Direct Observation of Orthogonal Orientation of an Aromatic Ring Attached to the Carbene Carbon in Fischer Carbene Complexes in Solution:  Diastereotopicity of Benzyl Protons as a Stereochemical Probe

Series of chromium, tungsten and iron aminocarbene complexes were prepared and electrochemically investigated. The influence of the type of coordination, of the substituent on the ligand phenyl ring and of the central metal atom on oxidation and reduction potentials was followed electrochemically using the Linear Free Energy Relationship (LFER) approach. The difference between the oxidation and reduction potentials reflects the energy of the HOMO-LUMO gap. The reduction of carbene derivatives strongly depends only on the nature of ligands and their substitution, but not on the nature of the central metal. On the other hand, the oxidation is practically independent of the ligand substitution, being influenced by both the nature of the central metal atom and the number of carbonyl groups (i.e. strong π-acceptors) present.

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“…The same conformation was also found in solution (8). The overlap of both π-systems in the most stable conformation is therefore low.…”

Section: Rotation Barriersupporting

confidence: 75%

M(0)- Aminocarbene Complexes (M=Cr,W,Fe) : Redox Behaviour Tuned by Metal and/or Ligand Modification

Ludvı́k¹,

Hoskovcová²,

Roháčová³

et al. 2007

ECS Trans.

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“…Compared to B or B 0 , the 1 H NMR signals of methyl in the products shift upfield due to the electron donation by N-alkenylation of pyrazole [27]. The anisotropic shielding effect as another important factor exists in the phenyl ring of P, which results in the up-field shifts of methyl in P (about 224 Hz) more obviously than in P 0 (about 4 Hz) [28]. It was observed from our 1 H NMR spectra that the minor tautomer B will lead to the main product P whereas the main tautomer B 0 to the minor product P 0 , and the reasons will be elaborated in Section 4.5.…”

Section: Michael Type Additionmentioning

confidence: 98%

An experimental–theoretical approach to the kinetics and mechanism of Michael type addition: α,β-Unsaturated tungsten Fischer carbene complex as the substrate

Gu¹,

Yang²,

Zhang³

et al. 2006

Journal of Organometallic Chemistry

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“…Therefore, the spatial orientation of the coordinated double bond was obtained from NOE experiments. The aromatic ring of aminocarbene complexes is known to be perpendicular to the plane defined by the metal, the carbene atom, and the nitrogen atom . For that reason there should be an NOE between o -hydrogens of the phenyl group either with one hydrogen atom of the chelated CH 2 group in the case of perpendicular arrangement (Figure , A) or with the −CH hydrogen of the chelated double bond when both double bonds are parallel (Figure , B).…”

Section: Resultsmentioning

confidence: 99%

Iron Aminocarbene Complexes Containing a Double CC Bond in the N-Substituent: Preparation and Reactivity

2001

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Reaction of N,N-diallylbenzamide with Na2Fe(CO)4 and Me3SiCl afforded chelated cis-tricarbonyl[(η2-N-allyl-N-allylamino)(phenyl)carbene]iron(0) directly. The same reaction of N-(3-buten-1-yl)-N-methylbenzamide proceeded with migration of the double bond to the allylic position, giving a mixture of chelated cis-tricarbonyl[(η2-N-(2-butenyl)-N-methylamino)(phenyl)carbene]iron(0) and nonchelated tetracarbonyl[(N-(2-butenyl)-N-methylamino)(phenyl)carbene]iron(0). N-(3-Buten-2,2-dimethyl-1-yl)-N-methylbenzamide, in which migration of double bond is not possible, gave a mixture of E and Z isomers of nonchelated tetracarbonyl[(N-(2,2-dimethyl-3-butenyl)-N-methylamino)(phenyl)carbene]iron(0). Thermolysis of the latter furnished 1-methyl-3,3-dimethyl-6-phenyl-1,2,3,4-tetrahydropyridine as the only product.

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Direct Observation of Orthogonal Orientation of an Aromatic Ring Attached to the Carbene Carbon in Fischer Carbene Complexes in Solution: Diastereotopicity of Benzyl Protons as a Stereochemical Probe

Abstract: Diastereotopicity of methylene protons of benzyloxy and benzylamino groups in Fischer carbene complexes serves as a stereochemical probe to reveal orthogonal orientation of the aromatic rings attached to the carbene carbon with respect to the metal-carbene π-plane in solution.

Cited by 12 publications

References 16 publications

M(0)- Aminocarbene Complexes (M=Cr,W,Fe) : Redox Behaviour Tuned by Metal and/or Ligand Modification

M(0)- Aminocarbene Complexes (M=Cr,W,Fe) : Redox Behaviour Tuned by Metal and/or Ligand Modification

An experimental–theoretical approach to the kinetics and mechanism of Michael type addition: α,β-Unsaturated tungsten Fischer carbene complex as the substrate

Iron Aminocarbene Complexes Containing a Double CC Bond in the N-Substituent: Preparation and Reactivity

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