Synthesis and structure of moderately stable metallaoxetanes: [cyclic](.eta.5-C5Me5)2(CH3)TaOCHRCH2 (R = H, C6H5). Investigations of their decomposition to olefin and (.eta.5-C5Me5)2Ta(:O)CH3 and evidence revealing that they are not intermediates in the deoxygenation of epoxides by [(.eta.5-C5Me5)2Ta(CH3)]

Whinnery, LeRoy L.; Henling, Lawrence M.; Bercaw, John E.

doi:10.1021/ja00020a019

Cited by 35 publications

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“…These latter "metallacyclization" reactions may involve the formation o f complexes such as the metallacyclobutenes Ta(CR=CRCHBu l )(OAr) 3 prepared f r o m Ta(=CHBu t )(OAr) 3 (THF) and RC=CR, 3 7 2 or heteroatomsubstituted metallacycles such as metallaoxetanes Cp* 2 Ta[OCH(C 6 H 4 -4-X)CH 2 ]Me, formed f r o m Cp* 2 Ta(=CH 2 )Me with substituted benzaldehydes O=CH(C 6 H 4 -4-X). 228 Cycloaddition reactions such as these will be detailed in Section 2.6.…”

Section: Reactivitymentioning

confidence: 99%

“…m Similarly, acetone and Ta(CH 2 CH 2 CH 2 )(OAr) 3 form Ta(OCMe 2 CH 2 CH 2 CH 2 )(OAr) 3 . Bercaw and co-workers 228 have studied the Wittig-like reactions of alkylidene complexes with organic carbonyls employing Cp* 2 Ta(=CH 2 )Me. Thus, treatment of Cp* 2 Ta(=CH 2 )Me with substituted benzaldehydes O=CH(C 6 H 4 -4-X) (X = H, Cl, CF 3 , CN or NO 2 ) provides the isolable metallaoxetane complexes, Cp* 2 Ta[OCH(C 6 H 4 -4-X)CH 2 ]Me.…”

Section: Other Metallacycles Including Cyclometallated Ligandsmentioning

confidence: 99%

“…The relative rates of these decompositions depend only slightly upon the nature of the para substituent of the metallaoxetane phenyl group and little on the solvent polarity, indicating only minor charge buildup in the transition state. 228 Finally, a number of other complexes containing cyclometallated ligands are described in other sections. Thus, the cyclometallated PMe 3 ligands T| 2 -CH 2 PMe 2 and r| 2 -CHPMe 2 are outlined in Section 2.5.3.6 and cyclometallated C 5 Me 5 ligands, for example, r| 6 -C 5 Me 4 CH 2 and TI 7 -C 5 Me 3 (CH 2 ) 2 , are described elsewhere.…”

Section: Other Metallacycles Including Cyclometallated Ligandsmentioning

confidence: 99%

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Niobium and Tantalum

Wigley

Gray

1995

Comprehensive Organometallic Chemistry II

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Section: Reactivitymentioning

confidence: 99%

Section: Other Metallacycles Including Cyclometallated Ligandsmentioning

confidence: 99%

Section: Other Metallacycles Including Cyclometallated Ligandsmentioning

confidence: 99%

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Niobium and Tantalum

Wigley

Gray

1995

Comprehensive Organometallic Chemistry II

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“…Early metal complexes containing multiply bonded ligands have drawn much attention. Among the recent highlights are a number of synthetic, structural, and reactivity studies of terminal chalcogenide (M = E, E = O, S, Se, Te), − imide, phosphinidene, and arsinidene (M = ER, E = N, P, As) species. − Concurrent with these works, interest in transition metal hydride chemistry has led to the characterization of a variety of monomeric and dimeric early metal polyhydrides. − Chemistry at the interface of these two areas has only begun to emerge. Bergman and co-workers 9 demonstrated the direct conversion of a terminal Ti-sulfide Cp* 2 Ti(S)py to the hydride species Cp* 2 TiH(SH) via the addition of H 2 , while Andersen et al have very recently described reactions of the Ti(III) hydride Cp* 2 Ti(μ-H) 2 Li(tmed) with water to give the oxide anion [Cp* 2 TiOLi(THF)] 2 .…”

Section: Introductionmentioning

confidence: 99%

Decamethylzirconocene-Chalcogenide-Hydride Complexes

Hoskin

Stephan

1999

Organometallics

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Stoichiometric reaction of [(C5Me5)2ZrH3]Li (1) with diphenylphosphine sulfide or selenide yields the bimetallic species [(C5Me5)2ZrH]2(μ-E) (E = S 2, Se 3). These reactions are proposed to proceed via an intermediate of the form [(C5Me5)2ZrH2(EPPh2)]- with concurrent loss of dihydrogen. Subsequent β-elimination of Ph2PH affords 2 and 3 via dimerization and loss of Li2E. The initial synthetic strategy to trap an anionic intermediate involved treatment of 1 with diphenylphosphine oxide. This approach failed, affording instead the tetrameric species [Ph2POLi(THF)]4 (4) and Cp*2ZrH2. An alternative, successful approach to an oxide anion involved the reaction of 1 with Me3NO. The resulting species [(C5Me5)2ZrH(OLi(THF))]2 (5) was isolated, and the species 2−5 have been structurally characterized. These results are presented and the implications discussed.

