Monomeric Group VI (M = molybdenum, tungsten) methylidyne complexes and their dimerization to nonclassical vinylidene-bridged Tp'(CO)2M(.mu.-CCH2)M(CO)2Tp' products

Jamison, Gregory M.; Bruce, Alice E.; White, Peter S.; Templeton, Joseph L.

doi:10.1021/ja00013a050

Cited by 54 publications

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“…A single resonance between 3.5 and 6.5 ppm is observed in the 1 H NMR spectrum, a doublet of triplets centered at 5.06 ppm ( 1 J(C,H) = 147.8 Hz, 3 J(P,H) = 3.1 Hz), with a relative integration of one. This suggests both a terminal methylidyne 20,24,[45][46][47][48][49][50][51] and a five-coordinate pseudo-square pyramidal structure, as in 4, without metal-arene interactions (vide infra; Scheme 3). The 31 P{ 1 H} and 13 C{ 1 H} NMR data further corroborate the proposed assignment of 4, with a doublet of doublets at dP 40.21 ppm ( 2 J(C,P) = 18.6 and 10.2 Hz) and a characteristic methylidyne resonance at dC 281.19 ppm, respectively.…”

Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

“…The 31 P{ 1 H} and 13 C{ 1 H} NMR data further corroborate the proposed assignment of 4, with a doublet of doublets at dP 40.21 ppm ( 2 J(C,P) = 18.6 and 10.2 Hz) and a characteristic methylidyne resonance at dC 281.19 ppm, respectively. 45,51 Scheme 3. Sequential Proton and Hydride Addition en route to Ketene Formation a a Carbide 1 was synthesized cleanly in situ via deprotonation of P2Mo(CH)(CO)(Cl) 4 with benzyl potassium.…”

Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

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CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

et al. 2019

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The mechanism originally proposed by Fischer and Tropsch for carbon monoxide (CO) hydrogenative catenation involves CC coupling from a carbide-derived surface methylidene. A single molecular system capable of capturing these complex chemical steps is hitherto unknown. Herein, we demonstrate the sequential addition of proton and hydride to a terminal Mo carbide derived from CO. The resulting anionic methylidene couples with CO (1 atm.) at low-temperature (-78 °C) to release ethenone. Importantly, the synchronized delivery of two reducing equivalents and an electrophile, in the form of a hydride (H-= 2e-+ H +), promotes alkylidene formation from the carbyne precursor and enables coupling chemistry, under conditions milder than those previously described with strong one-electron reductants and electrophiles. Thermodynamic measurements bracket the hydricity and acidity requirements for promoting methylidene formation from carbide as energetically viable upon formal heterolysis of H2. Methylidene formation prior to CC coupling proves critical for organic product release, as evidenced by direct carbide carbonylation experiments. Spectroscopic studies, a monosilylated model system, and Quantum Mechanics computations provide insight into the mechanistic details of this reaction sequence, which serves as a rare model of the initial stages of the Fischer Tropsch synthesis.

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Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

et al. 2019

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“…Reaction of 3 with pivaloyl chloride 11 Methylidyne 6, an off-white solid, was isolated by this procedure in 53% yield from 2.∑ Several other routes to the terminal methylidyne functionality have been documented. [12][13][14][15][16][17] Deprotonation of 6 was effected by benzylpotassium in thf, 18 giving the potassium-molybdenum carbido complex [K( 13 C)Mo{N(R)Ar} 3 ] 2 7 [d( 13 C) 494.5] 19,20 in 69% yield after recrystallization from pentane-thf. ** In thf solution 7 presumably exists as a thf solvate, but the indicated thf-free, benzene-soluble dimer stabilized by intramolecular K + -arene interactions 21 is readily obtained.…”

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confidence: 99%

A terminal molybdenum carbide prepared by methylidyne deprotonation

Peters¹,

Odom²,

Cummins³

1997

Chem. Commun.

