Facile Synthesis of Trialkoxymolybdenum(VI) Alkylidyne Complexes for Alkyne Metathesis

Tsai, Yi‐Chou; Diaconescu, and Paula L.; Cummins, Christopher C.

doi:10.1021/om000644f

Cited by 103 publications

(59 citation statements)

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“…(25); BBN = 9-borabicyclo[3.3.1]nonane]. [75] Although molybdenum-based alkyne metathesis catalysts were known, [76,77] work by Cummins, [78] Fürstner, [79] and Moore, [80] recently have demonstrated how these relatively inaccessible…”

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

confidence: 99%

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: 99%

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

2006

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“…[29] The synthesis starts with a metallaaziridine-hydride complex 16, which is known [30] to serve as a source of the three-coordinate , which rearranges to the alkylidyne complex via a 1,2-migration of the trimethylsilyl group. [31] Upon addition of 3 equivs.…”

Section: Trialkoxymolybdenum(vi) Alkylidynes Prepared From Metallaazimentioning

confidence: 99%

“…[29,42] Therefore, development of an alternative strategy for the preparation of trisamidomolybdenum(VI) alkylidynes was pursued.…”

Section: Molybdenum-based Catalysts Prepared Via Reductive Recycle Stmentioning

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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“…Finally, the singlet for the [CFMoH 3 ] isomer is found to have C 3v À . [20,21] In addition, the strong MoÀH frequency (1844.8 cm ). [16] Finally, Table 5 compares geometrical parameters and Mulliken charges computed for the three structures.…”

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confidence: 99%

[CH₃MoF], [CH₂MoHF], and [CHMoH₂F] Formed by Reaction of Laser‐Ablated Molybdenum Atoms with Methyl Fluoride: Persistent Photoreversible Interconversion through α‐Hydrogen Migration and Agostic Interaction

Cho

Andrews

2005

Chemistry A European J

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Simple molybdenum methyl, carbene, and carbyne complexes, [CH3--MoF], [CH2=MoHF], and [CH[triple chemical bond]MoH(2)F], were formed by the reaction of laser-ablated molybdenum atoms with methyl fluoride and isolated in an argon matrix. These molecules provide a persistent photoreversible system through alpha-hydrogen migration between the carbon and metal atoms: The methyl and carbene complexes are produced by applying UV irradiation (240-380 nm) while the carbyne complex is depleted, and the process reverses on irradiation with visible light (lambda>420 nm). An absorption at 589.3 cm(-1) is attributed to the Mo--F stretching mode of [CH3--MoF], which is in fact the most stable of the plausible products. Density functional theory calculations show that one of the alpha-hydrogen atoms of the carbene complex is considerably bent toward the metal atom (angle-spherical HCMo=84.5 degrees ), which provides evidence of a strong agostic interaction in the triplet ground state. The calculated C[triple chemical bond]Mo bond length in the carbyne is in the range of triple-bond values in methylidyne complexes.

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Facile Synthesis of Trialkoxymolybdenum(VI) Alkylidyne Complexes for Alkyne Metathesis

Cited by 103 publications

References 25 publications

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

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

Alkyne Metathesis: Catalysts and Synthetic Applications

[CH₃MoF], [CH₂MoHF], and [CHMoH₂F] Formed by Reaction of Laser‐Ablated Molybdenum Atoms with Methyl Fluoride: Persistent Photoreversible Interconversion through α‐Hydrogen Migration and Agostic Interaction

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Facile Synthesis of Trialkoxymolybdenum(VI) Alkylidyne Complexes for Alkyne Metathesis

Cited by 103 publications

References 25 publications

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

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

Alkyne Metathesis: Catalysts and Synthetic Applications

[CH3MoF], [CH2MoHF], and [CHMoH2F] Formed by Reaction of Laser‐Ablated Molybdenum Atoms with Methyl Fluoride: Persistent Photoreversible Interconversion through α‐Hydrogen Migration and Agostic Interaction

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[CH₃MoF], [CH₂MoHF], and [CHMoH₂F] Formed by Reaction of Laser‐Ablated Molybdenum Atoms with Methyl Fluoride: Persistent Photoreversible Interconversion through α‐Hydrogen Migration and Agostic Interaction