Jingjing Zhai,Fen You,Suting Xu,Ao Zhu,Xiaohui Kang,Yat-Ming So,Xiaochao Shi
A PNP-pincer ligand provides a versatile ligation framework, which is highly useful in organometallic chemistry and catalytic chemistry. In this work, by a de novo strategy, a simple and efficient synthetic pathway, has been developed to prepare the new iminodibenzyl-based PNP pincer proligand imin-RPNP(Li or H) (R = isopropyl, phenyl). By employing salt metathesis or direct alkyl elimination, we successfully synthesized a series of iminodibenzyl-PNP rare-earth-metal (Ln = Sc, Y, Dy, Ho, Er, Tm, Lu) complexes and characterized them by NMR and X-ray diffraction analyses. Upon addition of a borate and triisobutylaluminum (TIBA), the rare-earth-metal complexes 2-Y, 2-Dy, 2-Ho, 2-Er, and 2-Tm bearing the imin-PhPNP ligand exhibited unexpectedly high 3,4-selectivity (up to 95%) for the polymerization of 1,3-dienes (isoprene and myrcene); in particular, the chosen yttrium complex 2-Y promoted the 1,3-diene polymerization in a living manner. A computational study suggested that the sterically congested configuration around the metal center imposed by the imin-RPNP ligand might be the main reason for this unusual selectivity.
Dai Wu,Xiaojing Bai,Hong-Rui Tian,Weiting Yang,Zewen Li,Qing Huang,Shiyu Du,Zhong-Ming Sun
Two uranyl carboxyphosphonates (H2dipy)[(UO2)3(H2O)2(H2DPTP)2]·2H2O (DPTP-U1) and (H2bbi)[(UO2)4(H2O)2(HDPTP)2] (DPTP-U2) [H6DPTP = 2,5-diphosphonoterephthalic acid, dipy = 4,4′-bipyridine, bbi = 1,1′-(1,4-butanediyl)bis(imidazole)] were synthesized under hydrothermal conditions. The carboxyphosphonate ligand was formed through the in situ oxidation of (2,5-dimethyl-1,4-phenylene)diphosphonic acid mediated by UO22+. Single-crystal X-ray diffraction analyses reveal that DPTP-U1 possesses uranyl carboxyphosphonate layers that are separated by protonated dipy cations. Whereas DPTP-U2 is in a three-dimensional framework structure with channels filled by protonated bbi cations. The computational investigations give an insight into the nature of bonding interactions between uranium(VI) and carboxyphosphonate ligand. The spectroscopic properties were also studied.
Although nickel-based catalysts display good catalytic capability and excellent corrosion resistance under alkaline electrolytes for water splitting, it is still imperative to enhance their activity for real device applications. Herein, we decorated Ni 0.85 Se hollow nanospheres onto reduced graphene oxide (RGO) through a hydrothermal route, then annealed this composite at different temperatures (400 °C, NiSe 2 -400 and 450 °C, NiSe 2 -450) under argon atmosphere, yielding a kind of NiSe 2 /RGO composite catalysts. Positron annihilation spectra revealed two types of vacancies formed in this composite catalyst. We found that the NiSe 2 -400 catalyst with dual Ni-Se vacancies is able to catalyze the oxygen evolution reaction (OER) efficiently, needing a mere 241 mV overpotential at 10 mA·cm −2 . In addition, this catalyst exhibits outstanding stability. Computational studies show favorable energy barrier on NiSe 2 -400, enabling moderate OH − adsorption and O 2 desorption, which leads to the enhanced energetics for OER.
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