A series of tetravalent zirconium and hafnium complexes were supported by diarylamido-phosphino [PNP]- (bis(o-diisopropylphosphinophenyl)amide) ligand. The reaction of MCl4(THF)2 (M = Zr, Hf) with [PNP]Li in toluene at room temperature generates [PNP]MCl3 as solid in 60 % yield. Polyalkyl complexes which are lack of £]-hydrogen have been achieved in synthesis of [PNP]MR3 (R = Me, CH2SiMe3) or [PNP]M(CH2SiMe3)2(E) (E = Cl, Me) since we could control the desired product from steric effect. An X-ray diffraction study of [PNP]ZrCl3 showed it to be a chloride-bridged binuclear species {[PNP]MCl2(£g-Cl)}2 in which both metal atoms are 7-coordinate whereas that of [PNP]MCl3(THF) revealed a mononuclear, 7-coordinate core structure. The phosphine fluxional exchange were found in those complexes, monitoring variable temperature 31P NMR, their fluxionality were calculated by line shape analysis. By heating [PNP]M(CH2SiMe3)2(Cl) in solution, we can afford new alkylidene complexes [PNP]M(Cl)(=CHSiMe3) via intramolecular £\-abstraction. Through Eyring plot analysis, the activation energy of [PNP]Zr(CH2SiMe3)2(Cl) £\-abstraction is ∆H‡ = 16.49(19) kcal/mol and ∆S‡ = −25.64(19) cal/mol•K; [PNP]Hf(CH2SiMe3)2(Cl) £\-abstraction is ∆H‡ = 18.70(36) kcal/mol and ∆S‡ = −23.12(36) cal/mol•K. The mixture [PNP]Hf(=CHSiMe3)(Cl) could not isolate with any purification, but [PNP]Hf(=CHSiMe3)(CH2SiMe3) obtained through directly alkylation. Here we also identified multiple alkylidene derivatives of [PNP]M(=CHSiMe3)(X) (X = Cl, CH2SiMe3). The X-ray structured and solution NMR data of those alkylidene complexes can be ascribed to evidence of £\-agostic interaction with metal center. A novel zwitterionic complex [PNP]Zr(£g2-CHSiMe3)2(AlMe2) was characterized by X-ray and been received a bisalkylidene complex which was synthesized through addition Lewies acid (AlMe3) into [PNP]Zr(=CHSiMe3)(CH2SiMe3). Group 4 alkylidene was acting as catalyst to metathesize ethylene or norbornene. The complexes [PNP]M(=CHSiMe3)(Cl) have highly streotic selectivity catalyst for ring-opening metathesis polymerization (ROMP) of norbornene. It is important to emphasize the great significance of the catalyst discoveries and improvements for both academic research and industry.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0723112-105302 |
| Date | 23 July 2012 |
| Creators | Chang, Chih-Hsiang |
| Contributors | Chang, T.-H., Dong, T.-Y., Liang, L.-C., Lee, T.-Y. |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0723112-105302 |
| Rights | user_define, Copyright information available at source archive |
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