Organotantalum Bis(amidinate) Complexes:  Synthesis and Characterization of Methyl, Methylidene, Benzyl, and Imido Derivatives

Dawson, Denisha Y.; Arnold, John

doi:10.1021/om961052t

Cited by 61 publications

(46 citation statements)

References 33 publications

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“…212 The strategy has been widely use to access tantalum methylidene complexes. 213 More recently, Mindiola reported two elegant and related examples in which deprotonation of Ta-CH3 214 (Scheme 37a) and Nb-CH3 215 groups are effected by ylide Ph3P(CH2). Less common is the intermolecular hydride abstraction from a TM-CH3, which was recently described by our group after adding a salt of the trityl cation as hydride abstractor to [(PONOP)Ir(CH3)] 3.22 (PONOP = 2,6-bis(di-tert-butylphosphinito)-pyridine) (Scheme 37b).…”

Section: Protonolysis and Hydrogenolysismentioning

confidence: 99%

“…Deprotonation of the methyl ligand typically requires the use of a strong base, although milder bases have been reported to react in the gas phase . The strategy has been widely used to access tantalum methylidene complexes . More recently, Mindiola reported two elegant and related examples in which deprotonation of Ta−CH 3 (Scheme a) and Nb−CH 3 groups are effected by the ylide Ph 3 P(CH 2 ).…”

Section: Reactivitymentioning

confidence: 99%

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Methyl Complexes of the Transition Metals

Campos

López‐Serrano

Peloso

et al. 2016

Chemistry A European J

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Organometallic chemistry can be considered as a wide area of knowledge that combines concepts of classic organic chemistry, i.e. based essentially on carbon, with molecular inorganic chemistry, especially with coordination compounds. Transition metal methyl complexes probably represent the simplest and most fundamental way to view how these two major areas of chemistry combine and merge into novel species with intriguing features in terms of reactivity, structure, and bonding. Citing more than 500 bibliographic references, this review aims to offer a concise view of recent advances in the field of transition metal complexes containing M-CH3 fragments. Taking into account the impressive amount of data that are continuously provided by organometallic chemists in this area, this review is mainly focused on results of the last 5 years. After a panoramic overview on M-CH3 compounds of groups 3 to 11 which includes the most recent landmark findings in this area, two further sections are dedicated to methyl-bridged complexes and reactivity.

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Section: Protonolysis and Hydrogenolysismentioning

confidence: 99%

Section: Reactivitymentioning

confidence: 99%

Methyl Complexes of the Transition Metals

Campos

López‐Serrano

Peloso

et al. 2016

Chemistry A European J

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“…Previous work has shown that early metal acyl fragments possess significant oxy-carbene character due to the oxophilicity of the d 0 systems (see refs 8-10)…”

Section: Referencesmentioning

confidence: 99%

An Unusally Diverse Array of Products Formed upon Carbonylation of a Dialkylniobium Complex

et al. 2008

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The clean, efficient utilization of carbon monoxide as a C 1 source continues to represent a significant chemical challenge. Many homogeneous late metal-mediated industrial processes have been developed which center on the utility of well-studied transition metal acyl intermediates. 1 Stoichiometric reactions of carbon monoxide with simple alkyl and dialkylmetal complexes usually lead cleanly to carbonylation products. This is true irrespective of the precise conditions employed, although some substrates may require more forcing conditions (e.g., high temperature or pressure) than others. Through this stoichiometric chemistry, many of the classic primary steps in homogeneous late metal-mediated catalytic organometallic reactions, such as migratory CO insertion, have been identified. Herein we describe the carbonylation reaction of the dimethylniobium complex (BDI)Me 2 Nb(N t Bu) (1, BDI = β-diketiminate), 2 in which the relative amounts of an unusually wide range of products change dramatically in response to very modest changes in reaction conditions. Four different stable products, in which CO insertion takes place coupled with metal reduction, enediolate formation and C-H activation, are formed in these transformations. By careful adjustment of reaction conditions, the majority of these materials have been isolated and fully characterized.On adding 3.0 equiv of CO to a solution of 1 in THF at -72 °C, stirring rapidly for 5 min, then warming directly to room temperature, a brown solution was obtained from which a green product was isolated by crystallization. The products were identified as acetone and the Nb (III) dicarbonyl adduct (BDI)(CO) 2 Nb(N t Bu)(2, 42% isolated yield, Scheme 1), which can be considered to result from transfer of both methyl groups to one CO, followed by the displacement of acetone by two molecules of CO (ν CO (2) = 1988, 1893 cm −1 ). The formation of acetone was confirmed by both GC-MS (20% yield) 3 and isolation of the 2,4-dinitrophenylhydrazone derivative (43% yield). The release of a ketone and formation of a dicarbonyl adduct suggest analogies with previous work on dialkyl metallocenes of the group 4 triad 4 and on η 2 -acetone complexes in group 5 systems. 5,6The outcome of the reaction of 1 with CO may be altered dramatically by using pentane as the solvent in place of THF and by allowing the reaction mixture to remain at -72 °C for 2 h prior to warming to room temperature. In so doing, a second product may be isolated by crystallization, whose analytical data are consistent with its formulation as the enediolate species (BDI iPr )(Me 2 C 2 O 2 )Nb(N t Bu) (3, 54% yield, Scheme 1), presumably formed via the intramolecular coupling of two Nb-acyl fragments, 7-10 though other mechanisms cannot be ruled out. NMR spectral analysis of the crude reaction mixture indicates that the product distribution has inverted from 4:1 mixtures of 2:3 obtained when THF is used as the solvent to 1:4 mixtures of 2:3 obtained when pentane is used and longer reaction times are employed.Correspondenc...

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“…Benzamidinato complexes of tantalum are accessible by analogous routes. [195] The starting material of choice is again Me 3 TaCl 2 .…”

Section: Compounds With Metals In the High Oxidation State And The Anmentioning

confidence: 99%

Highlights in the Renaissance of Amidometal Chemistry

Kempe¹

2000

Angewandte Chemie International Edition

271

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Turning a disadvantage to an advantage: The rather disappointing reactivity of the metal - nitrogen bond in comparison to the metal - carbon bond resulted in the neglect of amidometal chemistry after its heyday at the end of the 1960s and beginning of the 1970s. Today it is precisely this disadvantage which is being applied through the use of amido ligands to produce inert complex fragments with well-defined reaction centers. In this way the chemistry of the early transition metals has been markedly enriched, and interesting alternatives to the classically regarded cyclopentadienyl ligands are now available.

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Organotantalum Bis(amidinate) Complexes: Synthesis and Characterization of Methyl, Methylidene, Benzyl, and Imido Derivatives

Abstract: A new series of tantalum complexes incorporating bis(trimethylsilyl)benzamidinate ligands has been prepared and fully characterized; examples include species with alkyl, alkylidene, and imido functionalities.

Cited by 61 publications

References 33 publications

Methyl Complexes of the Transition Metals

Methyl Complexes of the Transition Metals

An Unusally Diverse Array of Products Formed upon Carbonylation of a Dialkylniobium Complex

Highlights in the Renaissance of Amidometal Chemistry

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