膦氧化物

氧化膦（英语：Phosphine oxide，也称膦氧化物）是化学式为X₃P=O的含磷化合物。氧化膦可以是有机物或是无机物，当式中X为烷基或芳基时是有机磷化合物（如三苯基氧化膦），当式中X均为卤素时是无机物（如三氯氧磷）^[1]。

结构与分类

氧化膦分子内的P-O键较短且有极性^[2]。学界对P=O键的成因曾有争论，过去认为是氧上的孤对电子填充到磷d轨道上，形成了p-d反馈π键（该理论现在被用于解释氧化胺的不稳定性），然而氧化膦的双键事实上与酰基性质不同，计算化学的结果也并不支持此理论。也有研究用离子键X₃P⁺-O^-来解释其短键长与极性。现在得到较为普遍共识的理论是分子轨道理论的解释，该理论认为P=O键的特性是由于氧p轨道的一对孤对电子填充到P-X键上的反键轨道𝛔*，该理论受从头计算法结果支持^[3]^[4]。

叔氧化膦

叔氧化膦是最常见的氧化膦，其通式为R₃P=O，具四面体分子结构，叔氧化膦可以从叔膦氧化而来。

仲氧化膦

仲氧化膦衍生自仲膦（R₂PH），保持了四面体分子结构^[5]。仲氧化膦可以用作交叉偶联的偶联剂，也可用于合成手性膦配体，如二苯基氧化膦就是一种常见的市售仲氧化膦试剂^[6]。

仲氧化膦可以进一步氧化：

R₂P(O)H + H₂O₂ → R₂P(O)OH + H₂O

仲氧化膦的互变异构体为次亚膦酸（R₂POH）：

R₂P(O)H ⇌ R₂POH

伯氧化膦

伯氧化膦衍生自伯膦，具四面体分子结构。伯氧化膦会发生歧化，得到伯膦和次膦酸^[7]：

2 RP(O)H₂ → RP(O)(H)OH + 2 RPH₂

合成

氧化膦容易由有机膦的氧化合成，室温下空气中的氧气就足以将它们完全转化为对应的氧化膦：

R₃P + 1/2 O₂ → R₃PO

该反应通常是不可控的，因此会尽量在无空气体系中处理膦。

碱性较弱的膦，例如甲基二苯基膦可以使用过氧化氢氧化^[8]：

PMePh₂ + H₂O₂ → OPMePh₂ + H₂O

Wittig反应中会产生氧化膦副产物：

R₃P⁺CR'₂ + R"₂CO → R₃PO + R'₂C=CR"₂

氢氧化𬭸的受热分解会产生氧化膦：

[PPh₄]Cl + NaOH → Ph₃PO + NaCl + PhH

二卤化磷(V)水解时会产生氧化膦^[9]：

R₃PCl₂ + H₂O → R₃PO + 2 HCl

氯代膦能水解产生对应的仲氧化膦，如二苯基氯化膦：

Ph₂PCl + H₂O → Ph₂P(O)H + HCl

脱氧

实验室中常用三氯硅烷来还原氧化膦，工业上则会使用光气等试剂将氧化膦转化成氯化三苯基一氯𬭸（Ph₃PCl⁺Cl^-）后再单独进行还原^[10] ^[11]。对于手性的氧化膦分子，脱氧过程可以控制构型保持或反转，例如三氯硅烷与三乙胺的脱氧过程是利于构型反转的，而没有路易斯碱的反应过程是利于构型保持的^[12]。

HSiCl₃ + Et₃N ⇋ SiCl₃⁻ + Et₃NH⁺

R₃PO + Et₃NH⁺ ⇋ R₃POH⁺ + Et₃N

SiCl₃⁻ + R₃POH⁺ → PR₃ + HOSiCl₃

此法的泛用有部分得益于三氯硅烷低廉的价格，除了三氯硅烷外，也可以使用其他全氯硅烷（或其聚合物）如六氯乙硅烷（英语：hexachlorodisilane）。与三氯硅烷相比，全氯聚硅烷和相应的氧化膦，如Si₂Cl₆或Si₃Cl₈，在苯或氯仿中的脱氧反应产率更高。

R₃PO + Si₂Cl₆ → R₃P + Si₂OCl₆

2 R₃PO + Si₃Cl₈ → 2 R₃P + Si₃O₂Cl₈

母体

最简单的氧化膦（H₃PO）性质不稳定，在氧气与膦反应产物的质谱检测中被检测到^[13]，也能通过FT-IR在膦与臭氧的反应^[14]及膦、三氯氧钒和铬酰氯反应的基质分离物中检测到^[15]。据报道，通过白磷的电化学氧化，其能在水-乙醇溶液中相对稳定存在，并缓慢地歧化成膦和次磷酸^[16]。有研究报道了膦与一氧化氮在室温下催化聚合成P_xH_y的过程，通过热重分析质谱（TGA-MS）和衰减全反射傅里叶变换红外光谱（ATR-FTIR）分析，认为该过程是由氧化膦中间体脱水自缩合发生的^[17]。

