An Isolable Phosphinidene Oxide

doi:10.21203/rs.3.rs-4078058/v1

Download PDF

Article

An Isolable Phosphinidene Oxide

https://doi.org/10.21203/rs.3.rs-4078058/v1

This work is licensed under a CC BY 4.0 License

Journal Publication

published 15 Jul, 2024

Read the published version in Nature Chemistry →

Version 1

posted

You are reading this latest preprint version

Phosphorus monoxide (PO^•) was the first compound with a P–O bond to be spectroscopically detected in interstellar space. On Earth, PO^•, and related functionalized molecules such as R–P = O (R = OH, CH₃, OCH₃, Ph), have been studied in inert gas matrices at ultralow temperatures (3–15 K). These species are believed to be key intermediates in the degradation/combustion of organic phosphorus compounds (a class of chemicals that includes chemical warfare agents and flame retardants). However, despite numerous attempts, an isolable example of R–P = O has eluded synthetic chemists to date. Here we describe the use of an extremely bulky amine ligand to isolate the first two-coordinate phosphorus(III) oxide. Reactivity studies on this and other related compounds shows that phosphorus center can be readily oxidized, and that in doing so, the P–O bond remains intact, an observation that is of interest to the proposed reactivity of phosphorus monoxide (PO^•).

Physical sciences/Chemistry/Inorganic chemistry/Organometallic chemistry

Physical sciences/Chemistry/Chemical synthesis

Phosphorus monoxide (PO^•) is a heavy analog of the free radical nitric oxide (NO^•), however unlike NO^•, free PO^• readily polymerizes under ambient conditions or undergoes facile association reactions with other free radicals (e.g. OH^•). PO^• was first observed spectroscopically in 1931 and has since been detected in interstellar space.^[1,2] Functionalized R–P = O type molecules (phosphanones or phosphinidene oxides), are also known, albeit unstable at room temperature. For example, metaphosphorous acid (cis-HOPO) is proposed to be a key intermediate in the oxidation of organic phosphorus compounds such as phosphines.^[3,4] As with free PO^•, compounds such as CH₃PO,^[5] CH₃OPO,^[6] and PhPO^[7] can only be observed at extremely low temperatures (3–15 K) in inert gas matrices that mimic interstellar conditions. These studies point at the difficulties associated with the isolation phosphorus(III) oxides, which are prone to intermolecular polymerization pathways on account of their diminished π-bond energies when compared to their nitrogen analogs.

A common strategy for the isolation of highly reactive molecules is to trap these in the coordination sphere of metals. For example, work by Cummins has shown that phosphorus monoxide can be employed as a terminal ligand for the formation of a molybdenum complex with a terminal Mo–P = O bond (Fig. 1, A).^[8] It is worth noting that in terms of its electronic structure, this species should not be described as a phosphinidene oxide due to the short Mo–P bond (2.079(5) Å) and the linear Mo-P-O angle (177.6(8)^o), both of which imply significant d_π–p_π interactions between the metal center and phosphorus monoxide moiety. To the best of our knowledge, the synthesis of an isolable free phosphinidene oxide with a bent structure such as that predicted for R–P = O, (R = OH, CH₃, OCH₃, Ph) has not been achieved to date despite various attempts to characterize such compounds in the condensed phase.^[9] The first direct observation of a phosphenite RO–P = O (R = 2,6-di-tert-butyl-4-methylphenyl; B) was accomplished by pyrolyzing its cyclic trimer. This species was identified by ³¹P{¹H} NMR spectroscopy (singlet resonance at 238 ppm) and IR spectroscopy (ν_P=O = 1235 cm^–1).^[10] However, the monomer rapidly reverted to the starting material upon warming up to 272 K. Phosphinidene oxides have been stabilized when coordinated to transition metal centers or through interactions with main group Lewis acid/bases. The first isolable phosphinidene oxide complex was stabilized within the coordination sphere of chromium, as reported by Niecke and colleagues in 1980 (C), and several group six metal stabilized cases were reported later.^[11,12] More recently, Stephen and Liu successfully isolated a donor-acceptor stabilized phosphinidene oxide compound (D).^[13] Compounds stabilized exclusively by an external donor would come several years later with Braunschweig describing an N-heterocyclic carbene adduct of phosphinidene oxide,^[14] while Nikonov and co-workers reported a phosphine stabilized congener (E).^[15]

The availability of phosphinidene oxides stabilized by external Lewis bases prompted us to explore whether the use of an internal π-donor substituent would allow access to an isolable variant. In addition to the electronic stabilization offered by such a ligand, significant steric bulk would be required to circumvent the aforementioned oligomerization pathways. Herein, we describe the synthesis of an anionic imine stabilized phosphinidene oxide RNPO^– which can be further functionalized into a neutral amido-functionalized phosphinidene oxide R(R')NPO. These species represent the first examples of isolable two coordinate phosphorus(III) oxides.

In contrast to other kinetically stabilized main group species with multiple bonds, phosphinidene oxides R–P = O present a unique challenge. The use of steric protection is only viable at one end of the molecule, thus necessitating the presence of an R group capable of providing long-range steric shielding to prevent oligomerization. Inspired by the work of Goto and co-workers, in which they adopted meta-substituted terphenyl group to protect nitroso-selenocysteine (R–SeNO) and selenenic acids (R–SeOH),^[16] we synthesized compound 1 as an N-terminal protecting group (Scheme 1). In addition to the kinetic stabilization offered by steric bulk, the corresponding phosphine oxide precursors R–NPO^– are viable targets for compounds with P^III=O double bond character on account of their anionic charge. Electrostatic repulsion can effectively deter oligomerization or polymerization of such species. An exemplary case of this strategy is the isolation of the phosphaethynolate anion PCO^– and its analogs.^[17] However, it is crucial to note that upon losing the charge (through protonation, for instance), these anions readily oligomerize.^[18]

2.1 Isolation of anionic imine stabilized phosphinidene oxide RNPO^–

To achieve our goal, we reacted the chloro(imino)phosphane 2, which was synthesized according to a modified literature procedure,^[19] with KOTMS (Scheme 1). Upon treatment of 2 with 2.5 equivalents of KOTMS in tetrahydrofuran (THF), in situ ³¹P{¹H} NMR spectroscopy revealed a distinct singlet at 237.2 ppm, corresponding to the formation of 3. Interestingly, this reaction did not proceed via the expected intermediate R–N = P–OTMS followed by desilylation. Instead, it proceeds via a three-coordinate phosphite K[R–N–P(OTMS)₂], facilitated by the excess KOTMS, ultimately leading to the elimination of hexamethyldisiloxane OTMS₂ (see supporting information).

Structural confirmation of compounds 2 and 3 was obtained through single crystal X-ray diffraction analysis (Fig. 2). The crystal structure of 3 reveals a bent N-P-O moiety (116.85(11)°) and a P–O bond length of 1.501(2) Å. Notably, this P–O bond length closely resembles those observed in phosphinidene oxides stabilized by either acids or bases.^[11,14–15] The P–N bond elongates from 1.497(2) Å in 2 to 1.5822(19) Å. These bond lengths suggest that there is π-bonding character between both P–O and P–N. In fact, compound 3 can be rationalized as a heavier analog of nitrite (NO₂^–), exhibiting phosphorus-centered 3-center-4-electron (3c-4e) bonding.

