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Methoxyphosphinidene and Isomeric Methylphosphinidene Oxide Xianxu Chu, Yang Yang, Bo Lu, Zhuang Wu, Weiyu Qian, Chao Song, Xinfang Xu, Manabu Abe, and Xiaoqing Zeng J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b09201 • Publication Date (Web): 09 Oct 2018 Downloaded from http://pubs.acs.org on October 10, 2018

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Journal of the American Chemical Society

Methoxyphosphinidene and Isomeric Methylphosphinidene Oxide Xianxu Chu,¶ Yang Yang,¶ Bo Lu,¶ Zhuang Wu,¶ Weiyu Qian,¶ Chao Song,¶ Xinfang Xu,¶ Manabu Abe,‡ Xiaoqing Zeng*,¶ ¶

College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China. ‡Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima Hiroshima 739-8526, Japan.

Supporting Information Placeholder ABSTRACT: A rare oxyphosphinidene (Me–OP) has been generated in the triplet ground state through either photolysis (266 nm) or flash-vacuum pyrolysis (FVP, 700 °C) of methoxydiazidophosphine MeOP(N3)2. Upon ArF laser irradiation (193 nm), an unprecedented isomerization from Me–OP to the long-sought methylphosphinidene oxide (Me–PO) occurs in cryogenic Ne- and N2-matrices. Alternatively, the latter can be efficiently generated through photolysis (193 nm) or FVP (ca. 700 °C) of methylphosphoryl diazide MeP(O)(N3)2, in which the elusive nitrene intermediate MeP(O)(N3)N in the triplet ground state has been also observed by IR (with 15N-labeling) and EPR (|D/hc| = 1.545 cm–1 and |E/hc| = 0.00395 cm–1) spectroscopy.

Phosphinidenes R–P are fleeting species that feature as heavier congeners of nitrenes R–N.1 As a class of low-valent organophosphorus compounds (OPCs), phosphinidenes keep attracting enormous interest, not only due to broad applications as in situ phosphorus reagents in synthetic chemistry;2 they also form isolable complexes with diverse carbenes and transition metals in which the terminal phosphorus atom can be either nucleophilic or electrophilic.3 In contrast to the intensively explored in situ trapping and coordination chemistry of phosphinidenes, the attempts to obtain fundamental knowledge about the highly reactive “naked” phosphinidenes (Scheme 1) such as the parent molecules H–P (1),4 Me–P (2),5 Ph–P (3),6 and CH2=CH–P (4)7 are largely hampered by the facile inter- or intramolecular reactions under the formation conditions. Scheme 1. Typical phosphinidenes 1–7, oxyphosphinidene 8, and its isomer 9.

Intensive computational studies on Me–P (2) suggest a triplet ground state,5 resembling the well-established analogous nitrene Me–N.8 Despite the large barriers (> 20 kcal mol–1) for the rearrangement to phosphaethene CH2=PH,5,9 Me–P remains as yet

unobserved. Recently, triplet phenylphosphinidene Ph–P (3) has been generated in solid Ar-matrix through photoelimination of ethylene from the corresponding phenylphosphirane, and its oxidation to phenyldioxophosphorane was observed.6a By analogy, triplet mesitylphosphinidene (5) has been generated and spectroscopically characterized.10 The formation of silylphosphinidene from the reaction of atomic silicon and phosphane in Ar-matrix has also been reported.11 Thanks to the stabilizing donation of the lone-pair electrons of adjacent phosphorus or nitrogen atoms to the electron-deficient phosphinidene center, isolable (phosphino)phosphinidenes (R2P=P, 6)12 and transient aminophosphinidenes (R2N=P, 7)13 have been structurally characterized in the solid state and detected in the gas phase by mass spectrometry, respectively. Unlike alkyl-, aryl-, vinyl-, silyl-, phosphino-, and aminophosphinidenes, oxyphosphinidenes such as methoxyphosphinidene Me–OP (8) have been barely investigated; only the intriguing parent molecule H–OP has been computationally explored.14 According to the CCSD(T)/aug-cc-pVXZ calculation, H–OP prefers a triplet ground state with a singlet-triplet energy gap of 15.4 kcal mol–1, and the barrier for its isomerization to H–PO is 30.5 kcal mol–1.14a Phosphinidene oxides have been proposed as reactive organophosphorus synthons that can be either chemically trapped or coordinated with metals.15 The parent molecule H–PO has been identified as one of the emitting species in the chemiluminescence of white phosphorus16 and in the oxidation of phosphine.17 The spectroscopy and structure of H–PO have been thoroughly studied.18 Methylphosphinidene oxide Me–PO (9), an intermediate in the decomposition of flame-retardant methylphosphonate19 and an astrobiologically relevant candidate,20 is hitherto unknown experimentally, although the structures of Me– PO and its Cr(CO)5 complexes have been studied computationally.21 Although an isomerization between oxyphosphinidene R–OP and phosphinidene oxide R–PO remains hitherto unknown, similar transformation has been disclosed for sulfur-centered radicals R– SO• → R–OS• (R= CF3 and Ph).22 Additionally, the heavier congeners H–PS and HS–P have been detected with neutralizationreionization mass spectrometry.23 Continuing our interest in phosphorus-containing small molecules (e.g., OPN/PNO24 and OPNCO25), herein, we report a first-time generation, characterization, and photoisomerization of methoxyphosphinidene (8) and methylphosphinidene oxide (9, Scheme 2).

