429-42-5Relevant articles and documents
Electrochemical studies of the nickel catecholate complexes for detection of sulphur dioxide gas
Tembwe, Inonge,Ngila, J. Catherine,Kgarebe, Boitumelo,Darkwa, James,Iwuoha, Emmanuel
, p. 4314 - 4318 (2010)
Nickel catecholate complexes, bis(diphenylphosphino)ethanenickelcatecholate [(dppe)NiO2C6H34-R1] R1 = CH3 (1), C(CH3)3 (2), H (3) and F (4)] were studied using CV and
Controlling Metal-to-Oxygen Ratios via M=O Bond Cleavage in Polyoxovanadate Alkoxide Clusters
Petel, Brittney E.,Fertig, Alex A.,Maiola, Michela L.,Brennessel, William W.,Matson, Ellen M.
, p. 10462 - 10471 (2019)
In this manuscript, we further investigate the use of Lindqvist polyoxovanadate alkoxide (POV-alkoxide) clusters as homogeneous molecular models of reducible metal oxides (RMO), focusing on the structural and electronic consequences of forming one or two oxygen-deficient sites. We demonstrate the reactivity of a neutral POV-alkoxide cluster, [V6O7(OCH3)12]0, with a reductant, revealing routes for controlling metal-to-oxygen ratios in self-assembled polynuclear ensembles through post-synthetic modification. The outlook of this science is bolstered by the fact that, in both cases, O-atom removal reveals reduced V ions at the surface of the cluster. Extending our entry into small-molecule activation mediated by surface defect sites, we report the reactivity of mono- and divacant clusters with a model substrate, tert-butyl isocyanide, demonstrating the electronic consequences of small-molecule coordination to reduced ions in RMO materials.
Assessing the Electrocatalytic Properties of the (Cp*RhIII)2+-Polyoxometalate Derivative [H2PW11O39(RhIIICp*(OH2))]3- towards CO2 Reduction
Girardi, Marcelo,Platzer, Dominique,Griveau, Sophie,Bedioui, Fethi,Alves, Sandra,Proust, Anna,Blanchard, Sébastien
, (2018)
Storage of electricity produced intermittently by renewable energy sources is a societal issue. Besides the use of batteries and supercapacitors, conversion of excess electricity into chemical energy is also actively investigated. The conversion of CO2 to fuel or fuel precursors is an option that requires the use of a catalyst to overcome the high activation energy barrier. Of molecular catalysts, metal complexes with polypyridyl ligands are well represented, among which the [Cp*Rh(bpy)Cl]+ and [M(bpy)(CO)3X] (M = Re, Mn) complexes. As redox non-innocent ligand, the bipyridine ligand is generally involved in the reduction mechanisms. It is thus tempting to replace it by other redox non-innocent ligands such as vacant polyoxometalates (POMs). We have thus prepared [α-H2PW11O39(RhIIICp*(OH2))]3- which is closely related to [Cp*RhIII(bpy)Cl]+ by substitution of the monovacant [PW11O39]7- Keggin-type POM for the bipyridine ligand. Its activity towards CO2 reduction has been assessed in acetonitrile in the presence of water. Compared to [Cp*Rh(bpy)Cl]+ that produces formate selectively over CO and H2, the POM derived catalyst favors proton reduction over CO2 reduction.
Stereoelectronic and Resonance Effects on the Rate of Ring Opening of N-Cyclopropyl-Based Single Electron Transfer Probes
Grimm, Michelle L.,Suleman, N. Kamrudin,Hancock, Amber N.,Spencer, Jared N.,Dudding, Travis,Rowshanpour, Rozhin,Castagnoli, Neal,Tanko, James M.
supporting information, p. 2640 - 2652 (2020/02/18)
N-Cyclopropyl-N-methylaniline (5) is a poor probe for single electron transfer (SET) because the corresponding radical cation undergoes cyclopropane ring opening with a rate constant of only 4.1 × 104 s-1, too slow to compete with other processes such as radical cation deprotonation. The sluggish rate of ring opening can be attributed to either (i) a resonance effect in which the spin and charge of the radical cation in the ring-closed form is delocalized into the phenyl ring, and/or (ii) the lowest energy conformation of the SET product (5a￠+) does not meet the stereoelectronic requirements for cyclopropane ring opening. To resolve this issue, a new series of N-cyclopropylanilines were designed to lock the cyclopropyl group into the required bisected conformation for ring opening. The results reveal that the rate constant for ring opening of radical cations derived from 1′-methyl-3′,4′-dihydro-1′H-spiro[cyclopropane-1,2′-quinoline] (6) and 6′-chloro-1′-methyl-3′,4′-dihydro-1′H-spiro[cyclopropane-1,2′-quinoline] (7) are 3.5 × 102 s-1 and 4.1 × 102 s-1, effectively ruling out the stereoelectronic argument. In contrast, the radical cation derived from 4-chloro-N-methyl-N-(2-phenylcyclopropyl)aniline (8) undergoes cyclopropane ring opening with a rate constant of 1.7 × 108 s-1, demonstrating that loss of the resonance energy associated with the ring-closed form of these N-cyclopropylanilines can be amply compensated by incorporation of a radical-stabilizing phenyl substituent on the cyclopropyl group. Product studies were performed, including a unique application of EC-ESI/MS (Electrochemistry/ElectroSpray Ionization Mass Spectrometry) in the presence of 18O2 and H218O to elucidate the mechanism of ring opening of 7a￠+ and trapping of the resulting distonic radical cation.
Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
supporting information, (2020/03/13)
Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