DFT calculations were conducted to elucidate the electronic structure of 3. The optimized geometry (M06-2X/Def2-svp) is in good agreement with that obtained by X-ray crystallography (e.g. N1–P1: 1.601 Å; O1–P1: 1.522 Å). Natural bond orbital (NBO) analysis revealed the presence of a 3-center-4-electron (3c-4e) bonding interaction, with the N–P double bond contributing 57.3% to the system and the P–O double bond contributing 42.7% (refer to the resonance forms in Fig. 3a). This is supported by Wiberg bond indices (WBIs), which indicate similar bond orders for the N–P (1.25) and P–O (1.24) bonds. Mayer bond indices indicate a slightly higher bond order for P–O (1.64) compared to N–P (1.40). Nevertheless, both bond indices collectively confirmed the existence of multiple bonding character within the N-P-O moiety. Remarkably, in both WBIs and Mayer bond index, N–O showed a non-negligible bond order (0.16 in WBIs and 0.07 in Mayer). This observation underscores the delocalized nature of the N-P-O bonding interaction, with N–O exhibiting some degree of π bonding. Indeed, three molecular orbitals can be located in a simplified model (MeNPO^–), representing a classic three-center-four-electron system (Fig. 3b). The Natural Population Analysis (NPA) showed that both N (–1.06 a.u.) and O (–1.10 a.u.) carry significant negative charge, indicating both atoms can be used for further functionalization. To gain further insight into the reactive sight, a conceptual DFT calculation was conducted. The dual descriptor iso-surface showed that N1 has a larger negative Δf compared O1, which implies that N1 is a more nucleophilic center (Fig. 3c).^[20]

2.2. Functionalization of RNPO^– with electrophiles

To probe the reactivity of 3, benzyl bromide was selected as an electrophile, and was heated with 3 at 40°C for 12 h (Scheme 2). Monitoring the reaction mixture by in situ ³¹P{¹H} NMR spectroscopy revealed two new singlet peaks at 284.4 and 286.3 ppm.

The structure of the resulting product, 4, was confirmed by single crystal X-ray diffraction (Fig. 4). Crystallographic analysis confirms functionalization at the nitrogen atom, yielding a neutral amido-phosphinidene oxide. Notably, the P–O bond in 4 shortens significantly (1.447(6) Å), compared to that in compound 3 (1.501(2) Å). Additionally, the N–P bond in 4 elongated to 1.667(6) Å relative to 3 (1.5822(19) Å). This extended N–P bond length, while shorter than the standard N–P single bond predicted by Pyykkö (1.82 Å),^[21] indicates strong π donation from the nitrogen atom lone pair to the P–O π* bond. This π donation is further supported by the trigonal planar geometry of nitrogen (Σ°: 360.0°). In the context of the diagonal relationship between phosphorus and carbon,^[22] compound 4 can be regarded as a heavier analogue of an amide, as it exhibits strikingly similar geometric characteristics to such compounds, including shorter N–C bonds and a planar nitrogen center. An IR band corresponding the ν_P=O stretch for 4 was observed at 1186 cm^–1 (cf. 1097 cm^–1 for 3) suggesting an increase in the multiple bond character of the P–O bond. The blue-shift in the ν_P=O absorption aligns with the observation of a shorter P–O bond in the crystal structure, reinforcing the structural changes brought about by the chemical functionalization. These absorptions are slightly blue-shifted from reported vibrations for the phosphenite B (1252.6 and 1292.2 cm^–1),^[10] in line with the greater electron donating ability of imine and amide groups over an oxyl functionality.

The origin of the two singlets observed in the ³¹P{¹H} NMR spectrum of 4 was attributed to cis-trans isomerization about the N–P bond and was further investigated using Saturation Transfer Differential NMR (STD-NMR). In toluene solution at ambient temperature, 4 exists in two forms in a 1:6 ratio as shown by the ³¹P NMR spectrum (Fig. 5a). To prove that these two species are in exchange and to ascertain the exchange rate, a series of ³¹P 1D-EXSY experiments (Fig. 5d) were performed over a range of temperatures. These results are summarized in the Eyring plot (Fig. 5c) from which ΔH* = 19(2) kcal mol^–1, ΔS* = 3.8(60) cal mol^–1 K^–1 and ΔG*(298K) = 18(2) kcal mol^–1 can be calculated for the exchange process.

DFT calculations were carried out to gain a deeper understanding of the electronic structure of 4. Natural bond orbital (NBO) analysis revealed a similar 3-center-4-electron (3c-4e) interaction with the P = O moiety contributing more significantly to the overall electronic structure (65.3%) than the N = P component (34.7%) (see resonance forms in Fig. 6a). This observation was consistent with calculated Wiberg and Mayer bond indices (Table S3&S4). Notably, both σ-bonding and π-bonding orbitals were identified between phosphorus and oxygen (see Figs. 6b and 6c), providing further evidence of the double bond character of the P = O fragment in 4. Second order perturbation theory analysis, reveals strong donation from the lone pair of nitrogen into the P–O π* orbital (E(2) = 41.12 Kcal mol^–1). This donation aligns with the presence of the 3c-4e π bond in the NPO fragment, corroborating the structural evidence from crystallography. Energy calculations indicated that the trans-isomer represents the ground state, with the cis-isomer being 1.2 kcal mol^–1 higher in energy. The energy barrier for the isomerization process was determined to be 21.8 kcal mol^–1. These computational findings are in excellent agreement with the experimental observations obtained through STD-NMR, as the experimental measured energy barrier is 18(2) kcal mol^–1. Based on the predicted ground state, as well as the trans-geometry observed in crystallography, we can confidently assign the singlet at 284.4 ppm in ³¹P NMR spectrum to be the trans-isomer, while the peak at 286.3 ppm corresponds to the cis-isomer.

While the nitrogen atom in compound 3 is identified as the most nucleophilic position based on the dual descriptor analysis, it is noteworthy that the oxygen atom also carries a significant amount of negative charge. Given that the oxygen atom is less sterically hindered, we postulated that bulky electrophiles could be employed to access oxygen functionalized compounds. Treatment of 3 with ⁱPr₃SiOTf in benzene afforded 5, which features a singlet in its ³¹P{¹H} NMR spectrum at 169.0 ppm. The solid-state molecular structure of 5 was determined by single crystal X-ray diffraction (Fig. 4). This analysis revealed the presence of a silanolate-substituted N = P double bond with a N–P bond length of 1.544(2) Å. 5 exhibits comparable bond metrics to related compounds of general formula of R–N = P–OR′.^[23] Following silylation, the Mayer bond order for N–P increased from 1.40 in 3 to 1.79 in 5, while P–O bond order decreased from 1.64 to 1.01. This can be reasoned as 5 has a more localized N–P π bond.

