title: A theoretical analysis of substituent electronic effects on phosphine-borane bonds.
abstract: Phosphine-borane adducts are a well-known moiety in synthetic and coordination chemistry. These complexes form a dative bond in which the Lewis basic phosphorus atom donates electron density into an empty p-orbital of the Lewis acidic boron atom. However, donation of the phosphorus lone pair is not the only stabilizing interaction, as hyperconjugation and electrostatic interaction also play important roles in bonding. This paper describes a detailed density functional theory level (B3LYP) study completed to determine the impact electron-donating and withdrawing substituents have on phosphine-borane bonds through the investigation of a series of para-substituted PAr3-BH3and PH3-BAr3phosphine-borane adducts. Natural bond orbital (NBO) partitioning was used to calculate the distribution of electron density between the phosphine and borane fragments. Extended transition state and natural orbitals for chemical valence (ETS-NOCV) analysis was used to isolate contributions to the overall electronic interaction of the phosphine-borane adducts. Molecular orbital composition and charge donation was calculated using AOMix. The resulting data was correlated with Hammett σ constants.
authors.affiliation: Department of Chemistry, Stetson University, 421 N. Woodland Blvd. Unit 8271, DeLand, FL, 32723, USA. psibbald@stetson.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Sibbald
keywords: Borane; Dative Bond; Density functional theory; ETS-NOCV; Phosphine