Light-, Middle- and Heavy-Lanthanide Ate-Complexes Bearing Ln(Ⅲ)-Si bonds: Structural, Spectroscopic, and Bonding Analysis

Recent decades have witnessed a rapid development of the lanthanide silicon chemistry.In this research,by reacting[(THF)_(3)LisiPh_(3)]with Cp_(3)Ln(Ⅰ)(THF)(Ln(I)=Sm(Ⅰ),Tb(Ⅱ),Dy(Ⅰ),Yb(Ⅰ)or Cp_(2)Lu(Ⅱ)CI(THF),a series of middle-and heavy-lanthanocene monosilyl/disilyl ate-complexes([(DME)_(3)Lil[Cp_(3)Ln(Ⅱ)SiPh_(3)]and[(DME)_(3)Li[Cp_(2)Lu(Ⅱ)(SiPh_(3))_(2)])were synthesized.The structures of the obtained lanthanocene monosilyl/disilyl ate-complexes were determined by single crystal X-ray diffraction.Together with the previously reported[(DME)_(3)Li[Cp_(3)La(Ⅱ)SiPh_(3)]and[(DME);Lil[Cp_(3)Ce(Ⅱ)SiPha],a complex group comprising silyl light-,middle-and heavy-lanthanocene with identical core coordination pattern are presented.

Deep-blue organic light-emitting diodes based on a doublet d-f transition cerium(Ⅲ) complex with 100% exciton utilization efficiency

Compared to red and green organic light-emitting diodes(OLEDs),blue OLEDs are still the bottleneck due to the lack of efficient emitters with simultaneous high exciton utilization efficiency(EUE)and short excited-state lifetime.Different from the fluorescence,phosphorescence,thermally activated delayed fluorescence(TADF),and organic radical materials traditionally used in OLEDs,we demonstrate herein a new type of emitter,cerium(Ⅲ)complex Ce-1 with spin-allowed and parity-allowed d-f transition of the centre Ce^(3+) ion.The compound exhibits a high EUE up to 100% in OLEDs and a short excited-state lifetime of 42 ns,which is considerably faster than that achieved in efficient phosphorescence and TADF emitters.The optimized OLEDs show an average maximum external quantum efficiency(EQE)of 12.4% and Commission Internationale de L’Eclairage(CIE)coordinates of(0.146,0.078).

Conversion of Carbonyl Compounds to Olefins via Enolate Intermediate

Summary of main observation and conclusion A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C-O activation of enolates was developed.Besides ketones,aldehydes were also suitable substrates for the presented catalytic system to produce di-or tri-substituted olefins.It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols,which could not survive in other reported routes for converting carbonyl compounds to olefins.This method also showed good regio-and stereo-selectivity for olefin products.Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C-O activation of enolates,thus offering helpful contribution to current enol chemistry.

Dancing on Ropes-Enantioselective Functionalization of Preformed Four-Membered Carbocycles

Cyclobutane derivatives have been recognized as useful structural motifs in organic synthesis and drug design.With the revival of photochemistry,the enantioselective synthesis of cyclobutane derivatives using[2+2]-cycloadditions has garnered numerous attentions.On the other hand,enantioselec-tive functionalization of preformed four-membered carbocycles is emerging as an important complementary approach to access chiral cyclobutane de-rivatives with versatile structural patterns.Herein,we summarize recent advances in this field from 2012.To avoid undesired C—C bond cleavage driv-en by strain-releasing,it is crucial to choose compatible methods for enantioselective functionalization and meanwhile preserving intact four-membered ring skeleton.Guided by calculated hydrogenation enthalpies,which are used to evaluate the strain energy of indicated C—C bond,a clear picture of the developed methodologies on functionalization of four-membered carbocycles combining the strain energy and enhanced reactivity is presented.

A mixed-valent high spin(μ-hydroxo)dicobalt(Ⅱ/Ⅲ) complex and its end-on type dioxygen adduct: synthesis, geometric and electronic structure studies

A mixed-valent high spin (μ-hydroxo)dicobalt(Ⅱ/Ⅲ) complex bearing N,N′-bis(5-tertbutylsalicylidene)-1,2-diaminobenzene(Salophen^(tBu)) ligand was synthesized by reacting (Salophen^(tBu))Co(Ⅱ)(Py) with O_(2) at low temperature.This complex was isolated and structurally characterized by single crystal X-ray diffraction and infrared spectrum.Magnetic measurement showed a quartet ground state for this complex at room temperature,which was also supported by electron paramagnetic resonance (EPR)characterization.Computational investigations indicated the deviation of the equatorial N_(2)O_(2) coordination geometry around the Co(Ⅱ) center from plane stabilized the quartet state.The end-on type O_(2) adduct of this (μ-hydroxo)dicobalt(Ⅱ/Ⅲ) complex was isolated as dark-brown crystals and structurally and spectroscopically characterized.EPR measurement of this compound in solid state at room temperature presented an isotropic singlet at g~2,revealing the superoxide-like electronic feature of the coordinated O_(2) and was in line with the calculation results.The reactivity of the Co(Ⅲ)-O_(2) complex with N-hydroxyphthalimide,which can act as hydrogen atom donor,was also examined.