E-H Bond Activation of Ammonia and Water by a Geometrically Constrained Phosphorus(III) Compound.
Ontology highlight
ABSTRACT:
SUBMITTER: Robinson TP
PROVIDER: S-EPMC4648037 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:A geometrically constrained phosphine bearing a tridentate NNS pincer ligand is reported. The effect of the geometric constraint on the electronic structure was probed by theoretical calculations and derivatization reactions. Reactions with N-H bonds result in formation of cooperative addition products. The thermochemistry of these transformations is strongly dependent on the substrate, with ammonia activation being thermoneutral. This represents the first example of a molecular compound that reversibly activates ammonia via N-H bond scission in solution upon mild heating.
| S-EPMC8596738 | biostudies-literature
Project description:The ambiphilic nature of geometrically constrained Group?15 complexes bearing the N,N-bis(3,5-di-tert-butyl-2-phenolate)amide pincer ligand (ONO3- ) is explored. Despite their differing reactivity towards nucleophilic substrates with polarised element-hydrogen bonds (e.g., NH3 ), both the phosphorus(III), P(ONO) (1?a), and arsenic(III), As(ONO) (1?b), compounds exhibit similar reactivity towards charged nucleophiles and electrophiles. Reactions of 1?a and 1?b with KOtBu or KNPh2 afford anionic complexes in which the nucleophilic anion associates with the pnictogen centre ([(tBuO)Pn(ONO)]- (Pn=P (2?a), As (2?b)) and [(Ph2 N)Pn(ONO)]- (Pn=P (3?a), As (3?b)). Compound 2?a can subsequently be reacted with a proton source or benzylbromide to afford the phosphorus(V) compounds (tBuO)HP(ONO) (4?a) and (tBuO)BzP(ONO) (5?a), respectively, whereas analogous arsenic(V) compounds are inaccessible. Electrophilic substrates, such as HOTf and MeOTf, preferentially associate with the nitrogen atom of the ligand backbone of both 1?a and 1?b, giving rise to cationic species that can be rationalised as either ammonium salts or as amine-stabilised phosphenium or arsenium complexes ([Pn{ON(H)O}]+ (Pn=P (6?a), As (6?b)) and [Pn{ON(Me)O}]+ (Pn=P (7?a), As (7?b)). Reaction of 1?a with an acid bearing a nucleophilic counteranion (such as HCl) gives rise to a phosphorus(V) compound HPCl(ONO) (8?a), whereas the analogous reaction with 1?b results in the addition of HCl across one of the As-O bonds to afford ClAs{(H)ONO} (8?b). Functionalisation at both the pnictogen centre and the ligand backbone is also possible by reaction of 7?a/7?b with KOtBu, which affords the neutral species (tBuO)Pn{ON(Me)O} (Pn=P (9?a), As (9?b)). The ambiphilic reactivity of these geometrically constrained complexes allows some insight into the mechanism of reactivity of 1?a towards small molecules, such as ammonia and water.
| S-EPMC5095867 | biostudies-other
Project description:BackgroundWe suggest a new type of modeling approach for the coarse grained, particle-based spatial simulation of combinatorially complex chemical reaction systems. In our approach molecules possess a location in the reactor as well as an orientation and geometry, while the reactions are carried out according to a list of implicitly specified reaction rules. Because the reaction rules can contain patterns for molecules, a combinatorially complex or even infinitely sized reaction network can be defined. For our implementation (based on LAMMPS), we have chosen an already existing formalism (BioNetGen) for the implicit specification of the reaction network. This compatibility allows to import existing models easily, i.e., only additional geometry data files have to be provided.ResultsOur simulations show that the obtained dynamics can be fundamentally different from those simulations that use classical reaction-diffusion approaches like Partial Differential Equations or Gillespie-type spatial stochastic simulation. We show, for example, that the combination of combinatorial complexity and geometric effects leads to the emergence of complex self-assemblies and transportation phenomena happening faster than diffusion (using a model of molecular walkers on microtubules). When the mentioned classical simulation approaches are applied, these aspects of modeled systems cannot be observed without very special treatment. Further more, we show that the geometric information can even change the organizational structure of the reaction system. That is, a set of chemical species that can in principle form a stationary state in a Differential Equation formalism, is potentially unstable when geometry is considered, and vice versa.ConclusionsWe conclude that our approach provides a new general framework filling a gap in between approaches with no or rigid spatial representation like Partial Differential Equations and specialized coarse-grained spatial simulation systems like those for DNA or virus capsid self-assembly.
| S-EPMC2911456 | biostudies-literature
Project description:One-electron oxidation of the tetragonal Cu(II) complex [Bu(4)N][LCuOH] at -80 °C generated the reactive intermediate LCuOH, which was shown to be a Cu(III) complex on the basis of spectroscopy and theory (L = N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide). The complex LCuOH reacts with dihydroanthracene to yield anthracene and the Cu(II) complex LCu(OH(2)). Kinetic studies showed that the reaction occurs via H-atom abstraction via a second-order rate law at high rates (cf. k = 1.1(1) M(-1) s(-1) at -80 °C, ?H(‡) = 5.4(2) kcal mol(-1), ?S(‡) = -30(2) eu) and with very large kinetic isotope effects (cf. k(H)/k(D) = 44 at -70 °C). The findings suggest that a Cu(III)-OH moiety is a viable reactant in oxidation catalysis.
