Dihydrogen Tetrametaphosphate, [P4O12H2]2–: Synthesis, Solubilization in Organic Media, Preparation of its Anhydride [P4O11]2– and Acidic Methyl Ester, and Conversion to Tetrametaphosphate Metal Complexes via Protonolysis

Jiang, Yanfeng; Chakarawet, Khetpakorn; Kohout, Andrea Laura; Nava, Matthew; Marino, Nadia; Cummins, Christopher C.

doi:10.1021/ja5058339

Cited by 27 publications

(58 citation statements)

References 46 publications

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“…To the best of our knowledge, 1 is only the second example of the tetrametaphosphate ligand binding in a κ 4 fashion to a metal center. 38 The diamagnetically corrected 39 magnetic moment (μeff: 2.82 μB) was determined using the Evans method 40 and is consistent with an expected spin-only value (μeff: 2.83 μB) for a high-spin, S = 1 V III center. Next, we targeted systems with reduced V:P ratios using the Ph2P(O)OH acid as our P source.…”

Section: Scheme 2: Synthesis Of 1-4mentioning

confidence: 76%

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Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives

et al. 2018

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+ = ferrocenium). Electrochemical analysis of this reaction revealed a possible ECE mechanism that includes prior and subsequent electron transfer to this dimerization. The electronic structure of the dimer 4 was probed by SQUID magnetommetry and X-band EPR spectroscopy (100 K and 4 K). The dimer was found to contain two antiferromagnetically coupled V IV centers, as well as a small portion of monomeric V IV species, 2 + . In contrast to 2, oxidation of 1 resulted in an EC mechanism, the product of which remains unknown. Preliminary reactions with compounds 1 and 2 bearing free P=O groups were performed using H-atom donors to test their ability to undergo H-atom transfer in the context of the proposed "reduction-coupled oxo activation" mechanism; however, no clear reaction pathway supporting this mechanism was yet observed.Considerable interest lies in the structure and bonding of vanadium phosphate complexes due to their varied applications, such as in size-selective inorganic hosts, ion exchangers, and magnetic systems.1-4 From the industrial perspective, DuPont's "butox" process utilizes a surface vanadium phosphate oxide (VPO) catalyst for the oxidative conversion of butane to maleic anhydride (MA) on a 500 kt scale (Scheme 1a). The commodity chemical is used as a resin, a food additive, an agricultural chemical, as well as in pharmaceuticals. 5 The conversion of butane to MA is considered one of the most complex in industry, involving the abstraction of 8 H-atoms and the insertion of 3 O-atoms, as part of an overall 14 e -process. As such, this process has been the subject of extensive mechanistic investigations over the decades, 5-9 and continues to be the subject of considerable interest today.10-14 However, in spite of these extensive studies, no consensus mechanism yet exists as to the exact steps of this transformation.Recent gas-phase studies by Schwarz and co-workers have described the ability of simple oxidized oxide clusters, such as [P4O10] •+ or [V4O10]•+ , to abstract a H atom from methane or other simple hydrocarbons, through an H-atom transfer (HAT) process. It was further found that the in situ-generated [P4O10] •+ was more reactive than the metallic analog, [V4O10] •+ . [15][16] The increased reactivity upon P-incorporation into the clusters was further demonstrated by comparison of the smaller oxide cations, [VPO4] •+ and [V2O4]•+ , wherein the former was more reactive towards HAT than the latter. These experimental conclusions were further supported by theoretical work by Goddard and coworkers who proposed that the terminal P=O linkages in VPO are responsible for C-H functionalization at butane (Scheme 1b-c). The mechanism, coined "reduction-coupled oxo activation" (ROA), occurs as a result of the strong basicity at the P=O bond coupled with the neighboring high-valent, oxidative V V centers which undergoes reduction, 10, 12 and is in many respects analogous to well-studied proton-coupled electron transfer (PCET) reactions common to both biological and artificial systems. [17][18]...

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Section: Scheme 2: Synthesis Of 1-4mentioning

confidence: 76%

“…Pentane, tetrahydrofuran, diethyl ether, hexanes, and DCM (Aldrich) were dried using an MBRAUN-Solvent 38 were prepared according to literature procedures. Elemental analyses (C, H, N) were recorded at the University of California, Berkeley using a Perkin Elmer 2400 Series II combustion analyzer.…”

Section: Figurementioning

confidence: 99%

Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives

et al. 2018

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“…One is related to the farnesyltransferase (FTase). 48 In order to understand how FTase recruits the FPP substrate, Cui 80 These results remind us that the protonation state of DMAPP may be the key point but it is not considered in previous mechanisms for FPPS. Obviously, the protonation of the PPV 3− of DMAPP is of great importance on effecting the leaving ability of the PPV group to promote the first "ionization" (i.e., the breakage of C1′-O7′) in view of the basic organic reaction theory.…”

Section: Methodsmentioning

confidence: 99%

Protonation-Triggered Carbon-Chain Elongation in Geranyl Pyrophosphate Synthase (GPPS)

Zhou

Wang

et al. 2015

ACS Catal.

