Journal ArticlePrimary and Secondary Coordination Sphere Lewis Acid Interactions in β-Phosphinoethylborane-ligated Rhodium and Iridium ComplexesNichols, Brian R; Petersen, Jeffrey L; Dolinar, Brian; Popp, Brian VFlexible ambiphilic ligand scaffolds have garnered attention in catalysis due to their ability to adopt multiple binding orientations. Recently, several platinum group metal complexes featuring the flexible, ambiphilic b-phosphinoethylborane ligand were reported in the literature; however, the impact of primary coordination sphere ligands and solvent on the properties of the Lewis acidic borane moiety remain underexplored. Rhodium and iridium complexes ligated by 9-borabicyclo[3.3.1]nonanyl-based b- diphenylphosphinoethylborane were studied using a combination of crystallography and 11B NMR spectroscopy. The studies revealed that both the primary coordination sphere and solvent had an impact on the formation of Lewis acid–base adducts. Specifically, inner-sphere Lewis pair formation was dependent on the nature of the X-type ligand bound to the metal center. Similar dependencies were identified with solvents in which Lewis acid interaction was found to correlate with solvent donor number.Royal Society of Chemistry2025-07-3010621137New Journal of Chemistry1144-0546https://doi.org/10.1039/d5nj01429h2320495; 1336071; 1228336National Science Foundation