Nature Of The Synthesis And Reaction Of The Rare Earth Alkyl Compound Containing Amidino Multicore Study

Metal methylidene/carbene complexes play a crucial role in organometallic chemistry. However, the reactivities of methylidene/carbene complexes of rare-earth metals are rather unexplored, mainly due to intractable synthetic procedure of organolanthanide complexes with negative-valent of carbene ligand. This dissertation focuses on the synthesis of mixed methyl methylidene/carbene rare earth metal complexes with amidinate coligand, and the selective conversions of methyl and carbene ligands in these complexes, revealing a series of new reactivity patterns of these carbene species, by which several new methods of synthesizing the polymethyls rare-earth metal oxo and imido complexes were developed. Meanwhile a preliminary study on the reactivities of these novel rare-earth metal complexes was also carried out. In brief, we have synthesized fifty-nine new compounds, among which fifty-three were characterized by X-ray structural analysis. The main achievements are as follows:1. A series of mono(amidinate) rare-earth metal bis(aminobenzyl) complexes LLn(CH2C6H4NMe2-o)2 (L=PhC(NC6H4iPr2-2,6)2=NCNdipp, Ln=Sc(2-8), Y (2-9), Sm (2-10), Gd (2-11), Lu (2-12); L=o-Me2H4CH2C(NC6H4iPr2,6)2)=NCNdipp', Ln=Sc(2-13), Y (2-14), Gd (2-15), Lu (2-16)) were synthesized and characterized. The insertion reaction can take place between complexes 2-9,2-10,2-12 and 2-16 with CO2 smoothly, resulting in the corresponding carboxyl-bridged dual-core amidinate rare-earth metal complexes [LLn(μ-η2:η1-O2CCH2C6H4NMe2-o)(μ-η1:η1-O2CCH2C6H4NMe2-o)]2 (L=NCNdipp, Ln= Y(2-17), Sm(2-18), Lu(2-19); L= NCNdipp', Ln= Lu(2-20)). Phenyl isocyanate can also insert into the two Ln-C o-bonds of complexes 2-9,2-12, and 2-16 to form complexes LLn[OC(CH2C6H4NMe2-o)NPh]2(thf) (L=NCNdipp, Ln= Y (2-21), Lu (2-22); L= NCNdipp', Ln=Lu (2-23)) in high yields. We successfully developed a new method to synthesize the rare-earth metal imido complexes by treatment of rare earth bis(aminobenzyl) complexes [PhC(NC6H4'Pr2-2,6)2)]Lu(CH2C6H4NMe2-o)2 with 2,6-Diisopropylaniline at 120℃.2. The reactions of mono(amidinate) rare-earth metal bis(aminobenzyl) complexes with AIMe3 were intensively investigated. Mixed polymethysl methylidene/carbene rare-earth metal complexes{[PhC(NC6H4'Pr2-2,6)2]Ln(μ-Me)}3-(μ3-Me)(μ3-CH2) [Ln= Sc (3-1), Y (3-2), Lu (3-3)], [o-Me2NC6H4CH2C- (NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-Me)(μ3-CH2) (3-4) and heterobimetallic (Ln-Al) complexes [PhC(NC6H4'Pr2-2,6)2]Ln(AlMe4)2 [Ln= Sc (3-6), Lu (3-7)] can be obtained when different amount of AlMes were adopted in these reactions respectively. Meanwhile, the two species can convert to each other under certain conditions. Furthermore, unique and diverse reactivity patterns of these mixed polymethyls methylidene rare-earth metal complexes with some small molecules such as ketone, nitrile, PhN=NPh, imines, amines, alkynes, CS2 and CO2 have been established, demonstrating that methyl or methylidene replacement and addition of these complexes are controllable. For example, 3-1 reacts with ketones to form the methylidene transfer products {[PhC(NC6H4'Pr2-2,6)2]Sc(μ-Me)}3(μ3-Me)-(μ3-O) (4-1). Selective addition of methylene to cyano-carbon was found in the reaction of 3-2 and 3-3 with benzonitrile, yielding complexes {[PhC(NC6H4'Pr2-2,6)2]Ln-(μ-Me3)}3(μ3-Me)(μ-η1:η1:η3-CH2C(Ph)N) [Ln= Y (3-10), Lu (3-11)]. The reaction of 3-2 or 3-3 with PhN=NPh leads to the methylidene coupling to form the corresponding imido complexes {[PhC(NC6H4'Pr2-2,6)2](μ2-Me)3(μ3-Me)(μ3-NPh) (Ln= Y(5-2), Lu(5-3)) and CH2=CH2.5-2 can also be obtained by reacting 3-2 with PhN=CHPh or PhNH2. Complex 3-3 reacts with phenylacetylene to form unexpected alkenyl dianion complexes {[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-Me)-(μ-η1:η3-PhC=CMe) (3-12); while the formation of complex {[PhC(NC6H4'Pr2-2,6)2]-Lu(μ-CH3)}3(μ3-CH2)(μ3-C=CTMS) (3-14) by protonolysis ofμ3-Me was found in reaction of complex 3-3 with TMSC≡CH in high selectivity. In addition, Complex 3-3 can also react with CS2 to afford {[PhC(NC6H4'Pr2-2,6)2]Lu}3(μ-Me)2(μ3-CH2)-(μ-η1:η2:η2-S2C=CH2) (3-15) via continuous methyl addition and methane elimination reaction. More interestingly, the reaction of CO2 with complex 3-3 accompanied with portion degradation of CO2 occurred, giving a dimalonate-bridged six-metal complex {[PhC(NC6H4'Pr2-2,6)2]3Lu3(μ2-Me)2(μ3-O)(μ-η2:η2-O2CCH2CO2)}2 (3-16). All the reactions of the mixed polymethyl methylidene rare earth complexes mentioned above were described for the first time.3. Polymethyls rare earth oxo complexes {[PhC(NC6H4'Pr2-2,6)2]Ln(μ-Me)}3-(μ3-Me)(μ3-O) [Ln= Sc (4-1), Y (4-2), Lu (4-3)] were achieved by methylidene transfer reaction of complexes 3-1,3-2 and 3-3 with ketones such as cyclohexanone, acetophenone and benzophenone smoothly in good yield. The reactivities of polymethyls rare-earth metal oxo complexes with cyclohexanone, acetophenone and CS2 were explored further, selective conversion of methyl or oxygen ligand of 4-1～4-3 was observed in these reactions. For example, addition and protonolysis reactions ofμ3-Me can undergo respectively, according to the nature of ketones or the difference of metal centers, forming the corresponding mixedμ3-O and alkoxy complexes {[PhC(NC6H4'Pr2-2,6)2]Y(μ-Me)}30(μ3-OC6H10Me-1)(μ3-O) (4-4) or {[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-OC(Me2)C6H5)(μ3-O) (4-7) and enolate anion complex {[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-OC6H9)(μ3-O) (4-5). In addition, selective oxygen-sulfur exchange reaction occurred when 4-2 and 4-3 were treated with CS2. The formation of polymethyls rare-earth metal sulfide complexes {[PhC(NC6H4'Pr2-2,6)2]Ln(μ-Me)}3(μ3-Me)(μ3-S) [Ln= Y (4-8), Lu (4-9)] suggests a rare example of a higher reactivity of Ln-O bond than Ln-Cσ-bonds.4. Based on the reactivity studies on the mixed methyls carbene/methylidene rare-earth metal complexes toward some small molecules, three synthetic routes to the corresponding polymethyls imido complexes were developed successfully. The results showed that imido complexes {[PhC(NC6H4'Pr2-2,6)2]Ln(μ-Me)}3(μ3-Me)(μ-η1:η1:η3-NC6H5) [Ln= Sc (5-1), Y(5-2), Lu(5-3)],{[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-Me)(μη1-η1:η3-NC6H5Me2-2,6) (5-4),{[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ3-Me)(μη1-η1:η3-NC6H5R-p) [R=-Cl (5-5),-OMc (5-6)],{[PhC(NC6H4'Pr2-2,6)2]3Lu3(μ-Me)3}2 [μ-η3:η3-N(CH2)6N] (5-7) and {[PhC(NC6H4'Pr2-2,6)2]3Lu3(μ-Me)3}2[μ-η3:η3-(NC6H4)2] (5-8) can be synthesized in very good yield by treatment of complexes 3-1, 3-2 and 3-3 with a variety of amines, imines and azobenzene. Significantly, rare earth imido complex activated CO2 to yield the mixed acetate and phenylcarbamate complex {[PhC(NC6H4'Pr2-2,6)2]Lu(μ-Me)}3(μ-η1:η1-O2CCH3)3(μ-η1:η2-O2CCH3)-(μ-η1:η1:η2-O2CNPh)(5-9).