Synthesis of Molybdenum and Tungsten Complexes That Contain Triamidoamine Ligands of the Type (C6F5NCH2CH2)3N and Activation of Dinitrogen by Molybdenum

Kol, Moshe; Schrock, Richard R.; Kempe, Rhett; Davis, W. M.

doi:10.1021/ja00089a028

Cited by 129 publications

(153 citation statements)

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“…[200] The thuscomplexed MesN 3 51 V NMR spectra of such amido complexes, [202] which, for example, allow a quantification of electronic differences between terminal oxo, seleno, and telluro ligands. [203] The reaction of the respective molybdenum complex with TMSOTf gives 57, the reduction of which with one or two equivalents of Na(Hg) in the presence of N 2 leads to dinitrogen complexes (Scheme 47). Of note here is that N 2 can be activated stepwise and then partially reduced.…”

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

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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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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

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271

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“…[ 18,20,21] Because of the unreactivity of the N 2 À{MoA C H T U N G T R E N N U N G [N 3 N]} 2 dimer, Schrock et al used large R groups, such as HIPT to prevent its formation, thus limiting the reaction to the formation of…”

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confidence: 99%

“…[20][21][22] The [N 3 N]Mo À N 2 encounter complex, which is the starting point for the catalytic cycle, has been isolated [12,23] and structurally characterised, [23] unlike [Ar(R)N] 3 Mo À N 2 which has not been directly observed. The stability of [N 3 N]MoÀN 2 over its three-coordinate counterpart has been attributed to the interaction of the amine cap which destabilizes the d z 2 orbital sufficiently to favour the doublet spin state over the spin quartet, the former being the optimal spin state for binding N 2 .…”

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A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

Christian¹,

Stranger²,

Yates³

2008

Chemistry A European J

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The four-coordinate Mo[N(3)N] complex, [N(3)N] = [{RNCH(2)CH(2)}(3)N], R = 3,5-(2,4,6-iPr(3)C(6)H(2))(2)C(6)H(3) (HIPT), which is capable of converting N(2) to ammonia catalytically, reacts with N(2) in a similar manner to Mo[N(R)Ar](3) (R = tBu, Ar = 3,5-C(6)H(3)Me(2)) to form a dinitrogen-bridged dimer intermediate, but unlike its three-coordinate counterpart, N(2) cleavage is not observed. To rationalise these differences, the reaction of N(2) with the model Mo[NH(2)](3)[NH(3)] and full ligand Mo[N(3)N] systems was explored using density functional theory and compared with the results of an earlier study involving the model three-coordinate Mo[NH(2)](3) system. Although the overall reaction is exothermic, the final N-N cleavage step is calculated to be endothermic by 75 kJ mol(-1) for the model system when the Mo-amine cap bond length is fixed to mimic the constraints of the ligand straps, but exothermic by 14 kJ mol(-1) for the full ligand system. In the latter case, the slightly exothermic cleavage step can be attributed to the destabilization of the N(2) bridged dimer relative to the nitride product owing to the steric effects of the bulky R groups. The activation barrier for N-N cleavage is estimated at 151 kJ mol(-1) for the model system, more than twice the calculated value for Mo[NH(2)](3), and even greater, 213 kJ mol(-1), for the full ligand [N(3)N]Mo system. A bonding analysis shows that although the binding of the amine cap helps to stabilize the intermediate dimer, at the same time it destabilizes the metal d-orbitals involved in backbonding to the pi* orbitals on N(2). As a result, backdonation is less efficient and N-N activation reduced compared to the three-coordinate system. Thus, the increased stability of the intermediate dimer on binding of the amine cap combined with the reduced level of N-N activation and higher kinetic barrier, explain why N-N cleavage has not been observed experimentally for the four-coordinate Mo[N(3)N] system.

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“…[24] This seminal work demonstrates the utility of the triamidoamine ligand that has borne a rich cache of dinitrogen-activation chemistry. The use of extremely bulky hexaisopropylterphenyl (hipt) groups on the amide substituents prevents the formation of dinuclear, end-on-bridged molybdenum dinitrogen complexes [25] (which arise when smaller substituents are used) and results in the formation of a cavity where only small moieties (such as dinitrogen, protons, and electrons) may access the molybdenum center. [26,27] Reduction of the molybdenum chloride precursor under N 2 generates a terminal end-on-bound dinitrogen complex (Scheme 2 a).…”

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confidence: 99%

Revelations in Dinitrogen Activation and Functionalization by Metal Complexes

Kozak

Mountford

2004

Angew Chem Int Ed

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Synthesis of Molybdenum and Tungsten Complexes That Contain Triamidoamine Ligands of the Type (C6F5NCH2CH2)3N and Activation of Dinitrogen by Molybdenum

Cited by 129 publications

References 0 publications

Highlights in the Renaissance of Amidometal Chemistry

Highlights in the Renaissance of Amidometal Chemistry

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

Revelations in Dinitrogen Activation and Functionalization by Metal Complexes

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Synthesis of Molybdenum and Tungsten Complexes That Contain Triamidoamine Ligands of the Type (C6F5NCH2CH2)3N and Activation of Dinitrogen by Molybdenum

Cited by 129 publications

References 0 publications

Highlights in the Renaissance of Amidometal Chemistry

Highlights in the Renaissance of Amidometal Chemistry

A Comparison of N2 Cleavage in Schrock's Mo[N3N] and Laplaza–Cummins' Mo[N(R)Ar]3 Systems

Revelations in Dinitrogen Activation and Functionalization by Metal Complexes

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A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems