Interplay of ionic species in salts of homoleptic quaternary phosphonium cations bearing linear biphenyl moieties

• Main Authors: Tan, Monica Bernard, Sobolev, Alexandre N. N., Raston, Colin L. L., Dalgarno, Scott J. J., Ling, Irene
• Format: Article
• Published: MDPI 2023
• Subjects: QD Chemistry
• Online Access: http://eprints.um.edu.my/39120/

Quaternary phosphonium salts are popular candidates used in many chemical transformations and synthetic chemistry, notably in catalysis. We have examined the single crystals of two bulky phosphonium compounds, tetra(1,1 `-biphenyl]-4-yl) phosphonium dicyanamide (C48H36P+center dot N(CN)(2)(-), compound 1), and tetra(1,1 `-biphenyl]-4-yl) phosphonium bromide hydrate (C48H36P+center dot Br-, CH3CN, H2O, compound 2), and herein report the structural properties for the compounds with an emphasis on the influence of the ion-ion interaction towards self-assembly; the overall self-assembly for both structures is very similar, with subtle differences in the cell parameters. The symmetrical tetra (1,1 `-biphenyl]-4-yl) phosphonium cations in both compounds self-assembled to form robust stacked columns in the solid-state, with voids occupied by anions or solvent molecules. Quantitative examination of intermolecular interactions using Hirshfeld surface analysis found that classical and non-classical hydrogen bonding appears to be the dominant contributor in stabilizing the self-assembly in both cases. The present work can not only benefit in understanding the mutual interaction between the sterically encumbered tetra (1,1 `-biphenyl]-4-yl) phosphonium cations and between counterions, but also provide insights for the self-assembled arrays in the solid-state.