Synthesis of Molybdenum Nitrido Complexes for Triple-Bond Metathesis of Alkynes and Nitriles

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• 作者：Eric S. Wiedner ; Kimberley J. Gallagher ; Marc J. A. Johnson ; Jeff W. Kampf
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：July 4, 2011
• 年：2011
• 卷：50
• 期：13
• 页码：5936-5945
• 全文大小：973K
• 年卷期：v.50,no.13(July 4, 2011)
• ISSN：1520-510X

文摘

Complexes of the type N鈮o(OR)₃ (R = tertiary alkyl, tertiary silyl, bulky aryl) have been synthesized in the search for molybdenum-based nitrile鈥揳lkyne cross-metathesis (NACM) catalysts. Protonolysis of known N鈮o(NMe₂)₃ led to the formation of N鈮o(O-2,6-ⁱPr₂C₆H₃)₃(NHMe₂) (12), N鈮o(OSiPh₃)₃(NHMe₂) (5-NHMe₂), and N鈮o(OCPh₂Me)₃(NHMe₂) (17-NHMe₂). The X-ray structure of 12 revealed an NHMe₂ ligand bound cis to the nitrido ligand, while 5-NHMe₂ possessed an NHMe₂ bound trans to the nitride ligand. Consequently, 17-NHMe₂ readily lost its amine ligand to form N鈮o(OCPh₂Me)₃ (17), while 12 and 5-NHMe₂ retained their amine ligands in solution. Starting from bulkier tris-anilide complexes, N鈮o(N[R]Ar)₃ (R = isopropyl, tert-butyl; Ar = 3,5-dimethylphenyl) allowed for the formation of base-free complexes N鈮o(OSiPh₃)₃ (5) and N鈮o(OSiPh₂^tBu)₃ (16). Achievement of a NACM cycle requires the nitride complex to react with alkynes to form alkylidyne complexes; therefore the alkyne cross-metathesis (ACM) activity of the complexes was tested. Complex 5 was found to be an efficient catalyst for the ACM of 1-phenyl-1-butyne at room temperature. Complexes 12 and 5-NHMe₂ were also active for ACM at 75 掳C, while 17-NHMe₂ and 16 did not show ACM activity. Only 5 proved to be active for the NACM of anisonitrile, which is a reactive substrate in NACM catalyzed by tungsten. NACM with 5 required a reaction temperature of 180 掳C in order to initiate the requisite alkylidyne-to-nitride conversion, with slightly more than two turnovers achieved prior to catalyst deactivation. Known molybdenum nitrido complexes were screened for NACM activity under similar conditions, and only N鈮o(OSiPh₃)₃(py) (5-py) displayed any trace of NACM activity.