Triply Bonded Gallium≡Phosphorus Molecules: Theoretical Designs and Characterization

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• The synthesis and characterization of low-coordinate phosphorus and gallium compounds are of significant interest.
• Understanding the bonding and stability of heavier main group element multiple bonds is a fundamental challenge.

Purpose of the Study:

• To theoretically investigate the structural, bonding, and electronic properties of triple-bonded RGa≡PR compounds.
• To determine the influence of various substituents (R) on the stability and nature of the Ga≡P triple bond.

Main Methods:

• Density functional theory (DFT) calculations were employed using multiple functionals (M06-2X, B3PW91, B3LYP) and basis sets (Def2-TZVP, LANL2DZ+dp).
• Potential energy surfaces were analyzed to determine preferred molecular geometries.
• Bonding analyses, including Natural Bond Orbital (NBO), Natural Resonance Theory (NRT), and Charge Decomposition Analysis (CDA), were performed.

Main Results:

• All investigated RGa≡PR compounds favor a bent geometry with an approximate ∠Ga-P-R angle of 90°.
• Sterically demanding and electron-donating substituents (e.g., SiMe(SitBu₃)₂, SiiPrDis₂) are crucial for stabilizing the Ga≡P triple bond.
• The Ga≡P triple bond is characterized by one σ bond, one traditional π bond, and one donor-acceptor π bond.

Conclusions:

• The Ga≡P triple bond in RGa≡PR compounds exhibits unique bonding character, distinct from typical triple bonds.
• The stability of the Ga≡P triple bond is highly dependent on the nature of the substituent R.
• These findings suggest that the Ga≡P triple bond is inherently weak and requires specific substituents for stabilization, akin to acetylene analogues.