Synthesis，Characterization And Catalytic Behavior Of Lanthanide Complexes Supported By Dianionic Guanidinate And Bridged Bis(guanidinate)

A series of lanthanide complexes supported by dianionic guanidinate ligand([（NC₆H₄p-Cl）C（NiPr）₂]^2-) and bridged bis（guanidinate） ligands ([R（Me₃Si）NC（NR）N（CH₂）₃NC（NR）N（SiMe₃）R]（R=iPr，L；R=Cy，L′） were synthesized and well characterized, including dianionic guanidinate alkoxide complexes and bridged bis（guanidinate） borohydride, amide, benzyl, as well as divalent complexes. The catalytic activity of heterobimetallic dianionic guanidinate complexes of lanthanide and lithium [{Li（THF）（DME）}₃Ln{μ-η²η¹（iPrN）₂C（NC₆H₄p-Cl）}₃] in addition of diamines to carbodiimides affording the corresponding biguanidine compounds weretested. Activation of bis（guanidinate） lanthanide benzyl complexes with differentnitriles were studied. Furthermore, catalytic behavior of the lanthanide borohydride and amide complexes in polymeraztion of cyclic esters were studied. The mainachievements are as follows:1. The heterobimetallic dianionic guanidinate complexes of lanthanide and lithium[{Li（THF）（DME）}₃Ln{μ-η²η¹（iPrN）₂C（NC₆H₄p-Cl）}₃] were found to be highly efficientprecatalysts for the double addition of various diamines to carbodiimides to give thecorresponding biguanidine derivatives under mild condition, which provides an efficientway for the synthesis of biguanidines compounds.13new organic compounds weresynthesized. The activity depends on the central metals, the activity sequence is La> Nd> Y.2. Anhydrous LnCl₃reacted with [LiiPrNC（HNiPr）N（C₆H₄p-Cl）] and n-BuLi ata molar ratio of1:2:2in a THF solution affording heterometallic Ln-Li chloridesstabilized by two dianionic guanidinate ligands [{（iPrN）₂C[NLi（THF）₃（C₆H₄p-Cl）]}2Ln（μ-Cl2）Li（THF）₂]·nTHF [Ln=La （4-1）, Nd （4-2） n=2, Sm （4-3）, Yb （4-4）,Y （4-5） n=3] in good yields. Treatment of the chlorides with NaOiPr and KOtBu yielded the corresponding isopropoxides [{[（iPrN）₂CN（C₆H₄p-Cl）Li]₂（DME）（LiC l）Ln（OiPr）₂}₂]^2-[{Li（DME）₃}⁺]₂·3C6H14[Ln=Nd （4-6）, Sm （4-7）, Yb （4-8）, Y （4-9）] and tert-butoxides [{（iPrN）₂C（NC₆H₄p-Cl）Li（DME）（LiCl）}₂Ln（OtBu）₂]-[Li（DME）3]⁺·0.5C6H14（Ln=Nd （4-10）, Yb （4-11））. Attempts to synthesize the corresponding amide and guanidinate complexes by the reactions of4-2with LiNHC₆H₅and [LiiPrNC（HNiPr）N（C₆H₅）] led to the isolation of guanidinate lithium,[LiiPrNC（HNiPr）N（C₆H₄p-Cl）（THF）]₂.3. Reaction of LnCl₃with bridged bis（guanidinate） lithium salt LLi₂and L′Li₂afforded the monochlorides LLnCl（THF）₂[Ln=Nd （5-1），Sm （5-2），Eu （5-3），Yb（5-4），Y （5-5）]，LLnCl（DME）[Ln=Sm （5-6）, Yb （5-7）]，and L′Ln（-Cl）₂Li（THF）₂[Ln=Nd （5-8）, Sm （5-9）] respectively. All chloride complexes adopt monomeric structurein the solid state. The molecular structures indicate the coordination sphere of Ln in5-1⁵-9are more open than those in these complexes with unbridged guanidinateligands.4. Treatment of the chlorides with NaBH4at a molar ratio of1:1gave themonoborohydride complexes LLnBH4（DME）[Ln=Nd （5-10）, Yb （5-11）, Y （5-12）].X-ray crystal structure analyses of5-10⁵-12revealed each complex was monomerwith the central metal ligated by one L, one η³-BH4group and one DME.5. The monoborohydride complexes5-10⁵-12could serve as highly activesingle-site initiators for ROP of ε–CL and L-LA. Lanthanide metals have a profoundeffect on the activity，the active sequence is Y <Yb <<Nd. The most active and the bestcontrol over the molar mass for the two monomers were found for the system with5-10.6. Treatment of the chlorides with BnK at a molar ratio of1:1afforded themonobenzyl complexes LLnBn（DME）[Ln=Sm （6-1）, Yb （6-2）, Y （6-3）]. X-ray crystalstructure analyses of6-1⁶-3revealed each complex was monomer with the centralmetal ligated by one L, one η1-Bn group and one DME.7. LSmBn（DME）（6-1） reacted with4-methoxybenzonitrile to form the Ln-C bondinsertion product [LSm{-NH（C₆H₅（p-OMe））C=CC₆H₅}₂SmL]（6-4）; Treatment ofLSmBn（DME）（6-1） with two equiv of CH3CN resulted in an instantaneous reaction,giving C-H bond activation rather than insertion, yielding C₆H₅CH3and the noveldimeric crotonitrileamido complex [LSm（μ-（N,N′）-N（H）C（Me）=C（H）CN）]₂（6-5）. It is likely that it is formed as an intermediate which reacts further by insertion of anotherone equiv of acetonitrile, followed by a1,3-H shift, to give complex6-5. Treatment ofLYBn（DME）（6-3） with2-aminobenzonitrile resulted in an instantaneous reaction,affording the hydrogenolysis amido complex [LY（μ-（N,N′）-N（H）Ph（o-CN））]₂（6-6）.LSmBn（DME）（6-1） reacted with2equiv of isocyanatobenzene affording thediinsertion product [L′′Sm{μ-OC（CH₂Ph）N（Ph）}₂SmL′′]（6-7）（L′′=iPr（Me₃Si）NC（NiPr）N（CH₂）₃（SiMe₃）C（NiPr）₂（CN（Ph）O））. The result indicated that theisocyanatobenzene molecules inserted into the Ln-C bond and Ln-guan bondsimultaneously.8. Reaction of LYbCl（THF）₂（5-4） and LYCl（THF）₂（5-5） with one equiv ofNaNHAr （ArNH=2,6-iPr2C6H3NH）, gave the corresponding monometallic amidecomplexes LLn（NHAr）（DME） Ln=Yb （7-1） and Y （7-2）, while LYCl（THF）₂reacted with LiNHC₆H₅（o-CN） to form the bimetallic amide complex [LY（μ-（N,N’）-N（H）Ph（o-CN））]₂（6-6）. All the three amides are efficient initiators for polymerization of L-lactide. The catalytic performance is substantially different between the two kinds of amides. The polymerizations initiated by complex6-6proceeded ina living fashion as evidenced by the resulting polymers with narrow polydispersities, together with the linear natures of number average molecular mass versus conversion plots, while the polymerization system with complexes7-1and7-2provided the polymers with rather broad molecular mass distributions. However, the control of the systems with7-1and7-2get better when the temperature decreased to15oC and monomer concentration was0.5mmol/mL.9. LEuCl（THF）₂（5-3） reacted with1.2equiv Na（K） alloys afforded the firstdivalent bridged bis（guanidinate） lanthanide complex8-1（LEu）₂.