2.3 Formal oxidation reactions from P(III) to P(V)

While 3 is stable at ambient or even elevated temperature in both solution and the solid-state under an inert atmosphere, it readily reacts with trace amounts of moisture (Scheme 3). Upon exposing to one equivalent of H₂O at − 78°C, 3 undergoes conversion to a phosphorous acid derivative 6, which exhibit a doublet in ³¹P NMR at − 3.5 ppm (¹J_P–H = 572.4 Hz). The connectivity was confirmed by single crystal X-ray diffraction (Fig. 7). Compound 6 is structurally and electronically related to a carbodiphosphorane-stabilized dioxophosphorane recently reported by Vidović and co-workers.^[24] The most intriguing aspect of the structure is the protonation of the nitrogen atom instead of oxygen, with the anionic charge being delocalized solely between two oxygen atoms. This conclusion is supported by several key structural features, including the elongation of the N1–P1 bond length (1.719(2) Å) and the nearly identical P–O bond lengths (P1–O1: 1.473(3) Å and P1–O2: 1.487(3) Å), which fall within the typical range for a P = O double bond.^[21] Protonation of N1 was further confirmed by the observation of a resonance at 5.64 ppm in the ¹H NMR spectrum, and by NOESY NMR spectroscopy, which revealed correlation between the N–H resonance and the benzylic C–H adjacent to the central phenyl ring (see supporting information). This reactivity showcases that 3 represents a novel mononuclear phosphorous acid anhydride, distinguishing it from the previously known tetranuclear phosphorous acid anhydride P₄O₆.^[25]

In addition to hydrolysis, as a phosphorus(III) center, 3 can also undergo oxidative processes to form phosphorus(V) compounds. Reaction of a toluene solution of 3 and iodine at − 30°C gave rise to a light-yellow solution. In situ ³¹P NMR spectroscopy revealed a broad singlet at − 147.8 ppm corresponding to 7. Single crystals of 7 can be obtained by slow evaporation of a toluene/hexane solution. Single crystal X-ray diffraction allowed for structural authentication of this compound, revealing a di-iodide substituted phosphorus(V) center with short N1–P1 (1.560(5) Å) and O1–P1 bonds (1.457(6) Å). These bond lengths imply that the anionic charge remains delocalized between N1 and O1. Notably, the P–I bond lengths (mean bond length: 2.529 Å) are longer than any reported P(V)–I bond lengths, which typically range from 2.33 to 2.45 Å. The elongated P–I bond and the shortened N–P and O–P bonds can be attributed to strong back donation from the lone pairs of nitrogen and/or oxygen to the P–I σ* orbital, a phenomenon arising from the inherent weakness of the P–I bond (refer to the supporting information for DFT calculations). While the synthesis of OPI₃ was reported in 1973,^[26] this compound remains poorly characterized. To date, no crystallographic data are available for OPI₃ or its derivatives. The closest known compound is a Lewis acid-stabilized OPI₃ moiety reported by the Krossing group in 2006.^[27] Compound 7 represents the first crystallographically characterized OPI₂R derivative, shedding light on its structural properties.

The aforementioned oxidative process observed for 3 is not limited to iodine. When treated with one equivalent of diphenyl diselenide Se₂Ph₂, a new species 8 was detected by in situ ³¹P NMR spectroscopy. Compound 8 exhibits a singlet at − 23.2 ppm in its ³¹P{¹H} NMR spectrum, with a P–Se coupling constant of 398.7 Hz. The single crystal X-ray structure of 8 reveals a four-coordinate P(V) center. Structurally, 8 closely resembles 7, with relatively short N–P (1.557(2) Å) and P–O (1.474(2) Å) bonds. The P–Se bonds in 8 (mean bond length: 2.310 Å) are slightly elongated compared to the standard P–Se single bond (2.27 Å).^[21] Again, this elongation can be attributed to the delocalization of the anionic charge and back donation to the P–Se σ * orbital.

More than four decades after the first direct observation of phosphinite oxide RO–P = O at low temperature, we have shown that a free two coordinate phosphinidene oxide can be sufficiently stabilized to be isolated at ambient temperature. Electronically and sterically stabilized by a meta-substituted terphenyl group, a heavier analog of nitrite (NO₂^–) can be accessed as ArNPO^– (3), featuring a phosphorus center containing a three-center-four-electron (3c-4e) π-bond. Due to the delocalization of the anionic charge between nitrogen and oxygen, both atoms can be selectively functionalized depending on the electrophile employed. With small alkyl groups, N-functionalization takes place giving rise to the formation of an amido phosphinidene oxide 4, the first structurally validated compound of its class, which can be considered a heavier analog of amide. Alternatively, when reacted with a bulky silyl group, O-functionalization occurs, resulting in the generation of a silanolate-substituted N = P double-bonded species. Moreover, compound 3 displays versatility in its reactivity, as it can also undergo functionalization through oxidative transformations, as exemplified by reactions with iodine and diphenyl diselenide. Ongoing research efforts are dedicated to exploring additional reactivities of phosphinidene oxide compounds, further enhancing our understanding of their chemical properties and potential applications.

Acknowledgements

We thank the University of Oxford for access to Chemical Crystallography facilities.

General Considerations

All reactions and product manipulations were carried out under an inert atmosphere of argon or dinitrogen using standard Schlenk-line or glovebox techniques (MBraun UNIlab glovebox maintained at < 0.1 ppm H₂O and < 0.1 ppm O₂). Hexane (hex; Sigma Aldrich HPLC grade), pentane (pent; Sigma Aldrich HPLC grade), and toluene (tol; Sigma Aldrich HPLC grade) were purified using an MBraun SPS-800 solvent system. Tetrahydrofuran (THF; Sigma Aldrich, ≥ 99.9%) and d₈-THF (Eurisotop, > 99.5%) were distilled over a sodium metal/benzophenone mixture. C₆D₆ (Sigma Aldrich, 99.5%) was degassed prior to use. d₈-Toluene (Sigma-Aldrich 99%) was stirred over a Na/K alloy and filtered before use. All dry solvents were stored under argon in airtight ampoules over activated 3 Å molecular sieves. Commercial reagents were obtained from Sigma Aldrich, Fluorochem, Alfa Aesar and Santa Cruz Biotechnology. Potassium trimethylsilanolate (KOTMS) was dried under vacuum at 60 ^oC for 3 days before use. Triethylamine (NEt₃) was distilled over CaH₂ and degassed prior to use. Phosphorus trichloride was degassed prior to use. 5′-Bromo-2,2′′,4,4′′,6,6′′-hexakis(1-methylethyl)-1,1′:3′,1′′-terphenyl (HIPTBr)^[28] and benzylpotassium^[29] were synthesized following procedures described in the literature. Detailed experimental procedures for the synthesis of compounds 1 and 2 are listed in the supporting information.

