1,1′,2,2′-Tetralithioferrocene and 1,1′,2,2′,3,3′-Hexalithioferrocene: Useful Additions to Ferrocene Precursor Compounds

Abstract

The direct synthesis of 1,1´,2,2´-tetralithioferrocene from 1,1´,2,2´-tetrabromoferrocene is reported. In addition, the related 1,1´,2,2´,3,3´-hexalithioferrocene is also described, prepared directly from 1,1´,2,2´,3,3´-hexabromoferrocene. These lithioferrocenes may be isolated as orange red (tetralithio-) and red (hexalithio-) powders, respectively. When these are prepared in situ and reacted with chlorotrimethylsilane, the corresponding tetrakis-1,1´,2,2´-tetrakis(trimethylsilyl)ferrocene and 1,1´,2,2´,3,3´-hexakis(trimethylsilyl)ferrocene are obtained as red and crimson crystalline solids respectively. The single crystal structures of 1,1´,2,2´-tetrakis(trimethylsilyl)ferrocene, 11, and 1,1´,2,2´,3,3´-hexakis(trimethylsilyl)ferrocene, 12, have been determined and are described.

Synthetic Route to 1,1′,2,2′-Tetraiodoferrocene That Avoids Isomerization and the Electrochemistry of Some Tetrahaloferrocenes

“…In preliminary work, on the basis of our previous work on bromoferrocenes, , we had attempted the low-temperature α-dilithiation of 1,1′-diiodoferrocene in thf followed by iodine quenching. This always resulted in complex mixtures.…”

“…1,1′,2,2′-Tetrabromoferrocene (5.0 g, 10 mmol) dissolved in a mixture of hexane (150 mL) and diethyl ether (25 mL) was treated with a 4.5 molar excess of n -BuLi (18 mL of a 2.5 M solution, 45 mmol). After several minutes the characteristic red tetra-1,1′,2,2′-lithioferrocene began to precipitate from solution . After 1 h the reaction mixture was cooled to −30 °C and chloro-tri- n -butyltin (14.6 g, 45 mmol) was added.…”

“…N.B. : this compound may also be prepared via 1,1′,2-trilithioferrocene from 1,1′,2-tribromoferrocene by lithium–halogen exchange in hexane (with a few milliliters of diethyl ether added) by following the method used for the preparation of 1,1′,2,2′-tetrakis­(trimethylsilyl)­ferrocene in ref . Tri- n -butyltin chloride was used as the quenching reagent instead of the chlorosilane.…”

“…After several minutes the characteristic red tetra-1,1′,2,2′lithioferrocene began to precipitate from solution. 14 After 1 h the reaction mixture was cooled to −30 °C and chloro-tri-n-butyltin (14.6 g, 45 mmol) was added. After the solution was warmed to room temperature and stirred for a further 1 h, the reaction mixture was hydrolyzed with water (30 mL) and subsequently the organic layer was separated using additional ether as required.…”

Rearrangements and Migrations along the Ferrocene Periphery: On the Way to Planar‐Chiral and (Multi)Substitution Patterns

“…The negative charge can either be established by deprotonation using alkyl lithium reagents ( n / s / t BuLi) or sterically hindered lithium amides (LDA, LiTMP) [9] . Alternatively halogene‐metal‐exchange ( HME ) reactions using n ‐ or t ‐BuLi can be applied [10] . However, the kinetics between both routes differ.…”