Density functional B3LYP and B3PW91 studies of the properties of four cyclic organodiboranes with tetramethylene fragments

Molecular structure and vibrational spectra of 1,2-tetramethylenediborane (B2C4H12), 1,2:1,2-bis(tetramethylene)diborane (B2C8H18), 1,1-tetramethylenediborane (B2C4H12) and 1,1:2,2-bis(tetramethylene)diborane (B2C8H18), have been studied using quantum computational density functional B3LYP and B3PW91 methods and 6-31G*, 6-31G** and 6-31++G** basis sets. Natural bond orbital analyses have been carried out to study in detail the nature of the B—C, C—C and B—H bonds in these molecules. This study showed that all these compounds are thermodynamically stable in the gas phase, but bicyclic structures are more stable than monocyclic structures.