Synthesis and Characterization of a Family of Air-Stable Ferrocene- and Ruthenocene-Containing Primary, Secondary, and Tertiary Phosphines

The
synthesis and characterization of a family of air-stable primary,
secondary, and tertiary phosphines containing all possible combinations
of ethylferrocene and ethylruthenocene substituents are reported.
Each phosphine was characterized by 1H, 13C,
and 31P NMR spectroscopy, IR and UV–vis absorption
spectroscopy, mass spectrometry, and elemental analysis. With the
exception of primary ethylruthenocene phosphine 8a, all
of the title compounds have been studied by single-crystal X-ray crystallography.
Ferrocene-containing phosphines showed maximum absorption at wavelengths
of ca. 440 nm and qualitatively reversible oxidation waves in their
cyclic voltammograms with intensities scaling to the number of ferrocene
units present. The average metal–cyclopentadienyl centroid
distances observed for ferrocene-containing phosphines were shorter
than those of ruthenocene-containing phosphines, which also had maximum
absorption wavelengths of ca. 320 nm and underwent irreversible electrochemical
oxidation. Phosphines containing both ethylferrocene and ethylruthenocene
substituents displayed properties consistent with the presence of
both metallocene types.