Selectivity of Rh⋅⋅⋅H-C Binding in a σ-Alkane Complex Controlled by the Secondary Microenvironment in the Solid State

Area of Science:

• Organometallic chemistry
• Solid-state synthesis
• Catalysis

Background:

• Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques enable precise synthesis and characterization.
• Understanding alkane binding selectivity is crucial for designing new catalysts.
• Enzyme active sites offer models for controlled microenvironments in catalysis.

Purpose of the Study:

• To synthesize and structurally characterize a new σ-alkane complex using SMOM.
• To investigate the factors controlling alkane binding regioselectivity in rhodium complexes.
• To evaluate the catalytic activity of the new complex in 1-butene isomerization.

Main Methods:

• Single-crystal to single-crystal solid-state molecular organometallic (SMOM) synthesis and X-ray diffraction.
• Periodic Density Functional Theory (DFT) calculations.
• Non-covalent interaction (NCI) plots and Hirshfeld surface analyses.

Main Results:

• A novel σ-alkane complex, [Rh(tBu2PCH2CH2CH2PtBu2)(η2,η2-C7H12)][BArF4], was synthesized, featuring exo-alkane binding via C-H⋅⋅⋅Rh interactions.
• Comparison with a bis-cyclohexyl phosphine analogue revealed different binding regioselectivity (endo-binding).
• DFT calculations and surface analyses identified microenvironmental factors influencing binding selectivity, with parallels to enzymatic control.

Conclusions:

• Subtle changes in the ligand microenvironment significantly impact alkane binding regioselectivity in rhodium complexes.
• The synthesized σ-alkane complex demonstrates catalytic activity in 1-butene isomerization, with identified catalyst resting states.
• The study highlights the potential of SMOM techniques for designing sophisticated organometallic catalysts with enzyme-like control.