参考文献

[1]
D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam 1995. ISBN 0-444-89307-5.
[2]
D. B. Chesnut. The Electron Localization Function (ELF) Description of the PO Bond in Phosphine Oxide. Journal of the American Chemical Society. 1999, 121 (10): 2335–2336. doi:10.1021/ja984314m.
[3]
Gilheany, Declan G. No d Orbitals but Walsh Diagrams and Maybe Banana Bonds: Chemical Bonding in Phosphines, Phosphine Oxides, and Phosphonium Ylides. Chemical Reviews. 1994, 94 (5): 1339–1374. PMID 27704785. doi:10.1021/cr00029a008.
[4]
G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
[5]
Gallen, Albert; Riera, Antoni; Verdaguer, Xavier; Grabulosa, Arnald. Coordination Chemistry and Catalysis with Secondary Phosphine oxides. Catalysis Science & Technology. 2019, 9 (20): 5504–5561. doi:10.1039/C9CY01501A. hdl:2445/164459 .
[6]
Ackermann, Lutz. Catalytic Arylations with Challenging Substrates: From Air-Stable HASPO Preligands to Indole Syntheses and C-H-Bond Functionalizations. Synlett. 2007, 2007 (4): 0507–0526. doi:10.1055/s-2007-970744.
[7]
Horký, Filip; Císařová, Ivana; Štěpnička, Petr. A Stable Primary Phosphane Oxide and Its Heavier Congeners. Chemistry – A European Journal. 2021, 27 (4): 1282–1285. PMID 32846012. S2CID 221346479. doi:10.1002/chem.202003702.
[8]
Denniston, Michael L.; Martin, Donald R. Methyldiphenylphosphine Oxide and Dimethylphenylphosphine Oxide. Inorganic Syntheses. 1977, 17: 183–185. ISBN 9780470132487. doi:10.1002/9780470132487.ch50.
[9]
W. B. McCormack (1973). "3-Methyl-1-Phenylphospholene oxide". Org. Synth.; Coll. Vol. 5: 787.
[10]
Podyacheva, Evgeniya; Kuchuk, Ekaterina; Chusov, Denis. Reduction of phosphine oxides to phosphines. Tetrahedron Letters. 2019, 60 (8): 575–582. doi:10.1016/j.tetlet.2018.12.070.
[11]
van Kalkeren, Henri A.; van Delft, Floris L.; Rutjes, Floris P. J. T. Organophosphorus Catalysis to Bypass Phosphine Oxide Waste. ChemSusChem. 2013, 6 (9): 1615–1624. ISSN 1864-5631. PMID 24039197. doi:10.1002/cssc.201300368.
[12]
Klaus Naumann; Gerald Zon; Kurt Mislow. Use of hexachlorodisilane as a reducing agent. Stereospecific deoxygenation of acyclic phosphine oxides. Journal of the American Chemical Society. 1969, 91 (25): 7012–7023. doi:10.1021/ja01053a021.
[13]
Hamilton, Peter A.; Murrells, Timothy P. Kinetics and mechanism of the reactions of PH3 with O(3P) and N(4S) atoms. J. Chem. Soc., Faraday Trans. 1985, 2 (81): 1531–1541. doi:10.1039/F29858101531.
[14]
Withnall, Robert; Andrews, Lester. FTIR spectra of the photolysis products of the phosphine-ozone complex in solid argon. J. Phys. Chem. 1987, 91 (4): 784–797. doi:10.1021/j100288a008.
[15]
Kayser, David A.; Ault, Bruce S. Matrix Isolation and Theoretical Study of the Photochemical Reaction of PH3 with OVCl3 and CrCl2O2. J. Phys. Chem. A. 2003, 107 (33): 6500–6505. Bibcode:2003JPCA..107.6500K. doi:10.1021/jp022692e.
[16]
Yakhvarov, D.; Caporali, M.; Gonsalvi, L.; Latypov, S.; Mirabello, V.; Rizvanov, I.; Sinyashin, O.; Stoppioni, P.; Peruzzini, M. Experimental Evidence of Phosphine Oxide Generation in Solution and Trapping by Ruthenium Complexes. Angewandte Chemie International Edition. 2011, 50 (23): 5370–5373. PMID 21538749. doi:10.1002/anie.201100822.
[17]
Zhao, Yi-Lei; Flora, Jason W.; David Thweatt, William; Garrison, Stephen L.; Gonzalez, Carlos; Houk, K. N.; Marquez, Manuel. Phosphine Polymerization by Nitric Oxide: Experimental Characterization and Theoretical Predictions of Mechanism. Inorg. Chem. 2009, 48 (3): 1223–1231. PMID 19102679. doi:10.1021/ic801917a.

