Magnetostriction of Pseudobinary Compounds Pr_(0.15)Tb_xDy_(0.85-x)Fe_2(x=0 to 0.85)

The compound ingots of Pr0.15TbxDy0.85-xFe2 (x=0 to 0.85) were prepared by arc melting in a water Cu boat using arc furnace under a purified Ar atmosphere. Appropriate annealing (850℃, 100 h) can obtain single Laves phase compound. The magnetostriction for these systems will rise obviously when partially substituted Tb or Dy by Pr.

Nickel/Quinim Enabled Asymmetric Carbamoyl-Acylation of Unactivated Alkenes

Transition metal-catalyzed difunctionalization of tethered alkene has emerged as a prevailing tool for the expedient construction of synthetically valuable cyclic compounds.However,most efforts have been devoted to the reaction of styrene-type substrates due to their rigid scaffold and high reactivity.With respect to the difunctionalization of nonaromatic tethered olefin,especially the mono-substituted alkene,still remains largely underdeveloped.Herein,we disclose a nickel/Quinim complex and TBADT-cocatalyzed asymmetric carbamoyl-acylation of unactivated alkene tethered on nonaromatic carbamoyl chlorides with diverse aldehydes.The reaction exhibits broad substrate scope with good functional group tolerance,as well as high reaction efficiency and enantioselectivity.Both monosubstituted and 1,1-substituted alkenes can work well with either aliphatic or aromatic aldehydes under the current protocol,providing convenient access to an array of medicinally useful chiralγ-lactams derivatives bearing a convertible acyl functionality.This reaction showcases more application possibilities of the chiral Quinim ligand in the future asymmetric catalytic transformations.

Nickel-Catalyzed Regiodivergent Acylzincation of Styrenes with Organozincs and CO

Transition metal-catalyzed carbometallation of unsaturated hydrocarbons constitutes one of the most efficient synthetic methodologies for the construction of C—C bond.Recently,the incorporation of organometallic reagent with the CO gas as a nucleophilic acyl synthon could enable the acylmetallation reaction,which greatly increases the horizon of carbometallation chemistry.Herein,we report a nickel-catalyzed regiodivergent acylzincation of o-cyano cinnamate ester and o-cyano styrene,in which the cyano moiety intramolecularly captures zinc intermediates to trigger the tandem cyclization process.This protocol features mild conditions,broad substrate scope and excellent functional group tolerance,thus affording a diverse array of highly functionalized carbocyclic compounds.

Enantioselective Synthesis ofα-Alkenylatedγ-Lactam Enabled by Ni-Catalyzed 1,4-Arylcarbamoylation of 1,3-Dienes

The facile construction of chiral quaternaryα-alkenylated pyrrolidinones is a long-term challenge in organic synthesis.The asymmetric difunctionalization of 1,3-dienes represents the most compelling tool for assembling alkenylated compounds by regioselective 1,2-or 1,4-difunctionalization.Nevertheless,the manipulation of unactivated 1,3-dienes to forge the quarternary stereogenic center still remains largely underdeveloped.Herein,we disclose a nickelcatalyzed asymmetric 1,4-arylcarbamoylation of unactivated 1,3-dienes tethered on carbamoyl fluoride with readily available arylboronic acids,providing rapid access to the enantioenrichedα-alkenylated pyrrolidinones bearing the quaternary stereogenic center in high yields with broad functional group tolerance.Moreover,this chiral ligand-controlled asymmetric transformation overcomes the intrinsic substrate control with a preexisting chiral center.

Pd-catalyzed diastereoselective 1,1-diarylation of 1,1-disubstituted alkenes enabling the modular synthesis of 1,1,2,2-tetraarylethanes

The highly diastereoselective dicarbofunctionalization of substituted olefins still remains a daunting challenge in synthetic chemistry.Herein,we report a Pd-catalyzed diastereoselective 1,1-diarylation of 1,1-diarylethylene with chelation group free to enable the modular synthesis of smart material candidates,1,1,2,2-tetraarylethanes(TAEs),which represent the first protocol by assembling four different aryl groups into ethane motif.Preliminary mechanistic experiments suggest that the crucial Pd–H species generated in situ do not disengage from the alkene intermediate during the reaction.

