Synthesis Of Metal Complexes Incorporating With The Silyl Linked-bis(amidinate) Ligands And Reactions Between The Silyl-Substituted Methyllithium And Nitriles

The main research work of this dissertation is focused on the multi-dentate nitrogen-centered ligands, it consists of two parts: Study of the synthetic pathway of a novel class of silyl linked-bis(amidinate) ligands, synthesis of the alkali metal derivatives;Synthesis and characterization of novel metal complexes supported with the silyl linked-bis(amidinate) ligands. The details is as following:Chapter 1. A background introduction for the topic of this thesis. It is divided into three sections: (1) The application and progress of amidometal complexes in organic synthesis and catalysis;(2) The application and progress of amidinate metal complexes in organic synthesis and catalysis;(3) A brief introduction of β-diketiminato metal complexes.Chapter 2. A group of lithium compounds 2a-2d were prepared by the reactions of treating the α-H free benzonitrile with a series of dilithiated silyl-bridged diamines I, II, III and IV (Scheme 1). It underwent a rare and interesting silyl 1,1',3,3'-migration process in the reactions. These compounds were characterized by ¹HNMR, ¹³CNMR,elemental analysis and X-ray diffraction. Their structural configurations were discussed.Scheme 2 Synthesis of lithium derivatives of precursor IA concise study of the reactions between precursor I and benzonitrile were carried out for investigation of the thermodynamic stability of the silyl linked-bis(amidinate) ligand (Scheme 2).Scheme 3 Synthesis of sodium derivatives 2i-2jIn addition, the silyl linked-bis(amidinate) sodium compounds 2i and 2j were synthesized (Scheme 3). They exhibited the different coordination properties in contrast to those lithium compounds.PhNHScheme 4 Synthesis of metal complexes 3a-3oChapter 3. In order to synthesize the silyl linked-bis(amidinate) transition metal complexes, lithium derivates of 2a-2d were treated with the Group IV metal chlorides MCU (M = Ti, Zr and Hf) (Scheme 4). Complexes 3a-3o were obtained and they demonstrated various configurations involving the imido species, bis-silyl-brideged tri(amidinate) species, silyl linked imido amidinate species, the tetradentate bonding mode silyl linked-bis(amidinate) species and the binuclear species. The compounds were characterized by !HNMR, i3CNMR, elemental analysis and X-ray diffraction. There were some interesting rearrangement processes in those reactions. The mechanisms were proposed for them.Ti(C5H5)CI3 Ti(C5H5)CI3—-----------------------TiCI(C5H5) Ti(C5H5)C!3 PhT4a(Li2L = 2a) ^ , , 4b (Li2L = 2b)Ph\ / \CI(CSH5) 4c (Li2L = 2c) Scheme 5 Synthesis of metal complexes 4a, 4b and 4cChapter 4. Metal complexes with the mixed ligands environment were prepared by introducing the cyclopentadienyl ligand into this system. Treating 2a-2c with the104monocycolopentadienyl titanium trichloride gave the half-sandwich compounds 4a, 4b and 4c, respectively (Scheme 5). The nitrogen centered ligands were turned into silyl linked imido amidinate and diamido configurations. The former species was resulted from the intra molecular rearrangement reaction, which was proposed and depicted. Analogously, reacting 2a-2d with the monocycolopentadienyl zirconium trichloride gave the half-sandwich compounds 4d-4g (Scheme 6). The nitrogen centered ligands were adopted as tetradentate or tridentate silyl linked imino amidinate or non-bridge bis(amidinate) species. The factors leading to the variations and the formation of bi-zironium-nuclear compound 4g were discussed. Treating the ligands with cycolopentadienyl titanium dichloride or cycolopentadienyl zirconium dichloride gave the sandwich metal compounds 4h-4k (Scheme 7). The nitrogen centered ligands in them maintained the original skeleton of the silyl linked-bis(amidinate) ligands. However, not all the donative nitrogen atoms could bond with metal center due to the bulky hindrance from the cyclopentadienyls.Scheme 8 Synthesis of metal complexes 5a5 5b and 5cChapter 5. The reactions of 2a-2c with the tin tetrachloride gave a group of tin(IV) complexes 5a % 5b fP 5c (Scheme 8). They all contained two tin nuclear and actually were ionic complex salts, including the counter-ionic and zwitterionic species. They werecharacterized by 'HNMR, 13CNMR, elemental analysis and X-ray diffraction.Chapter 6. By treating the lithium compounds 2a-2d with the metal salt Ti(N'Bu)Cl2(Py)3, which contained the Ti=N imido double bond, a group of imido titanium compounds 6a, 6b, 6c and 6d were synthesized (Scheme 9). It contained the formation of imido bridge. The rearrangement process for product 6d was proposed. All compounds were characterized by 'HNMR, 13CNMR, elemental analysis and X-raydiffraction.6c (Li2L = 2c)Ph )s{ PhPhN^N\r/JiLi2L------------------ 'BuNTi' ^Ti'N'Bu6a(i-i2L = 2a) ^ feu 6b(Li2L = 2b)Py 6d (Li2L = 2d)Scheme 9 Synthesis of metal complexes 6a, 6b, 6c and 6dChapter 7. Modifications towards (SiMe3)2CHLi were made by introducing the donor N with silyl reagent Me2NSiMe2Cl, in order to synthesize novel silyl-substituted methyl metal compounds 7a and 7b. They were treated with nitriles. 7a was found to be highly active in catalyzing the polymerization reaction from nitriles to triazines. 7b was used to prepare the multi-dentate ligands. Potassium compound 7c was analogous to 7b, its reaction with benzonitrile was found to undergo the intramolecular rearrangement and give a six-membered-ring compound. Mechanisms for the above catalyze and rearrange reactions were proposed.