Triply Bonded Gallium≡Phosphorus Molecules: Theoretical Designs and Characterization.

The effect of substitution on the potential energy surfaces of triple-bonded RGa≡PR (R = F, OH, H, CH3 , SiH3 , SiMe(SitBu3 )2 , SiiPrDis2 , Tbt (C6 H2 -2,4,6-{CH(SiMe3 )2 }3 ), and Ar* (C6 H3 -2,6-(C6 H2 -2,4,6-i-Pr3 )2 )) compounds was theoretically examined by using density functional theory (i.e., M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The theoretical evidence strongly suggests that all of the triple-bonded RGa≡PR species prefer to select a bent form with an angle (∠Ga-P-R) of about 90°. Moreover, the theoretical observations indicate that only the bulkier substituents, in particular, for the strong donating groups (e.g., SiMe(SitBu3 )2 and SiiPrDis2 ) can efficiently stabilize the Ga≡P triple bond. In addition, the bonding analyses (based on the natural bond orbital, the natural resonance theory, and the charge decomposition analysis) reveal that the bonding characters of such triple-bonded RGa≡PR molecules should be regarded as [Formula: see text]. In other words, the Ga≡P triple bond involves one traditional σ bond, one traditional π bond, and one donor-acceptor π bond. Accordingly, the theoretical conclusions strongly suggest that the Ga≡P triple bond in such acetylene analogues (RGa≡PR) should be very weak.