Tantalum(V)-Based Metallocene, Half-Metallocene, and Non-Metallocene Complexes as Ethylene-1-Octene Copolymerization and Methyl Methacrylate Polymerization Catalysts
详细信息 查看全文
- 作者：Shaoguang Feng ; Gordon R. Roof ; and Eugene Y.-X. Chen
- 刊名：Organometallics
- 出版年：2002
- 出版时间：March 4, 2002
- 年：2002
- 卷：21
- 期：5
- 页码：832 - 839
- 全文大小：116K
- 年卷期：v.21,no.5(March 4, 2002)
- ISSN：1520-6041
文摘
The half-sandwich imido tantalum dichloride (
5-C5Me4H)Ta(=NtBu)Cl2 is prepared directlyfrom the reaction of the neutral constrained-geometry ligand Me2Si(C5Me4H)(tBuNH) andTaCl5 in refluxing toluene. The dichloride is cleanly converted to the corresponding imidotantalum dimethyl complex (5-C5Me4H)Ta(=NtBu)Me2 (2). Using the same syntheticstrategy, the neutral bulky chelating diamine ligand ArNH(CH2)3NHAr (Ar = 2,6-iPr2C6H3)is reacted with TaCl5 in toluene under mild reflux conditions, affording the six-coordinatetantalum complex [ArN(CH2)3NHAr]TaCl4, which is conveniently converted to the corresponding non-metallocene tantalum trimethyl complex [ArN(CH2)3NAr]TaMe3 (4) on treatment with an excess of MeMgBr. Alternatively, 4 can be prepared in better than 70% overallyield based on the diamine ligand from a one-pot synthesis by mixing the neutral diamineligand with TaCl5 followed by addition of an excess of MeMgBr. Reaction of Cp2TaMe3 with1 equiv of B(C6F5)3 in benzene or toluene produces an oily mixture containing bothCp2TaMe2+CH3B(C6F5)3- and Cp2TaMe2+[(C6F5)3B-CH3-B(C6F5)3]- in the solution phase.Subsequently, the reaction of Cp2TaMe3 with 2 equiv of Al(C6F5)3 cleanly generates thetantalocene cation-binuclear anion ion pair Cp2TaMe2+[(C6F5)3Al-CH3-Al(C6F5)3]- (5) ascolorless crystals. In bromobenzene-d5, reactions of Cp2TaMe3 with Lewis acids M(C6F5)3(M = B, Al) in a 1:1 ratio afford the expected cationic species Cp2TaMe2+CH3M(C6F5)3- asclean products. Reaction of the non-metallocene 4 with M(C6F5)3 is similar to that of Cp2TaMe3. When it is activated with 2 equiv of Al(C6F5)3, Cp2TaMe3 is active for syndiospecificMMA polymerization but inactive for olefin polymerization. In contrast, the non-metallocene4 has no activity for MMA polymerization but is active for olefin polymerization. Mostinterestingly, the half-metallocene 2, when activated with a suitable activator, is very active(with a catalytic efficiency of 1.2 × 106 g of polymer/((mol of metal) atm h)) for high-temperature (140 
C) olefin copolymerizations, producing low-density poly(ethylene-co-1-octene) copolymers with high molecular weight.
5-C5Me4H)Ta(=NtBu)Cl2 is prepared directlyfrom the reaction of the neutral constrained-geometry ligand Me2Si(C5Me4H)(tBuNH) andTaCl5 in refluxing toluene. The dichloride is cleanly converted to the corresponding imidotantalum dimethyl complex (5-C5Me4H)Ta(=NtBu)Me2 (2). Using the same syntheticstrategy, the neutral bulky chelating diamine ligand ArNH(CH2)3NHAr (Ar = 2,6-iPr2C6H3)is reacted with TaCl5 in toluene under mild reflux conditions, affording the six-coordinatetantalum complex [ArN(CH2)3NHAr]TaCl4, which is conveniently converted to the corresponding non-metallocene tantalum trimethyl complex [ArN(CH2)3NAr]TaMe3 (4) on treatment with an excess of MeMgBr. Alternatively, 4 can be prepared in better than 70% overallyield based on the diamine ligand from a one-pot synthesis by mixing the neutral diamineligand with TaCl5 followed by addition of an excess of MeMgBr. Reaction of Cp2TaMe3 with1 equiv of B(C6F5)3 in benzene or toluene produces an oily mixture containing bothCp2TaMe2+CH3B(C6F5)3- and Cp2TaMe2+[(C6F5)3B-CH3-B(C6F5)3]- in the solution phase.Subsequently, the reaction of Cp2TaMe3 with 2 equiv of Al(C6F5)3 cleanly generates thetantalocene cation-binuclear anion ion pair Cp2TaMe2+[(C6F5)3Al-CH3-Al(C6F5)3]- (5) ascolorless crystals. In bromobenzene-d5, reactions of Cp2TaMe3 with Lewis acids M(C6F5)3(M = B, Al) in a 1:1 ratio afford the expected cationic species Cp2TaMe2+CH3M(C6F5)3- asclean products. Reaction of the non-metallocene 4 with M(C6F5)3 is similar to that of Cp2TaMe3. When it is activated with 2 equiv of Al(C6F5)3, Cp2TaMe3 is active for syndiospecificMMA polymerization but inactive for olefin polymerization. In contrast, the non-metallocene4 has no activity for MMA polymerization but is active for olefin polymerization. Mostinterestingly, the half-metallocene 2, when activated with a suitable activator, is very active(with a catalytic efficiency of 1.2 × 106 g of polymer/((mol of metal) atm h)) for high-temperature (140 C) olefin copolymerizations, producing low-density poly(ethylene-co-1-octene) copolymers with high molecular weight.