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

Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques are used for the synthesis and structural characterization of the sigma-alkane complex [Rh(tBu(2)PCH(2)CH(2)CH(2)PtBu(2))(eta(2),eta(2)-C7H12)][BAr4F] (Ar-F=3,5-(CF3)(2)C6H3), in which the alkane (norbornane) binds through two exo-C-H...Rh interactions. In contrast, the bis-cyclohexyl phosphine analogue shows endo-alkane binding. A comparison of the two systems, supported by periodic DFT calculations, NCI plots and Hirshfeld surface analyses, traces this different regioselectivity to subtle changes in the local microenvironment surrounding the alkane ligand. A tertiary periodic structure supporting a secondary microenvironment that controls binding at the metal site has parallels with enzymes. The new sigma-alkane complex is also a catalyst for solid/gas 1-butene isomerization, and catalyst resting states are identified for this.

Automated summary

Single-crystal to single-crystal solid-state molecular organometallic (SMOM) techniques were used to synthesize and characterize a sigma-alkane complex with different alkane binding modes. The comparison, supported by analysis, reveals that the different regioselectivity is related to subtle changes in the local microenvironment surrounding the alkane ligand.