Reaction Of Rare Earth Organic Compounds

The ligand-based reaction of organometallic compounds is a valuable synthetic tool, because it allows the introduction of alternate substituents onto ancillary ligands. Such reaction has become a very powerful and efficient method for the synthesis of a wide variety of transition-metal organometallic derivatives, such as transition-metal-mediated dearomatization reactions. However, very few examples of ligand-based reactions of organolanthanides have been reported due to the facile cleavage of the original metal-ligand bonds under the reaction conditions involved, which makes the difficulties in accessing potentially suitable reactants and controlling the selectivity. In fact, the paucity of ligand-based reactions in lanthanide chemistry not only restricts the development of supported ligands but influences the evolution of lanthanide-based catalytic systems in a certain extent.To offer some new ideas for the lanthanide-based synthesis and catalytic systems, we investigated the selective transformation of N-H and O-H bond of the organolanthanide compounds and explored the new ligand-based organometallic reaction. In addition, we also searched the protonolyzation of organolanthanide compounds. Twenty-eight new organolanthanide complexes are synthesized and this paper consists of five chapters. The details are as follows:In chapter I, preface, the development of ketenes in organometallic chemistry and ligand-based reactions in recent years is summarized.In Chapter II, The reaction of [Cp₂LnNHPh]₂ with ketenes was studied and the addition products [Cp₂Ln(n-η¹:η³-OC(CHPhR)NPh)]₂[R = Et, Ln = Yb(2-1), Y(2-2), Tb(2-3); R = Ph, Ln = Er(2-4)] were got in good yields. We found that changing ketenes, increasing relative amounts of PhRCCO, heightening temperature or extending reaction time had no influence on these products. Noticeablely, in situ reaction of Cp₂YbCl, LiNHPh and Ph₂CCO, a rearrangement product [CpYb(η³-OC(CHPh₂)NPh)[μ-η¹:η³-OC(CHPh₂)NPh]₂U(THF)₂] (2-5) was got, which maybe induced by the excess LiOC(CHPh₂)NPh. Then, the reactions of [Cp₂LnNH"Bu]₂, [Cp₂ErNHEt]₂ with ketenes were envisaged. Similar to [Cp₂LnNHPh]₂, the reaction of [Cp₂YbNH"Bu]₂with ketene gave the single addition products [Cp₂Ln(μ-η¹:η³-OC(CHPh₂)N"Bu)₂ [Ln = Yb(2-6), Dy(2-7)]. But in the reaction of [Cp₂ErNHEt]₂ with excess PhEtCCO, the non-coupling double insertion product [Cp₂Er(PhEtCHCON(Et)COCEtPh)]₂ (2-8) could be obtained, revealing anovel reactivity of organometallic complexes toward ketenes. Further, the reaction of CpLn(NH"Bu)₂ with ketene was checked and the double insertion/rearrangement product [Cp₂Er(μ-η¹:η³-OC(CHPh₂)N"Bu]₂ (2-9) was gained. Regretfully, separation of the other rearrangement product Er[(μ-η¹:η³-OC(CHPh₂)N"Bu]₃ was unsuccessful. In a more research on the reaction of [Cp₂Ln(μ-Mz)]₃ with ketenes, several simple single insertion compounds into Ln-N were characterized, [Cp₂LnCu-OC(Mz)=CPhR)]₂ [R = Et, Ln = Yb(2-10); R = Ph, Ln = Yb(2-ll), Er(2-12)]. Finally, we found that ketene could react with cyclopentadienyl of organolanthanide compounds to transform into the functioned