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Scheme 2. Generation of Me–OP (8) and Me–PO (9).

The generation of Me–OP (8) was performed first by 266 nm laser photolysis of the highly explosive geminal diazide MeOP(N3)2 (Figure 1A) in solid Ne-matrix at 3 K. In the IR spectrum of the photolysis products (Figure 1B), the IR bands for the precursor vanish completely. In addition to HN3 (a; 3344.6, 2292.8, 2142.3, 1267.6, and 539.8 cm–1)26 and other unknown impurities arising from the synthesis of the diazide, a new species (c) with a set of IR bands at 2986.5, 2952.7, 2846.2, 1467.0, 1046.6/1029.3, and 756.9 cm–1 forms (Figure S1). These band positions coincide with the computed anharmonic IR frequencies for the most likely candidate species Me–OP in its triplet ground state (2997, 2958, 2911, 1466, 1052, and 751 cm–1, CCSD(T)/cc-pVTZ, Table S1). 0.8

a: HN3 b: MeOP(N3)2 c: MeOP d: MePO

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Figure 1. (A) IR spectrum of Ne-matrix isolated MeOP(N3)2. (B) IR spectrum of the Ne-matrix isolated laser photolysis (266 nm, 95 min) products of MeOP(N3)2. (C) IR difference spectrum reflecting the change of the Ne-matrix upon a 193 nm laser irradiation (6 min). The bands of impurities are marked with asterisks. For clarity, spectra B and C are 5-fold expanded along the vertical axis. To distinguish the IR bands of Me–OP, the matrix was subjected to an ArF excimer laser (193 nm) irradiation. The carrier of the aforementioned seven IR bands vanishes (Figure 1C). The selective depletion allows the identification of an additional weak band at 1172.6 cm–1 for Me–OP, which is also very close to the calculated IR frequency at 1169 cm–1. According to the computed vibrational displacement vectors, the strongest IR band observed at 1046.6 cm–1 corresponds to the stretching vibration mode (C–O), which exhibits a weaker matrix-site splitting band at 1029.3 cm–1. It is close to that of the (C–O) mode in CH3–OH (1034.6 cm–1, N2-matrix).27 Among the photolysis products, mainly a new species occurs with IR bands at 1249.9, 1194.7, 830.9, and 653.3 cm– 1 . The positions agree with the CCSD(T)/cc-pVTZ computed IR frequencies of 1245, 1184, 836, and 633 cm–1 for Me–PO (Table S2). The two bands at 1194.7 and 653.3 cm–1 associate with the (P=O) and (C–P) stretching vibrations, respectively. In line with the electronegativity of the substituents (F > Cl > Me), the frequency for (P=O) in Me–PO is lower than those in Cl–PO (1258 cm–1, Ar-matrix)28 and F–PO (1292.5 cm–1, Ar-matrix).29 The photo-induced isomerization from Me–OP to Me–PO is fully

