Effects of substituents on arsenic-tin triple bonds: A theoretical study

The potential energy surface for the unimolecular rearrangement XSnequivalent toAs --> TS --> Sn=AsX was investigated using the B3LYP and QCISD methods. To explore electronic effects on the relative stability of XSnequivalent toAs and Sn=AsX, first-row substituents (X = H, Li, BeH, BH2, CH3, NH2, OH, and F) have been used. Our theoretical findings suggest that the double bonded Sn=AsX species are always kinetically and thermodynamically more stable than the triply bonded XSnequivalent toAs isomers, regardless of the electronegativity of substituent X. Nevertheless, our model calculations based on the ONIOM(B3LYP/LANL2DZ:PM3) method indicate that an aryl group can, if sufficiently bulky, stabilize triply bonded XSnequivalent toAs molecules with respect to both isomerization and polymerization. That is to say, it is not electronic effects but steric effects that play a decisive role in stabilizing the Snequivalent toAs triple bond.