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 (C₆H₂-2,4,6-{CH­(SiMe₃)₂}₃), and Ar* (C₆H₃-2,6-(C₆H₂-2,4,6-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 R′Ga←PR′. 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.