Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

A convenient method for the generation of {Rh(PNP)}+ and {Rh(PONOP)}+ fragments: reversible formation of vinylidene derivatives.

ABSTRACT: The substitution reactions of [Rh(COD)2][BArF4] with PNP and PONOP pincer ligands 2,6-bis(di-tert-butylphosphinomethyl)pyridine and 2,6-bis(di-tert-butylphosphinito)pyridine in the weakly coordinating solvent 1,2-F2C6H4 are shown to be an operationally simple method for the generation of reactive formally 14 VE rhodium(i) adducts in solution. Application of this methodology enables synthesis of known adducts of CO, N2, H2, previously unknown water complexes, and novel vinylidene derivatives [Rh(pincer)(CCHR)][BArF4] (R = tBu, 3,5-tBu2C6H3), through reversible reactions with terminal alkynes.

SUBMITTER: Gyton MR

PROVIDER: S-EPMC6394201 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

A convenient method for the generation of {Rh(PNP)}+ and {Rh(PONOP)}+ fragments: reversible formation of vinylidene derivatives.

Gyton Matthew R MR Hood Thomas M TM Chaplin Adrian B AB

Dalton transactions (Cambridge, England : 2003) 20190201 9

The substitution reactions of [Rh(COD)2][BArF4] with PNP and PONOP pincer ligands 2,6-bis(di-tert-butylphosphinomethyl)pyridine and 2,6-bis(di-tert-butylphosphinito)pyridine in the weakly coordinating solvent 1,2-F2C6H4 are shown to be an operationally simple method for the generation of reactive formally 14 VE rhodium(i) adducts in solution. Application of this methodology enables synthesis of known adducts of CO, N2, H2, previously unknown water complexes, and novel vinylidene derivatives [Rh( ...[more]

PMID: 30729961

Similar Datasets

DFT calculations bring insight to internal alkyne-to-vinylidene transformations at rhodium PNP- and PONOP-pincer complexes.

Project description:Density Functional Theory (DFT) has been used to investigate the alkyne-to-vinylidene isomerisation reaction mediated by [Rh(PXNXP)]+ complexes (X = CH2: 2,6-bis(di-tert-butylphosphinomethyl)pyridine (PNP) and X = O: 2,6-bis(di-tert-butylphosphinito)pyridine (PONOP)) for terminal alkynes HC[triple bond, length as m-dash]CR, where R = t Bu and Ar' (3,5- t Bu2C6H3). Calculations suggest the reaction mechanism proceeds via the slippage of π-bound alkyne at the Rh centre into a Rh-alkyne σC-H complex followed by an indirect 1,2-H shift to give the Rh-vinylidene species. NBO (Natural Bond Orbital) analysis of the transition states corresponding to the latter indirect 1,2-H shift step indicates that the migrating hydrogen atom exhibits protic character and hence, the basicity of the H-accepting centre (Cβ) is controlled by the substituents at that same atom and can tune the 1,2-H shift transition state. QTAIM (Quantum Theory of Atoms in Molecule) and NBO analyses of the Rh-vinylidene complexes indicate that these species exhibit a Rh ← C dative bond as well as π-back bonding from the Rh centre into the empty p z orbital of the carbene centre (Cα), showing the Rh-vinylidene complexes are Fischer type carbenes. Analysis of the alkyne and vinylidene complex HOMOs show that the equilibrium between the isomers can be tuned by the P-Rh-P bite angle of the [Rh(pincer)]+ fragment. Dictated by the nature of the pincer backbone, wider bite angles shift the equilibrium toward the formation of the Rh-vinylidene isomer (e.g., X = CH2 and R = Ar'), while tighter bite angles shift the equilibrium more to the formation of the Rh-alkyne isomer (e.g., X = O and R = Ar').

| S-EPMC8696595 | biostudies-literature

Synthesis and Structural Dynamics of Five-Coordinate Rh(III) and Ir(III) PNP and PONOP Pincer Complexes.

