Tungsten vinylidenes and carbynes from terminal alkyne reagents

The thermal isomerizations of η1‐vinylidene complexes [(η5‐C5H5)(CO)(NO)W=C=CHR] [5a, R = Si(CH3)2C(CH3)3; 5c, R = C(CH3)3] as well as [(η5‐C5H5)(CO)(NO)Mo=C=CHC(CH3)3] (8), to the corresponding η2‐1‐alkyne complexes [(η5‐C5H5)(CO)(NO)W(η2‐H−C≡C−R)] [7a, R = Si(CH3)2C(CH3)3; 7c, R = C(CH3)3] and [(η5‐C5H5)(CO)(NO)Mo{η2‐H−C≡C−CHC(CH3)3}] (9) has been investigated. Activation parameters for the isomerization of 5a in [D6]benzene and 8 in [D8]toluene and [D5]ethanol were determined. In [D8]toluene η1‐vinylidene complex 5a undergoes a single step 1,2‐shift of the silyl group from Cβ to Cα. However, complex 8 shows dichotomous behavior. The isomerization 8 ⇄ 9, dependent upon the solvent applied, occurs by means of two different pathways: in a nonpolar solvent, 8 tautomerizes via the 1,2‐migration of the hydrogen atom to 9 and in ethanol this tautomerization proceeds by a multi‐step process via deprotonation‐protonation and subsequent reductive elimination. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…[9,19] In order to distinguish between these two possibilities we investigated the exchange rate in the presence of D …”

mentioning

confidence: 99%

η¹‐Vinylidene to η²‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

2003

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“…The W(1)--C----O groups are almost linear [average value 176.8 (5)°J. Both W(1)--P distances [average value 2-513 (1)A] are close to those found in the related complex [W(CO)3(dppe)(~HCO2-Me)] [average value 2.550 (3) A] (Birdwhistell, Nieter Burgmayer & Templeton, 1983). The Br(1)---W(1)---P angles are smaller than the Br (1) (7) 0.11781 (6) 4-40 (4) P(2) 0.2757 (1) 0-16591 (7) 0-02763 (6) 4.68 (4)…”

Section: Discussion Final Atomic Parameters Are Listed Inmentioning

confidence: 60%

Structure of trans-bromodicarbonyl[o-phenylenebis(diphenylphosphine)](p-tolylmethylidyne)tungsten(0)

Carriedo¹,

González²,

Sánchez³

1990

Acta Crystallogr C

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“…Noteworthy is that vinylidene complexes 22 (M = W) are not prepared from 3 (M = W) and terminal alkynes. This is in sharp contrast to the reactivity of the {W(CO) 3 (dppe)} site toward terminal alkynes, which readily yields the vinylidene complex mer ‐[W(=C=CHR)(CO) 3 (dppe)] 55. Protonation of both 21 and 22 with HBF 4 yields the cationic alkylidyne complex cis ‐[M(≡CCH 2 R)(CO)(dppe) 2 ] [BF 4 ] ( 23 ).…”

Section: Transformation Of Alkynesmentioning

confidence: 99%

Transformation of organic molecules on the low‐valent {M(Ph₂PCH₂CH₂PPh₂)₂} moiety derived from trans‐[M(N₂)₂(Ph₂PCH₂CH₂PPh₂)₂] or related complexes (M = MO, W)

Seino

Mizobe

Hidai

2001

The Chemical Record

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A zero-valent [M(Ph(2)PCH(2)CH(2)PPh(2))(2)] moiety (M = Mo, W) generated in situ by dissociation of the N(2) ligands in trans-[M(N(2))(2)(Ph(2)PCH(2)CH(2)PPh(2))(2)] can activate pi-accepting organic molecules including isocyanides and nitriles, which undergo the electrophilic attack caused by a strong pi-donation from a zero-valent metal center. Cleavage of a variety of C-X bonds (X = H, C, N, O, P, halogen) also occurs at their electron-rich sites through oxidative addition to form reactive intermediates, which subsequently degradate to yield smaller molecules either bound to or dissociated from the metal center. The mechanism is substantiated unambiguously by isolation of numerous intermediate stages.

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Tungsten vinylidenes and carbynes from terminal alkyne reagents

Cited by 64 publications

References 2 publications

η¹‐Vinylidene to η²‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

η¹‐Vinylidene to η²‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

Structure of trans-bromodicarbonyl[o-phenylenebis(diphenylphosphine)](p-tolylmethylidyne)tungsten(0)

Transformation of organic molecules on the low‐valent {M(Ph₂PCH₂CH₂PPh₂)₂} moiety derived from trans‐[M(N₂)₂(Ph₂PCH₂CH₂PPh₂)₂] or related complexes (M = MO, W)

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Tungsten vinylidenes and carbynes from terminal alkyne reagents

Cited by 64 publications

References 2 publications

η1‐Vinylidene to η2‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

η1‐Vinylidene to η2‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

Structure of trans-bromodicarbonyl[o-phenylenebis(diphenylphosphine)](p-tolylmethylidyne)tungsten(0)

Transformation of organic molecules on the low‐valent {M(Ph2PCH2CH2PPh2)2} moiety derived from trans‐[M(N2)2(Ph2PCH2CH2PPh2)2] or related complexes (M = MO, W)

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η¹‐Vinylidene to η²‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

η¹‐Vinylidene to η²‐Alkyne Isomerization of Tungsten and Molybdenum Complexes

Transformation of organic molecules on the low‐valent {M(Ph₂PCH₂CH₂PPh₂)₂} moiety derived from trans‐[M(N₂)₂(Ph₂PCH₂CH₂PPh₂)₂] or related complexes (M = MO, W)