Triggered by the observation of a short Bi⋯Bi distance and a Bi-Te-Bi bond angle of only 86.6° in the crystal structure of bis(diethylbismuthanyl)tellurane quantum chemical computations on interactions between neighboring Bi atoms in Te(BiR2 )2 molecules (R = H, Me, Et) and in (BiH3 )2 were undertaken. Bi⋯Bi distances atoms were found to significantly shorten upon inclusion of the d shells of the heavy metal atoms into the electron correlation treatment, and it was confirmed that interaction energies from spin component-scaled second-order Møller-Plesset theory (SCS-MP2) agree well with coupled-cluster singles and doubles theory including perturbative triples (CCSD(T)). Density functional theory-based symmetry-adapted perturbation theory (DFT-SAPT) was used to study the anisotropy of the interplay of dispersion attraction and steric repulsion between the Bi atoms. Finally, geometries and relative stabilities of syn-syn and syn-anti conformers of Te(BiR2 )2 (R = H, Me, Et) and interconversion barriers between them were computed.