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“…The second possible reaction pathway (path B in Scheme ) involves initial migration of the alkyl or aryl group to a CO ligand. Subsequently, the tantalum alkylidene complex attacks the acyl species much as the Cp* (Cp* = η 5 -C 5 Me 5 ) analog of 1 has been shown to attack aldehydes (see intermediate 9 ) …”

Section: Discussionmentioning

confidence: 99%

Reactions of Cp₂Ta(CH₂)(CH₃) with Substituted and Unsubstituted Metal Carbonyls (Groups 7, 8, and 9). Evidence for Intermediates Involved in the Carbon−Carbon Bond-Forming Steps of the Reduction and Deoxygenation of CO

Proulx

Bergman

1996

J. Am. Chem. Soc.

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The mechanisms of surface-catalyzed reactions that deoxygenate carbon monoxide (CO) and convert it into longer chain hydrocarbons are not well understood. Homogeneous models involving soluble, well-characterized organometallic complexes would be helpful in developing an understanding of these reactions. Reported here are transformations in which CH2, CO, alkyl, and aryl fragments incorporated in soluble metal complexes undergo a variety of changes that lead to new multicarbon ligands. In one example, treatment of the tantalum methylene complex Cp2Ta(CH2)(CH3) (1, Cp = η5-C5H5) with the methyl- or phenylrhenium pentacarbonyl complexes R−Re(CO)5 (R = CH3 (2a), Ph (2b)) above 0 °C leads to >90% yields of the bridging oxo complexes Cp2(CH3)Ta(μ-O)Re(CRCH2)(CO)4 (R = Me (3a) and Ph (3b)). Low-temperature NMR monitoring and use of a perfluoroalkyl ligand has provided information about the initial steps in these transformations. These demonstrate the first observation of “Wittig-like” attack of a metal alkylidene group on a CO ligand to give a zwitterion (e.g., fully characterized 16) followed by cleavage to oxometal and vinylidene complexes. In another example, the tantalum−methylene complex 1 reacts with the dinuclear metal carbonyls Co2(CO)8 and Fe2(CO)9 to yield new complexes (17 and 18) that incorporate a C3H2O2 ligand bridging three metal centers. Reaction of the tantalum−methylene complex with Re2(CO)10, Mn2(CO)10, or Fe(CO)5 leads to 19, 20, and 21, requiring even more deep-seated changes in which extensive rearrangement along with three-carbon coupling occurs. In this process, an oxygen atom is removed from one CO group, leading to the oxotantalum compound Cp2(CH3)TaO. The carbon atom from the transformed CO couples with two CH2 groups initially bound to tantalum, and the CH2 hydrogens are simultaneously rearranged to produce a CH3−C⋮C- ligand. This C3 fragment is stabilized by binding to a tantalum−late-metal chain. These products also contain the first examples of tantalum−carbon monoxide bridges. A reaction between 1 and Ru3(CO)12 that results in CO deoxygenation along with coupling of the CO carbon to methylidene groups and other CO carbons to yield the cluster complex Cp2(CH3)Ta(μ-O)Ru3(C4H4)(CO)9 (23) and the unstable free tantalum oxo species Cp2Ta(O)(CH3) is also reported. The TaRu3 product contains a 4-carbon cumulene ligand that bridges the three late-metal centers. The crystal structures of complexes 3b, 16, 17, 18, 19, 20, 21, and 23 are reported.

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Cited by 35 publications

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Niobium and Tantalum

Niobium and Tantalum

Decamethylzirconocene-Chalcogenide-Hydride Complexes

Reactions of Cp₂Ta(CH₂)(CH₃) with Substituted and Unsubstituted Metal Carbonyls (Groups 7, 8, and 9). Evidence for Intermediates Involved in the Carbon−Carbon Bond-Forming Steps of the Reduction and Deoxygenation of CO

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Cited by 35 publications

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Niobium and Tantalum

Niobium and Tantalum

Decamethylzirconocene-Chalcogenide-Hydride Complexes

Reactions of Cp2Ta(CH2)(CH3) with Substituted and Unsubstituted Metal Carbonyls (Groups 7, 8, and 9). Evidence for Intermediates Involved in the Carbon−Carbon Bond-Forming Steps of the Reduction and Deoxygenation of CO

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Reactions of Cp₂Ta(CH₂)(CH₃) with Substituted and Unsubstituted Metal Carbonyls (Groups 7, 8, and 9). Evidence for Intermediates Involved in the Carbon−Carbon Bond-Forming Steps of the Reduction and Deoxygenation of CO