Nickel catalyzed cross-coupling reactions are potential replacements for the more expensive palladium catalysts typically used. Nickel(0) complexes are more commonly used in these reactions despite being less air stable and more expensive than their nickel(II) counterparts. One issue with using nickel(II) complexes is that they can be square planar or tetrahedral in geometry and it is not yet fully known why nickel(II) complexes are observed in multiple geometries or which geometric form is better for cross-coupling catalysis. We studied nickel(II) diphosphine complexes using computational methods (M06, cc-pVDZ) in order to find energetic or geometric trends to explain the observed geometries from single crystal diffraction studies. Structural optimizations with known crystal geometries were compared with their ‘alternative’ non-observed geometry, and the resulting energy and geometric parameters were compared across groups of similar molecules. Unfortunately, the computational results failed to accurately predict known geometries. Qualitative observations from these calculations did show trends between phosphine backbone size and shape and the observed solid state geometry. While these results were less conclusive than initially hoped, they will still help future researchers predict the geometry of nickel(II) diphosphine complexes which could aid in improving nickel cross-coupling catalysis.

When computational chemistry fails: Modeling geometries of nickel(II) diphosphine complexes

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.