Student Major

Cell and Molecular Biology Chemistry

Presentation Abstract or Description

A series of five ferrocene derivatives with three, four, five, six, and seven methyl group substituents has been prepared and characterized by multinuclear NMR and elemental analyses. Starting with 1,1'-dimethylferrocene, Vilsmeier-Haack formylation followed by borohydride hydrogenation of the resultant aldehyde yielded trimethylferrocene in good yield. Repetition of these reactions produced tetramethylferrocene, pentamethylferrocene, hexamethylferrocene, and the first reported synthesis of heptamethylferrocene. All five polymethylated ferrocenes exist as a mixture of constitutional isomers. Chemical oxidation of heptamethylferrocene (Me7Fc) with silver tetrafluoroborate produced paramagnetic [Me7Fc]BF4. The structure of one isomer of [Me7Fc]BF4 was determined by single-crystal X-ray diffraction. Electrochemical studies of the entire series from ferrocene to decamethylferrocene reveal a highly linear shift of the redox potential (E1/2) for FeIII/FeII such that each additional methyl group lowers E1/2 by an average of 56 mV due to its inductive effect. Spectrophotometric studies of the series determined that the addition of each methyl substituent brings about a hypsochromic shift for the d-d transition, with the max for Me10Fc at approximately 420 nm, and that of unsubstituted ferrocene at 440 nm. A new triple-decker complex has been synthesized by the addition of a ruthenium electrophile, [Cp*Ru]PF6, (Cp* = C5Me5), to Me7Fc. This novel ruthenium-iron bimetallic, [Cp*RuMe7Fc]PF6, was produced in good yield and characterized by NMR and elemental analysis. While previous work established that reactions between electrophilic metal fragments and ferrocene derivatives with eight or more methyl group substituents readily form bimetallic complexes, reactions with ferrocene derivatives with six or fewer methyl groups brought about ring abstraction and afforded only monometallic products. Thus, it may be concluded that there is a "tipping point" in the series of polymethylated ferrocenes such that the electron-donating ability of seven methyl groups is just sufficient to stabilize a ruthenium-iron triple-decker complex, while ferrocene derivatives with six or fewer methyl groups are insufficiently robust to afford stable electrophilic addition products.

Presentation Format

Poster

Conference Name

American Chemical Society Spring 2024

Conference Date(s) and Location

March 17-21, 2024, New Orleans, LA

Faculty Mentor

Eric Watson

Quarter Award Was Given

Winter 2024

Document Type

Article

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