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Hoefler JC, Jackson D, Blümel J. Surface-Assisted Selective Air Oxidation of Phosphines Adsorbed on Activated Carbon. Inorg Chem 2024; 63:9275-9287. [PMID: 38722182 PMCID: PMC11110008 DOI: 10.1021/acs.inorgchem.4c01027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/24/2024] [Accepted: 04/25/2024] [Indexed: 05/21/2024]
Abstract
Trialkyl- and triarylphosphines readily adsorb onto the surface of porous activated carbon (AC) even in the absence of solvents through van der Waals interactions between the lone electron pair and the AC surface. This process has been proven by solid-state NMR techniques. Subsequently, it is demonstrated that the AC enables the fast and selective oxidation of adsorbed phosphines to phosphine oxides at ambient temperature in air. In solution, trialkylphosphines are oxidized to a variety of P(V) species when exposed to the atmosphere, while neat or dissolved triarylphosphines cannot be oxidized with air. When the trialkyl- and triarylphosphines PnBu3 (1), PEt3, (2), PnOct3 (3), PMetBu2 (4), PCy3 (5), and PPh3 (6) are adsorbed in a mono- or submonolayer on the surface of AC, in the absence of a solvent and at ambient temperature, they are quantitatively oxidized to the adsorbed phosphine oxides, 1ox-6ox, once air is admitted. No formation of any unwanted P(V) side products or water adducts is observed. The phosphine oxides can then be recovered in good yields by washing them off of the AC. The oxidation is likely facilitated by a radical activation of molecular oxygen due to delocalized electrons on the aromatic surface coating of AC, as proven by ESR. This easy and inexpensive oxidation method renders hydrogen peroxide or other oxidizers unnecessary and is broadly applicable to sterically hindered and even to air-stable triarylphosphines. Phosphines adsorbed at lower surface coverages on AC oxidize at a faster rate. All oxidation reactions were monitored by solution- and solid-state NMR spectroscopy.
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Affiliation(s)
- John C. Hoefler
- Department of Chemistry, Texas
A&M University, College Station, Texas 77845-3012, United States
| | - Devin Jackson
- Department of Chemistry, Texas
A&M University, College Station, Texas 77845-3012, United States
| | - Janet Blümel
- Department of Chemistry, Texas
A&M University, College Station, Texas 77845-3012, United States
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Benzie JW, Harmon-Welch GE, Hoefler JC, Bakhmutov VI, Blümel J. Molecular Dynamics and Surface Interactions of Nickelocene Adsorbed on Silica: A Paramagnetic Solid-State NMR Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7422-7432. [PMID: 35675156 DOI: 10.1021/acs.langmuir.2c00301] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
When grinding nickelocene with silica in the absence of a solvent at room temperature, it adsorbs on the surface within the pores. This has also been demonstrated visually by adsorbing green nickelocene in the pores of a large colorless silica gel specimen. While this dry adsorption and translational mobility of nickelocene within the pores is proven visually, the site-to-site mobility of the nickelocene molecules and their orientation toward the surface are not yet understood. In this contribution, mesoporous silica is used as the support material for a systematic solid-state NMR study of these issues. Paramagnetic 1H VT solid-state NMR and T1 relaxation times have been powerful tools for studying the dynamics of nickelocene on the silica surface. Herewith, the mobility of the surface-adsorbed nickelocene molecules in the pores could be quantified on the molecular scale. According to the obtained data, the nickelocene molecules move like a liquid on the surface. Isotropically moving molecules exchange places rapidly with surface-attached molecular states of nickelocene in a sample with submonolayer surface coverage. This finding is corroborated by a macroscopic visualization experiment. The states of the surface-attached horizontally oriented nickelocene molecules that are prevalent at temperatures below 200 K have been quantified. The temperature dependencies of the rate k in coordinates of ln(k) versus 1/T and ln(k/T) versus 1/T form ideal straight lines that allow the determination of the kinetic parameters Eact = 5.5 kcal/mol, A = 1.1 × 1010, ΔH‡ = 5.0 kcal/mol, and ΔS‡ = -15 eu. Investigating a sample with equal amounts of nickelocene and ferrocene in a submonolayer amount of 80% overall surface coverage shows that the different metallocenes mix on the molecular level on the silica surface.
