Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy2 PCH2 CH2 PCy2 )(η2 η2 -NBA)][BArF 4 ] (NBA = norbornane; ArF = 3,5-(CF3 )2 C6 H3 ) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy2 PCH2 CH2 PCy2 )(alkene) x ][BArF 4 ] are formed. The ethene ( x = 2) complex, [Rh(Cy2 PCH2 CH2 PCy2 )(ethene)2 ][BArF 4 ]-Oct , has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy2 PCH2 CH2 PCy2 )(ethene)2 ][BArF 4 ]-Hex , that has a hexagonal microporous structure ( P 63 22). The propene complex ( x = 1) [Rh(Cy2 PCH2 CH2 PCy2 )(propene)][BArF 4 ] is characterized as having a π-bound alkene with a supporting γ-agostic Rh···H3 C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d3 -propene, H2 C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 CHCD3 , using [Rh(Cy2 PCH2 CH2 PCy2 )(η2 η2 -NBA)][BArF 4 ] scrambles the D-label into all possible positions of the propene, as shown by isotopic perturbation of equilibrium measurements for the agostic interaction. Periodic DFT calculations show a low barrier to H/D exchange (10.9 kcal mol-1 , PBE-D3 level), and GIPAW chemical shift calculations guide the assignment of the experimental data. When synthesized using solution routes a bis-propene complex, [Rh(Cy2 PCH2 CH2 PCy2 )(propene)2 ][BArF 4 ] , is formed. [Rh(Cy2 PCH2 CH2 PCy2 )(butene)][BArF 4 ] ( x = 1) is characterized as having 2-butene bound as the cis -isomer and a single Rh···H3 C agostic interaction. In the solid-state two low-energy fluxional processes are proposed. The first is a simple libration of the 2-butene that exchanges the agostic interaction, and the second is a butene isomerization process that proceeds via an allyl-hydride intermediate with a low computed barrier of 14.5 kcal mol-1 . [Rh(Cy2 PCH2 CH2 PCy2 )(η2 η2 -NBA)][BArF 4 ] and the polymorphs of [Rh(Cy2 PCH2 CH2 PCy2 )(ethene)2 ][BArF 4 ] are shown to be effective in solid-state molecular organometallic catalysis (SMOM-Cat) for the isomerization of 1-butene to a mixture of cis - and trans -2-butene at 298 K and 1 atm, and studies suggest that catalysis is likely dominated by surface-active species. [Rh(Cy2 PCH2 CH2 PCy2 )(η2 η2 -NBA)][BArF 4 ] is also shown to catalyze the transfer dehydrogenation of butane to 2-butene at 298 K using ethene as the sacrificial acceptor.