Intermolecular Methyl Group Exchange and Reversible P–Me Bond Cleavage at Cobalt(III) Dimethyl Halide Species

The cobalt­(III) dimethyl halide complexes <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂X (X = Cl, I) were found to undergo a degenerate cobalt-to-cobalt transfer of the methyl ligands during isotopic labeling experiments. Extensive mechanistic studies exclude radical, methyl iodide elimination, and disproportionation/comproportionation pathways for exchange of the methyl groups between metals. A related cobalt­(III) dimethyl complex supported by the tridentate phosphine ligand MeP­(CH₂CH₂PMe₂)₂ showed dramatically slower methyl ligand transfer, indicative of a mechanism for intermetallic exchange with a requisite phosphine dissociation. Crossover experiments between cobalt­(III) dimethyl halide complexes supported by PMe₃ and MeP­(CH₂CH₂PMe₂)₂ are consistent with a dicobalt transition structure in which only one cobalt center requires phosphine dissociation prior to methyl transfer. An additional methyl group scrambling process between <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂I and free PMe₃ was also identified during the investigation and originates from reversible P–CH₃ bond cleavage

C–CN Bond Activation of Acetonitrile using Cobalt(I)

A cobalt­(I) methyl species, (PMe₃)₄CoCH₃, was found to promote C–CN bond oxidative addition of acetonitrile at ambient temperature. The isolated product of acetonitrile activation, <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂CN, was characterized by NMR, IR, and single-crystal X-ray diffraction studies and presents a higher valent metal in comparison to those previously observed for base-metal-mediated nitrile activations. A short-lived reaction intermediate was detected during nitrile cleavage and identified as <i>fac</i>-(PMe₃)₃Co­(CH₃)₂CN, the kinetic product of C–CN oxidative addition. Conversion of the kinetic product to <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂CN proceeds with a rate constant of [1.0(1)] × 10^–3 s^–1 at 27 °C

Intermolecular Methyl Group Exchange and Reversible P–Me Bond Cleavage at Cobalt(III) Dimethyl Halide Species

The cobalt­(III) dimethyl halide complexes <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂X (X = Cl, I) were found to undergo a degenerate cobalt-to-cobalt transfer of the methyl ligands during isotopic labeling experiments. Extensive mechanistic studies exclude radical, methyl iodide elimination, and disproportionation/comproportionation pathways for exchange of the methyl groups between metals. A related cobalt­(III) dimethyl complex supported by the tridentate phosphine ligand MeP­(CH₂CH₂PMe₂)₂ showed dramatically slower methyl ligand transfer, indicative of a mechanism for intermetallic exchange with a requisite phosphine dissociation. Crossover experiments between cobalt­(III) dimethyl halide complexes supported by PMe₃ and MeP­(CH₂CH₂PMe₂)₂ are consistent with a dicobalt transition structure in which only one cobalt center requires phosphine dissociation prior to methyl transfer. An additional methyl group scrambling process between <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂I and free PMe₃ was also identified during the investigation and originates from reversible P–CH₃ bond cleavage

C–CN Bond Activation of Acetonitrile using Cobalt(I)

A cobalt­(I) methyl species, (PMe₃)₄CoCH₃, was found to promote C–CN bond oxidative addition of acetonitrile at ambient temperature. The isolated product of acetonitrile activation, <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂CN, was characterized by NMR, IR, and single-crystal X-ray diffraction studies and presents a higher valent metal in comparison to those previously observed for base-metal-mediated nitrile activations. A short-lived reaction intermediate was detected during nitrile cleavage and identified as <i>fac</i>-(PMe₃)₃Co­(CH₃)₂CN, the kinetic product of C–CN oxidative addition. Conversion of the kinetic product to <i>cis,mer</i>-(PMe₃)₃Co­(CH₃)₂CN proceeds with a rate constant of [1.0(1)] × 10^–3 s^–1 at 27 °C

Data_Sheet_1_Plant-soil-enzyme C-N-P stoichiometry and microbial nutrient limitation responses to plant-soil feedbacks during community succession: A 3-year pot experiment in China.docx

