Organomagnesia: Reversibly High Carbon Dioxide Uptake by Magnesium Pyrazolates

A series of new pyrazolate and mixed pyrazolate/pyrazole magnesium complexes is described and their reactivity toward carbon dioxide is examined. The dimeric complex [Mg(pzt Bu, t Bu)2]2 inserts CO2 instantly and quantitatively forming the tetrameric complex [Mg(CO2·pzt Bu, t Bu)2]4 and monomeric donor-stabilized [Mg(CO2·pzt Bu, t Bu)2(thf)2]. Complexes of the type [Mgx(pzR,R)2 x(HpzR,R)y]n (R = iPr, tBu) engage in similar insertion reactions involving dissociation of the carbamic acid HOOCpzR,R. Even solid polymeric derivatives [Mg(pzR,R)2]n (R = Me, H) react instantaneously and exhaustively with CO2, the resulting [Mg(CO2·pz)2]m featuring a CO2 capacity of 35.7 wt% (8.2 mmol g-1). All described magnesium pyrazolates display completely reversible CO2 uptake in solution and in the solid state, respectively, as monitored via VT 1H NMR and in situ FTIR spectroscopy as well as thermogravimetric analysis. Fluorinated [Mg2(pzCF3,CF3)4(thf)3] does not yield any isolable CO2 insertion product but exhibits the highest activity in the catalytic transformation of epoxides and CO2 to cyclic carbonates.

In-depth study on the structures and properties of rare-earth-containing perovskite materials

Rare-earth-containing perovskite (RECP) materials have been extensively studied in various fields for their outstanding optical, electrical, magnetic and catalytic properties. In order to understand the clear relationship between structures and functions of RECP materials, the high-level and effective characterization technologies and analytic methods are absolutely necessary. Normally, diversiform measurement methods should be used simultaneously to analyze RECP materials clearly from different aspects, such as the phases, structures, morphologies, compositions, properties and performances. Therefore, this review will introduce the features and advantages of different analytic technologies and discuss their significances for the research on RECP materials. We hope that this review will provide valuable suggestions for researchers to promote the further research and development of RECP functional materials in the future.

Emergence of a New [NNN] Pincer Ligand via Si-H Bond Activation and β-Hydride Abstraction at Tetravalent Cerium

The cerium(IV) pyrazolate complexes [Ce(Me2 pz)4 ]2 and [Ce(Me2 pz)4 (thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me2 pz)3 (bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me2 pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si-H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2 pz)4 ]2 is treated with [Li{N(SiMe3 )2 }], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2 (Me2 pz)9 ] and the stable mixed-ligand ceric species [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] were obtained.