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reproducible in solid N2-matrix (Figure S2), where the observed IR band positions of Me–OP (2984.8, 2951.1, 2845.0, 1464.5, 1176.3, 1037.0/1028.0, and 757.3/747.4 cm–1) and Me–PO (1248.8, 1192.5/1189.8, 833.6, and 646.5 cm–1) shift slightly, implying weak interactions with the surrounding molecules within the matrix cages. In order to aid the identification of Me–PO, a more straightforward method for producing this species through the decomposition of methylphosphoryl diazide MeP(O)(N3)2 was applied. Upon a 193 nm laser irradiation, the diazide decomposes and yields Me–PO (d; Figure 2A). Concomitantly, another species bearing two IR bands at 2168.3 and 1288.9 cm–1 forms. The former is right between the two IR bands at 2179.5 and 2162.2 cm–1 for the two asymmetric N3 stretching vibrations (in-phase and out-ofphase) in MeP(O)(N3)2. Therefore, they belong very likely to the nitrene intermediate MeP(O)(N3)N. Given the computed intense absorption at 378 nm for MeP(O)(N3)N (Table S3), the matrix was subsequently exposed to the UV light (365 nm), leading to the sole depletion of the corresponding carrier (Figure 2B). Consequently, Me–PO (d), N3• (1648.7 cm–1),30 and an unknown species with an IR band at 1311.3 cm–1 were produced. The identification of triplet MeP(O)(N3)N is supported by the good agreement with the calculated IR spectrum (Table S4) and the 15N-labeling experiments (Figure S3).

Intensity

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Figure 2. (A) IR difference spectrum reflecting the change of the N2-matrix isolated MeP(O)(N3)2 upon the 193 nm laser irradiation (13 min). (B) IR difference spectrum reflecting the change of the N2-matrix upon subsequent 365 nm UV light irradiation (10 min). (C) The EPR spectra of the 266 nm laser photolysis products of MeP(O)(N3)2 in solid toluene at 5 K. Spectrum B is 5-fold expanded along the vertical axis for clarity, and the band of an unknown species is marked with asterisk. In spectrum C, the derived zero-field splitting parameters for MeP(O)(N3)N (signal I) are |D/hc| = 1.545 cm–1 and |E/hc| = 0.00395 cm–1; signal II (|D/hc| = 0.973 cm–1 and |E/hc| = 0.0017 cm–1) is tentatively assigned to ptoluene nitrene (|D/hc| = 0.978 cm–1 and |E/hc| < 0.002 cm–1).31 The formation of triplet MeP(O)(N3)N is confirmed by the observation of typical nitrene signals in the EPR spectrum of the 266 nm laser photolysis products of MeP(O)(N3)2 in solid toluene at 5 K (Figure 2C). The derived zero-field splitting parameters (ZFSPs) for MeP(O)(N3)N (|D/hc| = 1.545 cm–1 and |E/hc| = 0.00395 cm–1) are similar to those of FP(O)(N3)N (|D/hc| = 1.566 cm–1 and |E/hc| = 0.005 cm–1).29 Our attempts to obtain an EPR spectrum of MeOP failed since the signal is probably beyond the range of the Xband Bruker ELEXSYS E500 spectrometer (0–14500 G). Unexpectedly, a nitrene signal at 8220 G (|D/hc| = 1.535 cm–1 and |E/hc| = 0.0020 cm–1) was observed in the 266 nm laser photolysis


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of MeOP(N3)2 (Figures S5 and S6). The absence of the EPR signals for Me–OP is in line with the dramatic shift of the EPR signals of mesitylphosphinidene at 12750 and 12880 G (|D/hc| = 4.116 cm–1)10a comparing to that of p-toluene nitrene (6646.0 G, |D/hc| = 0.978 cm–1).31 Furthermore, spin-orbit coupling may have significant contribution to magnetic anisotropy in Me–OP, which can mix with the zwitterionic singlet (Me–O+=P–) as frequently observed in the analogous oxynitrenes (8000–10000 G, |D/hc| ≈ 2 cm–1).32 The generation of Me–OP and Me–PO can be independently performed in the gas phase through flash vacuum pyrolysis (FVP) of the respective precursors MeOP(N3)2 (Figure S7) and MeP(O)(N3)2 (Figure S8) at about 700 °C. It is noteworthy that both are thermally persistent in the gas phase, no noticeable IR bands for the fragmentation products (Me• and PO•) were observed. In contrast, Me–OP and Me–PO are photolabile. In addition to the photoisomerization from Me–OP to Me–PO, depletion of Me–PO occurs under the 193 nm laser irradiation (Figure S9), and the isomer CH2=P–OH with IR bands at 3632.5, 3145.6, 1367.2, 1070.2, 977.6, 829.4, 766.8, and 757.9 cm–1 can be tentatively identified by comparing with the computed frequencies at 3637, 3081, 1367, 1039, 983, 823, 764, and 752 cm–1 (Table S5). To estimate the thermal stability of Me–OP and Me–PO in the gas phase, the energy profiles for their interconversion (Figure 3) and isomerization with CH2=P(O)H and CH2=P–OH (Figure S10) were computed. Consistent with the observation in cryogenic matrices, computations conclusively suggest a triplet and singlet ground-state multiplicity for Me–OP and Me–PO (Table S6), and the singlet–triplet gaps (EST) are +15.7 and –42.9 kcal mol–1, respectively.