Synthesis of 3

To a solid mixture of 2 (150 mg, 0.134 mmol, 1.0 eq.) and KOTMS (42.5 mg, 0.331 mmol, 2.5 eq.), THF (15 ml) was added. The mixture was stirred vigorously for 5 min before all volatiles were removed in vacuo. Hexane (10 ml) was added to the residue, and the solution was filtered using a filter cannula. To the filtrate, a solution of 18-crown-6 (35 mg, 0.132 mmol; 0.99 eq.) in hexane (10 ml) was added, and the mixture was left standing overnight. 3 precipitated out of solution over the course of 24 h, the suspension was filtered and the resulting solid was washed with hexane (10 ml × 2) then dried in vacuo to afford 3 (120 mg, 0.086 mmol; yield: 64%) as a reddish white powder. Single crystals of 3 suitable for X-ray diffraction were obtained by slowly evaporating a concentrated toluene/hexane mixed solution of 3 in a − 35°C freezer for a week. Anal. Calcd for C₉₀H₁₂₅KNO₇P (M.W. 1403.06 g mol^− 1): C, 77.05; H, 8.98; N, 1.00; Found: C 75.49; H, 8.78; N, 1.12. ¹H NMR (600 MHz, C₆D₆): δ (ppm) 1.29 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.30 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.33 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 2.88 (sept, ³J_H–H = 6.8 Hz, 4H; CH(CH₃)₂), 3.00 (s, 24H; 18-crown-6), 3.42 (sept, ³J_H–H = 6.8 Hz, 8H; CH(CH₃)₂), 6.79 (t, ³J_H–H = 7.8 Hz, 1H; ArH), 7.12 (t, ⁴J_H–H = 1.6 Hz, 2H; ArH), 7.20 (s, 8H; ArH), 7.44 (d, ³J_H–H = 7.8 Hz, 2H; ArH), 7.86 (d, ⁴J_H–H = 1.6 Hz, 4H; ArH). ¹³C{¹H} NMR (151 MHz, C₆D₆): δ (ppm) 24.56, 24.72, 25.11 (s, CH(CH₃)₂), 30.77, 34.89 (s, CH(CH₃)₂), 69.87 (s; 18-crown-6), 117.11 (s), 120.60 (s), 129.15 (s), 129.19 (s), 130.33 (s), 134.75 (d, ³J_P–C = 8.6 Hz), 138.97 (s), 139.41 (s), 144.62 (s), 147.41 (s), 147.59 (s), 150.21 (s, d, ²J_P–C = 23.7 Hz) (ArC). ³¹P NMR (162 MHz, C₆D₆): δ (ppm) 237.2 (s). HRMS(m/z): [Anion + H₂O]⁺ calcd. For C₇₈H₁₀₃NPO₂, 1116.7721; found 1116.7736.

Synthesis of 4

A benzene solution (0.2 mL) of BnBr (1.3 mg, 0.0076 mmol, 1.07 eq.) was slowly added to a benzene solution (0.3 mL) of 3 (10 mg, 0.0071 mmol, 1.00 eq.). The mixture was heated for 12 hours in a sealed NMR tube before all volatiles were removed in vacuo. Hexane (0.5 ml) was added to the residue, and the mixture was filtered to obtain the filtrate. The solution was evaporated under vacuum to obtain a colorless oily residue, which was then triturated with MeCN to give 4 (6 mg, 0.0050 mmol; yield: 71%) as a white powder. Single crystals of 4 suitable for X-ray diffraction were obtained by slow evaporation of a concentrated hexane solution of 4 at room temperature. Anal. Calcd. for C₈₅H₁₀₈NOP (M.W. 1190.78 g mol^− 1): C, 85.74; H, 9.14; N, 1.18; Found: C 84.32; H, 8.97; N, 1.28. ¹H NMR (600 MHz, C₆D₆): δ (ppm) 1.17–1.20 (m, 24H; CH(CH₃)₂), 1.23 (d, ³J_H–H = 6.8 Hz, 12H; CH(CH₃)₂), 1.27–1.30 (m, 36H; CH(CH₃)₂), 2.86 (sept, ³J_H–H = 6.8 Hz, 4H; CH(CH₃)₂), 2.99 (sept, ³J_H–H = 6.8 Hz, 8H; CH(CH₃)₂), 5.03 (s, 2H; NCH₂Ph), 6.61 (t, ³J_H–H = 7.4 Hz, 2H; ArH), 6.77 (t, ³J_H–H = 7.4 Hz, 1H; ArH), 6.89–6.94 (m, 3H; ArH), 7.11 (s, 2H; ArH), 7.17–7.21 (m, 12H; ArH), 7.32 (d, ³J_H–H = 7.4 Hz, 2H; ArH). ¹³C{¹H} NMR (125 MHz, C₆D₆): δ (ppm) 24.23, 24.42, 24.67, 25.06 (s, CH(CH₃)₂), 30.97, 34.88 (s, CH(CH₃)₂), 47.96 (s; NCH₂Ph), 120.75, 130.87, 131.47, 131.73, 132.09, 133.53, 135.98, 137.03, 137.24, 139.98, 140.44, 141.17, 141.80, 146.88, 148.63 (s, ArC). ³¹P NMR (162 MHz, C₆D₆): δ (ppm) 284.4 (s, trans-isomer), 286.3 (s, cis-isomer). HRMS(m/z): [M + H₃O]⁺ calcd. For C₈₅H₁₁₁NPO₂, 1208.8347; found 1208.8295.

Synthesis of 5

A benzene solution (0.2 mL) of ⁱPr₃SiOTf (2.4 mg, 0.0078 mmol, 1.10 eq.) was slowly added to a benzene solution (0.3 mL) of 3 (10 mg, 0.0071 mmol, 1.00 eq.). The mixture was stirred for 1 min and filtered to obtain the filtrate. MeCN (5 ml) was added to the filtrate and the mixture was left in a in a − 35°C freezer overnight. The supernatant was removed and the resulting solid was dried in vacuo to afford 5 (7 mg, 0.0057 mmol; 78% yield) as a light yellow powder. Single crystals of 5 suitable for X-ray diffraction were obtained by slow evaporation of a concentrated hexane solution of 5 at room temperature. Anal. Calcd. for C₈₇H₁₂₂NOPSi (M.W. 1257.00 g mol^− 1): C, 83.13; H, 9.78; N, 1.11; Found: C 83.13; H, 9.39; N, 1.05. ¹H NMR (600 MHz, C₆D₆): δ (ppm) 0.83–0.84 (m, 21H; SiCH(CH₃)₂), 1.24 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.27 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.33 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 2.91 (sept, ³J_H–H = 6.8 Hz, 4H; CH(CH₃)₂), 3.12 (sept, ³J_H–H = 6.8 Hz, 8H; CH(CH₃)₂), 6.94 (t, ³J_H–H = 7.6 Hz, 1H; ArH), 7.08 (t, ⁴J_H–H = 1.6 Hz, 2H; ArH), 7.24 (s, 8H; ArH), 7.49 (d, ³J_H–H = 7.6 Hz, 2H; ArH), 7.91 (d, ⁴J_H–H = 1.6 Hz, 4H; ArH). ¹³C{¹H} NMR (151 MHz, C₆D₆): δ (ppm) 12.31 (s, SiCH(CH₃)₂), 17.44 (s, SiCH(CH₃)₂), 24.49, 24.55, 25.13 (s, CH(CH₃)₂), 30.93, 34.94 (s, CH(CH₃)₂), 120.89 (s), 123.18 (s), 129.48 (s), 130.59 (s), 130.76 (s), 131.96 (d, ³J_P–C = 9.6 Hz), 137.78 (s), 140.63 (s), 140.73 (s), 141.55 (d, ²J_P–C = 27.8 Hz), 147.06 (s), 148.39 (s) (ArC). ³¹P NMR (162 MHz, C₆D₆): δ (ppm) 169.0 (s). HRMS(m/z): [M + H]⁺ calcd. For C₈₇H₁₂₃NPOSi, 1256.9112; found 1256.9060.

