Unexpected formation of zinc bis[1,3-di(2-pyridyl)-2-azapropenide] during the thermolysis of methylzinc bis(2-pyridylmemyl)amide

Westerhausen, Matthias; Kneifel, Alexander N.

doi:10.1016/j.inoche.2004.03.032

Cited by 15 publications

(17 citation statements)

References 11 publications

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“…[5][6][7][8] The present study is concerned with the class of 3d-M(smif) 2 complexes ("smif" = 1,3-di(2-pyridyl)-2-azapropenide). Zn(smif) 2 was originally reported by Westerhausen and Kneifel in 2004. [9] Wolczanski and co-workers recently synthesized and characterized the homologous first row series from vanadium to nickel, including some of the cations.…”

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confidence: 99%

A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

et al. 2011

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We carry out a theoretical investigation of the recently reported M(smif)(2) series1,2 and find a number of interesting phenomena. These include complex potential energy surfaces with near-degenerate stationary points, low-lying states, non-trivial electron configurations, as well as non-innocent ligand behavior. The M(smif)(2) exhibit a delicate balance between geometry and electronic structure, which has implications not only for their reactivity but also for controlling their properties through ligand design. We address methodological issues and show how conceptual quantities such as oxidation states and electronic configurations can be extracted through a simple analysis of the electron and spin densities-without a complicated examination of the underlying orbitals.

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Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

et al. 2011

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“…For 1, nonbonding, carbon-based azaallyl orbitals are the HOMO and HOMO-1. Ligand-field orbitals drop in energy in going from Fe to Co to Ni, but the additional electron in 2 (vs 1) may reside in a ligand π* orbital, rendering 2 formally as Co 3+ (smif 1.5-) 2 . Discrete structural changes are difficult to assess because of delocalization into the py π* framework.…”

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confidence: 99%

“…Discrete structural changes are difficult to assess because of delocalization into the py π* framework. Oxidation of 2 with AgOTf affords magenta [(smif) 2 Co]OTf (2+, 81%), which possesses IL bands at 586 nm (23 000 M -1 cm -1 ) and 383 nm (13 000 M -1 cm -1 ). Symmetric (D 2d ) structural features of 2+ are consistent with its low-spin d 6 character.…”

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confidence: 99%

“…Complex 4 is a dimer in the solid state, as Figure 4 illustrates. In solution, 4 is emeraldgreen, with IL bands at 633 nm (52 000 M -1 cm -1 ) and 399 nm (37 000 M -1 cm -1 ), but orange crystals reveal its conversion to the amide dimer [(TMS) 2 NFe] 2 (smif) 2 (4 2 ). 1 H NMR spectral analysis affords a K eq value of ∼4 × 10 -4 M -1 (∆G°≈ 5 kcal/mol) for the reaction 2 4 a 4 2 .…”

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confidence: 99%

“…In solution, 4 is emeraldgreen, with IL bands at 633 nm (52 000 M -1 cm -1 ) and 399 nm (37 000 M -1 cm -1 ), but orange crystals reveal its conversion to the amide dimer [(TMS) 2 NFe] 2 (smif) 2 (4 2 ). 1 H NMR spectral analysis affords a K eq value of ∼4 × 10 -4 M -1 (∆G°≈ 5 kcal/mol) for the reaction 2 4 a 4 2 . The dimerization can be construed as either a diradical coupling or a nucleophile/electrophile event, and polar and nonpolar reactivity is anticipated for the smif backbone.…”

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confidence: 99%

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Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)₂M [M = Fe, Co, Co⁺, Ni; smif = {(2-py)CH}₂N] and [(TMS)₂NFe]₂(smif)₂

