Synthesis And Study On The Activation Of Organic Molecules By Ytterbium(Ⅱ) Complexes Bearing The Bridged Bis(Amidinates) Ligand

Divalent ytterbium complexes supported by bridged bis（amidinates）（L=[Me₃SiNC（Ph）N（CH₂）₃NC（Ph）NSiMe₃]） were synthesized and well characterized. Theredox reactions of ytterbium（II） complexes with carbodiimides，diazadienes，acetonitrileand imines were studied. Three lanthanide chloride complexes supported by two carbonatoms bridged bis（amidinates） ligand L′（L′=[Me₃SiNC（Ph）N（CH₂）₂NC（Ph）NSiMe₃]）were synthesized. The main results obtained are as follows:1. Reduction reaction of LYbCl（THF）₂with Na/K alloy gave the trinuclearmacrocyclic Yb（II） complex [Yb₃（μ2-L）₃]（1） at room temperature for2days. Becausethe crystals of complex1were difficult to abtain, bipyridine was added to facilitate thecrystallization of Yb（II） complex. However, the oxygen-bridged bimetallic trivalentytterbium complex （bipy）LYb（μ-O）YbL（bipy）（2） was synthesized, the formation ofcomplex2may attributed to the strong electron-donating ability of bipyridine increasingthe electron density around the central metal, which leaded complex1easier tocapaturing oxygen from THF or trace amounts of oxygen in the reaction. Reductionreaction of LYbCl（THF）2in the existence of YbCl3with Na/K alloy gave a newtrinuclear ytterbium（II） complex （DME）Yb（μ-η³-L）（μ-Cl）Yb（μ-Cl）（μ-η³-L）Yb（DME）（3）with the bis（amidinate） bridge and chloro bridge at40℃for3days. Complex3hasgood repeatability and crystalline quality. These complexes were characterized byelemental analysis and IR. The solid structures of these complexes were confirmed bythe X-ray diffraction. The solution behavior of diamagnetic complexes1and3werestudied by NMR, which was found that the structures of these complexes in solutionwere in accordance with their solid structures.2. The reaction of complex1with CyN=C=NCy in a molar ratio of1:1gave the Yb（III） complex [LYb{（NCy）2CC（NCy）2}YbL]（4） with a newly formed oxalamidinateligand via C-C coupling at the central C atoms of two carbodiimides. Complex4wascharacterized by elemental analysis, IR and X-ray diffraction. Single crystal structureanalysis showed that complex4is non-solvent monomeric structure.3. Complex1reacted with diazabutadienes [2,6-iPr₂C₆H₃N=CRCR=NC₆H₃iPr₂-2,6]（R=H, CH₃）（DAD） as a one-electron reducing agent to afford thecorresponding Yb（III） derivatives: the complexes containing a diazabutadiene radicalanion [LYb（iPr₂C₆H₃NCRCRNC₆H₃iPr₂）]（R=H （5）, R=CH3（6））. To further confirmthe central metal Yb in complexes5and6being in the3+oxidation state, the BVScalculation for both complexes was made. Indeed, the values equal to3.37for complex5and3.39for complex6.4. The reaction of complex3formed in stiu with acetonitrile in toluene wasstudied, which gave a new bimetallic ytterbium（III） diamine complexLYb（μ-NH）C（Me）=C（Me）YbL （7） via C-C coupling of two acetonitriles and abstractinga hydrogen atom from the solvent. The similar reaction of complex1formed in stiuwith acetonitrile in toluene was also studied. The product was fully characterized byelemental analysis, IR and X-ray diffraction which was proved to be complex7. Tofurther confirm the central metal Yb in complex7being in the3+oxidation state, theBVS calculation for complex7was made. Indeed, the value equal to3.44for complex7.5. The reaction of complex3formed in stiu with imine （C₆H₅C=NC₆H₄-p-Cl） intoluene was studied, which gave a new bimetallic ytterbium（III） diamine compound（Cl-p-C6H4NCHPhCHPhNC6H4-p-Cl）Yb（μ-L）Yb（μ-L）（8） via C-C coupling of twoimines and accompanied by ligand rearrangement. We also studied the reactions ofcomplex3with the other two imines （C₆H₅N=CHC₆H₄-p-Cl and C₆H₅N=CHC₆H₅）.Because separation of crystals was difficult, products were analyzed by LC-MS. Theproducts were confirmed to have the molecular ion peaks of the diamine compoundsgenerated by the coupling of imines, which should have a similar structure of complex8and be formed diamine complexes. 6. Reaction of bis（amidenates） dilithiums L′Li₂with LnCl₃in1:1moral ratioafforded three lanthanide chloride complexes [（μ-L′）Yb（μ-Cl）₂Yb（μ-L′）]₂（9）,[（μ-L′）Ln（μ-Cl）₂Li（THF）₂]₂（Ln=Sm （10）, Ln=Eu （11））.