phase spectroscopic techniques such as microwave spectroscopy.33 In conclusion, two prototypical low-valent organophosphorus compounds (OPCs), oxyphosphinidene (Me–OP) and phosphinidene oxide (Me–PO), have been generated and spectroscopically characterized for the first time. And, the stepwise photoisomerization from Me–OP to singlet Me–PO as followed by H-shift to CH2=P–OH has been observed in cryogenic matrices. The results from IR spectroscopy and quantum chemical calculations confirm a triplet ground state for Me–OP. Consistent with the theoretically calculated large barriers (> 30 kcal mol–1) for the isomerization reactions, both Me–OP and Me–PO can be also produced in the gas phase through the pyrolysis of their respective azide precursors MeOP(N3)2 and MeP(O)(N3)2 at ca. 700 ºC, thus enabling further studies of on their structures and reactivities as ligand-free species, such as the hitherto unexplored oxidation of oxyphosphinidenes and phosphinidene oxides with molecular oxygen, which is currently ongoing in our group.

ASSOCIATED CONTENT Supporting Information

Experimental details, theoretical methods, observed and calculated IR spectra, calculated vertical transition energies, atomic coordinates, and total energies, including Figures S1−S13 and Tables S1−S5 (PDF). This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author

[email protected]

Notes The authors declare no competing financial interests.

ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (21673147) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). We gratefully acknowledge Prof. C. Wentrup, Prof. P. R. Schreiner, and Dr. A. Mardyukov for stimulating suggestions.

REFERENCES Figure 3. Calculated potential energy profiles for the interconversion between Me–OP and Me–PO in the singlet and triplet states at the CCSD(T)/aug-cc-pVTZ//B3LYP/6-311++G(3df,3pd) levels. Molecules structures (bond lengths in Å, angles in ° in italics) calculated at the CCSD(T)/cc-pVTZ level are given. Importantly, the barriers for the isomerization, either in the singlet or triplet state, are larger than 40 kcal mol–1 (Figure 3), rendering their thermal interconversion unlikely even under the pyrolysis conditions (700 °C). The cleavage of the C–O in triplet Me–OP → Me• + PO• needs to surmount a lower barrier of 33.9 kcal mol– 1 , implying that the observed Me–OP → Me–PO photoisomerization occurs probably by dissociation (→ Me• + OP•) and recombination. The H-shifts in Me–PO to CH2=P–OH and CH2=P(O)– H need to overcome overwhelming barriers of 53.9 and 56.7 kcal mol–1, respectively. Therefore, Me–OP and Me–PO are thermally persistent species in the gas phase, and the determination of their molecular structures should be feasible by using suitable gas-

