Related Experiment Video
Updated: Mar 2, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
A Mixed-Ring Sandwich Complex from Unexpected Ring Contraction in [Re(η6-C6H5Br)(η6-C6R6)](PF6)
Giuseppe Meola1, Henrik Braband1, Daniel Hernández-Valdés1
1Department of Chemistry, University of Zurich , Winterthurerstr. 190, CH-8057 Zurich, Switzerland.
Abstract:
The contraction of coordinated aromatic hydrocarbons is a rare reactivity pattern in organometallic chemistry. We describe the conversion of a bromobenzene coordinated to a ReI center into a cyclopentadienyl aldehyde. Under mildly alkaline conditions, the expected phenol complex is formed with Re and 99Tc but under strong basic conditions; ring contraction occurs in close to quantitative yields for Re only. A mechanism for this unprecedented reaction is proposed based on 1H and 2H NMR spectra and density functional theory calculations.
More Related Videos
Related Concept Videos
Hybridization of Atomic Orbitals II
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
Hybridization of Atomic Orbitals I
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