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Geranyl pyrophosphate synthase (GPPS) is responsible for the formation of geranyl pyrophosphate (GPP), a key intermediate which has the potential to derive numerous functionally and structurally diverse groups of terpenoid natural products via the head-to-tail assembly of two isoprenoid building blocks (dimethylallyl diphosphate, DMAPP; isopentenyl diphosphate, IPP) in the initial step of carbon-chain elongation during isoprenoid biosynthesis. Elucidating the detailed catalytic mechanism in GPPS is of significant interests as it will stimulate the development of new technology in generating novel natural productlike scaffolds. It has been known that the catalytic reaction involves three sequential steps, namely "ionization− condensation−elimination", but the exact catalytic mechanism has remained controversial since the 1970s. By employing Born− Oppenheimer density functional quantum mechanics (B3LYP/6-31(+)G*)/molecular mechanics dynamics simulations, here we suggest that GPPS adopts a protonation-induced catalytic mechanism, in which there are two key points different from previously hypothesized mechanisms. The first point is the protonation of DMAPP which is essential in the initial "ionization" process but was not considered in previous mechanisms. The second point is the stereoselectivity of proton transfer (H S ) from IPP to H76 residue in the final "elimination" step as identified in our simulations, in contrast to the proton transfer from IPP (H R ) to DMAPP in previous hypotheses. Moreover, the free energy barrier of the whole assembly reaction is predicted to be 18.8 ± 0.6 kcal/mol, in agreement with the experimental value of 18.0 kcal/mol. Furthermore, the catalytic roles of the two Mg 2+ ions at the bottom of the active site are also discussed, and key residues (K44, R47, R94, R95, K180, K235, and E73 around DMAPP and IPP) responsible for the stabilization of transition states, intermediates, and/or product are clarified. These findings can assist site-directed mutagenesis experiments in protein engineering as well as inhibitor designs.

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“…In order to extend this synthetic method to other types of condensed phosphates, we also investigated protonation of the recently reported [PPN] O 12 ] with TFAA in acetone. 11 The treatment of 1 with TFA yielded no further protonation. However, protonation of 1 with TfOH in MeCN yielded [PPN] 4 [(P 4 O 12 ) 3 H 8 ] (3), which was isolated in 71% yield as a white solid upon precipitation of the product from the reaction mixture with 1,2-dimethoxyethane (DME).…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…Furthermore, metaphosphates are known to undergo acid-catalyzed hydrolysis, 10 thus preventing the rigorous isolation and characterization of protonated metaphosphates in aqueous media. Recently, our group has demonstrated that the [PPN] 11 Other examples of crystallographically characterized metaphosphate acids with organic counterions are the 3,5-xylidinium and 2-amino-5-chloropyridinium salts of dihydrogenhexametaphosphate 12,13 and the recently reported tetramethylammonium hydrogentrimetaphosphate. 14 Herein, we describe a general method for accessing tri-, tetra-, and hexametaphosphate acids in organic media, as well as a detailed analysis of their hydrogen-bonding properties.…”

Section: ■ Introductionmentioning

confidence: 99%

Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media, Structures, Hydrogen-Bonding Capability, and Implication of Superacidity

et al. 2016

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Metaphosphate acids cannot be thoroughly studied in aqueous media because their acidity is leveled by the solvent, and the resulting metaphosphates are susceptible to acid-catalyzed hydrolysis. Exploration of metaphosphate acid chemistry has now been made possible with the development of a general synthetic method for organic media soluble metaphosphate acids. Protonation of the [PPN](+) salts ([PPN](+) = [N(PPh3)2](+)) of tri-, tetra-, and hexametaphosphates results in five new metaphosphate acids, [PPN]2[P3O9H] (2), [PPN]4[(P4O12)3H8] (3), [PPN]4[P6O18H2]·2H2O (4), [PPN]3[P6O18H3] (5), and [PPN]2[P6O18H2(H3O)2] (6), obtained in yields of 80, 71, 66, 88, and 76%, respectively. Additionally, our synthetic method can be extended to pyrophosphate to produce [PPN][P2O7H3] (7) in 77% yield. The structural configurations of these oxoacids are dictated by strong hydrogen bonds and the anticooperative effect. Intramolecular hydrogen bonds are observed in 2, 4, and 5 and the previously reported [PPN]2[P4O12H2] (1), while intermolecular hydrogen bonds are observed in 3, 6, and 7. The hydrogen bonds in 3-7 possess short distances and are classified as low-barrier hydrogen bonds. Gas-phase acidity computations reveal that the parent tri- and tetrametaphosphoric acids are superacids. Their remarkable acidity is attributable to the stabilization of their corresponding conjugate bases via intramolecular hydrogen bonding.

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Dihydrogen Tetrametaphosphate, [P₄O₁₂H₂]^2–: Synthesis, Solubilization in Organic Media, Preparation of its Anhydride [P₄O₁₁]^2– and Acidic Methyl Ester, and Conversion to Tetrametaphosphate Metal Complexes via Protonolysis

Cited by 27 publications

References 46 publications

Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives

Synthesis, Characterization, and Electrochemical Analyses of Vanadocene Tetrametaphosphate and Phosphinate Derivatives

Protonation-Triggered Carbon-Chain Elongation in Geranyl Pyrophosphate Synthase (GPPS)

Crystalline Metaphosphate Acid Salts: Synthesis in Organic Media, Structures, Hydrogen-Bonding Capability, and Implication of Superacidity

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