Small-Molecule Activation within the Group 6 Complexes (η5-C5Me5)[N(iPr)C(Me)N(iPr)]M(CO)(L) for M = Mo, W and L = N2, NCMe, η2-Alkene, SMe2, C3H6O

Farrell, Wesley S.; Yonke, Brendan L.; Reeds, Jonathan P.; Zavalij, Peter Y.; Sita, Lawrence R.

doi:10.1021/acs.organomet.6b00131

Cited by 8 publications

(3 citation statements)

References 48 publications

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“…Cyclic products are formed by the reductive C–C coupling of two coordinated nitriles, often leading to five-membered metallacycles. − Two-electron reduction per two nitriles has been shown to result in the formation of the bridging diiminato ligand upon dimerization of nitriles adducts of low-valent metal centers. − This process involves reduction of a coordinated nitrile by a metal center with the formation of a radical, which then dimerizes with another equivalent of its congener to form the single C–C bond. Four-electron reduction of two nitrile ligands by low-valent Group 4–6 complexes led to formation of enediimido species related to 2 . − In those instances, the CC double bond is formed between two nitriles, which may be considered as a stepwise reduction to first form a diazavinylidene moiety that is further reduced by two metal centers to form the bridging enediimido group. The oxidation state of each metal center is thus increased by 2.…”

Section: Resultsmentioning

confidence: 99%

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

et al. 2017

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A new pathway of activation of C-H bonds of alkyl- and arylnitriles by a cooperative action of TaCl and PPh under mild conditions is reported. Coordination of nitriles to the highly Lewis acidic Ta(V) center resulted in an activation of their aliphatic and aromatic C-H bonds, allowing nucleophilic attack and deprotonation by the relatively weak base PPh. The propensity of Ta(V) to form multiple bonds to nitrogen-containing ligands is an important driving force of the reaction as it led to a sequence of bond rearrangements and the emergence of, in the case of benzonitrile, a zwitterionic enediimido complex of Ta(V) through C═C double bond formation between two activated nitrile fragments. These transformations highlight the special role of the high-valent transition metal halide in substrate activation and distinguish the reactivity of the TaCl-PPh system from both non-metal- and late transition metal-based frustrated Lewis pairs.

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Section: Resultsmentioning

confidence: 99%

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

et al. 2017

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“…Over the past decade, Sita et al have synthesized and characterized an extensive isostructural series of dinitrogen-bridged dimers which are capable of thermal or photochemical dinitrogen activation (Hirotsu et al, 2007a). The M-(μ-N 2 )-M cores, where M = Ti (Fontaine et al, 2010), V (Keane et al, 2014); Zr (Hirotsu et al, 2007b), Nb (Keane et al, 2014), Mo (Fontaine et al, 2010); Hf (Hirotsu et al, 2007b), Ta (Hirotsu et al, 2007a; Keane et al, 2014), W (Fontaine et al, 2010), are stabilized by a common ligand sphere composed of a Cp * ligand and an amidinate ligand on each metal, see Figure 1A (Yonke et al, 2011a,b; Keane et al, 2013; Farrell et al, 2016; Duman and Sita, 2017). The amidinate ligand can be functionalized at the N-donor atoms or central carbon.…”

Section: Introductionmentioning

confidence: 99%

Steric Switching From Photochemical to Thermal N2 Splitting: A Computational Analysis of the Isomerization Reaction {(Cp)(Am)Mo}2(μ-η1:η1-N2) → {(Cp)(Am)Mo}2(μ-N)2

Krewald

2019

Front. Chem.

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A μ-η 1 :η 1 -N 2 -bridged Mo dimer, {(η 5 -C 5 Me 5 )[N(Et)C(Ph)N(Et)]Mo} 2 (μ-N 2 ), cleaves dinitrogen thermally resulting in a crystallographically characterized bis-μ-N-bridged dimer, {(η 5 -C 5 Me 5 )[N(Et)C(Ph)N(Et)]Mo} 2 (μ-N) 2 . A structurally related Mo dimer with a bulkier amidinate ligand, ([N( i Pr)C(Me)N( i Pr)]), is only capable of photochemical dinitrogen activation. These opposing reactivities were rationalized as steric switching between the thermally and photochemically active species. A computational analysis of the geometric and electronic structures of intermediates along the isomerization pathway from Mo 2 (μ-η 1 :η 1 -N 2 ) to Mo 2 (μ-η 2 :η 1 -N 2 ) and Mo 2 (μ-η 2 :η 2 -N 2 ), and finally Mo 2 (μ-N) 2 , is presented here. The extent to which dispersion affects the thermodynamics of the isomers is evaluated, and it is found that dispersion interactions play a significant role in stabilizing the product and making the reaction exergonic. The concept of steric switching is further explored with theoretical models with sterically even less demanding ligands, indicating that systematic ligand modifications could be used to rationally design the N 2 activation energy landscape. An analysis of electronic excitations in the computed UV-vis spectra of the two complexes shows that a particular type of asymmetric excitations is only present in the photoactive complex.

