MicroED characterization of a robust cationic σ-alkane complex stabilized by the [B(3,5-(SF(5))(2)C(6)H(3))(4)](−) anion, via on-grid solid/gas single-crystal to single-crystal reactivity

Microcrystalline (∼1 μm) [Rh(Cy(2)PCH(2)CH(2)PCy(2))(norbornadiene)][S-BAr(F)(4)], [S-BAr(F)(4)] = [B(3,5-(SF(5))(2)C(6)H(3))(4)](−), reacts with H(2) in a single-crystal to single-crystal transformation to form the σ-alkane complex [Rh(Cy(2)PCH(2)CH(2)PCy(2))(norbornane)][S-BAr(F)(4)], for which the structure was determined by microcrystal Electron Diffraction (microED), to 0.95 Å resolution, via an on-grid hydrogenation, and a complementary single-crystal X-ray diffraction study on larger, but challenging to isolate, crystals. Comparison with the [BAr(F)(4)](−) analogue [Ar(F) = 3,5-(CF(3))(2)(C(6)H(3))] shows that the [S-BAr(F)(4)](−) anion makes the σ-alkane complex robust towards decomposition both thermally and when suspended in pentane. Subsequent reactivity with dissolved ethene in a pentane slurry, forms [Rh(Cy(2)PCH(2)CH(2)PCy(2))(ethene)(2)][S-BAr(F)(4)], and the catalytic dimerisation/isomerisation of ethene to 2-butenes. The increased stability of [S-BAr(F)(4)](−) salts is identified as being due to increased non-covalent interactions in the lattice, resulting in a solid-state molecular organometallic material with desirable stability characteristics.