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Synthesis of Molybdenum and Tungsten Alkylidene Complexes that Contain a tert-Butylimido Ligand

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Figshare2016-02-13 更新2026-04-29 收录
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A variety of molybdenum or tungsten complexes that contain a tert-butylimido ligand have been prepared. For example, the o-methoxybenzylidene complex W­(N-t-Bu)­(CH-o-MeOC6H4)­(Cl)2(py) was prepared through addition of pyridinium chloride to W­(N-t-Bu)2­(CH2-o-MeOC6H4)2, while Mo­(N-t-Bu)­(CH-o-MeOC6H4)­(ORF)2(t-BuNH2) complexes (ORF = OC6F5 or OC­(CF3)3) were prepared through addition of two equivalents of RFOH to Mo­(N-t-Bu)2­(CH2-o-MeOC6H4)2. An X-ray crystallographic study of Mo­(N-t-Bu)­(CH-o-MeOC6H4)­[OC­(CF3)3]2­(t-BuNH2) showed that the methoxy oxygen is bound to the metal and that two protons on the tert-butylamine ligand are only a short distance away from one of the CF3 groups on one of the perfluoro-tert-butoxide ligands (H···F = 2.456(17) and 2.467(17) Å). Other synthesized tungsten tert-butylimido complexes include W­(N-t-Bu)­(CH-o-MeOC6H4)­(pyr)2(2,2′-bipyridine) (pyr = pyrrolide), W­(N-t-Bu)­(CH-o-MeOC6H4)­(pyr)­(OHMT) (OHMT = O-2,6-(mesityl)2C6H3), W­(N-t-Bu)­(CH-t-Bu)­(OHMT)­(Cl)­(py) (py = pyridine), W­(N-t-Bu)­(CH-t-Bu)­(OHMT)­(Cl), W­(N-t-Bu)­(CH-t-Bu)­(pyr)­(ODFT)­(py), W­(N-t-Bu)­(CH-t-Bu)­(OHMT)2, and W­(N-t-Bu)­(CH-t-Bu)­(ODFT)2 (ODFT = O-2,6-(C6F5)2C6H3). Interestingly, W­(N-t-Bu)­(CH-t-Bu)­(OHMT)2 does not react with ethylene or 2,3-dicarbomethoxynorbornadiene. Removal of pyridine from W­(N-t-Bu)­(CH-t-Bu)­(BiphenCF3)­(pyridine) (BiphenCF3 = 3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-1,1′-biphenyl-2,2′-diolate) with B­(C6F5)3 led to formation of a five-coordinate 14e neopentyl complex as a consequence of CH activation in one of the methyl groups in one tert-butyl group of the BiphenCF3 ligand, as was proven in an X-ray study. An attempted synthesis of W­(N-t-Bu)­(CH-t-Bu)­(BiphenMe) (BiphenMe = 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2,2′-diolate) led to formation of a 1:1 mixture of W­(N-t-Bu)­(CH-t-Bu)­(BiphenMe) and a neopentyl complex analogous to the one characterized through an X-ray study. The metallacyclobutane complexes W­(N-t-Bu)­(C3H6)­(pyrrolide)­(ODFT) and W­(N-t-Bu)­(C3H6)­(ODFT)2 were prepared in reactions involving W­(N-t-Bu)­(CH-t-Bu)­(pyr)2(bipy), ZnCl2(dioxane), and one or two equivalents of DFTOH, respectively, under 1 atm of ethylene.
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2016-02-13
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