Synthesis and Solution Chemistry of Metal Hydrides from Cationic Rhodium(I) Catalyst Precursors [(L-L)Rh(NBD)]$ClO_4 (L-L=Fe({\eta}^5-C_5H_4PBu^t\;_2)_2,\;Fe{\eta}^5-C_5H_4PPhBu^t)_2)$

The hydrogenation catalyst precursors $[(L-L)Rh(NBD)]ClO_4\;(L-L=Fe({\eta}^5-C_5H_4PBu^t\;_2)_2,\;Fe({\eta}^5-C_5H_4PPhBu^t)_2$; NBD = norbornadiene) react with $H_2(1\;atm,\;30^{\circ}C$, MeOH) to yield $[(L-L)HRh({\mu}-H)_3RhH(L-L)]ClO_4$. These hydrido species are fluxional, and variable temperature NMR studies show the existence of a number of equilibria involving both fluxional and non-fluxional species. The synthesis, solution structures, and fluxional behaviors of these hydrides are described.