Uncovering the Role of Intra- and Intermolecular Motion in Frustrated Lewis Acid/Base Chemistry: Ab Initio Molecular Dynamics Study of CO2 Binding by Phosphorus/Boron Frustrated Lewis Pair [tBu(3)P/B(C6F5)(3)]
2014 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, no 9, 4598-4609 p.Article in journal (Refereed) Published
The role of the intra- and intermolecular motion, i.e., molecular vibrations and the relative motion of reactants, remains largely unexplored in the frustrated Lewis acid/base chemistry. Here, we address the issue with the ab initio molecular dynamics (AIMD) study of CO2 binding by a Lewis acid (LA) and a Lewis base (LB), i.e., tBu(3)P + CO2 + B(C6F5)(3) -> tBu(3)P-C(O)O-B(C6F5)(3) (). Reasonably large ensemble of AIMD trajectories propagated at 300 K from structures in the saddle region as well as trajectories propagated directly from the reactants region revealed an effect arising from significant recrossing of the saddle area. The effect is that transient complexes composed of weakly interacting reactants nearly cease to progress along the segment of the minimum energy pathway (MEP) at the saddle region for a (subpicosecond) period of time during which the dominant factor is the light-to-heavy type of relative motion of the vibrating reactants, i.e., the bouncing-like movement of CO2 with respect to much heavier phosphine and borane as main contributor to the mode that is perpendicular to the MEP-direction. In terms of how P...C and B...O distances change with time, the roaming-like patterns of typical AIMD trajectories, reactive and nonreactive alike, extend far beyond the saddle region. In addition to the dynamical portrayal of , we provide the energy-landscape perspective that takes into account the hierarchy of time scales. The verifiable implication of the effect found here is that the isotopically substituted (heavier) LB/LA pair should be less reactive that the normal and thus lighter counterpart.
Place, publisher, year, edition, pages
2014. Vol. 53, no 9, 4598-4609 p.
Research subject Organic Chemistry
IdentifiersURN: urn:nbn:se:su:diva-104394DOI: 10.1021/ic500284qISI: 000335547400040OAI: oai:DiVA.org:su-104394DiVA: diva2:724319
FunderBerzelii Centre EXSELENTKnut and Alice Wallenberg Foundation