Carbene complexes of zirconium. Synthesis, structure, and reactivity with carbon monoxide to afford coordinated ketene

Barger, P.T.; Santarsiero, Bernard D.; Armantrout, J.; Bercaw, John E.

doi:10.1021/ja00330a023

Cited by 84 publications

(33 citation statements)

References 4 publications

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“…60,62 Forming 5 at low temperature, adding 13 CO, and condensing EtOH into the reaction tube afforded EtOAc-13 C2, 8, unequivocally demonstrating the generation and ejection of parent ketene (Scheme 3). Alkylidene carbonylation has been demonstrated on a variety of molecular scaffolds, 13 but often requires CO overpressures, 58,[63][64][65] proceeds from activated Fischer carbene complexes, 13,[66][67][68] or occurs at bridging alkylidene ligands. [69][70] Rarely is this coupling achieved at monometallic complexes with carbene fragments derived from CO. 67,[71][72][73] Isotopic labeling studies were conducted in which 12 CO was added to 5.…”

Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

“…Alkylidene carbonylation has been demonstrated on a variety of molecular scaffolds, 13 but often requires CO overpressures, 58,[63][64][65] proceeds from activated Fischer carbene complexes, 13,[66][67][68] or occurs at bridging alkylidene ligands. [69][70] Rarely is this coupling achieved at monometallic complexes with carbene fragments derived from CO. 67,[71][72][73] Isotopic labeling studies were conducted in which 12 CO was added to 5. Mixed isotopolog P2Mo( 12/13 CO)3 was formed, consistent with either i) rapid exchange of the 13 CO ligand in 5 with free 12 CO and on-metal C-C bond formation or ii) 12 CO binding and C-C coupling preceding from a methylidene dicarbonyl complex.…”

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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“…Dihydrogen addition and ketene reduction from its most sterically favorable side provides the logic for the observed cis stereochemistry of the product. 2,9,10 The idea that a transition metal hydride could reduce a bound carbonyl in homogeneous solution had little precedent; hence, Cp 2 WCO and Cp 2 Nb(CO)H were selected for independent trials. As Scheme 3 also shows, those substrates yielded the zirconoxycarbenes Cp 2 WC(H)OZr(H)Cp* and Cp 2 (H)NbC(H)OZr(H)Cp* 2 , respectively.…”

Section: Acs Catalysismentioning

confidence: 99%

A Career in Catalysis: John E. Bercaw

Wolczanski

Chirik

2015

ACS Catal.

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On the occasion of Professor John Bercaw's 70th birthday, we reflect and highlight his distinguished career in organometallic chemistry and homogeneous catalysis. What began as a fundamental interest in the chemistry of bis(cyclopentadienyl)titanium compounds and their interaction with molecular nitrogen evolved into a vibrant and diverse program tackling some of the most important problems in catalysis. Using well-defined organometallic compounds, fundamental insights were gained in the mechanism of CO reduction; basic transformations of organometallic chemistry, such as alkene insertion and alkyl β-hydrogen elimination; the origin of stereocontrol in metallocene-catalyzed polymerization; and in the activation of hydrocarbons by electrophilic late transition metals.

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“…A host of metaloxycarbene complexes has also been prepared via nonnucleophilic addition to metal carbonyls, including metallacyclic metaloxycarbene complexes afforded by ring-closure reactions of η 2 -olefin complexes of titanocene, zirconocene or hafnocene, (η 4 -diene) metallocenes or alkylidene titanium complexes [125,171,[181][182][183][184][185].…”

Section: Metaloxycarbene Complexesmentioning

confidence: 99%

Recent advances in the field of multicarbene and multimetal carbene complexes of the Fischer-type

Bezuidenhout

Lotz

Liles

et al. 2012

Coordination Chemistry Reviews

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Carbene complexes of zirconium. Synthesis, structure, and reactivity with carbon monoxide to afford coordinated ketene

Cited by 84 publications

References 4 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 Career in Catalysis: John E. Bercaw

Recent advances in the field of multicarbene and multimetal carbene complexes of the Fischer-type

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