160

205

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“…90% of a single species (δ P = 23.7) without visible 183 W satellites, suggesting hydrolysis ultimately results in cleavage of the P−C(carbyne) bond with formation of P-phenylphosphinous acid and Templeton's binuclear vinylidene complex [W 2 (μ-CCH 2 ) (CO) 4 (Tp*) 2 ]. 33 This approach was also extended to an alkyl-substituted phosphine. Thus, the reaction of 1, n BuLi, and PCl 2 Cy provides [W(CPClCy)(CO) 2 (Tp*)] (4) in 65% yield (Scheme 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Chlorophosphino Carbyne Complexes of Tungsten

Colebatch

Hill

2016

Organometallics

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A range of chlorophosphinocarbyne complexes [W(CPClR)(CO) 2 (Tp*)] (R = Cl, Cy, Ph; Tp* = hydrotris-(3,5-dimethylpyrazol-1-yl)borate) has been prepared by reaction of chlorophosphines with the lithiocarbyne complex [W{ CLi(THF) n }(CO) 2 (Tp*)]. These complexes undergo nucleophilic substitution of chloride to enable the preparation of phosphinocarbynes bearing alkyl, aryl, alkynyl, aryloxy, and secondary phosphino substituents [W(CPRR′)(CO) 2 (Tp*)] (R = Ph, R′ = Me, Ph, CCPh, OPh, H; R = Cy, R′ = H). ■ INTRODUCTIONCarbynes L n MCR, as one of the simplest carbon-based ligands, and phosphines, as ubiquitous (spectator and noninnocent) ligands, both represent in their own way fundamental groups in organometallic chemistry. Despite dating back to Fischer's seminal report in 1973, 1 the appearance of carbyne complexes in the literature remains somewhat sporadic. A notable exception to this involves carbyne complexes serving as catalysts for alkyne metathesis, which continues to receive considerable attention. 2−8 Carbyne complexes bearing heteroatom carbyne substituents have been less studied, and in part this reflects limitations in synthetic methodologies that are typically distinct from classical Fischer or Schrock protocols. 9−16 We have enjoyed some success employing the "M-(CO) 2 (Tp*)" fragments (M = Mo, W; Tp* = 3,5-hydrotris-(dimethylpyrazolyl)borate)) for the construction of comparatively elaborate carbyne complexes, in particular those that bear heteroatomic carbyne subsitutents. 17−29 The combination of the bulky Tp* ligand (Tolman cone angle = 224°), 30 which affords kinetic stabilization, and the π-acidic CO coligands, which render the metal center relatively inert, allows modifications at the carbyne ligand to proceed, in many cases, without disruption of the MC linkage or M-(CO) 2 (Tp*) coordination sphere. In contrast to carbyne chemistry, phosphorus chemistry is very mature. Chlorophosphines are the quintessential building blocks for a myriad of phosphorus species due to the high reactivity of the P−Cl linkage and subsequent ease of nucleophilic substitution at this position.Combining these two principles we have considered the marriage of conventional organophosphorus chemistry with that of carbyne complexes. We have previously demonstrated that tertiary phosphinocarbyne complexes [M(CPPh 2 )-(CO) 2 (Tp*)] (M = W 2a, Mo 2b)) 21,29 and phosphonito carbynes [Mo{CP(O)(OEt) 2 }(CO) 2 (Tp*)] 21 are readily accessible from the bromocarbyne precursor [M(CBr)-(CO) 2 (Tp*)] (M = W 1a, Mo 1b) via lithium/halogen exchange with n BuLi and nucleophilic substitution of PClPh 2 or alternatively via palladium-catalyzed phosphination using PH-(O)(OEt) 2 , respectively. These complexes possess relatively inert phosphorus centers, undergoing conventional "phosphinetype" reactions with electrophiles, oxidants, and metal centers.In search of more versatile precursors, it has been found that the palladium-mediated protocol is also effective for the preparation of secondary phosphinocarbynes [W(CPHR)-(CO) 2 (Tp...

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Monomeric Group VI (M = molybdenum, tungsten) methylidyne complexes and their dimerization to nonclassical vinylidene-bridged Tp'(CO)2M(.mu.-CCH2)M(CO)2Tp' products

Cited by 54 publications

References 0 publications

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

A terminal molybdenum carbide prepared by methylidyne deprotonation

Chlorophosphino Carbyne Complexes of Tungsten

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