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“…As the structurally similar ligands, the chemistry of azaallyl ligands and their transition metal complexes has attracted much interest because of diverse bonding modes with different electronic properties brought by the substitution of the carbon atom in the allyl ligand by the N atom in the azaallyl ligand. − It can be concluded from the literature that there are several kinds of the azaallyl ligands and their coordination modes (Scheme ): ( A ) N-coordinated enamido mode, ,, ( B ) η 3 -coordinated 1-azaallyl mode, − ( C ) η 3 -coordinated 2-azaallyl mode, − and ( D ) η 3 -coordinated 1,3-diazaallyl mode , (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Formation of 2-Azaallyl Cobalt(I) Complexes by Csp³–H Bond Activation

et al. 2017

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Three novel unsymmetrical η3-2-azaallyl cobalt(I) complexes, [(2-PPh2)C6H4]CHN[CHC6H4(4-R)]Co(PMe3)2 (4–6) (R = H (4); Cl (5); and OMe (6)), were synthesized by the reactions of Schiff base ligands [(2-PPh2)C6H4]CHN[CH2C6H4(4-R)] (1–3) (R = H (1); Cl (2); and OMe (3)) with CoMe(PMe3)4 via sp3 C–H bond activation under mild reaction conditions. Complex {[(2-PPh2)C6H4]CHNCH3[CHC6H4(4-R)]Co(PMe3)2}I (7) as an 18e cobalt(III) salt was obtained through the reaction of 4 with iodomethane. The substitution reaction of complex 4 with carbon monoxide afforded the dicarbonyl cobalt(I) complex [(2-PPh2)C6H4]CH[NCHC6H4(4-R)]Co(CO)2(PMe3) (8). The molecular structures of complexes 4–8 were determined by single crystal X-ray diffraction.

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Small-Molecule Activation within the Group 6 Complexes (η⁵-C₅Me₅)[N(ⁱPr)C(Me)N(ⁱPr)]M(CO)(L) for M = Mo, W and L = N₂, NCMe, η²-Alkene, SMe₂, C₃H₆O

Cited by 8 publications

References 48 publications

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

Steric Switching From Photochemical to Thermal N2 Splitting: A Computational Analysis of the Isomerization Reaction {(Cp)(Am)Mo}2(μ-η1:η1-N2) → {(Cp)(Am)Mo}2(μ-N)2

Formation of 2-Azaallyl Cobalt(I) Complexes by Csp³–H Bond Activation

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Small-Molecule Activation within the Group 6 Complexes (η5-C5Me5)[N(iPr)C(Me)N(iPr)]M(CO)(L) for M = Mo, W and L = N2, NCMe, η2-Alkene, SMe2, C3H6O

Cited by 8 publications

References 48 publications

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl5–PPh3 Lewis Pair

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl5–PPh3 Lewis Pair

Steric Switching From Photochemical to Thermal N2 Splitting: A Computational Analysis of the Isomerization Reaction {(Cp*)(Am)Mo}2(μ-η1:η1-N2) → {(Cp*)(Am)Mo}2(μ-N)2

Formation of 2-Azaallyl Cobalt(I) Complexes by Csp3–H Bond Activation

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Small-Molecule Activation within the Group 6 Complexes (η⁵-C₅Me₅)[N(ⁱPr)C(Me)N(ⁱPr)]M(CO)(L) for M = Mo, W and L = N₂, NCMe, η²-Alkene, SMe₂, C₃H₆O

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

Activation of C–H Bonds of Alkyl- and Arylnitriles by the TaCl₅–PPh₃ Lewis Pair

Steric Switching From Photochemical to Thermal N2 Splitting: A Computational Analysis of the Isomerization Reaction {(Cp)(Am)Mo}2(μ-η1:η1-N2) → {(Cp)(Am)Mo}2(μ-N)2

Formation of 2-Azaallyl Cobalt(I) Complexes by Csp³–H Bond Activation