Multiple metal-carbon bonds. 15. Octahedral alkylidene complexes of niobium and tantalum by ligand-promoted .alpha. abstraction

Rupprecht, G. A.; Messerle, Louis; Fellmann, J. D.; Schrock, Richard R.

doi:10.1021/ja00540a010

Cited by 95 publications

(72 citation statements)

References 2 publications

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“…Its 31 P{ 1 H} NMR spectrum shows two singlets at À8.0 and À9.3 ppm in a 10:1 ratio corresponding to coordinated PMe 3 of syn-(4m) and anti-(4m), respectively. The formation of 4m from 3m is in fact quite similar to what has been found for other bisalkyl complexes upon addition of PMe 3 , for which the extrusion of one neopentyl ligand is observed upon coordination of extra donor ligands [59][60][61][62]. This probably shows that the surface might play the role of this ligand in generating directly 2 at room temperature in place of 3.…”

Section: Development Of An Equivalent Homogeneous Olefin Metathesis Csupporting

confidence: 83%

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

Blanc

Chabanas

Copéret

et al. 2005

Journal of Organometallic Chemistry

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Section: Development Of An Equivalent Homogeneous Olefin Metathesis Csupporting

confidence: 83%

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

Blanc

Chabanas

Copéret

et al. 2005

Journal of Organometallic Chemistry

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“…ii Intramolecular α proton migration has been known to be promoted in more sterically crowded circumstances, the first being ligand induced formation of tantalum neopentylidene complexes from tantalum dineopentyl complexes through addition of various phosphines or simply THF. xvii On the basis of all of the above reports, it is fair to say that there is ample precedent for intramolecular migration of a proton from a neopentylidene ligand to a dimethylpyrrolide ligand, even though there is no example of this particular reaction in the literature to our knowledge. It is not possible to determine on the basis of data in hand whether the proton migrates to the pyrrolide nitrogen directly or first to a pyrrolide α or β carbon atom.…”

Section: Resultsmentioning

confidence: 99%

Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes

Lichtscheidl

Müller

et al. 2012

Organometallics

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Seven bipyridine adducts of molybdenum imido alkylidene bispyrrolide complexes of the type Mo(NR)(CHCMe2R′)(Pyr)2(bipy) (1a–1g; R = 2,6-i-Pr2C6H3 (Ar), adamantyl (Ad), 2,6-Me2C6H3 (Ar′), 2-i-PrC6H4 (AriPr), 2-ClC6H4 (ArCl), 2-t-BuC6H4 (ArtBu), and 2-MesitylC6H4 (ArM), respectively; R′ = Me, Ph) have been prepared using three different methods. Up to three isomers of the adducts are observed that are proposed to be the trans and two possible cis pyrrolide isomers of syn alkylidenes. Sonication of a mixture containing 1a–1g, HMTOH (2,6-dimesitylphenol), and ZnCl2(dioxane) led to the formation of MAP species of the type Mo(NR)(CHCMe2R′)(Pyr)(OHMT) (3a–3g). DCMNBD (2,3-dicarbomethoxynorbornadiene) is polymerized employing 3a–3g as initiators to yield >98% cis,syndiotactic poly(DCMNBD). Attempts to prepare bipy adducts of bisdimethylpyrrolide complexes led to formation of imido alkylidyne complexes of the type Mo(NR)(CCMe2R′)(Me2Pyr)(bipy) (Me2Pyr = 2,5-dimethylpyrrolide; 4a – 4g) through a ligand-induced migration of an alkylidene α proton to a dimethylpyrrolide ligand. X-ray structures of Mo(NAr)(CHCMe2Ph)(Pyr)2(bipy) (1a), Mo(NAriPr)(CHCMe2Ph)(Pyr)(OHMT) (3d), Mo(NAr)(CCMe2Ph)(Me2Pyr)(bipy) (4a), and Mo(NArT)(CCMe3)(Me2Pyr)(bipy) (ArT = 2-(2,4,6-i-Pr3C6H2)C6H4; 4g) showed structures with the normal bond lengths and angles.

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“…As depicted in Scheme , α‐hydrogen (proton) abstraction offers an attractive method for the generation of high‐oxidation‐state alkylidene complexes. In this context, it was demonstrated that such processes can be induced by coordinating solvents 66. For example, yellow‐orange [Cl 3 Ta(CH 2 t Bu) 2 ][ 19 , Eq.…”

Section: Introductionmentioning

confidence: 99%

Molybdenum and Tungsten Imido Alkylidene Complexes as Efficient Olefin‐Metathesis Catalysts

2003

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Catalytic olefin metathesis has quickly emerged as one of the most often-used transformations in modern chemical synthesis. One class of catalysts that has led the way to this significant development are the high-oxidation-state alkylidene complexes of molybdenum. In this review key observations that resulted in the discovery and development of molybdenum- and tungsten-based metathesis catalysts are outlined. An account of the utility of molybdenum catalysts in the synthesis of biologically significant molecules is provided as well. Another focus of the review is the use of chiral molybdenum complexes for enantioselective synthesis. These highly efficient catalysts provide unique access to materials of exceptional enantiomeric purity and often without generating solvent waste.

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Multiple metal-carbon bonds. 15. Octahedral alkylidene complexes of niobium and tantalum by ligand-promoted .alpha. abstraction

Cited by 95 publications

References 2 publications

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

Bipyridine Adducts of Molybdenum Imido Alkylidene and Imido Alkylidyne Complexes

Molybdenum and Tungsten Imido Alkylidene Complexes as Efficient Olefin‐Metathesis Catalysts

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