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New Measurements of the Beam-Normal Single Spin Asymmetry in Elastic Electron Scattering over a Range of Spin-0 NucleiFree, publicly-accessible full text available April 1, 2023
Efficient Cobalt Catalyst for Ambient-Temperature Nitrile Dihydroboration, the Elucidation of a Chelate-Assisted Borylation Mechanism, and a New Synthetic Route to AmidesN,N-Diborylamines have emerged as promising reagents in organic synthesis; however, their efficient preparation and full synthetic utility have yet to be realized. To address both shortcomings, an effective catalyst for nitrile dihydroboration was sought. Heating CoCl2 in the presence of PyEtPDI afforded the six-coordinate Co(II) salt, [(PyEtPDI)CoCl][Cl]. Upon adding 2 equiv of NaEt3BH, hydride transfer to one chelate imine functionality was observed, resulting in the formation of (κ4-N,N,N,N-PyEtIPCHMeNEtPy)Co. Single-crystal X-ray diffraction and density functional theory calculations revealed that this compound possesses a low-spin Co(II) ground state featuring antiferromagnetic coupling to a singly reduced imino(pyridine) moiety. Importantly, (κ4-N,N,N,N-PyEtIPCHMeNEtPy)Co was found tomore »
Accurate Determination of the Neutron Skin Thickness of 208Pb through Parity-Violation in Electron ScatteringWe report a precision measurement of the parity-violating asymmetry APV in the elastic scattering of longitudinally polarized electrons from 208Pb. We measure APV=550±16(stat)±8(syst) parts per billion, leading to an extraction of the neutral weak form factor FW(Q2=0.00616 GeV2)=0.368±0.013. Combined with our previous measurement, the extracted neutron skin thickness is Rn−Rp=0.283±0.071 fm. The result also yields the first significant direct measurement of the interior weak density of 208Pb: ρ0W=−0.0796±0.0036(exp)±0.0013(theo) fm−3 leading to the interior baryon density ρ0b=0.1480±0.0036(exp)±0.0013(theo) fm−3. The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.