Rare Earth Pairs Of Anion Guanidine Synthesis And Reactivity

During the past 20 years, guanidinate anions have emerged as an extremely versatile class of ligands. From pure preparative chemistry to applications in various fields, the potential of metal guanidinate complexes is far from being exhausted. However, a number of white spots still exist. There are considerably fewer examples of complexes containing a guanidinate dianionic ligand than the monoanionic or neutral ligands, and the limited several examples were mailly concerned with main group and transition metals, which may astrict the general acquaintance with the coordination chemistry of guanidine and their potential application. This is surprising, given the fact that guanidinate dianions could function as a diamido ligand and may exhibitπdelocalization (Y conjugation) of the lone pairs on the sp2 hybridized nitrogen centers, with may endow it with more rich and novel coordination models and reaction properties. The lack of proper synthetic methodology may be the main hindrance. The above reasons inspired us to the research of the synthesis, reaction properties and the coordination models of lanthanide guanidinate dianionic complexes. 47 new complexes were synthesized,40 of them were characterized by X-Ray single crystal diffraction analysis. The main aspects of this thesis are as follows.1. We have developed a convenient and applicable methodology for synthesis of cyclopentadienyl-contained lanthanide guanidinate dianionic complexes by deprotonation of monoanionic guanidinate ligands. Firstly, monoanionic guanidinate intermediate complexes [Ln= Yb (2-1), Y (2-2), Er (2-3)] were synthesized by deprotonation of (iPrNH)2C=NPh with Cp3Ln, then by further deprotonation of Cp2Ln['PrNC(NPh)NH'Pr] with "BuLi afford guanidinate dianionic organolanthanide complexes Cp2Ln[('PrN)2CNPh]Li(THF)3 [Ln= Yb (2-10), Y (2-11), Er (2-12)]; Differently, under the same conditions, monoanionic guanidinate intermediate complexes CpLn[CyNC(NPh)NHCy]2(THF)n [Ln= Yb (2-5), Er (2-6), Gd (2-7)] were merely obtained by reaction of Cp3Ln with (CyNH)2CNPh, reaction of 2-5 with "BuLi give a complexe with mixed mono-/dianionic guanidinate ligands CpYb[CyNC(NPh)NCy][(CyN)2CNPhLi(THF)3] (2-18). Thus, guanidinate dianionic organolanthanide complexes Cp2Ln[(CyN)2CNPh]Li(THF)3 [Ln= Yb (2-13), Y (2-14), Er (2-15), Dy (2-16)] should be prepared by "one pot" reaction of equivalent mol of Cp3Ln with (CyNH)2CNPh and "BuLi; Similarly, Cp2Er[(CyN)3C]Li(THF)2 (2-17) can be obtained by continuous reaction of Cp2LnCl with [CyNC(NPh)NHCy]Li and nBuLi; Besides, reaction of Cp3Ln with C6H4[NC(NHCy)2-1,4]2 or C6H4[NC(NH'Pr)2-1,4]2 gave phenyl bridged diguanidinate complexes C6H4[(NC(NCy)NHCy)YCp2(THF)]2-1,4 (2-8) and C6H4[(NC(N'Pr)NH'Pr)YbCp2]2-1,4 (2-9), however, endeavor to synthesize the corresponding bridged dianionic guanidinate complexes by further deprotonation of (2-8) or (2-9) with "BuLi were unsuccessful. Significantly, two unanticipated products: a silicon insertion complex{[Cp2Y(Me2Si(O)NPh)][Li(THF)4]}2 (2-19) and a carbodiimide diinsertion complex Cp[nBuC(NCy)2]Yb{CyN[C(NCy)2]2Li(THF)} (2-20) were obtained during the exploration of other synthetic method for cyclopentadienyl-contained lanthanide guanidinate dianionic complexes.2. We initiatively studied the reaction properties of cyclopentadienyl-contained lanthanide guanidinate dianionic complexes. We found that, Cp2Ln[(RN)2CNPh]Li(THF)3 could react with chlorosilanes with the formation of tetra-substituted guanidinate monoanionic lanthanide complexes Cp2Ln[(RN)2C(NPhSiMe2R')] [R= Cy, R'= Me:Ln= Yb (3-1), Ln=Y (3-2), Ln= Er (3-3); R= Cy, R'=tBu:Ln= Yb (3-4), Ln= Er (3-5); R=iPr, R'=tBu:Ln= Yb (3-6), Ln= Er (3-7)]; Furthermore, Cp2Ln[(CyN)2CNPh]Li(THF)3 could react with Me2SiCl2 to afford the unprecedented four-numbered silicon-contained organic compound Me2Si(CyN)2C=NPh (3-8). Simultaneously, the coordinated guanidinate dianionic ligands can convert to guanidinate monoanionic ligands with acquirement of proton. These features are consistent with negative charges of the guanidinate dianion ligand delocalized on the three N atoms and thus demonstrate that the active site of the ligand is tunable.3. Initiatively studied the reaction of cyclopentadienyl-contained lanthanide guanidinate dianionic complexes towards acyl chloride. Different from the reactions of Cp2Ln[(RN)2CNPh]Li(THF)3 with chlorosilanes, the dianionic guanidinate ligand underwent a tandem acylation/elimination process to afford acylamino complexes, which indicated that, the generated acylation guanidinates were unstable, it inclined to eliminate dicarbodiimide moiety in succession. What is more significant, we found that the acylation site of the ligand is tunable, when R=iPr or Cy, acylation site is on the chelated N atom with lanthanide metal atom, to produce [Cp2LnOC(Ar)NR)]2 [R-iPr, Ar=Ph:Ln= Yb (4-1), Ln= Y (4-2), Ln= Er (4-3), Ln= Dy (4-4), Ln= Gd (4-5); R=iPr, Ar= 4-ClPh:Ln= Yb (4-6), Ln= Y (4-7), Ln= Er (4-8); R=Cy, Ar= Ph:Ln= Yb (4-9), Ln= Y (4-10), Ln= Er (4-11), Ln= Dy (4-12)]. However, when R = 2,6-iPr2C6H3, acylation site is on the N atom which coordinated to Li atom, to afford [Cp2YbOC(Ph)NPh)]2 (4-13), the analogously covertion of guanidinate ligands have never been reported before. Those results not only further illuminated the diversity active sites of the guanidinate dianionic ligands and their potential abundance reaction properties but also afford a new way for the preparation of asymmetry dicarbodiimides.4. By reaction of LnCl3 with in-situ generated dianionic guanidinate or mixed di-/monoanionic guanidinate ligands, a series of cyclopentadienyl-free lanthanide guanidinate dianionic complexes{Ln[(iPrN)2CNPhLi(THF)n][(iPrN)2CNPh]}2 [n= 2: Ln= Yb (5-1), Er (5-2); n= 3:Ln= Er (5-3)],{Y[(CyN)3CLi(THF)2][(CyN)3C]}2 (5-4) and{Ln[iPrNC(NPh)iPrNH][(iPrN)2CNPh]}2 [Ln= Yb (5-5), Er (5-6)] were obtained. To our surprise, different from the reactions of cyclopentadienyl-contained lanthanide guanidinate dianionic complexes,5-3 and 5-4 were inert toward chlorosilanes.