Triple-Bonded Boron≡Phosphorus Molecule: Is That Possible?

The effect of substitution on the potential energy surfaces of RB≡PR (R = H, F, OH, SiH(3), and CH(3)) is studied using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). There is significant theoretical evidence that RB≡PR compounds with smaller substituents are fleeting intermediates, so they would be difficult to be detected experimentally. These theoretical studies using the M06-2X/Def2-TZVP method demonstrate that only the triply bonded R'B≡PR' molecules bearing sterically bulky groups (R' = Tbt (=C(6)H(2)-2,4,6-{CH(SiMe(3))(2)}(3)), SiMe(SitBu(3))(2), Ar* (=C(6)H(3)-2,6-(C(6)H(2)-2,4,6-i-Pr(3))(2)), and SiiPrDis(2)) are significantly stabilized and can be isolated experimentally. Using the simple valence-electron bonding model and some sophisticated theories, the bonding character of R'B≡PR' should be viewed as R'BI PR'. The present theoretical observations indicate that both the electronic and the steric effect of bulkier substituent ligands play a key role in making triply bonded R'B≡PR' species synthetically accessible and isolable in a stable form.