Stereospecific Syntheses and Structures of Planar Chiral Bidentate η5:κS-Indenyl-Sulfanyl and -Sulfinyl Complexes of Rhodium(III)

Abstract

Axially chiral rac-1-(2-methyl-1H-inden-3-yl)-2-(methylsulfanyl)naphthalene (rac-3) was synthesized from methyl 2-(methylsulfanyl)-1-naphthoate through reaction with the di-Grignard reagent derived from 1-bromo-2-(2-bromopropyl)benzene, followed by acid-catalyzed dehydration of the intermediate indanol. Oxidation of rac-3 with m-CPBA gave the diastereomeric sulfoxides (aR*,RS*)-5 and (aR*,SS*)-6, with the relative configuration of 5 established using single-crystal X-ray diffraction. The dichloro[η5:κS-indenyl-sulfanyl and -sulfinyl]rhodium complexes rac-4, (pR*,SS*)-7, and (pR*,RS*)-8 were synthesized through reaction of the ligands rac-3, (aR*,RS*)-5, and (aR*,SS*)-6, respectively, with rhodium trichloride in 9:1 methanol/water solution heated under reflux. The use of water as a cosolvent was found to be critical for obtaining good yields in the complexation reactions. Solid-state structures for the racemic rhodium complexes were determined through single-crystal X-ray diffraction. The enantiomers of th...