Terminal Phosphinidene Complex Adducts with Neutral and Anionic O-Donors and Halides and the Search for a Differentiating Bonding Descriptor

The stability and some characteristic
bonding features of a variety
of ligand (L)-stabilized phosphinidene complexes derived from adduct
formation with halides, and both anionic or neutral O-donor bases
were explored. Furthermore, the main features of L → P pnictogen
bonding in such adducts were studied not only by using geometric criteria
such as L–P bond distances and pyramidalization or planarity
at P but also by turning the spotlight on bond-strength-related (including
atoms-in-molecules-derived) parameters, thermodynamic stability dependence
with electronic characteristics of the free ligand, and dative-bonding
participation. We propose the new relative positions of the
charge concentration band descriptor, τVSCC, which, together with the sign and magnitude of ∇2ρ at the bond critical point, constitutes the required criteria
to differentiate L–P linkages as van der Waals interactions,
dative bonding, or mostly covalent bonds.