Exploring (Ph2PCH2CH2)2E Ligand Space (E = O, S, PPh) in RhI Alkene Complexes as Potential Hydroacylation Catalysts



The ligands (Ph2PCH2CH2)2E (E = O, S, PPh) have been used to form a variety of RhI cations [Rh{(Ph2PCH2CH2)2E}(alkene)]+ (alkene = methyl acrylate, trimethylvinylsilane). Variable-temperature NMR spectroscopy shows that the methyl acrylate ligands undergo a fluxional process on the metal, via a κ1-carbonyl intermediate, while the trimethylvinylsilane complexes cannot access this intermediate and do not undergo the same process. Their reactivity in hydroacylation reactions with 1-pentanal have been investigated, and these studies further suggest the important role that a chelating substituent next to the aldehyde might play in productive hydroacylation.