Opposing steric and electronic contributions in OsCl2H2(PPr3i)2. A theoretical study of an unusual structure
Abstract
A theoretical study including full geometry optimization is carried out with the integrated molecular orbitals molecular mechanics (IMOMM) method on the OsCl2H2(PPr3i)2 complex. The trigonal prism coordination of this ML6 species is properly reproduced. The origin of this unusual coordination is tracked down to the balance between an electronic preference for a bicapped tetrahedral coordination and the need to relax the steric repulsions between the proximate Cl and PPr3i ligands. The geometrical distortion is shown to involve a significant destabilization of the electronic energy, thus showing the importance of steric contributions. Conflit entre facteurs ste′riques et e′lectroniques dans OsCl2H2(PPr3i)2. Une interpre′tation the′orique d'une structure e′tonnante.La ge′ome′trie du complexe OsCl2H2(PPr3i)2, optimise′e a l'aide de la me′thode hybride chimie quantique/me′canique mole′culaire (IMOMM) donne un re′sultat en bon accord avec l'expe′rience. On montre que la structure de type prisme trigonale resulte d'un compromis entre une structure de type tetraèdre bicappe′ pre′fe′re′e pour des raisons e′lectroniques et la ne′cessite′ d'e′loigner les ligands Cl et PPr3i. On montre e′galement que la structure expe′rimentale est fortement destabilise′e au point de vue e′lectronique, ce qui rēle l'importance de la contribution ste′rique.