The effect of substituents on the stability of triply bonded gallium[triple bond, length as m-dash]antimony molecules: a new target for synthesis.

The effect of substitution on the potential energy surfaces of RGa[triple bond, length as m-dash]SbR (R = F, OH, H, CH, SiH, SiMe(SitBu), SiiPrDis and NHC) is studied using density functional theory (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ + dp). The computational results show that all of the triply bonded RGa[triple bond, length as m-dash]SbR molecules have a preference for a bent geometry (i.e., ∠RGaSb ≈ 180° and ∠GaSbR ≈ 90°), which can be described using a valence bond model. The theoretical results show that because RGa[triple bond, length as m-dash]SbR has smaller electropositive groups, it could be both kinetically and thermodynamically stable and may be experimentally detectable. However, these theoretical results predict that the triply bonded R'Ga[triple bond, length as m-dash]SbR' molecules that have bulkier groups (R' = SiMe(SitBu), SiiPrDis, and NHC) are kinetically stable. In other words, both the electronic and the steric effects of bulkier substituent groups mean that it should be possible to experimentally isolate triply bonded RGa[triple bond, length as m-dash]SbR molecules in a stable form.