Synthesis And Structures Of Cyclohexyl Bridged Bis(amidate) Rare-Earth Metal Amides And Their Applications In C-N And C-C Bond Formation

Based on the two cyclohexyl amidate ligands HL1(HL1 = N,N’-(cyclohexane-1,2-diyl) bis(4-tert-butylbenzamide)), HL2(HL2= N,N’-(cyclohexane-1,2-diyl)bis(4-m ethoxybenzamide)), eight cyclohexyl bridged bis(amidate) rare-earth metal amides were synthesized in this thesis. All of them were well characterized by various means containing X-ray single crystal diffraction. We investigated the catalytic activity of some of the complexes on the synthesis of guanidines from the reaction of amines with carbodiimides. Meanwhile, the catalytic behaviors of these cyclohexyl bridged bis(amidate) rare-earth metal amides and the corresponding precursors RE[N(TMS)2]3 for the carboxylation of terminal alkynes with carbon dioxide were assessed. The main results are listed below.1. Reactions of HL1(HL1 = N,N’-(cyclohexane-1,2-diyl)bis(4-tert-butylbenzamide)) with neutral homoleptic rare-earth metal amides RE[N(Si Me3)2]3(RE = La, Nd, Sm, Yb, Y) in 1:1 molar ratio afforded five novel cyclohexyl bridged bis(amidate) rare-earth metal amides {L1RE[N(Si Me3)2]×THF}2(RE = La(1), Nd(2), Sm(3), Yb(4), Y(5)). The five complexes were isostructural, centrosymmetric and binuclear. These five complexes were characterized by X-ray single crystal diffraction and elemental analysis, and complexes 1 and 5 were also characterized with additional 1H NMR spectroscopy.2. Reactions of HL2(HL2= N,N’-(cyclohexane-1,2-diyl)bis(4-methoxybenzamide)) with neutral homoleptic rare-earth metal amides Ln[N(Si Me3)2]3(Ln =La, Nd, Sm) in 1:1 molar ratio afforded three novel cyclohexyl bridged bis(amidate) rare-earth metal amides {L2Ln[N(Si Me3)2]×THF}2(Ln = La(6), Nd(7), Sm(8)). The three complexes were also isostructural, centrosymmetric and binuclear. All of them were characterized by X-ray single crystal diffraction.3. We investigated the catalytic activitiy of complexes 1-5 on the synthesis of guanidines from the reaction of amines with carbodiimides. The influencing factors of reaction such as the dosage of the catalyst, reaction time and solvent etc. were screened in turn. The results showed all complexes had high activity in this reaction, and complex 2 demonstrated the highest activity. We examined the synthesis of guanidines of a lot of substrates in the presence of complex 2 and found it had a good substrates tolerance.4. The catalytic activity of cyclohexyl bridged bis(amidate) rare-earth metal amides 1, 2 and 5-8 for C-C bond formation was tested. It showed that the complexes exhibited high catalytic activities towards the carboxylation of terminal alkynes with carbon dioxide, and the complex 2 performed the best. Because it could activate the terminal alkynes, which made the reaction undergo smoothly under mild conditions, such as additive-free, a little amount of the catalyst, low temperature and atmospheric pressure. However, we found it had some limitation on the applicability of the substrates.5. The catalytic activities of neutral homoleptic rare-earth metal amides RE[N(Si Me3)2]3(RE = La(9), Nd(10), Sm(11), Yb(12), Y(13)) and La[N(TMS)2]3ï¹'Li Cl(14) for the carboxylation of terminal alkynes with carbon dioxide were assessed. It showed that those compounds also had high activity on this reaction. When the temperature was raised to 60 oC, the catalyst 11 showed the highest activity. Similarly, we found the applicability of the substrates is limited.