Simulations Suggest Possible Triply Bonded Phosphorus≡E13 Molecules (E13 = B, Al, Ga, In, and Tl)

Abstract

The effect of substitution on the potential energy surfaces of RE13 ☰ PR (E13 = B, Al, Ga, In, Tl; R = F, OH, H, CH3, SiH3, SiMe(Si t Bu3)2, Si i PrDis2, Tbt, and Ar* is studied using density functional theory (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ + dp). The theoretical results demonstrate that all triply bonded RE13 ☰ PR compounds with small substituents are unstable and spontaneously rearrange to other doubly bonded isomers. That is, the smaller groups, such as R 〓 F, OH, H, CH3 and SiH3, neither kinetically nor thermo-dynamically stabilize the triply bonded RE13 ☰ PR compounds. However, the triply bonded R ’ E13 ☰ PR´ molecules, possessing bulkier substituents (R´ = SiMe(Si t Bu3)2, Si i PrDis2, Tbt and Ar*), are found to have a global minimum on the singlet potential energy surface. In partic- ular, the bonding character of the R ’ E13 ☰ PR´ species is well defined by the valence-electron bonding model (model [II]). That is to say, R ’ E13 ☰ PR´ molecules that feature groups are regarded as R 0 -E13 P-R 0 . The theoretical evidence shows that both the electronic and the steric effects of bulkier substituent groups play a prominent role in rendering triply bonded R 0 E13 ☰ PR 0 species synthetically accessible and isolable in a stable form.