Amide C−N Bond Cleavage and Formation of Nitride Promoted by a Niobium(II) Cluster

Tayebani, Maryam; Feghali, Khalil; Gambarotta, and Sandro; Bensimon, Corinne

doi:10.1021/om970427n

Cited by 35 publications

(17 citation statements)

References 36 publications

(15 reference statements)

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“…The reaction may be also regarded as a formal metathesis of the Nb−Nb triple bond, perhaps present in (TMEDA) 2 Nb 2 Cl 5 Li(TMEDA) (calculated Nb−Nb bond order 2.76), with the ligand C−H bond to form a Nb−Nb doubly bonded Nb(III) complex (calculated Nb−Nb bond order 1.63). This behavior is in striking contrast with that of similar reactions performed with different amides, where similar cooperative interaction of the two Nb atoms gave instead C−N bond cleavage …”

Section: Discussioncontrasting

confidence: 94%

“…The preliminary results were encouraging. Simple chloride replacement by amide ligands formed highly reactive Nb(II) amides which either cleaved the amide C−N single bond or performed cleavage of the N−N bond of dinitrogen, forming dinuclear, high-valent derivatives . Since these two desirable but diversified transformations were determined simply by the nature of the amide substituents, we have embarked on a systematic study in an attempt to understand how the amide substituents determine the type of reactivity exhibited by Nb(II) species.…”

Section: Introductionmentioning

confidence: 99%

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Molecular Rearrangements of a Low-Valent Niobium Amide: Ligand C−H Bond Oxidative Addition and Reductive Elimination

et al. 1998

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Reaction of the dinuclear and divalent (TMEDA)2Nb2Cl5Li(TMEDA) with Ph2NK led to the formation of three different compounds. The first complex contains no amide ligands. It is a mixed-valence dinuclear and paramagnetic species with a typical face-sharing bioctahedral structure Cl2Nb2(μ-Cl)3(TMEDA)2 (1). The second complex, a trivalent and dinuclear {[(Ph2N)2Nb]2[μ-NPh(μ-η1:η2-C6H4)](μ-H)}{Li(TMEDA)2}·toluene (2) with one hydride and one cyclometalated aromatic ring, is the result of oxidative addition of the two metal centers to the C−H bond. In a subsequent reaction step, the oxidative addition is followed by reductive elimination to restore the C−H bond to form the neutral, dinuclear, and diamagnetic (Ph2N)2Nb{[μ-NPh(η6-C6H5)]2Nb}·ether (3) containing the two metals in formal oxidation states of +4 and 0. Ab initio and EHMO calculations have been carried out in an attempt to clarify the nature of the Nb−Nb interaction in the three complexes.

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Section: Discussioncontrasting

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Molecular Rearrangements of a Low-Valent Niobium Amide: Ligand C−H Bond Oxidative Addition and Reductive Elimination

et al. 1998

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“…The distances C2–C3 (1.51(2) Å) and C1–C2 (1.24(2) Å) are typical of single bond in the first case, and in agreement with the existence of a double bond in the second . Moreover, the distance Nb2–C3 (2.17(1) Å) corresponds to an usual single bond, while Nb1–C1 (2.28(1) Å) and Nb1–C2 (2.418(1) Å) are in the range of niobium(III)–olefin complexes. , The distance between the two niobium atoms (3.214(1) Å) in 5 is longer than those of other chlorido-bridged dinuclear complexes containing a Nb–Nb single bond, − but it is considerably shorter than those found for similar chlorido-bridged dinuclear niobium(V) derivatives (4.096–4.161 Å) , confirming that, together with the diamagnetic behavior of 5 in solution, there is an interaction between both niobium atoms, that could be interpreted as a dative Nb V ←:Nb III better than a Nb IV –Nb IV covalent single bond.…”

Section: Resultssupporting

confidence: 68%

An Effective Route to Dinuclear Niobium and Tantalum Imido Complexes

et al. 2017

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Thermal treatment of the trichloro complexes [MCl(NR)py] (R = tBu, Xyl; M = Nb, Ta) (Xyl = 2,6-MeCH) under vacuum affords the dinuclear imido species [MCl(μ-Cl)(NR)py] (R = tBu, Xyl; M = Nb 1, 3; Ta 2, 4) with loss of pyridine. Complexes 1-4 can be easily transformed to the mononuclear starting materials [MCl(NR)py] (R = tBu, Xyl; M = Nb, Ta) upon reaction with pyridine. While reactions of compounds 1 and 2 with a series of alkylating reagents render the mononuclear peralkylated imido complexes [MR(NtBu)] (R = Me, CHPh, CHCMe, CHCMePh, CHSiMe), the analogous treatment with allylmagnesium chloride results in the formation of the dinuclear niobium(IV) derivative [(NtBu)(η-CH)M(μ-CH)(μ-Cl)M(NtBu)py] (5). Additionally, the treatment of the starting materials 1 and 2 with the organosilicon reductant 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene yields the pyridyl-bridged dinuclear derivatives [MCl(μ-Cl)(NtBu)py](μ-NCHN) (M = Nb 6, Ta 7). Controlled hydrolysis reaction of 1 and 2 affords the oxo chlorido-bridged products [MCl(μ-Cl)(NtBu)py](μ-O) (M = Nb 8, Ta 9) in a quantitative way, while the treatment of these latter with one more equivalent of pyridine led to complexes [MCl(NtBu)py](μ-O) (M = Nb 10, Ta 11). Structural study of these dinuclear imido derivatives has been also performed by X-ray crystallography.

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“…At this early stage it is obviously premature to draw conclusions about which factors determine this noticeable difference of behavior and how to use this information for HDN catalysis purposes. So far we simply observe that, as a rather general trend, ,, this complex always performed two- or four-electron oxidative additions on the same substrate via cooperative interaction of the two metal centers.…”

mentioning

confidence: 95%

“…In this paper, we wish to communicate the results of the reaction of (TMEDA) 2 Nb 2 Cl 5 Li(TMEDA) , with two structurally similar anionic amides, dipyridylamide (Py 2 N) and diphenylamide (Ph 2 N), which led to oxidative cleavage of both the C−H and C−N bonds of the ligands and resulted in the formation of unique examples of diamagnetic and dinuclear Nb(III) amide derivatives.…”

mentioning

confidence: 99%