Complexes of High-Valent Rhenium Supported by the PCP Pincer

Kosanovich, Alex J.; Reibenspies, Joseph H.; Ozerov, Oleg V.

doi:10.1021/acs.organomet.5b00935

Cited by 24 publications

(19 citation statements)

References 48 publications

(86 reference statements)

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“…This procedure was applicable to compounds featuring CpFe(CO) 2 68 [ 193 ] or ferrocenyl 69 [ 194 – 195 ] moieties but also to palladium or platinium pincer complexes 70 [ 196 ] or arene–chrome carbonyl derivatives 71 [ 197 ]. It must be noted that when the organometallic complex possessed halogen–metal moiety, then Me 3 SiBr can induce halogen exchange [ 198 ].…”

Section: Reviewmentioning

confidence: 99%

Phosphonic acid: preparation and applications

Sevrain¹,

Berchel²,

Couthon³

et al. 2017

Beilstein J. Org. Chem.

139

103

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The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H3PO3) and that produce a phosphonic acid functional group simultaneously to the formation of the P–C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids.

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Section: Reviewmentioning

confidence: 99%

Phosphonic acid: preparation and applications

Sevrain¹,

Berchel²,

Couthon³

et al. 2017

Beilstein J. Org. Chem.

139

103

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show abstract

“…The remaining solids were washed with 3 × 5 mL of hexanes, yielding 4 in 72% yield as a purple solid (0.092 g, 0.19 mmol). 1 Synthesis of [κ 3 -Bn PPC]NiBr (6). To a stirred slurry of Ni(COD) 2 (0.647 g, 2.35 mmol) in 5 mL of diethyl ether was slowly added a solution of 5 (1.015 g, 2.352 mmol) in 5 mL of diethyl ether.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

β-Hydrogen Elimination and Reductive Elimination from a κ³-PPC Nickel Complex

Zimmerman

Fryzuk

2018

Organometallics

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The incorporation of a PPC donor ligand set onto nickel is described. While C–H activation routes using Ni(II) precursors and benzyl- and phenethyl-substituted diphosphines But 2PCH2CH2P(But)R failed, success was achieved via oxidative addition of the 2-bromo-benzyl-ligand precursor But 2PCH2CH2P(But)(CH2-o-C6H4Br) with Ni(COD)2 to generate [κ3-BnPPC]NiBr. Subsequent reaction with KBEt3H resulted in decomposition unless PPh3 was present, which allowed isolation of the tricoordinate Ni(0) complex [κ2-BnPP]Ni(PPh3). Reaction of [κ3-BnPPC]NiBr with EtMgCl also resulted in the formation of the Ni(0) ethylene complex, [κ2-BnPP]Ni(η2-C2H4), via β-elimination followed by reductive elimination. Deuterium-labeling studies are consistent with a reversible β-elimination process prior to reductive elimination, which scrambles the deuterium isotopes. Reaction of [κ3-BnPPC]NiBr with CH3Li results in the formation of the Ni(II) methyl complex, [κ3-BnPPC]Ni(CH3). Heating this species in the presence of PPh3 results in the formation of the Ni(0) derivative, [κ2-Bn‑o‑MePP]Ni(PPh3), in which reductive elimination of the methyl and aryl units has occurred. Reaction of [κ3-BnPPC]NiBr with heteroatom-containing species such as sodium isopropoxide, sodium 2-propanethiolate, and lithium methylphenylamide resulted in different outcomes depending on the heteroatom; with isopropoxide, the products isolated were geometric isomers of Ni(0) η2-acetone adducts, which presumably arise via a β-elimination–reductive elimination sequence; the analogous sulfur reagent generated isolable Ni(II) isopropyl thiolate species that was resistant to β-elimination upon thermolysis; with methylphenylamide, the Ni(II) amido complex could be isolated and structurally characterized; subsequent heating to 80 °C resulted in β-elimination followed by reductive elimination to generate a Ni(0) phenylimine complex. While the κ3-PPC donor set generates stable Ni(II) derivatives, further functionalization at nickel with hydride, alkyl, and heteroatom-containing moieties can lead to Ni(0) products via a combination of β-elimination and/or reductive elimination.

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“…The structural metrics and vibrational spectra are similar to related pincer Re carbonyl complexes. [24][25][26][27][28] Scheme 2. Synthesis of tricarbonyl complex ( tBu POCOP)Re(CO)3 (1).…”

Section: Resultsmentioning

confidence: 99%

Temperature and Solvent Effects on H2 Splitting and Hydricity: Ramifications on CO2 Hydrogenation by a Rhenium Pincer Catalyst

Bruch

Miller

2020

Preprint

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The catalytic hydrogenation of carbon dioxide holds immense promise for applications in sustainable fuel synthesis and hydrogen storage. Mechanistic studies that connect thermodynamic parameters with the kinetics of catalysis can provide new understanding and guide predictive design of improved catalysts. Reported here are thermochemical and kinetic analyses of a new pincer-ligated rhenium complex (tBuPOCOP)Re(CO)2(tBuPOCOP = 2,6-bis(di-tert-butylphosphinito)phenyl) that catalyzes CO2 hydrogenation to formate with faster rates at lower temperature. Because the catalyst follows the prototypical “outer sphere” hydrogenation mechanism, comprehensive studies of temperature and solvent effects on the H2splitting and hydride transfer steps are expected to be relevant to many other catalysts. Strikingly large entropy associated with cleavage of H2 results in a strong temperature dependence on the concentration of [(tBuPOCOP)Re(CO)2H]– present during catalysis, which is further impacted by changing the solvent from toluene to tetrahydrofuran to acetonitrile. New methods for determining the hydricity of metal hydrides and formate at temperatures other than 298 K were developed, providing insight into how temperature can influence the favorability of hydride transfer during catalysis. These thermochemical insights guided the selection of conditions for CO2 hydrogenation to formate with high activity (up to 364 h–1 at 1 atm or 3330 h–1 at 20 atm of 1:1 H2 CO2). In cases where hydride transfer is the highest individual kinetic barrier, entropic contributions to outer sphere H2 splitting lead to a unique temperature dependence: catalytic activity increases as temperature decreases in tetrahydrofuran (200-fold increase upon cooling from 50 to 0 °C) and toluene (4-fold increase upon cooling from 100 to 50 °C). Ramifications on catalyst structure-function relationships are discussed, including comparisons between “outer sphere” mechanisms and metal–ligand cooperation mechanisms.

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Complexes of High-Valent Rhenium Supported by the PCP Pincer

Cited by 24 publications

References 48 publications

Phosphonic acid: preparation and applications

Phosphonic acid: preparation and applications

β-Hydrogen Elimination and Reductive Elimination from a κ³-PPC Nickel Complex

Temperature and Solvent Effects on H2 Splitting and Hydricity: Ramifications on CO2 Hydrogenation by a Rhenium Pincer Catalyst

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Complexes of High-Valent Rhenium Supported by the PCP Pincer

Cited by 24 publications

References 48 publications

Phosphonic acid: preparation and applications

Phosphonic acid: preparation and applications

β-Hydrogen Elimination and Reductive Elimination from a κ3-PPC Nickel Complex

Temperature and Solvent Effects on H2 Splitting and Hydricity: Ramifications on CO2 Hydrogenation by a Rhenium Pincer Catalyst

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β-Hydrogen Elimination and Reductive Elimination from a κ³-PPC Nickel Complex