Fluorine substituent effects on dihydrogen bonding of transition metal hydrides

Abstract

Hydrogen and dihydrogen bonding of the fluorinated alcohol (CF₃)₂CHOH with the transition metal complex WH(CO)₂(NO)(PMe₃)₂ has been explored by a set of four exemplary density functional theory methods that comprises the BP86, PBE, B3LYP and TPSS functionals. The hydride, nitrosyl and carbonyl ligands of the tungsten complex have been considered as sites of protonation. The main effect of fluorination is an increased dihydrogen bond strength by about 15 kJ mol⁻¹. The [W]-H⋯H-OR dihydrogen bond is about 10 kJ mol⁻¹ stronger than the [W]-NO⋯H-OR hydrogen bond. Of the four DFT methods investigated, the BP86 functional provides the most satisfying quantitative as well as qualitative agreement with experiment. The geometry of the R[W]-H⋯H-OR linkage is significantly influenced by secondary dispersive intermolecular bonding. Linear and bent dihydrogen bonds are separated in energy only by about 1 kJ mol⁻¹, and represent local minima on the corresponding energy hypersurface.