| S-EPMC3213683 | biostudies-literature
Project description:A novel non-innocent ligand class, namely cationic single-centre ambiphiles, is reported in the phosphine-functionalised cationic tetrylene Ni0 complexes, [PhR DippENi(PPh3 )3 ]+ (4 a/b (Ge) and 5 (Sn); PhR Dipp={[Ph2 PCH2 SiR2 ](Dipp)N}- ; R=Ph, i Pr; Dipp=2,6-i Pr2 C6 H3 ). The inherent electronic nature of low-coordinate tetryliumylidenes, combined with the geometrically constrained [N-E-Ni] bending angle enforced by the chelating phosphine arm in these complexes, leads to strongly electrophilic EII centres which readily bind nucleophiles, reversibly in the case of NH3 . Further, the GeII centre in 4 a/b readily abstracts the fluoride ion from [SbF6 ]- to form the fluoro-germylene complex PhR DippGe(F)Ni(PPh3 )3 9, despite this GeII centre simultaneously being a σ-donating ligand towards Ni0 . Alongside the observed catalytic ability of 4 and 5 in the hydrosilylation of alkynes and alkenes, this forms an exciting introduction to a multi-talented ligand class in cationic single-centre ambiphiles.
| S-EPMC9302135 | biostudies-literature
Project description:One of the main tactics to access C-N bonds from inactivated C-H functionalities is direct transition metal-supported aminations. Due to the often harsh reaction conditions, the current goal in the field is the search for more mild and sustainable transformations. Herein, we present the first solvent-free thermally induced C-N bond formation driven by Au(III) salts. The general structure of the products was confirmed by 1H, 13C, 15N NMR, TGA-DTA and ATR/FT-IR analysis. Additionally, all derivatives were tested as catalysts in a three-component coupling reaction between phenylacetylene, benzaldehyde and piperidine and as anticancer agents on HL-60 and MCF-7 cell lines.
| S-EPMC8036695 | biostudies-literature
Project description:We conducted bulk RNA sequencing on cells sorted by fluorescence from micropatterned colonies treated with FGF8 and different concentrations of WNT3a, using a SOX2::mCitrine cell line to distinguish between SOX2 positive and negative cells. The sequencing revealed that SOX2 negative cells exhibited a definitive endoderm identity, while SOX2 positive cells showed epiblast identity.
2024-04-09 | GSE263291 | GEO
Project description:Two metastable NiIII complexes, [NiIII(OAc)(L)] and [NiIII(ONO2)(L)] (L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate, OAc = acetate), were prepared, adding to the previously prepared [NiIII(OCO2H)(L)], with the purpose of probing the properties of terminal late-transition metal oxidants. These high-valent oxidants were prepared by the one-electron oxidation of their NiII precursors ([NiII(OAc)(L)]- and [NiII(ONO2)(L)]-) with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Fascinatingly, the reaction between any [NiII(X)(L)]- and NaOCl/acetic acid (AcOH) or cerium ammonium nitrate ((NH4)2[CeIV(NO3)6], CAN), yielded [NiIII(OAc)(L)] and [NiIII(ONO2)(L)], respectively. An array of spectroscopic characterizations (electronic absorption, electron paramagnetic resonance, X-ray absorption spectroscopies), electrochemical methods, and computational predictions (density functional theory) have been used to determine the structural, electronic, and magnetic properties of these highly reactive metastable oxidants. The NiIII-oxidants proved competent in the oxidation of phenols (weak O-H bonds) and a series of hydrocarbon substrates (some with strong C-H bonds). Kinetic investigation of the reactions with di-tert-butylphenols showed a 15-fold enhanced reaction rate for [NiIII(ONO2)(L)] compared to [NiIII(OCO2H)(L)] and [NiIII(OAc)(L)], demonstrating the effect of electron-deficiency of the O-ligand on oxidizing power. The oxidation of a series of hydrocarbons by [NiIII(OAc)(L)] was further examined. A linear correlation between the rate constant and the bond dissociation energy of the C-H bonds in the substrates was indicative of a hydrogen atom transfer mechanism. The reaction rate with dihydroanthracene (k2 = 8.1 M-1 s-1) compared favorably with the most reactive high-valent metal-oxidants, and showcases the exceptional reactivity of late transition metal-oxygen adducts.
| S-EPMC5119486 | biostudies-literature
Project description:A strategy of dynamic covalent chemistry within constrained biaryls was developed for the modulation of axial chirality. The ring fusion partners of amide and aldehyde allowed the manipulation of ring/chain equilibrium and chirality transfer within cyclic diastereomeric hemiaminal. Dynamic covalent reactions (DCRs) with alcohols, thiols, and secondary amines further enabled the reversal of chirality relay and thereby regulation of axial chirality. Moreover, a combination of NMR, X-ray, and density functional theory results shed light on the structural basis of chirality transfer, exhibiting modest to excellent diastereoselectivity under thermodynamic control. The critical role of the amide unit in the modulation of axial chirality was also corroborated. Finally, the chiroptical signal was controlled through changing solvents, DCRs, and stimuli-responsive switching of DCRs.
| S-EPMC6648723 | biostudies-literature
Project description:Black phosphorus was compressed at room temperature across the A17, A7 and simple-cubic phases up to 30?GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X-ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple-cubic phase. The Rietveld refinement of the data demonstrates the occurrence of a two-step mechanism for the A7 to simple-cubic phase transition, indicating the existence of an intermediate pseudo simple-cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non-layered simple-cubic phase of phosphorus, opening new perspectives for the design, synthesis and stabilization of phosphorene-based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of Tc in phosphorus below 30?GPa is provided.
| S-EPMC5836885 | biostudies-other