Substituent Effects on the Stability of Thallium and Phosphorus Triple Bonds: A Density Functional Study.

ABSTRACT: Three computational methods (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP and B3LYP/LANL2DZ+dp) were used to study the effect of substitution on the potential energy surfaces of RTl?PR (R = F, OH, H, CH?, SiH?, SiMe(SitBu?)?, SiiPrDis?, Tbt (=C?H?-2,4,6-(CH(SiMe?)?)?), and Ar* (=C?H?-2,6-(C?H?-2, 4,6-i-Pr?)?)). The theoretical results show that these triply bonded RTl?PR compounds have a preference for a bent geometry (i.e., ?R?Tl?P ? 180° and ?Tl?P?R ? 120°). Two valence bond models are used to interpret the bonding character of the Tl?P triple bond. One is model [I], which is best described as TlP. This interprets the bonding conditions for RTl?PR molecules that feature small ligands. The other is model [II], which is best represented as TlP. This explains the bonding character of RTl?PR molecules that feature large substituents. Irrespective of the types of substituents used for the RTl?PR species, the theoretical investigations (based on the natural bond orbital, the natural resonance theory, and the charge decomposition analysis) demonstrate that their Tl?P triple bonds are very weak. However, the theoretical results predict that only bulkier substituents greatly stabilize the triply bonded RTl?PR species, from the kinetic viewpoint.

SUBMITTER: Lu JS 

PROVIDER: S-EPMC6152323 | biostudies-other | 2017 Jul

REPOSITORIES: biostudies-other