Synthesis of 6

To a solid mixture of 2 (30 mg, 0.0268 mmol, 1.0 eq.) and KOTMS (8.5 mg, 0.066 mmol, 2.5 eq.), THF (5 ml) was added. The mixture was stirred vigorously for 5 min before all volatiles were removed in vacuo. Hexane (10 ml) was added to the residue, and the solution was filtered using a filter cannula, and the filtrate was dried in vacuo again. THF (5 ml) was added to the residue and the solution was cooled to − 78 ^oC before a THF solution of H₂O (5 mg/ml, 0.12 ml, 0.033 mmol, 1.25 eq.) was added dropwise. The mixture was stirred for 20 min at − 78 ^oC then slowly warmed up to room temperature. (PPN)Cl (30.7 mg, 0.0536 mmol, 2 eq.) was then added to the mixture. The mixture was sonicated for 5 min and stirred for another 2 h before filtering to remove insoluble salts. The filtrate was dried under vacuum, and toluene (3 ml) was added to dissolve the residue. The solution was then stored in a − 35°C freezer for three days to crystallize. The supernatant was removed and the resulting solid was dried in vacuo to afford 6 (16 mg, 0.00966 mmol; 36% yield) as a white powder. Single crystals of 6 suitable for X-ray diffraction were obtained by slow diffusion of hexane into a concentrated THF solution of the product at room temperature. Anal. Calcd. for C₈₇H₁₂₂NOPSi (M.W. 1656.25 g mol^− 1): C, 82.67; H, 8.09; N, 1.69; Found: C 81.43; H, 7.77; N, 1.71. ¹H NMR (500 MHz, C₆D₆): δ (ppm) 1.28–1.31 (m, 72H; CH(CH₃)₂), 2.88 (sept, ³J_H–H = 6.8 Hz, 4H; CH(CH₃)₂), 3.38 (sept, ³J_H–H = 6.8 Hz, 8H; CH(CH₃)₂), 5.64 (s, 1H; NH), 6.94 (t, ³J_H–H = 7.4 Hz, 1H; ArH), 7.04–7.08 (m, 12H; ArH), 7.12–7.15 (m, 8H; ArH), 7.14 (d, ¹J_P–H = 572.4 Hz, 1H; PH), 7.21 (s, 8H; ArH), 7.39–7.43 (m, 12H; ArH), 7.47 (d, ³J_H–H = 7.4 Hz, 2H; ArH), 7.82 (d, ⁴J_H–H = 1.1 Hz, 4H; ArH). ¹³C{¹H} NMR (151 MHz, C₆D₆): δ (ppm) 24.56, 24.86, 25.90 (s, CH(CH₃)₂), 30.96, 34.93 (s, CH(CH₃)₂), 119.23 (s), 120.55 (s), 126.54 (d, J_P–C = 2.3 Hz), 127.39 (d, J_P–C = 2.5 Hz), 129.74-129.89 (m), 130.31 (s), 130.60 (s), 132.68 (s), 132.72 (s), 132.77 (s), 133.60 (s), 135.34 (s), 138.67 (s), 140.53 (s), 143.41 (s), 147.60 (s), 147.63 (s) (ArC). ³¹P NMR (202 MHz, C6D6): δ (ppm) -3.5 (d, ¹J_P–H = 572.4 Hz), 21.2 (s). ³¹P{¹H} NMR (202 MHz, C₆D₆): δ (ppm) − 3.5 (s), 21.2 (s, Ph3P = N = PPh3). HRMS(m/z): [Anion]⁺ calcd. For C₇₈H₁₀₃NPO₂, 1116.7732; found 1116.7732.

Synthesis of 7

A toluene solution (3 mL) of I₂ (18 mg, 0.07 mmol, 1.00 eq.) was slowly added to a toluene solution (5 mL) of 3 (100 mg, 0.07 mmol, 1.00 eq.) dropwise at − 35 ^oC. The mixture was stirred for 5 min before all volatiles were removed in vacuo. The oily yellow residue was then triturated with hexane to give 7 (102 mg, 0.0062 mmol; yield: 87%) as a brown powder. Single crystals of 7 suitable for X-ray diffraction were obtained by slow evaporation of a concentrated hexane/toluene solution of 7 at room temperature. Anal. Calcd. for C₉₀H₁₂₅NO₇PI₂ (M.W. 1641.84 g mol^− 1): C, 65.11; H, 7.49; N, 0.85; Found: C 61.65; H, 7.24; N, 0.72. ¹H NMR (500 MHz, C₆D₆): δ (ppm) 1.30 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.33 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 1.35 (d, ³J_H–H = 6.8 Hz, 24H; CH(CH₃)₂), 2.95 (sept, ³J_H–H = 6.8 Hz, 4H; CH(CH₃)₂), 3.26 (s, 24H; 18-crown-6), 3.47 (sept, ³J_H–H = 6.8 Hz, 8H; CH(CH₃)₂), 7.09 (d, ⁴J_H–H = 1.1 Hz, 2H; ArH), 7.21 (t, ³J_H–H = 7.5 Hz, 1H; ArH), 7.29 (s, 8H; ArH), 7.58 (d, ³J_H–H = 7.6 Hz, 2H; ArH), 8.07 (d, ⁴J_H–H = 1.1 Hz, 4H; ArH). ¹³C{¹H} NMR (125 MHz, C₆D₆): δ (ppm) 24.59, 25.03, 25.59 (s, CH(CH₃)₂), 30.82, 35.01 (s, CH(CH₃)₂), 70.06 (s, 18-crown-6), 120.72 (s), 129.51 (s), 131.43 (s), 132.93 (d, ²J_P–C = 9.0 Hz), 138.06 (s), 138.87 (s), 139.82 (s), 144.60 (s), 146.98 (s), 147.47 (s), 147.75 (s), 148.55 (s) (ArC). ³¹P{¹H} NMR (162 MHz, C₆D₆): δ (ppm) − 147.8 (br). HRMS(m/z): [M + H]⁺ calcd. For C₇₈H₁₀₁NPOI₂, 1352.5716; found 1352.5701.

