Synthesis And Characterization Of Amidate Rare-earth Metal Amides And Their Application In C-P And C-N Bond Formation

Based on amidate ligands HL1(HL1=[C6H5CONH(2,6-iPr2-C6H3)]), four amidatetrivalent rare-earth metal amides were synthesized in this thesis. All the complexes werefully characterized by various techniques including X-ray single crystal diffraction. Thecatalytic activities of the amidate rare-earth metal amides on the amidation of aldehydeswith amines were investigated; they were compared with the homoleptic amidaterare-earth metal complex as well. Meanwhile, The catalytic behaviors of these amidatetrivalent rare-earth metal amides for the hydrophosphonylation of both aldehydes andunactivated ketones were assessed, and they were compared with three known divalentrare-earth metal amides bearing the same or different amidate ligands. Furthermore, thecatalytic reactivities of amidate rare-earth metal amides toward amidination of anilinewith benzonitrile were preliminarily examined. The main results were listed below.1. Reactions of HL1with neutral homoleptic rare-earth metal amidesLn[N(SiMe3)2]3(Ln=Yb, Y) in2:1molar ratio afforded two novel bisamidatemonoamido trivalent rare-earth complexes Ln[N(SiMe3)2](κ2-L1)2(THF)(Ln=Yb (1), Y(2)). Complexes1and2were isostructural, with six-coordinated central metals and C1symmetric structures. Two amidate groups bound to central metal atom adopted thechelating coordination mode. Each molecule contained one coordinated amido N(SiMe3)2.These two complexes were characterized by X-ray single crystal diffraction andelemental analysis with additional1H NMR and13C NMR spectroscopy in the case ofcomplex2.2. Reactions of HL1with neutral homoleptic rare-earth metal amidesLn[N(SiMe3)2]3(Ln=Sm, Nd) in1:1molar ratio afforded two novel monoamidatebisamido trivalent lanthanide complexes Ln[N(SiMe3)2]2(κ2-L1)(THF)(Ln=Sm (3), Nd (4)). Complexes3and4were isostructural, with five-coordinated central metals and C1symmetric structures. The amidate group bound to central metal atom adopted thecommon chelating coordination mode. Each molecule contained two coordinated amidosN(SiMe3)2. These two complexes were characterized by X-ray single crystal diffraction.3. The catalytic activities of amidate trivalent rare-earth metal amides3and amidatedivalent rare-earth metal amides5and6for the amidation of aldehydes with amines weretested. We screened the reaction conditions such as the molar ratio of aldehyde to amine,the amount of catalyst, reaction time, solvent etc. in turn. And the comparison of catalyticactivity with neutral samarium amidate complex SmL14(μ-H)(THF)2(9) was alsoconducted. The results showed that complex3exhibited the highest activity. However,the neutral lanthanide amidate complex9without N(SiMe3)2exhibited poor activity. Weexamined the amidation of a variety of aldehydes and amines in the presence of complex3and found that the scope of substrates was limited.4. The catalytic activities of amidate trivalent rare-earth metal amides1,2andamidate divalent rare-earth metal amides {Ln[N(SiMe3)2](μ-O: κ2-L1)(THF)}2(Ln=Yb(5), Eu (6)), Eu2[N(SiMe3)2]2(μ-O:κ2-L2)2(THF)3(8)(HL2=[C6H5CONH(2,6-Me2-C6H3)]) for C-P bond formation were tested. The results showedthat all complexes above exhibited high catalytic activities towards the addition ofdialkyl phosphites to aldehydes. Complexes1,2and6could catalyze thehydrophosphonylation of unactivated ketones to give the great valuable biologicallyactive compounds α-hydroxy phosphonates in moderate to good yields. The catalyticreactions could be carried out smoothly in the presence of a very low loading of catalystat room temperature in a short time under solvent-free condition. Complex1showed thehighest reactivity and good substrates tolerance of the catalytic addition reactions.5. The catalytic activities of amidate trivalent rare-earth metal amides1,2and3,amidate divalent rare-earth metal amides6,8and {Yb[N(SiMe3)2](μ-O: κ2-L2)(THF)}2(7), and simple homoleptic rare-earth matal amides (Y[N(SiMe3)2]3and Eu[N(SiMe3)2]2)for the amidination of aniline with benzonitrile were preliminarily examined. The results showed that neither amidate rare-earth metal amides nor homoleptic rare-earth metalamides exhibited poor activities towards the amidination. Even if the reaction was carriedout using complex8up to10mol%at80oC for24h, the desired product monosubstituted amidine was only obtained in46%yield. Thus, the stratage of introducingamidate into the structure of rare-earth complex was proven to be no benificial toincreasing the catalytic activities of rare-earth metal amides.