Abstract Deprotonation of η 6-flourenechromium tricarbonyl (III) with excess t-BuOK in THF at 70 C yields [η 6-C 13 H 9 Cr (CO) 3]− K+(Ia), which isomerizes to η 5-C 13 H 9 Cr (CO) 3 Cr− K+(II) at temperatures above− 20 C.[η 6-C 13 H 9 Cr (CO) 3]− Li+(Ib) may be obtained in the solid state by treatment of III with BuLi in absolute ether followed by precipitation with n- hexane. Methylation of Ib and II with methyl iodide goes stereospecifically to give η 6-exo-( ...