Synthesis of 8

A benzene solution (0.2 mL) of Se₂Ph₂ (2.2 mg, 0.007 mmol, 1.00 eq.) was added to a benzene solution (0.3 mL) of 3 (10 mg, 0.007 mmol, 1.00 eq.). The mixture was stirred for 24 h before all volatiles were removed in vacuo. THF (0.5 ml) was added to the residue together with (PPN)Cl (8 mg, 0.014 mmol, 2.00 eq.). The mixture was sonicated for 5 min and then stirred for 2 h before filtered to remove insoluble salts. The filtrate was layered with hexane (6 ml) and left for 24 h before removing the supernatant. The remaining crystals were dried in vacuo to afford 8 (8 mg, 0.0041 mmol; yield: 59%) as a yellow powder. Single crystals of 8 suitable for X-ray diffraction were obtained by slow diffusion of hexane into a concentrated THF solution of the product at room temperature. Anal. Calcd. for C₁₂₆H₁₄₁N₂OP₃Se₂ (M.W. 1950.39 g mol^− 1): C, 77.59; H, 7.29; N, 1.44; Found: C 77.16; H, 6.96; N, 1.42. ¹H NMR (400 MHz, d₈-THF): δ (ppm) 0.98 (d, ³J_H–H = 7.0 Hz, 24H; CH(CH₃)₂), 1.10 (d, ³J_H–H = 7.0 Hz, 24H; CH(CH₃)₂), 1.22 (d, ³J_H−H = 7.0 Hz, 24H; CH(CH₃)₂), 2.83 (sept, ³J_H–H = 7.0 Hz, 4H; CH(CH₃)₂), 3.22 (sept, ³J_H–H = 7.0 Hz, 8H; CH(CH₃)₂), 6.61–6.67 (m, 8H; ArH), 6.95 (s, 8H; ArH), 7.08 (dd, ³J_H–H = 7.6 Hz, ⁴J_H–H = 1.5 Hz, 2H; ArH), 7.33 (d, ³J_H–H = 7.6 Hz, 4H; ArH), 7.43–7.48 (m, 13H; ArH), 7.54–7.60 (m, 16H; ArH), 7.66 (td, ³J_H–H = 7.6 Hz, ⁴J_H–H = 1.5 Hz, 6H; ArH). ¹³C{¹H} NMR (151 MHz, d₈-THF): δ (ppm) 24.47, 24.71, 25.23 (s, CH(CH₃)₂), 30.70, 35.20 (s, CH(CH₃)₂), 118.21 (d, J_P–C = 5.5 Hz), 120.43 (d, J_P–C = 2.1 Hz), 128.64 (d, J_P–C = 11.6 Hz), 128.83 (s), 128.86 (s), 128.94 (s), 129.43 (s), 130.12-130.25 (m), 130.34 (d, J_P–C = 4.5 Hz), 130.73 (s), 131.30 (d, J_P–C = 2.3 Hz), 132.03 (d, J_P–C = 2.7 Hz), 132.47 (s), 132.59 (d, J_P–C = 2.6 Hz ), 132.65 (d, J_P–C = 2.1 Hz), 132.97-133.08 (m), 134.51 (s), 135.57 (d, J_P–C = 2.0 Hz), 135.96 (d, J_P–C = 5.5 Hz), 138.70 (d, J_P–C = 10.7 Hz ), 139.52 (d, J_P–C = 6.3 Hz), 144.96 (s), 146.97 (d, J_P–C = 5.5 Hz), 147.23 (s), 147.88 (s) (ArC). ⁷⁷Se NMR (95.4 MHz, d₈-THF): δ (ppm) 512.7 (d, J_P–Se = 398.7 Hz ). ³¹P{¹H} NMR (162 MHz, C₆D₆): δ (ppm) − 23.2 with two satellites at − 24.5 and − 22.0 (s, J_P–Se = 398.7 Hz), 21.0 (s, Ph₃P = N = PPh₃). HRMS(m/z): [Anion]⁺ calcd. For C₉₀H₁₁₁NPOSe₂, 1412.6739; found 1412.6758.

