The room-temperature reaction between the Rh(I) precursor [Rh(COE) 2(acetone) 2]BF 4 (COE = cyclooctene) and a new thiophosphoryl-based SCS pincer ligand leads to oxidative addition of an sp 2-sp 3 C-C bond as the only observed outcome, despite the presence of accessible sp 3 C-H bonds. A DFT study reveals that the chemistry of the SCS system is controlled by π repulsion between occupied rhodium d orbitals and the lone-pair electrons on the two sulfur atoms. This repulsion gives rise to the thermodynamic selectivity for C-C over C-H cleavage, as it is attributed to the higher electronegativity of a methyl versus hydride ligand, thereby allowing more effective release of excessive π electron density. It is also demonstrated that the observed C-C and unobserved C-H cleavage pathways originate from a common intermediate that features a novel ν 3-C-C-H agostic interaction. The COE ligand is shown to play an important role by greatly stabilizing this intermediate, making it the only available entry point to both reaction pathways.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry