**4. Conclusions**

In this manuscript, we analyzed the ability of perchlorinated cyclopenta- and cyclohexatetrelanes to establish tetrel bonding interactions with both neutral and charged electron donors. We used Tr5Cl10 and Tr6Cl12 (Tr = Si and Ge) and HCN, HF, OH- and Cl- moieties as electron donor molecules. In relation to this, complex **11** involving cyclopentagermanane and OH- as a Lewis base obtained the largest binding energy value of the study. On the other hand, complex **14** involving HF and cyclohexasililane achieved the poorest interaction energy value of the study. We also demonstrated that the energetic cost of forming the 2:1 complex compensates the energy penalty of passing from chair to planar conformation in cyclohexasilane complexes **13** and **14**. In addition, we have observed a reinforcement of the interaction strength ongoing from Si to Ge in both cyclopenta- and cyclohexatetrelane systems, as it is commonly observed for other σ-hole interactions. Furthermore, we performed Atoms in Molecules (AIM) analysis to further characterize the interactions described above. Finally, several experimental examples retrieved from the Cambridge Structural Database (CSD) were shown in order to provide reliability to the results and to highlight the importance of these interactions in the solid state of cyclopenta- and cyclohexatetrelanes.

**Supplementary Materials:** Supplementary Materials are available online, cartesian coordinates of the complexes and results from the CSD search.

**Author Contributions:** A.B. and A.F. conceived and designed the calculations; A.B. and A.F. analyzed the data; A.B. wrote the paper.

**Funding:** We thank the MINECO/AEI (projects CTQ2014-57393-C2-1-P and CTQ2017-85821-R FEDER funds) for financial support. We thank the CTI for computational facilities.

**Conflicts of Interest:** The authors declare no conflict of interest.