Ghosh, P. N. & Ball, G. N. Die Ultravioletten Banden des Phosphoroxyds. Z. Phys. 71, 362–370 (1931).
Tenenbaum, E. D.; Woolf, N. J. & Ziurys, L. M. Identification of Phosphorus Monoxide (X²Π_r) in VY Canis Majoris: Detection of the First P–O Bond in Space. Astrophys. J. 666, L29–L32 (2007).
Chu, X.; Qian, W.; Lu, B.; Wang, L.; Qin, J.; Li, J.; Rauhut, G.; Trabelsi, T.; Francisco, J. S. & Zeng X. The Triplet Hydroxyl Radical Complex of Phosphorus Monoxide. Angew. Chem. Int. Ed. 59, 21949 –21953 (2020).
a) Fast, D. E.; Zalibera, M.; Lauer, A.; Eibel, A.; Schweigert, C.; Kelterer, A.-M.; Spichty, M.; Neshchadin, D.; Voll, D.; Ernst, H.; Liang, Y.; Dietliker, K.; Unterreiner, A. N.; Barner-Kowollik, C.; Grützmacher, H. & Gescheidt, G. Bis(mesitoyl)phosphinic Acid: Photo-Triggered Release of Metaphosphorous Acid in Solution. Chem. Commun. 52, 9917–9920 (2016); b) Liang, S.; Hemberger, P.; Neisius, N. M.; Bodi, A.; Grützmacher, H.; Levalois-Grützmacher, J. & Gaan, S. Elucidating the Thermal Decomposition of Dimethyl Methylphosphonate by Vacuum Ultraviolet (VUV) Photoionization: Pathways to the PO Radical, a Key Species in Flame-Retardant Mechanisms. Chem. Eur. J. 21, 1073–1080 (2015); c) Qian, W. Y.; Chu, X. X.; Song, C.; Wu, Z.; Jiao, M. Q.; Liu, H. W.; Zou, B.; Rauhut, G.; Tew, D. P.; Wang, L. N. & Zeng, X. Q. Hydrogen-Atom Tunneling in Metaphosphorous Acid. Chem. Eur. J. 26, 8205–8209 (2020).
Chu, X. X.; Yang, Y.; Lu, B.; Wu, Z.; Qian, W. Y.; Song, C.; Xu, X. F.; Abe, M. & Zeng, X. Q Methoxyphosphinidene and Isomeric Methylphosphinidene Oxide J. Am. Chem. Soc. 140, 13604–13608 (2018).
Zhao, X. F.; Chu, X. X.; Rauhut, G.; Chen, C. Y.; Song, C.; Lu, B. & Zeng, X. Q. Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH₃OPO and CH₃PO₂. Angew. Chem. Int. Ed. 58, 12164–12169 (2019).
Mardyukov, A.; Keul, F. & Schreiner, P. R. Isolation and Characterization of the Free Phenylphosphinidene Chalcogenides C₆H₅P=O and C₆H₅P=S, the Phosphorous Analogues of Nitrosobenzene and Thionitrosobenzene. Angew. Chem. Int. Ed. 59, 12445–12449 (2020).
Johnson, M. J. A.; Odom, A. L. & Cummins, C. C. Phosphorus Monoxide as a Terminal Ligand Chem. Commun. 1523–1524 (1997).
a) Stille, J. K.; Eichelberger, J. L.; Higgins, J. & Freeburger, M. E. Phenylphosphinidene Oxide. Thermal Decomposition of 2,3-Benzo-l,4,5,6,7-pentaphenyl-7-phosphabicyclo-[2.2.1]hept-5-ene Oxide. J. Am. Chem. Soc. 94, 4761–4763 (1972); b) Yoshifuji, M.; Nakayama, S.; Okazaki, R. & Inamoto, N. Phosphinidenes and Related Intermediates. Part 1. Reactions of Phosphinoylidenes (R–P=O) and Phosphinothioylidenes (R–P=S) with Diethyl Disulphide and Benzl. J. Chem. Soc., Perkin Trans. 2065–2068 (1973); c) Shigenobu, N.; Masaaki, Y.; Renji, O. & Naoki, I. Phosphinidenes and Related Intermediates. III. Reactions of Phosphinylidenes and Phosphinothioylidenes with Conjugated Dienes. Bull. Chem. Soc. Jpn. 48, 546–548 (1975); d) Niecke, E.; Zorn, H.; Krebs, B. & Henkel, G. (R₂NPO)₃: A Novel Heterocycle with λ³-Phosphorus by Trimerization of an Aminooxophosphane. Angew. Chem., Int. Ed. Engl. 19, 709–710 (1980); e) Cowley, A. H.; Gabbaï, F. P.; Corbelin, S. & Decken, A. Synthesis and Thermolysis of a Phosphorus(III) Oxalate. Evidence for the Generation of an Arylphosphinidene Oxide. Inorg. Chem. 34, 5931–5932 (1995); f) Gaspar, P. P.; Qian, H.; Beatty, A. M.; d’Avignon, D. A.; Kao, J. L. F.; Watt, J. C. & Rath, N. P. 2,6-Dimethoxyphenylphosphirane Oxide and Sulfide and their Thermolysis to Phosphinidene Chalcogenides—Kinetic and Mechanistic Studies. Tetrahedron 56, 105–119 (2000).
Quin, L. D.; Jankowski, S.; Sommese, A. G.; Lahti, P. M. & Chesnut, D. B. The First Direct Observation of a Phosphenite. J. Am. Chem. Soc. 114, 11009–11010 (1992).
Niecke, E.; Engelmann, M.; Zorn, H.; Krebs, B. & Henkel, G. Complex-Stabilization of an Aminooxophosphane (Phosphinidene Oxide). Angew. Chem., Int. Ed. Engl. 19, 710–712 (1980).
a) Alonso, M.; García, M. E.; Ruiz, M. A.; Hamidov, H. & Jeffery, J. C. Chemistry of the Phosphinidene Oxide Ligand. J. Am. Chem. Soc. 126, 13610–13611 (2004); b) Alonso, M.; Alvarez, M. A.; García, M. E.; Ruiz, M. A.; Hamidov, H. & Jeffery, J. C. Oxidation Reactions of the Phosphinidene Oxide Ligand. J. Am. Chem. Soc. 127, 15012–15013 (2005); c) Alonso, M.; Alvarez, M. A.; García, M. E.; García-Vivó, D. & Ruiz, M. A. Inorg. Chem. Chemistry of the Oxophosphinidene Ligand. 1. Electronic Structure of the Anionic Complexes [MCp{P(O)R*}(CO)₂]⁻ (M = Mo, W; R* = 2,4,6-C₆H₂^tBu₃) and Their Reactions with H⁺ and C-Based Electrophiles. Inorg. Chem. 49, 8962–8976 (2010); d) Alonso, M.; Alvarez, M. A.; García, M. E.; Ruiz, M. A.; Hamidov, H. & Jeffery, J. C. Chemistry of the Oxophosphinidene Ligand. 2. Reactivity of the Anionic Complexes [MCp{P(O)R*}(CO)₂]⁻ (M = Mo, W; R* = 2,4,6-C₆H₂^tBu₃) Toward Electrophiles Based on Elements Different from Carbon. Inorg. Chem. 49, 11595–11605 (2010).
Liu, L. L. & Stephan, D. W. An Imine–Gallium Lewis Pair Stabilized Oxophosphinidene via an Unexpected Phosphirene Rearrangement. Chem. Commun. 54, 1041–1044 (2018).
Dhara, D.; Pal, P. K.; Dolai, R.; Chrysochos, N.; Rawat, H. Elvers, B. J.; Krummenacher, I.; Braunschweig, H.; Schulzke, C.; Chandrasekhar, V.; Priyakumar, U. D. & Jana, A. Synthesis and Reactivity of NHC-Coordinated Phosphinidene Oxide. Chem. Commun. 57, 9546–9549 (2021).
Baradzenka, A. G.; Vyboishchikov, S. F.; Pilkington, M. & Nikonov, G. I. Base-Stabilized Phosphinidene Oxide, Imide and Sulfide. Chem. Eur. J. 29, e202301842 (2023).
a) Goto, K.; Yamamoto, G.; Tan, B. & Okazaki, R. A Novel Dendrimer-Type m-Terphenyl Substituent for the Kinetic Stabilization of Highly Reactive Species. Tetrahedron Lett. 42, 4875–4877 (2001); b) Shimada, K.; Goto, K.; Kawashima, T.; Takagi, N.; Choe, Y.-K. & Nagase, S. Isolation of a Se-Nitrososelenol: A New Class of Reactive Nitrogen Species Relevant to Protein Se-Nitrosation. J. Am. Chem. Soc. 126, 13238–13239 (2004); c) Masuda, R.; Kimura, R.; Karasaki, T.; Sase, S. & Goto, K. Modeling the Catalytic Cycle of Glutathione Peroxidase by Nuclear Magnetic Resonance Spectroscopic Analysis of Selenocysteine Selenenic Acids. J. Am. Chem. Soc. 143, 6345–6350 (2021); d) Masuda, R.; Kuwano, S. & Goto, K. Modeling Selenoprotein Se-Nitrosation: Synthesis of a Se-Nitrososelenocysteine with Persistent Stability. J. Am. Chem. Soc. 145, 14184–14189 (2023).
a) Goicoechea, J. M. & Grützmacher, H. The Chemistry of the 2-Phosphaethynolate Anion. Angew. Chem. Int. Ed. 57, 16968–16994 (2018); b) Hinz, A. & Goicoechea, J. M. The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes. Angew. Chem. Int. Ed. 55, 8536–8541 (2016); c) Tambornino, F.; Hinz, A.; Köppe, R. & Goicoechea, J. M. A General Synthesis of Phosphorus- and Arsenic-Containing Analogues of the Thio- and Seleno-cyanate Anions. Angew. Chem. Int. Ed. 57, 8230–8234 (2018); d) Ergöçmen, D. & Goicoechea, J. M. Synthesis, Structure and Reactivity of a Cyapho-Cyanamide Salt. Angew. Chem. Int. Ed. 60, 25286–25289 (2021); e) Hu, C. & Goicoechea, J. M. Synthesis, Structure and Reactivity of a Cyapho(dicyano)methanide Salt. Angew. Chem. Int. Ed. 61, e202208921 (2022).
Hinz, A.; Labbow, R.; Rennick, C.; Schulz, A. & Goicoechea, J. M. HPCO—A Phosphorus-Containing Analogue of Isocyanic Acid. Angew. Chem. Int. Ed. 56, 3911–3915 (2017).
Niecke, E.; Nieger, M. & Reichert, F. Arylmino(halogeno)phosphanes XP=NC₆H₂tBu₃ (X = Cl, Br, I) and the Iminophosphenium Tetrachloroaluminate [P≡NC₆H₂tBu₃]^⊕[AlCl₄]^⊖: the First Stable Compound with a PN Triple Bond. Angew. Chem. Int. Ed. Engl. 27,1715–1716 (1988).
a) Morell, C.; Grand, A. & Toro-Labbé, A. New Dual Descriptor for Chemical Reactivity. J. Phys. Chem. A 109, 205–212 (2005); b) Lu, T. & Chen, F. Multiwfn: A Multifunctional Wavefunction Analyzer. J. Comput. Chem. 33, 580–592 (2012); c) Lu, T. & Chen Q., in Conceptual Density Functional Theory (Liu, S. ed.), Wiley-VCH: Weinheim, Germany, pp. 631–647 (2022).
Pyykkö, P. & Atsumi, M. Molecular Single-Bond Covalent Radii for Elements 1–118. Chem. Eur. J. 15, 186–197 (2009).
Rayner-Canham, G. Isodiagonality in the periodic table. Found. Chem. 13, 121–129 (2011).
a) Chernega, A. N.; Antipin, M. Y.; Struchkov, Y. T.; Ruban, A. V & Romanenko, V. D. Structure of Organophosphorus Compounds. Part XLII. The Molecular Structure of the 2,6-Di-tert-butyl-4-methylphenyl Ester of N-[2,4,6-Tri(tert-butyl)-phenyl]Phosphenimidous Acid. J. Struct. Chem. 30, 957–962 (1989); b) Chernega, A. I.; Antipin, M. Y.; Struchkov, Y. T.; Ruban, A. V. & Romanenko, V. D. The Structure of Organophosphorus Compounds. Part XLIV. The Molecular Structure of the 2-Methylphenyl Ester of N-[2,4,6-tri(tert-butyl)phenyl] Imidophosphenous Acid. J. Struct. Chem. 31, 301–306 (1990); c) Niecke, E.; Detsch, R.; Nieger, M.; Reichert, F. & Schoeller, W. From Covalent to Ionic Bonding – Spontaneous Bond-Dissociation in Oxy-Substituted Iminophosphanes. Bull. Soc. Chim. Fr. 130, 25–31 (1993); d) Pötschke, N.; Barion, D.; Nieger, M. & Niecke, E. Chirale Iminophosphane durch Reaktion von Lithiumalkoholaten mit Chlor-(2,4,6-tri-tert.-butylphenylimino)phosphan. Tetrahedron 51, 8993–8996 (1995); e) Chernega, A. N & Romanenko, V. D. Molecular Structure of the (−)Menthyl Ester of N-(2,4,6-Tri-tert-butylphenyl)Imidophosphinous Acid. J. Struct. Chem. 37, 364–366 (1996); f) Kuprat, M.; Kuzora, R.; Lehmann, M.; Schulz, A.; Villinger, A. & Wustrack, R. Silver Tetrakis(hexafluoroisopropoxy)Aluminate as Hexafluoroisopropyl Transfer Teagent for the Chlorine/Hexafluoroisopropyl Exchange in Imino Phosphanes. J. Organomet. Chem. 695, 1006–1011 (2010); g) Eckhardt, A. K.; Riu, M.-L. Y.; Müller, P.; Cummins, C. C. Frustrated Lewis Pair Stabilized Phosphoryl Nitride (NPO), a Monophosphorus Analogue of Nitrous Oxide (N₂O). J. Am. Chem. Soc. 143, 21252–21257 (2021).
Liu, Z.; McKay, A. I.; Zhao, L.; Forsyth, C. M.; Jevtović, V.; Petković, M.; Frenking, G. & Vidović, D. Carbodiphosphorane-Stabilized Parent Dioxophosphorane: A Valuable Synthetic HO₂P Source. J. Am. Chem. Soc. 144, 7357–7365 (2022).
Greenwood, N. N. & Earnshaw, A. Chemistry of the Elements (2^nd ed.), Elsevier Butterworth-Heineman: Oxford (2005).
V. Kostina, N. Feshchenko, A. Kirsanov, Zh. Obs. Khim. 1973, 43, 209.
Gonsior, M.; Müller, L. & Krossing, I. Lewis Acid Stabilized OPI₃: Implications for the Nature of Free OPI₃. Chem. Eur. J. 12, 5815–5822 (2006).
Yandulov, D. V. & Schrock, R. R. Reduction of Dinitrogen to Ammonia at a Well-Protected Reaction Site in a Molybdenum Triamidoamine Complex. J. Am. Chem. Soc. 124, 6252–6253 (2002).
Bailey, P. J.; Coxall, R. A.; Dick, C. M.; Fabre, S.; Henderson, L. C.; Herber, C.; Liddle, S. T.; Loroño-González, D.; Parkin, A. & Parsons, S. The First Structural Characterisation of a Group 2 Metal Alkylperoxide Complex: Comments on the Cleavage of Dioxygen by Magnesium Alkyl Complexes. Chem. Eur. J. 9, 4820–4828 (2003).