Studying plant-soil feedback (PSF) can improve the understanding of the plant community composition and structure; however, changes in plant-soil-enzyme stoichiometry in response to PSF are unclear. The present study aimed to analyze the changes in plant-soil-enzyme stoichiometry and microbial nutrient limitation to PSF, and identify the roles of nutrient limitation in PSF. Setaria viridis, Stipa bungeana, and Bothriochloa ischaemum were selected as representative grass species in early-, mid-, and late-succession; furthermore, three soil types were collected from grass species communities in early-, mid-, and late-succession to treat the three successional species. A 3-year (represents three growth periods) PSF experiment was performed with the three grasses in the soil in the three succession stages. We analyzed plant biomass and plant-soil-enzyme C-N-P stoichiometry for each plant growth period. The plant growth period mainly affected the plant C:N in the early- and late- species but showed a less pronounced effect on the soil C:N. During the three growth periods, the plants changed from N-limited to P-limited; the three successional species soils were mainly limited by N, whereas the microbes were limited by both C and N. The plant-soil-enzyme stoichiometry and plant biomass were not significantly correlated. In conclusion, during PSF, the plant growth period significantly influences the plant–soil–microbial nutrient limitations. Plant-soil-enzyme stoichiometry and microbial nutrient limitation cannot effectively explain PSF during succession on the Loess Plateau.</p

Immune Cell Infiltration Types as Biomarkers for the Recurrence Diagnosis and Prognosis of Bladder Cancer

This study aimed to investigate the role of infiltrating immune cell types in diagnosing and predicting bladder cancer recurrence. This study mainly applied some algorithms, including Estimate the Proportion of Immune and Cancer Cells (EPIC), support vector machine-recursive feature elimination (SVM-RFE), random forest out-of-bag (RF-OOB) and least absolute shrinkage and selection operator (LASSO)-Cox regression analysis. We found six immune infiltrating cell types significantly associated with recurrence prognosis and two independent clinical prognostic factors. Infiltrating immune cell types (IICTs) based on the prognostic immune risk score (pIRS) models may provide significant biomarkers for the diagnosis and prognostic prediction of bladder cancer recurrence.</p

Structural Characterization of β‑Agostic Bonds in Pd-Catalyzed Polymerization

β-agostic Pd complexes are critical intermediates in catalytic reactions, such as olefin polymerization and Heck reactions. Pd β-agostic complexes, however, have eluded structural characterization, due to the fact that these highly unstable molecules are difficult to isolate. Herein, we report the single-crystal X-ray and neutron diffraction characterization of β-agostic (α-diimine)­Pd–ethyl intermediates in polymerization. Short C_α–C_β distances and acute Pd–C_α–C_β bond angles combined serve as unambiguous evidence for the β-agostic interaction. Characterization of the agostic structure and the kinetic barrier for β-H elimination offer important insight into the fundamental understanding of agostic bonds and the mechanism of polymerization

Additional file 1: of Biochemical and proteomics analyses of antioxidant enzymes reveal the potential stress tolerance in Rhododendron chrysanthum Pall

GO functional classification of all up-regulated proteins. (XLSX 67 kb

Additional file 1 of Acetylation proteomics and metabolomics analyses reveal the involvement of starch synthase undergoing acetylation modification during UV-B stress resistance in Rhododendron Chrysanthum Pall

Supplementary Material 1

Bimetallic C–C Bond-Forming Reductive Elimination from Nickel

Ni-catalyzed cross-coupling reactions have found important applications in organic synthesis. The fundamental characterization of the key steps in cross-coupling reactions, including C–C bond-forming reductive elimination, represents a significant challenge. Bimolecular pathways were invoked in early proposals, but the experimental evidence was limited. We present the preparation of well-defined (pyridine-pyrrolyl)­Ni monomethyl and monophenyl complexes that allow the direct observation of bimolecular reductive elimination to generate ethane and biphenyl, respectively. The sp³–sp³ and sp²–sp² couplings proceed via two distinct pathways. Oxidants promote the fast formation of Ni­(III) from (pyridine-pyrrolyl)­Ni-methyl, which dimerizes to afford a bimetallic Ni­(III) intermediate. Our data are most consistent with the subsequent methyl coupling from the bimetallic Ni­(III) to generate ethane as the rate-determining step. In contrast, the formation of biphenyl is facilitated by the coordination of a bidentate donor ligand