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Affiliation(s)
- Jordon W Benzie
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | | | - John C Hoefler
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | - Vladimir I Bakhmutov
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
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Arp FF, Ashirov R, Bhuvanesh N, Blümel J. Di(hydroperoxy)adamantane adducts: synthesis, characterization and application as oxidizers for the direct esterification of aldehydes. Dalton Trans 2021; 50:15296-15309. [PMID: 34636381 DOI: 10.1039/d1dt03243g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The di(hydroperoxy)adamantane adducts of water (1) and phosphine oxides p-Tol3PO·(HOO)2C(C9H14) (2), o-Tol3PO·(HOO)2C(C9H14) (3), and Cy3PO·(HOO)2C(C9H14) (4), as well as a CH2Cl2 adduct of a phosphole oxide dimer (8), have been created and investigated by multinuclear NMR spectroscopy, and by Raman and IR spectroscopy. The single crystal X-ray structures for 1-4 and 8 are reported. The IR and 31P NMR data are in accordance with strong hydrogen bonding of the di(hydroperoxy)adamantane adducts. The Raman ν(O-O) stretching bands of 1-4 prove that the peroxo groups are present in the solids. Selected di(hydroperoxy)alkane adducts, in combination with AlCl3 as catalyst, have been applied for the direct oxidative esterification of n-nonyl aldehyde, benzaldehyde, p-methylbenzaldehyde, p-bromobenzaldehyde, and o-hydroxybenzaldehyde to the corresponding methyl esters. The esterification takes place in an inert atmosphere, under anhydrous and oxygen-free conditions, within a time frame of 45 minutes to 5 hours at room temperature. Hereby, two oxygen atoms per adduct assembly are active with respect to the quantitative transformation of the aldehyde into the ester.
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Affiliation(s)
- Fabian F Arp
- Department of Chemistry, Texas A&M University, College Station, TX, 77842-3012, USA.
| | - Rahym Ashirov
- Department of Chemistry, Texas A&M University, College Station, TX, 77842-3012, USA.
| | - Nattamai Bhuvanesh
- Department of Chemistry, Texas A&M University, College Station, TX, 77842-3012, USA.
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, TX, 77842-3012, USA.
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Arp FF, Bhuvanesh N, Blümel J. Di(hydroperoxy)cycloalkane Adducts of Triarylphosphine Oxides: A Comprehensive Study Including Solid-State Structures and Association in Solution. Inorg Chem 2020; 59:13719-13732. [PMID: 32866378 DOI: 10.1021/acs.inorgchem.0c02087] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Four new di(hydroperoxy)cycloalkane adducts (Ahn adducts) of p-Tol3PO (1) and o-Tol3PO (2), namely, p-Tol3PO·(HOO)2C(CH2)5 (3), o-Tol3PO·(HOO)2C(CH2)5 (4), p-Tol3PO·(HOO)2C(CH2)6 (5), and o-Tol3PO·(HOO)2C(CH2)6 (6), have been synthesized and fully characterized. Their single crystal X-ray structures have been determined and analyzed. The 31P NMR data are in accordance with hydrogen bonding of the di(hydroperoxy)alkanes to the P═O groups of the phosphine oxides. Due to their high solubility in organic solvents, natural abundance 17O NMR spectra of 1-6 could be recorded, providing the signals for the P═O groups and additionally the two different oxygen nuclei in the O-OH groups in the adducts 3-6. The association and mobility of 3-6 were explored by 1H DOSY (diffusion ordered spectroscopy) NMR, which indicated persistent hydrogen bonding of the adducts in solution. Competition experiments with phosphine oxides allowed ranking of the affinities of the di(hydroperoxy)cycloalkanes for the different phosphine oxide carriers. On the basis of variable temperature 31P NMR investigations, the Gibbs energies of activation ΔG‡ for the adduct dissociation processes of 3-6 at different temperatures, as well as the enthalpy ΔH‡ and entropy ΔS‡ of activation, have been determined. IR spectroscopy of 3-6 corroborated the hydrogen bonding, and in the Raman spectra, the ν(O-O) stretching bands have been identified, confirming the presence of peroxy groups in the solid materials. The high solubilities in selected organic solvents have been quantified.
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Affiliation(s)
- Fabian F Arp
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Nattamai Bhuvanesh
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United States
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, United States
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Hubbard PJ, Benzie JW, Bakhmutov VI, Blümel J. Ferrocene Adsorbed on Silica and Activated Carbon Surfaces: A Solid-State NMR Study of Molecular Dynamics and Surface Interactions. Organometallics 2020. [DOI: 10.1021/acs.organomet.9b00800] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Patrick J. Hubbard
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | - Jordon W. Benzie
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | - Vladimir I. Bakhmutov
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, Texas 77845-3012, United States
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Hubbard PJ, Benzie JW, Bakhmutov VI, Blümel J. Disentangling different modes of mobility for triphenylphosphine oxide adsorbed on alumina. J Chem Phys 2020; 152:054718. [PMID: 32035468 DOI: 10.1063/1.5142568] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Triphenylphosphine oxide (TPPO, 1) has been adsorbed on neutral alumina by dry grinding of the components in the absence of a solvent. The adsorption proves translational mobility of 1 on the surface of alumina. Different surface coverages from a densely packed monolayer (99% coverage) to a dilute sub-monolayer (25%) have been produced. The samples have been studied by diverse multinuclear 1H, 13C, and 31P variable temperature solid-state nuclear magnetic resonance (NMR) techniques. The interactions of 1 with the surface are determined by hydrogen bonding of the P=O group to OH groups on the surface. The 31P solid-state NMR spectra prove that even at low temperatures, the molecules of 1 are highly mobile on the surface. Using T1 and T2 relaxation time analyses of the 31P resonance in the solid state at variable temperatures allowed the identification and quantification of two different modes of mobility. Besides the translational mobility that consists of jumps from one hydrogen-bonding OH site on the surface to an adjacent one, a rotational movement around the axis defined by the P=O group of 1 occurs.
