| Abstract: | The IPPP-INDO method is applied to study different interactions as well as transmission mechanisms of 77Se — 77Se coupling constants in cis- and trans-1,2-bis(methylseleno)ethene. Preferential conformations were determined using a modified version of the PCILO-CNDO method. The preferential conformation of the cis compound is such that nonbonding electron pairs of both Se atoms overlap to some extent. In this conformation a large and positive through-space transmission of the Fermi contact term of the 77Se — 77Se coupling takes place, which strongly depends on the Se — Se distances. The similarity between this coupling and others involving different nuclei is discussed. The total calculated coupling is in fair agreement with experimental values for similar compounds. The 77Se — 77Se coupling in the trans-compound is largely dominated by the orbital interaction, which is mainly transmitted through the vinyl π-electron system. |
