Reaction of 1-thiacyclohept-4-yne with 2 mols of E(NR)2SiR2[E=Sn,Ge;R=t Bu], [1] has led to the formation of digerma- and distannacyclobutenes, having an E-E bond[2]. The geometries of the latter molecules were optimized at BP86 [3], B3LYP, PBE, and M06 levels of theory using def2-TZVPP basis set. In all cases the vibrational frequency analyses, calculated at the same level of theory, indicated that the optimized structures are at the stationary points corresponding to local minima without any imaginary frequency. Calculations were performed using the GAUSSIAN 09 program[3]. The AIM 2013 package was used to obtain the bond properties. Wave function files were generated from the Gaussian output files at the BP86, B3LYP, PBE, and M06 levels of theory using def2-TZVP basis set to perform the AIM calculations. NBO analysis were also carried out with the internal module GAUSSIAN 09. The result show that in these complexes the s between E a single bond.