substituted cyclopentadienyl complex [(Cp₂Yb)₂(μ₃-O)Yb(μ-η¹:η²-C₅H₄C(O)=CPh₂)₂]Li(THF)₄ (2-13). Such functionization of cyclopentadienyl is rare in organometallic chemistry. The results demonstrate that both electronic and steric factors play an important role in determining the chem- and regio-selectivities of ketenes insertion into the Ln-N bond.In Chapter III, The reactivity of organometallic hydroxyide complexes was studied and revealed a series of ligand-based reaction of organolathanide compounds. [Cp₂Ln(μ-OH)(THF)]₂ synthesized in situ reacted with PhEtCCO to form the O-H addition products [Cp₂Ln(μ-η¹:η²-O₂CCHEtPh)]₂ [Ln = Er(3-3), Y(3-4)]. The formation of 3-3 and 3-4 not only represents the first example of the formal addition of unsaturated molecules to the O-H bond of organolanthanide hydroxides, but also provides a new route to lanthanide carboxylate complexes. However, treatment of [Cp₂Y(μ-OH)(THF)]₂ with 2 equiv of PhNCO affords the addition/CpH-elimination/rearrangement product [{Cp₂Y(THF)}₂(μ-η2:η2-O₂CNPh)] (3-5), containing an unusually PhNCO₂ dianionic ligand. The analogous [Cp₂Ln(THF)]₂(μ-η²:η²-O₂CNPh) [Ln = Yb(3-6), Er(3-7), Dy(3-8)] can be obtained in a higher yield by the treatment of [Cp₂Ln(μ-OH)(THF)]₂ with PhNCO followed by reacting with Cp₃Ln. The formation of 3-5-3-8 represents a unique reactivity of isocyanates toward organometallic complexes. In addition, the facile O-H addition to ketenes can also be exploited as another method to prepare lanthanide carboxylate complexes.In Chapter IV, the reaction of [Cp₂Yb(μ-OH)(THF)]₂ synthesized in situ with [Cp₂Yb(μ-CH₃)]₂ or Cp₃Yb forms the oxo-bridged compound [Cp₂Yb(THF)]₂(μ-O) (4-1), whereas the reaction of [Cp₂Er(μ-OH)(THF)]₂ with the LiCl adduct of Cp₂Er"Bu(THF)_x affords a unexpected μ-oxo lanthanocene cluster compound(Cp₂Er)₃(μ-OH)(μ₃-O)(μ-Cl)Li(THF)4 (4-3). Further, we found that [Cp₂Yb(μ-OH)(THF)]₂ was unstable and could transform to [Cp₂Yb]₂(μ-OH)₂(μ₃-O)[(YbCp)(THF)] (4-2). Complexes 4-1-4-3 were characterized by elemental analysis, IR, and mass spectroscopies, and them were also confirmed by the X-ray crystal structure analysis.In Chapter V, The protonolyzation reaction of organometallic complexes was studied. In all case of the reaction of phenylacetic acid with [Cp₂YbSEt]₂ and Cp₂Er[SC₆H₄(p-NH₂)](THF), the organic sulfur ligand not the cyclopentadienyl ligand was protonolyzed to form the steady carboxylate compound [Cp₂Yb(μ-η¹:η²-O₂C(CH₂Ph))]₂ (5-1) and [Cp₂Er(μ-η¹:η²i-O₂CCH₂Ph)]₂ (5-2). In addition, we found 3,5-dimethyl pyrazole coulde cleavage the Ln-S bond, too. Then, the reactivity of lanthanocene thiolates to H₂O was researched, and a lanthanide cluster oxide Cp₇Er₉O4_OH8(SC₂H₅)₄ (5-3) was gained, which provided a new method to compose lanthanide oxides. The abstraction of Cp or SEt in the hydrolysis reaction of [Cp₂Ln(μ-SEt)]₂ is competed. However, in the controlled hydrolysis of Nd(Tp^Me2)₂CH₃, the hydroxide intermediate would react with the Tp^Me2 ligand to afford a oxide complex [(η³-Tp^Me2)Nd(μ-η³-OBH(Pz)₂)]₂ (5-4). In addition, the part hrdrolysis of [Cp₂Er(μ-PzMe₂)]₂ by trace H₂O gave the [(Cp₂Er)₂(μ-OH)(μ-PzMe₂)] (5-5).