Synthesis, structures, and reactivity of mono- and bis(ferrocenyl)-substituted group 14 metallocenes

New mono- and bis(ferrocenyl)-substituted germanocenes and stannocenes have been synthesized in good yield by the reaction between group 14 dichlorides, (Cl2Ge.dioxane, Cl-2-Sn) and the lithium salts of the corresponding mono- and bis(cyclopentadienyl)-substituted ferrocenes. The X-ray crystal structure analyses of germanocenes 3a and 4a reveal a bent sandwich structure with an angle between the cyclopentadienyl planes of 45.4degrees and 40.9degrees for 3a and 4a, respectively. Mass spectrometry and electrochemical studies show the stabilization of the generated transient cations by ferrocenyl groups, particularly in the germanium series. Their reactions with electrophilic reagents such as catechol and cycloaddition with o-quinone also are reported and show, in the latter case, an increase of the specific reactivity of the dimethylcyclopentadienyl moiety.