et al. 2009

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Application of the dipyridylazaallyl ligand (2-py)CHNCH(2-py) (smif) to a series of first-row transition metals afforded (smif)2M n [n = 0, M = Fe (1), Co (2), Ni (3); n = +1, M = Co (2+)] and {(TMS)2NFe}2(smif)2 (4 2 ) via metathetical procedures. The Mössbauer spectrum of 1 (S = 0) and TDDFT calculations, including a UV−vis spectral simulation, reveal it to be a covalent, strong-field system with Δo estimated as ∼18 000 cm−1 and B ≈ 470 cm−1. (smif)2Co (2) has S = 1/2 according to SQUID data at 10 K. DFT calculations suggest that the odd electron is localized in a smif π* orbital, i.e., smif is redox-active. EPR-silent (smif)2Ni (3) has S = 1 (SQUID), and calculations show that the unpaired spins reside in the d z 2 and d x 2 −y 2 orbitals. X-ray structural parameters suggest that low-spin d6 1 and 2+ are relatively symmetric D 2d species, but 2 and 3 manifest a distortion in which one smif is canted in the plane perpendicular to the other. (smif)FeN(TMS)2 (4) is principally monomeric in solution, but reversibly dimerizes (K eq ≈ 10−4 M−1) via C−C bond formation in the azaallyl backbone to crystallize as {(TMS)2NFe}2(smif)2 (4 2 ). The azaallyl compounds possess extraordinary UV−vis absorptivities (ε ≈ 18000−52000) at 580 ± 15 nm and 406(25) nm that have been identified as intraligand bands with Cnb → smif π* character.

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(Z)‐Bis(alkylzinc)imido‐1,2‐di(2‐pyridyl)ethene: Intramolecular Stabilization of a Bis(alkylzinc)imide

2004

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Dedicated to Professor Nils Wiberg on the occasion of his 70th birthdayThe oxidative metal-mediated C-C coupling reaction of (2-pyridylmethyl)(trialkylsilyl)amines succeeds smoothly with dialkylzinc [Eq. (1)] or tin(ii) bis[bis(trimethylsilyl)amide].[1]The influence of the standard potential as well as the role of the steric demand of the nitrogen-bonded trialkylsilyl and zinc-bonded alkyl groups have been investigated.[2] The Nbonded trialkylsilyl substituent is obligatory to prevent side reactions. The reaction of dialkylzinc with 2-py-CH 2 NH 2 (py = pyridyl) yields several products which can be explained by a combination of oxidative C-C coupling and transamination reactions. After protolysis of this reaction mixture a small amount of cis-1,2-di(2-pyridyl)aminoethene (1; Scheme 1) can be isolated in a reproducible procedure.[3] However, we were not able to detect the zincated 1,2-di(2-pyridyl)aminoethene during the reaction. Amine 1 crystallized as the eneamine tautomer, an equilibrium with the imine tautomer was not detectable with spectroscopic methods.Even 30 years ago, doubly zincated primary amines of the type [RN(ZnR') 2 ] were of interest as catalysts for polymerization reactions, [4] however, these compounds were poorly characterized and more recent attempts to prepare bis(alkylzinc)alkyl-and -arylimides by zincation of primary alkylamines failed. [5,6]

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Unexpected formation of zinc bis[1,3-di(2-pyridyl)-2-azapropenide] during the thermolysis of methylzinc bis(2-pyridylmemyl)amide

Cited by 15 publications

References 11 publications

A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)₂M [M = Fe, Co, Co⁺, Ni; smif = {(2-py)CH}₂N] and [(TMS)₂NFe]₂(smif)₂

(Z)‐Bis(alkylzinc)imido‐1,2‐di(2‐pyridyl)ethene: Intramolecular Stabilization of a Bis(alkylzinc)imide

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Unexpected formation of zinc bis[1,3-di(2-pyridyl)-2-azapropenide] during the thermolysis of methylzinc bis(2-pyridylmemyl)amide

Cited by 15 publications

References 11 publications

A Theoretical Study of the 3d‐M(smif)2Complexes: Structure, Magnetism, and Oxidation States

A Theoretical Study of the 3d‐M(smif)2Complexes: Structure, Magnetism, and Oxidation States

Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)2M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}2N] and [(TMS)2NFe]2(smif)2

(Z)‐Bis(alkylzinc)imido‐1,2‐di(2‐pyridyl)ethene: Intramolecular Stabilization of a Bis(alkylzinc)imide

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A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

A Theoretical Study of the 3d‐M(smif)₂Complexes: Structure, Magnetism, and Oxidation States

Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)₂M [M = Fe, Co, Co⁺, Ni; smif = {(2-py)CH}₂N] and [(TMS)₂NFe]₂(smif)₂