[1] [1]
D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam 1995. ISBN 0-444-89307-5.

[2] [2]
D. B. Chesnut. The Electron Localization Function (ELF) Description of the PO Bond in Phosphine Oxide. Journal of the American Chemical Society. 1999, 121 (10): 2335–2336. doi:10.1021/ja984314m.

[3] [3]
Gilheany, Declan G. No d Orbitals but Walsh Diagrams and Maybe Banana Bonds: Chemical Bonding in Phosphines, Phosphine Oxides, and Phosphonium Ylides. Chemical Reviews. 1994, 94 (5): 1339–1374. PMID 27704785. doi:10.1021/cr00029a008.

[4] [4]
G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.

[5] [5]
Gallen, Albert; Riera, Antoni; Verdaguer, Xavier; Grabulosa, Arnald. Coordination Chemistry and Catalysis with Secondary Phosphine oxides. Catalysis Science & Technology. 2019, 9 (20): 5504–5561. doi:10.1039/C9CY01501A. hdl:2445/164459 .

[6] [6]
Ackermann, Lutz. Catalytic Arylations with Challenging Substrates: From Air-Stable HASPO Preligands to Indole Syntheses and C-H-Bond Functionalizations. Synlett. 2007, 2007 (4): 0507–0526. doi:10.1055/s-2007-970744.

[7] [7]
Horký, Filip; Císařová, Ivana; Štěpnička, Petr. A Stable Primary Phosphane Oxide and Its Heavier Congeners. Chemistry – A European Journal. 2021, 27 (4): 1282–1285. PMID 32846012. S2CID 221346479. doi:10.1002/chem.202003702.

[8] [8]
Denniston, Michael L.; Martin, Donald R. Methyldiphenylphosphine Oxide and Dimethylphenylphosphine Oxide. Inorganic Syntheses. 1977, 17: 183–185. ISBN 9780470132487. doi:10.1002/9780470132487.ch50.

[9] [9]
W. B. McCormack (1973). "3-Methyl-1-Phenylphospholene oxide". Org. Synth.; Coll. Vol. 5: 787.

[TL-10] [10]
Podyacheva, Evgeniya; Kuchuk, Ekaterina; Chusov, Denis. Reduction of phosphine oxides to phosphines. Tetrahedron Letters. 2019, 60 (8): 575–582. doi:10.1016/j.tetlet.2018.12.070.

[van_Kalkerenvan_Delft2013-11] [11]
van Kalkeren, Henri A.; van Delft, Floris L.; Rutjes, Floris P. J. T. Organophosphorus Catalysis to Bypass Phosphine Oxide Waste. ChemSusChem. 2013, 6 (9): 1615–1624. ISSN 1864-5631. PMID 24039197. doi:10.1002/cssc.201300368.

[12] [12]
Klaus Naumann; Gerald Zon; Kurt Mislow. Use of hexachlorodisilane as a reducing agent. Stereospecific deoxygenation of acyclic phosphine oxides. Journal of the American Chemical Society. 1969, 91 (25): 7012–7023. doi:10.1021/ja01053a021.

[13] [13]
Hamilton, Peter A.; Murrells, Timothy P. Kinetics and mechanism of the reactions of PH3 with O(3P) and N(4S) atoms. J. Chem. Soc., Faraday Trans. 1985, 2 (81): 1531–1541. doi:10.1039/F29858101531.

[14] [14]
Withnall, Robert; Andrews, Lester. FTIR spectra of the photolysis products of the phosphine-ozone complex in solid argon. J. Phys. Chem. 1987, 91 (4): 784–797. doi:10.1021/j100288a008.

[15] [15]
Kayser, David A.; Ault, Bruce S. Matrix Isolation and Theoretical Study of the Photochemical Reaction of PH3 with OVCl3 and CrCl2O2. J. Phys. Chem. A. 2003, 107 (33): 6500–6505. Bibcode:2003JPCA..107.6500K. doi:10.1021/jp022692e.

[16] [16]
Yakhvarov, D.; Caporali, M.; Gonsalvi, L.; Latypov, S.; Mirabello, V.; Rizvanov, I.; Sinyashin, O.; Stoppioni, P.; Peruzzini, M. Experimental Evidence of Phosphine Oxide Generation in Solution and Trapping by Ruthenium Complexes. Angewandte Chemie International Edition. 2011, 50 (23): 5370–5373. PMID 21538749. doi:10.1002/anie.201100822.

[17] [17]
Zhao, Yi-Lei; Flora, Jason W.; David Thweatt, William; Garrison, Stephen L.; Gonzalez, Carlos; Houk, K. N.; Marquez, Manuel. Phosphine Polymerization by Nitric Oxide: Experimental Characterization and Theoretical Predictions of Mechanism. Inorg. Chem. 2009, 48 (3): 1223–1231. PMID 19102679. doi:10.1021/ic801917a.

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