Synthesis of Molybdenum and Tungsten Alkylidene Complexes That Contain Sterically Demanding Arenethiolate Ligands
نویسندگان
چکیده
Imido alkylidene complexes of Mo and W and oxo alkylidene complexes of W that contain thiophenoxide ligands of the type S-2,3,5,6-Ph4C6H (STPP) and S-2,6-(mesityl)2C6H3 (SHMT = S-hexamethylterphenyl) have been prepared in order to compare their metathesis activity with that of the analogous phenoxide complexes. All thiolate complexes were significantly slower (up to ∼10× slower) for the metathesis homocoupling of 1-octene or polymerization of 2,3-dicarbomethoxynorbornene, and none of them was Z-selective. The slower rates could be attributed to the greater σ-donating ability of a thiophenoxide versus the analogous phenoxide and consequently a higher electron density at the metal in the thiophenoxide complexes.
منابع مشابه
Synthesis of molybdenum alkylidene complexes that contain the 2,6-dimesitylphenylimido ligand.
Compounds that have the formula M(NR)(CHR')(OR″)(Pyrrolide), where OR″ is "large" relative to NR and M = Mo or W, have been shown to be Z-selective olefin metathesis catalysts. In this communication we report a new route to Mo complexes in which the relationship between NR and OR″ has been reversed; i.e., the imido ligand is the sterically demanding 2,6-dimesitylphenylimido ligand (NAr*).
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We report the synthesis of Mo and W MAP complexes that contain O-2,6-(2,5-R2-pyrrolyl)2C6H3 (2,6-dipyrrolylphenoxide or ODPPR) ligands in which R = i-Pr, Ph. W(NAr)(CH-t-Bu)(Pyr)(ODPPPh) (4a; Ar = 2,6-disopropylphenyl, Pyr = pyrrolide) reacts readily with ethylene to yield a metallacyclobutane complex, W(NAr)(C3H6)(Pyr)(ODPPPh) (5). The structure of 5 in the solid state shows that it is approxi...
متن کاملSynthesis of Tungsten Imido Alkylidene Complexes that Contain an Electron-Withdrawing Imido Ligand
Tungsten NArR alkylidene complexes have been prepared that contain the electron-withdrawing ArR groups 2,4,6-X3C6H2 (ArX3, X = Cl, Br), 2,6-Cl2-4-CF3C6H2 (ArCl2CF3), and 3,5-(CF3)2C6H3 (Ar(CF3)2). Reported complexes include W(NArR)2Cl2(dme) (dme = 1,2-dimethoxyethane), W(NArR)2(CH2CMe3)2, W(NArR)(CHCMe3)(OTf)2(dme), and W(NArR)(CHCMe3)(ODBMP)2 (DBMP = 4-Me-2,6-(CHPh2)C6H2). The W(NArR)(CHCMe3)(...
متن کاملZ-Selective Olefin Metathesis Processes and Cis/Syndioselective ROMP with High Oxidation State Molybdenum Alkylidenes
Chapter 1 Reaction of W(CCMe 3)Cl 3(dme) with one equivalent of (3,5-Me 2C6H3NCH 2CH 2)3N)Li3 affords yellow, crystalline W(CCMe 3)(N3N) in good yield. The reactivity of this new alkylidyne complex towards terminal alkynes was investigated. Two other new tungsten alkylidynes, W(CCMe 3)(pyr) 3 (pyr = 2,5-dimethylpyrrolide) and W(CCMe3)(Ph 2N)3 were prepared by the addition of three equivalents o...
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The utility of W-alkylidene complexes for enyne ring-closing metathesis is demonstrated in a direct comparison with Mo-based analogs. Tungsten complexes lead to less alkyne oligomerization and higher levels of endo-selectivity and enantioselectivity.
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