Metallacyclopentane formation: A deactivation pathway for a tungsten(VI) alkylidene complex in olefin metathesis reactions

被引:48
作者
Wang, SYS
VanderLende, DD
Abboud, KA
Boncella, JM [1 ]
机构
[1] Univ Florida, Dept Chem, Gainesville, FL 32611 USA
[2] Univ Florida, Ctr Catalysis, Gainesville, FL 32611 USA
关键词
D O I
10.1021/om9708283
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
W(NPh)[o-(Me3SiN)(2)C6H4](CH2CMe3)(2), 2h, is quantitatively converted to a new metallacyclopentane complex, W(CH2CH2CH2CH2)(NPh) [o-(Me3SiN)(2)C6H4], 4, upon the addition of ethylene at T > 70 degrees C, The complex W(CH2CH2CH2CH2)(NPh)[o-(Me3SiN)(2)C6H4], 4, was also formed by the transmetalation reaction of W(NPh)[o-(Me3SiN)(2)C6H4](Cl)(2) With the corresponding Grignard reagent, BrMg(CH2)(4)MgBr, and also when W(NPh)[o-(Me3SiN)(2)C6H4](PMe3)(=C(H)t-Bu), 3, reacts with ethylene, Mechanistic studies suggest that 2h and 3 react with ethylene through a common base-free alkylidene intermediate which undergoes metathesis with ethylene and then generates a W(TV) intermediate which is converted to 4 by coupling two molecules of ethylene, This reaction is a deactivation pathway when 3 is used as an olefin metathesis catalyst for terminal olefins because ethylene is generated during the reaction, The tungsten(Iv) complex W(NPh)[o-(Me3SiN)(2)C6H4](PMe3)(2)(eta(2)-C2H4), 5, was observed during the reaction between 3 and ethylene, Complex 5 can also be synthesized from the diethyl complex W(NPh)[o-(Me3SiN)(2)C6H4](CH2CH3)(2), 2b, in the presence of PMe3, Addition of excess ethylene to 5 gives 4, The X-ray structure of 4 was determined.
引用
收藏
页码:2628 / 2635
页数:8
相关论文
共 42 条