Related Experiment Video
Updated: Feb 27, 2026

Synthesis and Structure Determination of µ-Conotoxin PIIIA Isomers with Different Disulfide Connectivities
Published on: October 2, 2018
Two Structurally Characterized Conformational Isomers with Different C-P Bonds
Sudipta Roy1,2, Kartik Chandra Mondal1,3, Subrata Kundu1
1Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany.
Abstract:
The cyclic alkyl(amino) carbene (cAAC) bonded chlorophosphinidene (cAAC)P-Cl (2/2') was isolated from the direct reaction between cAAC and phosphorus trichloride (PCl3 ). Compound 2/2' has been characterized by NMR spectroscopy and mass spectrometry. 31 P NMR investigations [δ≈160 ppm (major) and δ≈130 ppm (minor)] reveal that there are two different P environments of the P-Cl unit. X-ray single-crystal determination suggests a co-crystallization of two conformational isomers of (cAAC)P-Cl (2/2'); the major compound possessing a cAAC-PCl unit with CcAAC -P 1.75 Å. This C-P bond length is very close to that of (NHC)2 P2 [NHC=N-heterocyclic carbene]. The residual density can be interpreted as a conformational isomer with a shorter CcAAC -P bond similar to a non-conjugated phosphaalkene [R-P=CR2 ]. Our study shows an unprecedented example of two conformational isomers with different Ccarbene -element bonds. Additionally, Br (3c/3c'), I (4c/4c'), and H (5c/5c') analogues [(Me2 -cAAC)P-X; X=Br (3), I (4), H (5)] of 2c/2c'[(Me2 -cAAC)P-Cl] were also synthesized and characterized by NMR spectroscopy suggesting similar equilibrium in solution. The unique property of cAAC and the required electronegativity of the X (X=Cl, Br, I, and H) atom play a crucial role for the existence of the two isomers which were further studied by theoretical calculations.
Related Concept Videos
Stereoisomerism of Cyclic Compounds
Isomerism
Disubstituted Cyclohexanes: cis-trans Isomerism
In cyclohexane, the substituents can occupy different positions generating distinct isomers....
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomerism in Alkenes
An isomer is called cis-2-butene when the methyl groups are on the same side of the double bond, and the other stereoisomer, in which methyl groups are on the opposite side of the double bond, is called trans-2-butene. The cis and trans stereoisomers are not...
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...

