 kJ/mol less stable than the cis-isomer of hydroxyphosphanone ( 2a ), − and it was then not surprising that this least thermodynamically stable isomer (i.e., HPO 2 ) was only recently detected via infrared spectroscopy among several products formed during 193/266 nm laser photolysis of 2a in the Ar matrix at 2.8 K …”

“…Dioxophosphoranes are usually stabilized within a larger molecular framework and are, in some instances, deliberately released for detection/identification as well as further reactivity studies such as in the case of compounds 4 through 7 (Figure ). In fact, owing to the exceptional electrophilic characteristic of the three-coordinate phosphorus atom, the identity of dioxophosphoranes was normally established by either low-temperature matrix isolation procedures, − , high-temperature gas-phase analysis, intramolecular C–H/C–F bond activations, , or trapping experiments, that is, reactivity studies in the presence of, for example, alcohols, amines, or epoxides . The reactivity of transient dioxophosphoranes with different molecules actually represents a very useful approach for the phosphorylation/phosphonylation of organic molecules potentially yielding compounds, including the biologically important ones, that would be difficult to obtain by other synthetic methods. − For example, fragmentation of compounds that resemble 4 (Figure ) represents arguably the most versatile/valuable approach in generating synthetically usable RO 2 P fragments. ,, On the other hand, base-stabilized compounds such as 9 and 10 ( 8 is in fact produced by the photolysis of 4 at −75 °C in THF), including transition metal-stabilized RPO 2 complexes, are generally not reported to act as a source of the RO 2 P fragment that could be used for further reactivity studies. ,,− A similar conclusion could be reached for neutral but zwitterionic ( 11 , Figure ) − and anionic ( 12 ) − compounds (i.e., the O-deprotonated form of the monobasic tautomer of phosphonous acid) because they could be viewed as parent dioxophosphorane-containing species.…”

“…32 −50 In fact, parent dioxophosphorane 1a has been predicted to be more than 40 kJ/mol less stable than the cis-isomer of hydroxyphosphanone (2a), 42−50 and it was then not surprising that this least thermodynamically stable isomer (i.e., HPO 2 ) was only recently detected via infrared spectroscopy among several products formed during 193/266 nm laser photolysis of 2a in the Ar matrix at 2.8 K. 40 Dioxophosphoranes are usually stabilized within a larger molecular framework and are, in some instances, deliberately released for detection/identification as well as further reactivity studies such as in the case of compounds 4 through 7 (Figure 1). In fact, owing to the exceptional electrophilic characteristic of the three-coordinate phosphorus atom, the identity of dioxophosphoranes was normally established by either lowtemperature matrix isolation procedures, [6][7][8]40 high-temperature gas-phase analysis, 12 intramolecular C−H/C−F bond activations, 9,15 or trapping experiments, that is, reactivity studies in the presence of, for example, alcohols, amines, or epoxides. 1 The reactivity of transient dioxophosphoranes with different molecules actually represents a very useful approach for the phosphorylation/phosphonylation of organic molecules potentially yielding compounds, including the biologically important ones, that would be difficult to obtain by other synthetic methods.…”

Selective Preparation of Phosphorus Mononitride (P≡N) from Phosphinoazide and Reversible Oxidation to Phosphinonitrene

“…Complex 3-PN is stabilized by electrostatic interactions between O•••P with a shared potential electron density (ρ) of 0.0087 and a second Hessian eigenvalue (λ 2 ) of À 0.0087 as derived from a topological non-covalent interaction (NCI) analysis (Figure 5 and Table S4), [37] which is consistent with the computed properties of the O•••P interaction in the HO•••PO complex (Figure S8). [38] The O•••P distance in 3-PN of 3.166 Å is smaller than the sum of the van der Waals radii of O (1.52 Å) and P (1.80 Å), respectively. [39]…”