Schemes 1 to 3 are available in the Supplementary Files section.

There is NO Competing Interest.

POSI0308NatchemtemplateChenyang.docx
Supplementary Information for publication
2.cif
X-ray data compound 2
3.cif
X-ray data compound 3
4.cif
X-ray data compound 4
5.cif
X-ray data compound 5
6.cif
X-ray data compound 6
7.cif
X-ray data compound 7
8.cif
X-ray data compound 8
S2.cif
X-ray data compound S2
S3.cif
X-ray data compound S3
Schemes1to3.docx

Download PDF

Journal Publication

published 15 Jul, 2024

Read the published version in Nature Chemistry →

Version 1

posted

You are reading this latest preprint version

An Isolable Phosphinidene Oxide

Status:

Journal Publication

Version 1

Abstract

Figures

1. Introduction

2. Result and Discussion

2.1 Isolation of anionic imine stabilized phosphinidene oxide RNPO^–

2.2. Functionalization of RNPO^– with electrophiles

2.3 Formal oxidation reactions from P(III) to P(V)

3. Conclusions

Declarations

Methods

References

Schemes

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1

An Isolable Phosphinidene Oxide

Status:

Journal Publication

Version 1

Abstract

Figures

1. Introduction

2. Result and Discussion

2.1 Isolation of anionic imine stabilized phosphinidene oxide RNPO–

2.2. Functionalization of RNPO– with electrophiles

2.3 Formal oxidation reactions from P(III) to P(V)

3. Conclusions

Declarations

Methods

References

Schemes

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1

2.1 Isolation of anionic imine stabilized phosphinidene oxide RNPO^–

2.2. Functionalization of RNPO^– with electrophiles