Preparation and characterization of active niobium, tantalum and tungsten metathesis catalysts

Schrock, Richard R.; Rocklage, Scott M.; Wengrovius, Jeffrey H.; Rupprecht, G. A.; Fellmann, J. D.

doi:10.1016/0304-5102(80)87006-4

Cited by 159 publications

(63 citation statements)

References 9 publications

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“…(19)], or through addition of the parent biphenol or binaphthol to a bisamido precursor [Eq. (32)]. We have shown that catalysts prepared in situ for asymmetric metathesis reactions behave as well as catalysts that have been isolated and purified before use.…”

Section: It Soon Became Clear That [W(nar)(ch-tbu)(or)mentioning

confidence: 98%

“…Several dozen catalytic metathesis cycles could be observed for an olefin such as cis-2-pentene. [32] It was proposed that the tertbutoxide ligands "prevent reduction" of the metal and "promote metathesis." At that same conference I reported that an attempt to carry out a "Wittig-like" reaction between a tantalum alkylidene and a tungsten oxo complex to yield [W(CHtBu)(OtBu) 4 ] and [Ta(O)L 2 Cl 3 ], instead produced an unanticipated 18-electron oxo neopentylidene complex of tungsten [Eq.…”

mentioning

confidence: 99%

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Multiple Metal–Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture)

2006

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Its my great privilege to be here today, in a position I never thought possible. The story I will tell you I hope will give you some idea what I have contributed to the area for which the Nobel prize in chemistry was awarded this year.The story begins 32 years ago in 1973, the year the Nobel prize was shared by G. Wilkinson and E. O. Fischer. Wilkinsons Nobel lecture [1] concerned the nature of a single bond between a transition metal and a carbon atom in an alkyl group, and emphasized the fact that the metal-carbon bond is not inherently weak. E. O. Fischer in his Nobel Lecture [2] summarized the extensive chemistry of transitionmetal "carbene" complexes [3,4] that contain a metal-carbon double bond discovered by him and his group in 1964 (Scheme 1).[5] He also reported new "carbyne" complexes that contain a metal-carbon triple bond. [6] It was clear that metal-carbon single bonds were of great importance in the emerging area of homogeneous catalysis. However, no catalytic reactions involving species that contain metalcarbon double or triple bonds were known. When I went to the Central Research Department of E. I. DuPont de Nemours and Company in 1972, transition-metal organometallic chemistry and homogeneous catalysis were of great interest as a consequence of their huge potential in organic chemistry and therefore in industry.In the early 1970s inorganic chemists knew that many transition metal species containing a metal-carbon bond are subject to various modes of decomposition that are much more rapid than in a non-transition-metal species such as Zn(CH 2 CH 3 ) 2 or Al(CH 2 CH 3 ) 3 . The most common of these decomposition reactions involves transfer of a b hydrogen atom, from a metal-bound ethyl group (MÀCH 2 CH 3 ) for example, to the metal center (M) to yield a metal hydride and an alkene. The relative stabilities of high-oxidation-state "homoleptic" or "peralkyl" compounds such as [M{CH 2 Si-(CH 3 ) 3 } 4 ], [M(CH 2 C 6 H 5 ) 4 ], and [M{CH 2 C(CH 3 ) 3 } 4 ] (M = Ti, Zr, or Hf; Scheme 2), were rationalized on the basis of the fact that unlike a compound having an ethyl ligand, the alkyl ligands in these species lack b hydrogen atoms and so of course cannot undergo decomposition processes that involve b hydrogen atoms.[ 6 ] is stable at 22 8C. The methyl carbon is a with respect to the metal center; there is no b carbon atom and so no b hydrogens. However, methyl species are not

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Section: It Soon Became Clear That [W(nar)(ch-tbu)(or)mentioning

confidence: 98%

mentioning

confidence: 99%

Multiple Metal–Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture)

2006

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“…1.873 (9) 1.742 (9) 150.3 (7) 174.8 (7) 13 (1) 140 (1) 167 (1) 10 (1) 151 (1) 175 (1) 10 anti-Re(C-t-Bu)(CHFc)(ORF6h 1.88 (1) 1.70 (1) 114.8 (7) 174.0 (8) 25 Re(C-t-Bu)(CHOEt)(ORF6h(THFh 1.883 (9) '1.713 (8) 129.9 (6) 177.7 (8) 25 a py = pyridine; Ar' = 2,6-C6H3Me2; ORF6 = OCMe(CF3h; Fc = ferrocenyl; THF = tetrahydrofuran. All are syn rotamers unless otherwise noted.…”

Section: Re(c-t-bu)(ch-t-bu)(pyhi2mentioning

confidence: 98%

Olefin Metathesis by Well-Characterized Re(VII) Alkylidene/Alkylidyne Complexes

Schrock

Toreki

Vaughan

et al. 1993

Transition Metal Carbyne Complexes

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“…[18] They reasoned that if an alkylidyne complex was to catalyze the metathesis of Scheme 3. Postulated ring expansion mechanism of polymerization of 2-butyne by-product.…”

Section: Tungsten-basedmentioning

confidence: 99%

Alkyne Metathesis: Catalysts and Synthetic Applications

2007

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There has been rapid progress and growing interest in alkyne metathesis within the past decade. The availability of highly active catalysts as well as their applications in both organic synthesis and polymer chemistry has served to motivate the advancement of this field. In this article, the development of several different metathesis catalysts, including two heterogeneous ones, are reviewed with an emphasis on comparing strengths and weaknesses. In Section 4, the applications of alkyne metathesis to synthesis of natural products, conjugated polymers as well as shape-persistent macrocycles are discussed. In the last section, a comparison of alkyne metathesis to the well established alkene metathesis is given. Developing an alkyne metathesis catalyst with both high reactivity and robustness to air and moisture remains an unsolved problem of this important and useful reaction.

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Preparation and characterization of active niobium, tantalum and tungsten metathesis catalysts

Cited by 159 publications

References 9 publications

Multiple Metal–Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture)

Multiple Metal–Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture)

Olefin Metathesis by Well-Characterized Re(VII) Alkylidene/Alkylidyne Complexes

Alkyne Metathesis: Catalysts and Synthetic Applications

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