Experimental and four-component relativistic DFT studies of tungsten carbonyl complexes

Abstract

We present a theoretical and experimental study of the structure and nuclear magnetic resonance (NMR) parameters of the pentacarbonyltungsten complexes of η¹-2-(trimethylstannyl)-4,5-dimethylphosphinine, η²-norbornene, and imidazolidine-2-thione. The three complexes have a pseudo-octahedral molecular structure with the six ligands bonded to the tungsten atom. The η¹-2-(trimethylstannyl)-4,5-dimethylphosphinine-pentacarbonyl tungsten complex was synthesized for the first time. For all compounds, we present four-component relativistic calculations of the NMR parameters at the Dirac–Kohn–Sham density functional level of theory using hybrid functionals. These large-scale relativistic calculations of NMR chemical shifts and spin–spin coupling constants were compared with available experimental data, either taken from the literature or measured in this work. The inclusion of solvent effects modeled using a conductor-like screening model was found to improve agreement between the calculated and experimental NMR parameters, and our best estimates for the NMR parameters are generally in good agreement with available experimental results. The present work demonstrates that four-component relativistic theory has reached a level of maturity that makes it a convenient and accurate tool for modeling and understanding chemical shifts and indirect spin–spin coupling constants of organometallic compounds containing heavy elements, for which conventional non-relativistic theory breaks down.