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Affiliation(s)
- Patrick J Hubbard
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, USA
| | - Jordon W Benzie
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, USA
| | - Vladimir I Bakhmutov
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, USA
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, USA
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Guenther J, Reibenspies J, Blümel J. Synthesis and characterization of tridentate phosphine ligands incorporating long methylene chains and ethoxysilane groups for immobilizing molecular rhodium catalysts. MOLECULAR CATALYSIS 2019. [DOI: 10.1016/j.mcat.2019.110629] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Arp FF, Bhuvanesh N, Blümel J. Hydrogen peroxide adducts of triarylphosphine oxides. Dalton Trans 2019; 48:14312-14325. [PMID: 31475705 DOI: 10.1039/c9dt03070k] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Five new hydrogen peroxide adducts of phosphine oxides (p-Tol3PO·H2O2)2 (1), (o-Tol3PO·H2O2)2 (2), (o-Tol2PhPO·H2O2)2 (3), (p-Tol3PO)2·H2O2 (4), and (o-TolPh2PO)2·H2O2 (5), and the water adduct (o-Tol2PhPO·H2O)2 (6) have been synthesized and fully characterized. Their single crystal X-ray structures have been determined and analyzed. The IR and 31P NMR data are in accordance with strong hydrogen bonding of the hydrogen peroxide. The mono- versus dimeric nature of the adduct assemblies has been investigated by DOSY NMR experiments. Raman spectroscopy of the symmetric adducts and the ν(O-O) stretching bands confirm the presence of hydrogen-bonded hydrogen peroxide in the solid materials. The solubilities in organic solvents have been quantified. Due to the high solubilities of 1-6 in organic solvents their 17O NMR spectra could be recorded in natural abundance, providing well-resolved signals for the P[double bond, length as m-dash]O and O-O groups. The adducts 1-5 have been probed regarding their stability in solution at 105 °C. The decomposition of the adduct 1 takes place by loss of the active oxygen atoms in two steps.
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Affiliation(s)
- Fabian F Arp
- Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA.
| | - Nattamai Bhuvanesh
- Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA.
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA.
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Kharel S, Cluff KJ, Bhuvanesh N, Gladysz JA, Blümel J. Structures and Dynamics of Secondary and Tertiary Alkylphosphine Oxides Adsorbed on Silica. Chem Asian J 2019; 14:2704-2711. [PMID: 31168965 DOI: 10.1002/asia.201900632] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Indexed: 11/12/2022]
Abstract
The three secondary phosphine oxides [CH2 =CH(CH2 )4 ]2 HPO (1), [CH2 =CH(CH2 )5 ]2 HPO (2), and [CH2 =CH(CH2 )6 ]2 HPO (3), and two diphosphine dioxides, {[CH2 =CH(CH2 )6 ]2 PO(CH2 )7 }2 (4) and {[CH2 =CH(CH2 )6 ]2 PO(CH2 )4 }2 (5), incorporating long methylene chains, are described. The single crystal X-ray structures of 1, 2, and 5 have been determined. The phosphine oxides 3, 4, and 5 have been adsorbed on silica in submonolayer quantities to give 3 a-5 a. The 1 H, 13 C, and 31 P solid-state NMR spectra of polycrystalline 3-5 have been analyzed and compared with those of 3 a-5 a. The changes of the solid-state NMR characteristics upon adsorption and the surface mobilities of the phosphine oxides are discussed.
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Affiliation(s)
- Sugam Kharel
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas, 77842-3012, USA
| | - Kyle J Cluff
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas, 77842-3012, USA
| | - Nattamai Bhuvanesh
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas, 77842-3012, USA
| | - John A Gladysz
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas, 77842-3012, USA
| | - Janet Blümel
- Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas, 77842-3012, USA
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Arp FF, Ahn SH, Bhuvanesh N, Blümel J. Selective synthesis and stabilization of peroxides via phosphine oxides. NEW J CHEM 2019. [DOI: 10.1039/c9nj04858h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
MEKPO (methyl ethyl ketone peroxide) and other peroxides can be synthesized selectively and stabilized as hydrogen-bonded phosphine oxide adducts.
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Affiliation(s)
- Fabian F. Arp
- Department of Chemistry
- Texas A&M University
- College Station
- USA
| | - Shin Hye Ahn
- Department of Chemistry
- Texas A&M University
- College Station
- USA
| | | | - Janet Blümel
- Department of Chemistry
- Texas A&M University
- College Station
- USA
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