Tricarbonylrhenium(I) complexes of pentafluorophenyl-substituted indenyl ligands

Depending on ratios of starting materials and reaction conditions, treatmen t of sodium indenide (NaInd) with C6F6 and NaH in THF afforded 3-(pentafluo rophenyl)indene (1) or 1,3-bis(pentafluorophenyl)indene (2) in 65% and 80% yields, respectively, after aqueous workup and recrystallization from metha nol. Both 1 and 2 reacted quantitatively with NaH to afford the correspondi ng mono- and diarylated sodium indenides (3 and 4), respectively. The monoa rylated Ligand (3) reacted with Re(CO)(5)Br in THF at 65 degrees C for 2 h to afford pentacarbonyl(eta(1)-3-(pentafluorophenyl)-1-indenyl]rhenium(I) ( 5, 57%), which was thermally decarbonylated in decane to afford tricarbonyl [eta(5)-1-(pentafluorophenyl)indenyl] rhenium(I) (6, 85%). An analogous re action of the diarylated ligand (4) with Re(CO)(5)Br in THF at 65 degrees C directly gave tricarbonyl[eta(5)-1,3-bis(pentafluorophenyl (7) in 67% yiel d. All three rhenium carbonyl complexes were characterized by IR, NMR, elem ental analysis, and single-crystal X-ray diffraction. Infrared spectroscopi c measurements showed that each C6F5 substituent increases v(co) of eta(5)- indenylrhenium tricarbonyl complexes by 4 cm(-1) relative to the unsubstitu ted parent, demonstrating the strong electron-withdrawing capabilities of t he C6F5 group. Distinct, intermolecular C-H ... F-C interactions were ident ified in the crystal packing diagrams of 5-7.