Molybdenum Imido Alkylidene Complexes Containing N- and C-Chelating N-Heterocyclic Carbenes

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• 作者：Iris Elser ; Wolfgang Frey ; Klaus Wurst ; Michael R. Buchmeiser
• 刊名：Organometallics
• 出版年：2016
• 出版时间：December 27, 2016
• 年：2016
• 卷：35
• 期：24
• 页码：4106-4111
• 全文大小：410K
• ISSN：1520-6041

文摘

Six molybdenum imido alkylidene complexes bearing an N-chelating N-heterocyclic carbene (NHC), i.e., Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)₂ (1), Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)(OC₆F₅) (3), Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)(OCMe₃) (4), and their cationic counterparts [Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)]B(Ar^F)₄ (2), [Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OC₆F₅)]B(Ar^F)₄ (5), and [Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OCMe₃)]B(Ar^F)₄ (6), have been prepared. The influence of the alkoxide ligand on the loss of triflate in the hexacoordinated complexes 1, 3, and 4 resulting in the corresponding cationic complexes was studied. The 2-pyridyl-donor-functionalized NHC ligand renders the high oxidation state cationic molybdenum imido alkylidene complexes highly stable and in ultimate consequence mostly inactive in olefin metathesis even at elevated temperatures. Notably, the molybdenum imido alkylidene complex Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(1-mesityl-3-(C₉H₁₁)-imidazol-2-ylidene)(OTf) (9) with a C-chelating NHC formed via C–H activation and was isolated in 76% yield.