Construction of a low-valent thiolate-bridged dicobalt platform and its reactivity toward hydrogen activation and evolution

Low-valence transition metallic complexes have drawn longstanding attention due to their high reactivity toward catalytic transformation of various small molecules.Among these known complexes,the low-valence metal centres are commonly stabilized by neutral bulky ligands with strong electron-donating capacity.However,low-valence bimetallic complexes supported by anionic sulfur and cyclopentadienyl ligands are still difficult to obtain in high isolated yield.Herein,we report the synthesis and characteri-zation of two scarce thiolate-bridged Co^(I)Co^(II)and Co^(I)Co^(I)complexes bearing sterically demanding ligands through two stepwise one-electron reduction processes.Interestingly,the Co^(I)Co^(II)complex can facilely promote the homolytic cleavage of dihydrogen across the short Co−Co metallic bond to give a Co^(II)Co III dihydride bridged complex,which is capable of serving as a competent hydrogen atom transfer agent.Moreover,the anionic Co^(I)Co^(I)complex can trigger a stepwise hydrogen generation cycle involving several isolated and structurally well-characterized intermediates.

Electronic Structure of Thiolate-bridged Diiron Complexes and a Single-electron Oxidation Reaction＂ A Combination of Experimental and Computational Studies

Single-electron oxidation of a diiron-sulfur complex [Cpπ＊Fe（μ-bdt）FeCp^＊] （1, Cp^＊=η^5-C5Me5; bdt = benzene-1,2-dithiolate） to [Cp^＊Fe（μ-bdt）FeCp^＊]]^＋ （2） has been experimentally conducted. The bdt ligand with redoxactive character has been computationally proposed to be a dianion （bdt62-） rather than previously proposed monoanion （bdt^-） radical in 1 though it has un-equidistant aromatic C-C bond lengths. The ground state of 1 is predicted to be two low-spin ferrous ions （SFe= 0） and 2 has a medium-spin ferric ion （SFe= 1/2） and a low-spin ferrous center （SFe=0）, and the oxidation of 1 to 2 is calculated to be a single-metal-based process. Both complexes have no significant antiferromagnetic coupling character.

Synthesis,characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes

Thiolate-bridged hetero-bimetallic complexes[Cp^(*)M(MeCN)N_(2)S_(2)FeCl][PF_(6)](2,M=Ru;3,M=Co,Cp^(*)=η^(5)-C_(5)Me_(5),N_(2)S_(2)=N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate)were prepared by self-assembly of dimer[N_(2)S_(2)Fe]2 with mononuclear precursor[Cp^(*)Ru(MeCN)_(3)][PF_(6)]or[Cp^(*)Co(MeCN)_(3)][PF_(6)]_(2)in the presence of CHCl_(3)as a chloride donor.Complexes 2 and 3 exhibit obviously different redox behaviors investigated by cyclic voltammetry and spin density distributions supported by DFT calculations.Notably,iron-cobalt complex 3 possesses versatile reactivities that cannot be achieved for complex 2.In the presence of CoCp_(2),complex 3 can undergo one-electron reduction to generate a stable formally Co^(II)Fe^(II)complex[Cp^(*)CoN_(2)S_(2)FeCl](4).Besides,the terminal chloride on the iron center in 3 can be removed by dehalogenation agent AgPF_(6)or exchanged with azide to afford the corresponding complexes[Cp^(*)Co(MeCN)N_(2)S_(2)Fe(MeCN)][PF_(6)]_(2)(5)and[Cp^(*)Co(MeCN)N_(2)S_(2)Fe(N_(3))][PF_(6)](6).In addition,complexes 2,3 and 4 show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia.These results may be helpful to understand the vital role of the heterometal in some catalytic transformations promoted by heteromultinuclear complexes.

Palladium-catalyzed stereoselective trifluoromethylated allylic alkylation of 3-substituted oxindoles

An efficient catalytic methodology for trifluoromethylated allylic alkylation of 3-substituted oxindoles usingα-(trifluoromethyl)alkenyl acetates as the trifluoromethyl-containing allylic alkylation partner is described.The reaction proceeds smoothly with the incorporation of Pd(OAc)_(2) and(R)-BINAP,affording various functionalized trifluoromethyl-containing 3,3’-disubstituted oxindoles with high yields and good enantioselectivities.