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(14) (a) Francisco, J. S. Accurate ab initio spectroscopic properties of HOPx and HPOx (x=−1,0,+1). Chem. Phys. 2003, 287, 303–316. (b) Benkő, Z.; Streubel, R.; Nyulászi, L. Stability of phosphinidenes-Are they synthetically accessible? Dalton Trans. 2006, 4321–4327. (c) Nguyen, M. T.; Keer, A. V.; Vanquickenborne, L. G. In search of singlet phosphinidenes. J. Org. Chem. 1996, 61, 7077–7084. (15) For examples, see: (a) 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. 2005, 127, 15012–15013. (b) Niecke, E.; Engelmann, M.; Zorn, H.; Krebs, B.; Henkel, G. Complexstabilization of an aminooxophosphane (phosphinidene oxide). Angew. Chem., Int. Ed. 1980, 19, 710–712. (c) Alonso, M.; García, M. E.; Ruiz, M. A.; Hamidov, H.; Jeffery, J. C. Chemistry of the phosphinidene oxide ligand. J. Am. Chem. Soc. 2004, 126, 13610–13611. (16) Sterenberg, B. T.; Scoles, L.; Carty, A. J. Synthesis, structure, bonding and reactivity in clusters of the lower phosphorus oxides. Coord. Chem. Rev. 2002, 231, 183−197. (17) (a) Withnall, R.; Andrews, L. FTIR spectra of the photolysis products of the phosphine-ozone complex in solid argon. J. Phys. Chem. 1987, 91, 784−797. (b) Bauschlicher, Jr.; C. W. Heats of formation for POn and POnH (n = 1−3). J. Phys. Chem. A 1999, 103, 11126−11129. (18) Tackett, B. S.; Clouthier, D. J. HPO does not follow Walsh’s rules! Improved molecular structures from the spectroscopy of jet-cooled HPO and DPO. J. Chem. Phys. 2002, 117, 10604−10612, and references therein. (19) Liang, S.; Hemberger, P.; Neisius, N. M.; Bodi, A.; Grützmacher, H.; Levolois-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. 2015, 21, 1073−1080. (20) Lattelais, M.; Pauzat, F.; Pilmé, J.; Ellinger, Y. Electronic structure of simple phosphorus containing molecules [C,xH,O,P] candidate for astrobiology (x=1, 3, 5). Phys. Chem. Chem. Phys. 2008, 10, 2089−2097. (21) Krahe, O.; Neese, F.; Streubel, R. The quest for ring opening of oxaphosphirane complexes: a coupled-cluster and density functional study of CH3PO isomers and their Cr(CO)5 complexes. Chem. –Eur. J. 2009, 15, 2594−2601. (22) Xu, J.; Wu, Z.; Wan, H. B.; Deng, G. H.; Eckhardt, A. K.; Schreiner, P. R.; Trabelsi, T.; Francisco, J. S.; Zeng, X. Q. Phenylsulfinyl radical: gas-phase generation, photoisomerization, and oxidation. J. Am. Chem. Soc. 2018, 140, 9972–9978, and referenences therein. (23) Wong, T.; Terlouw, J. K.; Keck, H.; Kuchen, W.; Tommes, P. The thioxophosphane HP=S and its tautomer HSP, (thiohydroxy)phosphinidene, are stable in the gas phase. J. Am. Chem. Soc. 1992, 114, 8208−8210. (24) Zeng, X. Q.; Beckers, H.; Willner, H. Elusive O=P≡N, a rare example of phosphorus σ2λ5-coordination. J. Am. Chem. Soc. 2011, 133, 20696−20699. (25) Wu, Z.; Song, C.; Liu, J.; Lu, B.; Lu, Y.; Trabelsi, T.; Francisco, J. S.; Zeng, X. Q. Photochemistry of OPN: formation of cyclic PON and reversible combination with carbon monoxide. Chem. –Eur. J. 2018, 24, 14627–14630. (26) Himmel, H.-J.; Junker, M.; Schnöckel, H. On the reactivity of NH formed from photoinduced decomposition of HN3 in an Ar matrix at 12 K toward N2 and CO: A combined matrix isolation and quantum chemical study. J. Chem. Phys. 2002, 117, 3321–3326. (27) Bakkas, N.; Bouteiller, Y.; Loutellier, A.; Perchard, J. P.; Racine, S. The water-methanol complexes. I. A matrix isolation study and an ab initio calculation on the 1-1 species. J. Chem. Phys. 1993, 99, 3335−3342. (28) Schnöckel, H.; Schunck, S. Hochtemperaturhydrolyse von PCl3 und PBr3: IR-spektroskopischer Nachweis der matrixisolierten Moleküle OPCl und OPBr. Z. Anorg. Allg. Chem. 1987, 548, 161−164. (29) Li, D. Q.; Li, H. M.; Zhu, B. F.; Zeng, X. Q.; Willner, H.; Beckers, H.; Neuhaus, P.; Grote, D.; Sander, W. Decomposition of fluorophosphoryl diazide: a joint experimental and theoretical study. Phys. Chem. Chem. Phys. 2015, 17, 6433−6439. (30) Andrews, L.; Zhou, M. F.; Chertihin, G. V.; Bare, W. D.; Hannachi, Y. Reactions of laser-ablated aluminum atoms with nitrogen atoms and molecules. Infrared spectra and density functional calculations for the AlN2, Al2N, Al2N2, AlN3, and Al3N molecules. J. Phys. Chem. A 2000, 104, 1656−1661. (31) (a) Hall, J. H.; Fargher, J. M.; Gisler, M. R. Substituent effects on spin delocalization in triplet phenylnitrenes. 1. Para-substituted phenylnitrenes. J. Am. Chem. Soc. 1978, 100, 2029−2034. (b) Kuzaj, M.; Lüerssen, H.; Wentrup, C. ESR observation of thermally produced triplet nitrenes


