Alkyl dehydrogenation in a Rh(I) complex via an isolated agostic intermediate

A well-characterised 14-electron rhodium phosphine complex, [Rh((PPr3)-Pr-i)(3)][BAr4F], which contains a beta-CH agostic interaction, is observed to undergo spontaneous dehydrogenation to afford [Rh((PPr3)-Pr-i)(2)((PPr2)-Pr-i(C3H5))][BAr4F]; calculations on a model system show that while C-H activation is equally accessible from the beta-CH agostic species or an alternative gamma-CH agostic isomer, subsequent beta-H-transfer can only be achieved along pathways originating from the beta-CH agostic form.