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.