A comparison of non-covalent interactions in the crystal structures of two σ-alkane complexes of Rh exhibiting contrasting stabilities in the solid state

TY - JOUR

T1 - A comparison of non-covalent interactions in the crystal structures of two σ-alkane complexes of Rh exhibiting contrasting stabilities in the solid state

AU - Sajjad, M. Arif

AU - Macgregor, Stuart A.

AU - Weller, Andrew S.

N1 - Funding Information: We thank the EPSRC for funding via awards EP/W015498/1 and EP/W015552/1. Publisher Copyright: © 2023 The Royal Society of Chemistry.

PY - 2023/1/27

Y1 - 2023/1/27

N2 - Non-covalent interactions surrounding the cationic Rh σ-alkane complexes within the crystal structures of [(Cy2PCH2CH2PCy2)Rh(NBA)][BArF4], [1-NBA][BArF4] (NBA = norbornane, C7H12; ArF = 3,5-(CF3)2C6H3), and [1-propane][BArF4] are analysed using Quantum Theory of Atoms in Molecules (QTAIM) and Independent Gradient Model approaches, the latter under a Hirshfeld partitioning scheme (IGMH). In both structures the cations reside in an octahedral array of [BArF4]− anions within which the [1-NBA]+ cation system exhibits a greater number of C-H⋯F contacts to the anions. QTAIM and IGMH analyses indicate these include the strongest individual atom-atom non-covalent interactions between the cation and the anion in these systems. The IGMH approach highlights the directionality of these C-H⋯F contacts that contrasts with the more diffuse C-H⋯π interactions. The accumulative effects of the latter lead to a more significant stabilizing contribution. IGMH %δGatom plots provide a particularly useful visual tool to identify key interactions and highlight the importance of a -{C3H6}- propylene moiety that is present within both the propane and NBA ligands (the latter as a truncated -{C3H4}- unit) and the cyclohexyl rings of the phosphine substituents. The potential for this to act as a privileged motif that confers stability on the crystal structures of σ-alkane complexes in the solid-state is discussed. The greater number of C-H⋯F inter-ion interactions in the [1-NBA][BArF4] system, coupled with more significant C-H⋯π interactions are all consistent with greater non-covalent stabilisation around the [1-NBA]+ cation. This is also supported by larger computed δGatom indices as a measure of cation-anion non-covalent interaction energy.

AB - Non-covalent interactions surrounding the cationic Rh σ-alkane complexes within the crystal structures of [(Cy2PCH2CH2PCy2)Rh(NBA)][BArF4], [1-NBA][BArF4] (NBA = norbornane, C7H12; ArF = 3,5-(CF3)2C6H3), and [1-propane][BArF4] are analysed using Quantum Theory of Atoms in Molecules (QTAIM) and Independent Gradient Model approaches, the latter under a Hirshfeld partitioning scheme (IGMH). In both structures the cations reside in an octahedral array of [BArF4]− anions within which the [1-NBA]+ cation system exhibits a greater number of C-H⋯F contacts to the anions. QTAIM and IGMH analyses indicate these include the strongest individual atom-atom non-covalent interactions between the cation and the anion in these systems. The IGMH approach highlights the directionality of these C-H⋯F contacts that contrasts with the more diffuse C-H⋯π interactions. The accumulative effects of the latter lead to a more significant stabilizing contribution. IGMH %δGatom plots provide a particularly useful visual tool to identify key interactions and highlight the importance of a -{C3H6}- propylene moiety that is present within both the propane and NBA ligands (the latter as a truncated -{C3H4}- unit) and the cyclohexyl rings of the phosphine substituents. The potential for this to act as a privileged motif that confers stability on the crystal structures of σ-alkane complexes in the solid-state is discussed. The greater number of C-H⋯F inter-ion interactions in the [1-NBA][BArF4] system, coupled with more significant C-H⋯π interactions are all consistent with greater non-covalent stabilisation around the [1-NBA]+ cation. This is also supported by larger computed δGatom indices as a measure of cation-anion non-covalent interaction energy.

UR - http://www.scopus.com/inward/record.url?scp=85153945344&partnerID=8YFLogxK

U2 - 10.1039/D3FD00009E.

DO - 10.1039/D3FD00009E.

M3 - Article

AN - SCOPUS:85153945344

SN - 1364-5498

JO - FARADAY DISCUSSIONS

JF - FARADAY DISCUSSIONS

ER -