Synthesis And Organic Catalysis Of Lanthanide Clusters

The conversion of low-value organic molecules into high value-added organic compounds by catalysis is of great importance in biomedicine,industry and agrochemistry.In comparison to transition metals,rare earths exhibit many advantages in catalysis due to their own unique physical and chemical properties.In recent years,using lanthanide clusters for organic catalysis has been attracted great interest.In this work,we investigated a series of homogeneous or heterogeneous organosynthesis using lanthanide clusters or lanthanide clusters-based metal organic framework(MOFs).In addition,we focus on the chiral functionalization to synthesize chiral lanthanide clusters for asymmetric catalysis to obtain optically pure substances.Moreover,because of the well-defined crystal structures of lanthanide clusters,we endeavor to study the catalytic mechanism and structure-property relationship.Including the following progress:Hydroboration of amides via lanthanide clusters Ln16.We present the lanthanide clusters Ln16 derived from the assembly of Eu(NO3)3·6H2O and trifluoroacetylacetone ligands.The polynuclear Ln16 clusters are shown to act as efficient catalyst for the reduction of amides with broad substrate scope,and also can be applied for the synthesis of phenethylamine drug in gram-scale.The catalytic mechanism was investigated by NMR,single crystal X-ray diffraction and a series of control experiments.The results showed that the catalytic process involves the in-situ generation of {Ln16}-H metalhydrides and BH3 species for the reduction of amides in a multipath hydroboration.Hydroboration of amides via lanthanide clusters-based RuEu-phen-MOF.The flexible RuL3 propeller tridentate ligands coordinated with Eu(NO3)3·6H2O to form a lanthanide clusters-based RuEu-phen-MOF with Eu6 secondary building unites.The multinuclear structure of RuEu-phen-MOF was confirmed by X-ray powder diffraction and single-crystal structure simulation.Heterogeneous RuEu-phen-MOF were applied to the reduction of amides to amines with moderate to high yield(70-91%).RuEu-phenMOF can be recycled for five times with no significant decrease in the yield of amines(83%).The mechanism study shows that Eu6 cluster activated the amide,and then coordinated with BH3 to generate a tetracyclic ring active adduct.Subsequently followed by the transfer of active H from HBpin to achieve the reduction of the amide.Asymmetric cyanosilylation of aldehydes by chiral metal clusters of R-/S-Co3Ln2.Two pairs of chiral lanthanide-transition metal clusters R-/S-Co3Ln2(Ln=Tb and Dy)were synthesized using Schiff-based ligands.The as-prepared R-/S-Co3Ln2 chiral metal clusters exhibited good catalytic functionality in the asymmetric synthesis of chiral cyanohydrins,with high conversions of up to 99%,and medium to high enantiomeric excess(ee)values of up to 78%.The catalysis process followed a mechanism in which the bifunctional metal clusters of R-/S-Co3Ln2,containing Lewis acid sites and Lewis base sites,simultaneously activated the aldehydes and trimethylsilyl cyanide(TMSCN),respectively.Consequently,synergistic catalysis was realized.The enantioselectivity of the different aldehydes and stereochemical configuration of the resulting products are attributed to the formation of the steric chiral pocket via the external chiral ligands on the clusters.In addition,heterogeneous asymmetric cyanosilylation using R-/S-Co3Ln2 chiral metal clusters achieved high chemoselectivity and regioselectivity under mild conditions,and it could be recycled three times with no significant decrease in catalytic activity and enantioselectivity.Enantioselective synthesis,recognition and separation of C2 symmetric substances via chiral lanthanide clusters-based Δ-/Λ-RuEu-MOF.The chiral Δ-/Λ-RuEu-MOF constructed from chiral Ru(phen)3-derived tricarboxylate ligand and Eu2 lanthanide clusters.Its application to the synthesis of chiral BINOL was initially explored.The circular dichroism(CD)enantiodifferentiation between host and guest suggested thatΔ-/Λ-RuEu-MOF can be employed as chiral sensor to discriminate axial enantiomers.The mechanism study revealed that chiral recognition was attributed to the distinguishing binding affinities stemming from N…H-O hydrogen bonds and π-πstacking between host and guest.Moreover,Δ-/Λ-RuEu-MOF can be readily recycled and reused for successive enantioselective separation of BINOL up to 80% ee.