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and photochemically produced triplet cycloheptatrienylidenes. Angew. Chem. Int. Ed. Engl. 1986, 25, 480−482 (32) (a) Wentrup, C. Carbenes and nitrenes: recent developments in fundamental chemistry. Angew. Chem., Int. Ed. 2018, 57, 11508−11521. (b) Wasylenko, W. A.; Kebede, N.; Showalter, B. M.; Matsunaga, N.; Miceli, A. P.; Liu, Y.; Ryzhkov, L. R.; Hadad, C. M.; Toscano, J. P. Generation of oxynitrenes and confirmation of their triplet ground states. J. Am. Chem. Soc. 2006, 128, 13142−13150. (33) For an example, see: Nava, M.; Martin-Drumel, M.-A.; Lopez, C. A.; Crabtree, K. N.; Womack, C. C.; Nguyen, T. L.; Thorwirth, S.; Cummins, C. C.; Stanton, J. F.; McCarthy, M. C. Spontaneous and selective formation of HSNO, a crucial intermediate linking H2S and nitroso chemistries. J. Am. Chem. Soc. 2016, 138, 11441−11444.

Table of Contents



Figure 1. (A) IR spectrum of Ne-matrix isolated MeOP(N3)2. (B) IR spectrum of the Ne-matrix isolated laser photolysis (266 nm, 95 min) products of MeOP(N3)2. (C) IR difference spectrum reflecting the change of the Ne-matrix upon a 193 nm laser irradiation (6 min). The bands of impurities are marked with asterisks. For clarity, spectra B and C are 5-fold expanded along the vertical axis. 258x195mm (300 x 300 DPI)


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Figure 2. (A) IR difference spectrum reflecting the change of the N2-matrix isolated MeP(O)(N3)2 upon the 193 nm laser irradiation (13 min). (B) IR difference spectrum reflecting the change of the N2-matrix upon subsequent 365 nm UV light irradiation (10 min). (C) The EPR spectra of the 266 nm laser photolysis products of MeP(O)(N3)2 in solid toluene at 5 K. Spectrum B is 5-fold expanded along the vertical axis for clarity, and the band of an unknown species is marked with asterisk. In spectrum C, the derived zero-field splitting parameters for MeP(O)(N3)N (signal I) are |D/hc| = 1.545 cm–1 and |E/hc| = 0.00395 cm–1; signal II (|D/hc| = 0.973 cm–1 and |E/hc| = 0.0017 cm–1) is tentatively assigned to p-toluene nitrene (|D/hc| = 0.978 cm–1 and |E/hc| < 0.002 cm–1).31 258x195mm (300 x 300 DPI)



Figure 3. Calculated potential energy profiles for the interconversion between Me–OP and Me–PO in the singlet and triplet states at the CCSD(T)/aug-cc-pVTZ//B3LYP/6-311++G(3df,3pd) levels. Molecules structures (bond lengths in Å, angles in ° in italics) calculated at the CCSD(T)/cc-pVTZ level are given. 489x430mm (300 x 300 DPI)


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Graphic abstract 399x215mm (300 x 300 DPI)



Scheme 1. Typical phosphinidenes 1–7, oxyphosphinidene 8, and its isomer 9. 270x133mm (300 x 300 DPI)


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Scheme 2. Generation of Me–OP (8) and Me–PO (9). 270x115mm (300 x 300 DPI)


Methoxyphosphinidene and Isomeric ... - American Chemical Society

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