The chiral-at-metal rhenium complex [(η5-C5H5)Re(NO)(PPh3)(ClCH2Cl)]+ X– (1+ X–) undergoes dichloromethane ligand substitution by various neutral donor ligands (:L), i.e., ketones and sulfides, to form the corresponding adducts [(η5-C5H5)Re(NO)(PPh3)(L)]+ X– with retention of configuration of rhenium. Reactions are first order in both 1+ X– and :L concentrations. However, the experimental data could not identify the most favorable mechanism. Thus, DFT calculations were applied with :L = cyclohexanone, dimethyl sulfide, ethyl chloride, and dichloromethane. Two pathways were found: interchange (I) and neighboring group participation (NGP), anchimerically assisted by a PC=CH moiety of the PPh3 ligand. The stronger nucleophiles, i.e., cyclohexanone and dimethyl sulfide, undergo the I mechanism with frontside displacements of the dichloromethane ligand, while the weaker nucleophiles, i.e., ethyl chloride and dichloromethane, can react by either the same I or NGP mechanisms. Both lead to retention of configuration of rhenium.

Theoretical investigation of dichloromethane ligand substitution in [(η5-C5H5)Re(NO)(PPh3)(ClCH2Cl)]+, a functional equivalent of a chiral Lewis acid

ACS Spring Meeting 2021

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