Project description:The synthesis and characterization of a homologous series of five-coordinate rhodium(III) and iridium(III) complexes of PNP (2,6-( tBu2PCH2)2C5H3N) and PONOP (2,6-( tBu2PO)2C5H3N) pincer ligands are described: [M(PNP)(biph)][BArF4] (M = Rh, 1a; Ir, 1b; biph = 2,2'-biphenyl; ArF = 3,5-(CF3)2C6H3) and [M(PONOP)(biph)][BArF4] (M = Rh, 2a; Ir, 2b). These complexes are structurally dynamic in solution, exhibiting pseudorotation of the biph ligand on the 1H NMR time scale (? G? ca. 60 kJ mol-1) and, in the case of the flexible PNP complexes, undergoing interconversion between helical and puckered pincer ligand conformations (? G? ca. 10 kJ mol-1). Remarkably, the latter is sufficiently facile that it persists in the solid state, leading to temperature-dependent disorder in the associated X-ray crystal structures. Reaction of 1 and 2 with CO occurs for the iridium congeners 1b and 2b, leading to the formation of sterically congested carbonyl derivatives.

| S-EPMC6549213 | biostudies-literature

Oxidative Addition of C-Cl Bonds to a Rh(PONOP) Pincer Complex.

Project description:Straightforward procedures for the generation of rhodium(I) κCl-chlorocarbon complexes of the form [Rh(PONOP-tBu)(κ Cl-ClR)][BArF 4] [R = CH2Cl, A; Ph, 1; Cy, 2; tBu, 3; PONOP-tBu = 2,6-bis(di-tert-butylphosphinito)pyridine; ArF = 3,5-bis(trifluoromethyl)phenyl] in solution are described, enabling isolation of analytically pure A and crystallographic characterization of the new complexes 1 and 2. Complex 1 was found to be stable at ambient temperature, but prolonged heating in chlorobenzene at 125 °C resulted in formation of [Rh(PONOP-tBu)(Ph)Cl][BArF 4] 4 with experimental and literature evidence pointing toward a concerted C(sp2)-Cl bond oxidative addition mechanism. C(sp3)-Cl bond activation of dichloromethane, chlorocyclohexane, and 2-chloro-2-methylpropane by the rhodium(I) pincer occurred under considerably milder conditions, and radical mechanisms that commence with chloride atom abstraction and involve generation of the rhodium(II) metalloradical [Rh(PONOP-tBu)Cl][BArF 4] 6 are instead proposed. For dichloromethane, [Rh(PONOP-tBu)(CH2Cl)Cl][BArF 4] 5 was formed in the dark, but facile photo-induced reductive elimination occurred when exposed to light. Net dehydrochlorination affording [Rh(PONOP-tBu)(H)Cl][BArF 4] 7 and an alkene byproduct resulted for chlorocyclohexane and 2-chloro-2-methylpropane, consistent with hydrogen atom abstraction from the corresponding alkyl radicals by 6. This suggestion is supported by dynamic hydrogen atom transfer between 6 and 7 on the 1H NMR time scale at 298 K in the presence of TEMPO.

| S-EPMC9749114 | biostudies-literature

Electrocatalytic Azide Oxidation Mediated by a Rh(PNP) Pincer Complex.

Project description:One-electron oxidation of the rhodium(I) azido complex [Rh(N3 )(PNP)] (5), bearing the neutral, pyridine-based PNP ligand 2,6-bis(di-tert-butylphosphinomethyl)pyridine, leads to instantaneous and selective formation of the mononuclear rhodium(I) dinitrogen complex [Rh(N2 )(PNP)]+ (9+ ). Interestingly, complex 5 also acts as a catalyst for electrochemical N3- oxidation (Ep ?-0.23?V vs. Fc+/0 ) in the presence of excess azide. This is of potential relevance for the design of azide-based and direct ammonia fuel cells, expelling only harmless dinitrogen as an exhaust gas.

| S-EPMC5765409 | biostudies-literature

η2-Alkene Complexes of [Rh(PONOP-iPr)(L)]+ Cations (L = COD, NBD, Ethene). Intramolecular Alkene-Assisted Hydrogenation and Dihydrogen Complex [Rh(PONOP-iPr)(η-H2)].

Project description:Rhodium-alkene complexes of the pincer ligand κ3-C5H3N-2,6-(OPiPr2)2 (PONOP-iPr) have been prepared and structurally characterized: [Rh(PONOP-iPr)(η2-alkene)][BArF4] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; ArF = 3,5-(CF3)2C6H3]. Only one of these, alkene = COD, undergoes a reaction with H2 (1 bar), to form [Rh(PONOP-iPr)(η2-COE)][BArF4] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation. This difference in reactivity between COD and the other alkenes is proposed to be due to intramolecular alkene-assisted reductive elimination in the COD complex, in which the η2-bound diene can engage in bonding with its additional alkene unit. H/D exchange experiments on the ethene complex show that reductive elimination from a reversibly formed alkyl hydride intermediate is likely rate-limiting and with a high barrier. The proposed final product of alkene hydrogenation would be the dihydrogen complex [Rh(PONOP-iPr)(η2-H2)][BArF4], which has been independently synthesized and undergoes exchange with free H2 on the NMR time scale, as well as with D2 to form free HD. When the H2 addition to [Rh(PONOP-iPr)(η2-ethene)][BArF4] is interrogated using pH2 at higher pressure (3 bar), this produces the dihydrogen complex as a transient product, for which enhancements in the 1H NMR signal for the bound H2 ligand, as well as that for free H2, are observed. This is a unique example of the partially negative line-shape effect, with the enhanced signals that are observed for the dihydrogen complex being explained by the exchange processes already noted.

| S-EPMC8456414 | biostudies-literature

A Convenient Synthesis of 3,7'-Bisindole Derivatives.

Project description:An efficient and convenient method to synthesize highly functionalized 3,7'-bisindole derivatives has been developed via a Michael addition and cyclic condensation reaction of heterocyclic ketene aminals (HKAs) with 2-(1H-indol-3-yl)cyclohexa-2,5-diene-1,4-dione derivatives in ethanol-based solvents at room temperature. This strategy provides an efficient, environmentally friendly approach for easy access to various novel 3,7'-bisindole derivatives in moderate to good yields.

| S-EPMC6273136 | biostudies-literature

An efficient method for the preparation of styrene derivatives via Rh(III)-catalyzed direct C-H vinylation.

Project description:The development of a method for the Rh(III)-catalyzed direct vinylation of an aromatic C-H bond to give functionalized styrenes in good yield, using vinyl acetate as a convenient and inexpensive vinyl source, is reported. High functional group tolerance is demonstrated for electronically distinct arenes as well as different directing groups. Mechanistic investigation resulted in the characterization of a novel rhodium-metallacycle, which represents the first X-ray structure of a [1,2]-Rh(III)-alkenyl addition adduct.

| S-EPMC4446975 | biostudies-literature

A convenient method for the construction of triazole-bonded chalcone derivatives from acetophenone: Synthesis and free radical scavenging investigation

Project description:The substituted 1,2,3-triazole core is prevalent in numerous commercially available drugs utilized for a wide range of clinical applications. Simultaneously, chalcone represents a privileged framework discovered in natural products exhibiting intriguing bioactivities. In this study, we synthesized triazole-bonded chalcone compounds (4ax-4by), starting from a simple aromatic ketone, acetophenone, which underwent aldol condensation to give hydroxychalcone intermediate. In the second step, the hydroxyl group of chalcone compound was adducted with propargyl moiety through propargylation reaction. Then, the propargylated products underwent smooth copper-mediated azide-alkyne cyclization to give the triazole-bonded chalcones as the final products. They were characterized by IR, NMR and HRMS, and evaluated their radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH). Among the tested products, compound 4by was denoted as the most potent derivative which can inhibit DPPH radical in 91.62 ± 0.10% at 500 ppm.• Acetophenone as a simple ketone was modified to triazole-bonded chalcones.• Modification was performed through three steps reaction.• Final products exhibited free radical scavenging activity. Graphical abstract Image, graphical abstract

| S-EPMC10440577 | biostudies-literature

PNP

Project description:Towards personalized nutrition by prediction of glycemic responses

| PRJEB11532 | ENA

C-Methylated Spermidine Derivatives: Convenient Syntheses and Antizyme-Related Effects

Project description:The biogenic polyamines, spermidine (Spd) and spermine (Spm), are present at millimolar concentrations in all eukaryotic cells, where they participate in the regulation of vitally important cellular functions. Polyamine analogs and derivatives are a traditional and important instrument for the investigation of the cellular functions of polyamines, enzymes of their metabolism, and the regulation of the biosynthesis of antizyme—a key downregulator of polyamine homeostasis. Here, we describe convenient gram-scale syntheses of a set of C-methylated analogs of Spd. The biochemical properties of these compounds and the possibility for the regulation of their activity by moving a methyl group along the polyamine backbone and by changing the stereochemistry of the chiral center(s) are discussed.

| S-EPMC10296195 | biostudies-literature