Molybdenum and Tungsten Monoalkoxide Pyrrolide (MAP) Alkylidene Complexes That Contain a 2,6-Dimesitylphenylimido Ligand

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• 作者：Laura C. H. Gerber ; Richard R. Schrock ; Peter M眉ller
• 刊名：Organometallics
• 出版年：2013
• 出版时间：April 22, 2013
• 年：2013
• 卷：32
• 期：8
• 页码：2373-2378
• 全文大小：297K
• 年卷期：v.32,no.8(April 22, 2013)
• ISSN：1520-6041

文摘

Molybdenum and tungsten bispyrrolide alkylidene complexes that contain a 2,6-dimesitylphenylimido (NAr*) ligand have been prepared, in which the pyrrolide is the parent pyrrolide or 2,5-dimethylpyrrolide. Monoalkoxide pyrrolide (MAP) complexes were prepared through addition of 1 equiv of an alcohol to the bispyrrolide complexes. MAP compounds that contain the parent pyrrolide (NC₄H₄^{鈥?/sup>) are pyridine adducts, while those that contain 2,5-dimethylpyrrolide are pyridine free. Molybdenum and tungsten MAP 2,5-dimethylpyrrolide complexes that contain O-t-Bu, OCMe(CF₃)₂, or O-2,6-Me₂C₆H₃ ligands were found to have approximately equal amounts of syn and anti alkylidene isomers, which allowed a study of the interconversion of the two employing 1H鈥?sup>1}H EXSY methods. The K_eq values ([syn]/[anti]) are all 2鈥? orders of magnitude smaller than those observed for a large number of Mo bisalkoxide imido alkylidene complexes, as a consequence of the destabilization of the syn isomer by the sterically demanding NAr* ligand. The rates of interconversion of syn and anti isomers were found to be 1鈥? orders of magnitude faster for W MAP complexes than for Mo MAP complexes.